JP6287914B2 - Sand compaction pile material, sand compaction pile, and method for creating sand compaction pile - Google Patents

Description

  The present invention relates to a material for sand compaction pile used in a sand compaction pile method applied as a countermeasure for liquefaction of loose sand ground on land or to improve soft clay ground at sea, and sand compaction using the same. The present invention relates to a method for creating a pile and its sand compaction pile.

  A sand compaction pile method (hereinafter also referred to as an SCP method) is known as a conventional ground improvement method. Up to now, high-quality natural sand has been used as a material for sand piles in the SCP method. However, in recent years, sand piles are being built in many places, mainly in port construction, to protect natural resources. From the viewpoint, effective use of recycled materials such as steel slag such as recycled concrete aggregate, steelmaking slag, blast furnace slow-cooled slag, blast furnace granulated slag, etc. is promoted as an alternative material for natural sand.

  For example, it is known to use steelmaking slag 100% as a material for filling material in place of natural sand in the sand compaction pile method for the purpose of liquefaction countermeasures for sand ground or improving soft clay ground (for example, (Refer nonpatent literature 1).

  Also, the converter slag adjusted to a particle size of 20 mm or less, blast furnace slag, lime or cement or cement clinker in weight ratio, respectively, converter slag 100, blast furnace granulated slag 10-20, lime or cement or cement A material in which clinker is mixed at a ratio of 10:20 is known (for example, see Patent Document 1).

  Moreover, as a prior art relevant to an expansible solidified pile, the thing of patent documents 2-4 is known, for example. Patent Document 2 includes hard-fired quicklime powder (10 to 60%), an ammonium sulfate compound (0.1 to 5%), fine aggregate, sand, screenings, gypsum, granulated slag or rolling A ground improvement material and a ground improvement method using silicic acid component-containing materials such as furnace slag or lime ash are shown.

  In Patent Document 3, as a ground improvement material that expands and hardens by reacting with moisture in the ground to improve the ground, hard calcined lime powder, calcium sulfate-based hardened powder, and silicification modification Includes alunite-based granule, hard calcined lime powder (10-60%), aluminum sulfate-based compound (0.1-5%), fine aggregate, sand, screenings, gypsum, granulated Materials and methods using slag, converter slag, or silicic acid component-containing materials such as lime ash are shown.

  According to Patent Document 4, a large number of compacted piles are created on a sandy ground at a predetermined pitch, and the pile diameter is expanded (physical compaction) by returning the pile-forming casing, and the pile material is hydrated and expanded. In the sandy ground compaction method, which is a technology for compacting the ground between piles to a predetermined strength by expanding the pile diameter (chemical compaction), hard calcined lime, aluminum sulfate compound, concrete sand, gravel and granulated slag・ It has been shown to use a ground improvement material made of aggregate such as converter slag.

“Guide for using steelmaking slag for port construction”, Coastal Development Technology Research Center, Japan Steel Slag Association, 2004.9, P31-P33

Japanese Patent Laid-Open No. 56-41914 JP 2001-152149 A JP 2001-59217 A JP 2002-322638 A

  Since the above-mentioned recycled concrete aggregate and steel slag generally have alkaline characteristics, there is a concern that when used as a material for sand compaction pile, alkali is eluted into the surrounding ground and affects the environment. Therefore, when such materials are used, it is required to suppress the environmental impact due to alkali elution on the surrounding ground.

  In addition, the techniques described in the above-described conventional patent documents 2 to 4 and the like utilize the expansibility and solidification property to compact and improve the surrounding ground. However, when building a sand compaction pile close to an existing structure mainly in the land area, or when constructing a structure or road directly on the sand compaction pile, Due to the expansion characteristics of the pile material, there is a concern that it may adversely affect structures, roads, etc. in the long term, such as cracks, rises and sinks.

  The present invention has been made in view of the above, and is a material for sand compaction piles, sand compaction piles, and sand compaction piles that can suppress adverse effects on the surrounding environment while maintaining the effect of compacting the surrounding ground. The purpose is to provide a creation method.

