Influence of overconsolidation ratio on hydromechanical behavior of unsaturated silty soil under various shearing rates

Due to the limited land resources in major cities, reclamation becomes an optimal option to solve this issue, unsaturated soil is often involved in these projects, and the hydro-mechanical behaviour of this type of soil significantly are affected by the stress history and time effect. In this study, the overconsolidation ratio (OCR) effect of unsaturated silt under different shearing rates was studied through a series of constant water content tests. The specimens were under an effective confining pressure of 400 kPa. The samples were unloaded to 100 kPa, and 50 kPa to achieve different values of OCRs (4, and 8). The samples with different OCRs were then dried from saturated state to initial suction=100, 200, and 300 kPa via axis-translation, and then sheared at three different rates. The results show that higher strain rates led to a higher degree of saturation during shearing under different OCRs. The shear strength increased with increasing shearing rates while the maximum deviator stress decreased when OCR decreased. Higher OCRs resulted in larger volume change during shearing; similar behaviour was observed for increasing rates.