Pavement structure

Abstract

It suppresses damage to the heating system caused by frost heave. [Solution] The pavement structure (10) comprises a surface layer (40), a base course (20), a heat-generating layer (30) embedded between the surface layer (40) and the base course (20), or embedded in the surface layer (40), and a heat-insulating layer (16) containing synthetic foamed resin laid beneath the base course (20).

Description

Technical Field

[0001] The present invention relates to a pavement structure.

Background Art

[0002] Conventionally, in cold regions and the like, a technique of heating a pavement structure such as a road by road heating or the like is known. In the road heating technique, a heating layer having a heater is buried in the pavement structure for snow removal, freeze prevention, etc. on the surface of the pavement structure.

[0003] For example, Patent Documents 1 and 2 disclose a pavement structure in which a heat insulating material layer is provided directly below a heating layer. Specifically, in the pavement structure of Patent Document 1, a surface layer constituting the ground surface layer and a base layer supporting the same are provided, and the heating layer (heater) is buried in the base layer. And the upper roadbed installed directly below this heating layer is composed of a material with high heat insulation. In the pavement structure of Patent Document 2, a heat insulating material layer is laid directly below the heating layer (heater). And an upper roadbed and a lower roadbed are provided directly below this heat insulating material layer.

[0004] Also, Patent Document 3 discloses a pavement structure in which a surface layer, a base layer, an upper roadbed, and a lower roadbed are provided in this order from top to bottom. And in the pavement structure of Patent Document 3, the heating layer (heater) is buried between the surface layer and the base layer. And the lower roadbed is a foamed glass layer (heat insulating material layer) composed of a foamed body of waste glass.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] However, with the conventional technology described above, if the power to the heater in the heating layer is cut off, frost heave (a phenomenon in which the soil freezes and rises) occurs, which can cause not only deformation of the paved road surface but also the heater to break and damage the heating system itself, indicating room for improvement.

[0007] One aspect of the present invention aims to realize a pavement structure that can suppress damage to the heating system due to frost heave. [Means for solving the problem]

[0008] To solve the above problems, one aspect of the present invention is as follows.

[0009] [1] A pavement structure comprising a surface layer, a subgrade, a heat-generating layer embedded between the surface layer and the subgrade, or embedded in the surface layer, and a heat-insulating layer containing synthetic foamed resin laid beneath the subgrade.

[0010] [2] The thermal insulation layer has a compressive strength of 30 N / cm². 2 The above describes the pavement structure of [1].

[0011] [3] The pavement structure according to [1] or [2], wherein the roadbed comprises a lower roadbed and an upper roadbed, and the thickness of the lower roadbed is 10 cm to 50 cm.

[0012] [4] The heating layer includes a fibrous heating element made of a composite of stainless steel fibers and aramid fibers, and is a pavement structure of any of [1] to [3].

[0013] [5] A pavement structure of any of [1] to [4], wherein the thickness of the insulation layer is 2 cm to 15 cm.

[0014] [6] A pavement structure of any of [1] to [5], wherein the thickness from the upper surface of the surface layer to the lower surface of the insulation layer is 20 cm to 100 cm. [Effects of the Invention]

[0015] According to one aspect of the present invention, damage to the heating system due to freezing can be suppressed.

Brief Description of the Drawings

[0016] [Figure 1] It is a cross-sectional view showing a schematic configuration of an asphalt pavement road having a paving structure according to Embodiment 1 of the present invention. [Figure 2] It is a cross-sectional view showing a schematic configuration of a linear heater provided in a heating layer in the paving structure of FIG. 1. [Figure 3] It is a cross-sectional view showing a schematic configuration of an asphalt pavement road provided with a paving structure according to a modification of Embodiment 1 of the present invention. [Figure 4] It is a cross-sectional view showing a schematic configuration of a concrete pavement road having a paving structure according to Embodiment 2 of the present invention.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The present invention is not limited to each configuration described below, and various modifications are possible within the scope shown in the claims. In addition, embodiments or examples obtained by combining technical means respectively disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, by combining the technical means respectively disclosed in each embodiment, new technical features can be formed. All academic documents and patent documents described in this specification are incorporated herein by reference. Also, unless otherwise specified in this specification, "A~B" representing a numerical range is intended to mean "A or more (including A and greater than A) and B or less (including B and less than B)". Also, in the drawings, "UD" indicates the upward direction and "DD" indicates the downward direction.

