JP5654170B1 - Foaming agent for bubble shield method and bubble shield method - Google Patents

Abstract

Alpha olefin sulfonate is used as a foaming agent in a conventional bubble shield method. However, alpha olefin sulfonates have room for improvement in natural antifoaming properties and fish toxicity has been pointed out. An object of the present invention is to provide a foaming agent for a bubble shield method having sufficient low toxicity and biodegradability and excellent in natural defoaming property, and a bubble shield method using the same. A foam shielding agent for a bubble shield method comprising at least alpha olefin sulfonate and polyethylene glycol, and a bubble shield method comprising a step of excavating the ground using the foaming agent. The above problem has been solved. [Selection] Figure 1

Description

  The present invention relates to a foaming agent for a bubble shield method and a bubble shield method using the same, and more particularly, to a foaming method for a bubble shield method that has sufficient low toxicity and biodegradability and is excellent in natural defoaming properties. The present invention relates to an agent and a bubble shield method using the same.

  As is well known, the bubble shield method, which is a type of shield method, foams a liquid containing foaming agent to produce fine bubbles like a shaving cream, and then excavates the ground while injecting it into the face and chamber. It is a construction method to be performed. The bubble shield construction method improves the fluidity of the excavated soil by the bearing effect of the bubbles; it can prevent the adhering of the excavated soil in the chamber; It has been widely adopted in the industry.

  In addition, the excavated soil (bubble soil) in a state where the bubbles are mixed is in a muddy state having high fluidity, and in this state, there are cases where troubles are caused in loading and transportation. In addition, when washing is performed in an intermediate treatment plant for excavated soil, foam may be generated from the cellular soil, which may cause problems in the treatment equipment and drainage. In such a case, an antifoaming agent is sprayed and mixed as necessary to eliminate bubbles. However, the cost of such an antifoaming agent and the trouble of spreading the antifoaming agent evenly over the cellular soil are problems, and a solution is required. That is, there is a demand for a foaming agent for a bubble shield method that ensures the stability of bubbles during excavation and has the property of defoaming naturally without using an antifoaming agent after excavation (natural defoaming property). ing.

  Moreover, alpha olefin sulfonate is used as a conventional foaming agent (for example, refer patent document 1). However, it is pointed out that alpha olefin sulfonate has strong fish toxicity and room for improvement in natural defoaming properties (see, for example, Patent Document 2). Fish toxicity is a problem when excavated soil is reused as landfill or dumped into the sea.

JP 2007-2168 A JP 2012-197630 A

  Accordingly, an object of the present invention is to provide a foaming agent for a bubble shield method having sufficient low toxicity and biodegradability and excellent in natural defoaming property, and a bubble shield method using the same.

  According to the study of the present inventor, it was found that a foaming agent capable of solving the above problems can be provided by using an alpha olefin sulfonate and polyethylene glycol in combination, and the present invention has been completed.

That is, the present invention is as follows.
1. At least, a bubble shield method for foaming agent you containing an alpha-olefin sulfonate and polyethylene glycol,
The foaming agent for the bubble shield method is prepared by dissolving the alpha olefin sulfonate in water to form an aqueous solution of 0.025 to 1.0 w / v%, and 0.01 to 5 times the volume of the polyethylene glycol in the aqueous solution. It is prepared by blending at a ratio of
The foaming agent for a bubble shield method, wherein the polyethylene glycol has a weight average molecular weight of 100 to 600.
2 . A bubble shield method having a step of excavating the ground using the foaming agent for the bubble shield method according to 1 above.

The foaming agent for the bubble shield method of the present invention makes it essential to use alpha olefin sulfonate and polyethylene glycol in combination. By using polyethylene glycol in combination, the amount of alpha olefin sulfonate used can be reduced without reducing the foaming ability, and the fish toxicity problem can be solved. As a result, the excavated soil can be reused as landfill or dumped in the sea.
Further, by using polyethylene glycol together, the stability of the bubbles can be ensured during excavation, and the natural defoaming property of the cellular soil is improved. This facilitates the loading and transportation of the cellular soil, solves the problems caused by the generation of foam from the cellular soil, and solves the cost and labor associated with the antifoaming agent.

