基于图像测量非饱和膨润土三轴试验研究

Triaxial tests on unsaturated bentonite using digital image measurement method

对高庙子钙基膨润土掺砂样进行三轴试验,应用数码相机采集非饱和样剪切过程中试样表面的图像,运用Matlab软件对图像进行裁剪、二值化、寻找质心并进行标记,通过对标记点位置的变化确定剪切过程中试样的变形。发现Matlab图像处理结果与轴向位移传感器测量结果一致,说明图像测量方法可适用于非饱和土三轴试验的应变量测。相同净围压下,排气不排水剪切过程中非饱和土的体变随着吸力的增大而减小。发现非饱和土与饱和土的内摩擦角基本相同,在假定内摩擦角不变条件下得出粘聚力随吸力的变化规律。

A series of triaxial shear tests on Gaomiaozi Ca-bentonite-sand mixture specimens are conducted. The pictures of the unsaturated mixture specimen deformation during triaxial shearing are collected by the digital camera. With the application of Matlab software, the collected pictures are cropped, binarized, searched for their centroids and marked to analysis the deformation of the specimens. The results of Matlab image processing are consistent with the results of axial displacement transducer measurement, and thus the Matlab image processing method is feasible for measuring triaxial strains. Under the same net pressure, the volume change decrease with the suctions during triaxial shearing with constant water content. It is found that the unsaturated and saturated mixtures have the same angle of internal friction, and the relation between suction and cohesion are obtained on the basis of the assumption that the internal friction angle is constant.