Concrete pile embedding method

Abstract

The present invention provides a concrete pile embedding method that exhibits excellent filling properties when mixing mud and a hydraulic composition slurry in an excavated hole to manufacture the pile base reinforcement section, and a hydraulic composition slurry for pile base reinforcement used in this method. [Solution] A concrete pile embedding method comprising the following steps. Process 1: Using an excavation and mixing rod, drilling is carried out down to the supporting layer of the ground while injecting a drilling fluid containing water, filling the borehole with a drilling slurry containing soil and water, with a specific gravity of 1.8 or less. Step 2: After Step 1, a hydraulic composition slurry containing hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less, is injected into the excavated hole and mixed with the mud to construct the pile foundation. Step 3: After Step 2, a step of sinking a concrete pile into the base reinforcement portion of the pile in the excavated hole.

Description

[Technical Field]

[0001] This invention relates to a method for embedding concrete piles and a hydraulic composition slurry for reinforcing the base of piles. [Background technology]

[0002] Hydraulic compositions such as concrete and mortar are used in various fields such as civil engineering and construction. For example, in the embedding method of precast concrete piles, a slurry containing hydraulic powder is used as a root-stabilizing liquid, pile-perimeter fixing liquid, etc. In the precast concrete pile embedding method used in foundation work for structural construction, the ground is excavated down to the supporting layer using an excavation and mixing rod while injecting a drilling stabilization fluid. Then, a root-reinforcement fluid is injected into the borehole, and next, a pile-circumferential fixing fluid is injected while slowly raising the excavation and mixing rod. After that, the precast concrete pile is sunk into the borehole filled with the pile-circumferential fixing fluid. In this method, the excavation begins with the excavation of the ground, and at this time, in order to prevent the collapse of the borehole wall, the excavation is carried out while filling the borehole with a drilling stabilization fluid containing water-swellable clay such as bentonite.

[0003] Patent Document 1 discloses a foundation reinforcement method characterized by excavating the bottom of a pile hole to the shape and size required for foundation reinforcement, and then injecting mortar with a viscosity adjusted to 60 sec to 90 sec into the bottom of the pile hole using a cement milk pump and allowing it to harden. Patent Document 2 discloses a method for constructing a foundation reinforcement section for a pile body driven into the ground by an embedded pile construction method, characterized in that an injection material, which is a cement-based hardening agent and water with an underwater non-separating admixture added, is mixed with the ground of the foundation reinforcement section. In Patent Document 3, in the construction method of in-situ concrete piles or continuous diaphragm walls, (a) a step of forming an excavation hole by excavating a pile hole while stabilizing the hole wall of the pile hole with a stabilizing fluid such as muddy water; (b) after the completion of the excavation hole, injecting an air mortar composed of cement milk or mortar added with a foaming agent or a thickening agent, etc., whose specific gravity is adjusted to be greater than that of the stabilizing fluid and less than that of the placed concrete, into the bottom of the excavation hole, and stirring and mixing it with the slime deposited at the bottom; (c) after placing a steel cage in the excavation hole, inserting a tremie pipe to the bottom of the excavation hole, and while placing concrete, lifting the slime to the ground surface together with the air mortar to construct a structure. A construction method of in-situ concrete piles, etc., characterized by comprising the above steps, is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention provides an embedding method for concrete piles, which is excellent in filling property when mixing muddy water and a hydraulic composition slurry in an excavation hole to produce a root fixing part of a pile, and a hydraulic composition slurry for root fixing of a pile used in the method.

Means for Solving the Problems

[0006] The present invention relates to an embedding method for concrete piles having the following steps. Step 1: Using an excavation and agitation rod, excavating the ground to a support layer while injecting an excavation fluid containing water, filling the excavation hole with muddy water containing soil and water and having a specific gravity of 1.8 or less. Step 2: After Step 1, a hydraulic composition slurry containing hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less, is injected into the excavated hole and mixed with the mud to construct the pile foundation. Step 3: After Step 2, a step of sinking a concrete pile into the base reinforcement portion of the pile in the excavated hole.

[0007] Furthermore, the present invention relates to a hydraulic composition slurry for pile foundation reinforcement, which is used to manufacture the foundation reinforcement portion of a pile by mixing a hydraulic composition slurry with a specific gravity of 1.8 or less in an excavated hole. This invention relates to a hydraulic composition slurry for pile foundation reinforcement, which contains hydraulic powder and water, and in which the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less. [Effects of the Invention]

[0008] The present invention provides a concrete pile embedding method that offers excellent filling properties when mixing mud and a hydraulic composition slurry in an excavated hole to manufacture the pile base reinforcement section, and a hydraulic composition slurry for pile base reinforcement used in this method. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram illustrates a simulated evaluation device for evaluating the filling performance in a borehole in an example. [Modes for carrying out the invention]

[0010] [Concrete pile embedding method] The present invention relates to a concrete pile embedding method comprising the following steps. Process 1: Using an excavation and mixing rod, drilling is carried out down to the supporting layer of the ground while injecting a drilling fluid containing water, filling the borehole with a drilling slurry containing soil and water, with a specific gravity of 1.8 or less. Step 2: After Step 1, a hydraulic composition slurry containing hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less, is injected into the excavated hole and mixed with the mud to construct the pile foundation. Step 3: After Step 2, a step of sinking a concrete pile into the base reinforcement portion of the pile in the excavated hole.

