Consolidation Parameters: LOESS to PEAT
Typical consolidation parameters (Cc, Cr, Cv, Ca) by soil type for settlement analysis — compression index, recompression index, coefficient of consolidation, and secondary compression coefficient
| soil description | ca cc ratio max (dimensionless) | ca cc ratio min (dimensionless) | cc max (dimensionless) | cc min (dimensionless) | cc typical (dimensionless) | cr cc ratio max (dimensionless) | cr cc ratio min (dimensionless) | cv ft2 day max (ft^2/day) | cv ft2 day min (ft^2/day) | notes | ocr guidance | void ratio max (dimensionless) | void ratio min (dimensionless) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| LOESS | 0.008 | 0.002 | 0.3 | 0.05 | 0.15 | 0.15 | 0.08 | 2 | 0.1 | Windblown silt; collapse settlement (hydroconsolidation) key concern; ASTM D5333 for collapse potential; not moisture sensitive until wetting | OCR=2 to 6; collapse potential when wetted at low overburden; collapsible if double oedometer Cc(wet) > Cc(dry) | 1.2 | 0.5 |
| MEDIUM_CLAY | 0.012 | 0.005 | 0.5 | 0.15 | 0.3 | 0.2 | 0.1 | 0.5 | 0.05 | Medium stiff clay: Cv 0.05-0.5 ft2/day typical; Cc from Terzaghi Peck Cc~0.009(LL-10); secondary settlement minor for OC soils | OCR=1.5 to 3.0; lightly to moderately overconsolidated; higher shear strength than soft clay | 1.2 | 0.5 |
| NORMALLY_CONSOLIDATED_SILT | 0.015 | 0.005 | 0.4 | 0.1 | 0.2 | 0.18 | 0.08 | 1 | 0.05 | ML inorganic silt; Cc=0.1-0.4; Cv from Schmertmann (1955) correlation with qc; SPT less reliable | OCR~1.0 to 1.5; Cv higher than clay; short consolidation time; settlement occurs quickly | 1.5 | 0.5 |
| ORGANIC_SILT | 0.04 | 0.015 | 1.2 | 0.3 | 0.6 | 0.25 | 0.12 | 0.03 | 0.001 | ML-OL soils; organic silt: Cv typically 1-100x lower than equivalent inorganic silt; long term creep significant | OCR~1.0 to 1.5; secondary settlements often 20-40% of primary for organic silts | 3 | 1 |
| PEAT | 0.1 | 0.04 | 6 | 1.5 | 3 | 0.3 | 0.1 | 0.005 | 0.0001 | Fibrous peat Cc 3-10+; amorphous peat Cc 1-5; Ca/Cc 0.04-0.10 (Mesri 1973); Cv very low; H2O content 300-1000% | OCR~1.0; highly compressible; secondary consolidation often exceeds primary; not suitable as foundation material without improvement | 15 | 5 |
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