N.V. Lawson, P.H. Youll


The Port of Newcastle, N.S.W., Australia, is being deepened from 11m to 15.2m below chart datum to permit the navigation of 12 0,0 00 D.W.T. bulk coal vessels. Part of this project, which is expected to reach a cost of approximately A$9 0 million, involves the removal of two million cubic metres of rock, some of which is located outside the breakwaters and exposed to ocean waves (see Fig. 1). Drilling and blasting of rock in the area subjected to ocean wave activity is being carried out by two self elevating platforms. On completion of drilling and prior to blasting the platform must make a transition from being supported by its legs to floating so it can be removed from the blasting area. While the two self elevating platforms have been built with a very fast jacking rate of 6m/ minute, with a sophisticated shock absorbing system connecting the legs to the platform, the rigs cannot be j acked up or down when wave conditions exceed a certain limit. Even though the rigs can survive worse conditions than those allowable for jacking down by remaining on their legs at a sufficient height above the water, this would entail loss of drilling time, and the presence of the rigs in the channel could close the port to shipping. Thus from an operational point of view it is vital that present wave conditions are reliably described. Estimation of wave height by observation is difficult enough during daylight hours but is virtually impossible in darkness (drilling operations are carried out 24 hours/day). The dredging contractor (WestHam Dredging Co. Pty. Ltd.) therefore decided that a real time wave analysis system should be established and co-operated with The Maritime Services Board of N.S.W. in a joint project for this purpose.


wave analysis; realtime analysis; Newcastle, Australia

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