Method and system for mixing mud and steel-making slag

Abstract

To provide a method and system for mixing mud and steel-making slag which can obtain a sufficient mixing effect without performing special outfitting on a vessel, when mud such as dredge soil and steel-making slag are mixed by dropping while using a reclaimer vessel.SOLUTION: A method for mixing mud and steel-making slag is a method for mixing steel-making slag with mud using a reclaimer vessel having a conveyor, supplies steel-making slag to mud in an earth carrying barge, mixes the mud and the steel-making slag by a backhoe in a predetermined mixing time so as to obtain the quality corresponding to one time of dropping and mixing with a height of 2 m or more, supplies the mixed material to the reclaimer vessel and conveys the mixed material by a conveyor, drops and mixes the mixed material at a height of 2 m or more, and drops and mixes the mixed material at the height of 2 m or more at least twice.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method and system for mixing mud such as dredged soil with steelmaking slag. [Background technology]

[0002] Drop mixing has been known as a conventional method for mixing calcia-improved soil (a mixture of dredged soil and steelmaking slag / Non-Patent Document 5) (Patent Document 1). It has been reported that drop mixing from a height of 2 m or more three times can achieve a predetermined strength and wet density in the calcia-improved soil (Non-Patent Document 1).

[0003] A reclaimer ship is a work vessel that uses a backhoe or other tool to unload soil transported by a soil carrier during offshore reclamation work and other such work, and then discharges it to a landfill site or other location via a conveyor. When using such a reclaimer ship for drop mixing, the ship must be outfitted with equipment for supplying steelmaking slag, among other things. Furthermore, because two drop mixing steps are performed when discharging from the reclaimer ship, a third drop mixing step must be performed on land (Non-Patent Document 2, Patent Document 1).

[0004] Figure 7 shows a schematic diagram of conventional drop mixing using a reclaimer ship. The reclaimer ship in Figure 7 uses a backhoe BH or similar device to load dredged soil and calcia modifier such as steelmaking slag into a hopper HP at a specified volume ratio, which then supplies the material from the hopper HP to a belt conveyor BC. The first drop mixing occurs during this supply period, and the mixed material is then transported by the belt conveyor BC and supplied to a storage tank on land, where the second drop mixing occurs during this supply period. The mixed material is transported from the storage tank by a transport vehicle DP such as a dump truck, and then dumped from the transport vehicle DP into the landfill, where the third drop mixing occurs during this supply period.

[0005] Furthermore, in order to improve the efficiency of drop mixing, a calcia drop mixing vessel has been developed that is equipped with a calcia modifier supply system and adds a conveyor, as shown in Figure 8, and completes the third drop mixing at the time of discharge (Non-Patent Document 4, Patent Document 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-173285 [Patent Document 2] Japanese Patent Application Publication No. 2020-066916 [Non-patent literature]

[0007] [Non-Patent Document 1] Yosuke Yamakoshi, Yuzo Akashi, Hiroki Kanno, Yuichi Tanaka, Ayumu Matsumoto, and Takashi Shibuya, "Landfilling of CaO-improved Soil by Drop Mixing Method," 69th Annual Conference of the Japan Society of Civil Engineers, VI-312, pp. 623-624, 2014. http: / / library.jsce.or.jp / jsce / open / 00035 / 2014 / 69-06 / 69-06-0312.pdf [Non-patent document 2] Yuichi Tanaka, Masamasa Taka, Tadashi Imamura, Takashi Shibuya, Yosuke Yamakoshi, Yuzo Akashi, Yoshiyuki Kitano, and Hiroki Kanno, "Sea reclamation using improved calcia soil," Journal of the Japan Society of Civil Engineers, Vol. 70, No. 2, pp. I_888-I_893, 2014. https: / / www.jstage.jst.go.jp / article / jscejoe / 70 / 2 / 70_I_888 / _pdf / -char / ja [Non-patent document 3] Yuichi Tanaka, Kenichi Nakajima, and Soichiro Nonaka, "Mixing Characteristics of a Calcia Drop Mixing Ship," 76th Annual Academic Conference of the Japan Society of Civil Engineers, VI-65, 2021. [Non-patent document 4] Yuichi Tanaka, "Ocean 3, the Calcia Drop Mixing Ship - Large-scale, high-quality construction of improved soil is possible," Marine Voice 21 Autumn 2021, Vol. 35, pp. 16-19, https: / / www.umeshunkyo.or.jp / ronbun / pdf / MarineVoice_315b.pdf [Non-Patent Document 5] "Technical Manual for Utilizing Calcium-Improved Soil," Coastal Technology Center, 2017 [Non-patent document 6] Yosuke Yamakoshi, Yuzo Akashi, Hiroki Kanno, Yuichi Tanaka, Ayumu Matsumoto, and Takashi Shibuya, "Landfilling of CaO-improved Soil by Drop Mixing Method," 69th Annual Meeting of the Japan Society of Civil Engineers (September 2014) Summary of the Invention [Problem to be solved by the invention]

