Abstract: The invention relates to the immersion at a great depth of an offshore weight-structure comprising a concrete base having two multicellular compartments, the one being central and self-resistant and the other being peripheral and subjected to compensating pressures, at least one multitubular pylon fixed to the said base and having a working area installed above it out of the water, and an auxiliary float co-operating with each pylon. The invention is characterized in that ballasting is effected by partial filling of the said self-resistant central compartment to enable the beginning of the immersion to be effected and that the actual immersion is then effected by the action of the said auxiliary float having an elongated cylindrical shape and being partly filled and whose relative position in relation to the said base is varied by mechanical guiding means.

Abstract: Method and device for connecting submarine pipelines to a marine platform resting by its weight on the sea bed and called a weight-platform, whose object is to dispense with the intervention of frog-men which was necessary up till now to make such connections. The essential feature of the invention consists in inserting each pipeline to be connected in the base of the platform through a cavity whose dimensions are determined so as to enable both the installing of the fluid-tight sealing means necessary for the connecting operation and the free play of the pipeline during operation. That method and device are applicable to all marine oil fields to ensure the reliability of the connections and the reducing of the dangers of pollution.