JP5728845B2 - Method for estimating strength of modified dredged soil and method for modifying dredged soil - Google Patents

Description

  The present invention accurately estimates the strength of a mixed material of dredged soil and steelmaking slag in a technique for modifying the strength of dredged soil by mixing steelmaking slag in order to effectively use soft dredged soil in the sea area. The present invention relates to a strength estimation method that can be used, and a method for modifying a clay that can determine an appropriate mixing amount of steelmaking slag with respect to the clay.

For the purpose of improving the water quality environment, shallow areas and tidal flats are being created. Conventionally, shallow ground and tidal flats have been constructed by using a crushed stone to install an earth retaining submarine offshore, and then installing dredged soil as a filling material on the shore side (land side) and covering the surface with natural sand. Such a construction method is adopted.
On the other hand, Patent Document 1 discloses a technique for performing strength modification by actively utilizing the CaO content contained in the steel slag and mixing the steel slag with the clay. In this technique, the strength of the clay is improved mainly by a pozzolanic reaction between the CaO content of the steel slag and Si, Al, etc. of the clay. In this patent document 1, detailed examination is made about the amount of free CaO of steel slag to be used and the mixing ratio with respect to the clay, and conditions suitable for strength modification are shown.

JP 2009-121167 A

However, when the inventor further studied the technique of Patent Document 1, even if the type and mixing ratio of the steelmaking slag are the same, the strength development behavior is completely different depending on the mixed material (kneaded clay + steeling slag). It turns out that there is a case. In addition, even when similar steelmaking slag was mixed for the same clay, the strength could be seen to change.
As long as the mixed material of the clay and steelmaking slag is simply solidified, there is no particular problem with the technique of Patent Document 1, but it is designed to be structurally strong or easy to grow. In some cases, a specific strength is desired. In such a case, it is necessary to set conditions so that an appropriate strength can be ensured. However, as described above, it is difficult to obtain the expected strength with the technique of Patent Document 1, and the strength is increased by repeating various experiments. I had to set it empirically.

Therefore, the object of the present invention is to accurately estimate the strength of the mixed material of the clay and the steelmaking slag when the steelmaking slag is mixed to improve the strength of the clay. An object of the present invention is to provide a method for estimating the strength of the modified clay, which can realize an appropriate strength design.
In addition, another object of the present invention is to improve the dredged soil that can determine the appropriate mixing amount of the steel-making slag according to the design strength when the steel-making slag is mixed to modify the dredged strength. It is to provide a method.

In order to solve the above-mentioned problems, the present invention has analyzed the various intrinsic properties of the clay and steelmaking slag and the solidification behavior after mixing. As a result, the solidification of the modified clay is based on several important physical properties. It was found that the later strength can be accurately estimated, and thus an appropriate strength design can be realized. Therefore, it was found that by using this, an appropriate mixing amount of the steelmaking slag according to the design strength can be determined.
The solidification reaction between the clay and the steelmaking slag is considered to be related to the supply amount of Ca ions and OH ions from the steelmaking slag and the amount of Si leaching from the clay. As a result of further detailed studies by the present inventors, it was found that the Si content of the clay does not necessarily leached into the solution, and it is sufficient that the reactivity is high on the surface of the clay. That is, it was found that the more fine particles of the kneaded material, the higher the reactivity and the easier the strength. On the other hand, it is known that the fine particles in the clay also have an effect of adsorbing Ca. As a result of the study by the present inventors, when steelmaking slag is mixed with clay, it has been found that stable strength expression can be realized after a certain amount of Ca adsorption is finished in the Ca component supplied from the steelmaking slag. It was. Furthermore, it has been found that the steel slag to be reacted is much more influenced by the free CaO content than the component composition such as the CaO amount, and in addition, the ratio of slag particles having a particle size of 2 mm or less is important. And by using the estimation formula considering these factors, the strength of the mixed material of clay and steelmaking slag can be accurately estimated without performing various accuracy experiments, and the appropriate strength design of the mixed material It was found that can be realized. Moreover, it turned out that the optimal mixing amount of the steelmaking slag with respect to the clay can be determined while selecting the optimum steelmaking slag (composition, particle size) according to the design strength of the mixed material.

