SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
MODULE- 48C
Shear Strength
1.
In a drained tri-axial compression test, a saturated specimen of a
cohesion less sand fails under a deviator stress of 3 kgf/
when the
cell pressure is 1 kgf/
. The effective angle of shearing resistance of
sand is about
(A) 37° (B) 45° (C) 53° (D) 20°
Ans :
+3 =4
2.
c = 0 for sand
In a tri-axial test carried out on cohesion-less soil sample with a cell
pressure of 20 kPa, the observed value of applied stress at the point of
failure was 40 kPa. The angle of internal friction of the soil is
(A) 10°
(B) 15°
(C) 25°
(D) 30°
Ans :
3.
In an un-drained tri-axial test on a saturated clay, the Poisson's ratio
is
(a) (
(b) (
)
)
(c )
(d)
Ans :
Poisson’s ratio =
JH ACADEMY
⁄
(
)⁄
(
)
1
SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
4.
For a tri-axial shear test conducted on a sand specimen at a confining
pressure of 100 kN/m2 under drained conditions, resulted in a deviator
stress (s1-s3) at failure of 100 kN/m2. The angle of shearing resistance of
the soil would be
(a)
(c)
18.43
26.56
(b) 19.47
(d) 30
Ans :
5.
A sample of saturated cohesion-less soil tested in a drained tri-axial
compression test showed an angle of internal friction of 30 . The
deviatoric stress at failure for the sample at a confining pressure of 200
kPa is equal to
(a) 2000 kPa (b) 400kPa
(c) 600 kPa (d) 800 kPa
Ans:
(
)⁄
⁄
0.5 =
6.
A clay soil sample is tested in a tri-axial apparatus in consolidateddrained conditions at a cell pressure of 100
. What will be the
pore water pressure at a deviator stress of 40
?
(a) 0 kN/m2
(c) 40 kN/m2
(b) 20 kN/m2
(d) 60 kN/m2
Ans: (A)
Pore water pressure dissipates in CD test
7.
A direct shear test was conducted on a cohesion-less soil (c=0)
specimen under a normal stress of 200kN/m2. The specimen failed at a
shear stress of 100kN/m2. The angle of internal friction of the soil
(degrees) is
(A)
(C)
26.6
30.0
(B)
(D)
29.5
32.6
Ans:
8.
For a sample of dry, cohesion-less soil with friction angle, , the failure
plane will be inclined to the major principal plane by an angle equal to
(A)
(B) 45
(C) 45
(D)
45
Ans: (C)
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
9.
A field vane shear testing instrument as shown was inserted completely
into a deposit of soft, saturated silty clay with the vane rod vertical such
that the top of the blades were 500 mm below the ground surface. Upon
application of a rapidly increasing torque about the vane rod, the soil
was found to fail when the torque reached 4.6 Nm. Assuming
mobilization of un-drained shear strength on all failure surfaces to be
uniform and the resistance mobilized on the surface of the vane rod to
be negligible, what would be the peak un-drained shear strength
(rounded off to the nearest integer value of kPa) of the soil?
(A) 5kPa (B)10 kPa (C) 15 kPaD) 20 kPa
Ans:
(
4.6
C=1
)
*
+c
⁄
10. The effective stress friction angle of a saturated, cohesion-less soil is
38 . The ratio of shear stress tonormal effective stress on the failure
plane is
(A) 0.781 (B) 0.616 (C) 0.488 (D) 0.438
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
11. In an unconfined compression test on a saturated clay, the un-drained
shear strength was found to be 6 t/m2. If a sample of the same soil is
tested in and un drained condition in tri axial compression at a cell
pressure of 20 t/m2, then the major principal stress at failure will be
(a) 48 t/m2
(b) 32 t/m2
(c) 24 t/m2
(d) 12 t/m2
Ans:
(
)
12. A laboratory vane shear test apparatus is used to determine the shear
strength of a clay sample and only one end of the vane takes part in
shearing the soil. If T = applied torque, H = height of vane and D =
diameter of the vane, then shear strength of the clay is given by
(a)
(c)
*
*
(b)
+
+
*
(d)
*
+
+
Ans:
)
T =(
*
+
13. Which of the following laboratory tri axial test parameters should one
specify to be carried out in connection with the initial stability of
footing on saturated clay?
1.
2.
3.
Select the correct answer using the codes given below:
(a)1 alone
(b)2 alone
(c)1 and 3
(d)1, 2 and 3
Ans: ( A)
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
14. In an unconfined compression test on stiff clay, if the failure plane
made an angle of 520 to the horizontal, what would be the angle of
shearing resistance?
(a)160
(b)140
(c)120
(d)130
Ans:
45+
(
)
=
15. Which one of the following conditions is valid in case of unconfined
compression test in comparison to tri axial test?
