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7/29/2019 Past Paper 20102011
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1
UNIVERSITY OF GLAMORGANPrifysgol Morgannwg
Examinations: MAIN ASSESSMENT SESSION 2010/11
Exam paper version number:
Module Code:CE2S24
Module Title:Geotechnics & Engineering Geology
Academic Registry Use:
Date and time
Duration: (multiples of 30 mins only)
3 hours
The following items are provided to Candidates:
Examination Books (inc 2 sheets of graph paper)2 sheets of tracing paper
Figures Q1A, Q1B, Q1C, Q2, Q3, Q5A and Q5BEquation sheets 8pages
Instructions to Candidates:YES NO
Calculators are permitted
English Dictionaries are permitted
English
Foreign Language Dictionaries are permittedThis examination paper is an OPEN book examination
If YES, please specify literature permitted: ___________________________________
Answer any FOUR questions
All questions carry equal marksThe mark allocation includes, where appropriate, an allowance for style,organization and clarity.Start on a new page for the solution of each question and any late additionalsolution to a question.
This paper contains a total of examination questions. over no. of pages
FOR EXAMINATIONS OFFICE USE ONLY
Module Leader Admin Check
Print Name: Dr Rod Robinson Melanie Gapper
Signature: Rod Robinson Mel GapperContact Number:
Continued
6
18
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QUESTION 1
a. Discuss the engineering requirements that would be considered necessary to enable
a shallow foundation to perform satisfactorily over its design life. 6 marks
b. A series of square pad foundations are required to carry individual column loads of
350kN as illustrated in Figure Q1A. The load on the foundation will be rapidly
applied.
Stating appropriate assumptions, use Figures Q1B and Q1C to:-,
i. establish the over-design factor for the foundation using the EC7 design
approach 1combination 2 (A2+M2+R1) and comment on its value and
ii. determine the new over-design factor if the load had an eccentricity of
0.15m along the breadth of the foundation and comment on the effect this
may have on the original design
13 marks
6 marks
Total marks for Question 1 25 marks
See Equation Sheet
please turn over
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QUESTION 2
a. Prove a relationship between the active coefficient if earth pressure, ka and theeffective angle of internal friction, ', for a granular soil. 8 marks
b. A cantilever sheet pile retaining wall is illustrated in Figure Q2. It is required as
part of the temporary works for the construction of deep foundations for a bridge
pier. The soil properties and a cross section of the wall are given in Figure Q2. The
uppermost surface is level with the top of the wall and will carry a surcharge of
10kN/m2. The water table is well below the base of the wall.
Stating appropriate assumptions determine the required length of the sheet pilewall.
12 marks
c. During the excavation the ground water was found to be 2m below the original
ground level. Discuss how this would affect the retaining wall design.
5 marks
Total marks for Question 2 25 marks
See Equation Sheets
Please turn over
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QUESTION 3
a. Explain the effect the development of a tension crack would have on the slope
stability analysis on a trial slip surface. 4 marks
b. The slope profile and relevant soil properties for a total stress analysis on a trial
circular slip are given in Figure Q3 and Table Q3.
Stating appropriate assumptions determine the factor of safety using the (Swedish)
method of slices for the trial slip surface,:-
i assuming that a tension crack does not form,
ii if a tension crack 1.25m in depth forms near the crest of the slope and
iii comment on the stability of the slope, if necessary suggest suitable
remedial measures.
12 marks
5 marks
4 marks
Note: Return Figure Q3 with your answer book
Total marks for Question 3 25 marks
See Equation Sheet
Soil Data:
= 20kN/m3
cu = 20kN/m2
u = 25
Table Q3
Please turn over
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QUESTION 4
An embankment consisting of 10m of fill is to be placed on 2m of gravel which
is underlain by 4m of clay resting on well jointed sandstone. The water table is at
the surface of the gravel.
Considering only the settlement of the clay layer determine:
a the ultimate oedometer settlement beneath the centre of the embankment. 6 marks
b the time from the start of construction to 90% of the ultimate oedometer
settlement of the clay if the construction period is 6 months.
6 marks
c the extra height on the embankment needed to create a surcharge in order to
halve the time taken to reach 90% of the settlement in part (a).
13 marks
Soil Data
fill (above and below the water table) = 18kN/m3
mv = 2.710-4m2/kN
cv = 0.7m2/year
Total Marks for Question 4 25 marks
See Equation Sheet
please turn over
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QUESTION 5
A sandstone quarry near Pontypridd is to be developed for road aggregate in a small
valley which runs east to west. The quarry can be developed on the side of thevalley that proves to be most suitable. The results of a site investigation revealed:
that overlying the rock is a 0.5m thick layer of glacial till.
the top 2m of the rock are of weathering Grade 2 and the remainder of
Grades 1 and 0 as shown in Eurocode 7.
the rock mass data indicated in Table Q5.
a Indicate the essential points of the Eurocode 7 rock weathering classification and
briefly explain why the weathering profile found in the site investigation is typical
of South Wales. 7 marks
b Using Figures Q5A and Q5B as appropriate, and the tracing paper provided, plot a
stereo net analysis of the data in Table Q5 and suggest a suitable plan for the quarry
with particular regard to the stability of the faces. Justify the decisions you have
made by reference to the structural analysis.