[0008] When using a reclaimer ship to mix dredged soil and steelmaking slag, it is necessary to equip the reclaimer ship with equipment such as a steelmaking slag supply system, as shown in Figure 7. However, because this equipment increases construction time and costs, it is possible to omit it. However, if the steelmaking slag supply system is omitted, it will not be possible to supply steelmaking slag in the specified ratio, and it will not be possible to ensure three mixing drops.

[0009] In view of the problems of the prior art as described above, the present invention aims to provide a method and system for mixing mud and steelmaking slag that can achieve a sufficient mixing effect when using a reclaimer ship to drop and mix mud such as dredged soil with steelmaking slag, without requiring any special equipment on the ship. [Means for solving the problem]

[0010] A method for mixing mud and steelmaking slag to achieve the above object is a method for mixing mud and steelmaking slag using a work vessel equipped with a conveyor, Steelmaking slag is supplied to the mud inside the soil transport barge, and the mud and steelmaking slag are mixed using a backhoe for a specified mixing time so as to obtain a quality equivalent to one drop mixing from a height of 2m or more. The mixed material is then supplied to the work barge, transported by the conveyor, and dropped and mixed from a height of 2m or more. The mixed material is then dropped and mixed from a height of 2m or more at least twice.

[0011] According to this method of mixing mud and steelmaking slag, before drop mixing on the work ship, the mud and steelmaking slag are mixed with a backhoe on the soil transport ship to a height of 2 meters or more to achieve the quality required for a single drop mixing. Therefore, by performing drop mixing on the work ship at least two times, a mixed material equivalent to that obtained by performing drop mixing at least three times can be obtained. As a result, a sufficient mixing effect can be achieved without the need for special equipment such as a steelmaking slag supply system on the work ship, and mixed quality can be ensured. Furthermore, because the mud and steelmaking slag are already mixed when the mixed material is delivered from the soil transport ship to the work ship's conveyor, this prevents the steelmaking slag from scattering during the first drop mixing on the work ship's conveyor, which can prevent sufficient mixing, contributing to ensuring mixed quality.

[0012] In the above-mentioned method for mixing mud and steelmaking slag, it is preferable to set the mixing time to the time required to achieve at least one of the qualities of wet density, strength, suspended solids, or turbidity corresponding to one drop mixing, which more reliably ensures the quality of the mixture.

[0013] In this case, it is preferable to carry out a mixing time test in advance for at least one of the wet density, strength, amount of suspended solids or turbidity, and to set the mixing time based on the test results.

[0014] It is also preferable that the mixing time be set taking into consideration the volume of the mixed material in the soil transport barge and the bucket volume of the backhoe.

[0015] Alternatively, the mixing time may be set constant, and at least one of the water content of the mud, the particle size of the steelmaking slag, and the mixing ratio of the steelmaking slag may be set so as to obtain the target strength of the mixed material. This makes it possible to deal with cases where it is difficult to ensure a long mixing time (e.g., 120 minutes or more), where a strength equivalent to one drop mixing cannot be obtained in a normal mixing time (e.g., 60 minutes), or where it is difficult to conduct a preliminary mixing time test. The mixing time is preferably within the range of 30 to 120 minutes.