[0011] Step 1 involves using an excavation and mixing rod attached to a three-point pile driver or a suspended pile driver to excavate the ground down to the supporting layer while injecting a drilling fluid containing water, thereby filling the borehole with mud containing soil and water, with a specific gravity of 1.8 or less. In step I, after filling the borehole with drilling mud, the drilling and stirring rod is withdrawn.

[0012] The drilling fluid contains water. This water can be tap water, river water, lake water, groundwater, etc.

[0013] The drilling fluid may further contain water-swellable clay. Examples of water-swellable clays include smectite group clay minerals such as bentonite (including natural or synthetic bentonite), montmorillonite (including natural or synthetic montmorillonite), beidelite, nontronite, laponite, souconite, hectorite (including natural or synthetic hectorite), stivunsite, vermiculite, swellable synthetic fluorinated mica (Na-type, Li-type synthetic mica), and swellable mica, and one or more of these can be used. From the viewpoint of economy and availability, one or more selected from bentonite, montmorillonite, beidelite, nontronite, laponite, and hectorite are preferred as water-swellable clays, one or more selected from bentonite, montmorillonite, and hectorite are more preferred, and bentonite is even more preferred.

[0014] Water-swellable clay can be a commercially available product used for building and civil engineering foundation work. When using bentonite as the water-swellable clay, bentonite with a high montmorillonite content is preferred, and bentonite with a high amount of Na-montmorillonite, which has high hydration and water-swellability, is even more preferred. Examples of bentonite include Kunigel GS, Kunigel V1, and Kunigel MB from Kunimine Industries Co., Ltd., and Superclay, Neoclay, and Neomad from Hojun Co., Ltd.

[0015] In this invention, "water swelling property" refers to the swelling volume (cm³) of 2g of clay mineral, determined by applying the test method for bentonite specified in the 15th edition of the Japanese Pharmacopoeia. 3 The swelling force expressed as ) is 10cm 3 This refers to items weighing 2g or more.

[0016] The presence of water-swellable clay in the drilling fluid allows for excavation of the ground while preventing collapse of the inner wall surface of the drilled hole. The amount of drilling fluid injected into the ground should be determined appropriately, taking into account the properties and condition of the ground, so that the specific gravity of the resulting mud is 1.8 or less. The specific method for filling the ground with the drilling fluid is not particularly limited and can be carried out in accordance with known methods for injecting drilling fluid into the ground.

[0017] By injecting drilling fluid while drilling, a drilling slurry containing soil and water is prepared in the borehole. The soil is excavated soil generated from the ground, and examples of soil include gravel, sand, silt, and clay. If the drilling fluid contains the aforementioned water-swellable clay, the mud can contain water-swellable clay in addition to the clay contained in the soil.

[0018] The specific gravity of the resulting muddy water is preferably 1.8 or less, more preferably 1.78 or less, more preferably 1.75 or less, even more preferably 1.7 or less, even more preferably 1.69 or less, and preferably 1.5 or more, more preferably 1.52 or more, and even more preferably 1.55 or more, from the viewpoint of minimizing waste while improving packing efficiency.

[0019] Step 2 is a step, after Step 1, injecting a hydraulic composition slurry containing hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less, into the excavated hole and mixing it with the mud to construct the pile foundation.

[0020] The hydraulic composition slurry contains hydraulic powder. Hydraulic powders are powders that harden when mixed with water. Examples include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, sulfate-resistant Portland cement, low-heat Portland cement, white Portland cement, and eco-cement (e.g., JIS R5214). One or more of these can be used.

[0021] Furthermore, the hydraulic powder may contain blast furnace slag, fly ash, silica fume, anhydrous gypsum, etc., and may also contain non-hydraulic limestone fine powder, etc. As the hydraulic powder, one or more selected from blast furnace cement, fly ash cement, and silica fume cement, which are mixtures of cement and blast furnace slag, fly ash, silica fume, etc., may be used. It may also contain clay such as bentonite.

[0022] The hydraulic composition slurry contains water. Water can be sourced from sources such as tap water, river water, lake water, or groundwater.

