JP4633825B2 - Soil cement column and method for manufacturing soil cement column - Google Patents

Description

In particular, the present invention relates to a soil cement column used as a foundation of a structure and a manufacturing method thereof.

Conventionally, as a ground improvement method, a method called a soil cement column method is known. In this soil cement column method, a soil cement column is formed in the ground by agitating the soil cement solidified material and the original ground soil to form the foundation structure of the ground. Furthermore, as a technology in this field, a solidified soil described in Non-Patent Document 1 below is known. This Non-Patent Document 1 shows that tire chips produced by pulverizing old tires are mixed into the soil cement column in order to improve the toughness of the soil cement column (solidified soil).
Yoshio Mitarai et al., “Mechanical characteristics of rubber chip mixed solidified soil”, 42nd Geotechnical Research Conference Lecture Meeting, Geotechnical Society, July 2007, p. 487-488.

  However, in order to sufficiently improve the bending toughness of the soil cement column by mixing the tire chips, it is necessary to mix the tire chips by about 20 to 30% by volume with respect to the cement milk. As described above, when tire chips are mixed at a high mixing ratio, tire chips are hardly mixed with cement, and it is difficult to manufacture a uniform column. If the homogeneity of the column cannot be obtained, uniform strength and toughness cannot be obtained throughout the column, and the performance may be deteriorated. In addition, as the tire chip content increases, the strength of the column tends to decrease due to the relatively low cement content. Therefore, if the tire chip content is too high, it is difficult to obtain sufficient strength of the column, that is, sufficient seismic performance of the soil cement column as the foundation structure.

Accordingly, an object of the present invention to provide a method for producing a soil cement column and Soil cement column with improved toughness while suppressing strength reduction of soil cement column.

Soil cement column of the present invention, a hydraulic material, and soil, a soil cement column formed by curing a mixture comprising a rubber chip and the rubber tip is the hydraulic material Ri flaky tire chips der In contrast, it is mixed at a volume ratio of 10 to 15% .

This soil cement column is formed by mixing and hardening a hydraulic material, soil, and rubber chips. Rubber chips which are mixed here, Poisson's ratio is isotropic material close to 0.5, to improve the deformation follow-up performance of the soil cement column by being contained in the soil cement column. Therefore, the toughness of the finished soil cement column can be improved as compared with the case where the rubber chips are not mixed. In this case, since a flaky tire chip is employed as the rubber chip, the effect of improving the toughness of the soil cement column is higher than that of a normal tire chip obtained by pulverizing an old tire. Therefore, according to this soil cement column , the toughness of the soil cement column can be improved without excessively increasing the content of the rubber chips. As a result, it is possible to improve toughness while suppressing a decrease in strength of the soil cement column due to rubber chip inclusion.

  In this case, the flake-shaped tire chip is a flat-shaped piece having a longest side in a rectangular parallelepiped having the smallest volume among the cuboids circumscribing the small piece, which is not less than three times the length of the shortest side. It is good also as a granular material containing 80% or more.

A method of manufacturing a soil cement column of the present invention, a hydraulic material, and soil, a method for producing a soil cement column with a mixture curing step of curing a mixture containing a rubber chip and the rubber tip is flakes to Jo tire chips der Ri said hydraulic material characterized in that it is incorporated in the mixing ratio of the volume 10-15%.

  In this foundation structure manufacturing method, the foundation structure is formed by mixing and curing a hydraulic material, soil, and rubber chips. The rubber chip mixed here is an isotropic material having a Poisson's ratio close to 0.5, and improves deformation follow-up performance of the foundation structure by being contained in the foundation structure. Therefore, the toughness of the completed foundation structure can be improved as compared with the case where the rubber chips are not mixed. In this case, since a flaky tire chip is employed as the rubber chip, the effect of improving the toughness of the foundation structure is higher than that of a normal tire chip obtained by pulverizing an old tire. Therefore, according to this foundation structure, the toughness of the foundation structure can be improved without excessively increasing the content of the rubber chip. As a result, the toughness can be improved while suppressing the strength reduction of the foundation structure due to the rubber chip inclusion.

