Rock wall in weathered shale cut

[Cosimo]

I am investigating the feasibility of installing a rock wall along a cut in highly weathered & fractured shale on a golf course (central/north new jersey). Wall height up to 7' in a localized area, most of the wall is approx. 4'-5'. Question, what is the recommended method of determining active pressure on the rock wall (or any wall) in these soil conditions? It was suggested that one method may be to analyze it as a very dense granular soil with a high phi value, approaching 40. Doesn't seem right. Any text references on the topic would be appreciated. Thank you.

 

[oldestguy]

Does this shale expand when exposed to air and/or water? If so, conventional active pressure detrminations won't apply. You may even exceed passive pressure comps.

What do exposed cut slopes look like? Can you get by without a wall? Will a slope of 1/4 to 1 be acceptable?

 

[cap4000]

For a narrow width of backfill with a stable rock wall the active pressures are reduced by virtue of the vertical friction forces developed on both your new rock or concrete and the existing rock wall. What is your backfill width and how stable is your rock cut?? This method is rationalized similar to the ditch conduit loads by Marston or the silo equations by Janssen. Much lab testing has been done on concrete walls to verify this issue. These formulas use natural logs and the "e value" to arrive at the actual pressures. Good Luck.