Road clothes: definition, design. Typical constructions of road clothes of city roads

The appearance of ordinary road surfaces, which are transported, conceals a complex structure of several layers underneath. Each layer has its own device rules, characteristics and technological purpose. Provided that all layers are executed in good quality, a safe and durable coating can be obtained. This will be road clothes, which thus forms the basic infrastructure for the movement of cars.

The basic concept of pavement

The basis of roads is mostly asphalt concrete and cement concrete. In both cases, the characteristics of the binder components, fractions of crushed stone, sand, and other fillers can vary. Actually, the finished structure of such coatings can be considered as full-fledged road clothes. The definition provides for a common complex of layers of this coating, but each layer acts as a separate technological component, for which special requirements are imposed. To ensure the reliability of the coating, it is necessary to ensure that the stress arising from the movement of the transport elements in the structural elements does not have a destructive effect on the structure. To achieve this, a rational calculation of the characteristics of the structure, which the technologists produce before the beginning of road works, is possible.

What is considered in the pavement design?

Typical designs are developed as universal coverings for both urban roads and suburban routes. It does not matter whether it is a highway or a street. In the development of the project, the level of traffic intensity, the properties of the materials used, the loads, the hydrological and soil conditions, as well as other factors affecting the operation of road surfaces and foundations are taken into account. In roads with non-rigid coatings, structures with a small volume of stacked layers are envisaged. In particular, the design of this type of road clothes involves calculating the allowable deflection of the coating in unfavorable periods of the year, from the point of view of external conditions. The reversible deflection is calculated by one basic characteristic - the modulus of elasticity.

The resistance of the upper layers of the earth soil is also taken into account, on which the base will subsequently be laid. For this parameter, the technology introduces the amount of shear stress. If deviations from the norm of equilibrium in one of the layers, from the point of view of shearing, can result in residual deformation processes, the pavement design may involve a change in composition by adding new plasticizers and technical components that increase the stiffness of the base web.

Types of pavement

All typical designs of road clothes are divided into two categories - rigid and non-rigid. In this case, each technological model of the coating device provides for the use of specific moisture indicators, thickness, size of the sand fraction, gravel and, in general, the properties of the cement-sand substrate. Thus, the modulus of elasticity of the soil base, depending on the design used, can be on the average 300-500 kgf / cm ² . As an exception, we can mention structures that do not presuppose a sand layer for drainage. In this case, the design of non-rigid road clothes, designed for laying in conditions of sandy loam and sandy soils, is carried out. The modulus of elasticity of such a substrate can reach 1200 kgf / cm ² . There are different designs and the number of technological layers. This can be a compacted two-layer clothing, and a coating for 5-6 layers. Depending on the external conditions, project developers can add additional layers, for example, with the isolator function.

Typical construction of sidewalks

An important component in the improvement of urban infrastructure is the sidewalk. Its coverage also refers to the types of pavement, but, of course, with other technical and operational characteristics, designed for pedestrian traffic. The structures of pavements in different regions do not differ so much, as the climatic conditions have less impact on their coverages. Nevertheless, the design takes into account the category of the street, its purpose, the intensity of pedestrian traffic, the characteristics of the ground base, as well as the ratio of the sidewalk to the roadway. In a standard form, the construction of pavement can be realized in conditions of fortified soil with the use of asphalt and cement mortars. In some cases, ceramic and asphalt concrete slabs are used, as well as weak based on natural stone. In this case, the laying can be carried out in several layers, as in the case with conventional roads.

The basis of pavement

Perhaps this is the most critical part of the overall design, since it is the function of the bundle of the top coat with the soil, as well as the distribution of loads. In practical applications, the base provides a reduction in stress from the impact of the wheels, transferring the power potential to the ground. Thus, the basis due to the earthen cover creates in some way an amortization effect. But not always road clothes have suitable characteristics of the base, from the point of view of protection, from external influences. For example, the bottom layer can have optimal working qualities, but under the action of water it will gradually blur. And on the contrary, it can demonstrate resistance to climatic influences, but it is difficult to carry out the distribution of loads. In order to optimize various characteristics, builders also allocate functional strata in the structure of the base. Thus, the carrier part and auxiliary layers are separately considered. In such a structure, the base coat is responsible for mechanical resistance, and additional coatings resist the same precipitation.

Top part

The outer surface also performs a number of critical functions, the main one of which is the direct reception of loads from cars. Direct contact also takes place with respect to climatic precipitation, so the protective qualities in the upper part can be called universal. Multifunctionality of the outer coating is achieved due to several layers, as in the case with the base part. So, in order to increase the resistance to cracks in the coating, special interlayers are used, which may include geogrid and geotextiles, as well as modified astringent components. On the surface of the road wear has a special treatment, which also protects the coating from moisture and snow. And besides the protective qualities, the adhesion properties of the surface are also practiced. Special treatments, for example, are also used to improve the roughness and improve the coupling of roads with wheels.

Additional Layers

Depending on the operating conditions, the road surface can be affected by various negative factors. Not every typical design can meet increased loads, in terms of thermal, hydrological and mechanical effects. For example, non-rigid road clothes have a high capacity for drainage and do not need additional sandy floors, but their strength properties may require reinforcement. To do this, interlayers are created between the supporting part and the upper layers, and also technological layers of the polymer film between the base and the ground are laid.

Frost resistant layer

In terms of adverse climatic effects, the most damaging is frost. Protection in the event of exploitation in the conditions of negative temperatures provides for the use of granular materials, including sand, sand and gravel mixtures, slag and crushed stone. A kind of insulation can also be applied to the ground base, on which road clothes with base layers are formed. However, to prevent frost freezing the land cover is small - it is supplemented by fortified astringents, as well as hydrophobic mounds and non-gummy materials.

Drain interlayer

Technological layers of this type are used in areas with earthen linen from undrained soil. Mandatory inclusion of such layers is considered in regions with abundant precipitation. The main function of the drainage layer is to ensure drainage. In addition, the typical construction of road clothes of urban roads, in which the drainage layer is higher in relation to the depth of freezing, should be performed only from strong and frost-resistant materials.

Technological defects

The most dangerous phenomenon, which may entail misuse of the technology of pavement, are breaks. In such cases, there is a risk of complete destruction of the web throughout the thickness with the manifestation of sharp distortions of the structure profile. Less dangerous are the processes of peeling and dying, which involve superficial destruction as a result of the peeling of astringent elements and the loss of individual particles of mineral fill. Common mistakes with which standard pavement designs fit, can also trigger shifts and formation of potholes. The formation of open abyss also leads to extrusion of the soil onto the surface, which makes the coating unsuitable for operation.

Conclusion

In recent years, the technology of road pavement has changed little. The introduction of new solutions into the industry primarily involves technical support in the form of the appearance of modern machines, tools and equipment for the preparation and laying of different layers. Materials, from which road clothes of city roads are arranged, remain former. The basis of coatings is also made up of cement fillings, sand with gravel and binders. Of course, new and more modifying components with additives are increasingly being introduced, but they have a point character of improving the performance properties and do not radically change the characteristics of typical designs.