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RE: Geotech

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It is about the same everywhere.  You get one value for spread footings and
the caveat of 1" of differential settlement for any soil other than
unweathered sound limestone bedrock.

If that strikes you as odd.  Ask for the lateral seismic forces due to soil
for retaining or basement walls.  Some geotechs say it does not exist.
(Update: Chet Soydemer is currently working on this issue.)

But with all due respect to geotechs, it is a difficult medium to predict
behavior.  Consider the current sinking hotel that has yet to open in Las
Vegas (18" in the center due to DL only the last I heard).

I don't think our litigious nature has much to do with it.  I think that the
practice of geotechnical engineering needs to be developed more.

Harold Sprague, P.E.
The Neenan Company

-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)]
Sent: Wednesday, November 04, 1998 8:12 PM
To: SEAOC list message
Subject: Geotech

Here is a topic I would like to offer up for discussion.

It seems like no matter where the project I am working on is located, the
soils report recommendations are almost a foregone conclusion. Low bearing
values and limited information. Apart from the obviously poor sites where
piles or caissons are recommended, the typical values for a traditional pad
footing foundation are equivalent to UBC minimum values (a straight 2000

Every soils bearing relationship I have ever studied, the bearing capacity
is dependent on the configuration and depth of the foundation, but only once
has a soils report provided equations for bearing with site specific
coefficients to allow for increased values due to width and depth.

Is this a typical condition for the rest of you, or is Southern California
primarily lousy soil?

Are these values realistic, or are the Geo-tech reports heavily influenced
by the 267,000 lawyers in California?

Structural design forces per the 1997 UBC are heavily soil dependent. All of
the new base shear equations, zone factors, and period values are
interrelated with the parameters for the top 100 feet of soil. The soils
report will have a large impact on the configuration and economy of the
final design.

I would be interested in hearing your opinions.

Paul Feather PE