Cement-resistant stabilizing liquid

Abstract

To provide a stabilizing liquid that suppresses deterioration of a function of the stabilizing liquid due to cement components.SOLUTION: A stabilizing liquid is used in a cast-in-place concrete pile construction method using an earth drill method for ground backfilled with liquefied treated soil or improved soil, and contains bentonite, which is sodium bentonite or activated bentonite, and an acrylic polymer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a stabilizing solution used in a cast-in-place concrete pile construction method using an earth drill method. [Background technology]

[0002] A known stabilizing solution used for cast-in-place concrete piles by the earth drill method is one that contains bentonite and a water-soluble polymer such as CMC (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-140559 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, when constructing new piles on ground that has been backfilled with liquefied treated soil or improved soil after removing existing underground demolition sections, the cement components contained in the liquefied treated soil or improved soil will mix with the stabilizing liquid, reducing its functionality. [Means for solving the problem]

[0005] The stabilizing liquid for solving the above problems is a stabilizing liquid used in a cast-in-place concrete pile construction method using an earth drill method for ground backfilled with liquefied treated soil or improved soil, and contains bentonite, which is sodium bentonite or activated bentonite, and an acrylic polymer. Effect of the Invention

[0006] The stabilizing liquid of the present disclosure inhibits deterioration of the functionality of the stabilizing liquid caused by cement components. [Brief description of the drawings]

[0007] [Figure 1] Figure 1 is a graph showing the results of the repeated contamination test of the acrylic polymer stabilizing liquid (change in the concentration of the acrylic polymer due to cement contamination). [Diagram 2] Figure 2 is a graph showing the change over time in the funnel viscosity of the acrylic polymer stabilizing liquid and the cellulose polymer stabilizing liquid. [Diagram 3] Figure 3 is a graph showing the change over time in the water dehydration amount of the acrylic polymer stabilizing liquid and the cellulose polymer stabilizing liquid.

Mode for Carrying Out the Invention

[0008] The stabilizing liquid in this embodiment will be described in the following order. First, [1] the composition of the stabilizing liquid will be described, and then [2] the bentonite evaluation in the stabilizing liquid using test examples and [3] the cement resistance test of the acrylic polymer stabilizing liquid using test examples will be described. Further, [4] the repeated contamination test of the acrylic polymer stabilizing liquid using test examples will be described, and then [5] the heat-accelerated spoilage test of the acrylic polymer stabilizing liquid using test examples will be described.

[0009] [1] Stabilizing Liquid The stabilizing liquid is a water-bentonite-based liquid prepared for excavation in the in-situ pile method and is also called slurry. The stabilizing liquid contains water, (a) bentonite, and (b) an acrylic polymer. The stabilizing liquid may contain (c) a coagulating ion sequestering agent. In addition to (a) to (c), the stabilizing liquid may contain (d) additives such as a cellulose polymer and a dispersant.

[0010] The blending amount of each component in the stabilizing liquid is shown as the weight% on an external basis with respect to the water constituting the stabilizing liquid. The deterioration of the stabilizing liquid means that the function of the stabilizing liquid is reduced by coagulating ions such as calcium ions. The reduction in the function of the stabilizing liquid is an increase in the viscosity in the stabilizing liquid, the specific gravity due to the gelation of the stabilizing liquid, the water dehydration amount in the stabilizing liquid, and the like.

[0011] Cast-in-place pile construction methods include the earth drill method, the reverse method, and the all-casing method. The earth drill method, which is one of the cast-in-place pile construction methods, is a method of excavating the ground by rotating a drilling bucket and discharging the soil stored inside the bucket to the ground. In the earth drill method, the hole wall is protected by a surface casing at the surface and by a stabilizing liquid at deeper depths.

[0012] The ground to which the stabilizing solution is applied includes self-hardening liquefied soil and improved soil. In the cast-in-place pile method, after excavation is completed, a reinforcing bar cage made to a specified shape is placed in the hole, and then concrete is poured in using the tremie method to construct the pile. Hardening materials such as Portland cement and blast furnace cement contained in liquefied soil and improved soil dissolve calcium ions into the stabilizing solution.

