Hangcheng device

Abstract

To provide a pile construction device capable of fixing carbon dioxide caused by global warming in the ground during ground improvement using cement milk.SOLUTION: A pile construction device 1 comprises a mixer container 23 of an airtight mixer 10 into which cement and water are flowed and agitated to produce cement milk, carbon dioxide supply means 11 for supplying carbon dioxide into the mixer container 23, and a pumping pipe 32 for pumping the cement milk containing carbon dioxide in the mixer container 23 into the ground. Carbon dioxide resulting from global warming reacts with cement milk and is fixed in the ground as improved piles containing calcium carbonate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pile construction device that pumps and agitates cement milk into the ground to construct cement-improved piles. [Background technology]

[0002] One of the methods for constructing cement improvement piles is the deep mixing treatment method (CDM method). Generally, the deep mixing treatment method involves pumping cement milk, a mixture of cement, water, and admixtures, into soft ground using a dedicated work vessel (CDM vessel) or land-based facilities, and mechanically mixing it with the surrounding ground to mix it with the soil and sand in the soft ground. This method allows cement improvement piles to be constructed in the soft ground to improve the soft ground. The work vessel is a vessel capable of mixing cement, seawater, and admixtures at sea, and the materials are replenished at regular intervals. Generally, for every 1m of soil and sand in the ground, 3 The amount of cement added per unit is C=50-200kg / m 3 Cement milk is produced with a ratio of water (W) to cement (C) (approximately W / C = 0.6). This cement milk is pumped into the ground using a pressure pump. In offshore construction, improved piles may be constructed to a depth of more than 50m below the water surface.

[0003] Work vessels used exclusively for offshore construction emit carbon dioxide (CO2) during operation. Their engines often run on diesel or heavy oil A, and are used not only during work hours but also as a source of power for maintenance when the vessel is anchored overnight. With a recent shift in environmental awareness, hybridization using electricity for some of the power source has been considered and has proven successful. However, reductions in carbon dioxide emissions toward carbon neutrality are still insufficient.

[0004] In addition, cement contains a lot of calcium oxide (CaO), and when water is added to the cement milk, calcium ions (Ca 2+ ) and hydroxide ions (OH -) is produced. As a result, cement milk becomes alkaline and contains many calcium ions (Ca 2+ When carbon dioxide (CO2) is dissolved in this cement milk, the carbon dioxide reacts with water to form carbonic acid (H2CO3), and hydrogen ions (H + ) one by one to form hydroxide ions (OH - ) to neutralize the alkalinity. At the same time, carbonate ions (CO3 2- ) is a calcium ion (Ca 2+ ) to form calcium carbonate (CaCO3), which is fixed in the cement structure. In other words, carbon dioxide becomes calcium carbonate and is fixed in the cement structure.

[0005] Cement and construction companies have begun to consider and implement carbon dioxide fixation using this mechanism. By injecting carbon dioxide into the ready-mix concrete manufacturing process, they are hoping to increase the strength of the concrete by producing crystallized calcium carbonate, and have succeeded in reducing the amount of cement required. This also leads to a reduction in the amount of cement produced, which emits carbon dioxide.

[0006] Therefore, as a technique for immobilizing carbon dioxide during ground improvement, Patent Document 1 discloses a ground improvement method using carbon dioxide, which includes a spraying / mixing step of spraying a carbon dioxide absorbent or an aqueous solution containing a carbon dioxide absorbent that reacts with carbon dioxide and solidifies on the surface of the ground to be improved or mixing it into the ground, a penetration step of allowing the carbon dioxide absorbent to penetrate into gaps in the ground, and a reaction / solidification step of reacting the carbon dioxide absorbent with carbon dioxide or a gas containing carbon dioxide, solidifying the carbon dioxide absorbent, and leaving it in the gaps as a binder. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-163623 Summary of the Invention [Problem to be solved by the invention]

[0008] The ground improvement method described in Patent Document 1 involves taking atmospheric air directly into the ground of a slope or other such ground, and generating carbonates underground through a carbonation reaction between the carbon dioxide contained in the air and a carbon dioxide absorbent, which in turn suppresses the movement of soil particles, thereby improving the strength of the slope and increasing the safety factor against landslides during heavy rain. However, the ground improvement method described in Patent Document 1 alone is only able to fix a small amount of carbon dioxide, meaning it does not achieve the reduction in carbon dioxide needed to curb global warming. Therefore, it is necessary to explore other, less costly methods of fixing carbon dioxide in various fields.

