JP6598610B2 - Slope frost heave suppression structure and slope frost heave suppression construction method - Google Patents

Description

  The present invention relates to a slope frost heave restraining structure and a slope frost heave restraining method capable of restraining frost heave on a slope.

When the ground freezes, interstitial water is absorbed from unfrozen soil to frozen soil, ice lenses (ice layers parallel to the 0 ° C isothermal surface) grow, and the volume of the soil increases. Is a problem in the field. For example, Takahata loam (volcanic ash cohesive soil) is widely deposited around Hachinohe, and these are well-known as freezing soils.
The freezing of the ground occurs when the four factors of soil quality, temperature, moisture and load are collected. In particular, the former three factors are conventionally said to be three elements of frost heaving. Therefore, in order to suppress the frost heaving phenomenon, it is only necessary to take measures against one or more of these elements.
That is, conventionally, the following methods have been taken to suppress frost heave.

First, as a countermeasure against soil conditions, there is a replacement method that replaces the freezing depth with a material that does not cause freezing during freezing. Next, as a countermeasure against the temperature condition, there is a so-called heat insulation method that prevents the invasion of cold air from the ground surface by a heat insulating material or the like. As a countermeasure against the moisture condition, there is a water shielding method in which a layer for blocking capillary rising water necessary for frost heave occurrence is provided at a position below the maximum freezing depth.
In the field of road pavement, frost heaving countermeasures have been established to some extent, and in Hokkaido's national highway sidewalks, all roads are replaced uniformly and a replacement method with a thickness of 30 cm is adopted. However, there are many unsolved measures for frost heave measures in the slope, including research.

  When the surface layer freezes on slopes such as slopes, the soil rises perpendicular to the slope. And when it melts, the soil moves vertically downward by gravity. In this way, the soil repeats moving every time it freezes. In some cases, frost heaving in cuts causes surface layer deterioration to progress rapidly, causing slope failures due to rainfall, and damaging the cut concrete structure.

  Conventionally, in the field of civil engineering and construction, as a ground reinforcement for civil engineering applications such as road base materials, sidewalk foundation materials, temporary roads, retaining walls, levee slopes or slopes, to support heavy loads and prevent erosion, etc. In addition, a three-dimensional three-dimensional cell structure having a large number of honeycomb cells is used.

Such a honeycomb-like three-dimensional three-dimensional cell structure is characterized by being lightweight and excellent in strength due to the cell structure. Such a honeycomb-shaped three-dimensional three-dimensional cell structure is usually transported to a laying site in a folded state as a block having a certain size, and is used after being expanded on the site. In general, the blocks are laid as a plurality of blocks on the substantially flat or sloped ground surface, and the blocks are connected to each other, and not a single lump, but a large number of lumps, granular materials, and powders in each honeycomb cell. It is assumed that the solid material is filled with sand, crushed stone, or locally generated soil filler up to the top of the three-dimensional cell structure and rolled to exert its function as a ground reinforcement. .
For example, in Patent Document 1, a honeycomb-shaped three-dimensional reinforcing material is stretched and installed on a formed slope, and the cell is filled with volcanic ash, so that the slope can be vegetated without collapse by freezing. A honeycomb reinforcing slope that can be applied is described.

JP 2010-168888 A

  However, the technique described in Patent Document 1 has a problem that it is difficult to obtain volcanic ash near the site where frost heave suppression work is desired. If volcanic ash is transported from a distance, costs such as transportation costs will be incurred. In addition, when volcanic ash is used as a cell filling material, it may flow out of the cell gap due to rain or the like.

  The present invention has been made in view of the above-described conventional circumstances, and an object thereof is to provide a slope frost heave restraint structure and a slope frost heave restraint construction method that are easy to construct and can more reliably restrain frost heave. And

As a result of diligent study, the present inventors have found that the above object can be achieved by optimizing the filling material of the honeycomb-shaped three-dimensional solid cell structure, and have completed the present invention. That is, the present invention is as follows.
[1]
A structure that suppresses frost heaving so as to cover the slope,
A honeycomb-like cell in which a plurality of long pieces of resin or fiber sheets are juxtaposed in the width direction and partially joined in a staggered manner at predetermined intervals to each other, and this is stretched in a direction perpendicular to the width direction A block having a honeycomb-shaped three-dimensional three-dimensional cell structure having a filling material filled in each cell,
The slope frost heave suppression structure, wherein the filling material is an artificial lightweight aggregate obtained by firing and foaming expansive shale.
[2]
The slope frost heave suppression structure according to [1], wherein the artificial lightweight aggregate has a particle size of 0.075 mm to 37 mm.
[3]
The following steps:
(1) A plurality of long-sided resins or fiber sheets arranged in parallel in the width direction are partially joined to each other repeatedly at a predetermined interval, and this is stretched in a direction perpendicular to the width direction to form a honeycomb-like Prepare a block of a honeycomb-shaped three-dimensional cell structure forming a cell,
(2) Prepare artificial lightweight aggregate manufactured by firing and foaming expansive shale,
(3) While extending the block of the honeycomb-shaped three-dimensional cell structure using an auxiliary frame, laying it at a predetermined installation location on the slope,
(4) Filling each cell of the expanded cell structure with the artificial lightweight aggregate, removing the auxiliary frame, and then rolling.
Slope frost heave suppression construction method characterized by containing.

