Highway II practical

Highway Engineering (II) Practical Mandeep Pokhrel (06-116)

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Experiment No: 1

CALIFORNAI BEARING RATIO (CBR) TEST

Objective:

To determine the CBR value of the given sample in Lab.

Introduction

The CBR is a penetration test developed by the California Division of Highways as a

method for evaluating the stability of sub grade and other flexible pavement materials.

The test is empirical and results cannot be related accurately with any fundamental

property of a material.

The CBR is a measure of shearing resistance of the material under the controlled density

and moisture conditions.

Briefly the test consists of a cylindrical plunger, 50 mm diameter to penetrate the

pavement component material at 1.25 mm/minute. The loads for 2.5mm and 5mm are

recorded. The load is expressed as a percentage of standard load value at respective

deformation level to obtain CBR value.

Apparatus Required:

i) Loading Machine

ii) Cylindrical moulds

iii) Compaction Hammer

iv) Adjustable stem, perforated plate and dial gauge

v) Annular weight

vi) Filter Paper, Sieves, oven, balance

Procedure:

1) The optimum moisture of the soil under consideration was determined by using

modified proctor compaction test. Also the maximum dry density was determined

from the graph along with optimum moisture content.

2) About 5kg of oven dry sample was taken and sieved through 20 mm sieve. The

sample was mixed with the optimum moisture content. This sample was

compacted by Modified Protector test. The soil sample was placed in the mould in

5 layers and each layer was compacted by 4.89 kg hammer by applying 56 blows.

Soil sample was collected for determination of moisture content.

3) The collar was removed and excess soil trimmed of the sample was inverted, filter

papers were placed on the upper and lower sides.

4) A surcharge with annular hole at center was placed over the sample. Each

surcharge weight was about 5kg altogether.

5) The sample was then placed in a water tank for determining the expansion due to

water. The dial gauge was placed properly in its position and the initial reading of

dial gauge was noted.


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6) After allowing the soil sample to soak and swell for 4 days the final dial gauge

reading was noted.

7) The sample was allowed to stand vertical position for 15 minutes to drain of the

excess water. The sample along with the mould was weight and noted in order to

calculate the water absorbed.

8) The surcharge weight was again molded and the assembly with the base plate was

placed in compression machine.

9) The plunger was brought in contact with the top surface of sample. A seating load

of 4 kg was applied. The dial gauge for measuring the penetration was set to zero.

10) The load was applied smoothly at the rate of 1.25 mm/min.

11) The loads regarding were recorded for penetration of

25,50,75,100,125,175,200,300, 400, 500,600 and 700 and so on the division of

dial gauge.

12) The load was released and mould was removed from loading machine. A soil

sample from the top 3 cm collected and weight for moisture content

determination.

Observation and calculation:

Mould used:

Diameter of mould=150 mm

Height of mould =127 mm

Weight of mould =8.228 kg

Optimum moisture content(OMC):

The OMC of the soil sample was taken as 20%. (As the determination of OMC of soil

sample was already studied in Soil Mechanics, so it is not determined again due to time

constraint.)

CBR Value:

Penetration(mm) Load (Kg)

0.00 0.00

0.5 4.00

1.00 14.00

1.5 30.00

2.00 41.00

2.50 50

3.00 58

4.00 70

5.00 77.5

10.00 102.50

12.5 110.8


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CBR(%) = × 100

CBR2.5 mm = x 100 = 4.23%

CBR5 mm = x 100 = 3.89%

Conclusion:

Normally, CBR value at 2.5 mm penetration should be higher than at 5 mm penetration

and the higher value is taken as CBR value of soil. Hence, the CBR value of the given

soil sample was found to be 4.23%.

0

10

20

30

40

50

60

70

80

90

100

110

120

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Load

(kg)

-->

Penetration (mm)-->

LOAD-PENETRATION CURVE

Penetration(mm) Standard load(kg) Corrected observed load(kg)

2.5 1370 58

5.0 2055 80


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The initial concavity of Load-Penetration curve may be due to:

the bottom surface of the plunger or top surface of soil not being truly horizontal,

which results in impartial contact between plunger bottom surface & top surface

of specimen initially.

the top layer of specimen being too soft or irregular.

Engineering Application:

CBR test gives arbitrary strength of subgrade soil. The CBR test values obtained are used

empirically to design flexible pavement(thickness of the pavement is determined using

design charts based on CBR value) .


