Disciplines

Diaphragm wall

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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 hydromills, 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

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