Deterioration of the road surface. Normative service life and wear of road structures

Biggest Influence the wear of the coatings is exerted by moving vehicles. Under the load transmitted to the wheel, the tire is deformed (Fig. 6.7). At the same time, at the area of ​​the tire entry into the contact zone with the coating, compression occurs in the tire, and expansion occurs at the exit from the contact. Way, passable point on the busbar in the plane of contact l 1 , less than outside it l. Therefore, in the plane of contact, the point moves with an acceleration greater than how it moved before coming into contact with the coating. At the same time, the angular velocity a in the sectors is practically the same. Therefore, the point passes along the coating a path of a certain length with slipping instead of one rolling.

Rice. 6.7. Deformations of the wheel tire, contributing to the wear of the coating:
A - compression zone, B - tension zone

Under the action of these enhanced shear stresses in the plane of the track, abrasion of the coating and the tire of the car occurs. The greatest tangential forces and the greatest wear occur when the vehicle is braked. Wear during the movement of trucks is approximately 2 times greater than when driving cars. The greater the strength of the coating material, the smaller and more uniform the wear of the coating across the width. On coatings made of low-strength materials, the wear intensity is much higher, ruts and potholes are more often formed. The use of igneous rocks for crushed stone instead of sedimentary rocks reduces wear by 60%. Increasing the bitumen content from 5 to 7% reduces wear by 50-80%.

The wear of the coating within the carriageway and the thickness of the coatings occurs unevenly and abrasion ruts are formed on the coating along the rolling strips, the depth of which can vary from a few millimeters to 40-50 mm. In such ruts during rain, a significant layer of water is created, which leads to a decrease in the adhesion properties of the coating and hydroplaning.

Average wear over the entire coverage area h cf, mm, is:

h cf = k× h n, mm, where (6.1)

k- the coefficient of uneven wear, on average, is 0.6-0.7;

h n- the amount of wear in the rolling strip, mm.

For advanced pavements, wear is measured in mm, and for transitional pavements also in terms of material loss in m 3 /km.

Features of wear of rough road surfaces. The wear of the rough surface of road surfaces is manifested in a decrease in height and in the grinding of irregularities of macroroughness. The decrease in the macroroughness of coatings under the action of car wheels occurs in two stages (see Fig. 7.3). At the first stage, immediately after the completion of construction, the roughness of the coating is reduced due to the immersion of the grains of the crushed stone of the wear layer into the underlying layer of the coating. The magnitude of this immersion depends on the intensity and composition of the movement, the size of the crushed stone and the hardness of the coating. The hardness of the coating is estimated by the depth of immersion of the hardness tester needle and for asphalt concrete pavements it is divided into: very hard - 0-2 mm; hard - 2-5 mm; normal - 5-8 mm; soft - 8-12 mm; very soft - 12-18 mm. Cement-concrete coatings have absolute hardness.

Determination of wear of coatings by calculation. The average value of the decrease in the thickness of pavements per year due to wear can be determined by the formula of prof. M.B. Korsunsky (it should be noted that these studies were carried out more than 50 years ago and the quantitative values ​​of their results are hardly applicable to modern roads and cars):

h = a + b× B (6.2)

h- annual wear of the coating, mm;

a- a parameter that depends mainly on the weather resistance of the coating and climatic conditions;

b- an indicator that depends on the quality (mainly strength) of the coating material, the degree of its moisture, composition and speed of movement;

AT- traffic intensity, million gross tons per year; N» 0.001× AT (N- traffic intensity, avt./day).

Coating wear for T years, taking into account changes in the composition and traffic intensity in the future, in a geometric progression, can be determined by the formula

where (6.3)

h T- coating wear T years, mm;

N 1 - traffic intensity in the initial year, avt./day;

To\u003d 1.05-1.07 - coefficient taking into account changes in the composition of the movement;

q 1 - indicator of annual growth in traffic intensity, q 1 > 1,0.

Parameter values a and b are given in table. 6.6.

Table 6.6

Notes. 1. Averages a and b accepted for roads located in the zone of moderate moisture (III road-climatic zone) and built of stone materials that meet the requirements of the standards. 2. For roads with improved pavements located in the zone of excessive moisture (road-climatic zone II), the upper limits are accepted, and for roads located in areas with a dry climate (IV and V road-climatic zones), - lower limits values a and b. 3. For roads with crushed stone and gravel, located in the zone of excessive moisture, the lower limits are accepted, and in areas with a dry climate - the upper limits a and b. 4. If the width of the carriageway exceeds 7.0 m, then the value b decrease by 15%, and if it is less than 6.0 m, then b increase by 15%.

In recent years, tires with spikes or chains have been used to increase the stability of the movement of cars. Experience shows that this dramatically increases the wear and tear of road surfaces.

At the moment of contact with the coating, each spike strikes with high speed. The spike has a very small mass, but the repeated repetition of these blows in one place contributes to the weakening of the top layer of the coating. The stud coming out of the contact zone has a greater abrasive effect, where the tire, together with the stud, slides over the surface of the coating, abrading it.