[0018] 〔Embodiment 1〕 FIG. 1 is a cross-sectional view showing a schematic configuration of an asphalt pavement road R1 having a pavement structure 10 according to the present embodiment. The asphalt pavement road R1 is a sidewalk or a roadway paved with asphalt. By having the pavement structure 10, the asphalt pavement road R1 includes a road heating system and has an anti-freezing function.

[0019] The pavement structure 10 according to the present embodiment is provided on a roadbed 12 that has compacted the ground. The pavement structure 10 has a structure in which a sand laying layer 14, a heat insulating material layer 16, a roadbed 20, a heating layer 30, and a surface layer 40 are provided in this order from the roadbed 12 side toward the upper side. Hereinafter, each layer will be described in detail.

[0020] (Sand laying layer 14) As shown in FIG. 1, a sand laying layer 14 as an unevenness adjustment layer is laid on the upper side of the roadbed 12 that has compacted the ground. The sand laying layer 14 is composed of river sand or crushed sand. The thickness of the sand laying layer 14 is not particularly limited, but is preferably 1 cm to 10 cm, and more preferably 3 cm to 7 cm. The thickness of the sand laying layer 14 is, for example, 5 cm. Note that a protective sand layer may be laid on the upper side of the sand laying layer 14 with the heat insulating material layer 16 interposed therebetween, and the protective sand layer is composed of river sand or crushed sand. The thickness of the protective sand layer is not particularly limited.

[0021] (Roadbed 20) As shown in Figure 1, a subbase 20 is laid above the insulation layer 16. In other words, the subbase 20 is laid above the compacted subgrade 12 via a sand layer 14 and an insulation layer 16. The subbase 20 is intended to equalize the load from the surface layer 40 and consists of a lower subbase 21 and an upper subbase 22. The lower subbase 21 is composed of crushed stone (ungraded aggregate), steel slag, crushed stone, crushed gravel, mountain gravel, sand, etc. For example, the lower subbase 21 includes crushed stone with a particle size of 40 mm. The upper subbase 22 is composed of graded aggregate, graded aggregate, steel slag, etc. The upper subbase 22 is treated with asphalt stabilization to correct unevenness and uniformly transmit the load from above to the lower subbase 21. Specifically, the upper subbase 22 may contain a hot asphalt mixture consisting of coarse aggregate, fine aggregate, filler, and asphalt. Furthermore, to improve compatibility with the surface layer 40, the upper subbase 22 may contain asphalt emulsion. The thickness of the lower subbase 21 is not particularly limited, but is preferably 10cm to 60cm, and more preferably 15cm to 55cm. For example, the thickness of the lower subbase 21 is 20cm. Similarly, the thickness of the upper subbase 22 is not particularly limited, but is preferably 3cm to 20cm, and more preferably 5cm to 12cm. For example, the thickness of the upper subbase 22 is 5cm.

[0022] (Surface layer 40) As shown in Figure 1, a surface layer 40 is laid on top of the upper subbase 22. In other words, the surface layer 40 is laid on top of the lower subbase 21 via the upper subbase 22. The surface layer 40 transmits the load from above to the lower subbase 21. The surface layer 40 is an asphalt mixture layer composed of a heated asphalt mixture consisting of coarse aggregate, fine aggregate, filler, and asphalt. The thickness of the surface layer 40 is not particularly limited, but is preferably 2 cm to 15 cm, and more preferably 3 cm to 7 cm. For example, the thickness of the surface layer 40 is 3 cm.

