Modified soil

Abstract

To provide modified soil which can secure strength in a small mixture ratio of a steel-making slag compared to conventional calcia modified soil, and can increase a used amount of dredge soil.SOLUTION: Modified soil of dredge soil is obtained by mixing a steel-making slag with dredge soil and is added with an auxiliary material for securing strength, wherein blast furnace slag fine powder and / or cement as an auxiliary material are / is used, a mixture ratio X of the steel-making slag to the dredge soil is set to be 5 to 20 vol.%, an addition amount Y of the auxiliary material is set to be smaller than a reduction amount (Z-X) of the steel-making slag from a mixture ratio Z mol%, in standard modified soil having a mixture ratio Z vol% (Z>X) of the steel-making slag and a mixture ratio (100-Z) vol.% of the dredge soil, and a used amount of the dredge soil is increased compared to the standard modified soil by a degree (Z-X-Y) obtained by subtracting the addition amount Y of the auxiliary material from the reduction amount (Z-X).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to modified soil obtained by modifying dredged soil. [Background technology]

[0002] Conventionally, in standard calcia-modified soil, which is a mixture of dredged soil and calcia modifier (a material in which the particle size and composition of steelmaking slag have been adjusted, hereinafter referred to as "steelmaking slag"), the volume mixing ratio of steelmaking slag is often set to 25-30 vol% (see Non-Patent Literature 1). From the viewpoint of effective utilization of dredged soil, it is desirable to have a high mixing ratio of dredged soil and a low mixing ratio of steelmaking slag. However, it is known that reducing the mixing ratio of steelmaking slag from 30 vol% to 20 vol% or 10 vol% results in a decrease in the intensity of the modified soil (Non-Patent Literature 1, p. 4.2).

[0003] Patent Document 1 discloses a soil modification material for improving soil by mixing it with soil, comprising only steelmaking slag, or steelmaking slag and either granulated blast furnace slag or blast furnace slag fine powder, or both, and a soil modification method in which the mixing ratio of steelmaking slag is 10% by volume or more and 50% by volume or less relative to the soil as a mixing material (Claim 1, 7).

[0004] Patent Document 2 uses a paper sludge incineration ash-based modifier or cement as the modifier, reduces the volume mixing ratio of steelmaking slag to dredged soil, increases the treatment amount of dredged soil relative to the amount of modified treated soil, and through mixing of the paper sludge incineration ash-based modifier or cement, the strength of the modified treated soil is made equal to or higher than the strength of the mixed material composed of steelmaking slag and dredged soil before the volume mixing ratio is reduced, thereby disclosing a dredged soil modification treatment method (Claim 1). Patent Document 3 discloses a modified treated soil of cohesive soil, in which cohesive soil, steelmaking slag and a modifier are mixed, and the modifier is a paper sludge incineration ash-based modifier or cement, so that at least one of the low-temperature strength development property and the early-stage strength development property after mixing in the modified treated soil is improved (Claim 1). In Patent Documents 2 and 3, the volume mixing ratio of steelmaking slag to dredged soil is 10 to 30 vol%, and the mixing amount of the paper sludge incineration ash-based modifier or cement is 50 to 200 kg / m 3 is.

[0005] Patent Document 4 discloses a method for producing a solidified body, which comprises mixing dredged soil with a water content of more than 190%, steelmaking slag as an aggregate, and a binder composed of blast furnace slag fine powder and an alkaline stimulant, and solidifying the resulting mixture through a hydration reaction by the binder to obtain the solidified body (Claims 1 to 3), wherein the alkaline stimulant is at least one selected from ordinary Portland cement, blast furnace cement, slaked lime, and lime dust (Claim 4). [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] JP 2009-121167 A [Patent Document 2] JP 2021-059953 A [Patent Document 3] JP 2021-59699 A [Patent Document 4] JP 2011-246336 A [Non-Patent Documents]

