CONE PENETROMETER AND LIQUID LIMIT

The suitability of a simple expression, containing the specific gravity of soil particles, relating the plasticity index and compression index for soils at their plastic and liquid limits is tested by comparing predicted values with measured values of the compression index. A survey of the available research indicated that generally good correlation was found. It is considered possible that the relation should also depend on clay minerology although good agreement with the expression has been obtained on a wide range of soils. It is concluded that the cone penetrometer test described in BS 1377(1975) is simple, and although results do not correspond exactly with those determined using other devices, the water content at which a 30 deg, 80gf cone penetrates 20mm provides a useful index property for soils. (Author/TRRL)