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Highway Design Senior Project 2010
Part- I
Section-1: Introduction
There is a growing universal demand for well prepared professionals in all disciplines. In
addition, increased pressure has consequently been placed in educational institution to prepare
the required number of qualified professional to fulfill society’s need. It is imperative that there
is a large need in the industry for engineers with training and experience, and the academic
should move successfully to fill the need. This is especially true for in the situation of Ethiopia
where there is a lack of well trained and experienced urban engineer’s.
Therefore, the integration of academic program and exposing students to more practical project
results in well-seasoned and, well-educated professionals.
Thus, this high way design project is intended to equip the students with practical design
reinforcing what they have attained theoretically in the class.
It is already known that, for rapid economic, industrial and cultural growth of any country, a
good system of transportation is very essential. One of the transportation systems that are
economical for developing countries like Ethiopia is road. A well – designed road network plays
an important role in transporting people and other industrial products to any direction with in
short time. Roads, to satisfy their intended purpose, must be constructed to be safe, easy,
economical, environmentally friend and must full fill the needs of inhabitants. Being safe, the
number of accidents that can occur will be minimized. Easiness decreases operation cost,
pollution and even time cost. Economical roads assure their feasibility according to their plans
and initiate further construction of roads. Schemes that do not satisfy the needs of localities may
not get the maximum utilization of the surplus man power that is really to exist in the rural
community and also its economical value may also decrease. Therefore, from this project it is
expected to understand and to get acquainted with the above facts by going through on the
following design aspects.
1.1 General Background
ECSC, IUDS, Urban Engineering Department (UE)
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Highway Design Senior Project 2010
This high way design project is taken from the Hargele - Afder – Bare - Yet road project, which
is located in the Eastern part of the country in Somali National Regional State, Afder
Administrative Zone, Afder and Bare Woredas. The project is intended to facilitate the existing
and for the expected traffic load in the future, because the town is developing.
From this road we have given a stretch of 3 km emanating from station 12+500 to 15+500 for
this project to do geometric and pavement design in general.
1.2 Objectives
This final year design project on high-way has the following major objectives:-
To expose the prospective graduates to a detail and organized design on road projects;
To implement the knowledge that the prospective graduates have learned theoretically in
classes;
To ensure a good carrier development;
1.3 Brief Description of The Project Area
The Hargele - Afder – Bare - Yet road project, is located in the Eastern part of the country in
Somali National Regional State, Afder Administrative Zone, Afder and Bare Woredas. The
project starts at Hargele (5º13’N and 42º 11’E) and pass through Hargele, Afder, Bare, town and
ends at Yet. The project length is estimated to be 142.4km. The Location map together with the
topographic map of the project area is shown below.
Fig. 1.1 Project Location Map
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Highway Design Senior Project 2010
Fig. 1.3.3 Digitized Proposed Project Alternative Alignments
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Location of the Project Road
Highway Design Senior Project 2010
Climate:
One of the environmental factors that affect performance of pavements structures is climate.
Hence, climate data of the project area mainly rainfall intensity, in terms of mean monthly and
mean annual and, temperature are required. According to the map shown on National Atlas of
Ethiopian Atlas, the project area is located in the region of the lowest annual rainfall. The mean
annual rainfall in this region is 300mm per year. The rainfall of the project area is characterized
by the following rainfall distribution:
April, May and October The wettest Months
And in the remaining months The driest months.
Topography:
The terrain of the project area through which the road alignment traverses is rolling in substantial
section of the project which is intercepted by mountainous terrain in some sections.
Potential of the area:
In the project area limited crop production, livestock and livestock products are available in the
area of influence of the road project even though the area is under attention to reverse food
deficit. There is an initiative to change the area that the potential resources of oil mining and salt
production may attract private investors and governmental agencies.
1.4 Scope of the project
The scope of the project goes as far as designing the geometry and pavement of a given road
section, with its appropriate drainage structures.
Section-2: Geometric design
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Highway Design Senior Project 2010
2.1 Geometric design Control and Criteria
2.1.1 Terrain classification
2.1.1.1 Contour generation
The surveying data x, Y and Z coordinate taken from the road corridor using Hand Held GPS are
converted to a contour using GIS software.
2.1.1.2 Selection of center line
The center line of the road is delineated on the given road corridor using the contour elevations
by considering to have minimum earth work along the corridor.
2.1.1.3 Transverse terrain property
In order to know the type of the terrain along the selected center line or corridor, we took horizontal distance perpendicular to the center line and vertical elevation measurements across the road. Each measurement is taken longitudinally along the rod at 20m interval to get better terrain classification. The values obtained are summarized in index table 2-1.
Slop= (vertical elevation / horizontal elevation)*100
Therefore, we generalize the following terrains classification along the road corridor:
STATION
TERRAIN CLASSIFICATION
AVG. SLOPE (%)
From To
12+ 500 12+ 760 Rolling 23.14
12 + 760 13+ 080 Mountainous 26.63
13 + 080 13+ 520 Rolling 18.75
13 + 520 13+ 820 Mountainous 32.234
13 + 820 15 +500 Rolling 16.87
Table 2-2 Terrain Classification
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Highway Design Senior Project 2010
Fig 2-1 Generated contour.
2.1.2 Design traffic volume
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Highway Design Senior Project 2010
2.1.2.1 Traffic data analysis
In order to design the road, traffic data analysis is very important. Therefore, the secondary data of traffic analysis we get from the project site comprises traffic volume before design, during implementation and up to the design life time of the road. As the secondary data shows the project life is 15 year. The traffic volume data and the design life time are expressed in the following table.
Year Car 4 WD S/ Bus L/ Bus S/ Truck M/ Truck L/ TruckT &
TTOTAL
2008 0 4 6 2 12 4 2 14 44
2009 0 5 7 2 13 5 3 16 51
2010 0 5 7 2 14 5 3 16 52
2011 0 6 8 3 14 5 3 17 56
2012 0 6 8 3 15 5 3 18 58
2013 0 15 16 6 31 20 28 34 149
2014 0 16 17 7 34 21 30 37 160
2015 0 19 19 8 36 22 32 39 174
2016 0 19 21 8 38 25 35 41 184
2017 0 19 21 9 40 26 36 44 193
2018 0 20 22 9 43 28 38 46 205
2019 0 21 25 11 44 31 42 49 221
2020 0 22 26 11 47 32 44 52 232
2021 0 22 26 12 49 34 46 53 241
2022 0 22 29 12 52 35 48 56 253
2023 0 25 30 13 55 36 51 59 267
2024 0 25 32 13 57 39 54 60 279
2025 0 26 33 14 60 40 57 64 292
2026 0 27 34 14 62 43 60 67 307
2027 0 28 37 16 66 44 63 70 323
Table 2-3 Traffic data analysis
From the above data,
o Traffic volume when the road open =149 veh/day
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Highway Design Senior Project 2010
o Traffic volume at the end of the project life =323 veh/day
2.1.3 Road functional classification
Some of the factors which affect road design control and criteria are functional classification of
the road. In Ethiopian case, we have five functional classes based on AADT and importance of
the road.
Since, AADT of the project lies between 200-1000, and the road expected to serve centers of
provisional importance, the road could be main access road (class II).
2.2 Geometric Design Standard
Based on the traffic data obtained from the above table we decide the project design standard to
be (DS4).
Because:-
a) Even if the AADT at the opening of the road (2013) is 149 veh/day it will be greater than
200 veh/ day after five year and it is 323 veh/day at the end of design life (15 years). So it
fulfills the requirements of DS4. Since the recommended traffic volume for DS4 is 200-
1000 veh/day.(ERA)
b) The second reason is that since the area is an oil mining area, we expect the road will
accommodate the expected traffic volume during the design life time.
c) Based on the above reason, we decide the road to be DS4, to get full knowledge from the
whole project since the project is for academic purpose.
Therefore, we took the entire design element based on DS4. Refer the above information from
ERA manual Table 2.1.
From Design Standards vs. Road Classification and AADT table of ERA for DS4,
AADT=200 – 1000 vehicle/day
Surface type = paved
Carriageway = 6.7m
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Highway Design Senior Project 2010
Shoulder width =1.5m for rolling
= 0.5m for mountainous
Design speed = 70km/hr for rolling
= 60km/hr =for mountainous
2.2.1 Horizontal Alignment
Based on our proposal of the center line of the road, we have tangents and curves. The curves are
curve1, curve2, curve3, curve4, curve5, and curve6.
Based on our terrain classification, the curves fall in to different terrain classification that
leads us to determine the radius and different elements of each curve.
Curve Terrain type
Curve 1 Rolling
Curve 2 Rolling
Curve 3 Rolling
Curve 4 Error! Not a valid link.
Curve 5 Rolling
Curve 6 Rolling
Table 2-4 Horizontal curves and their terrain classification
Since our road is DS4, the minimum radius of each curve based on the terrain is:-
Minimum horizontal radius = 175m for rolling
= 125m for mountainous
Refer the following table for the rest of the design elements of DS4 (ERA standards)
Design Element Unit Flat Rolling Mountainous Escarpment Urban/Peri- Urban
Design Speed km/h 85 70 60 50 50
Min. Stopping Sight Distance m 155 110 85 55 55
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Highway Design Senior Project 2010
Min. Passing Sight Distance m 340 275 225 175 175
% Passing Opportunity % 25 25 15 0 20
Min. Horizontal Curve Radius m 270 175 125 85 85
Transition Curves Required Yes Yes No No No
Max. Gradient (desirable) % 4 5 7 7 7
Max. Gradient (absolute) % 6 7 9 9 9
Minimum Gradient % 0.5 0.5 0.5 0.5 0.5
Maximum Super elevation % 8 8 8 8 4
Crest Vertical Curve k 60 31 18 10 10
Sag Vertical Curve k 36 25 18 12 12
Normal Cross fall % 2.5 2.5 2.5 2.5 2.5
Shoulder Cross fall % 4 4 4 4 4
Right of Way m 50 50 50 50 50
Table 2-5: Table 2-6 of ERA Geometric Design Parameters for Design Standard DS4 (Paved)
2.2.1.1 Horizontal curve elements
Curve-1 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 390 (by measurement)
c) Point of intersection P.I=12+717.4m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
Vd=70km/hr…………….ERA, table 2.6
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Highway Design Senior Project 2010
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
Then,
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), in addition to this, in order to minimize cut and fill, we use R min=175m from the
standard.
Therefore, radius of curve=Rc=175m
e) Tangent (T1)
f) Point of curvature (PC)
P.C1= P.I1 - T1
=12+717.4 – 0+061.97
=12+655.43m
g) Length of the curve (L)
h) Point of tangency (P.T)
P.T1= P.C1+L1
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Highway Design Senior Project 2010
=12+655.43+119.12
=12+774.55m
i) External distance (E)
j) Middle ordinate (M)
k) Chord (Chord from P.C to P.T)
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Highway Design Senior Project 2010
Fig.2.2 elements 0f curve-1
Curve-2 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 330 (by measurement)
c) Point of intersection P.I=13+150.43m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
Vd=70km/hr…………….ERA, table 2.6
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
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Highway Design Senior Project 2010
Then,
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), in addition to this to prevent overlaps with curve 3, we use Rmin=175m from the
standard.
Therefore, radius of curve=Rc=175m
e) Tangent (T1)
Rmin = 175m
f) Point of curvature (PC)
P.C2= P.I2 – T2
=13+150.43– 0+051.84
=13+098.59m
g) Length of the curve (L)
h) Point of tangency (P.T)
P.T2= P.C2+L2
=13+98.59+100.79
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Highway Design Senior Project 2010
=13+199.38m
i) External distance (E)
j) Middle ordinate (M)
k) Chord (Chord from P.C to P.T)
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Highway Design Senior Project 2010
Fig 2.3 elements of curve-2
Curve-3 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 59.620 (by measurement)
c) Point of intersection P.I=13+363.64m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
Vd=70km/hr…………….ERA, table 2.6
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
Then,
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), in addition to this to prevent overlaps with curve 2, we use Rmin=175m from the
standard.
Therefore, radius of curve=Rc=175m
e) Tangent (T3)
Rmin = 175m
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Highway Design Senior Project 2010
f) Point of curvature (PC)
P.C3= P.I3 - T3
=13+363.64– 0+100.26
=13+263.38m
g) Length of the curve (L)
h) Point of tangency (P.T)
P.T3= P.C3+L3
=13+263.38+182m
=13+445.38m
i) External distance (E)
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Highway Design Senior Project 2010
j) Middle ordinate (M)
k) Chord (Chord from P.C to P.T)
Curve-4 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 90.810 (by measurement)
c) Point of intersection P.I=14+045.5m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
Vd=70km/hr…………….ERA, table 2.6
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
Then,
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Highway Design Senior Project 2010
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), so we use Rmin=175m from the standard.
But to make the curve smooth, we took R=236m, I.e. =RC=236m
e) Tangent (T4)
R = 236m
f) Point of curvature (PC)
P.C4= P.I4 – T4
=14+045.5– 0+239
=13+806.5m
g) Length of the curve (L)
h) Point of tangency (P.T)
P.T4= P.C4+L4
=13+806.5+374m
=14+180.5m
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Highway Design Senior Project 2010
i) External distance (E)
j) Middle ordinate (M)
k) Chord (Chord from P.C to P.T)
Curve-5 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 44.150 (by measurement)
c) Point of intersection P.I=14+756.69m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
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Highway Design Senior Project 2010
Vd=70km/hr…………….ERA, table 2.6
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
Then,
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), in addition to this, in order to minimize cut and fill, we use R min=175m from the
standard.
Therefore, radius of curve=Rc=175m
e) Tangent (T5)
Rmin = 175m
f) Point of curvature (PC)
P.C5= P.I5 – T5
=14+756.69– 0+70.97m
=14+685.72m
g) Length of the curve (L)
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Highway Design Senior Project 2010
h) Point of tangency (P.T)
P.T5= P.C5+L5
=14+685.72+134.85m
=14+820.57m
i) External distance (E)
j) Middle ordinate (M)
2cos1*5 RM
k) Chord (Chord from P.C to P.T)
Curve-6 Design computation
a) Terrain type = Rolling
b) Deflection angle Δ = 32.480 (by measurement)
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Highway Design Senior Project 2010
c) Point of intersection P.I=15+226.73m
d) Calculation of radius of the curve
Where, Rmin=minimum radius
Vd=70km/hr…………….ERA, table 2.6
ed= 8% (max design super elevation rate, ERA, table 2.6)
f=0.14 (ERA. Table 8.1 for ed=8%)
Then,
The calculated Rmin has no significant change from the recommended in ERA manual standard
(i.e., 175m), in addition to this, in order to minimize cut and fill, we use R min=175m from the
standard.
Therefore, radius of curve=Rc=175m
e) Tangent (T6)
Rmin = 175m
f) Point of curvature (PC)
P.C6= P.I6 – T6
=15+226.73m – 0+050.97
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Highway Design Senior Project 2010
=15+175.76m
g) Length of the curve (L)
h) Point of tangency (P.T)
P.T6= P.C6+L6
=15+175.76m +99.20m
=15+274.96m
i) External distance (E)
j) Middle ordinate (M)
k) Chord (Chord from P.C to P.T)
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Highway Design Senior Project 2010
2.2.1.2 Transition curve
When a vehicle traveling on a straight course enters a curve of finite radius, and suddenly
subjected to the centrifugal force which shock and sway. In order to avoid this it is customary to
provide a transition curve at the beginning of the circular curve having a radius equal to infinity
at the end of the straight and gradually reducing the radius to the radius of the circular curve
where the curve begins.
Mostly transition curves are introduced between:-
A/ between tangents and curves
B/ between two curves
Various forms of transition curves are suitable for high way transition, but the one most popular
and recommended for use is spiral.
Design of transition curve
Even if there are places to design transition curve, ERA design manual standard recommends
where and how to design this horizontal alignment design elements. Especially for Ethiopian
road, transition curves are a requirement for trunk and link road segments having a speed equal
to or greater than 80km/hr. (ERA)
But the characteristics of our project road segment is;-
Speed=60km/hr (for mountainous terrain)
Speed=70km/hr (for rolling terrain)
Terrain= mostly rolling and mountainous
Functional classification=Main access road.
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Highway Design Senior Project 2010
Therefore, based on the ERA standard all curves in the project will not have transition curve. So,
it will be a simple curve with out transition curve.
2.2.1.3 Super elevation
Curve-1
When a vehicles moves in a circular path, it is forced radially by centrifugal force. The
centrifugal force is counter balanced by super elevation of the road way and/or the side friction
developed between the tire and the road surface. The centrifugal force is the result of design
speed, weight of car, friction, and gravitational acceleration having the following relation ship.
Where, Fc= centrifugal force
W=weight of the car
V=design speed
g= acceleration due to gravity
R= radius of the curve
So, super elevation rate is changing the road cross section from the normal road to elevate
towards the center of the curve. I.e., it counteracts a part of the centrifugal force, the remaining
part being resisted by the lateral friction.
Terms in super elevation:
Tangent run out(Lt)
Super elevation runoff(Lr)
Tangent run out (Lt)
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Highway Design Senior Project 2010
It is the longitudinal length along the road designed to remove the adverse crown to a zero slope.
i.e., the outer edge of the road is raised from a normal cross slope to a zero slope which equal to
the grade level of the road (the level of the center line of the road).
Super elevation runoff length (Lr)
Super elevation run-off is a length of the road section from the point of removal of adverse
crown of the road to the full super elevated point on the curve.
Super elevation is equal to the length of transition curve when there is a transition curve. When
there is no transition curve i.e., when it is a simple curve,1/3rd of the length is placed on the curve
and 2/3rd of the length is placed on the tangent part(ERA). Therefore, we follow the second
standard to design our super elevation since all the curves do not have transition curve.
Design computation
A/ computation of super elevation run-off
Super elevation runoff length can be obtained from table 8.5 (ERA) using radius (Rc) and super
elevation rate (e), or it can be computed from the following formula. (AASHTO)
Where,
Lr=minimum super elevation run-off (m)
G=maximum relative gradient (percent)
n1=number of lanes rotated
Bw=adjustment factor for number of lane rotated
w=width of one traffic lane (in our case, w/2)
ed=design super elevation rate, percent
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Highway Design Senior Project 2010
Then, n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=0.55%, for Vd=70km/hr (AASHTO, exhibit 3-31)
Design speed(Km/h)(Vd) Maximum relative gradient(%)(G)
Equivalent maximum relative slope (%)
20 0.80 1:125
30 0.75 1:133
40 0.70 1:143
50 0.65 1:150
60 0.60 1:167
70 0.55 1:182
80 0.50 1:200
90 0.45 1:213
100 0.40 1:227
110 0.35 1:244
120 0.30 1:263
130 0.25 1:286
Table2-6 (Exhibit 3-27 Maximum relative gradients of AASHTO)
Therefore,
But ERA recommends Lr=52m for ed=8% and Rc=175m. Thus, take Lr=52m
B/ computation of tangent run out (Lt)
Tangent run-out can be computed using the following equation. (AASHTO)
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Highway Design Senior Project 2010
Where,
Lt =minimum length of tangent run-out
eNC=normal cross slope rate, percent
ed =design super elevation, percent
Lr=super elevation runoff length
Then,
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-34.67m
=12+655.43-0+034.67
=12+620.76m
The end of the super elevation runoff length is:-
=P.C+17.33m
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Highway Design Senior Project 2010
=12+655.43+0+017.33m
=12+672.76m
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=12+620.76-16.25m
=12+604.51m
End=12+620.76m
E/ station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is,
Beginning= station of beginning of adverse crown removal
=12+604.51m
End=station of beginning of adverse crown removal plus +R
=12+604.51+32.50m
=12+637.01m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 1=119.12m
Then the part of the curve to be full super elevated is
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Highway Design Senior Project 2010
=119.12-2*(1/3*Lr)
=119.12-2*(1/3*52)
=84.46m
F/ Then, the station of end of full super elevation is
=12+672.76+84.46m
=12+757.22m
G/ station of end of super elevation runoff is
=12+757.22+52m
=12+809.22m
H/ station of recovering adverse crown is
=12+809.22+16.25m
=12+825.47
Attainment of full super elevation:-
From three methods attaining full super elevation we use the method in which rotating the
surface of the road about the center line of the carriageway, gradually lowering the inner edge
and raising the upper edge, keeping the center line constant.
Illustration:
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Highway Design Senior Project 2010
Fig.2-4 Attainment of super elevation
Based on the above super elevation attainment, the results are shown on the following figure.
