Diaphragm Wall

A diaphragm wall is a structural concrete wall constructed in a deep trench excavation, either cast in situ or using precast concrete components. Diaphragms walls are often used on congested sites, close to existing structures, where there is restricted headroom, or where the excavation is of a depth that would otherwise require the removal of much greater volumes of soil to provide stable battered slopes.

Diaphragm walls are suitable for most subsoil and their installation generates only a small amount of vibration and noise, which increases their suitability for works carried out close to existing structures. In addition, floor slab connections and recessed formwork can be incorporated into the walls.

The walls generally range in thickness from 500 - 1,500 mm and can be excavated to depths of over 50 m. Excavation is typically carried out using rope-suspended mechanical or hydraulically-operated grabs.

The excavation stability is maintained by the use of a drilling fluid, usually a betonies slurry. This is a controlled mixture that has thixotropic properties, meaning that it exerts a pressure in excess of the earth and hydrostatic pressures on the sides of the excavation. The walls are constructed, using reinforced or unreinforced concrete, in discrete panel lengths generally ranging between 2.5 - 7 m. Purpose-made stop ends can be used to form the joints between adjacent panels, with a water bar incorporated across the joints.