Recently we were asked to help with a sinking footpath at the side of a resort lagoon. The engineer asked for screw piles spaced at 3m apart installed in the water as close to the edge of the existing footpath to support another concrete path, placed on top of the old one.
The area was in a reclaimed swamp so we expected the screw piles may go deep to achieve the 50kn (5 ton) safe work load.
Installing the screw piles with our drilling rig, equipped with a monitoring pressure gauge for informing the installer when the SWL is achieved, we found no ground carrying capacity even at 6m deep. At this depth, we needed to understand what the ground was like as beyond this depth there is a risk of side momentum on the pile {bending of the shaft under load in soft clay grounds}
A phone call to East Coast Screw Piers in house engineer (who has 25 years experience of this area) told us that the ground was estuarine silt and it was good enough to proceed another 4m deeper before further information would be required.
A SWL was obtained at 8m deep by our installer, depths were recorded and sent on to the engineer for certification to the client.