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Highway Design Senior Project 2010
Fig.2-5 Super elevation at entrance and exit for curve 1
Curve-2 Design computation
A/ computation of super elevation run-off
n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=0.55%, (AASHTO, exhibit 3-31)
Therefore,
But ERA recommends Lr=52m for ed=8% and Rc=175m. Thus, take Lr=52m
B/ computation of tangent run out (Lt)
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Highway Design Senior Project 2010
Tangent run-out can be computed using the following equation. (AASHTO)
Then,
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-34.67m
=13+98.59-0+034.67
=13+63.92m
The end of the super elevation runoff length is:-
=P.C+17.33m
=13+98.59+0+017.33m
=13+115.92m
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Highway Design Senior Project 2010
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=13+63.92 -16.25m
=13+47.67m
End=13+63.92m
E/ station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is
Beginning= station of beginning of adverse crown removal
=13+047.67m
End=station of beginning of adverse crown removal plus +R
=13+47.67m +32.50m
=13+080.17m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve-2=100.79m
Then the part of the curve to be full super elevated is
=100.79-2*(1/3*Lr)
=100.79-2*(1/3*52)
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=66.12m
F/ Then, the station of end of full super elevation is
=end of Lr+L
=13+115.92 +66.12m
=13+182.04m
G/ station of end of super elevation runoff is
=13+182.04 +52m
=13+234.04m
H/ station of recovering adverse crown are:
=13+234.04+16.25m
=13+250.29m
Curve-3 Design computation
A/ computation of super elevation run-off
Super elevation runoff length can be obtained from table 8.5 (ERA) using radius (Rc) and super
elevation rate (e), or it can be computed from the following formula. (AASHTO)
Then, n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=0.55%, (AASHTO, exhibit 3-31)
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Therefore,
But ERA recommends Lr=52m for ed=8% and Rc=175m. Thus, take Lr=52m
B/ computation of tangent run out (Lt)
Tangent run-out can be computed using the following equation. (AASHTO)
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-34.67m
=13+263.38 -0+034.67 m
=13+228.71m
The end of the super elevation runoff length is:-
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=P.C+17.33m
=13+263.38 +0+017.33m
=13+280.71m
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=13+228.71-16.25m
=13+212.46m
End=13+228.71m
E/ station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is
Beginning= station of beginning of adverse crown removal
=13+212.46m
End=station of beginning of adverse crown removal plus +R
=13+212.46+32.50m
=13+244.96m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 3=182m
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Then the part of the curve to be full super elevated is
=182-2*(1/3*Lr)
=182-2*(1/3*52)
=147.33m
F/ Then, the station of end of full super elevation is
=13+280.71m +147.33m
=13+428.04m
G/ station of end of super elevation runoff is:
=13+428.04 +52m
=13+480.04m
H/ station of recovering adverse crown is:
=13+480.04+16.25m
=13+496.29m
Curve-4 Design computation
A/ computation of super elevation run-off
Super elevation runoff length can be obtained from table 8.5 (ERA) using radius (Rc) and super
elevation rate (e), or it can be computed from the following formula. (AASHTO)
Then, n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=.55%, for Vd=70km/hr, (AASHTO, exhibit 3-31)
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Therefore,
But from ERA for ed=8% and v=70m/sec, by interpolation Lr=49.12m for Rc=236m. Thus, take
Lr=49.12m
B/ computation of tangent run out (Lt)
Tangent run-out can be computed using the following equation. (AASHTO)
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-32.75m
=13+806.5-0+032.75
=13+773.75m
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The end of the super elevation runoff length is:-
=P.C+16.37
=13+806.5+0+016.37m
=13+822.87m
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=13+773.75 -15.35m
=13+758.4m
End=13+839.25m
E/ station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*15.35
=30.7m
Then, the station is
Beginning= station of beginning of adverse crown removal
=13+823.39m
End=station of beginning of adverse crown removal plus +R
=13+823.39m +30.70m
=13+854.10m
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On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 4=374m
Then the part of the curve to be full super elevated is
=374-2*(1/3*Lr)
=374-2*(1/3*49.12)
=341.25m
F/ Then, the station of end of full super elevation is
=13+822.87+341.25m m
=14+164.12m
G/ station of end of super elevation runoff is:
=14+164.12m +49.12m
=14+213.24m
H/ station of recovering adverse crown is:
=14+213.24 +15.35m
=14+228.59m
Curve-5 Design computation
A/ computation of super elevation run-off
Super elevation runoff length can be obtained from table 8.5 (ERA) using radius (Rc) and super
elevation rate (e), or it can be computed from the following formula. (AASHTO)
Then, n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
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bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=.55%, for Vd=70km/hr, (AASHTO, exhibit 3-31)
Therefore,
But ERA recommends Lr=48m for ed=8% and Rc=175m. Thus, take Lr=52m
B/ computation of tangent run out (Lt)
Tangent run-out can be computed using the following equation. (AASHTO)
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-34.67m
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=14+685.72m -0+034.67m
=14+651.05m
The end of the super elevation runoff length is:-
=P.C+17.33m
=14+685.72+0+017.33m
=14+703.05m
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=14+651.05-16.25m
=14+634.80m
End=14+651.05m
E/ Station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is;
Beginning=station of beginning of adverse crown removal
=14+634.80m
End=station of beginning of adverse crown removal plus +R
=14+634.80m +32.50m
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=14+667.30m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 5=134.35m
Then the part of the curve to be full super elevated is
=134.35-2*(1/3*Lr)
=134.35-2*(1/3*52)
=99.68m
F/ Then, the station of end of full super elevation is
=14+703.05m +99.68m
=14+802.73m
G/ station of end of super elevation runoff are:
=14+802.73m +52m
=14+854.73m
H/ station of recovering adverse crown is:
=14+854.73m +16.25m
=14+870.98m
Curve-6 Design computation
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A/ computation of super elevation run-off:
Super elevation runoff length can be obtained from table 8.5 (ERA) using radius (Rc) and super
elevation rate (e), or it can be computed from the following formula. (AASHTO)
Then, n1=1, since the number of lane rotated is =1(AASHTO, exhibit 3-31)
bw=1, for one lane rotated(AASHTO, exhibit 3-31)
G=.55%, for Vd=60km/hr, (AASHTO, exhibit 3-31)
Therefore,
But ERA recommends Lr=48m for ed=8% and Rc=175m. Thus, take Lr=52m
B/ computation of tangent run out (Lt)
Tangent run-out can be computed using the following equation. (AASHTO)
C/ Location of super elevation run-off (Lr)
Since there is no transition curve (spiral) between the tangent and the curve in the project, 2/3 rd
of the super elevation length is placed on the tangent and 1/3rd of the length is placed on the
curve part.
i.e., (on the curve)
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(On the tangent)
Then,
The beginning of the super elevation runoff length is:-
=P.C-34.67m
=15+175.76m -0+034.67m
=15+141.10m
The end of the super elevation runoff length is:-
=P.C+17.33m
=15+175.76m +0+017.33m
=15+193.10m
D/ location of tangent run-out length
Beginning=beginning of Lr minus Lt
=15+141.10m -16.25m
=15+123.85m
End=15+123.85m
E/ station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
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Then, the station is
Beginning= station of beginning of adverse crown removal
=15+123.85m
End=station of beginning of adverse crown removal plus + R
=15+123.85m +32.50m
=15+156.35m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 6=99.20m
Then the part of the curve to be full super elevated is
=99.20-2*(1/3*Lr)
=99.20-2*(1/3*52)
=64.53m
F/ Then, the station of end of full super elevation is
=15+193.10+64.53m
=15+257.63m
G/ station of end of super elevation runoff is:
=15+257.63m +52m
=15+309.63m
H/ station of recovering adverse crown is:
=15+309.63m +16.25m
=15+325.88m
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Super elevation overlaps:
The end of tangent run out (super elevation runoff length) for curve 2 and the beginning of
tangent run out (super elevation runoff length) of curve 3 overlaps with an amount of:
Over lap= (13+250.29)-(13+212.46)
=42.83m
Therefore, this overlap length has to distribute on the curve part of each curve according to the
following.
Half of the overlap distance has to be added to the part of the curve. I.e. if the overlap length is d,
the part of super elevation on the curve will be
=1/3rd (Lr) +d/2
=17.33+42.83/2m
=38.475m
But this length has to be 40% of length of the corresponding curve.
Check:
Lc of curve 2=100.79m
Then, 40%*100.79=40.32>38.745m…………….OK!
Lc of curve 3=182m,
Then, 0.4*182=72.8>38.475m………………………OK!
Re-adjustment for super elevation stations.
Curve-2
1. The beginning of the super elevation runoff length is:-
=P.C-(34.67-21.415) m
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=13+98.59-(0+013.25)
=13+085.34m
2. The end of the super elevation runoff length is:-
=P.C+17.33m
=13+98.59+ (0+017.33+21.415) m
=13+137.34m
3. Location of tangent run-out length
Beginning=beginning of Lr minus Lt
=13+085.34m -16.25m
=13+069.09m
End=13+085.34m
4. Station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is
Beginning= station of beginning of adverse crown removal
=13+069.09m
End=station of beginning of adverse crown removal plus +R
=13+069.09m +32.50m
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=13+101.59m
On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve-2=100.79m
Then the part of the curve to be full super elevated is
=100.79-2*(1/3*Lr+21.415)
=100.79-2*(1/3*52+21.415)
=23.29m
5. Then, the station of end of full super elevation is
=end of Lr+23.29
=13+137.34m +23.29m
=13+160.63m
6. Station of end of super elevation runoff is
=13+160.63+52m
=13+212.63m
7. Station of recovering adverse crown is:
=13+212.63m +16.25m
=13+228.88m
Curve-3
1. The beginning of the super elevation runoff length is:-
=P.C-(34.67-21.415) m
=13+263.38 – (0+013.25) m
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=13+250.13m
2. The end of the super elevation runoff length is:-
=P.C+ (17.33+21.415) m
=13+263.38 + (0+38.75) m
=13+302.13m
3. Location of tangent run-out length
Beginning=beginning of Lr minus Lt
=13+250.13m -16.25m
=13+233.88m
End=13+250.13m
4. Station where outer and inner edge of the road will have the same normal cross fall i.e., 2.5%
It is a length(R) where total crown removal is attained.
So, R=2*Lt
=2*16.25
=32.50m,
Then, the station is
Beginning= station of beginning of adverse crown removal
=13+250.13m
End=station of beginning of adverse crown removal plus +R
=13+250.13m +32.50m
=13+282.63m
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On the same process we can do the super elevation at the exit of the curve.
We know that the length of curve 3=182m
Then the part of the curve to be full super elevated is
=182-2*(1/3*Lr+d/2)
=182-2*((1/3*52) +42.83/2)
=104.50m
5. Then, the station of end of full super elevation is
=13+302.13m +104.50
=13+406.63m
6. Station of end of super elevation runoff is:
=13+406.63m + 52m
=13+458.63m
7/ station of recovering adverse crown is:
=13+458.63m +16.25m
=13+474.88m
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Fig 2-6 profile, section and station of super elevation, tangent run out for all curves
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CURVE NUMBER
STATIONS
A B C D E F G H
Curve 1 12+604.51 12+620.76 12+637.01 12+672.76 12+757.22 12+792.97 12+809.22 12+825.47
Curve 2 13+069.09 13+085.34 13+101.59 13+137.34 13+160.63 13+196.38 13+212.63 13+228.88
Curve 3 13+233.88 13+250.13 13+282.63 13+302.13 13+406.63 13+442.38 13+458.63 13+474.88
Curve 4 13+756.4 13+773.75 13+789.10 13+822.87 14+164.12 14+197.89 14+213.24 14+228.59
Curve 5 14+634.80 14+651.05 14+667.30 14+703.05 14+802.73 14+838.48 14+854.73 14+870.98
Curve 6 15+123.85 15+141.10 15+156.35 15+193.10 15+257.63 15+293.38 15+309.63 15+325.88
Table 2-7 stations of super elevation, tangent run out for all curves.
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2.2.1.4 Curve widening
Widening on a curve is giving extra width on a road curves. This is because:-
It has been found that the drivers on curves have difficulty in steering their
vehicles to outer edge of road as they are able to on the straight because the rear
wheels do not follow precisely the same path as the front wheels when the
vehicles negotiates a horizontal curve or makes a turn.
Also there is psychological tendency to drive at greater clearance, when passing
vehicle on curved than on straights. Hence, there is dire necessity for widening
the carriage way on curves.
On curves the vehicles occupy a greater width because the rear wheels track
inside the front wheels.
Analysis of extra widening on horizontal curves
When vehicles negotiate a curve, the rear wheel generally do not follow the same track as
that of the front wheels. It has been observed that except at very high speed, the rear axle
of a motor vehicles remains in line with the radius of the curve. Since the body of the
vehicle is rigid, therefore, the front wheel will twist themselves at one angle to their axle,
such that vertical plane passing through each wheel is perpendicular to the radius of the
curve in order to trace the path on the curve. This is known as ‘off tracking’.
To determine width (W) it is necessary to select an appropriate design vehicle. The
design vehicle should usually be a truck because the off tracking is much greater for
trucks than for passenger car. (AASHTO) There fore, widening on horizontal curves
depend on:
The length and width of the vehicle
Radius of curvature
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Fig 2-7 widening of pavements on horizontal curves
Let;
L= length of wheel base of vehicle in m.
b=width of the road in m,
w=extra width in m,
R1=radius of the outer rear wheel in m,
R2= radius of the outer front wheel in m,
n=number of lanes
Rc= radius of curvature
The formula obtained from the above geometries for extra widening for more than one
lane (mechanical widening) is:-
The extra widening needed for psychological reasons mentioned above is assumed as:-
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There fore, total widening w will be:-
Widening attainment on curves
The following rules apply for attaining widening on both ends of the curve. (AASHTO)
A. widening should be done gradually and has to be realized on the inside edge of un-
spiraled curve (on simple curve) pavements.
B. In the case of a circular curve with transition curves, widening may be applied on the
inside edge or divide equally on either side of the center line.
C. On highway curves without transition curves widening should preferably be attained
along the length of super elevation runoff. A smooth fitting alignment would result from
attaining widening on-one half to two-third along the tangent and the remaining along the
curve.
D. Widening is not necessary for large radius greater than 250m.
Curve-1, 2, 3, 5, and 6 Design computations
Design data: Rc = 175m, n=2
L= take 6m (for the design vehicle usually a truck, corresponding to AASHTO, Single
unit (SU))
V=70m/sec
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For all curves having a radius between 120 to 250m ERA recommends a minimum of
widening width equal to 0.6m. But we recommend the calculated value 0.73m. So, all the
curves will have the corresponding value unless they are no less than the recommended
value by ERA. Therefore, this widening will be introduced at the inner edge of the
curves. Because all the curves are un spiraled curves.
Fig2-8.widening of pavement on curves
WIDENING WIDTH(M)
STARTING POINT OF WIDENING
STARTING POINT OF FULL WIDENING
LAST PT OF FULL WIDENING
END POINT OF WIDENING
REMARK
0.73 12+620.76 12+672.76 12+757.22 12+809.22 12+620.76
Table 2-8 widening stations for curve 1
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Curve-4 Design computation
Design data: Rc=236m, N=2, L= take 6m, V=70m/se
CURVE NO.
WIDENING
WIDTH(M)
STARTING POINT OF
WIDENING
STARTING POINT OF
FULL WIDENING
LAST PT OF FULL
WIDENING
END POINT OF
WIDENING
C1 0.73 12+620.76 12+672.76 12+757.22 12+809.22
C2 0.73 13+085.34 13+137.34 13+160.63 13+212.63
C2 0.73 13+250.13 13+302.13 13+406.63 13+458.63
C3 0.73 13+839.25 13+822.87 14+164.12 14+213.24
C4 0.61 14+651.05 14+703.05 14+802.73 14+854.73
C5 0.73 15+141.10 15+193.10 15+257.63 15+309.63
C6 0.73 12+620.76 12+672.76 12+757.22 12+809.22
Table2-9 Widening length and stations for all curves.
2.2.1.4 Site distance
Another element of horizontal alignment is the site distance across the inside of the
curves. Sight distance is the distance visible to the driver of a passenger car or the
roadway ahead that is visible to the driver. For highway safety, the designer must provide
sight distances of sufficient length that drivers can control the operation of their vehicles.
They must be able to avoid striking an unexpected object on the traveled way.
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Where there are site obstruction( such as walls, cut slops, buildings and longitudinal
barriers) on the inside of curves or the in side of the median lane on divided highways, a
design may need adjustment in the normal high way cross section or change in the
alignment if removal of the obstruction is impractical to provide adequate site distance.
Because of the many variables in alignment, in cross section and in the number, type and
location of potential obstructions, specific study is usually need for each individual curve.
With site distance for the design speed as a control, the designer should check the actual
conditions on each curve and make the appropriate adjustment to provide adequate
distance.
Two-lane rural highways should generally provide such passing sight distance at frequent
intervals and for substantial portions of their length.
Stopping site distance
Stopping sight distance is the distance required by a driver of a vehicle traveling at a
given speed to bring his vehicle to a stop after an object on the road way becomes visible.
The minimum stopping sight distance is determined from the following formula, which
takes into account both the driver reaction time and the distance required to stop the
vehicle. The formula is:
d= (0.278) (t) (v) +v2/ 254f
Where:
d = distance (meter)
t = driver reaction time, generally taken to be 2.5 seconds
V = initial speed (km/h)
F = coefficient of friction between tires and roadway (see Table 7-1)
OR the stopping site distance is given in ERA manual in the following table.
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Design Speed
(km/h)
Coefficient
of Friction (f)
Stopping Sight
Distance (m)
Passing Sight
Distance (m)
from formulae
Reduced Passing Sight Distance for design (m)
20 0.42 20 160 50
30 0.40 30 217 75
40 0.38 45 285 125
50 0.35 55 345 175
60 0.33 85 407 225
70 0.31 110 482 275
85 0.30 155 573 340
100 0.29 205 670 375
120 0.28 285 792 425
Table 2-10: Sight Distances
The coefficient of friction values shown in Table 2-10 have been determined from test
using the lowest results of the friction tests. The values shown in the third column of the
above table for minimum stopping sight distance are rounded from the above formula.
For the general use in the design of horizontal curve, the sight line is a chord of the curve,
and the stopping site distance is measured along the center line of the inside lane around
the curve.
The horizontal site line offset needed for clear site areas that satisfy stopping site distance
can be derived from the geometry for the several dimension explained in the following
figure.
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Fig 2-9 Site distance for horizontal curves
Relevant formulae are as follows:
Where = Deflection angle
R=radius (from the center line of the inner lane)
Design computation
Using the above formulas the stopping site distance(d), the line of site(S) and middle
ordinate(M) of each horizontal curves can be calculated from the data’s of each curve organized
in the following table below.
curve nodeflection angle(D)
Radius
(R),m
speed(V)
km/hr
driver reaction
time
(t) in sec.
Coefficient of friction(f)
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Curve 1. 39 173.325 70 2.5 0.31
Curve 2. 33 173.325 70 2.5 0.31
Curve 3. 59.62 173.325 70 2.5 0.31
Curve 4. 90.81 234.325 70 2.5 0.31
Curve 5. 44.15 173.325 70 2.5 0.31
Curve 6. 32.48 173.325 70 2.5 0.31
Table 2-11 different data about each curve
Curve Site line (S) in m.
Middle ordinate (M)
in m.
Stopping site distance(m)
Calculated distance in m
Recommended by ERA
curve 1 115.714 9.94 510.55 110
curve 2 98.454 7.14 510.55 110
curve 3 172.329 22.93 510.55 110
curve 4 333.72 69.81 510.55 110
curve 5 130.278 12.76 510.55 110
curve 6 96.945 6.92 510.55 110
Table2-12 Site distance elements
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Fig 2-10 stopping site distance of curve 1
Passing site distance
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Passing sight distance is the minimum sight distance on two-way single roadway roads
that must be available to enable the driver of one vehicle to pass another vehicle safely
without interfering with the speed of an oncoming vehicle traveling at the design speed.
Within the sight area the terrain should be the same level or a level lower than the
roadway. Otherwise, for horizontal curves, it may be necessary to remove obstructions
and widen cuttings on the insides of curves to obtain the required sight distance. The
passing sight distance is generally determined by a formula with four components, as
follows:
d1 = initial maneuver distance, including a time for perception and reaction
d2 = distance during which passing vehicle is in the opposing lane
d3 = clearance distance between vehicles at the end of the maneuver
d4 = distance traversed by the opposing vehicle
The formulae for these components are as indicated below:
d1 = 0.278 t1 (v – m + at1/2)
Where,
t1 = time of initial maneuver, s
a = average acceleration, km/h/s
v = average speed of passing vehicle, km/h
m = difference in speed of passed vehicle and passing vehicle, km/h
d2 = 0.278 vt2
Where,
t2 = time passing vehicle occupies left lane, sec.
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v = average speed of passing vehicle, km/h
d3 = safe clearance distance between vehicles at the end of the maneuver, is dependent on
ambient speeds as per Table 7-2 of ERA standard:
Table 7-2: Clearance Distance (d3) vs. Ambient Speeds
Speed Group (km/h)
Speed group(km/hr) 50-65 66-80 81-100 101-120
D3(m) 30 55 80 100
d4 = distance traversed by the opposing vehicle, which is approximately equal to 2/3 rd of
d2 whereby the passing vehicle is entering the left lane, estimated at:
d4 = 2d2/3
The minimum Passing Sight Distance (PSD) for design is therefore:
PSD = d1+ d2 + d3 + d4
Even if it is calculated using the above formula ERA recommends passing site distance,
so we use the value given by ERA design manual.
