非煤系地层浅层天然气赋存规律及瓦斯隧道工程防护方案

依托成都轨道交通19号线新红高瓦斯隧道区间,结合红层地区类似工程案例,探索非煤系地层浅层天然气(瓦斯)的运移机制;对气体赋存形式进行分类,并通过分层检测试验,探究新红高瓦斯隧道区间的瓦斯空间分布规律。研究表明:是否穿越或邻近浅层天然气气源断裂带,是非煤隧道是否会受瓦斯危害的关键;非煤系浅层天然气主要表现为孔隙型、裂隙型、吸附性和水溶性天然气4种赋存形式,其中吸附气、水溶气对定量化研究非煤系浅层天然气有一定影响;新红高瓦斯隧道区间的高低瓦斯纵向分界线高程约460 m,瓦斯浓度在隧道顶板上部地层普遍小于0.1%,在底板下部地层普遍大于1.0%,且随着地层深度的增加,地层含高浓度浅层天然气的概率增大。据此,提出针对非煤瓦斯隧道工程的综合性防护方案,采取修正线路设计方案、预抽排浅层天然气、超前地质预报、控制掘进技术、系统通风、自动化实时监测等综合性措施,预测、防范瓦斯对隧道工程的危害。

Occurrence Regularity of Shallow Natural Gas in Non-Coal Strata and Protection Scheme of Gas Tunnel Engineering

Relying on the Xinhong high gas tunnel section of Chengdu rail transit line 19,combined with similar engineering cases in red bed area,the migration mechanism of shallow natural gas(gas)in non-coal strata was explored.The gas occurrence forms were classified and the gas spatial distribution regularity in Xinhong high gas tunnel section was explored through stratified detection test.Results show that whether the tunnel crosses or is adjacent to the fault area of shallow natural gas source is the key to whether the non-coal tunnel will be damaged by gas.The occurrence forms of non-coal shallow natural gas are mainly manifested in pore type,fissure type,adsorbent and water-soluble natural gas,among which the adsorbed gas and water-soluble gas have certain influence on the quantitative study of shallow natural gas in non-coal measures.The elevation of the vertical dividing line between high and low gas in Xinhong high gas tunnel is about 460 m.The gas concentration is generally less than 0.1%in the upper stratum of the tunnel roof and more than 1.0%in the lower stratum of the tunnel floor.Moreover,with the increase of the depth of the stratum,the probability of the stratum containing high concentration shallow gas increases.Accordingly,a comprehensive protection scheme for non-coal gas tunnel engineering is proposed,and comprehensive measures such as revising the line design scheme,pre-pumping and draining shallow natural gas,advanced geological prediction,controlling tunneling technology,systematic ventilation and automatic real-time monitoring are adopted to predict and prevent the harm of gas to tunnel engineering.