NZ Geomechanics News Issue 104 December 2022 p. 78-82
The site of the New Dunedin Hospital straddles the location of the original shorelione prior to extensive reclamation works in the late nineteenth century. As a result, ground conditions vary. During the concept design phase, the design team arrived at piles as the logical foundation choice due to the high load and performance demands of the buildings as well as site constraints such as boundaries. To assess the risks and realise the benefits for the project, Tonkin & Taylor Ltd recommended a full scale trial of driven piles. Show more…Screwsol piles were installed and tested adjacent to bottom driven steel tube (BDST) displacement piles, providing a useful comparison with an alternative low noise and vibration option. Screwsol piles are constructed using an auger to displace soil and place concrete via the auger stem. This method is similar to CFA piles, except soil is displaced laterally by the auger rather than removed. Screwsol piles also incorporate a threaded shaft to furhter enhance shaft friction capacity. Pile driving analyser (PDA) testing was used to assess the as-built capacity of both pile types, and extensive monitoring was undertaken to measure noise andvibration levels, including attenuation with distance from the works.
The BDST pile capacities exceeded expectations by a significant margin. Screwsol piles may still be used for associated structure foundations, especially in sensitive areas where noise and vibration limits are critical.
Clearly a full scale pile trial test is not feasible for most projects. The NDH project provided a unique opportunity providing sufficient time for a piling trial in parallel with demolition of the previous building. Show less…
