JP2003055982A - Friction-reduced underground buried body and skin frictional force reducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a friction-reduced underground buried body allowing a significant reduction of friction in burying by constructing a friction reducing surface treatment agent (surface) layer on the surface of the buried body without requiring a lubricant injection using a compressor or the like or using a sheet. SOLUTION: This friction-reduced underground buried body is used for a method for constructing an underground structure by burying a ring body of split structure in the ground while adding more ring bodies. This buried body comprises a friction cutter formed at least on the lower end part and the surface layer formed of the surface treatment agent containing (a) a water absorptive resin, (b) a hydrophilic binder resin having an acid value of 40-500 mgKOH/g and (c) a solvent as essential components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction reducing underground deposit, and more particularly to a circumferential surface friction reducing technique for reducing friction generated between an outer peripheral surface of the deposit and a surrounding ground at the time of depositing. .

[0002]

2. Description of the Related Art A construction method for digging a submerged body in the ground to construct a structure in the ground is, for example, a caisson construction method in which the ground inside the submerged body is excavated, and the submergence is performed mainly by its own weight, or excavation. Not only that, there is a press-in construction method in which a downward force is applied to the submerged body to submerge it. Also, the force applied is
It may be applied by vibration or rotation as well as pushing.

Further, in the above-mentioned sinking and press-fitting, the conventional method for reducing the friction on the peripheral surface is as follows.
(1) There is a method of providing a friction cutter. That is, as shown in FIG. 4, the lower end portion of the deposit 1 is provided with a narrow and pointed portion called a blade portion 3 in order to reduce the penetration resistance into the ground 2 at the time of depositing. Further, a friction cutter 4 is provided on the outer side of the blade opening portion 3, and as the sinking progresses, the sinker 1 and the surrounding ground 2
A gap 5 is formed between the ground and the ground to reduce friction with the ground 2. It should be noted that some applicants have already proposed a technique of providing friction cutters in multiple stages (Japanese Patent Application No. 8-32779).
9).

Other methods for reducing the friction on the peripheral surface include
(2) There is a method of injecting a peripheral friction reducing material called a lubricant such as bentonite solution into a gap formed between the deposit and the ground by the friction cutter. This lubricant is usually a bentonite-water system, which is simply a mixture of bentonite and water, bentonite, mud oil, hygel and water in a weight ratio of 160: 40: 3: 1900, respectively. It is used as a mixture that is mixed with. Furthermore, "IMG lubricant" (brand name,
The super absorbent polymer is a main component), bentonite, a thickener and water in a weight ratio of, for example, 13: 250: 1: 19.
It is used as a mixed mixture such as 00. Further, (3) there is a method of covering the outer peripheral surface of the deposit with a thin steel plate or a polymer reinforced sheet (for example, called an NF sheet (trade name)) with less friction.

[0005]

However, it is difficult to sufficiently reduce the circumferential surface friction only by installing the friction cutter on the submerged body in the above (1). Since the ground intrudes into the gap between the surface of the deposit and the ground created by the friction cutter (the ground is tightened) to reduce the gap, the effect of the friction cutter may be reduced.

If the friction cutter is used frequently,
Even if the ground is tight and the sinker can be effectively sunk, in that case, the gap between the sinker and the ground formed by the friction cutter after sinking becomes a problem, and the gap is filled after sinking. There is also a problem that the construction becomes very complicated because the work of returning it is necessary.

Further, since the above-mentioned (2) injection of the lubricant is usually performed from the ground to the ground around the deposit body, it is difficult to confirm whether or not the outer peripheral surface of the deposit can be covered with the lubricant. In addition, when not injecting from the ground, it is necessary to preliminarily pipe in the deposit, and thus it becomes necessary to arrange injecting equipment and connect pipes at the construction site. Furthermore, it is pointed out that a large construction space for placing materials such as a compressor is required and that the operation noise of the compressor becomes a noise.

Further, when using the thin steel plate or polymer reinforced sheet (hereinafter referred to as a sheet) of the above (3), it is difficult to attach it to the submerged body, and an air jet is also used for this attachment. It may disturb the surrounding ground. Further, there is a problem that a sheet or the like remains between the deposit and the ground after the deposit.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems. It does not require injection of a lubricant using a compressor or the like, does not use a sheet, and rubs against the surface of a deposit. An object of the present invention is to provide a friction-reducing underground deposit that enables a significant reduction in friction during deposition by applying a reduction surface treatment agent (surface) layer.

In order to solve the above-mentioned problems, the first invention is a friction-reducing underground deposit body used in a construction method for constructing an underground structure by submerging a ring body having a divided structure and submerging it. The friction-reducing underground deposit has a friction cutter formed at least at a lower end portion thereof, and the water-absorbent resin (a) and the acid value of 40 to 500 are further provided on the surface of the deposit.
A friction-reducing underground deposit having a surface layer formed from a surface treatment agent containing a hydrophilic binder resin (b) of mgKOH / g and a solvent (c) as essential components.

As a result, the water-absorbent resin (a) applied to the surface of the friction-reducing underground deposit has an acid value of 40 to 500 mg.
The surface of the surface layer formed from the surface treatment agent containing KOH / g as the hydrophilic binder resin (b) and the solvent (c) as essential components absorbs moisture in the ground, and the surface of the deposit and the ground are separated. By supplying the swollen gel layer exhibiting a large friction reducing effect in a timely manner, it is possible to greatly reduce the frictional force between the surface of the deposit and the ground throughout the duration of the depositing work.

That is, since the friction-reducing underground deposit has a friction cutter formed at least at the lower end portion thereof, a method of constructing an underground structure by submerging into the ground while adding a ring body having a divided structure is provided. In doing
The tip of the deposit will easily enter the ground, and by reducing the ground pressure (earth pressure) applied to the side surface of the deposit, a friction reducing effect will be exhibited. By forming a surface layer of the surface treatment agent on the surface, the above-mentioned friction reducing effect of the swollen gel layer is also exhibited, and as a result, the effect of the friction cutter and the effect of the swollen gel layer are synergistic. Thus, the friction reducing effect is remarkably improved, and the above problems can be solved satisfactorily.