[0007] Non-Patent Document 1 "Manual on Technology for Utilization of Calcia-Modified Soil", Coastal Technology Research Center (published in February 2017) SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] As a method for enhancing the strength of calcia-modified soil, addition of ground granulated blast furnace slag is known, and experimental results when 1% and 3% of ground granulated blast furnace slag are added relative to the weight of dredged soil are described in Non-Patent Document 1 (Appendix 2-11). The wet density of the dredged soil is 1.3 g / cm 3 The 1% addition amount of ground granulated blast furnace slag when calculated as above corresponds to 10 kg / m when the amount of dredged soil at the time of mixing 20 vol% of steelmaking slag is 1040 kg / m 3 , which corresponds to 10 kg / m 3 , and similarly, the 3% addition amount corresponds to 31 kg / m 3 . In addition, when 30 vol% of steelmaking slag is mixed, the amount of dredged soil is 910 kg / m 3 , the 1% addition amount is 9 kg / m 3 , and the 3% addition amount is 27 kg / m 3 . In Patent Document 1, the addition amount of steelmaking slag is 10 to 50 vol%, and Table 1 therein describes an experiment in which 1 vol% of ground granulated blast furnace slag is added. If the density of the ground granulated blast furnace slag is 2.89 g / cm 3 , the addition amount is 28.9 kg per m of calcia-modified soil 3 .

[0009] Patent Document 2 is a modification treatment method that reduces the volume mixing ratio of steelmaking slag to dredged soil and increases the treatment amount of dredged soil. Patent Document 3 is a modified treated soil that improves the strength development at low temperature and the strength development in the early stage of mixing in modified treated clay soil. However, the volume mixing ratio of steelmaking slag to dredged soil is 10 to 30 vol%, which is insufficient for reducing the volume mixing ratio of steelmaking slag to dredged soil, and it does not disclose the limitation on the addition amount of the paper sludge incineration ash-based modifier and cement as modifiers when increasing the treatment amount of dredged soil.

[0010] Patent Document 4 relates to a dredged soil solidified body (9.8 N / mm 2The amount of blast furnace slag fine powder to be mixed into the stone material is 10-30 vol% (assuming the density of blast furnace slag fine powder is 2.89, this corresponds to 289-867 kg / m³). 3 However, such solidified dredged soil differs from modified dredged soil in terms of its strength, amount added, and uses.

[0011] In view of the problems of the prior art described above, the present invention aims to provide a modified dredged soil that can secure strength with a smaller mixing ratio of steelmaking slag compared to conventional calcia-modified soil, and that can increase the amount of dredged soil that can be used. [Means for solving the problem]

[0012] The modified soil for achieving the above objective is a modified dredged soil prepared by mixing steelmaking slag with dredged soil and adding an auxiliary material to ensure strength, wherein the auxiliary material is blast furnace slag fine powder. Use or Blast furnace slag fine powder and cement and Using the above, the mixing ratio X of the steelmaking slag to the dredged soil is set to 5 vol% or more and 20 vol% or less. The amount of the aforementioned auxiliary material added, Y, is at least 25 kg / m³ 3 In standard modified soil, which is dredged soil mixed with steelmaking slag, The standard mixing ratio of the aforementioned steelmaking slag is Z vol% (Z > X). 25-30 vol%, The mixing ratio of the dredged soil but (100-Z)vol% And, The amount of additive Y is made less than the amount of steelmaking slag reduction (ZX) from the aforementioned mixing ratio Z vol%, and the amount of dredged soil used is increased compared to the standard modified soil by the amount obtained by subtracting the amount of additive Y from the reduction (ZX) (ZXY).

[0013] According to this modified soil, the volume mixing ratio of steelmaking slag in standard calcia-modified soil Z(By setting the mixing ratio X of steelmaking slag to dredged soil to 5-20 vol% for a total steelmaking slag content of 25-30 vol%, and adding auxiliary materials to ensure strength, and by reducing the amount of auxiliary material Y added compared to the reduction in steelmaking slag (ZX) from the standard modified soil mixing ratio Z vol% (Z>X) and dredged soil mixing ratio (100-Z) vol%, the amount of dredged soil used can be increased by the amount obtained by subtracting the amount of auxiliary material Y added from the reduction (ZX) (ZXY). This makes it possible to obtain modified soil that can ensure strength with a smaller steelmaking slag mixing ratio compared to conventional standard modified soil, and that can also increase the amount of dredged soil used.

