Study On Overlying Strata Movement Law And Permeability In Coal-based Solid Waste Backfill Mining

Coal development has caused a series of ecological and environmental damage and geological disasters in mining areas,among which the discharge of coal based solid wastes such as gangue and the control of overlying rock movement are common issues faced by coal mining,seriously restricting the construction of green mines and green mining in China.However,coal based solid waste backfilling mining has significant advantages in terms of rock instability prevention and control,solid waste disposal such as waste rock,etc.However,the current conditions and environment of coal mining are relatively complex,especially for mining under water,and the filling materials are usually affected by the overburden stress and groundwater environment,making it difficult to predict and control their bearing compression deformation.At the same time,the movement and permeability of the overburden rock during backfilling mining under different enrichment rates still require further research.Therefore,this thesis adopts comprehensive research methods such as on-site investigation,theoretical analysis,indoor experiments,and numerical simulation,based on the actual environmental conditions of coal based solid waste backfill materials in mined out areas,develops a stress seepage interaction test system for backfill materials,tests the bearing compression characteristics of coal based solid waste backfill materials,and studies the i MPact of factors such as particle size grading of the backfill materials on the bearing compression deformation;The deformation,failure characteristics and permeability evolution of overlying rock during coal based solid waste backfilling mining were simulated and analyzed,and the key factors controlling overlying rock movement during backfilling mining were obtained;A design process for the enrichment ratio of coal based solid waste backfilling mining under aquifers is proposed.The following main research results have been achieved:(1)The basic characteristics such as mineral composition and microstructure of gangue solid waste materials were obtained through testing;A stress seepage effect test system for backfill materials has been developed,which is mainly composed of a model subsystem,an axial stress loading subsystem,a seepage subsystem,an outlet back pressure control and metering subsystem,a data acquisition and processing subsystem,and an auxiliary subsystem.The composition and functions of each component are described in detail.(2)The loading and compression characteristics of gangue backfill material under stress and stress-seepage action are obtained,the influence of seepage action on the bearing and deformation characteristics of backfill material is analyzed,and the anti-seepage performance of backfill material is studied,the sensitivity of backfilling material to load-bearing compression deformation due to particle size distribution,loading stress level and osmotic pressure is presented.(3)Based on the loading and compression nonlinear deformation characteristics of coal-based solid waste backfill material,a numerical model of overlying strata movement in backfill mining under aquifer is established,and the deformation and failure characteristics of overlying strata in backfill mining are analyzed,the effect of main factors such as filling rate on the permeability of overburden rock is studied,and the water-resisting effect of backfilling mining under different backfilling rate is revealed.(4)The design flow of coal-based solid waste backfill mining backfilling rate under aquifer is put forward,and the index of backfilling rate is determined based on concrete engineering cases,the deformation and failure of the overlying strata in the test area are analyzed by numerical simulation and theoretical calculation,and the rationality of the research results is verified.