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5.2. Read the text. Text b. Concrete arch dams.

1. Arch dam is a dam curved in plan and dependent on arch action for its strength. Arch dams are thin structures and require less material than any other type. So cost often is the basic reason for the choice of slender arch dams. Despite the weakness of the cylinder theory in the second half of the 19th century, the thin arch dams were a success. They showed that arch dams of unprecedented slenderness were perfectly feasible.

2. In the 17th century Spanish civil engineers had reached the point where they adapted the form of their dams to the topography of the sites. Gravity dams were used at sites which were wide and shallow, arch dams were built in narrow emplacement where the foundations were good hard rock.

3. An arch dam carries most of the water load horizontally to the abutments by arch action. The thrust thus developed makes it essential that the sidewalls of the canion be capable of resisting the arch forces.

4. In principle, an arch dam is visualized as consisting of a series of horizontal arches transmitting thrust to the abutments or a series of vertical cantilevers fixed at the foundations.

5. The horizontal component of the water load is resisted jointly by the arch and cantilever action. Near the bottom of the dam most of the load is carried by the cantilevers, while near the top the arches take more of the load.

6. It is necessary to mention that few arch dams have failed, in comparison with the more numerous failures of other types of dams.

7. The arched dam is defined as essentially gravity dam which in plan view is curved. The name arch-gravity dam is an alternative. So the term “arched dam” is taken to mean any dam which in plan view is curved, generally to a circular shape, but which at the same time resists the water pressure by its weight. In short, an arched dam is curved gravity dam.

8. Buttress dams comprise flat deck and multiple arch structures. They require about 60 per cent less concrete than gravity dams, but the increased formwork and reinforcement steel required usually offset the savings in concrete. This type of construction is not competitive with other types of dams when labour costs are high.

9. A buttress dam consists of sloping membrane which transmits the water load to series of buttresses at right angles to the axis of the dam.

10. There are several types of buttress dams. They fall into: round head buttress dams, diamond head buttress dams, multiple dome buttress dams.

5.3. Find in Text B English equivalents of the following:

глибока ущелина, арково-гравітаційна гребля, вигнутий у горизонтальній проекції, означати, дуговий, чинити опір тиску води, плоска плита, багатоаркова споруда, багатокупольна гребля, вартість праці, конкурувати, вісь, консоль, устої греблі, контрфорсна гребля з круглими оголовками, підпорка, арматурна сталь, тверда порода, розглядати, аварія, компенсувати економію, напір води.

5.4. Add two or three sentences to the given statements using the material of Text B.

1. The arched dam is defined as essentially gravity dam which in plan view is curved. 2. … 3. … 4. …

2. Buttress dams comprise flat deck and multiple arch structures. 2. … 3. …

3. Arch dams are thin structures and require less material than any other type. 2. … 3. … 4. …

4. The horizontal component of the water load is resisted jointly by the arch and cantilever action. 2. … 3. …

5.5. Divide the text into parts, state the microtopics of each part and express the contents of each part in one or two sentences.

5.6. Write a summary of Text B in English.

5.7. Project work. Work in groups of 3 or 4. Try to collect as much information about dams as possible. Get ready to present this information to your class and to answer questions about it. Present your summaries to the class and choose the summary that is the best.

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