Mix design method for fluidized soil

Abstract

To provide a blending design method of fluidized soil in which cement and steel slag as solidification materials are used, allowing acquisition of the optical amount of the solidification material for the optical blending ratio of the steel slag corresponding thereto.SOLUTION: In a blending design method of fluidized soil in which at least a part of cement used as a solidification material is replaced with steel slag, an amount of the solidification material to the target value of a uniaxial compressive strength is determined with a replacement ratio of 70% of the steel slag as a reference replacement ratio. The replacement ratio of the steel slag of 60-75% can be used for the blending design. The blending design method is desirably applied in a range of exceeding 65 kg / m3 of the amount of the solidification material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for designing the mix of fluidized soil in which a portion of the cement used as a solidifying agent is replaced with steel slag. [Background technology]

[0002] In order to reduce the amount of construction by-products generated and promote recycling, there has been a growing trend to adopt fluidized soil treatment methods that effectively utilize construction-generated soil as invert material or backfill material.

[0003] This fluidized soil treatment method involves disintegrating mud, which is mainly composed of cohesive soil, adding a solidifying agent to the resulting mud and mixing it to produce fluidized soil, and then placing this fluidized soil into the designated backfill area for backfilling. The solidifying agent typically used is mainly cement, cement-based solidifying agents, or lime, with additives added as needed.

[0004] In the aforementioned fluidized soil treatment method, various methods have been proposed to improve manufacturing efficiency and ensure the quality of the fluidized soil. For example, in Patent Document 1 below, the amount of solidifying agent added is determined according to the required uniaxial compressive strength, and the mixture of soil to be treated and slurry is 1 m 3 It is stated that the amount per unit should be 50 to 200 kg, preferably about 100 kg. Furthermore, Patent Document 2 below states that the solidifying agent contains cement and a substance having latent hydraulic properties (blast furnace slag), and that the amount of the substance having latent hydraulic properties is 40 to 400 parts by mass per 100 parts by mass of cement. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 2728846 [Patent Document 2] Japanese Patent Publication No. 2014-9487 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent Document 1, mentioned above, describes a basic design method for a fluidization treatment method that fluidizes soil to be treated, such as construction waste, when it is used for backfilling, backfilling structures, or filling cavities, in a state where its fluidity has been increased.

[0007] Furthermore, Patent Document 2 states that the solidifying agent consists of cement and blast furnace slag, and that the mixing ratio is 40 to 400 parts by mass of blast furnace slag per 100 parts by mass of cement. However, this range is quite broad, and in order to determine a specific mixing ratio, it was necessary to repeatedly change the mixing ratio and conduct strength tests, and to find the optimal mixing ratio through trial and error. Similarly, regarding the amount of solidifying agent, 1 m³ of construction-generated soil 3 While the recommended amount is 30-200 kg, this range is quite broad. To determine the specific amount of solidifying agent, it was necessary to repeatedly conduct strength tests and other measurements while varying the amount of solidifying agent, and to find the optimal amount through trial and error.

[0008] Therefore, the main objective of the present invention is to provide a method for designing the mix of fluidized soil, which uses cement and steel slag as solidifying agents, so that the optimal amount of solidifying agent can be obtained at the optimal mixing ratio of steel slag. [Means for solving the problem]

[0009] To solve the aforementioned problems, the present invention according to claim 1 is a method for designing the mix of fluidized soil in which a portion of the cement used as a solidifying agent is replaced with steel slag, The amount of the solidifying agent is 65 kg / m³ 3 Under conditions that apply to the extent exceeding, The standard replacement rate for the aforementioned steel slag is set at 70%. We will determine the relationship between the unconfined compressive strength and the amount of solidifying agent at this standard substitution rate of 70%, and then calculate the amount of solidifying agent needed to achieve the target unconfined compressive strength based on this relationship. A method for designing the mix of fluidized soil is provided.

