The evenness of the road surface is one of the main factors of traffic safety. But in the process of operation, a track inevitably appears, which impedes safe movement. What is the reason for its formation, how to avoid its appearance, is it possible to control the process of rutting and prevent it - we talked about this and many other things with the largest professional in this field, a professor at the Rostov State University of Civil Engineering, chairman of the board of directors of Avtodor-Engineering LLC Sergei Konstantinovich Iliopolov.

- Sergey Konstantinovich, what is the reason for the rut formation on the road?

- The main reason for rutting is explained by the processes of accumulation of residual deformations in the elements of the road structure, that is, in each layer of the road pavement and in the upper road layer of the roadbed. This is the so-called plastic track. The second and main reason is the wear of the top layer of the pavement as a result of the combined effect of wear and the premature abnormal destruction of the asphalt concrete layer under the influence of external factors, which include, along with the impact of wheels, precipitation, temperature drops and solar radiation. This track of destruction and wear is formed only in the upper, closing layer of the pavement. And it is good that in the industry normative documents issued last year in the ODN regulating the period of restoration or replacement of the upper layers of the coating, as well as in the GOST, which is being prepared, the concept of a wear layer has been introduced. Therefore, it is more correct to say that the second type of track is formed with premature destruction and wear of the pavement layer, that is, the top layer. In the real conditions of road operation, both of these factors also act together and significantly affect traffic safety. But they need to be separated not only in order to understand the reasons for the formation of rutting, but also in order to know how to deal with this rutting.

- Is it possible to get away from the plastic track in general and solve this issue normatively?

- It is absolutely impossible to get away from the plastic track. Even if we take into account all the factors at play, we will not be able to change the existing nature of the material. For example, any asphalt concrete is inherently an elastic-viscous plastic material, which has all the main manifestations inherent in this category of material: both fatigue in the perception of the load, and redistribution of the main frame material - crushed stone, which is in the composition of asphalt concrete, since the main element of asphalt concrete is dispersed asphalt binder structure, giving it the properties of an elastic-viscoplastic body. It is not an elastic body, it will accumulate permanent deformations as it is loaded. The only difference is that the elastic-plastic properties and the properties of the accumulation of permanent deformation of asphalt concrete are somewhat dependent on temperature.

I would like to note the absolute disregard for the physical nature of asphalt concrete when calculating non-rigid road pavements, where each body taken into account is taken as having elastic properties, which in its essence is not. This also eliminates permanent deformation after loading. As you know, when a load is applied, the body is deformed, and when it is removed, it must recover to its previous dimensions. Asphalt concrete under cyclic loading, being an elastic-viscoplastic body, cannot recover to the same parameters, it will recover, but a little less. This difference is called permanent deformation.

- Is it possible to control the process of rutting on our roads?

- With the existing regulatory framework it is impossible. Asphalt concrete, like other materials present in non-rigid pavement, as already mentioned, are accepted as rigid, not being such in essence.

- Is there a way out in this situation?

- It is necessary to improve the design standards for non-rigid pavements by introducing two additional controllable criteria into the calculation: the accumulation of the calculation of non-rigid pavements for the accumulation of permanent deformation and the formation of fatigue cracks. Asphalt concrete in the existing regulatory framework is considered as a material that can withstand any number of loads for the design period laid down in the standards. Until recently, depending on the road-climatic zone and the category of the road, this period was 18 years, today it is 24 years. These are the overhaul periods during which it is assumed that an absolutely elastic body, which is asphalt concrete, should work without breaking its continuity, more precisely, without the formation of fatigue cracks. This is a myth that anyone can understand. Even if steel, a much harder body, has fatigue, at the onset of which the metal breaks, then what can we say about asphalt concrete. In the modern regulatory framework, there is no difference for which road we design: with a traffic intensity of more than 110 thousand vehicles per day or 20 thousand vehicles per day. It is clear that the efficiency of asphalt concrete in different conditions will be different. The service life of the pavement is determined by the category of the road and the existing loads included in the calculation, but nowhere are requirements imposed on the resistance to fatigue destruction of asphalt concrete, on the basis of which the service life is not calculated, or for a given service life of the pavement, the period of operation is not determined and calculated, after which there are fatigue failures to plan repairs. It is precisely for this purpose that it is necessary to develop one of the two criteria that I named above.

