JP7318902B2 - Excavation Additives and Mud Pressure Shield Construction Method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an excavating additive used in excavation work in a mud pressure shield construction method, and a mud pressure shield construction method using the same.

When constructing underground infrastructure such as railroads, roads, tunnels, or utility tunnels for electricity, gas, water, etc., the shield construction method is often used. The shield construction method is a construction method in which a space is constructed by excavating the ground with a shield machine, and the excavated earth and sand are transported to the ground. The excavated earth and sand at a depth of several tens of meters underground is fluidized by adding water, excavation additives, etc., and then pumped, or carried out by a trolley without adding additives. .

A method of adding water to transport the excavated earth and sand is called a mud shield construction method, and a method of adding an excavation additive is called a mud pressure shield construction method. There are various other shield construction methods, but in recent years, the mud pressure shield construction method has been used relatively often.

In the mud pressure shield construction method, an excavating additive, which is an excavating additive, is injected into the excavated earth and sand in the chamber of the shield machine. As a result, excavated earth and sand are converted into mud having plastic fluidity to fill the chamber, and the shield jack generates mud pressure in the mud. The face is stabilized by counteracting the earth pressure against the earth and water pressure. As the excavating additive, a polymer-based material has been conventionally used.

For example, in Patent Document 1, an aqueous dispersion of an alkali-soluble polymer obtained by oil-in-water type (O/W type) emulsion polymerization of a monomer composition containing a monomer containing a carboxyl group is used as a mud filler (excavation additive). ) is described to be used as
Patent Document 2 describes that a water-in-oil emulsion (W/O emulsion) of an acrylamide-based polymer flocculant with an anionization rate of 5 to 50 mol% is used as a sludge material (excavation additive). ing.
In addition, in Patent Document 3, a thickener containing a water-in-oil emulsion (W/O emulsion) of a superabsorbent polymer and an anionic water-soluble polymer is added to a clay suspension and excavated. It is described to be used as a material.
In addition, Patent Document 4 describes an additive for earth pressure shield construction method (excavation additive) consisting of a water-soluble polymer compound containing cellulose ether and polyacrylamide as essential components, an alkaline earth metal and zeolite.

Japanese Patent Application Laid-Open No. 2003-155475 JP-A-6-193382 JP-A-8-199159 JP 2006-182962 A

As noted above, various embodiments of polymers have been proposed for use as drilling additives.
However, the emulsion (dispersion) type excavating additives as described in Patent Documents 1 to 3 have poor storage stability, and sedimentation and separation of emulsified particles such as sedimentation and creaming immediately after production, flocculation and precipitation. It is easy to cause state changes such as For this reason, at the construction site, it is necessary to store it in a place where the temperature change is small, and to stir it just before use.

In particular, in the W/O emulsion type as described in Patent Documents 2 and 3, the organic solvent used as the dispersion medium is a hazardous substance designated by the Fire Defense Law according to its flammability. Therefore, care must be taken in storage and handling. Moreover, the organic solvent, which is contained in the product in an amount of several tens of percent by mass, flows out to the surroundings as a COD (Chemical Oxygen Demand) component when added to the excavated earth and sand.

In the emulsion type, the intrinsic viscosity of the polymer contained is large and the cohesive force between polymer particles is large, so the concentration that can be dissolved in water is at most about 1% by mass in terms of polymer concentration (pure concentration). be. For this reason, it is difficult to adjust the amount of addition for appropriately acting as an excavation additive.

On the other hand, in the powder product containing inorganic substances as described in Patent Document 4, unlike the emulsion type, the polymer does not aggregate or precipitate, but when used at the construction site, it is diluted with water. and the soluble polymer concentration (pure concentration) remains below 1% by weight. Even with a powder product consisting only of a polymer, the upper limit of the concentration in an aqueous solution that can be adjusted on site is about 0.3% by mass, and the dissolution time at that time is one hour or longer, resulting in inferior workability.

The present invention has been made to solve the above problems, and has excellent storage stability, can easily adjust the contained liquid in a wide concentration range, and is easy to handle at the construction site and It is an object of the present invention to provide an excavation additive excellent in workability and capable of imparting good plastic fluidity to excavated earth and sand, and a mud pressure shield construction method using the same.

The present invention provides an aqueous solution-type excavation additive comprising a polymer having a specific composition and a specific intrinsic viscosity, which is excellent in handleability when diluted with water and imparts good plastic fluidity to excavated soil. It is based on what we have found.

