UNDERWATER CONSTRUCTION

what is underwater construction?

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

activities include

• power generation

• bridges

• water utilities

• ship husbandry

• industrial

mining pipeline

• power and gas transmission

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

underwater construction techniques

•wet construction&

•dry construction

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

dry construction

caisson &

cofferdam

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

working area of caissons

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.

working area of cofferdams

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

placing concrete under water

-pranay kumar(CVSR colg. of engg.)