Foundation Settlement Calculator

Estimate immediate elastic settlement and consolidation settlement of shallow foundations. Includes time estimate for 90% consolidation.

Inputs

Applied Pressure (q)

psf

Foundation Width (B)

Soil Elastic Modulus (E)

psf

Poisson's Ratio (ν)

Tab to move between fields

Results

Immediate Settlement

0.21 in

Consolidation Settlement

7.1 in

≈ 2 credit cards

Total Settlement

7.31 in

≈ 2 credit cards

Time for 90% Consolidation69.6 months

How to Use This Calculator

Enter applied foundation pressure (q), foundation width (B), soil elastic modulus (E), and Poisson's ratio.
Set compression index (Cc), initial void ratio (e₀), and other consolidation parameters.
Review immediate settlement, consolidation settlement, and total expected settlement.
Settlement exceeding 1 inch typically requires redesign or ground improvement.

How the result changes with Applied Pressure (q)

Applied Pressure (q)	Immediate Settlement	Consolidation Settlement	Total Settlement
2,090	0.22 in	7.1 in	7.32 in
7,065	0.76 in	7.1 in	7.86 in
13,035	1.4 in	7.1 in	8.5 in
18,010	1.94 in	7.1 in	9.03 in

What each input means

Applied Pressure (q): Net bearing pressure applied by the foundation. Total load divided by footing area.
Foundation Width (B): Width (or diameter) of the foundation for immediate settlement calculation.
Soil Elastic Modulus (E): Elastic modulus of the soil. Soft clay ≈ 50,000-200,000; stiff clay ≈ 500,000-1,000,000; sand ≈ 500,000-3,000,000 psf.
Poisson's Ratio (ν): Poisson's ratio of the soil. Clay ≈ 0.40-0.50; sand ≈ 0.25-0.35.
Compression Index (Cc): Compression index from consolidation test. Soft clay ≈ 0.3-1.0; stiff clay ≈ 0.1-0.3.
Initial Void Ratio (e₀): Initial void ratio of the compressible layer. Dense sand ≈ 0.4-0.6; soft clay ≈ 1.0-2.5.
Compressible Layer Thickness: Thickness of the compressible soil layer that will undergo consolidation.
Stress Increase at Mid-Layer (Δσ): Increase in vertical stress at the middle of the compressible layer, from Boussinesq or 2:1 distribution.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Applied Pressure (q) = 2000, Foundation Width (B) = 6, Soil Elastic Modulus (E) = 500000, Poisson's Ratio (ν) = 0.3 = 8 input(s) provided
Calculate Immediate Settlement
0.21 = 0.21
Calculate Consolidation Settlement
7.1 = 7.1
Calculate Total Settlement
Total Settlement
7.31 = 7.31
Calculate Time for 90% Consolidation
69.6 = 69.6

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