JP7344075B2 - Modified clay soil and method for producing modified soil - Google Patents

Description

The present invention relates to a modified clay soil that has improved strength development at low temperatures or in the early stage of mixing, and a method for producing the modified soil.

Dredged soil is generated during port construction, but as securing a disposal site has become an issue in recent years, effective use of dredged soil is required. As a method of effectively utilizing dredged soil, there is calcia modified soil that is a mixture of dredged soil and calcia modified material (a material in which the particle size and composition of converter steelmaking slag are adjusted) (for example, Patent Documents 1, 2, (Refer to Non-Patent Document 1), it is widely used in port areas as a construction material for shallow areas and tidal flats, submerged embankments, reclamation materials, etc.

Patent Document 3 discloses a method of mixing steelmaking slag (maximum particle size 10 mm or less, 20 to 150 kg/m ³ ) and blast furnace cement (40 to 100 kg/m ³ ) to soft soil, but it In comparison, the amount of steelmaking slag added is small.

Patent Document 4 describes the production of modified soil of high water content mud, which adds a water-absorbing material (25 to 100 kg/m ³ ) to mud with a high water content of 2.0 wL or more to prevent material separation and ensure strength. Although the method is disclosed, it is aimed at improving muddy soil with a high moisture content.

Japanese Patent Application Publication No. 2009-121167 Japanese Patent Application Publication No. 2011-206625 Japanese Patent Application Publication No. 2006-231208 Japanese Patent Application Publication No. 2019-148144

“Technical Manual for the Use of Calcia Modified Soil in Ports, Airports, Coasts, etc.” (Coastal Technology Research Center, published in February 2017) CIKMIT Arlyn Aristo, Takashi Tsuchida, Gengo Jiang, Hiroyasu Jiaju, Hideki Honda, Arata Yui "Strength expression characteristics of dredged marine clay solidified using steelmaking slag" Ground and Construction (Collection of Papers from the Japan Geotechnical Society of China Branch) Vol.35, No.1, pp.93-100, 2017 http://jgschugoku.jp/asset/00032/GE/Vol35/GE_vol35_11.pdf “Standards for the use of generated soil” Ministry of Land, Infrastructure, Transport and Tourism, Technical Investigation Division (2006) http://www.mlit.go.jp/tec/kankyou/hasseido/060810kijyun.pdf

Calcia modified soil is affected by curing temperature, so if it is constructed in winter or in cold regions where air and water temperatures are low, it may not reach the target strength (Non-Patent Document 1 (Appendix 2-10)). As a means to ensure strength, there are methods such as adding powdered blast furnace slag, reducing the particle size of the calcia modifier, and increasing the mixing ratio of the calcia modifier (Non-patent Document 1 (Appendix 2- 6, Appendix 2-7, Appendix 2-8, Appendix 2-11)). This method of adjusting the particle size of calcia-amended soil is complicated. The method of increasing the mixing ratio of the calcia modifier, for example, from the general 30 vol% to 40 vol%, decreases the ratio of dredged soil, which is not desirable from the viewpoint of effective use of dredged soil.

In addition, calcia modified soil is a material that develops strength over a medium to long term, and its strength is low in the initial stage after mixing (Non-Patent Document 2). Therefore, for several tens of hours immediately after mixing, it is difficult to transport by dump truck or the like or to work with heavy machinery on the calcia-improved soil. This problem cannot be solved by the above-mentioned method of increasing the mixing ratio of the calcia modifier or adding pulverized blast furnace slag powder.

In view of the problems of the prior art as described above, the present invention provides a modified clay soil and a method for producing the modified soil that can improve the strength development at low temperatures or the strength development at an early stage of mixing. With the goal.

The modified clay soil to achieve the above purpose is modified clay soil with a water content ratio of 1.1 to 2.0 wL (wL: liquid limit), and is a clay soil and steel making soil. Slag and modifying material are mixed,
The modification material is a paper sludge incineration ash-based modification material or cement ,
The 28-day strength of the modified soil after curing at 5°C is equal to or higher than the 28-day strength of the modified soil with clayey soil and steelmaking slag after curing at 20°C, and/or By determining the mixing amount of the modifying material so that the Cone index of the modified soil is 200 kN/m2 or more after 24 hours of mixing, ^the strength development at low temperatures in the modified soil is achieved. This improves at least one of the strength and the strength development property in the early stage of mixing.

