JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III UNDERGROUND COAL MINING TECHNOLOGY Previous Question Paper (March 2021 - R13/R15)

Opening a mine by surface drifts requires comprehensive geological, technical, and logistical data to ensure safety and economic viability. The essential information includes:

1. Geological Data: Detailed borehole logs to determine the depth, thickness, and gradient of the coal seam, along with the nature of the overburden and presence of any faults or water-bearing strata.
2. Topographical Survey: Accurate contour maps of the surface to select the optimal portal site, considering drainage, accessibility, and proximity to existing infrastructure.
3. Rock Mechanics: Data on the compressive strength and stability of the strata through which the drift will pass to design appropriate support systems.
4. Hydrological Data: Information on the water table and potential inflow rates to plan for pumping and dewatering requirements.
5. Operational Requirements: Projected production capacity, method of transport (conveyor or track), and ventilation requirements to determine the cross-sectional area and gradient of the drift.

An incline is a surface drift driven from the surface to intersect a coal seam at an angle. The construction process involves the following key stages:

1. Portal Construction: The initial entry point is stabilized using concrete or steel arches to prevent surface soil collapse.
2. Excavation: Drilling and blasting are typically employed. Holes are drilled into the face in a specific pattern, charged with explosives, and blasted.
3. Mucking and Loading: Broken rock is cleared using LHDs (Load-Haul-Dump machines) or mechanical loaders and transported to the surface.
4. Support Installation: As the face advances, immediate support is provided using roof bolts, steel arches, or shotcrete to ensure the stability of the arch-shaped or rectangular cross-section.
5. Gradient Control: The incline is usually driven at a gradient of 1 in 4 to 1 in 6 to facilitate conveyor belt installation or track-mounted transport.

Sketch Description: Imagine a cross-sectional view showing the surface portal leading into a downward-sloping tunnel. The tunnel is supported by steel arch girders spaced at regular intervals. A conveyor belt is shown running along the floor of the incline, with a ventilation duct suspended from the roof to supply fresh air to the advancing face.