A field method of determining soil permeability
Murphy, Walter Dewitt
Master of Science
The permeability of soil -- its capacity to transmit water under pressure -- may be determined by indirect or direct laboratory methods or by field methods. Most field methods are useful only below the water table, but in this study a procedure for use above the water table was investigated. The method consists of inserting into the ground a pipe which has on its end a perforated cylinder. Water is allowed to flow into the soil and the time for the head to drop a given distance is measured. In addition, the natural water content and porosity of the soil is required. A correlation is made between field tests and direct laboratory tests in order to obtain an empirical equation for permeability involving time and percentage of air voids. In addition, another expression for permeability is found by making use of Darcy's law as applied to a flow net for the apparatus. The use of a model study on dry sands is found very useful in determining the shape of the flow pattern. Although some additional studies should be made on certain aspects of the method, it is felt that it may be recommended for use as a field method of determining permeability.