Slope Stability analysis - Factor of Safety = 0

I am conducting a slope stability analysis on 4 cross sections of a slope. cross sections 1 and 2 run without issue; where cross sections 3 and 4 present a factor of safety of "0.00" (or "NG" in the report). This has indicated an error, as there should be at least some failure surfaces with a factor of safety. I have tried manipulating all of my inputs (removing the loads, etc.) with no change in the result. I have even tried re-creating the slope in a new file.

I have attached the report - which only shows cross section #4 without loads

Can you please help with this error.

Thanks

I took at look at your model. I had the same issue if I ran as you had it. However, I tested running without the top layer (surface 5) and model ran fine.

So I gave a closer look and saw that the bottom toe of surface 5 had the tip angle as obtuse, meaning a small part of it was technically a slope in the opposite direction as the main slope.

So I redrew that small section, recreated the surface and now model runs fine.  

Find model attached.

Best

AFM

not sure why this created a problem. I'm pretty sure all the other models have this bottom section that is not true vertical. but okay if the error is that small it's a easy fix.

regards