南宁膨胀土非线性流变模型研究

对南宁非饱和膨胀土进行一系列的加载-卸载固结蠕变试验，得到了不同含水率的膨胀土在不同应力水平下应变-时间曲线和不同时刻的应力-应变等时曲线簇。通过对膨胀土各阶段蠕变变形的分析，得到了膨胀土的固结蠕变是包含有黏弹性变形和黏塑性变形成分的非线性蠕变。采用模型流变与经验流变理论相结合的方法，将膨胀土的蠕变变形分成线性和非线性两部分进行分析，蠕变柔量和线性黏弹性模量随时间减小，而线性黏塑性模量随时间增大。结合膨胀土的线性黏塑性模型和非线性黏塑性经验模型，建立能够描述膨胀土非线性流变的黏塑性本构方程。根据试验所得数据，通过非线性拟合方法得到各模型参数，用该模型进行数值分析得到的理论与蠕变试验结果对比非常吻合。研究成果为实际工程提供了流变变形计算分析的可靠依据。

Study of nonlinear rheological model of Nanning expansive soils

A series of loading-unloading consolidation creep experiments are carried out on Nanning unsaturated expansive soils.Lots of stress-time curves of different moisture expansive soils and stress-strain isochronous curves are obtained under different stress levels.Through the various stages of creep deformation analyses,it is concluded that the creep deformation of expansive soil is a nonlinear creep,which contains viscoelastic deformation and viscoplastic deformation.Combined with empirical rheology and rheology model theory,the creep deformation of expansive soil is divided into two parts of linear and nonlinear ones.The creep compliances and the linear viscoelastic modulus decrease;while the linear viscoplastic modulus increase with time increasing.Considered linear viscoplastic model and nonlinear viscoplastic empirical model of expansive soil together,viscoplastic constitutive equation is proposed which can be used to describe the nonlinear rheologic characteristic of expansive soils.According to the experimental data,all parameters of this model under different stresses are determined by nonlinear fitting methods.It is shown that the regression curves calculated using this theory fit well with creep test results.The conclusions provide a reliable theoretical basis for the rheological model of expansive soils to further study.