[0023] (heating layer 30) The heating layer 30 is equipped with a linear heater 31. The heater 31 is a component of the road heating system of the pavement structure 10. The heater 31 is embedded in the surface layer 40 while laid on the upper surface of the upper subbase 22. That is, the heating layer 30 is embedded in the surface layer 40. At least the lower surface of the heater 31 is in contact with the upper subbase 22. In the pavement structure 10, the road surface of the asphalt pavement R1 is heated by energizing the heater 31. This melts snow on the road surface, allowing it to be removed, or prevents the road surface from freezing.

[0024] The configuration of the heater 31 and its burial position relative to the road surface are not particularly limited, as long as the temperature can be raised to a level sufficient to melt snow or prevent freezing. The configuration of the heater 31 and its burial position relative to the road surface can be appropriately set according to the heating conditions of the asphalt paved road R1. Generally, if the road surface temperature is above 0°C and below 10°C, the road surface can melt snow or prevent freezing. Furthermore, the heater 31 is not limited to an electrically heated heater that heats by applying electricity, but may also be a hot water heater that raises the temperature of the road surface by circulating hot water.

[0025] (10 characteristics of pavement structure) The pavement structure 10 comprises a surface layer 40 (surface layer), a base course 20, a heat-generating layer 30, and an insulating layer 16. The heat-generating layer 30 is provided between the surface layer 40 and the base course 20. The insulating layer 16 is a layer containing synthetic foamed resin and is laid on the underside of the base course 20.

[0026] In conventional pavement structures, frost heave occurs when the power to the heater in the heat-generating layer is turned off. This means that a configuration in which an insulating layer is installed directly beneath the heat-generating layer is insufficient to suppress frost heave. In other words, in conventional pavement structures, the insulating layer is installed directly beneath the heat-generating layer, relatively close to it, and is intended to improve the thermal efficiency of the heat-generating layer (improve the performance of the heater), but is insufficient to suppress frost heave. In conventional pavement structures, the insulating layer functions as (1) an upper subbase (Patent Document 1), (2) a mixture of insulating granular material and cement concrete or asphalt concrete (Patent Document 2), or (3) a lower subbase (Patent Document 3). Therefore, in conventional pavement structures, the insulating layer is not composed solely of insulating material, but also contains heat-conducting materials, and thus does not have sufficient insulating performance to suppress frost heave. For this reason, in conventional pavement structures, since the insulating layer is installed directly beneath the heat-generating layer, when the power to the heater in the heat-generating layer is turned off, an environment is created in which frost heave occurs even beneath the insulating layer. As a result, in conventional pavement structures, the heating system itself may be damaged.

[0027] According to the configuration of the pavement structure 10, as shown in Figure 1, the insulation layer 16 is laid not directly beneath the heating layer 30, but on the underside of the roadbed 20, that is, on the underside of the lower roadbed 21. Furthermore, the insulation layer 16 is a layer containing synthetic foamed resin, that is, a layer consisting only of insulation material containing synthetic foamed resin. Therefore, even if the power to the heater 31 of the heating layer 30 is turned off, the insulation layer 16 can suppress the intrusion of cold air into the roadbed 12, thereby suppressing the occurrence of frost heave. Thus, according to the pavement structure 10, damage to the heating system due to frost heave can be suppressed.

[0028] Furthermore, frost heave is related to the freezing depth. Here, the freezing depth is defined as the depth from the ground surface to the point where the ground temperature reaches 0°C, and it depends on meteorological conditions such as air temperature, as well as soil type and moisture content. In ground that causes frost heave, the moisture-containing ground near the freezing depth can be said to be frost-heavy ground. As a countermeasure against frost heave, a replacement method is generally adopted in which the frost-heavy ground near the freezing depth is replaced with a frost-heavy suppression layer containing non-frost-heavy material (material that does not contain moisture). Even when such a replacement method is adopted, cold air penetrates to the subgrade, and in the subgrade, groundwater from the unfrozen soil moves to the frozen soil, making it easier for ice lenses (layers of ice) to form.

