Diaphragm Walls

Diaphragm Walls

Diaphragm walls are constructed by excavating a series of rectangular panels keyed into each other to form a continuous wall. Panels are keyed into each other by using temporary formwork (stop ends).
Water bars (rubber membranes) can also be installed between panels by casting in place via the stop end. Excavation of the panels in soils and low quality rock are via either rope suspended or kelly bar mounted grabs. Excavation in more competent rock requires mills. In almost all cases the excavation is supported by drilling fluids such as bentonite or occasionally polymer slurries. This enables diaphragm walls to be constructed through almost any ground conditions.
 
Diaphragm walls are generally considered to provide the highest level of finish quality and water tightness of all retaining walls. Depending on final aesthetic requirements and the prevailing ground conditions, the exposed concrete face of a diaphragm wall generally requires less treatment than for other solutions which often require shotcrete coating or blockwork walls. However, as diaphragm walls are cast in ground some localised oversizing can occur and this may require trimming. The installation of water bars between panels provides a superior level of water tightness compared to other products such as secant pile walls which have cold joints between adjacent piles. Structurally, diaphragm walls provide a very efficient section which enables significant bending stresses to be accommodated. Thinner cross sections and the reduction of waling beams also make diaphragm walls an ideal solution in congested areas where maximising space is critical during construction and/or operation ofthe basement.
 
The higher cost of site establishment associated with diaphragm walls means that these systems are generally more suited to larger and/or deeper basements or where water tightness is a prime consideration. They are also highly cost effective on long straight wall sections, such as cut and cover tunnels.

Vibropile's range of kelly bar mounted hydraulic diaphragm wall grabs is capable of constructing diaphragm walls and barrettes from 450mm up to 1.2m thickness and up to 40m depth.