RELATIVE AIR PERMEABILITY AS FUNCTION OF SATURATION IN SOIL VENTING

A key parameter in modeling soil-venting systems is relative air perme ability, determined as a function of liquid saturation. The focus of t he present study was to characterize the relationship of the relative air permeability as a function of air saturation in soil-venting syste ms. A new laboratory apparatus was used to simulate the soil venting a nd measure the air permeability of soil samples. Sand samples wetted w ith mixtures of water and gasoline at different ratios were used. It w as revealed that the prediction of relative air permeability for moist noncohesive soil can be made in terms of intrinsic permeability and a ir-filled porosity alone, and not the type of liquid present in the po res. Comparisons of measured data with existing relations for relative air permeability as a function of total liquid saturation were made t o determine the most accurate and practical forms for engineering appl ications. For the sand sample used, the evaluation revealed that compa red to the existing relations, a derived second-order polynomial expre ssion provides a good estimate of relative air permeability and does n ot require estimation of soil-water-retention curve parameters.