JP2018150810A - Foam shield method and foaming material aqueous solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam shield method capable of bearing a high water pressure by improving a cut-off performance as foam mixed soil with a low water permeability coefficient can be formed and the unsaturated state of the foam mixed soil is kept for an extended period as long as possible.SOLUTION: A foam shield method is to form foam mixed soil by injecting foam into sediment at a working face and sediment within a chamber of a shield machine through generating foam at an expansion ratio between 10 times and 50 times with a foaming material aqueous solution produced by further mixing an anion surface active agent into a hydrophobic film agent solubilized with a water soluble solvent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a bubble shield method and a foaming material aqueous solution.

  The bubble shield method, which excavates while injecting bubbles created by special bubble material into the face or chamber, is known as an earth pressure shield method that can be applied to a wide range of layers from gravel soil layers to viscous soil layers.

According to Non-Patent Document 1, there is the following description as a feature of the bubble shield method.
(1) The fine shaving cream-like air bubbles improve the fluidity and water blocking properties of the excavated soil and prevent the excavated soil from adhering in the chamber. Among them, the construction principle regarding water-stopping is that the groundwater present in the soil particle gap is replaced with fine bubbles, so that the water-stopping of the excavated soil is improved and sandy groundwater level is high The excavation of the ground becomes easy and eruption from the screw conveyor can be prevented.
(2) Since the injected bubbles eliminate the free water in the gap and the bubbles fill the gap, the water permeability of the foam soil is very low, and the water stoppage at the screw conveyor discharge port is very good. .

  However, when the stability of bubbles is low or when bubbles are dissolved in groundwater, the unsaturation in the chamber is lost and fluidity and water stoppage are poor, resulting in frequent jets from the screw conveyor. It has been known. Therefore, conventionally, auxiliary work such as additionally injecting bubbles when the water stoppage is lowered or supplementing the water stoppage by using an ejection preventing agent in the screw conveyor is necessary.

  As a conventional technique for improving a foaming material, there is a method of reinforcing a bubble film with a water-soluble polymer or the like. For example, according to Non-Patent Document 1, a B-type formulation (cellulosic water-soluble polymer, “OK-2” added) or a C-type formulation (natural plant organic polymer, “OK- 3 ”is a standard formulation for soils with a large amount of coarse particles such as sand and gravel. However, this formula is similar to the mud pressure calculation of the amount of the added mud material and is based on the correction calculation of the soil particle composition. The main purpose is to improve soil removal without mixing and losing fluidity. In addition, since these foaming types are strong in foam, they do not penetrate narrow gaps, and the bubbles have a low foaming ratio (less than 6 times). Economically unsuitable.

  In addition, the water-stop mechanism of the prior art is based on the simple principle of eliminating free water in the gap with bubbles (that is, exchanging air and water). It becomes an important factor. Nevertheless, in the prior art aimed at improving the water-stopping property, for example, Patent Document 1 discloses a technique for making a mixture of a water-soluble polymer and a highly water-absorbent resin into bubbles, and Patent Document 2 discloses a water-soluble high Although molecular and gelling agent technologies are disclosed, these are foams with a lower magnification than the B type and the like. Here, “low magnification” means that the density of bubbles is large and the amount of water in the bubbles is large. Although it is possible to apply a thickener such as a water-soluble polymer, it is unsuitable for the water-blocking requirement of the bubble shield for which it is desired to increase the degree of unsaturation.

  Therefore, among the bubble stabilization techniques, although the effect of stabilizing the bubbles is much smaller than that of the above strong liquid film made of a water-soluble polymer, Non-Patent Document 2 describes stabilization with a low-molecular compound such as a higher alcohol. Techniques to do this are disclosed. This is a technique in which an ordered adsorbing layer is formed and stabilized by coordinating higher alcohol or the like on the surface of the bubble liquid film and reducing the ionic repulsion of the anionic surfactant on the bubble liquid film.

  As an application to the bubble shield method, Patent Document 3 discloses a technique that stabilizes foam with a higher alcohol and does not decrease fluidity. However, from the examples, the foam density is 0.16 (6.25 times in terms of foaming ratio), and since it is a low-magnification foaming, in fact, as mentioned above, it is necessary to increase the degree of unsaturation of the water shield of the foam shield. It is hard to say that it is effective for the demands of Moreover, in patent document 3, there is no description of the technical use and the effect for water-stop purposes.

