JP5674423B2 - Ground improvement method in caisson method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a ground reforming method around a caisson that has been laid using a friction reducing sheet that reduces sliding friction between the ground and a caisson housing.

  For example, when building a bridge pier in the ground or on the seabed, or when excavating a shaft for starting or reaching in shield construction, a structure with an inner blade-like edge formed at the tip, which has been conventionally called “caisson” A frame is used, and the “Caisson Method” using this “Caisson” is implemented. The “caisson method” includes, for example, a pneumatic caisson method, a press-in caisson method, and a PC well method.

"Pneumatic caisson method" is to set up an airtight work room at the lower part of the caisson, send compressed air into the work room, perform excavation work while preventing ingress of groundwater, and sink the caisson to a predetermined depth It is a construction method.
The "press-in caisson method" uses the caisson's own weight to press-sink the caisson into the ground, and the "open-type press-in caisson method" uses a hydraulic jack to press-sink the caisson into the ground. Press-in caisson method called “Caisson method”, “Air-type press-in caisson method (pneumatic caisson method combined with press-in method)” that presses and sinks caisson into the ground using air, or press-in caisson with a combination of these There is a construction method.

  Of these, if the “hydraulic press-fitting caisson method” is taken as an example, a rod-like support member called a “press-fit reaction force anchor” that has been driven in advance outside the excavation site is supported by a hydraulic jack, etc. Is hydraulically driven to cause the "caisson" to be pressed and settled by a predetermined stroke in the ground or on the sea floor. Then, the ground inside the caisson was excavated and discharged using a clamshell bucket or the like. In addition, by placing the succeeding chassis precast on the caisson that has been pressed and settled for a predetermined stroke and repeating the caisson press-in, mud excavation and discharge, and the subsequent expansion of the succeeding chassis, the predetermined depth is finally reached. A caisson shaft was built.

  The “PC well method” is a method in which the caisson is constituted by a precast member in each of the above-described methods. For example, a caisson is constructed by stacking cylindrical precast members and introducing stress by a post-tension method. Is a method in which a ground anchor or the like is used as a reaction force to press fit and settle.

In such a caisson method, the frictional resistance between the ground and the caisson housing generated when the caisson housing sinks or between the ground and the following housing is a problem.
In order to solve the problem of frictional resistance between the ground and the subsequent frame, the present inventors attached a friction reduction sheet unit to the outer peripheral surface of the tip of the caisson that is in sliding contact with the ground. A caisson method has been developed in which the friction reducing sheet is unwound and used so that the friction reducing sheet is gradually drawn out into the ground to reduce the sliding resistance between the ground and the caisson (Patent Document 1).

JP 2007-332554 A

  Here, in the caisson method using the friction reducing sheet, the sliding resistance between the ground and the caisson is reduced by the friction reducing effect of the friction reducing sheet. Later, if the friction reducing effect of the friction reducing sheet remains on the ground around the caisson, there is a concern that the stability and supporting force of the structure to be constructed may be reduced.

  In view of the above problems, the object of the present invention is to construct a caisson structure such as a caisson shaft or a caisson foundation by a caisson method by reducing sliding contact resistance between the ground and the caisson using a friction reducing sheet. An object of the present invention is to provide a ground reforming method in the caisson method that can eliminate the friction reducing effect of the ground around the caisson and enhance the stability of the caisson structure that has been laid.

  In order to solve the above-described problem, the ground reforming method in the caisson method according to the first aspect of the present invention is that the caisson structure is submerged into the ground by a predetermined stroke to construct a caisson structure having a predetermined depth. A caisson formed by interposing a friction reducing sheet having a friction reducing material for reducing sliding contact resistance between the ground and the caisson housing between the caisson housing and the caisson housing. The structure is characterized in that a friction reduction effect invalidation process is performed to eliminate the friction reduction effect of the friction reduction material of the friction reduction sheet.

  According to this aspect, after the construction of the caisson structure (caisson shaft, caisson foundation, etc.), the friction reducing effect is nullified to eliminate the friction reducing effect of the friction reducing material of the friction reducing sheet. And support for the structure to be constructed can be increased.

The ground reforming method according to the second aspect of the present invention is the ground reforming method according to the caisson method of the first aspect, wherein the friction reducing effect invalidating process is performed on the friction reducing material of the friction reducing sheet. It is characterized in that it is carried out by applying a friction reducing effect nullifying component that eliminates the friction reducing effect.
According to this aspect, the same effect as that of the first aspect can be obtained.

  The ground reforming method according to the third aspect of the present invention is the ground reforming method according to the caisson method of the second aspect, wherein the friction reducing material swells when it comes into contact with water, and expresses a friction reducing function by this swelling. The friction reducing effect invalidating component is formed by removing water from the swollen friction reducing material and eliminating the friction reducing function of the friction reducing material. It is.

The friction reducing material that swells when in contact with water and exhibits a friction reducing function due to this swelling is excellent in reducing the sliding friction with the caisson, and the sliding resistance between the ground and the caisson is excellent. Avoidance can be performed effectively.
And, as a friction reducing effect nullifying component that eliminates the friction reducing function of the friction reducing material, by using a component that acts to remove water from the swollen friction reducing material, from the swollen state that expresses the friction reducing function The non-swelled state in which the friction reducing function is lost can be surely lost.

  The ground reforming method according to the fourth aspect of the present invention is the ground reforming method according to the caisson method of the third aspect, wherein as the friction reducing effect nullifying component, calcium carbonate, calcium oxide, calcium hydroxide, polychlorinated Aluminum, aluminum sulfate, aluminum oxide, ferric chloride, calcium chloride, magnesium chloride, calcium acetate, magnesium acetate, polycondensate of amine compound and epichlorohydrin, polymer of cationic vinyl monomer, cationic vinyl monomer It is characterized by using at least one substance selected from the following copolymers.

  According to this aspect, as the friction reducing effect invalidating component, calcium carbonate, calcium oxide, calcium hydroxide, polyaluminum chloride, aluminum sulfate, aluminum oxide, ferric chloride, calcium chloride, magnesium chloride, calcium acetate, acetic acid Effective from swollen friction reducing material by using at least one substance selected from magnesium, amine compound and epichlorohydrin polycondensate, cationic vinyl monomer polymer, cationic vinyl monomer copolymer Thus, water can be released and the friction reducing material can be brought into a non-swelled state in which the friction reducing function is lost. In particular, a divalent or trivalent metal salt is preferably used, and calcium carbonate is particularly preferably used.

  The ground reforming method according to the fifth aspect of the present invention is the ground reforming method in the caisson method according to any one of the second to fourth aspects, wherein the friction reducing effect invalidating process is the friction reducing method. A grout material containing an effect nullifying component is injected between the ground and the caisson housing.

  According to this aspect, in addition to the effect similar to the effect of any one of the first to fourth aspects, the grout material including the friction reducing effect nullifying component is injected between the ground and the caisson housing. By eliminating the friction reduction effect of the friction reduction material by the friction reduction effect invalidating component, at the same time, the contact grout filling between the ground and the caisson housing is performed by the grout material, and the caisson that has been deposited is stabilized. Can be achieved.

  The ground reforming method in the caisson method according to the sixth aspect of the present invention is the ground reforming method according to the fifth aspect, further comprising an admixture for improving the fluidity of the grout material in addition to the grout material. It is characterized by doing.