[0016] In this case, it is preferable to conduct a blending test in advance for at least one of the water content of the mud, the particle size of the steelmaking slag, and the mixing ratio of the steelmaking slag, and to set the above-mentioned parameters based on the test results.

[0017] Furthermore, it is preferable to confirm that the mud and steelmaking slag are mixed at a predetermined ratio in the bucket of the backhoe when mixing with the backhoe, and then supply the mixed material to the work ship. The predetermined mixing ratio of the mud and steelmaking slag in the bucket can be confirmed by measuring the wet density.

[0018] Alternatively, the mixed material may be dropped into a soil hopper before being transported by the conveyor to perform drop mixing. If the height is less than 2 m, this drop mixing is considered supplementary, and if the height is 2 m or more, it is considered additional drop mixing. In the case of additional drop mixing at a height of 2 m or more, drop mixing at a height of 2 m or more may be performed once by the conveyor.

[0019] It is preferable that the backhoe is installed on the work boat, and the soil transport boat approaches the work boat to perform the mixing.

[0020] Alternatively, the backhoe may be installed on land, the soil transport boat may be brought ashore to perform the mixing, and after the mixing, the soil transport boat may be brought close to the work boat to supply the mixed material to the work boat.

[0021] In addition, other additive materials may be added and mixed when mixing with the backhoe.

[0022] It is also preferable to mix the mud in the soil transport barge with the steelmaking slag in a predetermined volume ratio.

[0023] Furthermore, it is preferable that the final destination of the dropping mixture on the work boat is the area where the mixed material is used, a soil transport boat, or the hopper of a tremie pipe.

[0024] In addition, if the final destination of the drop mixing on the work boat is land and the mixed material is dropped to a height of 2 m or more when it is put into the use area after dropping on land, drop mixing to a height of 2 m or more on the work boat may be performed at least once.

[0025] A mud and steelmaking slag mixing system for achieving the above object includes a work vessel having a conveyor, a soil transport vessel for transporting mud, and a backhoe for mixing the mud in the soil transport vessel with the steelmaking slag supplied to the soil transport vessel, The mixed material of the mud and the steelmaking slag is mixed by the backhoe for a predetermined mixing time so as to obtain the quality required for one drop mixing at a height of 2 m or more. The mixed material is supplied to the work ship, transported by the conveyor, and dropped to a height of 2 m or more for mixing. The mixed material is dropped and mixed from a height of 2 m or more at least twice.

[0026] According to this mud and steelmaking slag mixing system, before drop mixing on the work boat, the mud and steelmaking slag are mixed with a backhoe on the soil transport boat to achieve the quality required for a single drop mix from a height of 2m or more. Therefore, by performing drop mixing on the work boat at least two times, a mixed material equivalent to that obtained by drop mixing at least three times can be obtained. As a result, a sufficient mixing effect can be obtained without special equipment being required on the work boat.

[0027] In the above-mentioned mixing system, the work vessel has at least two of the conveyors, so that dropping mixing from a height of 2 m or more can be performed at least twice.

[0028] The work vessel may also have a soil hopper to which the mixed material is supplied, the soil hopper being configured to perform drop mixing of the supplied mixed material to a height of 2 m or more, and the drop-mixed mixed material may be supplied from the soil hopper to the conveyor. In this case, there may be only one conveyor performing drop mixing to a height of 2 m or more.