[0029] On the other hand, with the pavement structure 10, the intrusion of cold air into the roadbed 12 is suppressed by the insulation layer 16, so the movement of groundwater from the unfrozen soil portion of the roadbed to the frozen soil portion is suppressed. As a result, the pavement structure 10 improves the performance of preventing frost heave.

[0030] Furthermore, the aforementioned replacement method requires the formation of a frost heave suppression layer, which increases the total thickness of the pavement structure. This leads to increased construction costs for the pavement structure, including increased excavation volume and increased costs for replacement materials.

[0031] On the other hand, with the pavement structure 10, an insulating layer 16 is laid beneath the roadbed 20 to suppress the intrusion of cold air into the subgrade 12, so the total thickness of the pavement structure 10 can be reduced. As a result, the amount of ground excavation can be reduced, and the construction cost of the pavement structure 10 can be reduced.

[0032] Here, the total thickness of the pavement structure 10 is defined as the thickness from the top surface of the surface layer 40 to the bottom surface of the insulation layer 16. From the viewpoint of reducing the construction cost of the pavement structure 10, the total thickness is preferably 20 cm to 100 cm, and more preferably 25 cm to 70 cm. For example, the total thickness of the pavement structure 10 is 33 cm.

[0033] On the other hand, when a pavement structure is formed by replacing the insulation layer 16 with a frost heave suppression layer in Figure 1 using the replacement method, the total thickness of the pavement structure will be, for example, 63 cm. In this case, the total thickness of the pavement structure is defined as the thickness from the top surface of the asphalt mixture layer to the bottom surface of the frost heave suppression layer.

[0034] (Insulation layer 16) As shown in Figure 1, an insulating layer 16 is laid on top of the bedding sand layer 14. In other words, the insulating layer 16 is laid between the subgrade 12 and the base course 20 via the bedding sand layer 14. The insulating layer 16 is approximately parallel to the surface of the surface layer 40. Here, "approximately parallel to the surface of the surface layer 40" means that the angle it makes with the surface of the surface layer 40 is within ±15°.

[0035] (Thickness of insulation layer 16) The thickness of the insulation layer 16 is preferably 2 cm to 15 cm, and more preferably 3 cm to 10 cm. For example, the thickness of the insulation layer 16 is 5 cm. If the thickness of the insulation layer 16 is less than 2 cm, the insulation layer 16 will not be able to provide sufficient insulation performance. If the thickness of the insulation layer 16 exceeds 15 cm, the material cost of the insulation layer 16 increases, and the handling of the insulation layer 16 during installation tends to decrease due to its excessive thickness.

[0036] The insulation layer 16 has a compressive strength of 30 N / cm². 2 Preferably, the above conditions are met. More specifically, the thermal insulation layer 16 has a compressive strength of 30 N / cm². 2 It is preferable that the material is composed of the above-mentioned synthetic foamed resin. The compressive strength of the synthetic foamed resin is 30 N / cm². 2 If the compressive strength is less than 35 N / cm², the load on the insulation layer 16 will cause it to collapse, preventing it from exhibiting the desired insulation performance. Furthermore, the deformation of the insulation layer 16 tends to cause surface distortion of the asphalt pavement R1. The load on the insulation layer 16 is the sum of the pavement load and the wheel load, the sum of the pavement load and the crowd load, or the sum of the pavement load, wheel load, and crowd load. From the above perspective, the compressive strength is 35 N / cm². 2It is more preferable that the above values ​​are met. Furthermore, the upper limit of the compressive strength is not particularly limited, but the compressive strength is 100 N / cm². 2 The following is preferable. Compressive strength refers to the maximum stress up to 10% strain in a compressive strength test in accordance with JIS K7220 or JIS A9511.