If rutting is an obvious fact, then cracks are an insidious factor that is not always striking, but its influence and the need to take into account when calculating are sometimes more significant.

The first reason. Asphalt concrete is included in the calculation of the pavement with certain specified physical and mechanical properties, first of all, this is its modulus of elasticity. And we, even in everyday life, always call the strength of a certain structural element, consisting of asphalt concrete, the modulus of elasticity of asphalt concrete. And this is another root of evil. For pavement, the parameters and strength of not the material, but the layer are extremely important. Thus, the modulus of elasticity of a layer of asphalt mixture or asphalt concrete has a primary effect on the performance of even a non-rigid pavement. As soon as fatigue cracks form in this layer, discontinuity occurs. And with the same modulus of elasticity as a material, we get a sharp decrease in strength, since when breaking into blocks, the load distribution system fundamentally changes, and all lower layers will experience a much greater load in the crack zones. It would seem that they are elementary things, but no one talks about them today, they are the scourge of our highways.

The second reason. When we receive fatigue cracks, we get an abnormal state of non-rigid pavement. Under these conditions, the design schemes laid down in the standards no longer work, and the road clothes must continue to work.

For high-traffic highways with a traffic intensity of more than 100 thousand vehicles in four lanes, that is, roads of the first category, and often of the second category, the package of asphalt concrete layers should, as a rule, consist of three layers. And these three layers in total should not be less than a certain thickness - 28 cm. By the way, in the regulatory framework of the Russian Federation there is no criterion that would determine the recommended thickness of asphalt concrete layers and what it depends on. Today you will not find a single explanatory material anywhere that could indicate the factors that allow you to determine the minimum thickness of a package of asphalt concrete layers. We are approaching the development of this regulatory document, which will answer the question of why a package of asphalt concrete layers cannot be less than a certain value. This value is determined by the composition and intensity of movement and the need for this package to absorb the high-frequency part of the dynamic spectrum of the vehicle's impact. This criterion, in my opinion, is very important. The most high-frequency energy-consuming part of the dynamic action spectrum of automobiles should be absorbed by asphalt concrete, since it, having a certain continuity, contains an asphalt binder, that dispersed part in which, as in a viscous substance, these frequencies of automobile action are absorbed. What is frequency? This is a kind of influence determined by the wavelength. We must absorb that part of the dynamic spectrum, the wavelengths of which are comparable to the thickness of the asphalt concrete layer. With a decrease in this thickness, a significant part of the spectrum falls below, into those layers that are not able to resist this energy effect at long frequencies. And if crushed stone is located even further, this will mean a significant excess of the abrasion of the material and its transformation into stone flour within 5-7 years with a service life of the pavement of 24 years. There are no recommendations on this topic either, no criteria.

- Why are fatigue fractures more dangerous than plastic ones?

- Taking into account fatigue failures and avoiding their occurrence is very important. Fatigue cracks form on the lower edge of the last asphalt layer on top of the asphalt concrete layer stack, since it is this edge that experiences maximum tension. Therefore, we can get fatigue cracks on the bottom face of the last, third layer. The crack growth process is very fast. Within six months, we will receive a germinated crack, and with each subsequent layer the rate of its formation will be higher, because an ever smaller mass of asphalt concrete will resist tensile stress, the more the edges have always served as a stress concentrator. Thus, cracks appear on the surface of the coating, and they can be strictly transverse, and at an angle, and longitudinal, and networks of cracks. The problem is not even that it creates discomfort when driving, with the formation of a network of cracks, fragmentation of the asphalt concrete of the top layer of the pavement is quickly achieved, moisture will penetrate into the formed crack, but that the continuity of the package of asphalt concrete layers is disrupted, which at the same time radically change their distribution ability to lower layers. And the lower layers of the base begin to experience those stresses for which they are not designed in their physics. As a result, we sharply reduce the resource of the underlying layers, the working life of which significantly exceeds both 20 and 30 years. We are simply destroying this resource. Therefore, fatigue damage from the point of view of the durability of non-rigid road pavements is of fundamental importance.