Sample calculation
Curve 1
Data:
Design speed=70km/hr=v of passing vehicle
Assume the following values
T1=3.5 sec, T2=3sec, a=1.0m/sec2
V of passing vehicle=70km/hr
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V of passed vehicle=65km/hr
i.e., m=70-65=5km/hr
Then,
d1= 0.278 t1 (v – m + at1/2)
d1 = 0.278 *3.5* (70 – 5 + (1*3)/2) =64.71m
d2= 0.278 vt2= 0.278 *70*3 =58.38m
d3=55m, for design speed group=66km/hr-80km/hr
d4= 2d2/3 = (2*58.38)/3 =38.92m
Therefore, total passing site distance is,
PSD=d1+d2+d3+d4 = Error! Not a valid link.Error! Not a valid link.Error! Not a valid
link.Error! Not a valid link. =218.95m
Fig 2-11 Components of passing maneuver used in passing site distance.
2.2.2 Design of vertical alignment
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The two major aspects of vertical alignment are vertical curvature, which is governed by
sight distance criteria, and gradient, which is related to vehicle performance and level of
service. The purpose of vertical alignment design is to determine the elevation of selected
points along the roadway, to ensure proper drainage, safety, and ride comfort. So it is
important to use different series of grades and to create a smooth transition between these
grades parabolic curves are used. The vertical alignment includes:
Joining the grades with smooth curve.
Location of appropriate gradients.
2.2.2.1 Design consideration
2.2.2.1.1 Gradient and grade controls
Changes of grade from plus to minus should be placed in cuts, and changes from a minus
grade to a plus grade should be placed in fills.Highway should be designed to encourage
uniform operation throughout the stretch.In the analysis of grades and grade control, one
of the most important considerations is the effect of grades on the operating of the motor
vehicle.Determination of grades for vertical alignment the following are taken in to
consideration for;
1. The maximum limit of grades.
Visibility related to sight distance.
Stopping sight distance.
Passing sight distance.
Rider and passenger comfort.
Cost of vehicle operation
General appearance
Cut and fill (earth work)
2. The minimum limit of grades.
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Drainage purpose
In this project the two cases are taken in to account as recommended by ERA 2001.
2.2.2.1.2 Vertical curves
A vertical curve provides a smooth transition between two tangent grades. There are two
types of vertical curves. Crest vertical curves and sag vertical curves.
When a vertical curve connects a positive grade with a negative grade, it is
referred to as a crest curve.
When a vertical curve connects a negative grade with a positive grade, it is
termed as a sag curve.
In this project crest and sage curves are applied to create a smooth transition between
these grades.
Length of vertical curves
Crest curves:
For crest curves, the most important consideration in determining the length of the curve
is the sight distance requirement.
Sight distance
— stopping and
— passing sight distance
Sag curves:
For sag curves, the criteria for determining the length of the curve are:
vehicle headlight distance,
rider comfort,
drainage control and
General appearance.
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When the computed curve length for the above requirements is less than the minimum
curve length recommended by ERA2001, this recommended value is taken as curve
length.
Error! Not a valid link.Site distance (Both stopping and passing)
For Crest Vertical Curve
The stopping sight distance is the controlling factor in determining the length of a crest
vertical curve.
Minimum Length required for safe stopping calculated (from AASHTO)
When Sd ≥ Lvcmin
When Sd ≤ Lvcmin
The 100 in the above equations are to convert A from % into decimals.
Where Lvc min = Minimum length of vertical curve compute
Sd = Min. Stopping Sight Distance = 85 m for mountainous terrain.
Psd = Min. Passing Sight Distance = 225 m for mountainous terrain.
Sight distances should be checked during design, and adjustments made to meet the
minimum requirements. The following values should be used for the determination of
sight lines. Shown in the figures below:
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Fig 2-12 Site distance for crust curve
ERA Manual recommends that:
h1= Driver's eye height = 1.07 meters
h2 = Object height for stopping sight distance = 0.15 meters
= Object height for passing sight distance: = 1.30 meters
For sag Vertical Curve
Figure below shows the driver’s sight limitation when approaching a sag vertical curve.
The problem is more obvious during the night time when the sight of the driver is
restricted by the area projected by the headlight beams of vehicle. Hence, the angle of the
beam from the horizontal plane is also important. This design control criteria is known as
headlight sight distance. The headlight height of h = 0.6 m and upward angle for the
headlight projection cone of β =1° is normally assumed. The governing equations are
(from AASHTO)
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When Sd ≥ Lvcmin
When Sd ≤ Lvcmin
Fig 2-13 Site distance for sag curve
A driver may experience discomfort when passing a vertical curve. The effect of
discomfort is more obvious on a sag vertical curve than a crest vertical curve with the
same radius, because the gravitational and centripetal forces are in the opposite
directions. Some of the ride discomfort may be compensated by combination of vehicle
weight, suspension system and tire flexibility. The following equation has been
recommended by AASHTO as the minimum length of a vertical curve that will provide
satisfactory level of ride comfort.
Design standards from ERA manual:
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Design Element Unit Flat
Rol
ling
Mou
ntai
nous
Esc
arpm
ent
Urb
an/
Per
i-
Urb
an
Design Speed km/h 85 70 60 50 50
Min. Stopping Sight Distance m 155 110 85 55 55
Min. Passing Sight Distance m 340 275 225 175 175
% Passing Opportunity % 25 25 15 0 20
Max. Gradient (desirable) % 4 5 7 7 7
Max. Gradient (absolute) % 6 7 9 9 9
Minimum Gradient % 0.5 0.5 0.5 0.5 0.5
Crest Vertical Curve k 60 31 18 10 10
Sag Vertical Curve k 36 25 18 12 12
Table 2-13 Design Parameters for Design Standard DS4 (Paved)
Phasing: Even if we face phasing problem on vertical curve 1 with horizontal curve 3 and vertical curve 3 with horizontal curve 5, we took a corrective action by separating them again vertical curve 2 and horizontal curve 4 corrected by making the ends of the curves to end at a common station in the design process according to ERA.
2.2.2.2. Computation of gradients
1. Gradient of the first alignment (g1)
To calculate the first gradient;
Elevation of the first point = 1386 m
Elevation of the second point = 1395.4 m
Elevation difference = 1395.4-1386 = 9.4 m
Horizontal distance b/n the two points = (13+572)-(12+500) = 1072 m
Gradient (Slope) = elevation difference/horizontal distance
= (9.4/1072) = 0.0088
Gradient (Slope) g1 = 0.88 %
2. Gradient of the second alignment (g2)
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To calculate the second gradient;
Elevation of the first point = 1395.4 m
Elevation of the second point = 1375 m
Elevation difference = 1375-1395.4 = -20.4 m
Horizontal distance b/n the two points = (14+000)-(13+572) = 428 m
Slope (gradient) = elevation difference/ horizontal distance
= -20.4/430 = -0.0477
Gradient (Slope) g2 = -4.77 %
3. Gradient of the third alignment (g3)
To calculate the third gradient
Elevation of the first point = 1375 m
Elevation of the second point = 1377 m
Elevation difference = 1377-1375 = 2m
Horizontal distance b/n the two points = (14+480)-(14+000) = 480m
Gradient (Slope) = elevation difference/ horizontal distance
= (2/480) = 0.0042
Gradient (Slope) g3 = 0.42 %
4. Gradient of the forth alignment (g4)
To calculate the forth gradient
Elevation of the first point = 1377 m
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Elevation of the second point = 1352 m
Elevation difference = 1352-1377 = -25
Horizontal distance b/n the two points = (15+500)-(14+480) = 1020m
Slope (gradient) = elevation difference/ horizontal distance
= -25/1020 = -0.0245
Gradient (Slope) g4= -2.45%
Grade
Elevation
Elev. diff.
stationHorizontal
distance(m)Slope (%)First point
second point First point
Second point
g1 1386 1395.4 9.4 12500 13572 1072 0.88
g2 1395.4 1375 -20.4 13572 14000 428 -4.77
g3 1375 1377 2 14000 14480 480 0.42
g4 1377 1352 -25 14480 15500 1020 -2.45
Table 2-14: Summery of gradients of vertical alignment
2.2.2.5 Computation of vertical curve elements
There are three vertical curves in this project;
The first vertical curve is a crest curve connects a positive grade with a negative grade;
i.e. 0.88 % and -4.77 %.
The second curve is a sag curve connects a negative grade with a positive grade ;
i.e. -4.77 % and 0.42 %.
The third curve is a crest curve connects a positive grade with a negative grade;
i.e. 0.42 % and -2.45 %.
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1. For Curve one (crest curve)
Station of PVI = 13+572
Elevation PVI = 1395.4 m
Gradient, g1 = 0.88 %
Gradient, g2 = -4.77 %
Grade Algebraic difference of grades (A)
A = g2-g1 =0.88 - (-4.77) = /5.64/ = 5.64 %
Computation of the curve length
a) Curve length required for minimum curvature, k
The value of K = 18 for DS4 from design standard, and Mountainous
Lvcmin = AK = 5.64*18 = 101.58 m
But to get smooth vertical curve to different safety purpose we increase LVC from
101.58 to 120 m
b) Length required for safe stopping
When Sd ≥ Lvcmin
c) Length required for safe passing
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When Sd ≥ Lvcmin
d) Length required for ride comfort
e) Length required for aesthetic (appearance)
Lvcmin = 30 *A = 30*5.64 =169m
There fore the maximum of the above values Lvcmin = 301.90 m is to be provided as
curve length, but this curve length over lap with one side of horizontal curve. Therefore
we provide minimum curve length recommended by ERA2001, which is LC = 200m. So
this value is provided as curve length and we post traffic sign that prevent passing for that
specific area.
Curve grade tabulation
From above table 2-14; g1=0.88 %, g2 = -4.77 % and LVC = 200 m,
Elev.PVI = 1395.4 m
Elev.PVC = Elev.PVI – (g1* LVC/2 )
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= 1395.4 – (0.0088*200/2) = 1394.52 m
Finished grade = (Ele.PVC +g1x) + ((g2-g1) x2)/2LV
STA.PVC X g1*X%Tangent
grade(Ele.PVC+g1x)(g2- g1)x2)/2LVC
Finished grade
13472 0 0 1394.62 0 1394.52
13492 20 0.16 1394.77 -0.06 1394.64
13512 40 0.31 1394.93 -0.22 1394.65
13532 60 0.47 1395.09 -0.50 1394.54
13552 80 0.63 1395.24 -0.89 1394.32
13572 100 0.78 1395.40 -1.39 1393.99
13592 120 0.94 1395.56 -2.00 1393.54
13612 140 1.10 1395.71 -2.72 1392.99
13632 160 1.25 1395.87 -3.55 1392.31
13652 180 1.41 1396.03 -4.50 1391.53
13672 200 1.57 1396.18 -5.55 1390.63
Table 2-15 finished grade tabulation for curve-1
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Fig. 2-14 elements of vertical curve-1
2. Curve Two (sag curve)
Elements of sag curve.
Station of PVI = 14+000
Elevation PVI = 1383.63 m
Grade Algebraic difference of grades (A)
Gradient ( g1) = -4.77 % , Gradient(g2) = 0.42 %
A = g2-g1 = 0.42-(-4.77) = /5.18/ = 5.18 %
Computation of the curve length
a) Curve length required for minimum curvature, k
The value of K = 25 for DS4 design standard, and Rolling.
L =AK=5.18*25 = 129.50 m
But to get smooth vertical curve for different safety purpose we increase LVC from
129.50 to 150 m
b) Length required for safe stopping
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When Sd ≥ Lvcmin
c) Length required for safe passing
When Sd ≥ Lvcmin
d) Length required for ride comfort
e) Length required for aesthetic (appearance)
Lvcmin = 30 *A = 30*5.18 =155 m
There fore the maximum of the above values Lvcmin = 352.92 m is to be provided as
curve length. But to get smooth vertical curve for different safety purpose we increase
LVC from 352.92 to 362 m.
Curve grade tabulation
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From above table 2-14 ; g1= 0.42 , g2 = -4.77 , and LVC = 362 m, Elev.PVI = 1375 m
Elev.PVC = Elev.PVI – (g1* LVC/2)
= 1395.4 – (0.0042*362/2) = 1383.63 m
Finished grade= (Ele.PVC +g1x) + ((g2-g1) x2)/2LVC)
STA.PVC X g1*X%Tangent grade
(Ele.PVC +g1x)
((g2-g1)x 2 )
2LVCFinished grade
13819 0 0 1383.63 0 1383.63
13839 20 -0.95 1382.67 0.03 1382.70
13859 40 -1.91 1381.72 0.11 1381.84
13879 60 -2.86 1380.77 0.26 1381.03
13899 80 -3.81 1379.81 0.46 1380.27
13919 100 -4.77 1378.86 0.72 1379.58
13939 120 -5.72 1377.91 1.03 1378.94
13959 140 -6.67 1376.95 1.40 1378.36
13979 160 -7.63 1376.00 1.83 1377.83
13999 180 -8.58 1375.05 2.32 1377.37
14019 200 -9.53 1374.09 2.86 1376.96
14039 220 -10.49 1373.14 3.46 1376.61
14059 240 -11.44 1372.19 4.12 1376.31
14079 260 -12.39 1371.23 4.84 1376.07
14099 280 -13.35 1370.28 5.61 1375.89
14119 300 -14.30 1369.33 6.44 1375.77
14139 320 -15.25 1368.37 7.33 1375.71
14159 340 -16.21 1367.42 8.28 1375.70
14179 360 -17.16 1366.47 9.28 1375.75
14181 362 -17.25 1366.37 9.38 1375.75
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Table 2-16 finished grade tabulation for curve-2
Fig. 2-15 elements of vertical curve-2
Curve Three (Crest curve)
Station of PVI = 14+480
Elevation PVI = 1377m
Gradient (g1) = 0.42 %
Gradient (g2) = -2.45 %
Grade Algebraic difference of grades (A)
A = g2-g1 =0.42 - (-2.45) = /2.87/ = 2.87 %
Computation of the curve length
a) Curve length required for minimum curvature, k
The value of K = 31 for DS4 design standard, and Rolling
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Lvcmin = AK = 2.87*31 = 88.90 m
But to get smooth vertical curve to different safety purpose we increase LVC from
88.90 to 120
b) Length required for safe stopping
When Sd ≤ Lvcmi
c) Length required for safe passing
When Sd ≤ Lvcmi
d) Length required for ride comfort
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e) Length required for aesthetic (appearance)
Lvcmin = 30 *A =30*2.87 = 86 m
There fore the maximum of the above values Lvcmin = 220.47 m is to be provided as
curve length. But to get smooth vertical curve to different safety purpose we increase
LVC from 220.47 to 240m.
Curve grade tabulation
From above table: - g1=0.42, g2 = -2.45 and LVC = 240 m, Elev.PVI = 1377 m
Elev.PVC = Elev.PVI – (g1* LVC/2) = 1377– (0.0042*240/2) = 1376.50m
Finished grade= (Ele.PVC +g1x) + ((g2-g1) x2)/2LVC)
STA.PVC X g1*X%
Tangent grade
(Ele.PVC +g1x)
(g2-g1)x 2 )
2LVC
Finished grade
14360 0 0 1376.50 0 1376.50
14380 20 0.083 1376.58 -0.02 1376.56
14400 40 0.167 1376.67 -0.10 1376.57
14420 60 0.250 1376.75 -0.22 1376.53
14440 80 0.333 1376.83 -0.38 1376.45
14460 100 0.417 1376.92 -0.60 1376.32
14480 120 0.500 1377.00 -0.86 1376.14
14500 140 0.583 1377.08 -1.17 1375.91
14520 160 0.667 1377.17 -1.53 1375.64
14540 180 0.750 1377.25 -1.94 1375.31
14560 200 0.833 1377.33 -2.39 1374.94
14580 220 0.917 1377.42 -2.89 1374.53
14600 240 1.000 1377.50 -3.44 1374.06
Table 2-17 finished grade tabulation for curve-3
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Fig. 2-16 elements of vertical curve-3
Vertical
CurveA K LVCmin LVC adj
LVC provide
Sta. PVI Sta.PVC Sta.PVT Elev.PVI Elev.PVC
VC1 5.64 18 101.58 120 200 13+572 13+472 13+672 1395.4 1394.52
VC2 5.18 25 129.50 150 362 14+000 13+819 14+181 1375 1383.63
VC3 2.87 31 88.90 120 240 14+480 14+360 14+600 1377 1376.50
Table 2-18 summery of vertical curves
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2.2.3 Road cross sections
A cross sectional elements in the high way design pertains to those features which deals
with its width. They will normally consist of the carriage way, shoulders, right of way,
roadway width, pavement width, the median, side slopes, drainage features and earth
work profiles.
Carriage way:
The part of the road constructed for use by moving traffic as traffic lanes. For our project
for DS4 and main access road ERA recommends 6.7m.
Lane width
Feature of a high way having great influence on safety and comfort in the width of the
carriage way, due to this we use a lane width of 3.35 m which is recommended for DS4
road are shown in table 2.6 ERA 2001 for all roads design standards.
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Shoulders
Shoulder is:-
Is the portion of the road between the outer edges and the edges of the carriage-
way are called shoulders.
Is the portion of the roadway contiguous to the carriageway for the
accommodation of stopped vehicles; traditional and intermediate non-motorized
traffic, animals, and pedestrians; emergency use; the recovery of errant vehicles;
and lateral support of the pavement courses. It will provide wherever possible for
emergency stopping and lateral support of the carriageway pavement.
Where the carriageway is paved, the shoulder should also be sealed with a single
bituminous surface treatment. This has several advantages. It would prevent edge
raveling and maintenance problems associated with parking on a gravel shoulder.
Sealing of the shoulder is recommended under the following conditions:
Where the total resulting gradient exceeds 25 per cent, it is recommended for
paved shoulder as the width is only 1m; this will reduce the frequent
maintenance needs in mountainous and escarpment terrains.
Where the shoulder material is readily erodible or where the availability of
material for shoulder maintenance is restricted.
Wherever there is significant pedestrian traffic in town and village areas.
Based on the above idea, ERA recommends a shoulder width based on design standard
and terrain classification. So, for this project since most of the route has a terrain of
rolling we took 1.5m for shoulder width as recommended by ERA manual. So, we took
1.5m shoulder throughout the route simplicity of the construction.
Road way:
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It consists of the carriage way and shoulders and parking lanes. I.e., for this project road
way width will be 6.7+1.5+1.5=9.7m
Right-of-way
It is the width of the land secured and preserved to the public for road purposes. The
right-of-way should be adequate to accommodate all the elements that make-up the cross
section of the high way and may reasonably provide future development.
For this project having design standard of DS4, ERA recommends a right of way width to
be 50m for all terrain type.
Normal cross fall
Normal cross fall should be sufficient to provide adequate surface drainage whilst not
being so great as to make steering difficult, but it should facilitate drainage of the
pavement. It is depend up on the smooth of the surface and the intensity of the rain fall.
Therefore, we took 2.5% for normal cross fall for design standard of DS4 as
recommended by ERA.
Shoulder cross fall
It should be designed steeper than the pavement to facilitate quick drainage. Therefore we
took 4% for shoulder cross slope as recommended by ERA.
Side slope and back slope
Side slopes and back slopes should be designed to insure the stability of the road way and
to provide a reasonable opportunity for recovery of an out-of-control vehicle.
The selection of a side slope and back slope is depending on safety consideration, height
of cut or fill and economic consideration. ERA 2001 table 6.1 indicates the side slope
recommended for use in the design according to the height of cut and fill and the
material.
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material Height of slopeSide slope Back
slopecut fill
Earth or soil
0.0-1.0m 1:4 1:4 1:3
1.0-2.0m 1:3 1:3 1:2
Over 2m 1:2 1:2 1:1.5
rock Any height See standard details
Table2-19 Side and back slope
Depending to the given standard ratio our project is designed and set out the appropriate
and economical road section.
Fig 2-17 Elements of road cross section
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Section-3: Drainage Standards and Structure Design
3.1 General
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2.2 Minor drainage analysis and design
2.2.1 Hydrological/ Hydraulic Analysis of Ditch
-
-
-
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)a
-
-
-
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-
-
-
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Ө
1)
2)
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3)
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2.2.2 Structural design of ditch
)a
)b
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Catchment Area
A(ha) Ccupper elev.
lower elev.
