# Investigation of Debonding Effect in Internal Replacement Pipe System Under Lateral Loading
## 1 Introduction  
Water, wastewater, oil, and natural gas are examples of critical resources that are conveyed using pipelines, which typically serve as efficient and reliable transportation systems. As these systems age, maintenance, repair, and eventual replacement become necessary to ensure continued safety and reliability. For example, according to reports in [1; 2; 3; 4; 5; 6; 7], most oil and gas pipelines in the United States, Europe, and Australia are over 40 years old and need attention. Regular maintenance and monitoring of pipelines are essential for ensuring their continued integrity. There is an increasing interest in modernizing pipeline systems among various stakeholders, with numerous examples of notable advancements. Policymakers and utilities are responsible for delivering natural gas to customers; forexample, they widely acknowledge the imperative to expedite ongoing endeavors in replacing outdated infrastructure while also adopting innovative approaches to operations and maintenance [8; 9]. The integrity of buried pipelines is susceptible to multiple failure modes, encompassing corrosion, mechanical damage, material defects, and geohazards such as landslides and earthquakes. Among these failure modes, mechanical damage emerges as a prominent concern attributable to excavation activities, construction defects, or external forces, such as traffic loading, heavy equipment, or third-party interference. In practice, buried pipelines frequently face substantial transverse loads originating from excavation equipment or surface traffic, potentially jeopardizing their structural integrity [10]. The failure of pipelines is an unfortunate event with far-reaching consequences, encompassing economic, environmental, and, in extreme cases, human casualties [11; 12]. Thus, it is essential to comprehend the failure modes associated with deflection to develop effective strategies for regulation, inspection, maintenance, and repair. The rehabilitation of legacy pipes presents a crucial challenge in the modernization of aging infrastructure. Internal replacement pipe (IRP) technology is emerging as a promising solution to address this problem. IRP is a trenchless technology that involves the installation of a new, structurally reinforced pipe within the existing pipeline, thereby providing enhanced strength and longevity [13]. There are several benefits to using the IRP as a repair system for legacy pipelines. First, it eliminates the need for complete pipeline replacement, minimizing the associated costs, disruptions, and environmental impact. Second, IRP offers significant advantages over alternative methods by providing improved structural integrity, corrosion resistance, and increased capacity. Finally, IRP technology can be tailored to accommodate varying pipe diameters and lengths, making it suitable for a wide range of legacy pipeline rehabilitation projects. Recent studies have demonstrated the effectiveness of IRP technology in rehabilitating legacy pipelines. For instance, [PERSON] et al. [14] showed that IRP can significantly enhance the structural integrity of deteriorated pipes. Research activities have demonstrated that the use of IRP increases the load-bearing capacity of pipes while concurrently reducing the probability of leaks or failures [15; 16; 17; 18; 19]. The report produced by the U.S. Department of Energy emphasized the environmental benefits of IRP in natural gas pipelines, highlighting its potential to reduce greenhouse gas emissions by reducing system integrity risks [8]. These findings highlight the importance of IRP as an innovative, cost-effective, and sustainable approach for rehabilitating legacy pipelines. This approach also ensures the safety and reliability of pipeline distribution systems while minimizing environmental impacts. More precise estimates of the bending stiffness, nonlinearity, and debonding mechanism of composite sections are desired for the future development of the IRP trenchless technology [15; 16; 17; 18; 19; 20].