New CPT methods for evaluation of the axial capacity of driven piles

Abstract

High costs associated with offshore foundation installations have provided strong impetus to the offshore energy sector in the search for more reliable design methods. This paper provides a summary of an Industry sponsored project that led to the development of new CPT-based design methods for the evaluation of the axial capacity of driven piles. Particular attention was given to the need for the new methods to be applicable to large diameter offshore piles given that many existing methods are derived by calibration with capacities measured in static pile load tests on smaller diameter onshore piles. The basic mechanisms supporting the general format of the expressions proposed for shaft friction and end bearing in sands and clays are described. It is shown how the new expressions, which are calibrated against a database of the most reliable load tests reported in the literature, lead to better predictions of capacity compared to other methods and can also satisfactorily predict the capacity of piles driven into deposits comprising interbedded layers of sand, silt and clay. Recommendations for the prediction of pile displacements at working loads using CPT data are also presented.