# Safety Analysis and Condition Assessment of Corroded Energy Pipelines under Landslide Disasters
## 1 Introduction  
Pipelines are bestowed with a significance akin to a lifeline. With the ever-increasing global energy demand, pipeline construction is poised for a new era of rapid development [1]. As of 2022, China has constructed 15.5 \(\times\) 10\({}^{4}\) km of long-distance oil and gas pipelines, and it is projected to reach 24 \(\times\) 10\({}^{4}\) km by 2025 [2]. Owing to the complex geographical and climatic conditions in specific regions and considerations regarding project timelines and costs, a substantial number of pipelines will inevitably traverse areas prone to geological disasters. According to historical records, from 2009 to 2019, out of the 130,000 geological disasters in China, landslides accounted for 71% [3]. Pipeline damage caused by landslides is also the most hazardous of all geological disasters. Under the impact of landslides and with the increasing thrust from the soil, pipelines inevitably undergo tensile, compressive, and shear stresses, making them highly prone to deformation and even rupture. Given that some of pipelines have been in service for an extended duration,external and internal corrosion induced by soil and other mediums can significantly undermine the pipeline's load-bearing capability. This accelerates the likelihood of pipeline fractures and leaks, resulting in incalculable losses related to life, property, and energy [4; 5]. Numerous researchers have studied the condition of pipelines under landslide conditions to enhance their protective capabilities. In classifying landslide pipelines, [PERSON] [6] was the first to categorize them based on the angle between the direction that the pipeline is laying in and the landslide direction, differentiating them into transverse landslides, longitudinal landslides, and landslides at specific angles. In the case of transverse and longitudinal landslides, based on the analysis of the ultimate soil resistance [7], [PERSON] et al. [8] were the first to propose analytical solutions for elastic pipelines in elastoplastic soil under two different landslide scenarios. The variations in factors concerning pipeline landslides, soil-pipe contact, and semi-analytical issues have been further developed in subsequent research [9; 10; 11; 12]. Analytical methods were pioneered early on and served as guiding approaches in initial projects. However, due to the inherent simplifications in each model, there were inevitable accuracy issues in the results. With the advancement of computer technology, numerical simulation methods have become increasingly favored by scholars due to their efficiency and cost-effectiveness [13; 14; 15; 16]. A uniform landslide force load was conventionally employed for simplification, and this approach has gradually transitioned to a force distribution modeled by parabolic curves [17], further evolving into a more realistic fourth-power parabolic curve of the displacement [18]. Building upon the displacement load distribution of the fourth-power parabolic curve, [PERSON] et al. [19] investigated the strain distribution in transverse pipelines subjected to tensile and compressive stress caused by landslides. This led to the introduction of a criterion for pipeline failure based on relative stiffness. Beyond analytical and numerical simulation methods, some researchers have conducted extensive studies using full-scale, large-scale, and small-scale indoor experiments by establishing experimental platforms [20; 21; 22; 23; 24]. Pipelines in service face potential corrosion risks due to soil environmental changes in their buried locations [25]. Currently, most of the long-distance pipelines in use in China have been operational for over 20 years [26]. As time progresses, the protective coatings of these pipelines have started to deteriorate and peel off, causing the pipeline to be in direct contact with both the conveyed material and the enveloping soil. Consequently, this leads to internal and external corrosion, critically undermining the structural integrity and load-bearing capacity of the pipeline [27].