Using SEM Photos to Gain the Pore Structural Parameters of Soil Samples
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摘要: 以土工实验和计算机图像处理技术为基础, 探讨利用SEM照片获取土的孔隙结构参数的方法, 并以重塑粘性土为例进行实证分析.为获取孔隙结构参数, 首先分3个步骤对土样的SEM照片进行图像处理: 即照片格式转换、颗粒边际线探测和颜色充填; 然后针对黑白二元图像测算孔隙结构参数.从设计制备的重塑粘性土的三轴试验样品中, 选择了12个不同水分状态和密度状态的样品, 经风干和烘干后, 进行SEM测试, 每个样品拍摄了3个尺度的SEM照片, 放大倍数依次为500倍、1000倍、2000倍.之后, 对所获得的SEM照片进行了图像处理分析, 计算了相应的平面孔隙比和平面孔隙率.数据分析表明: SEM照片测算的孔隙参数与通常三相图计算的孔隙参数有关联, 测算数据可以反映土的孔隙结构特征; 样品的不同脱水方式对SEM照片测算的孔隙参数有影响, 与三相图法计算数据相比, 风干土样测算的数据略有偏大, 烘干土样测算的数据偏小; 同一土样不同比例尺的SEM照片测算出的孔隙参数有所不同, 邻近三相图法计算结果上下波动; 利用SEM照片提取土的结构信息是可行的, 对SEM照片进行图像处理分析是获取土的孔隙结构参数的有效办法.Abstract: Based on soil experimental technique and computer image processing, a method to gain the structural parameters of soil samples by using SEM photos has been discussed, and an example of remolded cohesive soil is offered.To gain structural parameters, three steps to process SEM photos are taken: photo transformation, edge detection and color-filling.Pore structural parameters of soil are calculated through color-filled binary images.12 samples of remolded cohesive soil with different moisture and density states have been selected to test the method.SEM photos in 3 scales have been taken for each sample, i.e.500×, 1 000× and 2 000×.Then all the SEM photos have been processed and plane porosity and void ratio have been calculated with Matlab.According to data analysis, some conclusions can be made as follows.Firstly, pore structural parameters calculated through SEM photos are relevant to those calculated through three-phase diagram and pore structural characteristics of soil can be reflected by them.Secondly, pore structural parameters calculated through SEM photos are influenced by the way of drying SEM samples.Those of air-dried samples are larger than the results of three-phase diagram, while those of heat-dried are smaller.Thirdly, pore structural parameters of the same sample calculated through SEM photos of different scales differ from each other and they fluctuate around those of three-phase diagram.Therefore, it is both feasible and effective to obtain pore structural parameters by SEM image processing and analysis.
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Key words:
- SEM photo /
- image processing /
- pore structural parameters /
- remolded cohesive soil
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表 1 试验用土的基本物性参数
Table 1. Basic parameters of experimental soil
表 2 SEM测试样品的编号及其密度和水分状态
Table 2. No.of SEM samples and its moisture & density states
表 3 SEM图像处理法测算的孔隙参数与三相图计算的孔隙参数的对比
Table 3. Comparison of pore structural parameters between SEM method and 3-phase diagram method
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