  Thus, stabilizing the bubbles and suppressing the decrease in fluidity is the purpose of the prior art including Patent Document 1, but there is still an effective measure for water stoppage, which is the most important issue of the bubble shield method. Not found.

  In addition, for example, in order to widely apply a large-section bubble shield method on the ground of a so-called “large depth” that is 40 m or deep underground, a technique for improving the water stoppage by desaturation by bubbles is extremely important. In addition, the bubble shield method, which is being frequently used for large-scale construction with a large depth and a large cross section, is required to deal with natural ground such as high water pressure aquifers and gravel layers. There is also a demand to use a foaming agent at a lower concentration in consideration of environmental impacts.

  Here, with reference to FIG. 2, the problem which the conventional bubble shield construction method has is demonstrated again. In FIG. 2, the shield machine 10 is in front of the cutter 2 on the front surface, the chamber 7 on the back surface of the cutter 2, the stirring blade 3 facing the chamber 7, the bubble inlet 4 on the back surface of the chamber 7 and the front surface of the cutter 2. A bubble discharge port 1, a screw conveyor 5 and a belt conveyor 6 on the back surface of the chamber 7, a discharge gate 9 interposed between the conveyors 5 and 6, a shield jack 8 and the like are provided.

  As shown in the figure, the groundwater level decreases from WL1 to WL2 (Y direction), and the face collapses due to drying, or the face in the front area A1 of the cutter 2 collapses due to running water. The decline is the main factor. When such a defective state occurs, the bubbles in the bubble mixed soil in the chamber 7 disappear, and as a result, air collects and accumulates in the upper part of the chamber 7 and the excavated soil that has lost its fluidity in the lower part is groundwater. It is deposited in a saturated state. Further, in some cases, ejection occurs from the screw conveyor 5. The main cause of this defective state is the lack of water resistance of the bubbles, but it can be said that there is a limit in functional design that leaves all the water-stopping in the chamber 7 to the simple air-water exchange action by bubble injection.

  As described above, the present inventors consider the boundary relationship between bubbles and water in the bubble mixed soil, and the bubble mixed soil forming technique capable of significantly lowering the water permeability than before, and the properties of the bubble liquid film In consideration of the infiltration of water into the foam mixed soil, a bubble mixed soil formation technology that can maintain the impervious state was devised, and this technology was applied to the bubble shield method.

Japanese Patent No. 312368 JP-A-2-16289 JP 2003-314191 A

Bubble Shield Method-Technical Document-August 2011 Shield Method Method Association Takehiko Fujimoto “Introduction to Polymeric Drugs” Sanyo Chemical Industries, 1992, p.581

  The present invention has been made in view of the above problems, and can form a bubble-mixed soil having a low water permeability coefficient, and can maintain the unsaturated state of the bubble-mixed soil as long as possible. An object of the present invention is to provide an air bubble shielding method and a foaming material aqueous solution which can improve water-stopping performance and can cope with high water pressure.

In order to achieve the above-mentioned object, the bubble shield method according to the present invention is a foaming material aqueous solution in which the hydrophobic film agent is completely solubilized with a water-soluble solvent and further mixed with an anionic surfactant. Bubbles are generated at a magnification of 50 times to generate bubbles, and the bubbles are injected into the sand and sand in the chamber of the shield machine to form a bubble mixed soil.
Another bubble shield method according to the present invention is a foaming material aqueous solution in which a hydrophobic film agent is solubilized with a water-soluble solvent and further mixed with an anionic surfactant at a foaming ratio of 10 to 50 times. Foaming is performed to generate bubbles in which the hydrophobic film agent is uniformly adsorbed and coordinated in the liquid film, and the bubbles are injected into the sand of the face and the sand in the chamber of the shield machine to form a bubble mixed soil. is there.

  The bubble shield method of the present invention is to foam a foaming material aqueous solution in which a hydrophobic film agent is solubilized with a water-soluble solvent and further mixed with an anionic surfactant at a high expansion ratio of 10 to 50 times. One characteristic is that the hydrophobic film agent is solubilized with a water-soluble solvent, and another characteristic is that it is foamed at a high magnification of 10 to 50 times. is there.

