EVALUATION OF ROCK MASS QUALITY ON FRACTRAL DIMENSION OF ROCK MASS DISCONTINUITY TRACE

Fractal theory、neural network and other new methods have been widely applied in the current qualitative or quantitative evaluation of rock mass quality. Based on the fractal characteristics of the self similarity of the surface of the rock mass, We applied fractal theory to study the fractal dimension of the surface trace of rock slope structure based on digital close range photogrammetry technology. Taking one side slope of pure moon quarry in Changchun as an example, We used the grid covering method to calculate the fractal dimension of the structural plane traces, and verified the fractal characteristics of traces. In addition, we also improved the grid coverage method, and used the rectangular grid coverage method which was proportional to the research scope to calculate the fractal dimension. The latter is closer to fractal theory and easier to program. It is found that the results of the two methods are similar, the more the trace number, the larger the fractal dimension, the more broken rock mass and the worse the mass, and the quality classification of rock mass can be more accurately determined by the rectangular grid method. Finally, we analyzed the fractal dimension and the RQD to determine the relationship between the fractal dimension and the RQD, and selected the RQD under the reasonable threshold, and got the rock mass quality evaluation method with the fractal dimension as the index. The research shows that the fractal dimension of the slope trace is 1.22and the fitting degree is 0.98and the quality of the slope rock mass belongs to the Ⅱ level. In addition, the improved calculation of the fractal dimension of the rectangular grid coverage method is easy to do. The calculation process is simplified and the result is reliable. A quantitative evaluation method of rock mass quality based on fractal dimension of trace line of rock mass structure is obtained.