I. Decide whether the following statements are true or false according to the text.

1. Submerged tunnels lie in the trenches dug through rock.

2. Blasting is one of the main methods used in the construction of rock tunnels.

3. The length of the holes varies from 2 to 5 meters.

4. After the explosion it is always necessary to construct a support.

5. Rings of steel beams or timber can prevent large fragments of rock from falling.

6. Tunnel-boring machines dig tunnels in sandstone.

7. Tunneling through soft earth is more dangerous than through rock.

8. Concrete sections are always used in earth tunnels.

9. When the air pressure inside the tunnel is equal to the pressure of the water outside, the water is kept out.

10. Submerged tunnels are the cheapest.

II. Answer the following questions.

1. What is done first to blast the rock?

2. How are holes bored?

3. Where do workers pack explosives?

4. When doesn’t the tunnel require extra support?

5. Why do workers insert long bolts through the rock?

6. How does a tunnel-boring machine work?

7. When do worker hold the soil in place with bolts, steel ribs and sprayed concrete?

8. Tunneling beneath bodies of water is more dangerous, isn’t it?

9. What tunnels are cheaper?

10. Do you know any submerged tunnels?

LANGUAGE FOCUS

I. Match the words with their synonyms.

1. Drill a) trench

2. Excavate b) mesh

3. Need c) permanent

4. Perilous d) require

5. Ditch e) bore

6. Net f) dangerous

7. Constant g) muck

8. Girder h) remote

9. Blasted rock i) beam

II. Match the words with their opposites.

1. Solid a) pack

2. Extract b) remote

3. Add c) cheap

4. Long d) behind

5. Complete e) separate

6. Expensive f) permanent

7. Connect g) start

8. Ahead h) short

9. Temporary i) soft

III. Fill in the words: feet, shallow, circular, mining, steel, conditions, waterproofed, cost, dangerous, downward.

The … industry has been the primary constructor of shafts. Depth of several thousand … are common. In public works projects, such as sewer tunnels, shafts are usually only a few hundred feet deep and because of their high … are avoided in the design stage whenever practical … shafts find many uses. Being essentially vertical tunnels, shafts involve the same problems of different types of ground and water … . Inflowing water is far more … during construction and generally intolerable during operation. Hence, most shafts are concrete-lined and … , and the lining installation usually follows only a short distance behind excavation. The shape is usually … , although, before current mechanized excavation methods, mining shafts were frequently rectangular. Mining … is called shaft sinking. In soil, shallow shafts are frequently supported with interlocking … sheet piling held by ring beams.

FOLLOW UP ACTIVITIES

Speak on:

1. Basic procedures in tunneling operations.

2. The construction of tunnels.

Unit 8: FAMOUS TUNNELS

Lead in:

1. What famous tunnels do you know?

2. Why are they called famous?

Find the following terms and memorize their meaning.

bank blow into determination divergence draw off duct banquet brick cylinder bricklayer chamber compressed air controversy drainage enlarge exhausts engineering failure fraction heading internal combustion lining motor traffic

flooding frames impede impel inch leaks prop propel purposes survey technique temporary underwater tunnel screw sealing shaft shield shotcreting sinking surface approach

Text 1: The Mersey Tunnel

1. The Mersey tunnel is one of the biggest underwater tunnel of the world. What other underwater tunnels do you know?

2. What are the construction techniques of underwater tunnels?

3. What are the purposes of underwater tunnels?

The cities of Liverpool and Birkenhead are joined by a tunnel which goes under the river Mersey. It is the famous Mersey Tunnel, one of the biggest underwater tunnels in the world. Its total length is over two and a half miles. During the year 1956 more than 10 million vehicles used the tunnel. Its construction has been a great engineering achievement. The work started in December 1925 on the Liverpool side and a few months later on the Birkenhead side. It had been decided to approach the work by driving from each bank of the river two pilot headings, an upper and a lower one, which would meet under the middle part of the river. Vertical shafts were sunk on both sides of the river and the excavation work began. At first the working face of the heading was broken up by compressed air drills, later explosives were used. The headings met on the 3rd of April, 1928, twenty-seven months after the work had begun. The divergences in line and level were found to be a fraction of an inch, showing how accurately and correctly the survey work and the determination of working levels had been done. The next stage of the work was the enlarging of the pilot headings into the full-sized tunnel. Steel, cast iron and concrete were used in lining the tunnel. From the very start it was realised that the ventilation of a tunnel of such length, which was to be used by vehicles propelled by internal combustion, would be a very difficult problem. Finally, a system of ventilation was adopted in which air is blown into the tunnel through ducts at roadway level and drawn off along the roof through exhausts. The Mersey Tunnel was completed in 1934. It was opened on the 18th of July, 1934. At the time it seemed a complete solution of the communication difficulties that had existed between Liverpool and Birkenhead. Today it is obvious that the solution has been only temporary. The ever-increasing exports from the port of Liverpool and the rapid development of Merseyside as an industrial centre have resulted in a great increase in motor traffic through the tunnel. Plans are now being made for the use of the space between the walls supporting the reinforced concrete roadway at the lower level of the tunnel (1840).

COMPREHENSION CHECK