Study on effective gas discharge radius of highway tunnels based on comprehensive index method
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 construc-tion 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 indica-tors(gas content,K1 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 φ90 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.
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