A Method for Predicting Pile Bearing Capacity From Dynamic Penetration Tests

Abstract

This paper presents a new method for predicting the axial capacity of piles from dynamic penetration tests which is based on the concepts of soil dynamics and principles of energy conservation. The energy delivered to the hammerrod-sampler system and transferred to the soil is computed from the numbers of blow counts Nspt and is analytically converted in a penetration dynamic force. The dynamic force allows the unit resistance mobilized in the SPT sampler (model) to be determined, which is then used to predict the unit resistance mobilized in a prototype pile. The strong direct relationship between the ultimate resistance of driven steel piles and the SPT dynamic force, without any bias of soil type, validates the method. Extension of the method to other pile types requires empirical parameters to account for installation effects. Predictions of 89 instrumented static pile load test database demonstrate that the proposed methodology can be efficiently used in the assessment of axial pile capacity, providing a practical way of increasing reliability in pile design by accounting for effects controlling dynamic penetration.