The present invention has been made on the basis of such findings and has the following gist.
[1] A method for estimating the strength of the mixed material (x) of the clay and the steelmaking slag when the steelmaking slag is mixed and reforming the clay, and based on the following formula (1) A method for estimating the strength of the modified dredged material, characterized in that an estimated value f (N / cm ² ) of the uniaxial compressive strength after the 28-day curing of (x) is obtained.
f = α × Ds × Sg × {(Co−Ch) / W a} (1)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: 3.6

[2] A method of modifying the clay by mixing steelmaking slag, wherein the target value of the uniaxial compressive strength after the 28-day curing of the mixed material (x) of clay and steelmaking slag is set to f _O (N / cm ² ), the mixing method of the clay is determined by determining the amount of steelmaking slag mixed with the clay based on the following formula (2).
f _O = α × Ds × Sg × {(Co−Ch) / W a} (2)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: 3.6

According to the strength estimation method of the modified clay of the present invention, when the strength of the clay is improved by mixing the steelmaking slag, the strength of the mixed material of the clay and the steelmaking slag can be accurately estimated. Thus, an appropriate strength design of the modified clay can be realized.
Further, according to the method for reforming clay according to the present invention, when steelmaking slag is mixed to improve the strength of the clay, an appropriate mixing amount of steelmaking slag according to the design strength can be determined. The clay can be modified to a desired design strength.
The method of the present invention as described above does not require repeated experiments for obtaining optimum conditions as in the prior art, and it is only necessary to perform a test using a reagent (slaked lime) on the clay to be modified. Therefore, it can be implemented very simply.

A graph showing the relationship between the steelmaking slag addition rate and the uniaxial compressive strength of the mixed material after 28-day curing for a mixed material in which steelmaking slag is mixed with different types of clay When different types of clay are mixed separately with slaked lime (calcium hydroxide reagent) and steel slag, the uniaxial compressive strength of the mixed material: 50 kN / m ² is expressed and the amount of slaked lime added Graph showing correlation A certain amount of steelmaking slag having a Ca concentration at a substantially constant level and a different free CaO content is added to the clay, and the mixed material of the clay and the steelmaking slag is a mixture of the free CaO content of the steelmaking slag and the mixed material 28. Graph showing the relationship with uniaxial compressive strength after daily curing The graph which shows the relationship between the grain size of steelmaking slag, and the uniaxial compressive strength after 28-day curing of a mixed material about the mixed material which mixed two types of steelmaking slag (particle size of 5 mm or less) with clay in the condition which changed the particle size A graph showing the relationship between the moisture content of the mixed material and the uniaxial compressive strength after 28 days of curing for the mixed material using only two types of steelmaking slag and changing only the water content ratio by combining the same clay and steelmaking slag. Steelmaking slag is added to the clay with the ratio of particles having a particle size of 0.075 mm or less by adding silica sand, and the mixed material of the clay and steelmaking slag has a particle size of 0.075 mm or less in the clay. Graph showing the relationship between the ratio of soil particles and uniaxial compressive strength after 28 days curing (strength ratio when uniaxial compressive strength of dredged soil before adding silica sand is “1”) The graph which shows the correlation with the estimated value of the uniaxial compressive strength calculated | required by this invention method, and the measured value of uniaxial compressive strength about the mixed material of Example 1. The graph which shows the measured value of the uniaxial compressive strength of a mixed material in Example 2 which modify | reformed the clay according to the mixing amount of the steelmaking slag determined by this invention method

  TECHNICAL FIELD The present invention relates to a technique for actively using a CaO content contained in steelmaking slag and mixing the steelmaking slag with dredged soil to effectively use soft dredged soil in the sea area. is there. Here, the steelmaking slag mixed with the clay is slag generated in the steelmaking process of the steel production process. For example, hot metal pretreatment slag (dephosphorization slag, desiliconization slag, desulfurization slag, etc.), converter decarburization, etc. Slag, electric furnace slag, secondary refining slag, etc. are mentioned, and one or more of these can be used.

