THE SPECIALTIES :
Slurry Wall / Plastic Cut-Off Wall
SLURRY
WALL,
DIAPHRAGM WALL [ DW ], PLASTIC CUT-OFF WALL, CUT-OFF WALL, CURTAIN WALL, are variation of the same basic technology and are all carried by Foundation Specialists.
Plastic Cut-Off Wall
by
Foundation Specialists
Definition of “Plastic
Cut-Off Wall.”
A ”Plastic
cut-off wall” is a deep-foundation technology,
employed to form impervious,
permanent, underground “diaphragm”
(or barrier),
to “seal off”
certain underground areas and prevent passage of fluids
[generally water],through it.
The use of the word
“Plastic” is to describe the very nature of the diaphragm, barrier
or membrane created with this
technology, in fact the “Plastic
Cut-Off wall” is made of a mix of bentonite,
cement, water and other components, proportioned in such a way to remain indefinitely plastic (and impervious) with
time.
The word “Cut-Off”
is meant to define the specific purposes of this technology, i.e. to
either stop the flow, to “Dam” the underground stream, or to surround and seal-off
an area, to prevent water inflow and water outflow from the encircled area. For this technology,
the medium employed to
“Cut-Off” is the Plastic Wall, or Plastic
Diaphragm that
has the effect of completely stopping the water flow at a chosen section of a river bed underlaid by [deep] alluvium,
or sealing-off an area[tipically underlaid by alluvium], surrounding it, with a cut-off wall along the entire perimeter.
Applications of “plastic cut-off wall”
Plastic Cut-off Walls are used to provide a totally impervious
underground diaphragm from the base of cofferdams to the lower end of the alluvium strata. Plastic Cut-off Walls are usually installed from the top of cofferdam, thus providing
also an impervious core to the cofferdam, in addition to sealing the areas below it.
Plastic Cut-Off Walls
are a very important medium for the protection of the environment, insofar
as the bentonite-cement mix also called self-hardening mud, or cement stabilized bentonite mud, is an extremely
stable material, unaffected by the leachates and contaminants produced by landfills.
Plastic Cut-Off walls
are used to construct impervious barriers around old and new landfills to prevent
leachates from contaminating the water table and the water streams around the landfill locations. For the purpose, the
cut-off walls are installed to depths sufficient to eliminate the possibility of polluting streams and water table by escaping
landfill leachates.
A very important application of
Plastic Cut-Off Walls in
areas with scarce rainfalls, shrinking water reservoirs,
dwindling water tables, deep alluvium and large rivers’ catching basins, is to close the underground outflow of water
within the alluvial river bed, by forming an underground continuous “dam” perpendicular to the river longitudinal axis, resembling a vertical gate inserted through the river bed to close the underground
water outflow.
Advantages of using Plastic Cut-Off Walls.
The
advantages of using plastic cut-off walls as described above, are several, self hardening Bentonite-Cement mud
are extremely stable chemically, are not affected by polluted and aggressive underground water.
By
remaining indefinitely plastic in time, Plastic Cut-Off Walls can deform
without cracks and fissures in response to the surrounding ground’s settlements, thus remaining as impervious as it was built, throughout time.
Experienced
Specialized Contractors can install Plastic Cut-Off Walls , totally impervious in any kind of alluvial formation, at a relatively
fast pace.
Foundation
specialists has expertly and successfully designed and installed Plastic Cut-Off Walls for over thirty years in the most
diverse soil and hydro-geological conditions.
THE SPECIALTY : DiaphragmWall
SLURRY WALL, DIAPHRAGM WALL [ DW ], PLASTIC CUT-OFF WALL, CUT-OFF WALL, CURTAIN WALL, are variation of the same basic technology and are all carried by Foundation Specialists.
