Unit 2. Bridge or Tunnel
Vocabulary. obstacle — препятствие water space — водный массив by means of — с помощью connect — соединять rapid increase — быстрый рост land-based — наземный trade and commerce — торговля cross over — пересекать bear in mind — иметь в виду sea current — морское течение vessel — судно seabed — морское дно provide — обеспечивать sufficient — достаточный require — требовать embankment- насыпь depend (on) — зависеть put into operation — запускать high-speed — высокоскоростной severe — суровый The vast water areas all over the world represent the world obstacles for people’s communication. A man has been striving to subdue water spaces by means of the main road connecting continents, islands, etc. because the economy becomes globolised.
The English Channel separating Great Britain and Europe the Straits of Gibraltar between Europe and Africa, the Bosporus between Europe and Asia, the Bering Strait connecting the Eurasian and American continents, Japanese-islands might offer the missing link for rapid increase land-based transportation to promote improved trade and commerce to facilitate greater economic integration.
Builders always have the choice between bridging and tunneling in crossing over or under a large waterway. Each sort of a structure offers its advantages and shortcomings. One should bear in mind the influence of strong sea currents, great water depth, and large capacity vessels with great boundary dimensions (the under clearance of the bridges must be about 65 m high not to prevent shipping), complicated geological seabed structure. Seabed silt is a rather soft foundation for supports footing. In addition these regions are seismically dangerous and constructional works must provide sufficient strength against seismic waves.
The advantages of the bridge crossing may be the following:
1. Low cost of construction in comparison with a tunnel structure though sometimes it may be quite the opposite.
2. Bridges require lower maintenance costs because tunnels call outlays for water discharging, ventilation, illumination, etc. The longer subaquatic structure is, the heavier outlays are required.
The advantages of the tunnel are:
1. Free shipping is very important under intensive navigation. Tunnels are much safer as compared to the bridge crossing because bridge supports must be calculated for the berthing impact. Being deep beneath the water surface, tunnels do not interfere with navigation. In addition, weather conditions cannot influence the traffic.
2. The architectural view of the tunnel is more attractive because there is no need for high approach embankments.
The final decision for choosing a bridge or a tunnel depends on many factors and not only on technical ones. In some cases bridges are much more preferable. In 1974 the bridge across the Bosporus was erected. In 1985 the bridge crossings connected some Japan islands.
The strait separating Denmark and Europe was also spanned by a bridge.
But the choice fell on a tunnel underneath the English Channel. In 1994 the railway tunnel from Great Britain to France was put into operation. It provides a high-speed rail link with shuttle trains reducing the travel time between the two countries to three-and-a-half hours. Needless to say that the cost of this tunnel is enormous. Another group of Japanese-islands were also connected by the tunnels in 1987. The problem «a bridge or a tunnel» is being discussed for the type of structures in the nearest future in Italy and across the Straits of Gibraltar and the Bering Strait. The choice falls on a bridge crossing in Europe and on a tunnel for the severe northern conditions.
Answer the questions: 1. What are the advantages of tunnels? 2. What are the disadvantages of tunnels? 3. What are the advantages of bridges? 4. What are the disadvantages of bridges?
Exercises: 1) Find the equivalents:
world obstacles; sea currents; boundary dimensions; seabed silt; maintenance costs; bridge supports; weather conditions; railway tunnel; travel time
2) Choose the best variant:
1. There always was a choice between bridging and tunneling in … over or under a large waterway. a) crossing b) crippling c) cruising
2. Bridges require lower maintenance … than tunnels. a) corrosion b) corrugations c) costs
3. Tunnels are much … as compared to the bridge crossing. a) saving b) saver c) safer
4. Weather conditions cannot influence the … through tunnels. a) traffic b) transfer c) transit
5. The cost of the tunnel under the English … is enormous. a) Cheddar b) Channel c) Canal
3) Find the opposites to the words:
gathering _____________
slow _________________
drawback_____________
allow_________________
bound (adj.) ___________
lessening _____________
small________________
shallow _____________
4) Are the sentences True or False? Correct the wrong ones:
1. ______ The Straits of Gibraltar separates Europe from Africa.
2. ______ The under clearance of the bridges must be over 60 m high not to prevent shipping.
3. ______ For the first time the Bosporus was bridged in 1973.
4. ______ Tunnels require lower maintenance costs.
5. ______ Vessels can navigate much easier if there are no bridges.
6. ______ The Bosporus bridge managed to withstand the wind blows up to 162 km per hour.
References: http: //www.bris.ac.uk/civilengineering/bridges/Pages.html
|
