How are bridge supporters are made from water bodies?

Question

I mean how are their base of supporters which supports a bridge is made?If it is with cement,does it gets fixed under water?Or if it is done after putting soil upto water level,wouldn't there be some other problems like erosion if the water is flowing?These all are only something what I thought when i saw a bridge which was supported by some pillars whose base was from a flowing large water body.Actually I want to know how are they made from water.

Answer 1

They are premade support beams. The holes are dug by a certain type of drill that uses a pounding motion.

Answer 2

There are a number of ways they can build the supports. One is to construct an area for the support to be placed in, pump out the water, and then construct the support. Another is to build the support on land and then place it, or sink it in the water where it is needed. Another is to build it as a floating structure, tow or float it into place and then sink it and build on it there. If you look at the London Bridge in Havasu Arizona, it was reconstructed on dry land and then the land was removed, that made the bridge the only way onto the island.