In a second aspect of the present invention, a surface layer made of the surface treatment agent is applied to concrete, steel material, or the surface of concrete or steel material forming the outer peripheral surface of the friction-reducing underground deposit. It is a friction-reducing underground deposit characterized by being formed on the ground. The third invention is
Furthermore, it is a peripheral frictional force reduction construction method characterized in that the friction-reducing underground deposit is sunk in the ground.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A deposit according to the present invention will be described with reference to FIGS. (Overall structure) As shown in FIG.
Has a tubular shape as a whole, and is arranged with the axial direction of the tubular shape being the vertical direction. The submerged body 1 is a synthetic segment, that is, a concrete segment piece (hereinafter simply referred to as a piece) 7 whose outer surface is covered with a steel plate is connected in the ring circumferential direction to assemble a concrete segment which is a short ring body 8. The ring bodies 8 are vertically stacked and connected,
The deposit 1 described above is configured (FIGS. 1A and 1B).
The ring bodies 8 are connected to each other or the pieces 7 are connected to each other by fastening with bolts (not shown). On the outer surface of the steel plate of the piece 7, a surface layer 14 of a surface treatment agent described later is formed.
Is provided.

A ring-shaped blade opening 3 is installed at the lower end of the lowermost ring 8 of the submerged body 1.
The ground will be submerged. The sinking in this embodiment is performed not only by the gravity due to the weight of the concrete segment, but also by a force applied downward by a hydraulic unit (not shown), that is, a pushing force. In parallel with such pushing, the inside of the submerged body 1 is excavated by the bucket 10 of the crane 9 (FIG. 1 (A)).

When the first ring body 8 is sunk, the ring bodies 8 of the next stage are stacked and connected from above, and the pushing and excavation are performed again. At the time of this pushing, the peripheral ground is pushed outward by the friction cutter 4 provided around the outer side of the blade opening 3, and a predetermined gap 5 is formed between the peripheral surface and the outer surface of the deposit 1 (Fig. 1 (B) (C)). By the action of the gap 5, the friction generated between the ground 2 can be reduced.

(Explanation of Urban Ring Press-in Construction Method) This is a typical construction method using a submerged body which is used in a construction method of press-fitting into the ground to construct an underground structure while adding a ring body having a divided structure of the present invention. An example of the urban ring press-fitting method will be described below. The urban ring (press-fitting) construction method, which is a typical construction method using a submerged body that is used in a construction method of press-fitting into the ground and constructing an underground structure, while adding the ring body of the split structure of the present invention, is a ring shape. This is a construction method in which the submerged body segments (Fig. 1 (8)) are sequentially inserted into the ground from the ground surface while being simultaneously excavated with a bucket (Fig. 1 (10)) or the like.

No earth retaining wall is required, and the rings that will be the shafts of the shafts are assembled and pressed in at the site in accordance with the press-fitting. Therefore, it is possible to construct a relatively deep shaft in a small site without the need for pre-drilling. Have advantages. However, in the above construction method,
Since the ring is sunk only by press fitting, the frictional force between the ring and the ground is large, and recently, the number of methods of installing piping between the ring and the ground and injecting lubricant is increasing, so the above features are fully utilized. There is the current situation that it does not exist.

(Explanation on Surface Treatment Agent) At the factory, a water absorbent resin (a) and a hydrophilic binder resin (b) having an acid value of 40 to 500 mgKOH / g are formed on the surface of the steel material which is the outer peripheral surface of the manufactured piece 7. And a surface layer comprising a surface treatment agent containing the solvent (c) as an essential component is applied.

The surface treatment agent of the present invention will be described below. First, the water absorbent resin (a) in the present invention will be described below. Water-absorbent resin (a) used in the present invention
Swells by absorbing water, and the absorption capacity of ion-exchanged water against its own weight is 3 times or more (25 ° C, 1
It is not particularly limited as long as it is a resin of (time). However, water-soluble or hydrophilic compounds (monomer and / or
Or, a synthetic water-absorbent resin obtained by cross-linking a polymer) with a cross-linking agent has a better balance of swelling ratio, water-soluble content, water-absorption rate, strength, etc. than natural water-swellable substances (gelatin, agar, etc.). These are preferable to natural water-swellable substances (gelatin, agar, etc.) because the balance can be easily adjusted.

As the water absorbent resin (a) as described above,
Specifically, for example, poly (meth) acrylic acid crosslinked product,
Crosslinked poly (meth) acrylic acid salt, crosslinked poly (meth) acrylic acid ester having sulfonic acid group, crosslinked poly (meth) acrylic acid ester having polyoxyalkylene group, crosslinked poly (meth) acrylamide, ( Meta)
Copolymerized cross-linked product of acrylate and (meth) acrylamide, hydroxyalkyl (meth) acrylate and (meth)
Copolymerized cross-linked product with acrylic acid salt, polydioxolane cross-linked product, cross-linked polyethylene oxide, cross-linked polyvinyl pyrrolidone, sulfonated polystyrene cross-linked product, cross-linked polyvinyl pyridine, saponified product of starch-poly (meth) acrylonitrile graft copolymer, starch- Poly (meth) acrylic acid (salt) graft cross-linked copolymer, reaction product of polyvinyl alcohol and maleic anhydride (salt), cross-linked polyvinyl alcohol sulfonate, polyvinyl alcohol-acrylic acid graft copolymer, polyisobutylene malein Examples thereof include acid (salt) cross-linked polymers. These water absorbent resins may be used alone or in combination of two or more.

In the present invention, it is preferable to use a salt-resistant water absorbent resin as the water absorbent resin (a). The reason why the salt-resistant water-absorbent resin is preferred is that the salt-resistant water-absorbent resin has a relatively high water absorption capacity of hard water containing a polyvalent metal, and when used as a surface treatment agent, is not significantly affected by the water quality in the soil, This is because it swells sufficiently and can exhibit sufficient friction reducing performance.

