JP6079489B2 - Soil classification treatment agent and classification treatment method - Google Patents

Description

  The present invention relates to a soil classification treatment agent for promoting classification treatment of the water-containing soil by adding to the water-containing soil, and a soil classification treatment method using the classification treatment agent.

In disaster-stricken areas and the like that were hit by the earthquake, debris, waste, and other contaminants were mixed, and in some cases, a large amount of water-containing soil contaminated with the soil itself was generated. In order to treat such soil, it is necessary to first separate the foreign material from the soil, and to treat the foreign material such as rubble separated from the soil by appropriate treatment methods such as incineration, pulverization, and landfilling. . For this reason, the classification process which classifies a foreign material and soil is needed.
The soil classification treatment is also performed, for example, at the construction site, when the soil is classified into gravel, sand, silt / clay, and when the necessary components are collected or the contaminated soil is treated, gravel, sand, silt / clay. It is also implemented as a process of dividing.

  The classification efficiency of soil becomes worse as the mesh opening of the sieve to be classified becomes finer and the moisture content of the soil to be treated becomes higher. A decrease in soil classification efficiency leads to a decrease in the amount of collected soil, an increase in the amount of waste to be disposed of or incinerated, an increase in the amount of incinerated ash generated, and a prolonged classification process itself. Accordingly, it is required to efficiently classify hydrous soil, improve the purity of necessary components, and shorten the classification time.

  Conventionally, in order to improve the soil classification efficiency, a method of drying the classification target soil with sun or the like and modifying it to a state that is easy to classify, adding a polymer flocculant such as an acrylamide synthetic polymer, etc. A method for modifying soil (for example, Patent Document 1) has been implemented.

However, in the method of drying the classification target soil,
(1) In the case of drying by the sun, the drying time is affected by the climate, and it takes time in the winter. In addition, rain countermeasures are necessary.
(2) Fuel costs are incurred when drying with a burner.
(3) A space for placing soil during drying is required.
There is a problem.

On the other hand, in the method of adding a polymer flocculant such as acrylamide synthetic polymer to soil,
(1) Since the amount added is small relative to the amount of soil, a highly efficient stirring device is required for uniform mixing with the soil.
(2) When the classified soil is returned to the field, the polymer flocculant, which is a synthetic substance, is also reduced along with the soil, and the synthetic substance remains in the soil for a long period of time, which is not environmentally preferable. In particular, the acrylamide-based synthetic polymer contains an acrylamide monomer suspected of having carcinogenicity, and it is not preferable that the acrylamide-based synthetic polymer is contained in the classification soil.
(3) With the addition of liquid polymers and emulsions, the moisture content of the soil increases and the classification efficiency decreases.
(4) When a powdered polymer is added in the form of powder, it takes a long time for the reaction, and a special stirring device is required. Moreover, Mamako (dama) is formed, and it is difficult to obtain an effect of promoting classification. .
There is a problem.

JP 2012-176394 A

  This invention makes it a subject to provide the soil classification processing agent without the trouble of the above conventional methods, and the soil classification processing method using this classification processing agent.

As a result of intensive studies to solve the above problems, the inventors of the present invention classified inorganic mineral powder having a ratio of water absorption (%) and bulk specific gravity (g / cm ³ ) of a predetermined value or higher to classify hydrous soil. It was found that the promotion effect is excellent.
That is, an inorganic mineral powder having a very high water absorption rate with respect to bulk specific gravity, when added to and mixed with water-containing soil to be classified, is uniformly dispersed on the soil surface, covering the surface of the soil particles and the soil surface. Immediately absorbs the free water of the soil, reforms the soil to a dry state, prevents the agglomeration of the soil particles, can significantly improve the classification effect by suppressing the formation of coarse granules .
In addition, even if the water absorption rate of the inorganic mineral powder is large, if the specific surface area is small, a larger amount of addition is required to cover the soil surface. The surface area is large, that is, the value of water absorption / bulk specific gravity is also an indicator of the size of the specific surface area, and if it is an inorganic mineral powder having a large water absorption / bulk specific gravity, the water-containing soil can be modified with a relatively small addition amount. can do.
The present invention has been achieved based on such findings, and the gist thereof is as follows.

