Engineers Australia

Setup of driven pile capacity with time in soft marine sediments

Ross Kristinof and Mark Thorn

Abstract

This paper describes the findings from a recent maritime project in Melbourne, Australia, which proved that substantial savings in pile lengths can be achieved in mixed clay-sand profiles if construction programs can accommodate longerterm restrike testing. During the design phase static load tests were undertaken on two preliminary test piles, with restrike dynamic testing continuing on both these test piles and associated reaction piles through a period up to 163 days following installation. Dynamic testing was also undertaken on the production piles up to as much as 70 days following installation. The tests indicated a general trend of increasing capacity with time, with differences being evident between pile types. Large shaft setups are evident after little more than 1 month, ranging up to values in excess of 6 times end of drive capacity. Whilst the tendency for high setups is clear, the data shows large scatter. However, much less scatter is observed when 1-day post installation is used as a reference point, with a more consistent trend-line through this data set.