Fractal evolution of a crack network in overburden rock strata due to coal mining

The distribution of cracks caused by underground coal mining strongly affects stability of overburden rocks, fluid flow in fractured rocks and ground surface subsidence. Understanding of the distribution and evolution of crack network is useful for predicting surface subsidence. In this paper, plane stress physical models are employed to investigate the spatial distribution of a crack network, By using fractal geometry, the statistical self-similarity of a spatial distribution of crack networks is proposed. Additionally, the evolution of a crack network with an increase of the mining length of advance is investigated. It is shown that, (1) the spatial distribution of a crack network displays fractal behavior, so, the fractal dimension can be used as an alternative indicator to describe quantitatively the complexity of the crack network, (2) the fractal dimension of the crack network increases with an increase of mining length.