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为了获取冻风积土在循环逐级加载过程中发生的动力损伤特征,通过对不同负温、围压及振动频率条件下的冻风积土试样进行动三轴试验,测得其动应力-应变曲线。按照冻风积土发生各向同性损伤及塑性应变增量垂直于屈服面的基本假设,利用塑性势函数F(Y,D,σ)相关联流动法则并按照R-O硬化定律建立了冻风积土加载过程中塑性损伤演化模型(P模型)。利用文中提出的有效应力分析方法对试验所测得总动应变中所包含的累积塑性变形部分进行分离,实现了对P模型中参数拟合的目标;根据一、三主应力对D-P屈服边界进行划分以确定加载过程中弹塑性变形特征。通过分析裂隙发展规律研究冻风积土内部塑性损伤演化过程,将累积塑性变形变化率曲线的拐点作为冻风积土发生塑性损伤的阈值,给出了确定初始发生塑性损伤的理论依据。研究结果表明:P模型与相关文献模型确定的塑性损伤变量变化规律具有一致性,为冻风积土路基或基础的动力灾害防治研究提供理论基础。
In order to obtain the dynamic damage characteristics of the frost aeolian soil during cyclic loading, the dynamic triaxial tests were carried out on the samples of frost aeolian soil under different negative temperature, confining pressure and vibration frequency, and the dynamic stress - strain curve. According to the basic hypothesis that the isotropic damage and the plastic strain increment are normal to the yield surface in the frozen aeolian soil, the frozen soil aeolian soil is established according to the law of plastic flow potential F (Y, D, σ) and the law of RO hardening Plastic damage evolution model (P model) during loading. By using the method of effective stress analysis presented in this paper, the cumulative plastic deformations contained in the total dynamic strain measured in the experiment are separated, and the target of fitting the parameters in P model is achieved. According to the primary and secondary principal stress, Divided to determine the elastoplastic deformation during loading. Based on the analysis of the law of fracture development, the infiltration evolution of cumulative plastic deformation rate curve is taken as the threshold for the plastic damage of frozen soil fouling. The theoretical basis for determining the initial plastic damage is given. The results show that the variation rules of plastic damage variables determined by P model and related literature model are consistent and provide theoretical basis for the research on the control of dynamic damage of frozen soil embankment or foundation.