JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B. Tech IV Year MINE GROUND CONTROL Previous Question Paper (March - 2021 - R16)

Inadequate ground control in mining operations poses significant safety and economic risks. The primary hazards include:

• Strata Failure and Roof Falls: Uncontrolled movement of the immediate roof can lead to sudden collapses, which are a leading cause of fatalities in underground mines.
• Rockbursts and Bumps: In deep mines, the sudden release of stored strain energy in brittle rock masses can cause violent ejections of rock, endangering personnel and damaging equipment.
• Floor Heave and Rib Spalling: Inadequate support leads to the deformation of the floor and sides, which can obstruct haulage ways, damage ventilation structures, and compromise the stability of pillars.
• Surface Subsidence: Poor control of underground voids can lead to uncontrolled surface subsidence, causing damage to surface infrastructure, buildings, and environmental degradation.
• Economic Loss: Frequent instability results in production delays, loss of expensive mining equipment, and the high cost of rehabilitation or abandonment of mine workings.

The scope of ground control in underground coal mines encompasses the scientific management of rock pressure to ensure the stability of excavations while maximizing resource recovery. Its applications include:

1. Design of Mine Workings: Determining optimal dimensions for galleries, pillars, and panels based on the depth of cover, rock mass strength, and the in-situ stress field to prevent pillar failure or excessive convergence.
2. Support System Selection: Designing and implementing active and passive support systems, such as roof bolts, cable bolts, steel arches, and hydraulic props, tailored to the geological conditions of the roof and sides.
3. Monitoring and Instrumentation: Utilizing convergence meters, load cells, and borehole extensometers to monitor strata behavior in real-time, allowing for proactive adjustments to support strategies.
4. Strata Control in Longwall Mining: Managing the caving of the goaf (waste area) and controlling the movement of the main roof to protect the longwall face equipment and ensure the safety of the working environment.
5. Hazard Mitigation: Implementing measures to prevent or manage coal bumps and gas outbursts by controlling the stress distribution around the working face.