[0023] In the hydraulic composition slurry, the mass percentage of water content to hydraulic powder content (water / hydraulic powder ratio (W / P)) is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and 50% by mass or less, preferably 48% by mass or less, and even more preferably 46% by mass or less, from the viewpoint of increasing specific gravity while maintaining ease of pumping and improving filling performance. Here, the water / hydraulic powder ratio (W / P) is the mass percentage (mass%) of water and hydraulic powder in the hydraulic composition slurry, and is calculated as water / hydraulic powder × 100. The water / hydraulic powder ratio is calculated based on the amount of powder that has the physical properties to harden through a hydration reaction. Also, if the hydraulic powder is cement, W / P may be expressed as W / C. Furthermore, if the hydraulic powder includes powders selected from those having properties that harden through hydration reactions such as cement, powders having pozzolanic properties, powders having latent hydraulic properties, and stone powder (calcium carbonate powder), then in this invention, the amounts of these powders are also included in the amount of hydraulic powder. In addition, if the powder having properties that harden through hydration reactions contains a high-strength admixture, then the amount of the high-strength admixture is also included in the amount of hydraulic powder. This also applies to other parts of mass related to the mass of the hydraulic powder.

[0024] The specific gravity of the hydraulic composition slurry is preferably 1.8 or higher, more preferably 1.82 or higher, even more preferably 1.84 or higher, and preferably 2.0 or lower, more preferably 1.98 or lower, and even more preferably 1.96 or lower, from the viewpoint of filling the bottom of the hole. The specific gravity of the hydraulic composition slurry is adjusted by changing the mass percentage of water content to hydraulic powder content (water / hydraulic powder ratio (W / P)) in the hydraulic composition slurry.

[0025] The viscosity of the hydraulic composition slurry is preferably 300 mPa·s or more from the viewpoint of suppressing bleeding, and preferably 1000 mPa·s or less, more preferably 900 mPa·s or less, and even more preferably 750 mPa·s or less from the viewpoint of pumpability and filling into the bottom of the pile. The viscosity of the hydraulic composition slurry is measured using a viscometer (RION Corporation, VISCOTESTER VT-04E, rotor No. 1, rotation speed: 62.5 rpm), after the rotor has been rotated for 1 minute and the viscosity has stabilized. The specific gravity of the hydraulic composition slurry is adjusted by changing the mass percentage of water content to hydraulic powder content (water / hydraulic powder ratio (W / P)) in the hydraulic composition slurry, and by adding a dispersant described later to the hydraulic composition slurry.

[0026] The hydraulic composition slurry preferably contains a dispersant from the viewpoint of pumpability and packing properties.

[0027] A polycarboxylic acid-based dispersant is preferred as the dispersant.

[0028] As polycarboxylic acid-based dispersants, copolymers of a monoester of polyalkylene glycol and (meth)acrylic acid with a carboxylic acid such as (meth)acrylic acid (for example, compounds described in Japanese Patent Publication No. 8-12397), copolymers of an unsaturated alcohol having polyalkylene glycol and a carboxylic acid such as (meth)acrylic acid, copolymers of an unsaturated alcohol having polyalkylene glycol and a dicarboxylic acid such as maleic acid, etc. can be used. Here, (meth)acrylic acid means a carboxylic acid selected from acrylic acid and methacrylic acid.

[0029] As a polycarboxylic acid-based dispersant, copolymers containing monomer (a1) represented by the following general formula (a1) as a constituent monomer are preferred from the viewpoint of dispersibility of hydraulic composition slurries. As a polycarboxylic acid-based dispersant, a copolymer (hereinafter referred to as component (A)) containing monomer (a1) represented by the following general formula (a1) and monomer (a2) represented by the following general formula (a2) as constituent monomers is more preferred.

[0030] [ka]

[0031] [During the ceremony, R 1a , R 2a : They may be the same or different, and may be a hydrogen atom or a methyl group R3a : A hydrogen atom or -(CH2) q (CO) p O(AO) n1 X 1a X 1a : A hydrogen atom or an alkyl group having 1 to 4 carbon atoms AO: An alkyleneoxy group having 2 to 4 carbon atoms n1: The average number of moles of addition of AO, a number from 1 to 300 q: A number from 0 to 2 p: A number of 0 or 1 represents.〕

[0032]

Chemical formula

[0033] 〔In the formula, R 4a , R 5a , R 6a : May be the same or different, a hydrogen atom, a methyl group or (CH2) r COOM 2a where (CH2) r COOM 2a is COOM 1a or another (CH2) r COOM 2a may form an anhydride with, and in that case, M of those groups 1a , M 2a does not exist. M 1a , M 2a : May be the same or different, a hydrogen atom, an alkali metal, an alkaline earth metal (1 / 2 atom), an ammonium group, an alkylammonium group, a substituted alkylammonium group, an alkyl group, a hydroxyalkyl group or an alkenyl group r represents a number from 0 to 2.〕

