Jawaharlal Nehru Technological University Hyderabad B.Tech III UNDERGROUND COAL MINING TECHNOLOGY Previous Question Paper (October - 2020 - R13)

Horizon mining is a method of coal extraction used in steeply dipping or irregular coal seams where the coal is accessed by main haulage roads driven horizontally through the rock strata at specific vertical levels. Instead of following the inclination of the seam, these main levels are developed in a plane parallel to the horizon. From these level roads, cross-measure drifts or inclines are driven to intersect the coal seams. This approach facilitates efficient locomotive haulage, simplifies ventilation, and allows for the centralized drainage of water, making it particularly suitable for large-scale operations in complex geological conditions.

The size of a mining panel and the number of openings (intake and return airways) are critical for safety, ventilation, and production efficiency. The influencing factors include:

• Geological Conditions: The presence of faults, folds, and the thickness of the coal seam dictate the maximum span of the panel to prevent roof instability.
• Ventilation Requirements: The number of openings must be sufficient to maintain air velocity within statutory limits while minimizing pressure drop. Higher gas emission rates require more intake and return paths.
• Strata Control: The depth of the seam and the strength of the roof and floor rocks determine the size of the pillars and the panel dimensions to avoid excessive stress concentrations.
• Method of Extraction: Mechanized longwall faces require larger, more regular panels compared to board-and-pillar methods to accommodate heavy machinery and minimize equipment relocation time.
• Production Targets: The required daily output influences the panel size; larger panels reduce the frequency of panel development and equipment shifting.
• Safety and Emergency Egress: Regulations mandate a minimum number of openings to ensure secondary means of escape and to provide independent ventilation circuits in the event of a fire or explosion.