[1] A soil classification treatment agent for promoting classification treatment of water-containing soil by adding to water-containing soil, wherein the ratio of water absorption (%) to bulk specific gravity (g / cm ³ ) is 500. A soil classification treatment agent comprising the above inorganic mineral powder.

[2] The soil classification process according to [1], wherein the pH of a suspension obtained by mixing the inorganic mineral powder with a liquid-solid ratio of water and inorganic mineral powder is 6 to 9. Agent.

[3] The soil classification treatment agent according to [1] or [2], wherein the inorganic mineral powder is diatomaceous earth.

[4] The soil classification treatment agent according to any one of [1] to [3], wherein the water content of the water-containing soil is 10% or more.

[5] A soil classification treatment method, wherein the soil classification treatment agent according to any one of [1] to [4] is added to and mixed with water-containing soil and then classified.

  According to the present invention, it is possible to remarkably improve classification efficiency by modifying water-containing soil, and it is possible to efficiently classify water-containing soil to a desired particle size in a short time.

It is a graph which shows the relationship between the water absorption rate / bulk specific gravity and classification rate of various additives based on the results of Example 2 and Comparative Examples 3, 5, 7, and 9. It is a graph which shows the relationship between the water absorption rate / bulk specific gravity and classification rate of various diatomaceous earth based on the result of Examples 4-6.

  Hereinafter, embodiments of the present invention will be described in detail.

The soil classification treatment agent of the present invention is a soil classification treatment agent for promoting the classification treatment of the water-containing soil by adding to the water-containing soil, the water absorption rate (%) and the bulk specific gravity (g / cm ³ ) It is characterized by comprising an inorganic mineral powder having a ratio of 500 or more.
In addition, the soil classification treatment method of the present invention is characterized in that such a soil classification treatment agent of the present invention is added to and mixed with water-containing soil and then classified.

  In the present invention, the water absorption rate, bulk specific gravity, pH, and water content of the water-containing soil are defined as follows.

<Water absorption rate of inorganic mineral powder>
Pure water is added to the dried inorganic mineral powder (weight W ₁ ) and allowed to stand for 30 minutes to completely settle the absorbed inorganic mineral powder, and the supernatant water floating on the top is sucked with a microsyringe and completely removed. After removing unabsorbed water, the weight is measured (weight W ₂ ), and the following formula is used.
Water absorption (%) = {(W ₂ −W ₁ ) / W ₁ } × 100
Here, the dry inorganic mineral powder refers to a state of 0% moisture content that does not reduce the weight any more even when heated.
The water absorption rate of the hydrous soil is measured in the same way.

<Bulk specific gravity of inorganic mineral powder>
The bulk specific gravity of the inorganic mineral powder is a tap bulk specific gravity measured using “POWDER TESTER TYPE-E” manufactured by Hosokawa Micron.

<PH of inorganic mineral powder>
In accordance with JGS-0211-2000 “pH test method for soil suspension”, pure water is added to the inorganic mineral powder so that the liquid-solid ratio (water / inorganic mineral powder volume ratio) is 5, and the mixture is stirred for 60 minutes. It is the value which measured pH with the pH meter with respect to the suspension obtained by mixing.
The pH of the soil was measured in the same manner as described above for the soil dried to a moisture content of 0%.

<Water content of hydrous soil>
It is a value measured in accordance with JIS A1203 “Method for measuring water content ratio of soil”.
The water content of the inorganic mineral powder is measured in the same manner.

<Specific gravity of hydrous soil>
The specific gravity of the hydrous soil was calculated from about 600 g of wet soil in a 500 mL cylinder, compacted and measured for volume, and the measured value and the weight of the collected soil.