[0034] In general formula (a1), R 1a is preferably a hydrogen atom from the viewpoint of availability. In general formula (a1), R 2aFrom the viewpoint of availability and copolymerizability with monomer (a22), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred. In general formula (a1), R 3a From the standpoint of availability, hydrogen atoms are preferred. In general formula (a1), X 1a From the viewpoint of ease of manufacture and the quality stability of the product, a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred. In general formula (a1), AO is an alkylene oxy group having 2 to 4 carbon atoms. From the viewpoint of availability and cost, a group selected from an ethylene oxy group and a propylene oxy group is preferred, and an ethylene oxy group is more preferred. It is preferable that AO contains an ethylene oxy group. In general formula (a1), n1 is the average number of moles of AO added, and from the viewpoint of the dispersibility of the hydraulic composition slurry, it is 1 or more, preferably 4 or more, more preferably 9 or more, and 300 or less, preferably 100 or less, and more preferably 30 or less. Furthermore, if the AO contains alkylene oxy groups with different numbers of carbon atoms in an average of n1 repeating units, these alkylene oxy groups with different numbers of carbon atoms may include random addition, block addition, or a mixture thereof. In the total AO, ethylene oxy groups are preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and it is preferable that the entire AO consists of ethylene oxy groups. For example, AO may also contain propylene oxy groups, butylene oxy groups, etc., in addition to ethylene oxy groups. In general formula (a1), from the viewpoint of availability, q is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0.

[0035] In general formula (a2), from the standpoint of availability, R 4a A hydrogen atom is preferred. In general formula (a2), R 5a The atom is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. In general formula (a2), from the standpoint of availability, R 6a A hydrogen atom is preferred. (CH2)r COOM 2a Regarding COOM 1a or other (CH2) r COOM 2a They may also form anhydrous compounds, in which case the M of those groups 1a M 2a It does not exist. M 1a and M 2a These are identical or different hydrogen atoms, alkali metals, alkaline earth metals (1 / 2 atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroxyalkyl groups, or alkenyl groups. M 1a and M 2a The alkyl group, hydroxyalkyl group, and alkenyl group each preferably have 1 to 4 carbon atoms. M 1a and M 2a Preferably, the same or different components are a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, or alkylammonium group; more preferably, a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), or ammonium group; even more preferably, a hydrogen atom, alkali metal, or alkaline earth metal (1 / 2 atom); and still more preferably, a hydrogen atom or alkali metal. (CH2) in general formula (a22) r COOM 2a r is preferably 0.

[0036] The copolymer of component (A) may contain constituent monomers other than monomer (a1) and monomer (a2) (hereinafter also referred to as monomer (a23)). Examples of monomer (a3) ​​include hydroxyethyl acrylate, hydroxyethyl methacrylate, 2-(methacryloyloxy)ethyl phosphate (HEMA-P), 2-hydroxyethyl acrylate (HEA), methyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate (HEMA), allyl sulfonic acid, methallyl sulfonic acid, and salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. Furthermore, constituent units can be made using one or more monomers selected from (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-(meth)acrylamide-2-methasulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, styrenesulfonic acid, etc. (Meth)acrylic means acrylic or methacrylic.

[0037] In the total constituent monomers of component (A), the proportion of monomer (a1) in the total amount of monomer (a1) and monomer (a2) is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, and preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0038] In the total constituent monomers of component (A), the proportion of monomer (a2) in the total amount of monomer (a1) and monomer (a2) is preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, from the viewpoint of achieving both dispersion retention and low viscosity of the hydraulic composition slurry.

[0039] (A) Of the total constituent monomers of component (A), the total amount of monomer (a1) and monomer (a2) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and preferably 99% by mass or less, from an economic standpoint.

[0040] The weight-average molecular weight (Mw) of component (A) is preferably 10,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, and preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, and even more preferably 50,000 or less, from the viewpoint of the dispersibility of the hydraulic composition slurry.

[0041] The weight-average molecular weight of component (A) was measured by gel permeation chromatography (GPC) under the following conditions. *GPC conditions Equipment: GPC (HLC-8320GPC), manufactured by Tosoh Corporation. Columns: G4000PWXL + G2500PWXL (manufactured by Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN=9 / 1 Flow rate: 1.0mL / min Column temperature: 40℃ Detection: RI Sample size: 0.2 mg / mL Standard substances: Polyethylene glycol equivalent (monodisperse polyethylene glycols with known molecular weights: 87,500, 250,000, 145,000, 46,000, 24,000)

[0042] (A) The polycarboxylic acid-based dispersant of component (A) can also be a combination of two or more dispersants with different average moles of AO added, monomer (a1), and monomer (a2).

[0043] If the hydraulic composition slurry contains a dispersant, the amount of the dispersant is preferably 0.001 parts by mass or more, more preferably 0.005 parts by mass or more, even more preferably 0.01 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of hydraulic powder, from the viewpoint of workability, flow retention, and economy.

[0044] The hydraulic composition slurry may also contain other components besides those mentioned above, to the extent that it does not affect the effects of the present invention. Examples include air-entraining agents, retarders, foaming agents, thickeners, foaming agents, waterproofing agents, fluidizing agents, etc. (excluding hydraulic powders and dispersants).

[0045] The hydraulic composition slurry is mixed with the mud in the borehole to produce the pile base reinforcement. The hydraulic composition slurry is mixed with the mud when injected into the borehole, but the mixing of the hydraulic composition slurry and the mud may be either uniform or non-uniform. In the case of uniform mixing, after injecting the hydraulic composition slurry into the borehole, the hydraulic composition slurry and the mud may be stirred and mixed. In step 2, the hydraulic composition slurry and the mud are mixed such that the volume ratio of the amount of hydraulic composition slurry to the amount of mud (mud / hydraulic composition slurry) is preferably 0.4 or more, more preferably 0.45 or more, even more preferably 0.5 or more, and preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less, from the viewpoint of the strength of the foundation reinforcement.

