Properties And Grout Diffusion Law Of Graphene Cement-based Anti-dispersive Grouting Water Plugging Composites

Coal mining with water retention on high confined Ordovician limestone aquifer is a major technical problem faced by coal mining.The most common and effective way to solve it is to modify aquifer by grouting,so that the strong aquifer becomes the weak aquifer or even the aquifer.The premise and key to realize the modification of grouting is to develop efficient and suitable grouting sealing material and master its basic performance law.With the grouting modification of high confined aquifer as the engineering background,aiming at the deficiencies of existing grouting materials in slurry anti-dispersibility,strength of grouting rock mass and impermeability,this paper comprehensively adopts laboratory testing,theoretical analysis and numerical simulation methods to research and develop graphene cement-based anti-dispersive composite grouting water plugging material.The influence of graphene on the rheological,mechanical and impermeable properties of materials was mastered,shear failure and seepage characteristics of the grain-rock interface were defined,diffusion laws and loss characteristics of PPGF grout were revealed,and grouting process parameters were proposed.The paper has obtained the following research results:(1)An anti-dispersive composite grouting water plugging material for coal mining in high confined aquifer was developed,and the effects of graphene content on PPGF slurry loss,diffusion distance,stone strength and permeability were revealed.The composition of anti-dispersive composite grouting water plugging material was proposed,the test method of anti-dispersive PPGF grout was improved,the grout loss calculation equation was established with grout flow rate and environmental water pressure as the main controlling factors,and the influence law of graphene dosage and dosage on grout rheology,fluidity,setting time,water consumption of standard thickening,loss amount,water dissolution rate and diffusion distance was revealed.And the influences on the compressive strength,toughness,shear failure characteristics and impermeability of PPGF stone body.(2)The microregulatory mechanism of graphene on cement reinforcement and permeability reduction was clarified,and the strength and toughness enhancement mechanism of PPGF material generated by the "elastic mesh" of graphene atomic stress transfer was revealed.The regulation mechanism of graphene on hydration rate,product and structure of cement was determined by microscopic testing method.The relationship between GR/C-S-H molecular structure failure,atomic stress distribution,radial distribution function and interfacial energy and the number and distribution state of graphene sheets under microscopic tensile action was revealed from the atomic scale,and the transfer,transfer and release law of atomic stress between graphene and calcium silicate hydrate during tensile deformation was clarified.The mechanism of enhancing the strength and toughness of PPGF material with the effect of "elastic mesh" was investigated.(3)The effect of graphene content on shear deformation and failure characteristics of PPGF-limestone cementation was revealed,and shear constitutive model and dilatancy model based on equivalent wall strength were established.The response relationship between graphene content,roughness of cementing surface,normal stress and shear deformation and failure characteristics of cementing body is revealed.A roughness degradation model of cementing surface considering wall strength characteristics is proposed.A shear failure prediction method of PPGFlimestone cementing body is determined by taking the fractal dimension RA value as the first abrupt drop of cementing body cracking and the second abrupt drop as the shear of cementing body.The shear constitutive model and dilatancy model of PPGFlimestone cement body based on equivalent wall strength were established.(4)A method to determine shear wear height,shear fracture mechanical opening and contact rate of cementation surface is proposed,and a nonlinear seepage model of PPGF-limestone cementation interface is constructed.The calculation method of shear wear height of the cementation surface was proposed,and the variation law of shear fracture mechanical opening and contact rate with graphene content,bonding surface roughness,normal load and shear displacement considering wall wear was obtained.The relationships among hydrostatic pressure,seepage flow line,seepage flow rate,equivalent permeability coefficient,critical hydraulic gradient and hydraulic gradient,and graphene content of PPGF-limestone cementation surface shear and nonlinear seepage model were established.(5)The rheological equation and diffusion model of PPGF grout considering water evolution effect were established,the diffusion law and loss characteristics of grout under static and dynamic water conditions were revealed,and the grouting process parameters were determined.The influence degree index λ of grout water evolution rate on the time-varying viscosity was put forward.The time-varying viscosity equations,rheological equations and spherical and cylindrical diffusion models considering grout water evolution effect were established,and the influence law of initial grouting pressure on the sudden change degree of pore pressure and volume strain under static water condition was revealed.The relationship between slurry nucleation time,diffusion distance,material ratio and initial grouting pressure under dynamic water condition was proved,and the grouting materials and process parameters of coal mining engineering cases with water preservation were determined.This thesis has 191 figures,32 tables and 214 references.