JP7509366B2 - Frost heave prevention system and frost heave prevention method - Google Patents

Description

The present invention relates to a frost heave prevention system and a frost heave prevention method that prevent frost heave of the ground surrounding a cylindrical object buried in paved ground.

In cold regions, cold air penetrates the ground, forming frost columns (ice lenses) inside the ground, causing the surface of the paved area to rise, resulting in frost heave, which can cause cracks in the paved area. When frost heaves in ground containing buried cylindrical objects such as manholes, gate valve boxes, and various underground infiltration facilities (side gutters, water collection inlets, storm water inlets, infiltration inlets), the amount of frost heaving in the ground around the cylindrical objects tends to be relatively large, as the cold air penetrates deep into the ground through the inside of the cylindrical objects, and the surface of the paved area around the cylindrical objects may rise several centimeters above the top surface of the cylindrical objects. In such cases, the buried area of the cylindrical objects may collapse, causing problems for pedestrians and vehicles. Therefore, in order to prevent frost heaving of the ground around a cylindrical object buried in a paved area, methods such as adding and mixing chemicals into the ground around the cylindrical object to lower the freezing temperature of the ground around the cylindrical object, a replacement method in which the ground around the cylindrical object is replaced with a material that is less susceptible to frost heaving, and a barrier method in which a water-impermeable layer is provided in the ground around the cylindrical object to prevent precipitation and groundwater from being replenished into the frost-heaving ground around the cylindrical object are sometimes used. In addition, a heat insulation method is sometimes used in which insulating materials such as molded crushed polystyrene foam members are laid around the cylindrical object (see, for example, Patent Document 1).

JP 2003-82698 A

However, the inventors have experimentally confirmed that there are cases where frost heaving of the ground surrounding the cylindrical object cannot be sufficiently prevented even when conventional construction methods are implemented.

In light of the above, the objective of the present invention is to provide a frost heave prevention system and a frost heave prevention method that can prevent frost heave of the ground surrounding a cylindrical object buried in paved ground.

In order to solve the above-mentioned problems, a first aspect of the present invention provides the following frost heave prevention system. That is, the first aspect of the present invention provides a frost heave prevention system for preventing frost heave of the ground surrounding a cylindrical object buried in a paved ground, the frost heave prevention system comprising: a water collection sheet that collects water from the ground surrounding a cylindrical object buried in a paved ground so that the cylindrical object extends in a vertical direction and has an upper end surface flush with the surface of the paved ground; and a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth, the drainage sheet being wrapped around the outer circumferential surface of the cylindrical object from the surface layer of the paved ground to a portion deeper than the predetermined depth, and the water collection sheet being buried along the radial direction of the cylindrical object and inclined downward toward the cylindrical object .
In addition, a second aspect of the present invention provides the following frost heave prevention system to solve the above problem. That is, the second aspect of the present invention provides a frost heave prevention system for preventing frost heave of the ground surrounding a cylindrical object buried in a paved area, the frost heave prevention system comprising a water collection sheet that collects water from the ground surrounding a cylindrical object buried in a paved area so that the cylindrical object extends in a vertical direction and has an upper end surface flush with the surface of the paved area, and a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth, the drainage sheet is wrapped around the outer circumferential surface of the cylindrical object from the surface layer of the paved area to a portion deeper than the predetermined depth, and a plurality of the water collection sheets are buried radially around the cylindrical object.

The water collecting sheet is preferably hydrophilic and water absorbent. The water collecting sheet is preferably layered alternately with the crushed stones in the vertical direction.