Return the tracing paper with your answer script.
18 marks
Dip (degrees) Bearing (degrees) (degrees)
Bedding planes 60 80 40Joint set 50 162 40
Table Q5
Total Marks for Question 5 25 marks
Return the tracing paper with your answer script
please turn over
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QUESTION 6
a. Explain, with sketches, why effective stress paths for soils tested in consolidated
undrained triaxial tests with pore pressure measurement curve to the left for
normally consolidated soils and to the right for over consolidated soils. 6 marks
b. A series of consolidated undrained triaxial tests with pore water pressure
measurements were carried out on four identical samples of normally consolidated
clay. All four samples were first consolidated at a confining pressure of 240kN/m2
and were then tested at the confining pressures shown in Table Q6.
i. Plot the modified total and effective stress failure envelopes and determine
the effective shear stress parameters.
ii. Sketch on the graph the total and effective stress paths for the four tests and
comment on them.
13 marks
6 marks
Confining pressure kN/m 40 60 120 240
Deviator stress at failure kN/m 88 100 130 188
Pore water pressure at failure kN/m -14 0 42 120
Results at failure for Consolidated Undrained Triaxial Tests
Table Q6
Total Marks for Question 6 25 marks
See Equation Sheet
End of Paper
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CE2S24 - Geotechnics & Engineering Geology
8
Soil Properties Foundation Properties
b = 18kN/m3.
sat = 20kN/m3.
c'= 0kN/m2
.'= 30.cu= 80kN/m
2.u= 0.
concrete = 24kN/m3.
UNIVERSITY OF GLAMORGANFaculty of Advanced Technology
Civil Engineering Scheme
Geotechnics & Engineering GeologyCE2S24
Figure Q1A
Scale: Not Required
0.5m
0.5m
B=1.25m
C
Axial LoadPermanent Load = 350kN
Pad FoundationWater Table
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Meyerhof Meyerhof Br Hansen Vesic EC7
Nc Nq N N N0 5.14 1.00 0.00 0.00 0.00
1 5.38 1.09 0.00 0.07 0.002 5.63 1.20 0.01 0.15 0.01
3 5.90 1.31 0.02 0.24 0.03
4 6.19 1.43 0.05 0.34 0.065 6.49 1.57 0.07 0.45 0.10
6 6.81 1.72 0.11 0.57 0.15
7 7.16 1.88 0.16 0.71 0.22
8 7.53 2.06 0.22 0.86 0.30
9 7.92 2.25 0.30 1.03 0.4010 8.34 2.47 0.39 1.22 0.52
11 8.80 2.71 0.50 1.44 0.66
12 9.28 2.97 0.63 1.69 0.84
13 9.81 3.26 0.78 1.97 1.05
14 10.37 3.59 0.97 2.29 1.29
15 10.98 3.94 1.18 2.65 1.58
16 11.63 4.34 1.43 3.06 1.9117 12.34 4.77 1.73 3.53 2.31
18 13.10 5.26 2.08 4.07 2.77
19 13.93 5.80 2.48 4.68 3.3020 14.83 6.40 2.95 5.39 3.93
21 15.81 7.07 3.50 6.20 4.66
22 16.88 7.82 4.13 7.13 5.51
23 18.05 8.66 4.88 8.20 6.50
24 19.32 9.60 5.75 9.44 7.66
25 20.72 10.66 6.76 10.88 9.01
26 22.25 11.85 7.94 12.54 10.59
27 23.94 13.20 9.32 14.47 12.43
28 25.80 14.72 10.94 16.72 14.59
29 27.86 16.44 12.84 19.34 17.12
30 30.14 18.40 15.07 22.40 20.09
31 32.67 20.63 17.69 25.99 23.59
32 35.49 23.18 20.79 30.21 27.72
33 38.64 26.09 24.44 35.19 32.59
34 42.16 29.44 28.77 41.06 38.37
35 46.12 33.30 33.92 48.03 45.23
36 50.59 37.75 40.05 56.31 53.40
37 55.63 42.92 47.38 66.19 63.18
38 61.35 48.93 56.17 78.02 74.90
39 67.87 55.96 66.76 92.25 89.01
40 75.31 64.20 79.54 109.41 106.05
41 83.86 73.90 95.05 130.21 126.74
42 93.71 85.37 113.96 155.54 151.94
43 105.11 99.01 137.10 186.53 182.80
44 118.37 115.31 165.58 224.63 220.7745 133.87 134.87 200.81 271.75 267.75
46 152.10 158.50 244.65 330.34 326.20
47 173.64 187.21 299.52 403.65 399.3648 199.26 222.30 368.67 496.00 491.56
49 229.92 265.50 456.40 613.14 608.5450 266.88 319.06 568.57 762.86 758.09
Bearing Capacity Factors for Strip Foundations
UNIVERSITY OF GLAMORGANFaculty of Advanced Technology
Civil Engineering Scheme
Geotechnics & Engineering GeologyCE2S24
Figure Q1B
Scale: Not Required
Date: May 2011
7/29/2019 Past Paper 20102011
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CE2S24 - Geotechnics & Engineering Geology
10
B=1.25m
C
Pad Foundation
UNIVERSITY OF GLAMORGAN
Faculty of Advanced TechnologyCivil Engineering Scheme
Geotechnics & Engineering Geology
CE2S24
Figure Q1C
Scale:
Not Required
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CE2S24 - Geotechnics & Engineering Geology
11
2.0
UNIVERSITY OF GLAMORGANFaculty of Advanced Technology
Civil Engineering Scheme
Geotechnics & Engineering GeologyCE2S24
Figure Q2 Date:
Drawing not to scale
4.0m
dSoil 2C = 0
= 35
sat = b = 20kN/m3.