It is the graph which plotted the air porosity va of each example of Table 2 for every elapsed time after excavation.

  Hereinafter, the foaming agent for the bubble shield method of the present invention will be described in more detail.

(Alpha olefin sulfonate)
The alpha olefin sulfonate used in the present invention can be represented by the following general formula (1).
RCH = CH (CH ₂ ) _n SO ₃ Z (1)
(In the formula, R is an aliphatic hydrocarbon group having 8 to 30 carbon atoms, n is 0 to 5, and Z is an alkali metal and / or an alkaline earth metal.)

  The aliphatic hydrocarbon group having 8 to 30 carbon atoms represented by R in the general formula (1) may be either saturated or unsaturated, and may be linear or branched. For example, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, oleyl group, linoleyl group, linolenyl group, etc. Is mentioned. Among these, those having 8 to 20 carbon atoms are preferable from the viewpoint of foaming power, and a tetradecyl group is particularly preferable.

  N in General formula (1) shows the average mole number of a methyl group, and is the range of 0-5. When the number of added moles exceeds 5, the foaming power is deteriorated.

  Z in the general formula (1) represents an alkali metal, an alkaline earth metal or a mixture of both, such as lithium, sodium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, barium, radium, and these The mixture of 2 or more types of these is mentioned. Of these, sodium, potassium, magnesium, calcium and barium are preferable, and sodium is particularly preferable.

(Polyethylene glycol)
The polyethylene glycol used in the present invention has the effect of improving the foaming ability of the alpha olefin sulfonate and reducing the amount used. Moreover, it has the effect of improving the natural antifoaming property of alpha olefin sulfonate.
From the viewpoint of enhancing the above effect, the polyethylene glycol used in the present invention has a weight average molecular weight of, for example, 62 to 1000 (including ethylene glycol) , preferably 100 to 600, and more preferably 200 to 400. In addition, in this invention , ethylene glycol (EG) can be included, and, thereby, the change to the cloudy jelly form of the foaming agent resulting from a temperature fall can be prevented. When using EG, it is preferable to mix | blend 10-100 mass% with respect to the mixture of the aqueous solution of alpha olefin sulfonate, and polyethyleneglycol, and it is further more preferable to mix | blend 20-50 mass%. Moreover, the weight average molecular weight said by this invention means the value measured by GPC (gel permeation chromatography) in polystyrene conversion.

The foaming agent of the present invention can be obtained by dissolving the alpha olefin sulfonate in water to form an aqueous solution, and blending the polyethylene glycol into the aqueous solution. In the following description, the foaming agent of the present invention diluted with water may be referred to as a “foaming material”.
The concentration of the alpha olefin sulfonate in the aqueous solution is, for example, 0.025-1. Is a 0w / v%, preferably 0.08~0.5 w / v%.
The concentration of this alpha olefin sulfonate is 1/5 or less of the prior art foaming agents. Nevertheless, the foaming agent of the present invention can be used together with polyethylene glycol to improve the natural antifoaming property without reducing the foaming ability. In addition, reducing the concentration of alpha olefin sulfonate can result in reduced fish toxicity.

In the foaming agent of the present invention, the blending ratio of the alpha olefin sulfonate and the polyethylene glycol is such that when the concentration of the alpha olefin sulfonate in the aqueous solution is 0.025 to 1.0 w / v% , the polyethylene glycol Is, for example, 0.01 to 5 times the volume of the aqueous alpha olefin sulfonate solution, preferably 0.02 to 3 times the volume.
If the blending ratio of polyethylene glycol is less than 0.01 times the volume, the blending amount is too small and the foaming effect may be reduced. On the other hand, if the capacity exceeds 5 times, the natural defoaming effect is reduced.

