考虑组构变化效应的饱和密砂循环本构模型

为了真实地描述饱和密砂在循环加载过程中的变形行为,需要引入考虑剪胀阶段组构变化的宏观参量。在已有的基于状态参量的本构模型基础上,引入反映组构变化的剪胀内变量,简称组构-剪胀内变量z。以相变线PTL作为参考线,采用基于相变的状态参量判断砂土在初始时刻和任意时刻体积变形的变化趋势,并通过z对剪胀比d的影响,考虑反向加载过程中塑性变形的累积,建立了一个针对饱和密砂的循环加载的弹塑性本构模型。该模型根据试验现象将已有模型中的塑性剪切模量区分为首次加载模量与再加载模量,能较好地模拟排水情况下砂土循环加载的胀-缩变化过程。最后,针对密砂的三轴排水情况,利用文中模型进行预测,并把预测结果与试验结果进行比较,结果表明该模型能够总体反映砂土循环加载的变形行为。

A cyclic constitutive model of saturated dense sands considering fabric change effects

To truly describe the reaction of saturated sands under cyclic loading, a parameter considering macroscopically dilatancy stage on fabric changes is necessary. Based on the existing constitutive model dependent on a state parameter, a fabric-dilatancy internal variable z considering the influence of the fabric change is introduced. It is still based on phase transformation state. With state parameter the deformation tendency of sand at any time or any conditions can be judged. Through the z effected on the dilatancy, plastic deformation accumulation is considered when load increment reversals. In this paper, an elastoplastic constitutive model of saturated dense sand under cyclic loading is established. According to experimental phenomenon analysis, plastic modulus in the existing model is modified, it can simulate well expansion shrinkage change process of sands under drained cyclic loading. Finally, in view of the dense sands during triaxial drained cyclic loading, a comparison between model simulations and a sequence of experimental results shows that the model can generally reflect the deformation behavior of being given sand.