DISCRETE ELEMENT SIMULATION FOR CRACK FRACTAL EVOLUTION LAWS ASSOCIATED WITH SLICING MINING IN SUPER THICK COAL STRATUM

This paper presents an approach of combining fractal geometry theory and UDEC discrete element numerical simulation method to study the fractal evolution law of mining-induced fracture of overburden rock. It can be applied to quantitatively evaluate development characteristics of mining fracture network in weakly consolidated overburden under the high-intensity mining in the western mining area. The research result indicates the following findings. The development and expansion of overlying rock fractures have good self-similarity under high-intensity mining conditions and the fractal dimension is between 0.461 and 1.488. The law of evolution can be divided into four stages including the dimensionality rapidly increasing stage,quickly reducing stage,stable stage,and periodically varying stage. In addition,the fractal dimension at each stage and the number of mining meet the logarithmic relationship,linear relationship and quadratic function relationship,respectively. With slice mining in huge coal stratum,the fitting curve of fractal dimension shows a high degree of similarity,has a certain periodicity,and shows a power function relationship. The research results provide scientific basis and technical reference for safe mining in western mining area and protection of water resources.