Axial Load-Displacement Behavior of Energy Pipeline Systems in Sand

Abstract

An experimental investigation program was undertaken to study the behavior of a prototype steel pipeline of 114.3 mm outer diameter and 1.35 m length in a sand subjected to a parallel soil mass movement in the longitudinal direction under saturated and unsaturated conditions. The experimental program included several axial load-displacement tests that were performed by varying the water table level. These tests were performed in a specially designed soil container that has provision of water/supply drainage system which facilities achieving different soil-matric suction profiles. The results of the experimental study suggest that matric suction has significant influence on the mechanical behavior of pipeline systems. The axial load that was transferred from unsaturated sand onto the pipe was determined to be 2–2.5-folds greater in comparison to saturated condition. Such an external axial force increment that is not anticipated from conventional design calculations may jeopardize the integrity of energy pipeline systems. For this reason, careful reevaluation is required of the existing design models and code provisions that are presently based on conventional soil mechanics. The study summarized in this paper suggests that the rational interpretation of the pipeline systems is possible by extending the principles of unsaturated soil mechanics.