As grout materials, mortar grout materials such as cement bentonite (hereinafter sometimes referred to as CB), polymer cement grout materials using synthetic resins, plastic grout materials using water glass, etc. Is used.
And the intensity | strength after hardening of the said grout material is decided by the water cement ratio of the said grout material. Accordingly, the water cement ratio is set to a predetermined range (usually 165% to 78%) in order to give the cured grout material sufficient strength. The predetermined range of the water-cement ratio can be changed depending on the strength required for the grout material after curing, and can generally be set in the range of about 170% to 70%.

  Here, for example, if a powder friction reducing effect nullifying component is added to a grout material having a predetermined water cement ratio, the viscosity of the grout material is increased, that is, the fluidity is lowered, and the grout material is injected. It may be difficult to do. When water is added, the fluidity is increased. However, when a large amount of water is added, the water-cement ratio increases, the strength of the grout material decreases, and at the same time, the water and the cement tend to be easily separated.

According to this aspect, by adding the admixture that improves the fluidity of the grout material, the fluidity of the grout material can be ensured without changing the water-cement ratio of the grout material.
For example, when calcium carbonate is used as the friction reducing effect nullifying component, the flowability of the grout material can be improved by adding a polycarboxylate type polymer surfactant with little risk of separation of water and cement. Can be improved.

  The ground reforming method according to the seventh aspect of the present invention is the ground reforming method in the caisson method according to any one of the second to fourth aspects, wherein the friction reducing effect invalidating process is the friction reducing method. A grout filling step in which a neutralizing agent containing an effect invalidating component is injected between the ground and the caisson enclosure, and after the friction reducing effect invalidation treatment, a grout material is injected between the ground and the caisson enclosure. It is characterized by performing.

According to this aspect, the friction reducing effect is invalidated by injecting a neutralizing agent containing the friction reducing effect invalidating component between the ground and the caisson housing to ensure the friction reducing function of the friction reducing material. Then, a grout filling process (contact grout) is performed using a normal grout material, and the caisson deposited can be stabilized.
In the case of this aspect, since the friction reducing effect nullifying component is not added to the grout material, there is no problem that the fluidity of the grout material is lowered by the addition of the friction reducing effect invalidating component as described above.

  According to the present invention, after the caisson is laid, the friction reducing effect is nullified by eliminating the friction reducing effect of the friction reducing material of the friction reducing sheet, so that the stability of the caisson laid and the supporting force for the structure to be constructed are increased. Can be increased.

It is a sectional side view which shows an example of the mechanical equipment used for construction of the caisson structure by a press fit caisson method. It is a top view which shows an example of the mechanical equipment used for construction | assembly of the caisson structure by a press fit caisson method. It is a sectional side view which shows an example of the caisson frame used for the ground improvement method in the caisson method of this invention. It is a cross-sectional view which shows an example of the caisson frame used for the ground improvement method in the caisson method of this invention. It is a sectional side view which shows the extension state of the friction reduction sheet | seat drawn out with the press injection sedimentation of a caisson housing. It is a perspective view which shows the various aspect of the caisson structure constructed | assembled by a caisson housing. It is a sectional side view showing an example of a friction reduction sheet unit. It is a sectional side view of the caisson housing used for description of friction reduction effect invalidation processing.

Hereinafter, the ground improvement method in the caisson method according to the present invention will be described with reference to examples. Although the press-in caisson method will be described as an example of the caisson method, it goes without saying that the present invention is not limited to the press-in caisson method, and can be applied to the above-described pneumatic caisson method and PC well method.
First, the outline | summary of the press-in caisson method for constructing the caisson shaft which performs the ground improvement method in the caisson method according to the present invention and the mechanical equipment necessary for executing the press-in caisson method will be described.

  FIG. 1 is a side sectional view showing an example of mechanical equipment used for construction of caisson structure by press-fitting caisson method, and FIG. 2 is a plan view showing an example of mechanical equipment used for construction of caisson structure by press-fitting caisson method. .

  There are three types of press-in caisson methods as described above. Here, a press-in caisson method combining an open-type press-in caisson method and a hydraulic press-in caisson method will be described. In this press-fitting caisson method, a caisson casing 1 having a caisson cutting edge 2 inclined at the tip is formed at the tip, a pressurizing girder 9 utilizing its own weight as a press-fitting settling means of the caisson casing 1, and a press-fitting device The hydraulic jack 13 is used.

  In this press-fitting caisson method, the caisson enclosure 1 is pressed and settled by a predetermined stroke into the ground G in the ground (including the seabed and under the river), and further mud soil (including earth and sand) R inside the caisson enclosure 1 is excavated. It discharges outside the caisson housing 1 (for example, on the ground). Then, a caisson structure (caisson shaft 5 in the present embodiment) having a predetermined depth is constructed by adding a subsequent concrete frame 4 as an example precast above the caisson frame 1. Such a caisson method is used when a shaft for constructing a pier, a shaft for starting or reaching when a shield tunnel 15 is constructed underground, or the like is constructed.

  As the mechanical equipment 6, a crane 7 that is installed and fixed on the ground around the site where the caisson shaft 5 is constructed, and a suspension that is attached to the lower end of a suspension wire that is suspended from the tip of a suspension arm of the crane 7. A hook (not shown) or a grab bucket 14 is present. The crane 7 shown in the figure is a crawler type crane that can move in any direction. However, the crane 7 is a fixed crane that is installed in a completely fixed state on the ground or a large crane that is supported by a larger portal machine frame. Of course, it is also possible to adopt.

  The hydraulic jack 13 is placed in advance in the ground where the caisson shaft 5 is constructed, and the caisson housing 1 is placed in the ground by a cooperative action with the earth anchor 17 which is a bar-like support member raised upward. It is a device for press-fitting into the ground G. In the illustrated mechanical equipment 6, twelve earth anchors 17 are provided as shown in FIG. 2, and one of the pressure girders 9 and two hydraulic jacks are used by using two of the earth anchors 17. 13 constitutes a set of press-fit sedimentation means. The hydraulic jack 13 used in the present invention is a center hole jack in which a hole for receiving the gripper rod is formed at the center. When the earth anchor 17 is clamped by the anchor chuck 18 provided at the lower end of the gripper rod, the hydraulic jack 13 is hydraulic. The jack 13 and the ground anchor 17 are connected, and when the anchor chuck 18 is released, the hydraulic jack 13 and the ground anchor 17 are disconnected.

  Further, the grab bucket 14 is constituted by a pair of bucket elements that are pivotably opened and closed and provided with comb-like claws for excavating the ground G at the tip. Can be captured and drained of the captured mud R. The hanging hook 16 is a hanging tool used when hanging, moving, and installing the caisson housing 1, the following housing 4, or the piece 19 (FIG. 6) that is an element of the following housing 4. is there.

  The caisson shaft 5 has the above-described configuration as an example, but it is of course possible to change or omit the partial configuration without departing from the gist of the present invention. For example, the shape of the caisson housing 1 is not limited to a cylindrical shape, and may be a square tube shape. If the rectangular tube-shaped caisson housing 1 is used, a rectangular tube shape as shown in FIGS. The caisson shaft 5 can be constructed. The caisson shaft 5 is not limited to the structure shown in FIGS. 6 (a) and 6 (b), in which the subsequent frame 4 formed in a cylindrical shape from the beginning is added, and the plate-like piece 19 is connected to the bolt joint. A structure as shown in FIGS. 6C and 6D, which is joined using 42, may be used.

  Further, the succeeding casing 4 crushed on the caisson casing 1 is not limited to a concrete casing but may be a casing formed of other materials such as steel. Further, the width dimension of the main sheet 35 and the joint sheet 37 is not necessarily the same dimension, and the width dimension of the joint sheet 37 can be shortened within a range in which the gap portion 36 can be closed.

