The present study investigates the consistency limits of two pure clay minerals kaolinite and montmorillonite, and the mixtures of each clay mineral with fine silica sand. Plotting the plasticity index data as a function of the liquid limit, allows the zones where mixtures with the same clay contents fall to be defined. In particular, the line corresponding to 50% clay (designated as the 0.5C-line), makes it possible to distinguish the points that lie above the line, namely silt (soils with clay < 50%), from the points lying below the line in the clay zone. A new plasticity chart, which aims to classify soils (< 425 μm) using the Atterberg limits, is defined. The silt and clay zones (separated from 0.5C-line) allow to classifing inorganic soils that contain platey clay minerals. Bolow these zones, should lie data of the soils that have particular characteristics (low plasticity), as organic soils and residual inorganic soils with non-platey clay minerals. This plasticity chart differs from that proposed by Casagrande, primarily in that the respective position of the silt and clay zones are reversed. In fact, on the new chart, the silt zone is found above the clay zone, because (contrary to what is believed) in inorganic soils, plasticity indexes being equal, the liquid limit increases as the clay content increases. As consequence, the clay zone lie below the silt zone (that is below the 0.5C-line). Several literature data from inorganic soils plotted on the two charts, confirm that the position of the clay and silt zones on Casagrande’s empirical chart are not accurate.

Classificazione dei terreni argillosi

GORI, UMBERTO
2005

Abstract

The present study investigates the consistency limits of two pure clay minerals kaolinite and montmorillonite, and the mixtures of each clay mineral with fine silica sand. Plotting the plasticity index data as a function of the liquid limit, allows the zones where mixtures with the same clay contents fall to be defined. In particular, the line corresponding to 50% clay (designated as the 0.5C-line), makes it possible to distinguish the points that lie above the line, namely silt (soils with clay < 50%), from the points lying below the line in the clay zone. A new plasticity chart, which aims to classify soils (< 425 μm) using the Atterberg limits, is defined. The silt and clay zones (separated from 0.5C-line) allow to classifing inorganic soils that contain platey clay minerals. Bolow these zones, should lie data of the soils that have particular characteristics (low plasticity), as organic soils and residual inorganic soils with non-platey clay minerals. This plasticity chart differs from that proposed by Casagrande, primarily in that the respective position of the silt and clay zones are reversed. In fact, on the new chart, the silt zone is found above the clay zone, because (contrary to what is believed) in inorganic soils, plasticity indexes being equal, the liquid limit increases as the clay content increases. As consequence, the clay zone lie below the silt zone (that is below the 0.5C-line). Several literature data from inorganic soils plotted on the two charts, confirm that the position of the clay and silt zones on Casagrande’s empirical chart are not accurate.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11576/2511973
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