The Mechanism Of Capillary-Film Water Migration In Freezing Soil And Its Experimental Study

Grouting reinforcement plugging has become a key construction technology for plugging groundwater and soft rock in coal mine construction projects.However,as the mining depth of coal mines continues to increase,deep rock grouting needs to simultaneously cope with the characteristics of high ground pressure,high water pressure,poor micro-fracture connectivity,and complex pore structure.The existing grouting theories,techniques and materials are difficult to adapt,which seriously threatens the safe exploitation of deep resources.To this end,this paper adopts the method of combining physical performance test of grouting material,theoretical analysis,model experiment,numerical simulation and field practice.Around the issue of the mechanism of splitting grouting diffusion in deep rock formations in coal mines,a systematic study of the mechanism of initiation and propagation of deep rock formations and the law of split grouting propagation in deep rock formations has been carried out.It has important theoretical significance and application value to solve the problem that the existing grouting theory and technology cannot meet the grouting problem of deep rock formations.The main research results are as follows:(1)Carried out experimental research on the rheology,mechanical properties and micro characteristics of cement slurry,cement-water glass slurry,and water glass-polyurethane grouting materials.The analysis found that the rapid setting,early strength and microstructure stability of the water glass-polyurethane grouting material are better than those of the other two grouting materials,the viscosity rheological equations were obtained respectively,which provided experimental basis for the subsequent analysis of splitting and diffusion theory.(2)Established a split grouting initiation model for deep coal mine strata,and obtained the initiation pressure and the initiation direction of the open hole section under different stress states;Mathematical models of longitudinal and lateral splitting propagation considering the geometric shape of the fracture and the time-varying viscosity of the slurry are constructed respectively;Taking the stress intensity factor K_I at the crack tip equal to the fracture toughnessK_IC as the fracturing criterion,the deep rock fracture diffusion equation considering the viscosity and rheological properties of the grout is proposed.The study found,the greater the elastic modulus,buried depth and lateral pressure coefficient of the injected rock mass,the higher the resistance encountered by splitting grouting,and the more difficult it is for the cracks to expand;At the initial stage of grouting,the plastic viscosity of the grout is low,and the grouting pressure and grouting rate are the main controlling factors for the range of grout splitting and spreading,when the viscosity of the slurry reaches a certain value,the viscosity becomes the main controlling factor of the spreading range of the slurry.(3)A high-pressure resistant three-dimensional simulation test platform was developed.Through grouting test research with a maximum axial pressure of 8 MPa and a maximum confining pressure of 5 MPa,the mechanism of cracking and diffusion in deep coal strata under different stress environments was clarified.Tests show that the initiation pressure is positively correlated with rock strength and confining pressure,and the sensitivity to confining pressure is much higher than axial pressure;Through experimental and theoretical comparison and analysis,the ratio of the grout fracture tensile strength of the closed bare hole section to the uniaxial tensile strength of the sample(2.5?3.0)was obtained,and the theoretical value of the initiation pressure of the bare hole section was revised accordingly.(4)Based on the ABAQUS/Standard module,using Fortran language to write embedded subroutines to define the time-varying viscosity of the slurry,by simulating crack expansion by prefabricated Cohesive units,a numerical calculation model for single-fracture splitting and diffusion of time-varying viscosity slurry is constructed;And based on the Monte-Carlo simulation method,the random fracture network is generated by embedding the MATLAB random fracture generation code to realize the simulation of the fractured rock formation;Through the POLARIS?Insert Coh Elem plug-in,the global embedding of the Cohesive bonding unit is implemented to simulate the weak rock formation.Finally,a numerical analysis method for splitting and diffusion of random fractures in two different rock formations with rheological grout fissures developed and weak is formed,and the analytical solution of initiation-expansion theory is verified.(5)It reveals the influence mechanism of different in-situ stresses,lithology,grouting materials,grouting parameters and other factors on grouting fracturing and diffusion in deep coal mines.Comprehensive analysis shows:The splitting pressure of the injected rock formation has nothing to do with grout viscosity,grouting rate,rock permeability and other factors,and is mainly affected by the depth of the formation(stress state)and the tensile strength of the rock,the grouting rate and the permeability of the rock formation are directly proportional to the grout diffusion radius,and the grout viscosity has an inhibitory effect on the grout diffusion;The influence of the permeability and tensile strength of the injected rock layer at a depth of 500m on the grouting pressure gradually decreases,and the ground stress becomes the main cause of the increase in the grouting pressure.(6)Taking the grouting treatment of the soft rock bottom heave of the-1000 m depot roadway in the east area of Guqiao Mine as the engineering background,water glass/polyurethane chemical grout is selected,and the obtained research results are used to determine the grouting parameters,a grouting method with high pressure and large flow(30 L/min)at the initial stage of grouting is proposed to initiate cracks and expand the grouting channel,and then reduce the flow(15 L/min).Subsequently,the grouting effect test using the transient electromagnetic method and the seismic electromagnetic three-field method showed that the grouting diffusion radius and the compactness of the rock formation reached the design requirements,and the floor heave of the roadway was effectively suppressed,and the expected treatment effect was achieved,thus verifying The correctness of the research results.