Fractal Character of Rock Mass Discontinuity Distribution and Evaluation of Rock Mass Quality

摘要

The rock mass discontinuity is studied via fractal theory though it appears existing irregularity in space and shows complexity of its network in structure, because it presents the property of self- similarity. Basic concepts of the fractal theory and calculating methods of fractal dimension applied to the structural rock mass are introduced. The fractal dimensions of the discontinuity distributions in the roadway surrounding rock masses at an underground mine are calculated by applying Box-dimension method, and the fractal character of the rock mass discontinuity distribution is testified. Analyzing values of the fractal dimensions, we find out that the higher the value is, the denser the discontinuity distribution is, the longer the length of discontinuity traces is, and the lower the rock mass quality grade is. It suggests that there is the feasibility of taking the fractal dimension of rock mass discontinuity as the factor of rock mass quality rating. According to the relationship between fractal dimension and engineering rock mass rating, a scheme of rock mass quality evaluation is put forward, which takes the fractal dimension of discontinuity distribution as an classifying index.