JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III Year ROCK MECHANICS ENGINEERING Previous Question Paper (August/September - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
What is the point load strength and give its formula?
Answer
The Point Load Strength Index is a measure of the strength of rock material determined by applying a concentrated load to a specimen until failure occurs. It is commonly used for field classification and estimation of the uniaxial compressive strength of rock.
The formula for the point load strength index (Is) is defined as:
Where:
- P is the failure load (in Newtons or kg).
- De is the equivalent core diameter (in mm), calculated as De2 = D2 for diametral tests or De2 = 4A / π for axial/irregular lump tests, where D is the diameter and A is the minimum cross-sectional area.
Determine the point load strength of a specimen of 50 mm diameter whose rupture was observed at 7500 kg.
Answer
Given:
- Diameter (D) = 50 mm
- Failure load (P) = 7500 kg
For a diametral test, the equivalent core diameter squared is equal to the square of the specimen diameter:
Using the point load strength formula:
The point load strength of the specimen is 3.0 kg/mm2.
What are the different methods to determine the dynamic elastic constants in the laboratory?
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Explain the ultrasonic pulse method.
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What are the theories of the mechanics of strata behavior?
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Explain beam theory and Hypotheses based on the law of deformation.
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Explain the supporting at the following places in a caving panel with a simple layout:
- Split galleries
- Dip Slices
- Goaf edges and
- Junctions.
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What is convergence?
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Explain the method of determination of convergence and interpretation of the same in Bord and Pillar method of workings.
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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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What is non effective width of mining?
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Explain the measures to be taken to reduce the damage of structure due to subsidence?
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Discuss about the stress distribution in Longwall workings.
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