To solve the problems that the borehole depth is shallow and the drilling efficiency is low during the gas drainage drilling in soft coal seam with current cuttings removal method, a new technology of reverse circulation pneumatic cuttings removal is proposed. The working principle of reverse circulation pneumatic cuttings removal is analyzed, and the kinetic equation of cuttings in the inner hole of the drill pipe is established. Through experiments, the pressure drop in the drill pipe is measured to reveal the effects of air velocity, cuttings mass flow rate, and cuttings particle size on the pressure drop in inner hole of the drill pipe. When the cuttings mass flow rate is constant, the pressure drop increases with the increase in air velocity. When the air velocity is constant, the pressure drop increases with the increase in cuttings mass flow rate. At low air velocity, the pressure drop of cuttings is primary. As the air velocity increases, the pressure drop ratio of cuttings decreases. Under the same conditions, the order of pressure drop with different particle size cuttings is coarse cuttings > medium cuttings > fine cuttings. Empirical equation of pressure drop coefficient of cuttings is established, which is in good agreement with the actual data.

针对松软煤层瓦斯抽放钻孔现有排屑方法存在的钻孔深度浅、钻进效率低的问题，提出了一种反循环气力排屑新技术。分析了反循环气动排屑的工作原理，建立了钻杆内孔钻屑的运动方程。通过实验测量钻杆内的压降，揭示风速、岩屑质量流量、岩屑粒径对钻杆内孔压降的影响。当岩屑质量流量一定时，压降随着风速的增大而增大。当风速一定时，压降随着钻屑质量流量的增加而增加。在低风速时，岩屑的压降是主要的。随着风速增大，岩屑压降比减小。相同条件下，不同粒度岩屑的压降顺序为粗岩屑>中岩屑>细岩屑。建立了岩屑压降系数经验方程，与实际数据吻合较好。