Constituent material properties and clast-size distribution of volcanic breccia

Volcanic breccia is a representative heterogeneous rock, As a preliminary study for determining its mechanical properties in laboratory and field experiments, its material properties and structural features were described. Three-dimensional clast-size distribution was also estimated for the study site using the theory of stereology. With this distribution determined, a numerical simulation was performed to investigate the relationship between the volumetric proportion of clasts in a sample and the areal proportion and maximum length of clasts on a lateral surface of the sample. The following observations were made: (1) coefficients of variation for volumetric proportion are dependent on the size of the sample, and became large when the size of the sample is small (2) samples with a small coefficient of variation can be selected at any size if a restriction is placed on the ratio, D-max/D-0, of the maximum length of clasts to the size of the sample; and (3) the volumetric proportion of clasts in each sample can be estimated from the observed areal proportions within an error range that depends on the whole volumetric proportion. (C) 2002 Elsevier Science B.V. All rights reserved.