瓦斯抽采钻孔堵塞段力学模型及其应用

建立瓦斯抽采钻孔堵塞段力学模型，基于施工地点的供风压力极值pmax ，求解相应临界堵塞段长度L0，当L＞L0时，钻孔将发生堵塞；研究了钻孔堵塞段退钻阻力的计算方法，分析了堵塞段长度和堵塞段内部气体压力对退钻阻力的影响规律。分析结果表明，在钻孔工程中，钻孔堵塞段内存在较高的气体压力是造成钻孔发生堵塞、难以退钻的主要原因，退钻阻力对堵塞段孔内气体压力变化非常敏感，采取降压退钻是减小退钻阻力的有效方法。应用钻孔堵塞段力学模型，分析了九里山矿钻孔施工现状，提出增大排渣空间、降低排渣阻力、提高钻杆强度技术措施，通过工业性试验，未出现断钻现象，钻进效率提高17％。

Clogging mechanical model and its application in gas extraction borehole

A clogging segment mechanical model is established on gas extraction horizontal borehole. Based on the air pressure extremes pmax of the construction site, we solve the corresponding critical clogging length L0 and find clogging will occur when L> L0. With the clogging segment mechanical model, we analyze the calculation method of the retreat drilling rod resistance in borehole. The influence rule of clogging length and air supplying system pressure on retreat drilling rod resistance is analyzed. Analysis results show that the main reason for difficult drilling clogging and retreat drilling rod is the higher pressure in borehole clogging segment. The retreat drilling rod resistance is especially sensitive to the change of air supplying system; therefore, the effective method of reducing the retreat drilling rod resistance is reducing the air supplying system pressure in borehole. The drilling construction status in Jiulishan coal mine is analyzed by using the clogging segment mechanical model, and three technical measures are put forward, including increasing slagging space, reducing slagging resistance and increasing drilling rod strength. When the improving measures are adopted, the pipe-sticking phenomena decreases, the drilling rod broken phenomenon are averted and the drilling efficiency increases by 17%.