Development of an innovative THM fully coupled three-dimensional finite element program and its applications

Abstract

A thermal-hydraulic-mechanical (THM) field coupling three-dimensional (3D) finite element (FE) program is developed for complex THM coupled problems in engineering practice. This 3D program incorporates a thermo-mechanical coupled constitutive model known as Tsinghua-Thermo-Soil. The program solves the hydraulic and mechanical fields together and the thermal field separately (i.e., the T-HM scheme). Validation is done against the analytical solutions of one-dimensional (1D) steady-state forced convection-conduction and 1D thermo-elastic consolidation processes. Additionally, effects of the dynamic viscosity coefficient and thermal expansion coefficient of water are analyzed for 1D thermo-elastic consolidation coupled problem. It is revealed that for soils in long-term consolidation and under high loading levels, convective effect is significant and the temperature distribution differs from that obtained by considering only heat conduction. A coupled THM problem of foundations involving an actual engineering energy raft is analyzed. The response of a linear elastic foundation under the combined effect of assumed long-term cyclic thermal loading and mechanical loading process is studied. The results demonstrate that heating leads to the locally accumulation of excess pore pressure and reduces settlement and differential settlement, while cooling has the opposite effects. Due to the heat injected into the foundation exceeding the heat extracted, the ground temperature within several meters of burial depth gradually increases over time, meanwhile the average differential settlement decreases.

Keywords

3D FEM / THM process / Thermal convection / Energy raft foundation / Serviceability state

CRediT authorship contribution statement

Ziqi Liu: Writing - review & editing, Writing - original draft, Visualization, Validation. Xiaohui Cheng: Supervision, Methodology, Conceptualization. Jie Xiao: Validation, Software.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This study was supported by the National Natural Science Foundation of China (Grant Nos. 51778338 and 52078274). The authors have received the funding from the Science and Technology Innovation 2025 Major Project (Ningbo Major Science and Technology Task Tackling Project, No. 2022Z224) and Ningbo ZCONE High-tech Holdings Co. Ltd., to which we hereby express our sincere gratitude.

The program is developed on the cloud-based nonlinear multi-field coupling platform “Yunfei”, which is independently developed by Beijing Yunlu Technology Co. Ltd. Users can access and submit simulation tasks through the Internet. The FE program can be automatically generated from a file containing weak form description written in a specific syntax, known as the FE language. Homepage of Beijing Yunlu Technology: http://en.ylsas.com/index.html.

The measured temperature data of the raft and ground are provided by Xiaogang Chen and Wen Guan. The authors express gratitude to them.

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