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44. Look through the text and find the words the first letters of which form the word given. You may do it in groups.

DEFORMATION PAVEMENT

MATERIAL MOISTURE

45. Anagrams. Rearrange the word to form another. Give the translation of the words created.

46. State the forms of the Passive Voice in the following sentences:

1.The subgrade is the underlying soil portion of the pavement structure which has been prepared to grade for the support either of the pavement is constructed.

2.When vertical pressure is exerted locally on the pavement it bends.

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3.The ability of subgrade to resist deformation under this pressure depends on its stiffness, and this is measured by the “modulus of subgrade reaction”.

4.It is expressed as pounds per square inch per inch.

5.When a pavement slab is laid directly on the subgrade, the phenomenon known as “mud pumping” is very apt to occur.

6.It is important that a granular no pumping subbase be used when the subgrade is of the type that will be damaged by mud pumping.

47. Find and state the functions of Participle Forms in the following sentences:

1.Rigid pavement distribute loads to the foundation, e.g., portland-cement- concrete pavement and bituminous, brick, or stoned lock pavement supported on a portland-cement-concrete base.

2.The modulus of subgrade reaction, now universally known by the symbol “k”, is the number of pounds per square inch of subgrade reaction per inch of slab deflection.

3.When a pavement slab is laid directly on the subgrade, the phenomenon known as “mud pumping” is very apt to occur.

4.The subbase is a layer of selected granular material placed on the subgrade for the pavement.

48. Substitute the synonymic words from the text for the underlined words in the following sentences:

1.The pavement, subgrade and subbase are the main gradients of a highway.

2.The pavement may be of two types: rigid and flexible.

3.The subgrade is the low gradient of the pavement structure.

4.The aim of the subbase is to reduce frost damage, improve drainage, etc.

49. Discuss the following questions with your partner.

1.What are the main components of a highway?

2.What kinds of pavements may there be?

3.What is a rigid pavement?

4.What is a subgrade?

5.What is the function of a subgrade in a highway?

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6.What is the unit of measurements of subgrade resistance?

7.What is a subbase of a highway?

8.What are the functions of a subbase?

50. Read the information about Roman roads and make a profile drawing of the roads described. Try to draw to scale. Do not forget to label the picture.

Pic. 18

The typical Roman road was bold in conception and construction. Where possible, it was built in a straight line from one sighting point to the next, regardless of obstacles, and was carried over marshes, lakes, ravines, and mountains. In its highest stage of development, it was constructed by excavating parallel trenches about 40 feet (1219,2 cm) apart to provide longitudinal drainage – a hallmark of Roman road engineering. The foundation was then raised about three feet above ground level, employing material taken from the drains and from the adjacent cleared ground. As the importance of the road increased, this embankment was progressively covered with a light bedding of sand or mortar on which four main courses were constructed:

1.The statumen layer 10 to 24 inches (250 to 600 millimetres) thick, composed of stones at least 2 inches (5 cm) in size;

2.The rudus, a 9-inch-thick (22,5 cm) layer of concrete made from stones under 2 inches in size;

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3.The nucleus layer, about 12 inches (30 cm) thick, using concrete made from small gravel and coarse sand;

4.For very important roads, the summum dorsum, a wearing surface of large stone slabs at least 6 inches (15 cm) deep.

The total thickness thus varied from 3 to 6 feet (91,44 to 182,88 cm). The width of the Appian Way in its ultimate development was 35 feet (1066,8 cm). The two-way, heavily crowned central carriageway was 15 feet (457,2 cm) wide. On each side it was flanked by curbs 2 feet (60,96 cm) wide and 18 inches (548,64 cm) high and paralleled by one-way side lanes 7 feet (213,36 cm) wide. This massive Roman road section, adopted about 300 BC, set the standard of practice for the next 2,000 years.

51.Tell of:

a)the main gradients of a highway structure;

b)the types of the pavements;

c)the characteristics of the subgrade;

d)the structure and the functions of the subbase.

