Study On The Influence Of Structural Surface Morphology On Shear Characteristics Of Non-Interpenetrated Jointed Rock Mass

As a complex engineering medium widely encountered in tunneling and slope problems,the damage penetration characteristics and strength properties of non-penetrating jointed rock masses are largely controlled by the morphology of the joint surface.At the present stage,the complex surface morphology of joints is simplified into saw-tooth joint morphology to study the influence of roughness on the shear characteristics of non-interpenetrated jointed rock mass.Based on this situation,a standard JRC joint model and a saw-tooth joint model with the same roughness were first established,and the failure characteristics and strength properties were compared and analyzed by direct shear test;secondly,a non-interpenetrated jointed rock mass model based on standard JRC curve was established,and the effects of normal load,connectivity rate and roughness on its failure characteristics and shear mechanical properties were studied by direct shear test,and the evolution of shear strength parameter with roughness and connectivity was also studied.The main research contents and results are as follows:(1)The numerical software commonly used in direct shear simulation of rock mass was compared from three aspects : calculation principle,implementation method and simulation effect,the global insertion of zero-thickness cohesive element method is outstanding in crack propagation,therefore,ABAQUS was selected to carry out direct shear test to study the shear characteristics of rock mass model;by comparing the shear strength of numerical simulation with the theoretical value of the empirical strength model,it was proved that the numerical simulation was reasonable.(2)A standard JRC joint model and a saw-tooth joint model with the same roughness were established,the macro and micro mechanical characteristics of the two types of joint models are compared and analyzed by direct shear test.(1)The failure mode of JRC joint model is tensile-shear composite failure,the failure cracks are mainly distributed in the convex part of the joint surface;the failure mode of the the saw-tooth joint model is climbing gnawing failure,and the failure cracks are evenly distributed on the shear plane.(2)The dilatancy effect of saw-tooth joint model is more prominent,the upper plate of the joint model moves upward along the serrated slope;the mutual occlusion of the second-order irregular undulating bodies limits the upward movement of the upper plate of the JRC joint model along the joint surface.(3)The peak shear stress and residual strength of the saw-tooth joint model and the standard JRC joint model are quite different,the average difference of shear strength is 36 %.(3)Direct shear numerical simulation of non-interpenetrated jointed rock mass model based on standard JRC curve was carried out,the effects of normal load,connectivity and roughness on the failure characteristics and mechanical properties of rock mass model were studied.(1)The normal load affects the development degree and development rate of cracks;the smaller the normal load is,the more obvious the brittleness of jointed rock mass is;the peak shear stress increases linearly with the increase of normal stress.(2)The connectivity rate affects the damage degree of the original joint surface and the through crack morphology of the rock bridge;the larger the connectivity rate,the more obvious the dilatancy effect;the peak shear stress decreases with the increase of the connectivity rate,when the joint surface roughness is small,the two are approximately linear,when the roughness of the joint surface is larger,the decrease rate of the peak shear stress gradually decreases.(3)Roughness affects the development rate and morphology of cracks;with the increase of roughness,the brittleness of rock mass is more obvious;the peak shear stress increases with the increase of roughness,and the greater the connectivity rate,the greater the rate of increase.(4)The evolution law of shear strength parameters with respect to connectivity and roughness is obtained,which provides a scientific basis for engineering practice.