[0014] In the modified soil described above, the amount of auxiliary material added Y is 25 kg / m³. 3 More than 100kg / m 3 The following is preferable (m 3 (Unit mixing volume of dredged soil and steelmaking slag). Furthermore, it is preferable that the mixing ratio X of the steelmaking slag is 5 vol% or more and 10 vol% or less in order to increase the amount of dredged soil used.

[0015] Furthermore, the aforementioned auxiliary Material cement and Blast furnace slag fine powder and If added, the amount of cement added will be at least 25 kg / m³ 3 This ensures strength.

[0016] Furthermore, the mixing ratio X of the steelmaking slag is 8 vol% or more and less than 10 vol%, and the auxiliary Material When the blast furnace slag fine powder is added alone, the amount of blast furnace slag fine powder added is at least 50 kg / m³. 3 This ensures strength.

[0017] Furthermore, the mixing ratio X of the steelmaking slag is 10 vol% or more and 20 vol% or less, and the auxiliary MaterialWhen the blast furnace slag fine powder is added alone, the amount of blast furnace slag fine powder added is at least 25 kg / m³. 3 This ensures strength.

[0018] Furthermore, the steelmaking slag and the auxiliary Material The total carbon dioxide emissions from these materials amount to 50 kg-CO2 / m³. 3 The following is preferable:

[0019] Furthermore, the amount of cement added is 50 kg / m³. 3 In the following cases, the steelmaking slag and the auxiliary Material The total carbon dioxide emissions from these materials amounted to 25 kg-CO2 / m³. 3 The following is preferable:

[0020] Furthermore, the unconfined compressive strength of the above-mentioned modified soil 28 days after mixing was 80 kN / m². 2 More than 2110kN / m 2 The following is preferable: [Effects of the Invention]

[0021] According to the modified soil obtained by modifying dredged soil according to the present invention, it is possible to secure strength with a smaller mixing ratio of steelmaking slag compared to conventional standard modified soil, and it is also possible to increase the amount of dredged soil used. [Brief explanation of the drawing]

[0022] [Figure 1] This graph shows the change over time in the unconfined compressive strength of the modified soil obtained using the mix design example of Example 1 (Table 2). [Figure 2]The graph shows the change over time in the unconfined compressive strength of the modified soil obtained using the mix design of Example 2 (Table 3). (a) shows the case where the steelmaking slag mixing ratio is 5 vol% and 8 vol% with the addition of auxiliary material, (b) shows the case where the steelmaking slag mixing ratio is 10 vol% with the addition of auxiliary material, and (c) shows the case where the steelmaking slag mixing ratio is 20 vol% with the addition of auxiliary material. [Modes for carrying out the invention]

[0023] The following describes embodiments for carrying out the present invention. In this embodiment, the modified soil obtained by modifying dredged soil is prepared by mixing steelmaking slag with the dredged soil at a volume mixing ratio X of 5 to 20 vol%, and adding either blast furnace slag fine powder or cement, or both, as an auxiliary material at an amount Y of 25 to 100 kg / m³. 3 (m 3 Strength is ensured by adding an auxiliary material (Y) to the standard volume of dredged soil and steelmaking slag (unit mixing volume). The amount of this auxiliary material (Y) is kept below the reduction (ZX) from the standard volume mixing ratio (Z vol%) of steelmaking slag in standard calcia-modified soil. The amount of dredged soil used is increased by the amount obtained by subtracting the amount of auxiliary material (Y) from the reduction (ZX) (ZXY) compared to standard calcia-modified soil. When both blast furnace slag fine powder and cement are used as auxiliary materials for the modified soil, their total is 25-100 kg / m³. 3 That is the case.

[0024] In the modified soil obtained by modifying the dredged soil described above, it is preferable that the mixing ratio X of steelmaking slag is 5 to 10 vol%. Furthermore, when cement is added as an auxiliary material, either alone or together with blast furnace slag fine powder, the amount of cement added should be at least 25 kg / m³. 3 This ensures strength.

