Do you know types of dams? Match the pictures with the types of dams.

PART 1

Find the translation of the following terms and memorize their meaning.

Answer the following questions. If you have any difficulties, look through the following text to get the necessary information.

a) Can you give the definition of the word “dam”?

b) What does the cost of a dam depend on?

c) What is your point of view?

Read the following text and write out

1) the words denoting the types of dams

2) the words denoting the forces acting on a dam

Text A                                                                                         

A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. Most dams have a section called a spillway, over which or through which it is intended that water will flow.

Dams may be classified according to structure and used material, intended purpose or height.

Based on structure and material dams may be subdivided into concrete dams (gravity, buttress, arch and multi-arch), timber dams, embankment dams (earth fill, rock fill) and masonry dams (such as gravity, buttress and multi-arch). The selection of the best type of a dam for a given site is a problem in both engineering feasibility and cost. Feasibility is governed by topography, geology and climate. The relative cost of the various types of dams depends mainly on the availability of construction materials near the site.

According to height, there are low dams (less then 30 m high), medium-height dams (between 30 and 100 m high) and high dams (over 100 m high). The height of a dam is defined as the difference in elevation between spillway crest and the lowest part of the excavated foundation.

Dams are built for the following reasons:

· to meet demands for human consumption, irrigation and industrial uses;

· to provide head for generating hydroelectric power;

· to protect against flooding from rivers or the sea;

· to improve navigation by increasing the depth of water in a river;

· to provide lakes for recreation and fisheries.

A dam must be relatively impervious to water and capable of resisting the forces acting on it. The most important of these forces are known to be gravity (weight of a dam which is the product of its volume and the specific weight of the material), hydrostatic pressure (it may act on both the upstream and downstream faces of the dam), uplift pressure (created when water under pressure finds its way between the dam and its foundation), ice pressure (exerted on the upstream face of a dam) and earthquake forces. The material underlying a dam also must be capable of withstanding the foundation pressures. Most failures of dams have been caused by failure of the underlying material.

Construction of dams and reservoirs requires the closest cooperation of engineers, soil-mechanics experts and geologists in the planning, design and construction so as to assure a maximum degree of safety of these structures.