In a third aspect of the present invention, there is provided the following frost heave prevention method for solving the above problems. That is, the third aspect of the present invention provides a frost heave prevention method for preventing frost heave of the ground surrounding a cylindrical object buried in a paved area, comprising the steps of: installing a cylindrical object at a location where the cylindrical object is to be buried so that the cylindrical object extends in a vertical direction and has an upper end surface flush with the surface of the paved area; laying a water collection sheet that collects water from the ground surrounding the cylindrical object; and laying a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth, in which the drainage sheet is wrapped in a cylindrical shape around the outer circumferential surface of the cylindrical object from a portion corresponding to the surface layer of the paved area to a portion deeper than the predetermined depth, and the water collection sheet is laid along the radial direction of the cylindrical object and at a downward incline toward the cylindrical object .
In addition, a fourth aspect of the present invention provides the following frost heave prevention method to solve the above problems. That is, the fourth aspect of the present invention provides a frost heave prevention method for preventing frost heave of the ground surrounding a cylindrical object buried in a paved area, comprising the steps of: installing a cylindrical object at a location where the cylindrical object is to be buried so that the cylindrical object extends in a vertical cylindrical shape and has an upper end surface flush with the surface of the paved area; laying a water collection sheet that collects water from the ground surrounding the cylindrical object; and laying a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth, the drainage sheet being wrapped in a cylindrical shape around the outer periphery of the cylindrical object from a portion corresponding to the surface layer of the paved area to a portion deeper than the predetermined depth, and a plurality of the water collection sheets being laid radially around the cylindrical object.

The water collecting sheet is preferably hydrophilic and water absorbent. It is preferable that the water collecting sheet and the crushed stone are stacked alternately in the vertical direction.

According to the present invention, water is collected from the ground surrounding a cylindrical object buried in paved ground by a water collection sheet, and the water collected by the water collection sheet is discharged into the ground deeper than a predetermined depth by a drainage sheet, so that the water within a predetermined depth of the ground surrounding the cylindrical object can be reduced and frost heaving of the ground surrounding the cylindrical object can be prevented.

1 is a cross-sectional view of a pavement to which a frost heave prevention system constructed in accordance with the present invention has been applied. Cross-sectional view of line AA in Figure 1. A cross-sectional view of a paved area showing the cylindrical objects installed at the intended burial locations. FIG. 2 is a cross-section of a pavement showing the tubes and drainage sheet installed and laid. (a) Cross-sectional view of a paved area showing crushed stone laid around a cylindrical object; (b) Cross-sectional view of a paved area showing a water collection sheet laid on top of the crushed stone; (c) Cross-sectional view of a paved area constructed using the frost heave prevention method of the present invention.

Below, we will explain the preferred embodiment of the frost heave prevention system and frost heave prevention method of the present invention with reference to the drawings.

First, an embodiment of the frost heave prevention system of the present invention will be described with reference to Figures 1 and 2. The frost heave prevention system, generally designated by the reference symbol 2 in Figure 1, comprises a water collection sheet 8 that collects water from the ground surrounding a cylindrical object 6 buried in a paved area 4, and a drainage sheet 10 that discharges the water collected by the water collection sheet 8 into the ground deeper than a predetermined depth.

The cylindrical object 6 in the illustrated embodiment includes a cylindrical concrete manhole 12 extending in the vertical direction and a disk-shaped metal lid 14 covering the upper opening of the manhole 12. As shown in FIG. 1, the upper end surface of the cylindrical object 6 (the upper surface of the lid 14) is embedded in the pavement 4 so as to be flush with the surface 4a of the pavement 4. The cylindrical object 6 is not limited to a configuration including the manhole 12 and the lid 14, but may be anything that extends in the vertical direction in a cylindrical shape and is embedded in the pavement 4 so that its upper end surface is flush with the surface 4a of the pavement 4, such as a gate valve box (not shown), various underground infiltration facilities (side drains, water collection basins, rainwater basins, infiltration basins), etc. The cylindrical object 6 may be made of an appropriate metal material such as steel or a synthetic resin material.

Referring to FIG. 2, a plurality of water collection sheets 8 (eight in the illustrated embodiment) are embedded radially around the cylindrical object 6 and at equal intervals in the circumferential direction of the cylindrical object 6. The water collection sheets 8 may be embedded at unequal intervals in the circumferential direction of the cylindrical object 6. For example, the intervals between the water collection sheets 8 may be narrowed in places inside the ground where water tends to accumulate relatively easily, and the intervals between the water collection sheets 8 may be widened in places inside the ground where drainage is relatively good. The number and size of the water collection sheets 8 may be determined arbitrarily depending on the amount and range of frost heaving of the ground in which the cylindrical object 6 is embedded.

