JP6050989B2 - Low toxic foam material used for bubble shield method and bubble shield method - Google Patents

Description

  The present invention relates to a foam material used in a bubble shield method, and relates to a low-toxic foam material capable of stably generating bubbles. The present invention also relates to a bubble shield method using a low-toxic bubble material.

  In the bubble shield method, which is a type of shield method, digging is performed while injecting fine bubbles in the shape of shaving cream into the face or chamber. In this construction method, the fluidity of the excavated soil is enhanced by the bearing effect due to the bubbles, and adhesion of the excavated soil in the chamber can also be prevented. Moreover, since the water | moisture content which exists in the clearance gap between soil particles is substituted by the bubble, the water stoppage of excavated soil is also raised. By these, smooth excavation can be performed while maintaining the stability of the face.

  Here, the excavated soil in a state where the bubbles are mixed is in a muddy state with high fluidity. Since it may be difficult to carry as it is, the defoaming material is mixed as necessary to eliminate the bubbles actively and make it suitable for transportation (for example, patent document). 1).

  In this bubble shield method, the excavated soil after defoaming may be reused for landfill. For this reason, it is required that the excavated soil after defoaming is suppressed in toxicity to such an extent that it does not cause trouble at the reuse destination. For example, the toxicity is required to be suppressed to such an extent that it does not affect fish that inhabit the landfill.

  In this regard, Non-Patent Document 1 describes that by temporarily placing excavated soil in the atmosphere for 3 days, the foam material (surfactant) used for excavation is naturally decomposed by bacteria, reducing the environmental impact of landfills. It states that it can be done. In addition, the present applicant has proposed that the activated carbon is mixed with the excavated soil so that the bubble material is adsorbed on the activated carbon and the influence on the fish is reduced.

JP 2006-348727 A

"Nikkei Construction" June 13, 2011 issue, Nikkei BP, P61

  It is considered that the toxicity of the excavated soil can be sufficiently reduced by temporarily placing the excavated soil described in Non-Patent Document 1 and mixing the activated carbon proposed by the present applicant. Is desired to be sufficiently low.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bubble material for a bubble shield method capable of stably generating bubbles while keeping toxicity low, and a drilling soil. An object of the present invention is to provide a bubble shield method that can keep toxicity low.

  In order to achieve the above object, the present invention is a foam material used in a bubble shield method, characterized in that it contains an alpha sulfo fatty acid methyl ester salt having a fatty acid residue having 12 or less carbon atoms.

  The present invention also relates to a bubble shield method for improving fluidity of excavated soil by mixing fine bubbles obtained by foaming of a foam material, wherein the foam material is carbon of fatty acid residues. The foaming agent is composed of an alpha sulfo fatty acid methyl ester salt having a number of 12 or less, and the foaming agent contains another foaming agent of a different type.

  In these inventions, the carbon number is preferably 8 to 12, and more preferably 12 or 10. Furthermore, the methyl ester salt is preferably a sodium salt.

  ADVANTAGE OF THE INVENTION According to this invention, the bubble material for the bubble shield construction method which can produce a bubble stably, restraining toxicity low can be provided. In addition, the toxicity of excavated soil discharged by the bubble shield method can be kept low.

(A) is sectional drawing of a shield machine. (B) is a figure explaining the composition of a bubble material. It is a figure explaining the observation result of bubble mixed soil. It is a figure explaining the result of a fish toxicity test, (a) shows a half-lethal concentration (LC50) in a raw material conversion value, (b) shows a half-lethal concentration in a product conversion value, respectively. It is a figure explaining the result of a persistence test. It is a figure explaining the result of a mini slump test.

  Hereinafter, embodiments of the present invention will be described. First, the outline of the shield machine used for the bubble shield method and the outline of the bubble material will be described.

  As shown in FIG. 1 (a), a shield machine 1 used in this construction method includes a skin plate 2, a partition wall 3, a cutter 4, a cutter motor 5, a bubble injection tube 6, a screw conveyor 7, a soil conveyor. A pressure sensor 8 is provided.

