A Model of void distribution in collapsed zone based on fractal theory

In order to calculate the grout volume in the collapsed zone in coal mine after mining, the fractal theory is used to study the feature of the void distribution in collapsed zone, and a fractal model forecasting the voidage in collapsed zone is put forward. The fractal dimension of block particles, pile size of rock block, pore, porosity in the model and relation among them are studied. The influence of lithology of overlying rock, mining width and mining height on the void distribution in collapsed zone is revealed. Combined with the characteristics of overburden failure, a simple and applicable calculation method of fractal dimension connected with the parameters of mining technology is proposed. The validity of the model has been verified in the engineering practice of grouting filling in collapsed zone in a coal mine in China. The model provides a theoretical basis for the design of grouting filling capacity in collapsed zone.