Molecular Dynamics Simulation and Lab‐Scale Experimental Testing of Water Migration in Unsaturated Expansive Clay

IF 3.6 2区工程技术 Q2 ENGINEERING, GEOLOGICAL

International Journal for Numerical and Analytical Methods in Geomechanics Pub Date : 2025-06-28 DOI:10.1002/nag.70004

Qiuyan Liu, Liuqun Dong, Genli Tang

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Abstract

The mechanical performances of expansive clay in semi‐arid areas deteriorate with the change in humidity and temperature due to its characteristics of water‐swelling and drying shrinkage. So, investigating the moisture migration in expansive clays is of great significance. This study employs molecular dynamics (MD) simulations to elucidate microscale water transport mechanisms in clay mineral pores, complemented by experimental validation using a novel horizontal migration apparatus across temperature gradients (5°C, 20°C, 40°C). Quantitative analysis reveals that temperature significantly influenced water migration, with the migration rates at 5°C and 20°C accounting for approximately 30% to 60% of the rate observed at 40°C. Based on the MD simulation results obtained, a modified Kozeny–Carman equation is presented to simulate the hydraulic conductivity at various temperatures. The microscopic flow behavior of clay minerals was compared with the macroscopic characteristics of clay. The results demonstrate that hydraulic conductivity varies non‐linearly with changes in matric suction. Under the same matric suction, the computed hydraulic conductivity obtained from MD is higher than that of the experimental simulation. The arrangement and connectivity of soil pores at a higher suction have a more pronounced impact on soil permeability. These results elucidate the moisture migration mechanisms in unsaturated expansive clay at the microscale.

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非饱和膨胀粘土中水运移的分子动力学模拟及实验室规模实验测试

半干旱区膨胀粘土的水胀和干缩特性导致其力学性能随湿度和温度的变化而恶化。因此，研究膨胀粘土中的水分迁移具有重要意义。本研究采用分子动力学（MD）模拟来阐明粘土矿物孔隙中的微观尺度水输送机制，并辅以实验验证，使用了一种新型的水平迁移装置，跨越温度梯度（5°C, 20°C, 40°C）。定量分析表明，温度对水迁移有显著影响，5°C和20°C时的迁移率约占40°C时观察到的速率的30%至60%。在MD模拟结果的基础上，提出了一个修正的Kozeny-Carman方程来模拟不同温度下的水导率。将黏土矿物的微观流动特性与黏土矿物的宏观流动特性进行了比较。结果表明，水力导电性随基质吸力的变化呈非线性变化。在相同基质吸力下，MD计算得到的水力导率高于实验模拟。吸力越大，孔隙的排列和连通性对土壤渗透性的影响越显著。这些结果阐明了非饱和膨胀粘土微尺度下的水分迁移机理。

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来源期刊

International Journal for Numerical and Analytical Methods in Geomechanics 工程技术-材料科学：综合

CiteScore

6.40

自引率

12.50%

发文量

160

审稿时长

9 months

期刊介绍： The journal welcomes manuscripts that substantially contribute to the understanding of the complex mechanical behaviour of geomaterials (soils, rocks, concrete, ice, snow, and powders), through innovative experimental techniques, and/or through the development of novel numerical or hybrid experimental/numerical modelling concepts in geomechanics. Topics of interest include instabilities and localization, interface and surface phenomena, fracture and failure, multi-physics and other time-dependent phenomena, micromechanics and multi-scale methods, and inverse analysis and stochastic methods. Papers related to energy and environmental issues are particularly welcome. The illustration of the proposed methods and techniques to engineering problems is encouraged. However, manuscripts dealing with applications of existing methods, or proposing incremental improvements to existing methods – in particular marginal extensions of existing analytical solutions or numerical methods – will not be considered for review.