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RE: Cassion Steel Casing check

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To clarify, designing underground structures to resist soil pressures is very similar to dancing with a very large woman.  Of course, the male is expected to lead, so the male guides his very large woman partner with his arms and similar body language.  These leading forces, felt in his arms as he guides his partner, are akin to the driving soil forces on, say a retaining wall or underground tank.  These are the active forces which are used to determine how strong our little man must be to guide his large mate.  These active forces are resisted by his muscles (equivalent to the retaining wall rebar).  The mass of his large mate, of course resists these forces, and even if he pushes really hard, her mass will resist the two of them from toppling over.  She represents passive soil forces.  The woman cannot push actively because she is not leading, he is.  However, she sure can resist being pushed over, just like the passive forces in the soil.  Granted this example has our plump partner acting more like a gravity wall, but soil passive forces can be thought of similarly.


So if you need some more insight, grab you a very large woman and try a waltz with her.  Try pushing her over and see what happens.  Then think of big pile of dirt resisting your efforts to knock her over.  Now I think you've got it.


ps:  It's best not to tell her what you are doing.



Bob Garner S.E.


From: Dilip Patel [mailto:dp_enco(--nospam--at)]
Sent: Thursday, April 09, 2009 1:10 PM
To: seaint(--nospam--at)
Subject: Cassion Steel Casing check


Do you check casing wall for hoop stress under active earth pressure only or you also check under passive earth pressure ?
Caisson is considered similar to tank under pressure, not as a column or sheet pile design.
Any thoughts ?