JNTU
JNTU B.Tech II DRILLING AND BLASTING Previous Question Paper (May - 2019 - R16)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
What are the causes for Bore hole deviation?
Answer
Bore hole deviation is primarily caused by factors related to the drilling equipment, the geological conditions, and the drilling technique employed. Key causes include:
- Drill String Characteristics: Use of a drill string with insufficient stiffness or improper diameter relative to the hole size, leading to bending under axial load.
- Geological Factors: Intersecting rock layers with varying hardness, dipping strata, or the presence of faults and fractures that deflect the bit along the path of least resistance.
- Drilling Parameters: Applying excessive feed force (weight on bit) beyond the capacity of the drill string, or improper rotation speeds that cause the bit to wander.
- Equipment Alignment: Incorrect initial setup or alignment of the drill rig mast relative to the intended hole trajectory.
Explain about double tube core barrels.
Answer
A double tube core barrel is a specialized drilling tool used to recover high-quality rock cores by protecting them from the erosive action of the circulating drilling fluid. It consists of an outer barrel that rotates with the drill string and an inner barrel that remains stationary or rotates independently on bearings.
The primary mechanism involves the drilling fluid circulating through the annulus between the outer and inner tubes, preventing the fluid from coming into direct contact with the core sample. This design minimizes core disturbance, prevents washing or erosion of soft formations, and significantly increases the percentage of core recovery in fractured or friable rock strata.
What are the factors affecting drilling?
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Explain Drill hole economics.
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Physico-mechanical properties affecting drillability.
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What is the mechanism of Blasting?
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Define the term Rock fragmentation.
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Define the term detonators.
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What are the sources of water pollution in mines?
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Write a short note on dimensional stone blasting.
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Part B
What are different types of drilling equipment that are being used in exploratory drilling? Describe about the rotary percussive drilling equipment used in mines? Explain in which conditions this kind of equipment is used?
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What is wire line drilling? Explain with a neat sketch how you are going to drill the holes with wire line drilling equipment.
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What is production drilling used in coal mines? Explain about different types of drill machines used in coal mines in both underground and opencast mines?
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Define bit wear. What are the factors you need to keep in mind while designing and selecting a drill bit?
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Explain about the following:
Thrust
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Flushing
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micro-bit drilling.
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What are the provisions regarding Storage, Transport and handling of explosives as per CMR 1957?
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What are drill patterns for underground excavations? Explain each one of them in brief with a figure.
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What is an environmental impact assessment (EIA)? How can you assess the EIA due to blasting, ground vibrations, fly rocks? What were the preventive measures?
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What is computer design of underground blasting? What are the factors you need to consider before doing an underground blasting? What are the precautionary measures you need to take?
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Why you need to do blasting for road construction? What are the precautions you need to take while blasting for road construction?
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