Development and application of digital image processing technology based soil tensile apparatus

Investigation on tensile properties using ionic soil stabilizer(ISS) contributes to better understanding about the modified mechanism of mechanical behavior such as cohesion. To overcome the defects of existing apparatus, a digital image processing technology-based soil tensile device which comprises displacement controlling module, loading holder module and data detecting module was developed. The soil shape in loading holder was designed as "8" shape to solve the problem about connection between soil and box without any adhesive force. The justification to design the "8" shape loading holder was verified by FLAC(3D). In addition, the loading holder had the function of sample preparation box that could avoid soil disturbance when transforming sample from preparation box to loading holder. Image capture device was added to record the process of deformation and failure of soil sample so that these recorded images can be analyzed by digital image processing software named Geo-PIV to study the deformation of soil in the period of tensile test. After finishing the tensile test, comparative trial and investigation on raw montmorillonite and modified montmorillonite by adapting ISS solution with certain concentration were carried out. The results indicate that the soil sample is under tension without stress concentration at the part of sample that contacts the loading holder through the analysis of recorded transformative image based on PIV. Furthermore, tensile strengths and moduli of the modified montmorillonite by ISS are lower than those of raw montmorillonite and the degree of reduction increases with increasing concentration of ISS solution. The data acquisition module is sensitive to the change of stress and strain. Consequently, the developed tensile apparatus is reasonable, reliable and sensitive.