Engineers Australia

A new application of radar in improving pile dynamic formulae used in the quality control of pile foundations

H. Tokhi, G. Ren and Y.M. Xie

Abstract

Installing piles into the ground is a very complex if not uncertain activity. This is particularly true from the point of view of proofing piled foundations. One of the methods currently available is the Dynamic or Energy Formulae that are the oldest and frequently used formulae in determining the bearing capacity of piles. The more recent methods are based on the Wave Equation Analysis and different formulations such as Case Method, TNOWave, CAPWAP® and TEPWAP were developed for pre-driving analysis and post-driving measurement applications. The energy or dynamic formulae, which were developed based on the Newtonian Impact theory, have been regarded as being unreliable and less accurate than the more analytical Wave Equation Analysis methods. The two main reasons for the poor performance of the dynamic formulae are that the hammer energy is assumed and that they do not take the dynamic resistance into account. The advent of new technologies in the construction industry has produced gradual improvements that have resulted in the dynamic method to be used on many projects with greater reliability. In this paper, a new application of radar called IBIS-S is proposed as well as site test results are presented using the Hiley, Gates and MnDOT formulae. The comparison of the results with the more rigorous PDA, CAPWAP® and the GRLWEAP™ analysis show that with the application of new and precise testing equipments, the dynamic formula can be used with greater accuracy than the Case method. It is also shown that the IBIS-S unit may also be used to estimate and evaluate the empirical parameters used in the CAPWAP® and GRLWEAP™ analysis. This approach enables evaluation of the pile capacity to be made more accurately using the dynamic equations.