Abstract
In-situ air permeability (Ka, insitu) is a rapid field measurement that provides important information on soil-gas and water transport properties in soil. The Ka, insitu can be determined by using a shape factor taking account of field flow geometry effects on one-dimensional air flow. In this study, effects of lateral and bottom boundary conditions on the shape factor (G) and subsequent Ka, insitu were investigated by combining finite-element numerical simulations and a model experiment with repacked sand in a container. Results showed that calculated and measured values of G and Ka, insitu were highly dependent on the bottom boundary, and especially that a shallow zero-flux bottom boundary caused an underestimation of Ka, insitu. This shows that special care must be taken to determine the shape factor with due consideration to the proper boundary conditions. This is especially critical in the case of impermeable layers such as highly-compacted subsurface soil or a shallow groundwater table.
