Using SEM Photos to Gain the Pore Structural Parameters of Soil Samples

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.