The salt-resistant water-absorbent resin according to the present invention is not particularly limited as long as it has a water absorption capacity of 10 times or more (25 ° C., 24 hours) in artificial seawater. Among the resins (a), those having a nonionic group and / or sulfonic acid (salt) group are more preferable, and those having an amide group or a hydroxyalkyl group are even more preferable. Examples of the salt-resistant water-absorbent resin (e) described above include, for example, copolymerized cross-linked products of (meth) acrylate and (meth) acrylamide, hydroxyalkyl (meth) acrylate and (meth) acrylate. Examples thereof include copolymer cross-linked products and vinyl pyrrolidone cross-linked products. Further, those having a polyoxyalkylene group or those having a vinylpyrrolidone ring are particularly preferable. Examples of such a water absorbent resin (a) include a copolymer crosslinked product of a (meth) acrylic acid ester having a methoxypolyoxyalkylene group and a (meth) acrylic acid salt, and a polyvinylpyrrolidone crosslinked product.

These salt-tolerant water-absorbent resins have the properties of water in soil (soft water, hard water, etc.) by using the water-absorbent resin.
It swells up to a certain magnification regardless of the above, and can more reliably exhibit sufficient friction reduction performance. Furthermore, the method for producing the water-absorbent resin (a) according to the present invention is not particularly limited, but for example, a monomer component containing a water-soluble ethylenically unsaturated monomer and, if necessary, a crosslinking agent is used. The method of superposing | polymerizing is mentioned. The water-absorbent resin (a) obtained by (co) polymerizing an ethylenically unsaturated monomer is more excellent in water absorbency against water and is generally inexpensive. The cross-linking agent is not particularly limited.

As the above-mentioned ethylenically unsaturated monomer,
Specifically, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, vinylsulfonic acid, (meth) allylsulfonic acid,
2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid,
2- (meth) acryloylpropane sulfonic acid, and alkali metal salts and ammonium salts of these monomers;
N, N-dimethylaminoethyl (meth) acrylate,
And its quaternary compounds; (meth) acrylamide, N,
(Meth) acrylamides such as N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, diacetone (meth) acrylamide, N-isopropyl (meth) acrylamide, (meth) acryloylmorpholine, and these monomers Derivatives of hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono ( (Meth) acrylate, polyalkylene glycol mono (meth) acrylate such as methoxy polypropylene glycol mono (meth) acrylate; N-vinyl-
N-vinyl monomers such as 2-pyrrolidone and N-vinylsuccinimide; N-vinylformamide, N-vinyl-N
-Methylformamide, N-vinylacetamide, N-
Examples thereof include N-vinylamide monomers such as vinyl-N-methylacetamide; vinylmethyl ether; and the like, but are not particularly limited. These ethylenically unsaturated monomers may be used alone or in combination of two or more.

Of the above-exemplified ethylenically unsaturated monomers, those composed of ethylenically unsaturated monomers having a nonionic group and / or a sulfonic acid (salt) group are more preferable because of high salt resistance. Examples of the monomer include 2-
(Meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2-
(Meth) acryloyl propane sulfonic acid, (meth) acrylamide, hydroxyalkyl (meth) acrylate, methoxy polyethylene glycol mono (meth) acrylate, N-vinyl-2-pyrrolidone and the like can be mentioned. Furthermore, an ethylenically unsaturated monomer having a polyoxyalkylene group or a pyrrolidone ring is particularly preferable.

When two or more ethylenically unsaturated monomers are used in combination as the monomer component, a more preferable combination is, for example, a combination of (meth) acrylic acid alkali metal salt such as sodium acrylate and acrylamide. , A combination of an alkali metal salt of (meth) acrylic acid and methoxypolyethylene glycol mono (meth) acrylate, and the like, but are not particularly limited.

By polymerizing the above monomer components,
A water absorbent resin (a) is obtained. Further, the water absorbent resin (a)
The average molecular weight, shape, average particle size, etc. of the water-absorbent resin (a) may be set according to the composition of the surface treatment agent, the type of binder, the physical properties, the working environment, etc., but are not particularly limited. The average particle diameter of 30 to 800 μm is preferable, 30 to 600 μm is more preferable, and 30 to 400 μm.
m is most preferred.

When the average particle diameter of the water absorbent resin (a) used in the present invention exceeds 800 μm, the particle diameter becomes too large, and the water absorbent resin (a) is added to the solvent (c) solution of the hydrophilic binder resin (b). Particles of the water-absorbent resin (a) tend to settle when mixed, which is not preferable. On the other hand, if the average particle diameter of the water-absorbent resin (a) is less than 30 μm, it becomes very difficult to handle (it easily scatters as fine powder), which is not preferable.

Next, the hydrophilic binder resin (b) having an acid value of 40 to 500 mgKOH / g, which constitutes the surface treating agent of the present invention, will be described. The hydrophilic binder resin (b) used in the present invention has an acid value of 40 to 500 mgK.
There is no particular limitation as long as it is OH / g, has a function of fixing the water absorbent resin (a) to the substrate as a binder, and is soluble in the solvent (c).

The acid value of the hydrophilic binder resin (b) is 40.
If it is less than mgKOH / g, if the hydrophilicity is too low, the swelling of the water absorbent resin (a) will be hindered, the absorption of moisture in the soil will decrease, and the swelling will not be sufficient, thus reducing the friction of the surface treatment agent. Performance will be significantly reduced. On the other hand, when the acid value of the hydrophilic binder resin (b) exceeds 500 mgKOH / g, the hydrophilicity is too high and the adhesion of the binder to the base material when absorbing water in the soil is too low, resulting in a coating film (surface layer). ) The whole is liable to peel off, causing a problem in durability as a surface treatment agent. For the above reasons, the acid value of the hydrophilic binder resin (b) is 40 to 500 mgKOH / g, and it is necessary to have an appropriate hydrophilicity.

The acid value of the hydrophilic binder resin (b) must be 40 to 500 mgKOH / g and 50 to 400 mgKOH in order to have an appropriate hydrophilicity and to maintain the binder function when absorbing water. / G is more preferable, and 70 mg to 300 mg KOH / g is even more preferable.

Next, the glass transition temperature of the hydrophilic binder resin (b) is not particularly limited, but it has high adhesion to the base material (precipitate piece) and is large when the base material (precipitate piece) is deposited. -20 ℃ from the point that it is difficult to peel off in the area
It is preferable to have a glass transition temperature at 120 ° C. If the glass transition temperature is −20 ° C. or lower, the surface treatment agent coating film (surface layer) tends to become sticky, and blocking may occur particularly when the deposited body pieces after coating are stacked and left to stand. Further, since the strength of the coating film (surface layer) for the surface treatment agent is insufficient, peeling is likely to occur when the substrate is submerged in the soil, which is not preferable. From this, it is more preferable that the glass transition temperature is 0 ° C. or higher.

