Diaphragm Wall [ DW ] is a technology carried by Foundation Specialists.

Diaphragm Wall can be designed and executed as a reinforced concrete retaining structure, in which case it will also be called “ Cast In Place Reinforced Concrete DiaphragmWall “. Diaphragmwall is  a “Top-Down Construction Technology” employed for Excavation Support in difficult soil conditions or whenever deep excavation has to be carried out in an environment where zero disturbance of the surroundings, including avoidance of water table lowering, and/or zero settlement of neighboring structures are a requirement.

DiaphragmWall is put in place using a segmental installation technique, [Primary and secondary DiaphragmWall  Panels of predetermined dimensions installed by following a proper  sequence] purposely and specifically designed for each soil formation and particular site requirements, in order to avoid any disturbance and subsidence to the surrounding areas.

In cohesionless soil formations under the water-table, the segmental excavation of Diaphragm Wall is generally carried out using bentonite suspension as the drilling fluid, in order to balance the action of the water-table and to maintain the excavation of the Diaphragm Wall perfectly stable until each single “ Panel ” is cast with concrete.

Once all the segments or “ Panels “ of the DiaphragmWall are cast, they are connected at the top by a reinforced concrete continuous beam  [ Coping ], after which, removal of soil on the excavation side can proceed, protected by the Diaphragm Wall.

The DiaphragmWall, depending upon depth of excavation and upon design loads to be applied on the “ earth side “ can be designed to act as a cantilever Diaphragm Wall or as an anchored DiaphragmWall, in this last case, soil or rock anchors shall be drilled,  installed and generally post tensioned, at one or more levels of the DiaphragmWall (as per design), when excavation reaches the required elevations.
Diaphragm Walls are used as the perimeter structural walls of building basements: the DiaphragmWalls can be properly reinforced to act as the buildings' shear walls. Buildings' columns can be integrated within the Diaphragm Walls, dowell bars for any application can be attached to the DiaphragmWall reinforcing cage prior to installation and in situ casting. DiaphragmWall technology was used by Foundation Specialists to design and construct the Marginal Wharfs of the very large deep water port facilities of the National Steel Corporation.
Common DiaphragmWall application:  large number of Deep Underground Parking Facilities and Deep Underground Building Basements, Steel Mills Pits, Underground Pumping Stations, have been built by Foundation Specialists using the
Top-Down Construction Sequence, by constructing Perimeter Walls, including Shear Walls and Columns with Diaphragm Wall Technology, prior to main deep excavation. 

Diaphragm Wall is sometime called Slurry Wall.

An other type of DiaphragmWall carried by Foundation Specialists is a Technology called Cut-Off Wall  or  Self-Hardening Plastic Cut-off Wall .

The Cut-Off Wall is a continuous and impermeable Diaphragm Wall, generally made using a mix of Cement+Bentonite, designed to remain indefinitely, both  sufficiently  plastic in order to follow soil movement and deformation without cracking and totally impervious.

DiaphragmWall  and  Cut-Off Wall are employed whenever there is a requirement for isolating a source of pollution from the surrounding water table, e.g. around Sanitary  Landfills or other source of polluting lechates. 

DiaphragmWall technology is used  in Dam Construction to achieve water--tightness in the soil or rock formations underlying the main dam or the cofferdams, whenever  grout curtains alone can not guarantee the needed results, as in the case of Dams or Cofferdams with underlying karstic limestone formations.

DiapragmWall are employed  to build river training walls, because Diaphragm Wall can be built sufficiently deeper than the maximum local scouring  depth , thus assuring zero collapse chance for the river dykes due to under-scouring during heavy floods.

The DiaphragmWall construction technology is also used to build deep continuous catching drains, when the deep trench is filled either with gravel or pervious concrete.

Barrettes or Barrette-piles, cast in place rectangular piles are a technology that uses the same equipment employed to execute the Diaphragm  Wall.

DiaphragmWall equipment and technology are used also to execute special design Pile-Column for large loads in Top-Down construction schemes.