Bearing characteristics and rock burst mechanism of wide coal pillar with defect along gob

Despite coal pillars exceeding 60 m in some mining areas,serious rock bursts still occur,and preliminary analysis suggests that the defect wide coal pillar formed by the excavation roadway inside is the primary cause of rock burst disasters. To investigate this,theoretical analysis,numerical simulation,and field monitoring were carried out,taking the Hongqinghe Coal Mine 3^-1103 working face 65 m wide coal pillar as the engineering background. The stress distribution characteristics of the wide coal pillar and the influence of the goaf on stress evolution were analyzed,while the structure formed by lateral roof collapse in the goaf and the influence of the coal pillar plastic zone were studied. The results were verified by numerical simulation and field microseismic monitoring,revealing the mechanism of rock burst under the condition of wide coal pillar with defect type. Under the influence of the goaf,the coal pillar near the goaf is prone to plastic failure,resulting in the transfer of stress to the outer coal pillar and increasing the concentrated static load in the coal pillar. The deformation and destruction of coal pillar and the existence of goaf result in the lengthening of the suspended roof of the lateral roof and the generation of strong dynamic load when the fracture occurs. Under the superposition of dynamic and static loads,rock burst is more likely to occur in roadway along the gob. Three prevention and control techniques for this type of rock burst are proposed:coal pillar physical modification,overall roof weakening,and coal pillar stress regulation.