1.3 diaphragm walls (1)

7/25/2019 1.3 Diaphragm Walls (1)

1/13

DIAPHRAGM WALLS


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.


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.


4/13

BASEMENT TOP-DOWN

CONSTRUCTION USING DIAPHRAGM

WALLS


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.


6/13

GRAB USED FOR EXCAVATION


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.


8/13

REINFORCEMENT


9/13

DIAPHRAGM WALL REINFORCEMENT

& CONCRETING


10/13

FINISHED WALL AFTER EXCAVATION


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.


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.


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.

1.3 diaphragm walls (1)

Documents