煤层钻孔失稳破坏的数值模拟研究

Numerical simulation of borehole failure in coal seam

高瓦斯松软煤层、软硬复合煤层和突出煤层深孔钻进是公认的世界性难题,煤层钻孔失稳破坏机理研究是破解该难题的基础与关键所在。为此,本文基于钻孔力学模型,运用数值模拟方法,对煤层钻孔周围的应力场、位移场分布规律进行了分析与探讨,得出了钻孔的破坏形式。研究表明:煤层钻孔主要以剪切破坏为主,孔壁处呈"V"状破坏和小部分拉伸破坏,孔周煤体深部呈共轭的"X"状剪切破坏;钻孔周围应力环境、煤层瓦斯压力、外界人为影响为影响钻孔稳定性的主要因素。

It is well known that the deep hole drilling in high gas soft coal seam,hard and soft compound coal seam and outburst coal seam is a worldwide problem,instable failure mechanism of borehole in coal seam is the fundamental and key research to solve above-mentioned difficult problem.Therefore,based on mechanics model of borehole,distribution law of stress field and displacement field around borehole in coal seam was analyzed and discussed by using numerical simulation method,and failure mode of borehole was acquired.Research results show that shear failure is the primary failure mode,＂V＂type failure and some tensile failure exist in borehole wall,conjugated＂X＂type shear failure exists in the deep part of coal body around borehole;stress environment around borehole,coalbed gas pressure and human influence are main factors which can impact borehole stability.