As can be understood by referring to Figures 1 and 2, the water collection sheet 8 in the illustrated embodiment is buried along the radial direction of the cylindrical object 6 and at a downward incline toward the cylindrical object 6. The water collection sheet 8 may be buried horizontally, but the angle θ between the horizontal plane and the water collection sheet 8 is preferably an angle (e.g., about 1° to 15°) at which the water collected by the water collection sheet 8 flows more easily along the water collection sheet 8 than when the water collection sheet 8 is buried horizontally (θ = 0°).

The water collection sheet 8 can be formed from a woven or nonwoven fabric of an appropriate synthetic resin material having water conductivity. Examples of the material of the water collection sheet 8 include nylon, polyester, polyolefin, and cellulose ester. The water collection sheet 8 is preferably hydrophilic and water absorbent, so that it can not only collect water flowing from above the water collection sheet 8 due to gravity, but also suck up and collect water from below the water collection sheet 8 against gravity, and can also collect water from the sides of the water collection sheet 8 (circumferential direction of the cylindrical object 6) as shown in FIG. 2.

As shown in Figures 1 and 2, the water collection sheets 8 are layered alternately with crushed stones 16 in the vertical direction. The crushed stones 16 preferably have relatively good water permeability, and may be, for example, crushed rocks, boulders, or concrete waste. The grain size of the crushed stones 16 may or may not be adjusted.

The drainage sheet 10 in the illustrated embodiment is wrapped around the outer periphery of the tubular object 6 in a cylindrical shape from the lower end 18a of the surface layer 18 of the paved land 4 to a portion deeper than a predetermined depth. The surface layer 18 in this specification may be a portion consisting of the surface layer of the paved land 4 and a base layer laid below the surface layer, or may be a portion consisting of only the surface layer of the paved land 4. The upper end of the drainage sheet 10 in the illustrated embodiment is positioned at the lower end 18a of the surface layer 18, but the position of the upper end of the drainage sheet 10 is not limited to the lower end 18a of the surface layer 18, and may be the upper end of the surface layer 18 (surface 4a of the paved land 4) or may be between the upper end of the surface layer 18 (surface 4a of the paved land 4) and the lower end 18a of the surface layer 18.

The above-mentioned predetermined depth can be set, for example, to the freezing depth, which is the depth at which the ground freezes due to cold air. The freezing depth differs depending on the region and fluctuates in relation to the minimum temperature, but the above-mentioned predetermined freezing depth can be set, for example, based on the average minimum winter temperature in the region to which the frost heave prevention system 2 is applied.

When determining the lower end position of the drainage sheet 10, for example, first, the freezing depth when the cylindrical object 6 is not buried is calculated based on the average minimum temperature in winter at the planned burial location of the cylindrical object 6. Next, the freezing depth of the ground surrounding the cylindrical object 6 when the cylindrical object 6 is buried at the planned burial location of the cylindrical object 6 is calculated. Normally, when the cylindrical object 6 is buried, cold air penetrates deep into the ground through the inside of the cylindrical object 6, so the freezing depth of the ground surrounding the cylindrical object 6 when the cylindrical object 6 is buried is deeper than the freezing depth when the cylindrical object 6 is not buried. For this reason, the freezing depth of the ground surrounding the cylindrical object 6 when the cylindrical object 6 is buried can be calculated by multiplying the freezing depth when the cylindrical object 6 is not buried by an appropriate coefficient. Next, the freezing depth of the ground surrounding the cylindrical object 6 at the planned burial location of the cylindrical object 6 is set as a predetermined depth. Then, the depth obtained by multiplying the set predetermined depth by an appropriate coefficient is determined as the bottom end position of the drainage sheet 10.