When the glass transition temperature of the hydrophilic binder resin (b) is 120 ° C. or higher, the binder layer becomes too hard, the adhesion to the deposit piece and the flexibility of the surface treatment agent coating film (surface layer). Is not preferable, and peeling and dropping of the water absorbent resin (a) are likely to occur when the depositing piece is submerged in the soil, which is not preferable. From this, it is more preferable that the glass transition temperature is 100 ° C. or lower, and 0 ° C. to 20 ° C.
And a glass transition temperature between 20 ° C. and 100 ° C. are more preferable because the softening component and the shape-retaining component are well balanced.

The weight average molecular weight (Mw) of the hydrophilic binder resin (b) is not particularly limited, but it is 30,000.
The range of 0 to 300,000 is preferable, and 50,000 to
The range of 200,000 is more preferable. By using the resin having the above-mentioned weight average molecular weight, it becomes easy to balance the toughness of the anti-adhesion material with the solubility in alkaline water.

The acid value of the present invention is 40 mgKOH / g to 50
The method for producing the 0 mgKOH / g hydrophilic binder resin (b) is not particularly limited, but the following α, β-unsaturated carboxylic acid monomer and an α, β-unsaturated carboxylic acid monomer copolymerizable therewith A copolymer that can be obtained by polymerization using an unsaturated monomer component composed of a monomer other than is preferable.

For example, the acid value of the present invention is 40 mgKOH /
Examples of the α, β-unsaturated carboxylic acid monomer used for producing the hydrophilic binder resin (b) of g to 500 mg KOH / g include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, etc. Α, β-unsaturated carboxylic acid; maleic anhydride, itaconic anhydride and other α, β-unsaturated carboxylic acid anhydrides; maleic acid monoester, fumaric acid monoester, itaconic acid monoester, etc. α, β- An unsaturated dicarboxylic acid monoester etc. can be mentioned. The α, β-unsaturated carboxylic acid monomer may be only one kind or two or more kinds.
Of these, acrylic acid and / or methacrylic acid, which are acrylic α, β-unsaturated carboxylic acids, are preferably used because they are inexpensive and have good copolymerizability with other unsaturated monomers.

Next, other monomers copolymerizable with the α, β-unsaturated carboxylic acid monomer include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, stearyl acrylate, methyl methacrylate and ethyl. Esters of (meth) acrylic acid with monohydric alcohol having 1 to 18 carbon atoms such as methacrylate, propyl methacrylate, butyl methacrylate, stearyl methacrylate; acrylonitrile,
Nitrile group-containing vinyl monomers such as methacrylonitrile; amide group-containing vinyl monomers such as acrylamide and methacrylamide; hydroxyl group-containing vinyl monomers such as hydroxyethyl acrylate and hydroxypropyl methacrylate; glycidyl methacrylate and the like Epoxy group-containing vinyl monomers; metal salts of α, β-unsaturated carboxylic acids such as zinc acrylate and zinc methacrylate; styrene, α
-Aromatic vinyl monomers such as methylstyrene; Aliphatic vinyl monomers such as vinyl acetate; Halogen-containing vinyl monomers such as vinyl chloride, vinyl bromide, vinyl iodide, vinylidene chloride; Allyl ether Kinds; Maleic acid derivatives such as dialkyl esters of maleic acid; Fumaric acid derivatives such as dialkyl esters of fumaric acid; Maleimide derivatives such as maleimide, N-methylmaleimide, stearylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide; itaconic acid Itaconic acid derivatives such as mono- and dialkyl esters, itaconic amides, itaconic imides, itaconic amide esters; alkenes such as ethylene and propylene; dienes such as butadiene and isoprene; vinyl ethers; 2- (meth) acryloylpropane Sulfonic acid Salt), 3-allyloxy-2
Examples thereof include unsaturated monomers having a sulfonic acid (salt) group such as hydroxypropane sulfonic acid (salt), polyalkylene glycol (meth) acrylates, and the like, and are used in one kind or in two or more kinds. be able to.

Among them, as the (meth) acrylic acid alkyl ester, esters having various properties can be easily obtained, and by appropriately combining them, Tg (hardness, softness) of the binder resin can be obtained. The adhesiveness to the substrate can be easily adjusted, and the copolymerizability with the α, β-unsaturated carboxylic acid monomer is relatively good, which is preferable.

The above-mentioned (meth) acrylic acid alkyl ester is 30% by weight to 1% based on the total amount of other monomers copolymerizable with the α, β-unsaturated carboxylic acid monomer as 100% by weight.
It is preferably used in an amount of 00% by weight, more preferably 50% by weight or more and 100% by weight or more. More preferably 60 to 100% by weight, still more preferably 70 to 1
It is 00% by weight. That is, when an acrylic monomer is used as the other monomer, the acid value of the present invention is 40 to 5
Hydrophilic binder resin (b) which is 00 mgKOH / g
Is a preferred embodiment.

The ratio of the above-mentioned α, β-unsaturated carboxylic acid monomer and the unsaturated monomer component consisting of another monomer copolymerizable therewith is not particularly limited, but for example, α, β-
When the unsaturated monomer component composed of the unsaturated carboxylic acid monomer and another monomer copolymerizable with the unsaturated carboxylic acid monomer is 100% by weight, the amount of the α, β-unsaturated carboxylic acid in all the monomer components is The proportion is preferably 7 to 80% by weight based on the whole unsaturated monomer components. It is more preferably 7 to 50% by weight. More preferably, it is 9 to 30% by weight.

The acid value of the present invention is 40 mg to 500 mgK.
OH / g hydrophilic binder resin (b), that is, other than α, β-unsaturated carboxylic acid monomer used as a raw material when producing a binder resin obtained by polymerizing the above unsaturated monomer component. The amount of the copolymerizable monomer of is 100% by weight of all the unsaturated monomer components composed of the above α, β-unsaturated carboxylic acid monomer and other monomer copolymerizable therewith. Preferably, it is 93 to 2 in all unsaturated monomer components.
0% by weight. It is more preferably 93 to 50% by weight. More preferably, it is 91 to 70% by weight.

