Applicability of CPT Capacity Prediction Methods to Driven Cast-In-Situ Piles in Granular Soil

Abstract

Databases used in developing cone penetration test (CPT)-based design methods for driven piles have been dominated by data for the preformed variant, with the driven cast-in-situ (DCIS) pile category poorly represented. A database of 30 DCIS piles was used to appraise the ability of seven established CPT-based methods for driven piles to predict the total capacity of DCIS piles in granular soil. A subset of instrumented piles within the database was used to appraise the ability of these methods to predict shaft and base resistances separately. In general, the UWA-05 method provided the most reliable predictions for total and base capacity, whereas the LCPC-82 method is recommended for prediction of shaft resistance using shaft coefficients for standard driven piles. The paper collated findings from the recent instrumented pile tests conducted by National University of Ireland (NUI) Galway examining the mechanisms of shaft resistance in DCIS piles. In spite of uncertainties regarding mechanisms affecting the shaft resistance of DCIS piles during installation, the data from the instrumented tests presented herein provide strong evidence that the shaft resistance of a DCIS pile in sand is comparable to that of a preformed displacement pile. The NUI Galway pile tests also showed that the normalized base resistances for preformed and DCIS piles are equivalent.