WHAT IS DIAPHRAGM WALL?

DIAPHRAGM WALL



Diaphragm wall are concrete or reinforced concrete walls constructed in slurry supported, open trenches below existing ground.
Diaphragm wall is a reinforced concrete structure constructed in situ panel by panel . The wall is usually designed to reach very great depth. Sometimes upto 50 m. It is generally reinforced concrete wall constructed in the ground using under slurry technique which was developed in europe.

Common use of diaphragm wall :-
1. Structural support for the construction of building basement with underground parking.
2. Add stability to landslides, highway cuts and deep building excavations including circular shafts.
3. Provide retaining wall in areas where severe limitations may be posed by noise, vibration, geology, water table and schedule.
4. Provide deep diaphragms where geometric precision and continuity at depth are vital for structural and hydraulic reasons.
5. Concrete is placed using the tremie pipe installation method. It can be constructed upto depth of 150 m.

Materials used for the diaphragm wall:-
1. Ordinary portland cement
2. Aggregates:- C.A size of 20 mm.
3. Sand :- Well graded sand consisting of 50 % course sand.
4. Water 
5. Admixtures :- If required shall be used as per IS 456-1978.
6. Reinforcement :- mild steel bars.
7. Bentonite :- Bentonite use shall conforms to IS 12584-1989.
8. Clay :- Clay shall conforms to IS 1498-1970.
9. Concrete mix :- Water cement ratio shall not be < 0.5.

PROCEDURE:-
1. Construction of guide walls
Guide wall is two parallel concrete beams constructed along the side of the wall as a guide to the clamshell which is used  for the excavation of diaphragm wall. Depth of the beam is typically 1.5 m.

2. Trench excavation
In normal soil condition, excavation is done using a clamshell or grab suspended by cables to a crane.

3. Excavation support
The sides inside the trench can collapse easily so we used bentonite slurry to protect the sides of soil and prevent side fall. It is specially selected fine clay conforming IS 12584-1989. Bentonite clay is mixed with portable water to make slurry with good viscosity. It has also low density around 1000 to 1200 kg/cu.m. The slurry will produce the great lateral pressure sufficient to retain the sides.

4. Placement of reinforcement 
Reinforcement is inserted in the form of mild steel cage, but may be required to lap few section in order to reach the required length or depth. When it doing bentonite slurry is still in trench.

5. Concreting
Placing of concrete is done using termie pipe to avoid segregation of concrete. As concrete being poured down, bentonite slurry will comes up due to its low density than concrete. Bentonite is then collected simultaneously in collecting tank for reuse of it. 

Comments

Popular Posts

TYPES OF CRACKS IN R.C.C COLUMNS

CHECKLIST FOR TERRACE WATERPROOFING (BRICK BAT COBA)

TYPES OF ALUMINIUM SECTION FINISHES.