[0046] Step 3 is the process of sinking a concrete pile into the base of the pile in the excavated hole after Step 2. In step 2, after filling the excavated hole with the foundation reinforcement portion, the concrete pile is sunk, the foundation reinforcement portion is hardened, and the ground and the pile are integrated.

[0047] [Hydraulic composition slurry for pile foundation reinforcement] In step 2 of the concrete pile embedding method of the present invention, the hydraulic composition slurry has excellent filling properties when mixed with the muddy water obtained in step 1 in the excavated hole to produce the pile base reinforcement portion. In other words, the present invention relates to a hydraulic composition slurry for pile foundation reinforcement, which is used to manufacture the foundation reinforcement portion of a pile by mixing a hydraulic composition slurry with a specific gravity of 1.8 or less in an excavated hole, The present invention provides a hydraulic composition slurry for pile foundation reinforcement, which contains hydraulic powder and water, and in which the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less.

[0048] The hydraulic composition slurry for pile root reinforcement of the present invention is the same as the hydraulic composition slurry in step 2 of the concrete pile embedding method of the present invention, and the embodiments described in the concrete pile embedding method of the present invention can be applied as appropriate. The slurry in the hydraulic composition slurry for pile root reinforcement of the present invention is the same as the slurry in step 1 of the concrete pile embedding method of the present invention, and the embodiments described in the concrete pile embedding method of the present invention can be applied as appropriate. The hydraulic composition slurry for pile root reinforcement of the present invention can be appropriately applied to the embodiments described in the concrete pile embedding method of the present invention. [Examples]

[0049] [Ingredients used] The components used in the examples and comparative examples are shown below. • Water: Tap water • Hydraulic powder: Blast furnace cement type B, manufactured by Sumitomo Osaka Cement Co., Ltd. • Polycarboxylic acid dispersant: Polymer synthesized by the following manufacturing method

[0050] Method for producing polycarboxylic acid-based dispersants 356 parts by mass of deionized water were charged into a glass reaction vessel (four-necked flask) equipped with a stirrer. The reaction vessel was purged with nitrogen while stirring, and heated to 80°C under a nitrogen atmosphere. Next, an aqueous monomer solution prepared by mixing 327 parts by mass of methacrylic acid (methoxypolyethylene glycol 23 mol) ester, 58 parts by mass of methacrylic acid, and 176 parts by mass of deionized water, an aqueous solution prepared by mixing 2.8 parts by mass of 3-mercaptopropionic acid and 27.7 parts by mass of deionized water, and an aqueous solution prepared by mixing 3.3 parts by mass of ammonium persulfate and 18.6 parts by mass of deionized water were added dropwise over 2 hours. After the dropwise addition was complete, an aqueous solution prepared by mixing 1.1 parts by mass of ammonium persulfate and 6.2 parts by mass of deionized water was added dropwise over 0.5 hours. After the dropwise addition was complete, the temperature was maintained at 80°C for 1 hour for maturation. Subsequently, the reaction solution was neutralized with an aqueous sodium hydroxide solution at a temperature below 80°C to obtain a polycarboxylic acid-based dispersant with a weight-average molecular weight of 37,000.

[0051] [Example 1, Comparative Example 1: Evaluation of filling properties using a simulated evaluation device] [Preparation of muddy water] Simulated mud was prepared by mixing sand, clay, and water. A mixture of No. 6 silica sand and No. 7 silica sand (mass ratio 8 / 2) was used as the sand, and Kasaoka clay and bentonite (Kunigel GS, manufactured by Kunimine Industries Co., Ltd.) were used as the clay. The sand and Kasaoka clay were mixed in a 7:3 (mass ratio), and water was added to adjust the specific gravity of the mud for each mixture type listed in Table 1. The viscosity of the mud was adjusted with bentonite to prevent separation. The specific gravity was measured using a mud balance (S-252a, manufactured by Nishinihon Shikiki Co., Ltd.).

[0052] [Preparation of hydraulic composition slurry for pile foundation reinforcement] The aforementioned water, hydraulic powder, and dispersant were mixed to prepare hydraulic composition slurries for pile foundation reinforcement of each type listed in Table 1. The specific gravity and viscosity of each hydraulic composition slurry are also shown in Table 1. The specific gravity was measured using a mud balance (S-252a, manufactured by Nishinihon Testing Machine Co., Ltd.). The viscosity was measured using a viscometer (RION Corporation, VISCOTESTER VT-04E, rotor No. 1, rotation speed: 62.5 rpm) after the rotor was rotated for 1 minute and the value stabilized. In Table 1, the amount of dispersant in each hydraulic composition slurry is the amount of solid content (effective content) per 100 parts by mass of hydraulic powder (parts by mass), and W / P (mass%) is the mass percentage of water content to hydraulic powder content in each hydraulic composition slurry (water / hydraulic powder).