Hereinafter, the strength estimation method of the modified clay, which is the first invention of the present application, will be described.
The strength estimation method of the modified clay is a method for estimating the strength of the mixed material (x) of the clay and the steelmaking slag when the steelmaking slag is mixed to improve the clay. ) To obtain an estimated value f (N / cm ² ) of uniaxial compressive strength after 28 days of curing of the mixed material (x).
f = α × Ds × Sg × {(Co−Ch) / W a} (1)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: Constant determined by the type of slaked lime used to determine Ch

  FIG. 1 shows that steelmaking slag (converter decarburization slag, particle size of 5 mm or less, slag particle size of 2 mm or less is 15% by mass, free CaO at various addition rates to dredged soil collected in different places (water areas). The content of 9 mass%) is added, and the uniaxial compressive strength after curing for 28 days is shown for the mixed material of this clay and steelmaking slag. According to this, when steelmaking slag having exactly the same particle size and composition is added to the clay, the strength does not develop until a certain addition amount, but the strength starts to appear when a certain addition amount is exceeded, and then one-dimensional. It was found that it increased. It was also found that there is a difference in the amount of steelmaking slag that begins to develop strength depending on the type of clay.

When steelmaking slag is added to the clay, the strength of the mixed material does not develop up to a certain addition amount as shown in FIG. 1, because the clay has an effect of adsorbing Ca, and this Ca adsorption is It is thought that this is because the strength begins to develop after the completion, which can be said to be a reaction suppressing effect exhibited by the clay. Under the assumption that the clay exhibits such a reaction suppressing effect, the present inventors mixed slaked lime (calcium hydroxide reagent) with the clay instead of the steelmaking slag, and conducted the same test. went. As a result, it turned out that the behavior similar to the case where steelmaking slag is added with respect to each clay is shown. Since the strength of the mixed material is not so high, the uniaxial compressive strength that can be regarded as a stable strength: addition amount of slaked lime expressing 50 kN / m ² and steelmaking slag (converter decarburization slag, particle size of 5 mm or less, free CaO content: FIG. 2 shows a correlation with the addition amount of 5 mass%). That is, each plot of FIG. 2 shows the addition amount of slaked lime with which uniaxial compressive strength: 50 kN / m ² is expressed and the addition amount of steelmaking slag when slaked lime and steelmaking slag are separately added to a certain type of clay. Show.
According to FIG. 2, a very strong correlation is recognized between the addition amount of slaked lime and steelmaking slag in terms of developing the strength of the mixed material. As an index for starting the strength development of the mixed material of steelmaking slag and clay, slaked lime (water It was considered that the minimum amount required to develop the strength when the calcium oxide reagent) was added was important.

  Furthermore, since it was thought that the influence of the CaO component in steelmaking slag was large in developing the strength of the mixed material, the relationship between the CaO content of the steelmaking slag and the mixed material was investigated. A very strong correlation was not observed between the strength and the CaO content of the steelmaking slag. As a result of further investigations, it was found that, among the Ca components in the steelmaking slag, the correlation between the amount of free CaO that is particularly reactive and the strength of the mixed material is high. Steelmaking slag (converter decarburization slag, particle size 5mm or less) with a free CaO content with a constant Ca concentration (about 35 to 40% by mass) and a certain amount (soil: steelmaking slag) = 70 volume%: 30 volume%), and the results of examining the uniaxial compressive strength after curing for 28 days for the mixed material of the clay and the steelmaking slag are shown in FIG. According to FIG. 3, it was found that as the free CaO content in the steelmaking slag increases, the strength of the mixed material increases, and thus this free CaO content is important as a parameter.

  Furthermore, since it is thought that the particle size of steelmaking slag strongly influences the reactivity, as a result of investigating the influence, it was found that the ratio of slag particles having a particle size of 2 mm or less has a great influence on the strength of the mixed material. 4 (a) and 4 (b), two types of steelmaking slag (converter decarburization slag, particle size of 5 mm or less) were converted into clay (the particle size of 0.075 mm or less of the clay particles under the condition of changing the particle size). The ratio between the slag particle size and the strength of the mixed material is shown. FIG. 4 (a) shows the same steelmaking slag in which the proportion of slag particles having a particle size of 0.075 mm or less is changed, and FIG. 4 (b) shows the same steelmaking slag in which the proportion of slag particles having a particle size of 2 mm or less is changed. The uniaxial compressive strength after curing for 28 days was examined for the mixed material of this clay and steelmaking slag (additional soil: steelmaking slag = 70 vol%: 30 vol%).

