The results of a laboratory research programme on the crushing of pumice sands compressed under one-dimensional conditions, at vertical effective stresses ′v up to 100 MPa are reported in the paper. Tests have been carried out on dry pumice sands with initial coefficient of uniformity Cu ranging from 1.18 to 1.66 and with diameters of particles ranging from 0.18 to 2mm. The pumice sands show considerable crushing of particles even at low stresses (about 150 kPa), due to both their intragranular and intergranular porosity. It is shown that the evolution of the grain-size distribution can be effectively represented by the following relation between the absolute value of the decrement of the generic characteristic diameter Dj and ′v: Dj= h/(K(1+C e –hlgv)), where C, h, K are positive parameters depending upon the nature and the initial grain-size distribution of the sand. This Verhulst type relation properly accounts for the existence of an upper limit to Dj. The Hardin’s coefficient of relative breakage also evolves according to a Verhulst type function showing that the pumice sands at high pressures attain a very “stable” gradation and structure.The results of the present research confirm the trend in the evolution of the grain-size distribution of other sands as pointed out in previous papers. It therefore appears that the Verhulst type relation between Dj and ′v holds its validity in general.
|Number of pages||0|
|Journal||MECCANICA DEI MATERIALI E DELLE STRUTTURE|
|Publication status||Published - 2012|