基于热力学并考虑体变及滞回效应的土-水特征曲线模型

A thermodynamics-based soil-water characteristic model with considering volumetric change and hysteresis

基于热力学内变量理论,提出能综合考虑毛细滞回效应和非饱和土体积变形影响的土-水特征曲线模型。热力学第二定律推导结果表明:毛细滞回现象和塑性变形本质上是一种耗散行为;吸力和饱和度的变化不仅与流相变化直接相关,而且也受到固相体积变化的约束与影响;土-水特征曲线的流相体积变化与固相变形之间存在相互耦合作用。从微观上阐明滞回现象产生的机制以及变形对吸力的影响,建立了考虑体变及滞回效应的土-水特征曲线一般性模型。然后采用边界面塑性理论,在只增加两个新参数的情况下,建立了一个简化的能描述毛细滞回及塑性孔隙比变化影响的新模型。最后,利用已有试验数据对这一模型进行了验证,结果表明,新模型能考虑土体变形的影响,并能较为准确地描述毛细滞回现象,模型预测结果与已有的试验数据吻合较好。

Based on the theory of thermodynamic with internal variables, a soil water characteristic curve model is developed, which can comprehensively consider the effect of capillary hysteresis and volume deformation of unsaturated soil. Based on the second law of thermodynamics, it is shown that both capillary hysteresis and plastic deformation represent some kind of dissipative behavior in nature. The suction is not only related to the changes of fluid phases, but also controlled by the deformation of solid phase. There is mutual coupling effect due to the interaction between the soil-water characteristics and the solid phase deformation. The mechanism of hysteresis phenomenon and the effect of deformation on the suction force are expounded from a microscopic standpoint and a general model of soil-water characteristic curve is established. Then a boundary surface plasticity model is developed, from which a simplified model is developed to describe the influence of the capillary hysteresis and plastic void ratio change. The model is validated using the experimental data. The results show that the new model can address the effect of soil deformation, and accurately describe the capillary hysteresis phenomenon.