## 1 Introduction  
Pipeline transportation is one of the five major transportation methods in the world and plays a crucial role in mechanical fields such as ships and offshore platforms [1, 2]. The use of pipeline transportation can improve the efficiency of large-scale fluid transportation and reduce costs. However, as the usage of pipelines increases, the risk of pipeline failures also increases [3]. Pipeline failures can cause serious safety accidents and huge economic losses, making pipeline maintenance and monitoring imperative. With the increasing attention to the environment, natural gas as a clean energy source has been vigorously developed. The demand for urban gas has been increasing, and urban underground gas pipeline networks are becoming more densely distributed. Many urban gas pipelines have been experiencing high accident rates. Gas leakage accidents can be divided into the following two categories: The first category is small hole leakage in gas pipelines in the soil, which accumulates in enclosed spaces and can cause accidents such as fires and explosions when encountering ignition sources. The second category is direct gas leakage to the ground space due to third-party damage to the pipelines, which can cause accidents such as explosions in densely populated communities and streets [4,5]. Pipeline leaks can have a serious impact on the environment. For example, if the oil pool and oil vapor cloud generated by pipeline leaks explode and burn in an open flame, it can cause serious economic losses and casualties to companies. The explosion of oil vapor clouds is a type of heavy gas diffusion that concentrates in the vicinity and has a significant impact on the environment [6]. Another example is the leakage of sewage pipelines, which can have a serious impact on soil and groundwater environments. The main manifestations include changes in soil physical and chemical properties, soil pollution, eutrophication of soil, resulting in groundwater pollution, reduction in freshwater resources, and soil erosion [7]. Acoustic-solid coupling analysis can provide a theoretical basis for pipeline leak detection, enabling timely detection of leaks and avoiding environmental pollution and safety accidents caused by pipeline leaks. Among the various methods for pipeline fault detection, guided wave-based pipeline fault detection technology has become a popular solution for non-destructive testing of pipelines due to its ability to propagate over long distances in waveguides and its sensitivity to defects [8, 9, 10]. Guided wave-based detection technology using ultrasonic guided waves is an important tool for pipeline fault monitoring, and accurately understanding the wave dispersion characteristics in pipelines is a prerequisite for accurately identifying pipeline faults [11]. Currently, widely used long-distance pipeline corrosion defect detection technologies include magnetic crawler, ultrasonic crawler, and ultrasonic guided wave detection [12]. Whether it is leakage magnetic crawlers or ultrasonic crawlers, strictly speaking, they are point-to-point measurement methods, and the detection efficiency is still relatively low. They usually require the pipeline contact area to have a high surface quality, and pipelines with coatings usually require the removal of the coating, which increases costs [13]. In comparison, ultrasonic guided wave detection technology has many advantages, such as long propagation distance and the ability to perform extensive testing using a fixed pulse-echo array at one location.