Mining-induced stress evolution characteristics of overlying strata under repeated mining

LUO Shenghu; GAO Jiabo; XIE Panshi; YAN Zhuangzhuang; TIAN Chengyang; MENG Zhihui; XIA Duanyang

doi:10.13347/j.cnki.mkaq.20241154

Abstract：Mining-induced stress concentration is one of the main reasons for the deformation and instability of coal and rock in stope.It is of great significance to master the evolution law of mining-induced stress of coal and rock in stope for preventing and controlling the dynamic disaster of coal and rock.In this paper,the macroscopic deformation and failure characteristics of overlying strata under repeated mining are analyzed by combining physical simulation with numerical simulation.The evolution path and dir-ection deflection characteristics of principal stress transfer in interbedded rock layer are studied,and the evolution mechanism of mining-induced stress in working face under repeated mining is revealed.The results show that during the mining process of the lower coal seam,the deformation and failure range of the interbedded rock layer increases first and then gradually stabilizes.A large number of micro-cracks appear in the interbedded rock layer below the upper coal floor,and the cracks are not connected with the upper coal floor.There is no secondary deformation and failure of the overlying rock.Under the action of repeated mining,the stress release range and principal stress deflection degree of the interbedded rock layer are increasing.Affected by the pressure relief of the upper coal floor and the deformation and failure range of the overlying rock,the stress concentration degree of the coal and rock in front of the working face is different.Affected by the pressure relief of the lower coal roof-pressurization of the upper coal floor-re-petitive pressure relief-pressurization of the lower coal roof-pressurization of the two coal seams,the deflection of the first principal stress angle of the interbedded strata is regional.In this process,under the action of overburden load transfer and upper coal floor stress release range,the peak value of coal abutment pressure in the front of the working face shows an evolutionary trend of first stable,then slowly increasing to rapidly increasing.When the ratio of working face advancing distance to working face length is greater than 1.2,the growth rate of mining stress peak value of working face increases rapidly,and the working face is prone to de-formation and instability.