Study on coupled thermo-hydro-mechanical processes in column bentonite test

Abstract

An unconventional numerical scheme is developed to simulate coupled thermo-hydro-mechanical (THM) processes in partially saturated medium. The non-isothermal, unsaturated fluid flow and mechanical processes are sequentially coupled by updating all the state variables using cellular automaton technique and finite difference method on spatial and temporal scale, respectively. A new cellular automaton updating scheme is proposed by introducing a fast successive relaxation index, which greatly improves the computational efficiency in the simulation of THM coupling process. This is implemented in a self-developed numerical system, i.e., an elasto-plastic cellular automaton (EPCA3D), which was used to numerically reproduce the coupled THM behavior of bentonite pellets in a column experiment that was heated up to 140 °C firstly and then was hydrated simulating the resaturation of the backfilling. By using the cellular automaton technique in EPCA3D, the challenging courses of the changing boundary conditions over time and space during the experiment are conveniently implemented. The EPCA3D was able to reproduce the main physical processes of the in laboratory column bentonite experiment within the heating and hydration phase. The modeling results for the evolution of temperature, relative humidity, water uptake and axial pressure are consistent with the experimental data in terms of trends and magnitudes, which verifies the realistic simulation with the developed model and contributes to a deeper understanding of the observed phenomena.