Slurry Walls are primarily used in unsupported excavation sites to keep groundwater from flowing in and out of sites. These walls are common in an assortment of geographical areas and are commonly used in flood control (dams/levees), mining, remediation and dewatering projects.
What Is Slurry?
Slurry is an engineered fluid consisting of pulverized clay and water forming a colloidal mixture.
Though slurry can be made from a variety of materials, it’s typically composed of a water & bentonite. Other popular materials include ground blast furnace slag and cement.
Slurry Wall Uses
Slurry walls are built to slow and/or prevent the flow of groundwater by forming a low permeability barrier.
How Is a Slurry Wall Created?
Slurry must be mixed properly before it can be used in an excavation. This is done before any other measures are acted upon. Next, the trench must be excavated. This is done in 20 to 40-foot lateral cuts or sets. As the trench is excavated, it is filled with slurry to support the excavation. Excavation advances to the confining layer, aquitard or designated elevation before the next cut is attempted.
The excavation process makes use of hydraulic excavators, which can dig deep into the earth. This machinery cannot penetrate rock, though this shortcoming isn’t usually an issue in the water-permeated areas that slurry walls are created within. Modified boom & sticks are used for digging beyond 25-foot depths to depths exceeding 80-feet.
Precautionary Measures & Safety
All slurry walls are created with a variety of engineers and operators overseeing the process. It’s important that the correct geological formations have been identified and confirmed before any work can be done. All walls must be the correct blend of materials to ensure that the trench stability is maintained as well as the functionality of the groundwater cutoff.