基于综合指标法的公路隧道瓦斯有效排放半径考察研究

Study on effective gas discharge radius of highway tunnelsbased on comprehensive index method

超前钻孔排放瓦斯作为公路隧道揭煤防突的优选技术措施,依据有效排放半径对超前钻孔进行合理布置,可在保证安全揭煤的前提下,大大优化现场钻孔施工量。采用了综合指标法对待揭煤层有效排放半径进行考察,该方法通过在隧道掘进面布置一组钻孔,对3个反映不同突出主导因素的防突指标(瓦斯含量、K_(1)值、S值)进行测定,分析确定出最优有效排放半径,以此提高测定结果的可靠性与准确性。以四川某隧道8号煤层作为考察研究对象,研究结果表明,该隧道采用直径90 mm的排放钻孔,在排放时间为12 h的条件下有效排放半径为1.6 m。现场运用该方法进行钻孔布置,钻孔施工量减少了56%,安全、高效地完成了揭煤作业。

Advanced drilling to discharge gas as an optimal technical measure for coal uncovering and outburst prevention in highway tunnels,reasonable arrangement of advanced drilling based on effective discharge radius,it can greatly optimize on-site drilling construction volume on the premise of ensuring safe coal uncovering.The use of comprehensive index method to evaluate the effective discharge radius of coal seams was proposed,this method involves arranging a group of drilling on the tunnel face,three outburst prevention indicators(gas content,K_(1)value,S value)that reflect different dominant factors of outburst were measured,and the optimal effective emission radius to improve the reliability and accuracy of the measurement results were analyzed and determined.Taking the No.8 coal seam of a certain tunnel in Sichuan as the research object,the results indicated that the effective discharge radius of a∅90 mm diameter discharge drilling under the condition of a discharge time of 12 hours was 1.6 m.Applying this conclusion to the drilling layout on-site reduced the amount of drilling construction by 56%,the coal uncovering operation was completed safely and efficiently.