2010 Question Paper,University Of Pune Question Paper,GEOTECHNICAL ENGINEERING,S.E. (Civil)(First Semester)

University Of Pune Question Paper
S.E. (Civil)(First Semester) EXAMINATION, 2010
GEOTECHNICAL ENGINEERING
(2008 COURSE)
Time : Three Hours Maximum Marks : 100
N.B. :— (i) Answer three questions from Section I and three questions
from Section II.
(ii) Answers to the two Sections should be written in separate
(iii) Neat diagrams must be drawn wherever necessary.
(iv) Figures to the right indicate full marks.
(v) Use of logarithmic tables, slide rule, Mollier charts, electronic
pocket calculator and steam tables is allowed.
(vi) Assume suitable data, if necessary.
SECTION I
1. (a) Clearly explain the use of knowledge of geotechnical engineering
in the construction of :
(i) embankment for road or railway
(ii) earth retaining wall. [6]
(b) Define the terms : water content, void ratio, degree of
saturation, specific gravity and state different methods to find
water content of a given soil with their suitability to different
types of soil. [6]
(c) Draw a neat sketch of particle size distribution curve for a
well graded soil and explain how Cc
and Cu
are obtained.
Give the IS criteria for classification of soil based on the values
of Cc
and Cu
. [5]
Or
(a) Draw a neat sketch to show change in the volume of soil
due to change in the water content for a cohesive soil and
define Atterberg limits. [6]
(b) Draw a neat sketch of plasticity chart as given by IS
and classify the soil with liquid limit = 75% and plastic
limit = 42% according to the chart. [6]
(c) A specimen of soil having a volume of 300 CC weighs
550 gm in wet condition. Determine voids ratio, degree of
saturation, porosity and water content of the soil specimen
if after oven drying at 105°C for 24 hours, its weight reduced
to 472 gm. Take G = 2.67. [5]
2. (a) State Darcy’s law, define coefficient of permeability and derive
equation for coefficient of permeability used in constant head
method. [6]
(b) With a neat sketch explain “quick sand condition” and derive
expression for critical hydraulic gradient. [6]
[3862]-105 3 P.T.O.
(c) The void ratio of a soil is 0.76 while its coefficient of permeability
is 1.2 × 10–4 cm/sec. If, keeping all other factors constant,
the soil is compacted so as to reduce the void ratio to 0.60,
what will be the coefficient of permeability of the soil if
3
.
1
e
k
e
æ ö
µ ç ÷ è ø +
[5]
Or
(a) Draw an illustrative flownet for a sheet pile and state any
four properties of flownet. State equation used to calculate
seepage through a dam using flownet and give the meaning
of all the terms in the equation. [6]
(b) With a neat sketch, describe pumping out method for
determination of coefficient of permeability of soil in the field,
for unconfined aquifer and derive the equation for coefficient
of permeability. [6]
(c) In order to compute the seepage loss through the foundation
of a dam, flownet was drawn. The flownet study gave number
of flow channels Nf
= 8 and number of equipotential
drops Nd
= 18. The head of water lost during seepage was
6 m. If the coefficient of permeability of foundation soil is
4 × 10–5 m/min, compute the seepage loss per meter length
of dam per day. [5]
3. (a) State and explain any four factors which influence compaction
of soil. [4]
(b) Explain how compaction control is achieved in the field using
a Proctor needle. [4]
(c) In a standard compaction test, on a soil sample having specific
gravity 2.7, the following test results were obtained :
Water Content Bulk Density
(%) (gm/cc)
5 1.89
8 2.13
10 2.2
12 2.21
15 2.16
20 2.08
Determine OMC, MDD, Void ratio, Porosity and Degree of
saturation at OMC. [8]
Or
(a) State the formula for stress in a soil mass, due to a point
load, at a point below ground level as given by Boussinesq
and give the meaning of all the terms in it. [4]
[3862]-105 5 P.T.O.
(b) With a neat sketch, explain the use of Newmarks influence
chart to find stress at a given point under a loaded
area. [6]
(c) A 2 m × 2 m square footing carries a gross load of 550 kN.
The footing rests at a depth of 1.5 m below ground level.
The subsoil consists of a 2 m thick layer of sand having a
unit weight of 18 kN/m3. The sand layer is underlain by
a 4 m thick layer of soft clay having unit weight of
17.2 kN/m3. Compute the maximum vertical stress at the
middle of the clay layer before and after the construction of
the footing. Use Boussinesq’s equation. [6]
SECTION II
4. (a) Explain Mohr-Coulomb failure theory and state Coulomb’s
law of shearing strength in total and effective stress
condition. [6]
compression test in comparison with the direct shear
test ? [6]
(c) A direct shear test was carried out on a cohesive soil sample
and the following results were obtained :
Normal Stress Shear Stress at Failure
(kN/m2) (kN/m2)
150 110
250 120
What would be the deviator stress at failure if a triaxial
test is carried out on the same soil with cell pressure of
150 kN/m2 ? [6]
Or
(a) State the factors affecting shear strength of soil and explain
the terms sensitivity and thixotropy. [6]
(b) Write a note on Vane Shear Test. [6]
(c) The shear strength parameters of a given soil are, C = 0.26
kg/cm2 and f = 21°. Undrained triaxial tests are to be
carried out on specimens of this soil. Determine deviator
stress at which failure will occur if the cell pressure be
2.5 kg/cm2. [6]
[3862]-105 7 P.T.O.
5. (a) Explain Rankine’s earth pressure theory for cohesionless
soils. [5]
(b) Explain Rehbann’s graphical method for evaluation of earth
pressure. [5]
(c) A retaining wall 9 m high retains a cohesionless soil, with
an angle of internal friction 33°. The surface is level with
the top of the wall. The unit weight of the top 3 m of the
fill is 2.1 t/m3 and that of the rest is 2.7 t/m3. Find the
magnitude and point of application of the resultant active
thrust. [6]
Or
(a) Explain active and passive states of plastic equilibrium. [5]
(b) State assumption in Rankine’s earth pressure theory. [4]
(c) A retaining wall, 7.5 m high, retains a cohesionless
backfill. The top 3 m of the fill has a unit weight of
18 kN/m3 and f = 30° and the rest has a unit weight of
24 kN/m3 and f = 20°. Determine the pressure distribution
on the wall. [7]
6. (a) Describe with figures, the modes of failure for finite and infinite
slopes. [8]
(b) Rock classification by RMR method. [4]
(c) Explain durability of rocks. [4]
Or
(a) Explain tests for determination of shear strength of
rocks. [8]
(b) Write short notes on causes and remedial measures of
Landslides. [8]