Date post: | 14-Jul-2015 |
Category: |
Engineering |
Upload: | pranay-kumar |
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introduction
• during the construction of bridges, dams or any other structure where the foundation part of the structure is most likely to lie underwater, we have to opt for underwater construction
• construction in water poses many difficulties especially in the places where there the depth is considerable
underwater construction techniques
almost any construction technique that can be used
abovewater can also be used underwater
underwater construction techniques
There are a number of products and materials that
have been formulated or developed specifically for
underwater work
wet construction
• a diver• evaluate the overall cost of
the work • considering time • equipment needs • the capability of a diver to
accomplish the specific task • a more gross than fine nature
caisson
•permanent structure• large hollow structure that sunk down
through the earth • used in construction of bridge piers,
building columns, dams, repair of ships... •keeps working environment dry
advantages of caisson
•economic • slight less noise and reduced vibrations •easily adaptable to varying site conditions •high axial and lateral loading capacity
cofferdams
• temporary structure • allows enclosed space to be pumped out, creating dry environment • enclosed coffers are commonly used for construction and repair of oil
platforms , bridge piers and other support structures built within or over water
• a cofferdam involves the interaction of the structure, soil and water. Loads imposed include the hydrostatic forces of the water as well as the dynamic forces due to currents and waves
• used for shallow construction having depth less than 10m.
advantages of cofferdam
• provides safe environment to work • contractors have design responsibilty • steel sheet piles are easily installed and removed• materials typically reused on other projects
placing concrete under waterThe satisfactory method of placing concrete underwater is by the use of tremie pipe
• a tremie is a water tight pipe • generally 250 mm in diameter
• capable of easy coupling for increase or
decrease of length • Funnel shaped hopper at its upper end and a
loose plug at the bottom• the concrete having a very high slump of about
15 to 20 cm is poured into the funnel
tremie method
placing concrete under water
tremie method
• lifted up and slight jerk is given, so that the concrete gets discharged
• again concrete is poured over the funnel, the pipe is slightly lifted amd given jerk
• in this way concrete work is progressed without stopping till the concrete level comes above the water level