[0037] Examples of synthetic foamed resins constituting the thermal insulation layer 16 include polystyrene-based resin foams, polyethylene-based resin foams, polyolefin-based resin foams such as polypropylene-based resin foams, polyurethane-based resin foams, and polyvinyl chloride-based resin foams. In addition to synthetic foamed resins, the thermal insulation layer 16 may also include laminated boards such as metal plates, synthetic resin films, and cement boards.

[0038] In particular, it is preferable that each insulation layer 16 is composed of a polystyrene resin foam with a closed-cell ratio of 90% or more. The reason for specifying a closed-cell ratio of 90% or more for the polystyrene resin foam is that if the closed-cell ratio of the polystyrene resin foam falls below 90%, the thermal conductivity of the insulation layer 16 tends to deteriorate due to the increase in moisture content caused by water absorption by the polystyrene resin foam.

[0039] The polystyrene foam having a closed-cell ratio of 90% or more is preferably an extruded foam. In other words, it is preferable that each insulation layer 16 is made of extruded polystyrene foam. This is because, as mentioned above, it has a high closed-cell ratio and suppresses the increase in moisture content, and furthermore, due to the structure of its cells, extruded polystyrene has high compressive strength in the thickness direction.

[0040] (Burial depth of insulation layer 16) The burial depth of the insulation layer 16 is set within a range where the ground beneath the insulation layer 16 does not freeze. Furthermore, this burial depth is set taking into consideration the load distribution on the insulation layer 16. The burial depth of the insulation layer 16 is set so that the 0°C surface is contained within the insulation layer 16. Here, the 0°C surface refers to a hypothetical surface where the ground temperature is 0°C. In the ground, the location of the 0°C surface is influenced by meteorological conditions such as air temperature, as well as soil type and moisture content.

[0041] (Heater 31) The heater 31 can be a conventionally known heater applied to a road heating system. For example, the heater 31 is the road heater disclosed in Utility Model Registration No. 3207189.

[0042] Figure 2 is a cross-sectional view showing the schematic configuration of a linear heater 31 provided in the heating layer 30. As shown in Figure 2, the heater 31 comprises a linear heating element 32 and a covering portion 36 that covers the linear heating element 32. The covering portion 36 has a multilayer structure, in which an insulating covering layer 33, a protective covering layer 34, and a fiber covering layer 35 are stacked in this order from the linear heating element 32 outward.

[0043] The linear heating element 32 includes a heating element that generates heat when an electric current is passed through it. Examples of the linear heating element 32 include a blended yarn composed of metal fibers and organic fibers, a nichrome wire, a carbon fiber, or a carbon heating element. In particular, the linear heating element 32 is preferably composed of a flexible heat-generating blended yarn. This flexible heat-generating blended yarn is made by blending a finite length stainless steel fiber with a finite length heat-resistant non-conductive yarn, and generates heat when an electric current is passed through it due to the contact resistance between the fine stainless steel fibers.

[0044] The heat-resistant, non-conductive yarn described above is preferably aramid fiber. That is, the heating layer 30 preferably includes a fibrous heating element made of a composite of stainless steel fiber and aramid fiber. A heater 31 including such a fibrous heating element has better resistance to breakage under bending and compression compared to a heater containing nichrome wire as the heating element. Therefore, a fibrous heating element made of a composite of stainless steel fiber and aramid fiber can be suitably used in road heating systems.

[0045] In the above-described fibrous heating element, the composite ratio of stainless steel fibers and aramid fibers should be such that, when energized, heat is generated due to the contact resistance between the fine stainless steel fibers. For example, the composite ratio of stainless steel fibers and aramid fibers is preferably 20% to 80% by weight and 80% to 20% by weight in terms of mass ratio.

[0046] Examples of aramid fibers include poly(p-phenylene terephthalamide) continuous long fibers (Twaron®, manufactured by Teijin Aramid BV, etc.), copoly(p-phenylene-3,4'-oxydiphenylene terephthalamide) continuous long fibers (Technora®, manufactured by Teijin Limited), and poly(metaphenylene isophthalamide) short fibers (Conex®, manufactured by Teijin Limited).

