We used 1.5 times the bench height but basically the same thing. In really unstable areas Mine Ops would build a berm maybe 5m away from the toe of the bench to (hopefully) catch any stray rocks that came crashing down.I've spent a fair amount of time in shovel pits. There was a rule that you had to be a certain distance from the working face. I want to say it was 2x the face but I can't remember. Haven't been in a mine in about 5 years.
seen the photos of Freeport in Indonesia, and now seen the photos of this one. All of them involved the movement of major league amounts of material (10+ million tonnes minimum).
A bit of research reveals that both open pits at the Highland Valley operation have been suffering slope stability issues since the late 1970s, so I will hazard a guess that the situation is not going to be new to them. From a report that's over 10 years old......... https://www.tandfonline.com/doi/abs/10.1080/1389526042000263324?journalCode=nsme19
Couple of interesting videos from Bingham Canyon. First one if I'd been the driller who put that hole pattern in I'd have been crapping myself thinking that my drill could have been on top of that lot..!!
2nd one is a time lapse of the 9-month process to dig through the bottom end of the slough and re-establish the haul road down to the bottom of the pit.