Applicability of Pile Driving Analyzer on Pile Seating on Rock

High strain dynamic test has the capability to overcome the typical drawbacks of static load tests. This dynamic testing follows wave mechanics principles for geotechnical or structural capacity verification during pile installation. The Pile Dynamic Analyzer (PDA) is a device with a wave mechanics algorithm to monitor pile installation during dynamic loading. This method estimates total driving resistance (or geotechnical resistance), which consists of dynamic and static resistance. A simple dynamic model (Case model) is applied to estimate the pile capacity. In the Case formula used in the PDA to calculate static resistance, ground conditions are represented by the Case damping factor, which is supposed to be selected carefully as it affects the calculation of maximum pile capacity (RMX). However, the selection of the factor is often believed to be less critical and less relevant to the actual ground conditions. Consequently, the PDA-estimated RMX may be questionable. Nevertheless, the final pile capacity obtained from the PDA is usually considered reliable, as it is processed using the Case Pile Wave Analysis Program (CAPWAP) analysis. This study reviews three projects involving PDA testing on rock and compares the damping factors and RMX values obtained by Case and CAPWAP methods. The results show that the RMX estimated by CAPWAP does not appear to have a clear relationship with the damping factors, which indicates the CAPWAP-calculated Case damping factor may not accurately represent rock ground conditions.