  In order to solve the above-described problems and achieve the object, the material for sand compaction pile according to the present invention is a material for sand compaction pile that is created in the ground by the sand compaction pile method, and has a particle size of 5 mm. As mentioned above, it consists of steel slag or recycled concrete of 40 mm or less.

  Further, another material for sand compaction pile according to the present invention is a material for sand compaction pile that is created in the ground by the sand compaction pile method, and is a steel slag or recycled concrete having a particle size of 10 mm or more and 40 mm or less. It is characterized by comprising.

  Further, another material for sand compaction pile according to the present invention is a material for sand compaction pile that is created in the ground by the sand compaction pile method, and is a steel slag or recycled concrete having a particle size of 15 mm or more and 40 mm or less. It is characterized by comprising.

  Further, the sand compaction pile according to the present invention is a sand compaction pile created in the ground by the sand compaction pile method, and is composed of a particulate material laminated vertically in two layers or more, and the lower layer is made of steel. In addition to the slag, the upper layer is made of the above-described material for sand compaction pile.

Further, the sand compaction pile according to the present invention is the above-described invention, wherein the portion of 2.5 / ρ × D ^1/2 (m) or more in the depth direction from the upper end is made of the material for sand compaction pile, The deeper part is made of steel slag. Here, ρ is the particle density (t / m ³ ) of steel slag, and D is the diameter (m) of the sand compaction pile.

  In addition, another sand compaction pile forming method according to the present invention is characterized by forming the above-described sand compaction pile.

  According to the present invention, steel slag or recycled concrete adjusted to a predetermined particle size range is used as a material for a sand compaction pile, and the expansibility of the steel slag or recycled concrete is used to reduce the risk of alkali elution into the surrounding ground. It is possible to improve the workability in rainy weather. In addition, it is possible to eliminate the possibility of long-term cracks, swells, subsidences, etc. in the surroundings and directly above structures and roads. Therefore, the adverse effect on the surrounding environment can be suppressed while maintaining the effect of compacting the surrounding ground.

FIG. 1 is a sectional side view showing a first embodiment of a sand compaction pile according to the present invention. FIG. 2 is a sectional side view showing a second embodiment of the sand compaction pile according to the present invention. FIG. 3 is a side sectional view showing Embodiment 3 of the sand compaction pile according to the present invention. FIG. 4 is a side sectional view showing a fourth embodiment of the sand compaction pile according to the present invention. FIG. 5 is a side sectional view showing a fifth embodiment of the sand compaction pile according to the present invention. FIG. 6 is a diagram illustrating the test apparatus according to the first embodiment of the present invention. FIG. 7 is an explanatory diagram of evaluation items of Example 1 of the present invention. FIG. 8 is a diagram showing an experimental model of Example 2 of the present invention. FIG. 9 is a diagram showing experimental results of Example 2 of the present invention.

  Hereinafter, embodiments of a material for a sand compaction pile, a sand compaction pile, and a method for producing a sand compaction pile according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  Here, steel slag includes steelmaking slag and blast furnace slag. Blast furnace slag includes blast furnace slow-cooled slag and blast furnace granulated slag.

  Steelmaking slag is a granular by-product mainly composed of lime generated in the steelmaking process, and refers to converter slag, hot metal pretreatment slag, secondary smelting slag, electric furnace slag, and the like.

  The blast furnace slow cooling slag is a crystalline rock-like one produced by pouring molten blast furnace slag into a yard and cooling it with air and appropriate water spray.

  The granulated blast furnace slag is a vitreous (non-crystalline) granular material produced by quenching molten blast furnace slag with pressurized water. Blast furnace granulated slag includes pre-furnace granulated slag and out-of-furnace granulated slag. In the following description, the blast furnace slag and the granulated blast furnace slag may be collectively referred to as blast furnace slag.

(Embodiment 1)
First, the first embodiment of the present invention will be described.
FIG. 1 is a diagram for explaining a sand compaction pile according to the first embodiment.
As shown in this figure, as the ground improvement material (the material for the sand compaction pile of the present invention) used as the material for the sand compaction pile 10 formed in the ground G below the ground surface GL, the following (1) to (3) By applying steel slag having a particle size distribution of any of the above, it is possible to reduce the environmental impact due to alkali elution on the surrounding ground.

