JP2004002889A - Additive for shield tunneling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an additive for a shield tunneling method having both flowability and water cut-off ability and to provide a shield tunneling method using the same. <P>SOLUTION: The additive for the shield tunneling method includes carboxymethylcellulose or its salt and bentonite, and the bentonite has at least one of the following properties when its solution is prepared: ΔV/▵C≥5, ΔK/ΔC≥7, ΔS/ΔC≥1, wherein, ▵C is the variation in bentonite concentration (wt.%), ΔV is the variation in funnel viscosity (sec), ΔK is the variation in yield value (lb/100ft<SP>2</SP>), and ΔS is the variation in gel strength (lb/100ft<SP>2</SP>). <P>COPYRIGHT: (C)2004,JPO

Description

(4) The present invention relates to a shielding method additive (particularly, an earth pressure-based shielding method additive) composed of carboxymethyl cellulose or a salt thereof and high-viscosity bentonite, and a shielding method using the same.

In the earth pressure shield construction method, excavation is performed by a cutter attached to the front of the shield machine, the excavated earth and sand is filled in the earth pressure chamber in the shield machine, and the earth pressure opposes the face pressure and groundwater pressure, etc. Has stabilized. The excavated earth and sand filled in the earth pressure chamber is discharged out of the earth pressure chamber using a conveyor, a pump, or the like.

に お い て In such an earth pressure shield method, excavation and earth removal are easy on a viscous ground made of fine particles such as clay and silt. On the other hand, in sandy and gravel ground where particles such as sand and gravel are constrained to each other, the water blocking property is low, so a cavity is created at the top of the cutter chamber during excavation, and sediment collapses along with spring water in this cavity. As a result, the stability of the face cannot be maintained. In addition, in the gravel ground, since the fluidity of the excavated earth and sand is poor, pumping cannot be performed and the earth cannot be easily discharged. Therefore, in excavation and earth removal of the gravel ground, hand-digging shields and mechanical shields are used, and earth removal and transportation are performed by belt conveyors and minecarts. However, it is not preferable from the viewpoint of economy and work efficiency.

Therefore, when excavating and discharging soil with poor fluidity and water-blocking properties, adding a mudifier to excavated earth and sand increases its viscosity and improves transportability or transportability. .

Conventionally, as a humidifier, a fibrous substance such as an inorganic fiber or a pulp fiber has been used to impart water stoppage, and a water-soluble polymer compound has been mainly used to impart fluidity. I have. As the water-soluble polymer compound, for example, water-soluble cellulose such as hydroxyethyl cellulose and carboxymethyl cellulose, and organic polymer compounds such as polyacrylic acid, polyacrylamide, polyvinyl alcohol, and starch are used. Also, in some cases, clay such as bentonite, clay, kaolin, and kibushi clay is used to impart fluidity to sand and gravel.

However, conventional fluidizing agents cannot simultaneously provide sufficient fluidity and water stopping properties. For example, when a fibrous substance is used as a muddy agent, a large amount of fibers are required to obtain water-stopping properties, and the equipment becomes large-scale, and easily separates from water to obtain sufficient water-stopping properties. I can't. In addition, when an aqueous bentonite solution is used as a mudifier, sufficient waterproofness cannot be obtained, and when the bentonite aqueous solution is injected from the tip of the face during excavation, the face becomes unstable.

JP-A-4-64625 (Patent Document 1) proposes an additive for pumping excavated earth and sand composed of water-soluble cellulose ether, and JP-A-7-82559 (Patent Document 2) discloses an additive for water pumping. A mudifier mixed with the above water-soluble polymer compound and clay has been proposed. Further, Japanese Patent Application Laid-Open No. 5-311985 (Patent Document 3) proposes an earth pressure shield method for pumping and treating excavated earth and sand with simple equipment without adding a mudifying agent such as bentonite. .

However, when a water-soluble polymer such as a water-soluble cellulose ether is used alone, the viscosity may decrease due to pressurization during excavation, or sediment may separate after mixing with excavated earth due to reduced water retention. . Further, a muddy agent obtained by adding a clay to a water-soluble polymer can impart a certain degree of water-stopping property and fluidity, but has a small slump value and insufficient fluidity for fluid transport through a pipe. Further, the gravel is easily separated and cannot be discharged stably and efficiently by the pump. In particular, it is difficult to excavate smoothly on the gravel ground while pumping the excavated soil.

