Study On The Mechanism Of Huge Thick Overburden Type Mine Seismicity In Ordos Mining Area Based On Joint Modeling Of Multiple Boreholes

With the large-scale development of coal resources in the west,the problems of high energy accumulation and frequent occurrence of huge thick overburden type Mine Seismicity are becoming increasingly prominent,seriously threatening the safety and efficient production of coal mines.Taking the Ordos deep mining area as the research object,this thesis systematically studied the ultimate fracture distance and energy release laws of the Cretaceous thick overburden under the influence of different factors using theoretical derivation,numerical simulation,engineering practice,and other research methods.Based on the geological large data and multi borehole joint modeling technology,the fracture evolution laws of the Ordos deep mining area thick overburden were studied,The action mechanism of various influencing factors on the fracture of extremely thick overburden rock is clarified.Based on theoretical derivation and numerical simulation results,the occurrence mechanism of extremely thick overburden rock type Mine Seismicity in Ordos mining area is revealed,and based on this,countermeasures for seismic mitigation and disaster elimination of extremely thick overburden rock type Mine Seismicity are proposed.The main research results are as follows:(1)Based on the geological drilling and rock physical and mechanical parameters collected from various mines in the deep mining area of Ordos,the thesis analyzes the variation range of parameters such as the thickness,burial depth,and rock type of various layers in the study area,especially the Cretaceous super-thick overburden layer,summarizes the mining conditions of typical layers in the study area,and analyzes typical cases of "super-thick overburden type" mining earthquakes,It is found that "extremely thick overlying rock type" Mine Seismicity often occur after multiple goafs are connected,and are closely related to the size of the goaf.(2)Based on Vlazov’s thick plate theory,this thesis studies the relationship between the extreme tensile stress inside the extremely thick overburden layer and the influencing factors such as the size of the goaf,the thickness of the extremely thick overburden layer,and the overlying load.It is theoretically deduced that the maximum tensile stress inside the extremely thick overburden layer is greatly affected by the short side of the goaf,and the maximum tensile stress in the extremely thick overburden layer continuously decreases with the increase of the thickness,and linearly increases with the increase of the overlying load.The energy transfer law after the fracture of the Cretaceous overlying strata is analyzed,and it is concluded that the energy released by the fracture of the overlying strata is positively correlated with the thickness of the overlying strata.(3)Using UDEC numerical simulation analysis method,the law of energy accumulation and fracture from initial mining to full mining of extremely thick overlying strata was studied,and a comparative baseline was established.With the aid of the multi borehole joint modeling method,the change in mechanical properties of rock mass along the bedding plane,the change in lateral thickness of rock mass along the bedding plane,and the change in spacing between the extremely thick overburden and the main mining coal seam along the bedding plane are introduced into the baseline model.The promotion or inhibition effects of various factors on the fracture of extremely thick overburden are studied.The results show that when the thickness of extremely thick overburden becomes thinner along the bedding plane,the mechanical properties become weaker along the bedding plane,and the distance from the coal seam becomes closer along the bedding plane,It will promote the fracture of extremely thick overlying strata,and on the contrary,it will inhibit the fracture of extremely thick overlying strata.(4)Based on theoretical derivation and numerical simulation results,the occurrence mechanism of giant thick overburden type Mine Seismicity in Ordos mining area was analyzed,and the impact of different attribute factors of giant thick overburden on giant thick overburden type Mine Seismicity was revealed.Based on the distribution of Mine Seismicity and surface subsidence during mining of working faces in the study area,the stability of giant thick overburden in the study area was analyzed,verifying the theoretical derivation and numerical simulation results,This thesis improves the reliability of the thesis,summarizes the disaster causing process of "giant thick overburden rock" mining earthquakes,and puts forward targeted seismic mitigation measures for giant thick overburden rock type mining earthquakes.There are 72 pictures,14 tables and 92 references in this thesis.