That is, the present invention provides the following [1] to [6].
[1] An excavation additive applied to a mud pressure shield construction method, which is an aqueous solution containing a polymer containing (meth)acrylamide and one or more compounds selected from (meth)acrylic acid and salts thereof as monomer components and the polymer has an intrinsic viscosity of 1.1 to 5.0 dL/g at 30° C. in a 1N sodium nitrate aqueous solution.
[2] The excavating additive according to [1] above, wherein the concentration of the polymer in the aqueous solution containing the polymer is 1 to 50% by mass.

[3] A mud pressure shield construction method in which the excavation additive according to [1] or [2] is added to the excavated earth and sand to turn the excavated earth and sand into mud.
[4] The mud pressure shield construction method according to [3] above, wherein the excavation additive and one or more clay minerals selected from smectite and bentonite are added together.
[5] The mud pressure shield construction method according to the above [3] or [4], wherein the excavation additive and a surfactant are added together.
[6] The mud pressure shield construction method according to the above [3] or [4], wherein the excavation additive, a surfactant, and a bubble stabilizer are added together.

ADVANTAGE OF THE INVENTION The excavation additive of the present invention has excellent storage stability, can easily adjust the contained liquid in a wide concentration range, and can impart good plastic fluidity to excavated earth and sand.
Therefore, by using the excavation additive, it is possible to improve the handling and workability of the excavation additive at the construction site of the mud pressure shield construction method.

Hereinafter, the excavating additive of the present invention and the mud pressure shield construction method using the same will be described in detail.
In this specification, "(meth)acryl" means acryl and/or methacryl, and "(meth)allyl" means allyl and/or methallyl.

[Excavation additive]
The excavating additive of the present invention is an excavating additive applied to the mud pressure shield construction method, and comprises (meth)acrylamide and one or more compounds selected from (meth)acrylic acid and salts thereof as monomer components. is an aqueous solution containing a polymer containing The polymer has an intrinsic viscosity of 1.1 to 5.0 dL/g at 30° C. in a 1N sodium nitrate aqueous solution.
Such a polymer aqueous solution type drilling additive has excellent storage stability and can be used as it is without dilution. Moreover, it may be diluted with water before use, in which case it is possible to adjust the solution concentration to an arbitrary value in a short period of time, and it is also excellent in handleability.
In addition, since it is an aqueous solution type, the risk of flammability due to organic solvents and the COD of mud and excavated surplus soil generated by addition to excavated soil are suppressed compared to W/O emulsion type.

(polymer)
The monomer component, which is the structural unit of the polymer, contains one or more compounds selected from (a) (meth)acrylamide and (b) (meth)acrylic acid and salts thereof. That is, the polymer is a copolymer containing at least two of (a) and (b) as monomer components. The polymer may contain monomer components other than (a) and (b). When the other monomer component is included, the ratio of the total content of (a) and (b) in the monomer component is preferably 90 mol% or more, more preferably 95 mol% or more, It is more preferably 98 mol % or more, and particularly preferably 100 mol %.

The monomer component (a) is one or more selected from acrylamide and methacrylamide. That is, one of these may be used alone, or two of them may be used in combination.

(b) of the monomer component is one or more compounds selected from (meth)acrylic acid and salts thereof. Salts of (meth)acrylic acid include, for example, salts of metals such as sodium, potassium, zinc, magnesium and aluminum. As the monomer component (b), acrylic acid and salts thereof are preferable from the viewpoints of the water solubility of the polymer and the suppression of COD of mud and excavated soil due to the addition of excavation additives. Acrylate is more preferred, and sodium acrylate and potassium acrylate are particularly preferred.

Other monomer components that can be contained in the constituent units of the polymer include, for example, carboxy group-containing monomers such as maleic acid and maleic anhydride, and unsaturated sulfo group-containing monomers such as vinylsulfonic acid and (meth)allylsulfonic acid. Anionic monomers such as monomers can be mentioned. Metal salts of these monomers such as sodium, potassium, zinc, magnesium and aluminum are also included.

The anionic degree (proportion of anionic monomer) of the polymer is preferably 5 to 90 mol%, more preferably 20 to 90 mol%, from the viewpoint of obtaining an excavating additive capable of imparting good plastic fluidity to excavated soil. 85 mol %, more preferably 30 to 80 mol %. For example, when the monomer component is a two-component polymer of acrylamide and sodium acrylate, the degree of anion (proportion of sodium acrylate in the monomer component) is preferably 5 to 90 mol%, more preferably 20 to 85. mol %, more preferably 30 to 80 mol %.
The degree of anion can be obtained from the monomer composition of the structural units of the polymer, and can be calculated from the anionic colloid equivalent value if the monomer components of the structural units of the polymer are known.

