松软突出煤层钻孔护壁力学作用机理分析

Analysis of Mechanism of Borehole Wall Protection in Soft Coal Seams with Outburst Threat

为了解决松软突出煤层钻进问题,提高钻进深度,为了有效阻止松软煤层抽采钻孔塌孔的情况,在讨论了不同钻孔护壁方法的技术原理的基础上,结合弹塑性"围岩-支护"理论,建立钻孔护壁力学模型,采用数值分析的方法,分析钻孔在不同内压条件下,钻孔周围煤体应力、变形量变化规律。研究结果表明,伴随孔壁内压增大,钻孔变形量呈减小趋势,最大主应力σ1峰值位置左移,塑性松动区呈缩小趋势;次主应力σ3对应曲线整体上移,钻孔周边的应力集中现象有增长趋势。通过钻孔护壁力学作用机理分析,应用钻孔护壁技术,可有效减小或阻止钻孔变形,预防塌孔,保证钻孔的最大排渣空间,有利于施工较深的瓦斯抽采钻孔。

Borehole wall protection technology is an effective tool to prevent the soft coal seam borehole collapse. Based on discusses of technical principles of borehole wall protection methods, combined with elasto - plastic surrounding rock and support theory, borehole wall protection mechanics model was created, by using numerical analysis method, under different interiaal stress the parameters were analyzed, such as stress in coal body around borehole, and deformation changes regulation. The research results showed that with the internal stress increase within the borehole wall, borehole deformation shows decreasing trend, the peak position of maximum principal stress o＇1 moves to the left, plastic loosen area shows shrinking trend; curve corresponding to the secondary princi- pal stress 0＂3 moves up; stress concentration phenomenon surrounding the borehole shows growth trend. Based on the analysis of mechanical effect mechanism of borehole wall protection, application of borehole wall protection technology can. effectively reduce or prevent borehole from deformation, and borehole collapse, so as to ensure the maximum slagging space in borehole, which is conducive to construction of deeper gas drainage borehole.