A new joint morphology parameter considering the effects of micro-slope distribution of joint surface

Abstract An accurate description of the morphology of a joint surface is necessary to interpret its shear behavior. Accurately distinguishing the shear behavior differences may be difficult if the defined morphology parameter ignores the micro-slope distribution of the joint surface. The initial climbing angle was therefore defined and used to characterize the micro-slope distribution of the ascent section of joint profile, and a new method was proposed for calculating the morphology parameter, M. The parameter M embodies anisotropy, and the values of M for all profile lines, which are selected on the same joint at equal intervals in one direction, are log-normally distributed. To study the mechanical effects of M, joint replicas with three different strengths were 3D-printed using the scanned point cloud information of the natural joint. An anisotropic direct shear test was conducted to obtain the joint shear parameters in eight directions. The results indicated that the new morphology parameter accurately reflects the anisotropic shear behavior of the joint, and displayed tangential, positive linear, and power relations with shear strength, apparent cohesion, and friction angle, respectively. Furthermore, an index for evaluating the shear failure characteristics, established by using the new morphology parameter, can effectively distinguish the differences between the climbing and shear-off behavior on the joint. The parameter M, which considers the micro-slope distribution, can thus correctly represent the physical and mechanical properties of a joint, and its application is conducive to the precise quantification of joint shear behavior.