A Driveability Study of Precast Concrete Piles in Dense Sand

Abstract

Abstract A research study was recently completed by University College Dublin to examine the performance of various pile types including open steel tubular piles, concrete precast piles, and helical piers. At the outset of this project, one of the key risks identified was that the concrete piles could not be installed to the target depth due to (i) insufficient energy from the available hammer and (ii) the onset of pile material damage. In order to mitigate this risk a detailed pile driveability analysis was completed to predict the installation performance during driving. Selecting an appropriate model for predicting the Static Resistance to Driving (SRD) was seen as a critical component of the driveability process in order to predict reasonable stresses and blow counts. This paper describes the procedures adopted for a base case driveability analysis and the outcome of the pile installations. A comparison of the SRD using other models (including the API and IC-05 methods) was conducted and the results were compared to SRD profiles derived from dynamic pile monitoring conducted on one of the concrete piles. The base case driveability analysis indicated that the piles could be installed with the available hammer equipment, however it was noted that the driving stresses were relatively high and approached the failure stress of the concrete as the pile approached the target penetration. While hard driving was observed in the field, all of the piles reached their design depth of 7m (23 ft) with the exception of one pile which refused due to structural failure near the pile head. The driveability analysis and the measured stresses were interpreted to identify the cause of failure for the single pile, which was linked to the material properties of that specific pile.