块度对顶煤放出率影响的数值模拟分析

Numerical Simulation of the Effect of Particle Size on Coal Caving Ratio

为了研究不同顶煤块度对顶煤放出率的影响,以及分析其影响因素,采用PFC2D模拟软件,对厚煤层综放开采散体顶煤在不同块度下的落放规律进行模拟,并应用散体介质力学理论进行分析,从而得出了顶煤块度与顶煤放出率之间的关系.研究结果表明:顶煤存在一个临界块度,当顶煤块度低于此值时,顶煤放出率较高,而高于此值时,顶煤放出率则大大降低.煤矸成拱及其相对运动是造成放煤损失的主要原因,并得出了煤矸成拱机率的KL,KC判据,以及煤矸分界线稳定性的相关因素.由此提出了提高顶煤放出率的相关措施:减小顶煤块度、增大放煤口尺寸、保持煤矸分界线稳定性,减少对它的扰动.

We study the effect of particle sizes on coal caving ratio and simulate the caving regularity of loose top-coal with different particle sizes using the PFC2D software and the mechanics of granular media.The result shows that there exists a critical value of the particle size of the top-coal.If this value is smaller than the critical one,the coal caving ratio is comparatively higher,otherwise,the coal caving ratio drops dramatically.The arch-forming of coal and gangue and their relative motion are main factors affecting the loss of caving coal.The criterion of the probability KL and KC of arch-forming and of the stability of boundary between top-coal and gangues is obtained.Reducing the size of particles,enlarging the size of the drawing coal window,improving the stability of the boundary between top-coal and gangues,and trying not to disturb the boundary are applicable methods to increase the coal caving ratio.