基于数字图像测量方法的分层试样剪切破坏特性研究

Study of the behavior of shear failure of layered soil samples based on digital image measurement methods

分层试样的强度及变形特征与单一试样有很大的区别,其剪切带的发生、发展过程等相关性质也不相同。本文在传统的三轴压缩仪上引进全表面数字图像测量系统,对分层试样及单一试样分别进行了三轴压缩试验,得到了试样的整体和局部的应力应变关系曲线以及试样全表面的变形信息。结果表明:在单一试样中夹杂其他试样的情况下,其分层试样对单一试样的影响与围压的大小密切相关,随着围压的增加影响程度变大,分层试样的性质更接近于位于试样两端的土层性质。同时,剪切带开始形成的时刻受分层土中强度较高的试样影响比较大,而与该试样在整个分层试样中所处的位置无关。剪切带完全形成的时刻取决于分层试样中间夹层试样的最后变形情况,而与中间夹层试样的类型无关。在同一试验条件下,分层试样及单一试样剪切带的形状、位置及倾角大体一致,但分层试样剪切带的带宽要大于单一试样的剪切带带宽。

The shear strength and deformation characteristic of layered specimen are very different from that of pure specimen,also is for the onset and the development of shear band.The whole-surface digital image technique is developed and used to measure the deformation distribution over the entire surface of layered soil specimens and pure soil specimen in triaxial tests.The entire and local stress-strain curve of the soil specimens can be also obtained.The test results indicates that,when the pure soil specimen is mixed up with other specimens,the effect of layered specimen on pure specimen is mainly due to the confining pressure.With the increase of confining pressure,the characteristic of layered specimen is close to that of the two ends specimen.Meanwhile,the moment for the onset of shear band is affected by the specimen with higher shear strength,and is not related to the position of the specimen.In addition,the moment for the penetration of shear band is due to the deformation of interlayered specimen in the middle part,and is not related to its component.For the same test condition,the shape,positon and angle of shear band of pure specimen and layered specimen are approximately consistent.But the width of shear band of layered specimen is bigger than that of pure specimen.