考虑冻融的粉质黏土统计损伤本构关系研究

发布时间：2018-06-18 22:40

本文选题：粉质黏土 + 冻融　；参考：《西北农林科技大学学报(自然科学版)》2016年12期

【摘要】：【目的】研究冻融作用下土的物理力学性质的变化,构建一种同时考虑荷载效应和冻融循环的损伤模型,为预测冻土地基反复冻融作用下的沉降变形提供理论基础。【方法】以青藏铁路沿线常见的粉质黏土为研究对象,制备了20组同一目标含水量(16%)和干容重(1.30g/cm3)的重塑试样,开展了3种正压力(100,200和300kPa)下的直接剪切试验,剪切变形速率控制为0.8mm/min。以粉质黏土的抗剪强度数据为基础,采用3种常用的分布函数(正态分布、对数正态分布和Weibull分布),分析了粉质黏土的抗剪强度分布特征。之后基于Weibull概率密度函数和Lemaitre等效应力原理,推导出三维应力条件下冻土的本构关系;采用Drucker-Prager强度准则反映荷载所致土结构损伤,并选取冻融数次后弹性模量描述冻融循环所致结构损伤,最后提出了一种同时考虑冻融作用和荷载效应的损伤变量,并嵌入冻土损伤本构关系,构建了损伤模型。采用冻融试验数据和三轴剪切试验数据,验证该模型的合理性。【结果】相比于正态分布和对数正态分布,粉质黏土的强度数据更符合Weibull分布规律,曲线吻合程度和最大偏差均最小。验证试验结果表明,构建的损伤模型的计算结果与试验结果的相关系数均高于0.70,说明该模型能够较好地描述粉质黏土冻融数次后的应力应变特征。【结论】成功构建了一种同时考虑荷载效应和冻融作用的损伤模型,这为统计损伤本构关系的研究和有效的工程应用提供了参考依据。
[Abstract]:[objective] to study the change of physical and mechanical properties of soil under freezing and thawing, and to construct a damage model that considers both the load effect and the freeze-thaw cycle. In order to provide a theoretical basis for predicting the settlement and deformation of frozen soil foundation under repeated freezing and thawing. [methods] taking silty clay along the Qinghai-Tibet Railway as the research object, 20 groups of remolded specimens of the same target water content (16%) and dry bulk density (1.30 g / cm ~ 3) were prepared. Three direct shear tests with positive pressure of 100200 and 300 KPA were carried out, and the shear deformation rate was controlled to 0.8 mm / min. Based on the shear strength data of silty clay, the characteristics of shear strength distribution of silty clay are analyzed by using three kinds of distribution functions (normal distribution, logarithmic normal distribution and Weibull distribution). Then, based on Weibull probability density function and Lemaitre equivalent stress principle, the constitutive relation of frozen soil under three-dimensional stress condition is derived, and Drucker-Prager strength criterion is used to reflect the structural damage induced by load. The elastic modulus is selected to describe the damage caused by freeze-thaw cycle several times. Finally, a damage variable considering both freeze-thaw effect and load effect is proposed, and the damage constitutive relation of frozen soil is embedded into the damage model. The rationality of the model is verified by using freeze-thaw test data and triaxial shear test data. [results] compared with normal distribution and logarithmic normal distribution, the strength data of silty clay accord with Weibull distribution law. The degree of curve coincidence and the maximum deviation are minimum. The results of the verification test show that, The correlation coefficient between the calculated results of the damage model and the test results is higher than 0.70, which indicates that the model can well describe the stress-strain characteristics of silty clay after freezing and thawing several times. [conclusion] A new kind of damage model has been successfully constructed and considered at the same time. Damage model of load effect and freeze-thaw effect, This provides a reference for the study of statistical damage constitutive relation and effective engineering application.
【作者单位】：西安理工大学岩土工程研究所;北京建筑大学土木与交通工程学院;
【基金】：国家自然科学基金项目(51408486;41572268) 北京市属高等学校高层次人才引进与培养计划项目(CIT&TCD20150101)
【分类号】：TU442

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