The duration of wear of asphalt concrete pavements during the operation of tires with chains and spikes is reduced by 2-3 times. Even on high-strength cast asphalt concrete pavements on German highways, on which cars equipped with studded tires move, ruts up to 10 mm deep are formed along rolling strips after 1-2 years.

Therefore, in the conditions of operation of Russian roads, the use of tires with spikes and snow chains on the roads common use should be strictly limited.

As a criterion for the limit state of the pavement in terms of wear, the value of permissible wear can be taken H and: for asphalt concrete pavements 10-20 mm; for crushed stone and gravel, treated with organic binders - 30-40 mm; crushed stone from durable crushed stone - 40-50 mm, gravel - 50-60 mm.

Based on this, road maintenance organizations, when accepting roads after construction or repair with reinforcement, should require builders to have a coating thickness greater than that calculated from the strength condition by the amount of permissible wear, i.e.

h n = h np + H and, mm, where (6.5)

h np- design thickness of the pavement from the condition of the strength of the pavement, mm.

Wear measurement. The annual wear in fractions of mm of cement concrete, asphalt concrete and other monolithic coatings is measured using benchmarks embedded in the thickness of the coating and a wear meter. With this method of wear measurement, brass reference cups are preliminarily laid in the coating. The bottom of the glass serves as the surface from which the reading is performed.

Wear is also determined using plates (grades) of trapezoidal shape made of limestone or soft metal, embedded in the coating and abraded together with it. To determine the wear of coatings can be used various kinds electrical or georadar devices used to measure the thickness of layers in layered half-spaces.

Having data on the actual wear of the coating and the maximum allowable wear, the coefficient of wear of the coating is determined.

CHAPTER 7. Patterns of changes in the main transport and operational characteristics of roads

Moving vehicles have the greatest influence on the wear of coatings. Under the load transmitted to the wheel, the tire is deformed (Fig. 6.7). At the same time, at the area of ​​the tire entry into the contact zone with the coating, compression occurs in the tire, and expansion occurs at the exit from the contact. The path traveled by a point on the bus in the plane of contact ℓ 1 is less than outside it ℓ. Therefore, in the plane of contact, the point moves with an acceleration greater than how it moved before coming into contact with the coating. At the same time, the angular velocity a in the sectors is practically the same. Therefore, the point passes along the coating a path of a certain length with slipping instead of one rolling.

Under the action of these enhanced shear stresses in the plane of the track, abrasion of the coating and the tire of the car occurs. The greatest tangential forces and the greatest wear occur when the vehicle is braked. Wear during the movement of trucks is approximately 2 times greater than when driving cars. The greater the strength of the coating material, the smaller and more uniform the wear of the coating across the width. On coatings made of low-strength materials, the wear intensity is much higher, ruts and potholes are more often formed. The use of igneous rocks for crushed stone instead of sedimentary rocks reduces wear by 60%. Increasing the bitumen content from 5 to 7% reduces wear by 50-80%.

Table 6.5

The most common deformations and destruction of cement concrete road surfaces

Rice. 6.7. Deformations of the wheel tire, contributing to the wear of the coating:

A - compression zone, B - tension zone

The wear of the coating within the carriageway and the thickness of the coatings occurs unevenly and abrasion ruts are formed on the coating along the rolling strips, the depth of which can vary from a few millimeters to 40-50 mm. In such ruts during rain, a significant layer of water is created, which leads to a decrease in the adhesion properties of the coating and hydroplaning.

The average wear value over the entire coverage area h СР, mm, is:

h СР = k×h Н, mm, where (6.1)

k - coefficient of uneven wear, on average 0.6-0.7;

h H - the amount of wear in the rolling strip, mm.

For advanced pavements, wear is measured in mm, and for transitional pavements also in terms of material loss in m 3 /km.

Features of wear of rough road surfaces. The wear of the rough surface of road surfaces is manifested in a decrease in height and in the grinding of irregularities of macroroughness. The decrease in the macroroughness of coatings under the action of car wheels occurs in two stages (see Fig. 7.3). At the first stage, immediately after the completion of construction, the roughness of the coating is reduced due to the immersion of the grains of the crushed stone of the wear layer into the underlying layer of the coating. The magnitude of this immersion depends on the intensity and composition of the movement, the size of the crushed stone and the hardness of the coating. The hardness of the coating is estimated by the depth of immersion of the hardness tester needle and for asphalt concrete pavements it is divided into: very hard - 0-2 mm; hard - 2-5 mm; normal - 5-8 mm; soft - 8-12 mm; very soft - 12-18 mm. Cement-concrete coatings have absolute hardness.

Determination of wear of coatings by calculation. The average value of the decrease in the thickness of pavements per year due to wear can be determined by the formula of prof. M.B. Korsunsky (it should be noted that these studies were carried out more than 50 years ago and the quantitative values ​​of their results are hardly applicable to modern roads and cars):

h = a + b×B (6.2)

h = a + , where (6.3)

h - annual wear of the coating, mm;

a - a parameter that depends mainly on the weather resistance of the coating and climatic conditions;

b is an indicator that depends on the quality (mainly strength) of the coating material, the degree of its moisture, composition and speed of movement;

B - traffic intensity, million gross tons per year; N»0.001×B (N - traffic intensity, avt./day).