[0010] In the invention described in claim 1 above, as will be described in detail in the subsequent [Experiment], specimens were fabricated by varying the replacement ratio of steel slag and the amount of solidifying agent respectively, and uniaxial compression strength tests were conducted. As a result, it became clear that the uniaxial compression strength shows a peak when the replacement ratio of steel slag is 70%. Therefore, with 70% of the replacement ratio of steel slag as the standard replacement ratio, the amount of solidifying agent corresponding to the replacement ratio of 70% obtained in the experiment was determined from the relational expression between the amount of solidifying agent and the uniaxial compression strength. As a result, it becomes possible to obtain the optimal amount of solidifying agent corresponding to the optimal blending ratio of steel slag.

[0011] Note In the invention, as will be described in detail in the [Experiment] described later, the amount of solidifying agent at which the replacement ratio of steel slag is 70% and the uniaxial compression strength peaks is estimated to be in the range exceeding 65 kg / m 3 Therefore, by using it within that range, a predetermined strength can be more reliably ensured.

[0012] Regarding the present invention according to claim 2, A method for designing the mix design of fluidized soil in which a portion of the cement used as a solidifying agent is replaced with steel slag, The amount of the solidifying agent is 65 kg / m³ 3 Under conditions applicable in a range exceeding a certain limit, the replacement rate of the steel slag is set to 60-75%, and the amount of solidifying agent for the target unconfined compressive strength is calculated from a relationship formula between the unconfined compressive strength and the amount of solidifying agent at the required replacement rate of steel slag, or the amount of solidifying agent for the target unconfined compressive strength is determined by linear interpolation between the line representing the amount of solidifying agent or the line representing the amount of solidifying agent closest to the intersection point of a predetermined replacement rate and the target unconfined compressive strength, using a graph showing the relationship between the replacement rate and the unconfined compressive strength with the amount of solidifying agent as a parameter. A method for designing the mixture of fluidized treated soil is provided.

[0013] In the invention described in claim 2 above, although the uniaxial compression strength peaks when the standard replacement ratio of steel slag is 70%, the applicable range of the replacement ratio is expanded so as to cope with cases where the usage ratio of steel slag is increased or strength is required at an early stage.

Effects of the Invention

[0014] As described in detail above, according to the present invention, in fluidized treated soil using cement and steel slag as solidifying agents, it becomes possible to obtain the optimal amount of solidifying agent corresponding to the optimal blending ratio of steel slag.

Brief Description of the Drawings

[0015] [Figure 1]This graph shows the relationship between the substitution rate and uniaxial compressive strength obtained in the experiment. [Figure 2] This graph shows the relationship between the substitution rate and flow value obtained in the experiment. [Figure 3] This is graph (1) showing the relationship between the amount of solidifying agent and the unconfined compressive strength at each substitution rate. [Figure 4] This is graph (part 2) showing the relationship between the amount of solidifying agent and the unconfined compressive strength at each substitution rate. [Figure 5] This graph shows the predicted relationship between the replacement rate and unconfined compressive strength for each amount of solidifying agent. [Modes for carrying out the invention]

[0016] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0017] Fluidized soil is prepared by mixing the soil to be treated with water to create a muddy mixture, then adding chemical admixtures such as dispersants as needed. Such fluidized soil is used for backfilling structures, post-construction backfilling, filling cavities, tunnel inverts, and embankments.

[0018] The soil to be treated can be construction waste generated during civil engineering or construction work, or clay, mountain sand, etc., collected from soil quarries. Tap water, river water, lake water, groundwater, etc., can be used as the water added to the soil to be treated.

[0019] The solidifying agent consists of cement and steel slag. While ordinary Portland cement is preferred as the cement, rapid-hardening Portland cement or other types may also be used.

