Study On The Water Loss Effect And Diffusion Characteristics Of Grout In Seepage Grouting Of Fractured Mudstone

Weakly cemented mudstone is widely distributed in the western mining area of China,which has special diagenetic environment and sedimentary process,forming its unique physical and mechanical properties.The deep mudstone mass contains a large number of fractures.Under the complex stress conditions such as engineering disturbance,new fractures are constantly generated,original fractures continue to expand,and then many fractures penetrate each other,transforming the fractured mudstone mass into the crushed mudstone mass.There are few researches on the permeability characteristics of grouting in fractured mudstone under the action of stress at present.Therefore,it is of great significance to understand the permeability characteristics of grouting in fractured mudstone under stress for scientific and effective development of mudstone grouting engineering.In this paper,the permeability characteristics of grouting in deep fractured mudstone based on the viscosity variation characteristics of dehydrated grout were studied by self-developed mudstone grouting test systems,theoretical analysis and numerical simulation.The research results obtained are as follows:(1)Based on laboratory tests,the parameters of cement-based grouting materials and mudstone foundation were obtained.The rheological properties of cement-based grout and the pore structure and mechanical properties of mudstone were analyzed,which provided basic parameters for the physical and numerical grouting tests for mudstone.(2)Nuclear magnetic resonance(NMR)and digital photographic measurement(DPM)were used to carry on the experimental study of the spontaneous imbibition characteristics of mudstone extracting water from cement grout.The water distribution and migration of mudstone during imbibition with ultrafine cement grout of different water-cement(W/C)ratios were tested by NMR,and surface deformation and water(from the cement grout)migration velocity(migration state)for mudstone samples with different initial water content were tested by DPM tests.The evolution equation of viscosity of dehydrated grout was constructed,which provided the parameters for coupling model of stress-grout flow in fractured mudstone.(3)Based on the failure characteristics of weak consolidated mudstone under uniaxial compression of“rock crushing was formed by the extension and connection of fractures”,firstly,the impacts of various water-cement(W/C)ratios of ultrafine cement grout material and normal loads F_N applied to fractures on grout nonlinear flow behavior through single and multiple rough plexiglass fractured samples were experimentally analyzed by an effective self-made grouting apparatus.(4)Secondly,based on the experiment of the spontaneous imbibition characteristics of mudstone extracting water from cement grout,the parameters of the ultrafine cement grout were adjusted,and the experiments of grout penetration in crushed mudstone under pressure were carried out by using the visualization grouting test system.The mechanical and microscopic characteristics of grouting reinforcement for mudstone were analyzed,which provided parameters for the numerical model of mudstone roadway floor deformation.(5)Based on the nonlinear elastic constitutive equation for large deformation of rock structure,Navier-Stokes equations for an incompressible viscous fluid using ALE,and the evolution equation of viscosity of dehydrated grout,coupling model of stress-grout flow in fractured mudstone considering the spontaneous imbibition characteristics of mudstone extracting water from cement grout(evolution characteristics of viscosity of dehydrated grout)was constructed,obtaining the coupling mechanism of stress-grout flow in fractured mudstone during grouting.(6)Taking the restoration of floor of the 1302 working face in Wujianfang coalfield as the research subject,seepage characteristics of grouting in fracture-microporous in mudstone roadway floor were studied by the numerical analysis.The crushed area of mudstone floor was determined by means of geological radar,drilling and coring.Then,based on the experimental results of mechanical properties of the grouting reinforcement for crushed mudstone,the numerical model of roadway surrounding rock deformation was constructed,then analyzing the deformation characteristics of roadway floor after grouting.