单轴压缩黏性土剪切带相互作用及损伤试验研究

剪切带损伤研究对于理解材料破坏机制和建立剪切带本构模型具有重要意义。为了研究单轴压缩黏性土样的剪切带损伤演化规律，根据纵向应变较高时清晰剪切带位置布置切向测线，对数字图像相关方法获得的结果进行双三次样条插值，从而获得光滑性较好的各种应变场。将土样整体的损伤变量-纵向应变曲线与各条剪切带的损伤演化曲线进行了对比。研究发现：（1）总体上，土样整体的损伤变量演化曲线呈线性，而各条剪切带的损伤变量演化曲线均上凹，这表明随着纵向应变的增加，各条剪切带的损伤发展越来越快；（2）各条剪切带的损伤变量演化曲线的轮廓线呈马尾形，这说明随着剪切带的逐渐发育，各条剪切带的相互影响和作用规律变强；（3）对于含水率较低的土样，平行或共线剪切带的损伤变量变化基本同步，特别是在剪切带充分发育之后，但两条剪切带的距离应较小；在一定时期，共轭或交叉剪切带中剪切带的损伤占优，这与剪切带的相互竞争有关，但若两条剪切带达到独立发展的程度，则二者的损伤变量变化可以同步；对于含水率较高的土样，各条平行或共轭剪切带的损伤变量变化基本同步，剪切带的相互作用不明显。

Experimental studies of damages and shear band interactions for clay specimens in uniaxial compression

Studies of damages in shear bands are important for obtaining a full understanding of failure mechanisms of materials, and for accurate modeling of deformations in shear bands. To study the distribution and evolution of damages in shear bands in clay specimens in uniaxial compression, monitored lines are arranged according to positions of clear shear bands along their tangential directions at higher longitudinal strains. Smooth strain fields at these lines are obtained using a bicubic spline interpolation function from results based on a digital image correlation method. The damage variable-longitudinal strain curves for entire specimens and shear bands are compared. It is found that in total the damage variable-longitudinal strain curves for entire specimens are linear, while those for shear bands are convex upward, suggesting that damage developments in shear bands become faster and faster as longitudinal strains increase. The envelop of the damage variable-longitudinal strain curves for shear bands is like a horse-tail, revealing that interactions among shear bands become intensive as deformation proceeds. For specimens with low moisture contents, changes in damage variables for shear bands are generally synchronic for parallel or co-linear shear bands, especially for well-developed shear bands, however, the shear band spacing cannot be large enough. The damages in one shear band between two conjugate or intersecting shear bands are dominant at a certain stage due to competition between them. However, if the two shear bands have developed fully, changes in damage variables can be synchronic. For specimens with high moisture contents, changes in damage variables for shear bands are generally synchronic for parallel or conjugate shear bands, reflecting weak interactions among shear bands.