  In the present invention, by using the artificial lightweight aggregate as the filling material of the honeycomb-shaped three-dimensional cell structure, the temperature decrease in the ground is suppressed by the heat insulation effect, and the frost heave is effectively suppressed. Displacement of the ground surface layer due to melting can be prevented. Artificial lightweight aggregate is easy to obtain and easy to install. Therefore, according to the present invention, it is possible to provide a frost heave restraining structure and a frost heaving restraint construction method that are easy to construct and can more reliably restrain frost heave.

It is a figure which shows typically the example of 1 structure of the slope frost heave suppression structure of this invention. It is the schematic of an example of the honeycomb-shaped three-dimensional solid cell structure used for the slope frost heave suppression structure of this invention. It is the schematic of an example of the block formed by filling the filling material in the three-dimensional three-dimensional cell structure of FIG. It is a figure which shows typically the mode of the slope which conducted the frost heaving experiment. It is a figure which shows the amount of solar radiation in the period when the frost heave experiment was conducted. It is a figure which shows the external temperature in the period which performed the frost heaving experiment. It is a figure which shows the underground temperature in Example 1. FIG. It is a figure which shows the underground temperature in the comparative example 1. FIG. It is a figure which shows the underground temperature in the comparative example 2. FIG. It is a figure which shows the displacement of the ground surface layer in Example 2. FIG. It is a figure which shows the displacement of the ground surface layer in the comparative example 1. FIG. It is a figure which shows the displacement of the ground surface layer in the comparative example 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically illustrating a configuration example of a slope frost heave suppression structure according to the present invention.
The slope frost heave restraining structure (slope structure 10) of the present invention is a slope frost heave restraining structure disposed so as to cover the slope 20, and is a plurality of long pieces arranged in parallel in the width direction. Honeycomb or three-dimensional three-dimensional cell structure in which honeycomb-like cells 3 are formed by repeatedly joining the resin or fiber sheets 2 in a staggered manner at predetermined intervals and stretching them in a direction perpendicular to the width direction. The filling material 4 is filled in each cell 3 of the body 1.
The slope structure 10 of the present invention is characterized in that the filling material 4 is an artificial lightweight aggregate produced by firing and foaming expansive shale.

  The honeycomb-shaped three-dimensional three-dimensional cell structure 1 (three-dimensional cell structure 1) constituting the slope frost heave suppression structure 10 according to the present invention is juxtaposed in the width direction as shown in FIGS. A plurality of long pieces of resin or fiber sheets 2 are repeatedly partially joined in a staggered manner at predetermined intervals, and are stretched in a direction perpendicular to the width direction to form a honeycomb-like cell 3. . Such a honeycomb-shaped three-dimensional three-dimensional cell structure 1 is generally used as a ground reinforcing material for civil engineering applications such as road base materials, sidewalk foundation materials, temporary roads and retaining walls in the field of civil engineering and construction. Although it can be a honeycomb-like three-dimensional three-dimensional cell structure 1 as shown in FIG. 2 that is used for supporting a load or preventing erosion, the present invention is not limited to this. The three-dimensional cell structure 1 can be, for example, Geoweb (registered trademark).

  The material of the resin or fiber sheet 2 is not particularly limited, but polyethylene is preferable from the viewpoint of weather resistance. The bonding interval (pitch) of the resin or fiber sheet 2 is preferably 400 to 800 mm. The joining is performed by means such as heat fusion. The width of the joint is usually 10 to 20 mm, and due to the presence of the constant width of the joint, two opposing corners are crushed toward the inner side of the cell in the cell shape that becomes a substantially rhombus during expansion ( (See FIG. 2).

  As shown in FIG. 2, a perforated sheet in which a plurality of large and small holes 2 a are provided in advance may be used as the long piece-like resin or fiber sheet 2 of the three-dimensional cell structure 1. These holes 2a also function as, for example, holes for connecting the blocks and holes for reducing the weight of the three-dimensional cell structure itself.