[Example 1]
Next, the outline | summary of the ground improvement method in the caisson method of this invention is demonstrated.
The ground reforming method in the caisson method of the present invention is the method of substituting the caisson housing 1 and the subsequent housing 4 into the ground, and between the ground G and the caisson housing 1 and the housing 4, the ground G, With respect to the caisson shaft 5 formed by sinking the caisson housing 1 and the housing 4 with a friction reducing sheet provided with a friction reducing material for reducing the sliding contact resistance between the caisson housing 1 and the housing 4, The friction reduction sheet is characterized in that the friction reduction effect is nullified by eliminating the friction reduction effect of the friction reduction material of the friction reduction sheet.

  The caisson laying process for forming the caisson shaft 5 is performed using, for example, the caisson housing 1 (see FIG. 3) provided with the friction reducing sheet unit 29 (see FIG. 7).

  A long friction reduction sheet 21 is wound and accommodated in, for example, a roll shape in the friction reduction sheet unit 29 installed in the sheet setting portion 22 of the caisson housing 1, and the wound friction sheet 21 is wound in the wound state. A roll-shaped friction reducing sheet 21 having a friction reducing material layer 30 provided on at least the inner surface of the sheet is accommodated in a box 230 so that it can be fed out as the caisson housing 1 settles on the ground G.

  As the caisson 1 sinks, the roll-like friction reducing sheet 21 of the friction reducing sheet unit 29 attached to the outer peripheral surface of the tip of the caisson housing 1 that is in sliding contact with the ground G is unwound to gradually remove the friction reducing sheet 21. In addition, the sliding contact resistance between the ground G and the caisson housing 1 and the succeeding housing 4 can be avoided by using it so as to extend into the ground G (see FIG. 5). The friction reducing sheet 21 accommodated in the friction reducing sheet unit 29 is not limited to the roll shape as long as the friction reducing sheet 21 is accommodated so as to be quickly drawn out, and is accommodated in a folded state. The storage state may be a combination of a roll shape and a folded shape.

  The friction reducing material layer 30 is preferably formed of a material that swells when contacted with water and exhibits a friction reducing function by the swelling. The material forming the friction reducing material layer 30 will be described in more detail later.

  Then, the caisson shaft 5 formed using the caisson housing 1 provided with the friction reducing sheet unit 29 is subjected to a friction reducing effect invalidating process, and the friction reducing effect of the friction reducing material layer 30 of the friction reducing sheet 21 is obtained. Disappear. As a result, the stability of the caisson shaft 5 that has been laid and the support force for the structure to be constructed can be increased.

As a method for eliminating the friction reducing effect of the friction reducing material, for example, there is a method in which a friction reducing effect invalidating component for eliminating the friction reducing effect is applied to the friction reducing material. When the friction reducing material is a material that swells when contacted with water and exhibits a friction reducing function due to this swelling, the friction reducing effect invalidating component acts to remove water from the swollen friction reducing material. The component to play can be used. As a result, the friction reducing material is changed from a swollen state (expressing a friction reducing function) to a non-swelled state (not expressing a friction reducing function), and the friction reducing effect can be eliminated.
The method for eliminating the friction reducing effect of the friction reducing material can be changed according to the type and construction scale of the friction reducing material, for example, the friction reducing effect of the friction reducing material by physical treatment such as heating and cooling. Can be eliminated.

<Friction reducing material>
Hereinafter, the material used for the friction reducing material layer 30 will be described.
The friction reducing material layer 30 is formed of a friction reducing resin coating containing water-absorbing resin (a), hydrophilic binder resin (b) and solvent (c) as essential components.

  The water-absorbing resin (a) used in the friction-reducing resin coating may be a resin that swells by absorbing water and has a water absorption ratio of 3 times or more (25 ° C., 1 hour) with respect to its own weight. If it does not specifically limit. However, the synthetic water-absorbent resin obtained by crosslinking a water-soluble hydrophilic compound (monomer and / or polymer) with a crosslinking agent, as exemplified below, has a swelling ratio and water capacity higher than those of natural water-swellable substances (gelatin, agar, etc.). These are preferable to natural water-swellable materials (gelatin, agar, etc.) because they have a good balance of dissolved content, water absorption rate, strength, etc. and can be easily adjusted.

  Specific examples of the water absorbent resin (a) as described above include, for example, a crosslinked poly (meth) acrylic acid, a crosslinked poly (meth) acrylate, and a poly (meth) acrylic acid having a sulfonic acid group. Cross-linked ester, cross-linked poly (meth) acrylate ester having polyoxyalkylene group, cross-linked poly (meth) acrylamide, cross-linked copolymer of (meth) acrylate and (meth) acrylamide, (meth) acrylic Copolymerized crosslinked product of hydroxyalkyl acid and (meth) acrylate, crosslinked polydioxolane, crosslinked polyethylene oxide, crosslinked polyvinylpyrrolidone, sulfonated polystyrene crosslinked product, crosslinked polyvinylpyridine, starch-poly (meth) acrylonitrile graft copolymer Saponification of coalescence, starch-poly (meth) acrylic acid (salt) graft cross-linking copolymer Coalescing, reaction products of polyvinyl alcohol and maleic acid (salt), cross-linked polyvinyl alcohol sulfonate, polyvinyl alcohol - acrylic acid graft copolymers, polyisobutylene maleic acid (salt) cross-linked polymer, and the like. These water-absorbing resins (a) may be used alone or in combination of two or more.

  In the present invention, it is preferable to use a salt-resistant water-absorbing resin as the water-absorbing resin (a). The reason why salt-resistant water-absorbent resins are preferred is that salt-resistant water-absorbent resins have a relatively high water absorption capacity of hard water containing polyvalent metals and are not significantly affected by the water quality in the soil when used in friction-reducing resin coatings. This is because the friction reducing effect can be exhibited.

  The salt-resistant water-absorbent resin in the present invention is not particularly limited as long as the water absorption ratio (25 ° C., 24 hours) in artificial seawater is 10 times or more. For example, the water-absorbent resin (a) exemplified above is used. Among them, those having a nonionic group and / or a sulfonic acid (salt) group are more preferred, and those having an amide group or a hydroxyalkyl group are more preferred. Examples of the salt-resistant water-absorbing resin as described above include, for example, a copolymer crosslinked product of (meth) acrylate and (meth) acrylamide, and a copolymer of hydroxyalkyl (meth) acrylate and (meth) acrylate. A crosslinked body etc. are mentioned. Further, those having a polyoxyalkylene group are particularly preferred. Examples of such a water absorbent resin (a) include a crosslinked copolymer of (meth) acrylate having a methoxypolyoxyalkylene group and (meth) acrylate.

  These salt-resistant water-absorbing resins can swell up to a certain magnification regardless of the nature of the water in the soil (soft water, hard water, etc.), and more reliably exhibit the friction reducing function. it can.

  Furthermore, the production method of the water-absorbent resin (a) used for the friction-reducing resin coating is not particularly limited. For example, a single amount containing a water-soluble ethylenically unsaturated monomer and, if necessary, a crosslinking agent. And a method of polymerizing body components. The water-absorbing resin (a) obtained by (co) polymerizing an ethylenically unsaturated monomer is excellent in water absorption with respect to water and is generally inexpensive. In addition, said crosslinking agent is not specifically limited.

