Abstract: A method for laying underwater pipelines in deep water, using the J launching technique, comprising joining together mixed-structure pipes consisting of a steel core reinforced with a composite material consisting of a hardenable material containing continuous fibers and in which:the continuous fiber is wound about the steel core as a helical winding which forms an angle of between 65.degree. and 87.degree. with the pipe axis;the ratio of the thickness of the composite layer to the thickness of the steel core is between 2 and 8;the weight of the mixed-structure pipe in water is between about 40 and 100 kg/m.

Abstract: Method and apparatus for laying an underwater pipe to straddle an already laid pipe, comprising fastening to the pipe to be laid, at appropriate distances apart, a set of trestles the heights of which are gradually increasing and decreasing consistent with the bend to be imparted to the pipe to be laid in order to have it positioned in the correct straddling relationship relative to the already laid pipe. Each trestle is connected to the pipe to be laid by flexible means which allow the trestle to move vertically, longitudinally and traversely relative to the pipe and to be suspended below and separate from the pipe as the pipe and trestle descend to the sea bed for proper positioning of the trestle substantially independent of the pipe.

Abstract: A semi-submersible pipelaying watercraft is disclosed, which is particularly suitable for operating under particularly hostile marine environments, said watercraft comprising a composite ramp of special construction for launching the pipe to be laid, a system for determining the craft's position and a control system, governed by electronic computers for automatically positioning the craft.An internal inclinable ramp is coactively combined with an external ramp and the internal ramp is equipped with a locking system and with a displacing system, hydraulic controls being provided for moving both the internal and external ramps. The electronic computers are two and one of them makes the calculations for determining the design parameters, whereas the other computer receives the actual data provided by the several sensors mounted aboard and processes them.

Abstract: An apparatus for digging a trench beneath a pipeline laid on the bottom of sea or a water body, in which a clamp arrangement is split into a wider sector portion and a narrower sector portion which, as they are united under the control of a driving mechanism, embrace the pipeline and allow a set of digging discs to excavate the ground beneath the pipeline. Provisions are made to remove the debris on completion of digging. The apparatus is driven along the pipeline and means are provided to maintain both the correct vertical trim of the entire apparatus and the correct position of the pipeline track.

Abstract: This invention relates to an improved method for rapidly laying a pipeline in deep water by an anchored floating means. The rapid laying is obtained by varying the forces exerted by winches mounted on the floating means in such a manner as to impart a rapid movement to the floating means, in the longitudinal direction of laying, for a distance equal to the length of the piece of pipe added to the free end of the pipeline to be laid. Before termination of the rapid movement there is applied to the floating means a compensating force, whose direction, sense and intensity are such that, together with the forces exerted by the winches, said compensating force opposes moment by moment the central elastic force which induces a damped oscillatory motion in the floating means. This oscillation is thus eliminated or drastically and rapidly dampened.

Abstract: A catamaran, adapted for use in laying a submerged pipeline, is provided with a slidable support for the pipeline, including a slightly inclined ramp integral with the awning deck of the catamaran for carrying out the operations for building the pipeline, a moveable stinger extending from the rear end of the catamaran, and an intermediate pipeline supporting element having its bow end hinged to the stern end of the ramp and its stern end pivotally hooked to the front end of the stinger. The stern end of the intermediate pipeline supporting element may be raised or lowered so that its angle of inclination may be varied and it may be locked in position at a selected angle of inclination through a castle-shaped member located abaft the catamaran and including two side frames fixed to the awning deck of the catamaran so that they straddle the intermediate pipeline supporting element and their lower ends are submerged.