# 6 minute solutions- geotech problem 71

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### #1 terzaghi83

terzaghi83

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Posted 06 February 2012 - 02:14 AM

I have 2nd edition, 3rd printing of this book. there is no errata available but am stumped as to how they arrive at a the solution.

In my book, problem 71 states " A group of 30 in diameter caissons is constructed for support of a bridge. The group is arranged in a 3 by 4....."

If you have this problem please let me know if the solution makes sense. I'm trying to find out how the heck they say that it is 10 feet below the 2/3L distance to get to the midpoint of the clay layer.

Thanks.

### #2 chess5329

chess5329

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Posted 06 February 2012 - 03:41 AM

I don't have the book with me that I can check for the problem, but try to use the 2:1 method for a group of piles to see if works close to the answer.....I hope this helps.

### #3 terzaghi83

terzaghi83

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Posted 08 February 2012 - 03:09 AM

Yeah, they use the 2:1 method to obtain the DeltaP. My question is how they come up with the distance from the 2/3 point on the caisson group to the midpoint of the clay layer as 10 feet.

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