According to this modified soil of clayey soil, in addition to clayey soil and steelmaking slag, a paper sludge incineration ash-based reforming material or cement is mixed as a reforming material, so that the clayey soil and steelmaking slag are mixed together. Compared to mixed materials, it is possible to improve at least one of the strength development at low temperatures and the strength development at the early stage of mixing in the modified soil, and it is possible to ensure at least one of the strength at low temperatures and the strength at the early stage of mixing.

In the modified clay soil, the steelmaking slag preferably has a maximum particle size of 5 to 40 mm and a volumetric mixing ratio of 10 to 30 Vol% with respect to the clay soil.

The mixing amount of the paper sludge incineration ash-based modifier is 50 to 200 kg per unit volume (m ³ ) of the mixed material of the cohesive soil and the steelmaking slag, and the mixing amount of the cement is 50 to 200 kg per unit volume (m 3 ) of the mixed material of the cohesive soil and steelmaking slag. It is preferable that the mixed material with the steelmaking slag weighs 50 to 200 kg per unit volume (m ³ ).

The method for producing modified clay soil to achieve the above purpose is to produce modified soil by modifying clay soil with a water content ratio of 1.1 to 2.0 wL (wL: liquid limit). There it is,
Mix steelmaking slag and modification material with clayey soil,
The modification material is a paper sludge incineration ash-based modification material or cement ,
The 28-day strength of the modified soil after curing at 5°C is equal to or higher than the 28-day strength of the modified soil with clayey soil and steelmaking slag after curing at 20°C, and/or By determining the amount of the modifier mixed so that the Cone index of the modified soil after 24 hours of mixing is 200 kN/m2 or more, ^the strength development at low temperatures and This improves at least one aspect of strength development in the early stage of mixing.

According to this method for producing modified soil for clayey soil, in addition to clayey soil and steelmaking slag, a paper sludge incineration ash-based reforming material or cement is further mixed as a reforming material, thereby producing clayey soil and steelmaking slag. It is possible to produce modified soil that improves at least one of the strength development properties at low temperatures and the strength development properties in the early mixing stage compared to mixed materials with One can be secured.

In the above-mentioned clay soil modification treatment method, it is preferable that the cement is made into a slurry form by adding water and then mixed.

According to the modified clay soil of the present invention and the method for producing modified soil, it is possible to improve at least one of the strength development at low temperatures and the strength development at an early stage of mixing in the modified soil. It is possible to ensure at least one of the strength of the mixture and the strength at the early stage of mixing.

1 is a flowchart for explaining main steps S01 to S04 of the method for producing modified clay soil according to the present embodiment. 2 is a graph showing the test results of a uniaxial compression test at 28 days old in Experimental Example 1. 2 is a graph showing the state of strength development in the early stage of mixing according to a cone penetration test after curing at 20° C. in Experimental Example 1. 2 is a graph showing the state of strength development in the early stage of mixing according to a cone penetration test after curing at 5° C. in Experimental Example 1. It is a graph showing the test results of the uniaxial compression test (steel making slag: 30 vol%) at 28 days old in Experimental Example 2. It is a graph showing the test results of the uniaxial compression test (steelmaking slag: 30 vol%) on the 28th day of material age when PS ash-based modifier is mixed in Experimental Example 2, comparing the curing temperatures of 5°C and 20°C. It is a graph showing the test results of the uniaxial compression test on the 28th day of the material age when PS ash-based modifier is mixed in Experimental Example 2, comparing the mixed amount of steelmaking slag with 20 vol% and 30 vol%. It is a graph showing the strength development situation in the early stage of mixing by a cone penetration test after curing at 20° C. with a mixed amount of steelmaking slag of 30 vol% in Experimental Example 2. It is a graph showing the strength development situation in the early stage of mixing by a cone penetration test after curing at 5° C. with a mixed amount of steelmaking slag of 30 vol% in Experimental Example 2. It is a graph showing the strength development situation in the early stage of mixing by a cone penetration test after curing at 20° C. with a mixed amount of steelmaking slag of 20 vol% in Experimental Example 2.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a flowchart for explaining the main steps S01 to S04 of the method for producing modified clay soil according to the present embodiment.

