Lateral Spreading of Coastal Slopes

[breezeear]

The lateral spreading results calculated using the equation of Youd (2002, see ASCE 2002 October version) and other methods are quite different. A same CA coastal slope lateral spread using Youd’s equation say, is 100 feet, while using Newmark analysis or Markdisi & Seed chart resulted a lateral spreading of 5 to 30 feet. All my calculations have been checked by several peers and should have no problem in calculation itself. The big difference is from the methods I used.

I don't know which method is more reliable? Is there any good reference that could assist me for a more reliable lateral spreading calculation? What kind of equations/charts you guys used for such calculation? Any comments or info are appreciated.

It should be noted the Youd’s equation is regressed on many historical lateral spreading slopes worldwide.

 

[BigH]

Can you explain what you mean by lateral spreading? Is this retrogression of coastal bluffs by erosion, etc. You've given not "time frame" for the spreading. Many bluffs appear stable for quite a while, then there is a slide due to bottom of bluff erosion - which can trigger other slides due to various geological settings. Check out Scarborough Bluffs in Ontario - this is a classic bluff retrogression with a lot of study over the years - in city-scape. There are other studies of Lake Erie bluffs in Ontario as well. Do a search of Scarborough Bluffs.

 

[damguy]

Youd's article notes that any lateral displacement greater than 6 m (19.7 ft) "should not be applied in engineering practice; such large predicted displacements do indicate, however, that displacements are likely to be large". The method by Youd may not be appropriate for your case.

 

[BigH]

Can you give Youd's reference details?

 

[damguy]

These three references provide the background information on Youd's method. The quote on my previous reply was obtained from the third reference below.

Bartlett, S.F. and T.L. Youd (1992). Empirical analysis of horizontal ground displacement generated by liquefaction-induced lateral spreads. Technical report NCEER-92-0021, National Center for Earthquake Engineering Research, State University of New York, Buffalo.

Bartlett, S.F. and Youd, T.L. (1995). Empirical Prediction of Liquefaction-Induced Lateral Spread. Journal of Geotechnical Engineering, Vol. 121, No. 4, April 1995.

Youd, T.L.; Hansen, C.M. and Bartlett, S.F. (2002). Revised Multilinear Regression Equations for Prediction of Lateral Spread Displacement. Journal of Geotechnical and Geoenvironmental Engineering, Volume 128, No. 12, December 2002, pp. 1007-1017.

 

[BigH]

Thanks damguy - so it is liquefaction spreading that is under discussion. I'll have to read up on some of the papers - now if I can find my handle/password for ASCE as I now have broadband!

 

[breezeear]

Thanks damguy, thanks everyone. I am talking about the third one:

Youd, T.L.; Hansen, C.M. and Bartlett, S.F. (2002). Revised Multilinear Regression Equations for Prediction of Lateral Spread Displacement. Journal of Geotechnical and Geoenvironmental Engineering, Volume 128, No. 12, December 2002, pp. 1007-1017.

It is about the liquefaction spreading of slopes. I will read the paper again and come back to disscuss.

 

[VAD]

While I know you are concerned about the calculation of lateral spread, I would be interested to know a bit about the problem at hand. Is this to do with a development of a site underlain by potentially liquefiable material. I presume that the concern about the spread may influence site use etc. Calculations in geotechnical engineering are often tempered by experience and judgement etc.

Just interested in the background of the project,if this is possible.