The soil classification treatment agent of the present invention comprises an inorganic mineral powder having a ratio of water absorption (%) to bulk specific gravity (g / cm ³ ) of 500 or more. In general, the water-containing soil to be classified has a water absorption rate of 48.58%, a bulk specific gravity of 1.04 g / cm ³ , and a water absorption rate / bulk specific gravity of 46.7. The inorganic mineral powder to be used has a water absorption / bulk specific gravity of 500 or more, which is 10 times or more.
As described above, the inorganic mineral powder having a large water absorption rate / bulk specific gravity and showing a large water absorption rate with respect to the bulk specific gravity efficiently covers the surface of the hydrous soil and effectively adheres (aggregates) the soil particles. To improve classification efficiency. The larger the water absorption / bulk specific gravity, the higher the soil particle covering effect by the fine inorganic mineral powder particles and the higher the water reforming effect. In the present invention, by selecting an inorganic mineral powder having a large water absorption rate / bulk specific gravity in this way, a markedly high classification promoting effect is obtained as compared with the prior art. The water absorption / bulk specific gravity is more preferably 1000 or more. The upper limit of the water absorption rate / bulk specific gravity is not particularly limited, and the higher the water absorption rate / bulk specific gravity is preferable from the viewpoint of the effect of promoting classification.

The inorganic mineral powder used in the present invention also has a pH of 6 to 9 measured for a suspension prepared by mixing the inorganic mineral powder with a liquid-solid ratio of water and inorganic mineral powder by the above-described method. Is preferred.
Thus, if the suspension is an inorganic mineral powder exhibiting neutrality, it is preferable in that the pH of the soil treated by adding this can be maintained neutral, and the soil quality is not changed.

  The inorganic mineral powder used in the present invention is not particularly limited as long as it satisfies the above water absorption / bulk specific gravity, preferably further satisfies the pH condition, and diatomaceous earth can be suitably used.

When such an inorganic mineral powder is used as a classification treatment, and the classification treatment of the hydrous soil, there is no particular limitation on the amount of the classification treatment to the hydrous soil, that is, the amount of the inorganic mineral powder, and the moisture content of the hydrous soil varies depending other properties, usually, 0.5 to 20 / ^{m 3} of inorganic mineral powders the volume of the water-containing soil, it is preferable to add particularly about 1 to 10 kg / ^{m 3.} If the amount of inorganic mineral powder added is too small, the classification efficiency cannot be improved sufficiently, and if it is too much, the workability is poor, the weight and volume of the treated soil increases, and more time is required for transportation, Furthermore, there is a problem that the amount of powder dust generation increases.

  If the inorganic mineral powder to be used is water-absorbed by water absorption, a sufficient water-absorbing effect cannot be obtained. Therefore, the inorganic mineral powder used in the present invention may be dried to a water content of 5% or less. preferable.

  After the inorganic mineral powder is added to the hydrous soil, the inorganic mineral powder is sufficiently mixed so that the inorganic mineral powder is uniformly dispersed in the hydrous soil, and then classified according to a conventional method.

  For mixing the hydrous soil and the inorganic mineral powder, for example, a mixing machine of an arbitrary system such as a ribbon type, a paddle type, a rotating drum type, or a construction heavy machine such as a backhoe or a bucket stabilizer can be used. Moreover, for the classification process, for example, any type of sieving machine such as a cylindrical sieve or a vibrating sieve can be used.

  In addition, although there is no restriction | limiting in particular as a water-containing soil used as the classification target in this invention, About the water content, it is preferable that it is about 10-50 normally, Preferably it is about 15-40%. In soils with a moisture content lower than the above lower limit, classification can be performed relatively efficiently without adding a classifier, and in hydrous soils with a moisture content higher than the above upper limit, the required addition amount of a classifier Is undesirably increased in terms of workability and economy.

  The classified soil may be returned to the place where the water-containing soil is collected, or may be used as a separate landfill material. At this time, the classified soil treated with the classification treatment agent of the present invention originally contains inorganic mineral powder present in natural soil, does not contain synthetic substances, and does not have problems such as environmental pollution.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Test soil]
The types and properties of the hydrous soil subjected to the classification treatment in the following examples and comparative examples are as follows.

[Additive]
The types and properties of the additives added to the hydrous soil in the following examples and comparative examples are as follows. The additives used were those with a moisture content of 0%.

