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.