Diaphragm wall

Diaphragm walls are vertical reinforced concrete walls driven into the ground, which serve to enclose the excavation, provide a barrier against groundwater and act as a load-bearing foundation element. They are particularly suitable for deep excavations, heavy loads and inner-city construction projects, and can be used on a temporary or permanent basis.

Encyclopedia: Diaphragm walls

General Advantages Basic principles Variants Quality References
Diaphragm walls

Diaphragm walls
in accordance with DIN EN 1538

Diaphragm walls are reinforced concrete walls installed vertically in the subsoil. They can fulfil structural, sealing and/or screening tasks and are suitable for both temporary and permanent use.

In order to seal off the bottom of the construction pit against rising groundwater, diaphragm walls are bonded with surrounding soil layers with a low water permeability or with artificially produced sealing slabs.

Diaphragm walls are particularly suitable for deep construction pits and as a deep foundation element with a structural function.

Common areas of application include:

  • Inner-city construction pits, e.g. for multi-storey underground car parks
  • Metro stations
  • Open-cut tunnelling
  • Shafts (launch and target shafts for pipe jacking or TBMs)
  • Primary support element in deep foundations (barrette)

We use diaphragm walls for the construction of single-phase cut-off walls to enclose contaminated sites in landfills and as part of flood protection measures.

1:21 Minuts

Animation – Diaphragm walls

04:07 Minuts

Explaining video – The diaphragm wall

Technical brochure
Construction pits

Technische Broschuere Baugruben
Construction pit walls (only available in German)
PDF

Benefits / Features
of diaphragm walls

  • Deformation behaviour: Due to their rigidity, diaphragm walls can be used to support loads from adjacent structures.
  • Waterproofing: Thanks to the minimal number of joints and suitable joint designs, diaphragm walls can be constructed to provide a watertight barrier against groundwater.
  • Load-bearing capacity: As foundation elements (barrettes), diaphragm walls can support high concentrated loads.
  • Construction process: The shorter construction time compared with bored pile walls saves both time and money.
  • Design: Slender wall cross-sections and flat surfaces create more usable floor space and increase cost-effectiveness.
  • Construction variants: A ‘top-down’ construction method without temporary anchoring is possible. This eliminates the need for consent from owners of neighbouring plots and minimises disruption to public spaces.
  • Permanent structure: As a permanent structure in accordance with ÖNORM, a separate external wall is not required, thereby saving further costs.
  • Support fluid: The bentonite slurry used in the process can be treated by desanding plants and reused multiple times.
  • Geothermal utilisation: Depending on the project, diaphragm walls can be combined with geothermal systems.
  • Construction: Low-noise construction with minimal vibrations is possible.
  • Application conditions: Can also be used where height is restricted, for example under bridges.
     

Basic facts

Diaphragm walls are designed and manufactured in accordance with DIN EN 1538 and the recommendations of the “Construction Pits” Working Group (Empfehlungen des Arbeitskreises “Baugruben”, EAB). The stability of the opening is verified in accordance with DIN 4126.

The soil is excavated using the grab method to create a rectangular slot in the soil, while at the same time the pit is filled with support fluid (bentonite suspension). Excavation is carried out in sections using a cable excavator and diaphragm wall grab. Guide walls are built beforehand along the route the diaphragm wall will follow to guide the grab.

In subsequent work stages, the suspension is regenerated, the reinforcement and a stop-end element are installed to form the next element, and concrete is poured using the contractor method (from the bottom up). The individual elements are lined up next to each other and are connected with special joint profiles so as to form a wall that, according to structural findings, is technically watertight.

Generally speaking, diaphragm walls are between 0.45m and 2m thick, at depths typically ranging from 20m to 40m. In each case, these depend on the type of grab used. Diaphragm wall cutters can also be used for depths of 40m and more.

The reinforcement cages of the diaphragm walls can be fitted with PE pipes as circulation conduits. This allows the diaphragm wall to be thermally activated as a solid absorber in contact with the ground. Since many different factors can influence the economic efficiency of the energy diaphragm wall during planning and execution, the designer of the energy system and the execution team must work closely together.

Design variants

Design variants
of diaphragm walls

The following variants are available:

  • Retaining wall and temporary construction pit system made of concrete or reinforced concrete
  • Foundation element (barrette) for very high loads
  • Energy diaphragm wall for geothermal use
High quality of execution

Quality assurance
with the diaphragm walls

We ensure a high quality of execution through:

  • Individually coordinated procedural instructions
  • Compliance with the requirements of the DIN EN 1538 execution standard
  • Checking the position, torsion and verticality of the slotted lamella using modern measurement technology such as inclinometers
  • Clear processes via our quality management system in accordance with DIN EN 9001:2015

Selected projects
Diaphragm walls