Modeling concrete piles in slope stability analysis

[learning2geotech]

In Slide2, is it realistic if the concrete piles are modeled with high cohesion (half of unconfined compressive strength) and high phi? I feel like that will completely ignore the possibility that the failure surface can slice through the concrete piles and render the analysis unrealistic

 

[DanielSgeo]

More to it than that. You have to consider the shear/bending capacity of the pile. My approach is to use slide (LEM) to calc the stabilizing load, then design the pile for that load.

 

[learning2geotech]

Can you please share references on how to do that on Slide2?

 

[DanielSgeo]

Landslides in practice by Derek Cornforth. I’m not sure if there is anything good online.

 

[geotechguy1]

If you have RSPile it's integrated with Slide2 for this purpose

 

[Doc09]

In principle, if you are using the Mohr-Coulomb model to represent your materials, then the concrete would be treated just as any other material you have defined in your slope stability model, and if the pile is not too rigid, the slip circles will indeed go through the pile not just around it.

Having said that, there is a lot that software like Slide cannot account for which renders the full use of (C) unjustified, especially if you are studying a shoring system. I normally design the pile based on the reactions I obtain from a structural analysis of the retaining system, then verify the global stability using Slide.

In the absence of a structural analysis / evaluation, I would recommend limiting C < 2000 Kpa and phi < 35. For micropiles, I would recommend a C < 1000 Kpa. These values have been observed to be reasonably conservative.