[0029] In the above-mentioned mixing method and system, the mud is preferably dredged soil, sandy soil, or mud with a fine particle content of 20% or more. [Effects of the Invention]

[0030] According to the method and system for mixing mud and steelmaking slag of the present invention, when mud such as dredged soil and steelmaking slag are dropped and mixed using a work vessel such as a reclaimer vessel, a sufficient mixing effect can be obtained without the need to equip the work vessel such as a reclaimer vessel with any special equipment. [Brief explanation of the drawings]

[0031] [Figure 1] 1 is a top view schematically showing a mud and steelmaking slag mixing system according to the present embodiment. FIG. [Figure 2] FIG. 2 is a side view showing a schematic diagram of the mixing system of FIG. 1. [Figure 3] 3 is a flowchart illustrating steps in a method for mixing mud and steelmaking slag using the mixing system of FIGS. 1 and 2. [Figure 4] 1A to 1C are diagrams showing the relationship between the number of drops (1 to 3 times) in a calcia drop mixing vessel and the variation in unconfined compressive strength in Non-Patent Document 3. [Figure 5] 1 is a graph showing the relationship between data intervals and frequency, illustrating an example of measurement of wet density after the first drop mixing. [Figure 6] 10 is a graph showing an example of measurement of mixing time and coefficient of variation obtained by a mixing time test during backhoe mixing. [Figure 7] FIG. 1 is a schematic diagram showing the construction of drop mixing using a conventional reclaimer ship. [Figure 8]FIG. 1 is a schematic diagram showing the construction of drop mixing using a conventional calcia drop mixing vessel. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a top view schematically showing a mud and steelmaking slag mixing system according to this embodiment. Fig. 2 is a side view schematically showing the mixing system of Fig. 1. Fig. 3 is a flowchart for explaining steps of a method for mixing mud and steelmaking slag using the mixing system of Figs. 1 and 2.

[0033] As shown in Figures 1 and 2, the mud and steelmaking slag mixing system 10 of this embodiment comprises a reclaimer ship 1, which is a work vessel having a conveyor 11 and a boom conveyor 12, a soil transport ship 2 that transports dredged soil and is moored alongside the reclaimer ship 1, a backhoe 13 mounted on the reclaimer ship 1, and a soil hopper 14 installed on the reclaimer ship 1 to temporarily store the mixed material of dredged soil and steelmaking slag.The backhoe 13 mixes the dredged soil in the soil transport ship 2 with the steelmaking slag supplied into the soil transport ship 2 from the gut barge 3, and supplies the mixed material to the soil hopper 14.The conveyor 11 transports the mixed material and performs a first drop mixing from a height of 2m or more, and then the boom conveyor 12 performs a second drop mixing from a height of 2m or more.

[0034] Each step S01 to S11 of the mixing method using the mixing system 10 of Figures 1 and 2 will be described with reference to Figure 3. First, a soil transporter 2 transports dredged soil (S01) and is brought alongside the reclaimer ship 1. Then, a gut barge 3 loaded with steelmaking slag is brought alongside the soil transporter 2, and the steelmaking slag is supplied in a predetermined volume ratio from the gut barge 3 in direction A to the dredged soil stored in a soil basin 2a inside the soil transporter 2 (S02). Note that the gut barge 3 may be replaced with a gut ship.

[0035] Next, the backhoe 13 uses the bucket 13a to mix the dredged soil and steelmaking slag in the soil tank 2a of the soil transport ship 2 for a predetermined mixing time (S03). This predetermined mixing time is a time that will produce a quality equivalent to one drop mixing from a height of 2 m or more.

[0036] Next, it is confirmed that the dredged soil and steelmaking slag mixed in the soil transport barge 2 are in a predetermined mixing ratio in the bucket 13a of the backhoe 13 (S04). The mixing ratio of the dredged soil and steelmaking slag in the bucket 13a can be confirmed, for example, by measuring the wet density, which will be described later. Note that this step S04 is preferably carried out as necessary for quality control purposes.

[0037] Next, the mixed material is supplied from the soil tank 2a of the soil transport ship 2 to the soil hopper 14 in direction B by the bucket 13a of the backhoe 13 shown by the dashed line in Figure 2 (S05). Next, the mixed material is supplied from the bottom of the soil hopper 14 in direction C to the lower end of the conveyor 11, and the conveyor 11 transports the mixed material diagonally upward D (first transport S06).