(1) Steel slag having a particle size of 5 mm to 40 mm (2) Steel slag having a particle size of 10 mm to 40 mm (3) Particle size of 15 mm to 40 mm Steel slag

(Embodiment 2)
Next, a second embodiment of the present invention will be described.
FIG. 2 is a diagram for explaining a sand compaction pile according to the second embodiment.
As shown in this figure, the sand compaction pile 20 is formed across the upper permeable layer G1 and the lower non-permeable layer G2. The permeable layer G1 has a superior groundwater flow W compared to the non-permeable layer G2. In the sand compaction pile 20 of the present embodiment, the steel slag having a particle size distribution of any one of the following (1) to (3) only at the depth portion 22 (portion of the permeable layer G1) where the groundwater flow W is dominant. By applying, it becomes possible to reduce the environmental impact due to alkali elution on the surrounding ground. In addition, about the depth location 24 located in the impermeable layer G2 of the sand compaction pile 20, it can comprise using the material for well-known sand compaction pile used conventionally.

(1) Steel slag having a particle size of 5 mm to 40 mm (2) Steel slag having a particle size of 10 mm to 40 mm (3) Particle size of 15 mm to 40 mm Steel slag

(Embodiment 3)
Next, a third embodiment of the present invention will be described.
FIG. 3 is a diagram for explaining a sand compaction pile according to the third embodiment.
As shown in this figure, the sand compaction pile 30 is formed on the ground G where the water flow W is dominant in the vicinity of the ground surface GL. In the sand compaction pile 30 of the present embodiment, the steel slag having the particle size distribution of any of the following (1) to (3) is applied only to the depth portion 32 near the ground surface GL where the water flow W is dominant. This makes it possible to reduce the environmental impact due to alkali elution on the surrounding ground. In addition, about the depth location 34 below the depth location 32, it can comprise using the material for well-known sand compaction pile used conventionally.

(1) Steel slag having a particle size of 5 mm to 40 mm (2) Steel slag having a particle size of 10 mm to 40 mm (3) Particle size of 15 mm to 40 mm Steel slag

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described.
FIG. 4 is a diagram for explaining a sand compaction pile according to the fourth embodiment.
As shown in this figure, the sand compaction pile 40 has a laminated structure composed of an upper layer 42, an intermediate layer 44, and a lower layer 46. The lower layer 46 is made of steel slag, and the upper layer 42 is made of the following (1), (2 The sand compaction pile 40 is formed using steel slag having a particle size distribution of In addition, the constituent material of the intermediate | middle layer 44 in the meantime is not specifically limited, It can comprise using the material for well-known sand compaction pile used conventionally.

(1) Steel slag having a particle size of 5 mm to 40 mm (2) Steel slag having a particle size of 10 mm to 40 mm

  Note that the sand compaction pile 40 of the present embodiment is not limited to a three-layer upper / lower laminated structure made of a particulate material, and may be a two-layer upper / lower laminated structure, or four or more upper / lower laminated structures. It may be.

(Embodiment 5)
Next, a fifth embodiment of the present invention will be described.
FIG. 5 is a diagram for explaining a sand compaction pile according to the fifth embodiment.
As shown in this figure, a portion 52 of 2.5 / ρ × D ^1/2 (m) or more in the depth direction from the upper end 50a of the sand compaction pile 50 is either one of the following (1) and (2) While producing using the steel slag which has a particle size distribution, the part 54 from the deeper to the lower end 50b is created with steelmaking slag. Here, ρ is the particle density (t / m ³ ) of steel slag, and D is the diameter (m) of the sand compaction pile.

(1) Steel slag having a particle size of 5 mm to 40 mm (2) Steel slag having a particle size of 10 mm to 40 mm

  With the structure of these sand compaction piles, the ground is compacted by the expansibility of the steelmaking slag at the bottom of the sand compaction piles, and at the same time, the upward expansion can be constrained by placing a material that does not expand over time. It becomes possible to suppress alkali elution from the ground and improve workability in rainy weather. In addition, it is possible to eliminate the possibility of long-term cracks, swells, subsidences, etc. in the surroundings and directly above structures and roads. Therefore, the adverse effect on the surrounding environment can be suppressed while maintaining the effect of compacting the surrounding ground.

