冻结重塑黏土分数阶蠕变本构模型分析

Analysis of fractional-order creep constitutive model of frozen reshaped clay

人工冻土的蠕变特性受温度场、水分场、应力场的相互影响,而传统的岩土本构模型未能考虑温度、含水率等因素。为了表达冻土介于理想固体和理想流体之间的某种“勾兑效应”,基于岩土的经验模型,将分数阶导数理论引入其中,建立受水、热、力三场耦合影响的人工冻土分数阶蠕变模型。将西安某煤矿黏土重塑并进行不同温度、含水率的单轴抗压和单轴蠕变试验,得到温度和含水率对冻结重塑黏土强度特性和蠕变特性的影响规律。分析冻结重塑黏土在不同负温、含水率及两种应力等级下的蠕变曲线,得到lg t-lgε曲线的线性关系,进而得出冻结重塑黏土分数阶蠕变模型相关参数与温度、含水率的函数关系。对比分数阶冻土蠕变模型试验值与计算值,发现该模型能够很好地反映冻土在不同应力等级下其蠕变随温度和含水率的变化规律,对指导寒区冻土工程设计与施工具有重要意义。

The creep behavior of artificial frozen soil is influenced by the interaction of temperature,moisture,and stress fields.However,traditional rock-soil constitutive models do not account for factors such as temperature and moisture content.To better represent the behavior of frozen soil as a material between an ideal solid and an ideal fluid,this paper introduced the fractional derivative theory to establish a fractional-order creep model for artificial frozen soil affected by the coupling of water,heat,and force fields,based on rock-soil empirical models.The effects of temperature and moisture content on the strength and creep characteristics of the frozen molded clay were obtained by reshaping the clay in Xi′an coal mine and uniaxial compressive strength and creep tests with different temperature and moisture content.By analyzing the creep curves of frozen reshaped clay under different negative temperatures,moisture contents,and two stress levels,a linear relationship between the lg t-lgεcurve was obtained and the relevant parameters of the fractional creep model of frozen reshaped clay with temperature and water content rate function were determined.Comparative analysis of the experimental and calculated values of the fractional-order frozen soil creep model shows that the model can effectively reflect the changes in creep of frozen soil with temperature and moisture content under different stress levels,which is useful for guiding the design and construction of frozen soil engineering projects.