单向压缩砂土试样应变局部化带测量及影响因素分析  

Measurements of strain localization band for sand specimens in uniaxial compression and analysis of its influencing of factors

作　　者：王学滨[1] 杜亚志[1] 潘一山[1] 张春野[1] 

机构地区：[1]辽宁工程技术大学力学与工程学院,辽宁阜新123000

出　　处：《西北农林科技大学学报（自然科学版）》2012年第12期191-200,共10页Journal of Northwest A&F University(Natural Science Edition)

基　　金：国家自然科学基金项目(50974069);国家重点基础研究发展计划项目(2010CB226803);辽宁省高等学校优秀人才支持计划项目(LJQ2011030)

摘　　要：【目的】研究各因素对单向压缩砂土试样应变局部化测量结果的影响,为岩土材料与剪切带相关问题的研究提供参考。【方法】利用基于牛顿-拉斐逊迭代及粒子群优化算法的数字图像相关方法,在单向压缩及应力控制加载条件下,对砂土试样的位移场和应变场进行观测,对直接计算得到的与通过对位移场微分得到的应变场的差异进行了比较,研究了子区尺寸及测点间距对计算结果的影响。【结果】欲得到分散性小的应变场结果,测点间距的取值应接近于子区尺寸;为了捕捉到清晰的应变局部化带,建议计算相邻图片的应变增量;随着载荷的增加,位移梯度带及应变局部化带的宽度有下降趋势;在压应力方向上,剪切带具有压应变局部化现象,而在垂直于压应力方向上,剪切带具有拉应变局部化现象;在宏观剪切裂纹出现之前,应变局部化带的宽度为3～5mm,与水平方向的夹角为48°～55°。【结论】测点布置过少会对应变局部化带的宽度及倾角的计算带来不利影响,子区过大虽能提高应变场的准确性,但也会高估应变局部化带的宽度。【Objective】 This study investigated the effects of various factors on the measured results for strain localization of sand specimen in uniaxial compression and provided important references for problems related to shear bands of geomaterials.【Method】 The displacement and strain fields of sand specimens in uniaxial compression and stress-controlled loading were measured by using of the digital image correlation（DIC） method based on the Newton-Raphson（N-R） iteration and particle swarm optimization（PSO） algorithm.The differences between the strain field obtained directly from the N-R iteration and that obtained by differentiating the displacement field were compared.The effects of the subset size and spacing of monitored points are investigated.【Result】 It is found that small spacing between subset centers,which was close to the subset size,leaded to a less scattered strain field.It is suggested that the strain increment between two adjacent images should be calculated to capture the apparent localized strain bands.The widths of the displacement gradient band and localized strain bands had a decreasing tendency as the increase of load acting on the specimen.In shear band,compressive and tensile strains were also concentrated in the direction of load and that orthogonal to the load,respectively.Prior to macroscopic cracks,the localized band widths were found to be in the range of 3-5 mm,and the inclination angles were 48°-55°.【Conclusion】 Less subset centers have a bad influence on measurements of localized band widths and their inclination angles.Larger subset size increases the accuracy of strain field but overestimates the widths of localized bands.

关 键 词：砂土试样 单向压缩 应变局部化 数字图像相关 粒子群优化 牛顿-拉斐逊迭代 

分 类 号：TU452[建筑科学—岩土工程]