Hello blrmdcr.  Search the literature for Sardis Dam to see what the Corps of Engineers did to stabilize it for a liquefiable foundation.  A LOT of analysis was required before they considered that to be an acceptable solution (including the transfer of forces from the piles to the surrounding soil, in 3D).  Sardis is in northern Mississippi, close enough to the New Madrid fault zone.  The design was done by the Vicksburg District, but there was also involvement (and publications) by the Waterways Experiment Station.

Remember that the steel has to be considered for both shear and bending.  Unless there is a distinct rupture surface within strong material above and below (very stiff soil or very weak rock that piles will penetrate), bending is likely to govern, and you may find that the moment capacity of the H piles doesn't make much difference at midslope, unless they are very tightly spaced.  At Sardis, the concrete piles (or, more accurately, the concrete beams pounded into the ground like piles) were very heavily reinforced for moment, and tightly spaced.  If the piles are at the top of a steep slope, the slope may just want to pull away from them, rather than being stabilized by them.  Whether they are worth pursuing all depends on slope geometry and materials.

Bon chance!

DRG