[0025] Furthermore, when the mixing ratio X of the steelmaking slag is 8 vol% or more and less than 10 vol%, an auxiliary Material Blast furnace slag powder is added alone, and the amount of blast furnace slag powder added is at least 50 kg / m³. 3Strength can be ensured by this. In addition, the mixing ratio X of the steelmaking slag is 10 vol% or more and 20 vol% or less, and the auxiliary Material The blast furnace slag fine powder is added alone, and the amount of blast furnace slag fine powder added is at least 25 kg / m³. 3 This ensures strength.

[0026] Furthermore, the unconfined compressive strength of the modified soil 28 days after mixing was 80-2110 kN / m². 2 It is preferable that this is the case. Furthermore, the standard volume mixing ratio Z of steelmaking slag in a standard calcia-modified soil consisting of dredged soil and steelmaking slag is 25-30 vol%.

[0027] For example, if the volume mixing ratio X of steelmaking slag in the modified soil according to this embodiment is set to 20 vol%, compared to the lower limit of 25 vol% for the volume mixing ratio Z of steelmaking slag in standard calcia-modified soil, the reduction in steelmaking slag in the modified soil (ZX) is 5 vol%, but the surface-dry density of the steelmaking slag is 3000 kg / m³. 3 Therefore, 1 m of modified soil 3 In this case, 5 vol% of steelmaking slag is 150 kg / m³ 3 This corresponds to a subsidy. Material The amount added, Y, is 150 kg / m³. 3 It is necessary to have less than 25-100 kg / m³ of blast furnace slag powder and / or cement as auxiliary materials. 3 Since it is added within the range, the final reduction in steelmaking slag is (150 kg / m³). 3 -Y)>0, and the final reduction amount is (150kg / m³). 3 -Y) can be added to the dredged soil, and the amount of dredged soil used can be increased compared to standard calcia-modified soil. Furthermore, with the modified soil according to this embodiment, by adding blast furnace slag fine powder and / or cement, it is possible to ensure strength with a smaller mixing ratio of steelmaking slag compared to conventional standard calcia-modified soil.

[0028] In the modified soil according to this embodiment, steelmaking slag and auxiliary MaterialThe total carbon dioxide emissions from these materials amount to 50 kg-CO2 / m³. 3 The following are examples of CO2 emission intensity from each material, as shown in Table 1.

[0029] [Table 1]

[0030] Table 1 shows that in this embodiment, 20 vol% of steelmaking slag was mixed with dredged soil, and 100 kg / m of cement (blast furnace type B) was added as an auxiliary material. 3 It can be seen that the total CO2 emissions from the material are highest when [a certain substance] is added, but the CO2 emissions from 20 vol% steelmaking slag are 1.7 kg-CO2 / m³. 3 , cement (blast furnace type B) 100 kg / m 3 The CO2 emissions are 44.0 kg-CO2 / m³. 3 The total is 45.7 kg-CO2 / m³. 3 (<50kg-CO2 / m 3 ) In contrast, for example, cement (blast furnace type B) is added to the dredged soil without using steelmaking slag at a rate of 200 kg / m 3 In the solidified soil prepared by adding the following, cement (blast furnace type B) 200 kg / m 3 The CO2 emissions are 89.8 kg-CO2 / m³. 3 Therefore, the modified soil according to this embodiment can reduce CO2 emissions derived from steelmaking slag and auxiliary materials compared to cement-solidified soil.

[0031] Furthermore, the amount of cement added is 50 kg / m³. 3 In the following cases, steelmaking slag and auxiliary Material The total carbon dioxide emissions from these materials amounted to 25 kg-CO2 / m³. 3 The following is possible:

[0032] Next, Examples 1 and 2 of the modified soil according to the present invention will be described below, but the present invention is not limited to these examples.