The polymer can be dissolved in water to form an aqueous solution. However, it is efficient to obtain an aqueous polymer solution from the time of polymer synthesis, and it is preferable to synthesize the polymer by aqueous solution polymerization. The aqueous solution polymerization can be performed by a known method, but since the excavating additive of the present invention is an aqueous solution type, it is preferable to synthesize a non-crosslinked polymer such as a linear polymer. For example, aqueous solution polymerization can be carried out by adding a redox polymerization initiator to an aqueous solution of the monomer components while stirring in a nitrogen stream. Examples of the redox polymerization initiator include a combination of a persulfate and an acid sulfite (or thiosulfate), a combination of a bromate and a sulfite, or a combination of a persulfate (or hydrogen peroxide) and A combination with a water-soluble tertiary amine and the like are included.

The concentration (pure concentration) of the polymer in the aqueous solution is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, still more preferably 10 to 30% by mass.
The concentration (pure concentration) of the polymer is the evaporation residue (non-volatile matter) of the aqueous solution. Specifically, the evaporation residue is obtained by placing about 5 g of the aqueous solution in an evaporation dish, weighing it, and then evaporating it to dryness at 105° C. and measuring the mass of the residue.
The aqueous solution has excellent storage stability in a dissolved state of the polymer, and can contain the polymer in a homogeneous state in a wide concentration range in the liquid of the drilling additive. Even when the aqueous solution (excavation additive) is diluted with water at the construction site and used, it is possible to obtain a uniform solution in a short time of several minutes by mixing with water and stirring. Excellent in nature. In addition, since the polymer has a predetermined intrinsic viscosity and the aqueous solution has an appropriate viscosity, it can be added to the excavated earth and sand as it is as an additive for excavation without dilution. can.

In addition to the polymer and water, the aqueous solution contains other substances such as additives added during polymer synthesis (for example, polymerization initiators, chain transfer agents, neutralizers, cross-linking agents, etc.). may be However, the polymer accounts for preferably 95% by mass or more, more preferably 98% by mass or more, and still more preferably 100% by mass or more of the components other than water in the aqueous solution.

(Intrinsic viscosity)
The polymer has an intrinsic viscosity of 1.1 to 5.0 dL/g, preferably 1.2 to 4.8 dL/g, more preferably 1.3 to 4 .5 dL/g.

The intrinsic viscosity is represented by [η] and is a value calculated using the following Huggins formula.
Huggins formula: η _SP /C=[η]+k'[η] ^2C
In the above formula, η _SP : specific viscosity (=η _rel −1), k′: Huggins constant, C: polymer solution concentration, η _rel : relative viscosity.
Polymer solutions with different concentrations are prepared, the specific viscosity _η is determined for each concentration solution, and the relationship _η /C vs. C is plotted, and the intercept value when C is extrapolated to 0 is the intrinsic viscosity ( [η]).

Intrinsic viscosity is also an index of molecular weight, and the smaller the molecular weight of the polymer, the lower the intrinsic viscosity tends to be. However, since the intrinsic viscosity is also affected by the polymerization conditions of the polymer, the degree of anion, etc., it does not necessarily correspond to the size of the molecular weight.
The intrinsic viscosity can be adjusted by adjusting the reaction temperature, the concentration of monomers in the reaction system, the type and concentration of the polymerization initiator, the concentration of the chain transfer agent, etc. when synthesizing the polymer. In general, when the reaction temperature is increased, the monomer concentration in the reaction system is decreased, the polymerization initiator concentration is increased, and the chain transfer agent concentration is increased, the intrinsic viscosity tends to decrease.

The excavating additive of the present invention is a polymer having the above-mentioned monomer component as a constitutional unit and has a specific intrinsic viscosity.
In addition, the intrinsic viscosity in the present invention is a value at 30° C. in a 1N sodium nitrate aqueous solution, and is a value measured using a Canon Fenske viscometer. Specifically, it is obtained by the method shown in the following examples.

