Mechanical-hydro-chemical Coupling Mechanism And Evolution Of Mining-induced Permeability Of Weakly Consolidated Mudstone In Alkaline Water Environment

Coal mining the western mining area of fragile ecological environment worsens,to improve the coal recovery rate and protect the ecological environment protection of water resources,in particular,this paper takes great south lake seven mine geological conditions as the research background,combining with laboratory experiments,theoretical analysis and numerical simulation method,weak cementation mudstone of alkaline water environment mechanical-hydro-chemical coupling mechanism and to study the evolution law of mining shale permeability,the main research results are as follows:(1)Through the weak cementation mudstone of alkaline water chemistry experiment,weak cementation mudstone with the increase of immersion ion concentration in the solution,alkaline enhancement and soak increases,the specimen in the skeleton fossil reduce cementation,mineral composition,porosity,mechanical properties on the macro performance for fall,weak cementation mudstone reduce the compressive strength,elastic modulus is reduced,due to the shrinking of cement mineral composition,the cohesive force with the increase of the reaction time and the basic trend of increase and decrease in chemical solution.(2)According to the permeability laboratory data of weakly consolidated mudstone,the permeability curve of weakly consolidated mudstone is in the shape of "S",and the permeability increases with the increase of alkalinity in soaking solution and the increase of soaking time.Combined with the state index of the element,the state of the element in the stages of elasticity,yield and failure was expressed in a mathematical form,and the function relationship between permeability and strain was established under different alkaline strength and different reaction time of weakly consolidated mudstone.(3)According to the weak cementation mudstone alkaline water chemistry experiment,based on water chemical damage and damage of uniaxial compression strength of different alkaline weak cementation mudstone is set up under different reaction time,the elastoplastic damage constitutive model,the parameters in the model a,r improvements in overall with alkaline chemical solution and the increase of immersion time presents the tendency of increase,combined with the relationship between permeability and strain,through the numerical simulation of the permeability curve was "S" type.With the increase of alkalinity in chemical solution and the increase of immersion time,the rate of permeability decline gradually increases in the stage of compaction and elasticity of mudstone,and the slope of permeability curve increases gradually in the stage of yield failure.(4)From the outside of the goaf to the central area of the goaf,the permeability recovered slightly from the original permeability through the permeability reduction zone to the permeability surge zone to the center.With the increase of coal thickness,the decrease of buried depth and the decrease of the distance between weakly cemented mudstone and coal seam,the permeability above the goaf increases.With the increase of the vertical distance between weakly consolidated mudstone and coal seam,the range of permeability surge area(yield and failure area)of mudstone decreases first and then increases.The paper has 74 figures,8 tables and 81 references.