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# RE: Active, At-Rest, Passive Soil Pressure

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• To: <seaint(--nospam--at)seaint.org>
• Subject: RE: Active, At-Rest, Passive Soil Pressure
• From: "J.R. Harris & Company" <jrharris(--nospam--at)ix.netcom.com>
• Date: Wed, 22 Aug 2001 10:04:57 -0600
 In regards to this whole issue I would like to ask those of you that design residential homes (or any structure where the top of the basement wall is braced/supported by a wood diaphragm) a question.   It is very difficult to get the soil loads out of the wall and into the diaphragm with 5/8" diameter A.B. (anything bigger and the contractor complains to the owner about overdesign and of course the owner believe the contractor and not the engineer).  How do you get the active pressures, not even at-rest, into the diaphragm?   For the very few homes I have designed I looked at the basement wall as a wall rigidly supported at it's left and right ends, and depending on conditions the base is either considered rigid or pinned.  The top I leave free, and design the wall for the resulting forces.  In this scenario the wall will deflect inward near midspan and some active pressures will be developed.  Where the wall is stiffer, such as at the corners, the loads will be closer to at rest pressures.  I design the wall for the forces I get from this analysis.  My reinforcing is much heavier that much of what I see in other engineer's drawings.  A lot of engineers in this area (Denver) throw 2-#7 top and bottom and maybe #4@24" each way centered in the wall.  All of my calculations indicate that a wall with this reinforcing is blown out of the water by at rest and active loads, but of course they are not failing.  Many are in clay soils but a good number are in sandy soils.  I understand the reasons the walls supporting clays are still working but the walls supporting sands are a mystery to me.   To me the performance of these walls indicates that designing this type of structure for at-rest pressures in very conservative.    P.S. assume you can't use buttresses.   Thanks Don Carroll