A 3D fully thermo–hydro–mechanical coupling model for saturated poroelastic medium

Abstract

Thermo–hydro–mechanical (THM) coupling prevails in all sorts of underground activities, and numerical simulation is an effective tool to understand THM coupling. The essence of performing THM coupling simulation lies in solving a system of partial differential equations (PDEs) with displacements (U), pore pressure (P) and temperature (T) as the primary variables. In previous studies, only the UPT and U-PT schemes are reported to solve the system PDEs. Another promising scheme UP-T was rarely explored. In addition, although multiple solution schemes are theoretically possible, the performance thereof varies. Few studies have ever compared the performance of different solution schemes. Moreover, the rock mass in hydrothermal fields is highly permeable wherein heat advection dominates. Advection-dominated heat transfer may lead to numerical oscillation, but how to stabilize the simulation in the 3D case was inadequately reported. In this study, we developed a new THM coupling simulator HENGYI in the context of the finite element method. The UP-T solution scheme was verified to be robust enough to simulate large engineering problems. The Streamline Upwind Petrov Galerkin method was generalized to 3D and applied to HENGYI to address the advection-dominated heat transfer. The performance of the UPT, UP-T and U-PT schemes was compared and the applicability of different solution schemes was found to be highly associated with the degree of coupling between primary variables. Great details are provided regarding the development of HENGYI. Thus HENGYI not only bridges the research gaps mentioned above but also provides a comprehensive understanding of THM coupling simulation techniques.