Research On Coupled Damage Evolution Mechanism And Strength Characteristics Of Shaft Lining Concrete Under High Pressure Water

The exploitation of coal resources has been extended to the deep,new shaft through water-bearing unstable stratum is getting thicker and thicker,water pressure which shaft lining endures is becoming more and more large.However,concrete as the main shaft material,the problem of damage evolution and strength development is becoming more and more serious under high groundwater pressure.Other than concrete in surficial air condition,the concrete of shaft lining is chronically under directly high hydraulic pressure load,then its damage evolution process and strength characteristic will be changed.This is a worthy scientific problems need to study.To this end,on the basis of considering the effect of groundwater seepage on the coupling of stress and deformation of shaft lining concrete,using the method of concrete mechanics test,similarity model test,theoretical analysis and numerical calculation,damage evolution mechanism and strength deformation characteristics of shaft lining concrete under high pressure water load are studied.Aiming at the problem of support in deep alluvium coal mine shaft,high strength and high permeability concrete with high density and good impermeability is formulated as shaft material,and its main physical and mechanical properties in the ground air environment are tested,which can provide reference for the change of physical and mechanical parameters of concrete under the action of high pressure water load,and provide the foundation for analytic solution and numerical calculation parameter selection.The coupling effects of three different factors,which are the size of water pressure,time of water pressure and strength grade of concrete are considered,mixed orthogonal test table was designed by SPSS software,and coupling damage experiment of concrete under the action of high pressure water is carried out.The results show that the intensity of peak strength of concrete is water pressure,concrete strength grade and hydraulic pressure time.Combined with the acoustic test results,Welbull statistical distribution theory,Lemaitre theory and theory of damage mechanics,coupling damage evolution equation of shaft lining concrete under high pressure water load is established,and constitutive equation under corresponding conditions is deduced based on the concrete strength theory.The hydraulic coupling permeability test of concrete under high pressure water was carried out by using rock three axis test machine,results show that the effect of pore water on the damage caused by concrete in the internal seepage is more obvious,accelerating deformation and failure process of specimen.Under the same conditions of pore water pressure increases,which concrete strength and secant elastic modulus obviously decreased.Based on theoretical analysis,a conceptual model of permeability evolution of shaft lining concrete under coupled seepage and stress condition is established.According to the different curing conditions,concrete lining is divided into three types:normal,saturated and sealed,experimental study on strength and deformation characteristics of concrete under high pressure water load is carried out.It is found that three kinds of concrete lining have obvious effect of water confining pressure,and the effect of confining pressure on sealing state is significantly higher than that of normal and saturated two states.The strength of concrete under high pressure water load is nonlinear increasing,fitting effect of Bresler three parameter strength failure criterion is the best.The relationship between axial strain and water confining pressure is increased linearly with the peak axial strain of the different strength grade of shaft lining concrete.Based on the similar model theory,model shaft is designed.According to the principle of orthogonal test design,concrete strength grade,thickness ratio and reinforcement ratio are taken as the influencing factors.Using quasi plane strain loading way,the model test of shaft lining under the direct action of high pressure water load is carried out,based on experimental result and theory of eight dimensional stress space strength,strength criterion and ultimate bearing capacity formula of shaft lining concrete are established.Based on the above strength criterion,brittle damage factor of high strength concrete is introduced,on the basis of considering coupling effect of groundwater seepage deformation,inrush mechanism of vertical shaft water outlet is analyzed.The analytical solution of ultimate water pressure of shaft lining under corresponding conditions is derived,and the main influencing factors are analyzed and compared.Based on ABAQUS/CAE stress seepage coupling analysis module,numerical calculation of stress damage of interaction between shaft and surrounding rock is carried out under coupling effect of groundwater seepage,dynamic coupling analysis of permeability coefficient and porosity was realized by using USDFLD.for subroutine.The results show that the maximum principal stress and damage of the shaft lining are different from the traditional coupling,it provides an effective way for dynamic coupling analysis.