  Specific examples of the ethylenically unsaturated monomer include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, citraconic acid, vinyl sulfonic acid, and (meth) allyl sulfonic acid. 2- (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, and alkali metal salts and ammonium salts of these monomers; N , N-dimethylaminoethyl (meth) acrylate and quaternized products thereof; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, diacetone (meth) acrylamide, N- Isopropyl (meth) acrylamide, (meth) acryloyl morpho (Meth) acrylamides such as ethylene, and derivatives of these monomers; hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; polyethylene glycol mono (meth) Polyalkylene glycol mono (meth) acrylates such as acrylate, polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, methoxypolypropylene glycol mono (meth) acrylate; N-vinyl-2-pyrrolidone, N-vinylsuccinimide N-vinyl monomers such as N-vinylformamide, N-vinyl-N-methylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, etc. Monomer, vinyl methyl ether; but like, but is not particularly limited. These ethylenically unsaturated monomers may be used alone or in combination of two or more.

  Among the ethylenically unsaturated monomers exemplified above, those composed of an ethylenically unsaturated monomer 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) acrylamide-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, (meth) acrylamide, and hydroxyalkyl. (Meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate and the like can be mentioned. Furthermore, an ethylenically unsaturated monomer having a polyoxyalkylene group is particularly preferred.

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

  A water-absorbing resin (a) is obtained by polymerizing the monomer components. The average molecular weight, shape, average particle size, etc. of the water-absorbent resin (a) may be set according to the composition of the friction reducing agent coating, the type of binder, physical properties, working environment, etc., and are particularly limited. However, the average particle diameter of the water absorbent resin (a) is preferably 30 to 800 μm, more preferably 30 to 600 μm, and most preferably 30 to 400 μm.

  When the average particle diameter of the water-absorbent resin (a) used in the friction-reducing resin coating exceeds 800 μm, the particle diameter is too large, and the water-absorbent resin (a) is added to the solvent (c) solution of the hydrophilic binder resin (b). When mixed, the particles of the water absorbent resin (a) are liable to settle, which is not preferable.

  On the other hand, when the average particle diameter of the water-absorbent resin (a) is less than 30 μm, the handling becomes very difficult (e.g., it is easily scattered as a fine powder), which is not preferable.

Next, the hydrophilic binder resin (b) constituting the friction-reducing resin paint will be described.
The hydrophilic binder resin (b) used in the friction reducing resin coating is (i) water-soluble or water-swellable, and (ii) has a function of fixing the water-absorbing resin (a) to the substrate as a binder. And (iii) is not particularly limited as long as it is soluble in the solvent (c). For example, (meth) acrylic acid ester copolymer, polyurethane, polyester, polycarbonate, polyvinyl alcohol resin, poly Examples thereof include a partial hydrolyzate of vinyl acetate and an ethylene-polyvinyl alcohol copolymer, and one or a mixture of two or more thereof can be used.

  If the hydrophilic binder resin (b) is too low in hydrophilicity, it inhibits the swelling of the water-absorbent resin (a), reduces the absorption of moisture in the soil, and reduces the friction reducing function of the paint for friction reducing agent. This is not preferable. On the other hand, when the hydrophilicity of the hydrophilic binder resin (b) is too high, the adhesive force of the binder to the base material is excessively reduced when water is absorbed in the soil, and the entire coating film is peeled off too quickly. For the reasons as described above, the hydrophilic binder resin (b) preferably has moderate hydrophilicity.

  The acid value of the hydrophilic binder resin (b) is preferably 40 mgKOH / g or more, more preferably 50 mgKOH / g or more, and more preferably 70 mgKOH / g or more in order to have appropriate hydrophilicity. preferable.

  When the acid value of the hydrophilic binder resin (b) is less than 40 mgKOH / g, the hydrophilicity becomes too low, which is not preferable. Moreover, in order to maintain the binder function at the time of water absorption, it is preferably 500 mgKOH / g or less, more preferably 300 mgKOH / g or less, and even more preferably 200 mgKOH / g or less. When the acid value of the hydrophilic binder resin (b) exceeds 500 mgKOH / g, the hydrophilicity becomes too high, which is not preferable.

  Next, the glass transition temperature of the hydrophilic binder resin (b) is not particularly limited, but the adhesion to the friction reducing sheet 21 serving as the base material and the workability when the base material is embedded in the ground G, From the viewpoint of coexistence of toughness of the coating film of the friction-reducing resin paint, it is preferable to have a glass transition temperature of -20 ° C to 120 ° C. When the glass transition temperature is −20 ° C. or lower, the coating film of the friction-reducing resin coating tends to be sticky. In particular, when the substrate after application is immediately wound and left, blocking may occur. In addition, since the strength of the friction-reducing resin coating is insufficient, it is not preferable because the base material is easily peeled when embedded in the ground G. For this reason, the glass transition temperature is more preferably 0 ° C. or higher.

  In addition, when the glass transition temperature of the hydrophilic binder resin (b) is 120 ° C. or higher, the adhesion preventing material layer becomes too hard, the adhesion to the base material, the flexibility of the coating film of the friction reducing resin paint becomes poor, Again, when the base material is embedded in the ground G, peeling and dropping of the water absorbent resin (a) are likely to occur, which is not preferable. From this, the glass transition temperature is more preferably 100 ° C. or less, and when the glass transition temperature is between 0 ° C. and 20 ° C. and between 20 ° C. and 100 ° C., the softening component and the shape retention component Good balance and more preferable.

  The weight average molecular weight (Mw) of the hydrophilic binder resin (b) is not particularly limited, but is preferably in the range of 30,000 to 300,000, and more preferably in the range of 50,000 to 200,000. By using the above resin having a weight average molecular weight, it becomes easy to balance toughness and solubility.

  As the hydrophilic binder resin (b), it is preferable to use an alkali water-soluble resin or a resin having an acid value of 40 to 500 mgKOH / g because the hydrophilicity can be easily adjusted by adjusting the acid value.

  Below, alkali water soluble resin is demonstrated. The alkaline water-soluble resin, which is one of the hydrophilic binder resins (b) constituting the friction-reducing resin coating, is a resin that dissolves in a 0.4% by weight NaOH aqueous solution and does not dissolve in neutral or acidic water. is there. The alkaline water-soluble resin is not particularly limited as long as it has the solubility defined above. For example, co-polymerization of an α, β-unsaturated carboxylic acid monomer and other monomers copolymerizable therewith. Coalescence can be mentioned.

In addition, although it is the solubility to the above-mentioned alkaline water, the solubility degree is not particularly limited, but the preferable solubility degree of the alkaline water-soluble resin as a binder resin that can be preferably used in the following description is shown. Moreover, although it is the term alkaline water-soluble resin, it may be expressed as an alkali-soluble resin in another expression. Since it is clearer to use the alkaline water-soluble resin, the alkaline water-soluble resin is used in this specification.
Moreover, although it is the solubility to the alkaline water of the alkaline water soluble resin which can be used preferably, it will not specifically limit unless the desired friction reduction effect | action is inhibited.

  This value is preferably 50% -100% for the alkaline water-soluble resin. More preferably, it is 60-100%. More preferably, it is 70-100 weight%. If no resin remains after filtration, it is dissolved.

  The production method of the alkaline water-soluble resin and the hydrophilic binder resin having an acid value of 40 to 500 mgKOH / g is not particularly limited, but the following α, β-unsaturated carboxylic acid monomer can be copolymerized with α, β- A copolymer obtainable by polymerization using an unsaturated monomer component composed of a monomer other than the unsaturated carboxylic acid monomer is preferred.

