Work out slope stability factor instantly with clear inputs, formula shown and shareable results.
For a long slope with a shallow planar slip surface, the factor of safety is the available shear strength divided by the driving shear stress: (c + gamma z cos²beta tan phi) / (gamma z cos beta sin beta). Cohesion helps most at shallow depth, which is why a cohesive slope can stand steeply until it is undercut.
Infinite slope stability
FoS = (c + gamma z cos²beta tan phi) / (gamma z cos beta sin beta)
Preliminary estimate only. Slope stability assessment must be carried out by a qualified geotechnical engineer with groundwater data and appropriate analysis methods.
FoS = (c + gamma z cos²beta tan phi) / (gamma z cos beta sin beta). For a long slope with a shallow planar slip surface, the factor of safety is the available shear strength divided by the driving shear stress: (c + gamma z cos²beta tan phi) / (gamma z cos beta sin beta).
Positive pore pressure reduces effective stress and therefore the frictional term. A slope stable when dry can fail after rainfall with no change in geometry at all.
This calculator takes 4 inputs: Slope angle, Soil cohesion, Angle of internal friction, Depth to slip surface. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.