Research And Application Of FDM Simulation Tetrahedral Mesh Geometric Adaptive Method For Mining Subsidence

There are various forms of coal seam distribution in China,among which the gently inclined coal seams are widely distributed.At present,the method of top coal caving is mostly adopted in the gently inclined coal seam.When using this mining method to mine the coal seam with shallow depth and large thickness,the overburden rock layer will be damaged and the surface movement deformation will be obvious.As the mining face advances,the overlying rock mass will undergo large deformation and large displacement movements.In order to ensure the life of the ground residents,we must fully understand the changes in the surface.In this paper,the geometric distortion re-division method of tetrahedral mesh is proposed to solve the problem of mesh distortion in finite difference method in simulating mining subsidence problem,and it is applied to the engineering example of gently inclined coal seam mining.The main research results of this paper are as follows:(1)The characteristics of surface subsidence induced by gently inclined coal seam mining and its FDM simulation method are summarized,and the main problems in the simulation method are analyzed.(2)A method for adaptive subdivision of mining subsidence FDM tetrahedral mesh is proposed.When the finite difference method is used in the simulation calculation process,if the node generates a large displacement,the distortion element will appear.At this time,the numerical calculation cannot be continued,and the accuracy of the subsequent numerical calculation decreases accordingly.By developing the relevant algorithm of FDM grid adaptive processing,the distortion element is searched and the distortion region is re-divided,the tetrahedron in the region is regenerated,and the quality of the tetrahedral element is improved,thereby satisfying the requirements of numerical calculation.After the geometric model is regenerated,according to the positional relationship of the former node and the element,the physical field quantity of the new node and the new element is interpolated to realize the physical field quantity transferring.(3)Taking the mining of 4106 working face of Anjialing No.1 Mine in Pingsuo,Shanxi Province as an example,the application of FDM mesh geometry adaptive method was carried out.According to the topographic map,drilling data and geological data of the research area,a three-dimensional geological model was established,and the model was imported into the finite difference software to simulate the surface deformation during the mining process.In the mining process,the distortion element is searched,then the numerical calculation is stopped,the mesh is adaptively re-divided,and then the calculation is resumed.The large deformation and large displacement movement of the overburden during the mining process are simulated,and the surface deformation is analyzed.The application of mesh adaptive technology in FDM is realized.