Research On Disaster Mechanism Of Strong Mining Tremors Induced By Mining Near The Goaf With Super-Thick Overlying Strata

Mining tremors is an inevitable dynamic phenomenon in deep mining.Focusing on the hot issue of frequent strong mining tremors(SMT)in Ordos mining area,in order to scientifically evaluate and rationally understand SMT and its disasters,and solve the existing problems of“inaccurate source and disaster control” in SMT control,using theoretical analysis,numerical simulation,field test and engineering practice,this thesis reveals the breeding and occurrence mechanism of SMT induced by mining along the goaf with super-thick overlying strata(STOS),explores the disaster mechanism induced by SMT disturbance,analyzes the influencing factors and degree of disaster effect caused by SMT dynamic load,and puts forward disaster prevention countermeasures targeted at reducing load induced by mining along the goaf with STOS.and the empirical research is carried out by industrial experiment.By using the high precision borehole television detection and surface rock movement monitoring and other means,the relationship between the breaking and migration law of the STOS and frequent SMT is investigated.Among them,before the occurrence of SMT,water in the hole,hole collapse,after the occurrence of SMT hole wall dislocation,broken seriously;Before and after the occurrence of the SMT,the surface rock movement presents two stages of“stepped” rise,which respectively correspond to the energy storage in the STOS and the rapid settlement of the STOS breaking and instability induced by the SMT.The SMT is driven by the breaking movement of the STOS.The disturbance scale of SMT is the largest and the rupture effect is the most obvious.Based on the relative moment tensor inversion method,the focal mechanism of mining tremors induced by successive strata rupture is analyzed.The results show that,before the occurrence of SMT,the dominant fracture mode of the focal point of mining tremors induced by step fracture of strata in different places under the STOS transform from compression and shear failure to compression and tension fracture.The SMT is the result of the continuous bottom-up and step fracture of strata in different places.The expansion of crack STOS,tensile fracture and shear slip are the fundamental cause of the SMT.The radiation displacement distribution characteristics and disturbance forms of three typical fracture types are calculated by inversion.The results show that the P and S waves of the tensile and compressive fracture type reach the peak of the radiation displacement at the angle of the fracture surface of 45°±kπ/2,and the disturbance intensity is the largest and the disaster effect is the most significant.The maximum radiation displacement at the angle of90°±kπ increases(√2-1)? in the positive direction of the disturbance distance and the disturbance intensity is the minimum.The peak and minimum values of P and S wave radiation displacements are obtained at 90°±kπ/4 and 67.5°±kπ/4,respectively,and the minimum radiation displacements are obtained when the disturbance distance increases(√2 + √2-1)?.The successful application of source stress inversion technique in underground coal mine mining scale is realized.The stress field distribution in vertical depth of different strata is studied quantitatively based on the stress shape factor R value.The results show that the structural stress of strata in various places of goaf mining has undergone a process of transformation from compressive stress field to tensile stress field.The R-value difference between the same strata of STOS before and after goaf mining and the adjacent areas of longitudinal depth substrata increases by more than 50% compared with the lower strata.The form mutation of stress field is the most significant,and the higher the intensity of caused SMT,the higher the level of disaster risk induced by SMT.By means of simulation,the propagation attenuation characteristics of SMT wave and the influence law of SMT dynamic load on the disaster effect of roadway were studied,the influencing factors and the degree of the disaster effect of SMT dynamic load were discussed,and the feasibility of reducing the disaster effect of SMT dynamic load by the weakening treatment of key strata was verified,in which the reduction degree reached 50% and the effect was significant.Field practice was carried out on 1208 working face with SMT disaster.After upgrading and optimizing the monitoring system as well as ground integrated monitoring system,the positioning accuracy of far-field source was improved to 40 m in the debugging stage.The measures to control the disaster of SMT are provided.The industrial tests of disaster prevention are carried out by overburden isolated grouting and pre-cracking of ultra-deep hole blasting.This thesis has 89 figures,10 tables and 135 references.