52. Work in groups of 4. Read one of the paragraphs and underline the key words (In one group students have to read different passages). What is the main idea of your excerpt? Render the text to your partners.

Student A

Pavement (part I)

Road traffic is carried by the pavement, which in engineering terms is a horizontal structure supported by in situ natural material. In order to design this structure, existing records must be examined and subsurface explorations conducted. The engineering properties of the local rock and soil are established, particularly with respect to strength, stiffness, durability, susceptibility to moisture, and propensity to shrink and swell over time. The relevant properties are determined either by field tests (typically by measuring deflection under a loaded plate or the penetration of a rod), by empirical estimates based on the soil type, or by laboratory measurements. The material is tested in its weakest expected condition, usually at its highest probable moisture content. Probable performance under traffic is then determined. Soils unsuitable for the final pavement are identified for removal, suitable replacement materials are earmarked, the maximum slopes of embankments and cuttings are established, the degree of compaction to

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be achieved during construction is determined, and drainage needs are specified.

In a typical rural pavement, the top layer of the pavement is the wearing course. Made of compacted stone, asphalt, or concrete, the wearing course directly supports the vehicle, provides a surface of sufficient smoothness and traction, and protects the base course and natural formation from excessive amounts of water. The basecourse provides the required supplement to the strength, stiffness, and durability of the natural formation. Its thickness ranges from 4 inches (10 centimetres) for very light traffic and a good natural formation to more than 40 inches (100 centimetres) for heavy traffic and a poor natural formation. The subbase is a protective layer and temporary working platform sometimes placed between the base course and the natural formation.

Pavements are called either flexible or rigid, according to their relative flexural stiffness. Flexible pavements (see figure, left) have base courses of broken stone pieces either compacted into place in the style of McAdam or glued together with bitumen to form asphalt. In order to maintain workability, the stones are usually less than 1.5 inches in size and often less than 1 inch. Initially the bitumen must be heated to temperatures of 300° – 400° F (150° – 200° C) in order to make it fluid enough to mix with the stone. At the road site a paving machine places the hot mix in layers about twice the thickness of the stone size. The layers are then thoroughly rolled before the mix cools and solidifies. In order to avoid the expense of heating, increasing use has been made of bitumen emulsions or cutbacks, in which the bitumen binder is either treated with an emulsifier or thinned with a lighter petroleum fraction that evaporates after rolling. These treatments allow asphalts to be mixed and placed at ambient temperatures.

Student B

Pavement (part II)

The surface course of a flexible pavement protects the underlying base course from traffic and water while also providing adequate tire friction, generating minimal noise in urban areas, and giving suitable light reflectance for night-time driving. Such surfaces are provided either by a bituminous film coated with stone (called a spray-and-chip seal) or by a thin asphalt layer. The spray-and-chip seal is used over McAdam-style base courses for light to moderate traffic volumes or to rehabilitate existing asphalt surfaces. It is relatively cheap, effective, and impermeable and lasts about 10 years. Its main disadvantage is its high noise generation. Maintenance usually involves further spray coating with a surface dressing of bitumen. Asphalt surfacing is used with higher traffic volumes or in urban

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areas. Surfacing asphalt commonly contains smaller and more wearresistant stones than the base course and employs relatively more bitumen. It is better able to resist horizontal forces and produces less noise than a spray-and-chip seal.

Rigid pavements are made of portland cement concrete. The concrete slab ranges in thickness from 6 to 14 inches. It is laid by a paving machine, often on a supporting layer that prevents the pressure caused by traffic from pumping water and natural formation material to the surface through joints and cracks. Concrete shrinks as it hardens, and this shrinkage is resisted by friction from the underlying layer, causing cracks to appear in the concrete. Cracking is usually controlled by adding steel reinforcement in order to enhance the tensile strength of the pavement and ensure that any cracking is fine and uniformly distributed. Transverse joints are sometimes also used for this purpose. Longitudinal joints are used at the edge of the construction run when the whole carriageway cannot be cast in one pass of the paving machine.

