Experimental Study On The Formation Process Of Reverse Fault And Its Influence On Footwall Coal Seam Mining

As a major geological structure that is abundant in coal mining,faults destroy the continuity and integrity of the strata.In particular,there are large tectonic stresses and residual energy in the rock mass around the reverse fault;when mining coal near the reverse fault,The interaction between mining and fault causes the stress field of the rock mass around the fault to change again,the rock strata to move again and destroy,and then the mine disasters such as water inrush and impact rock pressure are triggered.Therefore,it is particularly important to study the influence of the formation of reverse faults on coal seam mining.In this paper,the geomechanical mechanism of reverse faults was developed,and a geomechanical experimental system for the formation of reverse faults was developed to simulate the formation process of reverse faults.Accurately control the reverse fracture initiation position.The reverse fault formation test was carried out using the reverse fault formation geomechanics test system,and the characteristics of rock movement damage and stress variation during the formation of reverse faults were obtained.The study found that the formation of reverse faults can be divided into four stages:compressive deformation of rock strata,local initiation,reverse fault penetration,and up-and-down plate misalignment;the fault dip angle is mainly related to the mechanical properties of the rock,and the drop mainly depends on horizontal thrust;reverse fault In the process of formation,the horizontal stress of rock strata first rises,and the reverse fault breaks down and then drops steeply.The farther away from the fault the stress decreases,the horizontal stress gradually decreases after the upper and lower plates slide;after the rock formation is stable,the horizontal stress near the fault is greater than the initial stress,and the closer the stress is to the fault.In addition,the formation of reverse faults has little effect on the vertical stress of the coal seam floor.After the formation of the reverse fault,the mining test of the coal seam in the footwall was conducted,and the rock formation response law was obtained during the mining of the footwall.During the mining process of the lower coal seam,the tectonic stress near the fault and the superimposed abutment pressure superimposed on the stress of the rock near the fault in the lower plate,which eventually led to the activation of the fault;when the working face approaches the fault,the vertical stress in the rock formation on the upper plate shows a small stress concentration.The horizontal stress of the disk decreases due to the fracture of the underlying rock,and the closer to the fault,the greater the degree of reduction.The prefabricated fault footwall mining test was carried out and compared with the test results of the lower wall mining after the formation of the reverse fault.The results show that there is obviously a higher tectonic stress around the fault after the formation of the fault compared with the lower wall mining test of the prefabricated fault.In the mining process of the footwall,the overburden movement and damage are more severe,the fracture zone is higher,and the horizontal and vertical stress concentrations are larger than the prefabricated fault mining test,and the stress on the upper plate near the fault is concentrated,and the fault is activated near the fault.The horizontal stress of the rock layer drops sharply.