Bored piles are often larger diameter than conventional continuous flight auger (CFA) piles and are used to support greater loads, overcome underground obstructions, penetrate ground too hard to bore using a continuous flight auger or create piles with a cut-off level beneath the platform level. Because the rotary bored technique enables the reinforcement to be added into the open bore rather than into the ready poured concrete, as in CFA, it has the distinct advantage of allowing the cage to be the full depth of the pile.
They are formed by drilling through a temporary casing to the designed depth, using an auger or other tools such as drilling buckets, core barrels etc. to cope with a variety of ground conditions. The casing gives support to the pile through unstable ground and once the required depth is reached, the auger is removed, the reinforcement is added and the concrete poured. When the concrete reaches the required level, the casing is removed allowing it to be reused in future. In cases where the ground is still unstable at depth, support fluids such as bentonite or polymers can be added.
Van Elle's rotary capability, our experience and range of rigs is extensive, enabling us to install piles of all depths and diameters. We regularly design temporary cased rotary secant piled and contiguous piled retaining walls allowing for tighter vertical tolerances, and therefore greater retained heights, compared to that of traditional or cased CFA solutions.