L(m) s(%) Tc(s)TC provide
I Q(m3/s)
1 2.18 0.25 1410.5 1385 312.84 0.08 4.27 7.0 180 0.27
2 3.22 0.25 1408.5 1385 306.53 0.08 4.31 7.0 180 0.40
3 7.88 0.25 1406.5 1387 365.89 0.05 5.68 7.0 180 0.99
4 14.00 0.25 1410.5 1387 500.26 0.05 7.58 7.6 149 1.45
5 6.11 0.25 1410 1386 334.31 0.07 4.72 7.0 180 0.76
6 3.70 0.25 1408 1386 400.79 0.05 6.02 7.0 180 0.46
7 9.75 0.25 1400 1366 431.99 0.08 5.55 7.0 180 1.22
8 7.57 0.25 1393.5 1366 367.12 0.07 4.99 7.0 180 0.95
9 32.57 0.25 1391 1346 1082.8 0.04 14.40 14.4 135 3.06
10 0.82 0.25 1352 1346 354.64 0.02 8.62 8.6 165 0.09
Cath. L(m) W(m) A ha Cp Bed Slope%
L(m) Tc (s) Tcprovide I Qasp(m3/s)
1 95.35 6.85 0.0653 0.95 0.025 93.8 2.6633 7 180 0.031273
2 133.18 6.85 0.0912 0.95 0.025 130.9 3.4425 7 180 0.04368
3 318.91 6.85 0.2185 0.95 0.025 310.62 6.6964 7 180 0.104595
4 526.1 6.85 0.3604 0.95 0.025 495.06 9.5877 9.6 155 0.148584
5 213.72 6.85 0.1464 0.95 0.025 206.78 4.8952 7 180 0.070095
6 85.79 6.85 0.0588 0.95 0.025 93 2.6458 7 180 0.028137
7 188.37 6.85 0.129 0.95 0.025 190.74 4.6001 7 180 0.061781
8 183.74 6.85 0.1259 0.95 0.025 183.94 4.4733 7 180 0.060263
9 1206.4 6.85 0.8264 0.95 0.025 1136.71 18.184 18.2 110 0.241794
10 31.8 6.85 0.0218 0.95 0.025 45.68 1.5304 7 180 0.01043
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Q,asphalt(m3/s)Q,the land(m3/s) Q total n d
B( bottom) B(top) Velocity
Free board (m)
D provide
0.031 0.27 0.30 0.016 0.26 0.30 0.61 2.53 0.3 0.56
0.044 0.4 0.44 0.016 0.30 0.35 0.70 2.79 0.3 0.60
0.105 0.99 1.09 0.016 0.42 0.49 0.98 3.51 0.3 0.72
0.149 1.45 1.60 0.016 0.49 0.57 1.13 3.85 0.3 0.79
0.070 0.76 0.83 0.016 0.38 0.44 0.89 3.27 0.3 0.68
0.028 0.46 0.49 0.016 0.31 0.36 0.73 2.86 0.3 0.61
0.062 1.22 1.28 0.016 0.45 0.52 1.04 3.65 0.3 0.75
0.060 0.95 1.01 0.016 0.41 0.48 0.96 3.44 0.3 0.71
0.242 3.06 3.30 0.016 0.64 0.74 1.49 4.63 0.3 0.94
0.010 0.09 0.10 0.016 0.17 0.20 0.40 1.92 0.3 0.47
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3.3.3 Hydraulics design of
culvert
A culvert is a type of structure that can transmit water as full or partly full. It is a
structure that is designed hydraulically to take advantage of submergence to increase
hydraulic capacity. It is also used to convey surface runoff through embankments. A
culvert can be a structure, as distinguished from bridges, that is usually covered with an
embankment and is composed of structural material around the entire perimeter.
A culvert can be a structure that is 6 meters or less in centerline span length, or between
the extreme ends of openings for multiple boxes.
Full flow is not common for culverts unless governed by a high downstream water
surface elevation. Full flow can be described by fundamental pipe flow. Partly full flow
culverts follow the law of open channel flow and need to be classified as either sub
critical or supercritical flow to accomplish the design procedure.
The following are concepts that are important in the hydraulics of culvert design:
Critical depth- the depth at which the specific energy of a given flow rate is at a
minimum. For a given discharge and cross-section geometry, there is only one critical
depth.
Crown- the inside top of the culvert.
Outlet- has tail water equal to or lower than critical depth. For culverts with free outlets, a
lowering of the tail water has no effect on the discharge or the backwater profile
upstream of the tail water.
Improved Inlet- has an entrance geometry that decreases the flow constriction at the inlet
and thus increases the capacity of culverts. These inlets are referred to as either side- or
slope-tapered (walls or bottom tapered).
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Invert- is the flow line of the culvert (inside bottom).
Normal flow- occurs in a channel reach when the discharge, velocity, and depth of flow
do not change throughout the reach. The water surface profile and channel bottom slope
will be parallel. This type of flow will exist in a culvert operating on a steep slope if the
culvert is sufficiently long enough.
Slope - Steep water surface slope occurs where the critical depth is greater than the
normal depth. Mild slope occurs where critical depth is less than normal depth.
Submerged- A submerged outlet occurs where the tail water elevation is higher than the
crown of the culvert. A submerged inlet occurs where the headwater is greater than 1.2D.
Design criteria
Listed below by categories are the design criteria that should be considered for all culvert
designs.
Site criteria
Structure Type Selection
The type of drainage structure specified for a particular location is often determined
based on economic considerations. The following can serve as a guide in the selection of
the type of structure, proceeding from the most expensive to the least expensive. Culverts
are used where bridges are not hydraulically required, where debris is tolerable, and
where they are more economical than a bridge. Culverts can be concrete box culverts,
reinforced concrete pipe culverts, or corrugated metal culverts.
Length and Slope
The culvert length and slope should be chosen to approximate existing topography, and to
the degree practicable:
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the culvert invert shall normally be aligned with the channel bottom and
the skew angle of the stream, and
the culvert entrance shall match the geometry of the roadway.
Design Features
Culvert Sizes and Shape—the culvert size and shape selected is to be based on
engineering and economic criteria related to site conditions. In evaluating the suitability
of alternate materials, the selection process shall be based on a comparison of the total
cost of alternate materials over the design life of the structure that is dependent upon the
following:
durability (service life),
cost
availability
construction and maintenance ease
structural strength,
traffic delays
abrasion and corrosion resistance, and
water tightness requirements.
Inlet and Outlet Control
Inlet Control
For inlet control, the control section is at the upstream end of the barrel (the inlet). The
flow passes through critical depth near the inlet and becomes shallow, high velocity
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(supercritical) flow in the culvert barrel. Depending on the tail water, a hydraulic jump
may occur downstream of the inlet.
Typical shapes are rectangular, circular, elliptical, and arch.
Nomographs—The inlet control flow versus headwater curves, which are established
using the above procedure, are the basis for constructing the inlet control design
nomographs. Note that in the inlet control nomographs, HW is measured to the total
upstream energy grade line including the approach velocity head.
Outlet Control
Outlet control has depths and velocity that are subcritical. The control of the flow is at the
downstream end of the culvert (the outlet). The tailwater depth is assumed to be critical
depth near the culvert outlet or in the downstream channel, whichever is higher.
In a given culvert, the type of flow is dependent on all of the barrel factors. All of the
inlet control factors also influence culverts in outlet control.
Tailwater Elevation—based on the downstream water surface elevation. Backwater
calculations from a downstream control, a normal depth approximation, or field
observations are used to define the tailwater elevation.
Hydraulics—Full flow in the culvert barrel is assumed for the analysis of outlet control
hydraulics. Outlet control flow conditions can be calculated based on an energy balance
from the tailwater pool to the headwater pool.
Design Equations
Equations and Definitions
Losses
HL = HE + Hf+ Hv + Hb + Hj + Hg
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Where:
HL = total energy loss, m
HE = entrance loss, m
Hf = friction losses, m
Hv = exit loss (velocity head), m
Hb = bend losses, m
Hj = losses at junctions, m
Hg = losses at grates, m
Velocity
V = Q/A Where:
V = average barrel velocity, m/s
Q = flow rate, m3/s
A = cross sectional area of flow with the barrel full, m2
Velocity Head
Hv = V2/2g where g = acceleration due to gravity, 9.8 m/s2
Entrance loss
He = Ke (V2/2g) where Ke = entrance loss coefficient,
Friction Loss
Hf = [(19.63n2L)/R1.33] [V2/2g)
Where:
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n = Manning’s roughness coefficient
L = length of the culvert barrel, m
R = hydraulic radius of the full culvert barrel = A/P, m
P = wetted perimeter of the barrel, m
Exit Loss
Ho = 1.0 [(V2/2g) - (Vd2/2g)]
Where: Vd = channel velocity downstream of the culvert, m/s (usually neglected)
& Ho = Hv = V2/2g
Barrel Losses
H = He + Ho+Hf
H = [1 + Ke + (19.63n2L/R1.33)] [V2/2g]
Energy Grade Line—the energy grade line represents the total energy at any point along
the culvert barrel. Equating the total energy upstream and downstream of the culvert
barrel in the following relationship results:
HWo + ( Vu2/2g) = TW + (Vd2/2g) + HL
Where:
HWo = headwater depth above the outlet invert, m
Vu = approach velocity, m/s
TW = tailwater depth above the outlet invert, m
Vd = downstream velocity, m/s
HL = sum of all losses
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Hydraulic Grade Line—the hydraulic grade line is the depth to which water would rise in
vertical tubes connected to the sides of the culvert barrel. In full flow, the energy grade
line and the hydraulic grade line are parallel lines separated by the velocity head except at
the inlet and the outlet.
Nomographs (full flow)—The nomographs were developed assuming that the culvert
barrel is flowing full and:
TW > D, Flow Type IV Outlet Control or
dc > D, Flow Type VI Inlet Control
Vu is small and its velocity head can be considered a part
of the available headwater (HW) used to convey the flow through the culvert.
Vd is small and its velocity head can be neglected.
HW = TW + H - SoL
Where:
HW = depth from the inlet invert to the energy grade line, m
H = is the value read from the nomographs, m
SoL = drop from inlet to outlet invert, m
TW should be used if higher than (dc + D)/2.
The following equation should be used:
HW =ho+ H -SoL
Where:
ho = max of(TW ,(dc + D)/2)) m
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Adequate results are obtained down to a HW = 0.75D. For lower headwaters,
backwater calculations are required.
Outlet Velocity
Culvert outlet velocities should be calculated to determine the need for erosion protection
at the culvert exit. Culverts usually give outlet velocities that are higher than the natural
stream velocities. These outlet velocities may require flow readjustment or energy
dissipation to prevent downstream erosion. If outlet erosion protection is necessary, the
flow depths and Freud number may also be needed.
In Inlet Control
If water surface profile (drawdown) calculations are necessary, begin at dc at the entrance
and proceed downstream to the exit. Determine at the exit the depth and flow area. Use
normal depth and velocity. This approximation may be used since the water surface
profile converges towards normal depth if the culvert is of adequate length. The outlet
velocity may be slightly higher than the actual velocity at the outlet.
In Outlet Control
The cross sectional area of the flow is defined by the geometry of the outlet and
either critical depth, tailwater depth, or the height of the conduit:
Critical depth is used when the tailwater level is less than critical depth.
Tailwater depth is used when tailwater is greater than critical depth, but below the
top of the barrel.
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The total barrel area is used when the tailwater level exceeds the top of the
barrel
Roadway Overtopping
Roadway overtopping will begin when the headwater rises to the elevation of the
roadway. The overtopping will usually occur at the low point of a sag vertical curve on
the roadway. The flow will be similar to flow over a broad crested weir.
Qr= Cd L HWr 1.5
Where:
Qr = overtopping flow rate, m3/s.
Cd = overtopping discharge coefficient (weir coefficient) = kf Cr.
kt = submergence coefficient.
Cr = discharge coefficient.
L = length of the roadway crest, m.
HWr = the upstream depth, measured above the roadway crest, m.
Total Flow—calculated for a given upstream water surface elevation using equation. In
this equation, roadway overflow plus culvert flow must equal total design flow. A trial
and error process is necessary to determine the flow passing through the culvert and the
amount flowing across the roadway.
Performance Curves
A performance curve is a plot of flow rate versus headwater depth or elevation, velocity,
or outlet scour. The culvert performance curve is made up of the controlling portions of
the individual performance curves for each of the following control sections.
Design Procedure
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Step 1 Assemble Site Data and Project File
Hydrographic Survey - Data include
topographic, site, and location maps
embankment cross section
roadway profile
Step 2 Determine Hydrology. Minimum data required—drainage area maps and
discharge-frequency plots
Step 3 Designs Downstream Channel. Minimum data are cross section of channel and the
rating curve for channel
Step 4 Summarize Data on Design Form use data from Steps 1-3
Step 5 Select Design Alternative
Step 6 Select Design Discharge Qd
Step 7 Determine Inlet Control Headwater Depth (HWi)
for a box shape use Q per foot of width
Locate HW/D ratio using a straightedge
extend a straight line from the culvert size through the flow
rate
mark the first HW/D scale. Extend a horizontal line to the
desired scale, read HW/D, and note on Charts
Calculate headwater depth (HW)
multiply HW/D by D to obtain HW to energy grade line
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neglecting the approach velocity HWi = HW
including the approach velocity HWi = HW - approach
velocity head
Step 8 Determine Outlet Control Headwater Depth at Inlet (HWoi)
Calculate the tail water depth (TW) using the design flow rate and normal depth (single
section) or using a water surface profile
Calculate critical depth (dc)
locate flow rate and read dc
dc cannot exceed D
Calculate (dc + D)/2
Determine (ho)
ho = the larger of TW or (dc + D/2)
Determine entrance loss coefficient (KE) from ERA design manual Table7-2
Determine losses through the culvert barrel (H):
- use (L) if Manning’s n matches the n value of the culvert and- use (L1) to adjust
for a different culvert n value
L1 = L(n1/n)2
Where:
L1 = adjusted culvert length, m
L = actual culvert length, m
n1 = desired Manning n value
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n = Manning n value on chart
mark point on turning line
- use a straightedge and
- connect size with the length
read (H)
- use a straightedge
- connect Q and turning point and
- Read (H) on Head Loss scale
Calculate outlet control headwater (HW)
use equation above, if Vu and Vd are neglected
HWoi = H + ho - SoL
if HWoi is less than 1.2D and control is outlet control
- the barrel may flow partly full
- the approximate method of using the greater tailwater or (dc+ D)/2 may not be
applicable
- backwater calculations should be used to check the result and
- if the headwater depth falls below 0.75D, the approximate
- method shall not be used
Step 9 Determine Controlling Headwater (HWc)
compare HWi and HWoi, use the higher
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HWc = HWi, if HWi > HWoi
- the culvert is in inlet control
HWc = HWoi, if HWoi > HWi
- the culvert is in outlet control.
Step 10 Compute Discharge over the Roadway (Qr)
1. Calculate depth above the roadway (HWr)
HWr = HWc - HWov
HWov = height of road above inlet invert
2. If HWr 0, Qr = 0
If HWr > 0, determine Qr
Step 11 Compute Total Discharge (Qt)
Qt = Qd + Qr
Step 12 Calculate Outlet Velocity (Vo) and Depth (dn)
If inlet control is the controlling headwater
1. Calculate flow depth at culvert exit
use water surface profile
2. Calculate flow area (A)
3. Calculate exit velocity (Vo) = Q/A
If outlet control is the controlling headwater
1. Calculate flow depth at culvert exit
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weuse (dc) if dc > TW
weuse (TW) if dc < TW< D
weuse (D) if D < TW
2. Calculate flow area (A)
3. Calculate exit velocity (Vo) = Q/A
Step 13 Review Results
Compare alternative design with constraints and assumptions, if any of the
following are exceeded, repeat Steps 5 through 12
Step 14 Plot Performance Curve
Repeat Steps 6 through 12 with a range of discharges
Qmax if no overtopping is possible
Qmax = largest flood that can be estimated
Step 15 Related Designs
Culverts out let velocities
The high out let velocities observed at the culvert out let may results in excessive scour of
the channel in the vicinity of the outlet. The variety in the soil type of natural channels
and varying flowing characteristics at the culvert outlet enforces the use different
methods to control or protect the channel against potential damaging effects. Some of the
common used techniques to provide protection against scour are:
1. Minor structural element
2. Velocity protection devices
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3. Velocity control devices
Minor structural element
Provision of this Minor structural element is done when the culverts exit velocity is 30%
greater than that of the velocity in its natural channel. It minimizes the structural
instabilities. Example Cutoff walls.
Velocity protection devices
For exit velocity greater than 1.3 of velocity in natural channel and less than 2.5 of the
velocity in natural channel.In this case armoring riprap is used. This may be;
Concrete riprap, Vegetation,Synthetic sodding.
Velocity control device
For exit velocity greater than 2.5 of that of natural channels velocity. (In this case energy
dissipater is required.
Nomograph Design
Detail design for channel 4
The following steps show the procedures we followed step by Step to design a culvert for
channel-4 for in the project area especially near the station 15+440.
Step 1 Assemble Site Data and Project File
a. Site survey project file contains:
roadway profile and
embankment cross section
no sediment or debris problems and
Cross-Section
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Design criteria we have used 25yrs return period for our design purpose because our road
to be designed is DS4.
Step 2 Determining Hydrology using
Rational method equations yield
Q25=16.5m3/s, Q50=17.9m3/s
Step 3 Design Downstream Channel
Point Station, m Elevation, m
1 15+400 1346.3
2 15+410 1346.5
3 15+420 1346.7
4 15+430 1346.9
5 15+440 1346.9
6 15+450 1347.1
7 15+460 1347.2
8 15+470 1347.3
9 15+480 1347.4
10 15+490 1347.5
11 15+500 1347.6
Table 3-2 down stream station
Culvert Design-Example
X-Section At Tail Water
Chainage Dist, m Level
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15+400 0 1350.50
15+410 10 1350.30
15+420 20 1349.60
15+430 30 1348.00
15+440 40 1346.30
15+450 50 1348.20
15+460 60 1350.20
15+470 70 1352.00
15+480 80 1353.00
15+490 90 1354.20
15+500 100 1355.00
Table 3-3 X-Section At Tail Water
Step 3 Design downstream channel
0.00
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The stream channel can be approximated to trapezoidal channel
B= 10m Slope 2:1 H:V
Channel material- clean straight, no rims or deep pools n =0.03
no sediment debris problem
Slope (s) 0.006
Table 3-4 Down stream chanal
The rating curve for the channel calculated by normal depth yields:
Depth,mWidth (B), m Area,m2 P, m R,m S N V=(1/n)R^2/3S^1/2
Q=AV, m3/s
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0.10 10 1.02 12.24 0.08 0.006 0.03 0.49 0.50
0.30 10 3.18 12.24 0.26 0.006 0.03 1.05 3.34
0.50 10 5.50 12.24 0.45 0.006 0.03 1.52 8.33
0.70 10 7.92 12.24 0.65 0.006 0.03 1.93 15.29
0.73 10 8.30 12.24 0.68 0.006 0.03 1.99 16.55
0.76 10 8.70 12.24 0.71 0.006 0.03 2.06 17.91
0.90 10 10.62 12.24 0.87 0.006 0.03 2.35 24.95
1.00 10 12.00 12.24 0.98 0.006 0.03 2.55 30.58
1.05 10 12.71 12.24 1.04 0.006 0.03 2.65 33.64
1.10 10 13.42 12.24 1.10 0.006 0.03 2.75 36.85
1.20 10 14.88 12.24 1.22 0.006 0.03 2.94 43.77
1.50 10 19.50 12.24 1.59 0.006 0.03 3.52 68.69
1.700 10 22.78 12.24 1.86 0.006 0.03 3.91 89.01
Table 3-5 The rating curve for the channel calculated by normal depth yields:
Q (m3/s) TW (m) Elev,m asl Velocity(m/s)
0.5 0.1 1346.3 0.49
3.34 0.3 1346.5 1.05
8.33 0.5 1346.9 1.52
15.29 0.7 1346.9 1.93
16.55 0.73 1347.1 1.99
24.95 0.9 1347.2 2.06
30.58 1.0 1347.3 2.35
36.85 1.05 1347.3 2.55
Downstream
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Q m3/s Depth,m Elev,masl
0.50 0.10 1346.3
3.34 0.30 1346.5
8.33 0.50 1346.7
15.29 0.70 1346.9
16.55 0.73 1346.9
24.95 0.90 1347.1
30.58 1.00 1347.2
33.64 1.05 1347.3
36.85 1.10 1347.3
43.77 1.20 1347.4
68.69 1.50 1347.7
89.01 1.700 1347.9
Table 3-6 down stream rating curve
Step 5 Select Design Alternative
Shape - box Size - 3000 mm by 2000 mm
Material – concrete Entrance- Wingwalls, for 30o flare
Step 6 Select Design Discharge
Qd=16.5m3/5
Step 7 Determine Inlet Control Headwater Depth (HWi)
Use inlet control nomograph - Chart 7-6
a. D = 2 m
b. Q/B = 16.5/3 = 5.5
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c. HW/D = 1.2, for 30o flare
d. HWi = (HW/D)*D
= (1.2)(2m)
= 2.4m (Neglect the approach velocity)
Step 8 Determine Outlet Control Headwater Depth at Inlet (HWoi)
a. TW =0.73 m for Q50 = 16.5 m3/s
b. dc = 1.43 m from Chart 7-7 (ERA design manual)
Or, by using the formula we obtain the critical depth as follows:
dc=0.467*(Q÷B)2/3
=0.467*(16.5÷3) 2/3
= 1.46m which is similar to the value obtained from the nomogragh in
previous case. So let us take our dc=1.43, so that
(dc + D)/2 = (1.43 + 2)/2 = 1.71 m
And, ho = max(TW , (dc + D/2)),but our Tw=0.73m from step 8 above
ho = (dc + D)/2 = 1.71 m =>maximum value of the two.
e. Ke = 0.2 from Table 7-2 ERA mannual
f .Determine (H) - use Chart 7-8 (ERA design manual)
Ke scale = 0.2
culvert length (L) = 80 m
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n = 0.012 same as on chart
area = 6.0m2
H = 0.67m (from nomogragh 7-8)
g. HWoi = H + ho - SoL = .67 + 1.71 - (0.006)80 = 1.9 m
HWoi is less than 1.2D, but control is inlet control, outlet control
computations are for comparison only
Step 9 Determine Controlling Headwater (HWc)
HWc = HWi = 2.4 m > HWoi = 1.9
The culvert is in inlet control
Step 10 Compute Discharge over the Roadway (Qr)
a. Calculate depth above the roadway:
HWr = HWc – Hwov
= 2.4 – (1352.9-1348)
= -2.5m (This result shows that there is no any water flowing over the road).In
other word the level of water is 2.5m below the roadway.