As described above, it is difficult to achieve both the fluidity, the water stopping property, the water holding property, and the separation stability of the earth and sand with the conventional mudifier.
JP-A-4-64625 JP-A-7-82559 JP-A-5-311985

Accordingly, an object of the present invention is to provide an additive for a shielding method capable of achieving both water stoppage and fluidity, and a shielding method using the same.

Another object of the present invention is to provide a shield method additive and a shield method using the same, which can excavate excavated soil smoothly by pumping even in a gravel ground.

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, carboxymethylcellulose or a salt thereof (hereinafter, collectively referred to as CMC) as an additive for shield method (particularly, an additive for earth pressure-based shield method). When combined with a specific bentonite, it has been found that the separation stability with respect to earth and sand, the water blocking property, and the fluidity can be achieved, and that even in the case of gravel ground, it can be smoothly excavated, and the present invention has been completed.

That is, the additive for the shield method of the present invention is composed of carboxymethylcellulose or a salt thereof and bentonite. When an aqueous solution thereof is prepared, the bentonite has properties represented by the following formulas (1) to (3). Having.

ΔV / ΔC ≧ 5 (1)
ΔK / ΔC ≧ 7 (2)
ΔS / ΔC ≧ 1 (3)
(Where, ΔC is the amount of change in the bentonite concentration (% by weight), ΔV is the amount of change in the funnel viscosity (sec), ΔK is the amount of change in the yield value (lb / 100 ft ² ), and ΔS is the gel strength (lb / 100 ft ^2). ))

ベ ン ト The bentonite used in the present invention may have at least one of the above properties (1) to (3).

{Carboxymethylcellulose or a salt thereof may have a 1% by weight aqueous solution viscosity of 4000 to 12000 mPa · s, and an average degree of substitution can be selected from a range of about 0.5 to 1.5.

割 合 The ratio of carboxymethylcellulose or its salt (A) to bentonite (B) may be (A) / (B) = 40/60 to 90/10 (weight ratio).

添加 The additive of the present invention may further contain sepiolite.

で は In the shield method of the present invention, excavation is performed by using the above-mentioned additives.

る の で In the present invention, since CMC and high-viscosity bentonite are combined, it is possible to achieve both water stoppage and fluidity even in a small amount. Furthermore, it is excellent in fluidity and water retention as compared with conventional additives, and can be pumped even on a gravel ground, and can be excavated smoothly and efficiently.

シ ー ル ド The shield method additive of the present invention is composed of carboxymethylcellulose or a salt thereof and high-viscosity bentonite, and is advantageously used in an earth pressure shield method.

[Carboxymethylcellulose or a salt thereof]
Examples of the salt form of the CMC of the present invention include alkali metal salts such as sodium and potassium, ammonium salts, and the like, and may be a mixture of these salts. As CMC, carboxymethyl cellulose sodium salt is usually used.

The average degree of etherification of CMC (average degree of substitution with respect to the anhydrous glucose unit C6) can be selected, for example, from a range of about 0.5 to 3.0 (mol / C6), and in particular, 0.5 to 2.2 (mol / C6). C6) (for example, 0.5 to 2.0 (mol / C6)), preferably about 0.6 to 1.3 (mol / C6), and more preferably about 0.7 to 1.2 (mol / C6). It is.

For example, the viscosity of a 1% by weight aqueous solution of CMC (25 ° C., B-type viscometer, No. 4 rotor, 60 rpm) is 4000 to 12000 mPa · s, preferably 6000 to 12000 mPa · s, more preferably 8000 to 12,000 mPa · s. It is about 12000 mPa · s (for example, 8000 to 10000 mPa · s). If the viscosity of the 1% by weight aqueous solution of CMC is less than 4000 mPa · s, bleeding is likely to occur when excavated soil is transported by pipe. Further, when the viscosity is higher than 12000 mPa · s, the viscosity of the additive increases and not only the flowability decreases, but also in order to produce high viscosity CMC, it takes a lot of time and cost, and from an economic viewpoint, Is also not advantageous.

The average degree of polymerization of CMC is not particularly limited, but is, for example, about 10 to 1000, preferably about 50 to 900, and more preferably about 200 to 800.

Such a CMC can be obtained by various methods such as a conventional slurry method and a kneader method, for example, a step of reacting cellulose with alkali to produce alkali cellulose (arcelization step), and a reaction between alkali cellulose and monochloroacetic acid. And a step (carboxymethylation step) of producing carboxymethylcellulose by the above method.

As cellulose, various raw materials such as wood pulp and linter pulp can be used. As the alkali, alkali (lithium, potassium, sodium, etc.), ammonia and the like can be used. Sodium is usually used as the alkali. The alkali is usually used as a hydroxide or an aqueous solution.

