JP5897067B2 - Composition for producing soil solidified material and soil pavement method - Google Patents

Description

  The present invention relates to a composition for producing a solidified soil that can be advantageously used for soil pavement on the ground surface, and a soil pavement method using the composition.

  For the purpose of preventing weeding and softening of the ground surface, soil pavement is performed to cover the ground surface with a soil solidified layer. In general, a soil solidified layer is prepared by preparing a composition for producing a soil solidified product containing soil and a soil solidified material, and adding a water-containing composition to this to spread on the ground surface, followed by rolling. It is formed by forming a water-containing composition layer and then drying.

  Compared with concrete and asphalt, the soil solidified layer formed by soil pavement has the advantage that a natural scenery can be obtained. In addition, the soil solidified layer has high water permeability and water retention compared to concrete and asphalt, so it can temporarily hold rainwater. After the rain stops, the retained water gradually evaporates. However, the heat of vaporization also has the effect of reducing the ambient temperature and mitigating the heat island phenomenon. For these reasons, soil pavement is widely used for pavement in parks, gardens, farm roads, and promenades.

  As a reinforcing material for the soil solidified material layer, it has been studied to add a natural fiber reinforcing material such as bamboo chip or wood chip to the composition for producing a soil solidified material in advance.

  Patent Document 1 discloses a composition for forming a soil solidified product including soil, a soil solidified material, and bamboo chips as a composition for producing a soil solidified material for soil pavement. According to the Example of this patent document 1, the block-shaped test body formed in the column shape using the composition containing a pure sand soil, a soil solidification material, and a bamboo chip is each left at -20 degreeC and 20 degreeC for 1 day. Even after the operation is repeated 10 times, the uniaxial compressive strength is maintained at a high level, the shape is stable, and the stability against repeated freezing is excellent (FIGS. 10 and 12 of Patent Document 1). See).

JP 2008-260905 A

  However, the present inventor formed a soil solidified material layer on the ground surface in a cold region using a composition for producing a soil solidified material containing pure sand, solidified material (magnesium oxide) and bamboo chips. Thus, it has been found that when the minimum temperature of the day is below freezing, the strength of the soil solidified layer decreases, and a lot of partial peeling (swelling) occurs on the surface. The reason why the soil solidified layer formed on the ground surface showed a tendency different from that of the block-shaped specimen described in the example of Patent Document 1 in the stability against repeated freezing as follows is as follows. Conceivable. In the block-shaped specimen of Patent Document 1, the moisture content inside the specimen is uniform, and the volume expansion due to freezing of water inside the specimen progresses uniformly throughout the specimen, so that distortion occurs inside the specimen. Hateful. On the other hand, the moisture content of the soil solidified layer formed on the ground surface is different between the surface portion in contact with the outside air and the bottom surface portion in contact with the ground surface. For example, when frost falls, the surface part that is in contact with the outside air has a higher moisture content than the bottom part, and when the water on the ground surface oozes into the soil solidified layer, The water content is higher than the surface portion. For this reason, in the soil solidified layer, the expansion of the volume due to freezing of water inside the soil solidified layer proceeds unevenly between the surface portion and the bottom surface portion, distortion occurs inside the soil solidified layer, and the strength is increased. And partial delamination occurs.

  Accordingly, an object of the present invention is to provide a composition for producing a soil solidified product, which can form a soil solidified material layer having high stability against repeated repeated freezing on the ground surface in an industrially advantageous manner, and the soil thereof. It is providing the soil pavement method using the composition for solidified material manufacture.