In places where the local natural material is substandard for use as a base course, it can be “stabilized” with relatively small quantities of lime, portland cement, pozzolana, or bitumen. The strength and stiffness of the mix are increased by the surface reactivity of the additive, which also reduces the material's permeability and hence its susceptibility to water. Special machines distribute the stabilizer into the upper 8 to 20 inches of soil.

In deciding whether to use a flexible, rigid, or stabilized pavement, engineers take into account lifetime cost, riding characteristics, traffic disruptions due to maintenance, ease and cost of repair, and the effect of climatic conditions. Often there is little to choose between rigid and flexible pavements.

The properties of the base course material are usually determined by laboratory tests, although field tests are sometimes conducted to check that the construction process has achieved the designer's intent. Designers typically consider the possibility of structural failure resulting from a single overload and also from damage accumulating under the passage of many routine loads. Both of these types of failure are almost entirely caused by trucks.

Student C

Bituminous Pavement

Bituminous pavements are made with by-products of petroleum, such as asphalt. Weather and seasonal changes can cause roadways and the earth

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below them to rise or fall slightly. As these natural shifts occur, bituminous pavements allow the road surface to bend or flex slightly without breaking.

Bituminous material softens when heated and can be prepared and applied in a wide range of concentrations. Thin layers of bituminous material are sometimes applied with a pressure sprayer to the base course or the top course. The bituminous material seeps into the crushed rock and penetrates the tiny spaces between the compacted rocks, binding the aggregate together. To provide traction for moving traffic, a thin layer of aggregate may then be spread over the bituminous material and compacted.

Asphalt, a thick bituminous material, can be used directly as a pavement. Asphalt can be applied in thin overlays less than 2 cm (0.75 in) deep or in layers several centimeters deep, depending on the type of surface and its purpose. Asphalt is commonly mixed with aggregates for added strength and traction. The asphalt and aggregates are usually mixed and heated at a central location. The material is then transported to the construction site, where it is spread directly over the base course or top course and compacted. Asphalt surfaces are fairly easy to construct and repair.

Student D

Concrete Pavement

Concrete, or rigid, pavements are made from a mix of portland cement and aggregate. Concrete pavements have a long life and require little maintenance. Concrete is generally laid as a single thick layer directly over a base course. For heavily traveled roads, concrete layers can range in thickness from 20 to 36 cm (8 to 14 in). Concrete is usually laid in long sections or slabs of varying length. Metal bars or dowels inserted into the edges of the slabs help connect the joints where one slab ends and another begins.

Concrete is a strong material and can withstand compression, but it has poor tensile strength (resistance to being pulled). When the ground underneath expands and contracts from seasonal or weather changes, the concrete becomes prone to cracking. Cracks can occur at or near the joints where concrete slabs meet or on the slabs themselves. Deep cracks can allow the broken concrete slabs to move upward or downward, creating an uneven road surface. Metal bars or dowels inserted between the slabs help hold the slabs together. Reinforced concrete contains steel bars or mesh imbedded within the concrete layer. The steel helps hold concrete together over time, even if cracks occur. Unreinforced concrete may be used when cost is a factor, or where weather conditions are more mild. Unreinforced slabs have several shallow grooves cut into them, allowing the concrete to

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crack at defined points. The cracked slabs are kept in place by pressure and by the grainy texture of the concrete itself.

In order to maintain quality and uniformity, design standards are established for each functional road type. The number of traffic lanes is directly determined by the combination of traffic volume and speed, since practical limits on vehicle spacing means that there is a maximum number of vehicles per hour that pass through a traffic lane. The width of lanes and shoulders, which must strike a balance between construction cost and driver comfort, allows the carriageway width to be determined. Standards also specify roadside barriers or give the clear transverse distances needed on either side of the carriageway in order to provide safety in the event that vehicles accidentally leave the carriageway. Thus it is possible to define the total right-of-way width needed for the entire road, although intersections will add further special demands.

