铁路隧道穿越瓦斯煤系地层的旋喷围桩防突工法探析

为确保铁路隧道能够快速安全地穿越瓦斯突出煤系地层，依据《铁路瓦斯隧道技术规范》的防突规定及旋喷桩工艺特点，从“堵”“排”结合的角度，提出一种旋喷围桩快速防突的新型施工方法。首先，依据防突原理，针对超前综合防突和工作面综合防突，开展了“堵”“排”结合的旋喷围桩防突工艺研究； 然后，以叙毕铁路欧家湾高瓦斯隧道防突为例，进行了旋喷围桩防突工法中关于围桩桩径与瓦斯释放孔数量的多方案设计；最后，依据施工定额，结合工程量统计数据，从施工成本和施工时间方面将旋喷围桩防突工法与传统抽排防突措施进行比较。研究结果表明： 1)封闭的高强度旋喷桩加固了防突区域轮廓周线上煤层的地质结构，隔离了围桩内外的煤体，截断了煤与瓦斯突出向围桩外扩展的途径； 2)仅对围桩内突出煤层实施地质钻钻孔和瓦斯排放，使消突范围大大减小； 3)与传统抽排消突方案相比，旋喷围桩防突工法桩内释放孔数量减少为原设计的1/5～1/3时，地质钻钻孔总工程量可减少13%～22%，施工成本按基价计仅增加1.7%～10.5%，既安全高效，又简单易行。

Outburst Preventive Construction of Rotary Jet Grouting Enclosure Pile for Railway Tunnel Crossing Gas and Coal Rich Strata

To ensure rapid and safe railway tunnel crossing coal rich stratum without gas outburst, the outburst prevention specification of 〖WT５《TNR#I》〗Technical Code for Railway Tunnel with Gas〖WT５《TNR》〗 (2019) and the technological characteristics of rotary jet grouting pile are investigated. In addition, a new construction method for rapid outburst prevention of rotary jet grouting pile is proposed based on the blocking and releasing method. First, the proposed method is studied with respect to the advance comprehensive gas outburst prevention and tunnel face gas outburst prevention. Second, a case study is performed on the gas outburst prevention of Oujiawan high gas tunnel on Xuyong Bijie railway, and a multi scheme design of the pile diameter and the number of gas release holes is developed for the proposed method. Finally, the proposed method is compared with the traditional gas drainage method from the perspectives of construction cost and time. The results reveal the following: (1) The high strength jet grouting pile reinforces the geological structure of the coal seam on the contour lines of the gas outburst prevention area, isolates the coal outside the enclosure pile, and cuts off the way of coal and gas outburst extending the pile. (2) The gas outburst prevention range can be significantly reduced by releasing gas through geological drilling holes inside the enclosure pile. (3) Compared with the traditional gas outburst prevention methods, the number of releasing holes inside the enclosure pile and the total length of geological drilling holes of the recommended method are reduced by 4/5~ 2/3 and 13%~22%, respectively, and the construction cost is increased by only 1.7% ~10.5%, which is safe and efficient.