Further, in the method for producing a soil cement column of the present invention, the mixture curing step is performed by excavating the raw ground vertically downward by the soil cement column construction method, while removing the mixture of the hydraulic material, water, and rubber chips. It is good also as having the step of injecting into.

Further, in the method for manufacturing a soil cement column of the present invention, the flaky tire tip has a length of the longest side in the rectangular parallelepiped having the smallest volume among the rectangular solids circumscribing the small piece is more than three times the length of the shortest side. It is good also as a granule which contains 80% or more of the flat-shaped small pieces by weight ratio.

According to soil cement column and the manufacturing method of soil cement column of the present invention, it is possible to improve the toughness while suppressing strength reduction of soil cement column.

(First embodiment)
Hereinafter, a first embodiment of a soil cement column and a construction method thereof according to the present invention will be described in detail.

  The construction of the soil cement column is performed by a method called a “soil cement column method” as a method for improving the ground on which the structure is built. Specifically, as shown in FIG. 1, first, the construction machine main body is installed at a position where a soil cement column is to be formed on the ground to be improved, and the excavator agitator 11 is set (FIG. 1 (a)). ). Then, the excavator and agitating blade 13 at the tip of the excavator and agitator 11 are excavated into a columnar shape while being rotated vertically downward (FIG. 1B). After excavating to the depth of the column head, cement milk is injected into the excavator agitator 11 at a predetermined injection speed, and the excavation is performed while discharging the cement milk from the excavator agitating blade 13 (FIG. 1 (c)). The cement milk is premixed by the mixer 15 and continuously supplied to the excavator stirrer 11. In this discharge excavation, cement milk and raw ground soil 9 of the excavation part are mixed. Then, when the planned depth is reached, the discharge excavation is stopped.

  Thereafter, the injection of cement milk is stopped, and the excavation stirring blade 13 is reversely rotated to perform stirring and mixing for a predetermined time (FIG. 1 (d)). After that, stirring and mixing at the column tip position are performed while the excavation stirring blade 13 is rotated in the reverse direction (FIG. 2A). Thereafter, stirring and mixing are performed again up to the column tip position while the excavating stirring blade 13 is rotated in the reverse direction (FIG. 2B). Then, stirring is performed while pulling up at a predetermined speed while the excavation stirring blade 13 is rotated in the reverse direction (FIG. 2 (c)). After the excavation stirring blade 13 is completely lifted, the uncured slurry 2 is accumulated in a cylindrical shape (FIG. 2D). This slurry 2 is allowed to stand and harden, and after a predetermined curing period, a cylindrical soil cement column (foundation structure) 1 buried under the ground is completed (FIG. 2 (e)). A plurality of such soil cement columns 1 are normally constructed in parallel and function as a basic structure of a structure.

  Here, as shown in FIG. 1 (a), in order to improve the toughness of the soil cement column 1 in the cement milk injected into the excavator stirrer 11, rubber chips are mixed at a predetermined mixing ratio (for example, about a volume ratio). 10%). As the rubber chip to be mixed here, a flaky tire chip 7 is employed instead of a normal tire chip obtained by pulverizing a used tire (hereinafter referred to as “normal tire chip”). That is, the cement milk to be injected here is a mixture in which, in addition to the cement 3 and the water 5, a flaky tire chip 7 is further mixed. The finished soil cement column 1 has the cement 3, the base soil 9 , And flaked tire chips 7 are included.

  Here, the flaky tire chip 7 is a thin plate-like body that is generated as chips in the process of scraping the surface of a used tire in the manufacturing process of a retread tire. Ordinary tire chips produced by pulverizing used tires are in the shape of particles that are relatively spherical, whereas the flake-shaped tire chips 7 are mostly flat in shape. In particular, the flaky tire chip 7 includes many flat and long thin pieces.

