Coal–Rock Damage and Subsidence Control Technology in Deep-Mine Strip Mining Under Large Mining Heights

Abstract

A comprehensive approach incorporating field measurements, theoretical analysis, and numerical simulations was adopted to determine the strip-mining parameters for mining under large mining heights in kilometer-deep coal seams and achieve protective mining. Theoretical predictions were performed in strip mining′s maximum permissible ranges for surface deformation variables according to relevant measurements from adjacent fully mined zones. These predictions′ accuracy was verified, followed by an investigation into surface tilt, curvature, horizontal deformation, plastic zone distribution in coal pillars, and stress evolution under different recovery rates and cut widths. Surface deformation parameters′ peak magnitudes progressively increased with higher recovery rates, with surface tilt being the dominant controlling factor. When the recovery rate remained constant, variations in cut width had a minimal impact on surface deformation′s extreme values. Coal pillars′ elastic core ratio exhibited a gradual increase with expanding cut width. Moreover, the reduction in the elastic core ratio during mining became less pronounced with larger cut widths. Coal pillars′ maximum vertical stress decreased with increasing cut width. Vertical stress distribution patterns along coal pillars transitioned from single-peak to double-peak configurations through a central platform phase as cut widths increased from 60 to 100 m. Optimal strip-mining parameters were determined as 100-m cut width and 100-m pillar width by integrating surface deformation characteristics, plastic zone distribution, and stress evolution in coal pillars. Industrial trials were conducted to validate the proposed scheme.