Reinforced Soil Slope Design

[bucknell06]

I am trying to desin a reinforced soil slope and am looking to verify my design using a slope stability program. I have tried using RSS (from the FHWA site), but it seems to be overly conservative. I designed the reinforcement in accordance with the Design Guide presented on Mirafi's website.

The basics of the problem are:
1H:1V slope, 15' tall
Geotextile wrapped outer surface with rip rap face
reinforced soil - c = 0 phi = 30 unit weight = 125 pcf
Foundation Soil - c = 0 phi = 34 unit weight = 120 pcf
Retained backfill - c =0 phi = 30 unit weight = 125 pcf
surcharge = 250 psf
GW at 11' from crest of slope
Backslope = 0 degrees


Preliminary design in accordance with Mirafi's step by step design guide and using a FS=1.5 indicates a geogrid length of 17' and spacing of 2.5 to 4.0 feet. I modeled this in RSS and got a FS = 1.1.

Does anyone have experience with RSS? I know that the program has been upgraded significantly, but the only software I have access to is RSS and XSTABL. Is RSS ultra conservative?

Thanks

 

[jdonville]

bucknell06,

Check out FHWA NHI-00-043 and run your own calcuations based on the FHWA design guidance. There is also a relatively recent NCHRP publication available for MSE walls with flexible facing - I haven't read it but might be applicable to your application.

Jeff