Objective Shield tunnels are a primary method for long-distance oil and gas pipelines to cross rivers and lakes. Internal and external loads, such as temperature, transportation pressure, and buoyancy, can lead to issues like excessive displacement and stress beyond acceptable limits. Conducting research on the control of potential pipeline hazards is essential for ensuring safe operation.

Methods Taking the hazard treatment of the vertical displacement of a gas pipeline in a typical tunnel crossing section as an example, finite element models of the pipeline, rigid supports, and concrete piers were developed using ABAQUS software. The stress and displacement of the pipeline were analyzed under both water-filled and water-free tunnel conditions. By considering the pipeline layout, constraint types, support bolt conditions, and finite element analysis results, the causes of excessive vertical displacement were identified. To prevent recurrence, measures including bolt repair and corrosion protection, tunnel leak remediation, reinforcement of annular steel supports, and removal of concrete piers were implemented. Dynamic monitoring and data analysis of pipeline stress and displacement, considering temperature variation, operational pressure, self-weight, and buoyancy, were conducted using advanced monitoring technology.

Results In the water-filled condition, the maximum stress values of the pipeline were 300.20 MPa under operating conditions and 334.20 MPa under design conditions, indicating high-stress levels. After the water was drained, stress levels significantly decreased, with maximum values dropping to 171.46 MPa and 214.67 MPa, respectively. During the treatment process, minor fluctuations in pipeline stress and displacement were observed; the maximum stress amplitude was within 10 MPa, and the displacement amplitude did not exceed 10 mm in the monitoring section. During the winter supply securing period, although some fluctuations occurred, the minimum observed stress was 145.32 MPa, demonstrating a sufficient safety margin and stable pipeline operation.

Conclusion The fracture of support bolts poses significant safety risks for underwater tunnel-crossing pipelines, with water buoyancy being the direct cause of excessive vertical displacement. A control process encompassing the identification of potential hazards, cause analysis, and comprehensive treatment can be established through finite element analysis and advanced monitoring technologies. Given that variations in transportation conditions can lead to frequent fluctuations in pipeline stress and displacement, future assessment of their impact on pipeline fatigue life, based on monitoring data, is necessary for safety assurance.