Here, as an index for quantitatively representing the flatness of the shape of the small piece, an amount of “longitudinal / short-to-short dimension ratio” is defined. That is, the “longitudinal short dimension ratio” of the small piece is a rectangular parallelepiped 201 having the smallest volume among the rectangular solids circumscribing the small piece 200 as illustrated in FIG.
Longitudinal-short dimension ratio = length of the longest side of the rectangular parallelepiped (a) / length of the shortest side of the rectangular parallelepiped (c)
It is defined as The length-to-short dimension ratio is the ratio of the length of the longest side of the cuboid (a) to the length of the shortest side of the cuboid (c), in other words, in the longitudinal direction with respect to the thickness of the small piece. This is a value corresponding to how many times the length corresponds, and indicates the flatness of the small piece. The larger the length-to-short dimension ratio of the small piece, the flatter the shape of the small piece. When expressed in such an index, the tire chip usually contains many particles having a length-to-short dimension ratio of about 1 to 2, whereas the flaky tire chip 7 has a length-to-short dimension ratio of about 3 to 5. Contains many small pieces.

Such a flat small piece shape of the flaky tire chip 7 is generated as a chip of the cutting process after the flaked tire chip 7 cuts the used tire surface, which is a rubber molded body, in one direction. This is due to that. For example, the flaky tire chip 7 suitable for this construction method includes small pieces having a shape with a length-to-length ratio of 3 or more included in a weight ratio of 80% to less than 100%, and more preferably, Small pieces having a shape with a length-to-short dimension ratio of 5 or more are included in the weight ratio of 90% or more and less than 100%. The flake-shaped tire chip 7 more suitable for this construction method is a small piece having a shape ratio of 3 or more in the longitudinal direction, and a small piece having an aspect ratio of 1.5 or more is 80% or more by weight. It is contained less than 100%, and more preferably, small pieces having a shape with an aspect ratio of 2.5 or more are contained in a weight ratio of 90% or more and less than 100%. As illustrated in FIG. 3, the aspect ratio of the small piece is a rectangular parallelepiped 201 having the smallest volume among the rectangular parallelepipeds circumscribing the small piece 200.
Aspect ratio = length of the longest side of the rectangular parallelepiped (a) / length of the second longest side of the rectangular parallelepiped (b)
It is a value of the ratio of the length and width in the longitudinal direction of the small piece. In addition, in a generally available flaky tire chip, it is considered that small pieces that are extremely long and thin as the aspect ratio exceeds 15 are hardly mixed.

  The rubber chip such as the flake-shaped tire chip 7 is an isotropic material having a Poisson's ratio close to 0.5, and is contained in the soil cement column 1 to improve the deformation following performance of the soil cement column 1. . Therefore, compared with the case where such a rubber chip is not contained, the soil cement column 1 can obtain high toughness.

  Next, the evaluation of the toughness of the soil cement column 1 containing such a flaky tire chip 7 will be described. The present inventors conducted a compressive strength test of various soil cement columns including the soil cement column 1 in accordance with JIS A1216. In this compressive strength test, specimens F10, T10, T20, and T0 of four types of soil cement columns were produced.

  Among these, the specimen F10 has the same composition as the soil cement column 1 having the above-described configuration. In producing the specimen F10, the cement milk was mixed with 10% flaky tire chip 7 by volume.

  The flake-shaped tire chip 7 used here contains 94.6% by weight of small pieces having a length-to-short dimension ratio of 3 or more and an aspect ratio of 2.5 or more. The small pieces having an aspect ratio of 1.5 or more were contained in 97.9% by weight. In addition, small pieces having a length-to-short dimension ratio of 5 or more and an aspect ratio of 2.5 or more are included by 93.9% by weight, and the length-to-short dimension ratio is 3 or more and the aspect ratio is 1.5 or more. The small piece contained 97.1% by weight. In measuring the weight ratio, three groups of 100 g each of the flaked tire chips 7 were sampled, the powdery ones were visually removed for each group, and the longitudinal short dimension was measured using calipers. Select a small piece with a ratio of 5 or more, or a short-to-long dimension ratio of 3 or more, or an aspect ratio of 2.5 or more, or an aspect ratio of 1.5 or more and measure the weight to obtain the average weight ratio of the three groups. It was. Further, among the flake-shaped tire chips 7, those having a longitudinal short dimension ratio of 5 or more and an aspect ratio of 2.5 or more have a length of 3 mm or more and 15 mm or less, a width of 2 mm or less, and a thickness of 1 mm or less. Most of them had a length exceeding 15 mm.

