Effects of inelastic volume increase on fractured rock behaviour

This study investigated the correlation between inelastic volumetric deformation and the bearing capacity of fractured rock. Triaxial compression tests on marble specimens have been performed under constant and controlled deformation rates using a servocontrolled loading machine supported by an electro-hydraulic volume-measuring unit connected to a data acquisition system. The triaxial compression tests were carried out on two different marble samples under constant confining pressures ranging from 1-12.5 MPa. The results indicate that stress-inelastic volumetric strain curves are generally linear through the initial part of the post-failure curve where fractured rock behaviour is dominant. It was found that brittle rock loses its strength in the post-failure region depending on volumetric deformation; the slopes of post-failure curves change with an increase in confining pressure. As a result it is concluded that there is a relationship between strength and volumetric strain of fissured rock.