Diaphragm walls

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.

• Diaphragm walls offer a high level of security because they are extremely resistant to deformation and can thus absorb high loads from adjacent structures.
• The special joint profiles and low proportion of joints mean that diaphragm walls are technically watertight.
• As a foundation element (barrette), they can support very high concentrated loads.
• The construction period is shorter than that of bored pile walls, which saves time and money.
• Thin walls and flat surfaces create more usable space and increase economic efficiency.
• They can be constructed underground without disturbing the ground cover and without temporary anchors. This means that the project does not depend on the owners of neighbouring properties granting permission and reduces encroachment on public space.
• As a permanent structure in accordance with ÖNORM, they eliminate the need for a separate outer wall and thus save further costs.
• Desanding equipment is used to clean the support fluid (bentonite suspension), which means it can be used several times. This saves on resources.
• Energy diaphragm walls for geothermal use make the process even more environmentally friendly.
• The method enjoys a high degree of acceptance among local residents because it is low in noise and vibration-free.
• They can be installed under restricted working heights, e.g. under bridges.
   

Standards and regulations

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.

Production

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.

Energy diaphragm walls

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.

We ensure high execution quality with:

• Individually coordinated instructions
• Compliance with the requirements of execution standard DIN EN 1538
• Verification of the position, torsion and verticality of the diaphragm lamella with modern measuring technology such as inclinometers
• Clear processes governed by our quality management system in accordance with DIN EN 9001:2015

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