Reasonable layout range of lower mining roadways in the close and variable interval coal seams mining: a case study

Area of Science:

• Mining Engineering
• Geotechnical Engineering
• Rock Mechanics

Background:

• Close-distance coal seam mining presents challenges in predicting stress transfer.
• Upper coal seam extraction significantly impacts the stability of underlying strata and residual coal pillars.
• Optimizing lower coal seam roadway layout requires understanding stress distribution patterns.

Purpose of the Study:

• To investigate the stress transfer mechanism and pillar stability after upper coal seam extraction.
• To analyze the extent of the plastic zone in residual coal pillars.
• To propose a rational layout for lower seam roadways based on inter-seam spacing.

Main Methods:

• Development of a theoretical model for stress distribution in multiple goaves and coal pillars.
• Application of ground-penetrating radar (GPR) for stability and plastic zone analysis.
• Case study analysis of stress distribution and transfer in floor strata with variable inter-seam spacing.

Main Results:

• Identified a distinct stress gradient distribution from coal pillars to goaves.
• Observed significant stress concentration decrease and gradual return to original rock stress.
• Demonstrated increased stress transfer through coal pillars to goaves with greater floor strata depth.

Conclusions:

• The study provides insights into stress transfer mechanisms in multi-seam mining.
• A reasonable layout range for lower seam mining roadways is proposed.
• Findings offer valuable references for optimizing roadway design in similar mining conditions.