[0013] (a) Bentonite The main component mineral of bentonite, which is a layered silicate mineral, is montmorillonite. The content of montmorillonite relative to the total weight of bentonite is 40.0% by weight or more and 80.0% by weight or less, preferably 40.0% by weight or more, and more preferably 60% by weight or more and 80% by weight or less.

[0014] The bentonite may be sodium type bentonite or activated bentonite that has been subjected to an ion exchange treatment, and the bentonite is preferably sodium type bentonite.

[0015] In sodium bentonite and activated bentonite, the main cation that contributes to the cation exchange capacity (CEC) of the main mineral montmorillonite is sodium. In sodium bentonite, the proportion of sodium among the cations that contribute to the CEC of montmorillonite is 70% or more.

[0016] Sodium bentonite and activated bentonite have higher swelling properties and higher water retention properties due to the expansion of the interlayer spaces of montmorillonite than calcium bentonite.

[0017] The proportion of powder particle sizes of 63 μm or less in the sodium bentonite powder is preferably 80%, and more preferably 90% or more. The particle size of the bentonite can be obtained by a laser diffraction method using a laser diffraction type device. The laser diffraction type device that can be used is the MASTERSIZER3000 manufactured by Malvern.

[0018] The swelling power of bentonite is 15ml / 2g or more according to the Japan Bentonite Industry Association Standard Test Method (JBAS) "Swelling test method for bentonite (powdered)". The pH of bentonite is 9.5 or more and 11 or less according to the Japan Bentonite Industry Association Standard Test Method (JBAS) "pH measurement method for bentonite (powdered)".

[0019] The amount of bentonite may be 0.5% by weight or more and 6.0% by weight or less, preferably 2.0% by weight or more and 5.0% by weight or less, and more preferably 3.0% by weight or more and 4.0% by weight or less. If the amount is 0.5% by weight or more and 6.0% by weight or less, the stabilizing solution can easily obtain an appropriate viscosity, and deterioration of the stabilizing solution can easily be suppressed.

[0020] If the amount of bentonite used is 0.5% by weight or less, the weight ratio of powdered bentonite will be so low that the formation of mud cakes will be insufficient, and if the amount is too low, there will be a shortage of material for clogging.

[0021] (b) Acrylic polymer The acrylic polymer is adsorbed to the bentonite and acts as a protective colloid to enhance the wall-forming ability of the stabilized solution. The acrylic polymer has putrefaction resistance.

[0022] The blending amount of the acrylic polymer may be from 0.2 to 1.2% by weight, preferably from 0.2 to 1.0% by weight, and more preferably from 0.2 to 0.8% by weight.

[0023] (c) Coagulant sequestering agent The coagulating sequestering agent dissolves in water and reacts with coagulating ions such as calcium ions and magnesium ions to produce an inactive compound. The coagulating sequestering agent may be at least one selected from the group consisting of sodium bicarbonate (baking soda) and sodium carbonate (soda ash). More preferably, the coagulating sequestering agent is baking soda.

[0024] The amount of the cohesive sequestering agent may be from 0.0% to 0.8% by weight, preferably from 0.2% to 0.8% by weight, and more preferably from 0.2% to 0.6% by weight.

[0025] (d)Additives In addition to the above components (a) to (c), the stabilizing liquid may contain appropriate additives, a cellulose-based polymer, and a dispersant, as long as the above-mentioned effects are not impaired. The cellulose-based polymer dissolves in water and functions as a thickener for the stabilizing liquid.

