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Name: Noah
Status: student
Grade: 6-8
Location: CA
Country: USA
Date: Spring 2013


Question:
How are piers built in the water to support bridges?



Replies:
It depends on the riverbed. If it is solid rock, you could just pour concrete on top of it. If it is solid rock covered by several feet of mud, you would have to dig out the mud first. If the mud is very deep, you could drive lots of long poles into it, and support the pier on the poles. In any case, you would probably have to make a temporary dam all around where the pier is going to go, and pump out the water so you have a place to work.

Tim Mooney


Hi Noah,

Thanks for the question. Piers, also known as pilings, are built by hammering steel I-beams or wooden logs into the bottom of a river or other body of water. An older method to place pilings uses pressurized caissons. I do not believe this method is in use as it is more labor intensive and the power of modern hydraulic equipment suffices.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell


Hi Noah

Piers are built in (relatively) shallow water, the bottoms of which are typically sand and mud. So to establish a firm base in which to stick the pier to, piles are driven deep into the sand and mud and the pier is built on top of the piles.

Here is a picture from this URL of a pier built on piles:

http://www.google.com/imgres?imgurl=http://www.innerbanks.biz/images/l-dock.jpg&imgrefurl=http://www.innerbanks.biz/&h=225&w=300&sz=26&tbnid=BEIs8mrzvuf9pM:&tbnh=99&tbnw=132&prev=/search%3Fq%3Dpier%2Bconstruction%2Btechniques%26tbm%3Disch%26tbo%3Du&zoom=1&q=pier+construction+techniques&usg=__k_v2aA3rZDJmezciXMhacZVSIZU=&docid=aixH8Xh0UTwFlM&hl=en&sa=X&ei=l01UUYuLKbGQ0QGQxoDIDw&ved=0CEgQ9QEwBg&dur=870

The piles are driven into the mud by pile drivers. The following is a picture of a pile driver from this URL: http://www.google.com/imgres?imgurl=http://www.freepatentsonline.com/7004684-0-large.jpg&imgrefurl=http://www.freepatentsonline.com/7004684.html&h=1876&w=1885&sz=1986&tbnid=jM206r2w2DVcoM:&tbnh=90&tbnw=90&prev=/search%3Fq%3Dpier%2Bconstruction%2Btechniques%26tbm%3Disch%26tbo%3Du&zoom=1&q=pier+construction+techniques&usg=__aYwto0gvcUvUyxE6CgyDZAhh1Hc=&docid=N4UHzdcEKL_O8M&hl=en&sa=X&ei=l01UUYuLKbGQ0QGQxoDIDw&ved=0CD8Q9QEwAw It acts like a big hammer and it just drives the piles into the ground.

You can find a waterfront construction handbook from the state of Maine at this URL:

http://www.maine.gov/doc/nrimc/mcp/downloads/WaterfrontConstructionHandbook_Jan97.pdf

Sincere regards, Mike Stewart



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