Principles of Permeability Testing of Soils

The permeability of soils is a most important physical property since some of the major problems of soil and foundation engineering have to do with the recognition, evaluation, and proper handling of drainage problems encountered in the design and construction of structures. These problems include drainage of highways and airports, seepage through earth dams, uplift pressures beneath concrete dams and structures below ground water level, unwatering of excavated sites to permit construction in the “dry,” seepage pressures causing earth slides and failures of retaining walls, etc. In all of these, the permeability characteristics of soils have a controlling influence on the effective strength properties of the soils and on their responses under stress, and hence on stability conditions. Drainable soils will act essentially as “open systems” with free drainage and fully effective shearing strength, whereas soils of low permeability may act as “closed systems” under rapid application of stress, with the development of pore pressures and reduction in shearing strength. The determination of the permeability of soils is therefore a most important aspect of soil testing. The purpose of this paper is to formulate into a more complete form certain attitudes, concepts, and principles of a fundamental and comprehensive approach in permeability testing of soils and to increase the adequacy, reliability, and practical value of permeability data.