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Experiment No: 2

MEASUREMENT AND ANALYSIS OF SPOT SPEED

Objective:

To perform the spot speed studies to obtain the design speed, maximum safe speed,

minimum allowable speed and model speed.

Apparatus:

i) Stop watch.

ii) Measuring tape.

iii) Chalk.

Introduction:

Spot speed can be defined as the instantaneous speed of a vehicle at a specified location.

The spot speed is obtained by finding the running speed of the vehicle over a short

distance (50m) depending on the approximate speed at that location. Spot speed can be

presented by average speed, cumulative speed and model speed.

The spot speed is affected by physical features- pavement width, curves, gradients,

pavement conditions, design intersections as well as road side developments. In the

environment factors visibility, weather, traffic condition and motive of travel affects the

spot speed.

Principle:

Spot speed is instantaneous speed of the vehicle at a specified location.

98th percentile speed : The speed below which 98 % of all the vehicle travel is

used to design speed in geometric design. Sometimes 95th

percentile speed is used

for this purpose.

85th percentile speed : The speed below which 85 % of all the vehicle travel, is

used for determining the speed limits for traffic regulation. It is taken as limit of

safe speed in the road.

15th percentile speed : The speed below which 15 % of all the vehicle travel is

used to determine the lower speed limits on major highway facilities such as

Expressway. Vehicles travelling below this speed may cause hazards.

Spot speed can be measured by long base period method, recommended base

lengths are measured as follows :


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Average Speed of Traffic Stream (Km/h) Base Length (m)

<40 27

40-65 54

>65 81

Procedure :

1) A 50m stretch of road was selected, which was marked in the kerb by chalk.

2) One observer was stationed at the beginning of 50m and the other at the end.

3) When the vehicle just reached the initial marking a hand signal was given to the

second observer by the first observer. On the basis of signal, second observer

would start the stop watch and stopped it as the vehicle crossed the end mark.

4) The process was repeated for 100 observations.

5) Speed of each vehicle was calculated and frequency table was prepared for the

presentation of spot speed data.

Observation:

Location:Guheswori Fuel Pump Date:21-07-2010 Performed by:

Madhyapur,Thimi. Time:02:30 P.M. Anil Aryal(06-104)

Road: Araniko Highway. Weather:Cloudy. Dipak B.T.Chhetri(06-109)

Mandeep Pokhrel(06-116)

Rajesh Chaudhary(06-127)

Ramesh C. Ghimire(06-128)

Umesh K.C.(06-146)

Binaya Shakya(06-148)

S.N. TYPE OF VEHICLE

TIME (S) SPEED

(m/s) (km/h)

1 BUS 4.4 11.364 40.909

2 BUS 4.8 10.417 37.500

3 BUS 4.3 11.628 41.860

4 BUS 3.1 16.129 58.065

5 BUS 3.7 13.514 48.649

6 BUS 3.7 13.514 48.649

7 BUS 3.6 13.889 50.000

8 BUS 3.1 16.129 58.065


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9 BUS 3.8 13.158 47.368

10 BUS 3.6 13.889 50.000

11 BUS 4.1 12.195 43.902

12 BUS 5.7 8.772 31.579

13 BUS 5.6 8.929 32.143

14 BUS 3.9 12.821 46.154

15 BUS 8.3 6.024 21.687

16 BUS 5.2 9.615 34.615

17 MINI BUS 3.6 13.889 50.000

18 MINI BUS 5.4 9.259 33.333

19 MINI BUS 4.5 11.111 40.000

20 MINI BUS 4.8 10.417 37.500

21 MINI BUS 5.9 8.475 30.508

22 MINI BUS 5.5 9.091 32.727

23 MINI BUS 7.3 6.849 24.658

24 MINI BUS 5.8 8.621 31.034

25 MINI BUS 3.4 14.706 52.941

26 MINI BUS 3.9 12.821 46.154

27 MINI BUS 4.4 11.364 40.909

28 MINI BUS 4.2 11.905 42.857

29 MINI BUS 4.2 11.905 42.857

30 MINI BUS 4 12.500 45.000

31 MINI BUS 6.2 8.065 29.032

32 MINI BUS 5.6 8.929 32.143

33 MINI BUS 5.9 8.475 30.508

34 MINI BUS 6.4 7.813 28.125

35 MINI BUS 7.1 7.042 25.352

36 MINI BUS 5.1 9.804 35.294

37 MINI BUS 5.6 8.929 32.143

38 MINI BUS 8.5 5.882 21.176

39 MINI BUS 7.2 6.944 25.000

40 MINI BUS 5.2 9.615 34.615

41 MINI BUS 4.4 11.364 40.909

42 MINI BUS 5.4 9.259 33.333

43 MINI BUS 4.5 11.111 40.000

44 MINI BUS 4.8 10.417 37.500

45 MINI BUS 4 12.500 45.000

46 TRUCK 4.1 12.195 43.902

47 TRUCK 6.5 7.692 27.692

48 TRUCK 3.5 14.286 51.429

49 TRUCK 4.5 11.111 40.000


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50 MINI TRUCK 4.5 11.111 40.000

