Instability and burst-inducing mechanism of multiple key strata coal pillar system in deep fully mechanized mining face
The instability type of rock burst in the multi key strata coal pillar system of the deep fully mechanized mining face is a common type of rock burst in the deep mining area of Ordos.Currently,there is no unified and mature treatment plan,and the rock burst still occurs from time to time.The 3102 working face of a coal mine in the deep mining area of Ordos was taken as the engineering background,and theoretical analysis,numerical simulation,and on-site measurement were conducted,to study the rock burst mechanism induced by instability of the multi key strata coal pillar system.The spatial structural evolution law of the deep multi key strata coal pillar system was explored,the loading mode of the district coal pillar bearing multi key strata was studied,the deformation and stress transformation function relationship of the multi key strata wide coal pillar system was analyzed,and the engineering criterion for instability induced rock burst of the system was derived.The instability induced rock burst mechanism of the deep multi key strata coal pillar system was revealed:when both sides of the coal pillar is mined out,the low level"ILZ"and in-plane"DLZ"key broken rock group is loaded on wide coal pillar and lead to the compression deformation.Afterwards,the"DLZ"key rock group in the stope flexes or even breaks,transferring stress to the loading section of the coal pillar.When its bearing stress exceeds the instability threshold,the overall instability rock burst occurs.Numerical simulation was conducted to study the changes in stress magnitude and distribution characteristics of coal pillars in different shrinkage width conditions in the mining area.As the width of the bearing coal pillars in the section increases,the stress distribution changes from a platform-shape to a saddle-shape,and the degree of stress concentration and overall rock burst risk level continue to decrease.Field measurements have verified the anti-burst effect of the 120 m district coal pillar.