[0009] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a pile construction device that can fix carbon dioxide caused by global warming in the ground when improving the ground using cement milk. [Means for solving the problem]

[0010] As a means for solving the above problem, the invention relating to the pile construction device of claim 1 is a pile construction device that pumps and agitates cement milk into the ground to construct cement-improved piles, comprising: an airtight sealed container into which cement and water are poured and agitated to produce cement milk; carbon dioxide supply means for supplying carbon dioxide into the sealed container; and a pressure pipe for pumping the cement milk containing carbon dioxide in the sealed container into the ground. Equipped with The sealed container includes a mixer container and an agitator container that communicate with each other, and the carbon dioxide from the carbon dioxide supply means is supplied into the cement milk in the mixer container and / or the cement milk in the agitator container. It is characterized by the following. Furthermore, the invention relating to the pile construction device of claim 2 is a pile construction device that pumps and agitates cement milk into the ground to construct cement-improved piles, and is equipped with an airtight sealed container into which cement and water are poured and agitated to produce cement milk, a carbon dioxide supply means for supplying carbon dioxide into the sealed container, and a pressure pipe for pumping the cement milk containing carbon dioxide in the sealed container into the ground, wherein the sealed container comprises a mixer container and an agitator container that are connected to each other, and the carbon dioxide from the carbon dioxide supply means is supplied into the cement milk in the mixer container and into the cement milk in the agitator container. Claim 1 and 2 In the invention, an airtight sealed space ( Mixer vessel and agitator vessel)Cement and water are flowed into the sealed container, and carbon dioxide is supplied from the carbon dioxide supply means into the sealed space. Then, by supplying carbon dioxide into the sealed container, the carbon dioxide can be easily dissolved in the cement milk. As a result, cement milk containing calcium carbonate (carbonate) is produced by the reaction between the cement milk and the carbon dioxide. The cement milk in the sealed container is then pumped into the ground through a pressure pipe by a pressure pump. Then, carbon dioxide resulting from global warming is fixed in the improvement piles created in the ground; that is, the carbon dioxide becomes calcium carbonate and is fixed in the improvement piles in the ground. Moreover, the generation of calcium carbonate can increase the strength of the improvement piles, and the amount of cement added can be reduced as the strength increases due to the generation of calcium carbonate. 。

[0011] As mentioned above, when cement and water (or seawater) are mixed, the cement milk generates hydroxide ions (OH - ) is present in large amounts, resulting in a highly alkaline state (pH 11 or higher). In highly alkaline liquid cement milk, a large amount of carbon dioxide dissolves from the gas in contact with it. In other words, the carbon dioxide in the liquid cement milk is consumed by the above reaction, and as the amount of carbon dioxide in the cement milk decreases, the carbon dioxide in the gas in contact with the cement milk dissolves further into the cement milk due to its partial pressure. If the cement milk is stirred sufficiently at this time, the rate at which carbon dioxide is consumed and dissolved will be accelerated.

[0012] In addition, the cement milk mix (W / C = 0.6, C = 100 kg / m 3) has been experimentally confirmed that when cement milk is stirred in a sealed container, the carbon dioxide concentration in the gas in contact with the cement milk in the sealed container drops from 400-500 ppm to 0 ppm. In one example experiment, the carbon dioxide concentration in the air in a 30 L sealed container fell to 0 ppm after 90 minutes of stirring for 770 mL of cement milk. The gas-liquid ratio in this case was 40:1. In short, it is possible to capture and immobilize the carbon dioxide in the air in contact with the cement milk within the cement milk.

