Effects of shear rate on strength properties and pile-soil interface of marine soft clay

The CU triaxial tests and ring shear tests on interface between steel pipe pile and soil of a kind of intact marine soft clay with medium structure are carried out under influence of shear strain rate, and the variations of strength properties and pile-soil interface properties of the tested soil with shear strain rate are analyzed. Moreover, simulation tests on the reconsolidated soft clay around the pile after shearing are also conducted to analyze the strength behaviors of pile-soil interface. The results show that the shear strength and internal friction angle of the tested soil increase with the increasing shear strain rate monotonously, while the variation characteristics of the cohesion are opposite. Under the undrained condition, it is also found that the peak shear strength and internal friction angle of the pile-soil interface increase with the increasing shear strain rate, and the strain softening phenomenon becomes more obvious, however, the corresponding variations of residual shear strength and internal friction angle are very small. Although the peak shear strength of reconsolidated soil around the pile after large shear deformation tends to decrease, the residual shear strength increases, which shows the strength recovery characteristics of pile-soil interface.