Such cement milk and soil were mixed and cured to prepare a soil cement column having a cylinder with a diameter of 50 mm and a length of 100 mm. And this produced soil cement column was made into the test body F10. Here, the blending ratio of cement, water, and soil was set at a blending strength of 600 kN / m ² . In addition, the curing period of this specimen F10 is 74 days.

  Next, in producing the specimen T10, a normal tire chip having a volume ratio of 10% was mixed in the cement milk instead of the flaky tire chip. All other conditions were the same as those of the specimen F10, and a specimen T10 was produced in the same manner as the specimen F10. In addition, the curing period of this specimen T10 is 90 days.

  Further, in preparing the specimen T20, a normal tire chip having a volume ratio of 20% was mixed in the cement milk instead of the flaky tire chip. All other conditions were the same as those of the specimen F10, and a specimen T20 was produced in the same manner as the specimen F10. In addition, the curing period of this specimen T20 is 74 days.

  Further, when the specimen T0 is manufactured, rubber chips are not mixed in the cement milk. All other conditions were the same as those of the specimen F10, and a specimen T10 was produced in the same manner as the specimen F10. In addition, the curing period of this specimen T0 is 91 days.

  Each of the specimens F10, T10, T20, and T0 is subjected to a compressive strength test, and stress-strain curves showing the relationship between the compressive stress and the vertical strain are shown in FIG. 4, FIG. 5, FIG. 6, and FIG. 7 shows. In addition, the lower curve in FIGS. 4-7 is a curve which shows the side distortion | strain with respect to a vertical distortion. FIG. 8 shows the “toughness improvement ratio” for the specimens F10, T10, and T20.

  As shown in FIG. 9, the “toughness improvement ratio” is a stress-strain curve in which a yield point A and a point B where the vertical strain increases by 2% from the yield point A are taken, and the slope of the straight line AB is obtained. When the value is β, it is defined as “toughness improvement ratio of specimen X = β value in specimen T0 / beta value in specimen X” (X is F10, T10, T20). Such a toughness improvement ratio can be used as an evaluation index indicating how much the toughness of the soil cement column is improved by including a rubber chip. That is, it can be determined that the greater the toughness improvement ratio, the higher the toughness of the soil cement column.

Table 1 below summarizes the test results shown in FIGS.

  According to this result, the specimen F10 shows a higher toughness improvement ratio than the specimen T10, and further shows a higher toughness improvement ratio than the specimen T20. Therefore, when the rubber cement is included in the soil cement column, it was found that the flaky tire chip has a higher effect of improving the toughness of the soil cement column than the normal tire chip when compared with the same content.

Moreover, when the compressive strength of the specimen T0 is 600 kN / m ² , the compressive strength of the specimen T20 is reduced to 470 kN / m ² , and the specimen T20 is a defective product. This is considered to be due to an increase in the content of rubber chips having a relatively low strength in the soil cement column (that is, a decrease in the content of cement). In contrast, the specimen F10 has a compressive strength of 800 kN / m ² , and the compressive strength does not decrease even when compared with the specimen T0. This is considered to be due to the low content of rubber chips in the soil cement column. This can also be understood from the fact that the compressive strength of the specimen T10 is similar to that of the specimen F10.

  From the above, it has been found that the soil cement column 1 containing the flaky tire chips 7 can obtain sufficient toughness even if the mixing ratio of the flaky tire chips 7 in the cement milk is 10% by volume. That is, the content of the flaky tire chip 7 does not need to be excessively high, and sufficient toughness can be obtained with a content of less than half that of a normal tire chip. Therefore, if the flaky tire chip is used, it is possible to suppress a decrease in the compressive strength of the soil cement column due to the rubber chip inclusion, and it is possible to improve the toughness of the soil cement column sufficiently.

  In addition, since the necessary mixing ratio in cement milk can be kept small in the flaky tire chip, the cement milk is easily kneaded, and the flaky tire chip is easily mixed with cement, water, and soil. As a result, a homogeneous soil cement column can be easily obtained, and performance deterioration of the soil cement column can be suppressed. In addition, by employing the flaky tire chip, it is possible to effectively use the waste generated during the manufacture of the corrected tire.

