Ground engineering · Consolidation & preloading
Prefabricated vertical drains calculator
Radial consolidation with smear, time to target degree, triangular or square spacing.
Standard: Barron (1948) / Hansbo (1981) · Carrillo
Open the live calculator → All ground engineering calculators
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Drain spacing S | 1.5 | m |
| Pattern | Triangular (De = 1.05S) | |
| Band width a | 100 | mm |
| Band thickness b | 4 | mm |
| Smear ratio ds/dw | 2 | |
| kh/ks | 2 | |
| Method | Hansbo (with smear) | |
| ch | 3 | m²/yr |
| cv | 1.5 | m²/yr |
| Vertical drainage path | 8 | m |
| Target U (0–0.99) | 0.9 | |
| Check at time | 180 | days |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Equivalent diameter De | 1.575 | m |
| Drain diameter dw | 52 | mm |
| n = De/dw | 30.3 | |
| μ (hansbo) | 3.354 | |
| Time to U, radial only | – | days |
| Time to U, radial + vertical | – | days |
| Uh at check time | – | % |
| U combined at check time | – | % |
- ✗ Target reached by check time
Method, formulas and assumptions
- dw = (a + b)/2 (Rixner et al. 1986); De = 1.05S (triangle) or 1.128S (square)
- Barron: μ = n²/(n² − 1) ln n − (3n² − 1)/(4n²)
- Hansbo: μ = ln(n/s) + (kh/ks) ln s − 0.75
- Uh = 1 − exp(−8 Th/μ), Th = ch t / De²
- Carrillo: U = 1 − (1 − Uh)(1 − Uv)
Related ground engineering calculators
- Consolidation settlement — Primary settlement (NC or OC clay) and time to a degree of consolidation.
- 1D consolidation: multi-layer finite difference — Layered clay with different cv and mv, drained at the top, bottom or both. Solves the consolidation equation…
- Wick drains with preload: time–settlement (Hansbo) — Prefabricated vertical drains in a soft clay under a preload with surcharge. Equivalent drain diameter…
- Preloading with surcharge — Surcharge needed so that primary settlement under the permanent load is removed by a target time, with the…
- Settlement monitoring: Asaoka and hyperbolic prediction — Predicts the final settlement from settlement-plate readings at a constant interval by two independent…
- Stone columns (Priebe) — Area replacement ratio and basic settlement improvement factor for a stone column grid.
For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.