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利用透明土技术和激光散斑图像结合数字图像相关方法(DIC方法)测量土体内部的位移场,是研究土力学问题的一种新方法。通过试验研究不同粒径范围的熔融石英颗粒(中细砂0.1~0.3 mm、中砂0.3~0.5 mm、粗砂0.5~2 mm、细砾2~5 mm),揭示粒径对激光散斑图像质量、DIC查询窗口和位移场测量精度的影响。结果表明,不同粒径的熔融石英透明土模型产生的散斑场图像、灰度直方图明显不同;相同入射激光下,小粒径比大粒径模型获得更好质量的散斑图像。位移误差直方图显示,位移误差依赖于查询窗口尺寸和颗粒大小。通过平均灰度梯度调整查询窗口,不同粒径的透明土模型可以给出彼此相当的测量精度。数字和物理平移试验显示,由小粒径石英颗粒配置的透明土模型能够得到更高的测量精度。
It is a new method to study the soil mechanics problem by using the transparent soil technique and the laser speckle image combined with the digital image correlation method (DIC method) to measure the displacement field inside the soil. The effects of particle size on the laser speckle images were revealed by experimenting with fused silica particles (0.1-0.3 mm in fine sand, 0.3-0.5 mm in middle sand, 0.5-2 mm in grit and 2-5 mm in fine gravel) Quality, DIC Query Window and Displacement Field Measurement Accuracy. The results show that speckle field images and grayscale histograms are obviously different from the fused silica transparent soil model with different grain sizes. Speckle images with better quality are obtained with smaller particle size than those with the same incident laser. Displacement error histograms show that the displacement error depends on the size of the query window and the particle size. Through adjusting the query window by the average grayscale gradient, the transparent soil models with different particle sizes can give their equivalent measurement accuracy. Numerical and physical translation experiments show that the transparent soil model with small particle size quartz particles can achieve higher measurement accuracy.