基于非对称滞回的不同细粒含量融化粉砂本构模型

利用GDS动态三轴试验系统研究不同细粒含量粉砂土经历多次冻融循环后的动应力、动剪切模量、动剪切模量比和阻尼比变化规律.考虑动态过程中滞回曲线的非对称性,采用分段方程求解动力参数.结果表明,反复冻融循环对降低动应力、动剪切模量和动剪切模量比有很大影响,并使阻尼比增大.对此,建立了描述动剪切模量比、阻尼比与动应变变化关系的归一化经验模型,该模型适用不同的细粒含量和冻融次数条件,能给出良好的预测结果.进一步分析模型参数随试验条件的演化过程,确定细粒含量界限值为10％,且反复冻融后,细粒含量变化对参数a、c的影响减弱.模型参数和试验条件之间的回归关系可通过二元二次方程进行描述.建议在粉砂土动力响应分析中采用冻融循环5次后的土体参数.

Constitutive model of thawed silty sand with different fines content based on asymmetric hysteretic behavior

The dynamic stress, dynamic shear modulus, dynamic shear modulus ratio and damping ratio of silty sand with different content of fine particles were studied by GDS dynamic triaxial test system. Considering the asymmetry of hysteretic curve in dynamic process, the dynamic parameters are solved by piecewise equation. The results show that repeated freeze-thaw cycles have a great influence on the reduction of dynamic stress, dynamic shear modulus and dynamic shear modulus ratio, and increase the damping ratio. Therefore, a normalized empirical model describing the relationship between dynamic shear modulus ratio, damping ratio and dynamic strain is established. The model is suitable for different fine particle content and freeze-thaw times, and can give good prediction results. Furthermore, the evolution process of model parameters with experimental conditions was further analyzed, and the critical value of fine particle content was determined to be 10%. After repeated freezing and thawing, the influence of fine particle content on parameters a and c was weakened. The regression relationship between model parameters and experimental conditions can be described by binary quadratic equation. It is suggested that the soil parameters after 5 freeze-thaw cycles should be used in the dynamic response analysis of silty sand.