改进西原蠕变模型研究及二次开发计算*

为了研究黏土在不同应力水平下的蠕变规律，基于软黏土流变模型及已有的黏土蠕变试验结果，分析3种常用的经验蠕变模型对软土蠕变研究适用性，提出幂函数非线性元件，在传统西原模型的基础上引入非线性黏塑性体(NVPB)构成改进的西原模型。研究结果表明:幂函数描述黏土在低应力和高应力条件下所表现的变形特点都有着较高的准确度，改进西原模型能够较好地描述黏土蠕变的非线性问题以及黏土在高应力水平下的加速蠕变变形。利用自定义本构程序开发接口UMAT对该模型进行二次开发并对模型进行验证。改进的西原模型对比经典西原模型能够更好地描述在不同应力水平下软土的的蠕变变形特征。研究结果可为软土地区沉降预测提供理论参考。

Improved Nishihara creep model research and secondary development calculation

In order to study the creep law of clay under different stress levels,based on the soft clay rheological model and the existing clay creep test results,the applicability of three commonly used empirical creep models for the study of soft soil creep was analyzed,and a power function was proposed.Nonlinear elements,based on the traditional Nishihara model,introduce nonlinear viscoplastic body (NVPB) to form an improved Nishihara model.The research results show that the power function has high accuracy in describing the deformation characteristics of clay under low stress and high stress conditions,and the improved Nishihara model can better describe the nonlinear problem of clay creep and the high stress level of clay.under accelerated creep deformation.The model is re-developed and verified by using the custom constitutive program development interface UMAT.Compared with the classical Nishihara model,the improved Nishihara model can better describe the creep deformation characteristics of soft soil under different stress levels.The research results can provide a theoretical reference for subsidence prediction in soft soil areas.