Mixing test method and ground improvement method

Abstract

To provide a test method for determining the amount of solidification material to be added in the first stage in a ground improvement method in which the solidification material is added to ground material twice and stirred and mixed, which can quickly determine the optimal amount of solidification material to be added in the first stage. [Solution] The method includes a measurement process in which the ground material and solidification material are stirred and mixed, and then the pH of the ground material and the solidification material is measured multiple times by changing the amount of solidification material added to the ground material; and a first addition amount determination process in which, based on the measurement results obtained in the measurement process, the amount of solidification material to be added corresponds to the point where the pH on a characteristic curve representing the correlation between the amount of solidification material to be added to the ground material and the pH of the mixed soil changes from below a threshold value in the range of 10.5 to 12.5, to exceeding the threshold value.

Description

[Technical Field]

[0001] The present invention relates to a mix testing method and a ground improvement method using a solidifying agent. [Background technology]

[0002] Conventionally, in a method for solidifying the ground by mixing ground material with a solidification material, a method that can prevent an increase in the amount of solidification material used has been known. For example, Patent Document 1 discloses a ground improvement method characterized by adding and mixing a portion of the final amount of solidification material to the target improved soil, and then adding and mixing the remaining amount of solidification material. It is said that this method can prevent an increase in the amount of solidification material used. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-230821 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when adding the solidification agent in divided doses, there is currently no established method for determining the amount to be added in the first dose. One example is a method of setting the amount based on the unconfined compressive strength of a mix test without divided addition. The compressive strength of the solidification agent-mixed soil is determined by the strength at 28 days. The strength at 28 days can also be estimated from the strength at 7 days. In other words, it takes a considerable amount of time to determine in advance the optimal amount of solidification agent to be mixed into the ground material.

[0005] Therefore, the present invention aims to provide a mixing test method that can quickly determine the optimal amount of solidification material to be initially mixed into the ground material in a ground improvement method in which the solidification material is added to the ground material twice and stirred and mixed. [Means for solving the problem]

[0006] The present invention relates to a test method for determining the amount of solidification material to be added in the first addition in a ground improvement method in which the solidification material is added to ground material twice and stirred and mixed.

[0007] The blending test method of the present invention includes a measurement step in which the ground material and the solidification material are stirred and mixed, and then the pH of the mixed soil of the ground material and the solidification material is measured for each of a plurality of different amounts of the solidification material added to the ground material; and based on the measurement results obtained in the measurement step, when the amount of the solidification material added is increased according to a characteristic curve that represents the correlation between the amount of the solidification material added to the ground material and the pH of the mixed soil, The amount of solidification material added (kg / m 3 ) the rate of change of pH threshold exceeds From the state, the threshold The following will be and a first addition amount determination step of determining the amount of solidification material to be added that corresponds to the point at which the state transitions to the first addition amount.

[0008] In this way, in the mixing test method of the present invention, the amount of solidification material to be added to the ground material for the first time is determined from the pH measurement results of the mixed soil of ground material and solidification material, so that the amount of solidification material to be added for the first time to the ground material can be determined more quickly than when measuring the strength at 7 days or the strength at 7 days.

[0009] Further, in the blending test method of the present invention, in the first addition amount determination step, The aforementioned pH change rate Threshold 0.5% is It is preferable.

[0010] This allows the optimum amount of solidification material to be added to the ground material for the first time to be quickly determined.

[0011] The present invention also relates to a ground improvement method in which a solidifying material is added to ground material twice and then stirred and mixed.

[0012] The ground improvement method in the first aspect of the present invention includes a first solidification material mixing process in which the solidification material is added to the ground material and stirred and mixed, and a second solidification material mixing process in which the solidification material is further added to the ground material and stirred and mixed, and is characterized in that the amount of solidification material added in the first solidification material mixing process is the first amount added determined by the test method of the present invention.

[0013] This allows the amount of solidification material to be added to the ground material in the first addition to be optimally determined, resulting in greater unconfined compressive strength.

[0014] Further, a ground improvement method according to a second aspect of the present invention includes a first solidification material mixing step of adding the solidification material to the ground material and stirring and mixing the solidification material, and a second solidification material mixing step of further adding the solidification material to the ground material and stirring and mixing the solidification material, wherein in the first solidification material mixing step, the ground material and the solidification material are stirred and mixed, and then the pH of the mixed soil of the ground material and the solidification material is measured, and based on a characteristic curve created by the blending test method of the present invention, when the amount of solidification material added is increased according to the characteristic curve, the pH of the mixed soil becomes equal to or lower than the threshold value. The pH value corresponding to the point determined by The process proceeds to the second solidification material mixing step on the condition that the content of the solidification material exceeds the threshold value.

