Laboratory Investigation of the Effect of Initial Dry Density and Grain Size Distribution on Soil–Water Characteristic Curves of Wide-Grading Gravelly Soil

Wide-grading gravelly soils are often encountered in debris flow source areas. To perform stability analyses under rainfall conditions, the soil–water characteristic curves (SWCC) are significant. However, the studies for SWCC of wide-grading gravelly soils are rare. In order to investigate the effects of initial dry density and grain size distribution on the SWCCs of wide-grading gravelly, a large-scale osmotic column, allowing the measurement of both volumetric water content and matric suction at various levels, was fabricated for a series of osmotic column tests. The test data were best-fitted to Van Genuchten equation using a least-squares algorithm and found that both the initial dry density and grain size distribution had a greater effect on the SWCCs. An increase in the initial dry density resulted in an increase in water retention capacity. The air entry value and residual volumetric water content increased linearly with increases in the initial dry density, whereas the maximum slope of SWCC decreased linearly with increases in the initial dry density. The air entry value and residual volumetric water content increased linearly with increases in the fine content (particle diameter <0.075), whereas the maximum slope increases linearly with increases in the effective size, d10. © 2017, Springer International Publishing AG.