  The present inventors have obtained the knowledge that by using highly foamed bubbles having a foaming ratio of 10 to 50 times, it is possible to form a bubble mixed soil in an unsaturated state with low water permeability (high foaming technology). Here, “high foaming” means that foaming is performed in a range of foaming ratio of 10 to 50 times.

  In addition to the above-mentioned high foaming technology, the present inventors have further achieved a high water-stopping property that could not be obtained by the conventional technology without impairing the fluidity of the excavated soil by a technology that maintains the unsaturated state (water-impervious technology). The knowledge that it can be achieved is also obtained.

  This impervious technique is to inject a bubble having a hydrophobic film agent adsorbed therein to make the gap hydrophobic with the hydrophobic film agent. It is used as a technique for reducing the amount of water flowing into the bubble-mixed soil and maintaining the unsaturated state (that is, a technique for delaying the expansion of the water flow path).

  In the present invention, the hydrophobic film agent is an essential and useful component in both the high foaming technique and the impervious technique. In the prior art, it is used for stabilizing the liquid film by the mechanism of the adsorption film, but in the present invention, it is used as a functional material for imparting the hydrophobic property of the liquid film, particularly in the impervious technique.

  It is not clear by what principle the hydrophobic property of the bubbles adsorbed by the hydrophobic film agent acts as a resistance to water flow through the gap, but it is considered to be a specific phenomenon in the unsaturated state. It is known that the flow path of water is different between saturated and unsaturated states, and it is known that water flows through a narrow gap in the unsaturated state. If the gap is filled, it can be assumed that the water flow path is further narrowed and the capillary force acting on the unsaturated gap is weakened.

  The present invention is based on a combination of a plurality of elemental technologies of the above-mentioned high foaming technology and impervious technology, and by balancing the elements that make the bubble-mixed soil unsaturated and the elements that hold the unsaturated state, The water-stopping property can be greatly improved as compared with the prior art having a water-stopping mechanism based on an air-water exchange relationship between simple bubbles and free water.

  By foaming the foaming material aqueous solution at a high magnification and adding small bubbles with a density of 0.1 g / ml or less to the excavated soil, air-water exchange is facilitated and a highly unsaturated foam-mixed soil is formed. Can do. By maintaining this unsaturated state for a long time, it is possible to reduce the frequency of occurrence of ejection from the screw conveyor even in the case of stopping excavation for a short time.

  Here, in order to make the bubble density 0.1 g / ml or less, the foaming ratio may be adjusted to 10 times or more and injected. That is, the bubble density is 0.1 g / ml or less and the expansion ratio is 10 times or more.

  When the expansion ratio is small, the bubble liquid film becomes thick, and excess water is increased in the liquid film, so that bubbles are easily broken by the drainage phenomenon. Therefore, the lower limit of the expansion ratio is defined as 10 times.

  For example, by increasing the expansion ratio to 20 times, which is a range of 10 times or more, and making the liquid film thinner and generating smaller bubble diameters, stability is further increased, and the bubble density is 0.05 g / ml (corresponding to expansion ratio of 20 times) ), The degree of unsaturation due to air-water exchange is also increased, and the water stoppage is improved.

  For example, in the case of a natural ground with a large gap such as a gravel layer, it is possible to flow by adjusting the foaming ratio to 20 to 50 times by preparing a dilute solution with a foaming material aqueous solution concentration of 2 to 10% by mass. It is good to balance property and water-stopping property. On the other hand, in the case of a natural soil that needs to be prevented from sticking with a viscous soil layer, etc., a diluted solution in which the concentration of the foaming material aqueous solution is diluted to 0.5 to 5% by mass is prepared, and the foaming ratio is increased to 10 to 20 times. Adjust to balance fluidity and waterstop.

  In the bubble shield construction method of the present invention, an air bubble preparation device is required to counteract the soil and water pressure of the natural ground, which is the sum of the face soil pressure and water pressure acting on the front face of the face, and to act as an appropriate bubble earth pressure as a differential pressure. . With regard to this bubble production device, a large-sized compressor for producing a large amount of compressed air is required for large-section construction, but in practice, the expansion ratio is 50 times the limit of equipment. Therefore, the upper limit of the expansion ratio is defined as 50 times.

