Soil Gas Permeability as Influenced by Soil Gas-Filled Porosity
- Kevin P. McCarthy and
- Kirk W. Brown
The need to characterize the fundamental gas flow properties of soils has taken on new significance in recent years with the advent of induced soil venting as a remediation technique for contaminated soils. The purpose of this study was to characterize the relationship between soil gas permeability and soil gas-filled porosity, and the effect of various soil physical properties on this relationship. A gas permeameter was developed to study gas flow through undisturbed soil cores from two horizons in each of three soil series. Measurements of the pressure difference across the soil core at varying flow rates were used to calculate gas permeability (k), from soil having a range of soil gasfilled porosities (Ea). Bulk density, pore-size distribution, and particle-size distribution were also measured on each soil. In soils containing <20% clay, the relationship between the gas-filled porosity and the gas permeability was adequately represented by a linear equation across the range (0.4–33%) of gas-filled porosities tested. The linear equation was unique to each soil studied and a general equation representative of all soils could not be established. Structured soils exhibited greater permeabilities than poorly structured soils, presumably due to the larger inter-aggregate flow channels characteristic of structured soils. In poorly structured soils, finer textures were less permeable than coarser textures. Three of four soils with <20% clay exhibited anisotropic behavior, with higher permeabilities in the horizontal direction than in the vertical direction, related to their alluvial origin.
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