Schmertmann Elastic Settlement Calculator
By Mohan Dangi
Foundation Parameters
Soil Layer Details
| Layer | Thickness Δz (ft) | Corrected SPT N | Soil Type | Mid Depth (ft) | Auto Iz | Elastic Modulus Es (ksf) | IzΔz/Es | Remove |
|---|---|---|---|---|---|---|---|---|
| 1 | ||||||||
| 2 | ||||||||
| 3 |
Dynamic Schmertmann Strain Influence Diagram
Results
Click "Calculate Settlement" to generate results.
Schmertmann Method – Theory & Explanation
The Schmertmann method is widely used for estimating the immediate elastic settlement of shallow foundations resting on cohesionless soils. The method is based on vertical strain distribution beneath the footing and considers:
- Foundation geometry
- Foundation embedment depth
- Applied pressure
- Soil stiffness variation
- Strain influence distribution
- Layered soil conditions
Main Settlement Equation
ΔH = C₁ × C₂ × q × Σ(Iz Δz / Es)
| Parameter | Description |
|---|---|
| ΔH | Elastic settlement |
| C₁ | Depth correction factor |
| C₂ | Time correction factor |
| q | Net foundation pressure |
| Iz | Vertical strain influence factor |
| Δz | Thickness of soil layer |
| Es | Soil elastic modulus |
Depth Correction Factor
C₁ = 1 - [ 0.5 γ Df / (q - γDf) ]
Elastic Modulus Correlation
Es = 10(N + 15)
Schmertmann Strain Influence Distribution
- Maximum strain occurs at depth = 0.5B
- Influence depth generally extends to 2B
- Iz(max) = 0.5 for square footing
- Iz(max) = 0.6 for strip footing
Automatic Soil Classification
| SPT N Value | Classification |
|---|---|
| N < 4 | Very Loose Sand |
| 4 ≤ N < 10 | Loose Sand |
| 10 ≤ N < 30 | Medium Dense Sand |
| 30 ≤ N < 50 | Dense Sand |
| N ≥ 50 | Very Dense Sand |
Important Notes:
- Applicable mainly for cohesionless soils.
- Immediate elastic settlement only is calculated.
- Groundwater correction should be considered separately.
- Influence depth is generally limited to 2B below footing.
- Results are intended for educational and preliminary design purposes only.
References
- Schmertmann, J.H. (1970), Static Cone to Compute Static Settlement Over Sand , Journal of Soil Mechanics and Foundations Division, ASCE, Vol. 96, No. SM3, pp. 1011–1043.
- Schmertmann, J.H., Hartman, J.P., and Brown, P.R. (1978), Improved Strain Influence Factor Diagrams , Journal of Geotechnical Engineering Division, ASCE, Vol. 104, No. GT8, pp. 1131–1135.
- Bowles, J.E. (1996), Foundation Analysis and Design , 5th Edition, McGraw-Hill International Editions.
- Das, B.M. and Sivakugan, N. (2018), Principles of Foundation Engineering , 9th Edition, Cengage Learning.
- Coduto, D.P., Yeung, M.R., and Kitch, W.A. (2016), Foundation Design: Principles and Practices , 3rd Edition, Pearson Education.
- NAVFAC DM-7.1 (1982), Soil Mechanics, Foundations, and Earth Structures , Naval Facilities Engineering Command, U.S. Department of Defense.
- IS 6403 : 1981, Code of Practice for Determination of Bearing Capacity of Shallow Foundations , Bureau of Indian Standards.
- IS 8009 (Part 1) : 1976, Code of Practice for Calculation of Settlement of Foundations , Bureau of Indian Standards.
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