53. Read and study the following words. Make up sentences with them.

binder – вяжущий материал

black earth road – черное грунтовое покрытие bound – связанный

brick surface – клинкерная мостовая brittle – хрупкий

carrying layer – несущий слой chopped stone – колотый камень cobble – булыжник

cohesion – сцепление distortion – деформация durability – прочность

inlaid pavement – мозаиковая мостовая rolling stock – подвижной состав

rut – колея

to sag – провисать, прогибаться single out – выделять

slag – шлак

subgrade ground – грунт полотна swinging – раскачивание wearing surface – слой износа

54. Answer the questions:

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1.What are the main qualities required from the road pavement?

2.Why is the pavement the principal element of the road?

3.Are durability and smoothness of pavement constant during the year?

4.What is the wearing surface usually made of?

5.Why does the considerable cross-section of a roadway promote wear of the middle part of the pavement?

55. Read the text and check your answers.

Road Surfaces

Road surface (pavement) is a special strengthening of the carriage way of the road with the aim of creating hard and most possibly comfortable surface of rolling for the wheels of the rolling stock.

The surfacing (pavement) is laid either on the whole width of the roadway or on some part of its width.

The main qualities required of the road pavement are the pavement durability and the surface smoothness. Durability of the entire construction of the highway pavement is necessary for the sake of avoiding its sagging or breaking under the wheel pressure.

The upper layer must be durable in order to avoid the damage by the wheels and the formation of local distortion and ruts. At present rather considerable number of types of road pavements are used in road construction.

The pavement is the principal element of the road as it is directly subjected to the traffic.

It is on the qualities of pavement that the comfort of running depends. Durability and smoothness of some types of pavements may be not constant during a long period of time. The higher the type of the pavement is the less its durability depends upon the geophysical factors and the less the durability of this pavement changes during the year.

To provide for all the year round traffic along the road there is a tendency to build the pavements durability of which is more or less constant during the year and does not decrease in wet seasons. While considering the scheme of the pavement consisting of more than one layer it is usual to single out the wearing surface, the carrying layer, the foundation and subgrade ground. The wearing surface receives the direct action of wheels and is subjected to the vertical impacts and loads as well as horizontal ones. The wearing surface must be hard but not brittle. It must possess good resistance to grinding action.

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The wearing surface must ensure the smoothness of the pavement. Usually the wearing surface is made of mixture of stone materials and organic binder.

The carrying layer undergoes vertical forces from the wheels of the rolling stock. Such layers are made durable and bound.

They may be made of the rolled layer of broken stone and gravel and besides this, they may be made of the same materials treated with organic binding materials. Subbase undergoes the vertical forces from the carrying layer in the weakened state, the impacts of the wheels being considerably amortized by the above lying carrying lауеr and distributed by it over the large area.

The foundation layer material feels only compression. The foundation is made of sand layer, gravel layer and broken stone layer of soft rock. The road-bed-ground feels vertical pressure from the pavement. Constant durability or the least possible change of the durability independently of the season of the year is demanded of it. The construction of the subgrade and pavement must be done in such a way as not to permit the ground moistening beneath the lower limit of plasticity.

It is usual to divide all the types of pavements in the following way: 1) rigid pavements, resisting bending (cement and concrete), 2) flexible pavements which do not resist bending or which resist it but little.

There are some intermediate types of pavements between hard and soft ones. Road pavements may be classified according to the following features:

1)durability and constancy of qualities;

2)degree of using the local materials;

3)pavement layer structure.

According to the standard of technical classification of highways road pavements are divided into 4 groups as to the technical and economical indications:

1)improved capital types: asphalt and concrete, cement and concrete and inlaid pavements;

2)improved pavements of lightened type: black broken stone pavements, black gravel pavements, brick surfaces;

3)intermediate types: black earth roads, broken stone pavements, slag pavements, pavements of chopped stone and cobbles;

4)low types: earth pavements, pavements strengthened by different additions, graveled and wooden pavements.

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