(Second Embodiment)
Hereinafter, a second embodiment of a foundation structure and a manufacturing method thereof according to the present invention will be described with reference to FIGS. 10 and 11. As shown in FIG. 10, in the construction of this foundation structure, first, the original ground soil is scraped to the foundation bottom depth with a backhoe, and the soil is temporarily placed (FIG. 10 (a)). Thereafter, a predetermined amount of cement-based solidifying material (hydraulic material) 103 and flaky tire chip 7 are added to the base soil 109 to be improved (FIG. 10B). Thereafter, the base ground soil 109, the cement-based solidified material 103, and the flaky tire chip 7 are mixed and stirred with a backhoe bucket (FIG. 10C), and the mixed and stirred improved soil is compacted with a backhoe bucket. Alternatively, the improved soil may be rolled by the backhoe body (FIG. 10 (d)). Furthermore, after that, by rolling this with a roller (FIG. 11A), the improved soil is cured to form the foundation structure 101. Thereafter, the temporarily placed soil is backfilled (FIG. 11B), leveling is performed (FIG. 11C), and curing is performed for a predetermined period.

  The foundation structure 101 is formed by curing an improved soil obtained by mixing the raw ground soil 109, the cement-based solidified material 103, and the flaky tire chip 7. Similar to the soil cement column 1 described above, the foundation structure 101 can improve toughness by containing the flaky tire chip 7 and can also suppress a decrease in strength due to rubber chip mixing. .

(A)-(d) is a figure which shows the construction method of the soil cement column which concerns on 1st Embodiment of this invention. (A)-(e) is a figure which shows the construction method of the soil cement column which concerns on 1st Embodiment of this invention. It is a perspective view which shows the small piece of a flake-shaped tire chip, and the rectangular parallelepiped which has the minimum volume among the rectangular solids which circumscribe the small piece. It is a stress-strain curve of the specimen F10 obtained by our compressive strength test. It is a stress-strain curve of specimen T10 obtained by the present inventors' compressive strength test. It is a stress-strain curve of specimen T20 obtained by the present inventors' compressive strength test. It is a stress-strain curve of specimen T0 obtained by the present inventors' compressive strength test. It is a diagram which shows the relationship between the mixture ratio of the rubber chip of each specimen, and a toughness improvement ratio. It is a figure which shows the definition of a toughness improvement ratio. (A)-(d) is a figure which shows the construction method of the foundation structure which concerns on 2nd Embodiment of this invention. (A)-(c) is a figure which shows the construction method of the foundation structure which concerns on 2nd Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Soil cement column (base structure), 5 ... Water, 7 ... Flaked tire chip (rubber chip), 9,109 ... Raw ground soil, 101 ... Base structure, 200 ... Small piece, 201 ... Rectangular solid.

Claims (5)

A soil cement column obtained by curing a mixture including a hydraulic material, soil, and rubber chips,
The rubber tip is soil cement column, wherein the hydraulic material Ri flaky tire chips der to be mixed at the mixing ratio of the volume 10-15%. The flaky tire chip is
Of the rectangular parallelepipeds circumscribing the small pieces, a granular body containing 80% or more by weight ratio of flat-shaped small pieces whose length of the longest side in the rectangular parallelepiped having the smallest volume is at least three times the length of the shortest side. The soil cement column according to claim 1. A method for producing a soil cement column comprising a mixture curing step of curing a mixture including a hydraulic material, soil, and rubber chips,
The rubber tip method for manufacturing a soil cement column, wherein the hydraulic material Ri flaky tire chips der to be mixed at the mixing ratio of the volume 10-15%. The mixture curing step includes
The method according to claim 3, further comprising a step of injecting a mixture of the hydraulic material, water, and the rubber chip into the excavation portion of the original ground while excavating the original ground vertically downward by a soil cement column method. The manufacturing method of the soil cement column of description. The flaky tire chip is
Of the rectangular parallelepipeds circumscribing the small pieces, a granular body containing 80% or more by weight ratio of flat shaped small pieces whose length of the longest side in the rectangular solid having the smallest volume is three times or more of the length of the shortest side The method for producing a soil cement column according to claim 3 or 4, characterized in that

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