Pullout Resistance of Buried Pipeline in Cohesionless Soil Nearby Sloping Ground

Abstract

The vertical and lateral pullout capacity of a long pipeline buried in a cohesionless soil nearby sloping ground has been investigated by using lower-bound limit analysis in combination with finite elements and linear optimization. The ultimate uplift and lateral resistances offered by the pipeline in cohesionless soil have been computed for different combinations of embedment ratio, slope angle, distance between slope crest and center line of the pipe, and soil friction angle. The results obtained for a pipeline buried in cohesionless soil with a horizontal ground surface compared well with the existing theoretical and experimental data. The present work illustrates that being near sloping ground can cause a significant reduction in the pullout resistance of a buried pipeline as long as it is located within the optimum crest distance. The effect of being near sloping ground has been found to be greater for a larger slope angle. The normalized optimum crest distance depends on the embedment ratio, slope angle, and soil friction angle of the ground soil. For a pipe subjected to lateral pulling, the values of optimum normalized crest distance are found to be higher than the pipe subjected to uplift. The proximity of the stress state to yield for different crest distances is presented to illustrate the failure mechanism.