Slurry wall

[1] This technique is typically used to build diaphragm (water-blocking) walls surrounding tunnels and open cuts, and to lay foundations.

The density of the slurry mix must be carefully monitored and adjusted to produce the correct outward pressure to prevent the trench walls from collapsing.

The heavier concrete displaces the bentonite slurry, which is pumped out, filtered, and stored in tanks for use in the next wall segment, or it is recycled.

To prevent the concrete wall from collapsing into the newly excavated area, temporary supports such as tiebacks or internal crossbeams are installed.

When completed, the structure built within the walled-off area usually supports the wall, so that tiebacks or other temporary bracing may be optionally removed.

The slurry wall technique was first introduced in the 1950s during the excavations of the Red Line of the Milan Metro in Italy by the company ICOS (Impresa Costruzioni Opere Specializzate).