Diaphragm Walls
Diaphragm Walls provide a very stiff, strong and cost effective solution for the construction of permanent retaining walls and shaft walls. This method of wall construction yields far fewer construction joints than alternative systems such as bored pile or sheet pile walls.
Diaphragm Walls are particularly well suited to large open sites requiring deep excavations. Although shallower walls probably account for the majority of diaphragm walls installed; wall depths over 25 meters are almost the exclusive preserve of the system.
There is a variety of excavation equipment tools all designed to enable excavation to strict tolerances. In common use are: kelly mounted grabs, cable suspended grabs, high capacity hydraulic grabs and Hydrofraise reverse circulation cutters. The Hydrofraise is particularly useful for excavation through rock.
Diaphragm Wall thicknesses range from 500mm to 1500mm and are constructed as a series of primary and secondary panels varying in length from 2.8m to 7.5m to accommodate the geometry of the wall. The primary panels contain stop ends at either end of the panels prior to and during concreting of the panels, these stop ends are withdrawn following completion of concreting, leaving a prepared joint for the secondary panel to engage
Cross-section showing an example of a diaphragm-wall installed in difficult urban conditions