[0053] [Evaluation of filling properties using a simulated evaluation device] To evaluate the filling performance in the borehole, a simulated evaluation device, as shown in Figure 1, was constructed. A resin cylinder (with an inner diameter of 89 mm at the top, 44 mm at the bottom, and a height of 300 mm) as shown in Figure 1 was fixed with a clamp (not shown in Figure 1), and 400 mL of each of the prepared mud solutions from Table 1 were injected into a breathing bag (a polyethylene bag for measuring PC grout bleeding rate, manufactured by the Japan Society of Civil Engineers). The breathing bag containing the mud solution was then attached to the lower end of the resin cylinder as shown in Figure 1. Next, a rubber hose with a diameter of 2-3 mm was attached to a metal rod as shown in Figure 1, and the metal rod was fixed with a clamp (not shown in Figure 1) so that it did not touch the bottom of the breathing bag, about 2-5 mm away from the bottom. The rubber hose was secured to the metal rod with tape so that the injection direction of the end opening was downwards, as shown in Figure 1. A 500 ml syringe was attached to the end opening of the rubber hose opposite the breathing bag side, and each hydraulic composition slurry from Table 1, immediately after preparation, was injected into the mud water in the breathing bag by pushing the syringe through in about 10 seconds. After injecting 400 ml of hydraulic composition slurry, the metal rod was removed, and the mixture of mud water and hydraulic composition slurry was left to stand for 24 hours until the root reinforcement section hardened. The hardened root reinforcement section was removed from the breathing bag, and its filling performance was evaluated. The breathing bag was peeled off the hardened root reinforcement section, and it was lightly rinsed. When 400 ml of hydraulic composition slurry is filled into the breathing bag, the height is approximately 20 cm. Therefore, if the slurry is completely injected into the bottom of the breathing bag, for example, the height of the hardened root reinforcement section will be 20 cm. In other words, the closer the height ratio calculated as "injected height (cm) / 20 = height ratio" is to 1, the better the hydraulic composition slurry has pushed up the mud from the bottom of the borehole (breathing bag) and completely replaced it, indicating good filling performance. Also, if the bottom of the hardened root reinforcement section has not hardened in the shape of the bag and there are unfilled areas, it is considered that "there is a chip at the bottom," and the filling performance is judged to be poor. Table 1 shows the results regarding the height ratio of the filling and the presence or absence of chipping at the bottom. The pass / fail status of the filling was determined as follows: "◎" for a height ratio of 1.2 or less and no chipping at the bottom, "〇" for a height ratio greater than 1.2 but no chipping at the bottom, and "×" for a height ratio greater than 1.2 and chipping at the bottom. The results are shown in Table 1. Furthermore, the strength of the hardened foundation reinforcement section was measured for Examples 1-1, 1-2, and Comparative Example 1-1. The strength was measured according to the "Compressive Strength Test Method for Foundation Reinforcement Liquid and Pile Perimeter Fixing Liquid Used in Embedding Methods" of the Japan Concrete Pile Construction Technology Association, including curing and specimen preparation. The strength was measured after 14 days. The results are shown in Table 1.

[0054] [Table 1]

[0055] [Example 2, Comparative Example 2: Evaluation of Filling Properties in Field Tests] <Example 2-1> First, using an excavator, a cylindrical pile hole with a diameter larger than the outer diameter of the pre-fabricated pile was excavated to a predetermined depth while spraying water, and during this process, the excavated soil was mixed with the inner wall of the pile hole and / or the excavated soil was removed. This resulting pile hole is designated as pile hole 1. The lower end of pile hole 1 was excavated to an enlarged diameter to form an enlarged bulbous section. This enlarged bulbous section is designated as enlarged bulbous section 1. In this state, the inside of pile hole 1 and enlarged bulbous section 1 were filled with muddy water consisting of excavated soil and water. This muddy water was collected and its specific gravity was measured. Next, it was found to be 3.8 kg / m³. 3 The aforementioned polycarboxylic acid-based dispersant, 572 kg / m³ 3 Water, 1280 kg / m³ 3 A hydraulic composition slurry for pile root reinforcement was prepared by mixing blast furnace cement type B (manufactured by Sumitomo Osaka Cement Co., Ltd.) in a mixer, with a water / hydraulic powder ratio (W / P) of 45% by mass. The polycarboxylic acid-based dispersant was included as part of the water due to its very small amount. The obtained hydraulic composition slurry for pile root reinforcement was injected as a root reinforcement liquid from the bottom of the enlarged bulb section 1 through the discharge port of the hydraulic composition slurry attached to the excavator, while the excavator was raised at a predetermined speed and stirred, so that the slurry comprised 70% of the total volume of the enlarged bulb section 1 at each depth. Next, the same hydraulic composition slurry as the root reinforcement liquid was injected into the pile hole 1 as a pile-peripheral fixing liquid, and the hydraulic composition slurry and the mud in that section were stirred and mixed to form the pile-peripheral fixing section 1. The volume ratio of the amount of hydraulic composition slurry mixed to the amount of mud (mud / hydraulic composition slurry) was 0.14. The base reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 obtained as described above were core-drilled approximately 4 weeks later to create 4 to 6 specimens with a diameter of 50 mm and a height of 100 mm. The uniaxial compressive strength of the base reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 was measured 56 days (8 weeks) after construction. In addition, an unconsolidated sample was taken from the bottom of the base reinforcement section (enlarged bulb section 1) using the method described in Japanese Patent Application Publication No. 2012-237192, and 3 specimens with a diameter of 50 mm and a height of 100 mm were prepared and cured at room temperature for 4 weeks to measure the uniaxial compressive strength. The measurement method followed JIS A 1107 "Method for core sampling from concrete and method for testing compressive strength" and JIS A 1108 "Method for testing the compressive strength of concrete". The results are shown in Table 2.

