Geotechnical Engineering
Infinite Slope Factor of Safety Calculator
Screen shallow translational slope stability with an infinite slope model.
Parameter sketch
Infinite slope geometry
Labels update with the current input values so the formula symbols stay tied to the geometry.
Result
Factor of safety: 1.46
Normal stress
295.7
Driving stress
137.89
Pore pressure
59.14
Resisting stress
200.78
Factor of safety
1.46
Step-by-step calculation
- Normal stress = gamma z cos^2 beta = 295.7.
- Driving stress = gamma z sin beta cos beta = 137.89.
- Pore pressure ratio gives u = 59.14.
- FS = 200.78 / 137.89 = 1.46.
What this means
The slope is marginal in a screening sense and deserves closer evaluation.
Formula Used
FS = [c + (gamma z cos^2 beta - u) tan phi] / [gamma z sin beta cos beta]
Step-by-Step Example
A 25 degree slope with 3 ft soil thickness, c=75 psf, phi=28 deg, and ru=0.2 has a screening FS near 1.6.
Engineering Notes
Check units, assumptions, boundary conditions, groundwater, drainage, and whether the simplified method is appropriate before using a result in any project decision.
FAQ
When is this model appropriate?
It is most useful for shallow planar screening where the potential failure surface is roughly parallel to the ground.