Slope Stability Analysis Geotechnical Engineering

Analyze slope stability for earthworks, dams, and excavations. Calculate the safety factor (FS) for different geological conditions.

1. Slope & Soil Inputs

Slope angle (θ) [degrees]

Slope height (H) [m]

2. Soil Properties

Soil cohesion (c) [kPa]

Friction angle (φ) [degrees]

3. Water Table Depth

Water table depth [m]

Results

Theory & Formulas (Infinite‑Slope quick check)

Unit weights used (default): γ_unsat = 18 kN/m³, γ_sat = 20 kN/m³, γ_w = 9.81 kN/m³; submerged γ′ = γ_sat − γ_w.

Effective γ is a weighted average over height H using γ_unsat above water table and γ′ below it.

Driving shear stress (per unit width): τ = γ_eff · H · sinθ · cosθ
Shear strength on the plane (Mohr–Coulomb): τ_f = c + (γ_eff · H · cos²θ) · tanφ
Safety factor (Sliding): FS = τ_f / τ = [ c + γ_eff H cos²θ · tanφ ] / [ γ_eff H sinθ · cosθ ]
Safety factor (Overturning) (moment ratio about toe, same mechanics for this idealization): FS_OT = M_restoring / M_overturning = FS

Typical targets: FS ≥ 1.3 (temporary), FS ≥ 1.5 (permanent). Use detailed methods (Bishop, Janbu, Spencer) for final design.