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Re: Modulus of subgrade reaction

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The way I've always attacked these kinds of problems is to do two runs: one
with a k=50 pci and one with a k=300 pci thereby enveloping the soil
parameters. One run gives me a higher soil bearing pressure, the other
gives me the higher bending moment. This way is faster (than coord. with
geotech.) and is probably more accurate anyway than a geotech. giving a
precise value of k=231 pci.

Bill Allen

From: John Cannon Jones <jcjones(--nospam--at)>
To: 'seaoc(--nospam--at)'
Subject: RE: Modulus of subgrade reaction
Date: Thursday, February 12, 1998 11:55 AM

Bowles book uses modulus of subgrade reaction because it is easier to test
for that E or v.  You can directly test for k which is better than test for
another parameter and then calcing the one you actually need.

Back to the question at hand:

Contact a local geotech for this info.  In my local area values are
typically about 150 pci.  The geotechs in this area will typically include
this value in their reports to aid in slab design.

John Jones
Pell City, AL

-----Original Message-----
From:	AXB2%ENGPROJ%NTS(--nospam--at)
Sent:	Thursday, February 12, 1998 10:03 AM
To:	seaoc(--nospam--at)
Subject:	re:Modulus of subgrade reaction

The modulus of subgrade may be calculated from Timoshenko's Theory of 
Elasticity (2nd Edition) formula 212, page 370, with little mathematical 

k= E/(m(1-v^2)(A)^.5) 

k is subgrade modulus kips/in^3 
m is shape factor from accompanying table
v is Poisson's ratio (v=.4 may be used)
A is the area of the foundation
E is modulus of elasticity of the soil (should be based on tests)


----------------------[Reply - Original Message]----------------------

Sent by:"Shafat Qazi" <seaoc-ad(--nospam--at)>

Can anyone tell me what is a standard value for the modulus of subgrade
reaction for soil type S2?

I am trying to model a spring that will represent soil stiffness.

Thank you.