Cofferdam being built for south ramp
Temporary breakwater
dredged trench for unit No. 15
West arm
Cargo handling basin
30
Royal Hong Kong
Yacht Club
South ventilation
building
IIT*
Excavation for ramp construction
<=IITCI
Earth & rock fill cofferdam
Causeway Bay Typhoon shelter
Reclamation for Waterfront Road
Fig. 4. South ventilation building & south ramp temporary cofferdam
sists essentially of travelling rails cap- able of moving longitudinally and transversely and carrying fixed gas- flame cutting heads. This machine can be set to work to very fine tolerances cutting the plates square and true to width and length, and providing bevel edges where necessary.
When cut to size, pairs of plates are butt-welded by machine to form plate 35ft. 6 in. x 11ft. 8in. and rolled to correct curvature. This completes the preparation of plate.
In the meantime 8in. x 7in. tee stif- feners are pressed to the correct curva- ture and offered up to a ring jig where they are provided with a 'spider' and welded. Then, the ring stiffeners and the curved plate sections are offered up to the can jig where they are welded to form cans 11ft. 8in. x 34ft. Oin. diameter. Accuracy of cut- ting and fitting of all components is of prime importance in order to ensure good fit when the cans are brought together.
The next operation is to join the cans together, usually in groups of five to form tube sections 58ft. 4in. long. Where only four cans are joined the section is 46ft. 8in. long. The circum- ferential seams are welded both in- ternally and externally by machine as the cans are rotated on the mani- populator rolls.
As sections are completed they are transferred to one of the assembly positions where they are welded to- gether manually and fitted with dia- phragms. There are altogether fifteen. tunnel units thus formed and they vary between about 320ft. and 370ft. in length.
Before launching, the units have reinforcement fixed internally and are provided with bulkheads to seal the tube sections. The last operation just before launching is to concrete the keel. At this stage the unit weighs. about 4000 tons of which structural steel accounts for about 1000 tons.
Once unit has been side launched down the slipway it is taken alongside the fitting-out jetty and a further 15000 tons, or so, of concrete placed in and around the unit. The placing of con- crete in the unit is carefully controlled and the sequence planned so as to minimize stresses due to bending and shear of the unit as it is concreted up.
Placing of units
Before completed units can be taken out and placed in their correct positions, the sea bed has to be dredg- ed and a 2ft-minimum-thick crushed- stone bed placed accurately to line and
Far East BUILDER, June 1970