Soil improvement methods

Abstract

The objective of this invention is to provide a novel soil improvement method that can be used stably. [Solution] One aspect of the present invention is a soil improvement method comprising a preparation step of preparing conditioned soil and a stirring step of adding the conditioned soil to the soil and mixing it. The conditioned soil is derived from construction sludge.

Description

[Technical Field]

[0001] The present invention relates to a bracket and a soil improvement method. [Background technology]

[0002] Soil conditioners are used to improve the soil in agricultural land and other areas. For example, calcareous fertilizers are used as soil conditioners. Patent document 1 discloses a soil conditioner made from steelmaking slag. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2013-155273 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Soil conditioners need to be inexpensive and available in large quantities, and there is a growing need for more stable and reliable soil improvement methods. Therefore, the present invention aims to provide a novel soil improvement method that can be used stably. [Means for solving the problem]

[0005] In recent years, the large amount of waste generated in the construction process has become a problem, and construction sludge is one example. After diligent research by the inventors, they discovered that the above problem can be solved by utilizing construction sludge, and thus completed the present invention.

[0006] According to the present invention, the following is provided: [1] A method for improving soil, The preparation process for preparing the soil with improved temperature, A mixing process in which the above-mentioned soil conditioning and improvement soil is added to the soil and mixed, Equipped with, The above-mentioned soil improvement method uses soil conditioner derived from construction sludge. [2] The above preparation steps are The above construction sludge is mixed with lime components in a dewatering and solidification step to produce solidified sludge, The above solidified sludge is sieved to reduce the particle size to 30 mm or less in a sieving step, The soil improvement method described in [1], comprising: [3] The soil improvement method described in [2], wherein the amount of the above-mentioned lime component added is 3 to 20 parts by mass when the construction sludge is 100 parts by mass. [4] The soil improvement method described in any of [1] to [3], wherein the pH of the above-mentioned soil conditioner is 10 to 12. [5] The soil improvement method described in any of [1] to [4], wherein the moisture content of the above-mentioned soil conditioner is 30-45% as measured by a method compliant with JIS A 1203:2020. [6] The soil improvement method described in any of [1] to [5], wherein the soil is agricultural soil. [Effects of the Invention]

[0007] According to the present invention, a novel soil improvement method that can be used stably can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows the results of measuring the soil pH in the example. [Figure 2] Figure 2 shows the measurement results of the EC value of the soil in the example. [Modes for carrying out the invention]

[0009] The present invention will now be described in detail. The present invention is not limited to these descriptions. The features of the embodiments shown below can be combined with each other. Furthermore, each feature can constitute an invention independently. In addition, any element in the embodiments below that is not specified in the claims is an optional element and can be omitted.

[0010] <Explanation of Terms> In this specification, for example, the description "X to Y" means X or more and Y or less. In this specification, any number (for example, one or two) of "0"s may be added to the end of a numerical value. For example, one or two "0"s may be added after "1.4" to make "1.40" or "1.400".

[0011] 1 Soil improvement method The soil improvement method according to this embodiment includes a preparation step of preparing conditioned improved soil, and a stirring step of adding the conditioned improved soil to the soil and mixing them. The conditioned improved soil according to this embodiment is characterized by being derived from construction sludge.

[0012] 1.1 Preparation step In the preparation step according to this embodiment, conditioned improved soil derived from construction sludge, which is obtained by treating construction sludge, is prepared. That is, the preparation step according to this embodiment is, in other words, a method for manufacturing conditioned improved soil. The preparation step according to this embodiment includes a dehydration and solidification step of making construction sludge into solidified sludge, and a sieving step of sieving the solidified sludge.

[0013] 1.1.1 Dehydration and solidification step In the dehydration and solidification step according to this embodiment, a lime component is mixed into the construction sludge to make solidified sludge with a reduced water content ratio. The construction sludge according to this embodiment is a muddy industrial waste generated along with construction work and excavation work, and the cone index means less than 200 kN / m 2 . It is preferable that the construction sludge according to this embodiment satisfies the soil environmental standards. The pH of the construction sludge is, for example, 7 to 12, preferably 7 to 10, and more preferably 7 to 8.

[0014] The dehydration and solidification step according to this embodiment includes, for example, a step of allowing the construction sludge to stand and dehydrate, a step of adding a lime component to the dehydrated construction sludge (dehydrated sludge), and a step of mixing the construction sludge (dehydrated sludge) after the addition of the lime component. It is preferable that the dehydration and solidification step according to this embodiment further includes a step of allowing the construction sludge (dehydrated sludge) to stand after mixing.

[0015] The dewatering and solidification step according to this embodiment preferably includes a step of dewatering the construction sludge. It is preferable to use mud (mud-like sludge) as the construction sludge according to this embodiment. Here, the mud is construction sludge with a relatively low water content, generated by methods such as earth pressure balance shield tunneling.

