RU2373317C2 - Prestressed reinforced concrete slab for railway roads - Google Patents

Abstract

FIELD: construction, road engineering.

SUBSTANCE: invention is related to items made of precast reinforced concrete and is intended for application in construction of railway roads. Prestressed reinforced concrete slab for railway roads additionally comprises, in plane located within the limits from 60 to 80 mm off lower slab surface, horizontal through channels with diametre selected within the limits from 20 to 40 mm, which are oriented along rail track parallel to each other at the distance from three to seven minimal thicknesses of slab, starting from slab edge at the distance taken within the limits from one to two minimal thicknesses of slab. Inlet and outlet of through channels in slab ends are arranged with deepening in concrete, which is symmetrical to axis of channels in the form of cylindrical cavity with depth and diametre equal to half of minimal slab thickness, for introduction of shock-absorbing elastic cylindrical elements into slab end. Some plates are arranged with technological fixing rectangular cavities for pulling, stressing and fixation of steel ropes together with anchors with further monolithing with concrete. Width of such fixing cavities corresponds to minimal thickness of slab. Length is selected within the limits from one and a half to three minimal thicknesses of prestressed slab. Neighboring fixing cavities may be displaced relative to each other at the distance, which is not less than such between neighboring through channels.

EFFECT: improved reliability of railway roads, provision of high strength balance in track, increased bending strength of rails, higher weight-lifting capacity of rolling stock up to 30 t per axis and provision of motion safety.

4 cl, 7 dwg

Description

The present invention relates to the construction of railways, mainly to the block structures of the rail base.

Currently, rail transport both in Russia and around the world, in terms of improving the reliability of railway tracks with a sleeper base, is close to the limit of possibilities.

The reliability of the railway track according to the fundamental work of V.S. Lysyuk, V.N. Sazonova and L.V. Bashkatova is the property of the track to keep within the specified limits the value of all parameters characterizing the ability to perform the required functions (uninterrupted passage of trains at a set speed) under specified conditions operation (current maintenance and repairs). Moreover, the reliability of the track is quantified by the numerical values of its reliability, durability and maintainability.

In the context of an increase in traffic volumes and train speeds in recent decades, the desire to improve the reliability of railways in domestic and foreign practice was carried out in the following areas:

- increase the bending stiffness of the rails by increasing the linear mass of the rails;

- increase the rigidity of the rail base by increasing the density of the sleepers;

- increase the stiffness of the ballast by increasing the thickness of the ballast layer of rubble under the sleepers.

However, at present, the general opinion has been strengthened that a further increase in the linear mass of rails over 65 kg / m is impractical. During 1950-2000 rail weight in Russia was increased from 38.4 to 64.4 kg / m. The length of the main track with rails P65 and P75 has already reached 95%.

Nevertheless, the low efficiency of a further increase in the linear mass of R65 and P75 rails is evidenced by the percentage of their failures due to contact fatigue defects, which compared to 1950 for rails with q = 38.4 kg / m increased for all types in 2000 up to 45%, and for R75 rails up to 64%.

The density of the laying of sleepers has now increased to 1840-2000 pcs / km of railway track, which significantly increases the cost of both the construction of new and the repair of old tracks. The thickness of crushed stone ballast on domestic roads already reaches 1 m, and in some places exceeds it. The increase in speeds and axial loads observed all over the world with reinforced concrete sleepers significantly increased the vibration of the track and reduced the vibration resistance of all elements of the track, worsened the working conditions of the ballast prism and subgrade.

The upper structure of the track is the supporting structure of the railway track, which receives loads from the wheels of the rolling stock and directs their movement.

The organization of high-speed train traffic and an increase in axle loads on the rolling stock (in the future up to 30 t / axle) causes a significant increase in the stress-strain state of all elements of the railway track. The increase in cargo intensity leads to an intensive accumulation of residual deformations of the track, which complicates the maintenance of track reliability.

Experts believe that the only effective way to increase the reliability and volume of track development, to ensure the safety of railway transport are intensive methods associated with the increase of these factors due to the constructive improvement of railways without increasing their material consumption.

In addition, when searching for the best engineering solutions for the development of railway transport, it is necessary to consider the following wishes of the operators:

- creating a path of equal strength along its length;

- high bending strength of rails without increasing the mass of linear meter of rail;

- minimization of irregularities on the railway line;

- accelerating the construction of new tracks and simplifying replacement during repairs, reducing the downtime of the track during repairs of the canvas.

