Sometimes known as inground walls or barrier pile walls, palisade
walls using soldier piles with a capping beam is an effective measure
against cliff retention and ground subsidence.
Barrier pile walls utilize deep piles, either encased timber or
reinforced concrete piles, closely spaced which in-beds into the harder
subsoils, thus retaining the more unstable upper layers.
Often a capping
beam is used to link the piles, or used in conjunction with house piles
to ensure stable ground support.
See https://www.youtube.com/watch?v=9v1Ruab4seg&t=4s for a short look at how it is done.