Strain Distribution Measurement on a Surface of Soil Sample by Laser Speckle Method and Limit State Design of Soil Structures

激光散斑法测量土样表面应变分布及土结构极限状态设计

基本信息

批准号：
03452271
负责人：
UCHIDA Kazunori
金额：
$ 4.61万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

项目摘要

We developed a highly precise measuring system of local strain distribution on a surface of soil sample by the laser speckle method. The principle is based on that speckles move linearly depending on deformation of solid surface. The system is constituted of a CCD camera, a DSP image processing unit using a personal computer and a fast calculation method of correlation coefficients. The time required for image acquisition to display of strain distribution is about 4 seconds.Firstly, we measured local strain distributions on specimens for triaxial test. The results of strain-path controlled triaxial test was compared with the one of conventional drained triaxial test. The following characteristics for the strain-path controlled test are shown: the strain distribution is more uniform even in a large strain domain; the volume change in dilation is larger; the peak deviator stress is smaller by 10%.Then we applied this system to centrifuge model test to realize the real time and precise measurement of local strain distribution. This realization has the following valuable meanings: an acceleration at failure can be accurately determined by the real time measurement of strain distribution; the drastic saving time and improving accuracy can be obtained compared with the previous measurement by photos with markers; the design of important soil structures such as dams will be significantly progressed by comprehension of strain distribution from small to large strain. Furthermore, this system makes the centrifuge model test use for a tool of investigating the validity of numerical results as well as constitutive equations and parameters of soils.

我们开发了一种利用激光散斑法测量土壤样品表面局部应变分布的高精度测量系统。其原理是基于斑点根据固体表面的变形线性移动。该系统由CCD相机、使用个人计算机的DSP图像处理单元和相关系数的快速计算方法构成。图像采集显示应变分布所需的时间约为4秒。首先，我们测量了三轴试验样本的局部应变分布。将应变路径控制三轴试验的结果与常规排水三轴试验的结果进行了比较。应变路径控制试验具有以下特点：即使在大应变域中，应变分布也更加均匀；膨胀时体积变化较大；峰值偏应力小了10%。然后我们将该系统应用于离心机模型试验，实现了局部应变分布的实时、精确测量。这一实现具有以下有价值的意义：通过实时测量应变分布，可以准确确定失效时的加速度；与以前通过带标记的照片测量相比，可以大大节省时间并提高准确性；通过理解从小应变到大应变的应变分布，大坝等重要土壤结构的设计将取得显着进展。此外，该系统还使离心机模型试验成为研究数值结果以及土壤本构方程和参数有效性的工具。