For many decades, engineers have attracted considerable attention to the possibility of switching from sleeper rail bases to reinforced concrete from prefabricated slabs, beams, frames or bedding. In some countries there is some experience with the use of solid reinforced concrete foundations.

The cited works cite various data on the numerous advantages of solid reinforced concrete foundations, both precast and monolithic, but decades of hard research have not allowed replacing the sleeper base of railway tracks in the world of railway transport. The practical use of continuous (block) reinforced concrete rail supports is used only when laying separate tracks on bridges and tunnels, and also as the foundation of tram tracks.

It is no coincidence that the modern SNiP 32-01-95 “1520 mm gauge railways” in section 5 “The upper track structure” does not provide for the use of reinforced concrete slabs, frames or similar supports.

In addition, the authors of the work as the future of railways suggest a transition from a solid path to a reliable one, taking into account two directions of strategies:

1 - timely elimination of bumps on wheels and rails, as well as laying vibration-proof reinforced concrete sleepers with rubber gaskets;

2 - increasing the reliability and longevity of the track without increasing its material consumption: changing the shape of the top of the rail head according to the type of American rails 132 RE, using hinged butt pads instead of wedges, anti-strut crutch linings, eliminating the excess of the elevation of the outer rail in curves and laying the rail joints apart, and not by the corner.

Leading railway specialists hardly see today the prospects for the use of prefabricated block or monolithic reinforced concrete bases, which is due to the fact that such bases are usually associated:

- with excessive rigidity of the base, affecting the rapid wear of wheel sets;

- with a slight effect on the bending strength of rails;

- insufficient equal strength of the base of the path along the length, especially when using prefabricated reinforced concrete slabs of factory manufacture, especially the use of monolithic reinforced concrete bases for the climatic conditions of Russia is not realistic;

- with high consumption of reinforced concrete.

This is due to certain disadvantages of continuous reinforced concrete supports (prefabricated or monolithic), the elimination of which the present invention is devoted to.

From the prior art it is known to be laid on a ballast layer block frame-bed under-rail base of prestressed concrete (see, for example, US patent No. 3223328, CL 238-25, 1965). Each block of the known device for docking with each other has a protrusion at one end and a groove at the other. The blocks are prestressed using a beam of high-strength strings, with each string of longitudinal reinforcement being tensioned to 63.8 N (6.5 kg), and the entire bundle is joined by turns of reinforcement with a spiral pitch of 15 cm.

The upper surface of the block has a slope of 1/40 inward of the track. The width of the block on top is 37 cm, on the bottom 61 cm, height 40 cm, length 12 m. To connect the blocks to each other using jumpers made of prestressed reinforced concrete, metal plates welded to the reinforcement are on the inside of the blocks. The plates simultaneously serve as shock absorbers when transmitting side impacts or vibration, and due to their thickness, the distance between the blocks can be adjusted.

The well-known design of the block frame-lying rail track foundation provides smoother and safer train movements, lower maintenance costs and periodic track repairs, distributed transfer of moving loads to the main subgrade without large differences occurring with the rail-sleeper.

However, due to the relative displacements of individual structural elements, the normative characteristics of the rail track, in particular, its width, rail rail, are not preserved for a long time.

Also known is a prestressed multi-hollow reinforced concrete slab with a length of 6.24 m and a constant cross-sectional area along the entire length of the slab 250 × 30 cm for the manufacture of a continuous rail base, including four cylindrical holes with a diameter of 160 mm and three oval holes with a height of 160 mm and a width of 340 mm ( see, for example, the book of V. G. Albrecht and others. "Modern constructions of the upper structure of the track." - M .: Transport, 1975, p.165-1). To drain the water, the stove has a slope in both directions from the axis of the path.

Along the lateral faces of the slabs in the upper part there are protrusions - “shoulders” with a width of 50 mm, which allow underlaying the slopes of the ballast prism close to the lateral faces and, thus, prevent ballast contamination at the edge of the slab and drainage of water along its lateral faces. The plates are reinforced in the longitudinal direction by prestressed reinforcement with a diameter of 5 mm and in the transverse direction by rods of a periodic profile with a diameter of 10 mm. The mass of one plate is 8.5 tons, the length of the plates is 4.16 and 6.25 m.

