All 29 steel screw piles of the minimum intrusion foundation system have been inserted in 2 days by Helical Systems.
The initial “auger” pile section is screwed into the ground using a hydraulic torque motor. The torque motor was hung from an excavator which supplied hydraulic pressure to the motor. The size of the excavator arm allowed reach out to the pile positions, keeping the tracks of the excavator positioned in the centre of the building footprint for all of the 29 screw piles.
Extension sections are added until a suitable load bearing sub strata is reached. The result is minimum soil disturbance with no corrosive cement based products at tree root level.
The pile depth supports the building loads below the tree root level, allowing the roots to maintain growth below the building over the total site area without risks of catastrophic soil movement. An alternative application for this piling system is to provide under pinning support of foundations where building movement is experienced through soil heave or shrinkage.
A load bearing steel frame will be attached to the pile tops on which the building will be constructed. The frame will above existing ground level and form a 150mm ventilated air gap below the over floor, ensuring that root oxygenation is maintained.
Adoption of the foundation system for all the building envelope area is in excess of any planning requirements. If in the future the building is removed, the screw piles insertion can be reversed to remove the foundation footprint and restore the land to its original state.