The wear of the pavement over T years, taking into account changes in the composition and intensity of traffic in the future, in a geometric progression, can be determined by the formula

h Т = a×T + × , where (6.4)

h T - wear of the coating for T years, mm;

N 1 - traffic intensity in the initial year, avt./day;

K = 1.05-1.07 - coefficient taking into account the change in the composition of the movement;

q 1 - indicator of annual growth in traffic intensity, q 1 >1.0.

The values ​​of parameters a and b are given in Table. 6.6.

In recent years, tires with spikes or chains have been used to increase the stability of the movement of cars. Experience shows that this dramatically increases the wear and tear of road surfaces.

Table 6.6

Notes. 1. The average values ​​of a and b are taken for roads located in the zone of moderate moisture (III road-climatic zone) and built of stone materials that meet the requirements of the standards. 2. For roads with improved pavements located in the zone of excessive moisture (road-climatic zone II), the upper limits are accepted, and for roads located in areas with a dry climate (IV and V road-climatic zones), the lower limits of the values ​​of a and b. 3. For roads with crushed stone and gravel, located in the zone of excessive moisture, the lower limits are accepted, and in areas with a dry climate - the upper limits a and b. 4. If the width of the carriageway exceeds 7.0 m, then the value of b is reduced by 15%, and if it is less than 6.0 m, then b is increased by 15%.

At the moment of contact with the coating, each spike strikes at high speed. The spike has a very small mass, but the repeated repetition of these blows in one place contributes to the weakening of the top layer of the coating. The stud coming out of the contact zone has a greater abrasive effect, where the tire, together with the stud, slides over the surface of the coating, abrading it.

The duration of wear of asphalt concrete pavements during the operation of tires with chains and spikes is reduced by 2-3 times. Even on high-strength cast asphalt concrete pavements on German highways, on which cars equipped with studded tires move, ruts up to 10 mm deep are formed along rolling strips after 1-2 years.

Therefore, under the operating conditions of Russian roads, the use of tires with spikes and snow chains on public roads should be strictly limited.

As a criterion for the limit state of the pavement in terms of wear, the value of allowable wear H I can be taken: for asphalt concrete pavements 10-20 mm; for crushed stone and gravel, treated with organic binders - 30-40 mm; crushed stone from durable crushed stone - 40-50 mm, gravel - 50-60 mm.

Based on this, when accepting roads after construction or repair with reinforcement, road maintenance organizations should require builders to have a coating thickness greater than that calculated from the strength condition by the amount of permissible wear, i.e.

h P \u003d h PR + H I, mm, where (6.5)

h PR - the calculated thickness of the pavement from the condition of the strength of the pavement, mm.

Wear measurement. The annual wear in fractions of mm of cement concrete, asphalt concrete and other monolithic coatings is measured using benchmarks embedded in the thickness of the coating and a wear meter. With this method of wear measurement, brass reference cups are preliminarily laid in the coating. The bottom of the glass serves as the surface from which the reading is performed.

Wear is also determined using plates (grades) of trapezoidal shape made of limestone or soft metal, embedded in the coating and abraded together with it. To determine the wear of coatings, various types of electrical or georadar devices used to measure the thickness of layers in layered half-spaces can be used.

Having data on the actual wear of the coating and the maximum allowable wear, the coefficient of wear of the coating is determined.

The constant impact of the wheels leads to the gradual accumulation of various defects, and then to destruction. pavement or top layer.

As the pavement wears out, the thickness of the pavement may be less than required. In this case, subsidence, depressions, ruts, breaks are formed on the surface of the coating. Gravel forestry roads wear out by 2-7 mm per year, depending on the strength of gravel, crushed stone - by 5-8 mm. The wear of large-skeletal pavement of medium limestones and homogeneous burnt rocks is the same as on gravel roads. When using boiler slag, shells, heterogeneous burnt rocks, the wear is much higher and for brick rubble reaches 25 and boiler - up to 50-60 mm. With 1 mm of wear, the loss of road material per 1 km is as many cubic meters as the width of the road is meters.

Subsidences and depressions are formed due to a local decrease in the strength of the base soil, usually due to waterlogging in the spring and the formation of heavings in the winter. The reasons for the formation of subsidence are insufficient compaction of the subgrade during construction and the movement of heavy road trains, the impact of which the road was not calculated during the design. Ruts are formed on poorly rolled pavements from local compaction caused by the systematic movement of wheels along one track. Under the influence of the movement of wheels with a load oscillating on the springs, potholes and undulations appear on the surface. The development of unevenness is also influenced by climatic factors that contribute to the weakening of the cohesion and strength of pavements. So, due to saturation with moisture in autumn and freezing at the beginning of winter, stones of weak rocks are destroyed, which leads to a weakening of road pavements. When the wheels are exposed to the roadway, abrasion, crushing, breaking, shearing of particles and even tearing out of individual particles and deconsolidation of the coating are observed. As a result of the impact of all factors, the road is gradually destroyed if repairs are not carried out in a timely manner.