[0013] Claim 3 The invention relating to a pile construction device is a pile construction device that pumps and agitates cement milk into the ground to construct cement-improved piles, and is characterized by comprising: an airtight sealed container into which cement and water are poured and agitated to produce cement milk; carbon dioxide supply means for supplying carbon dioxide into the sealed container; bubble generating means arranged downstream of the carbon dioxide supply means for aerating the carbon dioxide from the carbon dioxide supply means; and a pressure pipe for pumping the cement milk containing carbon dioxide in the sealed container into the ground. Claim 3 In this invention, finely aerating carbon dioxide using a bubble generating means increases the total surface area of ​​bubbles per given volume, and the viscosity of the cement milk allows the carbon dioxide to remain in the cement milk for a longer period of time. This prevents the aerated carbon dioxide from escaping into the atmosphere during mixing in a sealed container, pumping through a pressure pipe, mixing with surrounding soil and sand in the ground, and hardening of the improved ground, allowing the carbon dioxide to efficiently react with the cement milk to produce calcium carbonate. The residence time of carbon dioxide-containing bubbles in the cement milk varies depending on their diameter, and bubbles with a diameter of several millimeters may also be used. Furthermore, nanobubbles, bubbles with diameters on the order of nanometers, and microbubbles, bubbles with diameters on the order of micrometers, may also be used. Claim 4 The invention relating to the pile construction device is as follows: ~ Any of 3The invention described in the above is characterized in that the pressure in the air space inside the sealed container is made higher than atmospheric pressure. Claim 4 In this invention, the pressure in the air space inside the sealed container is made higher than atmospheric pressure, which increases the rate at which carbon dioxide dissolves in the cement milk. As a result, the reaction between carbon dioxide and cement milk is promoted. This also makes it possible to shorten the stirring time required to fix a certain amount of carbon dioxide. Once dissolved, carbon dioxide crystallizes as calcium carbonate, so it does not return to the air space, but is fixed in the cement milk or in the improved pile using cement milk.

[0015] Claim 5 The invention relating to a pile construction device is a pile construction device that pumps and mixes cement milk into the ground to create cement-improved piles, and is characterized by comprising: an agitation vessel into which cement and water are poured and which mixes the cement and water to produce cement milk; a pressure pipe that pumps the cement milk in the agitation vessel into the ground; carbon dioxide supply means that supplies carbon dioxide into the pressure pipe; and bubble generation means that is located downstream of the carbon dioxide supply means and turns the carbon dioxide from the carbon dioxide supply means into bubbles. Claim 5In the invention, for example, in offshore construction using the deep mixing treatment method, when constructing a 30m deep cement improvement pile at a construction location 10m deep, in addition to atmospheric pressure, the lower end of the cement improvement pile is subjected to water pressure equivalent to a water depth of 40m and earth pressure equivalent to a water depth of 30m. Water pressure equivalent to a water depth of 10m also acts on the upper end of the cement improvement pile. In other words, the cement milk is pumped through the pressure pipe at a pressure greater than these pressures. By pumping carbon dioxide at the same pressure as the pumping pressure into the cement milk that is pumped through the pressure pipe at a pressure greater than atmospheric pressure, the carbon dioxide is easily mixed into the cement milk without floating up and dissolved, producing cement milk containing calcium carbonate. As a result, by pumping and supplying carbon dioxide into the pressure pipe, more carbon dioxide can be fixed than in the conventional method in which carbon dioxide is mixed at atmospheric pressure in a stirring vessel. Also, as claimed in claim 5 In the invention, the carbon dioxide is finely bubbled by the bubble generating means, which increases the total surface area of ​​bubbles for a given volume, and the viscosity of the cement milk allows the carbon dioxide to remain in the cement milk for a longer period of time. As a result, when the carbon dioxide is pumped through the pumping pipe, when it is mixed with the surrounding soil and sand in the ground, and when the improved ground hardens, the bubbled carbon dioxide does not escape into the atmosphere, and it is possible for the carbon dioxide to react with the cement milk efficiently to produce calcium carbonate.