[0033] <Example 1> Table 2 shows an example of a mix using dredged soil A (water content: 111.8%, liquid limit wL: 74.5%, fine particle content: 96.7%), the results of a uniaxial compression test according to JIS A 1216, and the calculated CO2 emissions. Figure 1 shows the change in uniaxial compression strength over time.

[0034] [Table 2]

[0035] Figure 1 and Table 2 show that when steelmaking slag was mixed with dredged soil A at a mixing ratio of 10 vol%, and cement (blast furnace type B) or blast furnace slag fine powder was added, the compressive strength increased, and it was possible to achieve a compressive strength greater than that when only 10 vol% of steelmaking slag was mixed. In addition, cement (blast furnace type B) or blast furnace slag fine powder was added as an auxiliary material at a rate of 50 kg / m³. 3 By adding this, a compressive strength greater than that of the case where only 30 vol% of steelmaking slag was used was achieved.

[0036] The steelmaking slag mixture has a mixing ratio of 10 vol% with 50 kg / m³ of blast furnace slag fine powder added as an auxiliary material. 3 When added, the modified soil 1 m³ of modified soil with a steelmaking slag mixing ratio of 30 vol% is as follows. 3 This allows us to increase the amount of dredged soil used per unit area by 183 liters. Density of blast furnace slag fine powder: 2890 kg / m³ 3 (= 2.89 kg / L) Reduction due to the use of steelmaking slag: 20 vol% = 200 L Amount of blast furnace slag fine powder used: 50 kg ÷ 2.89 kg / L = 17.3 L Increase in the amount of dredged soil used: 200L - 17.3L = 183L

[0037] Note that while blast furnace slag powder is added to the modified soil as an external addition, the amount added is small, so the volume increase due to the external addition is ignored in the above calculation example. For reference, the following is a calculation example where it is not ignored, but it can be seen that the increase due to the use of dredged soil is the same as when it is ignored. Amount of calcia-modified soil after adding blast furnace slag fine powder: 1000L + 17.3L = 1017.3L Amount of blast furnace slag powder used in calcia-modified soil after addition of blast furnace slag powder: 17.3L × 1000L / 1017.3L = 17.0L Increase in the amount of dredged soil used: 200L - 17.0L = 183L

[0038] <Example 2> Table 3 shows an example of a mix design using dredged soil B (water content: 180.9%, liquid limit wL: 120.6%, fine particle content: 89.4%), the results of a uniaxial compression test according to JIS A 1216, and the calculated CO2 emissions. Figures 2(a) to (c) show the change in uniaxial compressive strength over time. Note that in Table 3, the density of cement (blast furnace type B) is assumed to be 3.06 kg / m³. 3 The calculation was performed as follows. In addition, although blast furnace slag powder and cement (blast furnace type B) are added externally, the volume increase due to external addition was ignored in the calculation because the amount added was small.

[0039] [Table 3]

[0040] From Table 3 and Figures 2(a)-(c), when steelmaking slag is mixed with dredged soil B at a mixing ratio of 5 vol%, at least 25 kg / m³ of cement (blast furnace type B) is required. 3 The addition confirmed the development of strength. Furthermore, in the case of a 10 vol% steelmaking slag mixing ratio, at least 25 kg / m³ of cement (blast furnace type B) or blast furnace slag fine powder was added. 3 Adding this material increased the strength, making it possible to achieve a strength higher than that of a mixture containing only 10 vol% steelmaking slag. Furthermore, when the steelmaking slag mixture was 20 vol%, at least 25 kg / m³ of cement (blast furnace type B) or blast furnace slag fine powder was added. 3 By adding the above ingredients, the strength increased, and it was possible to achieve a strength higher than that when only 20 vol% of steelmaking slag was mixed in.

[0041] Furthermore, in the case of a steelmaking slag mixing ratio of 8 vol%, at least 50 kg / m³ of blast furnace slag fine powder should be added. 3 Adding this material increased the strength, making it possible to achieve a strength higher than that achieved when only 8 vol% of steelmaking slag was used.

[0042] Table 3 shows the results for 1 m³ of modified soil compared to standard calcia-modified soil with a steelmaking slag mixing ratio of 30 vol%. 3 This shows an increase in the amount of dredged soil used per unit area, and it can be seen that the amount of dredged soil used could be increased with any of the modified soils under each of the mixing conditions in Example 2.