As shown in FIG. 1, the method for producing modified clay soil according to the present embodiment involves preparing clay soil such as dredged soil with a water content ratio of 1.1 to 2.0 wL (wL: liquid limit) (S01 ), next, steelmaking slag with a maximum particle size of 5 to 40 mm is mixed with clayey soil (S02), and a paper sludge incineration ash-based modifier (hereinafter referred to as "PS ash") is added as a modifier. ) or cement (S03), thereby obtaining modified clay soil (S04). Note that step S02 and step S03 may be performed at the same time, or the steps may be switched.

The volumetric mixing ratio of steelmaking slag to clayey soil is 10 to 30 Vol%. Further, the mixed amount of PS ash-based modifier is 50 to 200 kg/m ³ , or the mixed amount of cement is 50 to 200 kg/m ³ . However, m ³ is the unit volume of the mixed material of cohesive soil and steelmaking slag.

Note that paper sludge incineration ash-based modifier (PS ash-based modifier) is a modifier made of paper sludge incineration ash or a modifier whose main component is paper sludge incineration ash. Other components may be mixed with the incinerated ash, but mixing of other components is not necessarily required. Paper sludge incineration ash is incineration ash (PS ash) produced when paper sludge (PS) generated in the paper manufacturing industry is incinerated to reduce its volume.

The method for mixing the PS ash-based modifier or cement is that if the PS ash-based modifier or cement is powder and is mixed as a powder, it is mixed using a mixer or backhoe. Further, the cement may be in powder form or in the form of a slurry by adding water, and in the case of making it into a slurry form, methods such as mixer mixing, backhoe mixing, falling mixing, and mixing in a pipe are used. Note that it is preferable to form the cement into a slurry when the amount of cement mixed is relatively small, such as about 50 kg/m ³ .

According to the modified clay soil according to the present embodiment, strength development at low temperatures is improved by mixing an appropriate amount of PS ash-based modifier or cement in addition to clayey soil and steelmaking slag. Even at low temperatures, it can maintain the same strength as conventional calcia-amended soil at room temperature. In addition, compared to conventional calcia-modified soil, strength development in the early stage of mixing has been improved, and the cone index qc = 200 kN/m ² (equivalent to type 4 construction generated soil (non-patent literature) 3)), it is possible to transport by dump truck within a few hours after mixing, and furthermore, the cone index qc = 400kN/m ² (the third Since it is possible to secure soil equivalent to soil generated from construction (Non-Patent Document 3), it is possible to work with construction machinery.

Next, Experimental Examples 1 and 2 regarding the present invention will be explained, but the present invention is not limited to these experimental examples.

[Experiment example 1]
Calcia modified soil is made by mixing dredged soil (liquidity limit wL = 66.5%, water content ratio 116.4% (1.75 wL)) with steelmaking slag (maximum particle size 5 mm, 30 vol%), and PS ash is added to this calcia modified soil. Modified soil was prepared by mixing a predetermined amount (50 kg/m ³ , 100 kg/m ³ ) of type B blast furnace cement or blast furnace cement, and after curing at 5℃ or 20℃, a uniaxial compression test ( JIS A 1216) and cone penetration test (JIS A 1228) were conducted. Figure 2 shows the test results of the uniaxial compression test on the 28th day of age. Figure 3 shows the strength development status in the early stage of mixing by a cone penetration test after curing at 20°C. Figure 4 shows the strength development in the early stage of mixing by cone penetration test after curing at 5°C.

