基于Weibull分布的黄土状土的单轴损伤模型  

WEIBULL RANDOM DISTRIBUTION BASED DAMAGE CONSTITUTION MODEL OF LOESSIAL SOILS UNDER UNIAXIAL COMPRESSION

作　　者：谢星[1,2] 王东红[3] 赵法锁[4] 

机构地区：[1]长安大学地球科学与资源学院西安710054 [2]西部矿产资源与地质工程教育部重点实验室西安710054 [3]机械工业勘察设计研究院测试公司西安710043 [4]长安大学地质工程与测绘学院西安710054

出　　处：《工程地质学报》2013年第2期317-323,共7页Journal of Engineering Geology

基　　金：中央高校基本科研业务费专项资金(CHD2010JC049);长安大学基础研究支持计划专项基金资助

摘　　要：通过扫描电镜和偏光显微镜对不同方向切面试样的观察,分析了损伤前后黄土状土微观结构的变化。分析结果表明:受力前黄土状土呈粒状架空接触结构,石英、长石、伊利石及高岭石等矿物在试样中分布杂乱无定向性。黄土状土的单轴压缩过程分为3个阶段:第一阶段为压密阶段,此阶段土体中微裂隙闭合,大孔隙变成为微孔隙;第二阶段为峰值应力前开始损伤阶段,此阶段土体微结构转为镶嵌微孔微胶结结构,颗粒之间产生滑移,原有和新生的小裂隙变宽、变长;第三阶段峰值应力后损伤快速发展,孔洞、裂隙连通,矿物发生明显定向。在此基础上,利用黄土状土微元强度服从Weibull随机分布的特点,运用统计损伤理论,并考虑到黄土状土的含水率、损伤门槛的影响,建立了考虑损伤门槛的损伤本构方程。以黄土状土的单轴压缩试验结果作为实例,进行了验证。理论计算结果与试验结果对比表明,该模型能够较好地描述黄土状土的变形破坏全应力-应变试验曲线。The change of loessial soil microstructure before and after damages is analyzed by observing different cross-sections of specimen with a scanning electron microscope and a polarizing microscope.The results show that at pre-loading,the loessial soil has granulometric bracket contact microstructure with quartz,feldspar,illite,kaolinite and other minerals distributed randomly and astatically.The uniaxial compression process of the loessial soil can be divided into three stages.The first stage is a compacted phase,when microcracks close up and macropores become microcracks.The second stage is an initial damage phase which begins prior to peak stress.The soil micro structure turns to a lightly cemented mosaic microporous structure with slippages produced between particles.The original and newborn small cracks get wider and longer.The third stage is a rapid damage development phase which occurs after peak stress.The pores and cracks are interconnected,and the minerals have a pronounced directional characteristic.On this basis,constitutive damage equations are established by applying statistical damage theory using the characteristic of loessial soil micro-unit strength following the Weibull stochastic distribution,and considering the moisture content and damage threshold of loessial soil.Verification is carried out by taking the results of loessial soil uniaxial compression tests.The comparison of calculated results with test results shows that this model can properly describe the complete stress-strain test curves for loessial soil deformation and failure.

关 键 词：黄土状土 微观结构 WEIBULL分布 损伤门槛 本构模型 

分 类 号：TU41[建筑科学—岩土工程]