Study On The Mining Pressure Behavior And The Support Technology Of The Shallow-buried Thin Layer Weakly-bonded Uranium Mine During Fully-mechanized Coal Mining

In this paper,a uranium mine is used as the engineering background.According to the physical and mechanical characteristics of shallow-buried thin-layer weakly-bonded soft rock,the physical and mechanical properties of weakly-bonded soft rock,the development of similar materials,numerical simulation and physical model tests are revealed.The law of mine pressure behavior of surrounding rock in fully mechanized mining face is studied.Combined with the deformation and failure characteristics of surrounding rock,the control effect of supporting structure on surrounding rock stability is studied,and the technical scheme of working face support is proposed.The main research results of this paper are as follows:(1)Through the study of the basic physical and mechanical properties of weakly cemented soft rock,it reflects that the soft rock has strong expansibility,poor cementation,easy muddy and disintegration in water,and obtained physical and mechanical parameters of uranium stratum..Through the analysis of the basic physical and mechanical properties and meso-features of weakly-bonded soft rock,the expansibility and material structure of the weakly-bonded soft rock in the uranium stratum and the physical and mechanical parameters of the uranium deposit and the existing strata are revealed.(2)Combining the physico-mechanical characteristics of shallow-buried thin-layer weakly-bonded uranium ore,through the configuration of a series of similar materials,the similar material ratio suitable for the uranium geological conditions is obtained,namely fine sand: gypsum: calcium carbonate: bentonite 4.5:0.5:0.2:0.3,6:0.6:0.2:0.2,3.5:0.5:0.3:0.2,and 4:0.5:0.3:0.2 are the ore bodies,mudstones,siltstones,and fine sandstones that simulate the physical model;The strip pressure test determined the corresponding model of the steel bracket in the similar model,and the concrete spray layer was simulated by the calcium carbonate liquid solidified coating.(3)Through the UDEC numerical simulation study,the distribution characteristics,vertical displacement and stress evolution of the overlying strata in the stope are analyzed,and the initial pressure is about 8.0 m and the periodic pressure step is about 3.0 m.Measurement and analysis system and membrane pressure sensor monitoring means,analysis and verification model test process,with the advancement of the working surface,the closer to the goaf,the larger the displacement,the maximum sinking amount is about 1.6 m,and the maximum sinking position is constant When moving forward,the maximum value of the vertical displacement of the topsoil is increasing continuously,and the maximum settlement is about 0.69 m;the pressure is removed from the goaf behind the working face,the overburden is sinking,the goaf is compacted,and the surrounding rock is far away from the goaf.The vertical stress gradually recovered to close to the original rock stress of 0.03~0.04 MPa,the stress peak gradually became larger,and the maximum value was about 0.07 MPa.The stress change near the measuring point near the goaf was significantly greater than other measuring points.(4)Through FLAC3 D,the numerical simulation analysis of the key supporting parameters of the working face is carried out to study the feasibility of different types of I-beam under 8 working conditions,and the 11# I-beam is selected with a spacing of 0.8 m;The large-scale three-dimensional similar model is used to test the selected supporting parameters.With the increase of the load,the displacement of the upper overburden increases,and the displacement of the top plate is 0.02 m.The displacement of the two gangs is small and the convergence is not obvious.The vertical stress increases with the increase of load,the load reaches the target value of 9 k N,and the maximum stress is about 0.05 MPa.The stress field decreases from the loading plate to the center of the model,and the closer to the loading surface,the greater the stress;The variation law can be roughly divided into the volatility growth phase to the stationary phase and the stepwise growth phase,and the load is increased to the target value.The stress values of the two gangs are smaller than the stress values of the top plate,and the support stress is about 0.02~0.04 MPa.