JPH07279105A - Construction method for preventing roadbed from frozenly rising - Google Patents

Abstract

PURPOSE:To prevent a subgrade from frozenly rising by spreading heat insulating ballast all over a subgrade, forming a subgrade course composed of asphalt over the aforesaid ballast, and thereby isolating low temperature over the ground. CONSTITUTION:Heat insulating ballast 2 where synthetic resin foams 4 are hardened by hydraulic binder 5 so as to be integrated, is spread all over a subgrade 1. The insulating ballast 2 is formed by mixing the synthetic resin forms 4 in a spherical or roughly spherical shape each with the hydraulic binder 5 such as cement and the like, and concurrently by kneading fibers, sands, miscible material and the as required. Next, a subgrade course 3 composed of asphalt, concrete and the like is formed over the heat insulating ballast. In a cold district, low temperature over the ground is isolated, the subgrade is prevented from being frozen, is also prevented from swelling up, and concurrently the thermal expansion coefficient of the heat insulating ballast is made small, so that the ballast itself is thereby prevented from being damaged. By this constitution, the durability of the subgrade course can thereby be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing frost heave of a roadbed for preventing roadbeds such as roads in cold regions from rising due to freezing of the roadbed below the roadbed.

[0002]

2. Description of the Related Art In cold regions, as shown in FIG.
A construction method is employed in which a cut gravel 6 is laid to a predetermined thickness above a roadbed 1 and a roadbed 3 made of asphalt, cement concrete or the like is laid above the gravel 6. According to such a construction method, when the outside air becomes low in temperature, the roadbed 1 containing a large amount of water is transmitted through the roadbed 3 and the cut gravel 6 and is volume-expanded by freezing, and the expanded volume is sufficiently increased in the cut gravel 6. There is a phenomenon that the roadbed 3 is affected without being absorbed and the roadbed 3 rises. This not only hinders the passage of traffic, but also causes pain in the roadbed 3 and requires repair work.

As one of the methods for preventing frost heave of such a roadbed 3, as shown in FIG. 4, a synthetic resin foam plate 8 having a sand layer 7 sandwiched between the roadbed 1 and the cut gravel 6 is interposed. There is a construction method in which the heat insulation of the synthetic resin foam plate 8 blocks the cold heat transmitted through the roadbed 3 to prevent the roadbed 1 from freezing.

[0004]

However, according to the above-mentioned conventional method, the synthetic resin foam plate 8 is cracked into fine pieces due to a load caused by the passage of vehicles on the roadbed 3 and the heat insulation effect cannot be sufficiently exerted. There is a point.
Further, when the water and sewage are buried, or when the road is dug back for repair work, the synthetic resin foam plate 8 becomes fine and hinders the surrounding environment. Furthermore, there is a problem in that the construction work is complicated by the work for laying the synthetic resin foam plate 8 and labor is required.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The means is to provide a plurality of synthetic resin foams on a roadbed with a hydraulic binder. After laying a heat-insulating ballast that has been solidified with, and then laying a roadbed made of asphalt or the like above it.

[0006]

According to the above-mentioned means, since the heat insulating ballast contains a plurality of synthetic resin foams and has heat insulating property, the transmission of the temperature is blocked by this and cannot be transmitted to the roadbed. Therefore, the freezing of the roadbed can be effectively prevented. Further, since the heat insulating ballast is hardened by the hydraulic binder, its shape is not damaged even when the load of the vehicle passing on the roadbed is applied. In addition, since it is lighter than the conventional cut gravel, it is easy to carry and laying work is also easy. Further, even when the road is dug back, only the synthetic resin foam does not separate and scatter, so that the surrounding environment is not damaged. Furthermore, since the heat-insulating ballast is lightweight, when the roadbed is soft ground, the weight is lighter by that much, so that the degree of ground subsidence can be reduced.

[0007]

Embodiments of the present invention will be described below. As shown in FIG. 1, the frost heave prevention method for the roadbed of this embodiment is as follows.
This is a method in which a heat insulating ballast 2 is laid on a roadbed 1 and then a roadbed 3 made of asphalt or the like is laid above it.

As shown in FIG. 2, the heat-insulating ballast 2 is formed by solidifying a plurality of synthetic resin foam bodies 4 with a hydraulic binder 5 to be integrated.

As for the size of the heat insulating ballast 2, various sizes can be manufactured in the manufacturing process, and the size used here is the same as that of the cut gravel.
It is sufficient if it is in the range of from 45 mm to 45 mm, and it is not particularly specified. Further, the outer shape is not limited to a spherical shape, and may be any outer shape such as various polygonal bodies and oval bodies, but if the outer shape is spherical, it is strong against stress and is difficult to crack. In addition, in the case of various polygons, there is an advantage that the gap between adjacent polygons is filled and the heat insulating effect is further improved.

When the synthetic resin foam 4 is spherical or substantially spherical beads, it is dispersed even when pressure or stress is applied to the heat insulating ballast 2, so that it has the advantage of being strong, but in particular, The beads are not limited to the beads, and may be crushed products of various shapes obtained by crushing a synthetic resin foam or other irregular shapes. When polystyrene is used as the raw material and is foamed so that the true specific gravity thereof is in the range of about 0.05 to 0.2, the strength of the material is high, and at the time of kneading with the hydraulic binder 5. It is economical because it does not collapse and does not use many raw materials. However, it is possible to use other kinds of raw materials or materials having different true specific gravities, although the effects are somewhat inferior. Furthermore, when a synthetic resin foam 4 having an average diameter in the range of 0.1 to 1.5 mm is used, when it is kneaded with the hydraulic binder 5 during the manufacturing process, There is an advantage that they are easy to mix and easy to manufacture.