DIAPHRAGM WALL
Diaphragm Wall can be designed and executed as a reinforced concrete retaining structure, in
which case it will also be called “ Cast In Place Reinforced Concrete DiaphragmWall
“. Diaphragmwall
is a “Top-Down Construction Technology” employed for Excavation Support in difficult
soil conditions or whenever deep excavation has to be carried out in an environment where zero disturbance of the surroundings,
including avoidance of water table lowering, and/or
zero settlement of neighboring structures are a requirement.
DiaphragmWall
is put in place using a segmental installation technique,
[Primary and secondary DiaphragmWall
Panels of predetermined dimensions installed by following a proper sequence] purposely and specifically designed for each soil formation
and particular site requirements, in order to avoid any disturbance and subsidence to the surrounding areas.
In cohesionless soil formations under the water-table, the segmental excavation of Diaphragm Wall
is generally carried out using bentonite suspension as the drilling fluid, in order to balance the
action of the water-table and to maintain the excavation of the Diaphragm Wall
perfectly stable until each single “ Panel ” is cast with concrete.
Once
all the segments or “ Panels “ of the DiaphragmWall are
cast, they are connected at the top by a reinforced concrete continuous beam [ Coping ], after which, removal of soil
on the excavation side can proceed, protected by the Diaphragm Wall.
The
DiaphragmWall,
depending upon depth of excavation and upon design loads to be applied on the “ earth side “ can be designed to
act as a cantilever Diaphragm Wall
or as an anchored DiaphragmWall,
in this last case, soil or rock anchors shall be drilled, installed and generally post tensioned,
at one or more levels of the DiaphragmWall
(as per design), when excavation reaches the required elevations.
Diaphragm Walls
are used as the perimeter structural walls of building basements: the DiaphragmWalls
can be properly reinforced to act as the buildings' shear walls. Buildings' columns can be integrated within the Diaphragm Walls,
dowell bars for any application can be attached to the DiaphragmWall
reinforcing cage prior to installation and in situ casting. DiaphragmWall
technology
was used by Foundation Specialists
to design and construct the Marginal Wharfs
of the very large deep water port facilities of the National Steel Corporation.
Common DiaphragmWall application:
large number of Deep Underground
Parking Facilities and Deep Underground Building Basements,
Steel Mills Pits, Underground Pumping Stations, have been built by Foundation Specialists
using the
Top-Down
Construction Sequence, by constructing Perimeter Walls, including Shear Walls and Columns with Diaphragm Wall
Technology, prior to main deep excavation.
Diaphragm Wall
is sometime called Slurry Wall.
An other type of DiaphragmWall carried by Foundation Specialists
is
a Technology called Cut-Off Wall
or Self-Hardening Plastic Cut-off Wall .
The Cut-Off Wall is a continuous and impermeable
Diaphragm Wall, generally made using a mix of Cement+Bentonite, designed to remain indefinitely, both sufficiently
plastic in order to follow soil movement and deformation without cracking and totally impervious.
DiaphragmWall
and
Cut-Off Wall
are employed whenever there is a requirement for isolating a source of pollution from the surrounding water table, e.g. around Sanitary Landfills or other
source of polluting lechates.
DiaphragmWall
technology is used in Dam Construction to achieve water--tightness in the soil or rock formations underlying
the main dam or the cofferdams, whenever grout curtains alone can not guarantee the needed results, as in the case of
Dams or Cofferdams with underlying karstic limestone formations.
DiapragmWall are
employed to build river training walls, because Diaphragm Wall can be built sufficiently
deeper than the maximum local scouring depth , thus assuring zero collapse chance for the river dykes due to under-scouring
during heavy floods.
The DiaphragmWall
construction technology is also used to build deep continuous catching drains, when the deep trench is filled
either with gravel or pervious concrete.
Barrettes or Barrette-piles,
cast in place rectangular piles are a technology that uses the same equipment employed to execute the Diaphragm Wall.
DiaphragmWall
equipment and technology are used also to execute special design Pile-Column for large loads in Top-Down
construction schemes.
