JP2019163637A - Soil material, manufacturing method of soil material, and ground construction method - Google Patents

Abstract

To provide a soil material, a manufacturing method of a soil material and a ground construction method having prescribed strength and water shielding property without using dredge soil.SOLUTION: A manufacturing method of a soil material mixes volcanic ash soil, water and steel slag while adjusting moisture content of the volcanic ash soil and the water at the time of mixing to 40 to 60 wt%, in which an uniaxial compressive strength 28 days after mixing is equal to or larger than 50kN/m, and a water permeability coefficient 91 days after mixing is equal to or smaller than 1.0×10m/s.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a soil material in which volcanic ash soil, steelmaking slag and water are mixed, a method for producing the soil material, and a ground formation method using the soil material.

  Conventionally, as a ground material that suppresses liquefaction and has a water-blocking performance, cement-modified soil in which solidified material such as cement is mixed with locally generated soil, or calcia modification such as steelmaking slag in dredged soil generated in port construction, etc. A calcia-modified soil in which a material is mixed is known (see Patent Documents 1 and 2).

  According to Non-Patent Document 1, volcanic ash is a natural pozzolana that can be widely distributed and collected in Japan, and is expected to improve the long-term durability of concrete, such as being used for breakwater concrete.

Japanese Patent No. 5014961 Japanese Patent No. 5318013

“Reactivity of volcanic ash and properties of concrete using volcanic ash” Monthly Bulletin No.729, February 2014

  When the conventional cement-improved soil is thrown into water and used, there is a problem that only the cement is washed and separated by water. In addition, calcia-modified soil, which is a mixture of dredged soil and steelmaking slag, is often difficult to procure dredged soil for construction far away from the coastal area, and dredged clay is highly viscous, so fine-grained steelmaking. There is a problem that mixing with slag, cement, or the like requires a long time and the working efficiency is lowered.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a soil material having a predetermined strength and water shielding performance without using dredged soil, a method for producing the soil material, and a ground preparation method. And

  In order to achieve the above object, according to the investigations, experiments and examinations of the present inventors, instead of dredged soil, volcanic ash soil having an appropriate fine grain content is used, and volcanic ash soil having an appropriate water content is highly alkaline. It has been found that by mixing steelmaking slag, it is possible to obtain a soil material that has high uniaxial compressive strength, can suppress liquefaction, and is excellent in water shielding performance.

The soil material for achieving the above object is a soil material in which volcanic ash soil, steelmaking slag and water are mixed, and the water content ratio at the time of mixing the volcanic ash soil and the water is 40 to 60% by weight, The uniaxial compressive strength after 28 days of mixing is 50 kN / m ² or more, and the hydraulic conductivity after 91 days of mixing is 1.0 × 10 ⁻⁷ m / s or less.

According to this soil material, the soil material mixed with volcanic ash soil, steelmaking slag and water has a water content ratio of 40 to 60% by weight when mixed with volcanic ash soil and water. The soil material can have a strength of 50 kN / m ² or more and a water permeability coefficient of 1.0 × 10 ⁻⁷ m / s or less after 91 days of mixing.

  In the soil material, it is preferable that the fine-grain content of the volcanic ash soil is 20% or more. Moreover, it is preferable that the said steelmaking slag is pH12 or more.

Another soil material for achieving the above object is a soil material obtained by mixing volcanic ash soil, steelmaking slag and water, and further mixing at least one of cement, blast furnace slag fine powder and blast furnace cement. The water content ratio when mixing the volcanic ash soil and the water is 40 to 80% by weight, the uniaxial compressive strength after 28 days of mixing is 50 kN / m ² or more, and the hydraulic conductivity after 91 days of mixing is It is 1.0 × 10 ⁻⁷ m / s or less.

According to this soil material, volcanic ash soil, steelmaking slag and water are mixed, and the soil material obtained by further mixing at least one of cement, blast furnace slag fine powder and blast furnace cement is a mixture of volcanic ash soil and water. When the moisture content at the time is 40 to 80% by weight, the uniaxial compressive strength after 28 days of mixing is 50 kN / m ² or more, and the hydraulic conductivity after 91 days of mixing is 1.0 × 10 ⁻⁷ m / s or less. It can be a soil material.

The method for producing a soil material for achieving the above object comprises mixing volcanic ash soil, water and steelmaking slag, adjusting the water content ratio when mixing the volcanic ash soil and water to 40 to 60% by weight, The uniaxial compressive strength after 28 days of mixing is 50 kN / m ² or more, and the hydraulic conductivity after 91 days of mixing is 1.0 × 10 ⁻⁷ m / s or less.

