Foundation Settlement Calculator

Calculator Inputs

Foundation type

Pressure type

Foundation pressure (kPa)

Width B (m)

Length L (m)

Foundation depth Df (m)

Soil modulus Es (kPa)

Poisson ratio ν

Shape factor Is

Rigidity factor Ir

Influence factor If

Water table factor

Embedment factor

Compression index Cc

Initial void ratio e0

Compressible layer thickness H (m)

Initial effective stress σ'0 (kPa)

Stress increase Δσ (kPa)

Coefficient mv (m²/kN)

Coefficient cv (m²/s)

Drainage path Hd (m)

Time for settlement estimate (years)

Creep settlement (% of primary + immediate)

Use site specific values whenever available. The calculator supports immediate settlement, primary consolidation, time rate effects, creep allowance, and distortion indicators.

Example Data Table

Sample footing inputs

Case	Pressure (kPa)	B (m)	L (m)	Es (kPa)	Cc	e0	H (m)	σ'0 (kPa)	Δσ (kPa)
Office footing A	180	2.0	3.0	18000	0.25	0.85	4.5	95	70
Warehouse footing B	220	2.5	2.5	24000	0.19	0.78	5.0	120	85
Strip footing C	140	1.8	6.0	15000	0.28	0.92	4.0	88	60

Formula Used

This calculator combines elastic immediate settlement, primary consolidation, time rate estimation, and an optional creep allowance for preliminary engineering review.

1) Immediate settlement
S_i = q × B × (1 − ν²) × I_s × I_r × I_f / E_s

2) Primary consolidation by compression index
S_c = [C_c / (1 + e₀)] × H × log₁₀[(σ′₀ + Δσ) / σ′₀]

3) Primary consolidation by m_v
S_c = m_v × Δσ × H

4) Time factor
T_v = c_v × t / H_d²

5) Degree of consolidation
For small T_v: U ≈ √(4T_v/π)
For larger T_v: U ≈ 1 − exp(−π²T_v/4)

6) Long term settlement
S_total = S_i + S_c + S_creep

These relations are simplified. Actual settlement depends on stress distribution, stratification, drainage conditions, stress history, groundwater, construction sequence, and footing rigidity.

How to Use This Calculator

Choose the footing shape and select whether your entered pressure is net or gross.
Enter footing dimensions, embedment depth, and elastic soil properties.
Provide consolidation inputs using either Cc and e0, or mv if that is your preferred method.
Enter cv, drainage path, and time to estimate settlement development with time.
Add optional correction factors for groundwater, embedment, rigidity, and influence.
Click the calculate button to show the results above the form.
Review immediate, consolidation, creep, and total settlement values with distortion indicators.
Use CSV or PDF export for documentation or early design comparison.

FAQs

1. What settlement types does this calculator estimate?

It estimates immediate settlement, primary consolidation settlement, time dependent settlement progress, optional creep settlement, and simple distortion ratios for preliminary footing review.

2. Can I use gross pressure instead of net pressure?

Yes. When gross pressure is selected, the tool subtracts a basic overburden estimate using foundation depth and an assumed unit weight to approximate net pressure.

3. When should I use Cc and e0?

Use Cc and e0 when you have consolidation test data and want a classic logarithmic primary settlement estimate for normally consolidated or lightly overconsolidated fine grained soils.

4. When is mv more useful?

Use mv when your investigation report gives coefficient of volume compressibility directly. It can provide a convenient settlement estimate for a defined stress range.

5. Does this replace a geotechnical design report?

No. This calculator is for screening, comparison, and concept design. Final settlement assessment should follow project specific investigation, laboratory testing, and professional interpretation.

6. Why is the drainage path important?

Drainage path controls consolidation speed. Shorter drainage paths usually increase the rate of dissipation of excess pore water pressure and reduce the time needed.

7. What does angular distortion indicate?

Angular distortion gives a simple measure of deformation severity across a span. Engineers often compare it with allowable serviceability limits for structural performance.

8. Why add a creep percentage?

Some soils continue deforming after primary consolidation. The creep percentage adds a practical allowance for long term movement when a detailed secondary compression model is unavailable.