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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。
A series of loading - unloading consolidation creep tests were carried out on unsaturated soils in Nanning. The strain - time curves and stress - strain isochronal curves of expansive soils with different water contents at different stress levels were obtained. Through the analysis of the creep deformation of expansive soils at various stages, the consolidation creep of expansive soils is obtained, which is a nonlinear creep including viscoelastic deformation and viscoplastic deformation. The creep deformation of expansive soil is divided into two parts: linear and non-linear. The creep compliance and linear viscoelastic modulus decrease with time, and linear viscoplasticity Modulus increases with time. Based on the linear viscoplastic model and the nonlinear viscoplastic model, the visco-plastic constitutive equation describing the nonlinear rheology of expansive soils is established. According to the data obtained from the experiment, the parameters of each model are obtained by nonlinear fitting method. The numerical analysis with the model is in good agreement with the creep test results. The research results provide a reliable basis for the calculation and analysis of rheological deformation for practical engineering.