Foundations

Elastic Settlement Calculator

Estimate immediate shallow-foundation settlement using net pressure, footing width, soil modulus, Poisson ratio, and an engineer-selected influence factor.

Engineering schematic

Immediate elastic settlement model

Static symbolic figure. Enter project values in the calculator fields below.

Shallow footing section showing net pressure, footing width, downward settlement, idealized stress influence zone, soil modulus, Poisson ratio, and influence factor. — Symbols
qnet
net service pressure applied at foundation level
B
footing width
Es, ν
soil elastic modulus and Poisson ratio
Is, si
combined influence factor and immediate settlement

Result

Estimated immediate settlement: 0.44 in

Pressure/modulus ratio

0.006

Elastic settlement

0.44 in

Influence factor

1.12

Step-by-step calculation

Elastic settlement
$s_i=\frac{q_{\mathrm{net}}B}{E_s}\left(1-\nu^2\right)I_s$
Substitution
$s_i=\frac{3\times6}{500}\left(1-0.3^2\right)\left(1.12\right)$
Estimated settlement
$s_i=0.44\ \mathrm{in}$

What this means

This is an immediate elastic settlement screening value. Compare total and differential movement against project-specific serviceability criteria using an appropriate subsurface model.

Important limitations

This calculation does not include consolidation, secondary compression, layered-soil integration, rigidity corrections, stress history, or construction sequence.

Assumptions

Homogeneous isotropic elastic soil idealization
Flexible footing influence represented by the entered factor
Net service pressure
Modulus represents the relevant stress range and influence depth

Formula Used

s_i=\frac{q_{\mathrm{net}}B}{E_s}\left(1-\nu^2\right)I_s

Step-by-Step Example

For qnet = 3 ksf, B = 6 ft, Es = 500 ksf, nu = 0.30, and Is = 1.12, the simplified immediate settlement is about 0.44 in.

Engineering Notes

Select modulus and influence factor for the soil profile, footing rigidity and shape, embedment, stress range, and drainage condition.
Settlement influence extends below the footing; a single modulus can be misleading where compressible layers occur within the stress bulb.
Calculate consolidation and secondary settlement separately where cohesive or organic soils govern time-dependent movement.
Foundation serviceability normally depends on differential settlement, angular distortion, construction sequence, and structural tolerance as well as total settlement.

FAQ

Is this total foundation settlement?

No. It estimates an immediate elastic component only. Consolidation, secondary compression, collapse, heave, and construction effects may also matter.

Which soil modulus should I use?

Use a project-specific modulus representative of the relevant strain level, drainage condition, and depth of influence. Modulus selection is often the largest source of uncertainty.

What is the influence factor?

It combines corrections that may account for footing shape, rigidity, embedment, and the point where settlement is evaluated. Use a value from the selected method, not a generic default without review.

Related Engineering Guides

Elastic Foundation Settlement ExampleFollow an SI-unit calculation and modulus sensitivity check.Foundation Settlement GuideDistinguish immediate, consolidation, secondary, and differential movement.Mat and Raft FoundationsSee why large foundations require a settlement profile and soil-structure interaction.