The way out of this situation is very simple. You cannot talk about certain things and phenomena until you control them. Neither rutting, nor fatigue fractures in the Russian Federation today are normatively defined anywhere, and no one controls this process, because it can be controlled only when you know how to calculate it, you know the laws of its formation.

Thus, two new criteria need to be urgently developed. The first one is the calculation of non-rigid road pavements for their service life, or reliability, which would allow calculating the accumulation of residual deformations in the form of transverse unevenness or plastic rutting during the design life of the non-rigid pavement. The second criterion is the calculation of non-rigid road pavements for the accumulation of fatigue damage. Until at the design stage we receive two graphs of the accumulation of residual deformation of fatigue fractures by years of the life cycle, we will not only manage these processes, but we will not even be able to meaningfully state the very fact of the existence of these problems.

- Is there a way to solve these problems? In which direction should you move?

- The state company Avtodor over the past five years has repeatedly stated at all levels that such criteria are necessary. Moreover, the main difficulties in the development of these criteria are not even that we have to admit the imperfection of methods for calculating pavements. We need new criteria for the level of the operational state of highways during the operation of non-rigid road pavements. The biggest problem that the State Company proposed to take on is those methods, knowledge, scientific schools that can implement and solve it. These are calculation methods, the development of criteria on the basis of which the methods will work. Today we have scientific schools that are not only able to resolve this issue, but are already working for the State Company Avtodor to resolve these problems. And I really hope that by the end of 2018 these criteria will be presented for testing. This will allow us to manage the processes that we are talking about, because today even the technical elite of the road industry does not have a clear understanding that all problems with the top layers of the coating, including increased turnaround times, cannot be solved only by the top layer of wear. There is an integral cumulative health indicator for the entire road structure.

Each element of the road structure, including the subgrade, makes its contribution to the formation of a plastic track or unevenness. The evenness of the upper layer of non-rigid pavement should start with the evenness of the upper layers of the subgrade, lower sub-layers, lower asphalt-concrete layers of the package, and the evenness of the upper, closing layer is their integral, summarizing indicator. So, all the problems that drivers face on our roads are fatigue fractures, rutting resulting from the destruction of the top layer, because all these parameters do not have not only criteria, but even an internal understanding of the need to take them into account.

- What are the main factors in determining the durability of pavements?

- It's about accumulation. If we are talking about rutting, then we recall that two factors contribute to it: the accumulation of permanent deformation in each element of the road structure plus the destructive and abrasive effect of the car wheels, for which the structure of the upper closing layer is primarily important. In order to control these processes, as I have already noted, it is necessary to create methods that take into account the accumulation and formation of residual plastic deformation in non-rigid pavement. Both humidity and temperature are of paramount importance for each item of clothing. Moisture, for example, for subgrade soil or sand and gravel mixture is important, because the strength of the subgrade is directly proportional to its density, and density is inversely proportional to moisture. Humidity will definitely be taken into account in these criteria. So for asphalt concrete: at 20 ° C it works in a completely different way than at 60 ° C. All these factors should be involved in the methodology for calculating non-rigid road pavements for the accumulation of permanent deformations. Likewise, fatigue is significantly dependent on the moisture content of the subgrade soil, since during waterlogging, the bearing capacity is generally lost and asphalt concrete will work in much more severe conditions, since it has practically nothing to rely on. Therefore, all of these factors are fundamental in determining the durability of pavements.

What do they wear out?

Unfortunately, in Russia, serious studies of premature wear and damage to the structure of the road surface are not carried out. Therefore, we will use the experience of specialists from the American state of Washington (not to be confused with the capital of the same name). This is the most northeastern state of the United States, the winter is snowy, although not very frosty. Studded tires are also used there, although less often (Americans prefer all-season). Despite this, the state of the roads cannot be called ideal.

To investigate the origin of the track, the Americans, in turn, turned to their northern neighbors. The Quebec National Institute of Optics has developed the Laser Rut Measurement System (LRMS). Instruments mounted on outriggers at the rear of the vehicle read the texture of the road surface every 3 millimeters. At the same time, video cameras followed the canvas. Computer systems analyzed the track width, depth and shape.