[0047] It is preferable that both stainless steel fibers and aramid fibers are of finite length and in a blended yarn state, as this makes them less susceptible to breakage under the aforementioned bending and compression. However, since stainless steel fibers and aramid fibers are rigid materials, it is difficult to obtain a blended yarn in the form of short fibers from the beginning. Therefore, a spun yarn-like yarn is obtained by blending a continuous long fiber bundle of stainless steel with a long fiber bundle of aramid, pulling them at a ratio sufficient to break the long fibers, and then twisting the yarn. This is also called a spun yarn, and the manufacturing method obtained by slashing long fibers is particularly suitable for this embodiment.

[0048] The insulating coating layer 33 is made of rubber. Examples of rubbers that make up the insulating coating layer 33 include natural rubber, isoprene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, and chloroprene rubber.

[0049] The protective coating layer 34 is made of synthetic resin. Examples of synthetic resins that make up the protective coating layer 34 include polyvinyl chloride, polyester, nylon, polybenzimidazole, polyetheretherketone, melamine, phenol, fluororesin, and polyphenylene sulfide.

[0050] The fiber coating layer 35 is composed of thermoplastic synthetic fibers. The fiber coating layer 35 is constructed in which the thermoplastic synthetic fibers are continuously wound around the outer surface of the protective coating layer 34 in a cylindrical or spiral manner, in the form of a round braid, woven or knitted fabric, or the like.

[0051] The single fiber fineness of the thermoplastic synthetic fiber is preferably 1000 dtex or higher. If the single fiber fineness is less than 1000 dtex, the compressive deformation load resistance of the resulting heater 31 may be reduced. However, if the fineness is too high, the handling properties will decrease, so the single fiber fineness is preferably 5000 dtex or less.

[0052] Examples of the thermoplastic synthetic fibers include polyester fibers, polyamide fibers, and polyethersulfone fibers, with monofilaments made of polyester being particularly preferred.

[0053] (modified version) Figure 3 is a cross-sectional view showing the schematic configuration of an asphalt pavement road R2 equipped with a pavement structure 10A according to a modified example of Embodiment 1.

[0054] (Overview of Pavement Structure 10A) The asphalt paved road R2 is a sidewalk or roadway paved with asphalt and equipped with a pavement structure 10A, and is particularly a highway. The pavement structure 10A is preferably applied to highways. The pavement structure 10A has the same configuration as the pavement structure 10 shown in Figure 1, with some exceptions. Only the differences between the configuration of pavement structure 10A and that of pavement structure 10 will be described. For the sake of explanation, components having the same function as those described in Figure 1 of Embodiment 1 will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0055] (Surface layer 40) In the pavement structure 10A, the surface layer 40 comprises an asphalt mixture layer 41 and an asphalt stabilization layer 42 as a base layer. The asphalt stabilization layer 42 is laid on top of the roadbed 20. The asphalt stabilization layer 42 corrects the unevenness of the roadbed 20 and uniformly transmits the load from above to the roadbed 20. The asphalt stabilization layer 42 is composed of a heated asphalt mixture consisting of coarse aggregate, fine aggregate, filler, and asphalt. The thickness of the asphalt stabilization layer 42 is not particularly limited, but is preferably 2 cm to 10 cm, and more preferably 3 cm to 6 cm. For example, the thickness of the asphalt stabilization layer 42 is 4 cm.

[0056] Furthermore, an asphalt mixture layer 41 is laid above the asphalt stabilization layer 42 as a surface layer. In other words, the asphalt mixture layer 41 is laid above the roadbed 20 via the asphalt stabilization layer 42. The asphalt mixture layer 41 transmits the load from above to the asphalt stabilization layer 42. The asphalt mixture layer 41 is composed of a heated asphalt mixture consisting of coarse aggregate, fine aggregate, filler, and asphalt. The thickness of the asphalt mixture layer 41 is not particularly limited, but is preferably 2 cm to 10 cm, and more preferably 3 cm to 5 cm. For example, the thickness of the asphalt mixture layer 41 is 3 cm.

