Slope Stability Calculator analyzes slope stability using input parameters such as soil type, slope angle, and groundwater conditions. It is useful for geotechnical and civil engineering projects. Learn how unit weight, cohesion, friction angle, and pore pressure control stability.
About units and symbols. Unit weight γ in kN/m³ (or lb/ft³), depth z in m (ft), cohesion c′ in kPa (psi), pore pressure u in kPa (psi), slope angle θ and friction angle φ′ in degrees.
About the infinite-slope model. It evaluates a shallow potential slide parallel to the ground surface—useful for long uniform slopes (cuts or embankments). It is a screening tool; detailed design may require limit-equilibrium software or site-specific investigations.
Calculation. The infinite-slope method expresses stability as a Factor of Safety (FoS), comparing resisting forces (cohesion and friction) against driving forces from soil weight and pore pressure.
FoS = [c′ + (γ z cos²θ − u) tanφ′] / (γ z sinθ cosθ).
- Example 1: γ = 18 kN/m³, z = 3 m, θ = 25°, c′ = 10 kPa, φ′ = 30°, u = 0 ⇒ FoS ≈ 1.55.
- Example 2 (marginal): same but u = 10 kPa ⇒ FoS ≈ 1.24.
- Example 3 (unsafe): increase θ to 35° with u = 10 kPa ⇒ FoS ≈ 0.92.
Corresponding tools.
See Retaining Wall Load Calculator (earth pressures), Cut & Fill, and conversions like Feet ⇄ Meters.