When the intrinsic viscosity of the polymer is within the above range, the polymer can impart good plastic fluidity to the excavated soil. In addition, since the intrinsic viscosity is relatively low, it is also excellent in miscibility with clay minerals, which will be described later. Good plastic fluidity can be stably imparted without causing a large change in the plastic fluidity imparted to earth and sand.

[Mud Pressure Shield Method]
In the mud pressure shield construction method of the present invention, the excavation additive is added to the excavated earth and sand to turn the excavated earth and sand into mud. Except for using the excavating additive of the present invention as an excavating additive, the work can be carried out in the same manner as in the known mud pressure shield construction method.
By treating excavated earth and sand using the excavating additive of the present invention, good plastic flowability can be imparted to the excavated earth and sand, and workability in obtaining mud is improved.
The mud referred to in the present invention refers to excavated soil that has been fluidized with an excavation additive and has plastic fluidity.

The excavated earth and sand to which the present invention is applied is not particularly limited as long as it has a soil quality to which a normal mud pressure shield construction method can be applied. Examples thereof include sandy silt/clay, sandy loam/clay, sandy soil, gravel soil, and the like. The excavation additive can impart good plastic fluidity to such excavated earth and sand, and improve the workability of the mud pressure shield construction method.

The excavating additive can be used by adding only the excavating additive to the excavated soil, or can be added together with one or more clay minerals selected from smectite and bentonite. These clay minerals impart water impermeability to the excavated soil due to their swelling and viscosity properties, and by using them together with the excavation additive, the workability of the mud pressure shield construction method, such as suppressing the bleeding of mud, is improved. can be further improved.

When the excavation additive is used in combination with the clay mineral, for example, 0.001 to 1 part by mass of the excavation additive is added to 100 parts by mass of the clay mineral-containing water containing 1 to 20% by mass of the clay mineral. , preferably 0.005 to 0.5 parts by mass, more preferably 0.01 to 0.1 parts by mass (preparation excavation additive) may be added to the excavated soil.

Examples of the clay mineral include smectite and bentonite, and one of these may be used alone, or two or more thereof may be used in combination. Examples of smectites include montmorillonite, beidellite, nontronite, saponite, hectorite, sauconite, and stevensite. Further, bentonite is a general term for clay containing montmorillonite contained in the smectite as a main component, and includes secondary components such as quartz, cristobalite, feldspar, and calcite.

In the mud pressure shield construction method of the present invention, the excavation additive may be added to the excavated earth and sand, and other additives may be added. The excavation additive and the additive may be mixed in advance before being added to the excavated earth and sand from the viewpoint of efficiency of site construction.

Examples of the other additives include surfactants, thickeners, water-absorbing resins, dispersants, and the like. These additives can be added as necessary within a range that does not interfere with the effects of the excavation additive. Among these, one type may be used alone, or two or more types may be used in combination. In addition, in the specific examples of various additives shown below, due to the various properties of each compound, some additives are duplicated among different types of additives.
The amount of each of the additives added depends on the type of excavated soil to be added, but is preferably 5 to 2000 parts by mass, more preferably 10 to 1000 parts by mass with respect to 100 parts by mass of the excavation additive. , more preferably 20 to 500 parts by mass.

In the mud pressure shield construction method, for example, the excavation additive and a surfactant as a foaming agent may be used in combination. The drilling additive can be used in conjunction with a surfactant without interfering with the lathering properties of the surfactant. That is, the excavation additive can be suitably applied to the bubble shield construction method among the mud pressure shield construction methods. When the excavation additive is used in combination with a surfactant, even if a thickener is added as a foam stabilizer, the foamability is not hindered.

In the mud pressure shield construction method, the surfactant is added as a foaming agent, and from the viewpoint of preventing aggregation of the anionic excavation additive, it is preferable to use an anionic surfactant. Examples of the surfactant include polyoxyethylene octylphenol, polyoxypropylene stearate, sorbitan monolaurate, alkyl sulfate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl ether sulfate, and alkylbenzenesulfonic acid. salts, α-olefin sulfonates, alkyl ether sulfate ester salts, alkyl ether carboxylates, α-sulfo fatty acid methyl ester salts, acyl-N-methyl taurine salts and the like.

The thickener is added as a bubble stabilizer in the bubble shield method when used in combination with the surfactant (foaming agent). Examples of the thickener include polyacrylic acid (salt), polyacrylamide, acrylic acid (salt)-acrylamide copolymer crosslinked product; methylcellulose, carboxymethylcellulose, guar gum, xanthan gum, starch glycolic acid, starch phosphate, Alginic acid, alginic acid propylene glycol ester, salts thereof, and the like.