Originalground level
Soil 2C = 0
= 35
sat = b = 21kN/m3
Soil 1C = 0
= 30
sat = b = 20kN/m3.
New excavatedground level
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Equatorial equal-area stereonet marked in 2 intervals
UNIVERSITY OF GLAMORGANPrifysgol Morgannwg
Faculty of Advanced Technology
Geotechnics andEngineering Geology
CE2S242010-2011
FIGURE Q5A
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Polar equal-area stereonet marked in 2 intervals
UNIVERSITY OF GLAMORGANPrifysgol Morgannwg
Faculty of Advanced Technology
Geotechnics andEngineering Geology
CE2S242010-2011
FIGURE Q5B
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15
EQUATION SHEET
Lateral Earth Pressures
a
ok
cz
2
Consolidation
i
iic
i
ioed C
e
H10log
1
r
si
S
mGe
oed v im H d = (Hi +Hf)/4
'
1
21 11
1 H
HH
e
eem
i
fi
v ii H
H
e
e
1
When Uv 60% : Tv =
4 100
2Uv %
When Uv 60% : Tv = 1.781 - 0.933 log10 (100 - Uv%)
Tv =C t
d
v
2Cv = k/(mv w)
Tv50 = 0.197 & Tv90 = 0.848
Continued.
sin1
sin1aK
aaaba qKKczKp 2
h
pv
R
PRslidingFOS
tan
MomentsDisturbing
MomentsResistinggoverturninFOS
B
e
B
Rp v
b
61
if
fi
c
eeC
1010 loglog
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EQUATION SHEET (CONTINUED)Slope Stability
360
2 rLa
sin
costan
W
WLcF
uau
Bearing Capacity
idsqiqdqsqcicdcscf FFFBNFFFDNFFFcNq 5.0
Depth & inclination factors
Assume all depth and inclination factors = 1 for shallow foundations.
Shape factors
Shape of base Fcs Fqs F sLong strip 1.0 1.0 1.0
Rectangle 1 + 0.2B/L 1 + 0.2B/L 1 - 0.4B/L
Square 1.3 1.2 0.8
Circle (diameter B) 1.3 1.2 0.6
Skempton's Nc values Meyerhofs correction for eccentric loading
Nc = 5(1 + B/5L)(1 + D/5B) B = B 2e
Piles
In claybucsuf AcNAcQ
In sand
)1(tan qbsf NAAKQ
FoSQ E n
WLgroup NSF n
ui f
Continued.
We
RcF
r
u
2
yPeW
rLcF
w
au
BLNccLBDQ cbu 2
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EQUATION SHEET (CONTINUED)
Eurocode 7 Bearing Capacity Equations
N = 2 (Nq 1) tan ' (for a rough base, such as a typical foundation)s
q= 1+ (B' / L') sin ' (for a rectangular foundation)
sq = 1 + sin ' (for a square or circular foundation)s = 1 0.3 (B' /L') (for a rectangular foundation)s = 0.7 (for a square or circular foundation)
1
1
q
cN
Nss (rectangular, square and circle foundation)
m
m
q
m
q
c
q
qc iicAV
Hi
N
iii
1
;cot
1;tan
1
WhereV = vertical load acting on foundationH = horizontal load (or component of inclined load) acting on foundationA' design effective area of foundation
L
B
L
B
mmB
1
2
when H acts in the direction of B';
B
L
B
L
mmL
1
2
when H acts in the direction of L'.
Stress Paths
Skemptons Equation 313 ABu
22
hvhv tands
= - u
103 K
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