Damage evaluation for rock mass through fractal dimension of joint fissures network

摘要

Since the failure of surrounding rock in deep-buried tunnel shows fractal characteristics in both time and space, the fractal dimension can offer the evidence for evaluating the quality and discribing damage process of deep rock mass. Based on the analysis of fractal characteristic of joint fissure during rock mass failure, the paper brought up a new method for estimating damage degree by fractal dimension, and established a tentative quantitative relationship among space dimension, fractal dimension, and damage variable. Its application could cover from zero dimension space or point to three dimensions space. Then through the mapping data and digital photo obtained from in situ investigation, the fractal dimension of surrounding rock in a specified section of the tunnel can be easily calculated by box counting method or directly by using the software Fractalfox. It was proved that the fractal dimension, implying much vital damage information such as integrity and roughness, would be helpful for evaluating damage degree and classifying quality of rock mass, moreover, the change of fractal dimension with time could be used to predict the exact time and place of surrounding rock failure.