Such a plate has the largest bearing area of the under-rail base, due to which stresses in the ballast layer and the subgrade and the rate of accumulation of residual deformations in them are significantly reduced. At the same time, the ballast prism is largely protected from clogging.

However, these plates have little crack resistance, in addition, with an increase in the load-carrying capacity of the track, a gauge broadening occurs, which is difficult to correct.

Closest to the proposed technical essence is a prestressed non-hollow reinforced concrete slab, which is an improved version of the previous multi-hollow prestressed reinforced concrete slab and includes tensile steel reinforcement in the form of strands of high-strength prestressed wire with a diameter of 5 mm laid in the longitudinal and transverse directions (see , for example, the book of Yu.D. Voloshko et al. “Rail track with block reinforced concrete supports.” - M.: Transport, 1980, p.21-22). The plate has a slope inside the track to the sides of the ends from the transverse axis. At the ends of the ends, angles are installed that direct water to both sides of the axis of the path, preventing it from falling into the gaps between the plates.

The use of a slab foundation using the well-known hollow-free reinforced concrete slab can significantly increase the crack resistance of the rail base and, consequently, the reliability of the railway track, and by reducing the height of the slab, the consumption of concrete and reinforcement is reduced in comparison with a multi-hollow prestressed slab.

However, the weak point in the rail track mounted from well-known prestressed concrete slabs as well as from the prototype slabs are joints, where the concrete base gets increased deflections, and residual deformations of the path accumulate faster than the rest.

The use of such plates, based on a monolithic concrete base, radically increases the rigidity of the upper track structure, which significantly increases the wear of the wheelsets. Probably, this circumstance explains the practical absence of such rigid foundations in the railway track, which found their application only in the construction of individual tracks on bridges and tunnels. If crushed stone ballast base is used, the lack of continuity between the joined plates causes uneven settlement of the ends of adjacent plates and, most importantly, a certain subsidence of steel rails at the joints of the plates. This, in turn, reduces the equal strength of the path along its length and causes the appearance of uneven paths.

The purpose of the invention is to increase the reliability of the railway track, the creation of elements of a prefabricated device of the upper structure of the track in the form of reinforced concrete slabs, which increase the equal strength of the track, increase the bending strength of steel rails with plates mounted on them.

The solution to the technical problem lies in the fact that the prestressed reinforced concrete slab for the construction of railways, including prestressing steel reinforcement from high-strength prestressed wire, laid in the longitudinal and transverse directions, as well as voids for fasteners and slopes for water drainage, additionally contains in the plane, located in the range from 60 to 80 mm from the bottom surface of the plate, horizontal through channels with a diameter selected in the range from 20 to 40 mm, oriented along the rail paths parallel to each other at a distance of three to seven minimum slab thicknesses, starting from the edge of the slab at a distance taken from one to two minimum slab thicknesses, while the entrance and exit of the through channels in the ends of the slab is made with a symmetrical axis of the channels by a recess in concrete in the form of a cylindrical cavity with a depth and diameter equal to half the minimum plate thickness, for introducing shock absorbing elastic cylindrical elements into the plate end.

In addition, the plate is equipped in its lower part with a fin, oriented perpendicular to the bottom surface of the plate and parallel to the longitudinal tensile reinforcement, with a height and width of the ribs selected in the range from 0.3 to 0.8 of the minimum thickness of the plate; moreover, the upper part of the plate can be made with recesses for supporting the rails and provided with holes for fastening the rails and draining the water. Some of the developed plates are equipped with rectangular mounting voids to accommodate the ends of steel ropes and anchors after their tension, followed by monolithic concrete. Such voids are open upward, oriented along the side length and communicate with through channels, while the width of the rectangular mounting voids corresponds to the minimum thickness, and the length varies from one and a half to three minimum plate thicknesses, and neighboring mounting voids can be displaced relative to each other along the path by a distance of shorter distance between adjacent channels. Through channels in the plates can be made with ribbed lining of metal or plastic. The proposed prestressed reinforced concrete slab to ensure the construction and technical characteristics and ensure the reliability and durability of the railway track should be made of concrete grade not lower than 35.

