Analysis of buried steel pipelines at watercourse crossings under liquefaction-induced lateral spreading

At watercourse crossings, buried steel pipelines typically transition from a shallow burial depth to a depth below the maximum scour depth of the watercourse channel. This paper investigates the pipeline response when such watercourse crossings undergo liquefaction-induced lateral spreading. The investigation is performed via non-linear finite element analyses (FEA) for a multitude of "generic" combinations of watercourse depth, liquefiable soil stratigraphy and pipe characteristics. The FEA provide peak pipeline strains and are used to define allowable peak permanent ground displacement (PGD) values for each "generic" case. It is shown that pipe strain is most intense at pipe overbends and that the allowable peak PGD increases with the depth of the watercourse, as there is less interaction between the strained overbend and the sagbend areas. Furthermore, allowable peak PGD increases slightly with pipe diameter and significantly with pipe wall thickness, while it reduces with soil friction and the inclination angle of the downward pipeline transition below the waterbed.