Wagstaff Piling was contracted to install the retention system for the Waterloo Station Box component of the Sydney Metro project. This project comprised the installation of a 900mm diameter hard-soft secant pile wall with a perimeter length of 450 metres and up 20 metres depth. The ground conditions consisted of sand overlying clay overlying sandstone. The station box perimeter was located directly on the boundary of congested city streets with multiple critical services adjacent to the excavation as well as a historic 150 year old church on high level footings with settlement issues.
Wagstaff Piling proposed the use of the cased CFA secant pile system to eliminate possible de-densification of the upper sand layer and ensure that the critical services and the adjacent historic church would not be affected or damaged. This was of critical importance to the project. The use of a large specialised Soilmec SR95 drill rig with high torque double rotary system was used for the cased CFA secant piles. The piles were successfully installed within a very tight program and with no damage to the adjacent infrastructure. We believe this to be the first use of large diameter cased CFA secant piles for an infrastructure project in Sydney. We consider the safety and production benefits provided by this system will be utilised on more projects into the future.
