ABSTRACT
The concept of air permeability of earth materials has been an important parameter to many branches of the earth sciences. Air permeability has been of particular interest to soil and agricultural scientists for decades as it relates to the aeration and gas exchange between soils and the atmosphere, to soil structure, and to the movement of surface and subsurface waters and its relation to irrigation problems. Additionally, chemical and petroleum engineers have exhaustively investigated the air permeability parameter as it relates to petroleum gas production and migration in oil field reservoirs. The more recent interest of soil gas movement in soils as it relates to the migration potential of hazardous, volatile vapors in the subsurface has focused renewed attention on the relationships between soil water content and the rate of gas movement through soils. Venting of gases from unsaturated soils has been used for the removal of methane from landfills, and noxious or explosive vapors that collect under and threaten buildings or utilities. A more recent offshoot of utilizing the permeable nature of soils to air flow is the evolution of a remedial strategy called soil vapor extraction, which involves inducing clean air flow through soils contaminated with highly volatile chemicals in an effort to strip them of contamination. The soil venting remedial technique is directly influenced by the air permeability parameter, where the design and engineering aspects and often the success hinge on its accurate quantification.