[0020] The aforementioned steel slag is a type of slag generated as a by-product in the manufacturing process of steel products, and can be broadly classified into blast furnace slag and steelmaking slag. Both have latent hydraulic properties and can therefore be used in the present invention. Blast furnace slag is produced in a blast furnace when components other than pig iron contained in iron ore are melted and separated from the ash content of auxiliary raw materials such as coke and limestone. Depending on the cooling method of the molten slag, there are granulated slag and slowly cooled slag, and further, there is blast furnace slag fine powder which is produced by crushing granulated slag into a fine powder. Steelmaking slag is a type of slag generated as a by-product in the process of manufacturing steel from pig iron or scrap iron, and can be divided into converter slag produced in a converter and electric furnace slag produced in the electric furnace steelmaking process.

[0021] The aforementioned steel slag requires dispersibility in the fluidized soil and a certain surface area for the hardening reaction, so it is preferable that it be in granular form, such as water-granulated slag, or in powder form, such as blast furnace slag fine powder obtained by crushing water-granulated slag. Rock-like materials such as slowly cooled slag and steelmaking slag are preferably processed into granular or powder form before use.

[0022] The blending design method for fluidized soil according to the present invention involves a fluidized soil in which a portion of the cement used as a solidifying agent is replaced with steel slag. The amount of solidifying agent is determined relative to the target value of unconfined compressive strength, with a replacement rate of 70% of the steel slag being used as the standard replacement rate. From the experiments described below, it was found that the unconfined compressive strength increases with increasing steel slag replacement rate, but peaks at a replacement rate of 70%, and decreases at higher replacement rates. Therefore, the amount of solidifying agent is determined using 70%, the replacement rate at which the unconfined compressive strength is maximized, as the standard replacement rate. The determination of the amount of solidifying agent is made possible because the same experiments revealed that the relationship between the amount of solidifying agent and the unconfined compressive strength at each replacement rate is a linear relationship that can be approximated by a linear equation. Using this relationship, the amount of solidifying agent relative to the target value of unconfined compressive strength can be determined.

[0023] To further explain the mix design method according to the present invention, the first step in the design is to investigate the soil type and properties of the soil to be treated. If the soil to be treated is fine-grained soil, water is added to the soil to break it up. If the soil to be treated is sandy soil, adjusted slurry is added to the soil and mixed. Then, the muddy soil is adjusted to a predetermined wet density. Fluidized treated soil with a high unit water content will have a large amount of bleeding water, raising concerns about differences in strength in the vertical direction and loss of integrity with the surrounding ground and existing structures. Typically, the wet density of muddy soil is 1.2 to 1.6 g / cm³. 3 The range is 1.5 to 1.6 g / cm³. 3 It is preferable that it be within this range.

[0024] Next, a target value for unconfined compressive strength is determined. The unconfined compressive strength used is that of the material at 7 days of age. The target value for unconfined compressive strength varies depending on the application of the fluidized soil (backfilling of underground structures, backfilling of civil engineering structures, filling of underground spaces, etc.), but is generally between 100 and 10,000 kN / m 2 This is often considered to be the case.

[0025] Subsequently, the amount of solidifying agent is determined from the relationship between the unconfined compressive strength and the amount of solidifying agent at a standard substitution rate of 70%, obtained from the experiment described below. Specifically, the amount of solidifying agent x for the target unconfined compressive strength y is calculated from the relationship between the unconfined compressive strength y and the amount of solidifying agent x at a substitution rate of 70%, shown in Figure 4: y = 14.266x - 675.

[0026] The replacement rate of the steel slag is 70% as the standard replacement rate. However, since the same tendency can be observed even when it is varied before and after that, the range may be expanded before and after that. Specifically, the replacement rate of the steel slag is preferably 60 to 75%. By making the replacement rate of the steel slag lower than the standard replacement rate (increasing the proportion of cement), it is possible to cope with structures that require strength at an early stage, the hydration rate becomes faster and it is less affected by low temperatures, the neutralization rate is suppressed from increasing, and it can be applied to structures with a small cover, etc. On the other hand, by making the replacement rate of the steel slag higher than the standard replacement rate (decreasing the proportion of cement), the amount of cement used is reduced and resource and energy savings become possible, and effects such as the expression of long-term strength, the suppression of cracking, and the improvement of chemical durability can be achieved.

