Research On Performance Optimization And Support Characteristics Of Fiber-toughened Geopolymer

At present,the scale of deep underground projects is unprecedented,and the construction of a series of national strategic projects such as energy mines,hydraulic structures,national defense projects,and nuclear waste disposal urgently need innovation and development of deep underground support structures and materials.It is the core scientific problem to solve the anti-large deformation disaster control.Which include develop a new type of composite material and structure with large deformation resistance,obtain the mechanical characteristics and response mechanism of the interface between fiber and matrix under large deformation,establish a macro and meso damage mechanical model that can describe the strain strengthening and multi-micro crack deformation characteristics of fiber-reinforced geopolymer.In view of the above problems,through the three-point bending and single fiber extraction experiments,related derivation and simulation,a mesoscopic material model based on the Monte Carlo method was established.Based on the strength criterion and energy criterion,the modification of fiber-reinforced geopolymer materials with CaSO4 whiskers was tested,and a performance prediction network was constructed.Combined with the deep tunnel engineering background of a mine in Shandong,the interaction model of supporting structure and surrounding rock under different working conditions was established,and the deformation and failure characteristics of the fiber-reinforced supporting structure were analyzed.The main research contents and results are as follows:?1?Based on the analysis of the mechanical characteristics of the interface between the fiber and the matrix,a mesoscopic CZM model that can describe the strain strengthening and multi-microcrack deformation characteristics of the fiber-reinforced geopolymer under dynamic loading was established.Fly ash,slag,solid particle alkali activator,CaSO₄ whisker and domestic PVA fiber were chosen as raw materials.The three-point bending experiment of the matrix and the single fiber extraction experiment at the meso level were tested.Based on the experiment,a mesoscopic CZM model of fiber-toughened geopolymer was established.The results show that,unlike the ECC material,the increase in fly ash in the geopolymer material can improve the crack tip toughness of the material,J_tip,and the ash-glue ratio is better at 0.5.The addition of CaSO₄ whiskers can reduce the chemical bond strength G_d between the fiber and the matrix,and improve the fiber bridging ability.The three-point bending model based on the idea of stochastic modeling can simulate the crack development well.?2?Aiming at the uncertainty of the ratio of fiber-reinforced polymer materials,the characteristics of materials with different ratios were studied through experiments and prediction networks.The results show that the effect is better when the whisker content is 1.5%,the maximum tensile strain capacity of the material were increased by 172.7%,and the degree of dispersion of properties is reduced by 84%.A material with a sand rate of 0-1.5 also has the ability to reduce the average adhesion of the matrix and the chemical bond between the matrix and the fiber interface.Appropriate wollastonite can improve the uniaxial compressive strength of the material,but it is not conducive to improving the ductility of the material.The relationship between the maximum tensile strain of the fiber-reinforced polymer material and the number of cracks has a positive exponential relationship.The prediction error of the established prediction network for the training group does not exceed 0.35%,and the prediction error for the prediction group generally does not exceed 7%.?3?The stochastic fiber distribution model was established by stochastic modeling,which was used to verify the deduction of the meso model.Based on the established CZM model,a macro and meso-coupling simulation of fiber reinforced geopolymer support structure in deep roadway was tested.The results show that the error between the fiber random distribution model and the experimental results is 2.51%,which proves that the meso model derivation and simplification are reasonable.The macro and meso-coupling simulations are in good agreement with the experimental results,simulating the crack development process everywhere,and explaining the effect of crack development on the stress-strain curve.The proper thickness of the spray layer can reduce the average strain of the surrounding surface of the surrounding rock by33.25%and the convergence of the vault by 20.36%.The paper has shown in 122 figures,42 tables and 165 references.