Human engineering activities and climate warming induce permafrost degradation in the Da Xing’anling Mountains, which may affect the distribution of permafrost and the safety of infrastructure. This study uses the electrical resistivity tomography method, in combination with field surveys and ground temperature monitoring, to investigate the distribution and degradation characteristics of permafrost and influencing factors at a typical monitoring site (MDS304) near the China-Russia Crude Oil Pipeline (CRCOP). The results show that the isolated permafrost in this area is vulnerable to further degradation because of warm oil pipelines and thermal erosion of rivers and ponds. The isolated permafrost is degrading in three directions at the MDS304 site. Specifically, the boundary between permafrost and talik is on both sides of the CRCOP, and permafrost is distributed as islands along a cross-section with a length of about 58–60 m. At present, the vertical hydrothermal influence range of the CRCOP increased to about 10–12 m. The active layer thickness has increased at a rate of 2.0 m/a from about 2.4–6.8 m to 2.5–10.8 m from 2019 to 2021 along this cross-section. Permafrost degradation on the side of the CRCOP’s second line is more visible due to the river’s lateral thermal erosion, where the talik boundary has moved eastward about 12 m during 2018–2022 at a rate of 3.0 m/a. It is 2.25 times the westward moving speed of the talik boundary on one side of the CRCOP’s first line. In contrast, the talik boundary between the CRCOP’s first line and the G111 highway also moves westward by about 4 m in 2019–2022. Moreover, the maximum displacement of the CRCOP’s second line caused by the thawing of frozen soil has reached up to 1.78 m. The degradation of permafrost may threaten the long-term stability of the pipeline. Moreover, the research results can provide a useful reference for decision-makers to reduce the risk of pipeline freeze-thaw hazards.

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.

Traditional methods for assessing the risk to linear engineering projects (e.g., pipelines, railways, power transmission lines, etc.) from landslides are constrained by the need for prior prediction of specific landslide geometries. This leads to complex processes and uncertain outcomes. This study proposes a fundamental paradigm shift: employing slope units as stable assessment units and directly evaluating their probability of overall instability as the hazard indicator. Furthermore, for the linear engineering segment traversing a given unit, its vulnerability and failure consequences can be predetermined and uniquely defined within the unit based on engineering attributes (e.g., crossing type, structural design parameters, socio-economic value), forming a "fixed-parameter" system. Consequently, the risk to linear engineering projects under landslide influence is simplified into a standardized formula: Unit Risk = Unit Landslide Probability (predicted) × Unit Linear Engineering Vulnerability (fixed) × Unit Linear Engineering Failure Consequence (fixed). The core advantages of this model lie in its generality and efficiency: 1) It is applicable to all types of mountainous linear engineering projects including pipelines, roads, railways, and transmission lines; 2) It is equally suitable for forward-looking risk assessment during the planning and design phase as well as for rapid risk screening during operation and maintenance; 3) By encapsulating complex uncertainties within the probabilistic assessment of the slope unit while standardizing vulnerability and consequence parameters, it transforms the evaluation process from "case-by-case judgment" to "standardized calculation". This method offers a promising novel pathway toward standardized and rapid assessment for managing the risk to linear engineering projects under landslide influence, holding significant application potential, particularly for the preliminary screening and systematic comparison of risks to long-distance projects under the influence of geohazards.