According to this method for producing a soil material, volcanic ash earth, steelmaking slag and water are mixed, and the water content ratio at the time of mixing volcanic ash earth and water is adjusted to 40 to 60% by weight. A soil material having a compressive strength of 50 kN / m ² or more and a water permeability coefficient of 1.0 × 10 ⁻⁷ m / s or less after 91 days of mixing can be obtained.

  The ground formation method for achieving the above object is to create the ground by placing the above-mentioned soil material or the soil material manufactured by the above-described manufacturing method.

  According to this ground preparation method, by using the above-mentioned soil material or the soil material manufactured by the above-described manufacturing method, a ground that has high uniaxial compressive strength, can suppress liquefaction, and has excellent water shielding performance. Can be created.

  In the ground preparation method, the soil material can be placed for landfill or backfill.

  ADVANTAGE OF THE INVENTION According to this invention, the soil material which has predetermined intensity | strength and water-insulating performance, without using dredged soil, the manufacturing method of a soil material, and the ground preparation method can be provided.

It is a flowchart for demonstrating the main processes of the manufacturing method of the earth material by this embodiment. It is a graph which shows the uniaxial compressive strength after mixing 28 days and mixing 91 days for every case (A-1 to D-3) among the results of Examples and Comparative Examples in Table 1. It is a graph which shows the relationship between the water permeability coefficient after mixing 91 days after the result of the Example of Table 1, and a comparative example, and a water content ratio. It is a graph which shows the relationship between the measurement result of pH of the steelmaking slag used in the present Example, and the water permeability after 28 days of mixing in the case of the water content ratio of 60%, 50% and 40% in Table 1. It is a graph which shows the relationship between the measurement result of pH of the steelmaking slag used in the present Example, and the uniaxial compressive strength after 28 days of mixing in the case of the water content ratio of 60%, 50% and 40% in Table 1. It is a cross-sectional schematic diagram which shows roughly the steel sheet pile back structure of a quay using the earth material of a present Example. It is a graph which shows the relationship between the uniaxial compression test result implemented after curing the sample extract | collected at the time of the ground preparation in a present Example for a fixed period, and the elapsed time after mixing. It is a graph which shows the relationship between the water permeability test result implemented after curing the sample similar to FIG. 7 for a fixed period, and the elapsed time after mixing.

Hereinafter, modes for carrying out the present invention will be described. The soil material according to the present embodiment is a mixture of volcanic ash soil with a fine particle content of 20% or more, steelmaking slag with high alkalinity, and water, and the water content ratio when mixing the volcanic ash soil and water is 40. By being -60% by weight, the uniaxial compressive strength after 28 days of mixing is 50 kN / m ² or more, and the hydraulic conductivity after 91 days of mixing is 1.0 × 10 ⁻⁷ m / s or less.

  Volcanic ash soil is a ground formed by the accumulation of volcanic ash, which generally contains a lot of soluble silica and reacts with calcium hydroxide in an alkaline environment to form calcium silicate hydrate and solidify. It is a soil that has sex. In Hokkaido and other countries, there are many active volcanoes, and volcanic ash soil can be procured at a low price.

In addition, there is ASTM C618 as a standard of pozzolanic material as an admixture for concrete, but this standard includes Class N (natural pozzolana is more than 70% of SiO ₂ + Al ₂ O ₃ + Fe ₂ O ₃ and SO ₃ It is specified that the loss on ignition is less than 4.0% and the loss on ignition is less than 10% (see Non-Patent Document 1), and the standard for evaluating the pozzolanic properties of volcanic ash is BS EN 196-5: 2005 (Pozzolanicity test for pozzolanic cements )

  The reason why the fine ash content of the volcanic ash soil is set to 20% or more is considered to be the same as the conditions of the dredged soil that is the raw material of the calcia-modified soil that solidifies by the same mechanism.

  As the steelmaking slag, a steelmaking slag generated in processes such as hot metal preliminary treatment, converter blowing, and casting can be used. Steelmaking slag having a high alkalinity means one having a pH of 12 or more or containing free CaO: f-CaO of 0.5% or more, preferably 1.0% or more. Steelmaking slag containing 0.5% or more, preferably 1.0% or more of f-CaO is the same as the conditions for steelmaking slag applied to calcia modified soil that is solidified by the same mechanism (solidification reaction by elution of Ca). (See Patent Documents 1 and 2, Coastal Technology Research Center “Technical Manual for Utilization of Calcia Modified Soil at Ports, Airports, Coasts, etc.” Appendix 2-5, 2017)).

