Deformations and failures of goaf-side entries driving adjacent to longwall top coal caving panel

Abstract

This paper utilizes physical and numerical model experiments to study the deformation and failure mechanisms of goaf-side entries driving adjacent to longwall top coal caving (GEDLTCC) panel. The physical model experiment reveals that the deformation and failure process of GEDLTCC can be divided into four stages: initial deformation stage I (− 47 m to 45 m behind the adjacent panel), rapid deformation stage II (45 to 150 m), deformation stabilization stage III (150 to 240 m) and compaction stabilization stage IV (beyond 240 m). Notably, large deformation of the GEDLTCC surrounding rock primarily occurs during stages II and III. This deformation is primarily attributed to the stress concentration resulting from the lateral cantilever beam structure above the goaf-side entry. Therefore, this paper proposed an innovative approach that employs roof pre-splitting technology to optimize the roof structure, thereby controlling the large deformation of GEDLTCC and automatically retaining entry. Numerical simulations and field applications show that after adopting the automatically retained entry by roof pre-splitting (ARERP) technology, the abutment pressure of the integrated coal and the convergence of roof-to-floor and two ribs were reduced by 6.49%, 79.25% and 60%, respectively. Therefore, ARERP technology can effectively control the deformation of the GEDLTCC.