This paper presents a constitutive model that predicts the water retention behaviour of compacted clays with evolving bimodal pore size distributions. In line with previous research, the model differentiates between the water present inside the saturated pores of the clay aggregates (the microstructure) and the water present inside the pores between clay aggregates (the macrostructure). A new formulation is then introduced to account for the effect of the macrostructural porosity changes on the retention behaviour of the soil, which results in a consistent evolution of the air-entry value of suction with volumetric deformations. Data from wetting tests on three different active clays (i.e. MX-80 bentonite, FEBEX bentonite, and Boom clay), subjected to distinct mechanical restraints, were used to formulate, calibrate, and validate the proposed model. Results from free swelling tests were also modelled by using both the proposed double porosity model and a published single porosity model, which confirmed the improvement in the predictions of degree of saturation by the present approach. The proposed retention model might be applied, for example, to the simulation of the hydromechanical behaviour of engineered bentonite barriers in underground nuclear waste repositories, where compacted active clays are subjected to changes of both suction and porosity structure under restrained volume conditions.

本文提出了一种本构模型，该模型可以预测具有不断变化的双峰孔径分布的压实粘土的保水性能。与先前的研究一致，该模型区分了存在于粘土骨料饱和孔隙内的水（微观结构）和存在于粘土骨料之间孔隙内的水（宏观结构）。然后引入一种新的配方，以说明宏观结构孔隙度变化对土壤保持特性的影响，从而导致吸气进气量随体积变形而不断变化。来自三种不同活性粘土（即MX-80膨润土，FEBEX膨润土和Boom粘土）的润湿测试数据均经过不同的机械约束，用于配制，校准，并验证提出的模型。通过使用提议的双重孔隙度模型和公开的单一孔隙度模型对自由溶胀测试的结果进行建模，这证实了本方法对饱和度预测的改进。拟议的保留模型可以应用于例如地下核废料储存库中工程膨润土屏障的水力学行为模拟，其中压实的活性粘土在受限的体积条件下会同时发生吸力和孔隙结构的变化。