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Crystal; wood, plastics; steel, stone; paper, limestone, glass, sand, clay; reinforced concrete; concrete, china

b)Listen to the text "Experimental Bridge". Try to find an exotic material for bridge building and fill in the chart.

c)Check your answers with the teacher or your groupmates

d)Read the transcript of the text on p 436 Look up the words you do not know in your dictionary

c) Do you think that using paper as a material for bridge building has a future? Give your reasons using the chart.

1. Topic. The city of beautiful bridges.

You arc a guide in St. Petersburg Tourists from the United States of America ask you to show them the bridge which you consider to be the most beautiful. They expect you to present information on:

1) the name of the bridge;

2) when it was constructed;

3) who it was designed by;

4) the construction materials which were used;

5) the way it looks;

6) how long, wide and high it is;

7) some interesting facts connected with this bridge; X) why you consider it to be the most beautiful.

2. Pairwork. Think of some good questions for the following answers The answers needn't be true

1 By means of computers 6 No doubt

2 Extremely talented 7 Nowhere

3. I'm afraid he'll object to it. 8 It is suitable

4 1 don't agree with you 9 Circular

5 Some cracks in the structure 10. In the rocky canyon

3. Bridge builders meet representatives of various design offices to choose the best project for the bridge each of them is to build

BUILDERS (1-5 students) You are responsible for building bridges in various places

- a road bridge across a sea strait which is 2000 m wide and about 50 m deep,

- a viaduct for road traffic across a rocky canyon which is 750 m wide and 100 m deep.

- a temporary pedestrian bridge across a river which is 30 m wide,

- a city bridge across a navigable river which is 500 m wide,

- a railway bridge across a highway which is 55 m wide

Listen to the reports of bridge designers presenting various projects and choose the most suitable for your task

BRIDGE DESIGNERS (1-6 students): Describe the project for the bridge which the engineers in your design office worked out. Try to persuade the builders to choose the project from your office (figures 1-6, p. 275).

4. Discussion. A new subway line is being built in the centre of the city, but the route is obstructed by a ship-going river You have to decide whether to build a tunnel or a bridge.

a) Read the following arguments which should be taken into consideration. Think of some more.

b) Discuss the problem m groups of 3-5 students in order to make a decision.

c) Fill in the chart and give your reasons

1. a) Travelling by ear* or train* we meet obstacle* — mountains or river*. Overcoming these obstacles has been one of the most difficult tasks for dvil engineers. On p. 275 you will And picture* illustrating (be text below. Read the text and rearrange the picture* according to the content* of the text.

TEXT И A

THE HISTORY OF BRIDGE AND TUNNEL BUILDING

1. An outstanding statesman once said in his speech, "There can be little doubt that in many ways the story of bridge-building is the story of civilization By it we can readily measure an important part of a people's progress " Great rivers are important means of communication, for in many parts of the world they have been, and still are, the chief roads But they are also barriers to communication, and people have always been concerned with finding ways to cross them.

2. For hundreds of years men have built bridges over fast-flowing rivers or deep and rocky canyons. Early man probably got the idea of a bridge from a tree fallen across a stream. From this at a later stage, a bridge on a very simple bracket or cantilever principle was evolved Timber beams were embedded into the banks on each side of the river with their ends extending over the water. These made simple supports for a central beam reaching across from one bracket to the other. Bndges of this type are still used in Japan, and in India. A simple bridge on the suspension principle² was made by early man by means of ropes, and is still used m countries such as Tibet. Two parallel ropes suspended from rocks or trees on each bank of the river, with a platform of woven mats laid across them, made a secure crossmg. Further ropes as handrails³ were added. When the Spaniards reached South America, they found that the Incas of Peru used suspension bridges made of six strong cables, four of which supported a platform and two served as rails.