  The inventor of the present invention is the soil particle size contained in the composition for producing a soil solidified product, the workability when forming a soil solidified material layer using the composition, and the soil solidified product formed using the composition. The stability of the layer against repeated freezing was examined in detail. As a result, if the amount of gravel and sand contained in the soil solidified composition increases, the stability against repeated repeated freezing decreases, while the soil contained in the soil solidified composition includes If the silt content and clay content of the soil increase, the stability against repeated repeated freezing increases, but cracks tend to occur when the water-containing composition is rolled to form a water-containing composition layer, and the soil solidified product It has been found that the workability when forming the layer is low. Relative to coarse soil (for example, pure sand or mountain sand) with a total content of gravel and sand of 80% by mass or more, and a total content of silt and clay of 25% by mass or more. A large amount of fine soil (for example, black and white soil or field soil) is used at a predetermined ratio, so that the workability when forming the soil solidified layer and the temporary formation of the soil solidified layer formed The present invention has been found by finding that a composition for producing a solidified soil excellent in stability against repeated freezing can be obtained.

  Accordingly, the present invention provides a mass ratio of crude soil having a total content of gravel and sand of 80% by mass or more and fine soil having a total content of silt and clay of 25% by mass or more. It exists in the composition for soil solidification manufacture containing in the range of 80: 20-30: 70, and also containing a soil solidification material.

  The present invention also includes soil containing particles having a particle size of 75 μm or more in an amount in the range of 75 to 88% by mass and soil particles having a particle size of less than 75 μm in an amount in the range of 25 to 12% by mass, And it exists also in the composition for soil solidification manufacture containing a soil solidification material.

  The present invention further includes a step of adding water to the composition for producing a soil solidified product of the present invention to prepare a water-containing composition, and after laying the water-containing composition on the ground surface, the water-containing composition is rolled onto the ground surface by rolling. There is also a soil pavement method including a step of forming a layer and a step of drying the hydrous composition layer to form a soil solidified layer.

By using the composition for producing a soil solidified product of the present invention, a soil solidified layer having high stability against repeated repeated freezing can be easily formed industrially.
Therefore, the soil pavement method of the present invention is particularly useful as a soil pavement method in a cold region.

It is a photograph which shows the peeling part which generate | occur | produced in the soil solidified material layer formed in the ground surface of a cold region using the composition for soil solidified material manufacture manufactured by the comparative example 1. FIG.

  Hereinafter, the composition for soil solidified product production and the soil pavement method of the present invention will be described. In the present invention, gravel is a soil particle having a particle size of 2 mm or more and less than 75 mm, sand is a soil particle having a particle size of 75 μm or more and less than 2 mm, and silt has a particle size of particle size. Soil particles in the range of 5 μm or more and less than 75 μm, and clay content means soil particles having a particle size of less than 5 μm. In addition, the content of gravel, sand, silt and clay in soil is a value measured by a method based on “Soil Grain Size Test Method” defined in JIS standard A1204 (2009). .

  The composition for producing a soil solidified product of the present invention includes coarse soil, fine soil, and a soil solidified material.

  The crude soil used in the present invention has a total content of gravel and sand of 80% by mass or more, preferably 85 to 95% by mass, particularly preferably 88 to 93% by mass. Examples of coarse soils include pure sand, mountain sand (also called mountain soil), and mixtures thereof.

  The fine soil used in the present invention has a total content of silt and clay of 25% by mass or more, preferably in the range of 25-50% by mass, particularly preferably in the range of 25-40% by mass. Examples of fine soils include black and white soil, field soil, and mixtures thereof.

  The mixing ratio of the coarse soil and the fine soil is in the range of 80:20 to 30:70, preferably in the range of 70:30 to 40:60, by mass ratio.

  The soil contained in the composition for producing a soil solidified product of the present invention contains soil particles having a particle size of 75 μm or more in an amount in the range of 75 to 88% by mass, and 25 to 12 soil particles having a particle size of less than 75 μm. It is preferable to contain in the quantity of the range of the mass%. The content of soil particles having a particle diameter of 75 μm or more is more preferably in the range of 80 to 88% by mass, and particularly preferably in the range of 80 to 85% by mass. The content of the soil particles having a particle diameter of less than 75 μm is more preferably in the range of 20 to 12% by mass, and particularly preferably in the range of 20 to 15% by mass.

