Driven Piles in Liquefied Sands
Driven Piles in Liquefied Sands
(OP)
I know from literature review that liquefied sands offer negligible resistance to piles under lateral loads though some pseudostatic approaches, reduced PY methods (Liu, Dobry and Wilson) and undrained shear strength approach (Wang and Reese), among others have been proposed. Recent research shows that resistance is negligible at initial deformations and there is no definite, developed or proposed PY curves to attend this condition (Weaver, Ashford and Rollins). I would like to know what you colleagues think about.





RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
I would recommend looking at the conditions that induce the lateral load that you are designing the piles for, as well as, the conditions underwhich the sands liquify. Additionally, while not impossible, sands 45 feet deep are difficult to get to liquify.
If the lateral loads and the liquifiacation of the sands can reasonably occur at the same time, then either the foundation system needs to be changed or the ground needs to be improved.
RE: Driven Piles in Liquefied Sands
A question about battered piles; I recall that several pile caps with battered piles have failed during earthquakes. The piles punched through the top of the cap. Are my recollections correct? If they are, is it still normal to design battered piles in earthquake prone areas?
RE: Driven Piles in Liquefied Sands
A relatively new program DFSAP is being used by Washington State DOT and you can download it free on their website. It apparently models the actual shape of the full scale tests by Rollins but uses the strain wedge method rather than P-Y curves. The comparisons it shows with LPILE also indicate more accurate results with non-liquefied loading.
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
http://w
RE: Driven Piles in Liquefied Sands
Wick drains have been used effectively to aid densification by stone columns or dynamic compaction. We got "textbook" results on one of our stone column projects.
Wick drains are NOT effective for dissipating excess pore pressure in "real time" during an earthquake.
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
To be effective in preventing high excess pore pressure, the drains and surrounding soil would have to permit enough drainage to allow up to 1% volumetric strain in something like 15 seconds without high seepage gradients. Consider it like a radial-flow consolidation problem. No matter how pervious the drain is, the flow is limited by the permeability of the soil (and of any "smear" from installation). The only way there can be a high gradient to cause rapid seepage flow is to have high excess pore pressure, in which case...it's too late.
Who did the centrifuge tests, and where were they published? Centrifuge scale modeling of a combined seepage and dynamic problem is quite difficult and commonly requires a pore fluid with viscosity different from that of water in order to get everything to scale right.
I've seen video of such drains in tailings being densified by blasting. See, for example, and for entertainment value:
http://www.rapidimpact.ca/inco_tailings_pond.htm
Watch the timing of the discharge. While the drains blew out a lot of water, they did not prevent high excess pore water pressure (hence, the large discharge), and they could not relieve much pressure during a 15-second earthquake.
DRG
RE: Driven Piles in Liquefied Sands
RE: Driven Piles in Liquefied Sands
UC Davis did some centrifuge studies:
http://www.neesgc.gatech.edu/content/view/35/33/
UC Berkeley developed finite element software to evaluate the drains:
http:
U-Texas did field testing:
http:
RE: Driven Piles in Liquefied Sands
Just use piles installed with blasting technique.