Examples of the water absorbent resin include crosslinked polyacrylic acid (salt), crosslinked polyacrylamide, acrylic acid (salt)-acrylamide copolymer crosslinked product, styrene-maleic anhydride (salt) copolymer crosslinked product, isobutylene- crosslinked maleic anhydride (salt) copolymer, polysulfonic acid (salt), starch-acrylic acid graft polymer, vinyl alcohol-acrylic acid (salt) copolymer, polyethylene glycol-acrylic acid (salt) copolymer, polyethylene oxide, crosslinked polyaspartic acid (salt), polyglutamic acid (salt), polyalginic acid (salt), and the like.

Examples of the dispersant include polyacrylic acid (salt), formalin condensate of naphthalenesulfonate, styrene-maleic anhydride (salt) copolymer, olefin-maleic anhydride (salt) copolymer, polyacrylic acid ( salt)-polyacrylamide copolymer, polystyrene sulfonic acid (salt) copolymer, alginic acid (salt) and the like.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to the following examples.
[Preparation of drilling additive material sample]
Drilling additive samples of Examples and Comparative Examples shown in Table 1 below were prepared. All of the drilling additive samples were acrylamide-sodium acrylate copolymers. The oil phase of the W/O emulsion (Comparative Example 3) is a hydrocarbon solvent (mineral oil).
Moreover, the method for measuring the intrinsic viscosity in Table 1 is as follows.

(Measurement of intrinsic viscosity)
The intrinsic viscosity of each excavation additive sample was obtained by the following procedure.
[1] Five Canon Fenske viscometers (No. 75 manufactured by Kusano Kagaku Co., Ltd.) were immersed in a neutral detergent for glassware for 1 day or longer, washed thoroughly with deionized water, and dried.
[2] About 0.3 g of each excavation additive sample in terms of polymer pure content (for example, about 1.5 g in the case of an aqueous solution type (Example 1) with a pure content concentration of 20% by mass). It was precisely weighed, added to deionized water under stirring at 500 rpm with a magnetic stirrer, stirred for 2 hours, and then allowed to stand still for 15 to 24 hours. After stirring again at 500 rpm for 30 minutes, the entire amount was filtered through a glass filter 3G2 to prepare a 0.2% by mass polymer aqueous solution.
The W/O emulsion type (Comparative Example 3) was added to a large excess of acetone for purification by precipitation, and the precipitate was vacuum-dried to form a powder, which was subjected to intrinsic viscosity measurement.
[3] 50 mL of 2N sodium nitrate aqueous solution was added to 50 mL of the 0.2% by mass polymer aqueous solution, and the mixture was stirred at 500 rpm for 20 minutes with a magnetic stirrer to obtain a 1N sodium nitrate aqueous solution with a polymer concentration of 0.1% by mass. This was diluted with a 1N sodium nitrate aqueous solution to prepare polymer sample solutions having five concentrations of 0.02, 0.04, 0.06, 0.08 and 0.1% by mass. A 1N sodium nitrate aqueous solution (1N—NaNO ₃ ) was used as a blank solution.
[4] Five viscometers were vertically installed in a constant temperature water bath adjusted to a temperature of 30°C (within ±0.02°C). After 10 mL of the blank liquid was put into each viscometer with a whole pipette, it was allowed to stand still for about 30 minutes in order to keep the temperature constant. After that, the liquid was sucked up using a dropper plug, allowed to drop naturally, and the time taken to pass the marked line was measured with a stopwatch to the nearest 1/100th of a second. This measurement was repeated 5 times for each viscometer, and the average value was taken as the blank value t ₀ .
[5] Each 10 mL of the polymer sample solution having five levels of concentration prepared above was placed in the five viscometers used to measure the blank solution, and allowed to stand for about 30 minutes to keep the temperature constant. After that, the same operation as the measurement of the blank solution was repeated three times, and the average value of the passage times for each concentration was taken as the measured value t.
[6] From the blank value t ₀ , the measured value t, and the concentration C [mass/volume %] (=C [g/dL]) of the polymer sample solution, relative viscosity η _rel , specific viscosity η _SP , and reduction Viscosity η _SP /C [dL/g] was obtained from the following relational expression.
η _rel =t/t ₀
η _SP =(t−t ₀ )/t ₀ =η _rel −1
From these values, the intrinsic viscosity ([η]) of each polymer was calculated according to the method of determining the intrinsic viscosity based on the above-mentioned Huggins equation.

