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看电影巧记雅思必备词汇:AIRPORTS ON WATER

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发表于 2016-7-9 22:37:51 | 显示全部楼层 |阅读模式
  下面新东方网雅思频道为大家整理了看雅思文章背雅思词汇:AIRPORTS ON WATER,供考生们参考,以下是详细内容。
          AIRPORTS ON WATER
          River deltas are difficult places for map makers. The river builds them up,
the sea wears them down ; their outline s are always changing. The changes in
China’s Pearl River delta, however, are more dramatic than these natural
fluctuations. An island six kilometers long and with a total area of 1248
hectares is being created there. And the civil engineers are as interested in
performance as in speed and size. This is a bit of the delta that they want to
endure.
          The new island of Chek Lap Kok(赤腊角), the site of Hong Kong’s new airport,
is 83% complete. The giant dumper trucks rumbling across it will have finished
their job by the middle of this year and the airport itself will be built at a
similarly breakneck pace.
          As Chek Lap Kok rises, however, another new Asian island is sinking back
into the sea. This is a 520-hecrare island built in Osaka Bay, Japan, that
serves as the platform. for the new Kansai airport. Chek Lap Kok was built in
different way, and thus hopes to avoid the same sinking fate.
          The usual way to reclaim land is to pile sand rock on to the seabed. When
the sealed oozes with mud, this is rather like placing a textbook on a wet
sponge: the weight squeezes the water out, causing both water and sponge to
settle lower. The settlement is rarely even: different parts sink at different
rates. So buildings, pipes, roads and so on tend to buckle and crack. You can
engineer around these problems, or you can engineer them out. Kansai took the
first approach; Chek Lap Kok is taking the second.
          The differences are both political and geological. Kansai was supposed to
be built just one kilometer offshore, where the seabed is quite solid. Fishermen
protested, and the site was shifted a further five kilometers. That put it in
deeper water (around 20 metres) and above a seabed that consisted of 20 metres
of soft alluvial silt and mud deposits. Worse, below it was a not-very-firm
glacial deposit hundreds of metres thick.
          The Kansai builders recognized that settlement was inevitable. Sand was
driven into the seabed to strengthen it before the landfill was piled on top, in
an attempt to slow the process; but this has not been as effective as had been
hoped. To cope with settlement, Kansai’s giant terminal is supported on 900
pillars. Each of them can be individually jacked up, allowing wedges to be added
underneath. That is meant to keep the building level. But it could be a tricky
task.
          Conditions are different at Chek Lap Kok. There was some land there to
begin with, the original little island of Chek Lap Kok and a smaller outcrop
called Lam Chau. Between them, these two outcrops of hard, weathered granite
make up a quarter of the new island’s surface area. Unfortunately, between the
islands there was a layer of soft mud, 27 metres thick in places.
          According to Frans Uiterwijk, a Dutchman who is the project’s reclamation
director, it would have been possible to leave this mud below the reclaimed
land, and to deal with the resulting settlement by the Kansai method. But the
consortium that won the contract for the island opted for a more aggressive
approach, It assembled the world’s largest fleet of dredgers, which sucked up
150m cubic metres of clay and mud and dumped it in deeper waters. At the same
time, sand was dredged from the waters and piled on top of the layer of stiff
clay that the massive dredging had laid bare.
          Nor was the sand the only thing used. The original granite island which had
hills up to 120 metres high was drilled and blasted into boulders no bigger than
two metres in diameter. This provided 70m cubic metres of granite to add to the
island’s foundations. Because the heap of boulders does not fill the space
perfectly, this represents the equivalent of 105m cubic metres of landfill. Most
of the rock will become the foundations for the airport’s runways and its
taxiways. The sand dredged from the waters will also be used to provide a
two-metre capping layer over the granite platform. This makes it easier for
utilities to dig trenches—granite is unyielding stuff. Most of the terminal
buildings will be placed above of pile-driving foundations above softer
areas.
          The completed island will be six to seven metres above sea level. In all.
350m cubic metres of material will have been moved. And much of it, like the
overloads, has to be moved several times before reaching its final resting
place. For example, there has to be a motorway capable of carrying 150-tonne
dump-trucks; and there has to be a raised area for the 15,000 construction
workers. These are temporary; they will be removed when the airport is
finished.
          The airport, though, is here to stay. To protect it, the new coastline is
being bolstered with a formidable twelve kilometres of sea defenses. The brunt
of a typhoon will be deflected by the neighbouring island of Lantau; the sea
walls should guard against the rest. Gentler but more persistent bad weather—the
downpours of the summer monsoon—is also being taken into account. A mat-like
material called geo-textile is being laid across the island to separate the rock
and sand layers. That will stop sand particles from being washed into the rock
voids, and so causing further settlement. The island is being built never to be
sunk.
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