1.3 diaphragm walls (1)
TRANSCRIPT
-
7/25/2019 1.3 Diaphragm Walls (1)
1/13
DIAPHRAGM WALLS
-
7/25/2019 1.3 Diaphragm Walls (1)
2/13
DIAPHRAGM WALLS
Diaphragm walls are underground structural elements commonly
used for retention systems and permanent foundation walls.
Diaphragm walls provide a water tight barrier and are
constructed with a minimum back slope subsidence.
They are formed from reinforced concrete and are constructed as
normal cast-in-place walls with support, which become part of
the main structure.
They can also be used as deep groundwater barriers.
-
7/25/2019 1.3 Diaphragm Walls (1)
3/13
SLURRY TRENCH METHOD
The slurry trench method involves the excavation of alternatingpanels along the proposed wall, using bentonite slurry to
prevent the sides of the excavation from collapsing.
The slurry trench technique was developed in urope and has
been used in the !nited "tates since the #$%&'s.
The 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 andacts as shoring to prevent collapse.
"lurry trench excavations can be constructed in all types of soil,
even below the ground water table.
-
7/25/2019 1.3 Diaphragm Walls (1)
4/13
BASEMENT TOP-DOWN
CONSTRUCTION USING DIAPHRAGM
WALLS
-
7/25/2019 1.3 Diaphragm Walls (1)
5/13
PROCEDURE
The panel dimensions (& to #&& cm thick and up to )m height,extending to the excavation bottom.
The installation starts with the construction of shallow concrete
or steel guide walls.
The excavation is then made using special equipment, such as the
thin-grab clamshell.
*entonite slurry is then pumped into the trench to provide
temporary support and a prefabricated reinforcing cage is
lowered in.
The bentonite slurry is then replaced by concrete and the
sequence proceeds onto the next panel.
-
7/25/2019 1.3 Diaphragm Walls (1)
6/13
GRAB USED FOR EXCAVATION
-
7/25/2019 1.3 Diaphragm Walls (1)
7/13
DIAPHRAGM WALLS
Diaphragm walls of shallow depths are often left unsupported
since they are classed as semi rigid structures.
+owever for deeper excavations support is required to restrict
lateral deflections.
Diaphragm walls are ideal for soft clays and loose sands
below the water table where there is a need to control lateral
movements.
-
7/25/2019 1.3 Diaphragm Walls (1)
8/13
REINFORCEMENT
-
7/25/2019 1.3 Diaphragm Walls (1)
9/13
DIAPHRAGM WALL REINFORCEMENT
& CONCRETING
-
7/25/2019 1.3 Diaphragm Walls (1)
10/13
FINISHED WALL AFTER EXCAVATION
-
7/25/2019 1.3 Diaphragm Walls (1)
11/13
APPLICATIONS
s permanent and temporary foundation walls for deep
basements.
n earth retention schemes for highway and tunnel proects.
s permanent walls for deep shafts for tunnel access.
s permanent cut-off walls through the core of earth dams.
n congested areas for retention systems and permanent
foundation walls.
Deep ground water barriers through and under dams.
-
7/25/2019 1.3 Diaphragm Walls (1)
12/13
BENEFITS OF DIAPHRAGM WALLS
/an be installed through virtually all soil conditions, to any
plan geometry and to considerable depths.
/an be constructed ahead of time and independent of other site
activities.
/an be constructed in relatively low headroom and in areas of
restricted access walls can be quickly formed several hundred
feet deep and through rock, with good control over geometry
and continuity.
-
7/25/2019 1.3 Diaphragm Walls (1)
13/13
DISADVANTAGES
They are relatively costly.
They are also unsuited to strong soils conditions where
penetration is slow and difficult due to the use of the slurry
trench method.