Effects of excavation size, rate, orientation, and depth on the hydromechanical response of argillaceous rocks

In this study, a sensitivity analysis is performed to investigate the effects of excavation size, rate, orientation, and depth on the hydromechanical response of Callovo-Oxfordian (COx) argillaceous rocks. The elasto-viscoplastic argillite model, which incorporates a non-local regularization technique, is employed. Initially, a series of drained biaxial tests are simulated to investigate the effects of the non-local approach on post-peak strain softening and the evolution of localized shear bands. Subsequently, the effects of excavation size are assessed by modeling excavations with different diameters. A novel scaling framework is proposed to assess size effects while using non-local techniques. Then, rate effects are analyzed by isolating the sources of delayed response in the rock, i.e., hydrodynamic lag, viscoplasticity, and creep. Additionally, different drifts parallel to the major and minor natural principal stresses are simulated to distinguish the impacts of material anisotropy and in-situ stress anisotropy on the host rock response. Finally, the influence of the excavation depth is examined through simulating three drifts at different depths within the COx. The results reveal the efficiency of the proposed scaling approach in analyzing size effects. Furthermore, altering the excavation orientation and depth results in varied COx responses mainly due to changes in in-situ stress conditions.