How do you do the slope stability analysis?

[Geotechnical76]

I would like to check how people do the slope stability analysis for these two cases using slope stability programs, WHEN THERE IS WATER TABLE(if there any consensus). Do you assume the following, if not what do you use?
1-Total stress analysis: Use total strength parameters ( cohesion,friction), NO water table is included in the analysis.
2-Effective stress analysis:Use total unit weight, effective cohesion, effective friction angle, INCLUDE the water table in the analysis.
Thanks.

 

[DRC1]

If you have an undrained condition and a cohesive soil, I would use a total stress concept as you described. For a drained analysis -effective stress, I would use the bouyant weight and generally the phi valuefor strength. Cphesion under a drained condition is not always well defined. I was taught never to use combined phi -c strength as these change with time and drainage and are very hard to corralete to actual field conditions.

 

[fattdad]

I'd do both.

f-d

¡papá gordo ain’t no madre flaca!

 

[PEinc]

If the soil is drained, I would use the moist unit weight above the water table and a saturated unit weight below the water table. The computer program will probably subtract the weight of water when looking below the water table. If not, then yes, use the buoyant weight below the water table. Check the program manual.

 

[Dirtguy4587]

As far as I know, most common slope stability software will handle effective vs. normal stress based on position of the phreatic surface (for drained analyses).