Diaphragm Walls

A diaphragm wall (D-wall) is a reinforced concrete structure constructed in situ panel by panel. In the basement market D-walls are often used on congested sites, close to existing structures where the excavation depth and ground conditions would prove problematic for piled walls. The D-wall construction sequence can be summarised as following: Construct guide wall at working platform level – typically two parallel concrete beams to control panel alignment. Excavate rectangular panels with rope-suspended mechanical or hydraulically-operated grabs. Where penetration is required through strong rock hydro mills, hydraulically operated reverse circulation trench cutters may be adopted. Support trench excavation with bentonite or polymer slurry to enable excavation below groundwater table in all ground conditions. Install temporary stop ends to form the joints between adjacent panels normally with a water stop included at the joint. Place the panel reinforcement cages and tremie the concrete. Most common applications for D-walls are:

• Deep basements
• Underground carparks and railway stations •
• Tunnel approaches
• Underpasses
• Shafts for tunnel ventilation
• Pump stations