All major highways of the state were subjected to similar control. The main difficulty was to distinguish the damage caused by the studs from wear and tear by trucks and ordinary (non-studded) passenger wheels. As it turned out, the track caused by each of these factors has its own characteristics. From the thorns, for example, two thin furrows arise, and beyond their limits the road is absolutely flat. And from the rest of the tires, including the truck ones, the tracks seem to be pressed through, there are characteristic elevations on the sides of both grooves. The asphalt does not wear off, but deforms and creeps into areas of reduced load.

Thus, it was possible to isolate wear from the studded tires. For example, on the I-5 highway, the track depth from them was 7 millimeters. An important clarification: the pavement was laid 40 (!) Years ago, 194 thousand cars pass along this road every day. For such circumstances, the wear is simply negligible!

WHAT DO YOU WEAR?

In Russia, the average service life of a road is 8 years. For the construction of roads in the United States, concrete is still used - a mixture of sand, gravel and cement. We have not used it since the times of the USSR - bitumen is cheaper in an oil-producing country. The concrete pavement has a characteristic feature: on average, every 10 meters the road is crossed by transverse joints filled with bitumen. This allows you to compensate for the flexibility of the material and reduce the effect of temperature fluctuations.

Concrete was replaced by asphalt concrete - a homogeneous black material containing, in addition to sand, crushed stone, minerals and binder bitumen, thanks to which the road turns into a single canvas. In addition, asphalt concrete has better adhesion properties. In America, where they prefer just concrete, shallow risks are applied to the not yet cured top layer to increase safety in wet weather, which diverts water.

WHY WEAR?

Each construction requires strict adherence to technology. On this side, asphalt concrete is more vulnerable. A lot of precision is required: two layers of asphalt concrete with a thickness of 60–80 millimeters are laid on an underlying layer of sand and crushed stone and kept for at least three days each. One layer of asphalt concrete is suitable only for the quietest streets, where less than 3000 cars pass per day. There are simply no such people in the Russian capital!

In practice, it turns out differently. Drivers scold the road workers for the restrictions, the city administration - for the terms. But few people understand how haste will turn out in the future. Satisfied drivers step on the gas on a barely cooled road.

The prescribed 72 hours are simply neglected. As well as two-layer technology. Why spend twice as much time and materials? Especially when overruns and non-compliance with deadlines can be seriously caught.

Even cutting and replacing the top damaged layer does not give a lasting effect. Because the ruts are a deformation of the coating as a whole, and not just a few centimeters removed. A year will pass, and the new surface, like a carbon copy, will show the defects of the old one. Therefore, such a scheme is not applied in Europe. If the road is in need of repair, it is completely closed. It is more expensive, but the result is more profitable ...

SHIP OR WHICK?

It turns out that studded tires are by no means the main source of rutting. Yes, their contribution is visible after careful computer processing, but it is minimal against the background of exposure to cold, heat, wind, heavy trucks and other vehicles. The quality work of engineers and builders is much more important. If everything is done correctly, then a flat and smooth road surface will delight drivers for decades.

Is it possible to convert our bad roads into good ones? The success of this venture is questionable. The layout of the streets of Russian cities, as well as the absence of a real alternative for most intercity routes, will lead to the fact that with a real major overhaul, entire areas will be swept by traffic paralysis. Of two evils - lack of roads and bad roads - choose the lesser. But thorns definitely have nothing to do with it ...

The track on the asphalt is, as a rule, the result of non-observance of the technology of its paving.

GERMAN ORDER

The use of studded tires has been banned in almost all of Germany since 1975. But the main reason for the ban is to increase the braking distance on clean asphalt! German winters are mild: if snow falls, it does not last long. Spikes are allowed only in the 15-kilometer zone near the border with Austria, in mountainous Thuringia and in several other places where snow or ice on the roads is the norm in winter. Familiar to us ruts are found even on the Autobahns, but, of course, not on such a scale. However, road control services are looking for flaws in their work. A report from the German Road Association (Deutscher Asphaltverband) identifies the main reasons for the ruts:

Errors in the design of the road; incorrect selection of the composition of the asphalt concrete mixture (does not correspond to the temperature and humidity of the environment);

Insufficient connection between asphalt layers;

Final control deficiencies.