Step 11 Compute Total Discharge (Qt)
In our calculation above we have determined the discharge over the road is (Qt=0)
because it has negative value. So the total discharge (Qt) is calculated
As follows:
Qt = Qd + Qr = 16.5 m3/s + 0 = 16.5 m3/s
Step 12 Calculate Outlet Velocity (Vo) and Depth (dn)
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Inlet Control
a. Calculate normal depth (dn):
Where we have used trial error method to calculate the normal depth of the flow in the
culvert
Q = (1/n)A* R2/3 S1/2 ,but A=B*dn,
where A=cross sectional area
B=width of the culvert
R=A/Pw, where A=cross sectional area
R=hydraulic radius of the culvert
Pw=wetted perimeter of the clvert
Pw=B+2dn ,B=3
16.5 m3/s= (1/0.012)(3*dn)[(3*dn)/(3+2dn)]2/3(0.05)0.5
= (3*dn)[3*dn/(3+2dn)]2/3 *(0.05)0.5
=>dn=1.08m as it is shown in the following table in order to convey the total
discharge (Qt=16.5). So our trials and their corresponding results are given in the table
below.
dn 1/n A R^2/3 S^1/2 V Q
0.2 83.33 0.60 0.3 0.1 2.2 1.3
0.25 83.33 0.75 0.4 0.1 2.5 1.9
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0.3 83.33 0.90 0.4 0.1 2.8 2.5
0.4 83.33 1.20 0.5 0.1 3.2 3.9
0.50 83.33 1.50 0.5 0.1 3.6 5.4
0.90 83.33 2.70 0.7 0.1 4.8 12.8
1.00 83.33 3.00 0.7 0.1 5.0 14.9
1.05 83.33 3.15 0.7 0.1 5.1 15.9
1.08 83.33 3.24 0.7 0.1 5.1 16.6
1.10 83.33 3.30 0.7 0.1 5.1 17.0
1.15 83.33 3.45 0.8 0.1 5.2 18.1
1.20 83.33 3.60 0.8 0.1 5.3 19.2
1.50 83.33 4.50 0.8 0.1 5.8 25.9
2.00 83.33 6.00 0.9 0.1 6.3 37.7
2.20 83.33 6.60 0.9 0.1 6.5 42.6
2.30 83.33 6.90 0.9 0.1 6.5 45.1
2.50 83.33 7.50 1.0 0.1 6.7 50.1
2.60 83.33 7.80 1.0 0.1 6.7 52.6
3.00 83.33 9.00 1.0 0.1 7.0 62.7
Table 3-7 Discharge trial
From the table above we determined our dn =1.08m.
A = (3)*1.08 = 3.24 m2
Vo = Q/A = 16.5/3.24
= 5.093 m/s >2.5*1.99m/s (down stream velocity).So energy dissipater is required to
the damage of adjacent structure and to protect scouring outlet of culvert.
Step 13 Review Results
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This step is the step of comparison of alternative design with constraints and
assumptions, if any of the following are exceeded we repeat, Steps 5 through 12 in order
to have a convenient and safe design.
barrel has:
((1352.9-1346.2) m-2.4m) = 2.5m of cover
L = 80m is OK, since inlet control
headwalls and wing walls fit site
allowable headwater (4.9 m) > 2.5 m is ok and
overtopping flood frequency > 25-year
So the design is ok!
3.3.4 Structural Design of Culvert
The following principles are specific to structural design of culverts:
All culverts shall be hydraulically designed.
Overtopping flood selected is generally consistent with the class of highway and the
risk at the site
Culvert location in both plan and profile shall be investigated to avoid sediment
build-up in culvert barrels.
Material selection shall include consideration of materials availability, and the service
life including abrasion and corrosion potentials.
Design Criteria
Listed below by categories are the design criteria that should be considered for all culvert
designs. The type of drainage structure specified for a particular location is often
determined based on economic considerations; Culverts can be concrete box culverts,
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reinforced concrete pipe culverts, or corrugated metal culverts; Concrete box culverts are
constructed with a square or rectangular opening, and with wing walls at both ends.
Design Computation
In this project we propose four culverts and one bridge based on the topography and the
flow direction.
Culvert 1 is at station =12+592.31m
Culvert 2 is at station =13+043.45m
Culvert 3 is at station =13+803.30m
Culvert 4 is at station =15+471.12m
Bridge 1 is at station =14+089m
For design purpose we took culvert number 4 at station15+471.12m as a sample for the
hydraulics and structural design of the culvert. We choose box culvert for our design
since it is easy to construction, to prevent scouring and settlement due to the soil type of
that area.
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Fig 3-3 station of culvert 4
Structural design of box culvert
Design data
Geometric data
Internal dimension=h=2
W=3m… (From the hydraulics)
Height of fill above the culvert=4.6m (from the profile)
Thickness of the slab=300mm (thickness is normally taken
as 1/10th to 1/15th of the span)
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External dimensions =h=2.3m and w=3.3m
Road width=6.7m
Span=3.3m
Concrete: take C25
Reinforcement
Take steel: S460
Geotechnical data
Unit weight of the soil =18kN/m3 (assumed)
Angle of repose of the soil, Ø=300 (assumed)
Design type
A live load of design truck.
Dead load, live load with water pressure from inside.
Design procedure
1/ Load
Dead load= (1*4.6) m*18kN/m3
=82.8KN/m2
2/ Tire contact area calculation:-
Contact area =L*w
Where w=500mm
L=2.28*10-3**(1+IM/100)*p
Where =load factor for the limit state under consideration
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=1.75(ERA, table 3-2)
IM= dynamic load allowance percent
=33% for other limit state
P=72.5KN for design truck
There fore, L= 2.28*10-3*1.75*(1+.33/100)*72.5 =290mm.
Fig 3-4 wheel load distribution
Distribution of wheel load:-
For height of fill > 0.6m
L’=L+1.15hf
W’=w+1.15hf (ERA section 3.8.6)
There fore, L’=0.29+1.15*4.6 =5.58m
W’=0.50+1.15*4.6 = 5.79m
But L’ is greater than the span of the culvert. There fore the intensity of the live loading
needs to be reduced proportionally.
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Reduced load= (72.5*3.6)/5.58 =46.77KN
Load with impact factor=1.25*46.77 =58.47KN
Intensity of live load on the slab:
Intensity=load/area
=load/ (culvert span*w’)
=58.47/ (3.6*5.79)=2.805KN/m2 =2805N/m2
3/ Load and reaction calculation
Dead load of the top slab:-
=0.3*1*25000=7500N/m2=75KN/m2
Total load on the culvert=Dead load +Live load
=82.8KN/m2+2.805kN/m2=85.605KN/m2=85605N/2
There fore,
Total design load on the top slab=85605N/2+7,500N/m2
=93,105N/m2
Weight of each wall (side wall) =2.3*0.3*25000=17,250N/m
Then, up ward reaction at the base
= [(93,105*3.3) + (2*17250)]/3.3*1
=103,559N/m2
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4/ Lateral pressure
Coefficient of active pressure (Ka) =
Lateral pressure due to dead and live load
=Total vertical load*Ka =85605*1/3 =28535N/m2
Lateral pressure due to the soil at depth of 2.6m:
=Ka**h =1/3*18000*2.6=15600N.m2
There fore,
Lateral intensity at top=28535N/m2
Lateral intensity at the bottom=28535+15600N.m2 =44135N/m2
Fig 3-5 Pressure diagram for live and dead load
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Fig3-5 Pressure diagram due to water
Fig 3-6 Final pressure diagram of the forces or loadings on the components of the culvert.
6/ Moments and shear force calculation
On account of symmetry, it is enough to consider half the frame AEFD for moment
distribution. As all members are of uniform thickness and have the same dimensions,
their moments of inertia are equal.
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Relative stiffness of members is:
KAD=1
KAE=KDF=1/2
Distribution factors are:
;
Fixed end moments are:
Joint member D A
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DC DA AD AB
DF 1/3 2/3 2/3 1/3
Fixed E.Mome.(KN.m) 111.8 -21.34 19.58 -52.49
balance -30.15 -60.31
-30.15
balance 42.04 21.02
carryover 21.01
balance -7. -14.01
carryover -7.005
balance 4.67 2.33
carryover 2.335
balance -0.778 -1.557
carryover -0.778
balance 0.519 0.259
carryover 0.259
balance -0.86 -0.173
carryover -0.086
balance 0.058 0.029
carryover 0.029
balance -0.01 -0.019
carryover -0.01
balance 0.007 0.003
carryover 0.003
balance -0.001 -0.002
Final end moments(KN.m) 73. -73. 28.85 -28.85
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Then the final end moments are:-
MDC=73.001KN.m;
MDA=-73.77KN.m
MAD=28.83KN.m
MAB=-28.85KN.m
7/ Reactions
For horizontal slab AB, carrying distributed load of 93105N/m2,
Vertical reaction RA=RB is:-,
For bottom slab DC, carrying distributed load of 103559N/m2,
Vertical reaction RD =RC is:-
For vertical member AD, the horizontal reaction HA at A is found by taking moments
about D. Thus,
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Fig3-7Shear force and axial forces
Bending moment calculation
Free bending moment at mid point E
Then, net bending moment at E,(top slab)=150830.10-28850
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=121980.10N.m
Again,
Free bending moment at mid point F (bottom slab) =
Then, net bending moment at F=167765.58-73000
=94765.58N.m
For vertical member AD, which is simply supported bending moment at mid span, is=
Then, net bending moment=
Components of the culvert Bending moment at the center(N.m)
Bending moment at ends(N.m)
Top Slab 121980.10 28850.00
Bottom slab 94765.58 73000.00
Side walls 20232.88 73000.00
Table3-8 Summary of bending moments of the culvert components
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Fig3-8 Bending moment for the components of the culvert
Reinforcement
Overall depth=300mm
Cover=50mm
Effective depth=d=300-50=250mm
Fcd= (0.68*fck)/c= (0.68*25)/1.5=11.33MPa
fyd=fyk/1.15=460/1.15=400MPa
Width (b) =1000mm
Top slab
At span/center
Depth checking
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There fore, the depth is adequate.
Area of steel (Ast,cal)=
Spacing(S) =
Provide 20mm diameter bars with minimum c/c spacing 250mm.
Support reinforcement
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Provide 20mm diameter bars with minimum c/c spacing 250mm.
Bottom slab
At span/center
Depth checking=
There fore, the depth required is adequate.
Area of steel (Ast,cal)=
Provide 20mm diameter bars with minimum c/c spacing 250mm.
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Support reinforcement
Provide 20mm diameter bars with minimum c/c spacing 250mm.
Side walls
At span/center
Depth checking=
There fore, the depth required is adequate.
Area of steel (Ast,cal)=
Spacing(S) =
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Provide 20mm diameter bars with minimum c/c spacing 250mm.
Support reinforcement
Provide 20mm diameter bars with minimum c/c spacing 250mm.
Section-4. Earth Work and Mass Haul Diagram
4.1 Earth Work
Earth work is conversion of natural ground condition to required sections and grades.
Earth work in high way design includes determination of cuts and fills, location of
borrow, waste sites, the free haul and over haul distance determination.
The careful attentions to limiting earthwork quantities through the preparation of a mass
haul diagram are essential elements in providing the best-combined horizontal, vertical,
and cross-sectional design. This is especially true when the design includes consideration
of the least cost in relation to earth works. Key terms associated with this process, as
listed in definitions, include:
Borrow - material not obtained from roadway excavation but secured by widening cuts,
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flattening back slopes, excavating from sources adjacent to the road within the
Right-of-way, or from selected borrow pits as may be noted on the plans.
Waste - material excavated from roadway cuts but not required for making the
embankment.
Free Haul - the maximum distance through which excavated material may be transported
without the added cost above the unit bid price.
Overhaul - excavated material transported to a distance beyond the free haul distance.
Economic Limit of Haul - distance through which it is more economical to haul
excavated material than to waste and borrow.
Clearing and garbing (m2) - the removal of top soil, trees, bushes and e.t.c
Excavation (m3) - the process of loosing and removal of soil and rocks. It can be done
for three reasons.
In order to maintain the grades for roads and drainage
For structure foundation
For borrow excavation
Embankment /compaction (m3k.hr) - densification of fill section of the road.
The steps involved in the computation of earthwork quantities and the development of the
optimal mass haul diagram are:
End area calculations
Earthwork calculations
Preparation of mass haul diagram.
Balancing earthworks using the mass haul diagram
Purpose of the preparation of earth work quantities and mass haul diagram
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To estimate cost of the (to limit the cost of construction)
For the proper distribution of excavated material
To determine amount and location of waste and borrow.
Amount of over haul in kilometer cubic meter can be determined.
To determine direction of haul.
Computation of earthwork
There are several ways of calculating earthwork but the most common is the average end
area method. This method consists of averaging the cut and fill quantities of adjacent
stations and multiplying by the distance between stations to produce cubic meters of
excavation and embankment between the two stations.
End Area Calculations
In this project we took 25 cross section that covers total distance of 500 m (from station
12 + 500 to 13+000 m)
Calculation procedure followed
Area at different cross section along the road with an interval of 20m station
is taken.
Read the elevations of existing profile along the right of way (50 m) from the
contour to plot the points.
Design proposed carriage way by providing a cross fall of 2.5% from the
center to both direction. Then the amount of cut and fill are determined at
each 20m stations (to calculate the end area areas we use AutoCAD software
program)
Preparation of mass haul diagram.
Volume calculation
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The volume of earth work from the successive cross sections can be computed by
different formulas like average end area method, (trapezoidal method) or primordial
formula.
Average end Area Method (trapezoidal method)
V=
Where :
V= volume in m3
A1and A2 is area of successive cross-section in m2
L= distance between successive cross section in m in this case 20 m.
The average end area method is simple and is generally preferred, so we choose this
method for this particular project.
The volume computed by this formula is likely to be higher than the true value in the case
of the section changing rapidly.
Estimation of earth work quantities
Based on:-
o Estimate of quantities
o Rate of abstract of work
Shrinkage and swelling should be included in estimating the quantities. According to
ERA 2001 there is a recommended shrinkage and swelling factor there fore the following
tables show the recommended values of Shrinkage factors
Type of soil Shrinkage factor
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Light soil (ordinary ground) 10-25%
Light soil(swamp ground) 20-40%
Heavy soil up to10%
Table 4-1 Soil shrinkage factor
4.2 Mass haul diagram
It is a graphical representation of the amount of earth work and embankment involved in
a project and the manner in which the earth is to be moved.
The mass haul diagram shows excavation (adjusted) and embankment quantities from
some point of beginning on the profile, considering cut volumes positive and fill volumes
negative. At the beginning of the curve the ordinate is zero, and ordinates are calculated
continuously from the initial station to the end of the project.
Mass haul diagram is a continuous curve showing the accumulated algebraic sum of the
cut (+ve) and fill (-ve) volume from some initial station for any succeeding section. The
horizontal axis represents distance and is usually expressed in meters or stations. The
vertical axis represents the cumulative quantity of earth work in cubic meter (m3).
The mass haul diagram allows determining direction of haul and the quantity of earth
taken from or hauled to any location. It shows balance point the station between which is
the volume of excavation. In this project horizontal axis represents stations from 12+500
to 13+000 and the vertical axis represents the cumulative volume.
Use of mass haul diagram
The mass haul diagram can be used to determine:
Proper distribution of excavated material
Amount and location of waste
Amount and location of borrow
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Amount of overhaul in kilometer-cubic meters
Direction of haul.
In proportion and enabling suitable plant, equipment or machinery.
For our project the mass haul diagram is drawn according to the following data. We use
swelling factor of 0 % and factor shrinkage 85 % because we assume the soil is ordinary
common soil so we consider only swelling.
Calculation of mass ordinates is performed and the results are shown below on the table.
Station End Area(m2) Dist Adj.factor Adj.cut Tot.Adj.cut vol. fill vol. Mass
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ance(m) ordinet(m3)cut Fill
12+500 15.64 48.35 0.85 13.29 0.00
12+520 11.95 81.06 20 0.85 10.16 234.49 1294.05 -1059.56
12+540 2.98 89.72 20 0.85 2.53 126.91 1707.81 -2640.46
12+560 0.00 125.60 20 0.85 0.00 25.34 2153.18 -4768.30
12+580 0.00 115.74 20 0.85 0.00 0.00 2413.38 -7181.68
12+600 0.24 79.78 20 0.85 0.21 2.08 1955.22 -9134.82
12+620 9.06 36.18 20 0.85 7.70 79.13 1159.64 -10215.34
12+640 2.35 43.15 20 0.85 2.00 97.05 793.37 -10911.67
12+660 60.34 0.86 20 0.85 51.29 532.86 440.18 -10818.99
12+680 95.33 0.00 20 0.85 81.03 1323.19 8.64 -9504.44
12+700 115.38 0.87 20 0.85 98.07 1791.02 8.74 -7722.15
12+720 123.29 6.48 20 0.85 104.80 2028.70 73.58 -5767.03
12+740 111.28 19.05 20 0.85 94.59 1993.91 255.35 -4028.47
12+760 108.40 29.66 20 0.85 92.14 1867.26 487.10 -2648.32
12+780 107.95 45.24 20 0.85 91.76 1838.95 748.97 -1558.34
12+800 151.88 50.51 20 0.85 129.10 2208.56 957.43 -307.21
12+820 99.01 76.88 20 0.85 84.16 2132.54 1273.84 551.49
12+840 104.34 78.86 20 0.85 88.69 1728.42 1557.42 722.49
12+860 95.42 82.83 20 0.85 81.11 1697.94 1616.97 803.47
12+880 82.88 101.51 20 0.85 70.45 1515.58 1843.46 475.59
12+900 72.19 101.21 20 0.85 61.36 1318.07 2027.19 -233.53
12+920 77.90 111.42 20 0.85 66.22 1275.74 2126.26 -1084.05
12+940 72.59 125.25 20 0.85 61.70 1279.14 2366.72 -2171.63
12+960 60.88 128.38 20 0.85 51.75 1134.47 2536.32 -3573.48
12+980 51.63 152.34 20 0.85 43.89 956.37 2807.19 -5424.30
13+000 49.85 165.54 20 0.85 42.37 862.60 3178.82 -7740.53
Table 4-2 mass ordinate
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Fig.4-1 Mass haul diagram
The direction of haul:
From station 12+640 to 12+740 to the left.
From station 12+740 to 12+860 to the right.
Economical Over Haul Distance
When costing the Earth moving, there are basic costs which are usually included in the
contracts for the project.
Cost of free haul :- any earth moved over distances not greater than the free haul
distance is cost only on the excavation of its volume.
Cost of over haul: - any earth moved over distances greater than the free haul distance is
charged both for its volume and for the distance in excess of the free haul distance over
which it is moved. This charge can be specified either for units of haul or for units of
volume.
Cost of waste: - any surplus or unsuitable material which must be removed from the site
and deposited in a tip is usually charged on units of volume. This charge can vary from
one section of the site to another depending on the nearness of tips.
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Cost of borrow: - any extra material which must be brought on to the site to make up the
deficiency is also usually charged on units of volume.
This charge can also vary from one section of the site to another depending on the
nearness of borrow pits.