  When foaming the foaming material aqueous solution by a high foaming technique, it is preferable that the hydrophobic film agent is uniformly adsorbed and coordinated with the bubble liquid film to form a highly stabilized adsorption layer. In that case, since the hydrophobic film agent is insoluble or hardly soluble in water, it is preferably dissolved in a water-soluble solvent to form a mixed solution. A bubble liquid film composed solely of an anionic surfactant component is a hydrophilic liquid film in which water and surfactant molecules are coordinated. An adsorbed liquid film using a hydrophobic film agent is both hydrophilic and hydrophobic. It can be inferred that it has properties. Thus, in order to generate bubbles in which the hydrophobic film agent is uniformly adsorbed in the bubble liquid film, it is preferable to completely dissolve the hydrophobic film agent in the water-soluble solvent and then solubilize in the aqueous foaming material solution. Therefore, in the present invention, a configuration in which “the hydrophobic film agent is solubilized with a water-soluble solvent” is an essential configuration. In addition, for example, in Patent Document 3, there is no description or suggestion of such a configuration.

  In the embodiment of the bubble shield method according to the present invention, the hydrophobic film agent is a solid substance at room temperature, insoluble or hardly soluble in water, and soluble or easily soluble in a water-soluble solvent. is there.

  Hydrophobic membrane agent is a solid substance at room temperature, insoluble or hardly soluble in water, and soluble or easily soluble in water-soluble solvent, so that hydrophobic membrane agent after air-water exchange with pore free water is As the liquid film is thinned due to spontaneous drainage or volatilization of the water or water-soluble solvent in the liquid film, it recrystallizes and precipitates in a thin film. The amount of hydrophobic membrane agent soluble in the liquid membrane and the crystal form at the time of insolubilization are not clear, but the deposited thin film does not dissolve in water, so the hydrophobic membrane agent is left insolubilized in the bubble-mixed soil. It is obvious that the gap between the bubble mixed soils is made a hydrophobic atmosphere by utilizing the characteristics. In addition, normal temperature shall be 15-25 degreeC by the Japanese Pharmacopoeia general rule here.

  In order to achieve the above-mentioned object, the foaming material aqueous solution according to the present invention is a foaming material aqueous solution for generating bubbles used in the bubble shield method, comprising 30 to 40% by mass of an anionic surfactant, A foaming agent aqueous solution containing 1 to 15% by mass of a hydrophobic film agent and 20 to 40% by mass of a water-soluble solvent, wherein the hydrophobic film agent is completely solubilized with the water-soluble solvent.

The water-soluble solvent is, for example, carbitols.
The hydrophobic film agent is, for example, dodecyl alcohol. In this case, the water-soluble solvent is preferably butyl carbitol.

  As can be understood from the above description, according to the bubble shield method and the foaming material aqueous solution of the present invention, the foaming material obtained by solubilizing a hydrophobic film agent with a water-soluble solvent and further mixing an anionic surfactant. Air bubbles are generated by foaming the aqueous solution at a foaming ratio of 10 to 50 times, and the air permeability is calculated by injecting the bubbles into the sand of the face and the earth and sand in the chamber of the shield machine to form the bubble mixed soil. It is possible to form a low-foam mixed soil, and to maintain the unsaturated state of the foam-mixed soil for as long as possible, thereby improving the water-stopping property and supporting high water pressure conditions. It becomes possible.

It is the schematic diagram explaining the bubble shield construction method of this invention. It is the schematic diagram explaining the conventional bubble shield construction method.

Hereinafter, embodiments of the bubble shield method of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram illustrating the bubble shield method of the present invention. The shield machine 10 shown in the figure has substantially the same configuration as the shield machine used in the conventional bubble shield method shown in FIG. 2, but the bubbles applied here are different.

  Bubbles to be used are generated by foaming a foaming material aqueous solution in which a hydrophobic film agent is solubilized with a water-soluble solvent and further mixed with an anionic surfactant at a foaming ratio of 10 to 50 times. The bubbles generated in this manner are injected into the earth and sand in the face and the earth and sand in the chamber 7 of the shield machine 10 to form a bubble mixed soil.

  First, in the bubble mixed soil formed by injecting bubbles into the soil of the face, the water barrier property and water stoppage of the face front area (A2 in the figure) are improved.