Like the water collection sheet 8, the drainage sheet 10 can be formed from a woven or nonwoven fabric of an appropriate synthetic resin material that has water conductivity. The material of the drainage sheet 10 may be nylon, polyester, polyolefin, cellulose ester, or the like. It is also advantageous for the drainage sheet 10 to be hydrophilic and water-absorbent. As shown by the arrows in Figures 1 and 2 indicating the flow of groundwater, the drainage sheet 10 discharges the water collected by the water collection sheet 8 into the ground deeper than a specified depth.

In the frost heave prevention system 2 described above, water is collected by the water collection sheet 8 from the ground surrounding the cylindrical object 6 buried in the paved land 4, and the water collected by the water collection sheet 8 is discharged by the drainage sheet 10 into the ground deeper than a predetermined depth, so that the water within a predetermined depth of the ground surrounding the cylindrical object 6 buried in the paved land 4 can be reduced, and frost heave of the ground surrounding the cylindrical object 6 can be prevented.

Next, an embodiment of the frost heave prevention method of the present invention will be described. Note that in the embodiment of the frost heave prevention method, components that may be the same as those in the embodiment of the frost heave prevention system 2 described above will be assigned the same reference numerals as those in the embodiment of the frost heave prevention system 2, and descriptions thereof will be omitted.

In the illustrated embodiment, a process is first carried out to install the cylindrical object 6 at the intended burial location so that it extends vertically in a cylindrical shape and its upper end surface is flush with the surface of the paved area. As shown in FIG. 3, when installing the cylindrical object 6, first, the ground 20 at the intended burial location of the cylindrical object 6 is excavated to form a hole 22 in the ground 20. Then, the cylindrical object 6 is installed in the formed hole 22 so that the upper end surface of the cylindrical object 6 (the upper surface of the lid 14) is flush with the ground 20 (the surface of the paved area).

After the cylindrical object 6 is installed at the intended burial location, a process is carried out to lay down a drainage sheet 10 that drains the water collected by the water collection sheet 8 into the ground deeper than a predetermined depth. In the illustrated embodiment, as shown in FIG. 4, the drainage sheet 10 is wrapped around the outer periphery of the cylindrical object 6 in a cylindrical shape from the part corresponding to the lower end 18a of the surface layer 18 of the paved land to the part deeper than the predetermined depth.

In the illustrated embodiment, the drainage sheet 10 is laid after the cylindrical object 6 is installed, but the process of installing the cylindrical object 6 and the process of laying the drainage sheet 10 may be performed simultaneously. In other words, before installing the cylindrical object 6 at the intended burial location, the drainage sheet 10 may be wrapped around the outer periphery of the cylindrical object 6, and the cylindrical object 6 with the drainage sheet 10 wrapped around it may be installed at the intended burial location.

After the cylindrical object 6 and drainage sheet 10 are installed and laid, a process of laying a water collection sheet 8 that collects water from the ground surrounding the cylindrical object 6 is carried out. Referring to FIG. 5, when laying the water collection sheet 8, first, crushed stone 16 is laid around the cylindrical object 6 so that the upper surface is inclined downward toward the cylindrical object 6, as shown in FIG. 5(a). The angle θ between the inclined upper surface 16a of the crushed stone 16 and the horizontal plane may be 0°, but from the viewpoint of making it easier for water to flow along the water collection sheet 8, it is preferably about 1° to 15°.

Next, as shown in FIG. 5(b), the water collection sheets 8 are laid on the inclined upper surface 16a of the crushed stone 16 along the radial direction of the cylindrical object 6. The water collection sheets 8 may be laid at unequal intervals around the circumference of the cylindrical object 6, but it is preferable to lay the water collection sheets 8 radially from the cylindrical object 6 as the center and at equal intervals around the circumference of the cylindrical object 6. Next, the water collection sheets 8 and the crushed stone 16 are alternately stacked in the vertical direction. Then, as shown in FIG. 5(c), the surface layer 18 of the pavement is constructed so as to be flush with the ground 20.

