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提出一种基于标点法的土体局部应变数字图像量测方法来测量加载过程中土样中部区域的应变。精度分析表明,利用该方法测得轴向应变和横向应变量测精度可达±0.007%,剪切应变量测精度可达±9.0×10-5;通过刚体平移试验分析了镜头畸变引起的系统误差分布规律,在保持目标区域尽量居中的前提下,系统误差可以控制在0.02%以内。给出了一个无侧限压缩试验的应用实例,在加载的各个阶段利用数码相机拍摄照片,借助数字图像处理技术得到各阶段节点位移进而求得标记区域内4个高斯点处的应变值,并对试样中部区域和试样整体的变形过程进行对比。结果表明,该方法可以真实详细地反映土样局部区域的变形演化过程。
A method of local strain digital image measurement based on punctuation was proposed to measure the strain in the middle region of soil during loading. Accuracy analysis shows that the accuracy of measurement of axial strain and lateral strain measured by this method can be up to ± 0.007% and the precision of shear strain measurement can reach ± 9.0 × 10-5. The system caused by lens distortion is analyzed by rigid body translation test The error distribution law, keep the target area as far as possible on the premise, the system error can be controlled within 0.02%. An application example of unconfined compression test is given. Digital images are taken at various stages of loading, and the displacement of each node in each stage is obtained by digital image processing to obtain the strain values at four Gaussian points in the marked area. The deformation of the central region of the specimen and the specimen as a whole is compared. The results show that this method can reflect the deformation evolution of local area in detail and accurately.