基于数字图像相关方法的单轴压缩黏土试样剪切带法向应变场观测  

Experimental Studies of Normal Strain Fields of Shear Bands of Clay Specimens in Uniaxial Compression Using Digital Image Correlation Method

作　　者：王学滨 张楠[2] 董伟[2] 潘一山 杜亚志[2] WANG Xuebin1,2, ZHANG Nan2, DONG Wei2, PAN Yishan2, DU Yazhi2(1. Institute of Computational Mechanics, Liaoning Technical University, Fuxin 123000, China; 2. College of Mechanics and Engineering, Liaoning Technical University, Fuxin 123000, Chin)

机构地区：[1]辽宁工程技术大学计算力学研究所,辽宁阜新123000 [2]辽宁工程技术大学力学与工程学院,辽宁阜新123000

出　　处：《应用基础与工程科学学报》2018年第1期177-189,共13页Journal of Basic Science and Engineering

基　　金：国家自然科学基金项目(51574144);辽宁省高等学校优秀人才支持计划(LR2015029);高等学校博士点专项科研基金(20132121110006)

摘　　要：剪切带内部变形观测对于正确认识材料的破坏机理具有重要意义.为了研究单轴压缩黏土试样剪切带法向各种应变场的分布及演变规律,在土样微裂纹刚出现时剪切带法向布置测线,对数字图像相关方法获得的结果进行双三次样条插值,获得光滑性较好的各种应变场.通过统计,获得剪切带法向最大剪切应变的均值和标准差的演变规律,以标准差开始快速增加的时刻作为剪切带萌生的条件.研究发现,（1）随着纵向应变的增加,剪切带中部的最大剪切应变快速、单调增加,而剪切带外部的最大剪切应变增速较慢,有时甚至会下降;（2）剪切带萌生对应于应力-纵向应变曲线的硬化阶段的初始阶段;（3）在剪切带出现不久,剪切带中部的水平和垂直方向线应变的值相差不大,随着剪切带的变形,水平线应变的增长速度高于垂直线应变的,水平线应变对最大剪切应变的贡献率逐渐大于垂直线应变的,而剪切应变对最大剪应变的影响不大.Studies of normal deformation characteristics of shear bands are important for obtaining a full understanding of failure mechanisms of materials. To study the distribution and evolution of normal strain fields of shear bands of clay specimens in uniaxial compression,some monitored lines are arranged at normal directions of shear bands when microcracks just occurred. Smooth normal strain fields at these lines were obtained using a bicubic spline interpolation function from results based on a digital image correlation method. The evolution of the mean and standard deviation of the maximum shear strains at these lines were obtained. The rapid increase in the standard deviation was regarded as the onset of a shear band. It is found that with an increase of the longitudinal strain the maximum shear strain at the center of a shear band rapidly and monotonously increases,while outside the band it slowly increases,and even a decrease is possible. The onset of a shear band corresponds to the initial hardening stages of compressive stress-longitudinal strains curves. There is no apparent difference between the values of horizontal and vertical linear strains at the center of a shear band after it is just originated. With deformation proceeds,the increase is faster for the horizontal linear strain than for the vertical linear strain,and thus the contribution of the horizontal linear strain to the maximum shear strain is progressively dominant. However,the shear strain only has a negligible influence on the maximum shear strain.

关 键 词：黏土试样 剪切带 硬化阶段 线应变 剪切应变 

分 类 号：TU454[建筑科学—岩土工程]