Acid value is 40 mgKOH / g to 500 mgK
The method for producing the hydrophilic binder resin (b), which is OH / g, is
The polymerization method is not particularly limited, and generally known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization and suspension polymerization can be used. Among them, solution polymerization in an organic solvent is preferable.

This makes it possible to produce the surface treatment agent of the present invention by directly mixing the water-absorbent resin with the solution or dispersion containing the hydrophilic binder resin (b) obtained by solution polymerization. Because. In addition, examples of the polymerization form include radical polymerization, anionic polymerization, cationic polymerization, coordination polymerization, and the like. Radical polymerization is preferable as an industrial production method.

Examples of the reaction vessel used for producing the raw material polymer include a tank reactor, a kneader, a tubular reactor such as a static mixer, and the like. These reactors can be used together if necessary. A dropping tank is also used if necessary. The pressure in the reaction vessel may be any of reduced pressure, normal pressure and increased pressure.

The radical polymerization initiator used in the radical polymerization is not particularly limited, but specific examples thereof include 2,2'-azobisisobutyronitrile and
Examples thereof include azo initiators such as 2,2′-azobis (2,4-dimethylvaleronitrile); peroxide initiators such as benzoyl peroxide and di-t-butyl peroxide. These radical polymerization initiators are 2
You may use together more than one kind.

The solvent used in the solution polymerization is not particularly limited as long as it does not interfere with the radical polymerization reaction.
For example, alcohols such as methanol, ethanol and isopropyl alcohol; aromatic hydrocarbons such as benzene and toluene; ketones such as acetone and methyl ethyl ketone; aliphatic esters such as ethyl acetate and butyl acetate;
Examples thereof include ethylene glycol and ethylene glycol derivative products such as ethylene glycol monomethyl ether, and propylene glycol derivative products such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate. Two or more kinds of these solvents may be used in combination.

Next, the solvent (c) used in the present invention will be described. The solvent (c) can be used without particular limitation as long as it is a known solvent used for ordinary paints, and for example, one or more of the solvents exemplified in the description of the method for producing an alkali water-soluble resin can be used. It can be used in combination of two or more kinds.

As a method of selecting the solvent (c), it is preferable to select a solvent having a boiling point, safety and the like suitable for coating on the substrate. If you select a solvent with a low boiling point, it will dry quickly, and the coating film (surface layer) can be formed in a short time, making thick coating easy, and if you select a solvent with a high boiling point, the working time can be extended. . By using an organic solvent as a medium, the water-absorbent resin does not swell due to water absorption that occurs when a medium containing water is used, and does not form a gel, which facilitates the coating operation. In addition, if a highly volatile solvent such as methyl ethyl ketone or methanol is used,
Since it dries in about a minute and dries much faster than when water is used as the medium, it is possible to move quickly to the next operation or process, which significantly shortens the construction period or the time required for coating the substrate. can do.

The surface-treating agent of the present invention does not impair the characteristics of the surface-treating agent as long as it contains the water-absorbent resin (a), the hydrophilic binder resin (b) and the solvent (c) described above as essential components. However, other additives (h) may include other resins, pigments, various stabilizers, various fillers, and the like.

The water-absorbent resin (a) having an acid value of 40 to 50
The ratio of the hydrophilic binder (b) and the solvent (c) to the other additive (h) of 0 mgKOH / g is not particularly limited, but in order to fully exert the characteristics of the surface treatment agent of the present invention, water absorption Resin (a), hydrophilic binder (b)
And the weight ratio of the combined solvent (c) to the whole ([(a) + (b) + (c)] / [(a) + (b) +
(C) + (h)] × 100 (%)) is preferably 50% or more, more preferably 70% or more, most preferably 80% or more.

Further, the ratio of the water-absorbent resin (a), the hydrophilic binder (b), the solvent (c) and the other additives (h) is not particularly limited, but the characteristics of the surface treatment agent of the present invention are not absent. In order to exhibit, the water-absorbent resin (a) is 5-60
% By weight, the hydrophilic binder (b) is 10 to 70% by weight,
The solvent (c) is preferably 5 to 70% by weight, the other additive (h) is preferably 0 to 50% by weight, and the water absorbent resin (a) is 10 to 10% by weight.
More preferably, 50 wt%, the hydrophilic binder (b) is 10 to 60 wt%, the solvent (c) is 10 to 60 wt%, and the other additives (h) are 0 to 30 wt%.

The method of applying the surface treatment agent of the present invention to the deposit piece is not particularly limited, and the surface treatment agent may be directly applied to the substrate, or a film formed separately may be used as a base with an adhesive or the like. You can attach it to the material. However, it is preferable to apply it directly to the base material from the viewpoints of ease of construction and adhesion to the base material.

The method of applying the surface treatment agent to the substrate is not particularly limited as long as it is a known application method. For example, a brush, a roller or the like may be used, or a spraying device such as a resin gun may be used. You may spray paint.

(Operation of Embodiment) As described above, the surface treatment agent of the present application is previously applied to the outer surface of the piece 7 constituting the deposit 1, that is, the concrete, the steel plate, or the coated surface of the concrete or the steel plate in the factory. Coating film (surface layer) 1
Install 4. The pieces 7 transported to the site are connected to form the submerged body 1 and are submerged in the ground as described above (FIG. 1 (A)). Along with this deposition, the ground is pushed away by the friction cutter 4 at the lower end of the deposit 1 to form a gap 5, and at the same time, the surface treatment agent coating film (surface layer) 14 on the outer peripheral surface of the deposit 1 is formed in the ground. To absorb and swell the groundwater, and form and supply a swollen gel layer having a remarkable friction reducing effect between the outer surface of the piece 7 and the ground. The water absorption rate of the surface treatment agent from the ground is of course affected by the groundwater content in the ground, etc., but the surface treatment agent of the present application is not limited to the type of the water absorbent resin (a) and the hydrophilic binder resin (b). By freely combining the acid value and the ratio (a) / (b), it is possible to meet the conditions such as the groundwater content in all ground. Also, if there is no groundwater leaching into the ground, it is possible to form a swelling gel layer by supplying water to the surface treatment agent from the ground along the outer peripheral surface of the deposit (or in advance). Is.