[0027] When the replacement rate is changed before and after the standard replacement rate of 70%, from the relational expression between the uniaxial compressive strength y and the amount x of the solidifying material at the required replacement rate shown in FIGS. 3 and 4 as described above, the amount x of the solidifying material for the target uniaxial compressive strength y may be calculated, or from the graph showing the relationship between the replacement rate and the uniaxial compressive strength with the amount of the solidifying material shown in FIG. 1 as a parameter, for the intersection of the predetermined replacement rate and the target uniaxial compressive strength, the amount of the solidifying material may be obtained by linearly interpolating the closest broken line of the amount of the solidifying material or between the broken lines of the amount of the solidifying material.

[0028] In this mix design method, the amount of the solidifying material is preferably applied in a range exceeding 65 kg / m 3 As a result of the [Experiment] described later, it can be estimated that the amount of the solidifying material at which the replacement rate of the steel slag of 70% becomes the peak value of the uniaxial compressive strength is in a range exceeding 65 kg / m 3 By applying in that range, a predetermined strength can be surely ensured.

[0029] 〔Experiment〕 An experiment was conducted to determine the optimum value of the replacement rate from the relationship between the replacement rate of the steel slag and the uniaxial compressive strength (at 7 days of age) for the fluidized soil in which a part of the cement used as the solidifying material was replaced with steel slag (fine powder of blast furnace slag).

[0030] In the experiment, the clay and sand shown in Table 1 were mixed in a ratio of 92% clay and 8% sand to prepare a treated soil with a fine-grained content of 85%. The density of the dry soil particles at this time was 2.65 g / cm³. 3 Next, water was added to this treated soil to produce muddy soil. The composition and properties of the muddy soil are shown in Table 2. Chemical admixtures were added to 1 m of muddy soil. 3 It was decided to weigh it out externally and add it when preparing the muddy soil.

[0031] [Table 1]

[0032] [Table 2]

[0033] In the experiment, muddy soil was prepared using a mortar mixer, then cement and steel slag were added, along with a chemical admixture, and the mixture was stirred. The flow value and wet density were immediately measured. After the measurements, a specimen (φ50 × 100 mm) was prepared for the unconfined compressive strength test.

[0034] The amount of solidifying agent (ordinary Portland cement and blast furnace slag fine powder) is 100 kg / m³. 3 , 200 kg / m 3 In each of these cases, the wet density, flow value, and unconfined compressive strength (7 days old) were measured when the substitution rate of blast furnace slag fine powder was varied. Wet density was calculated from the mass of the material when 500 ml of the material was placed in a 500 ml graduated cylinder. Flow value was measured in accordance with the cylinder method of the consistency test method in the Japan Highway Public Corporation standard, Test method for air mortar and air milk (JHS A 3113-1992). Unconfined compressive strength was measured in accordance with JIS A 1216:1998. The substitution rate is the ratio (%) of the amount of blast furnace slag fine powder to the amount of solidifying agent, for example, when the amount of solidifying agent is 100 kg / m³ 3 If you include it, when the substitution rate is 30%, cement70 kg / m 3 , blast furnace slag fine powder 30 kg / m³ 3 This is the result. The experimental results are shown in Tables 3 and 4, and Figures 1 and 2.

[0035] [Table 3]

[0036] [Table 4]

[0037] As shown in Figure 1, the amount of solidifying agent was 100 kg / m³. 3 , 200 kg / m 3 In all cases, it was found that the unconfined compressive strength peaked at a replacement rate of 70%. Therefore, by using a 70% replacement rate as the standard replacement rate and determining the amount of solidifying agent relative to the target unconfined compressive strength, it becomes possible to achieve the maximum strength relative to the amount of solidifying agent used, making this important in the mix design of fluidized soil.

