Diaphragm wall

A Soletanche Bachy expertise

A diaphragm wall is a support of excavation technique  used by Soletanche Bachy for almost 60 years.

paroi moulée / diaphragm wall / muro pantalla
Diaphragm wall technique

A diaphragm wall is a reinforced concrete curtain cast into the ground, mainly used for support and foundation works.


Created for all types of structures – underground stations, buildings, car parks, tanks, dams – and in all types of soil and rock and regardless of the environment, the diaphragm wall is a technique frequently used to provide a permanent support of excavation, build deep foundations or deep continuous cut-off walls.

Diaphragm Wall is one of the most common technique for Soletanche Bachy’s Core Business.

What are the advantages of this technique?

Suitable in presence of groundwater table

Favoured in urban environments, close to other existing in the vicinity, with limited headroom or within a small site footprint

The high inertia of diaphragm wall makes it much less subject to deformation

Can be used as a temporary or permanent structure

Soletanche Bachy’s advantages

Soletanche Bachy’s advantages

  • Expertise in this technique,
  • We design and build our own specific equipment, including several types of grabs and Hydrofraise®
  • More than 60 years of experience worldwide in-house materials laboratory to meet the requirements of each project,
  • Z-Lyze® digital platform to collect, analyse and monitor project data in real time.


A diaphragm wall involves excavating a trench, which can reach 90m depth and beyond, using a mechanical or hydraulic grab or a Hydrofraise® (technology developed by Soletanche Bachy) depending on the type of soil encountered.

paroi moulée / muro pantalla / Diaphragm wall


In general, the construction of a diaphragm wall follows the following steps:


Step 1

Construction of two parallel guide walls, made of low reinforced concrete casted on the working platform. These narrow guide walls have the following functions:

  • outline and precisely define the structure to be built
  • guide the, excavation tool,
  • provide an extra storage of support fluid
  • keep the reinforcement steel cages in place before and after concreting.


Concrete guide walls can be poured flush to existing structures and foundations. This allows to build diaphragm walls very close to nearby constructions.


Step 1.5:


Excavation phase is made of one or several overlapping bites forming a panel, with the help of a support fluid. The properties of this fluid and the length of the excavated panel are adapted to site conditions and presence of structures in the vicinity to guarantee an optimal trench stability at all times.

While excavated, the soil is progressively replaced by this support fluid, called “drilling slurry”. Usually, a specific type of clay (bentonite) is used. Bentonite forms a local cut-off barrier on the sides of the excavation. This barrier keeps the excavation open by applying a hydrostatic pressure that counteracts with earth pressure which tends to collapse the sides of panel.

Depending on specific ground conditions, bentonite can be replaced by biodegradable polymers. Other options are possible.

While excavating, the properties of the support fluid are regularly monitored, and corrected when necessary.



Step 2

Once excavation of a panel has been completed, the support fluid is recycled to limit the size and quantity of soil particles in suspension within the slurry. Then a reinforcement cage is placed in the panel. This cage can be pre-equipped with further elements, such as reservation pipes for ground anchors.


Once the reinforcement cage has been placed, plunge columns are put in place through the cage till the bottom of the excavated panel.

Concrete is then poured from platform level. The plunge columns allow to deliver concrete progressively from the bottom of excavation to the top. During this operation, the concrete encapsulates the steel cage and pushes out the support fluid which is pumped away and recycled.


Water tightness between two consecutive panels can be ensured:

  • Either by overlapping into the concrete of the adjacent panel (only possible when using an Hydrofraise® equipment
  • Or by using a temporary metallic joint CWS® on both sides of the panel. When removed, this joint leaves a waterstop rubber joint inside concrete. Second half of this joint will be sealed in concrete when pouring the adjacent panel.



Step 3:

Depending on design, a concrete capping beam can be casted to bound the top of panels together or prepare an interface with a further construction stage.

paroi moulée / diaphragm wall / muro pantalla

Once finished, earthworks can begin within the diaphragm wall perimeter. During these works, and depending of the finishing degree required, the concrete surface of the D-Wall can be trimmed.


The excavation phase can proceed in several phases. Depending on the support of excavation design, intermediate operations can be carried out, such as: construction of waling beams or strutting system, installation and pre-tensioning of ground anchors, construction of concrete slab and more.


The diaphragm wall thicknesses are usually: 0.50m; 0.60m; 0.80m; 1.00m; 1.20m; 1.50m; 1.80m.

Other specific thicknesses are possible, depending on countries.

Each step of the diaphragm wall process is complex and impacts the quality of the finished structure. Soletanche Bachy implements a range of methods and procedures based on its vast experience with requirements that exceed compliance with standards.


Excavation: For hydraulic grabs and Hydrofraise®, deviations are measured in real time using a range of high-precision sensors developed and patented by Soletanche Bachy and embedded down the hole. Deviations measured in real time are immediately corrected using electronic and mechanical means available to the operator.  Z-Lyze® tool is used to process computer data generated by on-board acquisition systems installed on each rig.


Concreting: during excavation and before concreting, physical and chemical properties of the support fluid are checked. When pouring concrete, a concreting curve is established in real time to detect any anomaly In the meantime, concrete is tested and fresh concrete samples are taken for further UCS testing. In the event of technical difficulties, our internal materials laboratory can carry out additional tests at the start of construction, to ensure the quality of the concrete.


Sonic integrity checks can be carried out the completion of a diaphragm wall panel, using tubes pre-installed with the reinforcement cage.

inclinometer controls can be used to monitor the diaphragm wall during the excavation and during the life of the structure.

Barrettes/ paroi moulée circulaire /poutre de couronnement /excavation de la boîte/cellules Osterberg

Execution controls and monitoring

Did you know?

The Soletanche Bachy group also has experience and expertise in other support techniques:


  • Sheet piles: metal sections fitted with joints and interconnected. Sheet piles are used to form a continuous supporting screen.
  • Contiguous or secant piles: a wall formed from a series of piles.
  • Berlin-type wall: composite retaining wall made using resistant vertical stiffeners and horizontal shielding made from wood, steel, concrete, etc., between those stiffeners.
  • Precast wall: composite retaining wall made from contiguous vertical prefabricated reinforced concrete elements, lowered into a grout excavation to make the lower section watertight.
  • Deep Soil Mixing: permanent or temporary support of excavation made with structural vertical beams installed in a soil cement material mixed in situ.
  • Sprayed concrete: unshuttered concrete structure created by spraying using a gun. This forms a consistent mass, compacted by its own kinetic energy.



élément préfabriqué / paroi moulée / prefa / diaphragm wall

Fishermen Wharf work site in Abu Dhabi

To obtain a specific facade finish or produce concrete with specific characteristics, Soletanche Bachy has developed and patented a technique allowing installation of a prefabricated element in the upper part of a diaphragm wall.