Slide 2 - Surficial Failure Surface 1

[learning2geotech]

See attached photo. To avoid these surficial failure surface, I set the minimum height of surface to 10 feet but I'm afraid that will ignore the real failure surfaces. What do you do to avoid these surficial surfaces?

 

[GeoPaveTraffic]

Options (depending on the specific software) to avoid these very shallow surfaces include:

1. Setting a minimal slide depth.
2. Setting a minimal slide weight.
3. Adding a nominal amount of cohesion to the soil.

All of these options require thought and experience so that you don't inadvertently miss a "real" slide plane of interest. Sorry, there is no magic bullet that will make these go away with risk of missing something important.

 

[MTNClimber]

I’m not sure which software you’re using but in Slope/W you can review the results of all slip surfaces analyzed in the model. I just sort the analyses by from lowest FOS to highest and review the lowest FOS slip surfaces until I find one that is critical. It takes a few seconds.

 

[EireChch]

we always ignore failures less than 0.5 deep, then review ones that are borderline and make a call if its possible

I would argue against adding cohesion as this affects all possible failures.

 

[Mccoy]

I’m not sure which software you’re using but in Slope/W you can review the results of all slip surfaces analyzed in the model. I just sort the analyses by from lowest FOS to highest and review the lowest FOS slip surfaces until I find one that is critical. It takes a few seconds.

That's exactly the same thing I do, I examine visually the graphical output of all critical surfaces within the lower FOS range and decide which ones are realistic and which ones look more like a potential result of surface erosion rather than of a potential sliding surface.

 

[GeoEnvGuy]

The analysis is telling you to look at the infinite slope stability. As the geotech you should be specifying the failure plane through the foundation materials you are concerned about and then let it optimize.

 

[EireChch]

GEG - I dont think its saying its an infinite slope issue. The slope failure is tiny, probably a few hundred mm. I would only be concerned with something bigger than 0.5-1m.