CAST-IN-PLACE REINFORCED CONCRETE  “DIAPHRAGM WALL” by Foundation Specialists, Inc. 

ABSTRACTS: Diaphragm Walls are cast-in-situ walls used as retaining structure,  perimeter walls of deep, multi-level basements and underground parking facilities, subways, subway stations, underpasses and shaft walls. bridge abutments, dams’ foundations, cofferdams, walls for underground water reservoirs, canal training walls, underground drainage and sewage covered canals, walls, seawalls, dry docks, pollution control. . FS diaphragm walls can also be used in fractured or karstic rock formations, to assure  imperviousness of dams' foundations.  “T”-Shaped diaphragm walls are used for deep-water wharfs. 

DIAPHRADM WALLS [ DW ] are technologies carried by Foundation Specialists, Inc..

DIAPHRAGM WALLS ARE TOP-DOWN CONSTRUCTION TECHNOLOGIES by Foundation Specialists, Inc.

Diaphragm Walls are a type of “Top-Down” Construction Technology used to put in place, construct,  Impervious Permanent Retaining Walls, Structures, Columns, etc.,  ahead of proceeding with the general excavation of the area. As such, DW can be constructed with different methods and equipment , depending on the Ground Formations concerned by the excavation to be supported by the DW. In formation with alternances of Soil and Rock, the excavation of DW is carried out using different equipment for Soil and for Rock, in the required sequence. 

DW are Ideally suited for Slope Protection of Large Deep Excavation in built-up areas, Deep Building Basements, Buildings’ Shear-Walls Foundations, Industrial Plants’ Pits, Mass Transit Subway Stations, Rolling Mills Pits, River Training Walls, City Canals Walls, Storm Drainage Walls, Warfs, Water  Pumping Stations , Sewage Treatment Plants, Sea Walls, and in any instance where a permanent reliable, indefinitely  impervious retaining structure is needed.     Cast in Place DW and Plastc Cut-of Walls are used also as the Impervious “core” of Earth Dams and cofferdams.  Diaphragm Walls , as above, are a Top-Down Construction Technology, and particularly suited for “difficult” soil formations and very deep excavations, in presence or absence of water table and both in cohesive and non-cohesive soil formations. Execution of DW is preceded  by the construction of R-C  Guide Walls. Guide Walls are to thin RC Concrete parallel walls two to three meters deep and built with the inner faces at a distance from each other equal to the DW thichness, with the purpose of assuring the perfect alinement of the panels or piles forming the DW, and  to serve also as a fix reference for DW Survey during execution, aside from being utilized to support the reinforcing bar cages during installation, and  to suspend the Rebar Cages in proper position during  pouring of concrete.  Excavation of DW is done in segments or single “panels” with horizontal length generally varying from 2.0 meters to 3.5 meters , depending on the parameters of the soil being excavated,  Standard Thickness of the DW varies from 600 mm to 1500mm and DW depth  can  reach 100 meters. Foundation Specialists, Inc. [FS] also executes “T” shaped DW used for wharfs construction in deep water.  Diaphragm Walls built to retain deep excavation will be generally Anchored  by  Post-Tensioned Ground Anchors either temporary or permanent,  or in case of building basements the support can be by temporary props to be removed once the basement permanent structure (slabs & beams) will have been built against the DW .

DW  installation produces  zero disturbance of the surroundings, including avoidance of water table lowering, and/or zero settlement of neighboring structures.

As stated here-above  Diaphragm Walls are  executed using a segmental installation technique, [generating Reinforced Concrete  D W  Panels of predetermined dimensions] 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 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 perfectly stable until each single “ Panel ” is cast with concrete.

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

The Diaphragm Wall, depending upon depth of excavation and upon design loads to be applied on the “ earth side “ can be designed to act as a cantilever or as an anchored retaining structure, in this last case, soil or rock anchors shall be drilled,  installed and generally post tensioned, at one or more levels (as per design), when excavation reaches the required elevation. In order to assure the water-tightness of Diaphragm Walls, and to provide construction Keys between DW Panels. The DW construction can be made using Primary and Secondary Panels, where Primary panels are cast with Removable  Form Joints.  

Diaphragm Wall is sometime called Slurry Wall.

An other type of Diaphragm Wall 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 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.

Cut-Off Walls are employed whenever there is a requirement for isolating a source of pollution from the surrounding water table, e.g. around Sanitary  Landfills, Mine Tailing, or other sources of polluting leachates.

Diaphragm wall are also constructed by Foundation Specialists, Inc using Contiguous Piles, Secant Piles, or Tangent Piles, provided with a Top Beam, and,  depending on the height and nature of the  soil formation to be retained, and the purpose of the retaining structure. The Pile-Wall can be self-standing or anchored , impervious or pervious.  FoundationSpecialists,Inc. is  ISO_9001-2015 Certified