Pilings, suit strata which will yield under pressure like sandy soil or other non-cohesive material. PowerPiles are efficient, combining soil replacement and compaction grouting elements. The effect is assisted by skin friction/cohesion and base resistance.
For insertion, PowerPiles polymer pillars comprise a geo-fabric shell, shrink-wrapped around an inner injection tube. They are compressed to about 30mm diameter. When inserted down pre-drilled holes, they are filled with Uretek geopolymer resins which expand chemically. This forces the geo-fabric shell force outwards from the injection tube as much as the surrounding soil will allow, out to a maximum of about 300mm.
Resin quantities are predetermined from geotechnical bore-hole information. Injection of the expanding resin mix is computer-monitored and controlled with precision. As the compressed tube/element is expanded from the bottom up, adjacent non-cohesive soil is displaced and compacted. The resin hardens and there is immediate increased support. The shape of the PowerPile is usually irregular, the shape being affected by the varying strength of ground resistance at the different depths. Compressive strength of PowerPiles can be 1000 kPa to 5000 kPa and more, if needed.
External installation means little disturbance to landscaping. PowerPiles can be inserted down to depths of 6000 mm, even from inside a normal domestic building, as they are flexible. There is minimal noise and the process is remarkably clean. Work can be done overnight. PowerPiles would normally be installed up to the underside of footings but shorter lengths may be lowered and expanded to locally ‘bridge’ individual weak layers and lenses at depth, transferring load and increasing the bearing capacity of weak foundations.
Installation of PowerPiles is convenient and precise:
- A 36 mm diameter hole is driven into the ground by machine.
- A compressed 30 mm diameter, shrink-wrapped, prefabricated PowerPile element is inserted manually.
- Its central 10 mm diameter pipe core is then connected to a computer-controlled extraction machine.
- Uretek resin is injected as the pipe is slowly withdrawn, expanding the element up to 350 mm in weak soil strata.