Laboratory Study on Soil Shear Strength under Unloading Conditions

In excavated earth structures (e.g. Deep Excavation, Cut slope, and Underground Construction etc.) unloading is the most predominant factor that affects on the behavior of soil mass. Although in engineering practice, loading mode is usually applied without really considering the influence of unloading factor; and shear strength parameters are often deduced from the conventional triaxial compression test. There are some doubts when applying the shear strength characteristic to analyze the stability of unloading cases. In this study, a comparison in soil shear strength between loading and unloading modes was pointed out, which was based on two series of tests for remoulded clay conducted on the Advanced Stress Path Triaxial Testing System. The test results showed that the quantities of shear strength in both cases were almost the same, but there were some discrepancies between them in the stress-strain and excess pore pressure characteristics.