Infinite Slope Stability (Factor of Safety)

Simple infinite slope model with dry, static water and seepage-parallel conditions. Use SI (kN/m³, kPa, m) or US (pcf, psf, ft) consistently.

Inputs

Current units: SI – γ in kN/m³, c′ in kPa, z in m.

Slope angle βdeg

Slip plane depth zm (vertical)

Unit weight γkN/m³ (natural / unsat)

Sat. unit weight γ_satkN/m³

Cohesion c′kPa

Friction angle φ′deg

Water table depth z_wm below surface (0 = at surface)

Condition

Results

Enter slope and soil parameters, then click Compute FS to see stresses and factor of safety.

Model assumes: infinite slope, plane parallel to surface at depth z, unit width, Mohr–Coulomb strength τ_res = c′ + σ′ tan φ′. For seepage-parallel case, driving shear from γ_sat, effective normal from γ′ = γ_sat − γ_w.

Parametric FS plot

Parameter to vary

Number of pointsfor curve

Uses current inputs, varying β around the specified value.

FS curve

Curve shows how FS changes when the selected parameter (β or z) is varied around the current input value.