Permeability Tests in Rigid-Wall Permeameters: Determining the Degree of Saturation, its Evolution, and its Influence of Test Results

This paper documents a method to determine the degree of saturation, Sr, of a soil specimen at any time during a rigid-wall permeameter test. This method first indicates that the tested specimen usually is not fully saturated. Then it is used to prove that the usual test termination criterion based on equality of inflow and outflow volumes may be misleading. Examples are provided where the two volumes were equal within 1 %, whereas Sr increased from 80 to 100 % and k increased by a factor of 4. Without knowing the technique to determine the Sr value at any time, the test would have been stopped prematurely and would have given some k(Sr) value for an unknown Sr with the risk of misinterpreting this result as k(Sr = 100 %). New equations for gas transfer between water and gas bubbles are also established and experimentally verified for specimens permeated with either deaired water or water over-saturated with air.