EDZ Formation and Associated Hydromechanical Behaviour around ED-B Tunnel: A Numerical Study based on a Two-Part Hooke's Model (TPHM)

The accuracy in modeling coupled processes in a clay/shale repository is largely determined by the validity of the constitutive relationships and related parameter values. As an attempt to more accurately model the Excavation Damaged Zone (EDZ) formation and associated hydromechanical behavior induced by excavation in clay/shale, a recently developed stress-strain relationship (a twopart Hooke’s model, abbreviated as TPHM) and associated formulations regarding rock hydraulic/mechanical properties were incorporated and implemented in FLAC3D in detail. TPHM is based on a macroscopic-scale approximation using a natural-strainbased Hooke’s law to describe elastic deformation for a fraction of pores subject to a large degree of deformation; an engineeringstrain-based Hooke’s law is used for the other part. The usefulness and validity of the TPHM and associated formulations are demonstrated by the consistency between simulation results and field observations from the ED-B tunnel at the Mont Terri site. The simulation results, which are sensitive to the constitutive relationships used in the model, capture both the observed displacements and the size of the damage zone, whereas the approach based on the conventional Hooke’s law underestimates both. The fracture modeling provide insight into the evolution of fractured zone that are impossible to be observed in field and are difficult to be considered with static stress analysis approaches.