The proposed prestressed reinforced concrete slab for the construction of railways is shown in figure 1 - view of the slab from the end (a) and top (b) with a section in figure 1, similar to a vertical section of a reinforced concrete sleepers, and in figure 2 - a simple rectangular section, both figures: 1 - the actual stove; 2 - slopes for water flow; 3 - through channels for pulling and fastening steel ropes during the assembly of plates in the link of the railway track; 4 - landing nest - a recess in the ends of the plates for fastening the elastic elements worn on steel ropes when assembling the developed plates in the link; 5 - ribbing of reinforced concrete slabs oriented parallel to the through channels; 6 - landing sites for steel track rails with periodic openings 7 for fastening the rails to the plates and 8 - periodic openings along the length of the plates for draining water.

Figure 2 also shows a section of rectangular prestressed concrete slabs with a flat upper surface: option A - with seven through channels; option B - with five through channels; option B - with three through channels with dimensions indicated in figures 1 and 2 and protected in the present invention.

The prestressed reinforced concrete slab 1 for railways may have a different cross-section and length, but the width should correspond to the width of the railway used in Russia and abroad, i.e. 2700 mm. The length of the plates can be from two to eight meters for the formation of rail links of railway tracks, characterized by a generally accepted length of 12.5 and 25 m, associated with the length capabilities of construction platforms and lifting mechanisms. The minimum thickness of the plates, taking into account the prestressing, can vary from 140 to 200 mm, taking into account the profile of the cross-section of the plates, the features of reinforcement and the purpose of the load carrying capacity of the track.

In this case, through channels, for placement of the tightening plates of steel ropes and the maximum load-bearing capacity of plates with strained steel ropes, it is advisable to place them at a distance of 60-80 mm from the bottom surface of the plates and use channels with a diameter in the range of 20 to 40 mm, taking into account possible sizes steel ropes stretched and strained during assembly of plates with certain tensile forces (ranging from 5 to 30 ton-force per rope).

The entrance to and exit from the slabs is made with cylindrical recesses in concrete (seating nests) for cylindrical elastic elements, which ensures the efficient operation of the designed slabs in the new upper track structure. The present invention provides, in particular, the possibility of manufacturing prestressed plates with recesses 6 for supporting steel rails and holes 7 for fastening rails with a plate, contains slopes 2 and along the length of the plates there are periodic openings 8 for water drainage.

Horizontal through channels 3 with a diameter of 20 to 40 mm are placed (Fig. 2) in a plane located at a distance of 60-80 mm from the bottom surface of the plate, and oriented along the rail parallel to each other at a distance of three to seven minimum plate thicknesses, a distance from the edge of the plate, which is one or two minimum plate thicknesses. To increase the adhesion of the reinforcement to the concrete of the plates after tensioning the reinforcement, the through channels can be made with ribbed lining of metal or plastic, laid in the manufacture of the plates.

The entrance and exit of the channels is made at the ends of the plates with symmetrical axis of the channels of the landing slots for cylindrical elastic elements located between the plates in the form of a cylindrical cavity with a depth and diameter equal to half the minimum thickness of the plate. In the lower part of the plates, to prevent lateral deformation of the path, a fin 5 can be made, oriented perpendicular to the lower surface of the plate and parallel to the longitudinal tensile reinforcement, with a height and width of the ribs of 0.3 to 0.8 of the minimum thickness of the plate.

For installation of the developed prestressed reinforced concrete slabs, part of the slabs should be made with technological cavities for pulling through them and the tension of steel ropes. The proposed technical solution provides for the manufacture of plates of rectangular mounting voids, open up, oriented along the long side along and communicating in the base with through channels for steel ropes (figure 3).

The width of such mounting voids corresponds to the minimum plate thickness, and the length is selected from one and a half to three minimum thicknesses of the prestressed plate, while adjacent mounting voids can be displaced relative to each other along the path by a distance not less than that between adjacent channels. Figure 4 shows the junction of the two links of the rail track with the extreme in the links plates in which the mounting voids are placed. These voids are monolithic with concrete along with anchors placed in the described mounting voids after tensioning the steel ropes and fixing their ends.

Outside of the stated parameters for the manufacture of prestressed concrete slab according to the proposed technical solution, the goal is not achieved.