[0015] This makes it possible to determine the optimal amount of solidification agent to be added to the ground material the first time, even if the ground environment at the work site changes and results in a discrepancy with the results of the previous mixing test. [Brief explanation of the drawings]

[0016] [Figure 1] Plot diagram showing the relationship between the amount of solidification material added to the ground material and the pH of the soil mixture of the ground material and solidification material DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will now be described in further detail. Unless otherwise specified, the symbol "to" in a numerical range indicates a range from above to below, and both ends of the range are included. Furthermore, when a numerical range is indicated, the upper and lower limits can be combined as appropriate, and the resulting numerical range is also considered to be disclosed.

[0018] The ground material used in the present invention is not particularly limited, but examples thereof include humus soil, peat, clayey soil, peaty soil, silty soil, and loamy soil.

[0019] Examples of solidifying materials used in the present invention include quicklime, slaked lime, cement, and cement-based solidifying materials. Two or more of these can be used in combination. Examples of cement include Portland cement and blast furnace cement. Examples of cement-based solidifying materials include ettringite-based materials, particularly mixed types, as well as pulverized and fired types.

[0020] [Measurement process] The method for mixing the solidifying agent in the blending test method of the present invention can be any conventional method, such as manual mixing or stirring using a stirring mixer. The solidifying agent can be added as a powder or as a slurry mixed with water or the like.

[0021] The blending test method of the present invention measures the pH of a soil mixture of a ground material and a solidification material, or a suspension of the soil mixture. While there are no particular limitations on the pH measurement method, examples include the indicator metal electrode method, the glass electrode method, and the semiconductor sensor method. Based on JGS 0211-2009 "pH Test Method for Soil Suspensions," the suspension of the soil mixture is prepared by adding water so that the mass ratio of water (including the water in the soil mixture) to the dry mass of the soil mixture is 5. The pH may also be measured while gradually adding the solidification material to the ground material.

[0022] [First addition amount determination process] Based on the results of measuring the pH of a soil mixture of ground material and solidification material or a suspension of the soil mixture, the amount of solidification material added is increased according to a characteristic curve that shows the correlation between the amount of solidification material added to the ground material and the pH of the soil mixture.The amount of solidification material added corresponding to the point where the pH changes from below a predetermined threshold to exceeding the threshold is determined as the first addition amount.The threshold pH range is 10.5 to 12.5, preferably 11 to 12.5, and more preferably 11.5 to 12.

[0023] Here, when the amount of solidifying material added is increased according to the characteristic curve, the amount of solidifying material added (kg / m 3 The threshold value may be set to the pH value corresponding to the transition point from a state where the rate of change in pH relative to the pH exceeds 0.5% to a state where the rate of change in pH is 0.5% or less. If the rate of change in pH is expressed as [pH / amount of solidification material added], the threshold value is 5.0 x 10 -3 (m 3 / kg). The threshold value can also be set in advance based on past performance, simulations, etc.

[0024] If the number of plots is insufficient and the threshold value cannot be determined, the mixed soil is prepared and the pH measured again.The test method of the present invention consists only of preparing the mixed soil and measuring the pH of the mixed soil, so it can be repeated multiple times in a day.

[0025] The pH change rate can also be determined by differentiating the approximation of the characteristic curve and finding the slope of the characteristic curve (the amount of pH change relative to the amount of solidification material added). Examples of approximation formulas for the characteristic curve include logarithmic and exponential functions. Since the characteristic curve can change depending on the number of plots, it is preferable to have at least four plots. If the number of plots is insufficient and the first addition amount cannot be determined, the mixed soil is prepared and the pH is measured again.

[0026] Furthermore, in humus and organic soil, the reason why the soil material inhibits the solidification of the solidification material is that the dissolved calcium ions react with the reactants (humic acid and fulvic acid) contained in the soil material to form calcium salts, which then cover the surface of unhydrated cement particles.The reason why the final unconfined compressive strength of the soil is greater when the solidification material is added twice rather than when the entire amount is mixed in one go is that by adding the solidification material the first time, the reaction occurs until the reactants are gone, allowing the solidification material's capabilities to be maximized when the solidification material is added the second time.

