针对川西南地区浅表地层天然气对隧道工程影响较大的问题，依托成眉线工程，运用地质分析、工程地质勘探方法，通过封孔聚气试验、分层检测试验，揭示研究区浅表层天然气分布富集规律及控制因素，分析浅层天然气富集对隧道产生的工程效应及对策。研究结论如下： 1）深部天然气更倾向于通过断层、节理裂隙运移至浅地表，在以黏土为盖层、卵石层为储层的第四系特殊储盖组合中形成天然气高体积分数富集。2）成眉线隧道工程高体积分数区主要分布在卵石层中，低体积分数区主要分布在强风化泥岩及部分卵石层中，微体积分数区主要分布在完整泥岩及上覆黏土层较薄的卵石层中。3）浅层天然气的存在不仅对隧道工程的施工安全、成本和施工工期产生影响，也是工程勘察的一大挑战；遇到浅层天然气问题，需要对隧道设计及方案进行调整，并提出防治措施建议、制定运营维护方案。

Shallow natural gas has considerably impacted tunnel engineering in the southwestern Sichuan region in China. To address this issue, based on geological analysis and engineering geological exploration, the distribution characteristics and factors controlling the shallow natural gas are analyzed via sealing gas accumulation tests and layered detection tests. The engineering effects and countermeasures of shallow natural gas enrichment on tunnel construction are analyzed. Results reveal that deep natural gas tends to migrate to the shallow surface via faults, joints, and fissures, forming a rich group with higher natural gas concentration in the Quaternary special reservoir caprock combination with clay as the caprock layer and pebble layer as the reservoir. The high, low, and slight gas concentration areas of the Chengdu-Meishan line tunnel are located in the pebble layer, strongly weathered mudstone and some pebble layers, and intact mudstone and thin pebble layer of the overlying clay layer. Moreover, shallow natural gas impacts construction safety, cost, and duration of tunnel engineering and poses a major challenge during engineering survey. To address this issue, tunnel design and plans must be optimized and prevention and control measures must be undertaken. Additionally, operation and maintenance plans must be devised in areas containing shallow natural gas.