Revolutions in piling are few and far between, but a number of market trends and technical innovations are coming together which could hold out the prospect of a major switch from concrete to steel as the preferred piling design choice for many locations.
A major obstacle to using steel in the past has been the perception that steel piles means driven piles, which equals noise and vibration nuisance. That perception is out of date, according to Milton Keynes based Dawson Construction Plant, which has pioneered the development of a new generation of hydraulically powered equipment that can install high capacity steel piles without noise or vibration.
Advantages such as being able to install retaining walls hard up against party walls or in other tight locations will also be of interest to many private developers and infrastructure operators.
Dawson forecasts a strong boost for steel from the recently highlighted problem of removing redundant concrete piles which are seen as effectively a form of solid pollution getting in the way of new works in our cities. Removal of steel piles when a site is redeveloped – increasingly that is going to be every 30 years or so for buildings – is much more straightforward than their concrete counterparts.
“Steel piles can now be put in very quickly without noise or vibration, and when the structure is being replaced the steel can simply be pulled out again even faster,” says Dawson’s Managing Director Robin Dawson. “We can extract piles in all soil conditions with quiet and vibration free plant. We can take out most shapes of pile. Stand-alone piles can be extracted as the rig uses the ground as reaction rather than adjacent piles. Extraction is quick, at up to 3m/minute, and it is safer than using the traditional vibrator and pulling with a crane.”
The new Dawson machinery significantly extends what has gone before to produce a piling rig that can install up to eight sheet piles at a time, with a pressing force currently of 200 tonnes per sheet. As the hydraulic system pushes in one pile, it reacts against other piles in the panel, making use of the friction between the pile and the ground. The Dawson system rig is not restricted to piling in straight lines – sheet piles can be driven in a box and the system is modular so the set up can be unbolted and rearranged easily.