Research On Surface Movement Rules Of Shallow Coal Seam Mining In Karst Developed Mining Area

Most of the coal resource concentrated areas in Guizhou Province are typical ’mountainous terrain + karst landform ’ areas.This paper focuses on the key factor of ’rock strata affected by karstification ’,aiming at the key scientific problem of ’ the mechanism of influencing factors of mining-induced surface movement in karst mining area ’,using physical test,numerical simulation,similar simulation and other research methods.The physical and mechanical parameters of rock mass in karst affected area were studied experimentally,and a random karst model was established in karst affected area.Combined with numerical simulation and similar simulation results,the following conclusions were obtained :(1)Based on a variety of physical tests on the natural control group and the threestage karstification limestone samples,combined with the pore distribution results,the pore type distribution of the natural control group is mainly large and medium pores.The number of medium and small pores in the karst treated samples has increased to a certain extent,and the distribution of small pores in the three-stage samples has increased more significantly.It can be seen that the three-stage small pores and micro pores have been fully developed.(2)Through the numerical simulation of the formation numerical model generated by the random cave and fracture model generation algorithm and the physical and mechanical parameters of different stages obtained by the karstification limestone test,in the stress distribution of the whole stratum,due to the influence of karst on the special structure of the stratum itself,there is obvious stress concentration around the karst fissures in the stratum.Due to the considerable volume of pores and karst caves in the5 % karst affected strata,as well as the overall rock density and mechanical parameter strength damage,the karst affected strata have a greater impact on the overall process of overlying strata migration caused by mining,making the surface subsidence more intense.(3)According to the results of comprehensive similar simulation experiments,in the process of coal seam mining activities under karst affected strata,in the process of breaking and bending subsidence of overlying strata in turn,due to the particularity of karst affected strata ’s own structure,the fracture zone has a higher development height,about 68 m,which causes the settlement value of the bending subsidence zone to further increase,the influence range involves the surface,and the surface settlement value is further increased.When the working face is advanced for a long distance,the development height of the fracture zone will be further improved,and the karst affected strata will have a greater impact on the settlement value of the surface corresponding to the goaf.