[0016] In this embodiment, the dewatering process preferably involves separating the mud into a supernatant and a residue (residual mud) after being allowed to stand for a predetermined period. The residue (residual mud) generated by the standing period is collected and becomes dewatered sludge.

[0017] The dewatering and solidification step according to this embodiment preferably includes a step of adding a lime component to the dewatered construction sludge (dewatered sludge). As the lime component according to this embodiment, for example, cement, slaked lime, and quicklime can be used, and the use of quicklime is particularly preferred. The amount of lime component added according to this embodiment can be appropriately adjusted according to the type of construction sludge, and specifically, it can be adjusted according to the cone index and water content, and can be mainly determined based on the cone index. For example, it is preferable to add 3 to 50 parts by mass of lime component per 100 parts by mass of dewatered sludge, more preferably 3 to 20 parts by mass, and even more preferably 5 to 10 parts by mass. By setting the amount of addition within this range, the cone index and water content of the treated soil can be within an appropriate range (specifically, after the sieving step described later, the cone index should be 200 kN / m³). 2 (The above, and the water content is 45% or less.)

[0018] The dewatering and solidification step according to this embodiment preferably includes a step of mixing the construction sludge (dewatered sludge) after the addition of the lime component. The step of adding the lime component and the step of mixing may be performed simultaneously (continuously). Specifically, the dewatered sludge and the lime component can be added to and mixed in a continuous mixer.

[0019] The dewatering and solidification step according to this embodiment preferably includes a step of letting the construction sludge (dewatered sludge) after mixing with lime components stand. After mixing with lime components, it is preferable to let it stand for, for example, 12 hours or more, preferably 18 hours or more, and even more preferably 24 hours or more. By allowing such a standing time, the exothermic reaction by the lime components progresses, the cone index increases sufficiently, and solidified sludge with a sufficiently reduced water content can be obtained, making clogging less likely in the sieving step described later and improving work efficiency.

[0020] 1.1.2 Sieving Step In the sieving step according to this embodiment, the solidified sludge is sieved to obtain tempered soil with a particle size of a specific size or smaller. Specifically, the sieving step according to this embodiment is a process of sieving the solidified sludge using a sieve with a predetermined mesh size. Here, the mesh size of the sieve used in the sieving step is preferably, for example, 30 mm or less, more preferably 25 mm or less, and even more preferably 20 mm or less. By using a sieve with such a mesh size, the particle size of the tempered soil becomes 30 mm or less, more preferably 25 mm or less, and even more preferably 20 mm or less. By setting the particle size of the tempered soil to such a value, the cone index increases further and the water content decreases further. Furthermore, having the particle size of the tempered soil within this range makes it easier to mix into agricultural land in the stirring step described later.

[0021] The pH of the soil conditioner according to this embodiment is adjusted as appropriate to the agricultural land to which it is applied, but is preferably 8 to 14, more preferably 10 to 12, and more preferably 10.5 to 12. When the pH is within this range, a mild neutralization reaction occurs when it is mixed into the agricultural land, and consequently the EC value does not increase easily.

[0022] The water content of the soil treated and improved according to this embodiment, as measured by a method compliant with JIS A 1203:2020, is preferably 20-50%, and more preferably 30-45%.

[0023] 1.2 Stirring process In the stirring step according to this embodiment, soil conditioner is added to the soil and mixed. Examples of soil used include agricultural land and embankment for construction work (for example, for residential land development or farmland development), and it is particularly preferable that the soil is used for agricultural land (agricultural soil).

[0024] In this embodiment, it is preferable that the soil conditioner is mixed while excavating the target soil. Depending on the scale, conventionally known mixing methods can be used. On a test scale (e.g., 10 kg or less), mixing can be done while excavating with a shovel, for example. For actual soil, a drive mixer (manufactured by Taguchi Kogyo Co., Ltd.) can be used, for example. Mixing while excavating results in a more uniform pH throughout the soil.

[0025] The amount of soil-conditioning and improving soil according to this embodiment is adjusted appropriately according to the desired pH. Agricultural land may deteriorate due to factors such as rainfall, fertilization, excessive use of organic matter, and nitrification by nitrogen fertilizers, which can lower the pH. As described above, the soil-conditioning and improving soil according to this embodiment has a high pH, ​​so by mixing it with such deteriorated agricultural land, it is possible to achieve a pH suitable for plant cultivation (for example, pH 6.0 to 7.5, preferably pH 6.5 to 7.0). When the pH of the target soil is 5 to 6, for example, the amount of soil-conditioning and improving soil according to this embodiment can be 5 to 50 parts by mass per 100 parts by mass of soil, preferably 10 to 40 parts by mass, and more preferably 20 to 30 parts by mass. The soil-conditioning and improving soil according to this embodiment has the characteristic that when mixed with soil, the pH of the soil increases gradually (relatively linearly with respect to the added mass). This is thought to be due to the buffering effect of the original soil and the soil-conditioning and improving soil. Therefore, the soil-conditioning and improving soil according to this embodiment has the characteristic that abrupt pH changes are less likely to occur when mixed, and it is easy to adjust to the target pH.

