The application of high strain dynamic pile testing to screwed steel piles

摘要

Screwed steel piles have been in commercial use in Australia for about 3 years and are becoming a popular foundation support for small to medium commercial structures. Although new to Australia this type of pile is described in the old British Foundations code CP4 -1954. In Australia they would previously have been described as micro-piles as they were used for small loadings only but they are now becoming used for more regular pile applications, with serviceability loads increasing to well over 1000kN. They comprise a relatively small diameter steel tube with one or more relatively large diameter screw flights near the toe and sometimes at intervals along the shaft. The structural and geotechnical design of these piles is still evolving. This paper will describe several projects where dynamic pile testing has been successfully used to demonstrate the capacity of these piles with a range of sizes, lengths and ground conditions. In one case a static load test was conducted after the dynamic test and provided a close correlation with the dynamic test result in a Grade A prediction. The general methodology used to conduct the successful tests with the PDA/CAPWAP system will be described.