GAS-DIFFUSION THROUGH COMPACTED SANDS

It is generally believed that D(e)/D0, which is the ratio of the gas diffusion coefficient in soils to that in free air, does not depend on the kind of diffusing gases if the gases do not react with the soil. This hypothesis was examined using N2, CH4, and H2 gases. Obtained values of D(e)/D0 were almost the same for these three gases. Next, the relationship between D(e)/D0 and n(a) was investigated experimentally in dry and wet sands, where n(a) is the air porosity. The sand samples were prepared by compaction. The percentage of fines contained in the sand was adjusted in the range from 0% to 50% by weight. The experimental results and the data from the literature show that the relationship in dry sand is described by the equation D(e)/D0 = n(a)-mu. The constant mu is dependent on the percentage of fines. The relationship in wet sand is more appropriately described by the equation D(e)/D0 = alpha(n(a) - beta) in the air porosity range less than 0.3 where alpha and beta are constants.