  The three-dimensional cell structure 1 is folded for each block, carried to the site, spread on the surface of the construction site, and the blocks are connected to each other. The sheet 2 is laid on the slope 20 by filling (inner packing) to the height of the sheet 2 (the top of the three-dimensional cell structure 1), rolling and compacting.

  The height of the resin or fiber sheet 2 of the honeycomb-shaped three-dimensional three-dimensional cell structure 1 used for the slope structure 10 according to the present invention is 75 to 300 mm, and the length (inside dimension) L of one side of the cell 3 Can be 200-500 mm. By setting the size of the cell 3 within the above range, the laying operation is facilitated. If the length of one side of the cell 3 exceeds 500 mm, the filling material tends to flow out, and if the length of one side of the cell 3 is smaller than 200 mm, it is difficult to fill the cell with artificial lightweight aggregate. Thus, the construction speed of the slope structure 10 as a whole is reduced.

  The filling material 4 is an artificial lightweight aggregate manufactured by firing and foaming expansive shale. By using an artificial lightweight aggregate as the filling material 4, the slope structure 10 of the present invention has excellent heat insulation performance. Further, by using the artificial lightweight aggregate, water permeability is good and water does not accumulate in the filling material 4, so that freezing is unlikely to occur.

Examples of such artificial lightweight aggregates include Pacific Calstone manufactured by Taiheiyo Cement Co., Ltd.
Pacific Calstone is a lightweight embankment material that is high in strength and has a light unit weight of 11 kN / m ^{3 of} saturated soil, but does not float on water. It has a high internal friction angle and can reduce loads such as lateral pressure. Furthermore, Pacific Calstone is an inorganic ceramic aggregate with a low slaking rate and high durability. The high hydraulic conductivity is also a civil engineering material that is resistant to liquefaction and is totally stable. In this way, Pacific Calstone is suitable for landfills and fills in places with a lot of water, and has high stability as fills. In addition, because construction is good, the work period can be shortened, plant installation is not necessary, and special equipment is not required for construction only by rolling and rolling, so it is economical even for small-scale properties. ing.

  The particle size of the artificial lightweight aggregate is not particularly limited, but is preferably 0.075 mm or more and 37 mm or less, for example.

In Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-168888) described above, volcanic ash is used as a filling material for the cell. However, this technique replaces soil that is likely to freeze with volcanic ash that is difficult to freeze (soil modification). Quality). On the other hand, in the present invention, the slope is covered with an artificial lightweight aggregate having excellent heat insulation performance, thereby preventing a decrease in the temperature of the ground and suppressing freezing. In this way, both technologies are different in nature.
In addition, volcanic ash has a small particle size and a small internal friction angle. When volcanic ash is used as the filling material, volcanic ash may flow out from the gap between cells due to rain or the like, but by using an artificial lightweight aggregate as in the present application, a stable slope structure 10 can be formed. Can do. Furthermore, since artificial lightweight aggregate is an industrial product, it is easier to obtain than volcanic ash.

Next, a method for laying such a slope structure will be described.
(1) Fix one end of the block to the top of the slope (slope) so that the width direction of the block is substantially perpendicular to the slope direction,
(2) Expand the block from the top to the bottom of the slope.
(3) When laying two or more blocks, after connecting one end of the next block to the other end of the block, the steps (1) to (2) are repeated, and (4) inside each cell, Fill with intermediate filling material (artificial lightweight aggregate) and roll.
For fixing the block in (1), for example, a method of hitting a pile inside the cell in the upper end row in the width direction of the block is preferably used.

Examples performed to confirm the effects of the present invention will be described below. In the following description, specific numerical values are given, but the present invention is not limited to these.
Examples and comparative examples performed for confirming the effect of suppressing frost heave will be described.
This experiment was conducted from the end of December 2014 to the middle of May 2015 on a sloping land (slope gradient 1: 1.5) in Hachinohe City, Aomori Prefecture.
As schematically shown in FIG. 4, the construction plane was divided into sections 30 aligned in the lateral direction, and different construction was performed in each section as shown below. The size of one section 30 was 2.5 m wide × 2.5 m high.
As shown in FIG. 4, a thermometer 31 was placed on the ground surface and in the ground, and the temperatures at the block portions and the depths in various locations of 350 mm, 700 mm, and 1400 mm were measured substantially perpendicularly from the ground surface.
Moreover, the displacement reference | standard pile 32 which shows a position was stood for every division. By measuring the position of the reference pile 32, the displacement of the ground surface layer was evaluated. Position measurement was performed three times on December 25, 2014, February 23, 2015, and May 18, 2015, and the displacement of the slope was evaluated by comparing them.
The change in the amount of solar radiation during this period is shown in FIG. 5, and the change in the outside air temperature is shown in FIG.