  The skin plate 2 is a steel tubular member that becomes the outer shell of the shield machine 1. The partition wall 3 is provided on the skin plate 2, and defines a chamber 9 in the front portion of the skin plate 2. The cutter 4 is a part that excavates the ground by rotation, and is disposed in front of the skin plate 2. The cutter motor 5 is a drive source for rotating the cutter 4 and is provided on the rear side of the partition wall 3. The driving force of the cutter motor 5 is transmitted to the cutter 4 through the support arm 10.

  The bubble injection tube 6 is a member that guides a fine bubble in the shape of a shaving cream obtained by foaming a foam material with a foaming device (not shown). Since the tip of the bubble injection tube 6 is located in front of the cutter 4, the guided fine bubbles are injected toward the face. The excavated soil excavated by the cutter 4 is mixed with bubbles by the rotation of the cutter 4 so that the fluidity is improved and flows into the chamber 9. And in the chamber 9, adhesion of excavation soil to a wall surface is suppressed by presence of a bubble. Moreover, since air bubbles enter between the soil particles, the water stoppage is also improved.

  The screw conveyor 7 is a member that discharges excavated soil flowing into the chamber 9 to the rear side. The earth pressure sensor 8 is a member that measures the pressure of the excavated earth flowing into the chamber 9. The propulsive force of the shield machine 1 and the amount of excavated soil discharged by the screw conveyor 7 are adjusted according to the pressure of the excavated soil measured by the earth pressure sensor 8.

  As shown in FIG. 1B, for example, the foam material that is the basis of the fine bubbles contains a foaming agent as a main component. And a bubble additive and a quality change prevention agent are added as needed.

  The foaming agent is a component that is a basis of bubbles, and a surfactant is used. This embodiment is characterized in that a sulfo fatty acid methyl ester salt is used as the foaming agent. This foaming agent will be described later.

  The bubble additive is a component that stabilizes and strengthens the bubbles. As the foam additive, a cellulose-based water-soluble polymer obtained using pulp as a main raw material, a natural vegetable organic polymer as a gelling agent, or the like is used. The anti-altering agent is a component for enhancing the preservability of the foam material, and an organic nitrogen compound or the like is used.

  Hereinafter, the foaming agent will be described in detail. The foaming agent is a main component that affects the properties of the generated bubbles, and occupies most of the foam material. This foaming agent is required to have a property of easily generating fine fine bubbles and a property of maintaining the generated bubbles for a certain period. In consideration of processing and reuse of excavated soil, it is desirable that the toxicity of the foam material be as low as possible.

  In this embodiment, the foaming agent was selected in consideration of these matters, and the knowledge that alpha sulfo fatty acid methyl ester salt was suitable was obtained. Alpha sulfo fatty acid methyl ester salt is a kind of anionic surfactant and is a long-chain alkyl carboxylic acid ester salt having a sulfo group at the α-position. This alpha sulfo fatty acid methyl ester salt is produced, for example, by sulfonated fatty acid methyl ester and neutralizing the resulting alpha sulfo fatty acid methyl ester with an aqueous solution of an alkali metal hydroxide (for example, sodium hydroxide). . Indication formula is shown below.

In addition, R in said formula (I) represents a linear alkyl group, and carbon number is 10 or less. The fatty acid residue in the present invention represents the total carbon number of R, —CH (—SO ₃ M) —, and —COO— of the ester in the formula (I).

  For the sulfonation mechanism of fatty acid methyl esters, see Smith and Stirton: JAOCS vol.44, P.405 (1967) and Schmid, Baumann, Stein, Dolhaine: Proceeding of the World Surfactants Congress Munchen, vol. 105, Gelnhausen, Kurle (1984) and H. Yoshimura: Oil Chemistry (JJOCS), 41, 10 (1992).

