Oil and gas pipelines represent critical infrastructure for energy transportation and are essential for ensurin g energy security. The seismic disaster risk assessment of these pipelines is of paramount importance for safeguarding energy supplies. Traditional assessment methodologies primarily focus on the structural integrity of the pipeline body, often neglecting the impact of auxiliary structures and site-specific disaster effects. This study proposes an enhanced risk assessment methodology to address these gaps. This research systematically compiles seismic damage case studies of pipelines from major seismic zones in China. By considering the interactions between auxiliary structure types, site conditions, and forms of disasters, 15 typical operating conditions are identified, and a seismic damage case database is constructed. We develop a failure probability model that integrates geotechnical parameters, structural responses, and ground motion characteristics to assess the impact of liquefaction, site amplification, fault activity, and collapse/landslide phenomena. Utilizing Particle Swarm Optimization (PSO) and Fuzzy Analytic Hierarchy Process (Fuzzy AHP) algorithms, this model quantifies the influence weights and coefficients of these disasters on pipeline auxiliary structures, forming a vulnerability matrix centered around Peak Ground Acceleration (PGA). Additionally, a dual-vulnerability assessment framework is established, and a failure probability formula accounting for the superposition effects of multiple disasters is proposed. This study marks a significant advancement, transitioning from traditional single-pipeline evaluations to “structure-disaster-site” coupling analysis, and provides a scientific basis for pipeline seismic design, operation, and maintenance under specific environmental conditions. This work contributes to the development of quantitative and refined seismic risk assessments for oil and gas pipelines.

The construction of the tunnels of Metro Line 4 and Gulou Station in central Nanjing poses a potential threat to the nearby historic building, Gulou Tower, due to the relatively small spacing and the deteriorated structure behaviors. Two aspects are important for the protection of Gulou Tower: (i) reducing the soil movement caused by the tunnel–station construction and (ii) increasing the total stiffness of this sensitive building. This research first presents the main features of two tunnels and the triple-arch tunnel as the connection between the two tunnels and Gulou Station. The details of the excavation means and construction procedures of the tunnels, together with the engineering measures that tend to reduce soil disturbance during tunnel excavation, are presented. Meanwhile, to improve the overall stiffness of Gulou Tower, additional support for the masonry terrace and the upper timber structure is also discussed. Moreover, the construction procedures of the tunnels and the station that could influence the settlement development of Gulou Tower are also suggested. The measured ground settlement and structure displacement are found to be limited to the allowable values, indicating that the aforementioned protective measures are adequate to protect hybrid timber–masonry historical structures nearby tunneling.