State of the Art Dynamic Load Testing of ACIP Piles in the Americas

Abstract

Augered Cast-in-Place (ACIP) piles have seen a rapid increase in demand. Factors such as high shaft resistance to volume-of-concrete ratio and fast, vibration-free installation with low noise, makes the ACIP pile a desirable deep foundation alternative. A variety of pile installation techniques exist that range from the typical hollow-stem augered ACIP pile to partial or full displacement pile. However, ACIP piles present challenges associated with as-built shape, structural integrity and relatively high load bearing capacity demands. Therefore, load testing techniques that increase reliability of load capacity determination are critical. In this paper, advances in the dynamic load testing techniques as applied to ACIP piles are presented. New techniques include the use of top transducers, the use of embedded instrumentation and testing recommendations specifically for ACIP piles. Top transducers speed up and facilitate load testing and increase the accuracy of top force measurement readings. Embedded instrumentation, particularly near the pile toe, helps improve the accuracy of pile wave speed assessment and calculated resistance distribution. Testing recommendations include the necessary hammer energy for optimal permanent penetrations per blow, which completely activate pile resistance while limiting over-prediction of ACIP bearing capacity in plastic soils. Additionally, a correlation between dynamic load test and static load test results recently performed on 47 ACIP piles tested in North and South America ranging from 16 to 30 inches in diameter is presented. Finally, supplemental testing and analysis techniques for further improvement of testing reliability and performance of ACIP piles are proposed, such as thermal integrity profiling and signal matching of the data from embedded sensors when available.