JPH07881B2 - Freezing prevention or soft ground improvement method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for improving frost or soft ground such as roads, and more particularly to a method for laying a plastic foam having heat insulation performance and drainage function on a road or the like. .

[Conventional technology]

Conventionally, there are more than 20 construction methods for freezing or soft ground improvement methods for roads, including replacement, embankment embankment, slow construction, vertical drain, sand compaction, quicklime pile, etc.

At present, the improvement of the conventional method and the development of the new method are still active, and the method of improving the frost or soft ground is being attempted (Japanese Patent Laid-Open No. Sho-06-2006).
50-161016, 52-80605, 50-86809, 48-4923
No. 3, Japanese Patent Publication No. 53-37107, No. 58-33328, No. 49-49056
issue). However, at present, none of the methods is a decisive improvement method.

The heat insulation method, which has recently received attention, has a compressive strength of 0.9 to 3.0 kg.
/ cm ² Expanded polystyrene block or plate-shaped material is used as the laying material, after digging the existing road surface part, this foam is placed and new pavement is constructed on it. It has been collected, especially in Northern Europe.

[Problems to be solved by the invention]

However, this method is also not a definitive solution to frost heave prevention.

In other words, this construction method uses expanded polystyrene for shear strength,
Since the compressive strength, tensile strength, frictional strength, restoration performance, etc. are not sufficient, the material is destroyed due to heavy objects such as automobiles, and the road may be depressed or wavy. In addition, since it does not have a drainage function, groundwater etc. tends to accumulate on the ground (roadbed), and it is likely to freeze up in winter.

The present invention aims to solve such conventional problems,
As a heat insulating foam to be laid, a heat insulating plastic foam having high compressive strength and high shearing force is provided with a drainage mechanism without impairing the function of the foam, and a water permeable layer is provided under the drainage heat insulating foam. A method for preventing frost heaving or improving soft ground is submitted.

In the method of the present invention, a plastic foam having a high compressive strength and a high shearing force capable of withstanding heavy objects is used to insulate the soil layer that easily freezes and the roadbed material is reduced, while preventing temperature drop and preventing freezing. The drainage mechanism and the water permeable layer provided in the heat insulating foam positively drain the groundwater, which causes soft ground, to reduce the water content in the roadbed and improve the strength of roads and soft ground.

[Means for solving problems]

That is, the present invention provides a plurality of particles for water permeation on a ground 10 on a heat insulating plastic foam 5 having a compressive strength of 3.5 kg / cm ² or more and a shear strength of 15 kg / cm ² or more and a thickness of 20 mm or more. The heat insulating foam 7 is provided so as to vertically penetrate the drainage hole 6a in which 6 is embedded by 0.1 to 10% per area, and the water permeable layer 8 having a drainage function is provided on the lower surface of the drainage hole 6a. This is a method for preventing frost heaving or improving soft ground, which is characterized by paving 3 on top.

[Action]

Groundwater is drained through the gap between the drain hole 6a of the heat insulating foam 7 and the water permeable layer 8, and the water in the subgrade is drained through the water permeable layer 8. Further, the ground 10 is insulated from the ground by the heat insulating foam 7.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to the drawings.

In FIG. 1, 1 is a roadway and 2 is a sidewalk. 3 is a surface layer of concrete or asphalt, and 4 is a roadbed. A water-permeable heat insulating foam 7 is provided under the roadbed 4. This water-permeable heat-insulating foam 7 has a plurality of water-permeable granules 6 embedded in a heat-insulating plastic foam 5 having a pressure strength of 3.5 kg / cm ² or more and a shear strength of 15 kg / cm ² or more and a thickness of 20 mm or more. The drainage holes 6a, 6a are provided so as to penetrate vertically by 0.1 to 10% per area.

This plastic foam 5 is 3.5 kg / cm ² (measurement method JIS K-6
767) or higher compression strength and 15 kg / cm ² (measurement method JIS K-7214)
It may be any one that has the above shear strength, and is preferably extrusion-crosslinked and foam-molded polyolefin foam 5a (US
P 4552708, Japanese Patent Application No. 57-225295 (Japanese Patent Laid-Open No. 59-115351),
No. 58-119643 (JP-A No. 60-11329) with an apparent density of 40 to 3
20 kg / m ³ (measuring method JIS K-6767) is preferable.

More preferably, crosslinked high density polyethylene foam 5b
[For example, Yuka Foam HD-1000 (trade name) manufactured by Mitsubishi Petrochemical Co., Ltd.] is preferable. The physical properties of this Yuka Foam HD-1000 are as follows.

A foam having a compressive strength of less than 3.5 kg / cm ² such as polystyrene foam has flexibility and is easily fit to the ground 10 so that the surface is easily corrugated, and a shear strength of 15 kg / cm ² or less is obtained. The foamed material has a tendency that the foamed material is easily cut due to the displacement (vertical movement) of the ground, and the cut portion has no heat insulating property and is easily frozen.

The reason for the apparent density of the polyolefin foam 5a in the range of 40~320kg / m ^3, when it is less than 40 kg / m ^3, compression strength, shearing-strength is weak, also exceed 320 kg / m ³ Is because the heat insulation performance is poor. More preferable apparent density is 45 to 195k
It is g / m ³ . The reason why the thickness of the polyolefin-based foam 5a is 20 mm or more is that if it is less than this, the heat insulating property is
This is because the shear resistance is poor and the load applied to the water permeable layer 8 increases. The thickness of the heat insulating foam 7 is about 50 mm in the Tohoku region, although it depends on the freezing index of the region and the required shear strength.