[0016] Claim 6 The invention relating to the pile construction device is as follows: 5 In any one of the inventions described above, the carbon dioxide supply means supplies carbon dioxide at a concentration higher than that in the atmosphere. Claim 6In this invention, exhaust gas with a carbon dioxide concentration higher than the 400 to 500 ppm in the general atmosphere, or high-concentration carbon dioxide separated and recovered from exhaust gas, is supplied, which makes it possible to promote the reaction efficiency of the carbon dioxide supplied to the sealed container and the cement milk, thereby shortening the stirring time in the sealed container.As a result, it is not necessary to set the cement milk production time longer than necessary, and it is possible to maintain an appropriate construction yield.

[0018] Claim 7 The invention relating to the pile construction device is as follows: 6 In any of the inventions described above, the carbon dioxide supply means is characterized in that it supplies exhaust gas directly from construction equipment, including work vessels used during offshore construction, or it separates and recovers carbon dioxide from exhaust gas from construction equipment, including work vessels, and supplies the recovered carbon dioxide. Claim 7 In the invention, for example, when a deep mixing treatment method is used for offshore construction, the amount of carbon dioxide emitted during the construction can be minimized. [Effects of the Invention]

[0019] The pile construction device according to the present invention can fix carbon dioxide resulting from global warming in the ground when carrying out ground improvement work using cement milk, for example, by the Clean Dumping Method (CDM method). [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic diagram of a pile construction device according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram of the pile construction device according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. A pile construction device 1 according to an embodiment of the present invention comprises a mixer 10 into which cement from a cement silo 4, seawater from a seawater tank 5, and an admixture (e.g., an air-entraining water reducer) from an admixture storage tank 6 are supplied and stirred by a stirring device 24 to produce cement milk, a carbon dioxide supply means 11 for supplying carbon dioxide into the mixer container 23, a bubble generating means 12 arranged between the carbon dioxide supply means 11 and the mixer container 23 and for aerating the carbon dioxide from the carbon dioxide supply means 11, a carbon dioxide supply pipe 13 extending from the bubble generating means 12 and having its tip arranged in the cement milk in the mixer container 23, an agitator 14 to which the cement milk containing carbon dioxide in the mixer container 23 is supplied and which stirs the cement milk containing carbon dioxide in an agitator container 27 by a stirring device 28, and a pressure pump 15 for pressure-feeding the cement milk containing carbon dioxide in the agitator container 24 to a ground improvement machine 34.

[0022] The pile construction device 1 according to this embodiment is applied when improving soft ground on the seabed using a deep mixing treatment method (offshore construction). For this purpose, the pile construction device 1 according to this embodiment is placed on a work vessel 20. The mixer 10 includes a highly airtight mixer vessel 23 and an agitator 24 for agitating cement, seawater, and admixtures within the mixer vessel 23. Note that a gas, preferably carbon dioxide, is pumped into the air space within the mixer vessel 23, thereby maintaining the pressure in the air space within the mixer vessel 23 at a level greater than atmospheric pressure.

[0023] The carbon dioxide supply means 11 supplies carbon dioxide to the cement milk in the mixer container 23 via a bubble generating means 12 and a carbon dioxide supply pipe 13 (described later). The carbon dioxide supply means 11 may be a compressor that compresses and supplies a gas containing carbon dioxide. The carbon dioxide-containing gas may be atmospheric air containing carbon dioxide, or exhaust gas containing carbon dioxide emitted from the work vessel 20. The carbon dioxide supply means 11 may also be a cylinder or tank that separates, captures, and concentrates carbon dioxide from exhaust gas from construction equipment, including the work vessel 20, used to improve soft seabed ground using a deep mixing treatment method, or from other facilities containing such exhaust gas. The carbon dioxide supply means 11 may also be a cylinder or tank that stores compressed liquefied carbon dioxide in a factory or other facility. The concentration of carbon dioxide supplied from the carbon dioxide supply means 11 should preferably be higher than the typical atmospheric concentration of 400 to 500 ppm.

[0024] The bubble generating means 12 is disposed downstream of the carbon dioxide supplying means 11, between the carbon dioxide supplying means 11 and the mixer container 23. The bubble generating means 12 turns the carbon dioxide from the carbon dioxide supplying means 11 into bubbles. The bubble generating means 12 is connected to the carbon dioxide supplying means 11 and the carbon dioxide supply pipe 13. The diameter of the bubbles containing carbon dioxide generated by the bubble generating means 12 is set appropriately. That is, bubbles have the property that as their diameter increases, they tend to burst in water, but on the other hand, they rise to the water surface faster, and as their diameter decreases, the residence time of the bubbles in water before they burst can be lengthened.

