富含有害气体地层长距离大埋深盾构穿越隧道接缝防气性能试验研究

Experimental Study on Gas-Proof Performance of Shield Crossing Tunnel Joints with Long Distance and Large Embedded Depth in Stratum Rich in Harmful Gases

摘要: 中俄东线天然气管道工程为长距离(10.23 km)、大埋深(40 m)长江盾构隧道穿越工程，经勘察其地层富含沼气等有害气体，有害气体的存在给项目施工和运营带来了巨大的安全隐患，对隧道接缝防气也提出了较高要求。本文设计了与实际隧道沟槽和密封垫高度和宽度等尺寸相同的内外两圈回型密封垫垫圈、带沟槽混凝土构件及预埋管道构成的模型试验装置，对不同工况下本穿越工程设计弹性密封垫的防气性能进行了直接测试和研究。试验结果表明，盾构外道密封垫在张开量5.6 mm、错缝量15 mm时，短期防气能力为2.03 MPa；在0.125 MPa较低气压的作用下，能测到微弱的气体泄漏。结合国内类似地层和工程的有害气体最高气压测量值等调研分析，可以判断在满足设计的张开、错缝验收标准情形下，本工程盾构隧道接缝具有足够的抵抗高压有害气体快速逸出或爆发式逸出的能力；但是，低气压下隧道接缝微弱泄漏的试验结果表明，需要警惕长期微泄漏情况下隧道内气体浓度累积带来的风险和危害，提前制定针对性的、切实可行的管控措施以保障施工与运营安全。

Abstract: The China-Russia eastern gas pipeline project is a long-distance (10.23 km), deeply buried (40 m) Yangtze River shield tunnel crossing project. It has been surveyed that its stratum is rich in harmful gases such as biogas. The existence of harmful gases has brought huge safety hazards to the construction and operation of the project, and higher requirements have been put forward for the gas-proof performance of tunnel joints. In this paper, a model test device consisting of two loops of inner and outer gaskets with the same dimensions as the actual tunnel groove and gasket height and width, concrete members with grooves, and embedded pipelines is designed. We conducted direct testing and research on the gas-proof performance of the elastic gasket designed for the project under different working conditions. The test results show that the short-term gas-proof capacity of the shield tunnel outer gasket is 2.03 MPa when the opening amount is 5.6 mm and the staggered seam amount is 15 mm; under the action of the lower pressure of 0.125 MPa, weak gas leakage can be detected. Combined with the investigation and analysis of the highest pressure measurement value of harmful gases in similar stratums and projects in China, it can be judged that under the condition of meeting the design acceptance criteria for opening and staggered seams, the joints of the shield tunnels project have sufficient resistance to the rapid or explosive escape of high-pressure harmful gases; however, the test results of the weak leakage of tunnel joints under low air pressure show that it is necessary to be alert to the risks and hazards caused by the accumulation of gas concentration in the tunnel under the condition of long-term micro leakage, and to formulate targeted and feasible control measures in advance to ensure construction and operation safety.