Study On The Evolution Of Destabilization Damage Of Fault With Slip-resisting Structures Under Mining Disturbance

Fault instability and failure is an important influencing factor to induce dynamic disasters in coal mines,which threatens the safe mining seriously.After much argumentation,the interior of the fault zone is not completely broken,but there are multiple slip-resisting structures with heterogeneity,high shear strength and high energy storage.They play a locking control role on the two sides of the fault.The existence of slip-resisting structures will change the law of fault activation and destabilization under mining disturbance,making the evolution of structural dynamic disaster different from the original understanding.In order to explore the evolution law of fault instability and failure under mining disturbance,based on on-site investigation and case analysis,this paper proposed a conceptual model of slip-resisting structure on fault and divided them into three types.Theoretical analysis was conducted on the crushing and shearing failure processes of slip-resisting structures within the fault,and the failure criterion of the slip-resisting structure was proposed based on the energy principle;According to the strength theory,the criterion of fault instability and failure was put forward.Taking the FZ18-1 normal fault of Zhaolou mine as the engineering background,the fault models with no slip-resisting structures,unbroken fracture structure,and hard rock bridge were designed.The physical simulation test of the interaction between fault and stope under coal mining was carried out,and the evolution laws of the deformation and failure of faults with different slip-resisting structures and their surrounding rocks and overlying strata of stope,the stress of coal floor,fault displacement,normal and shear stress of fault surface during coal mining were studied,and the common and different characteristics of the influence of different slip-resisting structures on faults under mining disturbance were clarified.Applying FLAC^3D numerical simulation software,considering different slip-resisting structures,a three-dimensional numerical model of fault and stope was established.The variation laws of fault surface displacement and shear stress,the stress evolution characteristics of fault and stope,and the variation laws of fault energy accumulation under the influence of mining were simulated and analyzed.Focusing on the previous rock friction sliding tests and on-site engineering cases,the laws of sliding,energy accumulation and release of slip-resisting structures on fault were analyzed,and the reasons for the instability and failure of the fault with slip-resisting structures were revealed.The research results are as followed:（1）The fault slip-resisting structures are classified into the unbroken fracture structure,the hard rock bridge,and the friction-prevent asperity.It is considered that the volume expansion point of the slip-resisting structure is an important basis for determining whether its destruction occurs or not,and the mechanical model of unstable sliding of faults containing slip-resisting structures was established.From the judgment of fault destabilization damage,the slip-resisting structure can increase the fault cohesion and improve its stability on some extent.（2）During the physical simulation of mining,the distal ends of the three different faults are first to be affected and appear displacement changes primarily when mining.The normal and shear stresses on the fault surface gradually increase as it approaches the working surface.Firstly,the fault without slip-resisting structures occurred instability and failure,and it generated the largest fault displacement.Secondly,the fault with unbroken fracture structure had the second largest fault displacement.Lastly,the fault with hard rock bridge had the smallest displacement,which means it was minimally affected by mining.When mining near the fault,the normal stress and shear stress in the fault zone increase significantly and have a high degree of variation.Especially for faults with hard rock bridge structures where the rate of increase in normal stress is the highest,and the shear stress and its concentration are the highest.（3）The fault displacement obtained from numerical simulation is similar to the conclusion of physical simulation experiments.Under mining disturbance,the sliding amount of fault with slip-resisting structures is relatively small,and the slip-resisting structures have a significant impact on the stability of faults.The peak shear stress on the fault plane appears near the slip-resisting structures,and the variation amplitude of the peak shear stress on the fault with hard rock bridge structure is smaller than that with unbroken fracture structures,indicating that the hard rock bridge structure is more stable.In general,the accumulated elastic strain energy and its variation amplitude of the fault zone gradually increase with the decrease of the distance between the working face and the fault,and the elastic strain energy rate of the fault without slip-resisting structures first changes greatly,while the elastic strain energy of the fault zone with the fault unbroken fracture structures and the hard rock bridge structures change relatively little.When mining near the fault,the change and accumulation degree of the elastic strain energy in the local range of the fault with slip-resisting structures increase,However,the variation of elastic strain energy of the whole fault is small.（4）From previous stick-slip results of rock friction sliding tests,energy storage and release characteristics of the normal fault in Huafeng coal mine,and the abnormal situation of F16 fault appeared no large slip before rockburst under long-term mining disturbance in Yima coalfield.The above phenomena show that the slip-resisting structures can control the slip of both sides of the fault,and play a role in maintaining the fault stability.However,it also will accumulate large elastic strain energy.If the fault has experienced a long period of intense mining disturbance,the slip-resisting structure will release huge amounts of energy at the moment of its instability,the fault will slip unsteadily in the meantime and cause a violent impact on the mining stope finally.The thesis includes 86 graphics,6 tables and 109 references.