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Dispersive clays occur frequently in nature, possessing properties detrimental to agronomic tillage practices and to engineering structures such as dams, terraces, channels, etc. Surface erosion occurs readily, since the fines are easily detached and suspended in runoff water. Where water can enter cracks in dispersive clays, subsurface erosion usually develops rapidly and extensively in areas of strong relief under favorable climatic conditions.
For many years, the Soil Conservation Service has relied upon the Laboratory Dispersion Test as the benchmark for identification of these problem clays. Improved sampling techniques and the supplementary use of two field identification tests have been extremely helpful in recent years, particularly in embankment zoning. Liming the surface layers of dispersed clay embankments has provided a satisfactory means for stabilization. Three lime-treatment jobs have not been damaged in seven years. Aluminum sulfate is being evaluated on a field trial basis.
clays, soil mechanics, earthwork, earth dams, piping (erosion), soil stabilization, soil aggregates, soil chemistry, soil tests
Civil engineer, Soil Mechanics, U.S. Department of Agriculture Soil Conservation Service, Stillwater, Okla.