  In the present embodiment, based on the above findings, an observation test of a bubble-mixed soil, a fish toxicity test and a survivability test of a foaming agent were performed. And it discovered that the alpha sulfo fatty acid methyl ester salt whose carbon number of a fatty acid residue is 12 or less (that is, R represents a linear alkyl group in said formula (I), and carbon number is 10 or less) is more suitable. It was. Hereinafter, each test will be described.

  First, the observation test of the bubble mixed soil will be described. In this observation test, an air bubble mixed soil was prepared by mixing a foaming agent foamed by a mixer with a sample soil collected from Dotan. After stirring until the bubbles were spread over the whole, this bubble mixed soil was spread on a vat and the state was observed. The observation was performed three times in total, immediately after expanding the bubble-mixed soil into the bat, 10 minutes after the expansion into the bat, and 30 minutes later.

  In addition, the foaming agent includes sodium alpha olefin sulfonate (AOS), which is a typical anionic surfactant, and sodium salt of alpha sulfo fatty acid methyl ester (C12MES-Na) having 12 carbon atoms in the fatty acid residue. The sodium salt of alpha sulfo fatty acid methyl ester having 10 carbon atoms (C10MES-Na) was used. The formula for each drug is shown below.

  Each drug was used in the form of a solution obtained by diluting a powdered product with water to a predetermined concentration in advance. As shown in FIG. 2, regarding the concentration of each drug, AOS was 0.45%, C12MES-Na was 0.90% and 0.60%, and C10MES-Na was 0.95%. Then, assuming that 30% of 8 times foamed bubbles were added to the ground, the amount of each drug added was determined. Specifically, each chemical | medical agent was added so that it might become 10.1 ml of bubbles (10.1g with a powder) with respect to 500g of Dotan. Hereinafter, the test results will be described.

  Regarding the foaming of each drug, it was confirmed that good fine bubbles with fine texture were obtained for AOS, C12MES-Na (0.90%), and C10MES-Na. On the other hand, for C12 MES-Na (0.60%), although the foaming itself was good, it was confirmed that the whole had a tendency of excessive moisture (becomes watery). From this, it can be said that C12MES-Na and C10MES-Na can produce fine bubbles of the same level as AOS by adjusting the concentration to about twice that of AOS. Moreover, although there exists a tendency of excess water, it can be said that foamability is favorable also about C12 MES-Na (0.60%).

  Regarding the persistence of bubbles, immediately after expanding the bubble mixed soil into the bat, in the bubble mixed soil using AOS, C12MES-Na (0.90%), and C12MES-Na (0.60%), A sufficient amount of air bubbles remained in the soil. Here, in the bubble mixed soil using C12MES-Na having different concentrations, all of the bubbles remained as compared with the bubble mixed soil using AOS. On the other hand, it was confirmed that in the bubble mixed soil using C10MES-Na, the bubbles easily disappear compared to other bubble mixed soil.

  It was confirmed that air bubbles remained on the soil surface and inside the soil in the air-mixed soil using AOS in a state of standing for 10 minutes. In the bubble mixed soil using C12MES-Na (0.90%), it was confirmed that a small amount of bubbles remained on the soil surface and a sufficient amount of bubbles remained inside the soil. In the bubble mixed soil using C12MES-Na (0.60%), it was confirmed that bubbles in the soil remained, although bubbles on the soil surface disappeared. In the bubble mixed soil using C10MES-Na, it was confirmed that bubbles did not remain on the soil surface but bubbles in the soil remained.

  In the state of standing for 30 minutes, in the bubble mixed soil using AOS, it was confirmed that bubbles on the soil surface disappeared but bubbles in the soil remained. In the cell-mixed soil using C12MES-Na (0.90%), it was confirmed that no bubbles remained on the soil surface, but some bubbles remained inside the soil. In the bubble mixed soil using C12MES-Na (0.60%), it was confirmed that bubbles in the soil remained as in the state after 10 minutes. In the bubble mixed soil using C10MES-Na, it was confirmed that bubbles in the soil remained as in the state after 10 minutes.