  The soil solidifying material used in the present invention is preferably a hydraulic soil solidifying material that hardens by reacting with water. As an example of a hydraulic soil solidification material, magnesium oxide, calcium oxide, a dolomite calcination thing, cement, and these mixtures can be mentioned. The soil solidifying material is preferably magnesium oxide, and particularly preferably magnesium oxide derived from seawater. Seawater-derived magnesium oxide means magnesium oxide obtained by baking magnesium hydroxide precipitated by adding slaked lime to seawater.

  The mixing ratio of the soil (total amount of coarse soil and fine soil) and the soil-solidifying material is in the range of 3 to 10 parts by mass, preferably 5 to 10 parts by mass of the soil with respect to 1 part by mass of the soil-solidifying material. This is the ratio.

  The composition for producing a soil solidified product of the present invention may contain a natural fibrous material as a reinforcing material, if desired. Examples of natural fiber reinforcements include bamboo chips, wood chips, cocoons, cocoons, cocoons, hemp and mixtures thereof. The content of the natural fiber reinforcing material is preferably in the range of 0.1 to 1.0 part by mass, and in the range of 0.3 to 0.8 part by mass with respect to 1 part by mass of the soil solidifying material. Is more preferable.

  The composition for producing a soil solidified product of the present invention can be produced by stirring and mixing soil, a soil solidified material, and, if necessary, a natural fiber reinforcing material at the above ratio. When the composition for producing a soil solidified product is stored for a long period of time, it is preferable to dry the soil and the natural fiber reinforcing material before mixing with the soil solidified material.

  Next, the soil pavement method using the composition for soil solidified product manufacture of this invention is demonstrated. In addition, before performing soil pavement, it is preferable to weed the ground surface of the construction target of soil pavement. Moreover, it is preferable to form a roadbed with crushed stones on the ground surface. By forming the roadbed, it becomes difficult for water that has oozed from the ground surface to enter the soil solidified layer, and the stability of the soil solidified layer against repeated freezing is further improved. The thickness of the roadbed is usually in the range of 10 to 100 mm.

  In the formation of soil pavement, that is, the formation of a soil solidified layer, first, water is added to the composition for producing a soil solidified product to prepare a water-containing composition. Water is added in small portions until the shape remains by gently grasping with a hand while stirring the composition for producing the soil solidified product. The amount of water used is usually in the range of 1.5 to 3.0 kg with respect to 10 kg of the soil solidified composition.

Next, after laying the water-containing composition on the ground surface, the water-containing composition layer is formed on the ground surface by rolling. After the formation of the water-containing composition layer, it is preferable to spray water in the water-containing composition layer in a range of 1 to ³ kg per 1 m ^{2 in} order to cause the hardening reaction by the soil solidifying material to proceed uniformly.

  Finally, the water-containing composition layer is dried to form a soil solidified material layer. The water-containing composition layer is usually dried by sun drying. The thickness of the soil solidified material layer is preferably in the range of 20 to 80 mm. The hardness of the soil solidified material layer is preferably in the range of 30 to 40 mm as measured by a Yamanaka hardness meter.

[Examples 1 to 4 and Comparative Examples 1 and 2]
(1) Materials used The following materials were prepared.
Coarse soil:
Pure sand (pebbles: 38.67%, sand: 51.47%, silt: 4.07%, clay: 5.80%)

Fine soil:
Upland soil (pebbles: 2.17 mass%, sand: 67.20 mass%, silt: 20.85 mass%, clay: 9.80 mass%)

Soil solidifying material:
Seawater-derived magnesium oxide (pavement expert, Ube Materials Co., Ltd.)

