Collapsible Loess in Iowa
1973
Handy, Richard L.
The collapsibility, or tendency towards rapid consolidation or settlement upon saturation by water, of many C-horizon loess soils constitutes and important physical property pertinent to soil genesis, erosion, and engineering. The potential of a loess soil to collapse upon saturation by water may be established from undisturbed samples saturated while under load in a consolidation testing machine. A more convenient criterion, that the saturation moisture cntent must not exceed the liquid limit, was regressed against 0.005 mm clay content determined by the hydrometer method, and indicated that C-horizon loess containing less than 20% 0.005 mm clay is very likely to be collapsible; with 30% clay there is a 50% probability of collapse, and with over 40% clay there is only a small likelihood of collapse. These percentages were compared to published clay content contours to estimate the areal extent of collapsible loess in Iowa. To convert to 0.002 mm clay content, hydrometer test 0.005 mm clay contents were regressed against pipette test 0.002 mm clay contents to give X₀₀₂ = 0.8X₀₀₅; thus the 0.002 mm clay contents corresponding to high, medium, and low probabilities of collapse are < 16%, 24%, and > 36% caly, respectively.
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