  Summarizing the above results, when C12MES-Na (0.90%) was used as the foaming agent, better properties, i.e., foaming properties, than when AOS was used during the period from stirring to 10 minutes later. It was confirmed that the air bubbles were good and the bubble persistence was also good. In addition, when about 30 minutes have passed since stirring, the amount of bubbles in the soil is less than when AOS is used, so that the foaming property after being discharged from the shield machine 1 is better than when AOS is used. It was confirmed that. For this reason, it is thought that it can fully be used as a substitute for AOS.

  When C12MES-Na (0.60%) was used as the foaming agent, it was confirmed that the initial foamability was better than when AOS was used. Moreover, although the persistence of the bubble in a stationary state is somewhat inferior to AOS, it is thought that there is no trouble in use. For this reason, it is considered that it can be used as a substitute for AOS.

  When C10MES-Na was used as the foaming agent, it was confirmed that the foamability and the persistence of the bubbles were lower than when AOS was used. However, since the difference from AOS is not so large, it is considered that it can be used as a foaming agent in a natural mountain where soil particles are easily loosened.

  Next, the fish toxicity test of the foaming agent will be described. In this fish toxicity test, the half lethal concentration (LC50) for Java medaka (Oryzias javanicus) was determined. This Java medaka is a medaka that lives in brackish water from the Malay peninsula to Java and Borneo, and has been reported to be relatively sensitive to chemical substances and useful as a test fish for seawater. In this embodiment, a fish toxicity test was conducted using juvenile fish that were known to be highly sensitive to chemical substances and were around 2 weeks after hatching.

  The test method will be described. In this test, a solution obtained by diluting a powdery product of each drug with water in advance was used. Specifically, a mixture of AOS, C12MES-Na, C14MES-Na, and C16MES-Na was used. Here, C14MES-Na is a sodium salt of an alphasulfo fatty acid methyl ester having 14 carbon atoms in the fatty acid residue, and C16MES-Na is a sodium salt of the alpha sulfo fatty acid methyl ester having 16 carbon atoms. An illustrative formula of C14 and C16MES-Na is shown below.

  In addition, in the product of each chemical | medical agent, the content rate of an object component differs. For example, as shown in FIG. 3, the AOS content in the AOS product is 75.6%, the MES content in the C12-MES product is 81.4%, and the MES content in the C14, C16-MES product is 98.2%. is there. In the fish toxicity test, it is necessary to make the amount of the target component uniform, so the amount of powder to be dissolved was determined in consideration of the content of the target component when diluting.

  In this fish toxicity test, 100 mL of a test solution having a predetermined concentration was prepared and maintained at 26 ° C. in an incubator. The test solution is obtained by dissolving an amount of a drug corresponding to the concentration in artificial seawater. From the viewpoint of obtaining a half lethal concentration (LC50), a plurality of types of test solutions from low concentration to high concentration were adjusted for each drug.

  Then, 10 juvenile Java medaka fish were introduced into the test solution, and an exposure test was conducted for up to 96 hours under 14 hours light conditions and 10 hours dark conditions. During the test period, the water was replaced with freshly prepared test water every day. The water quality of the test water was pH 7.9-8.4, the dissolved oxygen concentration was 5.4 mg / L or more, and the salt content was around 3.3%.

  The results of the fish toxicity test are shown in FIG. In obtaining this test result (LC50 for Java medaka), an analysis program (Ecotox-Statics, Society of Environmental Toxicology) was used, and the probit method was used based on the set concentration of each drug.

  In addition, since the content rate of an object component differs in the product of each chemical | medical agent, the comparison result (raw material conversion) at the time of arranging the density | concentration of an active ingredient is shown to Fig.3 (a). Further, from the viewpoint of comparison as a product, the comparison result (product conversion) of the product standard is shown in FIG. Furthermore, since the effect becomes clear, the LC50 of AOS, which is a typical foaming agent, was set to the value “1”, and the LC50 of other drugs was expressed as a ratio to the LC50 of AOS. If the LC50 of AOS has a concentration of “100” and the LC50 of C12MES-Na has a concentration of “1000”, the ratio is “0.1”. That is, the smaller the ratio value, the lower the fish toxicity.

