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.

我们通过激光斑点方法在土壤样品表面上开发了高度精确的局部应变分布系统。该原理基于该斑点根据固体表面的变形而线性移动。该系统由CCD摄像头，使用个人计算机的DSP图像处理单元以及相关系数的快速计算方法组成。图像采集显示应变分布所需的时间约为4秒。首先，我们测量了标本上的局部应变分布进行三轴测试。将应变路径控制的三轴检验的结果与常规排水三轴检验之一进行了比较。示出了应变路径控制测试的以下特征：即使在大型应变结构域中，应变分布也更均匀。扩张的体积变化更大。峰值偏差应力较小10％。然后我们将该系统应用于离心模型测试，以实现对局部应变分布的实时和精确测量。这种实现具有以下有价值的含义：可以通过应变分布的实时测量来准确确定失败时的加速度；与带有标记的照片相比，可以获得巨大的节省时间和提高精度。重要的土壤结构（例如大坝）的设计将通过理解从小到大菌株的应变分布来显着发展。此外，该系统使离心模型测试用于研究数值结果的有效性以及土壤的组成方程和参数。