[0026] [2] Bentonite evaluation: Test examples 1-9 [Formulation of Test Example 1] The stabilizing solution of Test Example 1 was prepared by adding the following components (a) to (c) to water. (a) Bentonite: Sodium bentonite Product name: Kunigel U (manufactured by Kunimine Industries Co., Ltd.) Bentonite content: 4.0% by weight (b) Acrylic polymer: Water-soluble acrylic polymer Acrylic polymer content: 0.6% by weight (c) Coagulant sequestering agent: soda ash Amount of coagulant sequestering agent: 0.0% by weight

[0027] [Composition of Test Examples 2 to 7] The stabilizing solution of Test Example 2 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to sodium-type bentonite (product name Kunigel VO (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0028] The stabilizing solution of Test Example 3 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to sodium-type bentonite (product name Kunigel VA (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0029] The stabilizing solution of Test Example 4 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to calcium-type bentonite (product name KUNIBOND (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0030] A stabilizing solution of Test Example 5 was prepared in the same manner as in Test Example 4, except that the blending amount of (c) soda ash was changed to 0.2% by weight. The stabilizing solution of Test Example 6 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to calcium-type bentonite (product name Kunibond C (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0031] A stabilizing solution of Test Example 7 was prepared in the same manner as in Test Example 6, except that the blending amount of (c) soda ash was changed to 0.2% by weight. The stabilizing solution of Test Example 8 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to activated bentonite (product name Kunigel CB (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0032] The stabilizing solution of Test Example 9 was prepared in the same manner as Test Example 1, except that the bentonite (a) was changed to activated bentonite (product name Neokunibond (registered trademark) (manufactured by Kunimine Industries Co., Ltd.)).

[0033] [Table 1]

[0034] [Table 2]

[0035] [Bentonite evaluation results] The properties of the stabilizing solutions of Test Examples 1 to 9 were measured immediately after preparation and one day after preparation. Tables 1 and 2 show the measurement results of Test Examples 1 to 9.

[0036] The properties of the stabilized liquid were measured, including funnel viscosity, apparent viscosity, plastic viscosity, yield value, gel strength, B-type viscosity, amount of dehydration, pH, electrical conductivity, and suspension stability.

[0037] The funnel viscosity was measured using a funnel viscometer. The funnel viscosity of the stabilized liquid is the flow time of 500 ml of stabilized liquid. The funnel viscosity of water is 18.5±0.5 seconds. The apparent viscosity, plastic viscosity, yield value, and gel strength were measured using a viscometer (35SA: manufactured by Funnel Instrument Company). The B-type viscosity was measured using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0038] The amount of dehydration was measured by pressurizing the dispersion to 0.3 MPa using a dehydration tester (filter press: manufactured by Fan Instrument Company) and measuring the amount of dehydration after 30 minutes of pressurization. The conductivity is a measurement value for estimating the electrolyte concentration and was obtained at 25°C using a conductivity meter (DS-12: manufactured by Horiba, Ltd.). The conductivity of distilled water was 1 (μs / cm) or less, and the conductivity of seawater was about 45,000 (μs / cm). The pH was measured at 25°C using a pH meter (D-54: manufactured by Horiba, Ltd.).

[0039] The suspension stability was measured for the stable solutions immediately after preparation and one day after preparation. In Tables 1 and 2, stable solutions in which good dispersion was confirmed by visual evaluation with no settling of solid particles even one day after preparation are marked with "O," and stable solutions in which the presence of precipitates or the like was confirmed one day after preparation are marked with "X."

[0040] As shown in Table 1, none of the stabilizing solutions of Test Examples 1 to 3 contain a cellulose-based polymer that functions as a thickener. On the other hand, it was confirmed that the stabilizing solutions of Test Examples 1 to 3 had the appropriate ranges for use in the cast-in-place pile method for all of the funnel viscosity, apparent viscosity, plastic viscosity, yield value, gel strength, B-type viscosity, dehydration amount, pH, and electrical conductivity immediately after preparation. It was also confirmed that the stabilizing solutions of Test Examples 1 to 3 had the properties within the appropriate ranges for use in the cast-in-place pile method, just like immediately after preparation, even after one day had passed since their preparation, and showed good suspension stability.

