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Diaphragm walls

Diaphragm walls are cast in-situ, concrete elements walls.They can serve as soil- and/or water-retaining structures and are capable of transferring large loads. Typical wall thicknesses are 0.40-0.60-0.80-1.00-1.20 and 1.50 metres, and large depths up to 60 metres can be attained. It is possible to work close to adjacent structures and integrate the walls with the final structure. Large retaining heights and high foundation loads can be attained. The trenches are dug using a special rope suspended grab.

The stability of the trench during excavation is guaranteed by introducing bentonite and water. When the trench has reached the desired depth, the bentonite suspension inside is de-sanded and replaced by a clean slurry.

Next, the joint sections and rebar reinforcement are inserted. The rebar cage has an open construction to guarantee proper adhesion to the concrete. In addition, spacers are placed to guarantee the required clearance to the side of the trench. The joint sections provide a good connection to the adjacent panel and are provided with waterstops to reduce the permeability to a minimum between the different panels of the wall. A tremie pipe is inserted inside the cage. Concrete is poured directly in the tremie pipe from the concrete mixer, using the contractor method. When casting has finished and the concrete has cured enough to be able to carry its own weight, the joint pipes are withdrawn.There are two principles for constructing slurry walls:the starter-follower method and the primary-secondary method. There also are multiple joint section systems.These must be selected in advance.

Application

Diaphragm walls can be applied for e.q.:

  • cellar walls in large-scale buildings, underground car parks and suchlike;
  • railway and subway tunnel walls;
  • foundation elements for buildings, viaducts, bridges and suchlike;
  • building pits in inner- city areas.

Ambient factors

  • The material used for diaphragm walls is large-scale and requires a fairly large surface area for the bentonite plant.
  • Storage and set-up space for the bentonite basins, desanding plant, joint sections, reinforcement cages and concrete mixers must also be taken into account.
  • Guide walls for the grab and for the stability of the top of the wall ust be constructed prior to production.

 

Pros and Cons

  • Diaphragm walls can be realised with little noise and vibrations.
  • Diaphragm walls have a very high load-bearing capacity.
  • Hard layers of soil can be penetrated without problems.
  • The system is not sensitive to small obstacles in the soil.
  • It is a product that can be used in tunnels and cellars without any significant finishing.
  • Absolute impermeability to water cannot be guaranteed.
  • Wall presentation is irregular.

Applicated

Name of project

Client

Krimpen aan de Lek, Riverbank reinforcement

GMB Civiel

Bergambacht, Embankment reinforcement Bergambacht-Ammerstol-Schoonhoven

Waterauthority Schieland - Krimpenerwaard

Delft, Motorway A4

Construction consortium A4All

Nijmegen, Upgrading pilons railway bridge

Prorail

Venlo, Construction pit Stadskantoor

Ballast Nedam Funderingstechnieken

Lekkerkerk, Riverbank reinforcement Nederlek

Waterauthority Schieland - Krimpenerwaard

Scheveningen, Reinforcement Boulevard

Combinatie Zeefront v.o.f.

Emmen, Construction pit Parking garage Westerstraat

Strukton Civiel Projecten

Veenendaal, Parking garage De Tricotage

Welling Didam

Rotterdam Maasvlakte, Quay wall Maasvlakte 2

Comb. Van Hattum en Blankevoort / BAM Civiel

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