Calibration of coupled hydro-mechanical properties of grain-based model for simulating fracture process and associated pore pressure evolution in excavation damage zone around deep tunnels

The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model (GBM) to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory, and to apply the calibrated model to simulating the formation of excavation damage zone (EDZ) around underground excavations. Firstly, a new cohesive crack model is implemented into the universal distinct element code (UDEC) to control the fracturing behaviour of materials under various loading modes. Next, a methodology for calibration of the components of the UDEC-Voronoi model is discussed. The role of connectivity of induced microcracks on increasing the permeability of laboratory-scale samples is investigated. The calibrated samples are used to investigate the influence of pore fluid pressure on weakening the drained strength of the laboratory-scale rock. The validity of the Terzaghi's effective stress law for the drained peak strength of low-porosity rock is tested by performing a series of biaxial compression test simulations. Finally, the evolution of damage and pore pressure around two unsupported circular tunnels in crystalline granitic rock is studied. (C) 2021 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V.