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

answer-books.

(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]

(b) What are the advantages and disadvantages of triaxial

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]

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

answer-books.

(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]

(b) What are the advantages and disadvantages of triaxial

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]

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