  Moreover, when the alkalinity of steelmaking slag is low, uniaxial compressive strength and water permeability can be adjusted by further mixing cement, blast furnace slag fine powder, or blast furnace cement. As the blast furnace slag fine powder, pulverized blast furnace granulated slag or one obtained by adding gypsum to this can be used. Blast furnace cement consists of fine blast furnace slag powder. The improved soil in which cement is mixed with volcanic ash soil shows almost no increase in uniaxial compressive strength and low permeability after 28 days of mixing, whereas volcanic ash soil, cement, steelmaking slag and water are mixed according to this embodiment. The improved soil (soil material) has a large increase in long-term strength after 28 days of mixing, and the water permeability also decreases. This is presumably because the pozzolanic reaction occurs between steelmaking slag and volcanic ash soil, and the strength is improved over the long term and the water permeability is lowered. For this reason, in the soil material further mixed with cement, blast furnace slag fine powder, or blast furnace cement, the upper limit of the water content ratio when mixing volcanic ash soil and water may be 80% by weight.

  Next, main steps of the method for producing a soil material according to the present embodiment will be described with reference to the flowchart of FIG. In a soil material manufacturing plant or the like, volcanic ash soil is stored in a charging hopper by a backhoe (S01), steelmaking slag is stored in another charging hopper by a backhoe (S02), and water is stored in a tank (S03). After preparing volcanic ash soil, steelmaking slag and water in this way, the volcanic ash soil from the input hopper is weighed with a weighing belt conveyor or the like (S04), and the steelmaking slag from the input hopper is measured with a weighing belt conveyor or the like. (S05), the water sent by the pump from the tank was weighed with a flow meter (06), and each of these weighed materials was transported and mixed with a continuous 2-shaft paddle mixer (S07) and mixed. The soil material is transported to the construction site and placed (S08), and cured for a predetermined period (S09).

By the manufacturing method described above, a soil material having a uniaxial compressive strength of 50 kN / m ² or more after 28 days of mixing and a water permeability coefficient of 1.0 × 10 ⁻⁷ m / s or less after 91 days of mixing can be obtained. . Moreover, when mixing a cement, blast furnace slag fine powder, or a blast furnace cement as needed, it mixes with water, is made into cement milk, and measures with a flowmeter etc. and mixes predetermined amount.

  Since volcanic ash soil has a lower natural water content and lower viscosity than dredged soil, it is preferable to use a continuous biaxial paddle mixer or the like as in this embodiment when mixing with steelmaking slag containing fine particles. Thereby, since it can mix in a short time, construction time can be shortened and construction cost reduction is realizable.

In addition, the measurement process (S04-S06) of volcanic ash soil, steelmaking slag, and water of FIG. 1 is performed as follows. About volcanic ash soil and water, volcanic ash soil and water are measured so that the water content ratio at the time of mixing volcanic ash soil and water may become 40 to 60 weight% (S04, S06). Steelmaking slag is measured so as to have a predetermined volume ratio α with respect to volcanic ash soil (S05). The volume ratio α can be obtained by the following equation (1) from the volume Vs of volcanic ash soil calculated from the wet unit volume mass and the actual volume Vc of steelmaking slag calculated from the surface dry density.
α = Vc / (Vc + Vs) (1)
Moreover, when adding cement, blast furnace slag fine powder, or blast furnace cement further, it adds to the earth material which mixed volcanic ash soil, steelmaking slag, and water, and is mixed and mixed.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

As shown in Table 1 below, the water content of the volcanic ash is adjusted to three levels of 40%, 50% and 60% by adding water to the volcanic ash (fine particle content: 33.3%, natural water content: 21.3%) as an example. After curing for a certain period of nine types of soil materials (A-1 to 3, B-1 to 3, C-1 to 3) mixed with three types of steelmaking slags A, B, and C with different f-CaO, A uniaxial compression test and a water permeability test were conducted. Moreover, the same test was implemented similarly except having used steelmaking slag D (D-1-3) from which f-CaO differs as a comparative example. The results are also shown in Table 1. The uniaxial compression test was performed based on JIS A1216: 2009 (soil uniaxial compression test method), and the water permeability test was performed based on JIS A 1218: 2009 (soil permeability test method). In the tables and drawings, the index of 冪 may be expressed by using E, for example, 7.8E-08 means 7.8 × 10 ⁻⁸ .