On the other hand, the bubbles are injected into the earth and sand in the chamber 7 (A3 in the figure) to form a low-permeability bubble-mixed soil, and in the bubble-mixed soil in the chamber 7 as in the conventional method. The problem is that the bubbles disappear, the air gathers and accumulates in the upper part of the chamber 7, and the excavated soil that has lost its fluidity accumulates in a state saturated with ground water, and the screw conveyor 5 erupts. Cannot occur.
Next, each component of the foaming material aqueous solution will be described in detail.

(Concentration of foaming material)
There are various types of surfactants that have foaming power, but considering the environmental effects such as groundwater contamination during drilling of bubble shields, early degradability and water toxicity after drilling, the foaming material aqueous solution applied by the method of the present invention As the type of foaming material used as the component, an anionic surfactant is preferable. Anionic surfactants can be selected from substances with excellent foaming power widely used as bases for synthetic detergents and shampoos. For example, alpha olefin sulfonate (abbreviation AOS), alkyl sulfate ester salt (AS) And anionic surfactants of various salts such as alkyl ether sulfate ester salt (AES), and one kind or a mixture of two or more kinds thereof can also be used.

  Among these, the alkyl ether sulfate ester salt is preferable for the generation of the high-magnification foamed bubbles in the method of the present invention, and if necessary, the alkyl ether sulfate ester salt having an ethylene oxide addition mole number of 5 mol or more is foamed. You may use 5-20 mass% with respect to anionic surfactant as a reinforcing agent.

  The compounding quantity in the foaming-material aqueous solution of the anionic surfactant which is a component of foaming-material aqueous solution is 20-50 mass%, Preferably it is 30-40 mass%.

(About the amount of hydrophobic membrane agent)
As the hydrophobic film agent that is a component of the foaming material aqueous solution, various hydrophobic substances that are hardly soluble or insoluble in water such as hydrocarbons and fluorines can be used unless the foaming property of the anionic surfactant is suppressed. . Since the hydrophobic film agent is dissolved in the water-soluble solvent, the hydrophobic film agent is selected by selecting a substance that is soluble in the water-soluble solvent to be used. In addition, since it is oriented as an adsorbing layer of the bubble liquid film, it is appropriately selected according to the structure of the hydrophobic group of the anionic surfactant and the type of functional group. For example, when an alkyl ether sulfate having 20 carbon atoms is used as an anionic surfactant, a higher alcohol having the same carbon number (for example, in the range of 18 to 22) has good compatibility.

  When the hydrophobic film agent is solid at room temperature, it is selected from linear aliphatic alcohols having 12 to 20 carbon atoms that are easily decomposable, such as dodecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, and eicosyl alcohol. And a mixture of two or more of these. The blending amount of the hydrophobic film agent in the foaming material aqueous solution is 0.2 to 30% by mass, and preferably 1 to 15% by mass, the unsaturated state can be maintained for a long time.

(About the amount of water-soluble solvent)
From the viewpoint of high foaming technology, the water-soluble solvent is a component for solubilizing the hydrophobic film agent in the foaming material aqueous solution. Further, it is useful for assisting the solubility of the anionic surfactant, lowering the viscosity of the liquid film during foaming to increase the expansion rate, and lowering the freezing point.

  Therefore, the water-soluble solvent that is a component of the foaming material aqueous solution is selected from those that do not suppress the foaming property of the foaming material and that can solubilize the hydrophobic film agent to be used. Examples of water-soluble solvents include cellosolve solvents (such as methyl cellosolve, ethyl cellosolve, n-propyl cellosolve, n-butyl cellosolve, isobutyl cellosolve, and phenyl cellosolve), carbitols (such as ethyl carbitol and butyl carbitol), and ethylene oxide. Examples thereof include polyoxyethylene lower alkyl ethers having an addition mole number of 3 to 10 (such as polyoxyethylene (3) methyl ether), diols (such as ethylene glycol, diethylene glycol, and polyethylene glycol) and mixtures of two or more thereof. Moreover, the compounding quantity in the foaming material aqueous solution of a water-soluble solvent is 5-50 mass%, Preferably it is 20-40 mass%.

