Nonlinear eleastic modeling of pipeline in sloping clay under high Ko.

Abstract

Numerous cases of pipeline failures are documented every year, triggering new problems for research and the need for re-examination of already established design guidelines and standards. The problem of soil/pipeline interaction has been thoroughly researched over the years; however, further investigation is required in some areas. This thesis presents an investigation. using numerical modeling to simulate the installation of a steel pipeline in overconsolidated clay. Some factors related to the site geometry (sloping ground) and construction methods (fill compaction), as well as the stiffness of the pipeline section, are also investigated. This study shows that the reaction of the soil mass to the trench excavation continued for as long as four years after backfilling. In addition, the following conclusions can be drawn from the results presented in this thesis: (1) When the pipeline is installed in a trench, at the base of a v-shaped depression, a higher total stress acts at the base and crown of the pipeline with level ground and smaller ground slopes causing more deformation in the pipeline section than with steep ground slopes. (2) A static, surcharge-type compaction for a reasonable duration is found to reduce damaging stresses at the base and crown of the pipeline, during and after surcharge loading. (3) A less rigid pipeline section would carry less of the weight of overlying fill material and will cause more of the load to be carried by the fill material on either side of the pipeline. This results in higher lateral pressure (in the pipeline section and slower dissipation of pore water pressure around the pipeline.