Modified Pressure Plate Apparatus and Column Testing Device for Measuring SWCC of Sand

The determination of soil-water characteristic curve (SWCC) is of major concern in unsaturated soil mechanics. For decades experimental and theoretical studies are performed to investigate the constitutive relationship between soil suction and volumetric water content. The major objective of our study is to generate an extensive experimental database for sand with a relevant suction range of just a few kPa. This database enables to derive conclusions on the sensitivity of hydraulic properties regarding different experimental procedures. Further, one objective is the comparison of results for SWCC derived from steady state and transient state tests. While the first type of tests considers equilibrium states, the subsequent test is related to non-equilibrium states. Experimental results are generated from a so called homogenous element test (modified pressure plate apparatus) and an initial boundary value experiment (column testing device) considering different hydraulic loading path directions. The experiments are analysed for sand with different initial states. Finally results are presented for SWCC including initial curves, main curves, and scanning paths. Discussion is focused on transient state versus steady state flow tests. No significant dynamic effects are observed for the sand studied. Results of well controlled element tests compare very well to initial boundary value experiments implying higher experimental efforts.