[0041] The stabilizing solutions of Test Examples 4 to 7 also do not contain any cellulose-based polymer that functions as a thickener. On the other hand, the stabilizing solutions of Test Examples 4 to 7 did not achieve the appropriate range of dehydration amount for use in the cast-in-place pile method immediately after preparation, and the suspension stability one day after preparation was also found to be outside the appropriate range for use in the cast-in-place pile method. The stabilizing solution of Test Example 7 was found to have a lower plastic viscosity and yield value than those of Test Examples 1 to 3, and to have a suspension stability applicable to the cast-in-place pile method.

[0042] The stabilizing liquids of Test Examples 8 to 9 also do not contain any cellulose-based polymers that function as thickeners. For the stabilizing liquid of Test Example 8, immediately after preparation, it was found to have appropriate ranges for all of funnel viscosity, apparent viscosity, plastic viscosity, yield value, gel strength, B-type viscosity, water loss, pH, and conductivity, which are used in the in-situ pile driving method. Also, even when one day has passed since the preparation of the stabilizing liquid of Test Example 8, it was found to have the properties within the appropriate range used in the in-situ pile driving method, just as immediately after preparation, and to exhibit good suspension stability. On the other hand, for the stabilizing liquid of Test Example 9, immediately after preparation, the water loss within the appropriate range used in the in-situ pile driving method could not be obtained, and the suspension stability immediately after preparation was also found to be outside the appropriate range used in the in-situ pile driving method.

[0043] From the above, as in Test Examples 1 to 3, a combination of sodium-type bentonite and an acrylic polymer can obtain a stabilizing liquid having properties within the appropriate range used in the in-situ pile driving method.

[0044] On the other hand, as in Test Examples 4 to 7, in the combination of calcium-type bentonite and an acrylic polymer, the apparent viscosity and plastic viscosity are lower than those of sodium-type bentonite. Even when soda ash is added, as observed between Test Examples 4 to 5 and Test Examples 6 to 7, in the combination of calcium-type bentonite and an acrylic polymer, variations can occur in the effect of adding a calcium sequestering agent and the properties of the stabilizing liquid. Thus, in terms of water loss and suspension stability, the combination of calcium-type bentonite and an acrylic polymer is inferior to sodium-type bentonite.

[0045] On the other hand, a combination of activated bentonite and an acrylic polymer as in Test Example 8 can provide a stabilizing solution having properties within the appropriate range for use in the cast-in-place pile method. However, even when a combination of activated bentonite and an acrylic polymer as in Test Example 9 is used, the properties of the stabilizing solution may vary so that the stabilizing solution does not have the properties within the appropriate range for use in the cast-in-place pile method. Thus, the combination of activated bentonite and an acrylic polymer is superior to calcium-type bentonite in terms of dehydration amount and suspension stability, but inferior to sodium-type bentonite.

[0046] [3] Cement resistance test: Test examples 21 to 28 [Formulation of Test Example 21] The stabilizing solution of Test Example 21 was prepared by adding the following components (a) to (c) and (f) to water. (a) Bentonite: Sodium bentonite Product name: Kunigel U (manufactured by Kunimine Industries Co., Ltd.) Bentonite content: 4.0% by weight (b) Acrylic polymer: Water-soluble acrylic polymer Acrylic polymer content: 0.6% by weight (c) Coagulant sequestering agent: soda ash Amount of coagulant sequestering agent: 0.0% by weight (f) Cement contamination: 0.8% by weight

[0047] [Composition of Test Examples 22 to 28] A stabilizing solution of Test Example 22 was prepared in the same manner as in Test Example 21, except that (f) the amount of cement contamination was changed to 1.2% by weight.

[0048] The stabilizing solution of Test Example 23 was prepared in the same manner as Test Example 21 except that the blending amount of (b) the acrylic polymer was changed to 0.4 wt % and the blending amount of (c) the coagulating ion-blocking agent was changed to 0.2 wt % from the stabilizing solution of Test Example 21.