[Evaluation of drilling additive material sample]
Various evaluations shown below were performed using each of the excavation additive samples described above. In addition, the results of each evaluation are shown for representative examples of excavation additive samples.
(1) Separation Resistance 90 mL of a drilling additive sample was placed in a 100 mL glass sample bottle (40 mm inner diameter of barrel), sealed, and allowed to stand at room temperature (20 to 25° C.). After 3 days, 7 days and 14 days, the state of solid-liquid separation was observed, and when separation occurred, the distance between the liquid surface and the separation interface was measured with a straight ruler.
The longer the distance, the more advanced the separation.

(2) COD
After arbitrarily diluting the drilling additive sample with water, it was measured in accordance with JIS K 0102: 2013 "17. Oxygen consumption by potassium permanganate at 100 ° C. (COD _Mn )" to obtain COD. .

Table 2 below shows the evaluation results of separation resistance and COD.

As shown in the evaluation results in Table 2, in the W/O emulsion type (Comparative Example 3), a separation interface was observed after 3 days, and precipitation occurred at the bottom after 14 days. It was possible to disperse. On the other hand, in the aqueous solution type (Example 2), no separation interface or precipitation was observed even after 14 days, and the aqueous solution state was maintained. From this, it can be said that the aqueous solution type is excellent in storage stability.
In addition, the W/O emulsion type contains an organic solvent, whereas the aqueous solution type contains water as a solvent and does not contain an organic solvent, so the COD value was lower. Therefore, the aqueous solution type excavation additive can suppress the COD of mud and excavated soil as compared with the W/O emulsion type.

(3) Dissolution rate In a 300 mL beaker, the excavation additive sample was added to pure water at a predetermined additive concentration so that the total amount was 200 g. This drilling additive sample-containing water was stirred at 1000 rpm with a magnetic stirrer using a cylindrical stirrer tip with a diameter of 1 cm and a length of 4 cm. The dissolution time was defined as the time when the viscosity of the excavation additive sample-containing water became almost constant.
The viscosity was measured using a B-type rotational viscometer (Brookfield digital viscometer "LV DVE") under the conditions of spindle S64, rotation speed 6 rpm, 25°C, and 1 minute (the same applies to the following viscosity measurements).

Table 3 below shows the dissolution time at each addition concentration. A shorter dissolution time indicates a faster dissolution rate.
In Table 3, for the powder type (Comparative Example 2) and the W/O emulsion type (Comparative Example 3), the viscosity is almost The time when it became constant was described as the dissolution time.

As shown in the evaluation results in Table 2, the powder type (Comparative Example 2) requires a dissolution time of 60 minutes even at an addition concentration of 0.2% by mass, and when the addition concentration is 1% by mass, it is lumps) remained. Further, in the W/O emulsion type (Comparative Example 3), the dissolution time was within 5 minutes at an addition concentration of 1% by mass or less, but it was difficult to achieve a uniform state at an addition concentration of 2% by mass. It became cake-like.
In contrast, the aqueous solution type (Example 2) had a dissolution time of 30 seconds even at an addition concentration of 50% by mass, confirming a high dissolution rate. From this, it can be said that the aqueous solution type drilling additive is excellent in handleability when diluted with water.

(4) Mixability with bentonite liquid Bentonite ("T-3", manufactured by Tachibana Material Co., Ltd.) was added to tap water so that the concentration was 8% by mass, and a fan turbine type stirring blade with a diameter of 75 mm was used. After stirring at 800 rpm for 30 minutes, the mixture was allowed to stand overnight to obtain a bentonite liquid.
An excavation additive sample was added to 500 mL of this bentonite liquid at an addition concentration of 0.1% by mass, and the mixture was stirred at 300 rpm using the stirring blade, and the viscosity of the bentonite liquid was measured every 10 seconds of stirring. The time required for the viscosity to reach the upper limit and no further increase (time to reach the upper limit) was defined as the time required for mixing with the bentonite liquid.

Table 4 below shows the time required for mixing each excavation additive sample with the bentonite liquid, the maximum viscosity, and the properties after mixing.