[0027] When the reaction that produces the calcium salt is completed and the reactants are gone, the pH of the ground material reaches the same level as the pH of the solidification material alone. Therefore, when the amount of solidification material added is increased according to the characteristic curve, the amount of solidification material added in the first addition is set to the point where the pH changes from below the threshold value in the range of 10.5 to 12.5 to exceed the threshold value, and the reactants that hinder the solidification of the ground material can be efficiently removed.

[0028] The blending test method of the present invention is usually carried out in a laboratory beforehand, but it can also be carried out on-site. Because it does not take much time to prepare the soil mixture and measure its pH, the first addition amount of solidification material can be determined quickly.

[0029] [Soil improvement method] The ground improvement method of the present invention includes a first solidification material mixing step and a second solidification material mixing step.

[0030] [First solidifying material mixing process] The first solidification material mixing step is a step of adding a solidification material to the ground material, stirring and mixing it to prepare a first mixed soil. The amount of solidification material to be added in the first solidification material mixing step is determined by the above-mentioned test.

[0031] According to another aspect of the present invention, in the first solidification material mixing step, the ground material and the solidification material are stirred and mixed, and then the pH of the soil mixture containing the ground material and the solidification material is measured, and based on the characteristic curve created by the blending test, the pH of the soil mixture may be determined to be above a predetermined threshold value before proceeding to the second solidification material mixing step. The pH may be measured directly on the soil mixture, or on a portion of the recovered soil mixture.

[0032] [Second solidifying material mixing process] The second solidification material mixing step is a step of adding a solidification material to the ground material, stirring and mixing the material to prepare a second soil mixture.

[0033] The amount of solidification material to be added in the second solidification material mixing process is determined by a separate blending test. After mixing the ground material and solidification material, the unconfined compressive strength of the soil mixture is measured for each of the different amounts of solidification material added in the second solidification material addition. Based on the measurement results, the total amount of solidification material required is determined from the relationship between the total amount of solidification material added and the unconfined compressive strength, and the amount of solidification material to be added in the second solidification material mixing process is determined.

[0034] The second solidification material mixing step may be carried out immediately after the first solidification material mixing step, or an interval of 20 minutes to several days may be provided.

[0035] Furthermore, the first solidification material and the second solidification material may be the same type of solidification material, or different types of solidification materials may be used.

[0036] The manner of the first and second addition of the solidification material in the ground improvement method of the present invention can be appropriately selected depending on the actual improvement method used. In the case of deep mixing, the mixing method can utilize the energy of agitator blades, screw augers, compressed air, or high-pressure fluids. In addition, in the case of this deep mixing method, the first addition can be made when the agitator / mixer shaft penetrates, and the second addition can be made when it is pulled out. In the case of surface mixing, a stabilizer or backhoe can be used. The solidification material can be added as a powder or as a slurry mixed with water. [Example]

[0037] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. [Materials used] (1) Ground material: humus soil (2) Solidification material: Cement-based solidification material (product name: GS225, manufactured by Taiheiyo Cement)

[0038] [Experiment 1: pH measurement test] The soil material was treated with 0, 50, 100, 150, 200, 300, 400 and 500 kg / m of solidification agent. 3 The soil was mixed in a mixing mixer, and the soil material and solidification material adhering to the mixing blades were collected, and the soil was further mixed thoroughly by hand to prepare a mixed soil. The pH of this mixed soil was measured using the glass electrode method.

[0039] The pH measurement results are shown in Table 1. In addition, as shown in Figure 1, a characteristic curve was created showing the relationship between the amount of solidification material added to the ground material and the pH of the mixed soil. As shown in Figure 1, when the amount of solidification material added was 50 kg / m 3 When the pH of the mixed soil exceeds the preset threshold of 10.5, the amount of solidification material added is 150 kg / m 3 The pH reached its upper limit at 150 kg / m2, and it was found that the pH of the mixed soil remained constant even if the amount of solidification material was further increased. 3 In the mixed soil, the amount of solidification material added (kg / m 3) transitions from a state where the rate of change in pH relative to the temperature exceeds 0.5% to a state where it falls below 0.5%.

