plate-forme semisubmersible sur colonnes

OBS: Pluriel : des plateformes, des plates-formes.
OBS: plateforme (sing.); plateformes (pl.) : Ces graphies, puisées des Rectifications de l'orthographe recommandées par le Conseil supérieur de la langue française, sont attestées dans le Petit Robert (2004).

OBS: Such a rig can drill with the lower hull resting on bottom or the hull may be floating and submerged below the water. Usually the distance between the lower hull and upper deck is fixed.
OBS: Column Stabilized Drilling Units ... are self contained and are supported by either lower displacement type hulls by means of columns or by large caissons with or without bottom footings. Drilling operations may be carried out in the floating condition, in which case the unit is defined as a semisubmersible, or when resting on the bottom, in which case the unit is defined as submersible. A semisubmersible drilling unit may operate either floating or resting on the bottom.