Pile Design with Liquefiable Soils
Pile Design with Liquefiable Soils
(OP)
Does anyone know a good reference paper or text for dealing with liquefiable layers in pile design. We're trying to feel comfortable with realistic amount of downdrag or strength loss that could occur in seismic event. Thanks for any help.





RE: Pile Design with Liquefiable Soils
You may want to do a search as this topic has been covered before. Look in "Technical Papers" on www.unisoftltd.com. This is Dr. Bengt Fellinius's software company.
RE: Pile Design with Liquefiable Soils
Scroll down to
Singh, P., Brandenberg, S. J., Boulanger, R. W., and Kutter, B. K. (2002). "Behavior of pile foundations in liquefied and laterally spreading ground." Proceedings ASCE/AEG/UMKC Geotechnical Conference, Kansas City, MO, April 6, 2002.
and
Brandenberg, S. J., Singh, P., Boulanger, R. W., and Kutter, B. L. (2001). "Behavior of piles in laterally spreading ground during earthquakes."The Sixth Caltrans Seismic Research Workshop, Radisson Hotel, Sacramento, CA, June 12-13, Paper 02-106.
Both of those are downloadable as .pdf files. Some of it is pure research; some of it is more easily applied.
Also, get the index in the December issues of the ASCE Jnl of Geotech Engrg and look through them.
RE: Pile Design with Liquefiable Soils
I say this to give you some comfort when you are somewhat forced to give bad news.
Regards
VOD
RE: Pile Design with Liquefiable Soils
RE: Pile Design with Liquefiable Soils
This permeability issue applies also to vertical drains installed to relieve pore pressure during the earthquake (mentioned by VoD). Unless the material is very clean AND the vertical drains are closely spaced, there isn't going to be a whole lot of drainage during 20 seconds of shaking. The volume of water that has to escape (in order to get just shake-down settlement and not liquefaction) could be 1 percent or more of the total volume of the soil. The water has to go somewhere, and fast.
RE: Pile Design with Liquefiable Soils
Personally, I couldn't find any references when I had to solve this problem - so, I assumed the design earthquake event, tried (using blowcount data primarily - not a lot of budget here...) to estimate what zones along the pile would liquefy, and then eliminated those zones (including a healthy F.S. multiplier) from the capacity analysis.
I suppose I would approach the problem in a similar manner if I had clay over a liquefiable sand, and I was concerned about downdrag. But if there was no clay soil in the subsurface profile, I'd just ignore the downdrag issue until someone shows me how a liquefied flowing sand can stick to the sides of a pile and pull down on it.
Zoom
RE: Pile Design with Liquefiable Soils