Using discrete element method (DEM) to create a cone penetration test (CPT)-based method to estimate the installation requirements of rotary-installed piles in sand

Abstract

Deep foundations may be used in a range of soil types where significant foundation resistance is required, but their installation is often associated with disturbance due to noise and vibration. Greater restrictions on use in urban and offshore environments is now commonplace. Screw piles and rotary-jacked straight-shafted piles are two potential methods of silent piling that could be used as alternative foundation solutions, but the effects of certain geometric and installation properties such as installation pitch, i.e., the ratio between vertical displacement and rotation, on the required installation torque and force in sand are not well understood. In this paper, the effects of installation pitch and base geometry on the installation requirements of a straight-shafted pile are simulated in three dimensions using the discrete element method (DEM). The installation requirements of straight-shafted piles into sand have been validated against centrifuge testing in three different relative densities. The DEM shows reductions in installation force can be achieved by increasing the installation pitch or including a conical tip. An existing cone penetration test (CPT)-based prediction method for installation requirements has been improved to include the effects of installation pitch and base geometry for rotary-installed piles in sand.