JP6000187B2 - Method for designing improved soil and method for producing cement-based solidified material - Google Patents

Description

  The present invention is based on the content of a substance (hereinafter referred to as “solidification inhibitory factor”) in the soil that inhibits the solidification of soil improved by mixing a solidifying material (hereinafter referred to as “improved soil”). The present invention relates to a method for designing the composition of soil.

  As the solidification inhibiting factors of the improved soil, water, allophane, humic acid and the like are mainly known. The solidification inhibition mechanisms of these factors are considered to be the formation of voids in the improved soil, the adsorption of calcium ions produced by cement hydration to the soil, and the inhibition of cement hydration, respectively. However, in actual soil improvement sites, these factors do not act alone but always act in combination. However, there are many unclear points about the combined action of these solidification inhibiting factors, which is one of the reasons why it is difficult to design the improved soil. For this reason, in the design of improved soil, in general, it is necessary to actually test various types of blends using the soil to be solidified (hereinafter referred to as “target soil”), and this effort of trial and error is reduced. Reduction is a big issue.

In relation to this problem, Patent Document 1 proposes a method for designing improved soil that is economical. That is, the method includes a step of performing at least one kind of soil test on the improved soil, a step of classifying the improved soil according to a classification criterion set based on a result obtained from the soil test, and the improvement Determining a test composition for soil and obtaining improved soil; performing a predetermined test on the improved soil to obtain a determination value; and determining whether or not a positive composition is necessary based on the determination value. It is a method to comprise.
However, the method has to go through at least five steps and is still considered a time-consuming method.

JP 2005-273387 A

  Accordingly, an object of the present invention is to provide a method by which an optimum composition of improved soil can be easily designed.

Therefore, the present inventors have studied various means for solving the above problems. In particular,
(1) Based on the content of the solidification inhibiting factor in the target soil and the strength of the improved soil, the characteristic values (parameters and indicators) that characterize the target soil were examined. Also,
(2) The characteristic values of the improved soil representing the relationship between the blending amount of alite, gypsum, and blast furnace slag powder related to strength development in the improved soil and the strength of the improved soil were examined. And
(3) The strength estimation formula of the improved soil including the characteristic value of the target soil and the characteristic value of the improved soil as variables was obtained. as a result,
(4) As shown in FIG. 4 to be described later, the prediction formula can accurately estimate the strength of various types of improved soil.
(5) If the estimation formula is used, the content of the solidification inhibiting factor in the target soil and the target strength of the improved soil, the blending amount of the solidification component to be included in the improved soil expressing the target strength, and the like. The present invention was completed by finding out that the optimum blending of the improved soil can be easily designed by determining the blending ratio of the solidifying material and the target soil.

That is, the present invention has the following configuration.
[1] The target soil calculated based on the moisture content of the target soil, the bitumen, humic acid, fulvic acid, allophane, and the amorphous phase excluding allophane in the target soil (hereinafter referred to as “target soil component”) Based on the characteristic value of the soil and the target strength of the improved soil, the blended design of the improved soil is calculated by calculating the blending amount of alite, gypsum, and blast furnace slag (hereinafter referred to as “solidifying component”). Method.
The solidifying component is mainly derived from the solidifying material.
[2] Based on the blending amount of the solidification component calculated through the following steps (A) to (C), the blending ratio of the solidifying material and the target soil is determined, and the blending design of the improved soil is performed based on the blending ratio. The improved soil compounding design method according to [1].
(A) The target soil for calculating the characteristic value of the target soil from the content ratio of the target soil component using the calculation formula (a) of the target soil characteristic value including the content ratio of the target soil component as a variable Characteristic value calculation step (B) Using the calculation formula (b) of the characteristic value of the improved soil including the characteristic value of the target soil and the strength of the improved soil as variables, the calculated characteristic value of the target soil and the improved soil From the target strength, using the formula for calculating the characteristic value of the improved soil (C) including the blending amount of the solidified component as a variable, the characteristic value calculating step of the improved soil (C) for calculating the characteristic value of the improved soil, Solidification component blending amount calculation step for calculating the solidification component blending amount from the calculated characteristic value of the improved soil