The carriageway of an unimproved dirt road consists of the same soil as the subgrade but is more compacted by traffic. In dry weather, such a canvas wears out with intense dust formation, and during rain it is washed away by water, and ruts form on the surface under the action of vehicles. Roads with a carriageway made of soil reinforced with any additives also have insufficient wear resistance, since ruts and potholes form on them, although to a lesser extent.

The surface of the dirt road is leveled with graders, and in their absence - with metal irons in the form of two metal ribs towed behind the machine. With frequent and timely flattening in summer, the dirt road can be kept level. Ironing should be done at the moment when the soil, after moistening (rain), begins to dry out, but is still freely cut off and moves with the iron, without sticking to it. This method allows you to eliminate only small irregularities. It is possible to restore the cross profile and destroy deep ruts, pits and potholes only with a grader. Planning and profiling by a grader is carried out in a drier state of the soil, but the moisture content must be sufficient for free cutting and moving it along the grader knife. When the track is deepened to 3-4 cm, it is advisable to plan the road surface with a grader.

High dust content in the air reduces the speed of movement and causes wear of engines, transmissions and chassis of vehicles. The dustiness of roads in the summer can be eliminated or significantly reduced by treating the soil surface with various materials. The most effective and frequently used is calcium chloride, which is poured in the form of a 20-30% solution or distributed as a powder. Salt consumption is 0.5-1 kg/m 2 in the primary treatment and 0.2-0.5 kg/m 2 in the subsequent. The dedusting period is 2-2.5 months. A good dust-removing effect is obtained by treating the soil surface with sulfite-alcohol bard to sulfite-cellulose alkalis.

The lye is preliminarily neutralized with the addition of 0.6% (by weight) of lime and poured at a rate of 2-3 l/m 2 . The treated surface becomes harder and shinier. With light rains, the sulphite lye dissolves, but as the road dries out, it hardens again. It is completely washed out only during prolonged rains. Sulfite-alcohol stillage is used in the form of a liquid 30% concentrate and is consumed at the first bottling in the amount of 1.5 l/m 2 (with subsequent 1 l/m 2). In powder form, the stillage is scattered at the rate of 0.5 l / m 2. Like liquor, bard gradually dissolves in water, and the dedusting effect decreases. Crude oil can also be used for dedusting. The recommended oil spill rate is 2 l/m 2 ; the period of dedusting action is 30-60 days.

Maintaining and repairing gravel pavements is in many ways similar to maintaining and repairing dirt roads. Under the influence of traffic on gravel roads, waves, combs, ruts, potholes occur. Consequently, in this case, the main work is to restore the evenness of the coating. The first profiling and planning of gravel roads is carried out in the spring, as soon as the pavement thaws by 15-20 cm, then gravel is scattered to compensate for wear; this is especially necessary when the thickness of the pavement is insufficient. Careful profiling is carried out before the final drying of the coating to eliminate all ruts and irregularities. During the summer, the coverage profile is distorted; to restore it, the gravel bark is fluffed up, and then it is profiled with a grader.

Below are some common problems and how to fix them.

Often there are large stones of crushed stone or gravel rolling on the surface or protruding from the coating. This phenomenon is observed in cases where there are large particles in the upper layer of gravel material - more than 25-30 mm. In order to combat the katun, an additional thin layer clothes made of fine gravel, preferably from an optimal mixture.

The disorder of the surface in dry weather indicates a lack of a binder material in the gravel, i.e., clay particles. To combat this phenomenon, it is best to water the surface of the gravel material with a 3% solution of calcium chloride, which increases cohesion and reduces dusting. You can also skim the top layer and add a small addition (5-7% of the weight of the layer) of loamy soil to it, and then roll the gravel clothes again in a wet state.

Fine undulations on the surface usually indicate an excess of small particles or rounded material in the gravel bed. To combat this phenomenon, the layer should be boiled up and larger (10-20 mm) particles of an angular, unrounded shape should be added to the gravel, or the ridges should be cut and the surface profiled.

If during rain the surface of a gravel road is covered with a thin film of clay solution, this indicates an excess of fine soil particles in the gravel material - dusty and clay. In this case, it is best to boil the top layer and add freshly slaked or quicklime in an amount of 3% of the weight of the layer to be treated.

Dry breaks in the bark usually indicate that the coating thickness is insufficient for road trains. Therefore, it is necessary to increase the thickness of the gravel layer. Large drawdowns and waves with a sufficient thickness of the coating indicate poor compaction of the embankment or the presence of mud bags in the body of the embankment. In this case, it is necessary to check the sufficiency of the height of the embankment above the groundwater level and the availability of drainage, as well as to additionally compact the coating by rolling with heavy pneumatic rollers. If large subsidence and waves reappear, then it is necessary to make transverse slots in the embankment to dry it, lay fascines inside the slots and cover them with dry soil, restore the coating.

Local destruction of the coating with the formation of pits indicates poor mixing of the mixture, and on gravel roads - poor wedging of gravel. In this case, perform patching: dirt is removed from the pits and gravel or rubble is scraped, and sheer walls are attached to the pit. The material obtained during the scraping is laid on the bottom, and imported gravel of the required composition is added on top. The layer of compacted material in the pit should be 1-2 cm above the coating, taking into account subsequent additional compaction.

