饱和砂土的循环边界面本构模型

Cyclic Constitutive Model of Saturated Sand Based on the Bounding Surface Theory

饱和砂土在循环加卸载过程中,土体发生显著的组构变化和塑性变形的累积.试验现象分析表明,循环过程中,砂土的首次与再循环塑性模量既有区别又有联系.因此,论文引入考虑组构变化的剪胀内变量,并提出循环塑性模量的关系式,真实描述上述两种现象;进而基于已有本构模型的基础,建立饱和砂土的循环边界面本构模型.最后,将饱和砂土的模型预测结果与三轴试验结果进行验证对比,得到较好地吻合,这表明该模型能够合理反映饱和砂土循环加卸载的变形行为.

Significant changes in fabric and accumulated plastic strain of saturated sand occur during the unloading-reloading process. Test results have shown that the plastic modulus in the first cycle is related to but different from that in the following loading cycles. To describe the deformation during the unloading-reloading process, a dilatancy internal variable accounting for the effect of fabric changes was introduced, and an expression of cyclic plastic modulus was proposed. A cyclic elasto-plastic boundary surface constitutive model of saturated sand was then established based on a previous monotonic model. The model is capable of simulating the cyclic stress-strain behavior of sand with different densities and confining pressures as well as under both drained and undrained conditions. The model has been validated against the cyclic test results of Ottaw sand, Fuji River sand and Toyoura sand with good agreement.