NOUVELLE M&Eacute:THODE DE DÉTERMINATION DE LA SPHÉRICITÉ DES SÉDIMENTS MEUBLES.

In this paper we show a new method to determine the sphericity of sand particles with sedimentary analysis. We use two different sieves: the one with open squares: the side is a and the diagonal d = a√2; the other with circular openings: the diameter is D. Experimentation shows that elements crossed the open-square sieves in diagonal positions. When we reported the cumulative curves into arithmetic or semi-logarithmic graphs, we used the value d and not the side square a. A sediment C, which is composed of not very angular or subspherical particles, is represented by two cumulative curves on the same graph. If a sediment A is very angular, the two curves are disconcerted. The sediment B is subspherical, the difference between the two curves is maximum, We call this difference δ which is equal to d-D. For C this difference is Δ, which is always inferior to δ. The absolute sphericity index Sa is the ratio Δ/δ in %. When the particles are very angular, sphericity values are 0—like A and when they are sphericals the index is 1 — like B. This index is determined with graphic solutions. The values obtained are comparable with those of visual charts. [ABSTRACT FROM AUTHOR]