[0038] The mixed material transported by the conveyor 11 is dropped from the upper end 11a of the conveyor 11 near the lower end of the boom conveyor 12 below, thereby performing a first drop mixing from a height of 2m or more (S07). Next, the boom conveyor 12 transports the dropped mixed material diagonally upward D (second transport S08), and the upper end 12a of the boom conveyor 12 drops the mixed material into the soil tank 5a of another soil transport ship 5 below, thereby performing a second drop mixing from a height of 2m or more (S09).

[0039] Next, when the mixed material in the soil tank 5a reaches a predetermined amount, the soil transport ship 5 moves to a predetermined water area (sea area) (S10) and dumps or crabs the transported mixed material directly into the water (sea) (S11).

[0040] According to the method and system for mixing dredged soil and steelmaking slag shown in Figures 1 to 3, before drop mixing is performed on the reclaimer ship 1, the dredged soil and steelmaking slag are mixed with a backhoe 13 inside the soil transport ship 2 for a predetermined mixing time that will achieve the quality required for one drop mixing from a height of 2m or more, so that by performing drop mixing from a height of 2m or more twice on the reclaimer ship 1, a mixed material equivalent to that obtained by performing drop mixing three times can be obtained. Therefore, a sufficient mixing effect can be obtained and mixed quality can be ensured without providing special equipment such as steelmaking slag supply equipment on the reclaimer ship 1.

[0041] Furthermore, the predetermined mixing time in step S03 is the mixing time required to obtain the quality equivalent to one drop mixing (one, two, or all of wet density, strength, suspended solids, and turbidity), thereby ensuring mixing quality more reliably. The required mixing time can be determined from a prior mixing time test and literature values ​​(such as the coefficient of variation described below). The mixing time is also set taking into consideration the volume of the material to be mixed in the soil transport barge 2 and the bucket capacity of the backhoe 13 (if there are multiple backhoes, the total capacity of the multiple buckets).

[0042] To set the required mixing time, a preliminary mixing time test is conducted in which samples are taken at regular intervals to measure changes in wet density, strength, suspended solids (SS) or turbidity. Wet density can be calculated using a bucket scale or similar. One example of a bucket scale that can be used is the Bucket Scale / LOADEX100 (product name) sold by Nihon Martz Co., Ltd. The preliminary mixing time test can also be conducted by measuring wet density and other parameters at regular intervals during the initial mixing of construction.

[0043] The amount of suspended solids or turbidity can be measured by conducting simulated experiments indoors, for example, using a method such as that shown in Figure 2 in "Verification of submerged breakwater construction methods using calcium carbonate-modified dredged soil to reduce pollution - Understanding turbidity characteristics" by Izumi et al. (Journal of the Japan Society of Civil Engineers, B3 (Marine Development), Vol. 75, No. 2, I_887-I_892, 2019 https: / / www.jstage.jst.go.jp / article / jscejoe / 75 / 2 / 75_I_887 / _pdf / -char / ja).

[0044] When strength is used as an indicator of quality, using Figures 4(a) to (c), which show the relationship between the number of drops in a calcia drop mixing boat and the variation in unconfined compressive strength as strength, as shown in Figure 8, as an example, the mixing time is set based on a separate backhoe mixing time test (samples are prepared for each mixing time, and specimens are prepared and strength tests are performed) so that the coefficient of variation or strength is close to the coefficient of variation of 0.332 (literature value) for the first drop mixing. Note that with regard to strength, the results of a cone penetration test or vane shear test may be used instead of the unconfined compressive strength test results.

[0045] Figure 5 is a graph showing the relationship between data intervals and frequency, illustrating an example of measurement of wet density in the first drop mixing, and is a measurement value obtained after one drop mixing (on the spreader) of dredged soil with a water content of 164.8% and steelmaking slag with a mixing ratio of 30 vol% on a reclaimer ship as shown in Figure 7. This measurement was performed on a different day from the drop mixing described in Non-Patent Document 6, when the test in that paper was conducted.

