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The flexural behavior of flexible buried pipelines subjected to lateral earth movements is investigated. Two types of pipeline materials, steel and then glass-fiber reinforced polymers (GFRP), are examined. Bending tests are conducted, where two parallel cables attached to a hydraulic actuator load the buried pipe. The study investigated three burial depth-to-diameter ratios (H/D = 3, 5, and 7) representing shallow to deep burial depths commonly used in energy pipeline construction. A three dimensional finite element model for this loading case has also been developed. Data from the numerical simulations are presented and compared to the experimental measurements. This paper provides an overview of the outcomes for this project. For example, while soil resistance was very similar for the two pipe types, the GFRP pipes demonstrated superior flexibility in longitudinal bending compared to the steel pipe. Furthermore, the finite element analyses were able to depict both this similarity in soil resistance, and the significant difference in flexural behavior of the two different pipe materials, the same phenomena observed during testing.

This paper presents simplified finite-element analysis procedures based on geometrical nonlinearity and ductile Mohr–Coulomb–Davis plasticity for analysis of bending behaviour of steel pipes subjected to lateral soil loading. A simple, and easy to implement, user-defined subroutine to represent soil stiffness using the Janbu model is also presented and discussed. The development of a three-dimensional (3D) finite-element model is presented, and its evaluation against experimental measurements is discussed. Data are presented for different burial depths of the pipe, including soil loading on the pipe as well as 3D responses, longitudinal bending deflections and pressure distribution along the pipe. It was shown that numerical analyses which include soil modulus dependency on confining pressure lead to effective 3D calculations of pulling forces, bending moments along the pipeline and flexural deformations, based on measured soil parameters. The 3D analysis model requires the use of lower order (linear displacement) elements, which overestimated peak mobilized load. However, those 3D calculations effectively provided the progress of both the load–deflection and longitudinal bending response of the steel pipe at embedment ratios up to 5 where most energy pipelines are buried.