Comprehension check

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

1. Construction crews can safely work underwater using a watertight chamber.

2. Most caissons have the shape of a triangle.

3. The walls are usually made of cardboard.

4. Caissons are filled with water after the construction is over.

5. The three main types of caissons are open, pneumatic and closed.

6. An open caisson has an open top and bottom.

7. The top edges are called cutting edges.

8. A pneumatic caisson is closed at the bottom.

9. It uses compressed air to keep water out of the working chamber.

10. This type of caisson consists of two sections.

11. Concrete is poured into the lower section.

12. Workers and materials move in and out of the lower section through bottom edges.

13. When workers enter or leave a pneumatic caisson they must pass through an airtight chamber.

14. If workers stay in a caisson for a long time they may develop bends.

II. Answer the questions

1. What is caisson in building?

2. What is the shape of caissons?

3. What are the kinds of caissons?

4. What is the difference between an open and pneumatic caisson?

5. What are the sections of a pneumatic caisson?

6. Why is concrete poured into the upper section?

7. What is an air lock?

8. How does an air lock operate?

9. Why is the pressure changed in an air lock?

10. What can happen if workers go through a change of pressure too quickly?

11. Are caissons used nowadays?

LANGUAGE FOCUS

III. Complete the sentence with the best answer (a, b or c) according to the information in the text

1. Caisson in building is a watertight chamber used

a) in the construction of roofs

b) in the construction of buildings

c) in the construction ofbridges and tunnels

2. All caissons are open … where digging takes place

a) at the bottom

b) on the top

c) at the cutting edges

3. As earth is removed the caisson sinks

a) under the weight of concrete in its working chamber

b) under the weight of an entrance shaft

c) under the weight of concrete in its upper section

4. Workers and materials move in and out of the lower section

a) through a shaft

b) through a working chamber

c) through a top section

IV. Put the words in the right order

1. If, may, of with, caissons, are filled, they, become, concrete, part, structure, the, finished.

2. What, made, are, the, of, walls, of caisson?

3. The, sink, caisson, under, can, the, concrete, of, weight.

4. Is, to, keep, air, water, compressed, used, out, of, chamber, the working.

5. Caissons, piers, pneumatic, bridge, support, deep, in, water, located.

6. An, is, to change, air lock, used, the air pressure.

7. Quick, may, change, cause, of, disease, pressure, caisson.