[0049] The stabilizing solution of Test Example 24 was prepared in the same manner as Test Example 21, except that the bentonite (a) was changed to sodium-type bentonite (product name Kunigel VA (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0050] A stabilizing solution of Test Example 25 was prepared in the same manner as in Test Example 24, except that (f) the amount of cement contamination was changed to 1.2% by weight. The stabilizing solution of Test Example 26 was prepared in the same manner as Test Example 24, except that (b) the amount of the acrylic polymer was changed to 0.4 wt % and (c) the amount of the coagulating ion-blocking agent was changed to 0.2 wt %.

[0051] The stabilizing solution of Test Example 27 was prepared in the same manner as Test Example 21, except that the bentonite (a) was changed to sodium-type bentonite (product name Kunigel VO (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0052] A stabilized solution of Test Example 28 was prepared in the same manner as in Test Example 26, except that (f) the amount of cement contamination was changed to 1.2% by weight from the stabilized solution of Test Example 27.

[0053] [Table 3]

[0054] [Table 4]

[0055] [Cement resistance test results] The properties of the stabilizing solutions of Test Examples 21 to 28 were measured immediately after preparation and one day after preparation. Tables 3 and 4 show the measurement results of Test Examples 21 to 28.

[0056] The properties of the stabilizing liquid were measured in the same manner as in Test Examples 1 to 9, including funnel viscosity, apparent viscosity, plastic viscosity, yield value, gel strength, B-type viscosity, amount of dehydration, pH, electrical conductivity, and suspension stability. The suspension stability was measured for the stabilizing liquid immediately after preparation and one day after preparation. Tables 3 and 4 show the amount of settling relative to the reference value for the stabilizing liquid in which good dispersion was observed with no settling of solid particles by visual evaluation even one day after preparation, and the lower the suspension stability value, the better the stability.

[0057] The stabilizing solutions of Test Examples 21 to 26 do not contain any cellulose-based polymer that functions as a thickener. The stabilizing solutions of Test Examples 21 to 26 were found to have the appropriate ranges for use in the cast-in-place pile method for all of the funnel viscosity, apparent viscosity, plastic viscosity, yield value, gel strength, B-type viscosity, dehydration amount, pH, and electrical conductivity immediately after preparation. In addition, the stabilizing solutions of Test Examples 21 to 26 were found to have the properties within the appropriate ranges for use in the cast-in-place pile method, as with the case immediately after preparation, even after one day had passed since their preparation, and to exhibit good suspension stability. Among Test Examples 21 to 26, in the case where a flocculating ion-blocking agent was added to the stabilizing solution as in Test Examples 23 and 26, it was found that high suspension stability was exhibited even when the acrylic polymer concentration was reduced.

[0058] The measured values ​​of the stabilizing solutions of Test Examples 27 and 28 immediately after preparation and after leaving them to stand overnight were either significantly outside the appropriate values ​​for use in cast-in-place concrete piles or were not measurable. It was found that there was a difference in the way the degradation occurred depending on the type of bentonite when using a combination of sodium bentonite and acrylic polymer.

[0059] The bentonite constituting the stabilizing liquid of Test Examples 21 to 28 was all sodium type bentonite, and had a swelling power of 15 ml / 2 g or more. On the other hand, the proportion of powder particle sizes of 63 μm or less in the bentonite constituting the stabilizing liquid of Test Examples 21 to 26 was 80% or more, while the proportion of 63 μm or less in Test Examples 27 and 28 was less than 80%.

[0060] From the above, the ratio of bentonite powder particle size of 63μm or less is 80% or more, and Na 2 When bentonite with an O content of 2% by weight or more is combined with an acrylic polymer, a stabilizing liquid having good resistance to deterioration of cement can be obtained. In addition, when the proportion of bentonite powder particles of 63 μm or less is 90% or more, a stabilizing liquid that is particularly good for cement can be obtained.