FIG. 2 is a graph showing the uniaxial compressive strength after mixing 28 days and mixing 91 days for each case (A-1 to D-3) among the results of Examples and Comparative Examples in Table 1. FIG. 3 is a graph showing the relationship between the water permeability and the water content ratio after 91 days of mixing, among the results of Examples and Comparative Examples in Table 1. From Table 1, FIG. 2, and FIG. 3, it turns out that a uniaxial compressive strength increases and the hydraulic conductivity becomes small as the curing period of a soil material becomes long. Moreover, about each case (A-1-C-3) of three types of steelmaking slag A, B, and C of an Example, while the uniaxial compressive strength after mixing 28 days exceeds 50 kN / m < ² >, mixing The hydraulic conductivity after 91 days became 1.0 × 10 ^-7 m / s or less.

In the steelmaking slag D of the comparative example, the uniaxial compressive strength after 28 days of mixing did not reach 50 kN / m ² for the cases (D-1, D-2) with a moisture content of 50% and 60%, and the moisture content was 40%. In case (D-3), it exceeded 50 kN / m ² , but as shown in FIG. 3, the hydraulic conductivity after 91 days of mixing was not less than 1.0 × 10 ⁻⁷ m / s for all the water content ratios. This is probably because the steelmaking slag D has a low f-CaO, a low pH, and a low alkalinity, as will be described later. The soil material as in this embodiment has a higher strength as the moisture content is lower. However, in experiments other than the cases shown in Table 1, the materials could not be kneaded when the moisture content was 30%. In addition, when the water content was 80%, the specimen did not stand by itself.

Example using the same volcanic ash and steelmaking slag D as shown in Table 1 and mixing blast furnace cement to a moisture content of 60% and adding blast furnace cement to 30kg / m ³ and 100kg / m ³ (D-5 , D-6) were tested in the same manner as in Table 1. The results are shown in Table 2 below.

Comparative Example (D-1) in Table 1 shows no mixing of blast furnace cement, 28 days after mixing, uniaxial compressive strength is less than 50 kN / m ² , and hydraulic conductivity exceeds 1.0 × 10 ^-7 m / s However, in the examples (D-5, D-6) mixed with blast furnace cement in Table 2, the uniaxial compressive strength after 28 days of mixing greatly exceeded 50 kN / m ² and the hydraulic conductivity was the stage after 28 days of mixing. It became 1.0 × 10 ^-7 m / s or less. The hydraulic conductivity is considered to be that the pozzolanic reaction occurs between steelmaking slag and volcanic ash soil, resulting in a decrease in water permeability over the long term. Also in Example (D-7), which has a high water content ratio of 80%, by adding blast furnace cement, a uniaxial compressive strength of 50 kN / m ² or more and a hydraulic conductivity of 1.0 × 10 ^-7 m / s or less are achieved. Could be achieved.

Next, Table 3 shows the results of measuring f-CaO and pH for steelmaking slags A to D shown in Tables 1 and 2. FIG. 4 shows the relationship between the measurement results of the pH of each steelmaking slag in Table 3 and the hydraulic conductivity after 91 days of mixing when the water content ratios in Table 1 are 60%, 50% and 40%. From FIG. 4, it is found that the pH is 11.9 or more when the condition that the water permeability coefficient is 1.0 × 10 ⁻⁷ m / s or less is obtained.

Further, FIG. 5 shows the relationship between the measurement results of the pH of the steelmaking slag shown in Table 3 and the uniaxial compressive strength after 28 days of mixing when the water content ratios shown in Table 1 are 60%, 50% and 40%. FIG. 5 shows that when the pH is 11.9 or more, the uniaxial compressive strength after 28 days of mixing greatly exceeds 50 kN / m ² . In addition, f-CaO was measured by ethylene glycol extraction-ICP emission spectrometry (Iron and Steel Institute method), and pH was measured by preparing a test solution according to Ministry of the Environment Notification No. 46-glass electrode method.

  In the soil material according to the present embodiment, Ca is eluted from the steelmaking slag and the solidification reaction proceeds, but the pH increases with the dissolution of Ca. As can be seen from Table 3, because the steelmaking slag D has less f-CaO and less pH than the steelmaking slags A to C, the uniaxial compressive strength is small and the water permeability coefficient is large, as shown in Table 1. . However, as mentioned above, when the steelmaking slag has insufficient pH or f-CaO, it is possible to satisfy the target strength and target permeability by adding cement, blast furnace slag fine powder, or blast furnace cement. is there.