In the cellulization step, the amount of alkali (such as sodium hydroxide) can be generally selected from the range of about 40 to 80 parts by weight, preferably about 45 to 75 parts by weight, based on 100 parts by weight of cellulose. In the slurry method, the amount of the alkali (such as sodium hydroxide) used is usually 40 to 70 parts by weight, preferably about 45 to 65 parts by weight, based on 100 parts by weight of the cellulose. Alcerization is often performed at a cellulose concentration of about 1 to 7% by weight in the slurry method and at a cellulose concentration of about 10 to 20% by weight in the kneader method. Further, the alkali concentration in the alcerization step varies depending on the slurry method, the kneader method, and the like. In the slurry method, the alkali concentration can be usually performed in an aqueous medium of about 1 to 20% by weight. It can be carried out in an aqueous medium of about 1 to 5% by weight.

The step of forming a cell may be performed in the presence of a suitable solvent. Examples of the solvent include water, alcohols (such as ethanol and isopropanol), ketones (acetone), and cellosolves (such as methyl cellosolve and ethyl cellosolve).

Ｃ The CMC thus produced can be purified by dewatering, washing and drying. If necessary, after the completion of the reaction, it may be treated with a peroxide such as hydrogen peroxide or peracetic acid to adjust the viscosity.

[Bentonite]
Bentonite is a clay having a chemical composition of SiO ₂ and Al ₂ O ₃ and containing montmorillonite as a main component. In addition to montmorillonite, it may contain minerals such as proteinite, quartz, and feldspar. The properties and functions of the same bentonite vary greatly depending on the place of production and brand.

ベ ン ト The bentonite of the present invention has a high viscosity, and is characterized by being able to impart high fluidity, water stoppage, water retention and wettability with a small amount of addition in combination with CMC.

In the bentonite of the present invention, when an aqueous solution thereof is prepared, ΔV / ΔC is 5 or more (for example, 7 to 50), where ΔC is a change in the bentonite concentration (% by weight) and ΔV is a change in the funnel viscosity (sec). ), Preferably 10 or more (for example, 10 to 45), more preferably 12 or more (12 to 40), and particularly about 20 to 40. In addition, (DELTA) V / (DELTA) C of the conventional bentonite is about 0.5-3.5. If ΔV / ΔC is less than 5, sufficient viscosity as an additive cannot be obtained, and the composition is not suitable for pumping.

Further, in the bentonite aqueous solution, assuming that the variation of the yield value (lb / 100 ft ² ) is ΔK, ΔK / ΔC is 7 or more (for example, 8 to 30), preferably 10 or more (for example, 10 to 25), particularly 12 About 20. Note that ΔK / ΔC of conventional bentonite is about 0.2 to 5.

Further, when the amount of change in gel strength (lb / 100 ft ² ) is ΔS, ΔS / ΔC is 1 or more (for example, 2 to 20), preferably 3 or more (for example, 3 to 15), more preferably 4 or more ( For example, about 4 to 15). Note that ΔS / ΔC of the conventional bentonite is about 0 to 0.4.

ベ ン ト The bentonite used in the present invention only needs to have at least one of the above characteristics.

The values of these relational expressions can be easily calculated by measuring the funnel viscosity, the yield value, and the gel strength of a bentonite aqueous solution having a concentration of 2.0 to 4.0% by weight.

ベ ン ト Furthermore, the bentonite used in the present invention has a high apparent viscosity and a high plastic viscosity, and has a small amount of dehydration and a high water retention.

ベ ン ト Such high-viscosity bentonite can be easily obtained, for example, from Kunimine Industries Co., Ltd. under the trade name “Kunigel GS”.

[Ratio between CMC and bentonite]
The ratio of CMC (A) to bentonite (B) used in the present invention is selected from a wide range of about 90/10 to 5/95 (weight ratio) in terms of solid content, depending on the type of ground. it can. Usually, (A) / (B) = 40 / 60-90 / 10 (weight ratio), preferably 40 / 60-80 / 20 (weight ratio), more preferably 50 / 50-80 / 20 (weight ratio). It is about. When the ratio of CMC (A) is less than 40% by weight, the mixed earth and sand obtained by mixing the earth and the additive with the additive is easily separated. On the other hand, when the proportion of CMC (A) is higher than 90% by weight, the viscosity of the additive increases and the fluidity decreases.

