GTU previous question papers -BE- Sem-Vth – Geotechnical Engineering – I- June -2011
GTU previous question papers
GUJARAT TECHNOLOGICAL UNIVERSITY
B. E. Sem. – V – Examination – June- 2011
Subject Name: Geotechnical Engineering – I
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) 1) Differentiate Physical weathering and Chemical weathering.
2) Differentiate Flocculated structure and Honeycombed structure.
3) Define phase diagram and draw phase diagrams in terms of void ratio ‘e’
and porosity ‘n’.
(b) An undisturbed soil sample has total weight of 2 0 gm, volume of 1200cc,
water content = 11 % and specific gravity G = 2.68. Compute (i) void ratio
(ii) porosity (iii) degree of saturation (iv) water content to make sample fully
saturated & (v) effective unit weight of the soil sample.
Q.2 (a) 1) Classify the given soil sample:-
G = 20 %│% N : 10 20 30 60 90 100
S = 78 %│
f = %│(Dmm): 1.28 2.98 3. 4.80 4.92 5.25
2) Differentiate between coarse grained soils (CGS) and fine grained soils
(FGS). A FGS has liquid limit of 65 % and plastic limit of 23 %. Classify the same.
(b) 1) Define the term ‘Soil Structure’ and briefly explain the commonly
observed soil structures.
2) Describe any one field identification test.
(b) 1) Define Toughness Index, Activity, Sensitivity and Thixotropy.
2) In a 10m thick sand deposit, ground water table (GWT) lies at 4.0m
depth below the GL. Sand deposit has γt = 18 kN/m3 & γsat = 20 kN/m3.
Compute effective stress values at the depths of 2.0m, 4.0m and 6.0m below the GL.
Q.3 (a) 1) Explain the factors affecting permeability of soils.
2) Define ‘Critical Hydraulic Gradient’ and briefly explain ‘Quick Sand’ condition.
(b) The following data were recorded while performing the compaction test:-
Water content (%): 10 14 20 25
Bulk density (kN/m3): 17.7 19.8 21.0 21.8 21.6
Plot the MDD-OMC curve and obtain the optimum water content and
maximum dry density. Calculate the water content necessary to completely
saturate the sample at its maximum dry density, assuming no change in the
volume. Also plot zero air voids curve. Take G = 2.68
Q.3 (a) A Falling Head permeameter accommodates a soil sample 6cm high and
50cm2 in cross sectional area. The permeability of the sample is expected to
be 1 x 10-4 cm/sec. If it is desired that the head in the Stand pipe should fall
from 30 cm to 10 cm in 40 minutes, determine the size of the standpipe
which should be used. If on the same soil sample a constant head of 200cm
is maintained for 2 hours then how much quantity of water will flow?
(b) 1) Briefly explain the factors affecting compaction.
2) During field compaction process, how the compacted density and the
moisture content can be checked?
Q.4 (a) 1) Briefly explain Coulomb’s, Mohr’s and Mohr-Coulomb’s failure
2) State merits and demerits of ‘Direct Shear Test’ and ‘Triaxial
(b) Determine the shearing strength parameters from the Direct Shear Test
results given below. The proving ring constant is 0.5 kg/Div.
Sr. No. Normal Stress (kg/cm2 ) Shear Force (kg)
1. 1.0 100
2. 2.0 150
3. 3.0 220
What would be shearing strength at the normal stress of 15 kg/cm2?
Q.4 (a) 1) Explain importance of ‘Unconfined Compression Test’ & ‘Laboratory
Vane Shear Test’.
2) Name and briefly explain the shear tests which may be performed based on the different drainage conditions.
Q.4 (b) From the Undrained Triaxial test results given below, determine the total
shear strength parameters c & φ by plotting conventional failure envelope or
modified failure envelope. Also state that at normal stress of 500 kPa, what
would be the shear strength?
Sr. No. Cell Pressure
1 100 180
2 200 320
3 300 50 0
Q.5 (a) Define the term ‘Consolidation’ and explain the same with the help of
Terzaghi’s Spring Analogy concept. State the assumptions used in
Terzaghi’s one dimensional consolidation theory.
(b) A 2.0 m x 2.0 m size footing placed at 2.0 m depth below the ground level
(GL) is transmitting net pressure intensity of 200 kPa. The ground water
table lies at 2.0 m depth below the GL. Using the data given below, divide
the clay stratum in three parts and compute the settlement due to
(i) Top layer : 2.0 m thick sand, γt = 18 kN/m3
(ii) Middle layer : 3.0 m thick NC clay, γsat = 20.1 kN/m3,
γd = 16.0 kN/m3, Liquid Limit = 80 % & G = 2.7
(iii) Bottom layer : sand
Q.5 (a) Define the terms coefficient of compressibility, coefficient of volume
compressibility, compression index and coefficient of consolidation. Explain
the ‘square-root time fitting method’ for determination of coefficient of consolidation.
(b) 1) Define the term ‘pre-consolidation pressure’ and briefly explain the
method for determination of the same.
2) During consolidation test, the void ratio is determined to decrease from
0.95 to 0.55 under the stress increment of 1.0 kg/cm2 to 2.5 kg/cm2.
Compute coefficient of compressibility, coefficient of volume
compressibility & compression index.