Settlement Analysis Calculator helps estimate vertical soil settlement under applied loads using either consolidation or elastic (immediate) methods. It provides preliminary values for use during early foundation design stages.
About consolidation settlement. Consolidation settlement occurs in saturated cohesive soils (like clays) due to gradual expulsion of water from soil pores under an applied load. It can take months or years to complete. Key parameters include the compression index (Cc), initial void ratio (e₀), layer thickness (H), initial effective vertical stress (σ′₀), and the increase in vertical stress (Δσ).
About elastic (immediate) settlement. Elastic settlement happens immediately after load application and is typical for coarse-grained soils (like sands) or the immediate elastic response of clay before consolidation. It depends on applied pressure (q), footing width (B), soil elastic modulus (E), Poisson’s ratio (ν), and an influence factor (Iₛ) that reflects footing shape and depth effects.
About units. All calculations are performed internally in SI units. Metric units are meters (m), kilopascals (kPa), and millimeters (mm). Imperial equivalents are feet (ft), pounds per square inch (psi), and inches (in). You can toggle the unit system to view and enter values in either system.
Calculation.
Consolidation formula (primary consolidation settlement):
s = (Cc / (1 + e0)) × H × log10((σ′0 + Δσ) / σ′0)
(where: Cc = compression index, e0 = initial void ratio, H = compressible layer thickness, σ′0 = initial effective vertical stress, Δσ = increase in vertical stress)
Elastic formula (immediate settlement):
s = (q × B × (1 − ν²) × Is) / E
(where: q = applied pressure, B = footing width, ν = Poisson’s ratio, Is = influence factor, E = soil elastic modulus)
Examples:
- Example 1 (Consolidation): Cc = 0.25, e₀ = 0.80, H = 2.0 m, σ′₀ = 100 kPa, Δσ = 50 kPa → s = (0.25 / 1.8) × 2 × log₁₀((100+50)/100) ≈ 19.2 mm
- Example 2 (Elastic): q = 200 kPa, B = 2.0 m, E = 20000 kPa, ν = 0.30, Iₛ = 1.12 → s = (200×2×(1−0.09)×1.12)/20000 ≈ 19.2 mm
- Example 3 (Elastic): q = 300 kPa, B = 1.5 m, E = 25000 kPa, ν = 0.25, Iₛ = 1.0 → s = (300×1.5×(1−0.0625)×1.0)/25000 ≈ 15.8 mm
Corresponding tools. To evaluate soil bearing capacity, use the Soil Bearing Capacity Calculator. To estimate loads on footings, try the Isolated Footing Load Calculator.
