Effect of Water Level Fluctuation and Its Rate on the Response of Earth Embankments with Buried Pipelines: Insights from Full-Scale Experiment and Numerical Modeling

The pipe culvert embedded in the embankment is a critical structure in hydraulic engineering; its stability under unsteady seepage flow is of paramount importance. However, the mechanical responses of embankment (containing pipelines) under water level fluctuations remain insufficiently studied, and further discussion is needed. This study aims to investigate the impacts of water level fluctuations on the deformation and seepage field of embankments, as well as the strain of pipelines, through full-scale experiments. Furthermore, a finite-element model based on seepage–stress coupling theory is developed to simulate the deformation behavior of the embankment and the evolution of the internal seepage field under varying fluctuation rates. Additionally, the mechanical response of the pipelines’ most critical cross section is analyzed. The results indicate that both circumferential and longitudinal pipe strains propagate downstream along the pipeline, exhibiting a nonmonotonic distribution. Moreover, the peak longitudinal strains at the pipe invert are more localized than the peak circumferential strains. The bending moment displays limited sensitivity to water level fluctuations, with a maximum variation of only 5.86% throughout the entire testing period. During the rapid water level rise phase (vh = 0.2 m/h, vh is the water level fluctuation rate), the displacement at the upstream slope monitoring point (0.2459 mm) was 2.36 times greater than that at the downstream slope monitoring point (0.1041 mm), whereas longer fluctuation durations (48 h) allowed the system to stabilize, leading to significant reductions in both pore-water pressure and overall displacement. These findings provide valuable guidance for the safe design, monitoring, and maintenance of pipeline-containing embankments in environments subject to frequent variations in reservoir levels.