[0040] [Table 1]

[0041] [Experiment 2: Solidification test] As shown in Table 1, the first solidification material was added to the ground material and mixed in a mixing mixer to prepare the first mixed soil. The second solidification material was then added to the first mixed soil and mixed again in a mixing mixer to prepare the second mixed soil. Cylindrical specimens measuring φ5 x 10 cm were then prepared in accordance with JGS 0821-2009, "Preparation of uncompacted specimens of stabilized soil." These specimens were sealed and cured at a room temperature of 20°C and a humidity of 90%, and the unconfined compressive strength was measured at 28 days old in accordance with JIS A1216, "Unconfined compression test method for soil."

[0042] [Table 2]

[0043] As shown in Table 2, the unconfined compressive strength of the improved ground was improved in Examples 1 to 5 compared to the Comparative Example. In particular, when the pH of the mixed soil was in the range of 10.5 to 12.5 and the amount of solidification material added (kg / m 3 ) the pH change rate for the soil changed from over 0.5% to 0.5% or less. The first addition of solidification material was 150 kg / m 3 In Example 3, the unconfined compressive strength of the improved ground was the maximum value. That is, the amount of the first solidification material added was set so that the pH of the mixed soil was in the range of 10.5 to 12.5, and the amount of the solidification material added (kg / m 3 ) is the point at which the pH change rate changes from over 0.5% to 0.5% or less. 3 Then, by stirring and mixing with different amounts of second solidification material added, it is possible to determine the optimal total amount of solidification material to be added for the desired uniaxial compressive strength of the improved ground.

[0044] Based on the above, in a ground improvement method in which solidification material is added in separate steps, the amount of solidification material added is divided into a first solidification material addition step and a second solidification material addition step. When the amount of solidification material added is increased according to the characteristic curve created in a mix test, the amount of solidification material added that corresponds to the point at which the pH of the soil mixture of ground material and solidification material transitions from a state below the threshold of 10.5 to 12.5 to a state above that threshold can be set as the amount of the first solidification material. In other words, by determining the point at which the pH of the soil mixture of ground material and solidification material transitions from a state below the threshold of 10.5 to 12.5 to a state above that threshold when the amount of solidification material added is increased according to the characteristic curve created in a mix test, the total amount of solidification material added to obtain improved ground with the required unconfined compressive strength can be minimized.

[0045] It should be noted that the present invention is not limited to the above-described embodiments or examples, and it is clear that the scope of the present invention can be modified or altered within a range that is obvious to those skilled in the art. It is also clear that the scope of the present invention is not limited to the above-described embodiments or examples, but also includes modifications and alterations thereof.

Claims

1. In a ground improvement method in which a solidification material is added to a ground material twice and stirred and mixed, a test method for determining the amount of the solidification material to be added in the first time is performed. A measuring process in which the ground material and the solidification material are stirred and mixed, and then the pH of the mixed soil of the ground material and the solidification material is measured for each of a plurality of different amounts of the solidification material added to the ground material; a first addition amount determination step, which determines, based on the measurement results obtained in the measurement step, the amount of solidification material to be added that corresponds to the point at which the rate of change in pH relative to the amount of solidification material to be added (kg / m 3 ) transitions from exceeding a threshold value to a state where the rate of change in pH is equal to or less than the threshold value when the amount of solidification material to be added is increased according to a characteristic curve that represents the correlation between the amount of solidification material to be added to the ground material and the pH of the mixed soil; A compounding test method, including:

2. In the first addition amount determination step, 2. The formulation testing method of claim 1, wherein the threshold pH change rate is 0.5%.

3. In this ground improvement method, solidification material is added to the ground material twice and mixed. A first solidification material mixing process of adding the solidification material to the ground material and stirring and mixing it; A second solidification material mixing step of further adding the solidification material to the ground material and stirring and mixing, The amount of the solidification material added in the first solidification material mixing step is the first amount added determined by the test method described in claim 1. A ground improvement method characterized by:

4. In this ground improvement method, solidification material is added to the ground material twice and mixed. A first solidification material mixing process of adding the solidification material to the ground material and stirring and mixing it; A second solidification material mixing step of further adding the solidification material to the ground material and stirring and mixing, In the first solidification material mixing step, the ground material and the solidification material are stirred and mixed, and then the pH of the mixed soil of the ground material and the solidification material is measured, The second solidification material mixing step is performed on the condition that the pH of the mixed soil exceeds the pH corresponding to the point determined by the threshold value based on the characteristic curve created by the blending test method according to claim 1 or 2. A ground improvement method characterized by:

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