The Effect of Pile Type on Design Parameters for Driven Piles

摘要

Recent attempts to establish design rules for the shaft capacity of piles based on effective stress concepts, have emphasized the need to establish the state of stress in the soil after installation of the pile. This is particularly true for driven piles where considerable remoulding of the soil near the pile takes place. As an introduction to more sophisticated model pile tests where radiographic techniques will be used to study the deformation pattern around a pile driven into a clay bed, simple preliminary studies have been conducted on a 'quarter-space' of clay. A specimen of clay is prepared in a D-shaped sample tube. The flat (vertical) surface is exposed and marked with a uniform grid of lines before covering the face with a perspex plate. A semi-circular pile may then be driven into the clay flush with the perspex plate, enabling the soil displacements to be monitored by successive photographs of the grid of lines. In this manner it has been possible to obtain detailed information of the displacement field in the soil around a driven pile. The difference in the displacement fields set up by driving open and closed-ended tubular piles, demonstrates that the type of pile must be a major consideration when choosing design parameters for piled foundations.