Dedusting of gravel pavements is carried out with the same materials as for unpaved roads. Repair of pavements from reinforced and stabilized soil for the most part reduced to the repair of surface treatment. The repair team must have a mobile (trailed) bitumen boiler at its disposal to heat the bitumen to operating temperature. The destroyed layer of surface treatment is scratched, dust and dirt are removed; the pothole is lubricated with hot bitumen at a rate of 0.5-0.8 l / m 2. After the contact layer has dried, bitumen is poured again and fine stone material is scattered on it to form a surface treatment layer; the technology is the same as for the construction of new layers.

When a layer of soil cement or soil bitumen is destroyed, a section of pavement is scraped and given holes in the plan rectangular shape, the bottom and walls are cleaned of dust and fines and filled with a new soil-cement or soil-bitumen mixture. If soil cement or soil lime is present in the coating, then a mobile concrete mixer mounted on a vehicle is needed to prepare a mixture of soil with cement or lime; the resulting pits and potholes are filled with a mixture. If soil bitumen is available, the mixture can be prepared on site, but in this case a mobile boiler is required to heat the bitumen.

Wear (abrasion)- the main type of destruction of the road surface, determines the conditions and terms of its service. Wear is a reduction in the thickness of the coating due to the loss of material during operation under the influence of car wheels and natural factors.

The wear of the coating occurs under the influence of tangential forces acting in the plane of the track of automobile wheels and caused by the work of tires to overcome frictional forces. Tangential stresses in the plane of the track cause abrasion of the road surface and tires of the car wheel along the entire route. Such stresses increase from a complex of influences that cause the wheel tire to slip in the track plane under normal rolling conditions. In addition, increased wear contribute natural factors, since the coating material is weakened when saturated with water, and in winter under the influence of its freezing.

The wear of the coating occurs across the entire width of the carriageway, but most of all on the rolling lanes, where the wheels of cars often pass in one track. In studies, the wear value is conventionally assumed to be uniformly distributed over the entire area of ​​the coating. Wherein average value wear h cf mm is h cf =kh n. where k is the coefficient of uneven wear, averaging 0.6-0.7; h„ is a certain amount of wear in the rolling strip, mm.

For improved coatings, wear is measured in millimeters, and for coatings of the transitional and simplest type, also in terms of the volume of material loss, m 3 /km.

In addition to wear, road surfaces are subject to deformation and destruction, which are described below and shown in Fig. 25 and 26.

Peeling- exposure of the coating surface, separation of surface thin films and flakes of the coating material deformed under the influence of water and frost, as well as car wheels. This process is especially intense in spring period with frequent heating of the upper layers of the coating by sunlight during the day and freezing at night. Peeling occurs the more intense, the higher the porosity and the lower the strength of the coating material. The peeling process also develops from the action of chlorides used in the fight against ice. They are especially harmful for cement-concrete coatings with a high content of surface pores. Chlorides increase the peeling of coatings indirectly, reducing the frost resistance of concrete. These effects contribute to the release of the latent heat of ice melting on the coating, as a result of which it thaws and then freezes again. To stop peeling, it is necessary to reduce the porosity of the upper part of the coating by treating it in summer with bitumen with a scattering of fine mineral material.

chipping- the subsequent process of destruction of the coating after peeling, in which larger grains of mineral material are separated from the coating. Not only coatings of the transition type are chipped, but also all improved coatings due to the loss of the bond between grains of materials. From porous cement-concrete coatings, the material crumbles as a result of increased peeling processes. Crushed stone grains that are poorly bonded to bitumen (silicon grains) fall out of asphalt concrete pavements. The reasons for the spalling of the coatings are also the low quality of the mixtures due to their transportation in dump trucks (sand residues fall into the coating), under-rolling of the coating in cold and rainy weather, etc. This process can be suspended by laying a protective layer.

Edge breaking- destruction of pavements in places of their interface with roadsides, which occurs most often in cases of heavy trucks moving over the edges of pavements. On cement-concrete pavements, in addition, the edges break off along the expansion joints when the quality of the concrete is poor or when there is no connection between the slabs. When the car moves through the seam, the plate flexes and, if there is no good connection between the plates, the wheel hits the edge of the next plate. During the construction of the road, the edges of the coating must be protected from breaking off, for which purpose reinforcing (edge) strips are arranged on the sides of the road. On those roads where there are no such lanes, they must be done when repair work Oh.

Waves are deformations formed on coatings with excessive plasticity. Upper layer asphalt concrete pavement under the action of tangential forces, especially when braking, shifts on slopes and at public transport stops. Waves, or folds, are formed mainly in hot sunny weather, when the coating is heated to 60 ° or more. On overly plastic soil and gravel surfaces treated with organic binders, waves can reach such sizes that driving on the road becomes impossible, because of them cars move to the side of the road. The formation of waves can be stopped by spreading fine, acute-angled mineral material, followed by rolling it with heavy rollers on metal rollers. A kind of waves are sagging, in which the material is shifted in the transverse direction. For example, at public transport stops, the material is shifted onto the curbs.

