Construction Bored Piles Animation

Описание: As the piles on this riverside site have to support large loads they are over 1m in diameter and 45m deep. They have to penetrate 10m – 11m of wet silty gravel before meeting impermeable London Clay. The top section of pile has to be encased in a permanent steel liner that is vibrated into place (not shown in its entirety). The upper levels of loose material are excavated using a bottom-opening rotating bucket. All drilling is done through Bentonite – a thrixotropic mud which helps to support the bore sides below the casing. When the rig driver detects that he is entering the clay layer by a change in the engine note, he changes to an auger drill bit. This is tested before entering the bore to ensure that it is firmly attached. When the bore is completed the Bentonite continues to circulate by means of an air lift in order to bring gravel debris up to the surface. This is removed using mechanical vibrating screens. When no debris is coming off the screens the airlift is removed. Reinforcement is lowered into place in the bore and a “tremie” tube fixed to ensure that concrete is delivered directly to the base of the pile, displacing bentonite at the top. Finally, concrete is pumped into the pile. It can take two days to complete each pile. A sample pile is load tested to prove the design, by jacking down from a beam held down by two anchor piles.