Abstract: Using the self-developed soil tensile strength tester, the tensile strength variations of the remolded granite residual soil with water content in wetting or drying process were studied. The microscopic mechanism of the tensile strength variation was investigated through the theories of cementation force and absorbed suction. The results show that the tensile strength first increases and then decreases with increasing the water content, and the relationships between tensile strength and water content on both sides of the peak value can be expressed by exponential functions. In the process of humidification, the tensile strength first increases and then decreases with the increase of moisture content, and the data on both sides of the peak are fitted by linear functions. In the drying process, three stages can be identified in the tensile strength, i.e. exponential increase stage, stable stage and slight decrease stage, the peak tensile strength is 4 times of tensile strengths at different moisture contents. The change of tensile strength of granite residual soil in the process of humidification with different water contents are mainly controlled by absorbed suction. While the change of tensile strength in the drying process is controlled by both absorbed suction and cementation force, the contribution of the cementation force to the tensile strength is more than 70%. The dry cracking process of soil corresponds to several stages of the tensile strength change in the drying process. In the drying process, absorbed suction is the source of the internal tensile stress of soil, indicating that absorbed suction is not only a contributor to tensile strength, but also a destroyer of tensile strength. The results of this study explain the formation source of the tensile strength of the soil and the main controlling factors of its change from another perspective.

Key words: tensile strength, granite residual soil, dry and wet process, absorbed suction, cementation force, dry cracking