Ask readers

Why do ruts appear in the asphalt?

9% - the climate is to blame

10% - from the surplus of cars

81% - because of the negligence of the road workers

The problem of rutting on the road worries the overwhelming majority of motorists, because the formed "rutting" becomes the cause of accidents, and with quite serious consequences. There is an opinion that the main culprit for the appearance of the track is the motorists themselves, who "shoe" their vehicles in studded tires. But, is this really the case?

The main reasons for the appearance of a rut

The track from the spikes is formed in the form of a small narrow strip, but the formed wider strips most likely appear from a large number of large traffic and flow. And, most likely, it is for this reason that "rutting" appears with heights and depressions.

From all, one conclusion is drawn that the main reason why the problem of rutting on the road arises is rather improperly carried out road works, as well as the extremely low quality of the coating and material itself. If we pay attention to the technical documentation of the coating, we will find a clear statement that the canvas must be laid in two layers. Moreover, the time period between them should be at least three days. But, as a rule, on domestic roads, even one layer cannot be laid in good faith. And it rarely meets even the minimum indicators, and according to experts, most of the roads in Russia are designed for use with a traffic intensity of no more than 500 cars per day.

NOTE
In addition, even if they lay asphalt according to technology, adhering to the norms and order, they do not even allow it to freeze for a day. Often, they immediately open the movement along the not yet formed canvas, from which drops and ruts appear.

There is one more reason that lurks in poor-quality repairs. Surely everyone noticed that when repairing a section of the road where there are already depressions, they simply remove the top layer of the canvas, without additional processing and strengthening of the base. That is, the problem remains, and it is covered with new asphalt. Of course, this type of "repair" is much cheaper, but there is little sense in carrying it out, as we can see.

NOTE
It is not enough to remove the old coating layer, because during use, not only the top sheet is deformed, but the entire "pillow". Therefore, it is necessary to build the foundation again to avoid the appearance of the ruts. An interesting fact about the construction of roads in Europe, where for quite a long time, "pit" and surface repairs are prohibited.

Therefore, it is clear that a low quality indicator of the material itself, improper performance of official duties and becomes the fundamental reason for the appearance of a rut. Of great importance is the role of the workers and managers themselves, because the quality of the work performed will allow the road to remain smooth for many decades. But, still a large percentage of people see the thorns as the culprit of the problem, even referring to the experience of their colleagues from Germany.

NOTE
Indeed, in Germany, since 1975, a ban has been introduced on the use of any tires with spikes, but this is not due to damage to the track, but to the large braking distance and inertia of such cars.

A categorical question arises, is it really possible to completely remake disgusting roads into good ones? Of course, experience shows that all this is real, but local specifics must be taken into account. For example, the high congestion of roads, the layout of streets, with long-term repairs, form a real collapse. But, at the same time, superficial repairs will not give any positive results, the road will shine only for the first year, and maybe much less. Therefore, it is much cheaper to completely block off a section of the road and carry out major repairs than to carry out patching every year.

NOTE
Today, officials prefer to choose less negative - bad roads. Summing up, I would like to remind you again that the spikes do not play any role in the destruction and formation of the track. The fault is not high-quality work and material.

Methods by which the problem of road rutting can be eliminated

As already found out, for a high-quality repair it is important not only to eliminate the track itself, but also to remove the underlying cause. Therefore, it is important to carry out not only superficial repairs, but also to thoroughly revise the "pillow". Identify deficiencies, determine the level of work and take appropriate measures.

In road construction companies, repairs are divided into two main subspecies:

1. Asphalt repair.
2. Concrete renovation.

In the first case, the process involves the use of two technologies:

1. The repair is carried out with a roadmap cutting, that is, such work allows you to completely remove the destroyed and damaged coating, followed by an analysis of the base. If the "pillow" is ready to serve one more season, then asphalt mixture is poured into the cut-out points. The cold type is often used, because hot asphalt in small sections is difficult to compact.
2. The second type of work takes into account the absence of a map clipping, as such. The technology involves filling the canvas with a cast mixture. Such a mixture does not even require compaction.