Natural fiber reinforcement:
Bamboo chips (length: 0.5-5.0cm, diameter: 0.05-0.4cm)
Wood chip (length: 1.0-3.0 cm, diameter: 0.1-0.4 cm)

(2) Manufacture of the composition for soil solidification manufacture The rough soil and the fine soil were stirred and mixed by the mixing ratio (mass ratio) of the soil mixture of Table 1 below to obtain a soil solidified product. Subsequently, the obtained soil solidified material, soil solidified material, and natural fiber reinforcing material are stirred and mixed at the mixing ratio (mass ratio) of the composition for soil solidified material production shown in Table 1 below, and the composition for producing soil solidified material is obtained. I got a thing.

Table 1
────────────────────────────────────────
Mixing ratio of soil mixture Mixing ratio of composition for soil solidified product ──────────────────────────────────── ─
Coarse soil: Fine soil Soil mixture: Soil hardener: Natural fiber reinforcement ─────────────────────────────────── ──────
Example 1 70:30 9.33: 1: 0.45 (bamboo chip)
Example 2 70:30 9.33: 1: 0.45 (wood chip)
Example 3 50:50 9.33: 1: 0.45 (bamboo chip)
Example 4 50:50 9.33: 1: 0.45 (wood chip)
────────────────────────────────────────
Comparative Example 1 100: 0 9.33: 1: 0.45 (bamboo chip)
Comparative Example 2 0: 100 9.33: 1: 0.45 (bamboo chip)
────────────────────────────────────────

(3) Evaluation About the composition for soil solidified material manufacture manufactured in Examples 1-4 and Comparative Examples 1 and 2, using the workability at the time of forming a soil solidified material layer, and the composition for soil solidified material manufacture The stability of the formed soil solidified layer against repeated freezing was evaluated. The following describes the workability in forming the soil solidified layer, the evaluation method of stability against repeated freezing of the soil solidified layer, and the evaluation criteria.

[Evaluation method and evaluation criteria for workability when forming a soil solidified layer]
While stirring the composition for producing a soil solidified product, water is added to the composition for producing a soil solidified solution little by little until the shape remains by gently holding it with hands to obtain a water-containing composition. The water-containing composition is spread on the ground surface and rolled using a plate compactor (weight: 42 kg, size of the rolling platen: 42 cm × 29 cm), and the water-containing composition is 1 m long × 1 m wide × 50 mm thick. Form a layer. It is visually observed whether cracks having a width of 3 mm or more and a length of 10 cm or more are generated on the surface of the hydrous composition layer. Those in which cracks have not occurred are accepted, and those in which cracks have occurred are rejected.

[Evaluation method and criteria for stability against repeated freezing of soil solidified layer]
While stirring the composition for producing a soil solidified product, water is added to the composition for producing a soil solidified solution little by little until the shape remains by gently holding it with hands to obtain a water-containing composition. Spread the water-containing composition on the ground surface in a cold region (typically, the region where the minimum temperature is below freezing in December and February is 60 days or more), and roll it down using a plate compactor. A water-containing composition layer of 1 m × 2 m × thickness 50 mm is formed. When a crack occurs in the water-containing composition layer, the crack portion is repaired with a broom. Next, after the water-containing composition layer is dried in the sun to form a solidified soil layer, it is allowed to stand for 12 to 5 months. During the standing, the hardness is measured using a Yamanaka hardness meter at a total of five locations near the four corners and near the center of the soil solidified layer, and the average is calculated. After standing, the average hardness measured by the Yamanaka hardness tester is 30 mm or more, and the surface of the soil solidified layer was not partially peeled (swelled) and passed, The average hardness measured by the Yamanaka hardness tester is reduced to less than 30 mm, and the surface of the soil solidified layer is partially peeled (swelled) is rejected.

  Table 2 below shows the evaluation results of workability and stability against repeated freezing, and the particle size distribution of soil in the composition for producing soil solidified material.