[3] The calculation formulas (a), (b), and (c) are represented by the following formulas (a), (b), and (c), respectively, according to the above [1] or [2]: Of improved soil formulation design.
Po = W + 30 * B + 10 * H + 10 * F + 2 * A-10 * Nc + 200 (a)
(In the formula, Po is the characteristic value (kN / m ² ) of the target soil, W is the moisture content of the target soil (weight ratio is expressed in%), B is the content of bitumen in the target soil (mass%), H Is the content of humic acid in the target soil (% by mass), F is the content of fulvic acid in the target soil (% by mass), A is the content of allophane in the target soil (% by mass), and Nc is the target soil (It represents the content (mass%) of the amorphous phase excluding allophane in the inside.)
Pi = {S− (0.032 × Po ² −34.9 × Po + 3500)} / {155 × exp (−0.002 × Po)} (b)
(In the formula, Pi is the characteristic value (kN / m ² ) of the improved soil, S is the strength (kN / m ² ) of the improved soil or the target strength (kN / m ² ) of the improved soil, and Po is the characteristic value of the target soil. (Represents kN / m ² )
Pi = C + 0.1 × G + 0.25 × B (c)
(In the formula, Pi is the characteristic value of improved soil (kN / m ² ), C is the blending amount of alite per 1 m ³ of improved soil (kg / m ³ ), and G is the blending amount of gypsum per 1 m ³ of improved soil. (SO ₃ conversion, kg / m ³ ), B represents the blending amount (kg / m ³ ) of blast furnace slag powder per 1 m ³ of the improved soil.
However, although alite and gypsum are essential components, blast furnace slag powder is an optional component.
[4] When a cement-based solidified material (premixed product of the solidified component) is used instead of the solidified component, the following formula (d) is used instead of the formula (c): [1] to [1] 3] The improved soil composition design method according to [3].
Pi = (c + 0.1 × g + 0.25 × b) × α (d)
(In the formula, Pi is the characteristic value of the improved soil (kN / m ² ), c is the content of alite in the cement-based solidified material (mass%), g is the content of gypsum in the cement-based solidified material (SO ₍₃ conversion, mass%), b represents the content (mass%) of the blast furnace slag powder in the cement-based solidified material, and α represents the blending amount (kg / m ³ ) of the cement-based solidified material in the improved soil.
[5] A cement-based solidified material is produced by mixing at least a cement clinker and gypsum based on the blended amount of the solidified component obtained by the blended design method for improved soil according to [2] or [3]. A method for producing a cement-based solidified material .

  According to the improved soil composition design method of the present invention, the optimum composition of the improved soil can be easily designed according to the type of target soil and the target strength of the improved soil. Moreover, according to the manufacturing method of the cement-type solidification material of this invention, the cement-type solidification material suitable for object soil can be manufactured. Furthermore, the cement-based solidified material of the present invention can reliably express the target strength of the improved soil.

It is a figure which shows the relationship between the content rate of a solidification inhibiting factor, and the uniaxial compressive strength of improved soil. However, the amount of cement solidifying material 1 (A) is 200kg ^/ m 3, (B) is 300 kg / ^{m 3.} It is a figure which shows an example of the linear relationship between the characteristic value of improved soil, and the uniaxial compressive strength of improved soil. (A) is a figure which shows the exponential function relationship between the inclination of the said approximate line, and the characteristic value of object soil, (B) is 2 between the intercept of the said approximate line, and the characteristic value of object soil. It is a figure which shows next function relationship. It is a figure which shows the fitting degree of the estimated value calculated | required using the estimated value of the measured value of uniaxial compressive strength of improved soil, and the intensity | strength of improved soil.

As described above, the present invention is a method for calculating the blending design of the improved soil by calculating the blending amount of the solidified component based on the target soil characteristic value calculated based on the content of the target soil component and the target strength of the improved soil. Etc.
Hereinafter, the present invention includes (1) characteristic value of target soil, (2) characteristic value of improved soil, (3) strength estimation formula of improved soil, (4) blending design procedure of improved soil, and (5) cement system The method for producing the solidified material and the cement-type solidified material will be described separately.

