非饱和土蠕变力学特性试验及经验模型研究

为了预测基质吸力对非饱和粉质黏土蠕变行为的影响，开展其非饱和蠕变经验模型的研究。基于粉质黏土的非饱和蠕变试验，尝试改进Mesri模型和Log-Modified模型。其中Mesri模型和Log-Modified模型的应力-应变关系均采用双曲线函数描述，通过初始切线模量建立其与基质吸力的联系，从而得到应力-基质吸力-应变关系。而Mesri模型和Log-Modified模型的应变-时间关系分别通过幂函数、三参数幂函数描述，分别整合两个模型，得到改进后的Mesri模型和Log-Modified模型。改进后的两个模型为应力-基质吸力-应变-时间模型，利用ε/D-ε关系曲线和幂次关系拟合得到应力-基质吸力-应变关系参数，依据lnε-lnt关系曲线确定改进Mesri模型的应变-时间关系参数，采用BFGS算法和通用全局优化法求解改进Log-Modified模型的应变-时间关系参数。将关系参数分别代入两个改进后的模型，得到相应的非饱和蠕变经验模型。对非饱和蠕变曲线进行辨识，对比两种改进模型的预测精度。结果表明:改进后的Log-Modified模型的预测效果较差，改进后的Mesri模型能较为准确地描述非饱和粉质黏土的蠕变特性。

An experimental study of the creep mechanical properties of unsaturated soil and empirical models

In order to predict the effect of matrix suction on the creep behavior of unsaturated silty clay, the empirical model of unsaturated creep is established. Based on the unsaturated creep test of silty clay, the Mesri model and Log-Modified model are improved. The stress-strain relationships of the Mesri model and Log-Modified model are described with a hyperbolic function. The relationship between stress-matrix suction and strain is established by the initial tangent modulus, and the relationship between stress-matrix suction and strain is obtained. The strain-time relationship of the Mesri model and the Log-Modified model are described with the power function and the three-parameter power function, respectively, and the modified Mesri model and the Log-Modified model are obtained. The two improved models are stress-matrix suction-strain-time models. The parameters of the stress-matrix suction-strain relationship are obtained by fitting the ε/D-ε relation curve with the power relation. According to the lnε-lnt relation, the strain-time relationship parameters of the improved Mesri model are determined, and the BFGS algorithm and the general global optimization method are used to solve the strain-time relationship parameters of the improved Log-Modified model. The relational parameters are replaced by two improved models, and the corresponding unsaturated creep empirical models are obtained. The unsaturated creep curves are identified and the prediction accuracies of the two improved models are compared. The results show that the prediction effect of the improved Log-Modified model is poor, and the improved Mesri model can accurately describe the creep characteristics of the unsaturated silty clay.