Geomechanics - Geomechanics and Ground Control - Mining Engineering Previous Year Questions

1

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

Bulk modulus of rock is defined as

A

$\frac{\text{shear stress}}{\text{volumetric strain}}$

B

$\frac{\text{hydrostatic pressure}}{\text{shear strain}}$

C

$\frac{\text{hydrostatic pressure}}{\text{volumetric strain}}$

D

$\frac{\text{shear stress}}{\text{shear strain}}$

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2

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

Radial stress on the excavation boundary of a circular tunnel is

A

always zero

B

always positive

C

always negative

D

positive in some area and negative in some area

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3

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

A point P (10, 3) MPa on the Mohr’s circle represents normal and shear stresses. If the centre of the Mohr’s circle is C (6, 0) MPa, the normal and shear stresses in MPa on the point diametrically opposite to P are

A

2, -3

B

4, -3

C

2, 3

D

4, 3

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4

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

A rock sample with a horizontal joint is subjected to 10 MPa of normal pressure as shown in the figure. The elastic modulus and Poisson’s ratio of the rock are 5.0 GPa and 0 respectively. If the normal stiffness (
k_nn) of the joint is 50 GPa/m, normal displacement at the top of the sample (
A’A line) in mm is

A

0.2

B

0.4

C

0.6

D

0.8

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5

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

The state of stress (
σ_xx,σ_yy,τ_xy) at a point below ground is found to be (5, 15, -3) MPa. The angle measured in the counter clockwise direction between the x-axis and the major principal axis in degree is

A

9.52

B

15.48

C

150.48

D

164.52

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6

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

The unconfined compressive strength of a cylindrical rock sample is 90 MPa. The angle of internal friction of the rock is 30°. If a confining pressure of 5 MPa is applied radially to the rock sample, the confined compressive strength in MPa is

A

92.88

B

95.00

C

105.00

D

110.0

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7

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

A circular opening of radius a is made underground in hydrostatic stress condition. The radial distance from the centre of the opening, where the tangential stress is twice the radial stress, is

A

a

B

√2a

C

√3a

D

2√3a

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8

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

In an experiment to determine rock thermal conductivity a disc of rock specimen is placed between two solid brass cylinders and one dimensional heat flow is created as shown. The readings of the thermocouple sensors with respect to zero potential are shown in the figure. Brass thermal conductivity is 90 W/m °C, and the thermocouple constant is 40 µV/°C. The rock thermal conductivity in W/m °C and the heat flux in W/m² respectively are

A

1.8, 1800

B

0.6, 1020

C

3.2, 540

D

2.1, 670

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9

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

What is the void ratio in the sandstone sample?

A

0.150

B

0.176

C

0.850

D

1.176

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10

2007 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2007

If the sandstone sample is fully saturated in water, the saturated density of the sample in kg/m³ is

A

1590

B

2234

C

2438

D

2531

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11

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

Q.4 A phreatic surface experiences a pressure

A

Less than atmospheric pressure

B

Equal to atmospheric pressure

C

More than barometric pressure

D

Less than barometric pressure

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12

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

Q.14 Under identical water head and roadway conditions for water dam construction, if P, Q, and R represent the thickness of flat dam, cylindrical dam and spherical dam respectively, the thickness would follow the order

A

R>P>Q

B

P>R>Q

C

P>Q>R

D

Q>P>R

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13

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

In a bi-axial stress field the vertical stress is 10 MPa and the Poisson ratio for the rock mass is 0.2. The horizontal stress in MPa is,

A

1.5

B

2.5

C

2.0

D

5.0

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14

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

From the stress-strain diagram shown below, the tangent and the secant moduli of elasticity in GPa are

A

4.0, 2.2

B

3.3, 2.3

C

3.3, 1.5

D

4.0, 1.5

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15

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

A bord and pillar operation is planned at a depth of 300 m in a strata of average unit weight 24.5 kN/m³ and compressive strength 15.50 MPa. If the width of the opening is 6 m considering a factor of safety of 1, the maximum possible extraction ratio in percentage is

A

28

B

34

C

45

D

53

Check answer

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16

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

Match the following:

Failure criteria	Relationship
P. Drucker - Prager	1. σ1 = σ3 + √(mσ3 + s2)
Q. Hoek - Brown	2. τ = c + σn tan φ
R. Mohr - Coulomb	3. [√( ( (σ1 - σ2)/2 )2 + ( (σ2 - σ3)/2 )2 + ( (σ3 - σ1)/2 )2 )] = A(σ1 + σ2 + σ3) + B

A

P-1, Q-3, R-2

B

P-3, Q-1, R-2

C

P-3, Q-2, R-1

D

P-1, Q-2, R-3

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17

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

The driving force for failure, on the potential failure plane is

A

187 N

B

1.87 kN

C

18.7 kN

D

1.87 MN

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18

2008 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2008

The ‘factor of safety’ of slope under given conditions is

A

0.7

B

0.9

C

1.1

D

1.3

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19

2009 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2009

The rock mass classification system that considers “active stress” factor is

A

Q-system

B

RMR

C

RQD

D

GSI

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20

2009 · Mining Engineering · Geomechanics and Ground Control · Geomechanics

Mining Engineering (MN) 2009

In a triaxial compression test if \( \sigma_1 \) is axial stress and \( \sigma_2 \) and \( \sigma_3 \) are confining stresses, then

A

\(\sigma_3 > \sigma_2 = \sigma_1 \)

B

\(\sigma_1 > \sigma_2 = \sigma_3 \)

C

\(\sigma_1 = \sigma_2 > \sigma_3 \)

D

\(\sigma_1 = \sigma_2 > \sigma_1 \)

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