(1) Characteristic value of the target soil The characteristic value of the target soil is a parameter that characterizes the target soil using the content rate of the target soil component and the like from the viewpoint of strength development of the improved soil including the target soil. It is expressed by the strength of the improved soil including the target soil.
Here, the content ratio of the target soil component is the water content ratio of the target soil, the content ratio of bitumen in the target soil, the content ratio of humic acid, the content ratio of fulvic acid, the content ratio of allophane, and allophane. The content of the amorphous phase is excluded.
The water content ratio is a water content / mass ratio of the target soil expressed in%, and can be measured in accordance with, for example, JGS0121-2009 “Soil Water Content Test Method” of the Geotechnical Society. As for the content rates of bitumen, humic acid, and flavic acid, for example, Onoda Research Report No. 20, page 11-24 (1980). In addition, allophane is a kind of amorphous aluminum silicate clay mineral that is abundant in volcanic ash clay, and the content of allophane is, for example, “acid oxalate extraction method”, Bulletin of Rakuno Gakuen University, 28 ( 1), and can be measured according to pages 7 to 45 (2003). Moreover, the amorphous phase (amorphous inorganic component) excluding allophane is silicate minerals such as allophane-like aluminum and iron, silicic acid that is amorphous with respect to X-rays present in soil, Weathered inorganic gels such as alumina and iron oxide, and more strictly speaking, minerals including iron minerals such as low crystalline goethite, although not necessarily amorphous. The content of the amorphous phase excluding allophane is based on, for example, “Study on Quantification of Allophane and Amorphous Inorganic Components in Soil”, Agricultural Technology Research Institute Report No. 29, pages 1 to 48 (1977) Can be measured.
As shown in FIG. 1 to be described later, among the target soil components, water content, bitumen, humic acid, flavic acid, and allophane are factors that inhibit the strength development of the improved soil. On the other hand, the amorphous phase excluding allophane is a factor that promotes the strength development of the improved soil. As described above, the strength of the improved soil is complicated by the combined action of the solidification inhibiting factor and the solidification promoting factor coexisting in the soil.

In view of the combined action of the solidification inhibiting factor and the solidification promoting factor, the characteristic value of the target soil has the content of the target soil component as an explanatory variable, and the strength of the improved soil containing the target soil and the cement-based solidifying material as a target variable. Calculated by the multiple regression equation. The following formula (a) is an example of the calculation formula.
Po = W + 30 * B + 10 * H + 10 * F + 2 * A-10 * Nc + 200 (a)
However, in the formula, Po is a characteristic value (kN / m ² ) of the target soil, W is a water content ratio of the target soil (weight ratio is expressed in%), B is a bitumen content (% by mass) in the target soil, H is the content of humic acid in the target soil (% by mass), F is the content of fulvic acid in the target soil (% by mass), A is the content of allophane in the target soil (% by mass), and Nc is the target It represents the content (mass%) of the amorphous phase excluding allophane in the soil.

(2) Characteristic value of the improved soil The characteristic value of the improved soil is a parameter that characterizes the improved soil by using the blending amount of the solidifying component in the improved soil from the viewpoint of strength development of the improved soil. Expressed in intensity.
Here, the blending amount of the solidifying component is the blending amount of alite per unit amount (1 m ³ ) of the improved soil (kg / m ³ ), the blending amount of gypsum (kg / m ³ ), and the blast furnace slag It is a blending amount (kg / m ³ ). The solidifying component is mainly derived from a cement-based solidifying material. The strength of the improved soil can be measured in accordance with, for example, JIS A 1216-2009 “Soil Uniaxial Compression Test Method”.

In order to obtain the relational expression between the blending amount of the solidified component and the strength of the improved soil from the necessity in blending design, the blending amount of the solidified component is used as an explanatory variable, and the strength of the improved soil containing the solidified component is used as a target variable. By performing multiple regression analysis, a calculation formula for calculating the characteristic value of the improved soil is obtained. The following formula (c) is an example of the calculation formula.
Pi = C + 0.1 × G + 0.25 × B (c)
However, in the formula, Pi is the characteristic value of the target soil (kN / m ² ), C is the blending amount of alite per 1 m ³ of the improved soil (kg / m ³ ), G is the blending of gypsum per 1 m ³ of the improved soil Amount (SO ₃ conversion, kg / m ³ ), B represents the blending amount (kg / m ³ ) of blast furnace slag powder per 1 m ³ of the improved soil. Moreover, the value obtained by measuring by the Rietveld method is used for the alite content.
When a cement-based solidified material (premix product) containing a certain amount of the solidified component is used instead of the solidified component, the following formula (d) is used instead of the formula (c).
Pi = (c + 0.1 × g + 0.25 × b) × α (d)
However, in the formula, Pi is the characteristic value (kN / m ² ) of the target soil, c is the content of alite in the cement-based solidified material (% by mass), and g is the content of gypsum in the cement-based solidified material ( SO ₃ conversion, mass%), b represents the content (mass%) of the blast furnace slag powder in the cement-based solidified material, and α represents the blending amount of the cement-based solidified material per 1 m ³ of improved soil (kg / m ³ ). . Moreover, the value obtained by measuring by the Rietveld method is used for the alite content.

