An Investigation on Local Shearing Mechanisms of Irregular Dentate Rock Joints Using the PFC

Abstract

Joint surfaces are widely distributed in natural rock mass, and their shear mechanical properties play an important role in determining the safety and stability of rock mass. Previous studies rarely discussed the contribution degree of different joint protrusions to resisting shear stress. In this study, seven irregular dentate joint profiles were proposed to represent the geometric morphology of natural joints. Joint samples were subjected to direct shear tests under constant normal stress using the particle flow code (PFC). First, the reliability of the research scheme was verified by routine test results. Secondly, based on the microcrack tracking module and the force chain analysis, the local failure modes of the joint sample after and during the shearing process are discussed in detail. The relationship between the shear stress and the number of microcracks was studied. Finally, based on the measuring circle function, the variation law of the mean stress at different joint protrusions during the shearing process was tracked. The maximum stress of each protrusion before the shear stress peak was introduced to quantitatively describe the contribution of local protrusions to shear stress. There was an important link between the size of the protrusion and the stress it can withstand. During the shearing process, the local shearing mechanism of the joint surface is controlled by the distribution of joint protrusions. The research results of this paper can provide a good idea for the follow-up joint surface research.

Shear damage mechanisms of jointed rock mass: a macroscopic and mesoscopic study

“…This study addressed these challenges by utilizing the ABAQUS, employing the method of global embedding of zero-thickness cohesive elements to accurately replicate the shear process of jointed rock mass with various roughness. The observations made in this study during the evolution of subtle fractures in the jointed rock closely resemble those found by Huan et al 58 , Bahaaddini et al 59 , Meng et al 60 , which used discrete element software PFC to observe microcrack propagation during shear. Taking Bahaaddini’s study 59 as an example, in which they investigated the degradation of roughness during shear and its impact on jointed rock shear behavior, in the pre-yielding stage, the model only generated small cracks, and when the shear stress reached the yielding shear stress, tensile cracks appeared at the protrusions.…”

“…After completing the laboratory tests, numerical simulations can further verify the correctness of the test results. The numerical simulations by Huan et al 58 , Bahaaddini et al 59 , Meng et al 60 , and Han et al 62 show a good consistence with test data. However, the simulated data in this tests show some deviations from the displacement-stress curve obtained in the lab tests.…”

“…Scholars have utilized Discrete Element Method (DEM) software, particularly Particle Flow Code (PFC), for simulations to investigate the internal damage of rocks. Huan et al 58 employed PFC to conduct constant normal stress direct shear tests on joint specimens and studied the local failure modes during the shear process. Bahaaddini 59 used PFC to explore the impact of rock joint roughness and continuity on the mechanical behavior of rock structures.…”