As shown in Figure 2, the unconfined compressive strength of the calcia-amended soil aged 28 days after curing at 5°C was less than half that of the calcia-amended soil aged at 20°C, whereas the strength at low temperatures decreased. , modified soil cured at 5℃ and further mixed with PS ash-based modified material or cement is equivalent to or higher than calcia modified soil cured at 20℃ under the conditions of 50kg/m ³ and 100kg/m ³ . It showed an unconfined compressive strength of , and the strength development at low temperatures was improved, and even at low temperatures, it was possible to secure strength equal to or higher than conventional calcia modified soil at room temperature.

As shown in Figure 3, in the case of calcia modified soil cured at 20℃, it takes time to develop strength after mixing, but when PS ash-based modified soil is mixed at 50 kg/m ³ and 100 kg/m ³ 20 In the case of modified soil cured at ℃, the target value of Cone index qc = 200kN/m ² is reached within a few hours after mixing, and then the cone index qc = 400kN/m ² is quickly reached, which ensures normal workability. , the strength development at the early stage of mixing was improved, and the strength at the early stage of mixing was ensured.

As shown in Figure 4, when using the same mixture and curing at 5℃, the strength development of calcia modified soil is greatly delayed, but when PS ash-based modified soil is mixed at 100 kg/ ^m3 , qc = 3 hours later. The target value of 200kN/m ² was reached. When cement was mixed, the initial strength development effect was somewhat small, and when 100 kg/m ³ was mixed, the target value of qc = 200 kN/m ² was reached in about 16 hours. Strength development in the early stage of mixing at low temperatures was improved when PS ash-based modifier was mixed at 100 kg/m ³ or more, and strength could be secured in the early stages of mixing even at low temperatures. Furthermore, even when mixing cement, it is thought that if the amount exceeds 100 kg/m ³ but does not exceed 200 kg/m ³ , the strength development in the early stages of mixing at low temperatures will be considerably improved.

[Experiment example 2]
Calcia modified soil made by mixing dredged soil (liquidity limit wL = 107.2%, water content ratio 157.4% (1.5wL)) with steelmaking slag (maximum particle size 5 mm, 20vol% or 30vol%), and this calcia modified soil Modified soil was prepared by mixing predetermined amounts (50 kg/m ³ , 100 kg/m ³ , 200 kg/m ³ ) of PS ash-based modified material or blast furnace cement B type, and the soil was heated at 5℃ or 20℃. After curing, a uniaxial compression test (JIS A 1216) and a cone penetration test (JIS A 1228) were conducted. Figure 5 shows the test results of the uniaxial compression test (steelmaking slag: 30vol%) on the 28th day of age. Figure 6 shows the test results of the uniaxial compression test (steelmaking slag: 30vol%) on the 28th day of age when PS ash-based modifier was mixed, comparing the curing temperatures of 5°C and 20°C. Figure 7 shows the test results of the uniaxial compression test on the 28th day of age when PS ash-based modifier was mixed, comparing the mixed amount of steelmaking slag with 20vol% and 30vol%. Figure 8 shows the strength development in the early stage of mixing by a cone penetration test after curing at 20°C with a mixed amount of steelmaking slag of 30 vol%. Figure 9 shows the strength development in the early stage of mixing by a cone penetration test after curing at 5°C with a mixed amount of steelmaking slag of 30 vol%. Figure 10 shows the strength development status in the early stage of mixing by a cone penetration test after curing at 20°C with a mixed amount of steelmaking slag of 20 vol%.

As shown in Figure 5, the unconfined compressive strength of the calcia-amended soil aged 28 days after curing at 5°C was about 1/3 of that of the calcia-amended soil aged at 20°C; When mixing wood or cement, the strength increases as the mixing amount increases from 50 kg/m ³ to 200 kg/m ³ even when cured at 5°C, and when the mixing amount is 50 kg/m ³ or more, the strength increases when cured at 20°C. The strength of this soil was confirmed to be higher than that of calcia-amended soil, and strength development at low temperatures was improved.

As shown in Figure 6, when PS ash-based modifier is mixed, as the mixing amount increases from 50kg/ ^m3 to 200kg/ ^m3 , the strength difference due to the curing temperature difference between 20℃ and 5℃ becomes smaller. It was confirmed that the influence on strength development at low temperatures was reduced.