In the second case, the use of two technologies is also implied:

1. In the same way, a part of the web, the so-called "map", is cut out, after which the reinforcement is laid in the pre-cut grooves. Before installation, fittings, coating, base are carefully processed and cleaned. After that, they just proceed to the direct pouring.
2. Repair without cutting "cards" is carried out using special fillers. That is, the track is cleaned, debris, dust is removed, the surface layer is removed, as a rule, no more than 0.2 mm. Then it is treated with special solutions and emulsions based on cement.

Track prevention

In Europe, for example, the main reasons for the appearance of a track are caused by the ingress of water with the subsequent destruction of the canvas. Of course, in our country there are also sections of roads that are built in accordance with all the rules. Therefore, it would be reasonable to carry out prevention of destruction, to save the layer using a variety of technologies.

The problem of rutting on the road can be solved with the help of special emulsions, which are poured into the formed pores and provide protection against moisture ingress. The disadvantages of this method include only the need to periodically restore the protective layer every two years.

In addition to the use of various solutions and emulsions, a so-called wear layer is also used. This is a layer of asphalt road, consisting of 1 cm of asphalt and 1 cm of crushed stone sunk into the road. This coating protects the road from moisture, and also helps to improve traction with the wheels. According to its technical parameters, this type allows you to preserve the original appearance of the road, but on condition that initially the work on the arrangement of the roadway was carried out taking into account all the rules and regulations.

Track- this is the deformation of the transverse profile of the carriageway with the formation of grooves and ridges along the run-up strips due to uneven wear and the accumulation of plastic deformations in the pavement, as well as residual deformations in the layers of road pavement and subgrade, which occurs with repeated exposure to the wheels of cars.

Most often, the track is formed on non-rigid road pavements with a coating of asphalt concrete and other bitumen-mineral mixtures, however, an abrasion track can also form on cement-concrete pavements. Like most other deformations, the track is formed when an unfavorable combination of two groups of factors:

external factors- load effects, climatic factors, especially air temperature and solar radiation, as well as the conditions for moistening the subgrade soil;

internal factors- physical and mechanical characteristics of the road structure: shear stability, structural condition, strength and degree of compaction of the road pavement and subgrade, the type of soil and its properties.

The most important of all rutting factors is the impact of heavy multi-axle vehicles. The rutting process begins simultaneously with the opening of road traffic. At first, it goes slowly, affecting only the top layer of the pavement, and then spreads to other layers of pavement and to the subgrade. However, in the case when the material of a certain layer of the pavement is poorly compacted or has low strength and shear resistance, permanent deformations accumulate in this layer and appear on the surface of the pavement.

The nature and reasons for the formation of ruts, as well as the dynamics of their development, can differ significantly according to the seasons of the year (Fig. 5.14).

Rice. 5.14. Dynamics of the development of components of the total track depth by seasons

First of all, the track can be formed due to the additional compaction of the pavement layers, if they were not sufficiently compacted during construction. For this reason, the track is formed in the first year of operation. Experience shows that additional compaction of the pavement is completed after the passage of 300 thousand standard truck axles.

In the НDM-4 program, it is assumed that the initial underconsolidation is the reason for the formation of ruts in 20% of cases. However, this value was obtained on the condition that the subgrade does not participate in the ruts formation process. If we take into account the participation of the roadbed, then the share of insufficient compaction of the layers of the road pavement will be 5-10% of the total number of reasons for the formation of ruts.

Wear (abrasion) the coating under the action of the wheels of the car occurs during braking and when driving in traction mode due to the inevitable slippage of the tire in the zone of contact of the wheel with the coating. Wear is about the same throughout the year, unless studded tires are used in winter. Taking this into account, we can assume that in countries with short winters, the share of ruts due to wear of the pavement is about 5%.

Plastic deformations pavements are the cause of 15-20% of asphalt-concrete pavements rutting, which consist in the accumulation of vertical residual deformations due to increased ductility, i.e. a decrease in the structural viscosity of asphalt concrete at high temperatures, which, in turn, occurs due to a decrease in the viscosity of bitumen or the viscous shear resistance of bitumen (Figure 5.15).

