Numerical Investigation of Soil–pipeline Interaction Effects on the Seismic and Surface Load Responses

Pipelines are among the main systems for conveying fluids over long distances and are typically installed below ground level along most of their alignment. These systems are widely employed for transporting water, petroleum, natural gas, and other fluids, as well as for serving as utility corridors. During seismic events, buried pipelines may experience both transient and permanent ground deformations.

In this study, the influence of key parameters-including pipe wall thickness, burial depth, and soil type-on the behavior of underground pipelines subjected to surface loading and earthquake waves was investigated using PLAXIS 2D. Three pipe diameters and various burial depths were analyzed in both homogeneous and composite soil layers to evaluate pipeline crown displacement.

The results show that pipe displacement tends to increase with larger pipe diameters and greater burial depths under various soil conditions and wall thicknesses. Pipelines installed in loose sand demonstrated higher seismic sensitivity compared to those embedded in clay soils, where lower displacement values were observed. Increasing the pipe wall thickness, and consequently its stiffness, resulted in a noticeable reduction in displacement. Additionally, the crown displacement was found to rise with increasing surface loads and pipe diameters, especially at shallow embedment depths. Furthermore, pipelines placed in composite soil exhibited improved performance, with reduced displacements compared to those in uniform soil layers.

The observed behavior indicates that both geometric properties, such as diameter and thickness, and geotechnical conditions, such as soil type and layering, play critical roles in controlling pipeline response under seismic and surface loading. The improved performance in composite soils suggests that soil stratification can enhance system stability, while loose sand conditions amplify seismic effects due to lower stiffness.

The findings of this study provide quantitative relationships that can help explain how burial depth, pipe geometry, and soil conditions influence pipeline displacement under different loading scenarios.