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 Subject : Re:Shear strength of soil for liquefaction.. 12/19/2019 11:05:43 AM 
Robert Pyke
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Topic : Shear strength of soil for liquefaction

The publications by Stark and Olson have now been superseded by Sadrekarimi (who I believe was Olson's student), ASCE Vol 140, No.12, December 2014. Sadrekarimi places great emphasis on the "style of loading" - triaxial, simple shear, whatever. See https://www.slideshare.net/RobertPyke4/pyke-static-and-cyclic-liquefaction-annotated for a more complete discussion. But these references apply only to very loose sands that are subject to static liquefaction. The questioner in this case said that his/her problem was "borderline liquefiable" so that it sounds like the "residual strength" after cyclic liquefaction is more applicable. Starting with the late Professor Harry Seed there have been various estimates of this quantity, mostly in terms of SPT blowcounts or CPT tip resistance, but there is necessarily a lot of uncertainty in these estimates as the actual strength under a monotonic loading following a cyclic loading is sensitive to the exact gradation including fines content, the style of loading and the drainage conditions (all of which are not well represented by penetration resistance), particularly if the material in question is "borderline liquefiable". If the problem is critical, then a special laboratory testing program is called for, but in ordinary practice this might be too time consuming and expensive, so the best course it to adopt a design strategy that takes the question off the table because the short answer is that nobody knows what the long answer is.
 Subject : Re:Shear strength of soil for liquefaction.. 12/18/2019 03:39:18 PM 
Kelly Cabal
Posts: 5
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Topic : Shear strength of soil for liquefaction

I also received this response via e-mail:

I suggest that the following publication by Seed and Pestana be used (see specifically Chapter 5) to determine the residual shear strength, see equations 5.2 and 5.4.
https://www.nrc.gov/docs/ML1635/ML16354A368.pdf

By: Fernando Cuenca, TetraTech
 Subject : Re:Shear strength of soil for liquefaction.. 12/18/2019 02:51:21 PM 
Jerome Blunck
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Topic : Shear strength of soil for liquefaction

You may want to also review the following references:

Chang, C.-Y.; Tang, Y. K.; Mok, C. M.; Tang, H. T.; Power, M. S.; and Stepp, J. C., "Development of Shear Modulus Reduction Curves Based on Lotung Downhole Ground Motion Data" (1991). International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics. 16.

Ishihara, K., 1994, Evaluation of Residual Strength of Sandy Soils, XIII ICSMFE, 1994, New Delhi, India.
Kramer, S.L. and Wang, C-H, 2015, Empirical Model for Estimation of the Residual Strength of Liquefied Soil, Journal of the Geotechnical Engineering Division, ASCE, Vol., 141, No. 9, May.

Rayamajhi, D., Nguyen, T.V., Ashford, S.A., Boulanger, R.W., Lu, J., Elgamal, A., and Shao, L.M., 2013, Numerical Study of Shear Stress Distribution for Discrete Columns in Liquefiable Soils, ASCE Journal of Geotechnical Engineering, Vol. 140, No. 3
 Subject : Re:Shear strength of soil for liquefaction.. 12/18/2019 01:03:49 PM 
MATTHEW ROGERS
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Topic : Shear strength of soil for liquefaction

Agree with the Olson references as well, you also have to look at the slope stability from the perspective of the increase in pore water pressure as well as undrained strength rather than trying to assign a c or phi value.
 Subject : Re:Shear strength of soil for liquefaction.. 12/18/2019 12:20:45 PM 
Dan Peluso
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Topic : Shear strength of soil for liquefaction

A couple of references are suggested

Stark, Timothy & Mesri, Gholamreza. (1992). Undrained Shear Strength of Liquefied Sands for Stability Analysis. Journal of Geotechnical Engineering. 118. 10.1061/(ASCE)0733-9410(1992)118:11(1727).

Olson, Scott & Stark, Timothy. (2002). Liquefied strength ratio from liquefaction case histories. Canadian Geotechnical Journal - CAN GEOTECH J. 39. 629-647. 10.1139/t02-001.