The following points were found from the results of FIG. Basically, steelmaking slag with a finer particle size is assumed to contribute to the reaction, and this tendency appears even in the ratio of slag particles with a particle size of 0.075 mm or less, but in terms of correlation with strength, the particle size is 2 mm or less. It was found that the ratio of slag particles was highly correlated. The reason for this is not necessarily clear, but it is estimated that large particles have poor reaction activity due to their small surface area, whereas fine particles alone are presumed to have poor reaction activity due to reaction with CO ₂ in the atmosphere. It is considered that an appropriate particle size is important.

  On the other hand, dredged soil caused by dredging has its own characteristics, and the characteristics fluctuate even when dredging from the same water area. As a result of analyzing this influence, it was found that the influence of the water content ratio is large. FIG. 5 shows a mixture of two types of steelmaking slag (converter decarburization slag, particle size of 5 mm or less), with the same combination of clay and steelmaking slag, changing only the water content ratio (slag: steelmaking slag = 70 volumes). %: 30% by volume), the relationship between the water content ratio and the uniaxial compressive strength after curing for 28 days was examined. According to FIG. 5, it was found that the strength of the mixed material decreased as the water content ratio increased, and there was a clear correlation between the water content ratio and the strength.

Furthermore, as a result of proceeding with the analysis focusing on the grain size of the clay, it was found that the ratio of the clay particles having a particle size of 0.075 mm or less is important. Steelmaking slag (converter decarburization slag, particle diameter of 5 mm or less) is added to the clay whose ratio of particles having a particle diameter of 0.075 mm or less has been reduced by adding silica sand, and a mixture of this clay and steelmaking slag ( The uniaxial compressive strength after curing on the 28th was examined for the clay (steel making slag = 70 vol%: 30 vol%). FIG. 6 shows the relationship between the ratio of the soil particles having a particle size of 0.075 mm or less in the clay and the strength thereof. Here, the vertical axis in FIG. 6 indicates the strength ratio when the uniaxial compressive strength before dredged silica sand (ratio of soil particles having a particle size of 0.075 μm or less: 90 mass%) is “1”. Indicated.
According to FIG. 6, it turns out that the intensity | strength of a mixed material is changing according to the ratio of the soil particle of 0.075 mm or less in the clay. This indicates that the ratio of the fine particles is important in order to stably develop the strength like the paste portion in concrete.

From the above results, by using a specific strength estimation formula as shown below, it is only necessary to add a reagent (slaked lime) to the modification target clay and obtain the amount of reagent that gives a predetermined strength. It was found that the strength of steel and slag mixed material can be estimated accurately. That is, in the preliminary test, slaked lime is mixed with the clay to be modified, and the blended amount of slaked lime when the uniaxial compressive strength after the 28-day curing of the mixed material is 50 kN / m ² , Based on the following formula (1), the estimated value f (N / cm ² ) of the uniaxial compressive strength after the 28-day curing of the mixed material (x) is obtained.
f = α × Ds × Sg × {(Co−Ch) / W a} (1)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: Constant determined by the type of slaked lime used to determine Ch

