LAB MANUAL
Geotechnical
Engineering – II
Unit 5:
1. It is proposed to lay a suitable type of foundation at a
depth of 1.50m below the GL on soil a c-Φ soil with c=30 Kpa and Φ=25°, γ=17.50
kN/cum. Given Nc’=14.80; Nq’=5.60; Nγ’=3.20. Estimate the ultimate bearing capacity
of a (i) 2m wide strip footing, (ii) 2m wide square footing, (iii) 2m wide
circular footing. Comment on the results.
2. A 2m wide square footing is laid at a
depth of 1.20 m below the GL on a c-Φ soil with c=40 Kpa and Φ=20°, γ=17
kN/cum. Given Nc’=11.80; Nq’=3.90; Nγ’=1.70. Using Terazaghi’s theory, compute
the ultimate bearing capacity when the GWT is
(i) 5m below GL (ii) 2m below GL (iii) at GL.
Assume the change
in shear parameters due to saturation is negligible.
3. Explain the types of shear failures
experienced by shallow foundations. Mention the parameters to decide type of
shear failure.
4. A continuous
footing of width 2.5m rests 1.5m below the ground surface in clay. The
unconfined compressive strength of the clay is 150kN/m2. Calculate
the ultimate bearing capacity of the footing. When there is no effect of water
table and when water table reaches ground surface. Take γ=19kN/m3,
γsat=20kN/m3
5. What is a strip
footing? When it is preferred?
6. List out
different types of foundations. State the circumstances to go for combined
foundations
7. A continuous
footing of width 2.5m rests 1.5m below the ground surface in clay. The
unconfined compressive strength of the clay is 150kN/m2. Calculate
the ultimate bearing capacity of the footing. When there is no effect of water
table and when water table reaches ground surface. Take γ=19kN/m3,
γsat=20kN/m3.
8 Define the following:
i) Net ultimate bearing capacity.
ii) Unit soil pressure.
iii) Allowable
bearing capacity.
9. A square footing
1.8mx1.8m is placed over loose sand of bulk density 1.6g/cc, saturated density
1.82g/cc and at a depth of 0.8m. The angle of shearing resistance is 300.
Determine the ultimate bearing capacity when there is no effect of water table
and when it is submerged (for φ= 300, Nc=30.14, Nq=18.4 and Nγ=15.1).
10. Differentiate
between Safe bearing Capacity and Allowable bearing capacity.
Unit 6:
1. Distinguish
between immediate and consolidation settlements. What are the limits of maximum
and differential settlements according to I.S. codes?
2. A raft
foundation of size 20m X 30m exerts a uniform pressure of 180kN/m2
on sub soil. Determine the immediate settlement of soil by assuming E= 45Mn/m2
and poisons ratio 0.5.
3 Discuss the
situations for adopting the SPT test for determining the bearing capacity.
4. Determine the
allowable bearing capacity of a 1.5m X 1.5m square footing placed at a depth of
2.0m in a sandy deposit having a unit weight of 19kN/m3 with SPT value of 37.
Water table is at depth of 1.5m. Determine the allowable bearing capacity for
50mm permissible settlement after applying suitable corrections for SPT value.
Unit 7:
1. A 300mm dia.
Pre-cast RCC pile is driven in to a clay bed to a depth of 9m. The average
properties of the clay along the shaft of pile include, c = 40 kPa; α = 0.74.
However, the un-confined compressive strength of clay at tip of the pile was
found to be 120 kPa. Estimate the safe load carrying capacity of the pile with
a FOS of 3.
2. Explain the
construction and use of “Under-reamed Pile foundations”.
3. A group of 20
piles, arranged in 4x5 pattern are provided in a Clay deposit to a depth of
12m.The size of each pile is 600mm dia provided at a c/c spacing of 1.80m. The
average properties of the clay are qu=160kPa, adhesion factor=0.58. Determine
the safe load carrying capacity of the pile group. Adopt FS=2.50.
4. Give
classification of piles.
5. A group of 15 piles of 450mm diameter
each are arranged in 3 x 5 pattern to a depth of 9m in a 16m thick medium stiff
clay. The average unconfined compressive strength of clay is found to be 120
kPa. The adhesion factor between concrete and in-situ clay is found to be 0.58.
Estimate the safe load carrying capacity of the pile group with an overall
factor of safety of 3.0, if the center to center spacing of piles is 0.9m
6. Write a note on
“Dynamic formulae” and comment on their validity
7. A R.C.C. pile of
size 30cm X 30cm and 10m long is driven into coarse sand with unit weight of
16kN/m3 and angle of internal friction of 310. What is
the allowable load on the pile? For φ=310, N q= 16 and N γ = 14.Take
K=1.0 and factor of safety of 3.0.
8. What is negative
skin friction in piles? Explain.
9. Sketch an open
well foundation and show the various components. Explain the functions of
various components
10. Explain the
“Pile Load Tests” in detail
Unit 8:
1. Describe various
types of Caisson Foundations and comment on their suitability.
2 Explain in detail
the procedure of “Sinking of Well foundations”.
3. With the help of
a neat sketch, show the components of an “Open Caisson” and explain the
function of each component.
4. With the help of
neat sketch, show the components of a “Pneumatic Caisson” and explain their
function. Also explain the procedure of sinking of “Pneumatic Caissons”.
wat abt theory
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