[0025] In the pile construction device 1 according to this embodiment, the diameter of the carbon dioxide-containing bubbles is set to be relatively small in order to increase the residence time of the bubbles in the cement milk. In this embodiment, the carbon dioxide-containing bubbles generated by the bubble generating means 12 may be, for example, microbubbles, bubbles with a diameter on the order of micrometers, or nanobubbles, bubbles with a diameter on the order of nanometers.

[0026] The carbon dioxide supply pipe 13 extends from the bubble generating means 12 and is airtightly inserted into the mixer vessel 23, with its tip placed in the cement milk. It is preferable to bring the tip of the carbon dioxide supply pipe 13 as close as possible to the bottom surface of the mixer vessel 23. As a result, bubbles containing carbon dioxide from the bubble generating means 12 are aerated into the cement milk in the mixer vessel 23 through the carbon dioxide supply pipe 13. In addition, the cement milk containing carbon dioxide in the mixer vessel 23 is supplied into the agitator vessel 27 of the agitator 14.

[0027] The agitator 14 includes a highly airtight agitator container 27 and an agitator device 28 that agitates the cement milk containing carbon dioxide in the agitator container 27. The agitator container 27 is connected to the mixer container 23 via an openable / closeable valve (not shown). A pressure pipe 32 is connected to the agitator container 27 via an openable / closeable valve (not shown). The pressure pipe 32 is connected to the pressure pump 15. The pressure pipe 32 is connected to a flexible hose 33. The tip (lower end) of the flexible hose 33 that is connected to the pressure pipe 32 is positioned close to the upper part of the agitator blades 35A of the agitator shaft 35 that is a component of the ground improvement machine 34 and that penetrates the seabed ground while agitating it. In the pile construction device 1 according to this embodiment, the carbon dioxide supply pipe 13 is airtightly inserted into the mixer container 23, and its tip is disposed in the cement milk in the mixer container 23, but the carbon dioxide supply pipe 13 may be airtightly inserted into the agitator container 27, and its tip may be disposed in the cement milk in the agitator container 27. Alternatively, the carbon dioxide supply pipe 13 may be branched into two, and the tip of one carbon dioxide supply pipe 13 may be disposed in the cement milk in the mixer container 23, and the tip of the other carbon dioxide supply pipe 13 may be disposed in the cement milk in the agitator container 27.

[0028] Next, the operation of the pile construction device 1 according to this embodiment will be described. First, cement is fed into the mixer vessel 23 of the mixer 10 from the cement silo 4, seawater flows in from the seawater tank 5, and admixtures flow in from the admixture storage tank 6. The cement, seawater, and admixtures are supplied into the mixer vessel 23 at a predetermined mixing ratio using respective measuring devices (not shown). The cement, seawater, and admixtures in the mixer vessel 23 are then stirred and mixed by the stirrer 24, and cement milk is produced. At the same time, carbon dioxide is supplied from the carbon dioxide supply means 11 to the bubble generation means 12. Nanobubbles or microbubbles containing carbon dioxide are then generated in the bubble generation means 12. The nanobubbles or microbubbles containing carbon dioxide from the bubble generation means 12 are aerated into the cement milk in the mixer vessel 23 via the carbon dioxide supply pipe 13.

[0029] When the cement milk is stirred by the stirrer 24 in the mixer container 23, the nanobubbles or microbubbles containing carbon dioxide burst in the cement milk, dissolving the carbon dioxide in the cement milk. As a result, the cement milk reacts with the carbon dioxide to produce calcium carbonate (carbonate), and the calcium carbonate and ultimately the carbon dioxide are immobilized in the cement milk. Therefore, the concentration of the nanobubbled or microbubbled carbon dioxide supplied from the carbon dioxide supply means 11 via the bubble generation means 12 is higher than the concentration in the atmosphere, which is 400 to 500 ppm, and therefore the reaction efficiency can be promoted and the stirring time by the stirrer 24 of the mixer 10 can be shortened.

