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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY ME SEMESTER II EXAMINATION SUMMER 2017 Subject Code: 2724309 Date:29/05/2017
Subject Name: Soil Structure Interaction
Time: 02:30 PM to 05:00 PM Total Marks: 70 Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks. Q.1 What do you understand by Winkler foundation? Derive its equation for
finding slope, deflection, moment, shear and load for a beam resting on
elastic foundation.
07
Differentiate contact pressures under perfectly flexible footings and
perfectly rigid footings in detail. Support your answer with neat sketches
for sand and clay.
07
Q.2 Estimate the immediate settlement of a concrete footing 1.5m x 1.5m in
size founded at a depth of 1.5m in silty soil whose modulus of elasticity
is 87kg/cm2. The footing is expected to transmit a unit pressure of 210
kN/m2. Take 0.34, If 0.83 for rigid footing.
07
What is mat foundations? Explain rigid method and elastic plate method
for the analysis of mat foundation. State the recommendations given by
ACI for mat foundation analysis.
07
OR
Calculate the foundation pressures and moments for a beam of 40m span with
three point loads of 2500 kN each spaced equally 10m apart from each other.
Take K 1.32 x 107 kg/m2 and E 2.01 x 109 kg/m2.
07
Q.3 Show the differential equation of the elastic curve applicable to laterally
loaded piles and explain concept of p-y curve.
07
As steel pile of 610mm outside diameter with a wall thickness of 25mm
is driven into loose sand (Dr under submerged condition to a
depth of 20m. The submerged unit weight of the soil is 8.85 kN/m3 and
Ø 34o. The EI value of the pile is 4.56 x 102 MN-m2. Compute the
ground line deflection of the pile under lateral load of 268 kN at ground
level under free head condition by Reese and Matlock method. Assume
nh 6 MN/m3.
07
OR
Q.3 Enlist the various factors affecting the magnitude of the coefficient of
subgrade reaction (kv and kh). Explain the influence of width B on
coefficient of vertical soil reaction in detail. Support your answer with
necessary plots.
07
A steel pile of 610mm outside diameter and 560mm inside diameter is
driven into medium dense sand under submerged condition which is
having relative density 60% and angle of internal friction is 38o.
Compute the ultimate resistance of the pile by Broms method. Assume
the yield resistance of the pile section as 1.3fyZ. Assume fy
2800kg/cm2, submerged unit weight of the soil as 8.75kN/m3, e/d
non-dimensional yield moment 462 and non-dimensional lateral
resistance 80.
07
Q.4 What do you mean by curved failure surfaces? Explain logarithmic spiral
method for determining passive earth pressure of sand with neat sketch.
07
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A steel pipe pile of outside diameter 650mm and wall thickness of
25mm is driven into saturated cohesive soil upto a depth of 15m. The
undrained cohesive strength of the soil is 25kPa. The submerged unit
weight of soil is 9.5kN/m3. Construct curves for static loadings at
depth of 5 10 metres. Take ε50 0.02, Pu +0.5x/d)cxd.
07
OR
Q.4 A 400mm square wooden pile is driven 6m below ground level in preloaded
clay. The load to be applied is 1m above the ground. Determine
the ultimate load that can be applied on a pile with Mu 130kNm.
Assume Kh 16 MN/m2, E 10 X 102 MN/m2 and cohesion of clay
1kg/cm2.Assume e/R 1.83, Zf/R 1.42, m 0.62. Use IS 2911 method
only.
07
Explain in detail Poulos-Davis-Randolph approach for assessing vertical
bearing capacity of piled raft foundation.
07
Q.5 A vertical vibration test was conducted on a 1.5 m x 0.75 m x 0.70 m
high concrete block in an open pit having depth 2.0 which is equal to the
anticipated depth of actual foundation. The test was repeated at different
settings of eccentric masses. The data obtained from the tests are
given below:
SR No. θ fnz Amplitude at
Resonance
(Microns)
1 36 41 13
2 72 40 24
3 108 34 32
4 144 31 40
The soil is sandy in nature having angle of internal friction Ø=35° and
saturated density γsat=20 kN/ m3. The water table lies at a depth of3.0 m
below the ground surface. Probable size of the actual foundation 4.0 x
3.0 x 3.5 m high. Determine the values of Cu, E and G to be adopted for
the design of actual foundation. Limiting vertical amplitude of the
machine is 150 microns. For test block,σv1 =43 kN/m3 ,σv2=13.44
kN/m3
for actual foundation ,σv1 =61kN/m3 ,σv2 =63.76kN/m3
Mass of oscillator and motor is 100kg.
10
Define coefficient of elastic uniform compression, coefficient of elastic
uniform shear, coefficient of elastic non-uniform shear, coefficient of
elastic non-uniform compression, damping ratio.
04
OR
Q.5 Discuss in detail Barkans method and Pauw's analogy for foundation
soil system.
07
Design the foundation for a gas engine with vertical cylinder and
vertically oscillating parts, for the following data:
i. Total weight of engine 45 kN
ii. Speed of rotation 260 rpm
iii. Unbalanced vertical force 10 kN
iv. Base dimension of the engine 1m x 2.5m
v. Elevation of machine base above ground 1m vi. Weak silty sand exits to a depth of 0.5m followed by a dense
sand to a depth of 6m. The unit weight of moist sand is 17
kN/m3.
07