A blade drive shaft assembly (100) for a road saw comprising a shaft (120), a first mounting plate (125), a spacer removably fitted (126) on the shaft (120), a second mounting plate (127) removably fitted on the shaft (120), a mounting plate fixing adapted to secure the second mounting plate (127) to the shaft, a first circular saw blade mounted between the first mounting plate and the spacer (126), and a second circular saw blade mounted between the second mounting plate (127) and the spacer (126), wherein the first mounting plate (125) is integrally formed with the shaft (120) from a single piece of metal. A road saw incorporating the assembly is also described, as well as a method of forming, filling and compacting a trench and a method of making a blade drive shaft assembly.

An apparatus for locating an elongate object in the seabed is disclosed. The apparatus comprises a body and a pair of jetting swords arranged on lateral sides of the elongate object to form a trench in the seabed. Chain cutters arranged on lateral sides of the elongate object cut respective parts of a trench in the seabed and are moveable relative to the body between a stowed position and a deployed position, independently of the jetting swords.

A system for laying an underwater pipeline on a bed of a body of water has a construction site to form a string of an underwater pipeline, the string being defined by a curved portion shaped substantially like a portion of the bed of the body of water characterized by an abrupt change in slope; at least two vessels to transfer, in the body of water, the string from the construction site to a laying site in the body of water and substantially on the vertical of a path along which to lay the string; and a plurality of floating devices configured to be coupled to the string and so as to selectively support and sink the string in the body of water, and progressively lay the string along the path on the bed of the body of water.

Pipe burial apparatus are disclosed that include sets of rotary nozzle cutters configured to straddle a pipe that is to be buried and a nozzle array connected to a nozzle supply pipe in a manner that places the nozzle supply pipe in a cutting path of a rotary nozzle cutter. The nozzle supply pipe may be actuated to alternatingly move the nozzle array between a position straddling the pipe being buried and a cutting position that is below the pipe being buried.

A trench cutting apparatus and method, the apparatus comprising a central support element comprising at least one jetting outlet and a cutting element configured to be driven around the central support element. The trench cutting apparatus is configured to be operable in a mechanical cutting mode in which the cutting element is driven around the central support element to cut material forward of the trench cutting apparatus, and a jet cutting mode in which a pump is activated to eject fluid from the at least one jetting outlet to fluidize or cut material forward of the trench cutting apparatus.

A subsea trencher for arranging at least partly into the seabed a subsea pipeline, includes at least one cart that separately carries at least one trench tool and is configured to run along the subsea pipeline. trench tool is configured to work the seabed underneath the subsea pipeline. A subsea support frame carries heavy subsea equipment connected to the trench tool for operating the trench too. When the subsea support frame is fixed to the cart, the subsea trencher is configured to load the assembled weight of the cart and subsea support frame onto the subsea pipeline as the subsea trencher runs on the subsea pipeline. When the subsea support frame is separate from the cart, the subsea support frame is configured to be suspended above the seabed or arranged beside the subsea pipeline at a distance from the subsea pipeline as the cart runs along the subsea pipeline.

A wheel cutter tractor for inserting a cable into a trench is disclosed. The tractor comprises a wheel cutter for cutting a trench, and tracks for moving the tractor relative to the trench. A cable support tray supports the cable in a first position displaced from the wheel cutter in a direction transverse to a direction of travel of the tractor, and in a second position above the wheel cutter. A cable grab and lifting device transfers the cable into the cable support tray.

An apparatus for locating an elongate object in the seabed is disclosed. The apparatus comprises a body and a pair of jetting swords arranged on lateral sides of the elongate object to form a trench in the seabed. Chain cutters arranged on lateral sides of the elongate object cut respective parts of a trench in the seabed and are moveable relative to the body between a stowed position and a deployed position, independently of the jetting swords.

A trencher includes a trencher body; a cable detection mechanism disposed at a front portion of the trencher body; a chain mechanism and a jet mechanism disposed in the center of a bottom portion of the trencher body; a first track mechanism and a second track mechanism, the first track mechanism being disposed on a first side of the bottom portion of the trencher body, and the second track mechanism being disposed on a second side of the bottom portion of the trencher body; and a soil discharging component disposed at a rear portion of the trencher body.

A subsea trencher for arranging at least partly into the seabed a subsea pipeline, includes at least one cart that separately carries at least one trench tool and is configured to run along the subsea pipeline. The trench tool is configured to work the seabed underneath the subsea pipeline. A subsea support frame carries heavy subsea equipment connected to the trench tool for operating the trench too. When the subsea support frame is fixed to the cart, the subsea trencher is configured to load the assembled weight of the cart and subsea support frame onto the subsea pipeline as the subsea trencher runs on the subsea pipeline. When the subsea support frame is separate from the cart, the subsea support frame is configured to be suspended above the seabed or arranged beside the subsea pipeline at a distance from the subsea pipeline as the cart runs along the subsea pipeline.