Bearing characteristics of broken stone column in goaf of large dip angle coal seam and stability mechanism of gob-side entry retaining

JIA Housheng; WANG Yibo; WANG Weijun; YAO Qiangling; LIU Shaowei; LI Chao; PENG Bo; ZHANG Zhouping; MI Zhiwei

doi:10.13247/j.cnki.jcumt.20250013

Abstract：In order to reveal the bearing characteristics of rock pillars in goaf of large dip angle coal seam and its influence mechanism on the stability of surrounding rock of gob-side entry re-taining,taking the gob-side entry retaining of 24152 large dip angle coal mining face in Huas-han Mine as the engineering background,the formation law and bearing characteristics of rock pillars in goaf of large dip angle coal seam were mastered by theoretical analysis,numerical simulation and field observation,and the in-fluence mechanism of rock pillars on the stability of gob-side entry retaining in large dip angle coal seam was revealed.The results show that the shape of gravel accumulation in goaf is mainly affected by coal seam dip angle,coal seam thick-ness,direct roof thickness and other factors.The coal seam dip angle is greater than the natu-ral angle of repose is the premise of the formation of gravel column.The length of gravel col-umn in goaf increases rapidly with the increase of coal seam dip angle and decreases linearly with the increase of coal seam thickness.With the increase of direct roof thickness,the length of gravel column increases first and then decreases.The variation characteristics of the com-pactness of the crushed stone column are relatively consistent with the variation characteristics of the formation length of the crushed stone column,and determine the bearing characteristics of the crushed stone column and the stress environment state around the retained roadway.Under the condition of coal seam dip angle of 40°,coal seam thickness of 3.7 m and direct roof thickness of 3 m,the stress difference of the roof area on the side of the goaf,which plays a leading role in the stability of the surrounding rock of the retained roadway,does not exceed 1 MPa.According to the bearing characteristics of rock pillars in goaf of large dip angle coal seam and the stability mechanism of gob-side entry retaining,the technical key of surrounding rock stability of gob-side entry retaining in large dip angle coal seam is put forward.The sup-port in roadway should have the basic characteristics of high overall strength,large deforma-tion of surrounding rock and impact resistance on the side of goaf.Based on this,a rigid-flexi-ble integrated roadway support for gob-side entry retaining in steeply dipping coal seam is de-veloped.The support is composed of a unilateral support structure and a high-resistance retractable beam.The high-resistance retractable beam is hinged with the unilateral support structure,which can continuously maintain the overall structural stability during the large deformation of the surrounding rock of the retaining roadway,so as to synergistically control the large deformation of the surrounding rock of the retaining roadway.The field engineering practice results show that the formation process and geometric shape of the broken stone column are highly consistent with the theoretical and numeri-cal analysis results.The rigid-flexible integrated roadway support is stable,and the maximum roof subsidence during severe mining is within the allowable range of the support body.The surrounding rock control effect of gob-side entry retaining well effect.