The hydraulic binder 5 is cement, lime,
Among them, gypsum and the like are most preferable because cement is strong in strength, has excellent water resistance, and is relatively inexpensive. As cement, ordinary Portland cement,
In addition to Portland cement such as early-strength Portland cement, blast furnace cement, silica cement, fly ash cement, etc. can be used, and it is preferable to use them depending on the application. It is more preferable that the ratio of the water-bonding material of the hydraulic binder 5 is within 30% because the water absorption rate is small and the expansion and contraction rates due to water absorption are further reduced.

The synthetic resin foam 4, the hydraulic binder 5 and water as described above, or, if necessary, fibers, sand, various admixtures, etc. are kneaded, molded into a predetermined shape, dried and solidified. It is made, but it is more preferable that the total specific gravity is 0.8 or more, and most preferably in the range of 1.0 to 1.5 because the synthetic resin foam maintains the heat insulating property and the strength is high.

Next, the performance test results of the heat insulating ballast will be described based on [Table 1] and [Table 2].

[0014]

[Table 1]

As shown in [Table 1], four samples of Examples 1 to 4 having different water cement ratios (W / C) were blended. These are all ordinary portland cements as hydraulic binders, so that the volume is 1 m ³ .
It is a mixture of water, high-performance AE water reducing agent and synthetic resin foam beads. The synthetic resin foam beads are made by foaming polystyrene and have an average diameter of 0.7 mm and a true specific gravity of 0.
1 was used. The mixture mixed under such conditions was formed into a spherical shape having an average diameter of about 10 mm and solidified. The performance test results of Examples 1 to 4 thus created are shown in [Table 2].

[0016]

[Table 2] [Test Method] (1) Water absorption rate is according to JIS A 1135. (2) Compressive strength is according to JIS R5201. (3) The expansion coefficient due to water absorption is according to JIS A 1129. (4) Freeze-thaw resistance is according to ASTM C 666 A method (in water). Regarding (2), (3), and (4) above, concrete molded products with the same composition as the heat insulating ballast were prepared and tested.

From this [Table 2], the water cement ratio (W /
In Examples 1 and 2 in which C) is 25% and 30%, the water absorption rate is small at about 8 and about 9, the compressive strength is large at 320 and 280, and the expansion rate due to water absorption is 0.01 and 0.02. It was found to be superior to any of Examples 3 and 4 which were small and had a water-cement ratio (W / C) of more than 30%. In the comparative example, a commercially available expanded shale artificial lightweight aggregate (trade name: Asanolite) was used, but it was found that Examples 1 to 4 of this heat insulating ballast were superior in water absorption rate.

Next, an experimental example of a roadbed antifreezing method performed by using the heat insulating ballast of Example 1 will be described based on [Table 3]. The roadbed 3 shown in FIGS. 1 and 4
Uses asphalt concrete, A-1, B-
Observation points indicated by symbols such as 1 correspond to [Table 3] below.

[0019]

[Table 3]

As is clear from [Table 3], it was found that the construction method of the present invention can suppress the temperature decrease of the roadbed to substantially the same level or more as compared with the conventional construction method. Also,
As can be seen from [Table 2], this adiabatic ballast has a small water absorption rate and an excellent freeze-thaw resistance, so that it may occur even when the water content in the inside is frozen at a temperature below the freezing point. However, since the heat insulating ballast itself is not broken by the volume expansion, it is durable.

Although the embodiment shown in FIG. 1 shows an example in which only the heat insulating ballast is laid between the roadbed and the roadbed,
Other materials such as gravel may be used as necessary, and in this case, the technical scope of the present invention is also included.
In addition to asphalt, the roadbed includes concrete and others.

[0022]

As is apparent from the above description, according to the method for preventing frost rise of a roadbed of the present invention, since the heat insulating ballast contains a plurality of synthetic resin foams, it has heat insulating properties, so that the transmission of temperature is prevented. Is blocked by this, and cannot be transmitted to the roadbed. Therefore, the freezing of the roadbed can be effectively prevented. Further, since the heat insulating ballast is hardened by the hydraulic binder, its shape is not damaged even when the load of the vehicle passing on the roadbed is applied. In addition, because it is lighter than the conventional cut gravel, it is easy to transport,
Also, the laying work becomes easy. Further, even when the road is dug back, only the synthetic resin foam does not separate and scatter, so that the surrounding environment is not damaged. Furthermore, since the heat-insulating ballast is lightweight, when the roadbed is soft ground, the weight is lighter by that much, so that the degree of ground subsidence can be reduced. In addition, adiabatic ballasts have a low water absorption rate, a high freeze-thaw resistance, and a low expansion rate due to water absorption and freezing, so even if the water content inside them freezes due to a temperature below freezing. Since the volume expansion does not damage the heat insulating ballast itself, it is durable. Furthermore, since the heat insulating ballast can be manufactured in a large amount in various sizes and shapes in a factory, it is possible to sufficiently meet the demand demand.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of a road made by the method of the present invention.

FIG. 2 is a cross-sectional explanatory view of a heat insulating ballast.

FIG. 3 is an explanatory view of a cross section of a road made by a conventional method.

FIG. 4 is a cross-sectional explanatory view of a road made by a conventional method.

[Explanation of symbols]

 1 Roadbed 2 Insulating ballast 3 Roadbed 4 Synthetic resin foam 5 Hydraulic binder

Claims (1)

[Claims] 1. A roadbed made of asphalt or the like is laid on the roadbed after laying a heat-insulating ballast, which is made by solidifying a plurality of synthetic resin foams with a hydraulic binder, and is integrated therewith. Anti-freezing construction method for roadbed.