The plastic foam 5 having the above performance is the ground below
It has the effect of preventing a temperature drop of 10 and keeping it at a temperature at which it does not freeze easily.

This heat insulating foam 7 has a drain hole 6a in which a plurality of water permeable particles 6 are embedded (see FIG. 2). This drain hole 6a is the fifth
Shown in an enlarged view of the figure. That is, the granules 6b are adhered or fused to each other so that a water-permeable gap of 5 to 65% is formed on their surfaces, and the structure allows water to easily pass through the gap 6c. Moreover, it is desirable that the granules 6b have a cutting ability, and it is preferable that the granules 6b are made of solidified plastic, wood chips or the like. More preferably, thermoplastic resin such as expanded polystyrene, expanded polypropylene, expanded polyethylene, etc., spherical expanded granules having a particle size of 3 to 8 mmφ are mixed with asphalt and a polymer adhesive so as to be sprinkled, and then solidified and permeable. A foamed heat insulating material having 25 to 60% pores is preferable (the granules are manufactured by Mitsubishi Petrochemical Badishe Co., Ltd. and Kita Nippon Chemical Industry Co., Ltd. under the trade name of styrodren).

The granules 6b have excellent heat-insulating and water-proof properties and exhibit an excellent drainage effect without clogging. The physical properties of this styrodren are as follows.

Instead of the granules 6b, a foam chip 6d such as polystyrene or polypropylene as shown in FIG. 6 (a) or a deformed chip 6e as shown in FIG. 6 (b) may be used. These chips 6d and 6e have their surfaces melted by pressurized steam in a mold and welded to each other.

Since the drain hole 6a is made of the above-mentioned water permeable structure and material, the water permeable layer (water permeable object) 8 having a drainage function below the groundwater that causes frost heave, for example, the aforementioned styrodren, gravel layer, Since it can be drained to the fiber layer of the palm and has a heat insulating function, it prevents the temperature lowering of the lower side of the drain hole 6a and fulfills functions such as frost prevention. This drain hole 6a is 0.1-10% per area, and the vertical penetration is 0.1%.
The following is poor in drainage function and 10% or more adversely affects the mechanical strength of the heat insulating foam 7.

Further, the density of the drain holes 6a is preferably 0.3 to 5.0%. The density of the drainage holes 6a also varies depending on the area, but 4000 mm ×
There are about 3 holes of 50mmφ per 340mm. Below this drainage hole 6a, a water-permeable material 8 having a drainage function [for example, the aforementioned styrodren (trade name)] is provided. The water-permeable object 8 is provided as shown in the plan view of FIG. 3 and the cross-sectional view of FIG. 4, and the surrounding water drained from the drain hole 6a is guided from the water permeable layer 8 to the rainwater basin 9 or the like. Get burned. Further, this water passes through the drain pipe 9a and flows into the sewage 9b, etc.
Drain surface moisture and reduce water content in the subgrade.

The water-permeable object 8 having a drainage function has a heat insulation function, a pressure resistance function, and a drainage function. The planar shape is not particularly limited to a lattice shape, a branch shape, or the like, but the material is preferably the same as that of the granules 6b of the drainage holes 6a, and styrodren having a more preferable heat insulating property is preferable. Styro drain has a pore volume for continuous water passage of about 30%, so that it can be drained smoothly without clogging for a long time.
This is because even if water adheres to the polystyrene foam and freezes, it absorbs the freezing pressure due to the excellent physical properties of the foamed styrene as a buffer material. The size of the object 8 is about 150 mm wide and 300 mm deep, although it varies depending on the region.

〔The invention's effect〕

The ground by the method of the present invention can reduce the water content of the roadbed and the roadbed by lowering the groundwater level, stabilize the roadbed and the roadbed, and reduce the roadbed material by supplementing the shearing force. The weight of the roadbed is reduced, and the subsidence of the roadbed, which is a remarkable phenomenon in soft ground, can be reduced. Furthermore,
Since the foam has a heat insulating property, it can prevent frost heave.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of the ground by the method of the present invention, FIG. 2 is a plan view showing the arrangement of the drainage holes 6a, FIG. 3 is a plan view of the water permeable layer 8, and FIG. FIG. 5 is a sectional view taken along line A, FIG. 5 is an enlarged sectional view taken along line BB of FIG. 2, and FIGS. 6A and 6B are perspective views showing two examples of chips used in the present invention. 10 ... Ground, 5 ... Insulating plastic foam, 6 ...
Granules, 6a ... Drainage holes, 7 ... Thermal insulation foam, 8 ... Water permeable layer (object with drainage function), 3 ... Pavement (surface layer).

Claims (2)

[Claims] 1. A compressive strength of 3.5 kg / cm ² on the ground and 1
Insulating plastic foam with a shear strength of 5 kg / cm ² or more and a thickness of 20 mm or more is installed so that drainage holes filled with multiple water-permeable particles are vertically penetrated by 0.1 to 10% per area. A method for preventing frost heaving or improving soft ground, comprising providing a water-permeable layer having a drainage function on the lower surface of the drainage hole and paving on the heat insulating foam. 2. The method for preventing frost heave or improving soft ground according to claim 1, wherein the heat insulating plastic foam is a high density polyethylene foam.