Rice. 5.15. Track resulting from viscoplastic softening of the binder:

1 - the initial position of the crushed stone; 2 - position of crushed stone after displacement; 3 - crushed stone; 4 - a film of a binder

Simultaneously with vertical, horizontal residual deformations also accumulate, when, under the action of shear stresses, asphalt concrete particles are squeezed out to the sides. These deformations continuously increase with repeated repeated applications of the load, as a result of which ridges or shafts appear on the sides of the track.

The accumulation of plastic deformations in the asphalt concrete pavement occurs in summer when the air temperature is above 25-30 ° C, at which the temperature of the pavement rises to 40-60 ° C and above. The calculated temperature of asphalt concrete is 40-50 ° C and higher, depending on the viscosity of bitumen.

The depth of the plastic track depends on the initial viscosity of the bitumen, the composition of the asphalt concrete, the number of load applications and its magnitude, and the thickness of the asphalt concrete layer.

Structural failure and permanent deformation of the coating and base layers. Under the action of repeatedly applied loads in the pavement layers, conditions can arise when vertical or horizontal stresses exceed the local maximum permissible stress values ​​and destruction of the continuity or structure of the layer material begins with a loss of strength and shear resistance. The consequence of this is an accelerated accumulation of permanent deformations and the formation of a track, which appears after a critical number of applications of heavy load for a given pavement structure.

Structural deterioration of the pavement occurs approximately the same throughout the year, and in the base layers they accumulate most of all in the spring, when the strength of the pavement is lowest. The depth of the track due to structural destruction depends on the strength of the pavement, crack resistance, shear resistance, service life of the pavement, load, etc.

Of the total number of cases of rutting, structural destruction is noted in 25-35% of cases. In the НDM-4 program, where the role of the subgrade is not taken into account, this share is taken equal to 50%, i.e. this is one of the most important reasons for rutting.

Residual deformations in subgrade soils are the cause of rut formation in 20-30% of cases. Many works have been devoted to the problem of accumulation of residual deformations in the subgrade, including uneven residual deformations. The general view of the curve of accumulation of residual deformations in the roadbed during the year has been established, from which it follows that it occurs most actively in the spring. On the curve of the dependence of the depth and shape of the track on the resistance of the soil to indentation and shear, one can distinguish the phase of compression and compaction, the phase of local shears and the phase of extrusion or buckling of the soil to the sides.

There are mathematical models for calculating the magnitude of uniform and non-uniform residual deformations in the subgrade. However, they need further improvement and, in particular, take into account the recovery of a part of the accumulated deformations, which can occur in summer and winter.

This is the general character of rutting as a combination of all possible factors.

The main characteristic of a track is its depth. The total track depth can be determined based on the diagram shown in fig. 5.16:

h К = h УК + h В, where (5.5)

h UK - the size of the deepening on the surface of the pavement due to the accumulation of residual deformation in the layers of the pavement and in the subgrade, mm;

The average height of the embankment ridges on the left and right sides, formed due to plastic deformations in the asphalt concrete layer and the subgrade, mm.

Rice. 5.16. Basic track parameters:

1 - line of the surface of the coating after construction; 2 - the same, after the formation of a track; 3 - measuring rod

The depth of the deepening in the general case is

h УК = h g У + h И + h АБ + h О + h Г, where (5.6)

h g У - track gauge due to additional compaction of road pavement and subgrade soil, mm;

h И - track depth due to wear (abrasion), mm;

h АБ - track gauge due to plastic deformations in asphalt concrete layers, mm;

h О - track depth due to structural deformations in the base layers, mm;

h Г - track depth due to the accumulation of residual deformations in the roadbed, mm.

At the initial stage of research, it is possible to neglect the consideration of the track depth formed due to wear (abrasion), since the share of cars equipped with studded tires in our country is small.

It is also possible to omit the calculation of the track depth due to additional compaction of the pavement layers for the operated roads, since this phenomenon, as a rule, stops after a year of operation of the road.

Then the total track depth will be determined by the formula

h К = h АБ + h О + h Г + h V. (5.7)

In recent years, the problem of track control has become one of the most important on the roads of Russia. This is due to the fact that in the composition of the traffic flow there is an increase in the share of heavy multi-axle vehicles, which accelerate the process of ruts formation and the share of high-speed passenger cars, for which the ruts pose the greatest danger.