  When C12MES-Na was used, the ratio was 0.0167 (48 h) and the ratio was 0.0199 (96 h) in terms of the active ingredient in FIG. From this result, it can be said that the fish toxicity of C12MES-Na is about 1/60 to 1/50 of the fish toxicity of AOS. In the product conversion of FIG. 3 (b), the ratio was 0.0179 (48h) and the ratio was 0.0213 (96h), so it was confirmed that the fish toxicity was sufficiently low even at the product level.

  On the other hand, when C14 and C16 MES-Na are used, the ratio is 2.1 (48h) and the ratio is 2.5 (96h) in terms of the original substance, and the ratio is 2.75 (48h) and the ratio is 3.29 (in terms of product). 96h). From this result, it was confirmed that the fish toxicity of C14, C16 MES-Na is equivalent to AOS.

  It is known that fish toxicity affects the gills of fish, and it is said that as the carbon number increases, the adverse effect is considered to decrease. Therefore, even when C10MES-Na is used, the fish toxicity is considered to be sufficiently low as in the case of using C12MES-Na.

  Next, the persistence test will be described. In this survivability test, the residual ratio of the foaming agent introduced into seawater or river water is measured over time. As shown in FIG. 4, in this embodiment, two types of tests, C12MES-Na, which obtained good results in the previous two tests, and AOS, which is a typical foaming agent, were tested. And as a solution, two types of seawater and river water were prepared, and the test was performed by adjusting the drug concentration to 5 mg / L and 50 mg / L for each.

  AOS is known as a biodegradable drug among surfactants. In support of this, in this persistence test, it was confirmed that the residual rate was lowered relatively early. For example, in seawater with a concentration of 50 mg / L, the residual rate became less than half after 3 hours and decreased to about 10% after 6 days. Similar results were obtained with river water at a concentration of 50 mg / L. Even at a concentration of 5 mg / L, the residual rate of both seawater and rivers decreased to about 10% after 3 days.

  On the other hand, although C12MES-Na did not reach AOS, it showed an appropriate decomposability. For example, in the river water test, 80% to 90% of the concentration of 50 mg / L and 5 mg / L remained in the liquid at the passage of 1 day, but the remaining rate at a concentration of 50 mg / L after 3 days. Was 15%, and the residual ratio was reduced to 35% at a concentration of 5 mg / L. Further, after 6 days, the residual ratio decreased to 1 to 2% for both the concentrations of 50 mg / L and 5 mg / L.

  As for seawater, 80% to 90% of both 50 mg / L and 5 mg / L remained in the liquid after 3 days. Thereafter, for a concentration of 50 mg / L, the residual rate decreased to 66% after 6 days and to 20% after 14 days. Furthermore, it decreased to 2% after 28 days. For a concentration of 50 mg / L, the residual rate dropped to 38% after 6 days and to 1% after 14 days.

  From this persistence test, it was confirmed that C12MES-Na requires more time for biodegradation than AOS, particularly in seawater. However, since the residual rate after 14 days in C12MES-Na is 20% at a concentration of 50 mg / L, and the fish toxicity of C12MES-Na is extremely low compared to AOS, there is no practical problem. it is conceivable that.

  The following was confirmed by each test described above.

  Regarding toxicity to fish inhabiting seawater, it was confirmed that the toxicity of MES-Na having a fatty acid residue of 12 or less carbon atoms was extremely low compared to the toxicity of AOS. Regarding foaming properties (foaming properties), it was confirmed that C12 and C10MES-Na were not inferior to AOS. Regarding the persistence of the generated bubbles, it was confirmed that C12MES-Na was not inferior to AOS. Moreover, although C10MES-Na is inferior to AOS, it has been confirmed that it is suitably used if it is a natural mountain where the soil particles are easily loosened.

