Analysis Of Viscoplasticity And Large Deformation Of Surrounding Rock In Deep Roadway

With the increase of mining depth,engineering accidents increase,and due to the need of tunnel construction,it is necessary to analyze the rheological and large deformation phenomena in the process of tunnel excavation and maintenance,especially in the soft rock mass,it is easy to cause the tunnel structure instability failure.According to the phenomenon of rheology and large deformation of tunnel,the corresponding analytical solution or semi analytical solution is given,the main research results are as follows:(1)The generalized Bingham’s elasto-viscoplastic combined model is adopted,combined with non-associated flow rule,based on the basic equations of solid mechanics,the analytical expressions of elasto-viscoplastic stress and deformation of circular roadway surrounding rock are established by using MC and HB criteria respectively.The implicit function f(t)is solved by MATLAB software,and then the stress and deformation distribution in elastic viscoplastic MC and HB rock mass are obtained.(2)Based on the obtained analytical solutions of elasto-viscoplastic stress and deformation of the surrounding rock of circular roadway,the sensitivity analysis of parameters is carried out,the laws of stress and deformation under different support force,Poisson’s ratio,Young’s modulus,viscosity coefficient and dilatancy angle are obtained: under the same supporting force,the radius of initial plastic zone corresponding to HB criterion is larger than that of MC criterion,and the radius of initial plastic zone is related to the support force;the initial plastic zone increases with the increase of Poisson’s ratio,while the radius of viscoplastic zone decreases with the increase of Poisson’s ratio;the radial and tangential stresses at the same position in the surrounding rock decrease with the increase of Young’s modulus,the influence of Young’s modulus on HB rock mass is greater than that on MC rock mass;the radial and tangential stresses at the same position in the surrounding rock increase with the increase of the viscosity coefficient;the radial and circumferential stresses at the same position in the surrounding rock increase with the increase of the shear expansion angle,and the smaller the dilatancy angle is,the faster the viscoplastic zone develops.(3)In order to predict GRCs and plastic zone of circular roadway surrounding rock in elasticplastic coupling strain softening rock mass,in view of the large deformation problem,the finite strain analytical solution of the surrounding rock of circular roadway is obtained.The Lagrangian coordinates considering the motion of material points are analyzed comprehensively.The analytical solution is compared with the numerical solution to verify the correctness and reliability of the analytical solution proposed in this paper.Finally,the effects of relevant parameters such as young’s modulus,Poisson’s ratio and dilatancy angle are systematically studied.The proposed finite strain solution is more reasonable and can correctly predict the actual displacement of large deformation in underground engineering,especially in extremely soft rock under high stress environment.The effectiveness of the method is verified by comparing with the field test results of Zhongyi tunnel.(4)In order to improve the application of surrounding rock characteristic curve in roadway remodeling,a simple method is proposed.The wall displacement and plastic(residual)radius of rock mass with any mechanical behavior can be predicted by the surrounding rock characteristic curve(GRC).This method has nothing to do with the mechanical behavior of surrounding rock,that is,it can be applied to any rock mass with mechanical behavior.The method is compared with the previous published examples.The critical excavation radius of the required gap and its corresponding plastic and residual radius can be determined theoretically.For a constant remolding radius,the increment of the wall displacement and plastic radius(and residual radius)decreases gradually,and the above three variables tend to their critical values,that is,to reach the required clearance radius.When the rock mass becomes ductile,that is,the critical plastic shear strain increases from 0 to infinity,and the thickness of plastic zone and residual zone decreases.There are 77 pictures,7 tables and 165 references in this dissertation.