3106F.5.4 Lateral Spreading — Free Field
The earthquake—induced lateral deformations of the slope or embankment and associated foundations soils shall be determined for the Level 1 and Level 2 earthquakes using the associated PGA at the ground surface (not modified for liquefaction). If liquefaction and/or strength loss of the site soils is likely, the following shall be used in the analyses, as appropriate:
- Residual strength of liquefied soils
- Strengths compatible with the pore-pressure generation of potentially liquefiable soils
- Potential strength reduction of clays
The presence of the foundation system shall not be included in the "free field" evaluations.
Initial lateral spread estimates shall be made using the Newmark displacement approach documented in NCHRP Report 611 [6.6] or other appropriate but similar procedures.