Comb- a type of destruction of transitional type coatings, mainly gravel, and sometimes - improved type of lightweight coatings. The comb has the appearance of regular, more or less clearly defined transverse protrusions, alternating with recesses. To eliminate this shortcoming, it is necessary to carry out surface scarification with subsequent correction of the road profile by motor graders and rolling.

shifts- pavement deformations that occur under the action of tangential forces from the wheels of vehicles, especially in the places of their braking. Shears are formed mainly in the absence of proper bonding of the coating to the base or the top layer of the coating to the bottom. Shifts are accompanied by cracks. In places of shear, especially in cracks, the coating begins to collapse.

dents- recesses in plastic coatings in the form of imprints of the pattern of car tires or tracks of caterpillar vehicles, formed in hot weather.

cracks, formed on cement concrete pavements, are usually a sign of insufficient strength and the beginning of destruction. Transverse thermal cracks are formed when long distances between seams and in cases where bonding has occurred concrete slabs with the base and they lost the ability to move with temperature changes.

Longitudinal cracks occur with a non-uniformly compacted subgrade - when its edges, compacted less than the middle, begin to precipitate. Oblique cracks appear above local voids - subgrade sediments and with insufficiently strong coatings.

Transverse temperature cracks are formed on coatings, the surface of which is treated with organic binders, with a sharp decrease in air temperature in autumn and with large temperature drops in winter. They are regularly distributed at certain distances from each other (6-10 m). They are formed due to insufficient resistance of the coating material to thermal stresses.

Axial cracks on asphalt concrete pavements appear due to poor mating of the asphalt concrete mix of two adjacent strips when the hot mix adjoins the previously laid cold strip. Oblique cracks are the development of transverse and longitudinal cracks with insufficient coating strength.

crack grid occurs on the road surface, as a rule, with insufficient strength of the base. Especially often, a network of cracks is formed in the spring, when waterlogged soil causes large deflections of the base under load. The more rigid coating material does not withstand such deflections, as a result of which cracks appear. All types of the above cracks are shown below.

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GOU VPO TYUMEN STATE

ARCHITECTURAL AND CONSTRUCTION UNIVERSITY

Department of Building Materials

TEST

By discipline

"Standardization, metrology, certification"

on the topic: "Regulatory service life and wear road structures"

Tyumen 2011

Literature

Chapter 1. Elements of pavement, basic terms and definitions

Road pavement is a multilayer artificial structure, limited by the carriageway of a motor road, consisting of a road surface, base layers and an underlying layer, perceiving the repeated impact of vehicles and weather and climatic factors and ensuring the transfer of traffic load to the upper part of the subgrade.

Non-rigid road pavements include pavements with layers made of different kind asphalt concrete (tar concrete), from materials and soils reinforced with bitumen, cement, lime, complex and other binders, as well as from weakly cohesive granular materials (crushed stone, slag, gravel, etc.).

There are the following elements of pavement:

Coating - top part pavement, perceiving forces from the wheels of vehicles and subjected to direct impact atmospheric factors.

Layers of surface treatments can be arranged over the surface of the coating for various purposes(layers to increase roughness, protective layers, etc.).

Foundation - a part of the pavement structure located under the pavement and providing, together with the pavement, the redistribution of stresses in the structure and the reduction of their magnitude in the soil of the working layer of the subgrade (underlying soil), as well as frost resistance and drainage of the structure.

DEFINITIONS

A road structure is an engineering structure consisting of a pavement and the upper part of the subgrade within the working layer.

Strength (bearing capacity) of a road structure is a property that characterizes the ability of a road structure to perceive the impact of moving vehicles and weather and climatic factors.

The operability of a road structure is the property of a road structure to maintain a margin of safety for the repeatedly repeated impact of automobile loads within the calculated, overhaul periods of service.

The service life of a road structure is the period of time within which its strength and reliability decrease to the design level, the maximum allowable for traffic conditions.

Reliability of pavement - the probability of failure-free operation of pavement within the estimated (normative) overhaul life.

The level of pavement reliability is a quantitative indicator of reliability, defined as the ratio of the length of strong (non-deformed) sections of the road to its total length.

Regulatory overhaul period of pavement - the time period established by the current norms from the moment of construction to the overhaul or between overhauls.

Chapter 2

When designing pavement, the following principles should be followed:

a) the type of pavement and the type of pavement, the design of the pavement as a whole must meet the transport and operational requirements for the road of the corresponding category and the expected composition and traffic intensity in the future, taking into account the change in traffic intensity during the given overhaul periods and the expected conditions of repair and maintenance;

b) the design of clothing can be adopted as a standard or developed individually for each section or a number of sections of the road, characterized by similar natural conditions (soil of the working layer of the subgrade, its moisture conditions, climate, availability of local road-building materials, etc.) with the same design loads . When choosing a clothing design for given conditions, preference should be given to a typical design that has been proven in practice in given conditions;

c) in areas insufficiently provided with standard stone materials, it is allowed to use local stone materials, industrial by-products and soils, the properties of which can be improved by treating them with binders (cement, bitumen, lime, active fly ash, etc.). At the same time, we must strive to create a structure that is as least material-intensive as possible;

d) the design must be technological and provide the possibility of maximum mechanization and industrialization of road construction processes. To achieve this goal, the number of layers and types of materials in the structure should be minimal;

e) when designing, it is necessary to take into account the actual conditions for conducting construction works(summer or winter technology and etc.).