[0026] Furthermore, when the soil conditioner-improved according to this embodiment is mixed, the difference (absolute value) between the EC value before and after mixing is preferably 0.3 mS / cm or less, more preferably 0.1 mS / cm or less, and even more preferably 0.05 mS / cm or less. Conventionally, when pH adjusters used in agricultural land are used, the EC value increases sharply, so it may be necessary to use other materials in combination to adjust the EC value. However, since the soil conditioner-improved according to this embodiment undergoes a gradual chemical reaction (neutralization reaction), the EC value does not increase easily.

[0027] The permeability coefficient of the soil after mixing with the soil conditioner-improved soil according to this embodiment is 1.0 × 10⁻⁶. -2 ~1.0×10 -5 It is preferably cm / s, and 1.0 × 10 -2 ~1.0×10 -4 A value of cm / s is more preferable. The permeability coefficient of the soil after mixing with the soil conditioner can be adjusted by the particle size and permeability coefficient of the soil conditioner, as well as the degree of soil compaction. [Examples]

[0028] The present invention will be described in more detail below based on the following examples. The examples described below are merely representative examples of the present invention and should not be interpreted as narrowing the scope of the invention.

[0029] <Preparation of soil conditioning and improvement> For construction sludge, a cone index of 200 kN / m³ meets the soil environmental standards. 2 Sludge (sludge-like sludge) with a pH of less than 20 mm was used. The pH of the sludge used was 7-8. After standing for a specified period, it was separated into supernatant and residue (residual sludge). The residue (residual sludge) generated by standing was collected and used as dewatered sludge. Next, 8 parts by mass of quicklime were added and mixed with 100 parts by mass of dewatered sludge in a continuous mixer. After mixing in the quicklime, it was left to stand for 24 hours or more to solidify the sludge. The solidified sludge was sieved through a sieve with a mesh size of 20 mm, and the particle size was 20 mm or less and the cone index was 200 kN / m 2The above soil with improved quality was obtained. The pH of the soil with improved quality was 10.53, and the EC value was 0.08 mS / cm. Also, the water content ratio measured by the method compliant with JIS A 1203:2020 was 40.9%. Furthermore, the permeability coefficient measured by the method described later was 4.41×10 -3 cm / s.

[0030] <Addition Test of Soil with Improved Quality><​​​​​​​​​​​​​​​​​​​​​​​ Figure 1 shows the pH measurement results, and Figure 2 shows the EC value measurement results. As shown in Figure 1, the pH of the soil increased gradually (relatively linearly with respect to the added mass) upon addition of the soil conditioner. When the amount of soil conditioner used was 25 parts by mass relative to 100 parts by mass of the original soil, the pH value increased by approximately 1, reaching pH 6.98. Furthermore, as shown in Figure 2, the EC value of the soil increased gradually upon addition of the soil conditioner. When the amount of soil conditioner used was 25 parts by mass relative to 100 parts by mass of the original soil, the difference (absolute value) in EC value compared to the start of the test (before mixing) was 0.04 mS / cm. In addition, the permeability coefficients of the deteriorated agricultural soil and the recovered soil were 7.03 × 10⁻⁶, respectively. -3 cm / s and 5.51 × 10 -3 The reading was cm / s. Thus, by using soil conditioner, the pH of the degraded soil could be gradually increased, and the EC value remained almost unchanged during this process.

Claims

1. A soil improvement method, The preparation process for preparing the soil with improved temperature, A mixing step in which the aforementioned soil conditioner and improved soil is added and mixed, Equipped with, A soil improvement method in which the aforementioned conditioned soil is derived from construction sludge.

2. The aforementioned preparation step is A dewatering and solidification step involves mixing lime components with construction sludge to create solidified sludge, The solidified sludge is sieved to reduce its particle size to 30 mm or less in a sieving step, The soil improvement method according to claim 1, comprising:

3. The soil improvement method according to claim 2, wherein the amount of the lime component added is 3 to 20 parts by mass when the construction sludge is 100 parts by mass.

4. The soil improvement method according to claim 1 or 2, wherein the pH of the soil conditioner is 10 to 12.

5. The soil improvement method according to claim 1 or 2, wherein the moisture content of the treated soil, as measured by a method compliant with JIS A 1203:2020, is 30 to 45%.

6. The soil improvement method according to claim 1 or 2, wherein the soil is agricultural soil.

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