JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III UNDERGROUND MINING TECHNOLOGY Previous Question Paper (September - 2021 - R16)

For a 3.6 m thick coal seam at a depth of 150 m, the Board and Pillar method is the most suitable development technique. Given the dip of 1 in 9 (approx. 6.3 degrees), the layout must account for gradient-based transport and drainage.

Design Parameters:

• Panel Size: A panel of 150 m x 150 m is proposed to maintain ventilation efficiency and limit the number of active development faces.
• Gallery Dimensions: Galleries are driven 4.8 m wide and 3.0 m high, leaving a pillar size of 25 m x 25 m (center-to-center) to ensure stability at 150 m depth.
• Development Cycle: Using LHDs (Load-Haul-Dump units) of 1.5-2.0 m³ capacity, the cycle involves drilling, blasting, loading, and roof bolting.

Layout Description:

The development is carried out using a multi-heading system (typically 5 headings) to facilitate efficient ventilation and transport. The LHDs load coal from the face and transport it to a central Feeder Breaker located at the panel entry. From the feeder breaker, coal is transferred to a Chain Conveyor, which then discharges onto the Belt Conveyor installed in the main intake heading.

Operational Requirements:

1. Ventilation: Auxiliary fans with flexible ducting are required to deliver fresh air to the face, as LHDs are diesel-powered.
2. Support: Systematic roof bolting is mandatory. Given the 3.6 m seam, roof bolts of 1.8 m length should be installed in a 1.2 m x 1.2 m grid pattern.
3. Gradient Management: Since the seam dips at 1 in 9, the belt conveyor must be equipped with anti-runaway devices and hold-back brakes. Water sumps must be established at the lowest point of the panel to facilitate pumping.

To achieve the target of 300 t/shift, two LHD units operating in parallel across different headings are recommended, assuming a cycle time of 45-60 minutes per loading operation.