三轴加载过程中土体剪切带的细观演化规律

Meso-evolution of Shear Band of Loess under Triaxial Loading Process

为揭示土体在加载过程中剪切带的细观演化规律,以陕西宝鸡某原状黄土为对象,进行了天然含水率条件下的三轴剪切试验,并在试验过程中采用CT技术进行了实时监测扫描,得到不同应变条件下各断面的CT切片。基于CT重建技术分析了试样在受荷条件下局部裂隙扩展逐渐贯穿形成完整剪切带的过程,推导了CT值与密度的定量关系,发现了等压固结条件下试样的端部约束效应较明显,揭示了不同应变条件下的CT值的变化规律。试验结果表明:在峰值强度前试样逐渐压密,在峰值强度后裂隙开始形成,并在接近残余强度时充分发育;各级应变下典型横剖面的局部CT值与密度均呈正态分布,随应变增加波峰位置下降,波形逐渐变宽。研究成果为岩土材料在受力过程的细观演化定量分析中提供了参考与借鉴。

In an attempt to reveal the meso-evolution of shear band of soil in loading process,triaxial test was performed on an undisturbed loess specimen obtained from Shaanxi,China,and real-time CT scanning was conducted to obtain specimen slices at different strain conditions.The process of local cracks developing into global shear band was reproduced under triaxial loading conditions.The relationship between CT value and soil density was deduced.End restraint phenomenon was observed under isotropic consolidation condition,and the variation in CT mean value against axial strain was analyzed.The further development of cracks was mainly in post-failure stage,and reached stable at residual strength state.Along a typical horizontal section,the local CT value and density show normal distribution,which reflects the reduction of peak value and the widening of waveform with the rising of axial strain.