Fractal characteristics of mesofractures in compressed rock specimens

The fractal dimension of geometric pattern of cracks on the surface of plate specimens of three rocks, namely, marble, sandstone and limestone, was calculated using Box counting method. The variation of the fractal dimension D with the stress level in each specimen (containing either a central circular hole or a central slot which makes different angle with the loading direction) as well as the variation of self-similarity range with lithology and grain size were analyzed. The results show that the D-value increased during the process of microcracks' initiation and their coalescence into the main fracture but remained unchanged as the macrofracture developed further. The upper scale limit of self similarity range is about two to ten times the grain size of three rocks tested, but shown no relation with the pre-existing rock fabric in the specimens.EI7877-8823