Simplified Air Permeameters for Soil in Place

Abstract A simplified basic design is described and utilized in the construction of three field air permeameters. The basic design incorporates features of a gasometer and consists of a float, an annular water‐filled reservoir and an inlet tube. The float, which is open‐bottomed, rests on the water in the reservoir, to form an air chamber. The inlet tube is affixed to the soil and is also fastened to the inner wall of the reservoir. The air from the air chamber enters into the soil by passing down through a tube, which forms the inner wall of the reservoir, and through the inlet tube into the soil. The float falls as the air enters the soil. The rate of fall is a measure of the permeability. The effective volume of air provided by this type of permeameter is much larger than that provided by previous equipment of similar size. Each of the three field air permeameters was designed for one of these special purposes: (a) to measure permeability to a given depth, (b) to measure permeability to a given depth and be able to use a part of the same equipment for other types of physical measurements, without disturbing the soil, (c) to measure permeability of thin soil layers, as crusts, or silted‐over surface soil. Data are given to show the type of results which can be obtained with these permeameters.