Here, the strength expression in the mixed material of the clay and the steelmaking slag is the same mechanism as the pozzolanic reaction in the cement, and Ca supplied from the steelmaking slag reacts with the Si content of the clay and Ca-Si- Strength is developed by generating the H ₂ O compound. Accordingly, it is considered that the amount of water that is inversely proportional to the strength in the case of reactions such as Ca amount, Si amount, and cement affects the strength development. As a result of analyzing by combining such viewpoints and various characteristics of the steelmaking slag and clay described above, the above strength estimation formula has been found. That is, as a parameter related to the amount of Ca, there is a Ca supply amount from steelmaking slag, which is a ratio Sg obtained by dividing the mass of slag particles having a particle size of 2 mm or less in the mixed material by the mass of steelmaking slag in the mixed material. And free CaO amount Co. On the other hand, there is a reaction suppression effect due to the adsorption of Ca by the clay, and this reaction suppression effect is an index based on the amount of slaked lime obtained until the predetermined strength of the mixed material is obtained, which is obtained in a prior test. The free CaO that contributes to is represented by (Co-Ch). In addition, the strength development is the ratio between (Co-Ch) and the moisture contained in the mixed material (seawater and water brought in by dredged soil, or seawater and water added further) in the same way as the binder / water in cement. It largely depends on (Co-Ch) / Wa. As for Ch, “mass of slaked lime until a predetermined strength of the mixed material is developed × 1.5” is set as shown in FIG. 2. The rate has a strong correlation. Comparing the added amount of slaked lime with the free CaO content in steelmaking slag calculated based on the free CaO content in steelmaking slag, the free CaO content in steelmaking slag is 1 This is because the equivalent of 5 times is required. On the other hand, with respect to the Si component, the parameter due to the amount of soil in the clay has a contribution of the ratio Ds of clay particles having a particle size of 0.075 mm or less in the mixed material. By multiplying these, the skeleton of the strength index is obtained, and this is multiplied by a constant α for applying to the uniaxial compressive strength, and the estimated value f (N / cm ) of the uniaxial compressive strength of the mixed material (x). ² ) .
Here, the constant α is determined by the type of slaked lime used for obtaining Ch (for example, the particle size and / or purity that affects the activity), and is usually selected in the range of about 3 to 4.

In the prior test for obtaining Ch, for example, the rising point of strength is obtained by mixing while changing the amount of slaked lime added to the clay to be modified, and measuring its compressive strength. Is possible. Although the test method is not particularly limited, JIS-R-5201: 1997 “Physical test method of cement” 8.3.1 Mixing of cement paste (1) Kneading method and Geotechnical Society “Soil test Method and explanation ”Chapter 5 In accordance with the mixing method of specimen preparation by tamping the stability degree, sufficient data can be obtained if it is evaluated at the level of several liters.
In the past, the strength of the mixed material of clay and steelmaking slag could not be clearly predicted, or it was necessary to determine the mixing conditions to obtain the desired strength by repeating the experiment, but by applying the method of the present invention By simply conducting a preliminary test using a reagent (slaked lime) on the clay to be modified, it is possible to easily estimate the strength of the mixed material. It is possible to easily set in advance.

Next, a method for reforming clay, which is the second invention of the present application, will be described.
When the steelmaking slag is mixed to improve the clay, if the target strength (design strength) of the mixed material is given, the mixing amount of the steelmaking slag for obtaining the target strength can be obtained by the above strength estimation formula. .
That is, in the modification method of dredged material of the present invention, when the target value of 28 days uniaxial compressive strength after curing of the mixed material and dredged material steel slag (x) was _{^{f O (N / cm 2)}} , the following (2) Based on the formula, determine the amount of steelmaking slag mixed with the clay .
f _O = α × Ds × Sg × {(Co−Ch) / W a} (2)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: Constant determined by the type of slaked lime used to determine Ch

As described above, since the strength of the mixed material obtained by the strength estimation formula of the present invention has a high correlation with the actual measurement value, the amount of steelmaking slag mixed according to the target strength f 2 _O is calculated by the above formula (2). By determining, the steelmaking slag can be mixed with the brazing material in an appropriate mixing amount according to the target strength f 2 _O.
When a predetermined amount of steelmaking slag is mixed with dredged soil to improve the strength, the mixing method may be to put a predetermined amount of steelmaking slag into the dredged mud and mix it. As a method of mixing, for example, a method of mixing using a heavy machine such as a backhoe, a method of mixing while putting mud and steelmaking slag in an appropriate ratio into a continuous mixer, and a predetermined amount of mud and steelmaking slag are measured in a batch mixer The method of charging and mixing can be applied. In addition, the construction method of the mixed material is, for example, a method of constructing in the sea through a tremmy pipe etc. in a state where there is fluidity immediately after mixing. And a method of construction by bottom open barge can be applied. In addition, when used in the land, for example, a method of transporting and mixing with a truck after mixing, a method of mixing a predetermined amount of steelmaking slag at the site where mud is generated, and curing as it is can be applied.
The dredged soil (mixed material) modified by mixing steelmaking slag is preferably used mainly as an earthwork material or embankment material in water, but can also be used as an earthwork material on land.

