基于数字图像测量技术的砂土剪切带分析

在进行土工试验时，土样端部摩擦效应和初始缺陷都可以引起试样的不均匀变形，进而形成宏观的剪切带。基于数字图像测量技术改进了GDS多功能三轴仪，进行砂土的固结排水三轴试验，获得了试样在不同时刻的应变等值线云图和局部应力-应变全曲线，研究了试样端部的摩擦效应。结果表明，端部摩擦显著地影响试样的力学特性，对径向应变的影响可达10%。通过在砂土试样中放置粉质黏土块的方法获得了宏观不均匀土样，并测试其剪切带的形成过程。测试结果表明，试样在两种材料的界面处形成不连续刚度，引起变形的不均匀发展，进而形成宏观的剪切带而破坏。

Shear band analysis of sand based on digital image processing technique

End friction effect and initial defect of sample both can cause inhomogeneous deformation,then form macroscopic shear band in soil test.The triaxial equipment of GDS is improved based on digital image processing technique,and used to do drained test of sand.The strain nephogram and local stress-strain complete curve at each sampling time point are recorded;then end friction effect is researched.The result shows that the end friction has significant effect on mechanical properties of sand sample.The radial strain error reaches 10%.The macroscopic inhomogeneous sample is got by putting silt clay block into sand sample;and the formation process of shear band is tested.The evolution of shear band during the loading process shows that the discontinuation of stiffness formed at interface of two materials;with inhomogeneous deformation developing,the macroscopic shear band is fully formed,so as to fracture.