Optimization Of Structural Parameters And Drift Layout Of Downward Layered Unclassified Tailings Paste Filling Stope

Filling mining method has a wide application prospect,especially after the mine enters deep mining,its application range will be greatly improved.Downward slicing filling mining is one of the important methods in filling mining,and full tailings paste filling is also the main filling process trend at present.As an important bearing unit of the drift stope,the stability of the full tailings paste filling roof is of great significance to ensure the safe and efficient production of the mine.The structural parameters of the downward cemented filling stope and the layout of the stope route are the key factors affecting the stability of the filling roof.In view of this,taking a copper mine in Jiangxi as the background,this paper comprehensively adopts the combination of indoor test,theoretical analysis,numerical simulation and field monitoring to analyze the stability of the filling roof from the perspectives of the strength of the whole tailings paste filling body,the roof load of the stope route and the layout scheme of the layered stope route.The main research contents and results are as follows:(1)Mine is often filled with full tailings paste with a lime-sand ratio of 1:4 and 1:8,and the mechanical parameters of the paste filling body with the two ratios are tested.The research results show that the uniaxial compressive strength of the paste filling body with a lime-sand ratio of 1:4 is 5.03 MPa,the uniaxial tensile strength is 0.64 MPa,the elastic modulus is 0.65 GPa,the Poisson’s ratio is 0.2,and the cohesive force is 1.15 MPa,the internal friction angle is45°;the uniaxial compressive strength of the paste filling body with a lime-sand ratio of 1:8 is1.85 MPa,the uniaxial tensile strength is 0.19 MPa,the elastic modulus is 0.14 GPa,and the Poisson’s ratio is 0.28.The cohesive force is 0.4MPa and the internal friction angle is 41°,which provides a basis for further research.(2)Seven load calculation schemes including total soil column theory,Platts theory,combined rock beam theory,Terzaghi theory,classical Janssen theory,Xie Jiayang theory and Bibaumann theory were used to calculate the roof load and overburden of the mining approach.The relationship between the number of layers and the analysis of the calculation results show that it is more reasonable to use the classical Janssen theory to calculate the roof load value of the mining approach.Therefore,the theoretical relationship between the roof load and the overlying filling layers is established,and the ultimate load is proposed,which does not change with the increase of the number of overlying filling layers.(3)In the downward horizontal layered paste filling mining,the paste filling body with high lime-sand ratio is usually used as the bearing layer.At present,the thickness of the bearing layer is generally calculated by the simplified beam and plate model,and the calculation results are quite different from the actual engineering.A calculation model with a section size of 5m× 4m was established for the mining approach,and a sudden change model of the roof displacement cusp was constructed.The results show that: when the thickness of the bearing layer is less than 1.2m,a continuous plastic zone is formed at the corners of both sides of the access roof;when the thickness of the bearing layer is 1.0～1.2m,the eigenvalue of the displacement mutation changes from positive value to negative value.It is obtained that when the section size of the mining approach is 5m×4m,the ultimate thickness of the bearing layer of the backfill roof is 1.2m.(4)In the downward layered filling mining method,a filling weak surface will be formed between different routes,and the mechanical strength of the weak surface will be significantly reduced.Therefore,numerical simulation method is used to study the distribution of the filling weak surface,the azimuth angle and the roof of the filling body.stability relationship.The results show that the stability of the backfill roof is the highest when the upper and lower stratified mining approaches are arranged vertically.(5)Considering the actual safety of the mine project,it is finally recommended that when the section size of the mining approach is 5m×4m,the thickness of the bearing layer is 1.5m,and the upper and lower layers of the mining approach are arranged vertically.The on-site monitoring results show that the mechanical state changes little during the exposure of the paste backfill roof,which can effectively play a bearing role and ensure the safety of production and operation in the mine stope.The rationality of the theoretical research is further verified,and the basis for the production design of the downward horizontal layered paste filling mining method is provided.