Friday, 18 December 2009
Piling at Tidemill School
You might have been wondering what was going on at the site of the new Tidemill School this morning with this strange looking machine - in fact it is the start of installation of the foundations for the building. This machine is used to put piles into the ground before the building can be built.
Piles are effectively underground columns which are used to support buildings, bridges and other civil engineering structures. They stop the building from sinking into the soil, which would otherwise compact with construction of something heavy on top of it. The piles usually extend quite a long way into the ground, right down as far as the bedrock, so that they will bear the weight of the building.
The machine you see here is being used to install what are known as 'continuous flight augur' piles. It's the quietest and most vibration-free method of installing piles, which is why it is usually used in urban areas.
The big 'corkscrew' or augur is driven into the ground to the required depth, and the soil comes up to the surface by the action of the screw. As the augur is removed, concrete is pumped into the bottom of the hole through a void in the shaft of the augur to fill the hole. If you tried to take the augur out before putting the concrete in, the hole would simply collapse because of the ground pressure around it. Once the hole is full of concrete and the augur has been removed, a reinforcement cage is lowered into the hole, to complete the structural system of the pile.
The piling contractor is Miller Piling - you can find more information about the CFA system and this type of machine on their website.