Beam Behavior of Buried Rigid Pipelines

The behavior of buried pipelines as beams on elastic foundations is analyzed, and two potential failure modes investigated. First, shear forces at bell and spigot joints in pipelines may lead to leakage at the joint or even fracture of the pipe at the bell. High shears develop where, through poor construction or control, the pipeline is supported by the bells resting on the trench floor. Significant shears occur where cells are cut for the pipe bells such that the pipeline rests on the pipe barrels. Equations presented estimate shears from conditions of applied load and bedding support, from pipeline geometry, and from elastic moduli of O-ring gaskets and pipeline bedding. Second, broken back failure of buried rigid pipes may occur beneath a heavy wheel load. Graphs facilitate calculation of maximum bending moment from surface load, cover depth, pipe geometry, and elastic properties of pipe and bedding. Firm bedding enhances resistance to failure in both shear and moment.