In the swollen gel layer formed by absorbing water and swelling, the portion in contact with the surrounding ground is flow-deformed with almost no force in the swollen layer when the deposit is sunk. As a result, the submerged body can be sunk without almost transmitting the frictional force of the ground to the submerged body, and the frictional force reduction effect can be exhibited. In actual use, consider the ground conditions and construction conditions to determine the optimum surface treatment agent specifications and application range.

As described above, by using the surface treating agent of the present invention, the effect of reducing the frictional force on the peripheral surface, which is equal to or more than that in the case of injecting a lubricant, using a thin steel plate or a polymer sheet, can be exhibited. Also, regarding the friction cutter, it is also possible to omit the intermediate friction cutter, and to reduce the friction cutter width to the extent that the contact grout after depositing the deposit can be made unnecessary. It is possible by examining.

The surface treatment agent coating film (surface layer) 1 of the present application
Due to the water swelling of No. 4, a swollen gel layer 15 (FIG. 3) is formed on the outer surface of the deposit 1, and the friction cutter 4 and the friction reducing effect can be synergistically exhibited.

(Effects of the Embodiment) According to the above embodiments, it is not necessary to inject a lubricant using a compressor or the like as in the conventional case. Therefore, a lubricant injecting facility (compressor,
(Piping, etc.) and its setup (pipe installation, pipe connection, etc.) can be saved, cost can be reduced, and the space for the lubricant injection equipment is not required, so construction can be performed in a smaller space, compressor noise Since there is no need for thin steel plates and polymer reinforced sheets as in the past, there is no need for an air jet, and the surrounding ground is not disturbed.
A great effect can be obtained in many respects such that the sheet does not remain between the deposit and the ground.

(Other Embodiments) In the above embodiments, the piece 7 is a synthetic segment, that is, a segment made of reinforced concrete (RC) whose outer surface is covered with a steel plate. Although the surface treatment agent coating film (surface layer) 14 is provided, the piece 7 may be a steel segment or a concrete segment in other embodiments. The surface-treating agent coating film (surface layer) is applied to the surface of the steel material, the coated steel material in advance, or the outer surface of precast concrete or painted precast concrete.

(Preferred Embodiment) In a preferred embodiment of the friction-reducing underground deposit, the surface layer formed of the surface treatment agent forms the outer peripheral surface of the friction-reducing underground deposit. , Steel, or a form formed on a coating film applied to concrete or steel. With such an embodiment, as described above, the effects of the present invention can be sufficiently exhibited.

Further, according to the peripheral frictional force reduction construction method of burying the friction-reducing underground deposit body in the ground, the structure is built in the ground by burying the deposit body in the ground by the caisson method, the press-fitting method and the like. In the construction method described above, it is possible to significantly reduce the friction at the time of sunk, and it is possible to perform the construction more efficiently and easily than before, while suppressing the influence on the surroundings. Such a method for reducing the frictional force on the peripheral surface is also one of the present inventions.

[0063]

[Examples] The following are examples. The present invention will be described more specifically, but the present invention is not limited thereto. The acid value of the hydrophilic binder resin (b) is JI
SK6901 "Liquid unsaturated polyester resin test method"
It was measured based on the test method described in 4.3 of the application clause. However, when the hydrophilic binder resin (b) does not dissolve in the solvent specified by the test method, a solvent that dissolves is appropriately used and measurement is performed according to the above test method.

[Production Example 1] A water absorbent resin was prepared by the following method. That is, a kneader equipped with a thermometer and a blade (stirring blade), the inner surface of which was lined with ethylene trifluoride and having a capacity of 1.5 L was used as a reactor, and a methoxy polyethylene glycol methacrylate was used in the reactor. (Molecular weight 512) 58.38 g, methacrylic acid (molecular weight 86.09) 3.56 g, sodium methacrylate (molecular weight 108) 212.69 g, polyethylene glycol diacrylate 1.4 as a crosslinking agent
and 350.37 g of ion-exchanged water as a solvent were charged. The ratio of the cross-linking agent in the monomer component is 0.14 mol%.

By flowing hot water of 50 ° C. into the jacket, the above aqueous solution was stirred under a nitrogen gas stream while stirring.
Heated to ° C. Next, the polymerization initiator 2,2′-azobis- (2-amidinopropane) dihydrochloride (molecular weight 2
71.27, chemical product V-50 manufactured by Wako Pure Chemical Industries, Ltd.)
10 g of a 10.0 wt% aqueous solution was added and stirred for 10 seconds, then the stirring was stopped and the mixture was allowed to stand. The ratio of the polymerization initiator to the monomer component is 0.2 mol%.

The polymerization reaction was started immediately after the addition of the polymerization initiator, and after 90 minutes, the internal temperature reached 100 ° C. (peak temperature). Then, the contents were aged for 30 minutes while flowing warm water of 80 ° C. through the jacket. Thereby, a hydrogel was obtained. After completion of the reaction, the blade was rotated to disintegrate the hydrous gel to a fine state, and then the reactor was inverted to take out the hydrous gel.

The hydrogel thus obtained was dried at 140 ° C. for 3 hours using a hot air circulation dryer. After drying, the dried product was crushed using a desktop simple crusher (manufactured by Kyoritsu Riko Co., Ltd.). As a result, a water absorbent resin (1) having an average particle diameter of 170 μm was obtained.

Production Example 2 Hydrophilic Binder Resin (b)
Was prepared by the following method. That is, in a tank-type reactor having a capacity of 50 L equipped with a thermometer and a dropping device, acrylic acid of 0.
50 kg, ethyl acrylate 2.40 kg, methyl methacrylate 0.20 kg, polymerization initiator 2,2′-azobis- (2,4-dimethylvaleronitrile) 12 g,
Also, 3 kg of a solvent, methyl alcohol, was charged.
In addition, 1.15 kg of acrylic acid, 1.9 kg of methyl acrylate, 3.95 k of methyl methacrylate were added to the dropping device.
g, 2,2'-azobis- (2,4-dimethylvaleronitrile) 25 g, and a mixed solution of 7 kg of methyl alcohol was charged.

