Effect of Pile Driving on Static and Dynamic Properties of Soft Clay

Abstract

A full-scale closed-ended pile was driven into a deep deposit of soft clay that was instrumented with inclinometers and pore pressure transducers at three radial locations and three depths. This paper presents the results and interpretation of both field measurements of shear-wave velocity and the laboratory testing program performed on pre-pile and post-pile “undisturbed” specimens. A companion paper provides full details of the site investigation, field measurements of excess pore pressure, and the deformation field around the pile. Shear-wave velocity profiles at four radial distances were obtained as a function of time following pile driving using the suspension logging method. Compressibility characteristics for this soil were determined through one-dimensional constant rate of consolidation tests carried to very high stresses. Shear strength testing included anisotropically consolidated undrained triaxial tests performed on specimens at two confinement levels to study the effect of fabric and evolving anisotropy. Direct simple shear testing was performed on specimens in their normal vertical orientation, and rotated 90° to observe changes in structure/fabric orientation after pile installation.