Research On Influencing Factors And Risk Identification Of Rockburst In Lower Delaminated Working Face In Folded Structure Area

The conditions in the folded structure area are complex,and due to the influence of tectonic stress,it is easy to accumulate a large amount of elastic energy in extremely thick coal seams.Especially,the arrangement of the lower layered working faces across multiple upper layered working faces is prone to stress concentration and buckling damage,which can have a serious impact on the production of the mine due to the compression effect of the folded structure wings and the remaining coal pillars after upper layered mining,Therefore,intelligent identification and early warning of rock burst risk is the key to further prevention and control of rock burst.Based on theoretical analysis,numerical simulation,field investigation,and engineering practice,this thesis analyzes the regularity of mine earthquake activity in the lower layered working face in the folded structure area,determines the main influencing factors of the induced impact of the lower layered working face in the folded structure area,proposes the stress evolution characteristics of the layered working face under high tectonic stress conditions in the folded structure area,and clarifies that the stress field in the folded structure area is an important force source condition that causes the impact of the lower layered working face,Using early warning indicators,we conducted spatiotemporal early warning research and application,and achieved intelligent risk identification and early warning by constructing an early warning indicator system for rock burst.The following research results were obtained:(1)Based on the historical impact appearance in Yanbei area,it was found that most of the impact in the folded structure area was mainly caused by floor heave damage.Through analyzing the characteristics of mining earthquake activity in the lower layered working face of the folded structure area,It is found that the seismic energy of the first mining face in the lower slicing is smaller,but its activity frequency is more frequent;During the mining of the first mining face in the lower slicing,the mining earthquake activity gradually extends to the high roof,and the mining earthquake activity presents a periodic accumulation distribution phenomenon in the time sequence,with a subordinate concentration characteristic.(2)Based on the multi factor coupling analysis method,the disaster areas caused by rock burst are superposed and coupled.The overall influencing factors within the mining area are determined as burial depth and coal thickness,while the local influencing factors are fold structure,working face squareness,and mining layout.Based on the analysis of the overall influencing factors of the mining area,it is found that the main factor affecting the lower layered working face in the folded structure area is the folded structure,and is easily affected by the superposition of overlying residual coal pillars,resulting in stress concentration.(3)Based on the theoretical basis of the energy storage characteristics of stopes in extra-thick coal seams,and through the simulation of stopes under folded structures,the vertical stress variation law of roadway surrounding rocks in the first mining face under folded structures and the stress characteristics of "roof coal seam floor" are revealed,the lower stratified working face is significantly influenced by the overlying legacy coal pillar,and the stress on the side of the legacy coal pillar formed in the mining hollow area on 04 and 05 as well as on 05 and 06 increases sharply,which may cause destabilization and induce strong dynamic phenomenon in the lower stratified working face.Indicating that high stress provides a necessary force source condition for the occurrence of impact,and the greater the stress,the easier it is to occur buckling failure.(4)Intelligent risk identification and early warning of high-energy events in the lower layered working face in the folded structure area are conducted through various monitoring and early warning indicators of rock burst,and its early warning effectiveness is verified through on-site spatiotemporal early warning applications.The confusion matrix is introduced to quantitatively evaluate the early warning effect of various parameter early warning indicators,and an intelligent identification and early warning indicator system for rock burst risk is established.This thesis has 77 maps,23 tables,and 87 references.