(3) Strength Estimation Formula of Improved Soil The present inventors have studied the relationship between the characteristic value of the target soil, the characteristic value of the improved soil, and the strength of the improved soil, and obtained the following knowledge. That is,
As shown in FIG. 2, the strength (uniaxial compressive strength) of any improved soil can be approximated using a linear function (straight line) of the characteristic value of the improved soil. In addition, as shown in FIG. 3, the slope of the straight line can be approximated using an exponential function of the characteristic value of the target soil included in the improved soil (A), and the intercept of the straight line is included in the improved soil. It can be approximated using a quadratic function of the characteristic value of the target soil (B).
Therefore, if the slope of the linear function is replaced with the exponential function of the characteristic value of the target soil and the intercept of the linear function is replaced with the quadratic function of the characteristic value of the target soil, the strength of the improved soil is The formula for estimating the strength of the improved soil expressed in terms of characteristic values is obtained. The following formula (b ₀ ) is an example of the estimation formula.
S = {155 × exp (−0.002 × Po)} × Pi + (0.032 × Po ² −34.9 × Po + 3500) (b ₀ )
However, where, S is the target intensity of strength (kN / ^{m 2)} or improved soil improvement soil, Pi is the characteristic value of the modified soil (kN ^/ m 2), the characteristic value of Po is the target soil (kN / ^{m 2} ).
As shown in FIG. 4 to be described later, the predicted value of the strength of the improved soil obtained by using the equation (b ₀ ) is in good agreement with the actually measured value regardless of the age of the improved soil.
Then, when the formula (b ₀ ) is transformed with respect to Pi, the following formula (b) is obtained.
Pi = {S− (0.032 × Po ² −34.9 × Po + 3500)} / {155 × exp (−0.002 × Po)} (b)

(4) Formulation procedure of improved soil The procedure is shown in the following (i) to (vi).
(I) The water content ratio of the target soil and the content ratio of the target soil component are measured according to the test method and the like.
(Ii) Based on the measured value, the characteristic value (Po) of the target soil is obtained using the equation (a).
(Iii) From the Po value and the target strength (S) of the improved soil, the characteristic value (Pi) of the improved soil is obtained using the equation (b).
(Iv) The blending amount of the solidifying component is determined from the Pi value using the formula (c). Alternatively, when a cement-based solidified material (premixed product of the solidified component) containing a certain amount of the solidified component is used instead of the solidified component, the formula (d) is used instead of the formula (c). Obtain the amount of cementitious solidifying material.
(Vi) The solidified component and the target soil are mixed according to the blending amount of the solidified component. Or according to the compounding quantity of the said cement-type solidification material, a cement-type solidification material and object soil are mixed.

(5) Manufacturing method of cement-based solidified material and cement-based solidified material The manufacturing method of the cement-based solidified material of the present invention includes at least a cement clinker based on the blending amount of the solidified component obtained by the blended design method of the improved soil. And a method of producing a cement-based solidified material by mixing gypsum. Of the solidified components, blast furnace slag powder is an optional component.
Moreover, the cement-based solidified material of the present invention is a cement-based solidified material produced by using the above-described method for producing a solidified material. Next, the solidified component in the cement-based solidified material will be described.

  The cement clinker is not particularly limited, and examples thereof include ordinary Portland cement, early-strength Portland cement, ultra-high-strength Portland cement, medium heat Portland cement, low heat Portland cement, and Portland cement clinker such as sulfate-resistant Portland cement, and Portland cement. And one or more selected from cements such as cement, blast furnace cement, silica cement, and ecocement.

The gypsum is not particularly limited, and examples thereof include one or more selected from dihydrate gypsum, flue gas desulfurization gypsum, phosphate gypsum, titanium gypsum, hydrofluoric gypsum, smelted gypsum, hemihydrate gypsum, anhydrous gypsum, and the like. . Among these, anhydrous gypsum is preferable in terms of high strength development, and anhydrous gypsum obtained by heating dihydrate gypsum recovered from gypsum waste with a heating device can also be used.
Moreover, the specific surface area of the plaster of the gypsum is preferably 2000 to 12000 cm ² / g, more preferably 3000 to 8000 cm ² / g, further preferably 4000 to 6000 cm ² / g, and particularly preferably 4500 to 5500 cm ² / g. . When the value is out of the range of 2000 to 12000 cm ² / g, the strength development property of the solidified material may be lowered.

