| The ecological environment damage and pollution caused by the large-scale development and utilization of coal are becoming increasingly prominent.The grouting and filling technology for overlying strata can not only alleviate the problem of coal mining collapse,but also deal with some coal mining waste.At the same time,it can also play a role in preventing and controlling water damage in mines with hidden dangers of overlying strata separation.It has been widely used.The grouting material for overlying strata separation has always been mainly fly ash.In recent years,With the expansion of application scope,the demand for filling materials has increased,and coal gangue as an alternative grouting material has attracted attention.However,issues such as coal gangue as a separation layer grouting material and the properties of the slurry after mixing with fly ash still need to be studied.This article studies the basic properties of mixed slurries with different ratios of coal gangue and fly ash,analyzes the factors that affect slurry diffusion such as water evolution,viscosity,and density of slurries with different ratios,and constructs a visualized overlying rock separation grouting model to simulate the slurry diffusion law and pressure change law in the cavity under different conditions,Finally,the impact of mixed slurry on the mining of overlying rock separation layer grouting face was analyzed and evaluated.The thesis achieved the following results:(1)The chemical composition of coal gangue and fly ash was tested and analyzed.The orthogonal experimental method was used to test and analyze the influence of changes in volume concentration,coal gangue particle size,and the mass ratio of fly ash to coal gangue on the density,viscosity,and water release rate of the slurry.The slurry viscosity reduction test was also designed.(2)The basic properties of the mixed slurry of coal gangue and fly ash under different pressure conditions were tested and analyzed.The water release rate of the mixed slurry under pressure conditions can be divided into three stages: rapid water release stage,slow water release stage,and water release stop stage.The influence of pressure,coal gangue proportion,and coal gangue particle size on the water release rate and water release rate was analyzed.(3)Based on the actual working conditions on site,a physical simulation test model was established to analyze the flowability of slurry with different ratios of coal gangue and fly ash.Furthermore,the impact of increasing the amount of coal gangue on the viscosity and stability of the slurry was analyzed,and the variation rules and distribution characteristics of grouting pressure inside the separation layer cavity were summarized.(4)By using the "water inrush coefficient" method,the impact of grouting in the overlying rock separation layer on the working face was evaluated and analyzed.Based on factors such as the thickness of the protective layer under the overlying rock separation layer and the water pressure of the water filling aquifer in the separation layer under actual on-site working conditions,the maximum grouting pressure was determined.Combined with the water seepage rate of the slurry,the impact of grouting on the water inflow of the working face was analyzed,and suggestions for water prevention and control measures in the grouting filling working face were proposed. |
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