Analysis of transient data from infiltrometer tests in fine-grained soils

Data collected during ring infiltrometer tests are often analyzed while ass uming either that the effect of gravity is negligible (early-time, transien t data) or that it is dominant (late-time, steady-state data). In this pape r, an equation is proposed for interpreting both early-time and late-time d ata measured during infiltration tests under falling head conditions. It is shown that the method used by previous authors for interpreting early-time data is a special case of the proposed equation. The equation is applied t o data collected during tests performed in fine-grained soils, and results are discussed. The analysis suggests that to assume a priori values of the soil sorptive number, as indicated in the literature for various soils, may in some cases lead to severely underestimated values of the saturated hydr aulic conductivity. Conversely, in low permeability soils, to assume steady -state gravity drainage may lead to order of magnitude overestimates of the saturated hydraulic conductivity, A dimensionless analysis provides charac teristic times that correspond either to the duration of the log-log half s lope displayed by early-time data or to the log-log unit slope characterist ic of late-time data.