  In addition, in the conventional construction method of the sand compaction pile method, for example, there are the following methods (A) to (E), but the present invention is applicable to any construction method.

(A) A method of creating a compacted sand pile that vibrates the casing pipe using a vibro hammer and compacts it in a rebounding manner.
(B) A method for creating a compacted sand pile in which a casing pipe is rotationally press-fitted and the casing pipe is compacted back to back using a forced lifting device.
(C) A method in which sand is spread to the side of the casing pipe while the casing pipe is pulled up, and the sand pile is compacted and formed.
(D) After rotating and pressing a casing pipe having a double pipe structure including an inner pipe casing and an outer pipe casing to reach a predetermined depth, the inner pipe casing is lifted up and down while discharging the material as the casing pipe is pulled up. How to create a hard sand pile.
(E) A method for creating a sand pile in which a casing pipe equipped with an excavation / expansion head that is eccentric at the tip is rotationally press-fitted and the casing pipe is compacted back to back.

  In addition, with regard to recycled concrete such as recycled concrete aggregate conventionally used as a material for sand compaction pile, by adjusting the particle size distribution similar to that of steel slag in the present invention, the environmental impact due to alkali elution on the surrounding ground is reduced. It is possible to reduce.

Example 1
First, Example 1 of the present invention will be described.
Here, in order to verify the effect of the present invention, using a test apparatus 60 as shown in FIG. 6, a water flow test was performed on the steel slag whose particle size was adjusted, and the influence of alkali elution after water flow was examined. As a test column simulating a sand compaction pile, an acrylic cylinder 62 having an inner diameter of 150 mm and a length of 450 mm is used, and a 150 mm steel slag layer 64 is arranged on the upstream side, and a 300 mm soil layer 66 is arranged on the downstream side. did. The acrylic cylinder 62 is fixed in a watertight manner using a tie rod 68, a holding plate 70, an O-ring 72, a screw 74, etc., the cock 76 is opened, water is supplied to the test column, and water is passed therethrough. The pH was measured for the water coming out of the. Various evaluations are performed from the relationship between the measured pH and the amount of water flow to verify the effect of the present invention. The evaluation items were the following three items (1) to (3). Each evaluation item can be obtained from the relationship between the water flow rate and the pH exemplified in FIG.

(1) Ratio of water flow rate where alkali influence appears after water flow (based on the case without particle size adjustment)
(2) Amount of increase in pH after sufficient water flow (based on no particle size adjustment)
(3) Water flow ratio at which the pH once increased starts to decrease (based on the case of no particle size adjustment)

  Table 1 shows the experimental conditions and a summary of the results.

  As shown in Table 1, when steel slag having a particle size of 5 mm or more and 40 mm or less is applied compared to the case without particle size adjustment (case: A-0, maximum 40 mm-minimum 0 mm) (case) : A-5) The above-mentioned (1) “the ratio of the amount of water passing through which alkali influence appears after passing water” was increased, and the effect of delaying the appearance of alkali influence was confirmed.

  In addition, when steel slag having a particle size of 10 mm or more and 40 mm or less is applied (case: A-10), in addition to the above (1) “Water flow rate ratio at which alkaline influence appears after water flow” Thus, (2) the effect of suppressing the “pH increase after passing water (maximum value)” was also confirmed.

  When steel slag having a particle diameter of 15 mm or more and 40 mm or less is applied (case: A-15), (1) “Water flow rate ratio where alkali influence appears after water flow”, (2) In addition to “pH increase after water flow (maximum value)”, (3) “Water flow rate ratio at which pH once increased starts to decrease” is reduced, confirming the effect of significantly reducing total alkali elution amount did it.

