Numerical Simulation Of Evolution Process For Excavation Damaged Zone In Rock Under Coupled Thermal-mechanical (TM) Condition

In geothermal development, third oil exploitation engineering, it must relate to the excavation of a damaged zone around man-made openings in geologic formations under coupled thermal-mechanical (TM) condition. The formation and its subsequent spatial and temporal evolution of excavation damaged zone(EDZ), being considered as a coupled process among thermal, hydraulic mechanical, and damage fields, which is a significant issue for evaluating the engineering stability and safety, and for optimizing the supporting parameters. Recently, aiming to the study of the strategic energy storage and the radioactive waste disposal, a significant development in EDZ characterization and coupled thermal-mechanical (TM) modeling has been achieved.A coupled TM model during the rock failure is proposed in this paper when the damage is considered as a key factor that controls the TM coupling. The model is solved using numerical method by programming on the base of COMSOL Multiphysics, a powerful PDE-based multiphysics modeling environment using finite element method. The proposed TM model is firstly utilized to simulate the TM response of the elastic medium and it is validated by comparing the numerical results with the analytical solutions. Secondly the proposed TM model with damage evolution incorporated is validated by comparing the numerical results with the experimental observation of the failure process around circular openings under uniaxial compression.At last, the model is employed to predict EDZ under TM conditions and the numerical results indicate that, the damage zone is dominantly controlled by in-situ stress conditions, and the thermal pressure also has an important influence on the initiation and evolution of EDZ. At last the EDZ development of rock mass under considering the influence to parameter of temperature conditions has been numerically simulated for the process of rock coupled thermal-mechanical experiment, and the numerical results denote that the influence of temperature to EDZ is more than boundary loads’, it is necessary for using coupled thermal-mechanical model to analyze problems for ground stress and temperature boundary conditions in numerical simulations.