  For example, as an α, β-unsaturated carboxylic acid monomer used for the production of an alkaline water-soluble resin and a hydrophilic binder resin having an acid value of 40 to 500 mgKOH / g, for example, acrylic acid, methacrylic acid, maleic acid Α, β-unsaturated carboxylic acids such as itaconic acid and fumaric acid; α, β-unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; maleic acid monoester, fumaric acid monoester and itaconic acid mono Examples include α, β-unsaturated dicarboxylic acid monoesters such as esters. The α, β-unsaturated carboxylic acid monomer may be only one type or two or more types. Among 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 that can be copolymerized with the α, β-unsaturated carboxylic acid monomer include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl Esters of C1-C18 monohydric alcohols such as methacrylate, butyl methacrylate, stearyl methacrylate and (meth) acrylic acid; nitrile group-containing vinyl monomers such as acrylonitrile, methacrylonitrile; acrylamide, methacrylamide, etc. Amide group-containing vinyl monomers; hydroxyl group-containing vinyl monomers such as hydroxyethyl acrylate and hydroxypropyl methacrylate; epoxy group-containing vinyl monomers such as glycidyl methacrylate; zinc acrylate , Metal salts of α, β-unsaturated carboxylic acids such as zinc methacrylate; aromatic vinyl monomers such as styrene and α-methylstyrene; aliphatic vinyl monomers such as vinyl acetate; vinyl chloride, odor Halogen-containing vinyl monomers such as vinyl iodide, vinyl iodide and vinylidene chloride; allyl ethers; maleic acid derivatives such as dialkyl esters of maleic acid; fumaric acid derivatives such as dialkyl esters of fumaric acid; maleimide, N-methyl Maleimide derivatives such as maleimide, stearylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide; Itaconic acid derivatives such as mono and dialkyl esters of itaconic acid, itaconic amides, itaconic imides, itaconic amide esters; alkenes such as ethylene and propylene Class: butadiene, isoprene and other die Vinyl ethers; unsaturated monomers having a sulfonic acid (salt) group such as 2- (meth) acryloylpropanesulfonic acid (salt), 3-allyloxy-2-hydroxypropanesulfonic acid (salt), polyalkylene A glycol (meth) acrylate etc. can be mentioned, It can use by 1 type (s) or 2 or more types in these.

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

  The (meth) acrylic acid alkyl ester is preferably used in an amount of 30% to 100% by weight based on 100% by weight of the total amount of other monomers copolymerizable with the α, β-unsaturated carboxylic acid monomer. More preferably, it is used in an amount of 50 to 100% by weight. More preferably, it is 60-100 weight%, More preferably, it is 70-100 weight%. That is, the use of an acrylic monomer as another monomer is a preferred embodiment as a form of an alkaline water-soluble resin as the hydrophilic binder resin (b).

  The proportion of the unsaturated monomer component composed of the above α, β-unsaturated carboxylic acid monomer and another monomer copolymerizable therewith is not particularly limited. For example, α, β-unsaturated carboxylic acid When the unsaturated monomer component consisting of a monomer and another monomer copolymerizable therewith is 100% by weight, the proportion of α, β-unsaturated carboxylic acid in the total monomer component is preferably Is 7 to 80% by weight in the total amount of unsaturated monomers. More preferably, it is 7 to 50% by weight. More preferably, it is 9 to 30% by weight.

  When the ratio of the α, β-unsaturated carboxylic acid monomer in all monomers in the alkaline water-soluble resin is less than 7% by weight, the hydrophilicity tends to be too low due to the low acid value. On the other hand, if the ratio exceeds 80% by weight, the hydrophilicity becomes too high, and problems are likely to occur.

Α, β-unsaturation used as a raw material for producing a hydrophilic binder resin having an acid value of 40 mgKOH / g or more and 500 mgKOH / g or less, that is, a binder resin obtained by polymerizing the unsaturated monomer component. The amount of the copolymerizable monomer other than the carboxylic acid monomer is the unsaturated monomer comprising the above α, β-unsaturated carboxylic acid monomer and another monomer copolymerizable therewith. Based on 100% by weight of all components, preferably 93 to 20% by weight in all of the unsaturated monomer components. More preferably, it is 93 to 50% by weight. More preferably, it is 91-70 weight%.
If the proportion of the α, β-unsaturated carboxylic acid monomer is less than 20%, the hydrophilicity is lowered, and if it exceeds 93%, the hydrophilicity becomes too high.

The method for producing the alkaline water-soluble resin is not particularly limited, and generally known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like can be used. Is preferred. This is because a friction-reducing resin coating can be produced by mixing a water-absorbing resin as it is with a solution or dispersion containing an alkaline water-soluble resin obtained by solution polymerization.
Moreover, radical polymerization, anionic polymerization, cationic polymerization, coordination polymerization, etc. are mentioned as a polymerization form, However, radical polymerization is preferable as an industrial manufacturing method.

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

  Next, the radical polymerization initiator used in the radical polymerization is not particularly limited. Specific examples thereof include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethyl). Azo initiators such as valeronitrile) and peroxide initiators such as benzoyl peroxide and di-t-butyl peroxide. Two or more kinds of these radical polymerization initiators may be used in combination.

  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; acetone , Ketones such as methyl ethyl ketone; aliphatic esters such as ethyl acetate and butyl acetate; ethylene glycol derivatives such as ethylene glycol and ethylene glycol monomethyl ether; propylene glycol derivatives such as propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate Etc. Two or more of these solvents may be used in combination.

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

  Further, as a method for selecting the solvent (c), it is preferable to select a solvent having a boiling point, safety, etc. suitable for application to the substrate. If a low-boiling solvent is selected, it can be quickly dried and a coating can be formed in a short time, so that thick coating and the like are easy, and if a high-boiling solvent is selected, the working time can be extended. By using an organic solvent as a medium, the water-absorbing resin does not swell due to water absorption when a medium containing water is used, and the coating operation is facilitated because it does not become a gel. In addition, when a highly volatile solvent such as methyl ethyl ketone or methanol is used, it can be dried in about 10 minutes and can be transferred to the next operation or process quickly because it dries much faster than when water is used as a medium. The construction period or the time required for application to the substrate can be remarkably shortened.

  As long as the friction-reducing resin paint of the present invention contains the water-absorbent resin (a), the hydrophilic binder resin (b) and the solvent (c) described above as essential components, the characteristics thereof are not impaired. As other additives (h), other resins, pigments, various stabilizers, various fillers and the like may be contained.

  The ratio of the water-absorbing resin (a), the hydrophilic binder (b) and the solvent (c) to the other additive (h) is not particularly limited, but in order to fully exhibit the characteristics of the friction-reducing resin paint, Ratio ([(a) + (b) + (c)] / [(a) + (b) + () of the total of the resin (a), the hydrophilic binder (b) and the solvent (c)) c) + (h)] × 100 (%)) is preferably 50% or more, more preferably 70% or more, and most preferably 80% or more.

  Also, the ratio of the water-absorbing resin (a), the hydrophilic binder (b), the solvent (c) and other additives (h) is not particularly limited, but in order to fully exhibit the characteristics of the friction-reducing resin paint. The water-absorbing resin (a) is 5 to 60% by weight, the hydrophilic binder (b) is 10 to 70% by weight, the solvent (c) is 5 to 70% by weight, and the other additives (h) are 0 to 50% by weight. %, The water-absorbing resin (a) is 10 to 50% by weight, the hydrophilic binder (b) is 10 to 60% by weight, the solvent (c) is 10 to 60% by weight, and the other additives (h) are 0%. -30% by weight is more preferred.

<Ineffective component to reduce friction reduction effect>
Next, the friction reducing effect nullifying component that eliminates the friction reducing effect of the friction reducing material layer 30 formed by the friction reducing resin coating will be described.
When using a friction reducing material that swells when in contact with water and exhibits a friction reducing function due to this swelling, use a component that removes water from the swollen friction reducing material as a friction reducing effect invalidating component. Is effective.