On the other hand, as described above, alpha olefin sulfonate has a problem of strong fish toxicity. For this reason, in order to dump excavated soil into the sea or reuse it as landfill, it is necessary to temporarily store excavated soil for about 3 days to reduce the content of alpha olefin sulfonate. However, depending on the excavation site, it may be extremely difficult to secure a space for temporarily placing a large amount of excavated soil. In such a case, it is preferable to further appropriately set the blending amount of the alpha olefin sulfonate and the polyethylene glycol. Specifically, the concentration of the alpha olefin sulfonate in the aqueous solution is, for example, 0.092 to 0.165 w / v%, and the blending amount of polyethylene glycol is 3.0 with respect to the alpha olefin sulfonate aqueous solution. It is better to set the capacity to ~ 1.2 times. More preferably, the concentration of the alpha olefin sulfonate in the aqueous solution is, for example, 0.110 to 0.147 w / v%, and the blending amount of polyethylene glycol is 2.3 to the alpha olefin sulfonate aqueous solution. It is good to set to 1.5 times capacity. According to the said form, when dumping offshore, the alpha olefin sulfonate density | concentration normally calculated | required in this industry will be far less, and it becomes possible to discard excavated soil as it is, without temporarily placing it.

The bubble shield method in the present invention includes a step of excavating the ground using the foaming agent.
When the foaming agent of the present invention is used for the bubble shield method, the foaming material obtained by diluting the foaming agent of the present invention with water is foamed by a foaming apparatus, and the resulting bubbles (bubble amount = foaming material amount × foaming) (Magnification) is continuously sent to the excavation surface and mixed with the excavated soil (bubble mixing ratio = amount of bubbles ÷ amount of excavated soil), etc., and the method is well known in the art.
When using the foaming agent of the present invention, the usage amount, foaming ratio, bubble mixing ratio, the operating conditions of the shielding machine, etc. can be appropriately determined according to the type and nature of the ground. Reference can be made to documents such as Shield Construction Method Technology Association (August 2011), but the amount used is, for example, 5 to 100% by volume, preferably 20 to 80% by volume of bubbles with respect to 1 m ^{3 of} earth and sand. It is good to use and the expansion ratio is about 2 to 15 times, for example.

  In addition, the foaming agent of the present invention can be used in combination with various conventionally used admixtures as necessary within a range not inhibiting the foaming effect. Examples of these admixtures include known water-soluble polymers (such as methylcellulose and sodium polyacrylate), thickeners (such as xanthan gum, guar gum, and sodium alginate), clay minerals (such as bentonite), and superabsorbent resins. be able to.

  In addition, an antifoamer can also be used together with the foaming agent of this invention as needed. In this case, the use amount of the antifoaming agent is about 0.1 to 0.5% by volume with respect to the foaming agent, and this amount is 10 to 50% with respect to the use amount of the prior art. The type of antifoaming agent is not particularly limited, and those used in the industry can be selected as appropriate.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, this invention is not restrict | limited to the following example.

Examples 1-2
Preparation of foaming material and amount of bubbles As the alpha olefin sulfonate, a trade name “Lipolane LB-440” manufactured by Lion Corporation was used. Lipolane LB-440 is a mixture of RCH═CH (CH ₂ ) _n SO ₃ Na and RCH ₂ CH (OH) (CH ₂ ) _m SO ₃ Na (carbon number of R 14).
Further, as polyethylene glycol, a trade name “PEG # 300” manufactured by NOF Corporation was used. The weight average molecular weight of PEG # 300 is 300.
The alpha olefin sulfonate was dissolved in water to prepare an aqueous solution. The concentration of alpha olefin sulfonate in the aqueous solution was 0.4 w / v% . The polyethylene glycol was added to this aqueous solution at a volume of 1.00 times that of the aqueous solution.
This foam was used at the bubble shield construction site in northern Kyushu.
Incidentally, the drilling length was 12m ³ excavated earth and sand from the drilling start point and first ring further 2 ring drilling length was 12m ³ excavated earth and sand, further 3 ring drilling length the next sediment was 12m ³ drilling, likewise sediment When the digging length excavated by 12n (m ³ ) is an n-ring, the foamed material was used at the tunnel excavation site of 253 ring (Example 1) and 254 ring (Example 2).
At this site, first, using a foaming device in a shield machine, the foaming material is foamed at a foaming ratio of 4 times so that the bubbles are in the range of 35 to 40% by volume of the excavated soil (excavated earth and sand). Mixed with excavated soil in shield chamber. As a result, the amount of bubbles was 4760 and 4810 liters with respect to 12 m ^{3 of} earth and sand.
Next, the load conditions on the shield machine were examined as face soil pressure, cutter pressure, and average thrust. The results are shown in Table 1 below. The excavation speed of the shield machine was 25 to 30 mm / min, and the actual excavation time was 40 to 45 min / ring.

