Find in the text the synonyms of the following words.

 

1) performance - …	5) final - …
2) difficult - …	6) outline - …
3) function - …	7) basis - …
4) oppose - …	8) weight - …

Match the words with their opposites.

 

1) convex	a) straight
2) sloped	b) simple
3) stability	c) instability
4) complicated	d) collect
5) dissipate	e) appear
6)distribute	f) horizontal
7) thick	g) wide
8) narrow	h) curved
9) vertical	i) thin
10) submit	j) resist

Fill in the correct prepositions then choose any five items and make sentences.

1) to be curved ___ plan; 2) to be capable ___ resisting; 3) to be ___ concrete; 4) ___ comparison ___ sth.; 5) because ___ the narrow base; 6) an approach ___ arch analysis; 7) to be designed ___ this basis; 8) ___ a usual manner; 9) to take care ___ sth.; 10) to be similar ___ sth.; 11) to provide ___ sth.

 

Make adjectives from the following words then choose any five items and make your own sentences.

stiffness, hydraulics, horizon, importance, strength, to close, to minimize, width, narrowness

 

Translate the following words into Russian.

Строительные работы, собственный вес, слегка изогнутый, напор воды, распределение давления, непроницаемое основание, отводить воду, уменьшать утечку воды, размеры плотины, заливать поочередно, сбрызгивать водой, боковая поверхность, предотвращать сцепление блоков, соседние секции, обеспечивать доступ, просачиваться в плотину, ремонт затворов и клапанов, достигать стабильности, особенно эффективный, вертикальные и горизонтальные направления, береговые устои, многочисленные разрушения, замешивание и выдерживание бетона, слой раствора, гарантировать лучшее сцепление, давать усадку, выделять тепло, обладать устойчивостью, тонкое поперечное сечение.

Reading Task: C

 

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

 

outside base	succession	settlement
sloping	axis	to harm
membrane	space	spread footings
to transmit	to vary	to range
water load	formwork	poor foundation
a series of	a beam	cantilever action
right angle	diaphragm	to slide up
upright buttresses	stiffener	a gap
a flat-slab dam	a brace	to relieve
a multiple-arch dam	buckling	mat foundation
aggregate	width	a great deal of
acceptable	articulation	a cut-off wall
flat adj	i.e.	powerhouse
a slope	rigidly	saving
a slab	to attach	removal
reinforced concrete	overburden	asphaltic putty
water-treatment plants	a trench	water tightness

 

 

Read the text carefully paying attention to the words in italics. Answer the following question.

What parts does a buttress dam consist of?

 

Text C Buttress Dams

 

A buttress dam consists of a sloping membrane which transmits the water load to a series of buttresses at right angles to the axis of the dam. Concrete-buttress dams reduce material in the wall itself by using support buttresses around the outside base. There are several types of buttress dams, the most important ones being the flat-slab and the multiple-arch.

In locations where aggregate for concrete is not available in a sufficient quantity and the foundation rock is acceptable, flat-slab buttress dams may be constructed as well. In cross-section buttress dams resemble gravity dams, but with flatter upstream slopes. In a buttress dam a slab of reinforced concrete rests on a succession of upright buttresses. Their thickness and spacing between them must be sufficient to support the concrete slab and the load exerted by the water in the reservoir. Buttress spacing varies with height of dam. Closely spaced buttresses can be less massive and the slabs can be thinner but then more formwork is required. Concrete beams of diaphragms used as stiffeners between adjacent buttresses or concrete braces may be utilized to resist buckling of the buttresses. Sometimes hollow buttresses are used to increase the effective buttress width. One of the most interesting features of the flat-slab dam is its articulation, i.e. the slab is not rigidly attached to the buttresses. The joint between the slab and buttress is filled with asphaltic putty or some other compound. This permits each slab to act independently, and even minor settlement of the foundation may seriously harm the structure. Flat-slab and buttress dams are particularly adapted to wide valleys where a long dam is required and where foundation materials are of low strength. Placing the buttresses on spread footings one can reduce the foundation pressures. Flat-slab dams may be built on materials ranging from fine sand to solid rock. But the maximum practical height must be necessarily less on poor foundations.

The multiple-arch dams require a better foundation than the flat-slab dams do. Arches for a multiple-arch dam are designed in the same manner as for a single-arch dam, but cantilever action is commonly not taken into account. The design of a multiple-arch dam is more economical for high dams, where the savings in concrete and reinforcing steel are considerable.

Buttress dams are subjected the same forces as gravity and arch dams. Because of the slope of the upstream face, ice pressures are not usually important as the ice tends to slide up the dam. Uplift pressures are relieved by the gaps between the buttresses. The total uplift forces are usually small and can generally be neglected except when a mat foundation is used.

Buttress dams usually require only one-third to one-half as much concrete as gravity dams of similar height but they are not necessarily less expensive because a great deal of formwork and reinforcing steel is required. Since a buttress dam is less massive than a gravity dam, the foundation pressures are less and a buttress dam may be used on foundations which are too weak to support a gravity dam. If the foundation material is permeable, a cut-off wall extending to rock should be provided. The height of a buttress dam can be increased by extending the buttresses and slabs. Usually buttress dams are used where a future increase in reservoir capacity is expected. Powerhouses and water-treatment plants are usually placed between the buttresses of dams in order to obtain some savings in cost of construction.

The removal of overburden down to a suitable foundation and excavation of a trench for the cutoff wall are the first steps in the construction of buttress dams. Great care must be taken in the construction of formwork, handling of concrete and placing of reinforcing steel in order to obtain the strength and water tightness of the thin sections inherent in buttress dams. Deck and buttresses are placed in lifts of 12 ft or more, the buttress construction being kept well in advance of the deck. Keyways are required in all construction joints. Since buttress dams require much less concrete than gravity dams, the time for construction is usually less and the problem of water diversion somewhat simplified.

Comprehension Check