[Evaluation of classification promotion effect]
In the following examples and comparative examples, the classification promoting effect is as follows: 300 g of a sample (hydrous soil after adding or mixing additives or hydrous soil without addition) is sieved with a 4.75 mm opening defined in JIS Z8801. The particle was subjected to classification treatment for 20 seconds, the weight of the particles passing through the sieve was measured, and the classification rate was evaluated by calculating the following formula.
Classification rate (%) = {particles passing through sieve (g) / 300 (g)} × 100

[Measurement of soil pH]
In the following Examples and Comparative Examples, the pH of the soil was measured based on JGS-0211-2000 described above for classified soil obtained by classifying treated soil or untreated soil. When investigating the change with time of pH, the pH was similarly measured according to JGS-0211-2000 for soil that had been cured indoors for 3 days and 10 days in a wet state.

[Examples 1 and 2 and Comparative Examples 1 to 11]
300 g of water-containing soil A was sampled, and the additives shown in Table 3 were added so as to have the amount shown in Table 3 as the amount added to the water-containing soil (however, in Comparative Example 1 the additive was not added). After stirring for 1 minute (rotational speed: 120 rpm), the classification rate and pH (stirring time at the time of pH measurement: 60 minutes) were examined.

Table 3 shows the following.
In Example 2 in which 15 kg / m ^{3 of} diatomaceous earth was added to Comparative Example 1 without addition, the classification rate can be increased to 8.3%. In Comparative Examples 2 to 9 using inorganic mineral powder having a small water absorption rate / bulk specific gravity other than diatomaceous earth, the classification rate is low. Moreover, from Comparative Examples 10 and 11, it can be seen that when the amount of the water-absorbent resin is increased, the viscosity of the soil increases and the classification rate decreases.

From the results of Example 2 and Comparative Examples 3, 5, 7, and 9, the relationship between the water absorption rate / bulk specific gravity and the classification rate when the additive amount is 15 kg / m ³ is shown in FIG.
FIG. 1 shows that the classification rate is remarkably improved when the water absorption / bulk specific gravity is 500 or more.

[Example 3, Comparative Examples 12 and 13]
300 g of water-containing soil B was sampled, and the additives shown in Table 4 were added to the amount shown in Table 4 as the amount added to the water-containing soil (however, in Comparative Example 12 no additives were added) After stirring for 1 minute (rotation speed: 120 rpm), classification was performed with a sieve having an opening of 4.75 mm, and the pH of the obtained classified soil was measured (stirring time at the time of pH measurement was 60 minutes), and the change with time was measured. .
In the additive-free Comparative Example 12, the change with time of pH was measured for the hydrous soil B in the same manner.
The results are shown in Table 4.

  From Table 4, when alkaline powder such as quick lime (calcium oxide) is added, the pH of classified soil becomes highly alkaline even after 10 days, whereas it is neutral itself like diatomaceous earth. It can be seen that when inorganic mineral powder is added, the pH of the classified soil is not changed.

[Examples 4 to 6]
300 g of hydrous soil C was sampled, diatomaceous earth shown in Table 5 was added to the hydrous soil so as to be 15 kg / m ^3, and the mixture was stirred with a spatula for 1 minute (rotation speed 120 rpm). Are shown in Table 5.

  The relationship between the classification rate and the water absorption / bulk specific gravity is shown in FIG.

  From the results of Examples 4 to 6, it can be seen that even with the same diatomaceous earth, the greater the water absorption / bulk specific gravity, the better the classification promoting effect.

Claims (5)

A soil classification treatment agent for promoting classification treatment of water-containing soil by adding to water-containing soil, wherein the ratio of water absorption (%) and bulk specific gravity (g / cm ³ ) is 500 or more. A soil classification treatment agent comprising a mineral powder.   The soil classification treatment agent according to claim 1, wherein the pH of a suspension obtained by mixing the inorganic mineral powder at a liquid-solid ratio of 5 to water and the inorganic mineral powder is 6 to 9.   The soil classification treatment agent according to claim 1 or 2, wherein the inorganic mineral powder is diatomaceous earth.   The soil classification treatment agent according to any one of claims 1 to 3, wherein the moisture content of the hydrous soil is 10% or more.   A soil classification treatment method, comprising adding and mixing the soil classification treatment agent according to any one of claims 1 to 4 to water-containing soil and then classifying the mixture.

Images