  Therefore, if C12MES-Na or C10MES-Na is used as the main component (bubble agent) of the bubble material for the bubble shield method, it can be said that bubbles can be generated stably while keeping toxicity low.

  The above description of the embodiment is for facilitating the understanding of the present invention, and does not limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof. For example, you may comprise as follows.

  In the above-described embodiment, C12MES-Na and C10MES-Na were tested as alpha sulfo fatty acid methyl ester salts of fatty acid residues having 12 or less carbon atoms, but are not limited to these drugs. For example, regarding the portion of the methyl ester salt, even if it is another type of alkali metal salt such as potassium, it is considered that the main portion for functioning as a foaming agent is common, and thus the same effect is obtained.

  Further, regarding the foaming agent, even if the agent has fewer carbon atoms in the fatty acid residue than C10MES-Na, fine bubbles are obtained by stirring and fine bubbles are obtained. As long as it remains for the same amount of time, it can be suitably used. For example, alpha sulfo fatty acid methyl ester salt (C8MES) having 8 carbon atoms in the fatty acid residue can be suitably used.

  The foaming agent used in the present invention is not particularly limited as long as it contains an alpha sulfo fatty acid methyl ester salt (MES) having a fatty acid residue having 12 or less carbon atoms. And from a viewpoint of ensuring handling property, the content ratio of the MES to the total amount of the foaming agent to be used is preferably 1 to 100% by mass, more preferably 20 to 100% by mass, and further preferably 30 to 90% by mass. .

  The MES used in the present invention is preferably a single compound, but may be a mixture as long as the fatty acid residue contains MES having 12 or less carbon atoms. When using a mixture, the MES having 10 to 12 carbon atoms in the fatty acid residue is 10 to 100% by mass, the MES having 14 carbon atoms in the fatty acid residue is 0 to 90% by mass, and the MES having 16 carbon atoms is 0. It is preferable to contain in the range of -10 mass% since favorable fish toxicity can be ensured.

  The foaming agent used in the present invention is a known surfactant having a different type (corresponding to other foaming agent), for example, alkyl sulfate (AS), polyoxyethylene alkyl sulfate ( AES), alpha olefin sulfonate (AOS), and polyoxyethylene alkyl ether (AE) can be used in combination. When other foaming agents are used in combination, when the total amount of MES and the other foaming agent is 100% by mass, it is preferable that MES is 10 to 90% by mass because good fish toxicity can be secured. .

  By the way, when plural types of foaming agents are mixed and used, there is a finding that the fluidity of excavated soil is impaired depending on the combination. Therefore, a mini-slump test with multiple types of foaming agents was performed. In this mini slump test, C12MES-Na was used as the foaming agent according to the present invention, and AOS, AES, and AS were used as the other foaming agents. And bubble mixed soil was produced using these foaming agents.

  First, a test sample will be described. As shown in FIG. 5, the first sample was prepared using an AOS solution having a concentration of 0.45% as a foaming agent. The second sample was prepared using an AES solution having a concentration of 0.45% as a foaming agent, and the third sample was prepared using an AS solution having a concentration of 0.45% as a foaming agent. The fourth sample was made using a C12MES-Na solution with a concentration of 0.90% as a foaming agent, and the fifth sample was made using a C12MES-Na solution with a concentration of 0.60% as a foaming agent. Is. The foaming agent used in the sixth sample is a solution containing AOS having a concentration of 0.225% and C12MES-Na having a concentration of 0.45%. The foaming agent used in the seventh sample is a solution containing 0.225% AES and 0.45% C12MES-Na. The foaming agent used in the eighth sample is a solution containing AS having a concentration of 0.225% and C12MES-Na having a concentration of 0.45%.

