为了研究深部煤层抽采钻孔变形失稳的主控因素，分析了抽采钻孔变形失稳机理，建立了三维数值模型，研究了钻孔埋深、侧压系数等对钻孔稳定性的影响，最后确定了地应力为抽采钻孔变形失稳的主控因素。结果表明：①随着钻孔埋深的增加，钻孔围岩的最大垂直位移、最大水平位移和最大垂直应力都随之增加，并且埋深扩大1倍，位移最大增加6.11倍，最大垂直压力增加1倍，最大垂直应力所处位置距钻孔表面距离不断增大，但垂直应力集中系数基本不变。②随着侧压系数的增大，钻孔围岩的最大垂直位移和最大水平位移都增大，最大垂直位移增加速率较快，并且侧压系数扩大1倍，钻孔的最大位移变为原来的3.29倍；钻孔最大垂直应力随之缓慢增加。③孔径和瓦斯压力对钻孔稳定性影响较小。孔径或瓦斯压力的增加导致钻孔的最大垂直位移、最大水平位移和最大垂直应力都缓慢增加。④采用套管对钻孔进行支护，钻孔变形得到一定的控制，最大垂直位移和最大水平位移都明显减少，最大垂直应力所处位置至钻孔的距离与应力集中系数都减小，并且PP套管效果最佳。⑤由埋深和侧压系数（地质构造）决定的地应力是钻孔失稳的根源，是影响抽采钻孔稳定性的主控因素。研究结果可以为矿井瓦斯治理提供理论基础。

In order to study the main controlling factors of borehole deformation and instability in deep coal seam, firstly, the mechanism of borehole deformation and instability is analyzed. Secondly, a three-dimensional numerical model is established to study the influence of borehole buried depth and pressure coefficient on borehole stability. Finally, the in-situ stress is determined as the main controlling factor of borehole deformation and instability. The results show that:① with the increase of borehole depth, the maximum vertical displacement, maximum horizontal displacement and maximum vertical stress of surrounding rock increase, and the burial depth increases by one time, the maximum displacement increases by 6.11 times, the maximum vertical pressure increases by one time, the distance between the maximum vertical stress position and the borehole surface increases, but the vertical stress concentration factor is basically unchanged. ② With the increase of the lateral pressure coefficient, the maximum vertical displacement and the maximum horizontal displacement of the surrounding rock of the borehole increase, and the maximum vertical displacement increases faster, and the maximum displacement of the borehole becomes 3.29 times of the original when the lateral pressure coefficient is doubled; the maximum vertical stress of the borehole increases slowly with it. ③ Hole diameter and gas pressure have little influence on borehole stability. The maximum vertical displacement, maximum horizontal displacement and maximum vertical stress increase slowly with the increase of pore diameter or gas pressure. ④ When the casing is used to support the borehole, the borehole deformation is controlled to a certain extent, the maximum vertical displacement and the maximum horizontal displacement are significantly reduced, the distance between the maximum vertical stress and the borehole and the stress concentration factor are reduced, and the effect of PP casing is the best. ⑤ The in-situ stress determined by buried depth and lateral pressure coefficient(geological structure) is the source of borehole instability and the main controlling factor affecting the stability of extraction borehole. The research results can provide a theoretical basis for mine gas control.

0 引言

1 抽采钻孔变形失稳机理分析

   1.1 初始状态下钻孔围岩的力学分析

   1.2 煤层抽采钻孔变形失稳机理

2 抽采钻孔变形失稳的影响因素分析

   2.1 数值模型建立

   2.2 抽采钻孔变形失稳影响因素分析

3 结论