[0046] Figure 6 is a graph showing an example of the measurement of the mixing time and the coefficient of variation obtained by the mixing time test when mixing with a backhoe. 3 Two backhoes were used to mix dredged soil with a moisture content of 114.4% with steelmaking slag at a mixing ratio of 30 vol%, and samples were taken at eight points at regular intervals to measure the wet density and calculate the coefficient of variation.

[0047] When wet density is used as an indicator of quality, the mixing time is set based on a mixing time test, with the backhoe mixing time corresponding to 0.038, which is the coefficient of variation of the wet density of the first drop mix, as shown in Figure 5. For example, when applied to Figure 6, the mixing time becomes 33 minutes, as shown by the dashed line in the figure.

[0048] Furthermore, by dropping the mixed material after backhoe mixing inside the soil transport ship 2 into the soil hopper 14 in step S05, which supplies the mixed material to the reclaimer ship 1, supplemental dropping mixing can be performed, for example, once at a height of 1m, which contributes to improving the mixing quality. Furthermore, if a drop height of 2m or more can be ensured in the soil hopper 14, backhoe mixing plus three times of dropping mixing at a height of 2m or more can be performed, which further contributes to improving the mixing quality. Alternatively, dropping mixing at a height of 2m or more using a conveyor can be performed only once.

[0049] As described above, according to this embodiment, until the mixed material has been completely removed from the reclaimer ship 1, that is, until the final drop mixing to the drop destination on the reclaimer ship 1 is completed, the mixed material is subjected to two drop mixings at a height of 2m or more, including two drop mixings by conveyor, and one drop mixing in a soil hopper plus one drop mixing by conveyor.

[0050] Furthermore, by equipping the backhoe 13 used for backhoe mixing with a machine guidance system (see, for example, JP 2022-142443 A) and mixing the inside of the soil barge evenly, the required mixing time can be shortened. Furthermore, when supplying steelmaking slag to the soil barge 2, a guidance system for supplying the slag evenly onto the soil barge 2 may be used (for example, by dividing the soil tank of the soil barge into four sections along its length and adjusting the number of times steelmaking slag is added to each section).

[0051] In addition, in Figures 1 to 3, backhoe mixing is performed using a backhoe 13 mounted on the reclaimer ship 1, but this is not limited to this.A soil transport ship may be docked in advance, and a backhoe installed on a quay or the like may be used to perform backhoe mixing as a single drop mix on the soil transport ship, and then the mixed material may be transported and supplied to the reclaimer ship 1.

[0052] In addition, the mixing time for backhoe mixing can be set to a fixed time, for example, within a range of 30 to 120 minutes, and at least one of the moisture content of the dredged soil, the particle size of the steelmaking slag, and the volumetric mixing ratio of the steelmaking slag can be set so that the target strength of the mixed material is obtained. This makes it possible to deal with cases where it is difficult to ensure a mixing time longer than 120 minutes, where a normal mixing time (for example, 60 minutes) cannot achieve the quality, such as strength, equivalent to one drop mixing, or where it is difficult to conduct a preliminary mixing time test.

[0053] That is, for example, if it is difficult to ensure a mixing time of 120 minutes because long mixing times reduce construction efficiency, or if 60 minutes of mixing with a backhoe does not achieve the strength equivalent to one drop mix, then a mix that is likely to provide strength should be selected.Mixtures that are likely to provide strength include reducing the particle size of the steelmaking slag (for example, changing the maximum particle size from 25 mm or less to 5 mm or less), increasing the steelmaking slag mixing ratio (for example, changing from 20 vol% to 30 vol%), and reducing the water content of the dredged soil, and multiple combinations of these can also be used.

[0054] The mixing ratio of steelmaking slag is affected by the water content of the dredged soil and the particle size of the steelmaking slag, so it is preferable to select a mix that will provide the required strength through prior mix testing. Also, selecting a mix with sufficient margin based on the results of prior mix testing will more reliably ensure strength during construction.

