Study on the effect of mining height on overburden strata movement in longwall mining

Abstract

Abstract The mining height of a coal seam is a critical factor influencing the detachment, collapse, and formation of the collapse angle of the strata during strata movement. To clarify the mechanism by which mining height affects strata movement characteristics, a physical model experiment was conducted based on the geological conditions of the Panel 122104 in Caojiatan Coal Mine in Shaanxi. The experiment examined strata movement at mining heights of 1 m and 10 m, identifying differences in detachment, collapse behavior, and collapse angles under these two conditions. The results indicate the following: Delamination range directly governs collapse patterns, with higher stress concentration accelerating delamination initiation and expanding affected zones. 1 m mining height exhibits a “ superposed fixed beam” structure with lower strength compared to the “fixed beam + cantilever beam” configuration under 10 m height. A model estimating collapse step shows 9.13% average error. Strata structure dictates collapse angle mechanisms: Pseudo-plastic deformation under 1 m height determines collapse angle through vertical tensile stress boundaries, whereas 10 m height exhibits brittle fracture behavior with collapse angles approximating fracture angles. Periodic collapse volume above working face directly correlates with mine pressure intensity and is positively correlated with the caving step distance, collapse angle, and caving range. These parameters show higher values under 10 m mining height, resulting in more pronounced mine pressure manifestations compared to 1 m conditions.

Keywords

• Mining height
• Overburden movement
• Delamination
• Collapse angle
• Structural instability