68. Match, translate and answer the following questions. Make abstracts of the texts.

a) Zoned embankments

b) Diaphragm-type dams

c) Rock-fill dams

1) _________ are built of coarse rock, which provides structural stability with a concrete membrane on the upstream slope as a water barrier.

• Where is a concrete membrane as a water barrier used?

2) __________ have a thin central section of concrete, steel or timber which serves as a water barrier, while the surrounding earth or rock fill provides stability. Thin concrete sections are easily cracked by differential (перепад) earth loads, and it is difficult to obtain a perfectly watertight barrier from timber or steel. In addition, the diaphragm must be tied into bedrock or a very impermeable material is required if excessive seepage is to be avoided.

• What serves as a water barrier, while the surrounding earth or rock fill provides stability?

• Thin concrete sections are easily cracked by differential earth loads, aren’t they?

• Is it difficult to obtain a perfectly watertight barrier from timber or steel?

• What is required if excessive under seepage is to be avoided?

3) __________ usually have a central zone of selected material to form a relatively impermeable core and outer shells of more pervious material for stability. This construction is widely used in earth dams and is always selected when suitable materials are available. Even though clay is a highly impermeable material it is not always possible to build the best core from this material. The most satisfactory cores are made of clay mixed with sand and fine gravel.

• Why has this type of dam a central zone of selected material?

• Is this construction widely used in earth dams?

• When is this type of dam always selected?

• Is it always possible to build the best core from clay?

• What are the most satisfactory cores made of?

69. Fill in the table giving short answers to the questions.

Kinds of dams Questions	Masonry dams			Embankment dams
	Gravity dam	Arch dam	…	Earth-fill dam	…
1. What is a shape of the dam?
2. What does a dam consist of?
3. What is the dam built of?
4. What types of the dam are there?
5. Where is the dam built? What foundation does the dam require?
6. What forces are the most and the least important in the dam?
7. What should the attention be paid to in order to reduce leakage?
8. Choose the best for every kind of dams: a) - the most expensive, b) - less expensive as less concrete is used, c) - usually expensive as well as a gravity dam because of formwork and reinforced steel, d) - less expensive than masonry dams, e) - the cheapest if proper material is available
9. Can you give the examples of every kind of dams? (names)
10. Are there other kinds of dams? What are they? (give as many as possible)