シ ー ル ド The additive for the shield method of the present invention is obtained by mixing CMC and bentonite. The additive concentration is appropriately selected depending on the target earth and sand, and can be used after being diluted with water such as tap water to an appropriate range (for example, about 1% to 3% by weight). CMC and bentonite may be mixed together in the form of an aqueous solution or solid, or one of them may be an aqueous solution. In the shield method additive of the present invention, even if the amount used is small, high water stopping property and fluidity can be imparted.

粘度 The viscosity of the shielding method additive of the present invention in a 1.0% by weight aqueous solution is about 800 to 7000 mPa · s, preferably about 1000 to 6500 mPa · s. If the viscosity is less than 800 mPa · s, bleeding is likely to occur due to low viscosity. On the other hand, when the viscosity is higher than 7000 mPa · s, the fluidity is reduced and the pump cannot be pumped.

シ ー ル ド The shield method additive of the present invention may contain a conventional water-soluble polymer compound or clay in addition to CMC and bentonite.

Examples of the water-soluble polymer compound include water-soluble cellulose ethers such as methylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylethylcellulose, sodium polyacrylate, polyacrylamide, sodium alginate, polyvinyl alcohol, and starch. And the like.

Examples of clay include clay, kaolin, Kibushi clay, and Gimello clay.

Furthermore, the additive of the present invention may be used in combination with conventional bentonite. Conventional bentonite includes Hoyo bentonite (Gunma bentonite), Akita bentonite, Yamagata bentonite, Niigata bentonite, and Wyoming bentonite. The ratio between the conventional bentonite (C) and the high-viscosity bentonite (D) used in the present invention can be selected from a wide range that does not impair the water-stopping property, the fluidity, and the like. For example, (C) / (D) = 99/1 to 50/50 (weight ratio), preferably (C) / (D) = 95/5 to 60/40 (weight ratio), more preferably about 90/10 to 70/30 (weight ratio). It is.

The additive for shield method of the present invention may further contain sepiolite. Sepiolite is a fibrous magnesium silicate having a chemical composition of Si ₁₂ Mg ₈ O ₁₂ .nH ₂ O. Sepiolite is relatively unaffected by the electrolyte, can impart salt resistance, and exhibits high gel strength, and can therefore impart fluidity even to ground containing salt such as seawater. The amount of sepiolite used can be selected, for example, from a range of 1 to 50 parts by weight, preferably 3 to 30 parts by weight, particularly about 5 to 25 parts by weight, based on 100 parts by weight of CMC.

シ ー ル ド The additive for shield method of the present invention can be added to earth and sand during excavation and / or earth removal. Since the earth and sand containing the additive of the present invention can achieve both water stoppage and fluidity, it is possible to stabilize the face of the shield machine and to perform pumping. In addition, water retention, wettability, and stability of separation of earth and sand are high, and separation of earth and sand can be effectively prevented. Therefore, the present invention further includes a shield method in which excavation is performed using the additive, particularly a shield method in which excavated earth and sand can be pumped as a slurry at the time of earth removal in the earth pressure system shield method.

The amount of additive, type of soil, can be selected from a wide range depending on the nature, for example, with respect to earth and sand 1 m ^3, injection rate 10 to 60% by volume, preferably 15 to 50 volume%, more preferably 20 About 40% by volume.

The present invention can be applied to various types of ground, for example, ground containing gravel, sand, fine sand, clay, silt, and the like. It is especially effective for excavation of gravel ground.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Examples 1 to 5
(Preparation of additives for shield method)
CMC having a 1% by weight aqueous solution viscosity (25 ° C., B-type viscometer No. 4 rotor, 60 rpm) of 9500 mPa · s and an average degree of substitution of 0.77 (trade name: CMC Daicel <2280>; Daicel Chemical Industries, Ltd.) )) And high-viscosity bentonite (trade name: Kunigel GS, manufactured by Kunimine Industries Co., Ltd.) in the following ratio in terms of solid content, and adding 1.0% by weight of an additive using tap water. An aqueous solution was prepared and the viscosity was measured.

Example 1: CMC / bentonite = 30/70 (weight ratio)
Example 2: CMC / bentonite = 40/60 (weight ratio)
Example 3: CMC / bentonite = 50/50 (weight ratio)
Example 4: CMC / bentonite = 80/20 (weight ratio)
Example 5: CMC / bentonite = 90/10 (weight ratio)

(Test soil)
The composition of the test soil was 30% by weight of gravel (maximum particle size 20mm), 61% by weight of fine sand (maximum particle size 5mm), and 9% by weight of clay and silt (maximum particle size 2mm). The water content was 10% by weight.