When assembling rail links or installing new upper structures of the railway track using the inventive prestressed reinforced concrete slab, the latter are laid out so that the through channels 3 in the slabs (Figs. 1-3) connected to the link or long package are aligned (Fig. 4 ) Then, steel ropes 9 are passed through the through channels, onto which cylindrical elastic elements 10 are worn, securing them in the recesses in the form of a cylindrical cavity — the landing seat 4 — at the ends of the plates. The ends of the steel ropes 9 after tension are fixed with anchors in the rectangular mounting cavities 11 of each pair of extreme link plates. Reinforcement tension is carried out using jacks, after which the beginning and end of each rope is anchored.

After tensioning, reinforcing ropes are monolithic with quick-hardening cement-sand mortar and rails are laid and fixed on rails mounted on the pre-stressed concrete slabs offered.

The proposed prestressed reinforced concrete slab for railways allows to increase the bending strength and equal strength of the track without increasing its rigidity due to the tightening of concrete slabs that do not bend on stretched steel ropes, but are capable of vibration to effectively absorb periodic loads. The new technical solution allows you to quickly mount lengthy structures from the developed plates, which ensure the stability of the subgrade, regardless of the expansion or subsidence of the part of the canvas that occurs with a traditional rail-sleeper track.

The production of prestressed reinforced concrete slabs according to the invention is not a problem and can be organized at existing prefabricated reinforced concrete product factories and production lines for the formless molding of prestressed reinforced concrete slabs of the Spankrit type.

The claimed technical solution allows you to build a flexible, well-oriented horizontally, without the possibility of subsidence at the joints of adjacent plates, the upper track structure with increased bending strength of the rails and provided equal path strength. A significant area of abutment of a long-length package of plates on a ballast or subgrade allows significantly more efficient (compared to a sleeper base) to transfer loads from a moving composition to the ground, with minimization of theft, lateral shifts and other negative phenomena.

The new solution, especially when using jointless rail tracks, will increase the speed of trains, reduce the main resistivity of the track to train movement and thereby save fuel and electricity for traction. At the same time, the installation time for railway tracks is significantly reduced due to the quick assembly of plate links on ballast substrates.

Especially effective is the use of such links for soft soils, permafrost conditions. The cost-effectiveness of the proposed prestressed reinforced concrete slabs is associated with the speed of construction and repair of the track, the possibility of manufacturing a ballast of small thickness, virtually no clogging, increasing the reliability and durability of the track.

Claims (4)

1. Pre-stressed reinforced concrete slab for railways, including prestressing steel reinforcement made of high-strength prestressed wire, laid in the longitudinal and transverse directions, as well as voids for fasteners and slopes for water flow, characterized in that it additionally contains in a plane located within from 60 to 80 mm from the bottom surface of the plate, horizontal through channels with a diameter selected in the range from 20 to 40 mm, oriented along the rail parallel to each other at From three to seven minimum slab thicknesses, starting from the edge of the slab at a distance taken from one to two minimum slab thicknesses, the inlet and outlet of the through channels at the ends of the slab are made with a symmetrical axis of the channels, a recess in concrete in the form of a cylindrical cavity with depth and diameter equal to half the minimum plate thickness for introducing shock absorbing elastic cylindrical elements into the plate end, and part of the plates is made with technological fixing rectangular voids for pulling, tensioning and fixing with reinforced ropes together with anchors followed by monolithic concrete, while the width of such fixing voids corresponds to the minimum plate thickness, and the length is selected from one and a half to three minimum thicknesses of the prestressed plate, and adjacent fixing voids can be displaced relative to each other by a distance not less than that between adjacent through channels. 2. Pre-stressed reinforced concrete slab for railways according to claim 1, characterized in that it is equipped in its lower part with a fin, oriented perpendicular to the bottom surface of the slab and parallel to the longitudinal tensile reinforcement, with the height and width of the ribs selected in the range from 0.3 to 0 , 8 minimum plate thickness. 3. A prestressed reinforced concrete slab for railways according to claim 1 or 2, characterized in that the upper part of the slab is made with recesses for supporting the rails and provided with holes for fastening the rails, and the through channels are made with a ribbed lining made of metal or plastic. 4. Pre-stressed reinforced concrete slab for railways according to claim 1, characterized in that it is made of concrete grade not lower than B 35.

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