Climate warming accelerates permafrost thawing, causing warming‐driven disasters like ground collapse and retrogressive thaw slump (RTS). These phenomena, involving intricate multiphysics interactions, phase transitions, nonlinear mechanical responses, and fluid‐like deformations, and pose increasing risks to geo‐infrastructures in cold regions. This study develops a thermo‐hydro‐mechanical (THM) coupled single‐point three‐phase material point method (MPM) to simulate the time‐dependent phase transition and large deformation behavior arising from the thawing or freezing of ice/water in porous media. The mathematical framework is established based on the multiphase mixture theory in which the ice phase is treated as a solid constituent playing the role of skeleton together with soil grains. The additional strength due to ice cementation is characterized via an ice saturation‐dependent Mohr–Coulomb model. The coupled formulations are solved using a fractional‐step‐based semi‐implicit integration algorithm, which can offer both satisfactory numerical stability and computational efficiency when dealing with nearly incompressible fluids and extremely low permeability conditions in frozen porous media. Two hydro‐thermal coupling cases, that is, frozen inclusion thaw and Talik closure/opening, are first benchmarked to show the method can correctly simulate both conduction‐ and convection‐dominated thermal regimes in frozen porous systems. The fully THM responses are further validated by simulating a 1D thaw consolidation and a 2D rock freezing example. Good agreements with experimental results are achieved, and the impact of hydro‐thermal variations on the mechanical responses, including thaw settlement and frost heave, are successfully captured. Finally, the predictive capability of the multiphysics MPM framework in simulating thawing‐triggered large deformation and failure is demonstrated by modeling an RTS and the settlement of a strip footing on thawing ground.

中文翻译：

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模拟多孔介质冻结和融化的热-水-机械耦合质点法


气候变暖加速了永久冻土的融化，导致地面塌陷和倒退性解冻塌陷（RTS）等变暖引发的灾难。这些现象涉及复杂的多物理场相互作用、相变、非线性机械响应和类流体变形，给寒冷地区的地质基础设施带来越来越大的风险。本研究开发了一种热-水-机械（THM）耦合单点三相质点法（MPM）来模拟多孔介质中冰/水解冻或冻结引起的时间依赖性相变和大变形行为。数学框架是基于多相混合理论建立的，其中冰相被视为固体成分，与土壤颗粒一起起到骨架的作用。由于冰胶结而产生的额外强度通过冰饱和相关的莫尔-库仑模型来表征。使用基于分步的半隐式积分算法求解耦合公式，该算法在处理冷冻多孔介质中几乎不可压缩的流体和极低渗透率条件时可以提供令人满意的数值稳定性和计算效率。首先对两种水热耦合案例（即冷冻包裹体解冻和 Talik 闭合/打开）进行基准测试，以表明该方法可以正确模拟冷冻多孔系统中传导和对流主导的热状态。通过模拟一维解冻固结和二维岩石冻结示例，进一步验证了完全 THM 响应。与实验结果取得了良好的一致性，并成功捕获了水热变化对机械响应（包括解冻沉降和冻胀）的影响。 最后，通过对 RTS 和解冻地面上条形基础的沉降建模，证明了多物理场 MPM 框架在模拟解冻引发的大变形和破坏方面的预测能力。