(Slump test)
The above additives were mixed with the test soil and the properties of the mixed soil were evaluated according to the concrete slump method of JIS A1101 (using a 15 cm slump cone). The ratio of the additive (aqueous solution) to the test soil is 0% by volume, 15% by volume, 20% by volume, 25% by volume, and 30% by volume with respect to 1000 cm ³ of the test soil. Moreover, the fluidity of the earth and sand was measured for the test earth and sand containing 30% by volume of the additive.

The results are shown in Table 1.

Comparative Example 1
CMC having a 1% by weight aqueous solution viscosity (25 ° C., B-type viscometer No. 4 rotor, 60 rpm) of 9500 mPa · s and an average degree of substitution of 0.77 (trade name: CMC Daicel <2280>; Daicel Chemical Industries, Ltd.) )) Was prepared using tap water to prepare a 1.0% by weight aqueous solution of an additive. The obtained additive was mixed with the test earth and sand in the same manner as in the example, and then a slump test was performed.

Comparative Example 2
A 1.0% by weight aqueous solution of an additive was prepared from high-viscosity bentonite (trade name: Kunigel GS, manufactured by Kunimine Industries Co., Ltd.) using tap water. The obtained additive was mixed with the test earth and sand in the same manner as in the example, and then a slump test was performed.

Comparative Example 3
CMC having a 1% by weight aqueous solution viscosity (25 ° C., B-type viscometer No. 4 rotor, 60 rpm) of 5150 mPa · s and an average degree of substitution of 0.89 (trade name: CMC Daicel <2260>, Daicel Chemical Industries, Ltd. )) And bentonite produced in Gunma were prepared in 1.0% by weight of an additive using tap water. The obtained additive was mixed with the test earth and sand in the same manner as in the example, and then a slump test was performed.

The results are shown in 2.

As is clear from Tables 1 and 2, the earth and sand mixed with the additive of the example showed a higher slump value than the comparative example, and did not cause further material separation, and all were pumpable.

For reference, Table 3 shows the properties of the high-viscosity bentonite of the example and the bentonite produced in Gunma of the comparative example. The measurement conditions were as follows: after preparing the mud by stirring with a homodisper at 5000 rpm for 10 minutes, leaving it to stand for 24 hours, and stirring again for 2 minutes, and then measuring.

Claims (14)

An additive for shielding method comprising carboxymethylcellulose or a salt thereof and bentonite, wherein bentonite has at least one of the properties represented by the following formulas (1) to (3) when an aqueous solution thereof is prepared. Additive for shield method with two properties.
ΔV / ΔC ≧ 5 (1)
ΔK / ΔC ≧ 7 (2)
ΔS / ΔC ≧ 1 (3)
(Where, ΔC is the amount of change in the bentonite concentration (% by weight), ΔV is the amount of change in the funnel viscosity (sec), ΔK is the amount of change in the yield value (lb / 100 ft ² ), and ΔS is the gel strength (lb / 100 ft ^2). )) The additive according to claim 1, wherein ΔV / ΔC is 10 to 45. The additive according to claim 1, wherein ΔK / ΔC is 10 to 25. The additive according to claim 1, wherein ΔS / ΔC is 3 to 15. 2. The additive according to claim 1, wherein the viscosity of a 1% by weight aqueous solution of carboxymethyl cellulose or a salt thereof is 4000 to 12000 mPa · s. 2. The additive according to claim 1, wherein the viscosity of a 1% by weight aqueous solution of carboxymethyl cellulose or a salt thereof is 6,000 to 12,000 mPa · s. The additive according to claim 1, wherein the average degree of substitution of carboxymethylcellulose or a salt thereof is 0.5 to 3.0. 2. The additive according to claim 1, wherein the salt of carboxymethyl cellulose is a sodium salt. The additive for a shield method according to claim 1, wherein the ratio of carboxymethylcellulose or a salt thereof (A) and bentonite (B) is (A) / (B) = 40/60 to 90/10 (weight ratio). The additive for a shield method according to claim 1, wherein the ratio of carboxymethylcellulose or a salt thereof (A) and bentonite (B) is (A) / (B) = 40/60 to 80/20 (weight ratio). 添加 The additive according to claim 1, further comprising sepiolite. {Circle around (2)} An additive for a shielding method comprising carboxymethylcellulose or a salt thereof and bentonite, wherein the viscosity of a 1% by weight aqueous solution of carboxymethylcellulose or a salt thereof is 6,000 to 12000 mPa · s. シ ー ル ド A shield method for excavating using the additive according to claim 1 or 12. 14. The shield method according to claim 13, wherein the additive and the excavated earth and sand are discharged as a slurry by a pump.