Rock mass characterization by fractal dimension

Fractal theory is used in the present study to develop a more reliable method for rock mass characterization. Field studies have been carried out in opencast mines of dolomite, limestone, fluorite; sandstone and shale in coalmines. Fractal dimension of blasted fragments ( D frag) and in situ rock blocks ( D in situ) is calculated using size distribution curves according to Schumann's model. Based on the co-relation between Uniaxial Compressive Strength (UCS) and D frag, it is observed that change in fractal dimension is nominal beyond the UCS value of 20. From the co-relation between Bieniawaski's Rock Mass Rating (RMR) and D in situ, it is found that there is a sharp increase in fractal dimension for RMR greater than 40. Co-relation between RMR and D frag/ D in situ shows that as RMR increases, D frag/ D in situ ratio decreases. Rock mass classification based on fractal geometry is suggested.