Study On The Overlying Rock Movement And Surface Subsidence Control Of Solid Backfilling Mining

The roof control of caving mining is dominant in our country,which causes serious surface subsidence,accompanys a large amount of structures damaged.And gangue etc.waste also has a large-scale land occupation which causes secondary geological disasters of landslide,spontaneous combustion,dust etc.By solid backfilling mining method,overlying rock movement and surface subsidence can be controled effectively and a amount of gangue consumed.It has important significance to study on the overlying rock movement and surface subsidence control of solid backfilling mining.Regarded a work face of Liujia block mine field in Fuxin as research background,based on the optimization of compression deformation properties of solid backfilling materials,the geological survey,properties of solid backfilling material tests,mechanical analysis,numerical simulation and similar material simulation are carried out,laws of overlying rock movement and surface subsidence are researched systematically,main research results are as follows:When the maximum particle size of gangue is controlled 50 mm and n=0.3 of Talbol's theory,the gradation is ideal and the gradation of undisturbed gangue can be optimized and closes to the ideal gradation by "fine crushing" processing,and the optimization of gangue gradation enhances the resistance ability of compressive deformation of the solid backfilling body.The compression process of gangue-loess mixed backfilling material has typical non-linear characteristics which is divided into three stages of rapid deformation stage,slow deformation stage and stability stage.The "fine crushing" gangue-loess mixed backfilling material whose the dry weight ratio of "fine crushing" gangue and loess is 5:2 and the water content of loess 12% has the better resistance ability of compressive deformation and integrity is the optimized mix proportion design of solid backfilling material.It is built the elastic foundation beam and nonlinear foundation beam equation respectively on direct roof rock and calculating examples are solved by numerical solution,compared with the results of the elastic foundation beam equation and nonlinear foundation beam equation,the maximum deflection and equilibrium deflection are approximately equal of the direct roof rock,but the maximum rotation angle,bending moment,hear force and curvature of the elastic foundation beam are all smaller.It is built and obtained the analytic solution that the overlying rock movement mechanics equation which taken account of coal body zone,hydraulic support zone,backfill zone.And under the solid backfilling mining method,the influence of deflection,abutment pressure,bending moment,hear force and curvature of direct roof rock is analyzed when the coefficient of subgrade reaction,elastic modulus of roof rock beam,buried depth and roof rock beam thickness change and results showed that the influence of the coefficient of subgrade reaction is the greatest.Numerical simulation and similar material simulation results showed that the subsidence process of overlying rock of the solid backfilling mining both are rapid growth,steady growth and finally reaches stability and from bottom to top are divided into regularly caving zone,fracture zone and bending zone,the subsidence factor of overlying rock increases with the working face pushes on,and without irregularly caving zone in the moving and destructing areas.The numerical simulation results also showed that the backfilling ratio increased,the degree of damage to the overlying rock and the thickness of regularly caving zone,fractured zone both decreased.After the backfilling ratio reached 80%,the effect is not obvious which increases the backfilling ratio to decrease destroying degree and extend of overlying rock.When the backfilling ratio is 70%,the growth rate of subsidence factor is the most fastest,and the higher the backfilling ratio is,the faster the stability of overlying rock and the earlier into fully adopt state.Under different solid backfilling ratio,the change trend of the surface subsidence and horizontal deformation are almost same with the working face pushes on,the change of early stage is fast,later stage is slowly.In the similar material simulation test,the compression curve of the actual solid mixed backfilling material is transformed into the theoretical compression curve of the simulated material by similar scale and the simulation of the actual compression process is realized of the solid mixed backfilling material,the accuracy and engineering of experimental are improved.In the numerical simulation results,the maximum surface deformation of 70% backfilling ratio exceeds the grade I damage evaluation standard of brick-concrete structure building and 80% backfilling ratio in the grade I damage evaluation standard,and the control standard of backfilling ratio is 80% of the solid backfilling method in engineering application.In the Sunjiawan coal seam of Liujia block,under 80% backfilling ratio,the surface subsidence of the gangue-loess mixed backfilling material is predicted by the probabilistic integration method,the predicted value of maximum subsidence is close to that of numerical simulation and the degree and range of surface deformation under not sufficiently mining conditions are less than full mining conditions.