ELH = FH distance + (Unit Price of Borrow/ Unit Price of Overhaul)
Where: ELH = Economic limit of haul
FH = Free haul distance
Assume that
Ec = cost of excavation per unit volume(m3)
Hard excavation to embankment = 273 birr/m3
Excavation an unsuitable = 62 birr/m3
Bc = cost of borrow per cubic meter per station = 15 birr/m3
OHc = cost of over hauling per unit volume-station = 12 birr /m3
FH = Free haul distance = 120m (6 station)
ELH = FH + (Bc / OHc)
= 120/20 + 15/12 = 7.25 station or 145 m
Therefore the economic haul distance is 145 m.
Total free haul volume = VD + FW
= 3500 +1500 =5000 m3 from mass haul diagram
Total borrow =AB + LH = 4000 +7800 = 11800m3
Cost of earth work = cost of borrow +cost of excavation + cost of over haul
Cost of borrow = Total volume of borrow *cost of borrow per meter cubic
=11800m3*15 birr/100m3 = 1770 birr
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Cost of excavation = volume of excavation * cost of excavation per meter cubic
Volume of excavation = DJ + FI = 7000 +4900 = 11900m3
Cost of excavation = 11900*273 birr/100m3 =32,487 birr
Cost of over haul = over haul volume *cost of over haul per station meter.
For loop 1
Over haul volume 1 = area CJM + area UEO
= 43,750 + 70,000 = 113750 m3
For loop 2
Over haul volume 2 = area ESP+ area QRG
= 96,250 + 87,500 = 183,750 m3
Total Over haul volume = 113750 + 183,750 = 297,500 m3
Cost of over haul = 297,500 m3 *12 birr/100m3
= 35,700 birr.
Total cost of earth work = cost of borrow +cost of excavation + cost of over haul
= 1770 birr + 32,487 birr + 35,700 birr.
= 69,957 birr
Section-5: Pavement design
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Pavement design is the process of developing the most economical combination of
pavement layers (thickness, type) to suit the soil foundation and withstand the load due to
cumulative traffic during the design life or period.
The design standard described here presents the pavement design standard which will be
utilized in the course of the design works all in accordance with ERA Pavement Design
manuals and other internationally recognized Pavement Design Standards. The main
design parameters for the pavement design include:
Estimating the amount of traffic
Assessing and evaluating the strength of sub grade soil
Locally available construction materials
Drainage Conditions
Environment factors
In this standard, traffic volume, Sub grade type, construction materials and local factors
are the main design inputs.
The traffic volume will be determined from the traffic counts in terms of AADT
(Average Annual Daily traffic) we take this value from the given data. We determine the
Sub grade type and strength from the given CBR % (California Bearing Ratio) Values.
The basic idea in building a pavement for all-weather use by vehicles is to prepare a
suitable Sub grade, provide necessary drainage and construct a pavement that will:
Have sufficient total thickness and internal strength to carry expected traffic
loads;
Have adequate properties to prevent or minimize the penetration or internal
accumulation of moisture, and
Have a surface that is reasonably smooth and skid resistant at the same time, as
well as reasonably resistant to wear, distortion and deterioration by weather.
The sub grade ultimately carries all traffic loads.
The basic idea in building a pavement for all weather use by vehicles is:
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To prepare a suitable sub grade
Provide necessary drainage and
Construct a pavement that will have sufficient total thickness and internal strength
to carry expected traffic loads, and distribute them over the sub grade soil without
overstressing.
Design inputs
In this pavement design, the design inputs are summarized into two main parameters,
traffic load in terms of cumulative ESA and Subgrade strength interim of CBR. The
overall required strength is read from charts or graphs which preset pavement catalogues
in which each pavement composition is classified based on ranges of traffic loading (T 1-
T8) and Subgrade strength (S1-S6) maximum CBR value. Therefore we provide flexible
pavement for our road project.
Flexible pavements
Flexible pavements are intended to limit the stress created at the sub grade level by the
traffic traveling on the pavement surface, so that the sub grade is not subject to significant
deformations. In effect, the concentrated loads of the vehicle wheels are spread over a
sufficiently larger area at sub grade level.
A flexible pavement is one, which has low (bending) flexural strength, and the load is
largely transmitted to the sub grade soil through the lateral distribution of stresses with
increasing depth.
The pavement thickness is designed such that the stresses on the sub grade soil are kept
with in its bearing capacity and the sub grade is prevented from excessive deformation.
The strength and smoothness of flexible pavement structure depends to a large extent on
the deformation of the sub grade soil.
A flexible pavement must satisfy a number of structural criteria or considerations;
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The sub grade should be able to sustain traffic loading without excessive
deformation; this is controlled by the vertical compressive stress or strain at this
level.
Bituminous materials and cement-bound materials used in road base design
should not crack under the influence of traffic; this is controlled by the horizontal
tensile stress or strain at the bottom of the road base.
The road base is often considered the main structural layer of the pavement,
required to distribute the applied traffic loading so that the underlying materials
are not over stressed. It must be able to sustain the stress and strain generated
within it with out excessive or rapid deterioration of any kind.
In pavements containing a considerable thickness of bituminous materials, the
internal deformation of these materials must be limited; their deformation is a
function of their creep characteristics.
The load spreading ability of granular sub base and capping layers must be
adequate to provide a satisfactory construction platform.
Elements of the conventional flexible pavement
Tack coat
Is a very light application of asphalt usually asphalt emulsion diluted with water
used to ensure the bond between the surface being paved (surface course) and the
overlying course.
Essential requirements of tack coat
It must be very thin.
It must uniformly cover the entire surface to be paved.
It must be allowed to break or cure before the HMA is laid.
Prime coat
Is an application of low viscosity cut-back asphalt to an absorbent surface, such as
un treated granular base on which an asphalt layer will be placed.
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Its purpose is to bind granular base to the asphalt layer.
The prime coat penetrates the underlying layer, plugs the voids, and forms water
tight surface.
Surface course
The surface course is the top course of an asphalt pavement, sometimes called the
wearing course
It is usually constructed by dense graded hot-mix asphalt
It must be:
Tough to resist distortion under traffic and provide a smooth and skid-resistant
riding surface.
Waterproof to protect the entire pavement and sub grade from the weakening
effect of water.
Binder course
Sometimes called the asphalt base course is the asphalt layer below the surface
course.
It is placed for two reasons:
First, the HMA is too thick to be compacted one layer, so it must be placed in two
layer.
Second the binder course generally consists of larger aggregates and less asphalt
and does not require a high quality as the surface so replacing a part of the
surface course by the binder course results in a more economical design.
Base course
The base course is the layer of material immediately beneath the surface course.
It may be composed of well graded crushed stone (unbounded), granular material
mixed with binder, or stabilized materials. It is the main structural part of the
pavement and provides a level surface for laying the surface layer.
Sub base course
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Construct using local and cheaper materials for economic reason on top of the
sub grade. It provides additional help to the base and the upper layers in
distributing the load. It facilitates drainage of free water that might get
accumulated below the pavement.
Sub grade
It is the foundation on which the vehicle load and the weight of the pavement
layers finally rest. It is an in situ or a layer of selected materials compacted to the
desirable density near the optimum moisture content.
Fig 5-1 Road layer
The basic key elements for designing of pavements are:
Traffic class
Sub grade strength
5.1 Traffic volume analysis
Traffic classes are depends on ESAs & vehicle classification;
Where ESAs are based on:
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Vehicle classification
Cumulative traffic volume ( T )
Equivalency factor (EF)
Vehicle classification from the give data
Passenger vehicles Freight vehicles
Cars Small trucks
4WD Medium trucks
Small bus Heavy trucks
Large bus Articulated trucks
Cumulative traffic volume ( T )
T = AADT1*(p)*(D)*365((1+i)N -1)/i
Where, AADT1 traffic volume when the road is open (2013)
i = growth rate = 7 %, it is given
N = design period = 15, it is given
P = lane distribution factor =1 (100%) ERA/AASHTO
D = directional distribution factor = 0.5 this accounts for any
directional variation in total traffic volume or loading pattern.
Equivalency factor (EF)
EF= (Axle i/8160)n
Where, n is usually 4.5
Axles i = load in kg
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The Cumulative number of vehicles are depends on AADT (2013) & Diverted
traffic (2013), then we use the sum of both traffic volume.
To calculate equivalent standard axles (ESAs) by using, Cumulative number of
vehicle (T) and Equivalency factor (EF).
5.2 Axle load survey and equivalent factor computation
From the axle load survey data of each vehicle, the equivalent factor is computed and
summarized in the following table. Refer to annex for the detail computation.
Classification of vehicles
Day 13 Day 14 Day 15 Day 16 Day 17 Day 18 T0TAL
EFNO. EF NO. EF NO. EF NO. EF NO. EF NO. EF NO. EF
car 0.00
4 WD 0.00
S/Bus 10 0.3 10 0.31 10 0.54 10 0.54 10 0.44 10 0.75 60 2.87 0.05
L/Bus 10 8.3 10 8.89 10 3.89 10 10 10 8.90 10 10.9 60 50.86 0.85
S/Truck 5 0.0 5 0.02 0.00
M/Truck 10 0.3 10 0.91 10 0.09 10 3.86 10 6.02 10 0.16 60 11.28 0.19
L/Truck 10 83.3 10 55.5 10 46.7 10 49.8 10 91.40 10 58.4 60 385.02 6.42
T/Trailer 10 192.6 10 165 10 117 10 145 10 145.5 10 112 60 878.39 14.64
5.3 Traffic class determination
Calculation of ESAs by using the above Axle load survey
EF= (Axle i/8160)^4.5 T = AADT1*(p)*(D)*365((1+i)N -1)/i
i= 7% P= 1 D= 0.5
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Classification of vehicles
Day 13 Day 14 Day 15 Day 16 Day 17 Day 18 T0TAL
EF AADT1
Cumula. No. Veh.
ESAs (10^6)NO. EF NO. EF NO. EF NO. EF NO. EF NO. EF NO. EF
car 0.00 0 0 0.00
4 WD 0.00 21 96307 0.00
S/Bus 10 0.3 10 0.31 10 0.54 10 0.54 10 0.44 10 0.75 60 2.87 0.05 18 82549 0.00
L/Bus 10 8.3 10 8.89 10 3.89 10 10 10 8.90 10 10.9 60 50.86 0.85 7 32102 0.03
S/Truck 5 0.0 5 0.02 0.00 38 174270 0.00
M/Truck 10 0.3 10 0.91 10 0.09 10 3.86 10 6.02 10 0.16 60 11.28 0.19 31 142167 0.03
L/Truck 10 83.3 10 55.5 10 46.7 10 49.8 10 91.40 10 58.4 60 385.02 6.42 51 233888 1.50
T/Trailer 10 192.6 10 165 10 117 10 145 10 145.5 10 112 60 878.39 14.64 38 174270 2.55
Sum 4.11
Table 5-1 ESAs computation
ESAs = 4.11*10^6
Based on this traffic analysis the main access belongs to the traffic class T5 which is in the
range of (3 to 6)*10^6 ESAs.
CBR test from the given data is 4% from 0 km to 24km and our road project is between
12.5 km to 15.5 km. According to ERA 2002 design manual CBR test (3-4) % fails in to
the soil class sub grade strength S2 .Therefore our road project design is based on traffic
class T5 and sub grade strength S2.
5.4 Selection of economical section
By using T5 and S2 the economical pavement selected from the catalog of pavement types
and configuration for design of road section. Chart (1, 2, 3, 4, 7 and 8) selected for
comparison purpose.
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Materials abbreviationpric(m 3 )inbi rr
Double surface dressing DSD 1000
Flexible bituminous surface FBS 2050
Bituminous surface BS 900
Bituminous road base, RB BRB 1045
Granular road base, GB1-GB3 GRB(1-3) 560
Granular sub base GS GSB 250
Granular capping layer, or selected sub grade fill, GC GCL or SSF 200
Cement or lime stabilized road base1, CS1 C or LSRB1
Cement or lime stabilized road base2, CS2 C or LSRB2 810
Cement or lime stabilized sub base, CS C or LSSB 860
Table 5-2 Material and price
Chart 1 Chart 2
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Chart 3 Chart 4
Chart 7 Chart 8
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Materials
THICKNESS OF THE CHARTS (mm) Price
Birr/m3
Price (Birr )
chart1 chart2 chart3 chart4 chart7 chart8 chart1 chart2 chart3 chart4 chart7 chart8
DSD 50 50 50 1000 50 50 50
FBS 50 50 50 2050 102.5 102.5 102.5
BRB 125 1045 130.63
GRB(1-3) 200 150 175 150 560 112 84 98 84
GSB 275 275 225 250 68.75 68.75 56.25
GCLorSSF 200 200 200 200 200 225 200 40 40 40 40 40 45
CorLSRB2 250 225 200 810 202.5 182.25 162
CorLSSB 225 860 193.5
Total 270.75 376.5 309.25 408.75 329.38 400.5
Table 5-3 Economical section
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From the above charts, chart 1 is more economical than others but it is not technically
feasible, because mostly it is used for maintenance purpose. Therefore, we choose chart 3
with bituminous surface (HMA). The thickness of each layer summarized as follows:
Station(km)
Materials Layer thickness(mm)
12 +500- 15+ 500
FBS 50
GRB(1-3) 175
GSB 275
GCL or SSF 200
Table 5-4 selected section
Section-6: Provision of traffic controls
Signings and Markings
They are directly related to the design of the highway or street and futures of traffic
control’s and operation that the designer should consider in the geometric layout of such
facilities. The potential for future operational problems can be significantly reduced if
signing and marking are treated as an integral part of the highway design.
The extent to which signs and markings are used depends on the traffic volume, type of
facility and the extent of traffic control appropriate for save and efficient operation.
Generally highway signs are three types as per AASHTO practice
Regulatory signs: to indicate the rules for traffic movement (prohibitory and
mandatory).
Mandatory signs for stop and yielding.
Prohibitory signs for curve movements, weight and speed limitation etc
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Warning or danger or cautionary signs: to indicate conditions that may involve
risk to highway users.
Guide or information signs: to direct traffic along a route or towards a distention.
Physical obstructions in or near our road way project should be removed in order to
provide the appropriate clear zone. Where removal is impossible, such objects should be
adequately marked by painting or by use of other highly visible material.
Where the object is in the direct line of traffic, the obstruction and marking there on
preferably should be illuminated at night by flood lighting; where there is not practical,
the object markings should be effectively reflectorized.
Post mounted delineators are another type of marking devises used to guide traffic,
particularly at night. Reflector units are installed at certain height & spacing to delineate
the road way where alignment changes may be confusing & not clearly defined.
The importance of traffic control devices
Give timely warning of hazardous situation when they are not self evident
Regulating traffic by imparting messages to the drivers about the need to
stop, give way or yielding & limit their speed
Give information as to highway routes, directions & point of intersection.
The general guide lines for the provision of traffic signings
It should be installed only by the authority of law with proper enforcement
measures to respecting the signs.
It should be provided only after traffic engineering studies & sound judgments.
Excessive use of signs should not be resorted to.
They should be legible & understood to those who using it (visibility, lettering,
symbols, locations, simplicity, uniformity & standard size).
Location, height & maintenance of traffic signs
The location, reflecting & lighting of signs are important considerations.
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The signs should be located on the risk side of the road where the drivers will be looking
at them. On hill roads, they should be fixed on the valley side of the road & mounted on
the posts. According to AASHTO practice the signs in rural areas shall be mounted at a
height of at least 1.5m measured from the bottom to the pavement.
The sign posts should be maintained in proper position & legible at all time. Damaged
signs should be replaced immediately. Periodic painting of signs should be a routine part
of maintenance.
Road markings provisions
These markings are used as a means of controlling & guiding traffic of roads & safety.
These are:
Carriage way marking-which includes center line strip, traffic line strip, no over
taking zone, stop lines , pedestrian &cyclist crossings , route directions etc.
Object markings-which should contains Krebs markings, culvert head wall
markings, & other objects adjacent to the carriage way.
The general guide lines of longitudinal pavement markings
Solid lines are restrictive & cannot be crossed.
Broken lines are restrictive in character & vehicle can cross it safely.
Double lines indicate maximum restrictions.
When combination of solid & broken lines are used, and the traffic moves to the
right(left), a vehicle should not cross the continuous line adjacent to the
right(left) of broken lines on the lane which the vehicle moving.
Pavement marking colors shall be white (optional crossing) & yellow (not
crossing).
On rural areas the center line marking of the pavement segment & gaps shall be doubled
in length than an urban location, due to less traffic congestions. In addition the length of
gaps shall be shorter near approaches, intersections & on curves than on straight reaches.
The gap shall be half the value on straight sections.
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Traffic lane lines
The division of the carriage way in to separate lanes for traffic traveling in the same
directions on either side of the center line or median strip helps to promote travel in
proper lanes by promoting safety & ensuring maximum capacity.
No overtaking zone marking
These markings shall be provided on summit curves, horizontal curves & tangents in two
or three lane highways where overtaking & passing maneuvers must be prohibited,
because of non availability of safe overtaking sight distance or other hazardous
conditions. The marking for “No overtaking” zone consists of a combination lines along
the center line. The combination lines consist of a double line, the left hand element of
which shall be a solid barrier line & the right hand element also either a normal broken
center line or solid barrier governing the traffic from the opposite direction. Where a olid
barrier line is to the right of the broken line, the overtaking restriction shall apply only to
the opposing the traffic. If both lines are solid lines, “No overtaking” is permitted in both
directions.
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Fig 6-1. For areas on which “No overtaking” is permitted in both directions.
Fig.6-2 a normal broken center line for areas on which passing is permitted safely in both
directions.
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Fig.6.3 solid barrier line & the right hand element broken center line for areas on which
a solid barrier line is to the right of the broken line, the overtaking restriction in one
direction
Pavement edge lines or strips
These shall be used to indicate the edges of carriageway on which no Krebs are provided.
They serve as a visual guidance for the drivers, indicating to them the limits up to which
the driver can safely venture. They especially are useful during adverse weather & poor
visibility. Where the paved shoulder is of a lesser structural strength than the main
pavement, the edge lines are used to promote travel on the main pavement itself.
Edge lines shall be in the form of single continuous lines placed about 15cm from the
edge & the width of the lines shall be 15-20cm. Based on the above guide lines &
principles as per AASHTO & ERA manuals we recommended that:
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On the crest curve, from station (PC)=13+472 to (PT) =
13+672 “overtaking” is not permitted hence the solid barrier
marking lines along with center line must be provided. In
addition to this post mounted traffic signs that show ascent or
descent summit curve must be provided on the risk side of
the road.
On horizontal curves, from PC=12+655.43 to
PT=12+774.55, from PC=13+098.59 to PT=13+199.38,
PC=13+263.38 to PT=13+445.38, from PC=13+806.5 to
PT=14+180.50, from PC=14+685.72 to 14+820.57, and from
PC= 15+175.76 to PT=15+274.96 , here also “overtaking” is
not permitted therefore the solid barrier marking lines along
with center line must be provided. And post mounted traffic
signs that show speed limitation, to the right hand & to the
left hand horizontal curve sign must be provided on the risk
side of the road & visible to the traffic.
On the tangent curve, from station (PT) = 12+774.55 to
station (PC) =13+098.59, similar manner as to horizontal
curves.
Section-7: Environmental consideration
Environmental assessment: the identification and evaluation of the likely effects of a
proposed policy, program, or project on the environment; alternatives to the proposal;
measures to be adopted to protect the environment; a standard tool for decision making.
Environmental Issues Include
Noise from all types of equipment and traffic
Air quality / emissions and dust problems from all types of equipment and traffic
Impact on natural and planted vegetation: removal or trimming of only those plants
and trees directly affected by the implementation of the Project will be permitted.
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Provisions for pedestrians and non-motorized traffic.
Access to properties /access to the site
Soil stability and earthworks
Effect on watercourses and water quality
Effects on adjacent land.
Material disposal
Equipment operation and disposal
Disposal of waste and reinstatement of land
Therefore the above factors will considered during construction of this project.
Erosion
When natural conditions are modified by the construction of a road, it marks the start of a
race between the appearance of erosion and the growth of vegetation. Disturbance during
construction can upset the often delicate balance between stabilizing factors, such as
vegetation, and others which seek to destabilize, such as running water. In some cases
erosion might result in cumulative impacts far beyond the road itself, affecting slopes,
streams, rivers, and dams at some distance from the initial impact.
Side-tipping of spoil materials
Spoil material from road cuttings can kill vegetation and add to erosion and slope
stability problems. Large amounts of spoil can be generated during construction in
mountainous terrain. Sometimes it is difficult to design for balances between cut and fill
volumes of earth at each location, and haulage to disposal sites may be expensive. This
creates a need for environmental management of tipped material.
During construction we shall not interrupt or interfere with the flow of irrigation waters
without making prior arrangements with and obtaining the agreement of the irrigation
authorities. The contractor shall allow in his program for the construction of those works
which might interface with the flow of irrigation waters to be carried out at such times as
will cause the least disturbance to irrigation operations.
