Techniques & Systems

Contiguous Bored Pile Retaining Walls

This system involves constructing discrete piles in a line to form a retaining wall. The piles are typically spaced out with their centres 150mm greater than their diameter; for example, 600mm diameter piles at 750mm centres. They are drilled with diameters between 600mm and 1200mm and depths up to 30.0 metres.

Contiguous piles are installed using either Rotary or Continuous Flight Auger methods, depending upon existing ground conditions and retained heights. Individual piles are drilled on a hit and miss basis to avoid damage to recently cast piles.

Contiguous piled walls are used to provide retaining structures where ground water is not present above the excavated level. In general, the soils need to be sufficiently self-supporting to ensure that they do not fall through the gaps between individual piles.

Reinforcement cages are designed to suit the retained heights and any propping forces acting on the wall.