Experimental Study On Filling Characteristics And Bearing Capacity Combined With Gangue Of Multi-source Coal Based Solid Waste Materials

The massive mining of coal resources has made great contributions to the development of the national economy;however,it brings negative environmental effects such as surface subsidence or collapses and produces a large number of solid wastes.Backfill mining technology has been widely used because of its high resource recovery,small surface subsidence,and environmental protection.Based on the national key research and development projects,the concept of green mining of coal resources,and the comprehensive utilization of solid waste resources,the work studied the optimal proportion of filling materials used in the caving zone in the goaf with multi-source coal-based solid waste materials.Coal gangue,fly ash,desulfurization gypsum,gasification slag,furnace bottom slag in the east of Ningxia were used as raw materials for laboratory experiments and theoretical analysis.The pipeline transportation characteristics of the filling slurry and the mechanical properties and bearing characteristics of the filling cement have laid an important foundation for the research project.The main achievements of the study are as follows:The research results provide a scientific basis to prepare filling slurries for the comprehensive utilization of multi-source coal-based solid wastes.(1)Based on testing the microphysical morphology and chemical composition of solid waste materials,the response surface methodology was used to optimize the characteristics of the filling slurries of multi-source coal-based solid wastes under different ratios,and the optimal ratio of multi-source solid-waste materials used to prepare the filling slurry was obtained: 49.5% of gangue,8.3% of fly ash,4.1% of desulfurization gypsum,6.2% of gasification slag,and 6.2% of furnace bottom slag.(2)The large experimental platform for filling the caving zone in the goaf was constructed,and the filling experiment was carried out with the prepared filling slurry of multi-source coal-based solid wastes.The flow characteristics and diffusion law of the filling slurry in the gangue dispersion of the caving zone in the goaf were obtained under mining at the different inclination angles of coal seams.(3)The influences of the compositions of multi-source coal-based materials on the strength of the filled consolidated body specimens of different ages and the mechanical properties of the filling body bearing were studied by analyzing the microscopic material structure of the filled consolidated body and testing the uniaxial loading of the consolidated body specimen and the acoustic emission.The evolution characteristics of new materials generated in the specimens at different ages were obtained,and the strength evolution law and acoustic emission characteristics of the multi-source coal-based solid-waste filling body were revealed.The uniaxial compressive strength of the specimen at the age of 3 days was stable at about 0.3 MPa,which is about 22% strength at the age of 28 days.Uniaxial compressive strength at 14 d was stable at about 1.3 MPa,which was about 80%strength at 28 d.Uniaxial compressive strength at 28 d was stable at about 1.7 MPa,and the maximum was 2.8 MPa.(4)The pipeline transportation characteristics of the filling slurry of multi-source coal-based solid wastes were studied using the numerical simulation method and FLUENT software.The flow velocity and pressure distribution rules of the filling slurry were analyzed under different pipeline turning angles,filling slurry densities,pipeline inlet pressures,and pipeline diameters.The pipeline transportation velocity and pressure distribution characteristics of the filler slurry were revealed to prove the pipeline transportation flow characteristics of the filling slurry of multi-source coal-based solid wastes.(5)A combination experiment was used to carry out the uniaxial compression test and acoustic emission test of the filling body.The analysis of fractal theory was used to study the carrying characteristics of the filling combination and obtain the phased characteristics of the filling combination.Besides,the work revealed the compressive mechanical properties of the filling combination formed by gangue and filling slurries in the goaf zone and the particle interaction mechanism inside the filling combination.(6)Based on the research of filling characteristics and bearing capacity of multi-source coal-based solid-waste materials,the achievements have laid an important foundation and strong supports for the national key research and development projects.Figure [114] table [27] reference [179]...