Slurry wall
|
|
A slurry wall is a type of wall used to build tunnels, open cuts and foundations in areas of soft earth close to open water or with a high water table.
A special clamshell-shaped digger is used to excavate a hole. The hole is kept filled with slurry (a mixture of bentonite and water) at all times to prevent collapse. Once the first hole is completed to design depth, or bedrock, an adjacent hole is dug in the same manner. Eventually, once a particular length is reached, a reinforcing cage is lowered into the slurry-filled pit and the pit is filled with concrete from the bottom up. The concrete displaces the bentonite slurry which is pumped out and recycled. On completion, digging within the now concrete wall-enclosed area can proceed. To prevent the concrete wall from collapsing into the newly open area, tiebacks (anchors) are installed. These are steel rods drilled through the concrete wall out into the soil or bedrock on the other side. Grout is pressure pumped into the anchor holes so that the rods become attached to bedrock or soil. Once excavation is complete, construction of the structure inside the wall can begin. When completed, the structure itself prevents the wall from collapsing and so the tiebacks may be removed.
Slurry wall construction is the type used to construct the "bathtub" that surrounds most of the World Trade Center site.
See also: retaining wall