Abstract
The shaft friction of a pile under rapid loading has been considered to be composed of radiation damping, viscous damping and stiffness of soil. The stiffness and the radiation damping of soil can be determined by laboratory tests and numerical analyses, but an appropriate testing method has not been established on the viscous damping at pile - soil interface. The object of this paper is to devise an apparatus to investigate the viscous damping at pile - soil interface. By rotating a cylindrical rod of a 31.8mm diameter embedded in a clay specimen with various speeds, the dynamic torque resistance is measured and the viscous damping is evaluated. The test results show that the dynamic component of the shaft friction normalized by a static shaft friction indicates a unique relationship independent of clay type, consolidation pressure and the OCR. Furthermore, the coefficients α and β in the dynamic friction equation introduced by Randolph indicate larger values than those presented by previous reserchers.
