Traffic Loading Effects on Rehabilitated Cast Iron Distribution Pipelines

Pipelines buried beneath roadways experience deformation due to traffic loading throughout their service life. For a jointed cast iron pipeline, traffic loading causes displacement and rotation at each joint. When rehabilitating buried cast iron pipes using trenchless technology, the repair is designed to withstand the imposed displacement and rotation. Introducing a circumferential crack to the host pipe represents an extreme scenario for a repair. A finite element model is developed to evaluate cast iron pipeline deformations caused by HS-20 truck loads applied at the ground surface. The loading is applied to the pipe as a distributed load using Boussinesq’s solution for point loads on a semi-infinite elastic half-space. The pipe-soil interaction is modeled as soil springs with linear-elastic behavior. The cast iron joints are modeled with axial, shear, and rotational springs using previously published data based on laboratory testing of field-sampled cast iron joints. The present model is then compared with analytical solutions, past finite element analyses, and past experimental data to verify and validate deformed shape, rotation at the joints and circumferential crack, and relative offset at the circumferential crack. Following validation, properties of a cured-in-place pipe repair are applied to the model and the predicted offsets and rotations tabulated. The results can inform full-scale testing procedures, justifying the experiment geometry, input loads, and corresponding displacements necessary to evaluate the performance of new pipeline repair technologies over a simulated design life.