[0030] Therefore, even if the nano- or micro-bubbled carbon dioxide aerated in the cement milk in the mixer vessel 23 does not burst but rises to the surface in the cement milk and is released from the cement milk into the air, the pressure (air space) inside the sealed mixer vessel 23 is greater than atmospheric pressure, so the carbon dioxide released into the air space in the mixer vessel 23 becomes more likely to dissolve in the cement milk. Subsequently, the cement milk containing carbon dioxide and calcium carbonate is supplied into the agitator vessel 27 of the agitator 14 and stirred again by the stirring device 28.

[0031] Next, the cement milk containing carbon dioxide and calcium carbonate in the agitator vessel 27 is pumped by the pressure pump 15 through the pressure pipe 32 and flexible hose 33 to a position in the ground close to the top of the mixing blades 35A of the mixing shaft 35. Then, as the mixing shaft 35 rotates and is pulled out of the ground, the cement milk containing carbon dioxide and calcium carbonate discharged from the tip of the flexible hose 33 and the surrounding soil and sand in the ground are mixed by the mixing blades 35A to create a cement-improved pile (not shown).

[0032] Furthermore, the carbon dioxide is bubbled as nano- or micro-bubbles by the bubble generating means 12 and aerated into the cement milk, thereby lengthening the residence time of the carbon dioxide in the cement milk. As a result, the aerated carbon dioxide can be maintained in a state in which it can dissolve in the cement milk throughout the entire process of constructing cement-improved piles, from the mixing stage in the mixer vessel 23 and the agitator vessel 27, to the pumping stage through the pumping pipe 32, the mixing stage with the surrounding soil and sand in the ground, and the hardening stage of the improved ground, and the carbon dioxide can react with the cement milk at any stage of the entire process to reliably produce calcium carbonate.

[0033] As described above, the pile construction device 1 according to this embodiment includes at least the mixer container 23 (sealed container) of the airtight mixer 10 into which cement and water are poured and stirred to produce cement milk, carbon dioxide supply means 11 that supplies carbon dioxide into the mixer container 23, and a pressure pipe 32 that pressure-feeds the cement milk containing carbon dioxide in the mixer container 23 into the ground. As a result, carbon dioxide is supplied into the airtight mixer container 23 of the mixer 10, so that the carbon dioxide can be easily dissolved in the cement milk. In short, by using the airtight mixer container 23, the carbon dioxide supplied into the mixer container 23 cannot escape to the outside, thereby improving the efficiency of dissolving the carbon dioxide in the cement milk.

[0034] Carbon dioxide resulting from global warming reacts with the cement milk to form improved piles containing calcium carbonate, which are then immobilized in the ground. In other words, carbon dioxide reacts with the cement milk to form improved piles containing calcium carbonate, which are chemically immobilized in the ground. Furthermore, the formation of calcium carbonate increases the strength of the improved piles, and as a result of this increased strength due to the formation of calcium carbonate, the amount of cement added can be reduced.

[0035] In the pile construction device 1 according to this embodiment, an admixture, such as an AE admixture, is mixed into the mixer container 23 of the mixer 10. A delayed AE admixture is often used as this AE admixture. The effect of the AE admixture is that by reducing the amount of water added, the total amount of cement milk supplied to the ground can be reduced, preventing the ground from becoming loose and ensuring strength quality. Reducing the amount of pumped cement milk also leads to improved construction efficiency. Furthermore, using a delayed AE admixture makes it difficult for the cement milk to harden during the time it takes for the agitator shaft 35 of the ground improvement machine 34 to excavate to a predetermined depth.

[0036] On the other hand, adding an AE admixture causes a certain amount of air to be contained in the cement milk. Therefore, the carbon dioxide contained in this amount of contained air is physically fixed in the ground in addition to being chemically fixed in the ground as calcium carbonate by reaction with the cement milk as described above. Therefore, for example, the amount of AE admixture added is set to 2.5 to 4.0 times the amount of cement added. This increases the amount of gas contained in the cement milk, allowing more carbon dioxide to be contained in the increased gas and physically fixed.

