Slurry Cut Off Wall
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A slurry is, in general, a thick suspension of solids in a liquid. Examples of slurries include:
A mixture of water and cement to form concrete
A mixture of water, gelling agent, and oxidizers used as an explosive
A mixture of water and Bentonite used to make slurry walls
A mixture of wood pulp and water used to make paper
A mixture of water and animal waste used as fertilizer
Meat slurry, a food product
An abrasive substance used in chemical-mechanical polishing, a semiconductor manufacturing process
A mixture of ice crystals, water and freezing point depressant, called slurry ice
A wet-process cement rawmix
A mixture of water, ceramic powder and various additives (e.g., dispersant) used in the processing of ceramics.
A mixture of water and a starch (normally corn starch) used to thicken liquids to make a culinary sauce; usually for a clear sauce, as the product will be translucent. It is comparable to and often the same as a gravy.
Slurry wall technologies enable cost effective elimination of groundwater flow. The construction of soil-bentonite slurry cut-off walls has been used in thousands of slurry wall construction projects due to its technical advantages over other barrier technologies.
WHAT ARE SLURRY WALLS / CUTOFF WALLS?
Slurry walls are non-structural barriers (Cutoff Walls, Slurry Trenches) that are constructed underground to impede groundwater flow. Slurry walls have been used for decades to provide cost-effective, long-term solutions for many groundwater control and groundwater remediation problems.WHAT METHODS ARE USED IN SLURRY WALL CONSTRUCTION?
Slurry wall construction starts with the “slurry excavation technique”, which was developed in Europe and has been used in the United States since the 1940s. The slurry wall construction technique involves excavating a narrow trench that is kept full of an engineered fluid or “slurry”. The slurry exerts hydraulic pressure against the trench walls and acts as shoring to prevent collapse. Slurry trench / slurry wall / cutoff wall excavations can be performed in all types of soils, even below the groundwater table.Slurry trench /slurry wall / cutoff wall excavations are normally performed with hydraulic excavators and their widths can vary from 1.5 to 5.0 feet. Excavation depths greater than 100 feet require the use of a crane and clam bucket or other specialty equipment. In most cases, the excavation will “key” 2.0 to 3.0 feet into a low permeability stratum such as clay or bedrock to assure minimal leakage under the final wall. In some cases, “hanging” slurry walls / slurry trenches/ cutoff walls, which penetrate the groundwater table, are used to stop the movement of floating contaminants or gases. After an excavation segment is completed, the excavator backs up and begins a new overlapping segment to create a continuous trench. Once sufficient excavation is complete, trench backfilling begins.
Bentonite slurry is the most common excavation fluid used in a slurry trench. Bentonite clay and water are combined in a colloidal mixer and the resulting slurry is pumped, as required, through a pipe to the excavation site. In addition to stabilizing the excavation, bentonite slurry forms a “filter cake” on the slurry trench walls that reduces the slurry wall’s final soil permeability.
It is common for the slurry trench to be backfilled with a mixture of excavated soil, dry bentonite, and bentonite slurry. Walls of this composition provide a low cost barrier with low soil permeability and good chemical resistance. Excavated soil is placed on the work platform adjacent to the trench. A bulldozer tracks and blades the material to produce soil-bentonite backfill, which has a consistency of wet concrete. The backfill is placed into the end of the slurry trench, in a manner that displaces the slurry forward toward the ongoing excavation. The excavation/backfill routine continues until the slurry wall is complete.
Much of this information comes from the slurry wall page on our website. For more information about this an other services, please see our site.