Quantitative Research on the Evolution of Mesoparameters at Out of the Shear Band of the Air-Dried Clay

摘要

Based on the axial symmetry principle, three undisturbed and three remoulded cylindrical specimens of the air-dried clay were made into six half-cylinders through the axial symmetry plane, which were carried out on the unconfined compression tests. In the meantime, to investigate the mesostruc-tures, the CCD camera system was developed with the long work distance telecentric microscope lens. By using the image collection system, a series of mesoimages of six clay samples at out of the shear band were captured under different loading states. According to these images, the evolution of mesoparameters of the air-dried clay was studied along increasing loads. Then, through images processing, the mesoimages were transformed into binary images (white areas were congregate particles while black areas were voids). So, the five mesoparameters such as area porosity, particles circularity, particles fractal dimension, particles orientation and Euler number extracted from the series of binary images were defined and analyzed quantitatively using the statistical method. The results show that: (1) the evolution curve shows that the preferable correlation exists in area porosity, particles circularity, particles fractal dimension and Euler number for undisturbed and remoulded clay while the correlation of other parameters does not exist. (2) Especially, with regard to the undisturbed clay, the correlation between particles circularity and particles fractal dimension can be fitted by the quadratic polynomial curve. Moreover, the correlation for the remoulded clay between particles circularity and particles fractal dimension is linear relationship. (3) This study also indicates that there isn't defined and uniform quantitative regression formula between five mesoparameters and the stress of samples in view of the complexity of clay actual mesostructues. It is gratifying that the evolution of some mesoparameters at out of the shear band of the air-dried clay along increasing loads had been qualitatively drawn from the regression analysis.