Experimental Research On Joint Surface State And The Characteristics Of Shear Failure

Joint surface state is one of the important factors which control mechanical properties of rock mass. In order to describe the joint surface state and investigate its evolution regularity during the shearing process, this paper design a set of joints failure experiments:rock joints are manufactured though indirect tensile method firstly, then we splice the fractured rock specimens into a whole again. Each specimen is sheared under different normal stress with RYL-600 rock shear test machine. Before and after each shearing test, Talysurf CLI 2000 3D surface topography instrument is used to scan the joint surface in order to obtain surface morphology information of the joint together with the software Talymap.Six fractal curves with different fractal dimension which constructed by computer are used for simulation shear testing instead of joint profiles for purpose to explore the relationship between joint shear strength and fractal dimension.The main research results are as follows:(1) 3D visualization of the superficial morphology of joint is realized.(2) Referring to 2D parameters of joint surface state, the 3D morphology parameters of joint is expanded on the base of existing 3D roughness parameters.(3) The variation rules of 3D morphology parameters of joint during shearing process are summed up. The parameters show that the surface roughness obviously decreases and the surface becomes smooth with the increase of cyclic shearing tests which exhibit good agreement with the experimental results.(4) 42 joint profiles'fractal dimension of 14 rock specimens are calculated out, and the relationship between JRC and fractal dimension D is analyzed. Furthermore, two empirical formulas are suggested: JRC=29.35(D-1)0.46, which can be used to estimate the joint shear strength. Through comparing the joint surface fractal dimension, the average of fractal dimension and JRC of the corresponding joint's profiles, it is found that the three parameters are consistent with each other in describing the joint roughness.(5) Considering the effect of fractal dimension, a correction coefficient K which related to fractal dimension is introduced to modify the formula of rock joint shear strength:...