The deformation and fracture of rocks are a process of energy dissipation and release. For the layered and jointed rock masses, the estimation of strength and energetics parameters during loading procedures is a challenge because of their complex structures. The paper proposes a methodology for the energetics parameter estimation of layered and jointed rock masses based on the revised Hoek-Brown failure criterion, which is appropriate for the rock mass with significant directional difference. The PFC3D numerical simulation was used to simulate the triaxial compressive test of rock pieces (𢁒50mm×100mm) and jointed rock masses (𢁒m×2m). For the layered rock mass, the numerical models involved one bedding surface with different dip angles. For the modelling of jointed rock mass, the diverse joint frequencies and predominant attitudes were considered. The uniaxial compressive strength of layered and jointed rock pieces was used to replace that of intact rock pieces in the Hoek-Brown failure criterion to estimate the triaxial compressive strength of rock masses, and the results showed good performance validated with the simulated triaxial stress-strain curves of big size models. Furthermore, combining with energy balance theory, the equations of accumulative elastic energy and dissipation energy corresponding to the failure point during triaxial compressive process were derived based on the revised Hoek-Brown failure criterion. The estimated energetics parameters were proved to be accurate by the validation with simulated energy curves under triaxial compressive condition. The methodology proposed in the paper could supply effective estimations of triaxial compressive strength and energetics parameters of layered and jointed rock masses.
The mechanical parameters of jointed rock mass are difficult to be measured directly by rock mechanics tests because of their complex structures and the limitations of the test methods. How to determine their mechanical parameters and failure process has been a challenge of rock mechanics study. In 1980, Hoek and Brown derived the estimation method of mechanical strength parameters of rock mass, i. e. Hoek-Brown failure criterion (H-B criterion). The H-B criterion, combined with Geological Strength Index (GSI) and Mohr-Coulomb Criterion has become the most widely used criterion in rock engineering (Hoek and Brown 1997; Cai et al. 2004; Marinos et al. 2005; Dinc et al. 2011; Hoek et al. 2011; Jiang 2017).