Site investigation · Laboratory: strength & consolidation
Coefficient of consolidation (root-time & log-time) calculator
cv from Taylor's t90 and Casagrande's t50, with permeability from k = cv·mv·γw.
Standard: AS 1289.6.6.1 · ASTM D2435
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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 |
|---|---|---|
| Specimen height at increment | 18.6 | mm |
| Drainage | Double (top & bottom) | |
| t90 (root-time) | 6.8 | min |
| t50 (log-time) | 1.7 | min |
| mv for the increment | 0.35 | 1/MPa |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Drainage path | 0.009 | m |
| cv (Taylor) = 0.848 Hdr²/t90 | 5.67 | m²/yr |
| cv (Casagrande) = 0.197 Hdr²/t50 | 5.27 | m²/yr |
| Permeability (from Taylor cv) | 0.000 | m/s |
- ✓ Methods agree within factor 2
Method, formulas and assumptions
- Drainage path = 18.6/2/1000 = 0.0093 m
- cv (Taylor) = 0.848 Hdr²/t90 = 0.848*0.0093^2/(6.8/525960) = 5.6729 m²/yr
- cv (Casagrande) = 0.197 Hdr²/t50 = 0.197*0.0093^2/(1.7/525960) = 5.2715 m²/yr
- Permeability (from Taylor cv) = 5.6729/31557600*0.35/1000*9.81 = 6.172e-10 m/s
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.