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RE: Subgrade Modulus for Mat Foundations

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Tom and Thor,

 

The problem I’m having is that without a “plate load test” there are few correlation for Vertical Subgrade modulus. You can calculate a spring constant based on soil parameters, for example shear wave velocity.

 

From: Tom.Hunt(--nospam--at)fluor.com [mailto:Tom.Hunt(--nospam--at)fluor.com]
Sent: Thursday, January 29, 2009 10:58 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Subgrade Modulus for Mat Foundations

 


Thor,

I could be wrong but I do not think LRFD for soil has caught on in the U.S.  Personally I think the concept has issues as most foundation limits are based on arbitrarily accepted serviceability limit.  That is, the limiting factors for soil are normally acceptable settlements so the soil never really reaches a true failure mode such as can happen in steel or concrete design.

Thomas Hunt, S.E.
Fluor



"vicpeng(--nospam--at)telus.net" <vicpeng
01/29/2009 10:40 AM
Please respond to seaint

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seaint(--nospam--at)seaint.org

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RE: Subgrade Modulus for Mat Foundations

 




What do you require for LRF design?
Thor


Email on the go, sent by TELUS

-----Original Message-----

From: Tom.Hunt(--nospam--at)fluor.com
Sent: Thu, 29 Jan 2009 10:27:02 -0800
To: <seaint(--nospam--at)seaint.org>
Received:  29 Jan 2009 18:27:56 +0000
Subject: Re: Subgrade Modulus for Mat Foundations

Joe,

The typical geotechnical recommendations for large mats would include
guidance for allowable soil bearing, potential total and differential
settlement, and an appropriate modulus of subgrade reaction suitable for
the engineer to develop one way soil springs for a computer model.  For
large mats the trick is normally in providing the correction factors for
size effects as oppose to just reporting the 1 foot by 1 foot plate test
results.  Typically soil bearing is given in either ksf or psf, settlement
in inches, and MSR in kcf, kci, or pci.

Thomas Hunt, S.E.
Fluor





"Souther, Joseph" <SoutherJT(--nospam--at)cdm.com>
01/29/2009 10:00 AM
Please respond to seaint

To
<seaint(--nospam--at)seaint.org>
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Subject
Subgrade Modulus for Mat Foundations







As a geotechnical engineer, I wish to provide geotechnical design
parameters to the structural engineer for design of a large (100 to 200
foot) circular mat foundation. What parameters does the structural expect?
What units (US job) are used for the design?
Thanks
Joseph T Souther, PE
CDM
11811 NE 1st Street, Suite 201
Bellevue, WA 98005
Reception:  (425) 453-8383
Direct/Fax:  (425) 519-8328
Mobile:       (425) 766-7517
www.cdm.com

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