数字图像测量技术在土工三轴试验中的应用

将数字图像测量技术应用于常规土工三轴试验，解决了常规土工三轴试验传统变形测量中的一系列难题。自主研发了三轴图像测量系统，发展历程可概括为3个阶段：（1）基于边缘识别的三轴试样变形图像测量，通过跟踪边缘位置的变化确定土样的径向变形，识别橡皮膜上的白色标志线确定土样的轴向变形；（2）基于角点识别的三轴试样变形图像测量，用方形标志块将橡皮膜表面离散成若干单元，测量跟踪单元每一角点（节点）的位置，可得任意时刻的土样表面节点的位移，应用有限元技术，可以得到土样表面的位移（变形）场和应变场；（3）三轴土样变形全表面数字图像测量，以基于角点识别的前表面三轴试样变形测量为基础，增设一组平面镜，用一台摄像机实现了圆柱体土样360度全表面的变形测量，得到每一时刻的表面变形场和应变场。三轴土样变形数字图像测量系统具有传统测量方法无可比拟的优点，对于推动土力学，特别是土的本构关系研究具有重要价值。

Application of digital image processing technique to measuring specimen deformation in triaxial test

Application of digital image processing technique to measuring specimen deformation in triaxial test can solve a series of problems about deformation measurement in traditional triaxial test. This paper introduces the development of triaxial image measuring system, which can be divided into three stages: (1) Digital image measurement system based on edge recognition, which determines the radial deformation of soil specimen by tracking the changes of the edge location and axial deformation of soil specimen by identifying the white mark line. (2) Digital image measurement system based on corner recognition, which measures and tracking each corner point (node) position, and obtains the displacement of soil surface node at any moment; we can obtain the displacement (deformation) field and strain field of the soil surface by using the finite element technique. (3) Whole surface digital image measurement system, based on the front surface corner recognition, together with two reflection mirrors situated inside the triaxial cell, a 360 degree coverage of specimen’s deformation could be achieved using only one video camera. Digital image measurement system for measuring specimen deformation in triaxial test has the unparalleled advantages comparing with traditional measurement methods, especially in the research of the constitutive model.