Pavement should be designed with the required level of reliability, which is understood as the probability of failure-free operation during the overhaul period. Structural failure in terms of strength can be physically characterized by the formation of longitudinal and transverse unevenness of the pavement surface associated with structural strength (transverse irregularities, ruts, fatigue cracks), followed by the development of other types of deformations and fractures (frequent cracks, a network of cracks, potholes, subsidence, breaks etc.). Defect nomenclature and methodology quantification they are determined by special standards used in the operation of roads.

Normative service life - the operational overhaul period (from the moment the road is put into operation until the first major overhaul) - is a parameter that is set at the design stage. Depending on it, building materials are selected that perceive various design loads.

In the absence of regional norms, the estimated service life of pavement may be assigned in accordance with the recommendations of Table 2.1

The service life of pavement is the period of time within which the bearing capacity of the road structure decreases to a level that is maximum allowed by traffic conditions.

Repair of pavement is carried out when the calculated level of pavement reliability and the corresponding limit state of the pavement in terms of evenness are reached during operation.

The reliability of pavement is understood as the probability of failure-free operation of the structure during the entire period of operation before repair. Quantitatively, the level of reliability represents the ratio of the length of strong (undamaged) sections to the total length of the pavement with the corresponding value of the strength factor.

Regulatory overhaul periods of pavement service and the corresponding standards of reliability levels are taken according to Table. 2.2

road automotive coating overhaul

Table 2.2 Norms of overhaul (calculated) service life (T o) and norms of reliability levels (K H) of non-rigid pavements

Notes

1. Intermediate values taken by interpolation (for K H and T o).

2. When calculating the layers of strengthening of capital and lightweight pavements, it is allowed to reduce the service life norm by 15% from the minimum values ​​while maintaining the reliability level norm.

When solving practical problems related to the assessment of the actual service life of non-rigid pavements and the transport and operational qualities of roads, they are guided by the maximum permissible operating conditions of the pavement in terms of evenness "i", depending on the level of pavement reliability.

The service life of the pavement is the period of time within which the adhesion properties of the pavements (capital and lightweight pavements) decrease or the wear of the pavement surface (transitional and lower pavements) increases to the values ​​​​maximum allowed by traffic conditions.

The norms of the overhaul service life of pavements (T p) on roads with capital and lightweight pavements are taken depending on the intensity of traffic in the first year after construction or work on the device of rough surfaces during road repairs (Table 2.3).

Table 2.3

Chapter 3

3.1 Assessment of the quality and condition of the road

The quality of the road is the degree of compliance of the entire complex of indicators of the technical level, operational status, engineering equipment and facilities, as well as the level of maintenance regulatory requirements, changing during operation as a result of the impact of vehicles, meteorological conditions and content levels. Consumer properties of the road - a set of its transport and operational indicators (TEP AD), directly affecting the efficiency and safety of work road transport reflecting the interests of road users and the impact on environment, must be maintained in such a way that it loses its capacity to a minimum by the end of the estimated operational period. Consumer properties include those provided by the road: speed, continuity, safety and ease of movement, throughput and level of traffic congestion; the ability to pass cars and road trains with axle loads permitted for movement. To preserve consumer properties, it is necessary to carry out diagnostics of highways, for timely intervention and prevention of limit states of road characteristics. Diagnostics includes the examination, collection and analysis of information about the parameters, characteristics and conditions of operation of roads and road structures, the presence of defects and the reasons for their occurrence, the characteristics of traffic flows and other information necessary for assessing and predicting the condition of roads and road structures in the course of further operation. The assessment of the quality and condition of roads is carried out by:

* when putting the road into operation after construction in order to determine the initial actual transport and operational condition and compare it with regulatory requirements;

* Periodically during operation to monitor the dynamics of changes in the state of the road, predict this change and plan repair and maintenance work;

* when developing an action plan or project for reconstruction, overhaul or repair to determine the expected transport and operational state, compare it with regulatory requirements and evaluate the effectiveness of the planned work;

* after performing works on reconstruction, overhaul and repair in the areas of these works in order to determine the actual change in the transport and operational condition of the roads.

To assess the condition of roads and road structures, it is necessary to collect and analyze a significant amount of basic background information on the following indicators, parameters and characteristics:

1. General information about the road:

Number and title of the road, area of ​​its location;

Management body and service organization;

Assessment of the level of road maintenance for the last 12 months.

2. Geometric parameters and characteristics:

The width of the carriageway, the main fortified road surface and fortification strips;

Shoulder width, incl. fortified; type and condition of roadside reinforcement; longitudinal slopes;

Cross slopes of the carriageway and roadsides;

Radii of curves in the plan and the slope of the turn;

The height of the embankment, the depth of the excavation and the slopes of their slopes; state of the subgrade;

The visibility distance of the road surface in plan and profile.

3. Characteristics of pavement and pavement:

Pavement design and type of pavement;

Strength and condition of pavement and pavement (presence, type, location and characteristics of defects);

Longitudinal evenness of the coating;

Transverse evenness of the coating (rutting);

Roughness and coefficient of adhesion of the coated wheel.

