There are methods of analysis based on soil type and geometry but there are few guidelines. British Columbia (Canada) Forest Practices Code present some general guidelines for mountainous regions. Are you looking for guidelines for the design of roads on steep slopes? Is it in rock or soil and what kind of soil?
The problem with this site is that in the past there was a large-scale landslide. So the rock, (schist) has a very mixed-up character, and even after drilling the site it is hard to say where we may encounter in-place bedrock. Usually we find a slide plane, but at this site there was no distinguishable slide plane. The site is too narrow for a re-alignment; we have considered a wall but cost is a factor. The site is a fill slope failure that extends for approximately 60m. Thanks for your reply.
One brief comment: since the failure occurred in a fill slope, you might replace the existing fill with a lightweight material. This will reduce the driving forces -
As a side note:
Malibu, California is located on an ancient landslide; CALTRANS is frequently repairing the Pacific Coast Highway in this area... This is one place where California actually could slide into the Pacific!
