It is difficult to obtain a reliable water-retention curve (WRC) for coarse-grained soils without organic matter. As a result, the field behavior of draining layers in engineering problems may be poorly predicted. The main goal of this paper is to develop predictive methods for the WRC of coarse-grained soils based on long-column, long-duration drainage test data and available soil properties. The paper first shows that predictive models perform poorly for coarse-grained soils, but four descriptive models can correctly fit the test data. Second, it provides predictive equations for the air-entry value (AEV), residual suction ur, and residual water content θr as simple functions of the effective size d10 and void ratio e. Third, it provides new formulas that relate d10 and e to the parameters of descriptive models; thus, enabling them to become very simple to use predictive models for ed10 > 0.05 mm. The paper finally shows that small variations in d10 and e have more influence on the saturated permeability than on the WRC parameters.
R. Chapuis, I. Masse, B. Madinier
Geotechnical Testing Journal