The Influence of Clay-Like Materials Plasticity Used as Infills, on Jointed Rocks Mechanical Behavior

Abstract

The Rock mass is often described as an anisotropic material with several discontinuities within its structure ranging from joints, bedding plans to faulting. In the present study, the effects of infills plasticity on rock mass behavior during failure were investigated. Thus, a series of experiments have been conducted on both soils and cement blocks reconstituted to reflect jointed rock behavior. Different soil materials (obtained by mixing clay and sand) were subject to the cone penetration test and the unconsolidated undrained triaxial test to determine their plasticity index and their unconfined compressive strength. Then, several jointed blocks using the aforementioned soil materials as infill were subject to a uniaxial compression test to assess their maximum stress and investigate their deformation and failure mode. Results showed that stiffer infills would induce a more brittle behavior in the jointed rock while softer infills would instead favor rock deformation and a sharp decrease of its strength. It was also observed that both infill' cross-section and thickness will affect the rock resistance but its deformation will largely be influenced by the later. In the end, some law equations were proposed to draw the mathematical relationship between the jointed rock maximum stress, its deformation at failure and the infill plasticity.