[0056] <Example 2-2> The amount of polycarboxylic acid-based dispersant in the hydraulic composition slurry for pile root reinforcement is 7.7 kg / m³. 3 The amount of water used is 568 kg / m³. 3 Except for the difference in the procedure, the same steps were followed as in Example 2-1, and the same evaluation was performed. The results are shown in Table 2.

[0057] <Comparative Example 2-1> First, using an excavator, a cylindrical pile hole with a diameter larger than the outer diameter of the pre-fabricated pile was excavated to a predetermined depth while spraying water, either by mixing the excavated soil with the inner wall of the pile hole or by removing the excavated soil. This resulting pile hole is designated as pile hole 1. The lower end of pile hole 1 was excavated to an enlarged diameter to form an enlarged bulbous section. This enlarged bulbous section is designated as enlarged bulbous section 1. In this state, the inside of pile hole 1 and enlarged bulbous section 1 were filled with muddy water consisting of excavated soil and water. This muddy water was collected, and the specific gravity of the actual muddy water was measured using the method described above. Next, the specific gravity was 644 kg / m³. 3 Water, 1074 kg / m³ 3A hydraulic composition slurry for pile root reinforcement was prepared by mixing blast furnace cement type B (manufactured by Sumitomo Osaka Cement Co., Ltd.) in a mixer, with a water / hydraulic powder ratio (W / P) of 60% by mass. The obtained hydraulic composition slurry for pile root reinforcement was injected as a root reinforcement liquid at 33% by volume of the total volume of the expanded bulb section 1, while stirring at the bottom of the expanded bulb section 1, through the discharge port of the hydraulic composition slurry attached to the excavator. Next, another 33% by volume of the total volume of the expanded bulb section 1 was injected while being pulled up and stirred, and finally, 34% by volume of the total volume of the expanded bulb section 1 (totaling 100% by volume) was injected while moving it up and down twice to form the root reinforcement section. Next, the same hydraulic composition slurry as the root reinforcement liquid was injected into the pile hole 1 as a pile perimeter fixing liquid, and the hydraulic composition slurry and the mud water in that section were stirred and mixed to form the pile perimeter fixing section 1. The volume ratio (muddy water / hydraulic composition slurry) of the amount of the hydraulic composition slurry mixed with the amount of the mud was 0.2. The root reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 obtained as described above were core-drilled approximately 4 weeks later to prepare 4 to 6 specimens with a diameter of 50 mm and a height of 100 mm. The uniaxial compressive strength of the root reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 was measured 56 days (8 weeks) after construction, as in Example 2-1. Also, as in Example 2-1, an unconsolidated sample was taken from the bottom of the root reinforcement section (enlarged bulb section 1), and 3 specimens with a diameter of 50 mm and a height of 100 mm were prepared and cured at room temperature for 4 weeks to measure the uniaxial compressive strength. The results are shown in Table 2.

[0058] <Comparative Example 2-2> First, using an excavator, a cylindrical pile hole with a diameter larger than the outer diameter of the pre-fabricated pile was excavated to a predetermined depth while spraying water, either by mixing the excavated soil with the inner wall of the pile hole or by removing the excavated soil. This resulting pile hole is designated as pile hole 1. The lower end of pile hole 1 was excavated to an enlarged diameter to form an enlarged bulbous section. This enlarged bulbous section is designated as enlarged bulbous section 1. In this state, the inside of pile hole 1 and enlarged bulbous section 1 were filled with muddy water consisting of excavated soil and water. This muddy water was collected, and the specific gravity of the actual muddy water was measured using the method described above. Next, the specific gravity was 644 kg / m³. 3 Water, 1074 kg / m³ 3A hydraulic composition slurry for pile foundation reinforcement was prepared by mixing blast furnace cement type B (manufactured by Sumitomo Osaka Cement Co., Ltd.) in a mixer, with a water / hydraulic powder ratio (W / P) of 60% by mass. The obtained hydraulic composition slurry for pile foundation reinforcement was injected as a foundation reinforcement liquid from the bottom of the enlarged bulb section 1 through the discharge port of cement milk attached to the excavator, while stirring, so that the amount of the slurry at each depth was 100% by volume relative to the total volume of the enlarged bulb section 1, and the excavator was raised at a predetermined speed. Next, the same hydraulic composition slurry as the foundation reinforcement liquid was injected into the pile hole 1 as a pile perimeter fixing liquid, and the cement milk and the mud in this section were stirred and mixed to form the pile perimeter fixing section 1. The volume ratio of the amount of hydraulic composition slurry mixed to the amount of mud mixed (mud / hydraulic composition slurry) was 0.2. The root reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 obtained as described above were core-drilled approximately 4 weeks later to create 4 to 6 specimens with a diameter of 50 mm and a height of 100 mm. The uniaxial compressive strength of the root reinforcement section (enlarged bulb section 1) and pile-perimeter fixing section 1 was measured 56 days (8 weeks) after construction, as in Example 2-1. Also, as in Example 2-1, an unconsolidated sample was taken from the bottom of the root reinforcement section (enlarged bulb section 1), and 3 specimens with a diameter of 50 mm and a height of 100 mm were prepared and cured at room temperature for 4 weeks, and the uniaxial compressive strength was measured. The results are shown in Table 2.