[0037] Furthermore, according to the pile construction device 1 of this embodiment, the pressure in the air inside the mixer vessel 23 is set higher than atmospheric pressure. As a result, the rate at which carbon dioxide dissolves in the cement milk can be increased. This can promote the reaction between carbon dioxide and cement milk.

[0038] Furthermore, according to the pile construction device 1 of this embodiment, the carbon dioxide supply means 11 supplies carbon dioxide at a concentration higher than that in the atmosphere. As a result, it is possible to promote the reaction efficiency of the carbon dioxide supplied into the mixer vessel 23 reacting with the cement milk, and it is possible to shorten the mixing time in the mixer vessel 23 of the mixer 10. As a result, it is not necessary to set the production time of the cement milk longer than necessary, and it is possible to maintain an appropriate construction yield.

[0039] Furthermore, the pile construction device 1 according to this embodiment is provided with bubble generating means 12, which is disposed downstream of the carbon dioxide supply means 11, i.e., between the carbon dioxide supply means 11 and the mixer vessel 23, and which bubbles the carbon dioxide from the carbon dioxide supply means 11. By bubbling the carbon dioxide with the bubble generating means 12, the residence time of the carbon dioxide in the cement milk can be extended. This allows the aerated carbon dioxide to be dissolved in the cement milk throughout all steps of the construction of cement-improved piles, from the mixing stage in the mixer vessel 23 and the agitator vessel 27 to the hardening stage of the improved ground, and makes it possible to reliably produce calcium carbonate at any stage of the entire process.

[0040] Furthermore, in the carbon dioxide supply means 11 of the pile construction device 1 according to this embodiment, when an embodiment is adopted in which the exhaust gas from the construction equipment including the work vessel 20 when using the deep mixing treatment method for offshore construction is supplied as is, or the carbon dioxide in the exhaust gas from the construction equipment including the work vessel 20 is separated and recovered and supplied, the amount of carbon dioxide emitted during the construction can be minimized, particularly when using the deep mixing treatment method for offshore construction.

[0041] In the pile construction device 1 according to the present embodiment described above, the bubble generating means 12 is provided, and the carbon dioxide supply pipe 13 is airtightly inserted into the mixer container 23, with its tip placed in the cement milk; however, it is also possible to not provide the bubble generating means 12, but to connect the carbon dioxide supply pipe 13 directly to the carbon dioxide supply means 11, and insert the carbon dioxide supply pipe 13 airtightly into the mixer container 23, with its tip placed in the air inside the mixer container 23 or in the cement milk.

[0042] Therefore, in an embodiment in which the tip of the carbon dioxide supply pipe 13 is placed in the cement milk in the mixer container 23, carbon dioxide from the carbon dioxide supply means 11 can be directly supplied into the cement milk. Then, the carbon dioxide is aerated into the cement milk, and the bubbles containing carbon dioxide easily burst while rising, so the rate at which the carbon dioxide dissolves into the cement milk can be increased. As a result, the reaction between the carbon dioxide and the cement milk is further promoted.

[0043] Furthermore, in the pile construction device 1 according to this embodiment, the carbon dioxide supply pipe 13 extending from the bubble generating means 12 is airtightly inserted into the mixer container 23, and its tip is placed in the cement milk, but in other embodiments of the pile construction device 1, the tip of the carbon dioxide supply pipe 13 extending from the bubble generating means 12 may be connected to the pressure pipe 32, and the carbon dioxide supply pipe 13 and the pressure pipe 32 may be connected to each other.

[0044] In the pile construction apparatus 1 according to this other embodiment, the mixer vessel 23 and the agitator vessel 27 do not need to be airtight vessels with high airtightness, and they may simply be agitator vessels for mixing cement, water, and admixtures. In the pile construction apparatus 1 according to this embodiment, the cement milk is pumped through the pressure pipe 32 at a pressure significantly greater than atmospheric pressure, and carbon dioxide is pumped into the cement milk in the pressure pipe 32 at a pressure approximately equal to the pressure of the pumping, so that the carbon dioxide does not float to the surface and is easily dissolved in the cement milk, thereby forming an improved pile containing calcium carbonate.

