An index value for characterizing hardsetting soils by fall-cone penetration

The measurement of fall-cone penetration on air-dried and slowly rewetted subsamples (< 1 mm) at different water contents characterizes hardsetting and non-hardsetting soils by differences in their maximum resistance to penetration (RP_max), the water content (WC_max) at RP_max, and the amount of water adsorbed between the two values of 0.5 × RP_max, called ‘insensitivity’ I. The insensitivity I is strongly correlated with the contents of organic matter and iron oxides which are considered as soil components improving aggregation. The insensitivity may be used to identify hardsetting soils. These have I-values < 7, whereas non-hardsetting soils have I-values > 10.