(About the concentration of diluted solution)
The foaming material aqueous solution to be applied in the method of the present invention is to uniformly mix a foam reinforcing agent, an organic acid and / or water as necessary in addition to the anionic surfactant, the hydrophobic film agent and the water-soluble solvent. Can also be easily obtained. In addition, when foaming this foaming material aqueous solution, the density | concentration of the dilution liquid diluted with water beforehand and making liquid is 0.2-10 mass% of a foaming material aqueous solution, Preferably it is 0.5-5 mass% . The dilution concentration may be selected in consideration of the foaming method and soil conditions. For example, if the bubble diameter and homogeneity can be adjusted satisfactorily using the foam cylinder method used in the bubble shield construction, the lower limit concentration of the diluent can be used from a low concentration of 1% by mass or less. On the other hand, in order to obtain a high water-stopping effect in the case of a natural ground with poor soil conditions, the lower limit concentration of the diluted solution is preferably 2% by mass or more.

(About expansion ratio)
Since the liquid film moisture is smaller as the bubble density is smaller, it is easy to be in an unsaturated state by air-water exchange with free water in the excavated soil. It is preferable that the bubbles are foamed as high as possible and the bubble diameter is reduced to reduce the water permeability of the excavated soil. More specifically, the foam density is preferably 10 times or more because the cell density is preferably 0.1 g / ml or less. High foaming technology is technically possible up to 500 times foaming, but due to mechanical limitations of foaming equipment that can be used in bubble shield construction, practically 50 times foaming is suitable.

(Effect confirmation experiment and its result)
The present inventors conducted experiments to confirm the effect of improving the hydraulic conductivity of the bubble mixed soil formed by the bubbles applied by the bubble shield method of the present invention and the effect of improving the duration of the unsaturated state of the bubble mixed soil. It was.

<Experiment and results of verifying the stability of bubbles and defoaming properties>
Each foaming material aqueous solution was foamed at a dilution concentration shown in Table 1 below, and highly foamed bubbles 1 to 6 (Examples 1-1 to 1-6, respectively) and comparative bubbles (Comparative Examples 1-1 to 1-3). ) Was evaluated, each foam was evaluated, the foamable magnification and the bubble diameter were measured, and the stability of the bubbles and the defoaming property of the bubbles were compared.

[Diluted solution]
The foaming material aqueous solution was dissolved in water at the dilution concentrations exemplified in Table 1 to prepare a diluted solution.
[Foaming method]
The foamed cylinder is a stainless steel tube (tube diameter 25A, length 25cm) filled with fillers such as cotton-like stainless fine fibers and glass beads, and compressed air is applied to this at an arbitrary pressure (0 to 400kPa). Washed away. The amount of compressed air for each pressure and the discharge amount of the diluent were measured in advance for each condition, and the expansion ratio (volume ratio) was calculated from the ratio between the bubble volume and the diluent volume. A fixed amount of the diluent was discharged by a metering pump into a foamed cylinder in which compressed air was flowed to forcibly foam.
[Experimental result]
Table 1 shows the measurement results and the evaluation results.

  From Table 1, all of the six examples show good results regarding the stability of the bubbles. In addition, good results have been obtained with respect to forced defoaming of bubbles using an antifoaming agent.

<Experiment and results on the permeability coefficient and the persistence of the unsaturated state when the saturation is changed>
Next, the present inventors conducted various experiments on the sustainability of the unsaturated state of the examples and the comparative examples at various saturation levels with various saturation levels.

  Dilution liquid (concentration 5 mass%) of high foaming 2 (Example 1-2) in Table 1 and dilution liquid (concentration 3 mass%) of A type (Comparative Example 1-1) are foaming ratios in Table 2 below. To produce bubbles (Examples 2-1 to 2-4 and Comparative Examples 2-1 to 2-4, respectively), and adjust the water content of the experimental sand to change the degree of saturation of the bubble-mixed soil. The imperviousness of soil and the retention of unsaturated state were compared.

  Here, the bubble mixing ratio (Q = bubble volume / excavated soil volume) was 30%, and the bubble mixed soil was prepared by kneading into experimental sand having different saturation. Under these conditions, the permeability coefficient was measured by the following permeability test method. In addition, a constant water pressure was applied to the bubble-mixed soil in the permeable container to observe the change in the amount of drainage over time, and this was evaluated as the durability of the unsaturated state.

[Conditions for experimental sand]
Experimental sand is silica sand No. 5 [commercial product washed with water to remove dust and clay, etc. and dried, maximum particle size 1.18 (mm), dry density 1.36 (g / cm ³ ), water permeability 1.87 × 10 ^-1 (cm / sec, water permeability test result according to this example), the water content ratio of porosity 19%] was adjusted.

