Shale Rock Slope Stability Formula 1

[cap4000]

I have a situation with a 50 foot high nearly vertical well cemented shale cliff with a residential development 20 feet away from its base. Does anyone have a safe rock bank cut typical formula. For example clay cohesive soils are temporarily stable depending on its cohesion and friction values. Rock is a whole different animal and depends mainly on the tension crack formations and locations. Any feedback would be appreciated as I am currently designing an anchored rock fall netting for this situation.

 

[theCorkster]

Cap4000:

You've got two issues that you should get a good engineering geologist and/or geotechnical engineer to evaluate. Your correct in that jointing and fracturing of the shale are going to control the stability of the slope, and the only way to understand the impact on any design is to have the formation mapped. Once the geologic portion of the problem is understood, you should expect to have the formation sampled in order to provide cohesion characteristics of the shale for anchor design.

Without this information, you'll be designing blindfolded with one hand tied behind your back, even with the best rock slope stability computer program there is. Good luck!

 

[DRC1]

Talk to a good engineering Geologist. The primary factor will be strike and dip of the joints. Several years ago they had several rock slides on the NY Throughway. Cause was found to be unfaverable jointing

 

[cvg]

DRC1 is correct re: strike and dip. we excavated a rock spillway for a dam. Overnight there was a rock slide which buried the excavator and resulted in a change order to haul out all the extra rock. Luckily, no injuries. Resulted from unfavorable dip angle which was away from the slope.