Contiguous piled walls are formed by installing bored piles in a continuous line with small gaps between adjacent piles, typically 75 to 150 mm. They provide structural support and limit ground movement during excavation, but they are not watertight. They are well suited to retaining structures in stable ground where groundwater control can be managed separately, and they can be installed with minimal vibration, making them ideal in urban environments.
Basic Technique
The wall consists of bored piles typically installed at centres 150mm greater than their diameter. Retained soil between the piles is exposed during excavation, and a spray concrete application with reinforced mesh can be applied as a lining to secure the exposed soil, and resist groundwater pressures for both temporary and permanent retained wall solutions.
Piles are installed, in a sequence determined by boring conditions. The wall is not watertight and measures may be required to prevent wash-out of ‘fines’ between the piles, e.g. shotcrete or gunite applications. Each pile is reinforced with a steel cage designed to resist bending moments and shear. Pile diameters of 350-1200mm are offered, retaining up to 15 metres.
