I finally figured out why my post holes kept caving in on a rocky slope near Chattanooga
Took me 3 extra days of digging and resetting before I realized I needed to wet the ground first and use a clamshell digger instead of the power auger. Anyone else dealt with loose shale that just won't hold a post straight?
Wet ground and a clamshell digger... that's exactly what I ended up doing on a job near Knoxville last year. The trick for me was letting the water soak in for 15 minutes before even touching the shovel. Saved me from fighting with collapsing walls every few inches.