[0045] 1, the carbon dioxide supply pipe 13 may be branched into two, with the tip of one of the carbon dioxide supply pipes 13 being placed in the cement milk in the mixer vessel 23, and the tip of the other carbon dioxide supply pipe 13 being connected to the pressure pipe 32. Also, the pile construction apparatus 1 according to the embodiment shown in FIG. 1 may be branched into three, with the tips of two of the carbon dioxide supply pipes 13 being placed in the cement milk in the mixer vessel 23 and the agitator vessel 27, respectively, and the tip of the remaining carbon dioxide supply pipe 13 being connected to the pressure pipe 32.

[0046] The pile construction device 1 according to the present embodiment described above is used when improving soft ground on the seabed using the deep mixing treatment method, but it may also be used when improving soft ground on land. Furthermore, although the pile construction device 1 according to the present embodiment is used for the deep mixing treatment method, it can also be used for other ground improvement methods using cement milk. [Explanation of symbols]

[0047] 1 pile construction device, 10 mixer (sealed container), 11 carbon dioxide supply means, 12 bubble generating means, 13 carbon dioxide supply pipe, 14 agitator, 15 pressure pump, 20 work vessel, 23 mixer container, 27 agitator container, 32 pressure pipe, 34 ground improvement machine

Claims

1. A pile construction device that pumps and mixes cement milk into the ground to create cement-improved piles, an airtight container into which cement and water are poured and stirred to produce cement milk; a carbon dioxide supply means for supplying carbon dioxide into the sealed container; A pressure pipe for pressure-feeding the cement milk containing carbon dioxide in the sealed container into the ground; Equipped with The sealed container includes a mixer container and an agitator container that communicate with each other, A pile construction apparatus characterized in that carbon dioxide from the carbon dioxide supply means is supplied into the cement milk in the mixer vessel and / or the cement milk in the agitator vessel.

2. A pile construction device that pumps and mixes cement milk into the ground to create cement-improved piles, an airtight container into which cement and water are poured and stirred to produce cement milk; a carbon dioxide supply means for supplying carbon dioxide into the sealed container; A pressure pipe for pressure-feeding the cement milk containing carbon dioxide in the sealed container into the ground; Equipped with The sealed container includes a mixer container and an agitator container that communicate with each other, A pile construction device characterized in that carbon dioxide from the carbon dioxide supply means is supplied into the cement milk in the mixer vessel and into the cement milk in the agitator vessel.

3. A pile construction device that pumps and mixes cement milk into the ground to create cement-improved piles, an airtight container into which cement and water are poured and stirred to produce cement milk; a carbon dioxide supply means for supplying carbon dioxide into the sealed container; a bubble generating means disposed downstream of the carbon dioxide supply means for generating bubbles from the carbon dioxide from the carbon dioxide supply means; A pressure pipe for pressure-feeding the cement milk containing carbon dioxide in the sealed container into the ground; A pile construction device comprising:

4. 4. The pile construction device according to claim 1, wherein the pressure in the air space inside the sealed container is made higher than atmospheric pressure.

5. A pile construction device that pumps and mixes cement milk into the ground to create cement-improved piles, a mixing vessel into which cement and water are poured and which mixes the cement and water to produce cement milk; a pressure pipe for pressure-feeding the cement milk in the agitation vessel into the ground; a carbon dioxide supply means for supplying carbon dioxide into the pressure pipe; a bubble generating means disposed downstream of the carbon dioxide supply means for generating bubbles from the carbon dioxide from the carbon dioxide supply means; A pile construction device comprising:

6. 6. The pile construction device according to claim 1, wherein the carbon dioxide supplying means supplies carbon dioxide having a concentration higher than that in the atmosphere.

7. A pile construction device as described in any one of claims 1 to 6, characterized in that the carbon dioxide supply means supplies exhaust gas from construction equipment, including work vessels used during offshore construction, as is, or separates and recovers carbon dioxide from exhaust gas from construction equipment, including work vessels, and supplies the recovered carbon dioxide.

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