51 MINI TRUCK 4.8 10.417 37.500

52 MINI TRUCK 3.1 16.129 58.065

53 MINI TRUCK 4.5 11.111 40.000

54 MINI TRUCK 4.7 10.638 38.298

55 MINI TRUCK 4.1 12.195 43.902

56 MINI TRUCK 5.1 9.804 35.294

57 MINI TRUCK 6.1 8.197 29.508

58 MINI TRUCK 3.6 13.889 50.000

59 MINI TRUCK 4.7 10.638 38.298

60 MINI TRUCK 3.9 12.821 46.154

61 MINI TRUCK 4.1 12.195 43.902

62 MINI TRUCK 4.4 11.364 40.909

63 TRIPPER 5.4 9.259 33.333

64 TRIPPER 2.8 17.857 64.286

65 TRIPPER 5.1 9.804 35.294

66 TRIPPER 6.1 8.197 29.508

67 TRIPPER 4.7 10.638 38.298

68 TRIPPER 6.9 7.246 26.087

69 TRIPPER 3.3 15.152 54.545

70 TRIPPER 6.9 7.246 26.087

71 TRIPPER 4.6 10.870 39.130

72 PICK UP 3.4 14.706 52.941

73 PICK UP 4 12.500 45.000

74 PICK UP 5.2 9.615 34.615

75 PICK UP 5.3 9.434 33.962

76 PICK UP 4.8 10.417 37.500

77 PICK UP 3.6 13.889 50.000

78 PICK UP 4.8 10.417 37.500

79 PICK UP 4.7 10.638 38.298

80 PICK UP 4.2 11.905 42.857

81 CAR 3.5 14.286 51.429

82 CAR 3.8 13.158 47.368

83 CAR 3.6 13.889 50.000

84 CAR 4.3 11.628 41.860

85 CAR 4.9 10.204 36.735

86 CAR 5 10.000 36.000

87 CAR 5.6 8.929 32.143

88 CAR 5.1 9.804 35.294

89 CAR 5.6 8.929 32.143

90 CAR 3.9 12.821 46.154


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91 CAR 5.6 8.929 32.143

92 CAR 3.4 14.706 52.941

93 CAR 3.7 13.514 48.649

94 CAR 3.6 13.889 50.000

95 PAJERO 6.8 7.353 26.471

96 PAJERO 2.8 17.857 64.286

97 PAJERO 4.8 10.417 37.500

98 PAJERO 7.1 7.042 25.352

99 AMBULANCE 3.3 15.152 54.545

100 MICROBUS 4.3 11.628 41.860

SPEED MEAN FREQUENCY CUMULATIVE CUMULATIVE

RANGE SPEED FREQUENCY FREQUENCY(%)

20-25 22.5 4 4 4

25-30 27.5 10 14 14

30-35 32.5 18 32 32

35-40 37.5 23 55 55

40-45 42.5 17 72 72

45-50 47.5 16 88 88

50-55 52.5 7 95 95

55-60 57.5 3 98 98

60-65 62.5 2 100 100

0

10

20

30

40

50

60

70

80

90

100

20 25 30 35 40 45 50 55 60 65

Cu

mu

lati

ve F

req

uen

cy(%

) -->

Speed(km/h) -->

CUMULATIVE SPEED DISTRIBUTION CURVE


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Calculation:

a) From frequency distribution curve, modal speed corresponding to maximum

frequency is 37.5km/h.

b) From cumulative speed distribution curve,

a) Lower speed limit for regulation (15th percentile speed) = 28km/h.

b) Upper speed limit for regulation (85th percentile speed) = 46.5km/h.

c) Speed for geometric design purpose(98th

percentile speed) = 56.8km/h

c) Mean speed = = = 39.987km/h.

d) Standard deviation = = 9.358 km/h.

e) Coefficient of variance = 100% = 100% = 23.40%.