A deep track makes it difficult for the car to maneuver when overtaking, causes lateral slip, lateral vibrations and loss of stability when leaving the track, which leads to a decrease in driving speed and an increase in accidents. Ruts are especially dangerous for driving during the period of rains and melting snow, when a layer of water forms in the ruts, as a result of which there is a decrease in the adhesion qualities of the surface, the prerequisites for the occurrence of aquaplaning with a loss of vehicle control are created. During thaws and frosts, ice forms in the rut, during blizzards and snowfalls, snow is deposited and compacted, which is difficult to remove with snow plows.

In order to find the correct solution to eliminate the ruts in each specific case, it is necessary to carry out a deep analysis of the causes of their formation. There is not and cannot be one solution that is applicable in all cases. It should be a wide range of design and technological solutions, allowing you to choose the most effective in each case.

In the process of maintenance and repair of roads, mainly the ruts formed due to abrasion of the pavement and the accumulation of plastic deformations in the pavement layers are eliminated. The track formed due to the accumulation of residual deformations in the base layers and in the subgrade, as a rule, is eliminated during major repairs or reconstruction of roads.

Rutting on the roads: looking for the culprit and understanding the reasons.

Each owner of a motor vehicle, when moving along the highways and highways of our beloved Motherland, has repeatedly encountered such an unpleasant phenomenon as rutting on the roads. Track is a type of deformation of the asphalt concrete pavement in the roadway. Rutting on roads is one of the most common problems on domestic roads, as well as the most dangerous, because it is often accompanied by road traffic injuries. Of course, we all dream of perfect asphalt pavement and no less perfect car suspension, and we often scold negligent road builders. Let's talk about who is responsible for the current quality of the road surface and what are the causes of rutting on the roads.

Rutting on the roads: the causes of education.

As a rule, rutting on the roads occurs due to the following reasons:

1. Violation of the technology of road construction.

The quality of the base prepared for asphalt has an influence on the strength of the upper layers of the asphalt concrete pavement. These are works on the preparation of sand and crushed stone and other types of work. High-quality compaction of sand and crushed stone and natural foundations, maintaining the required proportions of components in accordance with regulatory documents, SNiP, GOST, adherence to asphalt laying technology are all important aspects of a good result.

Design documentation for the construction of highways should be developed taking into account climatic, landscape and other terrain features. Also, the categories and capacity of roads, etc., must be taken into account.

Therefore, it is necessary to carry out only with the help of organizations with highly qualified employees capable of fully performing all stages of work.

2. Poor quality of materials used for road construction.

The materials used in the construction of road pavements play an important role in the quality of asphalt concrete pavement. If the materials do not meet the required technical parameters, an accelerated deformation of the pavement occurs. Potholes, cracks, chipping, abyss, subsidence, ruts, as well as collapse of shoulders can be observed on the roadbed. Eliminates many deformations. Patching repairs can significantly extend the life of asphalt if carried out in a timely manner.

2. Decompression of the pavement structure.

Decompression of the pavement structure can be observed in several cases:

• Precipitation getting into road clothes;
• Production near the pavement structure.

3. Improper road maintenance.

Often the roads are used improperly, on the roads it is unacceptable:

• Violation of weight control. Overloading of trucks has a deplorable effect on the asphalt-concrete road surface;
• Violation of the terms of the current repair. The penetration of precipitation through cracks and holes leads to decompaction of the pavement structure;
• Violation of conditions. In case of poor maintenance of roads in winter, cars are forced to drive along a "knurled path", as a result of which the load on a certain section of the road increases and a track appears.

3. Climatic aspects.

Today, more and more often you can find climatic anomalies, atypical weather phenomena for a certain area. Excessive heat, or, on the contrary, frost, can seriously affect the road. Precipitation, or its absence, changes in the landscape, groundwater and many other aspects of natural phenomena can affect the quality of the roadbed.

Rutting on the roads: who is to blame?

Thus, we can conclude that there may be many guilty persons here. These are road construction companies, material suppliers, service organizations, motorists themselves, accidental cataclysms, etc. After all, it is important not only to carry out high-quality road construction, but also to preserve the result of the work.