  Each sample was produced in the same procedure as the observation test of the bubble mixed soil described above. That is, each foaming agent of the said density | concentration was foamed with the mixer, was mixed with the mountain sand as sample soil, and was stirred until the bubble spreads to the whole. The amount of each drug to be added was determined on the assumption that 30% of 8 times foamed bubbles were added to the ground. Specifically, each chemical | medical agent was added in the ratio from which a foaming agent will be 20.3g with respect to 1 kg of mountain sand.

  A mini slump test was performed on each of the prepared samples. In this mini slump test, a mini slump cone (top inner diameter 50 ± 0.5 mm, lower end inner diameter 100 ± 0.5 mm, height 150 ± 0.5 mm) defined in JIS A 1171 was used. The procedure was performed in accordance with the slump test specified in JIS A 1101. Briefly, the sample is divided into approximately equal three layers and packed into mini slump cones. Each layer pokes uniformly after a leveling stick. Then, the top surface of the sample packed in the mini slump cone is leveled with the top end of the cone, and the mini slump cone is gently pulled up vertically. Then, the drop is measured in units of 0.5 cm at the center of the sample, and this is used as a slump. In the mini-slump test, the bubble mixed soil was also observed. In this observation, the bubble-mixed soil after the completion of the stirring was spread on a bat to observe the state. Hereinafter, the test results will be described.

  Regarding the mini-slump test, a sample having a slump value of 2.5 cm to 10.0 cm and bubbles remaining in the whole and having a feeling of grouping was regarded as acceptable. This is because if this condition is satisfied, the necessary fluidity can be obtained for the excavated soil. And four samples other than the 3rd sample containing AS among the 1st-5th samples which contain a foaming agent alone satisfied this standard.

  That is, regarding the slump value of each sample, the first sample (AOS) is 6.5 cm, the second sample (AOS) is 4.5 cm, the fourth sample (C12MES-Na, 0.90%) is 3.0 cm, Five samples (C12MES-Na, 0.60%) were 2.5 cm. On the other hand, the third sample (AS) was 0.5 cm.

  The sixth to eighth samples in which C12MES-Na and other foaming agents were mixed all met the above criteria. That is, regarding the slump value of each sample, the sixth sample (AOS + C12MES-Na) was 4.5 cm, the seventh sample (AES + C12MES-Na) was 2.5 cm, and the eighth sample (AS + C12MES-Na) was 4.5 cm. .

  Moreover, in the seven samples excluding the third sample, the entire bubble mixed soil was whitish, and it was confirmed that the bubbles were mixed in the entire bubble mixed soil. On the other hand, in the third sample, it was confirmed that the remaining amount of bubbles was small.

  From these results, it was confirmed that the fluidity of C12MES-Na was not impaired even when used in combination with other foaming agents. In particular, in combination with AS, it was confirmed that there was a remarkable effect. That is, in the third sample of AS alone, the slump value was 0.5 cm and failed, but in the eighth sample in which C12MES-Na and AS were used in combination, the slump value was 4.5 cm and was within the acceptable range. The slump value could be increased.

DESCRIPTION OF SYMBOLS 1 ... Shield machine, 2 ... Skin plate, 3 ... Bulkhead, 4 ... Cutter, 5 ... Cutter motor, 6 ... Bubble injection pipe, 7 ... Screw conveyor, 8 ... Earth pressure sensor, 9 ... Chamber, 10 ... Support arm

Claims (4)

A bubble material used in the bubble shield method,
A foam material for a bubble shield method comprising an alpha sulfo fatty acid methyl ester salt having a fatty acid residue having 12 or less carbon atoms.   The foam material for a bubble shield method according to claim 1, wherein the fatty acid residue has 12 or 10 carbon atoms.   The bubble material for a bubble shield method according to claim 1 or 2, wherein the methyl ester salt is a sodium salt. It is a bubble shield construction method that improves the fluidity of excavated soil by mixing fine bubbles obtained by foaming of foam material,
The cellular material is
A foam shielding method comprising a foaming agent comprising an alphasulfo fatty acid methyl ester salt having a fatty acid residue having 12 or less carbon atoms and another foaming agent different from the foaming agent.