Retaining Wall Factor of Safety 1

[fzlo]

I've been trying to find the typical safety factor for overturning for a retaining wall. IBC states that the minimum overturning safety factor was at 1.5 but I had a talk with one of the geotechs that I went to school with and he had told me that the minimum for overturning is 2.0 and that 1.5 is too low to start an analysis.

 

[ProgrammingPE]

I've always designed retaining walls to meet the IBC code limit of 1.5. You're always welcome to be more conservative especially if it is early in design, and the ground elevations may change.

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[Tomfh]

Is 1.5 the only factor you apply? Often in codes you apply another factor (Eg a capacity reduction factor) which results in roughly 2:1 factor of safety

 

[fzlo]

Tomfh,

I have never used another factor for the retaining wall. The most I have changed it is when I use the ASCE load combination which gives me a factor of 1.67

 

[Shanman_]

1.5 factor of safety for overturning is correct. Unless you are dealing with a seismic load case, in which you may use a factor of safety of 1.1 as allowed by the IBC. There is no additional rule I've ever heard of going above and beyond that.

The only time I've heard a Geotech talk about safety factors when he/she is determining soil values to recommend their reports (ie: 6,000 psf tested bearing strength becomes 3,000 psf bearing allowable based on factor of safety of 2.0 for Dead Plus Live or 4,000psf allowable based on 1.5 factor of safety for Short-term conditions such as wind and seismic)

 

[Teguci]

Greater than 1.0

I've used 1.5 for overturning and 2.0 for sliding with bearing being whatever safety factor the geotech has already baked in.