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This paper describes the procedure and results of laboratory permeability-settlement tests on samples from a river deposit containing about half sand and half gravel. The tests were conducted (1) on specimens containing the sand fraction passing the No. 4 sieve, (2) on specimens containing the sand fraction plus various percentages of gravel with 3/4-in. maximum particle size, and (3) on specimens containing the sand fraction plus various percentages of gravel with 3-in. maximum particle size. The tests of (1) and (2) above were made on specimens of 8-in. diameter and 5-in. height, whereas those of (3) were made on large-scale specimens of 19-in. diameter and 9-in. height. The specimens were placed at different densities, and settlements were measured during a definite loading schedule during the permeability test. The results show that the permeability of both the small and large specimens containing 20 to 50 per cent gravel was considerably less than the permeability of the sand fraction alone. In addition, the permeability of specimens containing the 3/4-in. material was somewhat greater than those containing the 3-in. material. The permeability decreased with increase in placement density and, with the exception of the specimens containing 3/4-in. material, decreased with increasing load. The settlements increased with load and generally increased with gravel content. The study shows that the differences between the results of the small and large-scale tests are sufficient to justify the use of the latter where a reasonably close value of the permeability is required.
Jones, Chester W.
Engineer, U. S. Bureau of Reclamation, Denver, Colo.