Graphical Representation of the Mechanical Analyses of Soils

In view of the lack of uniformity in proposals for the graphical representation of grain-size distribution, this paper is presented in an effort to correlate various existing methods and concentrate them into one method which the writer believes would make a good standard for graphical representation. A semi-logarithmic co-ordinate system is used with the grain sizes plotted as abscissas on a logarithmic scale and cumulative percentages by weight plotted as ordinates. With curves so plotted, the grain-size distribution curves have been conventionalized by introducing straight lines. Such lines can be designated briefly by their slopes and intercepts so that data from various soils may be tabulated or plotted on drawings for purposes of comparison. The value of mechanical analysis is discussed briefly. Further recommendation is made for nomenclature of soil fractions. In doing so there is an attempt to conform closely to the widely accepted classification used by the Bureau of Chemistry and Soils, United States Department of Agriculture, but to make the separations at recurring cycles of log 2 and log 6. Other classifications are also discussed.