川东北红层浅层天然气赋存特征隧道瓦斯等级判定

Occurrence Characteristics of Shallow Natural Gas and Grade Determination of Tunnel Gas in Red Beds in Northeast Sichuan

红层在有利条件组合下,会储存有浅层天然气,当隧道穿越该类储层时,会对施工造成较大安全隐患。文章以川东北苍巴高速、S411旺苍公路项目为依托,通过对项目隧道天然气检测数据的分析,总结了川东北地区浅层天然气的赋存特征,提出了钻孔内测试浓度换算为掌子面绝对涌出量的方法,根据现场测试、计算,判定了隧道瓦斯等级,并与目前的浅层天然气隧道瓦斯等级判断方法进行了对比,证明其思路是基本可行的,可以在改进和完善测试方法后,结合现行瓦斯规范进行更准确的判断。

Under the combination of favorable conditions,shallow natural gas will be stored in the red bed.When the tunnel passes through this kind of reservoir,it will cause great potential safety hazard to the construction.Based on the project of Cang Ba Expressway and S411 Wangcang highway in Northeast Sichuan,this paper summarized the occurrence characteristics of shallow natural gas in the northeast of Sichuan Province by analyzing the data of natural gas detection in the project tunnel,and put forward a method to convert the test concentration in the borehole into the absolute emission of the tunnel face.According to the field test and calculation,the gas grade of the tunnel is determined.And compared with the current shallow natural gas tunnel Judgement,it is proved that the idea is almost feasible.After the improvement and improvement of the test method,the judgment can be more accurate combined with the current gas standard.