Concrete Slurry walls are slurry walls
constructed to carry structural loading. These slurry walls are backfilled
with steel reinforcing and concrete, and used as retaining walls, basement
walls, or as the walls of tunnels especially when groundwater presents
a problem for construction. There are at least two kinds of structural
walls; diaphragm (or cast-in- place) walls and precast walls. Concrete
slurry walls are usually excavated under bentonite slurry in alternating
panels. The length of the panel depends on site conditions and the length
of the excavating tool, typically a slurry clam bucket. In addition to
excavating and backfilling, concrete slurry wall panel must be treated
to ensure the integrity of the joints and the quality of the concreting
operation.
Diaphragm walls are the most common concrete slurry walls. After excavating,
the panels of a diaphragm wall must be "desanded" to remove excess
sand that accumulates on the bottom or is suspended in the slurry. Next,
prefabricated steel reinforcing or "rebar cages" are lowered
to the panel. The rebar cages may also support future structural or utility
connections using "knockouts" that are pre-set in the wall. Next,
the panel is filled with a high slump concrete which is placed in the wall
through tremie pipes, to prevent segregation of the wet concrete. After
the primary panels are set, the secondary panels are created between the
primary panels to complete the wall. Control of verticality and careful
cleaning of the concrete is important to the quality of the seal between
panels. Sometimes steel beams (soldier piles) are used to better reinforce
the connection between the primary and secondary panels, this is referred
to as the "soldier pile tremie concrete" (SPTC) method. The appearance
of the completed wall is a direct reflection of the soil excavation. In
some cases, the surface of the wall can be covered with paint or shotcrete
for a better visual effect.
Precast concrete slurry walls are built
utilizing precast concrete panels, either reinforced or prestressed, which
are inserted into slurry filled trenches. The precast elements are usually
placed in a special C-B slurry to seal the joints. When settlement is critical,
the bottom of the precast panel can be set into tremie concrete. The main
advantage of the precast walls is the ability to have an architectural
appearance of the completed wall.
Concrete slurry walls are often used as the walls for a variety of deep
excavations where the space is intended to be permanently useable. Sometimes
concrete slurry walls are used to accelerate the construction of large
buildings using the "top-down" construction approach where the
basement and the upper floor are constructed simultaneously after a concrete
slurry wall is installed to support the basic structure. Also, the "cover
and cut" construction developed in Europe, has enabled construction
of underground structures in congested areas in a more expedient and efficient
manner. With this method, cast-in-place or precast slurry walls are placed
as the perimeter finished walls of the underground structure. The top cover
is then poured on grade, leaving access openings through which the mass
excavation under the top cover and between the slurry walls is performed.
This method can minimize the disturbance of traffic and other above ground
activities. Such activities are restored while the remaining work takes
place below the cover slab. Concrete slurry walls are also used to support
bridge abutments and other structures which must carry vertical loadings
and horizontal earth loads.
If you have an immediate or future application for any
of our specialty construction techniques, please
contact us. If you need additional information please e-mail us at:
info@inquip.com,
or call one of our offices.
