SOIL-WATER CHARACTERISTIC CURVES FOR COMPACTED CLAYS

Soil-water characteristic curves (SWCCs) are presented for four compac ted clay barrier soils that were prepared at different compaction wate r contents (dry, wet, and optimum water content) and compactive effort s (standard and modified Proctor). The SWCCs were measured in the labo ratory using pressure plate extractors. The shape of the SWCC depends on compaction water content and compactive effort, but compaction wate r content is more important. Compaction at higher compaction water con tent or with greater compactive effort results in larger air entry. Al so, clays with higher plasticity index have greater air-entry suction. Changes in the shape of the SWCC are consistent with changes in pore size that occur by varying compaction conditions and with the mineralo gical composition of the soils. These changes in the SWCC also are ref lected in the van Genuchten and Brooks-Corey parameters, which were ob tained from least-squares fits to the SWCC data. Regression equations are presented that can be used to estimate the van Genuchten parameter s alpha and n from compaction water content, compactive effort, and pl asticity index.