A KEANE EYE: Just say, ‘Screw it’

Perhaps one of its biggest strengths is one of its biggest drawbacks. It requires a machine with a planetary drive head (generally an excavator) to install the pile, which is readily available, but because this is readily available it means that people without the necessary expertise can install them.That aside, there are quite a few companies around Australia with the necessary expertise to provide engineered foundations using screw piles, and between them they are coming up with a variety of applications that showcase their capabilities.Screw piling has a lot of good things going for it:It is fast and ready to use as soon as it is installed; It is cost-effective; It does not require specialised, expensive equipment to install; Compared to driven piles, it has no vibration and considerably less noise; No concrete is required; andIt can be used for temporary applications, removed with virtually no trace, and often re-used.It seems as if Australia is leading the way in developing these applications. Type “screw pile” into your Google search engine and have a look at how far down the list you have to go before you see the first overseas web reference come up. With the level of competition in the local market, the climate exists for the market to develop further, and you would think that a time would come when some companies look at taking their expertise overseas in a big way.Temporary work camps are an ideal application. If the buildings are demountable, why shouldn’t the foundations be as well? Apart from allowing the screw-in piles to be removed after the camp is removed, the piles can be re-used. Concrete is not required and set-up times can be quite fast. In remote areas, doing away with the need to mix concrete can be a godsend. In cyclone areas (in combination with temporary structures designed to withstand those conditions) screw piles make sense because they resist uplift and provide a firm anchor for the temporary structures. This could include appropriately designed roofing systems designed to provide cover for hardstands where equipment is worked on.If doing away with the need to mix concrete can be a godsend in remote areas, imagine how much of a buzz it would be if you did not have to do that for a remote bridge. There are a few precast concrete bridge systems out there these days, and they have real benefits on routine bridges in allowing them to be built quickly with a bare minimum of equipment.Yet those benefits are only half being delivered if you need to bring in a pile driver and mix concrete for a pile cap before you start to erect the precast bridge. Having a precast pile cap that integrates with screw-in piles goes a long way towards preserving the benefits of having a precast bridge system in the first place.It does not have to be a road bridge: using screw piles makes sense for small bridges crossing gullies and small watercourses, or just levelling out the terrain, for walking trails and cycle paths in areas that are difficult to access. The size of pile required should generally be within the hydraulic capabilities of a mini excavator that can get into most areas.A few people have developed systems that integrate screw piles with slabs for house foundations in areas with difficult soils that can cause cracking in conventional slabs.Others have anchors designed specifically for road signs and light poles, and screw piles have been used recently for towers on a major cross-country high voltage powerline. The piles do not have to go in vertically – they have been used horizontally to stabilise embankments to prevent land slip, and have been used to counter hydraulic uplift on sunk structures.For those with a licence to innovate, there are still a lot of opportunities out there to marry screw piles to other permanent and temporary structures.

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