The above methyl alcohol solution was heated to 65 ° C. with stirring under a nitrogen gas atmosphere and reacted for 20 minutes. Thereby, the polymerization rate of the content was adjusted to 70%. Subsequently, while maintaining the internal temperature at 65 ° C., the above mixed solution was uniformly added dropwise over 2 hours from the dropping device. After the dropping was completed, the contents were aged at 65 ° C. for another 3 hours. After the reaction was completed, 10 kg of methyl alcohol was mixed with the content to obtain a 33 wt% methyl alcohol solution of the hydrophilic binder resin (1).

The hydrophilic binder resin (1) thus obtained had a weight average molecular weight of 140,000 and an acid value of 129 mgKOH.
/ G. As a result of differential scanning calorimetry of the hydrophilic binder resin (1), the hydrophilic binder resin (1) had two glass transition temperatures in the range of -80 ° C to 120 ° C. The resulting methyl alcohol solution of hydrophilic binder resin (1) was desolvated using a twin-screw extruder to obtain cylindrical pellets having a diameter of 3 mm and a length of 3 mm. 10 g of the pellets were put into 500 g of a 0.4 wt% sodium hydroxide aqueous solution in a beaker at room temperature and stirred with a magnetic stirrer, and after 4 hours, they were completely dissolved.

Production Example 3 Hydrophilic Binder Resin (b)
Was prepared by the following method. That is, in a tank-type reactor having a capacity of 50 L equipped with a thermometer and a dropping device, acrylic acid of 0.
58 kg, methyl acrylate 1.925 kg, ethyl acrylate 2.15 kg, methyl methacrylate 2.95 k
g, the polymerization initiator 2,2′-azobis- (2,4-
33 g of dimethylvaleronitrile) and 15 kg of methyl alcohol as a solvent were charged.

The above methyl alcohol solution was heated to 65 ° C. with stirring under a nitrogen gas atmosphere and reacted for 5 hours. Thus, a 33 wt% methyl alcohol solution of the hydrophilic binder resin (2) was obtained. The obtained binder resin has a weight average molecular weight of 110,000 and an acid value of 55 mgK.
It was OH / g.

Production Example 4 Hydrophilic Binder Resin (b)
Was prepared by the following method. That is, acrylic acid 4. was added to a tank reactor having a capacity of 50 L equipped with a thermometer and a dropping device.
40 kg, methyl acrylate 1.005 kg, ethyl acrylate 2.15 kg, polymerization initiator 2,2′-azobis- (2,4-dimethylvaleronitrile) 33 g,
Also, 15 kg of methyl alcohol, which is a solvent, was charged.

The above methyl alcohol solution was heated to 65 ° C. with stirring under a nitrogen gas atmosphere and reacted for 5 hours. As a result, a 33 wt% methyl alcohol solution of the hydrophilic binder resin (3) was obtained. The hydrophilic binder resin (3) thus obtained had a weight average molecular weight of 120,000 and an acid value of 450 mgKOH / g.

Comparative Production Example 1 A comparative binder resin was prepared by the following method. That is, acrylic acid 0.2 was added to a tank-type reactor having a capacity of 50 L equipped with a thermometer and a dropping device.
0 kg, methyl acrylate 1.925 kg, ethyl acrylate 2.15 kg, methyl methacrylate 3.33 k
g, the polymerization initiator 2,2′-azobis- (2,4-
33 g of dimethylvaleronitrile) and 15 kg of methyl alcohol as a solvent were charged.

The above methyl alcohol solution was heated to 65 ° C. with stirring under a nitrogen gas atmosphere and reacted for 5 hours. As a result, a 33 wt% methyl alcohol solution of the comparative binder resin (1) was obtained. The comparative binder resin (1) obtained had a weight average molecular weight of 100,000 and an acid value of 20 mgKOH / g.

Comparative Production Example 2 A binder resin for comparison was prepared by the following method. That is, acrylic acid 5.8 was added to a tank-type reactor having a capacity of 50 L equipped with a thermometer and a dropping device.
67 kg, ethyl acrylate 1.738 kg, polymerization initiator 2,2′-azobis- (2,4-dimethylvaleronitrile) 33 g, and solvent methyl alcohol 15 kg were charged.

The above methyl alcohol solution was heated to 65 ° C. with stirring under a nitrogen gas atmosphere and reacted for 5 hours. As a result, a 33 wt% methyl alcohol solution of the binder resin (2) for comparison was obtained. The binder resin obtained had a weight average molecular weight of 110,000 and an acid value of 605 mg.
It was KOH / g.

Example 1 50 parts by weight of the water absorbent resin (1) produced in Production Example 1 and 33% by weight methyl alcohol solution 1 of the hydrophilic binder resin (1) produced in Production Example 2
50 parts by weight and 50 parts of 2-butanone as a solvent are mixed.
By dispersing, the surface treatment agent according to the present invention (1)
Got

Next, the surface treatment agent (1) was applied to a thickness of 1 m.
m, diameter 50 mm, length 600 mm steel pipe surface (inner,
The coating amount was 1.2 kg / m ^{2 on} both outsides, and the surface was coated with a uniform brush, left overnight, and dried to obtain a steel pipe (1) on which a surface treatment agent was applied. Next, the steel pipe (1) on which the surface treatment agent has been applied is placed on the site of Nippon Shokubai Co., Ltd. (Suita City, Osaka Prefecture).
Standing vertically on the ground, rotating and pressing it into the ground, the pressure input at that time was measured by measuring. Press fit is 2
The pressure input at that time was summarized in Table 2.

For the press-in, one press-in is about 10 cm,
The pressure input (kg) at the time of press-fitting about 5 cm, which is almost the middle, was taken as the value of the pressure input (kg). Further, the steel pipe (1) on which the surface treatment agent was applied was prepared by swelling the surface (both the inside and outside of the pipe) with water 10 minutes before press fitting.

As a result, as can be seen from Table 2, the press-fitting force is almost constant regardless of the press-fitting depth, and the press-fitting force gradually increases depending on the press-fitting depth. Comparative Example 1 (uncoated steel pipe)
It can be seen that the frictional force between the side surface of the steel pipe / ground pipe is almost zero even when compared with. In addition, since the pressure input remains almost unchanged from the 1st to the 3rd days, the friction reduction effect is almost at the initial stage on the 2nd and 3rd days, even from the 1st day, near the tip of the steel pipe buried in the ground. You can see that it is maintained as well.
This is because the surface treatment agent applied to the steel pipe has a sustained release property and absorbs moisture in the ground, so that the steel pipe surface (surface treatment agent surface) / between the ground on the second and third days as well. It is considered that this is because the swollen gel layer having a large friction reducing effect is supplied.