Table 2
────────────────────────────────────
Grain distribution of soil Soil solidified layer Soil solidified layer Temporary repetition of freezing to form ──────────────── Gravel + sand: silt + clay Stability with respect to workability ─────────────────────────────────────
Example 1 83.91: 16.10 pass Pass Example 2 Same as above Pass Pass Example 3 79.76: 20.27 pass Pass Example 4 Same as above Pass Pass ────────────── ──────────────────────
Comparative Example 1 90.14: 9.87 Pass Fail Comparative Example 2 69.37: 30.65 Fail Pass──────────────────────── ────────────

  As is apparent from the results in Table 2, the composition for producing a soil solidified product according to the present invention having a particle size distribution of soil (Examples 1 to 4) has high workability during the formation of a soil solidified layer, and this is used. The soil solidified layer formed in this way is highly stable against repeated freezing. On the other hand, the composition for producing a soil solidified material (Comparative Example 1) having a high total content of gravel and sand in the soil has high workability during formation of the soil solidified layer. The formed soil solidified layer has low stability against repeated freezing, and in mid-December, the average hardness measured by the Yamanaka hardness tester decreased to 25 mm, and as shown in FIG. Partial exfoliation (swelling) was observed on the surface of the soil solidified layer. On the other hand, the composition for producing a soil solidified product (Comparative Example 2) having a large total content of silt and clay in the soil easily causes cracks during the formation of the soil solidified material layer and has low workability.

[Example 5]
Crude soil [mountain sand (gravel: 24.03 mass%, sand: 62.82 mass%, silt: 9.16 mass%, clay: 4.00 mass%)] and fine soil [black ink Soil (sand content: 69.06% by mass, silt content: 22.94% by mass, clay content: 8.00% by mass)] was mixed with stirring at a ratio of 50:50 to prepare a soil mixture. The obtained soil mixture had a total content of gravel and sand of 79.70% by mass and a total content of silt and clay of 20.3% by mass.

  The above-mentioned soil mixture was air-dried for 1 week, and the soil mixture after drying, and the soil-solidifying material (magnesium oxide derived from seawater) and bamboo chips air-dried for 1 week were in a mass ratio of 6.04: 1: 0.45. The composition for producing a soil solidified product was obtained by stirring and mixing at a ratio. The obtained composition for producing a solidified soil was put in a bag, sealed and stored for 3 months.

  After storage, the seal was removed and the soil solidified composition was removed from the bag. A soil solidified layer was formed using the extracted composition for producing a soil solidified material in the same manner as the stability evaluation method for repeated temporary freezing. When the formed soil solidified layer was allowed to stand for 12 to 5 months, partial peeling (swelling) was not observed on the surface of the soil solidified layer.

Claims (5)

A composition for producing a soil solidified product for soil pavement on a ground surface in a region where the minimum temperature is below freezing point in a period between December and February, including soil and a soil solidifying material, for 60 days or more. And the soil contains soil particles having a particle diameter of 75 μm or more in an amount in the range of 75 to 88 mass% and soil particles having a particle diameter of less than 75 μm in an amount in the range of 25 to 12 mass%, The soil content is in the range of 3 to 10 parts by mass with respect to 1 part by mass of the soil solidifying material, and the composition is 0.1 to 1.0 parts by mass with respect to 1 part by mass of the soil solidifying material. A composition comprising a range of amounts of natural fiber reinforcement .   The composition according to claim 1, wherein the soil content is in the range of 5 to 10 parts by mass with respect to 1 part by mass of the soil solidifying material.   The soil is 80:20 by mass ratio of coarse soil having a total content of gravel and sand of 80% by mass or more and fine soil having a total content of silt and clay of 25% by mass or more. The composition according to claim 1, which is mixed at a ratio in a range of ˜30: 70. The composition according to any one of claims 1 to 3, wherein the soil-solidifying material is magnesium oxide. 5. A soil pavement method for a ground surface in an area where the minimum temperature is below freezing in the period between December and February is 60 days or more, and the method according to claim 1. Adding water to the composition to prepare a water-containing composition, spreading the water-containing composition on the ground surface, and then rolling to form a water-containing composition layer on the ground surface; and drying the water-containing composition layer And forming a soil solidified layer.