Statystyczne wskaźniki uziarnienia gruntów sypkich

Abstract

STATISTICAL INDICES OF GRAIN SIZE OF SEDIMENTS Summary A possibility of comparison of the results of studies on various soils from various regions is a base of a wide application of granulometrical analysis in geological researches. An analysis of the rich literature devoted to this problem, made by the present author, illustrates that a considerable inhomogeneity of methods of presenting the results of studies on grain-size distribution of sediments exists. The paper presents numerous statistical indices of grain-size distribution of sediments and gives theoretical bases to examine the grain-size distribution of sediments, definition, main statistical indices of grain-size distribution and methods of determination of these indices. Among the analytical and graphic-analytical methods presented above, the latter is thought by the author to be the better one. The graphic-analytical, methods is quicker and simplified one, more useful in calculating the indices characterized by adequate precision for practical purposes and corresponding in this respect to the indices precisely calculated by means of analytical methods (method of moments). The results of grain-size distribution are presented in the form of grain-size distribution curves in a system: scale of probability - scale phi (Φ), (in the graph paper of probability, Fig. 1). The usability of such a system applied to present the results of grain-size distribution can still more be visible when solving the problem of the distribution type that represents the grain-size distribution of genetically various deposits (normal distributions, lognormal distributions a.o.). A comparison of the main statistical indices of grain-size distribution, presented in scale phi, is given in Table I. Based on the equations of regression and on the diagrams of dependence between the standard deviation σΦ presented by G. M. Friedman (1962), and the coefficient of sorting of P. D. Trask (1930, 1932), the present author gives a new classification of deposits based on the value of the standard deviation of D. L. lnman (1952), and on the inclusive graphic standard deviation σI of R. L. Folk and W. C. Ward (1957), it can be seen in Table III.