Theory of soil air movement due to pressure fluctuations

✍ Scribed by B.A. Kimball; E.R. Lemon

• Publisher: Elsevier Science
• Year: 1971
• Weight: 876 KB
• Volume: 9
• Category: Article
• ISSN: 0002-1571
• DOI: 10.1016/0002-1571(71)90020-3

✦ Synopsis

An equation has been derived from which the air pressure at any point in the soil can be calculated from the variance spectrum of air pressure at the soil surface. From the equation, two additional equations have been derived, one permitting the calculation of the root mean square (rms) vertical velocity, and the second permitting the calculation of the rms displacement of the soil air. Using the latter two equations and an empirical equation to describe spectra obtained from field measurements, calculations showed that frequencies higher than 1 c/sec make the largest contribution to soil air velocity. Similar calculations showed that low frequencies below 1 c/day make the largest contributions to displacement. The contributions of high frequencies to both velocity and displacement were predicted to attenuate rapidly with depth. Increasing permeability caused a roughly proportional increase in the predicted velocity and displacement for most of the conditions studied. The total predicted rms velocity at the surface for all frequencies in the air pressure spectrum was of the same order of magnitude as values computed by other workers for single pressure waves.