Examples 2 and 3 Instead of using the surface-treated steel pipe (1) coated with the surface-treating agent (1) in Example 1, the surface-treating agent (2) having the composition shown in Table 1 or Surface-treated steel pipe coated with (3) (2) or (3)
The same operation as in Example 1 was carried out except that was used, and the pressure input at the time of press-fitting is summarized in Table 2.

As can be seen from Table 2, in Examples (2) and (3) using the surface-treating agents (2) and (3), almost the same as the above Example (1) However, it can be seen that there is almost no increase in the press-fitting force due to the press-fitting depth, and the frictional force between the steel pipe and the ground is almost 0, compared with Comparative Example 1.

[Comparative Example 1] Example 1 was the same as Example 1 except that the untreated steel pipe coated with nothing was used instead of the surface-treated steel pipe (1) coated with the surface treatment agent (1). The same operation was performed, and the pressure input at the time of press-fitting is summarized in Table 2.

As can be seen from Table 2, the press-fitting force of the uncoated steel pipe clearly increases with the press-fitting depth, and the increase is almost proportional to the press-fitting depth. It is considered that this is because a large frictional force acts between the steel pipe and the ground during press fitting, so that the press input increases in proportion to the surface area of the steel pipe pressed into the ground.

Comparative Examples 2 and 3 Instead of using the surface-treated steel pipe (1) coated with the surface-treating agent (1) in Example 1, a comparative surface-treating agent (1) having the composition shown in Table 1 was used. ) Or (2) was used, the same operation as in Example 1 was performed, and the press-fitting force during the press-fitting is summarized in Table 2.

As can be seen from Table 2, in Comparative Examples 2 and 3, the press-in force and its increase are smaller than those in Comparative Example 1 using the uncoated steel pipe, but the press-in force is clearly increased.
It is expected that the causes are different between Comparative Examples 2 and 3, but it is considered that a certain amount of frictional force acts between the steel pipe and the ground in both cases.

In Comparative Example 2, since the acid value of the binder resin of the surface treatment agent is too low (20 mgKOH / g), it is considered that the surface treatment agent cannot sufficiently swell with water and the effect of reducing the friction on the surface is small. On the other hand, in Comparative Example 3, conversely, the acid value of the binder resin of the surface treatment agent is too high (605 mg
Since KOH / g), the entire coating film (surface layer) easily swells due to one-time water absorption, and most of the coating film (surface layer) peels and disappears with one press-fitting. It is considered that this is because a portion where the friction reducing effect is not gradually generated from a portion near the tip of the. In any case, it is clear that the friction reducing effect, which is a feature of the present application, is large, has a sustained release property, and cannot maintain the high friction reducing effect throughout the press-fitting time (3 days this time). .

The composition of the surface treatment agent used in Examples and Comparative Examples is shown in Table 1, and the steel pipe was press-fitted into the ground, and the pressure input at that time was measured.

[0091]

[Table 1]

[0092]

[Table 2]

[0093]

As described above, by using the submerged body of the present invention in the construction method of constructing an underground structure by submerging the ring body of a divided structure into another while constructing the underground structure, Even without injecting a lubricant using a compressor or the like, a water absorbent resin (a) preliminarily applied to the outer surface of the deposit, a hydrophilic binder resin (b) having an acid value of 40 to 500 mgKOH / g, and a solvent Since the surface treatment agent containing (c) as an essential component absorbs moisture in the ground or newly supplied water, a swollen gel layer having high lubricating performance is formed between the ground body and the ground, so that the ground body The frictional force on the peripheral surface is reduced, and it can be easily sunk. As a result, it is not necessary to provide piping to the deposit, and there is no need to arrange injection equipment or connect pipes at the construction site. Furthermore, there is no need for a large space for placing materials such as a compressor. There is also no noise from the compressor. Further, it is not necessary to use a thin steel plate or a polymer reinforced sheet as in the conventional case, and it is possible to avoid that a solid sheet remains between the deposit and the ground after the deposit.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the present invention,
(A) is a side view in which a part of the overall outline is shown in a vertical section,
(B) is a partially enlarged view of (A), and (C) is a partially enlarged view of (B).

FIG. 2 is an enlarged perspective view of an essential part of FIG.

FIG. 3 is a conceptual diagram showing an operation of one embodiment of the present invention and is a diagram corresponding to FIG. 1 (C).

FIG. 4 is a vertical cross-sectional view of a deposit body having a friction cutter provided at a conventional blade opening portion.

[Explanation of symbols]

1 sinking body 2 ground 3 blade 4 friction cutter 6 gap 7 split ring (piece) 8 ring body 9 cranes 10 buckets (excavator) 11 Friction cutter in the middle 12 plate materials 13 volt 14 Surface treatment agent coating (surface layer) 15 Swelling gel layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Akira Hattori             4-1-1 Koraibashi, Chuo-ku, Osaka City, Osaka Prefecture               Nippon Shokubai Co., Ltd. (72) Inventor Kazuyoshi Sato             6100, Mikkajiri, Kumagaya-shi, Saitama Japan Steel             Tube Light Steel Co., Ltd.

Claims (3)

[Claims] 1. A friction-reducing underground deposit used in a construction method for constructing an underground structure by submerging a ring body having a split structure, the friction-reducing underground deposit comprising: It has a friction cutter formed at least at its lower end, and further has a water absorbent resin (a) and an acid value of 40
A friction-reducing underground deposit having a surface layer formed of a surface treatment agent containing a hydrophilic binder resin (b) of ~ 500 mgKOH / g and a solvent (c) as essential components. 2. The surface layer is formed on concrete, steel material, or a coating film applied to concrete or steel material, which forms an outer peripheral surface of the friction-reducing underground deposit. The friction-reducing underground deposit according to claim 1. 3. A method for reducing frictional force on a peripheral surface, wherein the friction-reducing underground deposit according to claim 1 or 2 is submerged in the ground.