[0055] The key to the drop mixing method is to supply dredged soil and steelmaking slag to the conveyor at a specified ratio. For example, if 7m of the conveyor is filled with only dredged soil and 3m with only steelmaking slag, even if the ratio is 7:3 when viewed from a 10m distance on the conveyor, only dredged soil and slag will collide with the inclined plate when dropped, and the expected drop mixing effect will not be achieved. For this reason, backhoe mixing on the soil transport ship is performed using the bucket capacity (10m in the case of a reclaimer ship). 3 ~12m 3 It is necessary to mix them to the specified ratio within the range of (approximately) the specified ratio.

[0056] Furthermore, in the drop mixing method, dredged soil and steelmaking slag are supplied onto the conveyor in sequence, and if the dredged soil and steelmaking slag are not mixed sufficiently, the steelmaking slag may fly out when the dredged soil falls from the belt conveyor, and the required amount of steelmaking slag may not be mixed with the dredged soil.Therefore, it is desirable that the steelmaking slag is mixed with the dredged soil on the belt conveyor so that it does not fly out during drop mixing.

[0057] Furthermore, when using calcia-improved soil as a ground material, it is necessary to ensure the target strength, and strict control of strength and density is carried out. However, when the purpose is to suppress contamination in deep excavation backfilling, etc., variations in strength and density are acceptable.

[0058] Although the embodiments for carrying out the present invention have been described above, the present invention is not limited to these, and various modifications are possible within the scope of the technical concept of the present invention. For example, in Figures 1 to 3, the second dropping mixture S09 is dropped into the soil transport barge 5, but the present invention is not limited to this, and the dropping destination may be the hopper of a tremie pipe or an area of ​​use (for example, the back of a revetment).

[0059] In addition, if the destination of the boom conveyor 12 in Figures 1 and 2 is land, and the mixed material is dropped and mixed to a height of 2 m or more when it is poured into the usage area after being dropped on land, it is acceptable to perform drop mixing to a height of 2 m or more on the reclaimer ship at least once.

[0060] In addition, the mud targeted by this invention is preferably 2.0 × wL or less, since high moisture content exceeding 2.0 × wL (wL: liquid limit) is likely to cause material separation problems. In the case of high moisture content exceeding 2.0 × wL, it is preferable to add a modifier such as PS ash before mixing with the backhoe.

[0061] Other additive materials may also be added as needed. In addition to the modifiers mentioned above, such additive materials include, for example, ground blast furnace slag, lime, and cement to ensure strength, and carbon materials such as biochar for carbon storage and carbon dioxide fixation, calcium carbonate, and seashells (effective utilization). While it is difficult to install additional supply systems for these materials on drop mixer ships or reclaimer ships, the present invention performs backhoe mixing prior to drop mixing, making it easy to add these additive materials. [Industrial Applicability]

[0062] According to the method and system for mixing mud and steelmaking slag of the present invention, when backhoe mixing is performed before drop mixing and mud such as dredged soil and steelmaking slag are drop mixed using a work vessel such as a reclaimer vessel, a sufficient mixing effect can be obtained without special equipment being provided on the work vessel such as a reclaimer vessel, and the mud and steelmaking slag are sufficiently mixed during drop mixing, so that the cost of mixing work is reduced and mixing quality can be ensured. [Explanation of symbols]

[0063] 1 Reclaimer ships, work boats 2 Soil Carrier 2a Earthen tank 3. Gut Barge 5 Another soil carrier 10 Mixed Systems 11 Conveyor 12 Boom conveyor 13 Backhoe 13a Bucket 14 Sand Hopper

Claims

1. A method for mixing steelmaking slag into mud using a work vessel equipped with a conveyor, comprising: Steelmaking slag is supplied to the mud inside the soil transport barge, and the mud and the steelmaking slag are mixed with a backhoe for a predetermined mixing time so as to obtain a quality equivalent to one drop mixing from a height of 2 m or more. The mixed material is supplied to the work ship, transported by the conveyor, and dropped to a height of 2 m or more for mixing. A method for mixing mud and steelmaking slag, comprising dropping the mixed material to a height of 2 m or more at least twice.