Comparative Examples 1-3
Preparation of foaming material and amount of bubbles Using the alpha olefin sulfonate used in Examples 1 and 2, this alpha olefin sulfonate was dissolved in water to prepare an aqueous solution. The concentration of the alpha olefin sulfonate in the aqueous solution was 2.0 w / v% , and this was used as the foaming material of the comparative example.
The foaming material of this comparative example was used on the same bubble shield construction site as Examples 1-2.
The place of use is 259-261 rings.
In this field, first, using a foaming device in a shield machine, the foaming material of the comparative example is foamed at a foaming ratio of 4 times, and the bubbles are in the range of 35 to 40% by volume of the excavated soil (excavated earth and sand). As such, it was mixed with the excavated soil in the shield chamber. As a result, the amount of bubbles was 4150 to 4790 liters with respect to 12 m ^{3 of} earth and sand.
Next, the load state on the shield machine was examined in the same manner as in Examples 1-2. The results are shown in Table 1 below. The excavation speed of the shield machine is the same as in Examples 1-2.

  From the result of Table 1, Examples 1-2 which used the foaming agent of this invention are equivalent machine load in the same bubble injection condition compared with Comparative Examples 1-3 which used the conventional foaming agent. The situation was revealed, and it was found that the excavation performance was not inferior.

Example 3
The natural defoaming property of the foam of the cellular soil produced in Examples 1 and 2 was examined.
That is, the excavated cellular soil was carried out onto a shaft, sampled by a certain amount, measured for mass and moisture content, and then the air porosity va was obtained by the following formula.

The approximate value of the air porosity Va (%) can be obtained by the following equation when the water density ρw is 1.0.
va (%) = 100−ρd × (100 / ρs + w)
In the above formula, ρs represents the density (g / cm ³ ) of the soil particles, ρd represents the dry density (g / cm ³ ) measured on site, and w represents the moisture content (%).

  The results are shown in Table 2. The air porosity va was measured after the lapse of 0.5 hours, 1.5 hours, 2.5 hours, and 3.5 hours.

Comparative Example 4
In the same manner as in Example 3, the natural defoaming property of the foamed soil bubbles produced in Comparative Examples 1 and 2 was examined. The results are shown in Table 2.

Comparative Example 5
In the same manner as in Example 3, the natural defoaming properties of the foamed soil bubbles produced in Comparative Example 3 were examined. The results are shown in Table 2. In Comparative Example 5, an antifoaming agent (FT-01 manufactured by Keihin Soil Co., Ltd., main component name = dimethylpolysiloxane) was added to 12 m ³ of cellular soil immediately after 261 ring excavation, and 1.0 volume% ( 21 liters) and the antifoaming property was examined.

FIG. 1 is a graph in which the air porosity va of each example in Table 2 is plotted for each elapsed time after excavation.
From the results shown in Table 2 and FIG.
(1) The air porosity va of Example 3 using the foaming agent of the present invention is 20.8% when 0.5 hour has passed after excavation, but after 3.5 hours has passed, it is 8.5. % (Down about 12%).
(2) On the other hand, the air porosity va of Comparative Example 4 is 24.6% when 0.5 hour has passed after excavation, and it is only reduced to 21.2% even after 3.5 hours. (Down about 3%).
(3) Although an antifoaming agent is added to the cellular soil of Comparative Example 5, the air porosity va is 15.9% when 0.5 hour has elapsed after excavation, and after 3.5 hours have elapsed. Is 10.9%, which is inferior to the natural antifoaming property of the foaming agent of the present invention.

