中文摘要：

基于结构体损伤概念和非饱和土力学，利用边界面塑性理论，提出了一个可以描述循环荷载作用下非饱和土力学特性的弹塑性本构模型。在BBM（Barcelona Basic Model）模型的基础上，利用土的持水曲线建立了常含水率下吸力与土体应力之间的耦合作用关系；通过屈服面的大小的改变来反映土体结构性的变化，建立了与累积塑性应变相关的损伤规律。同时，修正了常用边界面理论中映射准则，引入可移动映射中心的概念，将加载、卸载过程的映射准则进行统一，以反映循环荷载下土体产生的滞回特性。通过与相关文献以及本文的循环三轴试验结果的比较，表明本文模型能够较好地模拟非饱和黄土在循环荷载作用下的力学特性。

英文摘要：

Within the framework of the plastic bounding surface model, and based on the structural damage theory and the unsaturated soil mechanics, an elasto-plastic model for unsaturated soils under cyclic loading has been elaborated. Firstly, on the basis of the Barcelona basic model, the water retention curve is employed to couple the suction and mechanical stresses under constant water condition. Secondly, the size of yielding surface is assumed to depend on the soil structure damage, and a law of structure degradation is given, linking the structure damage with accumulated plastic strain increments. Besides, by incorporating the concept of mobile mapping origin, the bounding surface model is modified to unify the mapping rule used during both loading and unloading so as to simulate the phenomenon of hysteretic properties under cyclic loading. Comparisons between experimental results or published data and model simulations show that the elaborated model is capable of describing the unsaturated loess behaviors under cyclic loading.