(a) Minor principal stress = 0
(b)Minor principal stress = 0.5 X major principal stress
(c)Minor principal stress = major principal stress
(d)Major principal stress = 3 X minor principal stress
Ans: ( A )
16. Unconfined compression test is most suitable for determining the
1. Sensitivity of clays
2. Settlement of embankments
3. ‘Strength’ of partially saturated clay sample
4. ‘Strength’ of fully saturated clay sample
(a) 1, 2, 3 and 4
(b) 2 and 3 only
(c) 3 and 4 only
(d)1 and 4 only
Ans: ( D )
17. A shear test was conducted on a soil sample. At failure the ratio of
to
is equal to unity. Which one of the following shear tests
represents this condition?
(a) Drained tri-axial compression test
(b) Un-drained tri-axial compression
test
(c) Un-drained tri-axial compression test
(d) Unconfined compression test
Ans: ( D )
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
18. In a tri axial test at failure, major principal stress was 180 kPa, minor
principal stress was 100 kPa, and pore pressure was 20 kPa. The tangent
of the angle of shearing resistance of the sandy soil tested is
(a)1/3
(b)2/7
(c)1/2/√
(d)1/6
Ans:
(
)⁄
(
)⁄
√
19. A soil sample tested in a tri axial compression apparatus failed when the
total maximum and minimum principal stresses were 100 kPa and 40
kPa, respectively. The pore pressure measured at failure was 10 kPa.
The effective principal stress ratio at failure is
(a)2.5
(b)3.0
(c)2.75
(d)2.0
Ans:
20. Assertion (A) Shear parameters ‘C’ and
conditions of shear test.
vary with drainage
Reason (R): Shear parameter ‘C’ and
are dependent on water content of soil.
Codes:
(a) Both A and R are true and R is the
correct explanation of A
(b) Both A and R are true but R in not a
correct explanation of A
(c) A is true nut R is false
(d) A is false but R is true
Ans : ( A )
JH ACADEMY
6
SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
21. A tri axial test was conducted on a granular soil. At failure
= 4. The
effective minor principal stress at failure was 100 kPa. The values of
approximate
and the principal stress difference at failure are,
respectively
(a)450 and 570 kPa (b)400 and 400 kPa
(c)370 and 300 kPa (d)300 and 200kPa
Ans :
(
)⁄
⁄
=
22. A dry sand specimen is put through a tri axial test. The cell pressure is
50 kPa and the deviator stress at failure is 100 kPa, the angle of internal
friction for the sand specimen is
(a) 150
(b)300
(c)370
(d)450
Ans :
23. A soil fails under an axial vertical stress of 100 KN/m2 in unconfined
compression test. The failure plane makes an angle of 50 0 with the
horizontal. The shear parameters ‘c’ and ‘ ’ respectively will be
a) 41. 9 KN/m2, 00
b) 50.0 KN/m2, 00
c) 41.9 KN/m2, 100
d) 41. 9 KN/m2, 100
Ans:
JH ACADEMY
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
24. A clay soil specimen when tested in unconfined condition gave an
unconfined compressive strength of 100 KN/m2.A specimen of the
same clay with the same initial condition is subjected to a UU tri axial
test under a cell pressure of 100 KN/m2. Axial stress (in KN/m2) at
failure would be
(a)150
(b)200
(c)250
(d)300
Ans :(B)
25. If ‘S’ is the shear strength, ‘C’ and are shear strength parameters, and
‘ ’ is the normal stress at failure, then Coulomb’s equation for shear
strength of the soil can be represented by
(a) C = S +
(b) C = S -
c) S =
(d) S =
Ans :
S =C +
26. Assertion (A): Stress paths can be plotted for stress conditions during
tri axial test.
Reason (R): It is not possible to control
drainage in a tri axial test.
Codes:
(a)Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R in not a correct explanation of A
(c) A is true nut r is false
(d)A is false but R is true
Ans :
(C)
27. What does the confining pressure used in tri axial compression tests on
an undisturbed soil sample represent?
a) The in-situ total normal stress
b) The in-situ lateral stress
c) The in-situ effective principal stress
d) The in-situ shear stress
Ans: (B)
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
28. In the consolidated drained test on a saturated soil sample, pore water
pressure is zero during
(a) Consolidation stage only
(b) Shearing stage only
(c) Both consolidation and shearing stages
(d) Loading stage
Ans: (C)
29. In Mohr’s diagram, a point above Mohr’s envelope indicates
(a) Imaginary condition
(b) Safe condition
(c) Imminent failure condition
(d) Condition of maximum obliquity
Ans: (A)
30. Assertion (A): In the case; of unconfined compression test, Mohr’s
circle passes through the origin.
Reason (R): The major principal stress is
zero.
