Modeling of buried pipelines in dense sand for oblique movement in vertical–lateral plane

Finite-element modeling of pipelines buried in dense sand under oblique loading in vertical (upward)–lateral load space is presented. The prepeak hardening, postpeak softening, density, and confining pressure–dependent behavior of sand are considered in simulations. A monotonic displacement-controlled loading is applied where pipe is displaced at an angle ranging from 0° (vertical upward) to 90° (lateral). The plots of vertical and lateral components of oblique force (load paths) resulting from the displacement-controlled loading show a significant nonassociated response for shallow burial depths and lateral loading cases. The restraint to vertical displacement during lateral displacement increases the lateral resistance. A simplified approach based on maximum vertical and lateral restraints, together with an inclination factor, is proposed to estimate the maximum oblique resistance.