综放面坚硬顶煤放煤特性的正交数值分析

Orthogonal numerical analysis of caving characteristics of hard top coal on fully mechanized caving face

为了研究综放工作面坚硬顶煤的放出规律,基于正交试验和颗粒流基本理论,利用PFC^(3D)程序,针对坚硬顶煤压裂块体大小和分布层位的不同,根据低位放顶煤支架掩护梁角度及其与顶煤块体的摩擦系数、采空区煤矸堆积特性等放煤通道条件,选取相关因素不同水平值进行放顶煤的正交数值模拟,得出了坚硬顶煤放煤特性及顶煤块度大小、分布层位、掩护梁角度、摩擦系数这4个因素对顶煤回收率的影响规律。结果表明,顶煤块度大小及分布层位是影响回收率的决定因素,块度从下向上增大分布时,放煤效果最好;大块煤体在中低位时,放煤过程呈现明显的脉冲式,放煤效果差;煤体块度越大成拱能力越强,大块煤体在中低位时竖向运移速度慢、接触应力大、成拱能力强。正交模拟分析可得出最优放煤条件,能够为坚硬顶煤压裂、支架结构改进等提供理论依据。

In order to study the characteristics of hard top-coal caving in fully mechanized caving face, based on orthogonal test and particle flow theory, using the PFC3 D program, aim at the different size and distribution horizons of hard top coal fracturing blocks, according to the coal caving channel conditions such as the angle of the cover beam of the low-level top coal caving support, the friction coefficient with the top coal block, and the coal gangue accumulation characteristics in the goaf, the orthogonal numerical simulation of the top coal caving was carried out by selecting different levels of relevant factors, obtained the characteristics of hard top coal caving and the influence of top coal block size, distribution horizon, cover beam angle and friction coefficient on the top coal recovery rate.The results show that the size and distribution horizon of the top coal lump are the determinants of the recovery rate.When the block degree increases from bottom to top, the coal caving effect is the best;When the big block coal is in the middle and low position, the coal caving process presents an obvious pulse type, the coal caving effect is poor;the bigger the coal block, the stronger the arching ability.When the big blocks are in the middle or bottom part of top-coal, the vertical movement speed is slow, the contact stress is large, and the arching capability is strong.The orthogonal simulation analysis can obtain the optimal top-coal caving conditions, which can provide an important basis for the fracturing of hard top-coal and the improvement of support structure.