2. A method for mixing mud and steelmaking slag as described in claim 1, wherein the mixing time is set to the time required to obtain at least one of the qualities of wet density, strength, suspended solids, or turbidity corresponding to one drop mixing.

3. A method for mixing mud and steelmaking slag as described in claim 2, wherein a mixing time test is conducted in advance for at least one of the wet density, the strength, and the amount of suspended solids or turbidity, and the mixing time is set based on the test results.

4. 3. The method for mixing mud and steelmaking slag according to claim 2, wherein the mixing time is set taking into consideration the volume of the mixed material in the soil transport barge and the bucket volume of the backhoe.

5. A method for mixing mud and steelmaking slag as described in claim 1, wherein the mixing time is set to a constant value, and at least one of the water content of the mud, the particle size of the steelmaking slag, and the mixing ratio of the steelmaking slag is set so as to obtain the target strength of the mixed material.

6. A method for mixing mud and steelmaking slag as described in claim 5, wherein a blending test is conducted in advance for at least one of the water content of the mud, the particle size of the steelmaking slag, and the mixing ratio of the steelmaking slag, and the setting is made based on the test results.

7. A method for mixing mud and steelmaking slag as described in claim 1, wherein when mixing with the backhoe, it is confirmed that the mud and the steelmaking slag are in a predetermined mixing ratio in the bucket of the backhoe, and then the mixed material is supplied to the work ship.

8. 2. The method for mixing mud and steelmaking slag according to claim 1, wherein the mixed material is dropped into a soil hopper before being transported by the conveyor, thereby performing drop mixing.

9. 2. The method for mixing mud and steelmaking slag according to claim 1, wherein the backhoe is installed on the work boat, and the mixing is performed by bringing the soil transport boat close to the work boat.

10. A method for mixing mud and steelmaking slag as described in claim 1, wherein the backhoe is installed on land, the soil transport ship is brought ashore to perform the mixing, and after the mixing, the soil transport ship is brought close to the work ship to supply the mixed material to the work ship.

11. A method for mixing mud and steelmaking slag according to claim 9 or 10, wherein other additive materials are added and mixed when mixing with the backhoe.

12. 2. A method for mixing mud and steelmaking slag according to claim 1, wherein the mud in the soil transport barge and the steelmaking slag are mixed in a predetermined volume ratio.

13. A method for mixing mud and steelmaking slag as described in claim 1, wherein the final destination of the dropping mixture on the work boat is the area where the mixed material is used, a soil transport boat, or the hopper of a tremie pipe.

14. A method for mixing mud and steelmaking slag as described in claim 1, wherein if the final destination of the drop mixing on the work boat is land and the mixed material is dropped to a height of 2 m or more when it is introduced into the usage area after dropping on land, drop mixing to a height of 2 m or more is performed on the work boat at least once.

15. A system for mixing mud and steelmaking slag, comprising: a work vessel having a conveyor; A soil transport ship that transports mud, a backhoe that mixes the mud in the soil transport ship with the steelmaking slag supplied to the soil transport ship; The mixed material of the mud and the steelmaking slag is mixed by the backhoe for a predetermined mixing time so as to obtain the quality required for one drop mixing from a height of 2 m or more. The mixed material is supplied to the work ship, transported by the conveyor, and dropped to a height of 2 m or more for mixing. A mixing system for mixing mud and steelmaking slag configured to perform drop mixing of the mixed material at least twice from a height of 2 m or more.

16. The mud and steelmaking slag mixing system according to claim 15, wherein the work vessel has at least two of the conveyors.

17. The work vessel has a soil and sand hopper to which the mixed material is supplied, The soil hopper is configured to drop and mix the supplied mixed material to a height of 2 m or more, The mud and steelmaking slag mixing system according to claim 15, wherein the dropping mixed material is supplied from the soil hopper to the conveyor.

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