| In order to obtain the analytical solution of the surrounding rock stress field of deep tunnel in layered jointed rock mass,the obstacle function algorithm based on fmincon optimization function is used to solve the mapping function.According to the reliability theory of underground engineering,the structural failure criterion of mapping convergence is established.Based on the results of the analytical solution,the shape effect and size effect of the change of the geometric parameters of the three core arch roadway with straight wall on the surrounding rock stress are analyzed.The joint is approximated as a crack around the tunnel.The influencing factors of the stability of the joint surface around the tunnel are analyzed.The anisotropic law of the stress intensity factor due to the change of the inclination angle and position of the crack is studied.The relationship among the polar angle of the tunnel,the inclination angle of the dominant propagation structural plane of the crack and the crack initiation angle is revealed.The main research work is as follows:(1)When the obstacle function algorithm based on fmincon optimization function is used to map the tunnel boundary to the unit circle in the complex plane,the conformal mapping from the outer domain of the tunnel boundary to the outer domain of the unit circle can be realized by taking the number of sampling points m=18 and the number of Ck n=6,which is better than the traditional algorithm.Based on the structural failure criterion,it will converge when the mapping accuracy is ?3?31.74%.(2)Taking the straight wall three core arch roadway as an example,the relationship between the geometric parameters of the tunnel and the surrounding rock stress is analyzed.The results show that:the growth rate of stress concentration factor in the arc region of the roadway with small rise span ratio is larger;the maximum value of stress concentration factor in the arc region of the roadway with width height ratio close to 1 is closer to the spandrel,the maximum value is closer to the foot of the wall,and the maximum value is smaller;on the contrary,the maximum value of stress concentration factor in the arc region of the roadway with width height ratio far away from 1 is far away from the spandrel,When the ratio of width to height is equal to 1,the maximum stress concentration factor appears at the foot of the wall,which is approximately equal to that at the spandrel.(3)Taking the Lumaolin lead zinc mine of Xiangrong Mining Co.,Ltd.in Puding County,Guizhou Province as the engineering background,the occurrence of structural plane of surrounding rock of main transportation roadway is investigated.Based on the mapping function,the properties of jointed rock around the roadway,the stress state of joint plane and the influence of tunnel size and shape on the stability of joint plane are analyzed.(4)According to the complex function form for stability discrimination of joint surface of tunnel surrounding rocks,the regularity of stress intensity factors of joint crack tip at different inclination angles around tunnel is studied.The results show that the mechanical behavior of crack tip around tunnel under surrounding pressure is mainly influenced by type ? stress intensity factor K?,The value of K? is anisotropic with the change of crack inclination and position.(5)Considering the relationship between secondary crack and unloading surface of excavation of tunnel,the relationship between extreme angle of tunnel,inclination of dominant propagating structural surface of crack and initiation angle is studied,and the theoretical analysis results are verified by finite element software ABAQUS.The research results show that the crack tip at different parts of tunnel edge corresponds to different inclination angle of advantageous propagating structural surface ?0.When the crack inclination angle is ?=?0,the secondary crack propagates unstably along the direction of the cracking angle ?0 and parallel to the unloading surface of the tunnel excavation. |
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