Fixing our eyes upon the size distribution characteristics of fragments by blasting, we made experiments on crushing of uniform size cubic blocks which are made of cement mortar. The results obtained with the good reproducibility are as follows,
1) Rosin-Rammlar-Bennt diagrams of all blasting fragments were made of straight lines, so we admitted that the sizedi stribution of fragments may be characterized by Rosin-Rammlar distribution function.
2) With constants which were found from lines for each fragment, namely the size distribution constant (n) and the absolute size constant (De), we calculated mean particle size (Dp) and specific surface area (Sw) through
Dp=Deγ(1/n+1)
Sw=Φ/ρp·104·1/De {γ(1-1/n)-0.0010 (1-1/n)}/1-(1/n)
where Φ= specific shape factor of crushing products which are given surface shape factor (φs) and volume shape factor (φv) through Heywood's method, ρp=density of crushed particles.
3) From optimum straight line through our experimental data, we found out following formulas,
a) The relation between the mean particle size and charge depth (W).
Dp=206-33.2·InW
b) The relation between the specific surface area ratio and charge depth one,
SN/Sw0=4.72e1.40 (W/W0)
where SW0=specific surface area of original block, W0=max. charge depth, distance of center of block.