4. Artificial structures:

Location, type, length and dimensions of bridges, overpasses, overpasses, tunnels;

Load capacity of bridges, viaducts and flyovers;

The presence and height of curbs;

Type and condition of the bridge deck;

Availability, material, type, size and condition of pipes.

5. Arrangement and equipment of roads:

Kilometer signs and signal posts;

Road signs, their location, condition and compliance with the rules and regulations of placement;

Road marking, its condition and compliance with the norms and rules of application;

Fencing, their design, location, length, condition, compliance with the norms and rules of installation;

Lighting;

Junctions, intersections with automobile and railways, their type, location, compliance with design standards;

Bus stops and pavilions, recreation areas, parking and parking areas, their main parameters and their compliance with regulatory requirements;

Additional lanes of the carriageway and transitional speed lanes, their main parameters.

6. Characteristics of driving on the road:

The intensity of traffic on the characteristic stages and the dynamics of its change over the past 3-5 years;

The composition of the traffic flow and the dynamics of its change, highlighting the share of cars and trucks of various carrying capacities, buses, and other vehicles;

Data on traffic accidents for the last 3-5 years, linked to mileage and highlighting the number of accidents by road conditions.

In addition to the basic initial information for various management tasks and the formation of a common automated road database (ABDD), the diagnostic process can collect Additional Information, in particular: The specific volume of additionally collected information is determined by the agreement (contract) for the performance of work on the diagnosis and assessment of the condition of roads

The final result of the assessment is a generalized indicator of the quality and condition of the road (P d), which includes a comprehensive indicator of the transport and operational condition of the road (KP D), an indicator of engineering equipment and arrangement (K OB) and an indicator of the level of operational maintenance (K O):

P d \u003d KP D K OB K E. (3.1)

Indicators P d, KP D, K OB, K e are criteria for assessing the quality and condition of the road. Their standard values ​​for each category are taken in accordance with the current regulatory and technical documents. A road condition is considered to be normative, in which its parameters and characteristics provide the values ​​of the complex indicator of the transport and operational condition not lower than the standard one (KP D KP N) during the entire autumn-spring period. Acceptable, but requiring improvement and increase in the level of maintenance, is considered such a condition of the road, in which its parameters and characteristics provide the value of the complex indicator of the transport and operational condition in the autumn-spring period below the standard, but not below the maximum allowable (KP N > KP D > KP P).

Table 3.1 Standard values KP N (numerator) and maximum allowable KP P (denominator) values ​​of a complex indicator of the transport and operational condition of roads

Note. The criteria for identifying difficult sections of rough and mountainous terrain are adopted in accordance with note 1 to clause 4.1 of SNiP 2.05.02-85. Inadmissible, requiring immediate repair or reconstruction, is considered such a state of the road, in which the value of the complex indicator of the transport and operational state of the road in the autumn-spring period is below the maximum permissible (KP D< КП П).

3.2 Formation of an information data bank on the state of roads

Based on the results of road diagnostics, an automated road data bank (ARDB) is formed and systematically updated. ABDD is essential element road condition management systems. It is an automated information and analytical system containing periodically updated information about roads, artificial structures, vehicle traffic, road accidents, service facilities, etc. a set of issues related to the management of the state of roads. Depending on the tasks to be solved, the traffic police are divided into industry-wide and local. Industry-wide data banks operate in the system of the state road management body and contain mainly technical data on roads and artificial structures, as well as information on the movement of vehicles, road accidents, service facilities, etc. A set of calculation and analytical programs that are part of the structure of industry-wide banks data, is focused mainly on solving issues related to managing the state of the federal highway network, including the planning of repair work and the distribution Money allocated for road works. Local databanks operate in various bodies road management and include technical data on individual roads (road sections) and artificial structures, as well as information on the movement of vehicles, accidents, service facilities on these roads. In addition, these databanks may contain specific modules responsible for separate directions administrative and economic activities of road organizations.

Table 3.2 Enlarged composition of the sectoral automated road data bank (ABDD) (name of databases)

3.3 Road maintenance planning

Table 3.3 Types of road works depending on partial coefficients K pc i

Repair planning based on "compliance indices"

The "compliance index", assigned by an expert, is understood as the level of compliance of the condition of road sections with traffic safety requirements in combination with compliance with the regulatory requirements for grip and evenness of the pavement, the presence of a turn and reinforced shoulders in these sections.

The use of the "conformity index" does not replace the economic criterion, but serves as a tool for analyzing the results of diagnostics, primarily in areas of concentration of road accidents and planning road repair work in conditions of insufficient funding.

When determining the priority of repair work, they are guided by Table 3.4, using which a weighted average indicator of the priority of repair work can be established.

Table 3.4

Note. Areas that do not require repair are assigned a priority or condition score of 5.

Chapter 4

Table 4.1

Literature

1. VSN 41-88 Norms of overhaul service life of pavements

2. ODN 218.046-01 Design of pavement

3. ODN 218.0.006 Rules for the diagnosis and assessment of the condition of roads

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