Recently, a novel approach (phase field damage model) enabled the simulation of compression and tension-induced cracks quasi-statically and captured crack propagation within the FEM (finite element method) framework. However, the application of the phase-field damage model is restricted by the calibration of the crack diffusion parameter, which cannot be directly measured. In this study, we proposed a new elastoplastic phase-field damage model, calibrated from the AE (Acoustic emission) moment tensor inversion and ultrasonic wave velocity measurement. The phase-field damage variable is determined from P wave velocity measurement and acoustic moment tensor inversion. Specular decomposition is performed on the damaged tensor to distinct tensile and compressive microcracks. The evolution between tensile and compressive phase-field damage variables is hence to be considered independently. The proposed model shows great consistency with the laboratory observations and the application of the proposed model in COMSOL software enables to capture the quasistatic propagation of both tensile and shear fractures.
The understanding of discontinuities is still an arduous task for rock mechanics, and the formation of geotechnical incidences (You et al. 2021; Li et al. 2022), akin to rock bursts, roof sagging and large tunnel deformation, may more or less relate to discontinuities. The discontinuities are, however, of different lengths and scales, ranging from several millimetre microcracks in laboratory tests to kilometres of underlying faults, which can induce high-energy earthquakes. Also, the propagation and coalescence of multiple discontinuities would generate a complex secondary stress field and complicate geotechnical hazard management. Hence, the simulation of microcracking behaviour numerically is difficult.
A novel and recent new approach to simulate the mechanical response of discontinuities is to use the phase-field damage method in FEM (Li et al. 2023). The application of the phase-field damage method provides another attitude to smear the discontinuous boundary into the phase damage field (You et al. 2021). The initiation, propagation, and coalescence of microcracks can be simulated according to the multi-field coupling solver. This innovative approach avoids the requirement of any shape functions, compared with previous XFEM methods, but enables a more physical description regarding the profile of discontinuities (advantages compared to the DEM methods) (Li et al. 2023). The phase-field damage method has been introduced into different materials (e.g., rock and metal) and shows significant power in simulating discontinuities.
