Modeling of flexible pipe for culvert application under shallow burial condition

Flexible thermoplastic pipes under field and laboratory loading conditions have been examined in the present study. The flexible pipes were tested under truck loading application with shallow soil cover. The pipe-soil system response includes soil stresses around and above the buried pipes, vertical pipe crown diametral strain, and circumferential pipe wall strains. Modeling the pipe-soil system is made using plane strain and thin ring assumptions. A thin ring model using Castigliano's theorem is developed to analyze the behavior and response of a flexible pipe under well defined loading conditions and simulate the behavior of the buried pipe under the live load application. Laboratory work was carried out to study the pipe behavior and response under two-point, three-point, and four-point loading configurations. The thin ring model predictions show good agreement with classical solutions specially valid for two-point and three-point loading configurations. Laboratory results were also in good agreement with the predictions. Laboratory results show that the maximum tensile strain for the four-point loading test occurs at inner pipe crown region. Comprehensive efforts were made to correlate the thin ring model predictions with the field test results; however, it appears that the thin ring model cannot be used to simulate the effect of the live load application. A major source of the differences between the predicted and measured values is attributed to the applied load magnitude. A further investigation was carried out to examine the applicability of the model to study the general pipe behavior. The predicted hoop pipe wall strain profile was found to be similar to that of the reported strain profile by Rogers under overall poor soil support condition.{09}Comparison of soil stress distribution shows that the 2D prediction approach provides nonconservative results while the FE analysis agrees more favorably with the measured pressure data. Overall, FE analysis shows that a linearly elastic isotropic model for the surrounding soil and flexible pipes with a fully bonded pipe-soil interface provides a reasonable prediction for soil pressures close to the buried pipes.