Conclusion:

From the experiment, it can be concluded that the lower limit of speed of vehicles

travelling in Araniko highway in Madhyapur Thimi section is 28 km/h and higher limit is

46.5 km/h. In other words, if the vehicles travel with speed less than 28km/h than it

causes traffic congestion and safe speed limit at this section of road is of 46.5 km/h.

Similarly, the geometric design speed for the road can be taken as 56.8 km/h and largest

proportion of vehicle ply at speed of 37.5km/h at this road.

Engineering Application:

This test is helps us to know the traffic load intensity on road. It also helps to obtain

design speed and speed variation of vehicles plying on a road which is to be extended or

reconstructed.

0

5

10

15

20

25

20 30 40 50 60

No

. o

f ve

hic

les(

fre

qu

en

cy)-

->

Speed(km/h)-->

FREQUENCY DISTRIBUTION CURVE OF SPOT SPEEDS


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Experiment No: 3

MEASUREMENT OF DEFLECTION OF PAVEMENT SURFACE

Objective:

i) To determine the use of the Benkelman beam to measure the pavement deflection

under a heavily loaded truck.

ii) Evaluation of structural performance of flexible pavement.

iii) To measure the elastic deformation of pavement under the wheel load.

Apparatus:

i) Benkelman Beam.

ii) Markers.

iii) Test Vehicle (heavily loaded truck).

Theory:

The pavement section, which have been subjected to traffic, deform elastically under a

load. The elastic deflection depend upon various factors.

The Benkelman beam is a handy instrument which is most widely used for measuring the

deflection of pavements. The instrument consists of lever 3.6m long pivoted 2.44 m from

the end carrying the contact point which rests on the surface of the pavement. The

deflection of the pavement surface produced by the test load is transmitted to the other

end of the beam where it is measured by a dial gauge or recorder. The movement at the

dial gauge end of the beam is one half of that of at the contact point end. The load on the

dual wheel can be the range 2.7 to 4.1 tons.

The beam is pivoted at 1/3rd its way and is carried by a frame which is supported on 3

adjustable legs. A dial gauge is mounted on frame in such a way that it measures

movement of the beam resting on the road surface.

Procedure :

1) 10 points(minimum) along the outer wheel path (60 cm from the pavement edge

for narrower pavements & 90 cm from pavement edge for pavement having width

more than 3.5 m) for each lane were selected for observation.

2) The rear wheel of the vehicle was brought near the marked points and the probe

of the beam was inserted between the dual wheels so that the top rests on the road

where the deflection was measured. The dual wheels were centered over the

marked point.

3) The standard wheel load of 4085 kg is used for the test. The tire pressure being

5.6 kg/cm2.

4) The dial gauge reading was noted initially in the position described above.


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5) The truck was driven forward at a slow speed and dial gauge readings were taken

when the truck stopped at 2.7 m and 9 m from the measuring point, and when the

recovery(rebound) was equal to 0.025 mm per minute or less.

6) Pavement temperature was recorded at the interval of 1 hour & the tire pressure

was checked and adjusted if necessary at the interval of 3 hours during the study.

7) The final and intermediate dial reading are subtracted from the initial readings.

Discussion:

Two kinds of deflection measurement are possible:

a) Rebound deflection, which is the recoverable deflection or the elastic deflection.

In a well designed road, the deflection is entirely elastic and recoverable.

b) Residual deflection, which is the non-recoverable deflection. As a pavement ages,

it losses a portion of its elastic property and permanent deflection takes place.

The rebound deflection value D at any point is given by following two conditions:

If Di - Df ≤ 0.025 mm,D = 0.02(Do - Df) mm

If Di - Df ≥ 0.025 mm,D = 0.02(Do - Df) + 0.02K(Di - Df) mm

In the second case, correction for vertical movement of front leg is done.

The value of K is given by

K = (3d-2e)/f

Where,d=distance between bearing & rear leg.

e=distance between dial gauge & rear leg.

f= distance between front & rear leg.

The value of K of Benkelman beam available in Nepal is 2.91.

Conclusion:

Thus, the process to measure the rebound deflection of the flexible pavement surface was

comprehended. The beam gave the measures of the deflection on the pavement surface

due the axle load of vehicle(8170 kg). Two beams give the deflection of the wheels

simultaneously. The readings of the deflections were directly noted by the dial gauges.

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Highway II practical