As shown in the evaluation results in Table 4, the aqueous solutions (Examples 1 to 3 and Comparative Example 1) required less than 20 seconds to mix with the bentonite solution. In addition, since the intrinsic viscosity was within a predetermined range (Examples 1 to 3), a gel-like mixture having appropriate viscosity and fluidity and excellent handleability was obtained.
On the other hand, the W/O emulsion type (Comparative Example 3) continued to increase in viscosity even after being stirred for 60 seconds or more, and the mixture with the bentonite liquid became non-fluid and sticky.

(5) Fluidity of Sandy Soil A bentonite solution was prepared in the same manner as in (4) above except that the concentration of bentonite in the evaluation in (4) above was 10% by mass.
An excavation additive sample was added to this bentonite solution at an addition concentration of 0.4% by mass, and the mixture was manually stirred for 30 seconds using a spatula to prepare a mixed solution.
To 500 mL of sandy soil shown below, add 100 mL of the above mixture (20% by volume with respect to sandy soil), stir with a Hobart mixer at 60 rpm for 30 seconds, turn upside down, and again at 60 rpm for 30 After stirring for 2 seconds, treated soil samples were obtained.

The sandy soil used has a particle size composition of 4 parts by mass of gravel with a particle size of 2 mm or more and less than 75 mm, 32 parts by mass of sand with a particle size of 0.075 mm or more and less than 2 mm, and silt with a particle size of 0.005 mm or more and less than 0.075 mm. and 30 parts by weight of clay having a particle size of less than 0.005 mm. Also, the water content was 49% and the bulk specific gravity was 1.9 g/cm ³ .
In addition, each physical property value of the soil is a value measured based on JIS A 1204:2009 for particle size composition and JIS A 1203:2009 for water content ratio. Bulk specific gravity is obtained by filling a 1 L graduated cylinder with soil, measuring the mass of the soil, and tapping the graduated cylinder 1 to 2 times / minute 5 times from a height of 3 ± 0.5 cm. It is a value obtained from the measured volume and mass (hereinafter the same).

The treated soil samples obtained were evaluated for the following items. These evaluation results are shown in Table 5 below.
(5-1) Flow value A flow value was measured by a flow test conforming to JIS R 5201:2015 using a mortar flow tester. A higher flow value indicates a lower viscosity. In this evaluation, if the flow value is in the range of 145 to 190 mm, it can be said that the spread is moderate and the viscosity is good.
(5-2) Plastic Fluidity During the flow test, the presence or absence of plastic fluidity was evaluated by visual observation. Evaluation criteria are as follows.
◯: Water and soil (mud) spread uniformly without separation.
x: Water and soil (mud) were separated, and only water spread.
(5-3) Bleeding water 500 g of the treated soil sample was placed in a plastic bag of 10 cm x 20 cm and allowed to stand at room temperature (25°C) for 3 hours, and the presence or absence of bleeding water was checked. When bleeding water was confirmed, the generated bleeding water was sucked up with a syringe, and the amount of bleeding water was measured. The amount of bleeding water is preferably 0, ie, no bleeding water is generated.

(6) Fluidity of gravel soil A bentonite solution with a concentration of 10% by mass was prepared in the same manner as in (5) above.
An excavation additive sample was added to this bentonite solution at an addition concentration of 0.2% by mass or 0.4% by mass, and the mixture was manually stirred for 30 seconds using a spatula to prepare a mixed solution.
Add 150 mL of the above mixed solution (30% by volume to the gravel soil) to 500 mL of gravel soil shown below, stir at 60 rpm for 30 seconds using a Hobart mixer, turn over, and stir again at 60 rpm for 30 seconds. and treated soil samples were obtained.

The gravel soil used was 50 parts by weight of gravel with a bulk specific gravity of 2.5 g/cm ³ and a grain size of 2 mm or more and less than 10 mm, and 50 parts by weight of river sand with a bulk specific gravity of 1.8 g/cm ³ and a grain size of 0.74 mm or more and less than 2 mm. and had a water content of 8% and a bulk specific gravity of 1.9 g/cm ³ .

The obtained treated soil samples were evaluated for flow value, plastic fluidity and bleeding water amount in the same manner as in (5) above. These evaluation results are shown in Table 5 below.