Example 4
Anionic Surfactant Concentration and Sea Surface Reclamation As people's interest in the global environment increases, monitoring and regulation of chemical substances is becoming stricter. Under such circumstances, large-scale construction in urban areas requires the use of excavated soil for sea surface reclamation. There is a case where the excavated soil generated from a long-distance / large-section tunnel is buried in the sea surface even with the bubble shield method, and there is concern about the influence of the foaming agent alpha-olefin sulfonate on aquatic organisms. Until the agent concentration satisfies the acceptance standard value, measures are taken to temporarily place excavated soil and reduce the anionic surfactant concentration by biodegradation by microorganisms.

Acceptance standard value of anionic surfactant concentration As one example, there is the following acceptance standard value of anionic surfactant concentration.
The foaming agent of the bubble shield method is a conventional special foaming agent (component: alpha olefin sulfonate).
Acceptance reference value = (acute toxicity reference value LC ₅₀ of the special foaming agent) × (bubble mixing ratio) × (special foaming agent stock concentration) × (safety factor)
・ 96 hours and half lethal concentration LC _{50 of} special foaming agent: 6,600ppm
・ Bubble mixing ratio: 35%
・ Special foaming agent concentration: 3%
-Safety factor: 0.01
From the above formula, the acceptance standard value is 0.693 mg / liter.

Preparation of foaming material As the alpha olefin sulfonate, the product name “Lipolan LB-440” manufactured by Lion Co., Ltd. used in Example 1 was used, and the product name “PEG” manufactured by NOF Corporation was used as polyethylene glycol. # 300 "was used.
The alpha olefin sulfonate was dissolved in water to prepare an aqueous solution. The concentration of alpha olefin sulfonate in the aqueous solution was 0.147 w / v% . The foamed material was prepared by adding 1.5 times the volume of the polyethylene glycol to the aqueous solution. This foaming material was foamed at a foaming ratio of 8 times, and mixed so that the bubbles would be 35% by volume of the simulated soil to obtain a specimen.

Anionic Surfactant Concentration Test The anionic surfactant concentration test of the specimen was performed by methylene blue absorptiometry (JIS K0102 30.1.1).
This measurement method uses methylene blue, which is a cationic dye, by utilizing the property that an anionic surfactant forms an ion aggregate with a cationic dye and is extracted into an organic solvent such as chloroform. The amount is extracted and quantified.

Test content 10 liters of test sample was dropped into 10 liters of seawater, 250 ml of the supernatant eluted every predetermined time was collected, and the anionic surfactant concentration was measured every elution time. In addition, as a specimen before dropping into seawater, various specimens temporarily placed at various times as shown in Table 3 below were used.

The test results are shown in Table 3.
The anionic surfactant concentration at a temporary storage time of 0 days and an elution time of 0 days is 0.48 mg / liter. This is below the acceptance standard value, and it was found that sea surface landfilling is possible without temporary placement of excavated soil.

  The foaming agent for the bubble shield method of the present invention can reduce the amount of alpha olefin sulfonate used without reducing the foaming ability, can solve the problem of fish toxicity, and fills excavated soil. It can be reused as soil or dumped in the sea. In addition, since it has excellent natural antifoaming properties, it becomes easy to load and transport cellular soil, eliminate problems caused by foaming from cellular soil, and solve problems and costs associated with defoaming agents. can do. Since the foaming agent of the present invention has been confirmed to have excellent biodegradability due to microorganisms contained in standard activated sludge, it can be used without any environmental problems.

Claims (2)

At least, a bubble shield method for foaming agent you containing an alpha-olefin sulfonate and polyethylene glycol,
The foaming agent for the bubble shield method is prepared by dissolving the alpha olefin sulfonate in water to form an aqueous solution of 0.025 to 1.0 w / v%, and 0.01 to 5 times the volume of the polyethylene glycol in the aqueous solution. It is prepared by blending at a ratio of
The foaming agent for a bubble shield method, wherein the polyethylene glycol has a weight average molecular weight of 100 to 600. A bubble shield method having a step of excavating the ground using the foaming agent for the bubble shield method according to claim 1 .

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