A Study On Laws Of Movement And Damage Of Overlying Strata And Development Of Water Flowing Fractured Zone In Yushenfu Mining Area

Coal mining will lead to the failure of stress balance in overlying strata to form water flowing fractured zone.The movement and damage of overlying strata and the development law of water flowing fractured zone have important guiding value for the prediction and prevention of water inrush accident in coal mining.Due to the fact that coal seam is buried underground,it is difficult to observe the movement damage of overlying strata and the development of water flowing fractured zone during mining,,numerical simulation can be used to solve this problem.Yushenfu mining area is rich in coal resources,but the depth of coal seam is shallow,and the main aquifer is located in the shallow part of the surface,hasty and high-intensity mining is likely to cause aquifer leakage,cause water inrush,and worsen the ecological environment.In this paper,we take Yushenfu mining area as the research area,use the discrete element numerical simulation software to set models according to the actual drilling data,analyse the movement and damage of overlying strata and the development law of water flowing fractured zone,verify the reliability and accuracy of the model by the measured data.Then the influence of geological factors and mining factors on the movement and damage of overlying strata and development of water flowing fractured zone is explored.Finally the effects of two water-retaining mining methods,strip mining and strip filling mining,on restraining the movement and damage of overlying strata in goaf are analyzed.The main research results and conclusions are as follows:(1)In this paper,discrete element numerical simulation software is used,and the actual borehole data and physical and mechanical parameters of rock strata are taken as the modeling basis,the key stratum theory is used to divide the block,then we analyze the movement and damage of overlying strata and the development law of waterconducting fracture zone under mining conditions.It is found that:In shallow buried strata,with the development of mining,a stress arch will form over the goaf.The inner stress arch is the stress unloading zone,the edge is the stress concentration zone,and the surface forms the tensile stress zone.;not only the process of mining will develop upward fractured zone,downward fractured zone will also occur on the surface due to tensile stress.Because the main aquifer in the study area is located on the surface,the large thick mining in shallow buried strata will lead to the penetration of upward and downward fractured zones and cause groundwater leakage,The simulation results are in agreement with the measured data in the mining area and the accuracy of the model is verified.(2)By using the control variable method,the influences of mining thickness,mining depth,water-proof clay stratum thickness and key stratum on the moment of overlying strata and development of water-conducting fracture zone are investigated,it is found that: the mining thickness affects the vertical migration space of overlying strata,the smaller the mining thickness is,the vertical displacement of overlying strata cannot reach the deflection value;the mining depth affects the load of the rock strata,the greater the mining depth is,the greater the load of the rock strata near the coal seam is,and the more likely it is to break;because of its special physical and mechanical properties,water-proof clay stratum can effectively restrain the connection of upward and downward fractured zones;Because of its large thickness and high strength,the key stratum can slow down the speed of moving damage.At the same time,it is found that the ratio of the height of the water flowing fractured zone to the mining thickness of each model is basically around 25,and when the thickness of water-proof clay layer exceeds 40 m,the upward and downward fractured zones are basically not connected,which is close to the measured data in the research area and verifies the reliability of the conclusion.(3)In shallow buried stratum,large thickness mining can easily lead to the development of water flowing fractured zone to the surface.,if we limit the mining thickness,coal resources will be wasted,strip mining and strip filling mining can not only restrain the movement and damage of overlying strata and the development of water flowing fractured zone,but also effectively improve the mining rate of coal seam by increasing the support body and reducing the fracture distance of rock strata,and the effect of strip filling mining is better than strip mining.