Further, the blast furnace slag powder is obtained by pulverized granulated slag obtained by quenching and crushing molten slag produced as a by-product when producing pig iron in the blast furnace, or by gradual cooling and crushing. An example is a pulverized product of slowly cooled slag. Among these, since it is excellent in latent hydraulic property, it is preferably a pulverized product of granulated slag, and more preferably blast furnace granulated slag as defined in JIS A 6206.
Blaine specific surface area of the blast furnace slag powder is preferably 3000 cm ² / g or more, more preferably 6000 cm ² / g or more, more preferably 8000 cm ² / g or more. When the value is less than 3000 cm ² / g, the initial strength development of the solidified material may be low. Moreover, the upper limit of this value is 20000 cm < ² > / g from the point of a grinding | pulverization cost. The blast furnace slag can be obtained by pulverization with a pulverizer such as a ball mill or a jet mill.
The basicity of the blast furnace slag powder is preferably 1.7 or more, more preferably 1.8 or more, and still more preferably 1.9 or more. If the value is less than 1.7, the strength development property of the solidified material may be lowered. Moreover, the upper limit of this value is 3.0 from the ease of acquisition. The basicity is calculated using the following formula.
Basicity = (CaO + MgO + Al ₂ O ₃ ) / SiO ₂
However, the chemical formula in the formula represents the content (% by mass) of the compound represented by the chemical formula in the blast furnace slag powder.
The cement-based solidified material of the present invention can also contain admixtures such as coal ash, fly ash, and limestone powder in addition to the alite, gypsum and blast furnace slag powder as long as strength development does not decrease. .

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this Example.
1. Strength test of improved soil 200 kg of cement-based solidified material (two types of 1 and 2) of the composition shown in Table 2 (however, gypsum is converted to SO ₃ ) for 1 m ^{3 of the} target soil partially shown in Table 1 and 300 kg powder was added and mixed with a soil mixer for 3 minutes to prepare improved soil. Next, after the improved soil was put into a mold having an inner diameter of 3.5 cm and a height of 7 cm, it was sealed and cured at 20 ° C., in accordance with JGS0821-2008 “Method for preparing specimen without compaction of stabilized soil”. A specimen was prepared. Incidentally, the Blaine specific surface area of the powder used was ^{3450cm 3 / g, 4670cm 3 /} g anhydrous gypsum 4710cm ³ / g, in the blast furnace slag powder with gypsum.
Using this specimen, uniaxial compressive strength was measured in accordance with JIS A 1216-2009 “Soil Uniaxial Compression Test Method”. Some of the results are shown in Table 3 (addition of cement-based solidification material at 200 kg / m ³ ) and Table 4 (addition of cement-based solidification material at 300 kg / m ³ ).

2. Derivation of the above formulas (a) to (c) Using the numerical values of all 35 types of target soil including Tables 1 to 4, multiple regression analysis was performed to obtain the above formulas (a) to (c).

3. Example of Formulation of Improved Soil Based on the silty clay, a reagent containing each solidification inhibiting factor shown in Table 5 was added, the water content was 65.0%, the bitumen was 0.25% by mass, and the humic acid was 6.4% by mass. %, 6.7% by mass of fulvic acid, and 13.9% by mass of allophane (simulated soil, but not including the amorphous phase excluding allophane). The characteristic value of the target soil was calculated to be 417.4 kN / m ² using the equation (a).
The allophane used was P-1 manufactured by Shinagawa Kasei, the humic acid used was sodium humate manufactured by Ternite, and the bitumen used tannic acid manufactured by Fuji Chemical Industry. The water content was determined according to JGS0121-2009 “Test method for soil water content ratio” by the Geotechnical Society. 20, based on pages 11-24 (1980), allophane content is based on "acid oxalate extraction method", Rakuno Gakuen University Bulletin, 28 (1), pages 7-45 (2033) And measured.
Further, cement-based solidifying material used was alite, the ratio of gypsum (SO ₃ equivalents), and the content of the blast furnace slag powder (mass%), respectively 55.0: 5.0: 30.0, The specific surface area of Blaine is 3850 cm ² / g.

Next, from the characteristic value of the target soil and the target strength of the improved soil (3500 kN / m ² at the age of 28 days), the characteristic value of the improved soil is calculated to be 133.6 kN / m ² using the equation (b). did. And the compounding quantity of the said cement-type solidification material in improved soil was determined to be 230 kg / m < ³ > using the characteristic value of this improved soil, and said (d) Formula.
Next, 250 kg of the solidified material per 1 m ^{3 of the} simulated soil was added and mixed with a soil mixer for 3 minutes to prepare improved soil. The improved soil was put into a mold having an inner diameter of 5 cm and a height of 10 cm, and a specimen was prepared in accordance with JGS 0821-2008. The specimen was sealed and cured at 20 ° C., and a uniaxial compression test was conducted according to JIS A 1216: 2009. As a result, the uniaxial compressive strength at the age of 28 days was 3640 kN / m ² , which was similar to the target strength.
As described above, the improved soil composition design method of the present invention can easily design the optimum soil composition according to the type of target soil and the target strength of the improved soil without trial and error. .

