Study On Diffusion Characteristics Of Clay Cement Slurry In High Pressure Floor Strata And Grouting Modification Technology In The Longquan Coal Mine

Floor water gushing not only poses a serious threat to the safety of mining areas,but also causes a large amount of waste of water resources.Especially for the North China type coalfields,which are threatened by the strong karst aquifer water of Ordovician limestone in the basement of coal measure strata,the water-conducting cracks can be blocked by grouting method to prevent floor limestone water from flooding into the mine.Based on the floor grouting water preservation project of Longquan Coal Mine in Shanxi Province,and analyze the characteristics of grout distribution,pore pressure and volumetric strain change in the rock stratum under different ratio of grout and different grouting pressure,the relationship between grouting diffusion property,grouting ratio and grouting pressure is revealed,which provides a basis for the determination of grouting transformation parameters.The main research results are as follows:(1)The diffusion process of the grout in the limestone layer containing high confined water during the grouting process is studied.The process of grout diffusion can be regarded as the process of grout dispels the water: the grout enters the rock at a high pressure,and under the push of the grouting pressure,the grout constantly dispels the water and advances along the pores.The analysis shows that in the process of the slurry diffusion,the pressure is constantly lost due to the pressure of confined water,the friction of rough pores and the viscosity of the slurry itself.When the slurry diffusion reaches a certain degree,the grouting pressure is not enough to push the slurry forward,and the maximum diffusion distance is reached at this time.(2)The influence of the ratio of clay-cement grout on the diffusion property was analyzed.Considering the time-varying effect of slurry viscosity,the slurry distribution,pore pressure change and diffusion distance change with time of slurry with different ratio in the process of grouting were compared and analyzed,and the conclusion was drawn that the diffusion property of slurry with different ratio was related to the initial viscosity and time-varying coefficient of slurry viscosity: The larger the initial viscosity of the slurry,the smaller the resistance and the better the diffusion performance,and the time varying coefficient of viscosity determines the length of the free diffusion of the slurry.(3)The diffusion law of grout in different rock strata under different grouting pressures is analyzed,and the grouting transformation parameters are determined.Considering the fluid-structure coupling effect caused by the movement of grout and water in the rock layer,the distribution of grout in different rock layers,the temporal and spatial variation of pore pressure and the change of volume strain in the process of grouting were analyzed under different initial grouting pressures,and the conclusions were drawn as follows: The larger the porosity and permeability of the rock,the smaller the resistance of the slurry diffusion process.The larger the initial pressure,the better the diffusion performance of the grout,but too large initial grouting pressure will cause the plastic deformation of the rock mass.