[Example 1]
The clays A to C shown in Table 1 were used as the modification target clays, and the steelmaking slags a to c shown in Table 2 were used as the steelmaking slag added thereto. For some dredged soils, silica sand was added to adjust the particle size. Steelmaking slag was mixed with the clay under the combinations and mixing conditions as shown in Tables 3 and 4, and the estimated value of the uniaxial compressive strength after 28 days of curing of this mixed material was determined by the method of the present invention. The slaked lime used for the prior test in this example is a special slaked lime for industrial use (JIS-R-9001: 2006), and the constant α in the formula (1) was 3.6. Further, the preliminary test for obtaining Ch was carried out by measuring the slaked lime with respect to each clay, mixing it with a mortar mixer, and molding and solidifying it with a 50φ × 1100 mm mold. The uniaxial compressive strength of the sample cured for 28 days in the sealed state was measured, and Ch was determined from the rise of the strength. Moreover, in order to confirm the correlation with the measured value of the estimated value calculated | required, the uniaxial compressive strength after 28 days sealing curing of each mixed material was measured. The results are also shown in Table 3 and Table 4.
FIG. 7 shows the correlation between the estimated value of the uniaxial compressive strength obtained by the method of the present invention and the measured value of the uniaxial compressive strength. Both values correspond well, and according to the present invention, various conditions are satisfied. Nevertheless, it can be seen that it is possible to estimate the compression strength comprehensively.

[Example 2]
When the steelmaking slag was mixed with the clay A shown in Table 1 to improve the strength, the target value (average value) of the uniaxial compressive strength after curing for 28 days was set to 500 kN / m ² . As the steelmaking slag, one having a free CaO content of 3.5% by mass was used. For steel slag to be used, after the ratio of the particle diameter 2mm or less slag particles during implementation assessed by a particle size distribution measurement was determined to 28% by weight mixture of more steelmaking slag (2). At this mixing ratio, a large amount of batch type mixer was used to mix a large amount of clay and steelmaking slag, and samples were taken at a plurality of locations. FIG. 8 shows the results of actual measurement of the uniaxial compressive strength after the 28-day curing of the mixed material. According to this, because of mass production, there is some variation in the grain size of the clay and steelmaking slag, and although there is some range in strength, the average value is 506 kN / m ² . Therefore, according to the clay reforming method of the present invention, it is possible to determine an appropriate mixing amount of the steelmaking slag according to the design strength, and to confirm that the clay can be modified to a desired design strength. did it.

Claims (2)

A method for estimating the strength of a mixed material (x) of clay and steelmaking slag when mixing steelmaking slag and modifying the clay,
A method for estimating the strength of the modified clay characterized by obtaining an estimated value f (N / cm ² ) of uniaxial compressive strength after 28 days of curing of the mixed material (x) based on the following formula (1).
f = α × Ds × Sg × {(Co−Ch) / W a} (1)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: 3.6 A method of reforming clay by mixing steelmaking slag,
If mixed material dredged material and steel slag 28 days target value of the uniaxial compressive strength after curing of (x) was ^{_{f O (N / cm 2)}} , a mixture of steel slag for dredged material on the basis of the following equation (2) A method for reforming dredged soil, wherein the amount is determined.
f _O = α × Ds × Sg × {(Co−Ch) / W a} (2)
However, Ds = [mass of clay particles having a particle size of 0.075 mm or less in the mixed material (x)] / [mass of solid content of the mixed material (x)] × 100 (%)
Sg = [mass of steelmaking slag particles having a particle diameter of 2 mm or less in the mixture (x)] / [mass of steelmaking slag of the mixture (x)] × 100 (%)
Ch: The mass of slaked lime in 1 m ³ of the mixed material when slaked lime is mixed with the clay to be modified in the prior test and the uniaxial compressive strength after the 28-day curing of the mixed material becomes 50 kN / m ^2. (Kg) x 1.5
Co: free CaO contained in steelmaking slag, and the mass of free CaO in 1 m ^{3 of the} mixed material (x) (kg)
Wa: Mass of moisture in mixed material (x) 1 m ³ (kg)
α: 3.6

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