[0059] The method for measuring the specific gravity of each muddy water in Table 2 involved preparing a 200 mL container, filling it to the brim with muddy water, measuring its weight (in grams), and dividing the weight of the muddy water by its volume (200 mL) to obtain the specific gravity of the muddy water. The specific gravity and viscosity of the hydraulic composition slurry used for root reinforcement of each pile, as shown in Table 2, are also shown. The specific gravity of the hydraulic composition slurry used for root reinforcement of each pile shown in Table 2 was measured using a mud balance (S-252a, manufactured by Nishinihon Shiki Co., Ltd.). The viscosity of the hydraulic composition slurry used for root reinforcement of each pile, as shown in Table 2, was measured using a viscometer (RION Corporation, VISCOTESTER VT-04E, rotor No. 1, rotation speed: 62.5 rpm). The viscosity was measured after the rotor was rotated for 1 minute and the value stabilized.

[0060] Table 2 shows the strength of the unconsolidated sample of the root reinforcement section (enlarged bulb section 1) and the average core strength for each example and comparative example, the average core strength of the pile perimeter fixing section, and the cement reduction rate calculated using the following formula.

[0061]

number

[0062] • Amount of hydraulic powder per unit volume injected into the enlarged bulb section 1 [kg / m³] 3 ] = Amount of hydraulic powder per unit volume in cement grout [kg / m³ 3 ] × Injection rate relative to the total volume of the enlarged bulb portion 1 [volume %] • Total volume of the enlarged bulb section 1 [m³ 3 ] = Excavator stirring radius [m] × Excavator stirring radius [m] × π × Excavation length of enlarged bulb section 1 [m]

[0063] [Table 2]

[0064] In Table 2, Examples 2-1 and 2-2, compared to Comparative Examples 2-1 and 2-2, show a higher cement reduction rate in the base reinforcement section (enlarged bulb section 1), yet exhibit higher uniaxial compressive strength in the base reinforcement section after 56 days (8 weeks). This indicates superior filling performance when manufacturing the base reinforcement section of a pile.

[0065] In Table 2, the amount of dispersant in the hydraulic composition slurry for root reinforcement of each pile is the amount of solid content (effective content) per 100 parts by mass of hydraulic powder (parts by mass).

Claims

1. A concrete pile embedding method comprising the following steps. Process 1: Using an excavation and mixing rod, drilling is carried out down to the supporting layer of the ground while injecting a drilling fluid containing water, filling the borehole with a drilling slurry containing soil and water, with a specific gravity of 1.8 or less. Step 2: After Step 1, a hydraulic composition slurry containing hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less, is injected into the excavated hole and mixed with the mud to construct the pile foundation. Step 3: After Step 2, a step of sinking a concrete pile into the base reinforcement portion of the pile in the excavated hole.

2. The concrete pile embedding method according to claim 1, wherein the hydraulic composition slurry further contains a dispersant, and the viscosity of the hydraulic composition slurry is 300 mPa·s or more and 1000 mPa·s or less.

3. The concrete pile embedding method according to claim 2, wherein the dispersant is a polycarboxylic acid-based dispersant.

4. A hydraulic composition slurry for pile foundation reinforcement, used to manufacture the pile foundation reinforcement portion by mixing a hydraulic composition slurry with a specific gravity of 1.8 or less in an excavated hole, A hydraulic composition slurry for pile foundation reinforcement, comprising hydraulic powder and water, wherein the mass percentage of water content to hydraulic powder content (water / hydraulic powder) is 50% by mass or less.

5. The hydraulic composition slurry for pile root reinforcement according to claim 4, further containing a dispersant, wherein the viscosity of the hydraulic composition slurry is 300 mPa·s or more and 1000 mPa·s or less.

6. The hydraulic composition slurry for pile root reinforcement according to claim 5, wherein the dispersant is a polycarboxylic acid-based dispersant.

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