It is well known that the typical swelling behavior of expansive soils is mainly caused by the nanoscale electrochemical phenomena on the surface of their main constituent mineral (i.e., smectite). In this study, the hydro-mechano-chemical (HMC) model for unsaturated expansive soils, which combines the macroscale soil skeleton behavior and the nanoscale interlaminar behavior of mineral crystals based on the surface phenomena is proposed within a double structure framework. The soil skeleton behavior is modeled using the Cam clay type model based on Bishop's effective stress, which considers the degree of saturation-induced hardening. Thus, it is capable of describing hydraulic collapse. Furthermore, the interlaminar behavior is demonstrated through the interlaminar force equilibrium of clay mineral crystals. To describe the swelling process during wetting, namely the crystalline and osmotic swellings, the hydration and osmotic forces acting on the mineral crystals are related to the degree of saturation. Through simulations of a series of the suction-controlled oedometer tests and the swelling pressure tests with various solutions for FEBEX bentonite, it is indicated that the proposed model demonstrates that it can comprehensively describe the typical HMC behavior of expansive soils.

众所周知，膨胀土的典型膨胀行为主要是由其主要成分矿物（即蒙脱石）表面的纳米级电化学现象引起的。在这项研究中，在双重结构框架内提出了非饱和膨胀土的水力-机械-化学（HMC）模型，该模型结合了宏观土壤骨架行为和基于表面现象的矿物晶体纳米级层间行为。土壤骨架行为使用基于 Bishop 有效应力的 Cam 粘土类型模型进行建模，该模型考虑了饱和引起的硬化程度。因此，它能够描述水力坍塌。此外，层间行为是通过粘土矿物晶体的层间力平衡来证明的。为了描述润湿过程中的溶胀过程，即结晶溶胀和渗透溶胀，作用在矿物晶体上的水化和渗透力与饱和度有关。通过对FEBEX膨润土各种溶液的一系列吸力控制固结仪试验和膨胀压力试验的模拟，表明所提出的模型表明它可以全面描述膨胀土的典型HMC行为。