I generally use an undrained shear strength in the range of 300 to 800 psf, depending on the factors involved.
Last Edited On: 12/18/2019 12:22:00 PM By Dan Peluso
 Subject : Shear strength of soil for liquefaction.. 12/18/2019 11:59:25 AM 
Kelly Cabal
Posts: 5
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Topic : Shear strength of soil for liquefaction

This question was submitted by a CalGeo member. Please reply if you have any advice!

When evaluating the overall shear strength of soil subject to liquefaction, what value do you typically use? The soil is very silty sand with varying amounts of clay. It is borderline liquefiable soil, but for the sake of argument we are assuming it will all liquefy. The question comes in what strength would you assume? The application is slope stability, not foundations. A fill slope would be partially supported by shallow GW alluvium starting at mid-slope and continuing to some distance in front of the toe. Beyond the alluvium, there is bedrock so the slope and beyond would be largely supported by bedrock, but a portion of the slope would be on potentially liquefiable soil.

I have seen values of 9-degrees friction angle and zero cohesion; and zero friction and 300 psf cohesion. I am asking if your firm has found values that seem to work or if you have favorite reference you consult in this situation.

I sincerely appreciate hearing back from everyone. Remember there is no singularly correct answer to this question. It is almost entirely a personal preference based on past experience. I would like to know if there is any consensus on this or not.
 Subject : Re:Design requirements for lateral spreading - new code.. 09/12/2019 10:26:26 AM 
Robert Pyke
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Topic : Design requirements for lateral spreading - new code

At least part of the problem is that many estimates of lateral spreading displacements (and of the occurrence of liquefaction and the magnitude of earthquake-induced settlements) are excessively conservative. See the expanded version of the presentation that I gave recently at the 2nd Ishihara Colloquium, sponsored by EERI and held at San Diego State University last month:

https://www.linkedin.com/pulse/improved-analysis-potential-lateral-spread-earthquakes-robert-pyke
 Subject : Re:Design requirements for lateral spreading - new code.. 09/12/2019 10:07:07 AM 
Yvette Wilson
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Topic : Design requirements for lateral spreading - new code

Doug-Thank you for your reply and the link to the references.
 Subject : Re:Design requirements for lateral spreading - new code.. 09/12/2019 09:59:46 AM 
Doug Schwarm
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Topic : Design requirements for lateral spreading - new code

Kelly - You ask an excellent question. Be sure that first you're taking advantage of the 12" allowance in ASCE 7-16 Table 12.13-2. (And yes, it's not yet the official CA code, but building department generally allow using the updated guidance). Then, detail for ductility according to 12.13.9.3.4.

If the "tolerable displacement" approach is unacceptable (you're designing a hazardous waste facility or a Microsoft Millionaire's house, for example) then consider the Caltrans approach in Memo to Designers 20-15. The Caltrans website has been wonly for some time now, so here's links to the manuals in our technical library.

https://www.dropbox.com/s/cd96lzbswfrvf2d/Caltrans%20MTD%2020-15%20Lateral%20Spreading%202008.pdf?dl=0

and

https://www.dropbox.com/s/cu97db2j0d5dm20/Caltrans%20MTD%2020-15%20Lateral%20Spreading%202008%20Att%201.pdf?dl=0

This approach is being updated but the guidance is not yet published.

Hope this helps,
Doug
 Subject : Design requirements for lateral spreading - new code.. 09/12/2019 09:33:18 AM 
Kelly Cabal
Posts: 5
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Forum : Discussion Forum
Topic : Design requirements for lateral spreading - new code

This question was posed by a CalGeo member:

I am looking to find out if there are members or resources available that can help with pile design for lateral spreading. I am finding that the lateral loads are so high in the crust (passive pressure times 3), the piers are cost prohibitive for single family homes. In the past, we have used mat slabs, but the new code is going to require piles. Any help or guidance is appreciated.
 
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