Claims (5)

  Based on the moisture content of the target soil, the characteristic value of the target soil calculated based on the content of amorphous phase excluding bitumen, humic acid, fulvic acid, allophane, and allophane in the target soil, and the target strength of the improved soil, An improved soil blending design method that calculates the blending amount of alite, gypsum, and blast furnace slag and blends the improved soil. Based on the blending amounts of alite, gypsum, and blast furnace slag calculated through the following steps (A) to (C), the blending ratio of the solidified material and the target soil is determined, and the blending of the improved soil is based on the blending ratio. The method for designing improved soil according to claim 1, wherein the design is performed.
(A) Formula for calculating characteristic values of target soil including water content ratio of said target soil, bitumen, humic acid, fulvic acid, allophane, and amorphous phase content excluding allophane in target soil as variables (a) ) To calculate the characteristic value of the target soil from the content of the amorphous phase excluding bitumen, humic acid, fulvic acid, allophane, and allophane in the target soil ( B) Using the formula (b) for calculating the characteristic value of the improved soil including the characteristic value of the target soil and the strength of the improved soil as variables, the improved soil is calculated from the calculated characteristic value of the target soil and the target strength of the improved soil. Using the calculation formula (c) for the characteristic value of the improved soil, including the blending amounts of alite, gypsum, and blast furnace slag as variables, From the calculated characteristic value of the improved soil, , Gypsum, and for calculating the amount of blast furnace slag, blending of the solidified component amount calculating step The blending design of improved soil according to claim 1 or 2, wherein the calculation formulas (a), (b), and (c) are represented by the following formulas (a), (b), and (c), respectively. Method.
Po = W + 30 * B + 10 * H + 10 * F + 2 * A-10 * Nc + 200 (a)
(In the formula, Po is the characteristic value (kN / m ² ) of the target soil, W is the moisture content of the target soil (weight ratio is expressed in%), B is the content of bitumen in the target soil (mass%), H Is the content of humic acid in the target soil (% by mass), F is the content of fulvic acid in the target soil (% by mass), A is the content of allophane in the target soil (% by mass), and Nc is the target soil (It represents the content (mass%) of the amorphous phase excluding allophane in the inside.)
Pi = {S− (0.032 × Po ² −34.9 × Po + 3500)} / {155 × exp (−0.002 × Po)} (b)
(In the formula, Pi is the characteristic value (kN / m ² ) of the improved soil, S is the strength (kN / m ² ) of the improved soil or the target strength (kN / m ² ) of the improved soil, and Po is the characteristic value of the target soil. (Represents kN / m ² )
Pi = C + 0.1 × G + 0.25 × B (c)
(In the formula, Pi is the characteristic value of improved soil (kN / m ² ), C is the blending amount of alite per 1 m ³ of improved soil (kg / m ³ ), and G is the blending amount of gypsum per 1 m ³ of improved soil. (SO ₃ conversion, kg / m ³ ), B represents the blending amount (kg / m ³ ) of blast furnace slag powder per 1 m ³ of the improved soil. In place of the alite, gypsum, and blast furnace slag powder, when using a cement-based solidified material (a premixed product of alite, gypsum, and blast furnace slag powder), the following (d) is used instead of the formula (c). The method for blending and designing improved soil according to claims 1 to 3, wherein a formula is used.
Pi = (c + 0.1 × g + 0.25 × b) × α (d)
(In the formula, Pi is the characteristic value of the improved soil (kN / m ² ), c is the content of alite in the cement-based solidified material (mass%), g is the content of gypsum in the cement-based solidified material (SO ₍₃ conversion, mass%), b represents the content (mass%) of the blast furnace slag powder in the cement-based solidified material, and α represents the blending amount (kg / m ³ ) of the cement-based solidified material in the improved soil. A cement-based solidified material is produced by mixing at least cement clinker and gypsum based on the blending amounts of alite, gypsum, and blast furnace slag powder obtained by the improved soil blending design method according to claim 2 or 3. A method for producing cement-based solidified material .

Images