[0061] [4] Repeated contamination test: Test examples 31-39 [Formulation of Test Example 31] The stabilizing solution of Test Example 31 was prepared by adding the following components (a) to (c) to water. (a) Bentonite: Sodium bentonite Product name: Kunigel VA (manufactured by Kunimine Industries Co., Ltd.) Bentonite content: 4.0% by weight (b) Acrylic polymer: Water-soluble acrylic polymer Acrylic polymer content: 0.6% by weight (c) Coagulant sequestering agent: sodium bicarbonate Amount of coagulant sequestering agent: 0.4% by weight

[0062] [Composition of Test Examples 32 to 38] A stable solution of Test Example 32 was prepared in the same manner as in Test Example 31, except that the blending amount of (c) the coagulable ion sequestering agent was changed to 0.2% by weight.

[0063] A stable solution of Test Example 33 was prepared in the same manner as in Test Example 31, except that the blending amount of (c) the coagulable ion sequestering agent was changed to 0.0 wt %.

[0064] The stabilizing solution of Test Example 34 was prepared in the same manner as Test Example 31, except that the bentonite (a) was changed to sodium-type bentonite (product name Kunigel U (registered trademark) (manufactured by Kunimine Kogyo Co., Ltd.)).

[0065] A stabilizing solution of Test Example 35 was prepared in the same manner as in Test Example 31, except that the blending amount of (b) the acrylic polymer was changed to 0.4% by weight. A stabilizing solution of Test Example 36 was prepared in the same manner as in Test Example 35, except that the blending amount of (b) the acrylic polymer was changed to 0.3% by weight.

[0066] A stabilizing solution of Test Example 37 was prepared in the same manner as in Test Example 35, except that the blending amount of (b) the acrylic polymer was changed to 0.2% by weight. A stable solution of Test Example 38 was prepared in the same manner as in Test Example 35, except that (c) the coagulating ion sequestering agent was changed to soda ash.

[0067] [Formulation of Test Example 39] The following components (a) to (d) were added to water to prepare a stabilizing solution of Test Example 39. (a) Bentonite: Sodium bentonite Product name: TB-250 (manufactured by Tachibana Material Co., Ltd.) Bentonite content: 3.0% by weight (b) Acrylic polymer content: 0.0% by weight (c) Amount of coagulant sequestering agent: 0.0% by weight (d) Cellulosic polymer: carboxymethyl cellulose Product name: DKS-280 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Cellulosic polymer blend content: 0.1% by weight

[0068] [Table 5]

[0069] [Table 6]

[0070] [Table 7]

[0071] [Table 8]

[0072] [Table 9]

[0073] [Table 10]

[0074] [Table 11]

[0075] [Results of repeated contamination tests] For the acrylic polymer stabilizing liquids of Test Examples 31 to 38, the liquefied soil was added to each stabilizing liquid, stirred, and then left for 24 hours, and the properties of the stabilizing liquid were measured, including funnel viscosity, specific gravity, B-type viscosity, amount of dehydration, pH, electrical conductivity, free water generation rate, and residual concentration of the acrylic polymer. After leaving for 24 hours, the stabilizing liquid was stirred, liquefied soil was added, left for 24 hours, and the properties of the stabilizing liquid were measured four times. The liquefied soil was prepared by mixing clay mineral (product name: Tochiklay (registered trademark)), product name: Kunigel V2 (registered trademark), and blast furnace cement in water, curing at 40°C for 7 days, and then disintegrating the mixture into powder of 4.75 mm or less. The amount of liquefied soil dissolved and mixed into the stabilizing liquid during excavation by the earth drill method was assumed to be 20% of the excavation volume, and the amount of soil added per contamination was set.

[0076] A staining test was repeatedly carried out using the same contents as the acrylic polymer for the stabilizing liquid using the cellulose-based polymer of Test Example 39. Since the concentration of the active ingredient in the liquid acrylic polymer is one-fourth that of the solid cellulose-based polymer, the amount of the cellulose-based polymer blended was set to one-fourth that of the acrylic polymer, and the active ingredient was aligned.