As shown in Figure 7, when the amount of steelmaking slag mixed in modified soil is reduced, the developed strength ^decreases . As a result, it was confirmed that the material exhibited a 28-day strength equivalent to or higher than that of calcia modified soil containing 30 vol% steelmaking slag cured at 20°C.

As shown in Figure 8, it takes time for calcia modified soil to develop strength, but when PS ash-based modifier or cement is mixed, strength development is improved in the early stage of mixing. In the case of steelmaking slag 30vol% and curing at 20℃, the target value of Cone index qc = 200kN/ ^m2 is exceeded after 24 hours when the mixing amount of PS ash-based modifier is 50kg/m3 ^or more and the cement is mixed. The condition was that the amount was 100 kg/m ³ or more.

As shown in Figure 9, in the case of steelmaking slag 30vol% and low temperature curing at 5℃, the cone index qc = 200kN/ ^m2 after 24 hours is higher than the target value because the amount of PS ash-based modifier mixed is The conditions were 200kg/m ³ or more, and the amount of cement mixed was 100kg/m ³ or more.

As shown in Figure 10, in the case of steelmaking slag 20vol% and curing at 20℃, the cone index qc = 200kN/ ^m2 after 24 hours is greater than the target value when the mixed amount of PS ash-based modifier is 100kg/m2. The condition was ^m3 or more.

Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the technical idea of the present invention. For example, the modified clay soil according to the present invention can be used for shallow area/tidal flat construction materials, submerged embankment materials, ground materials, etc., but is not limited thereto.

According to the present invention, in modified soil in which clayey soil, steelmaking slag, and PS ash-based modifying material or cement as a modifying material are mixed, strength development at low temperatures and strength development at an early stage of mixing can be improved. Since it is possible to improve the strength at low temperatures and the strength at the early stage of mixing, it is possible to ensure workability in winter and in cold regions, and also for normal construction such as transportation by dump trucks and work with construction machinery. can ensure sex.

Claims (5)

A modified soil obtained by modifying clay soil with a water content ratio of 1.1 to 2.0 wL (wL: liquid limit),
Cohesive soil, steelmaking slag and modification material are mixed,
The modification material is a paper sludge incineration ash-based modification material or cement ,
The 28-day strength of the modified soil after curing at 5°C is equal to or higher than the 28-day strength of the modified soil with clayey soil and steelmaking slag after curing at 20°C, and/or By determining the mixing amount of the modifying material so that the Cone index of the modified soil is 200 kN/m2 or more after 24 hours of mixing, ^the strength development at low temperatures in the modified soil is achieved. A modified clay soil that has improved at least one of its properties and its early mixing properties. The modified clay soil according to claim 1, wherein the steelmaking slag has a maximum particle size of 5 to 40 mm and a volumetric mixing ratio to the clay soil of 10 to 30 vol%. The mixing amount of the paper sludge incineration ash-based modifier is 50 to 200 kg per unit volume (m3) of the mixed material of the clayey soil and the steelmaking slag,
The modified clay soil according to claim 1 or 2, wherein the mixed amount of the cement is 50 to 200 kg per unit volume (m3) of the mixed material of the clay soil and the steelmaking slag. A method for producing modified soil obtained by modifying clay soil having a water content ratio of 1.1 to 2.0 wL (wL: liquid limit),
Mix steelmaking slag and modification material with clayey soil,
The modification material is a paper sludge incineration ash-based modification material or cement ,
The 28-day strength of the modified soil after curing at 5°C is equal to or higher than the 28-day strength of the modified soil with clayey soil and steelmaking slag after curing at 20°C, and/or By determining the amount of the modifier mixed so that the Cone index of the modified soil after 24 hours of mixing is 200 kN/m2 or more, ^the strength development at low temperatures and A method for producing modified clay soil, which improves at least one of the properties of strength development in the early stage of mixing. The method for producing modified clay soil according to claim 4, wherein the cement is made into a slurry by adding water and then mixed.

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