摘要
钻孔钻进过程的实验室模拟及失稳现象捕捉,是钻孔失稳破坏机制研究的关键环节。通过构建模拟煤层钻进过程中钻孔失稳监测系统及方法,探讨了轴压、吸附平衡压力、气体种类及煤的变质程度对钻孔稳定性的影响规律,得出不同试验条件下的孔周煤体应力变化及孔壁、孔底破坏特征。研究结果表明:随轴压及吸附平衡压力的增大,孔周煤体峰值应力最大值逐渐增大,孔壁变形及孔底破坏趋于严重,甚至发生喷孔;与N2相比,当煤样吸附CO2时,孔周煤体峰值应力最大值较大,孔壁变形及孔底破坏也较为严重;随煤的变质程度的加大,孔周煤体峰值应力最大值及卸压范围呈先增大后减小的趋势,试验所用焦煤应力集中现象及孔壁、孔底破坏程度最为严重。
The laboratory simulation and the capture of instability phenomenon for the borehole drilling process are the key links in the study on the borehole instability and failure mechanism. Through establishing the monitoring system and method of borehole instability during the drilling process in the simulated coal seam,the influence of axial pressure,adsorption equilibrium pressure,gas type and metamorphic degree of coal on the borehole stability was discussed,then the stress change of coal body around the borehole and the failure characteristics of borehole wall and bottom under different experimental condi-tions were obtained. The results showed that with the increase of axial pressure and adsorption equilibrium pressure,the maximum peak stress of coal body around the borehole increased gradually,and the deformation of borehole wall and the failure of borehole bottom tended to be more serious,even the borehole blowout occurred. Compared with nitrogen,when the coal samples adsorbed carbon dioxide,the maximum peak stress of coal body around the borehole was larger,and the deformation of borehole wall and the failure of borehole bottom were also more serious. With the increase of the metamorphic degree of coal,the maximum peak stress and the pressure relief range of coal body around the borehole increased first and then decreased,and the stress concentration phenomenon and the failure degree of borehole wall and bottom for the coking coal used in the experiments were the most serious.
引文
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