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As offshore exploitation moves to deeper waters, ocean currents become the prevailing hydrodynamic loads on pipelines, and at the same time a sloping seabed is always encountered. The prediction of lateral soil resistance is vital in evaluating pipeline on-bottom stability. Unlike previous pipe-soil interaction models used mainly for horizontal seabed conditions, a pipe-soil interaction model for current-induced downslope and upslope instabilities is proposed by using the limit equilibrium approach. The Coulomb's theory of passive earth pressure for the sloping seabed is incorporated in the derivation. The model verification with existing full-scale tests shows good agreement between the experimental results and predicted ones. Parametric study indicates that the effect of slope angle on pipeline lateral soil resistance is significant in the examined range of slope angle from -15° to 15°. The critical pipeline embedment and corresponding passive pressure decrease approximately linearly with increasing slope angle. Key words: submarine pipeline, on-bottom stability, sandy seabed, analytical study, pipe-soil interaction, sloping seabed. Lorsquee l'exploitation en mer passe a des eaux plus profondes, les courants oceaniques auront un effet d'hydrodynamisme plus repandu sur les pipelines, et entre temps, le fonds marins en pente est toujours rencontre. La prediction de la resistance laterale du sol est par rapport au fond de stabilite. Contrairement aux modeles precedents d'interaction tuyau-sol principalement pour des conditions de fonds marins horizontaux, un modele d'interaction tuyau-sol pour le courant induit dans le bas de la pente et les instabilites de pente ascendante est proposee en utilisant l'approche d'equilibre limite. La theorie de Coulomb de la pression de la terre passive pour les fonds marins en pente est incorporee dans la derivation. La verification du modele avec les essais existants de la pleine echelle montre une bonne concordance entre les resultats experimentaux et ceux prevus. L'etude parametrique indique que l'effet de l'angle de la pente sur la resistance des sols laterale du pipeline est importante dans la gamme etudiee d'angle de pente de -15° a 15°. L'enfouissement du pipeline critique et la pression passive correspondante diminue environ lineairement avec l'angle de la pente croissante. [Traduit par la Redaction] Mots-cles: pipeline sous-marin, stabilite sur le fond, fond de mer sableux, etude analytique, interaction de la conduite-sol, fond en pente., Introduction Lateral soil resistance is one of the fundamental issues in submarine pipeline on-bottom stability design for hydrodynamic loading conditions in offshore environments (Wagner et al. 1989; Det Norske Veritas [...]

Unlike previous mechanical actuator loading methods, in this study, a hydrodynamic loading method was employed in a flow flume for simulating ocean currents induced submarine pipeline stability on a sandy seabed. It has been observed that, in the process of pipeline losing lateral stability in currents, there usually exist three characteristic times: (1) onset of sand scour; (2) slight lateral displacement of pipeline; and (3) breakout of pipeline. An empirical linear relationship is established between the dimensionless submerged weight of pipeline and Froude number for describing pipeline lateral stability in currents, in which the current-pipe-soil coupling effects are reflected. Scale effects are examined with the method of 'modeling of models,' and the sand particle size effects on pipeline stability are also discussed. Moreover, the pipeline stability in currents is compared with that in waves, which indicates that the pipeline laid directly upon the sandy seabed is more laterally stable in currents than in waves. DOI: 10.1061/(ASCE)0733-9399(2007)133:10(1086) CE Database subject headings: Submarine pipelines; Ocean waves; Stability; Sea floor; Hydrodynamics.