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Ports and harbours - A port for any storm

News - Hong Kong Special typhoon anchors for the cranes and a vast dredging operation are key features at CT9, Hong Kong's latest container terminal. Adrian Greeman reports

Even before dredging was complete this year for Hong Kong's new Container Terminal Nine (CT9) the latest super-giant container ships were already tying up at the first three berths. Three more quayside berths are due for completion this year along with a government owned marine basin, which will service a chemical waste treatment plant alongside the container terminal.

The new resource, the city's biggest, keeps Hong Kong at the top of the world capacity league.

It completes the Kwai Chung container complex with six berths along some 1,900m of new quayside, capable of handling the future '22-across' container vessels. Behind will be handling and stacking yards on part of an overall 150ha site, mostly reclaimed from the sea.

All this enormous capacity will be needed. Demand continues to expand, especially with the growth of the so-called Pan Pearl River delta region of southern China where economic output will grow from $630bn this year to over $1,000bn in 2010 and perhaps double that in 2020.

Once running at full capacity CT9 will annually shift at least 2.6M TEUs, which is bigger than the total capacity of many of the world's other container ports.

But it has been a while coming. The currency collapse which hammered all the Asian economies in the late 1990s and political issues as China took over the Special Administrative Zone in 1997 held up the development; only after some complicated swapping of berths between various operators did the long-planned scheme get under way. Joint clients Modern Terminals, Hong Kong International Terminals and Asia Container Terminals appointed Scott Wilson and Maunsell for the design and supervision in 1999.

Even when site work began at the start of 2000 there was an early hold-up with disposal of dredged mud; some of the harbour bottom deposits were heavily contaminated with both domestic waste and industrial run-off from the heavily populated districts west of Kowloon.

The Hong Kong government insisted that main contractor Hyundai Engineering & Construction and its partner China Civil Engineering Construction Corporation change plans to dispose of the mud off the mainland and use instead the sealed tips at East Sha Chau just off the end of Lantau island.

'It costs more of course, ' says Jonathan Meigh, deputy project manager from Scott Wilson, 'because these dumps are controlled and capped with clean material.'

Altogether the dredging operation meant taking 24M. m 3ofmaterial away before bringing clean sand from deepwater to build up the new land at the south eastern end of Tsing Yi island where the container complex is sited. Fortunately most of the mud was uncontaminated;

it is removed to prevent later settlement problems.

'There is an area of the reclaim where we have left the mud layer, however, ' says Meigh. This is on the south and west sides of the project. Here there is a little more time available to allow a nine or twelve month surcharging option to work, to force consolidation.

'We have installed wick drains here at 1.3 to 1.5m centres down to maximum of 30m or so, ' explains Meigh. Rather than place these from barges the contractor waited until the material was dumped and used land-based rigs to place the drains through the new sand blanket. Much of that stockpiled material is now being redistributed to finish the remaining parts of the reclamation Surprisingly, the project has not featured extensive use of the jumbo suction hopper dredgers that have worked on the recent Disneyland reclamation at Penny's Bay. 'One or two bigger boats were used, ' says Meigh 'but mainly a fleet of smaller trailers and grab dredgers has done the donkey work.' They have moved most of the mud and around 37M. m 3of fill sand.

To deepen channels where Hong Kong's granite bedrock comes near the surface some 28,000m 3or so of harder material has been carved away with the toothed cutters. The port entry channel, and berthing and turning areas need to be 15.5m deep to take the biggest post-Panamax container ships.

The contract also included deepening approaches.

The most complex part of the design work has been on the quayside structure itself, a suspended insitu concrete slab supported on just under 2,000 tubular steel piles ranging from 30m-65m, filled with reinforced concrete.

But at many of the pile locations ground anchors are also needed; these will resist substantial uplift forces from typhoon wind and wave action.

At some parts of the quay the effects will be magnified because of anchor points installed to tie down the very large container handling cranes.

'Wind forces can be strong enough in Hong Kong to knock over even these very heavy cranes, ' says Meigh. Each of the high capacity cranes can be tied down at four corners to steel plate anchor points in the event of high winds.

Even though the structure of the quay wall is conventional, comprising insitu concrete beams of about 6m to 8m length with an insitu deck, some fairly complex analysis has been needed to work out the uplift points. The consultant ran the structure through Microstrand software for the analysis.

Physical modelling for the sloping seawall protection where the quay meets the main reclaim was done at Delft Laboratory in the Netherlands.

The rock mound seawall has French Sogreah-designed Accropodes for armouring. The specially shaped units need precise placing to make sure they interlock as designed.

Most of the quay structure and sea wall has now been finished and the last of the 350m long berths should be ready for handover by the end of this year.

Work is now largely focused on finishing various container yard handling facilities and buildings at present. Particularly important is handing over the reclamation to the foundation contractors for the new Stonecutters cable stay bridge, whose 1,000m main span will connect CT9 to CT8, the previously completed terminal across the harbour.

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