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Slurry Walls

The construction of the concrete slurry wall is the most established field of activity for the company. During the past thirty-five years, Bencor has completed many difficult and challenging projects in the United States and throughout the world. Bencor is one of the worldwide leaders in the field of slurry wall construction.

 

Structural slurry walls are used as both temporary and permanent earth retention systems to support the sides of deep excavations as well as to provide cut-off barriers and load bearing elements. Cast-in-place slurry walls are one method Bencor uses for the construction of vertical continuous walls to form a diaphragm in natural or filled soils. These walls are cast-in-place in a trench excavation and can be reinforced. The resultant reinforced diaphragm walls are used to form structural load-bearing elements as temporary or permanent retaining walls, or as foundations. Moreover, relatively total impermeability to groundwater seepage is achieved by these walls.

 

The range of application for reinforced diaphragm walls includes basements, retaining walls for deep excavations, underground railways, and walls for pumping stations, quays, cofferdams, and shafts. Since reinforced walls are designed and constructed as a series of panels, there is no practical limit to their overall length. Individual panels usually range in sizes between 15 to 30 feet in length, with standard widths ranging between 24, 30, 36 and 48 inches. Depths of the wall have exceeded 200 feet regularly. Possible shapes of walls, depending on the purpose of the wall, include right angles, polygonal, T-shaped and cross-shaped walls.

 

Slurry wall trench excavation is generally performed by specially developed CLAM SHELL BUCKETS. These buckets are custom designed and built for each job in-house by Bencor. The buckets operate mechanically - free hanging from heavy-duty cranes to insure capability of excavation through the toughest

materials. Moreover, free hanging buckets help insure correct alignment and verticality of construction.

 

During the excavation process the trench is kept filled with a BENTONITE SLURRY suspension to stabilize the trench walls and to prevent caving. The slurry is mixed on-site and pumped into the trench as excavation proceeds. Density and viscosity are carefully checked and maintained during excavation and prior to placing concrete.

 

In the past ten years, Bencor has developed and improved excavation of very difficult geological formations through the use of the HYDROMILL. As it progresses in the trench excavation, the hydromill continuously demolishes soil and/or rock from the bottom of the trench. The machine then returns this excavated material via the bentonite slurry through a very powerful suction pump. The material is pumped from the trench to the desanding unit, where it is cleaned and then returned to the trench.

 

Steel reinforcement CAGES are fabricated on site and formed into three-dimensional cages for each panel. The cage is lowered by crane into the slurry-filled trench and positively located with spacers for accurate centering and adequate concrete coverage. Once positioned properly, CONCRETE is poured through TREMIE PIPES via gravity in a continuous operation. The concrete is generally poured at high slumps to insure fluidity through the pipes and throughout the panel and around the cage. Rate of concreting can range

typically from 80 to 120 cubic yards per hour. As the concrete displaces the bentonite slurry it is pumped back to the holding reservoir and stored for re-use, treatment and /or disposal.

 

GROUND ANCHORS are also frequently utilized with slurry walls to help economically design these types of retaining walls. Since the ground anchors provide intermediate points of support at one or more levels, they reduce bending moments and consequently reduce added dimensions, reinforcement, and depth-of-toe requirements. Anchors eliminate the need for strutting within the excavation and leave it free of obstructions. This aspect can be particularly valuable in congested urban locations with limited surrounding space for equipment and materials. Anchors may be of two basic types, in rock or unconsolidated alluvium and may be either permanent or temporary.

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