Next, volcanic ash, steelmaking slag, blast furnace cement, and water are mixed by a continuous twin-shaft paddle mixer (100 m ³ / h) to produce a soil material. An example of ground formation as a water countermeasure layer / liquefaction countermeasure layer will be described. The cross-sectional schematic diagram of the steel sheet pile back structure of this quay is shown in FIG. The steel sheet pile back structure of the quay in FIG. 6 is a steel sheet pile in contact with seawater on the back side (land side) with a backside stone placed on the land side with the soil material of this embodiment. It is. As shown in FIG. 1, the soil material is transported after being mixed and placed and then cured for a predetermined period.

The soil material used for the steel sheet pile rear structure of the quay in Fig. 6 is to add water so that the water content of the volcanic ash is 65% to the volcanic ash (fine particle content of about 35%, average natural water content 26.6%), Steelmaking slag was added to a volume ratio of 35%, and blast furnace cement was added and mixed at 50 kg / m ³ min. FIGS. 7 and 8 show the results of conducting a uniaxial compression test and a water permeability test after curing the samples (collected from nine places) collected during the ground preparation for a certain period of time. As shown in FIG. 7, the uniaxial compressive strength increased with the lapse of the post-mixing period, and the uniaxial compressive strength after 28 days of mixing exceeded 50 kN / m ² . The uniaxial compressive strength without liquefaction is 50-100 kN / m ² or more (“Pre-mixing Method Technical Manual” Coastal Technology Research Center, 2008), but this test result greatly exceeds this. Moreover, as shown in FIG. 8, the hydraulic conductivity decreased with the passage of the period after mixing, and the hydraulic conductivity became 1.0 × 10 ⁻⁷ m / s or less in all cases after 91 days of mixing. Thus, the steel sheet pile back structure of the quay of FIG. 6 was able to be provided with the water shielding countermeasure layer and the liquefaction countermeasure layer made of the soil material according to this example.

  Next, Table 4 shows a comparison between the volcanic ash used in the soil material of this example and the literature values (ASTM C618) for each condition when using volcanic ash as an admixture for concrete. As can be seen from Table 4, the volcanic ash used in this example is also applicable as an admixture for concrete. The ignition loss test was performed based on JIS R 5202.

  As mentioned above, although the form and Example for implementing this invention were demonstrated, this invention is not limited to these, A various deformation | transformation is possible within the range of the technical idea of this invention. For example, the steel sheet pile rear structure in FIG. 4 is not limited to a quay, but can be applied to a seawall. In addition, the soil material according to the present invention is not limited to use on the steel sheet pile back structure of a quay or revetment, but can be used for other ground preparations, for example, used for land reclamation and backfilling. it can.

  According to the soil material, the soil material manufacturing method and the ground preparation method of the present invention, by using volcanic ash soil, a soil material having a predetermined strength and water shielding performance can be obtained without using dredged soil. By using this soil material, it is possible to effectively take measures for water shielding and liquefaction in ground formation.

Claims (7)

A soil material that mixes volcanic ash soil, steelmaking slag and water,
The water content at the time of mixing the volcanic ash soil and the water is 40 to 60% by weight,
The uniaxial compressive strength after 28 days of the mixing is 50 kN / m ² or more,
A soil material having a hydraulic conductivity of 1.0 × 10 ⁻⁷ m / s or less after 91 days of mixing.   The soil material according to claim 1, wherein a content of fine particles of the volcanic ash soil is 20% or more.   The soil material according to claim 1 or 2, wherein the steelmaking slag has a pH of 12 or more. A soil material that mixes volcanic ash soil, steelmaking slag and water,
Further mixing at least one of cement, blast furnace slag fine powder and blast furnace cement;
The water content at the time of mixing the volcanic ash soil and the water is 40 to 80% by weight,
The uniaxial compressive strength after 28 days of the mixing is 50 kN / m ² or more,
A soil material having a hydraulic conductivity of 1.0 × 10 ⁻⁷ m / s or less after 91 days of mixing. Mixing volcanic ash soil, water and steelmaking slag, adjusting the water content ratio at the time of mixing the volcanic ash soil and the water to 40-60 wt%,
The uniaxial compressive strength after 28 days of the mixing is 50 kN / m ² or more,
The method for producing a soil material, wherein the water permeability after 91 days of mixing is 1.0 × 10 ⁻⁷ m / s or less.   A soil creation method for creating a ground by placing the soil material according to any one of claims 1 to 4 or the soil material produced by the production method according to claim 5.   The ground preparation method according to claim 6, wherein the soil material is placed for landfill or backfill.

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