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The contractor shall comply with the following: Meet the requirements of regulations.
Consult, with the engineer before locating and constructing project offices and sheds and
installing construction plant. Prevent pollution of any kind to adjacent property resulting
from the construction operation. Sites containing cement, line and similar items shall be
suitably protected from rain and flood. Natural streams or channels adjacent to the works
of this contract shall not be disturbed without the approval of the engineer.
Management of Waste Materials
Management of waste materials: all excavated material to be disposed off-site in
locations approved by the local regulatory agency. No material is to be disposed down
slope without specific approval of the site engineer, and will be approved only if existing
drainage, agricultural land, housing, and slope stability is not affected. All waste oils to
be disposed of in accordance with existing environmental regulations.
Remedial Measures
Prevention
When planning new roads or changes in width or alignment, sensitive natural
environments should be identified early in the planning process so that alternate routes
and designs may be considered. Wherever possible, road developments should be located
more than one kilometer away from sensitive areas to avoid severe impacts on flora and
fauna. Water crossings should be minimized, and buffer zones of undisturbed vegetation
should be left between roads and after courses. Groundwater recharge areas should be
avoided, and major roads should not be constructed through national parks or other
protected areas. Advantage should be taken of opportunities to twin new road corridors
with previously established transport rights-of-way, such as railway lines.
Animal crossings
As we know Somale region has a lot of camel and goat and other wild animal .Animal
crossings can be used to assist the migration of these animals. At important crossing
points, animal tunnels or bridges have sometimes been used to reduce collision rates,
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especially for protected or endangered species. Tunnels are sometimes combined with
culverts or other hydraulic structures. These measures are expensive and used only at a
few locations where they are both justified (by the importance of the animal population
and the crossing route) and affordable (relative to the cost of the project and the funds
available.
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Annexes
Annexe-1 terrain classification data
station Elv.diff.(m) H.distance(m) Slope (%) Terrain classification
Remarks
12+500 10 64.62 15.48 Rolling
12+520 12 49.09 24.44 Rolling
12+540 12 44.14 27.19 Mountainous
12+560 16 72.95 21.93 Rolling
12+580 16 61.61 25.97 Mountainous
12+600 20 88.62 22.57 Rolling
12+620 22 104.2 21.11 Rolling
12+640 24 109.36 21.95 Rolling
12+660 24 94.49 25.40 Mountainous
12+680 24 96.69 24.82 Rolling
12+700 26 109.72 23.70 Rolling
12+720 26 115.4 22.53 Rolling
12+740 26 111.19 23.38 Rolling
12+760 26 106.85 24.33 Rolling
12+780 28 106.19 26.37 Mountainous
12+800 30 110.63 27.12 Mountainous
12+820 30 107.58 27.89 Mountainous
12+840 30 108.26 27.71 Mountainous
12+860 28 100.08 27.98 Mountainous
12+880 28 102.46 27.33 Mountainous
12+900 28 107.74 25.99 Mountainous
12+920 26 114.21 22.77 Rolling
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12+940 26 95.19 27.31 Mountainous
12+960 24 85.46 28.08 Mountainous
12+980 24 92.68 25.90 Mountainous
13+000 20 76.43 26.17 Mountainous
13+020 22 89.62 24.55 Mountainous
13+040 28 101.46 27.60 Mountainous
13+060 26 92.29 28.17 Mountainous
13+080 26 92.76 28.03 Mountainous
13+100 24 97.52 24.61 Rolling
13+120 26 118.78 21.89 Rolling
13+140 24 104.16 23.04 Rolling
13+160 26 136.26 19.08 Rolling
13+180 26 116.46 22.33 Rolling
13+200 26 104.63 24.85 Rolling
13+220 26 95.84 27.13 Mountainous
13+240 26 103.46 25.13 Mountainous
13+260 26 98.53 26.39 Mountainous
13+280 24 91.86 26.13 Mountainous
13+300 20 112.18 17.83 Rolling
13+320 4 99.49 4.02 Rolling
13+340 8 115.2 6.94 Rolling
13+360 10 126.58 7.90 Rolling
13+380 12 101.27 11.85 Rolling
13+400 12 100.37 11.96 Rolling
13+420 14 105.34 13.29 Rolling
13+440 16 104.77 15.27 Rolling
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13+460 18 99.32 18.12 Rolling
13+480 22 112.79 19.51 Rolling
13+500 22 103.12 21.33 Rolling
13+520 24 100.46 23.89 Rolling
13+540 26 102.99 25.25 Mountainous
13+560 26 93.67 27.76 Mountainous
13+580 26 86.25 30.14 Mountainous
13+600 30 98.06 30.59 Mountainous
13+620 30 92.25 32.52 Mountainous
13+640 28 80.12 34.95 Mountainous
13+660 28 75.52 37.08 Mountainous
13+680 28 72.91 38.40 Mountainous
13+700 30 81.44 36.84 Mountainous
13+720 32 98.29 32.56 Mountainous
13+740 32 103.67 30.87 Mountainous
13+760 32 102.5 31.22 Mountainous
13+780 32 104.98 30.48 Mountainous
13+800 32 93.3 34.30 Mountainous
13+820 32 104.76 30.55 Mountainous
13+840 30 128.59 23.33 Rolling
13+860 30 135.71 22.11 Rolling
13+880 30 145.89 20.56 Rolling
13+900 28 145.95 19.18 Rolling
13+920 28 141.63 19.77 Rolling
13+940 26 152.86 17.01 Rolling
13+960 22 153.32 14.35 Rolling
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13+980 20 131.94 15.16 Rolling
14+000 16 115.77 13.82 Rolling
14+020 14 107.45 13.03 Rolling
14+040 12 96.56 12.43 Rolling
14+060 8 45.36 17.64 Rolling
14+080 8 30.59 26.15 Mountainous
14+100 4 41.6 9.62 Rolling
14+120 4 24.73 16.17 Rolling
14+140 8 42.08 19.01 Rolling
14+160 8 54.93 14.56 Rolling
14+180 8 58.2 13.75 Rolling
14+200 10 76.44 13.08 Rolling
14+220 10 67.47 14.82 Rolling
14+240 12 69.23 17.33 Rolling
14+260 12 62.82 19.10 Rolling
14+280 12 63.81 18.81 Rolling
14+300 14 72.11 19.41 Rolling
14+320 14 71.83 19.49 Rolling
14+340 14 70.36 19.90 Rolling
14+360 14 72.4 19.34 Rolling
14+380 12 65.94 18.20 Rolling
14+400 12 66.38 18.08 Rolling
14+420 12 65.11 18.43 Rolling
14+440 12 64.56 18.59 Rolling
14+460 12 64.36 18.65 Rolling
14+480 12 66.09 18.16 Rolling
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14+500 12 65.26 18.39 Rolling
14+520 12 65.94 18.20 Rolling
14+540 12 68.3 17.57 Rolling
14+560 12 67.52 17.77 Rolling
14+580 12 68.97 17.40 Rolling
14+600 12 69 17.39 Rolling
14+620 12 62.41 19.23 Rolling
14+640 12 61.49 19.52 Rolling
14+660 12 61.43 19.53 Rolling
14+680 12 60.15 19.95 Rolling
14+700 12 58.29 20.59 Rolling
14+720 14 83.74 16.72 Rolling
14+740 14 85.15 16.44 Rolling
14+760 14 101.46 13.80 Rolling
14+780 12 90.01 13.33 Rolling
14+800 12 95.51 12.56 Rolling
14+820 14 110.72 12.64 Rolling
14+840 14 108.07 12.95 Rolling
14+860 14 105.75 13.24 Rolling
14+880 14 103.65 13.51 Rolling
14+900 14 100.27 13.96 Rolling
14+920 14 94.31 14.84 Rolling
14+940 14 87.69 15.97 Rolling
14+960 14 81.65 17.15 Rolling
14+980 14 79.81 17.54 Rolling
15+000 16 96.04 16.66 Rolling
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15+020 16 93.13 17.18 Rolling
15+040 16 88 18.18 Rolling
15+060 16 85.64 18.68 Rolling
15+080 16 83.05 19.27 Rolling
15+100 16 78.25 20.45 Rolling
15+120 16 76.14 21.01 Rolling
15+140 16 74.54 21.46 Rolling
15+160 16 73.3 21.83 Rolling
15+180 16 71.11 22.50 Rolling
15+200 16 62.19 25.73 Mountainous
15+220 16 61.9 25.85 Mountainous
15+240 16 62.19 25.73 Mountainous
15+260 16 60.52 26.44 Mountainous
15+280 16 60.96 26.25 Mountainous
15+300 12 59.21 20.27 Rolling
15+320 12 67.21 17.85 Rolling
15+340 10 61.63 16.23 Rolling
15+360 8 55.67 14.37 Rolling
15+380 8 71.14 11.25 Rolling
15+400 6 55.63 10.79 Rolling
15+420 4 35.66 11.22 Rolling
15+440 6 89.63 6.69 Rolling
15+460 6 99.54 6.03 Rolling
15+480 8 86.28 9.27 Rolling
15+500 6 59.36 10.11 Rolling
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Annexe-2 Natural ground profile and the finished road grade elevation
Station Natu. ElevationGrade
ElevationStation Natu. Elevation
Grade Eleation
12+500 1384.30 1386.00 13+360 1398.60 1393.60
12+520 1384.50 1386.18 13+380 1398.00 1393.80
12+540 1384.30 1386.36 13+400 1396.70 1393.98
12+560 1384.50 1386.53 13+420 1395.30 1394.16
12+580 1384.30 1386.71 13+440 1394.20 1394.33
12+600 1385.00 1386.89 13+460 1394.00 1394.51
12+620 1386.10 1387.06 13+480 1394.00 1394.67
12+640 1387.30 1387.24 13+500 1393.40 1394.73
12+660 1388.40 1387.42 13+520 1393.00 1394.68
12+680 1389.50 1387.60 13+540 1393.00 1394.51
12+700 1390.20 1387.77 13+560 1392.50 1394.23
12+720 1390.30 1387.95 13+580 1391.80 1393.84
12+740 1390.30 1388.13 13+600 1390.50 1393.34
12+760 1390.00 1388.31 13+620 1390.00 1392.73
12+780 1389.90 1388.48 13+640 1389.50 1392.00
12+800 1390.10 1388.66 13+660 1388.90 1391.18
12+820 1389.70 1388.84 13+680 1387.70 1390.24
12+840 1389.00 1389.01 13+700 1386.00 1389.28
12+860 1389.00 1389.19 13+720 1385.40 1388.32
12+880 1388.80 1389.37 13+740 1385.00 1387.30
12+900 1388.60 1389.55 13+760 1385.00 1386.40
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12+920 1388.90 1389.72 13+780 1384.00 1385.40
12+940 1388.60 1389.90 13+800 1383.50 1384.50
12+960 1388.40 1390.01 13+820 1384.10 1383.59
12+980 1387.70 1390.26 13+840 1385.40 1382.63
13+000 1387.50 1390.43 13+860 1384.50 1381.76
13+020 1387.00 1390.61 13+880 1384.00 1380.96
13+040 1387.00 1390.79 13+900 1382.10 1380.21
13+060 1387.30 1390.96 13+920 1380.23 1379.53
13+080 1387.20 1391.14 13+940 1379.00 1378.89
13+100 1387.90 1391.32 13+960 1376.00 1378.34
13+120 1389.00 1391.50 13+980 1374.30 1377.80
13+140 1389.80 1391.67 14+000 1373.50 1377.34
13+160 1390.30 1391.85 14+020 1372.40 1376.93
13+180 1390.90 1392.30 14+040 1371.50 1376.58
13+200 1390.60 1392.21 14+060 1368.90 1376.30
13+220 1393.10 1392.38 14+080 1368.00 1376.06
13+240 1395.10 1392.56 14+100 1369.30 1375.88
13+260 1397.00 1392.74 14+120 1372.00 1375.77
13+280 1398.10 1392.91 14+140 1374.00 1375.70
13+300 1398.80 1393.01 14+160 1374.30 1375.70
13+320 1399.30 1393.27 14+180 1377.90 1375.76
13+340 1399.30 1393.45 14+200 1377.00 1375.84
ECSC, IUDS, Urban Engineering Department (UE)
183
Highway Design Senior Project 2010
Station Natural
Elevation
Grade Elevation
Station Natural
Elevation
Grade Elevation
14+220 1377.60 1375.90 14+880 1367.50 1367.20
14+240 1378.00 1376.00 14+900 1367.60 1366.70
14+260 1378.20 1376.10 14+920 1367.00 1366.20
14+280 1378.10 1376.20 14+940 1366.30 1365.70
14+300 1378.20 1376.30 14+960 1365.90 1365.25
14+320 1378.10 1376.35 14+980 1365.70 1364.80
14+340 1377.80 1376.40 15+000 1365.60 1364.30
14+360 1377.80 1376.51 15+020 1365.60 1363.80
14+380 1377.30 1376.56 15+040 1365.60 1363.30
14+400 1377.20 1376.57 15+060 1365.00 1362.80
14+420 1378.00 1376.53 15+080 1365.00 1362.30
14+440 1376.40 1376.45 15+100 1364.90 1361.80
14+460 1376.10 1376.32 15+120 1365.00 1361.30
14+480 1375.60 1376.14 15+140 1363.90 1360.80
14+500 1375.30 1375.91 15+160 1363.70 1360.30
14+520 1375.00 1375.64 15+180 1363.80 1359.85
14+540 1374.40 1375.31 15+200 1363.00 1359.40
14+560 1374.20 1374.94 15+220 1363.00 1358.70
14+580 1373.60 1374.53 15+240 1362.40 1358.40
14+600 1373.00 1374.08 15+260 1359.60 1357.90
14+620 1372.10 1373.60 15+280 1357.80 1357.40
14+640 1371.30 1373.10 15+300 1356.00 1356.90
14+660 1370.80 1372.60 15+320 1354.40 1356.40
14+680 1369.80 1371.10 15+340 1353.80 1355.90
14+700 1369.50 1371.60 15+360 1352.20 1355.40
ECSC, IUDS, Urban Engineering Department (UE)
184
Highway Design Senior Project 2010
14+720 1369.40 1371.10 15+380 1351.90 1354.90
14+740 1369.00 1370.64 15+400 1351.90 1354.45
14+760 1369.00 1370.20 15+420 1351.90 1353.96
14+780 1368.50 1369.70 15+440 1349.90 1353.47
14+800 1368.00 1369.20 15+460 1346.00 1353.00
14+820 1368.10 1368.70 15+480 1351.00 1352.59
14+840 1367.90 1368.20 15+500 1353.00 1352.00
14+860 1367.70 1367.70
Annexe-3 Nomograph
ECSC, IUDS, Urban Engineering Department (UE)
185
Highway Design Senior Project 2010
ECSC, IUDS, Urban Engineering Department (UE)
186
Highway Design Senior Project 2010
ECSC, IUDS, Urban Engineering Department (UE)
187
Highway Design Senior Project 2010
Anexe-4 Axle load survey and EF computation
Traffic count for day 13, Small Bus
axle1 axle2 Axle EF1 Axle EF2 Total EF
SB (25) 3300 3350 0.017 0.018 0.035
SB (14) 1150 1650 0.000 0.001 0.001
SB (25) 1800 2850 0.001 0.009 0.010
SB (25) 2250 3850 0.003 0.034 0.037
SB (25) 2300 3800 0.003 0.032 0.035
SB (25) 2250 4000 0.003 0.040 0.043
SB (25) 2350 3000 0.004 0.011 0.015
SB (25) 2400 3800 0.004 0.032 0.036
SB (25) 2350 3050 0.004 0.012 0.016
SB (25) 2400 4400 0.004 0.062 0.066
Sum 0.295
ECSC, IUDS, Urban Engineering Department (UE)
188
Highway Design Senior Project 2010
Large Bus
axle1 axle2 axleEF1 Axle EF2 Total EF
LB (45) 3800 6200 0.032 0.291 0.323
LB (45) 4400 6600 0.062 0.385 0.447
LB (45) 3350 5400 0.018 0.156 0.174
LB (60) 6000 7450 0.251 0.664 0.915
LB (45) 3850 7050 0.034 0.518 0.552
LB (45) 4350 6000 0.059 0.251 0.310
LB (62) 7000 9150 0.502 1.674 2.176
LB (62) 5450 9600 0.163 2.078 2.240
LB (45) 4050 7450 0.043 0.664 0.707
LB(45) 3550 6750 0.024 0.426 0.449
Sum 8.292
Medium truck
axle1 axle2 axle3 axleEF1 axleEF2 Axle EF3 Total EF
MT 2850 5400 0.009 0.156 0.000 0.165
MT 1600 1350 0.001 0.000 0.000 0.001
MT 1700 1550 0.001 0.001 0.000 0.001
MT 2200 3300 0.003 0.017 0.000 0.020
MT 1500 1600 0.000 0.001 0.000 0.001
MT 2300 2500 0.003 0.005 0.000 0.008
MT 2450 2250 0.004 0.003 0.000 0.007
MT 2850 3700 0.009 0.028 0.000 0.037
MT 1800 1600 0.001 0.001 0.000 0.002
MT 1600 2700 0.001 0.007 0.000 0.008
Sum 0.250
ECSC, IUDS, Urban Engineering Department (UE)
189
Highway Design Senior Project 2010
Large truck
axle1 axle2 axle3 axle4 Axle EF1 Axle EF2
Axle EF3
Axle EF4
Total EF
LT 6450 15950 0.35 20.41 0.00 0.00 20.756
LT 4200 5250 0.05 0.14 0.00 0.00 0.188
LT 6050 14200 0.26 12.10 0.00 0.00 12.358
LT 5950 11800 0.24 5.26 0.00 0.00 5.500
LT 6250 14300 0.30 12.49 0.00 0.00 12.787
LT 8250 9900 9850 1.05 2.39 2.33 0.00 5.770
LT 8950 10700 10750 1.52 3.39 3.46 0.00 8.358
LT 4800 8950 0.09 1.52 0.00 0.00 1.607
LT 7000 13000 0.50 8.13 0.00 0.00 8.632
LT 5900 12600 0.23 7.06 0.00 0.00 7.297
Sum 83.253
ECSC, IUDS, Urban Engineering Department (UE)
190
Highway Design Senior Project 2010
Truck trailer
axle1 axle2 axle3 axle4 axle5 axle6axle EF1 axle EF2
axle EF3
axle EF4
axle EF5
axle EF6 totalEF
TT 6050 15250 11000 11400 0.26 16.68 3.83 4.50 0.00 0.00 25.27
TT 6300 15000 8350 9450 0.31 15.48 1.11 1.94 0.00 0.00 18.84
TT 6350 14600 7950 9150 0.32 13.71 0.89 1.67 0.00 0.00 16.60
TT 5900 14800 8750 9750 0.23 14.57 1.37 2.23 0.00 0.00 18.40
TT 5750 13200 8300 7100 0.21 8.71 1.08 0.53 0.00 0.00 10.53
TT 6150 11400 11600 11300 13100 0.28 4.50 4.87 4.33 8.42 0.00 22.40
TT 6950 15800 7750 9500 0.49 19.56 0.79 1.98 0.00 0.00 22.82
TT 2350 17000 8050 9200 0.00 27.19 0.94 1.72 0.00 0.00 29.85
