Study On Shear Mechanical Properties Of Anchored Jointed Rock Mass Under Constant Normal Stiffness Boundary Conditions

With the continuous development of society,it has become normal for some key infrastructure construction projects to be buried between 1000 m and 2000 m.Therefore,how to ensure the safety of deep rock mass engineering has become one of the key problems urgently to be solved at present.A large number of engineering practices show that the dilatancy deformation of deep rock mass will be constrained by the surrounding rock mass,resulting in the normal stress acting on the target rock mass will change with the change of shear displacement,which is more consistent with the constant normal stiffness boundary.Therefore,it is of great engineering significance to study the shear mechanical properties of jointed rock mass under constant normal stiffness boundary conditions for the stability control of deep rock mass.In order to solve this problem,laboratory tests,numerical simulation and theoretical analysis were used to analyze the influence laws of shear mechanical properties of jointed rock mass before and after anchorage under different normal stiffness,joint surface roughness and initial normal stress.On this basis,a mechanical analysis model was proposed to characterize shear strength of jointed rock mass under constant normal stiffness.The main conclusions are as follows:(1)There are obvious differences in shear mechanical behavior of jointed rock mass under different boundary conditions,and this difference is mainly reflected in the stable change stage of shear and dilatancy displacement.Under the constant normal stress boundary condition,the shear stress curve of jointed rock mass shows stress softening,and the dilatancy displacement of jointed rock mass is larger.Under the constant normal stiffness boundary condition,the shear stress curve of jointed rock mass shows stress hardening or stress strengthening.(2)The sensitivity of normal stiffness,roughness of joint surface and initial normal stress to peak shear stress and peak normal stress of jointed rock mass is different.The joint surface roughness has the greatest influence on the peak shear stress.Normal stiffness has the greatest influence on peak normal stress.(3)By comparing the wear degree of joint surface under different influencing factors,it can be seen that the wear degree of joint surface is positively correlated with normal stiffness,roughness of joint surface and initial normal stress,and the core influencing factors can be summarized into two aspects: normal stress level and roughness of joint surface.(4)The anchorage effect of bolt can be summarized into two aspects: one is to increase the equivalent shear strength of jointed rock mass;On the other hand,the dilatancy displacement of jointed rock mass is further constrained,and with the increase of normal stiffness,roughness of joint surface and initial normal stress,the shear action of bolt decreases.(5)In this paper,Fourier series is used to characterize the dilatancy effect of anchorage jointed rock mass,and the resistance of anchorage rock mass is analyzed according to the principle of minimum complementary energy and deformation characteristics of anchorage rock mass,so as to build a mechanical analysis model of shear strength of anchorage jointed rock mass under constant normal stiffness boundary conditions.This paper has 71 figures,20 tables and 81 references.