  Hereinafter, the friction reducing effect nullifying component for the friction reducing material layer 30 that exhibits a friction reducing function by swelling with contact with water will be described. However, the friction reducing effect invalidating component of the present invention is not limited thereto. Needless to say, the friction reducing material layer 30 can be selected in accordance with the action mechanism of the friction reducing effect of the material.

  Examples of the friction-reducing effect nullifying component for the friction-reducing material layer 30 that exhibits a friction-reducing function by swelling in contact with water include calcium carbonate, calcium oxide, calcium hydroxide, polyaluminum chloride (PAC), and sulfuric acid. Aluminum, aluminum oxide, ferric chloride, calcium chloride, magnesium chloride, calcium acetate, magnesium acetate, or the like can be used. In particular, it is preferable to use a metal salt that generates a divalent or trivalent polyvalent metal ion, and it is particularly preferable to use calcium carbonate.

  As shown in a test (Example 5) to be described later, calcium carbonate effectively releases water from the swollen friction reducing material so that the friction reducing material has lost its friction reducing function. Can do. In addition, calcium carbonate is relatively inexpensive and advantageous in terms of construction cost.

  In addition, the cement which is the main component of the grout material usually contains a polyvalent metal compound such as calcium oxide or aluminum oxide. It is also possible to use the friction reduction effect invalidating component originally contained in the grout material for the friction reduction effect invalidating process described later.

  Moreover, when the water-absorbing resin (a) described above is anionic, a cationic material can be used as a friction reducing effect nullifying component. When the water absorbent resin (a) is cationic, an anionic material can be used as a friction reducing effect nullifying component.

  As a material used as a friction reducing effect invalidating component for the friction reducing material layer 30 formed by the friction reducing resin coating containing the anionic water-absorbing resin (a), a cationic polymer compound can be used, for example, A polycondensate of an amine compound such as ammonia, alkylamine, polyalkylenepolyamine, and epichlorohydrin, or a polymer or copolymer of a cationic vinyl monomer can be used.

  Examples of the amine compound include monomethylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, n-hexylamine, n-octylamine, benzylamine, monoethanol. Examples include amine, diethanolamine, triethanolamine, dimethylaminoethanol, methyldiethanolamine, 2-hydroxypropylamine, hydroxyethyloxyethylamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine, and polyethyleneimine.

  Examples of the cationic vinyl monomer include 2- (methacryloyloxy) -ethyltrimethylammonium chloride, 2- (acryloyloxy) -ethyltrimethylammonium chloride, 2- (methacryloyloxy) -ethylbenzyldimethylammonium chloride, 2 Examples include-(acryloyloxy) -ethylbenzyldimethylammonium chloride, acrylamidopropyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylaminoethyl (meth) acrylate salt, dimethylaminopropyl (meth) acrylamide salt, and the like.

[Example 2]
Next, the ground improvement method in the caisson method of the present invention will be described in more detail.
As described above, the ground improvement method in the caisson method of the present invention is the caisson method using the caisson housing 1 provided with the friction reducing sheet unit 29 and reducing the sliding resistance between the ground and the caisson. After the shaft 5 is constructed, the friction reduction effect invalidation process is performed on the ground around the caisson. The friction reduction sheet 21 of the friction reduction sheet unit 29 is provided with a friction reduction material layer 30 that swells when it comes into contact with water and exhibits a friction reduction function by this swelling.

  The caisson shaft can be constructed by, for example, a press-fitting caisson method described in Japanese Patent Application Laid-Open No. 2007-332554. That is, (1) Edge cutting / mound installation process, (2) Primary press-fitting preparation process, (3) Primary press-fitting / digging process, (4) Secondary press-fitting preparation process, (5) Secondary press-fitting / digging process, (6) This is performed by sequentially executing a press-fitting / digging completion step and a (7) bottom slab concrete placing step.

  When the friction reducing sheet 21 is composed of a metal sheet, a “friction reducing sheet drawing process” is performed between the (6) press-fitting / excavation completion process and the (7) bottom slab concrete placing process, Although it is possible to remove the friction reducing sheet 21 sent out from the reduction sheet unit 29, the ground reforming method in the caisson method of this embodiment does not perform the “friction reducing sheet drawing step”, and the friction reducing sheet The case where it remains between the ground G and the wall surface of a caisson is demonstrated.

[Invalidation of friction reduction effect]
In the present embodiment, the case where the friction reduction effect invalidating process is performed simultaneously with the contact grout will be described. Contact grout is a grout material that has strength equal to or greater than that of natural grounds for the purpose of restoring the strength of the ground surrounding the caisson and ensuring the adhesion between the caisson and the surrounding ground and increasing the peripheral frictional force. After placing the bottom slab concrete, it is injected between the ground and the wall surface of the caisson to fill the gap.

  FIG. 4 is a cross-sectional view showing an example of the caisson housing used in the ground improvement method in the caisson method of the present invention. The caisson housing 1 and the subsequent housing 4 constituting the caisson shaft 5 are provided with an injection hole 50 for injecting the grout material 51 between the ground G and the wall surface 52 of the caisson shaft 5. From the injection hole 50, a grout material 51 added with the friction reducing effect nullifying component stirred by a stirring means (not shown) such as a mortar mixer is inserted between the ground G and the wall surface 52, such as a grout pump. Injection is performed using a pressure injection means (not shown) (see FIG. 8). In addition, the grout material is injected from the lower caisson housing, and sequentially to the upper housing.

  The friction reducing material layer 30 of the present embodiment swells when contacted with water as described above, and expresses a friction reducing function by this swelling. Therefore, as the friction reducing effect nullifying component, a component (for example, calcium carbonate) that has an effect of removing water from the swollen friction reducing material is used.

  As described above, the cement that is the main component of the grout material contains calcium oxide and aluminum oxide, which are components that invalidate the friction reducing effect. However, the water-cement ratio set so that the hardened grout material has a strength necessary for stabilizing the caisson structure such as the caisson shaft 5 usually cancels the friction reducing function of the friction reducing material layer 30. Does not contain a sufficient friction reducing effect nullifying component.

In this example, the ratio of water cement that provides the strength necessary for stabilizing the caisson structure is obtained, but the grout does not contain a friction reducing effect invalidating component sufficient to counteract the friction reducing function of the friction reducing material. A grout material in which the friction reducing effect nullifying component is further added to and mixed with the material is used.
The friction reducing effect nullifying component added to the grout material is selected according to the type and amount of the friction reducing material between the ground G and the wall surface 52, and depending on the type of the friction reducing effect nullifying component. The amount of addition necessary to eliminate the friction reducing effect of the friction reducing material is determined.

  The grout material 51 injected from the injection hole 50 is in contact with the friction reducing material layer 30 provided on the friction reducing sheet 21, that is, the friction reducing effect invalidating component and the friction reducing material layer included in the grout material 51. 30 is contacted, and water is removed from the friction reducing material layer 30 swollen with water by the action of the friction reducing effect nullifying component. Accordingly, the friction reducing material layer 30 can be changed from a swollen state that exhibits a friction reducing function to a non-swelled state in which the friction reducing function has disappeared, and thus the friction reducing function can be lost. .

Here, as the grout material, generally, a mortar grout material such as CB, a polymer cement grout material using a synthetic resin, a plastic grout material using a water glass system, or the like is used.
Since the strength after curing of the grout material is determined by the water cement ratio of the grout material, the water cement ratio is within a predetermined range (usually, 165% to 78%) in order to give the grout material after curing sufficient strength. ). The predetermined range of the water-cement ratio can be changed depending on the strength required for the grout material after curing, and can generally be set in the range of about 170% to 70%. is there.

