The rock mass discontinuity

owing to its property of self-similarity

can be addressed with the fractals although it is irregular in space and complex in network structure. The present study has testified the fractal characteristics of rock mass discontinuity distributions based on the calculation of the fractal dimensions of discontinuity distributions in the roadway surrounding rock masses at an underground mine with the application of the box-dimension method. By analyzing the fractal dimension values

this investigation shows that the higher the value is

the denser the discontinuity distribution

the longer the discontinuity traces

and the lower the rock mass quality; and it is shown that taking the fractal dimension of rock mass discontinuity distribution as the index of rock mass quality rating is feasible. By comparing the fractal dimensions calculated above with the corresponding rock mass grades classified by the standard for engineering rock mass rating

a scheme of rock mass quality classification

which takes the fractal dimension of the discontinuity distribution as the classifying index

is proposed.