[0057] Furthermore, the pavement structure 10A according to a modified example of Embodiment 1 provides the same effects and advantages as the pavement structure 10 shown in Figure 1.

[0058] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0059] Figure 4 is a cross-sectional view showing the schematic configuration of a concrete paved road R3 having the pavement structure 10B according to this embodiment. The concrete paved road R3 is a sidewalk or roadway paved with concrete. By having the pavement structure 10B, the concrete paved road R3 is equipped with a road heating system and has a frost heave prevention function. The structure of the surface layer 40B and the base course 20B of the pavement structure 10B according to this embodiment differs from the pavement structure 10 according to Embodiment 1.

[0060] The surface layer 40B is a concrete layer. The concrete material constituting the surface layer 40B can be the same concrete material used for the surface layer of conventional concrete pavements. In the pavement structure 10B according to this embodiment, the heat-generating layer 30 is embedded in the surface layer 40B. More specifically, the heater 31 of the heat-generating layer 30 is embedded in the concrete layer that makes up the surface layer 40B.

[0061] Furthermore, as shown in Figure 4, a subgrade 20B is laid above the insulation layer 16. In other words, a subgrade 20B is laid above the compacted subgrade 12 via a sand layer 14 and an insulation layer 16. The subgrade 20B consists of only one layer, not two layers consisting of a lower subgrade and an upper subgrade. The subgrade 20B is composed of crushed stone (ungraded crushed stone), steel slag, crushed stone, crushed gravel, mountain gravel, sand, etc. For example, the lower subgrade 21 contains crushed stone with a particle size of 40 mm. The thickness of the subgrade 20B is not particularly limited, but is preferably 5 cm to 70 cm, and more preferably 15 cm to 55 cm. The thickness of the subgrade 20B is, for example, 20 cm.

[0062] Even with the configuration of the pavement structure 10B according to this embodiment, the insulation layer 16 is laid on the underside of the roadbed 20B, not directly beneath the heat-generating layer 30. Furthermore, the insulation layer 16 is a layer containing synthetic foamed resin, that is, a layer consisting only of insulation material containing synthetic foamed resin. Therefore, even if the power to the heater 31 of the heat-generating layer 30 is turned off, the insulation layer 16 can suppress the intrusion of cold air into the roadbed 12, thereby suppressing the occurrence of frost heave. Thus, according to the pavement structure 10B, damage to the heating system due to frost heave can be suppressed. [Explanation of Symbols]

[0063] 10, 10A, 10B Pavement Structure 12 Roadbed 14 Sand layer 16. Insulation layer 20, 20B Roadbed 21 Lower subgrade 22 Upper subgrade 30 Heating layer 31 Heater 40, 40B surface layer 41 Asphalt mixture layer 42 Asphalt stabilization layer Routes R1 and R2 are asphalt-paved roads. R3 Concrete paved road

Claims

1. The surface and, Roadbed and Between the surface layer and the roadbed, or a heat-generating layer embedded in the surface layer, A pavement structure comprising a thermal insulation layer containing synthetic foamed resin laid beneath the aforementioned roadbed.

2. The aforementioned insulation layer has a compressive strength of 30 N / cm². ２ The pavement structure according to claim 1 is as described above.

3. The aforementioned roadbed comprises a lower roadbed and an upper roadbed. The pavement structure according to claim 1 or 2, wherein the thickness of the lower subbase is 10 cm to 60 cm.

4. The pavement structure according to claim 1 or 2, wherein the heating layer includes a fibrous heating element made of a composite of stainless steel fibers and aramid fibers.

5. The pavement structure according to claim 1 or 2, wherein the thickness of the insulation layer is 2 cm to 15 cm.

6. The pavement structure according to claim 1 or 2, wherein the thickness from the upper surface of the surface layer to the lower surface of the insulation layer is 20 cm to 100 cm.

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