  Adding the friction reducing effect nullifying component of the powder such as calcium carbonate to the grout material having a predetermined water cement ratio increases the viscosity of the grout material, that is, lowers the fluidity, and injects the grout material. It may be difficult to work. In particular, when the friction reducing sheet is left in the ground G, if the fluidity is low, it is difficult for the friction reducing sheet to go around between the friction reducing sheet and the ground ground G. There is a risk that it will not be able to contact sufficiently.

In such a case, an admixture that improves the fluidity of the grout material can be added. Thus, the fluidity of the grout material can be ensured without changing the water cement ratio of the grout material and without separating water from the grout material.
For example, when calcium carbonate is used as the friction reducing effect nullifying component, it is desirable to add a polycarboxylate type polymer surfactant as an admixture.

  According to the present embodiment, since the grout material including the friction reduction effect invalidating component is injected between the ground and the caisson housing, the friction reduction effect of the friction reducing material can be obtained by the friction reduction effect invalidating component. Simultaneously with the disappearance, contact grout filling between the ground and the caisson housing with the grout material can be performed to stabilize the caisson deposited.

[Example 3]
Another example of the ground improvement method in the caisson method according to the present invention will be described. In Example 1, the friction reduction effect invalidation process was performed using a grout material to which a substance as a friction reduction effect invalidation component was added.
In this example, since the friction reducing effect nullifying component contained in the cement which is the main component of the grout material is used, the water cement ratio of the grout material is lowered, that is, the amount of cement is increased. It is an Example which performs the friction reduction effect invalidation process using the grout material which raised the density | concentration of the friction reduction effect invalidation component contained in a grout material.
The caisson shaft 5 can be constructed by the same method as in the second embodiment. Therefore, the detailed description is abbreviate | omitted.

  When a caisson structure such as a caisson shaft or caisson foundation is constructed on a general ground, a water cement ratio of about 165%, for example, is used as a grout material of the caisson structure. This water-cement ratio is set based on the properties of the ground on which the caisson structure is constructed, the strength required for the caisson structure, and the like.

  Although the cement contains calcium oxide and aluminum oxide, which are components that invalidate the friction reduction effect, the water cement ratio (hereinafter referred to as normal water) set based on the properties of the ground and the required strength as described above. In some cases, the ratio is sometimes referred to as a cement ratio). In most cases, the friction reducing effect invalidating component sufficient to cancel the friction reducing function of the friction reducing material layer 30 is not included.

  Here, by reducing the water cement ratio of the grout material and increasing the amount of cement in the grout material, the concentration of the friction reducing effect nullifying component contained in the grout material can be increased. That is, the friction reduction effect nullification process can be performed by using a grout material having a lower water cement ratio than usual. For example, the friction reduction effect invalidation process is performed using a grout material in which a normal water cement ratio (about 165%) is set to 120% to 78%.

If the water-cement ratio is low, the fluidity of the grout material will be low, making it difficult to fill the grout, and increasing the amount of cement used will increase the cost, so the water will exceed the value calculated based on the properties of the ground. Setting the cement ratio low is not common.
However, as in this embodiment, for the purpose of increasing the concentration of the friction reducing effect nullifying component, by setting the water cement ratio lower than the value calculated based on the properties of the ground, etc. It is possible to perform the friction reduction effect invalidating process without adding any chemicals and to ensure the stability of the caisson structure. In addition, it is possible to perform the friction reduction effect invalidation process simultaneously with the normal grout filling process, which is excellent in that there is no problem of cost increase due to an increase in the process.

  In the case where the viscosity of the grout material is increased and the fluidity is lowered by lowering the water-cement ratio, as in the case of Example 2, an admixture that improves the fluidity of the grout material is added. Is effective.

[Example 4]
Another example of the ground improvement method in the caisson method according to the present invention will be described. In this embodiment, the friction reduction effect invalidation process is performed by injecting a neutralizing agent containing a friction reduction effect invalidation component between the ground and the caisson housing, and after the friction reduction effect invalidation process, the grout material is added. A grout filling step of injecting between the ground and the caisson housing is performed. That is, this is an example in which the friction reduction effect invalidation process is performed by injecting the friction reduction effect invalidation component separately from the grout material. The caisson shaft 5 can be constructed by the same method as in the second embodiment. Therefore, the detailed description is abbreviate | omitted.

[Invalidation of friction reduction effect]
The friction reduction effect invalidation process in the present embodiment is performed by adding a neutralizing agent containing the friction reduction effect invalidation component from the injection hole 50 (FIG. 4) provided in the caisson casing 1 or the subsequent casing 4 to the ground. And the wall surface of the caisson shaft 5 (the wall surface of the caisson housing 1 or the housing 4).

  As the neutralizing agent including the friction reducing effect nullifying component, when the friction reducing effect invalidating component is a solid such as a powder, the friction reducing effect invalidating component is dissolved or dispersed in a solvent. Can be used. When the friction reducing effect nullifying component is a liquid or a highly fluid gel substance, the friction reducing effect invalidating component can be used as it is as a neutralizing agent. Moreover, what was diluted with the solvent can also be used.

[Grout filling process]
A grout filling step is performed on the ground after the friction reduction effect invalidation processing, that is, the ground where the friction reduction effect of the friction reducing material is lost. As the grout material, a general grout material (a mortar grout material, a polymer cement grout material, a plastic grout material, etc.) is used. The method of injecting the grout material between the ground and the caisson housing is the same as the method of injecting the grout material including the friction reducing effect nullifying component, and the description thereof will be omitted.

  As described above, the friction reducing effect invalidating process is performed by injecting the neutralizing agent containing the friction reducing effect invalidating component between the ground and the caisson housing to ensure the friction reducing function of the friction reducing material. After that, the grout filling process (contact grout) is performed using a normal grout material, and the caisson deposited can be stabilized.

According to this embodiment, the friction reduction effect invalidation process and the grout filling process are separated, so that the water-cement ratio is predetermined as in Example 2 for the neutralizing agent used for the friction reduction effect invalidation process. Since there is no restriction on the amount of water for making the above range, it is easy to ensure the fluidity of the neutralizing agent.
Further, since it is not necessary to add a friction reducing effect nullifying component to the grout material used in the grout filling step, when the friction reducing effect invalidating component is a solid such as a powder such as a powder, its addition Therefore, there is no problem that the fluidity of the grout material decreases.

  In this embodiment, it is not necessary to completely eliminate the friction reducing effect of the friction reducing material by the friction reducing effect invalidating process using the neutralizing agent including the friction reducing effect invalidating component, and the friction reducing effect is invalidated. The friction reducing effect nullifying component in the cement contained in the grout material used in the grout filling step performed after the treatment may act to finally ensure the stability of the caisson structure.

[Example 5]
Tests were conducted by using calcium carbonate, polyaluminum chloride, calcium acetate, magnesium acetate as the friction reducing effect nullifying component, and mixing the friction reducing effect invalidating component with the grout material (Example 5-1 to Example). 5-4, Example 5-6, Example 5-7). As a comparative example, a grout material (water cement ratio of 165%) to which a friction reducing effect nullifying component was not added was used (Comparative Example 1). Example 5-5 is a test example in which the amount of the friction reducing effect nullifying component is increased by lowering the water cement ratio as compared with Comparative Example 1. In Example 5-1 and Example 5-6, a polycarboxylate type polymer surfactant was added as an admixture. Table 1 shows the composition of each grout material tested.

