Numerical Simulation Of The Top-coal Caving Law Under Vibration Condition

The key to top-coal caving is whether the top-coal can be successfully drawn, and the arching during top-coal caving seriously affects the top-coal drawing effect. Currently, the research about active intervention on block top coal drawing by improving its liquidity and breaking arch is relative limited. In this paper, particle flow code numerical simulation research on exciting breaking arch was carried on based on the analysis of block top coal arching during caving, and the influence factors to the excitation flow effect of top coal were analyzed, then the determination method of optimal excitation parameter was discussed.Based on the top coal arching mechanism and arching shape analysis, the influence of four factors on top-coal drawing effect was simulated through particle flow code, and the four factors are respectively the top-coal blocks' fragmentation size, spatial distribution, the shield beam angle and the friction coefficient between the top-coal and the shield beam. According to the analysis of contact stress between top coal blocks, the existence of drawing arching was verified by combining with the change law of top coal blocks' kinetic energy during caving, and the pulse type caving under the action of arching-arch breaking was revealed. The effect law of the above factors on top coal caving was obtained based on orthogonal analysis, showing that top-coal blocks' size was the key factor to arching, and top-coal blocks' spatial position, especially the layer of bigger blocks, was the determinant of top coal's recovery ratio.Based on the determining to the range of natural frequency of coal-block samples,complied with anylisis of the supports' stability of fully mechanized caving face.the security of its related components and the supportting effect to top coal, principles which the intervention breaking arch with low and high frequency is used on the shield beam to improve drawing results of top-coal.By means of orthogonal numerical simulation, the influence of following three factors:top-coal blocks' layer distribution, intervention frequency and amplitude to amounts of top-coal caved and maximum contact stress between top-coal blocks are analyzed, effective ranges of intervention frequency and amplitude are obtained, effectiveness of low intervention frequency and amplitude to improve drawing results of top-coal is verified. Based on the above, Effective intervention caving parameter in QinShui Coalfield hard top-coal is optimal selected.