Codes:
a). Both A and R are true and R is the correct explanation of A
b). Both A and R are true but R in not a correct explanation of A
c). A is true nut r is false
d). A is false but R is true
Ans :( C )
31. Shear failure of soils takes place when
a). The angle of obliquity is maximum
b).Maximum cohesion is reached in cohesive soils
c). reaches its maximum value in cohesion less soils
d). residual strength of the soil is exhausted
Ans:( A )
32. A CD tri axial test was conducted on a granular soil. At failure
was
3.0. The effective minor principal stress of failure was 75 kPa. The
principal stress difference at failure will be
(a) 75 kPa
(b) 150 kPa
(c) 225 kPa
(d) 300 kPa
Ans:
=225
=150KPa
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
33. In a direct shear test, the shear stress and normal stress on a dry sand
sample at failure are 0.6 kg/cm2 and 1 kg/cm2 respectively. The angle of
internal friction of the sand will be nearly
(a) 250
(b) 310
(c) 370
(d) 430
:
34. Laboratory vane shear test can also be used to determine
(a) Shear parameters of silty sand
(b) Shear parameters of sandy clay
(c) Liquid limit of silty clay
(d) Plastic limit of clayey silt
Ans: (B)
35. Which one of the following expressions represents the shear strength of
soil at point X? Angle of shear resistance of soil is
and symbols
stand for unit weight of water, saturated soil,
submerged soil and dry soil respectively.
(a)
(b)[
(c)
(d)(
(
)
]
)
Ans: ( C )
36. Which one of the following is the appropriate tri axial test to assess the
immediate stability of an unloading problem, such as an excavation of a
clay slope?
(a) UU test
(c) CD test
(b) CU test
(d) Un-consolidated drained tests
Ans: ( B )
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
37. Consider the following features of direct shear test:
1. Failure takes place on the predetermined plane.
2. It is a quick test.
3. Drainage conditions cannot be changed.
4. Failure of the sample is progressive.
Which of these are the disadvantages of direct shear test?
(a)1, 2 and 3
(b)1, 3 and 4
(c)1, 2 and 4
(d)3 and 4
Ans: (A)
38. A footing is resting on a fully saturated clayey strata. For checking the
initial stability, shear parameters are used from which one of the
following?
(a)
(b)
(c)
(d)
Consolidation non-drained test
Unconsolidated drained test
Unconsolidated non-drained test
Unconsolidated non-drained test with pore pressure measurement
Ans: (A)
39. For the determination of shear strength parameters, c and
the laboratory, the test to be conducted will be
(a)
(b)
(c)
(d)
, of soil in
Tri axial compression test
Sieve analysis
Compaction test
Relative density test
Ans: (A)
40. In a consolidated drained tri axial test, a specimen of clay fails at a cell
pressure of 60 KN/ . The effective shear strength parameters are
KN/
and
determine the compressive strength
KN/ .
a) 105.2
b) 29.5
c)
30.0
d) 32.6
Ans:
JH ACADEMY
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
41. A direct shear test was conducted on a cohesion less soil (c=0).
Specimen under a normal stress of 200KN/ . The specimen failed at a
shear stress of 100KN/ . The angle of internal friction of soil is
a)
c)
26.6
b) 29.5
30.0
d) 32.6
Ans:
42. If the principal stresses in a two dimensional case are -10 MPa and 20
MPa respectively, then maximum shear stress at the point is
a)
b)
c)
d)
10 MPa
15 MPa
20 MPa
30 MPa
Ans:
(
)
43. If the effective stress parameters of a soil are =10 KPa and =
,
the shear strength on a plane within the saturated soil mass at a point
where the total normal stress is 300 KPa and pore water pressure is 150
KPa will be
a)
b)
c)
d)
90.5 KPa
96.6KPa
101.5KPa
105.5KPa
Ans:
10+150
44. In a drained tri axial compression test conducted on dry sand, failure
occurred when deviator stress was 218 KN
at a confining pressure
of 61 KN
. What is the effective angle of shearing resistance and
inclination of failure plane to major principle plane?
a)
b)
c)
d)
Ans:
JH ACADEMY
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SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
45. If an element of a stressed body is in a state of pure shear with a
magnitude of 80N/
, the magnitude of maximum principal stress at
that location is
a)
b)
c)
d)
80 N/
113.14 N/
120 N/
56.57N/
Ans:
12+ (295-120)
N/
46. What is the shear strength in terms of effective stress on a plane within
a saturated soil mass at a point where the total normal stress is 295 KPa
and the pore water pressure 120KPa? The effective shear strength
parameters are
12 KPa and =
.
a)
b)
c)
d)
113 KPa
65 KPa
43 KPa
12 KPa
Ans: (A)
47. Vane test is normally used for determining in situ shear strength of
a)
b)
c)
d)
Soft clays
Sand
Stiff clays
Gravel
Ans: (D)
48. The appropriate field test to determine the un-drained shear strength of
soft clay is
a)
b)
c)
d)
Plate load test
Static cone penetration test
Standard penetration test
Vane shear test
Ans: (d)
49.
= KN/ and
unconfined test
a) 42.84 KPa
b) 21.42 KPa
c) 45.76 KPa
d) 12.45 KPa
JH ACADEMY
determine the compressive strength of
13
SUB: GEOTECHNICAL ENGINEERING
MODULE-48C
Ans :
Compressive strength = 2
JH ACADEMY
=82.84 KN/
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