Liquefaction - Lateral resistance - Pile foundation

[Dakka]

Hi
Please consider a soil strata:
Layer 1: Non liquefied soil : 0m to 6m
Layer 2: Liquefied soil : 6m to 10m
Layer 3: Non Liquefied soil : beyond 10m
When you analyze a Pile foundation (4-Pile system) for the Seismic case using Soil-Spring approach, Can you take into account the lateral resistance offered by the Layer 1?
Or because it is above a Liquefied layer, it is free to slide in lateral direction & doesn't offer any Lateral resistance?
Does the phenomenon of Lateral spreading has any effect on the above, meaning, say Lateral spreading is not encountered, then the lateral resistance from layer 1 can be anticipated and for vice versa, later resistance is not offered?
Any codal or literature reference which addresses the design of Pile foundation under liquefaction using Soil springs is highly appreciated.
Please help.
Thanks in advance.
Best.

 

[HTURKAK]

Eurocode 8 Part 5 Clause 5.4.2 Piles and piers (4)P The side resistance of soil layers that are susceptible to liquefaction or to substantial strength degradation shall be ignored.

I will suggest you to look Pile Design and Construction Practice ( By Michael Tomlinson ..) The following excerpt is useful to see the concept for simplified analysis..
Consider also the downdrag forces developing during seismic event..

 

[EireChch]

Boulanger et al 2003 - Piles founded in Liquefied and Lateral Spreading Ground - this is the industry standard for assessing piles as you have stated.

If you have a site that is on level ground then there is no risk of lateral spreading. Soils need free faces or sloping ground to spread.

If you have sloping ground then Layer 1 is free to ride on top of the liquefied soil below and apply a lateral force. This is nearly equivalent to full passive pressure so it is a high lateral loading.

If you dont have free face or sloping ground then you can take resistance from Layer 1.