Temporary Roof Pillar Cyclic Induced Collapse: Beam Mechanics Analysis of Thickness and Limit Length

This study explores the principles of beam mechanics in the context of the combined mining method of roof pillar induction caving and non-pillar sublevel caving. Its objective is to determine optimal structural parameters for temporary pillars and induced caving step distance, thereby offering vital mechanical guidance for the implementation of this new mining approach. Leveraging beam theory, the study simplifies the stress-related challenges faced by temporary roof pillars throughout various mining stages. It establishes a mechanical load model and deduces the corresponding relationship between temporary roof pillar thickness and limit length, adhering to limit strength control conditions for tension and shear stresses, was derived and determination of optimal geometric parameters for temporary roof pillars. To validate the feasibility of this new mining method, focusing on the sharply inclined medium-thick ore body in the DaXin Manganese Mine. The study calculates unique limit length values were calculated for temporary roof pillar thicknesses ranging from 6 to 13 m during different mining stages. Considering fracture patterns of similar roof pillars in the middle section, practical engineering experience, and the roof pillar induction recovery process, a comprehensive assessment recommends a temporary roof pillar thickness of 10 m for the first mining stage, corresponding to a limit length of 31 m. For the continuous mining stage, a temporary pillar thickness of 10 m is advised, with a corresponding limit length of 14 m. These research findings provide theoretical references for the technical transformation of mining methods in sharply inclined medium-thick ore bodies and deep areas. Highlights A combination mining method of roof pillar induction caving and non-pillar sublevel caving is proposed. Based on the beam theory, the relationship between the thickness of temporary top column and the limit length is derived. This study a simplified model of thickness and limit length of temporary roof pillar is established using beam theory.