首页
登录
职称英语
AIRPORTS ON WATERRiver deltas are difficult places for
AIRPORTS ON WATERRiver deltas are difficult places for
游客
2025-02-17
7
管理
问题
AIRPORTS ON WATER
River deltas are difficult places for map makers. The river builds them up, the sea wears them down; their outlines are always changing. The changes in China’s Pearl River delta, however, are more dramatic than these natural fluctuations. An island six kilometres 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, 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-hectare island built in Osaka Bay, Japan, that serves as the platform for the new Kansai airport. Chek Lap Kok was built in a 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 seabed 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 kilometre offshore, where the seabed is quite solid. Fishermen protested, and the site was shifted a further five kilometres. 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 recognised 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 the site of the existing island. Only a limited amount of pile-driving is needed to support building 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 defences. The brunt of a typhoon will be deflected by the neighbouring island of Lan-tau; 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. This island is being built never to be sunk.
Questions 1-5
Classify the following statements as applying to
(A)Chek Lap Kok airport only
(B)Kansai airport only
(C)Both airports
Write the appropriate letters A ~ C in boxes 1 - 5 on your answer sheet. [br] built in a river delta
选项
答案
A
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3960448.html
相关试题推荐
Itisdifficulttoconceivehow,evenforthosepeoplewelldisposedtorulethe
LAG:A、appeardifficultB、altersignificantlyC、dartsimplyD、gazeaboutE、movef
Althoughitisoftendifficultto(i)______someoneascharmingasHank,hiscoll
Difficultworkingconditionsthatrangedfrommerely______toextremelyintimidat
Justbecause,asaphotographer,Friedlander(i)______placesthatmostpeoplec
Aleadingchemistbelievesthatmanyscientistshavedifficultywithstereochemi
Ina(i)____societythatworshipsefficiency,itisdifficultforasensitivea
Congressishavinggreatdifficultydevelopingaconsensusonenergypolicy,pri
Oftenthedifficultiesofgrowingupinthepubliceyecausechildprodigiesto
AlthoughsomeskepticspointstoArcticplacessuchasthehighlatitudesof
随机试题
ThefollowingcontainsthemaininformationofDirectionforUse.Youarerequir
Everyonewouldhaveheardthefamousphrase"Angerisoneshortofdanger".
Astheworld’surbanpopulationgetsbigger,citiesarestrugglingtoprovid
临时用电工程必须经编制、审核、批准部门和使用单位共同验收,合格后方可投人使用。
5岁男孩,1周前不慎跌倒,被一钝物碰撞鼻根部,当时右侧鼻腔有少量流血,未作特别处
建设单位应当将大型的人员密集场所和其他特殊建筑工程的消防设计文件报送公安机关消防
下列泥石流类型中,按泥石流的流体性质分类的是()。 A.水石流B.泥流C
藏獒是世界著名的大型猛犬,原产于我国青藏高原,其性格刚毅,力大凶猛,是世界上唯一
客户风险的基本面指标不包括()。A.品质类指标 B.技术类指标 C.实力类
依据《危险化学品安全管理条例》的规定,下列说法错误的是()。A.个人不得购买
最新回复
(
0
)