The Factor of Safety is defined as the ratio of the available shear strength of the soil,
to that required to keep the slope stable. It is common practice to use the following
empirical guidelines for slope stability assessments:
|
Factor of Safety
|
Guidelines for limit equilibrium of a slope
|
|
< 1.0
|
Unsafe
|
|
1.0 - 1.25
|
Questionable safety
|
|
1.25 - 1.4
|
Satisfactory for routine cuts and fills,
Questionable for dams, or where failure would be catastrophic
|
|
> 1.4
|
Satisfactory for dams
|