[0043] While 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 idea of ​​the present invention. For example, in this embodiment, blast furnace type B cement was used, but the present invention is not limited to this, and other types of cement may be used.

[0044] Furthermore, although the present invention relates to modified soil obtained by modifying dredged soil, such modification can increase the amount of dredged soil that can be used, thereby promoting the utilization of dredged soil. Therefore, it can be considered as a method for modifying and utilizing dredged soil. In other words, the method of utilizing dredged soil involves mixing steelmaking slag with the dredged soil and adding auxiliary materials to ensure strength, thereby modifying and utilizing the dredged soil. The auxiliary materials used are blast furnace slag fine powder and / or cement. The mixing ratio X of the steelmaking slag to the dredged soil is set to 5-20 vol%. The amount of auxiliary material added Y is less than the reduction in steelmaking slag (ZX) from the standard modified soil with a standard mixing ratio Z vol% (Z>X) of steelmaking slag and a mixing ratio of (100-Z) vol% of dredged soil. The amount of dredged soil used is increased by the amount obtained by subtracting the amount of auxiliary material added Y from the reduction (ZX) (ZXY) compared to the standard modified soil. [Industrial applicability]

[0045] The modified soil of the present invention makes it possible to secure strength with a smaller mixing ratio of steelmaking slag compared to conventional calcia-modified soil, and also makes it possible to increase the amount of dredged soil that can be used. Therefore, it can contribute to promoting the effective utilization of dredged soil, which is waste generated by dredging work.

Claims

1. This is modified dredged soil, which is made by mixing steelmaking slag with dredged soil and adding auxiliary materials to ensure strength. As the aforementioned auxiliary material, blast furnace slag fine powder is used, or blast furnace slag fine powder and cement are used. The mixing ratio X of the steelmaking slag to the dredged soil is 5 vol% or more and 20 vol% or less, and the amount Y of the auxiliary material added is at least 25 kg / m³. In a standard modified soil prepared by mixing steelmaking slag with dredged soil, the standard mixing ratio Z vol% (Z > X) of the steelmaking slag is 25 to 30 vol%, and the mixing ratio of the dredged soil is (100 - Z) vol%. The amount of additive Y is made less than the amount of steelmaking slag reduced (Z-X) from the mixing ratio Z vol%, Modified soil obtained by increasing the amount of dredged soil used compared to the standard modified soil by the amount obtained by subtracting the amount of auxiliary material added Y from the reduction amount (Z-X) (Z-X-Y).

2. The modified soil according to claim 1, wherein the mixing ratio X of the steelmaking slag is 5 vol% or more and 10 vol% or less.

3. When cement and blast furnace slag fine powder are added as auxiliary materials, the amount of cement added is at least 25 kg / m³ ３ The modified soil according to claim 1.

4. The mixing ratio X of the aforementioned steelmaking slag is 8 vol% or more and less than 10 vol%, When the blast furnace slag fine powder is added alone as the auxiliary material, the amount of blast furnace slag fine powder added is at least 50 kg / m³. ３ The modified soil according to claim 1.

5. The mixing ratio X of the steelmaking slag is 10 vol% or more and 20 vol% or less. When the blast furnace slag fine powder is added alone as the auxiliary material, the amount of blast furnace slag fine powder added is at least 25 kg / m³. ３ The modified soil according to claim 1.

6. The total carbon dioxide emissions from the steelmaking slag and the auxiliary material amounted to 50 kg-CO2. ２ / m ３ The modified soil according to claim 1, which is as follows:

7. The amount of cement added is 50 kg / m³. ３ If the following conditions are met, the total carbon dioxide emissions from the steelmaking slag and the auxiliary material are 25 kg-CO2 ２ / m ３ The modified soil according to claim 1, which is as follows:

8. The unconfined compressive strength after 28 days of mixing is 80kN / m ２ or more and 2110kN / m ２ or less, the modified soil according to claim 1.

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