JNTU
JNTU B.Tech IV MINE GROUND CONTROL Previous Question Paper (July - 2023 - R15)
Question paper consists of Part A and Part B. Part A is compulsory (25 marks). Part B consists of five units (10 marks each), answer one question from each unit.
Part A
What is swelling and its affect on the rock mass?
Answer
Swelling is the process of volume increase in certain rock types, such as clay-bearing shales or mudstones, caused by the absorption of water into their mineral structure. This process leads to the development of internal swelling pressure when the expansion is constrained.
The effect on the rock mass includes the degradation of structural integrity, loss of rock strength, and the exertion of significant additional loads on support systems like rock bolts, arches, or liners, which can lead to premature failure of mine excavations.
Estimate the horizontal stress on a rock at a depth of 1000m, if poisson ratio is 0.15.
Answer
The horizontal stress (σh) in a rock mass at a given depth can be estimated using the relationship derived from the theory of elasticity, assuming the rock is laterally confined and unable to deform horizontally. The formula is given by:
Where:
- ν (Poisson's ratio) = 0.15
- σv (Vertical stress) = ρ × g × h
Assuming a standard rock density (ρ) of 2500 kg/m³ and gravitational acceleration (g) of 9.81 m/s², the vertical stress at 1000m depth is approximately 25 MPa. Substituting the values:
Thus, the estimated horizontal stress is approximately 4.41 MPa.
Describe the advantages of chock type supports.
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What are the factors that affect the convergence in the gate roads?
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Briefly describe the roof testing.
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Describe about cable bolting.
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What is the effect of water on the factor of safety of slopes?
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Describe the need of embankments and its design features.
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What are the various parameters of subsidence?
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Describe about the measurement of subsidence.
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Part B
Describe the constraints on ground control and the corresponding design.
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Explain the characteristic properties of coal measure strata and explain them.
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Explain different theories of the mechanics of strata behavior of mines.
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Discuss the manifestations of strata pressure in Underground Longwall workings.
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What are the different methods of measurement of Insitu stresses? Explain them in detail.
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Explain the Flat Jack method with a suitable diagram.
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What are the features of Shield Supports? Explain them along with the limitations.
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Explain about the performance of Powered Roof supports in detail.
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What is Load bearing capacity of supports? Describe them.
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Discuss the desired loading bearing capacities of supports with different roof types and with respect different working heights.
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Explain the type of failure of rock slopes occur in coal measure strata with the help of suitable diagrams.
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Explain the boundary stresses and stress concentration around circular opening with different in situ stress conditions with the help of suitable diagrams.
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What are different theories of subsidence? Explain the factors influence the subsidence.
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Explain the damages caused due to subsidence and suggest to minimize the damages.
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Explain the phenomena of rock burst with suitable example.
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Outline the method of detection and localization of rock burst.
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Mention the methods of controlling of rock bursts.
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