[0038] Furthermore, as shown in Figure 2, fluidity improves with increasing substitution rate of blast furnace slag fine powder, and this trend is particularly pronounced at substitution rates of 50% or higher. At this point, the fluidity at a substitution rate of 70% corresponds to a solidifying agent amount of 100 kg / m³. 3 , 200 kg / m 3 Experiments revealed that good workability can be obtained at any of these substitution rates, and that sufficient fluidity can also be obtained at substitution rates in the vicinity of these rates (60-75%).

[0039] Next, we will examine the range of solidifying agent quantities at which the uniaxial compressive strength peaks at a substitution rate of 70%. In other words, we will examine the range of solidifying agent quantities at which the present invention is well applicable, with a substitution rate of 70% as the standard substitution rate.

[0040] Similar to the experiment described above, the amount of solidifying agent was 50 kg / m³. 3In this study, the wet density, flow value, and unconfined compressive strength (at 7 days of age) were measured when the substitution rate of blast furnace slag fine powder was varied (Table 5). Based on these results, the amount of solidifying agent (50, 100, 200 kg / m³) at each substitution rate shown in Tables 3 to 5 was determined. 3 The relationship between ( ) and uniaxial compressive strength was graphed, and an approximate formula was derived from these three points. The results are shown in Figures 3 and 4.

[0041] [Table 5]

[0042] As shown in the graphs in Figures 3 and 4, it was found that the relationship between the amount of solidifying agent and the uniaxial compressive strength at each substitution rate can be approximated by a linear equation with fairly high accuracy.

[0043] Using this approximation formula, when the amount of solidifying agent is changed in more detail, the relationship between the substitution rate and the unconfined compressive strength can be predicted, as shown in Figure 5, when the amount of solidifying agent is 60 kg / m³. 3 The uniaxial compressive strength peaks at a substitution rate of 50%, and at higher substitution rates, the uniaxial compressive strength tends to decrease sharply. 3 In this case, the peak of the unconfined compressive strength occurs between 50% and 70% of the replacement rate, and the amount of solidifying agent is 70 kg / m³. 3 , 80 kg / m 3 In this case, the peak of the unconfined compressive strength occurs at a replacement rate of 70%. Therefore, the amount of solidifying agent is 65 kg / m³. 3 The range exceeding this can be estimated to be the range in which the uniaxial compressive strength peaks at a substitution rate of 70%. From these results, the formulation design method according to the present invention uses a solidifying agent amount of 65 kg / m³. 3 It is desirable to apply this to a range exceeding that limit.

Claims

1. A method for designing the mix design of fluidized soil in which a portion of the cement used as a solidifying agent is replaced with steel slag, A method for designing the mix of fluidized soil, characterized in that, under the condition that the amount of the solidifying agent exceeds 65 kg / m³, the replacement rate of the steel slag is set to 70% as the standard replacement rate, a relationship formula between the unconfined compressive strength and the amount of solidifying agent at this standard replacement rate of 70% is determined, and the amount of solidifying agent for the target unconfined compressive strength is calculated based on this relationship formula.

2. A method for designing the mix of fluidized soil, wherein a portion of the cement used as a solidifying agent is replaced with steel slag, A method for designing the mix of fluidized soil, characterized in that, under the condition that the amount of the solidifying agent is applied in a range exceeding 65 kg / m³, the replacement rate of the steel slag is set to 60-75%, and the amount of solidifying agent for the target unconfined compressive strength is calculated from a relationship formula between the unconfined compressive strength and the amount of solidifying agent at the required replacement rate of steel slag, or the amount of solidifying agent for the target unconfined compressive strength is determined from a graph showing the relationship between the replacement rate and unconfined compressive strength with the amount of solidifying agent as a parameter, by linearly interpolating the closest line of solidifying agent amount or between line of solidifying agent amounts to the intersection point of a predetermined replacement rate and the target unconfined compressive strength.

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