[Permeability test method]
Air bubbles were added to the experimental sand at a predetermined air bubble mixing ratio, and kneaded quickly while being careful not to get entrained air bubbles during kneading, to prepare air bubble mixed soil, and immediately filled the water permeable cylinder. As the permeable cylinder, an acrylic container with an inner diameter of 30 mm (height 80 cm) and a pressure vessel with an inner diameter of 50 mm (height 80 cm) were used, and the amount of drainage from the lower part of the permeable cylinder was measured to calculate the permeability coefficient. In addition, a constant water pressure (0.03 MPa to 0.05 MPa) was applied to the upper part of the permeable cylinder, and the time for which the unsaturated state was maintained was measured.
[Experimental result]
Table 2 shows the measurement results.

  From Table 2, it can be seen that in each of the examples with different degrees of saturation, the hydraulic conductivity is reduced as compared with the comparative example, and the duration of the unsaturated state is longer.

<Experiment and results of verifying fluidity effect>
Next, the present inventors conducted experiments to confirm the fluidity of Examples and Comparative Examples at various bubble mixing ratios by varying the bubble mixing ratio.

  For the high foaming 2 (Example 1-2) and the A type (Comparative Example 1-1) and B type (Comparative Example 1-2) in Table 1, dilutions were prepared at the dilution concentrations shown in Table 3 below (respectively, Examples 3-1 and 3-2, Comparative Examples 3-1 and 3-2), and the foaming ratio was changed within the range shown in Table 3 to produce a plurality of types of bubbles. For each bubble, change the bubble mixing ratio Q (bubble volume / excavated soil volume) within the range shown in Table 3, knead into the following gravel sample soil collected from the site, and visually determine the slump value and appearance. The fluidity effect was determined.

[Sample soil]
Soil quality: Gravelly soil, grain size (75.6% gravel, 21.9% sand, 2.5% silt clay), water content 8.5%.
[Fluidity test method]
Sample soil (20 liters) was put into a pot mixer for concrete, bubble foaming was generated with a large foam cylinder in the same manner, and a predetermined amount was added to the mixer and mixed.
[Experimental result]
Table 3 shows measurement results and evaluation results.

  From Table 3, the comparative example was a bubble with a low expansion ratio, and a slump value was obtained, but all were deformed by the material separation, and no homogeneous plastic fluidity was confirmed. On the other hand, it was confirmed that the cells with high expansion ratios in the examples all have a well-organized material, uniform plastic fluidity, and good fluidity.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Bubble discharge port, 2 ... Cutter, 3 ... Stirring blade, 4 ... Bubble injection port, 5 ... Screw conveyor, 6 ... Belt conveyor, 7 ... Chamber, 8 ... Shield jack, 9 ... Soil discharge gate, 10 ... Shield digging Machine

Claims (5)

Bubbles are generated by foaming a dilute solution of a foaming material aqueous solution in which the hydrophobic membrane agent is completely solubilized with a water-soluble solvent and mixed with an anionic surfactant at a foaming ratio of 10 to 50 times. ,
A bubble shield construction method in which the bubbles are injected into the soil of the face and the soil in the chamber of the shield machine to form a bubble mixed soil. A hydrophobic film agent is solubilized with a water-soluble solvent and further mixed with an anionic surfactant, and a diluted solution of the foaming material aqueous solution is foamed at a foaming ratio of 10 to 50 times to form the hydrophobic film on the liquid film. The film agent generates bubbles with homogeneous adsorption and coordination,
A bubble shield construction method in which the bubbles are injected into the soil of the face and the soil in the chamber of the shield machine to form a bubble mixed soil. A foaming material aqueous solution for generating bubbles used in the bubble shield method,
30-40% by weight of anionic surfactant, 1-15% by weight of hydrophobic membrane agent, 20-40% by weight of water-soluble solvent,
A foaming material aqueous solution in which the hydrophobic film agent is completely solubilized with the water-soluble solvent.   The foaming material aqueous solution according to claim 3, wherein the water-soluble solvent is carbitols. The hydrophobic film agent is dodecyl alcohol;
The foaming material aqueous solution according to claim 3, wherein the water-soluble solvent is butyl carbitol.

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