<Example 1>
A block was stretched on the slope by the steps (1) to (4) described above, and filled with Taiheiyo Culstone manufactured by Taiheiyo Cement Co., Ltd., which is an artificial lightweight aggregate. The thickness of the cell structure was 100 mm.

<Example 2>
In the same manner as in Example 1, the block was spread on the slope, and Pacific calstone was filled as a filling material. The thickness of the cell structure was 150 mm.

<Comparative Example 1>
In the same manner as in Example 1, the block was spread on the slope, and crushed stone was filled as the filling material. The thickness of the cell structure was 100 mm.

<Comparative example 2>
No measures were taken for the cell structure, and the slope was exposed.

  About Example 1 and Comparative Examples 1 and 2, the underground temperature change is shown in FIGS. Moreover, about Example 2, Comparative example 1 and 2, the displacement of the Y direction (horizontal direction) and Z direction (height direction) of a displacement reference | standard pile is shown in FIGS.

First, regarding the underground temperature, in Comparative Example 2 (FIG. 9) without countermeasures, both the ground surface temperature and the underground temperature are low. Then, the temperature drop is suppressed. Comparing Comparative Example 1 (FIG. 8) filled with crushed stone with Example 1 (FIG. 7) filled with calstone, Example 1 has a higher underground temperature than Comparative Example 1, especially the ground surface. The difference is large in a portion close to (block portion, 350 mm, 700 mm).
As for the temperature of the block part, in the comparative example using crushed stone or generated soil as the filling material, it is often 0 ° C. or less when the outside air temperature is low, but Example 1 using calstone In general, the temperature of 0 ° C. or higher is stably maintained. That is, it can be seen that the heat insulation performance is improved by using calstone (artificial lightweight aggregate) as the filling material.

Regarding the displacement of the ground, in Comparative Example 2 (no countermeasures), the surface of the ground is lifted by freezing by comparing December and February in FIG. 12, and comparing February and May, It can be seen that the ground is sinking by melting. At this time, it can be seen that the sinking ground surface layer does not return to the same position as the beginning, but moves to a lower position.
In Comparative Example 1 (FIG. 11) using crushed stone as the filling material, although the amount of displacement is smaller than that of Comparative Example 6 without countermeasures, frost heave has occurred, and the ground due to frost heaving and thawing has occurred. It can be seen that it is displaced.

  In Example 2 using calstone as the filling material, it can be seen that the ground position is hardly displaced over the evaluation period from December to May as shown in FIG. That is, it is presumed that the ground is not lifted due to freezing and the ground is not lowered due to melting.

  As is clear from the above results, by adopting the slope frost heave suppression structure of the present invention, the temperature decrease in the ground is suppressed by the heat insulation effect, and the frost heave is effectively suppressed. It was found that this displacement can be prevented.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be appropriately changed without departing from the spirit of the invention.

  By using the slope frost heave suppression structure according to the present invention, frost heave can be effectively suppressed and can be widely used as a slope frost heave suppression structure and a frost heave suppression construction method.

1 Honeycomb three-dimensional cell structure (3D cell structure)
2 resin or fiber sheet 3 cell 4 filling material 10 slope frost heave suppression structure 20 slope

Claims (3)

A structure that suppresses frost heaving so as to cover the slope,
A honeycomb-like cell in which a plurality of long pieces of resin or fiber sheets are juxtaposed in the width direction and partially joined in a staggered manner at predetermined intervals to each other, and this is stretched in a direction perpendicular to the width direction A block having a honeycomb-shaped three-dimensional three-dimensional cell structure having a filling material filled in each cell,
The slope frost heave suppression structure, wherein the filling material is an artificial lightweight aggregate obtained by firing and foaming expansive shale.   The slope frost heave suppression structure according to claim 1, wherein the artificial lightweight aggregate has a particle size of 0.075 mm or more and 37 mm or less. The following steps:
(1) A plurality of long-sided resins or fiber sheets arranged in parallel in the width direction are partially joined to each other repeatedly at a predetermined interval, and this is stretched in a direction perpendicular to the width direction to form a honeycomb-like Prepare a block of a honeycomb-shaped three-dimensional cell structure forming a cell,
(2) Prepare artificial lightweight aggregate manufactured by firing and foaming expansive shale,
(3) While extending the block of the honeycomb-shaped three-dimensional cell structure using an auxiliary frame, laying it at a predetermined installation location on the slope,
(4) Filling each cell of the expanded cell structure with the artificial lightweight aggregate, removing the auxiliary frame, and then rolling.
Slope frost heave suppression construction method characterized by containing.

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