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3. Read the text carefully and do the tasks that follow:
Modern highways are complex engineering structures. They are intended for high-speed motor traffic. The road pavement must continuously provide good riding qualities and be capable of withstanding the dynamic loads influenced by passage of vehicles. Pavements and road subgrades are subject to the influence of many natural factors such as heating by the sun, freezing, thawing, moistening by rain, etc. Complex physical processes develop in the subgrade caused by variations in moisture distribution and an increase in subsoil moisture content. An excessive moisture content quickly causes the subsoil to lose its strength and may lead to disintegration of the road foundation. The many and varied factors of pavement performance have to be taken into account by the designer and constructor who have to provide for the maximum stability of the subgrade and for the maximum strength of the pavement.
Roads are built in the most varied natural conditions - in broad plains and hills, sandy deserts and in mountains. In all these diverse and complex conditions the road engineer has to be able to find correct engineering and economic solutions. Because of this, A highway paved with concrete
when solving construction problems related to road he has to make use of natural and historical sciences, i.e. geology, climatology, hydraulics, hydrology, etc. He must be able to design highways so as to ensure comfort and safety of transportation.
The road-building operations become complicated because of the extensive length of the construction site – often tens and hundreds of kilometers. The task of the road engineer is to mechanize and technically develop the road-building operations and to provide for the most efficient and complete mechanization of the entire construction process. This is true to such operations as earthworks, sand and gravel quarrying, stone crushing and cement-concrete surfacing.
Finally, when the highway is put into service, its maintenance and the provision for uninterrupted traffic become of the utmost importance of the national economy. The engineer in charge of the highway operation must ensure the maintenance of the road quality under all traffic and weather conditions.
With the growth of traffic density a demand for greater amenities will come. It will be necessary to provide the national road system with hotels and restaurants, service stations and repair shops, where drivers and passengers may rest and vehicles be serviced and repaired. Attention should be given to such questions as fitting roads into the landscape in plan and in profile, planting trees, so as to improve their aesthetic value.
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