颗粒图像测速技术在离心试验变形分析中的应用

APPLICATION OF PARTICLE IMAGE VELOCIMETRY TO DEFORMATION ANALYSIS IN CENTRIFUGAL TESTS

由于颗粒图像测速技术的可遥控性和实时性,可用于离心机试验中进行土体变形测量。将土体划分为若干细小单元,通过单元的颗粒组成纹理,可以追踪单元的位移,从而确定土体的变形。以此为依据,建立一套系统来实现离心机试验中土体模型的变形监测,包括高分辨率数码相机、精确控制点、土体可识别纹理。试验后对系列图片进行数字化处理,并对实验中产生的各种误差加以修正,得到需要的变形数据。基于测速技术原理的分析,该系统的位移测量精度可以达到0.04mm,准确度0.02mm左右。在砂土边坡的离心试验中应用该系统,分别量测模型边坡在离心加速度增加过程中产生的变形和地下水上升过程中渗流引起的变形,试验结果规律性好,可以反映模型土体各个位置不同时刻的位移情况。表明该系统适用于离心环境中的模型试验,是研究其完整物理过程的重要工具。

Since the technique of particle image velocimetry（PIV） can be controlled remotely and in real time,it is applied to the measurement of soil deformation in centrifugal tests. Soil model is divided into a number of fine elements. The displacement of each element can be traced by recognizing the texture of the soil element. A system is configured to measure slope deformations in centrifugal tests. After processing the test images with error correction,soil deformations can be achieved. The precision and accuracy of this method is estimated as 0.04 and 0.02 mm,respectively,based on the analysis of PIV theory. Two examples are used to illustrate the function of the system. One is to measure the slope deformation when the centrifugal acceleration is increased. The other is to measure the deformation induced by the rise in groundwater table. The analysis gives reasonable results in the two examples and illustrates the capability of the system for measuring displacements in the entire slope field at different moments. It is verified that the system is an important tool for studying the physical process.