Mechanical response and dilatancy characteristics of deep marble under different stress paths: A sight from energy dissipation

Dilatancy is a fundamental volumetric growth behavior observed during loading and serves as a key index to comprehending the intricate nonlinear behavior and constitutive equation structure of rock. This study focuses on Jinping marble obtained from the Jinping Underground Laboratory in China at a depth of 2400 m. Various uniaxial and triaxial tests at different strain rates, along with constant confining pressure tests and reduced confining pressure tests under different confining pressures were conducted to analyze the mechanical response and dilatancy characteristics of the marble under four stress paths. Subsequently, a new empirical dilatancy coefficient is proposed based on the energy dissipation method. The results show that brittle failure characteristics of marble under uniaxial compression are more obvious with the strain rate increasing, and plastic failure characteristics of marble under triaxial compression are gradually strengthened. Furthermore, compared to the constant confining pressure, the volume expansion is relatively lower under unloading condition. The energy dissipation is closely linked to the process of dilatancy, with a rapid increase of dissipated energy coinciding with the beginning of dilatancy. A new empirical dilatancy coefficient is defined according to the change trend of energy dissipation rate curve, of which change trend is consistent with the actual dilatancy response in marble under different stress paths. The existing empirical and theoretical dilatancy models are analyzed, which shows that the empirical dilatancy coefficient based on the energy background is more universal.