  Using an experimental apparatus in which a friction reducing sheet provided with a friction reducing material layer is disposed between the caisson housing and the ground, the grout materials having the composition described in Table 1 (Examples 5-1 to 5-7, and Comparative Example 1) was injected and cured between the caisson housing and the ground. About each grout material, the flow test value, the friction restoring force, and the intensity | strength of the grout material after hardening were investigated. The friction restoring force was measured by a tensile test. These results are shown in Table 2.

The flow test value is a value indicating the fluidity and filling property of the grout material. The higher this value, the better the fluidity and the better the filling property. The friction restoring force is a value by which the friction reducing effect invalidating ability can be evaluated. It can be said that the higher this value, the higher the friction force and the higher the friction reducing effect invalidating ability.
In addition, the filling properties of Example 5-3, Example 5-4, and Example 5-7 in which the flow test value was not measured were visually confirmed, and Example 5 in which the friction restoring force was not measured The state of the ability to nullify the friction reduction effect for 1 and 5-6 was judged by visual confirmation and pulling using a machine.

[Friction reduction sheet unit]
An example of a friction reducing sheet unit provided in the caisson housing 1 will be described in order to reduce the sliding resistance between the caisson housing and the ground to construct the caisson shaft 5.
As shown in FIG. 7, the friction reducing sheet unit 29 includes a long friction reducing sheet 21 wound up in a roll shape, and a friction reducing material layer 30 is provided on at least the inner surface of the sheet in the wound state. The provided roll-shaped friction reducing sheet 21 is accommodated in the box 230 so that it can be fed out.

  The box 230 is filled with a granular water-stopping agent 28 that swells when it comes into contact with water and develops water-stopping properties (FIGS. 3 and 7). And the said friction reduction material layer 30 of the said friction reduction sheet | seat 21 swells when it contacts with water, and is formed with the material which expresses a friction reduction function by this swelling.

Further, as shown in FIG. 7, the box 230 is formed in a double tube structure of an inner box 25 and an outer box 23, the roll-shaped friction reducing sheet 21 is accommodated in the inner box 25, and the water-stopping agent 28 Is filled in the space between the inner box 25 and the outer box 23. The friction reducing sheet 21 is held in the inner box 25 so as to be freely rotatable. That is, between the left and right side plates of the inner box 25 facing each other, a winding shaft 24 serving as a rotating shaft of the rolled friction reducing sheet 21 in a wound state is stretched horizontally.
Further, the outer box 23 is integrally provided with a reinforcing rib 231 on its inner wall surface as a pressure strengthening portion. As the friction reducing sheet 21, a metal (iron) sheet can be used, and a film, a woven fabric, a knitted fabric, a non-woven fabric, or the like can be used. Of course, the material is not limited to this.

  As shown in FIG. 7, the outer box 23 is a substantially rectangular box-like member that is formed by appropriately bending a metal thin plate, and its outer end surface is substantially not protruded from the outer peripheral surface of the housing portion 20. It is set to be flush. The friction reducing sheet 21 passes through the slit 26 formed in a part of the inner box 25 and the feeding opening 27 formed in the outer box 23, so that the caisson casing 1 and the subsequent casing 4 installed thereabove. It is led to the ground along the outer peripheral surface. The feeding opening 27 is provided with a rubber plate 233 to enhance the sealing performance.

  As shown in FIG. 4, the friction reducing sheet unit 29 including the outer box 23, the winding shaft 24, the inner box 25, the water-stopping agent 28, the friction reducing sheet 21, and the rubber plate 233 includes the caisson housing 1. A plurality of units are provided in a state of being substantially connected over a plurality of locations along the outer peripheral surface of each.

  As the friction reducing sheet 21, for example, a thin iron plate having a thickness of about 0.2 mm to 0.3 mm can be adopted, and the surface thereof is smoothly processed. The desired friction reducing action and the friction reducing material layer 30 described below are used. The friction-reducing sheet 21 has a mechanical strength sufficient to withstand unwinding and pulling-out, while exhibiting excellent coating properties and pasting properties.

  As described above, the friction reducing material layer 30 is provided on the inner surface of the friction reducing sheet 21 by coating or pasting. In the present embodiment, the friction reducing material layer in the molten state is gradually increased from the winding base end side of the friction reducing sheet 21 toward the leading end side with respect to the inner surface of the friction reducing sheet 21. A raw material is applied to form a friction reducing material layer 30 in a laminated state composed of a plurality of layers. Here, as the raw material, the friction reducing material layer 30 is obtained by previously applying a friction reducing resin coating material, which contains the water absorbent resin (a), the hydrophilic binder resin (b), and the solvent (c) as essential components to the base material. Is formed. Further, as the water-stopping agent 28, specifically, the water-absorbing resin (a) is used.

  The friction reducing sheet 21 accommodated in the friction reducing sheet unit 29 is not limited to the roll shape as long as the friction reducing sheet 21 is accommodated so as to be quickly drawn out, and is accommodated in a folded state. The storage state may be a combination of a roll shape and a folded shape. When the friction reducing sheet 21 is folded and stored, the friction reducing sheet 21 is preferably formed of a film, a woven fabric, a knitted fabric, a non-woven fabric or the like, and can be formed of metal if it is thin and flexible.

1 caisson housing, 2 caisson blade, 3 steel sheet pile,
4 Subsequent frame, 5 Caisson shaft, 6 Mechanical equipment,
7 crane, 9 pressure girder,
13 hydraulic jack (press-fit device), 14 grab bucket,
15 shield tunnel, 17 earth anchor,
18 anchor chuck, 19 pieces,
20 Housing part, 21 Friction reducing metal sheet, 22 Sheet installation part,
23 outer box, 24 winding shaft, 25 inner box, 26 slit,
27 Feed opening, 28 Water stop agent, 29 Friction reducing sheet unit,
30 friction reducing material layer, 42 bolt joint,
50 injection hole, 51 grout material, 52 wall surface,
230 box, 231 reinforcing rib, 233 rubber plate, 280 sealing part,
G ground, R mud (earth and sand),
a water-absorbing resin, b hydrophilic binder resin,
c Solvent, h Additive

Claims (2)

When constructing a caisson structure having a predetermined depth by sinking the caisson body into the ground by a predetermined stroke, friction between the ground and the caisson body reduces frictional resistance between the ground and the caisson body. In the caisson structure formed by the sedimentation of the caisson housing through the friction reducing sheet provided with the reducing material,
For the friction reducing material of the friction reducing sheet, while performing a friction reducing effect invalidating process that causes a friction reducing effect invalidating component to disappear the friction reducing effect,
The friction reducing effect invalidation process, by injecting a grout comprising the friction reducing effect invalidation component between said caisson skeleton and the ground, have lines at the same time as the filling step of the grout,
The ground reforming method in the caisson method, wherein the grout material is a grout material having a water cement ratio lower than the water cement ratio set based on the properties of the ground and the required strength after hardening . In the ground improvement method in the caisson method according to claim 1 ,
The friction reducing material swells when contacted with water, and is formed of a material that expresses a friction reducing function by this swelling.
The friction reducing effect invalidating component is to remove water from the swollen friction reducing material, and to eliminate the friction reducing function of the friction reducing material,
As the friction reducing effect invalidating component, calcium carbonate, calcium oxide, calcium hydroxide, polyaluminum chloride, aluminum sulfate, aluminum oxide, ferric chloride, calcium chloride, magnesium chloride, calcium acetate, magnesium acetate, amine compound and epichlorohydrin A ground reforming method in the caisson method, characterized by using at least one substance selected from a polycondensate, a polymer of a cationic vinyl monomer, and a copolymer of a cationic vinyl monomer.

Images