As shown in the evaluation results in Table 5, the aqueous solution type (Example 3) provides a suitable flow value and good viscosity in both sandy soil and gravel soil, and also has a plastic flow. It was also confirmed that the In addition, no bleeding water was observed in the sandy soil. It can be said that the aqueous solution type can perform excavated sediment treatment that imparts good plastic fluidity to various soil properties in a wide range of addition concentrations.
On the other hand, in the case of the W/O emulsion type (Comparative Example 3), although a suitable flow value was obtained for the treated soil sample of sandy soil, the treated soil sample was hard and did not impart plastic fluidity. In addition, the occurrence of bleeding water was confirmed for sandy soil. Regarding the treated soil sample of gravel soil, when the excavation additive sample was added at a concentration of 0.4% by mass, the flow value was small, the treated soil sample was hard, and plastic fluidity was not imparted. The excavation additive sample of Comparative Example 3 had a high intrinsic viscosity, and as a result of strong agglomeration, it is considered that the addition was excessive. Therefore, it can be said that the W/O emulsion type must be adjusted and used by obtaining an appropriate addition amount according to the soil quality.

(7) Combined use with a surfactant To tap water, an excavation additive sample (Example 3) was added at an addition concentration of 1.2% by mass, and "OK-2" ( Daiichi Kasei Sangyo Co., Ltd., carboxymethyl cellulose, powder) was added and sufficiently stirred at 500 rpm using a fan turbine type stirring blade with a diameter of 75 mm.
Next, "OK-1" (manufactured by Daiichi Kasei Sangyo Co., Ltd., sodium α-olefin sulfonate, liquid) was added as a surfactant (foaming agent) at an addition concentration of 1% by mass. A foaming test was conducted by stirring at 1500 rpm for 2 minutes using the stirring blade.
Using a 2 L plastic container, the volume (foaming volume) of the sample liquid after stirring was measured, and the foaming ratio was calculated by the following formula.
Foaming ratio [times]=volume of foaming/volume of sample solution before foaming For comparison reference, the same foaming test as above was performed also in the case where the excavation additive sample was not added.

As a result, both when the excavation additive sample (Example 3) was added and when it was not added, the bubble ratio was 4.5 times or more, indicating that the excavation additive sample can be used in combination with a surfactant without any problem. confirmed.

(8) Fluidity of Sandy Soil by Foaming Liquid Each sample liquid prepared in the evaluation of (7) above was foamed to a foaming ratio of 4.5 to prepare a foaming liquid.
To 500 mL of the same sandy soil as used in (5) above, 75 mL of the foaming liquid (15% by volume relative to the sandy soil) was added, stirred at 60 rpm for 30 seconds using a Hobart mixer, and then turned upside down. and stirred again at 60 rpm for 30 seconds to obtain a treated soil sample.

The obtained treated soil samples were evaluated for flow value, plastic fluidity and bleeding water amount in the same manner as the evaluation in (5) above. These evaluation results are shown in Table 7 below.

(9) Fluidity of Gravel Soil by Foaming Liquid A foaming liquid similar to that prepared in the evaluation of (8) above was prepared.
Using the same gravel soil as used in (6) above, treated soil samples were obtained in the same manner as in (8) above.

The obtained treated soil samples were evaluated for flow value, plastic fluidity and bleeding water amount in the same manner as the evaluation in (5) above. These evaluation results are shown in Table 6 below.

As shown in the evaluation results in Table 6, the foaming liquid using the excavation additive sample (Example 3) was used in both sandy soil and gravel soil, regardless of the presence or absence of the addition of a foam stabilizer. was also found to impart good viscosity and plastic flow. Also, no bleeding water was observed.

Claims (6)

An excavation additive applied to a mud pressure shield construction method, comprising (a) (meth)acrylamide and (b) one or more compounds selected from (meth)acrylic acid and salts thereof as monomer components. , an aqueous solution containing a polymer in which the total content of the (a) and the (b) in the monomer component is 98 mol% or more, and the proportion of the anionic monomer in the polymer is 20 to 85 mol% . , an excavating additive, wherein the polymer has an intrinsic viscosity of 1.1 to 5.0 dL/g at 30° C. in a 1N sodium nitrate aqueous solution. The drilling additive according to claim 1, wherein the concentration of said polymer in the aqueous solution containing said polymer is 1-50% by weight. A mud pressure shield construction method, wherein the excavation additive according to claim 1 or 2 is added to excavated earth and sand to turn the excavated earth and sand into mud. The mud pressure shield construction method according to claim 3, wherein the excavation additive and one or more clay minerals selected from smectite and bentonite are added together. The mud pressure shield construction method according to claim 3 or 4, wherein the excavation additive and a surfactant are added together. The mud pressure shield construction method according to claim 3 or 4, wherein the excavation additive, a surfactant, and a bubble stabilizer are added together.