3. All these bridges made possible crossings only over narrow rivers The type of temporary floating bridge,⁴ the pontoon bridge, has been used for military purposes; military engineers can construct a temporary bridge on this principle, able to carry all the heavy equipment of a modem army, in an extremely short time.

The idea of driving wooden piles into the bed of the river m order to support a platform was put into practice 3,500 years ago. This is the basis of the 'trestle' or pile bridge' which makes it possible to build a wider crossing easier for the transport of animals and goods

4 With the coming of the railway in the 19th century there was a great demand for bridges, and the railways had capital for building them The

first railway bridges were built of stone or brick. In many places long lmes of viaducts were built to carry railways; for instance, there are miles of brick viaducts supporting railways to London.

The next important development m bridge-building was the use of iron and, later, steel. The first iron bridge crossed the river Severn in Great Britain.

The idea of a drawbridge,⁶ a bridge hinged so that it can be lifted by chains from inside to prevent passage, is an old one. Some St. Petersburg bridges were built on this principle

A modem bridge probably demands greater skill from designer and builder than any other civil engineering project. Many things should be taken into consideration, and these may vary widely according to local conditions. In deciding what type of bridge is most suitable the designer has to consider the type and weight of the traffic, and width and depth of the gap to be bridged, the nature of the foundations and the method of erecting the bridge. The designer has to calculate carefully how the various loads would be distributed and to decide which building materials are more suitable for carrying these loads.

Tunnels

5. Tunnelling is difficult, expensive and dangerous engineering work. Tunnels are built to provide direct automobile or railway routes through mountain ranges, under or over rivers. They can also provide underground channels for water, sewage or oil. Before the 19th century men had not acquired enough skill in engineering to carry out extensive tunnelling. Tunnels, however, were known in ancient times. They were, for instance, driven into the rock under the Pyramids of Egypt, and the Romans built one in Rome for their chief drain, parts of which still remain. One of the earliest tunnels known was made in Babylon. It passed under the Euphrates river, and was built of arched brickwork being 12 feet high and 15 feet wide.

Other ancient tunnels were built for water supply and for drainage

6. Modem tunnels are often very long and deep The Simplon Tunnel on the France-to-Italy railway, for example, is 12 miles long and in one place the peaks of the Alps rise over 6,000 feet above it. Some tunnels are over 50 feet in diameter Many are circular in cross-section. Others are horseshoe- shaped,⁷ with a level floor on which it is easy to lay permanent roads and railways.

Tunnel Under Channel

7. Connecting the Isles of Great Britain to mainland Europe is a fantasy that can be dated back nearly 200 years.

We can name very few projects against which there existed a deeper and more powerful prejudice than the construction of a railway tunnel between Dover and Calais

The objections have been cultural, political and, of course, military The British government objected to the scheme mainly because they thought that the enemy could easily invade England through such a tunnel.

The first suggestion to construct a tunnel came from Napoleon in 1800. His engineers even drafted a tunnel plan, but Britain and France were at war at that time.

In 1988 the question of a Channel Tunnel was studied afresh by a group of French and British engineers and the work actually began They agreed to start boiing for the Eurotunnel on both English and French Coasts.

The Tunnel runs under the sea through a layer of dense chalk which is known to be free of cracks and allows water to penetrate it slowly

The work proceeded very quickly and was successfully completed in about six years. The Tunnel was opened to traffic on May 7, 1994.

Two main tunnels, with service tunnel between, carry one-way rail traffic.

8 Original estimate was 7 2 billion dollars at current exchange rates, but cost to date is 13.1 billion dollars shared between Britain, France and other investors. So far the project is not quite profitable and still needs more investments.

Cars and trucks carried by rail make the crossing in 35 minutes, about an hour less than by ferry. Passengers remain in their vehicles.

The Tunnel personnel does its best to make passengers feel comfortable and safe during the crossing. But as it was mentioned by the commercial director of the Tunnel, they still have many serious problems and one of them is security. Nevertheless, the authorities are sure to be able to solve all the problems successfully.

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