Editing Slurry wall (section)

==Construction==
[[File:Ausführung-Schlitzwand.png|thumb|Sequence of constructing a slurry wall]]
While a trench is being excavated to create a form for a wall, it is simultaneously filled with [[slurry]] (usually a mixture of [[bentonite]] and water).  The dense but liquid slurry prevents the trench from collapsing by providing outward pressure, which balances the inward hydraulic forces and also retards water flow into the trench. 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.

Slurry walls are typically constructed by starting with a set of concrete guide walls, typically {{convert|1|m}} deep and {{convert|0.5|m}} thick. The guide walls are constructed near the ground surface to outline the desired slurry trench, and to guide the excavation machinery. Excavation is done using a special clamshell-shaped [[excavator|digger]] or a [[hydromill trench cutter]], suspended from a crane. The excavator digs down to design depth (or bedrock) for the first wall segment.  The excavator is then lifted and moved along the trench guide walls to continue the trench with successive cuts as needed.  The trench is at all times kept filled with slurry to prevent its collapse, but the fluid filling allows the excavation machinery and excavation spoil to be moved without hindrance.

Once a particular depth of trench is reached, a [[rebar|reinforcing cage]] is lowered into the slurry-filled pit and the pit is filled with [[concrete]] from the bottom up using [[tremie]] pipes. 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.

Slurry walls are successively extended to enclose an area, blocking water and softened earth from flowing into it.  Once the concrete has hardened, excavation within the now concrete-wall-enclosed area can proceed. To prevent the concrete wall from collapsing into the newly excavated area, temporary supports such as [[Tieback (geotechnical)|tieback]]s 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.