GTE-2

1. Subject Code
CED1122 R12
VNR VIGNANA JYOTHI INSTITUTE OF ENGINEERING AND TECHNOLOGY
(AUTONOMOUS)
B.Tech. III Year II Semester Adv. Supplementary Examinations, June/July, 2015
GEOTECHNICAL ENGINEERING-II
(CE)
Time: 3Hours Max. Marks: 70M
PART-A
(Answer ALL Questions)
1. Answer in one sentence 5X1=5M
a) In a Standard Penetration Test, the number of blows for the first 15 cm penetration, second
15 cm penetration and the last 15 cm penetration is 9, 14 and 16 respectively. Find the
observed N-value.
b) Find the factor of safety of an infinite slope having a slope angle of 280
. The slope consists
of cohesionless soil with angle of internal friction of 310
.
c) When movement of a wall under the earth pressure from a sandy backfill was prevented,
the lateral earth pressure was half of the vertical pressure at a point. Find the angle of
internal friction of the backfill.
d) Name the IS code dealing with the permissible settlement.
e) As per Engineering News formula, what is the ratio of loss of energy in driving energy in
the case of drop hammer to that of steam hammer?
2. Answer the following in two sentence each 5X2= 10M
a) In a rock core drilling, the sum of lengths of rock pieces having length more than 100 mm is
750 mm. If the length of run is 1 m, find RQD.
b) A temporary trench with vertical sides is to be excavated in a purely cohesive soil with unit
weight of 19 kN/m3
and cohesion of 25 kPa. Determine the initial depth upto which the
trench can be excavated without any lateral support. Taylor’s stability number for this case
is equal to 0.261.
c) Say true or false and justify your answer: The greater the depth of tension cracks, the
greater is the cohesion of clayey soil
d) If the gross ultimate bearing capacity of a foundation is 300 kPa, the unit weight of the soil
is 20 kN/m3
and the depth of the foundation is 1.5 m, find the gross safe bearing capacity
adopting a factor of safety of 3.
e) Can you apply dynamic formulae to piles driven in loose saturated sand? Justify your
answer.
3. Answer the following in brief 5X3=15M
a) Enumerate the topics that must be included in a soil investigation report.
b) A 15-m high embankment is inclined at 300
to the horizontal. If angle of internal friction
and cohesion are respectively 150
and 15 kPa, find the factor of safety with respect to
cohesion. The unit weight of the soil is 17.5 kN/m3
. Assume the slope to be infinite.
c) State the assumptions made in Coulomb’s earth pressure theory.
d) Distinguish between immediate and consolidation settlement.
e) What is meant by ‘Negative skin friction’? What are the situations where this is developed?
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2. PART – B
Answer any FOUR Questions 4X10=40M
4. a) The inner diameters of sampling tube and that of cutting edge of a sampler are 70 mm and
68 mm respectively, their outer diameters are respectively 72 mm and 74 mm. Determine the
inside clearance, outside clearance and area ratio of the sampler. Comment on the suitability
of the sampler for collecting undisturbed sample. 7M
b) Discuss the limitations of the static cone penetration test 3M
5. An embankment 10-m high is inclined at angle of 400
to the horizontal. A slip circle method
analysis gives the following forces per running metre.
∑ Shearing forces = 450 kN
∑ Normal forces = 873.2 kN
∑ Neutral forces = 218.2 kN
The length of the failure arc is 22.0 m. Soil tests in the laboratory indicate that angle of internal
friction is 150
and cohesion is 20 kPa.
Find the factor of safety with respect to
i. Shear strength
ii. Cohesion.
6. A retaining wall, 4.5 m high retains soil with cohesion of 20 kPa, angle of internal friction of 300
and unit weight of 20 kN/m3
, with horizontal surface level with the top of the wall. The backfill
carries a surcharge of 30 kPa. Compute the total active thrust on the wall and its point of
application. Use Rankine’s theory for solving the problem and state the assumptions made in
the theory.
7. Following are the results of plate load test conducted on a 600-mm square plate at a depth of 2
m below the ground surface on a sandy soil which extends upto a large depth. Determine the
available factor of safety against shear failure and settlement of footing of size 3 m x 3 m
carrying a load of 1100 kN located at a depth of 2 m from the ground surface.
Load Intensity, kPa 0 50 100 150 200 250 300 350 400
Settlement, mm 0 1.0 2.0 3.75 5.5 8.15 11.75 17.0 22.5
8. A footing 1.5 m x 1.5 m is placed at a depth of 1.8 m in stratum of saturated clay extending upto
a depth of 5 m from the ground level. The unconfined compressive strength, submerged unit
weight, liquid limit, and specific gravity of solids of the clay are 110 kPa, 9 kN/m3
, 40%, and
2.65 respectively. Determine the allowable bearing capacity for the footing if the factor of
safety against shear failure is not to be less than 3 and consolidation settlement is not to be
more than 75 mm. The ground water table is quite close to the ground level.
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3. 9. A 4-pile group arranged in a square pattern with c/c spacing of 1.0 m is used as a foundation
for a column carrying a load of 800 kN. The piles of length 15m and diameter 300mm are
driven in sandy soil of unit weight of 19.81 kN/m3
and angle of internal friction of 360
. The
ground water table is at the ground surface. The earth pressure coefficient and angle of wall
friction can be taken as 1.5 and 270
respectively. Take Nq = 58 for φ = 360
. Find the available
factor of safety against shear failure. Also, find the settlement of the pile group, if the results of
pile load test conducted on a single pile are given below.
Load, kN 0 100 200 300 400 500 600
Settlement, mm 0 1.0 2.5 6.0 8.0 15.0 35.0
******
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