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WHAT ARE DIAPHRAGM WALLS?

Diaphragm Wall

Diaphragm walls are continuous walls built below ground level. They are generally built top down, i.e. starting from the ground level and with R.C.C. (Reinforced Cement Concrete). They are commonly constructed for deep basements or for extensive underground spaces.
 
Diaphragm walls act as a waterproof barrier between the inside and the surrounding earth. The system of diaphragm walls also acts as an excavation support system during top down construction method and allow for a high rise project to proceed upwards at the same time as the construction of basement. With the equipment available today, diaphragm walls of more than 50 m depth and 1 to 1.2 m thickness can be realized.

HISTORY OF DIAPHRAGM WALL SYSTEM

The first diaphragm walls were tested in 1948 and the first full scale diaphragm wall was built by Icos in Italy in 1950 with bentonite slurry support as a cut-off wall. Icos constructed the first structural diaphragm wall in the late 1950s for the Milan Metro. Diaphragm walls were introduced in the US in the mid 1960s by European contractors. The first application in the US was in New York City [ in year 1962] for a 7m diameter by 24m deep shaft, that was followed by the Bank of California in San Francisco, the CNA building in Chicago, and the World Trade Center in New York. The majority of diaphragm wall projects in the US are located in six cities Boston, Chicago, Washington DC, San Francisco and New York.
 
Diaphragm walls are extensively used in the Central Artery/Tunnel project (CA/T) in Boston, Massachusetts as the work in the CA/T involved construction of many cut and cover tunnels under the existing artery road.

SALIENT FEATURES OF DIAPHRAGM WALL SYSTEM

  • Can be designed to take very high structural loads, thus used as excavation supports.
  • The water tight walls formed can be used as permanent structural walls. 
  • Limited number of construction joints in the wall improves the walls water tightness.
  • Work may be carried out right against existing structures and the line of wall may be adjusted to any shape in plan. 
  • Diaphragm wall construction is relatively quiet, and minimum noise and vibration levels make it suitable for construction in urban areas.
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