Study on top coal caving law of fully-mechanized top coalcaving mining based on random medium theory

In order to further understand the top coal caving law of the fully-mechanized top coal mining, a theoretical analysis and a numerical simulation combined method was applied to study the dynamic evolution of the top coal caving during the top coal caving process of the fully-mechanized top coal mining. The paper pointed out the limit of the conventional ellipsoid theory applied to analyze the top coal caving form. The study results showed that the top coal caving form and the evolution law obtained from the numerical simulation could be well fitted with the theoretical analysis results and showed that the random medium theory would be feasible applied to the analysis on the caving process of the fully-mechanized top coal caving. When the top coal caving height was small, the caving mass would be cutting spheres at the tail beam. The suitability of the conventional ellipsoid theory would be low. With the caving height increased, the caving mass would be steadily changed to be cutting spheres at the tail beam and the shaft deflection angle would be steadily reduced. The caving of the fully-mechanized top caving mining mainly would be the top coal above the tail beam. At a same caving height, the top coal caving quantity of the periodical caving would be higher than the initial top coal caving quantity and the shaft deflection angle would be higher than the initial top coal caving.