Underground pipeline reliability under longitudinal impact load
Abstract
Abstract The paper presents the results of numerical solution obtained by the modified finite difference method according to the Wilkins scheme, to a two-dimensional unsteady-state problem of the plane shock wave propagation in an underground elastic pipeline, interacting with surrounding soil. Soil is considered to be an undeformable body moving relative to the pipeline at a given velocity. The value of the friction force depends on radial stress in the pipeline, determined by numerical solution to the problem. Changes in longitudinal and radial stresses over time and pipeline length, of velocity and displacements for fixed sections of the pipeline are obtained. Two times increase in values of longitudinal and radial stresses was detected in the case of active Coulomb friction at the pipeline-soil contact. The increase in stress values occurs due to the friction force acting in the direction of wave propagation. At significant values of the friction force on the outer surface of the pipeline, the hypothesis of flat sections is fulfilled for all its sections. This result justifies the consideration of similar problems of underground pipelines earthquake resistance in a one-dimensional statement. The results also make it possible to identify the mechanisms of the stress state formation in an underground pipeline interacting with soil, which can be used in seismic resistance calculation of underground trunk pipelines.