基于PFC的放顶煤放煤机理数值模拟OA

Based on particle flow numerical simulation software PFC2D,three kinds of caving steps of 0.6 m,1.2 m and 1.8 m are simulated,respectively.The results show that the release rates of three steps are 86%,83%and 74%,the gangue content are 12%,6%and2%.According to the movement characteristics of coal and the change law of contact force field,the development process and mechanism of dynamic multi-layer arch structure are discussed.The top coal caving process is a dynamic process of the formation and destruction of multi-layer arch structure.The space limitation level of top coal move-ment in different positions is different,which results in different top coal movement states.When the ground pressure above the arch structure is greater than the friction force between the top coal particles in the arch structure,the arch structure will be destroyed and the top coal will rush to the coal caving port.Because the top coal migration velocity in the arch crown is far greater than that in both sides of the arch foot,the vault layer of the arch structure continuously develops upward,forming the arch structure of high layer.The top coal gushing to the coal drawing opening may form arch structure.It is considered that the top coal caving body along the strike of working face should be a continuous ellipsoid,and the reasonable caving step should be the width of an ellipsoid.It is proposed to break the arch by vibration of the tail beam of the support,and the simulation experiment proves that the method can effectively improve the coal caving efficiency.