As described above, according to the frost heave prevention method of the illustrated embodiment, water is collected by the water collection sheet 8 from the ground surrounding the cylindrical object 6 buried in the paved ground, and the water collected by the water collection sheet 8 is discharged by the drainage sheet 10 into the ground deeper than a predetermined depth, so that the water within a predetermined depth of the ground surrounding the cylindrical object 6 buried in the paved ground can be reduced, and frost heave of the ground surrounding the cylindrical object 6 can be prevented.

2: Frost heave prevention system 4: Paved land 4a: Surface of paved land 6: Cylindrical object 8: Water collection sheet 10: Drainage sheet 12: Manhole 14: Lid 16: Crushed stone 16a: Sloping upper surface of crushed stone 18: Surface layer of paved land 18a: Lower end of surface layer of paved land

Claims (8)

A frost heave prevention system for preventing frost heave of the surrounding ground of a cylindrical object buried in a paved area, comprising:
The pavement is provided with a water collection sheet that collects water from the surrounding ground of a cylindrical object that extends vertically and is buried so that its upper end surface is flush with the surface of the pavement, and a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth ,
The drainage sheet is wrapped around the outer circumferential surface of the cylindrical object in a cylindrical shape from the surface of the paved land to a portion deeper than the predetermined depth,
A frost heave prevention system in which the water collection sheet is embedded along the radial direction of the cylindrical body and inclined downward toward the cylindrical body . A frost heave prevention system for preventing frost heave of the surrounding ground of a cylindrical object buried in a paved area, comprising:
The pavement is provided with a water collection sheet that collects water from the surrounding ground of a cylindrical object that extends vertically and is buried so that its upper end surface is flush with the surface of the pavement, and a drainage sheet that discharges the water collected by the water collection sheet into the ground deeper than a predetermined depth ,
The drainage sheet is wrapped around the outer circumferential surface of the cylindrical object in a cylindrical shape from the surface of the paved land to a portion deeper than the predetermined depth,
A frost heave prevention system in which the water collection sheets are buried in multiple locations radially around the cylindrical object . The frost heave prevention system according to claim 1 or 2 , wherein the water collecting sheet is hydrophilic and water absorbent. The frost heave prevention system according to claim 1 , wherein the water collecting sheets are layered alternately with crushed stones in the vertical direction. A frost heave prevention method for preventing frost heave of the surrounding ground of a cylindrical object buried in a paved area, comprising:
A step of installing the cylindrical object at a location to be buried so that the cylindrical object extends in a vertical direction and the upper end surface is flush with the surface of the pavement;
A step of laying a water collection sheet that collects water from the ground surrounding the cylindrical object;
and laying a drainage sheet that drains the water collected by the water collection sheet into the ground deeper than a predetermined depth.
The drainage sheet is wrapped around the outer circumferential surface of the cylindrical object in a cylindrical shape from a portion corresponding to the surface layer of the paved land to a portion deeper than the predetermined depth,
A frost heave prevention method in which the water collection sheet is laid along the radial direction of the cylindrical body and inclined downward toward the cylindrical body . A frost heave prevention method for preventing frost heave of the surrounding ground of a cylindrical object buried in a paved area, comprising:
A step of installing the cylindrical object at a location to be buried so that the cylindrical object extends in a vertical direction and the upper end surface is flush with the surface of the paved area;
A step of laying a water collection sheet that collects water from the ground surrounding the cylindrical object;
and laying a drainage sheet that drains the water collected by the water collection sheet into the ground deeper than a predetermined depth.
The drainage sheet is wrapped around the outer circumferential surface of the cylindrical object in a cylindrical shape from a portion corresponding to the surface layer of the paved land to a portion deeper than the predetermined depth,
A frost heave prevention method in which a plurality of the water collection sheets are laid radially around the cylindrical object . The frost heave prevention method according to claim 5 or 6 , wherein the water collecting sheet has hydrophilicity and water absorbency. The frost heave prevention method according to any one of claims 5 to 7 , wherein the water collecting sheets and crushed stones are stacked alternately in the vertical direction.