(Example 2)
Next, a second embodiment of the present invention will be described.
As an experiment regarding the vertical length of the upper layer of the sand compaction pile according to the present invention, an upper member P1 (consisting of any of blast furnace slow-cooled slag, blast furnace water granulated slag, crushed concrete, and sand) as shown in FIG. A sand compaction pile P made of member P2 (consisting of steelmaking slag) is created in a soil tank G0 (ground tank ground is a uniform ground with a relative density Dr = 70% using Toyoura standard sand). Then, the expansion reaction of the steelmaking slag of the lower member P2 was promoted by setting the ground as an alkaline atmosphere, and the surface lifting amount at the upper end Pa of the sand compaction pile was measured. The experiment parameters were the material of the upper member P1 and the length L1 of the upper member P1, and a total of 16 cases of experiments were conducted. In any case, the material of the lower member P2 was steel slag, and the length of the lower member P2 was L2. Table 2 shows the experimental conditions and the outline of the experimental results (surface lifting amount).

Moreover, the index regarding the length L1 of the upper member is λ (= L1 × ρ / D ^1/2 ), and FIG. 9 shows the relationship between the surface lift amount of the upper end Pa and λ as a result of the reaction promotion experiment. As shown in this figure, it can be seen that if the distance is larger than λ = 2.5, the surface floating amount is greatly reduced.

  Therefore, it is desirable to set the length L1 of the upper member P1 necessary for suppressing the surface lifting of the sand compaction upper end Pa accompanying the expansion reaction of the steelmaking slag of the lower member P2 as follows.

L1 ≧ 2.5 / ρ × D ^1/2 (m)
Here, ρ is the particle density (t / m ³ ) of steel slag, and D is the diameter (m) of the sand compaction pile.

  As described above, according to the present invention, the use of steel slag whose particle size is adjusted to a predetermined particle size range as a material for sand compaction pile, and utilizing its expansibility, there is a risk of alkali elution into the surrounding ground. In addition, the workability in rainy weather is improved. In addition, it is possible to eliminate the possibility of long-term cracks, swells, subsidences, etc. in the surroundings and directly above structures and roads. Therefore, the adverse effect on the surrounding environment can be suppressed while maintaining the effect of compacting the surrounding ground.

  As described above, the material for sand compaction pile according to the present invention, the sand compaction pile, and the method for constructing the sand compaction pile can be used to improve the ground as a countermeasure for liquefaction of loose land sand, or soft clay ground on the sea. It is useful for improvement, and is particularly suitable for suppressing adverse effects on the surrounding environment while maintaining the effect of compacting the surrounding ground.

10, 20, 30, 40, 50 Sand compaction pile 22, 24, 32, 34 Depth location 42 Upper layer 44 Middle layer 46 Lower layer 52, 54 Part G Ground G1 Permeable layer G2 Non-permeable layer GL Ground surface

Claims (6)

It is a material for sand compaction pile that is created in the ground by the sand compaction pile method,
A material for sand compaction pile, comprising a steel slag having a particle diameter of 5 mm or more and 40 mm or less or recycled concrete. It is a material for sand compaction pile that is created in the ground by the sand compaction pile method,
A material for sand compaction pile, comprising a steel slag having a particle size of 10 mm or more and 40 mm or less or recycled concrete. It is a material for sand compaction pile that is created in the ground by the sand compaction pile method,
A material for sand compaction pile, comprising a steel slag having a particle size of 15 mm or more and 40 mm or less or recycled concrete. Sand compaction pile built in the ground by sand compaction pile method,
Consists of particulate material that is laminated in two or more layers above and below,
A sand compaction pile, wherein the lowermost layer is made of steelmaking slag, and the uppermost layer is made of the material for sand compaction pile according to any one of claims 1 to 3. The portion of 2.5 / ρ × D ^1/2 (m) or more in the depth direction from the upper end is made of the material for sand compaction pile, and the deeper portion is made of steel-making slag. 4. Sand compaction pile according to 4.
Here, ρ is the particle density (t / m ³ ) of steel slag, and D is the diameter (m) of the sand compaction pile.   A method for producing a sand compaction pile, comprising producing the sand compaction pile according to claim 4 or 5.

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