TT 6850 13600 9150 9150 0.45 9.96 1.67 1.67 0.00 0.00 13.76
TT 6450 11000 11000 10800 10100 0.35 3.83 3.83 3.53 2.61 0.00 14.16
Sum 192.63
ECSC, IUDS, Urban Engineering Department (UE)
191
Highway Design Senior Project 2010
Traffic count for day 14,Small Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
SB (25) 2300 3450 0.003 0.021 0.024
SB (25) 2250 2500 0.003 0.005 0.008
SB (25) 2350 3700 0.004 0.028 0.032
SB (25) 2250 4400 0.003 0.062 0.065
SB (25) 2200 3950 0.003 0.038 0.041
SB (25) 1750 2800 0.001 0.008 0.009
SB (25) 2200 3250 0.003 0.016 0.019
SB (25) 2300 3500 0.003 0.022 0.026
SB (25) 2550 4300 0.005 0.056 0.061
SB (25) 2150 3550 0.002 0.024 0.026
Sum 0.311
Large Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
LB (45) 2100 5950 0.002 0.241 0.244
LB (45) 4150 7550 0.048 0.705 0.753
LB (62) 4600 7900 0.076 0.864 0.940
LB (62) 6600 9200 0.385 1.716 2.101
LB (62) 6600 9200 0.385 1.716 2.101
LB (62) 4000 6700 0.040 0.412 0.452
LB (45) 3900 5800 0.036 0.215 0.251
LB (45) 3400 6000 0.019 0.251 0.270
LB (62) 5300 8250 0.143 1.051 1.194
LB (45) 4200 7100 0.050 0.535 0.585
Sum 8.890
ECSC, IUDS, Urban Engineering Department (UE)
192
Highway Design Senior Project 2010
Medium truck
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
MT 1700 1850 0.001 0.001 0.002
MT 3650 3200 0.027 0.015 0.042
MT 3150 2250 0.014 0.003 0.017
MT 3250 3300 0.016 0.017 0.033
MT 2800 6650 0.008 0.398 0.406
MT 3250 2700 0.016 0.007 0.023
MT 1700 1150 0.001 0.000 0.001
MT 1850 1400 0.001 0.000 0.002
MT 2600 5950 0.006 0.241 0.247
MT 2750 5150 0.007 0.126 0.134
Sum 0.906
Large truck
Axle1 Axle2 Axle3 Axle4 Axle5Axle1 Ef
Axle2 EF
Axle3 EF
Axle4 EF
Axle5 EF
Total EF
LT 4350 7700 7650 0.06 0.77 0.75 0.00 0.00 1.58
LT 4800 8400 9850 11050 11250 0.09 1.14 2.33 3.91 4.24 11.72
LT 7750 10500 10950 0.79 3.11 3.76 0.00 0.00 7.66
LT 4100 2950 2900 0.05 0.01 0.01 0.00 0.00 0.06
LT 7600 11200 11300 0.73 4.16 4.33 0.00 0.00 9.21
LT 7000 12100 9050 0.50 5.89 1.59 0.00 0.00 7.98
LT 5200 5300 0.13 0.14 0.00 0.00 0.00 0.28
LT 4100 3800 0.05 0.03 0.00 0.00 0.00 0.08
LT 5750 15250 0.21 16.68 0.00 0.00 0.00 16.88
LT 3650 3550 0.03 0.02 0.00 0.00 0.00 0.05
Sum 55.50
ECSC, IUDS, Urban Engineering Department (UE)
193
Highway Design Senior Project 2010
Truck trailer
Axle1 Axle2 Axle3 Axle4 Axle5 Axle6Axle1 Ef
Axle2 EF
Axle3 EF
Axle4 EF
Axle5 EF
Axle6 EF
Total EF
TT 4100 4550 2700 2550 0.05 0.07 0.01 0.01 0.00 0.00 0.13
TT 5350 10850 11050 8900 9250 0.15 3.60 3.91 1.48 1.76 0.00 10.90
TT 7800 12950 10050 8150 9400 0.82 7.99 2.55 0.99 1.89 0.00 14.25
TT 6050 14600 9250 9100 0.26 13.71 1.76 1.63 0.00 0.00 17.36
TT 8450 11600 11650 11000 7200 7900 1.17 4.87 4.96 3.83 0.57 0.86 16.27
TT 6650 10950 11500 10500 13300 0.40 3.76 4.68 3.11 9.01 0.00 20.96
TT 6500 15000 8300 8700 0.36 15.48 1.08 1.33 0.00 0.00 18.25
TT 5200 16300 10300 10600 0.13 22.50 2.85 3.25 0.00 0.00 28.73
TT 5200 16000 9700 11000 0.13 20.70 2.18 3.83 0.00 0.00 26.84
TT 7900 13100 9400 6500 0.86 8.42 1.89 0.36 0.00 0.00 11.53
Sum 165.22
Traffic count for day 15,Small Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
SB (25) 3450 5050 0.021 0.115 0.136
SB (25) 4000 4450 0.040 0.065 0.106
SB (25) 2150 3850 0.002 0.034 0.037
SB (25) 2400 3900 0.004 0.036 0.040
SB (25) 2200 4150 0.003 0.048 0.050
SB (25) 2200 4150 0.003 0.048 0.050
SB (25) 2450 4050 0.004 0.043 0.047
SB (25) 2550 4050 0.005 0.043 0.048
SB (25) 2050 2650 0.002 0.006 0.008
SB (25) 2300 2900 0.003 0.010 0.013
ECSC, IUDS, Urban Engineering Department (UE)
194
Highway Design Senior Project 2010
Sum 0.536
Large Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
LB(45) 4400 7100 0.062 0.535 0.597
LB(24) 2300 3350 0.003 0.018 0.022
LB(45) 3600 6850 0.025 0.455 0.480
LB (45) 3750 5100 0.030 0.121 0.151
LB (45) 4250 7200 0.053 0.569 0.622
LB (45) 3600 4250 0.025 0.053 0.078
LB (45) 3900 5600 0.036 0.184 0.220
LB (45) 3650 5150 0.027 0.126 0.153
LB (45) 6050 7400 0.260 0.644 0.904
LB (45) 3950 7350 0.038 0.625 0.663
3.890
Medium truck
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
MT 2800 2050 0.008 0.002 0.010
MT 2150 3700 0.002 0.028 0.031
MT 2150 3400 0.002 0.019 0.022
MT 1900 2150 0.001 0.002 0.004
MT 2800 2050 0.008 0.002 0.010
MT 1850 2400 0.001 0.004 0.005
MT 1750 1700 0.001 0.001 0.002
MT 2250 1850 0.003 0.001 0.004
MT 1600 1200 0.001 0.000 0.001
MT 1750 1450 0.001 0.000 0.001
0.0907
ECSC, IUDS, Urban Engineering Department (UE)
195
Highway Design Senior Project 2010
Large truck
Axle1 Axle2 Axle3 Axle4 Axle5 Axle6Axle1 Ef
Axle2 EF
Axle3 EF
Axle4 EF
Axle5 EF
Axle6 EF
Total EF
LT 8000 11800 0.91 5.26 0.00 0.00 0.00 0.00 6.17
LT 4400 3800 0.06 0.03 0.00 0.00 0.00 0.00 0.09
LT 4900 3600 3650 0.10 0.03 0.03 0.00 0.00 0.00 0.15
LT 6200 12300 0.29 6.34 0.00 0.00 0.00 0.00 6.63
LT 8200 11800 11800 10950 6950 7750 1.02 5.26 5.26 3.76 0.49 0.79 16.57
LT 5950 15100 0.24 15.95 0.00 0.00 0.00 0.00 16.19
LT 4800 4750 0.09 0.09 0.00 0.00 0.00 0.00 0.18
LT 5250 5200 0.14 0.13 0.00 0.00 0.00 0.00 0.27
LT 5500 3700 3500 3000 2100 0.17 0.03 0.02 0.01 0.00 0.00 0.23
LT 4350 4900 0.06 0.10 0.00 0.00 0.00 0.00 0.16
Sum 46.66
ECSC, IUDS, Urban Engineering Department (UE)
196
Highway Design Senior Project 2010
Truck trailer
ECSC, IUDS, Urban Engineering Department (UE)
Axle1 Axle2 Axle3 Axle4 Axle5 Axle6
Axle1
Ef
Axle2
EF
Axle3
EF
Axle4
EF
Axle5
EF
Axle6
EF
Total
EF
TT 5800 4200 2450 2600 2350 1400 0.22 0.05 0.00 0.01 0.004 0.0004 0.28
TT 6300 14500 8400 8650 0.31 13.29 1.14 1.30 0.00 0.00 16.04
TT 8250 16300 11200 9300 1.05 22.50 4.16 1.80 0.00 0.00 29.51
TT 4150 4850 3100 3100 0.05 0.10 0.01 0.01 0.00 0.00 0.17
TT 3750 5250 3100 3150 0.03 0.14 0.01 0.01 0.00 0.00 0.19
TT 6900 10300 7900 6600 0.47 2.85 0.86 0.38 0.00 0.00 4.57
TT 7900 11950 11900 11300 8050 7850 0.86 5.57 5.46 4.33 0.94 0.84 18.00
TT 4050 5100 2950 3050 0.04 0.12 0.01 0.01 0.00 0.00 0.19
TT 5650 15900 9400 10500 0.19 20.12 1.89 3.11 0.00 0.00 25.31
TT 5350 15400 8400 11300 0.15 17.43 1.14 4.33 0.00 0.00 23.04
117.3
197
Highway Design Senior Project 2010
ECSC, IUDS, Urban Engineering Department (UE)
198
Highway Design Senior Project 2010
Traffic count for day 16
Small Bus
Axle1 Axle2 Axle3 Axle1 Ef Axle2 EF Axle3 EF Total EF
SB (25) 1600 2850 0.001 0.009 0.000 0.009
SB (25) 2300 3300 0.003 0.017 0.000 0.020
SB (25) 2250 4250 0.003 0.053 0.000 0.056
SB (25) 2100 3950 0.002 0.038 0.000 0.040
SB (25) 2300 3250 0.003 0.016 0.000 0.019
SB (25) 2250 4050 0.003 0.043 0.000 0.046
SB (25) 2200 4150 0.003 0.048 0.000 0.050
SB (25) 4000 5700 0.040 0.199 0.000 0.239
SB (25) 2450 3550 0.004 0.024 0.000 0.028
SB (25) 1950 3750 0.002 0.030 0.000 0.032
Sum 0.541
ECSC, IUDS, Urban Engineering Department (UE)
199
Highway Design Senior Project 2010
Large Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
LB (45) 3850 6400 0.034 0.335 0.369
LB (45) 4150 6400 0.048 0.335 0.383
LB (45) 3900 6900 0.036 0.470 0.506
LB (62) 6100 7650 0.270 0.748 1.018
LB (45) 3750 7450 0.030 0.664 0.694
LB (62) 4850 9950 0.096 2.441 2.537
LB (45) 5500 10550 0.169 3.177 3.347
LB (45) 3500 6350 0.022 0.324 0.346
LB (45) 4300 6500 0.056 0.359 0.415
LB (45) 2850 6700 0.009 0.412 0.421
10.036
Medium truck
Axle1 Axle2 Axle3 Axle4 Axle5Axle1 Ef
Axle2 EF Axle3 EF
Axle4 EF
Axle5 EF Total EF
MT 1850 1600 0.001 0.001 0.000 0.000 0.000 0.002
MT 2750 5550 0.007 0.176 0.000 0.000 0.000 0.184
MT 1950 2300 0.002 0.003 0.000 0.000 0.000 0.005
MT 4600 10200 3800 3300 3450 0.076 2.730 0.032 0.017 0.021 2.875
MT 2200 3550 0.003 0.024 0.000 0.000 0.000 0.026
MT 4450 6800 0.065 0.440 0.000 0.000 0.000 0.506
MT 3000 4500 0.011 0.069 0.000 0.000 0.000 0.080
MT 1850 5150 2800 0.001 0.126 0.008 0.000 0.000 0.135
MT 2550 4000 0.005 0.040 0.000 0.000 0.000 0.046
MT 2250 1850 0.003 0.001 0.000 0.000 0.000 0.004
3.863
ECSC, IUDS, Urban Engineering Department (UE)
200
Highway Design Senior Project 2010
Large truck
Axle1 Axle2 Axle3 Axle1 Ef Axle2 EF Axle3 EF Total EF
LT 4150 5250 0.048 0.137 0.000 0.185
LT 7300 10850 10800 0.606 3.604 3.530 7.740
LT 6000 13600 0.251 9.961 0.000 10.212
LT 7700 16300 0.770 22.503 0.000 23.273
LT 4350 4250 0.059 0.053 0.000 0.112
LT 4350 4300 0.059 0.056 0.000 0.115
LT 5950 7600 7600 0.241 0.726 0.726 1.694
LT 4400 4600 0.062 0.076 0.000 0.138
LT 7800 11750 0.816 5.159 0.000 5.975
LT 4850 6150 0.096 0.280 0.000 0.376
49.821
Truck trailer
Axle1 Axle2 Axle3 Axle4 Axle5 Axle6Axle1 EF
Axle2 EF
Axle3 EF
Axle4 EF
Axle5 EF
Axle6 EF
Total EF
TT 5150 3450 3700 3500 3650 0.13 0.02 0.03 0.02 0.03 0.00 0.22
TT 5950 13550 9550 8800 0.24 9.80 2.03 1.40 0.00 0.00 13.47
TT 7650 11900 11900 11400 7000 8200 0.75 5.46 5.46 4.50 0.50 1.02 17.70
TT 7850 15000 9850 9950 0.84 15.48 2.33 2.44 0.00 0.00 21.10
TT 7500 11900 11800 11200 6600 8550 0.68 5.46 5.26 4.16 0.38 1.23 17.18
TT 5550 13250 9600 11500 0.18 8.86 2.08 4.68 0.00 0.00 15.80
TT 5300 15800 9400 10300 0.14 19.56 1.89 2.85 0.00 0.00 24.44
TT 5850 14700 8850 9350 0.22 14.14 1.44 1.85 0.00 0.00 17.65
TT 5300 4350 3100 3300 0.14 0.06 0.01 0.02 0.00 0.00 0.23
TT 6200 14800 7950 9250 0.29 14.57 0.89 1.76 0.00 0.00 17.51
ECSC, IUDS, Urban Engineering Department (UE)
201
Highway Design Senior Project 2010
145.30
Traffic count for day 17 ; Small Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
SB (25) 2250 3800 0.003 0.032 0.035
SB (25) 2500 4800 0.005 0.092 0.097
SB (25) 2550 4150 0.005 0.048 0.053
SB (25) 2550 4400 0.005 0.062 0.067
SB (25) 2200 4100 0.003 0.045 0.048
SB (25) 2600 3750 0.006 0.030 0.036
SB (25) 2250 4250 0.003 0.053 0.056
SB (25) 1500 2750 0.000 0.007 0.008
SB (25) 2450 3600 0.004 0.025 0.030
SB (25) 2250 2700 0.003 0.007 0.010
0.440
Large Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
LB (45) 2350 3550 0.0037 0.0236 0.0273
LB (45) 4050 6700 0.0428 0.4118 0.4546
LB (60) 4250 7550 0.0531 0.7049 0.7581
LB (45) 3800 4800 0.0321 0.0918 0.1239
LB (45) 3850 7400 0.0340 0.6441 0.6781
LB (62) 5750 10000 0.2070 2.4969 2.7038
LB (45) 3650 7400 0.0268 0.6441 0.6708
LB (45) 3850 5700 0.0340 0.1990 0.2330
LB (45) 4400 6900 0.0621 0.4701 0.5322
LB (62) 7250 9650 0.5874 2.1270 2.7144
8.8963
ECSC, IUDS, Urban Engineering Department (UE)
202
Highway Design Senior Project 2010
Medium truck
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
MT 2750 9600 0.007 2.078 2.085
MT 2250 1800 0.003 0.001 0.004
MT 2200 1850 0.003 0.001 0.004
MT 2650 3700 0.006 0.028 0.035
MT 2550 4700 0.005 0.084 0.089
MT 2700 2100 0.007 0.002 0.009
MT 3650 9700 0.027 2.177 2.204
MT 3900 8850 0.036 1.441 1.477
MT 3400 4700 0.019 0.084 0.103
MT 2100 2350 0.002 0.004 0.006
6.016
Large truck
Axle1 Axle2 Axle3 Axle1 Ef Axle2 EF Axle3 EF Total EF
LT 2650 2050 0.006 0.002 0.000 0.008
LT 6400 14350 0.335 12.683 0.000 13.018
LT 5800 17050 0.215 27.552 0.000 27.767
LT 6200 15750 0.291 19.282 0.000 19.573
LT 5600 3450 3550 0.184 0.021 0.024 0.228
LT 6150 14400 0.280 12.883 0.000 13.163
LT 7000 8350 9150 0.502 1.109 1.674 3.285
LT 7450 12500 12350 0.664 6.815 6.455 13.934
ECSC, IUDS, Urban Engineering Department (UE)
203
Highway Design Senior Project 2010
LT 5600 4700 0.184 0.084 0.000 0.267
LT 4900 4250 0.101 0.053 0.000 0.154
Sum 91.3984
Truck trailer
Axle1 Axle2 Axle3 Axle4 Axle5Axle1 Ef
Axle2 EF Axle3 EF
Axle4 EF
Axle5 EF
Total EF
TT 4050 4650 2650 2650 0.04 0.08 0.01 0.01 0.00 0.14
TT 5150 3650 3750 3250 3400 0.13 0.03 0.03 0.02 0.02 0.22
TT 8750 14400 10100 11000 1.37 12.88 2.61 3.83 0.00 20.70
TT 6550 14050 8800 9400 0.37 11.53 1.40 1.89 0.00 15.20
TT 4500 4350 2350 2450 0.07 0.06 0.00 0.00 0.00 0.14
TT 6150 15400 8000 8900 0.28 17.43 0.91 1.48 0.00 20.10
TT 6600 13750 8550 9400 0.38 10.47 1.23 1.89 0.00 13.97
TT 6950 12300 11700 11800 11400 0.49 6.34 5.06 5.26 4.50 21.65
TT 6850 12350 11800 10450 10700 0.45 6.45 5.26 3.04 3.39 18.60
TT 7700 16200 10500 13300 0.77 21.89 3.11 9.01 0.00 34.78
145.48
Traffic count for day 18; Small Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
SB (25) 2150 4250 0.002 0.053 0.056
SB (25) 2450 4000 0.004 0.040 0.045
SB (25) 2250 4050 0.003 0.043 0.046
SB (25) 2150 3500 0.002 0.022 0.025
SB (25) 3350 6000 0.018 0.251 0.269
SB (25) 2050 3900 0.002 0.036 0.038
SB (25) 3350 5450 0.018 0.163 0.181
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Highway Design Senior Project 2010
SB (25) 2200 3900 0.003 0.036 0.039
SB (25) 1500 2750 0.000 0.007 0.008
SB (25) 2400 4000 0.004 0.040 0.044
Sum 0.750
Large Bus
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
LB (62) 6000 7450 0.251 0.664 0.915
LB (45) 4350 6450 0.059 0.347 0.406
LB (45) 3850 5900 0.034 0.232 0.266
LB (45) 4000 7650 0.040 0.748 0.788
LB (45) 4050 6150 0.043 0.280 0.323
LB (62) 5850 5800 0.224 0.215 0.439
LB (45) 5750 10750 0.207 3.457 3.664
LB (45) 5000 9450 0.110 1.936 2.046
LB (45 5150 8350 0.126 1.109 1.235
LB (62) 3800 7700 0.032 0.770 0.802
Sum 10.885
Medium truck
Axle1 Axle2 Axle1 Ef Axle2 EF Total EF
MT 1300 1350 0.0003 0.0003 0.001
MT 2500 4800 0.0049 0.0918 0.097
MT 1850 1750 0.0013 0.0010 0.002
MT 1850 1850 0.0013 0.0013 0.003
MT 2400 1650 0.0041 0.0008 0.005
MT 2300 3150 0.0034 0.0138 0.017
MT 2400 2450 0.0041 0.0045 0.009
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Highway Design Senior Project 2010
MT 1950 1350 0.0016 0.0003 0.002
MT 2350 3250 0.0037 0.0159 0.020
MT 1750 1400 0.0010 0.0004 0.001
Sum 0.155
Large truck
Axle1 Axle2 Axle3 Axle1 Ef Axle2 EF Axle3 EF Total EF
LT 6450 14500 0.347 13.291 0.000 13.638
LT 7300 13300 0.606 9.010 0.000 9.616
LT 5000 8700 8700 0.110 1.334 1.334 2.779
LT 3300 2900 0.017 0.010 0.000 0.027
LT 4350 4280 0.059 0.055 0.000 0.114
LT 6300 14600 0.312 13.708 0.000 14.020
LT 6700 1000 10500 0.412 0.000 3.110 3.522
LT 7850 12000 0.840 5.672 0.000 6.512
LT 7200 11700 0.569 5.061 0.000 5.630
LT 4350 8550 8550 0.059 1.234 1.234 2.527
Sum 58.384
Truck trailer (TT)
Axle1 Axle2 Axle3 Axle4 Axle5 Axle6Axle1 Ef
Axle2 EF
Axle3 EF
Axle4 EF
Axle5 EF
Axle6 EF
Total EF
TT 7450 14550 9400 9150 0.66 13.50 1.89 1.67 0.00 0.00 17.73
TT 4150 4250 2200 2200 0.05 0.05 0.00 0.00 0.00 0.00 0.11
TT 4050 4050 2950 3200 2800 3450 0.04 0.04 0.01 0.01 0.01 0.02 0.14
TT 7200 13300 9100 9850 0.57 9.01 1.63 2.33 0.00 0.00 13.55
TT 4150 4800 2800 2950 0.05 0.09 0.01 0.01 0.00 0.00 0.16
ECSC, IUDS, Urban Engineering Department (UE)
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Highway Design Senior Project 2010
TT 7600 13200 8600 8550 0.73 8.71 1.27 1.23 0.00 0.00 11.94
TT 6350 16200 10800 10800 0.32 21.89 3.53 3.53 0.00 0.00 29.27
TT 4250 4250 2300 2250 0.05 0.05 0.00 0.00 0.00 0.00 0.11
TT 5550 15050 10300 10800 0.18 15.71 2.85 3.53 0.00 0.00 22.27
TT 4600 10750 10650 11800 11700 0.08 3.46 3.31 5.26 5.06 0.00 17.17
Sum 112.44
Part –II
Drawings
ECSC, IUDS, Urban Engineering Department (UE)
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