Soil Settlement: Terzaghi & AASHTO Guide
The Soil Settlement Calculator predicts immediate, primary consolidation, and secondary compression using Terzaghi’s 1D theory and AASHTO methods. It includes preload, wick drains, and time-rate analysis for footings and embankments.
What is Soil Settlement?
Vertical deformation under load. Types:
- Immediate: Elastic (sand)
- Consolidation: Pore water expulsion (clay)
- Secondary: Creep (long-term)
Why Control Settlement?
Prevents:
- Differential Settlement: Structure tilt
- Pavement Cracking: Embankment
- Utility Damage: Pipes
- Costly Remediation: Grouting
Use with our Aggregate Calculator for preload fill.
Settlement Components
| Type | Equation | Time |
|---|---|---|
| Immediate | S_i = q B (1-ν²)/E_s | Instant |
| Consolidation | S_c = (Cc H / (1+e0)) log((σ'0 + Δσ)/σ'0) | Months–years |
| Secondary | S_s = (Cα H / (1+e0)) log(t2/t1) | Decades |
How to Calculate
Step-by-step:
- Determine Δσ: Boussinesq or 2:1
- Classify OCR: NC, OC
- Compute S_c: Cc or Cr path
- Time-rate: Tv = Cv t / H_d²
- Preload: Remove after 90% consolidation
Our calculator automates all.
Practical Applications
Used for:
- Buildings: Mat foundations
- Embankments: Approach fills
- Tanks: Ring walls
- Bridges: Abutments
Pair with our Concrete Calculator for footings.
Tips for Mitigation
Best practices:
- Wick Drains: Reduce t90 by 90%
- Preload + Surcharge: Over-consolidate
- Deep Foundations: Piles to bedrock
- Soil Improvement: Stone columns
Common Mistakes to Avoid
Avoid:
- Ignoring OCR: Overestimate S_c
- No Time-Rate: Delay construction
- Wrong H: Partial drainage
- No Secondary: Long-term issues
Advanced Considerations
For complex cases:
- 3D effects (finite layer)
- Undrained loading
- Rate-dependent creep
- PVD smear zone
Conclusion
Accurate settlement prediction prevents structural distress. Our Soil Settlement Calculator delivers Terzaghi-compliant results instantly. Combine with our Steel Weight Calculator for sheet piles. Explore our full suite of Construction Calculators for complete geotech design.