Do you use the new seismic screen analysis for slope stability yet?

[MeGE]

DMG Special Publication 117 and the Recommended Procedure for Implementation of DMG Special Publication 117, recommends using a seismic screen analysis for determination of the seismic coefficent for slope stability analyses. We have found that the screen procedure yields seismic coefficents on the order of 0.5 to 0.7 of the peak ground acceleration. (Santa Cruz County is located to several major faults and has experienced severe ground shaking in the recent past, most notably the 7.1M 1989 Loma Prieta Earthquake). Some of our peers, with both geotechnical and geologic backgrounds, continue to use a maximum seismic coefficient of 0.15g, which is based on Seed's research.

The Geotechnical Engineers of Santa Cruz County would like to determine what other people are using and what really is the current state-of-practice in our area. So....how do you determine the seismic coefficient for seismic slope stability analyses?

R. Dees
G.E. 2623
Santa Cruz, California

 

[Focht3]

While I'm a licensed C.E. in California, I haven't practiced there in over a decade, so I'm a little rusty on the current earthquake stuff. Your question gives me an excuse to get boned up again -


If you intend to argue against the use of the CGS (formerly DMG) SP 117 "seismic screen analysis technique" (see

http://gmw.consrv.ca.gov/shmp/SHMPsp117.asp

), then you'll need a lot more than some (generally anonymous) on-line opinions on the subject. First, you will need to be able to cite specific examples where the procedure produces erroneous results. Then you'll have to show that Seed's work is still the best approach. And that will take a lot more than, "this is how we all do it around here."

Don't get me wrong - I'm not saying that the "seismic screen analysis technique" is better than Seed's recommendation. I'm simply reflecting on what it will take to effect a change in CGS's recommendations...when dealing with one of the local governmental agencies.

As a side note: I couldn't find a reference to a "seismic screen analysis technique" on the cited web site. And when I read (ahem, skimmed) the Special Publication, I didn't see anything particularly troublesome...

Please enlighten us with specific references, preferably on-line resources. We're happy to act as a sounding board for you -



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