[0077] As shown in Tables 5 to 10, each of the stabilizing solutions of Test Examples 31 to 38 was found to stabilize the funnel viscosity, specific gravity, B-type viscosity, pH, and electrical conductivity, amount of dehydration, and rate of free water generation over four repeated tests.

[0078] For example, the stabilized solutions of Test Examples 31, 32, 34 to 36, and 38 had funnel viscosities in the range of 21.5 seconds or more and 25.8 seconds or less, and were found to have a funnel viscosity variation of 1.0 seconds or less over the four repeated tests. The stabilized solutions of Test Examples 33 and 37 had funnel viscosities in the range of 25 seconds or more and 31 seconds or less, and were found to have a funnel viscosity variation of 5.0 seconds or less over the four repeated tests.

[0079] On the other hand, the stabilizing solution of Test Example 39 had a funnel viscosity in the range of 20.5 seconds or more and 23.5 seconds or less, and it was found that the funnel viscosity decreased with each repeated test.

[0080] The stabilizing solutions of Test Examples 31, 32, 34 to 36, and 38 had a specific gravity in the range of 1.009 to 1.030, and were found to suppress the variation in specific gravity to 0.015 or less in all four repeated tests. The stabilizing solutions of Test Examples 33 and 37 had a specific gravity in the range of 1.024 to 1.052, and were found to give a variation in specific gravity of 0.022 or less in all four repeated tests.

[0081] The stabilizing solution of Test Example 39 had a specific gravity within the range of 1.014 to 1.046, and it was found that the specific gravity decreased with each repeated test.

[0082] The stabilizing solutions of Test Examples 31, 32, 34 to 36, and 38 each showed a low dehydration amount, and it was confirmed that the variation in the dehydration amount for each level was suppressed throughout the four repeated tests. The stabilizing solutions of Test Examples 33 and 37 showed a slightly lower dehydration amount, and it was confirmed that the variation in the dehydration amount was suppressed throughout the four repeated tests.

[0083] On the other hand, the stabilizing solution of Test Example 39 showed a dehydration amount within the range of 11 ml to 82 ml, and it was found that the dehydration amount increased significantly with each repeated test.

[0084] For example, the stabilizing solutions of Test Examples 31 to 39 were found to suppress the free water generation rate to 0% in all four repeated tests.

[0085] From the above, it is possible to obtain a stabilizing solution having good resistance to deterioration of liquefied treated soil by combining sodium-type bentonite with an acrylic polymer, as in the stabilizing solutions of Test Examples 31 to 38. In this case, it is preferable that the proportion of particles of the sodium-type bentonite powder of 63 μm or less is 80% or more.

[0086] Furthermore, a comparison of Test Examples 31 and 32 with Test Example 33 shows that the addition of a cohesive ion-blocking agent increases the deterioration resistance of the liquefied treated soil.

[0087] As in the stabilizing solutions of Test Examples 31 and 35 to 37, when the amount of the coagulating ion-blocking agent is 0.4 wt%, the amount of the acrylic polymer can be reduced because the same deterioration resistance is obtained when the amount of the acrylic polymer is 0.3 wt% as when the amount of the acrylic polymer is 0.6 wt%.

[0088] As shown in Fig. 1, when the blending amount of the coagulating ion sequestering agent is 0.4 wt%, the higher the blending amount of the acrylic polymer, the higher the residual concentration of the acrylic polymer after the repeated contamination test. Therefore, when the blending amount of the coagulating ion sequestering agent is 0.4 wt%, the higher the blending amount of the acrylic polymer, the more repeatedly the stabilizing solution can be reused.

[0089] [5] Heat-accelerated spoilage test: Test Examples 51-54 [Combination of Test Examples 51 and 52] The following components (a) to (c) and (g) were added to water to prepare a stabilizing solution for Test Example 51. As component (g), a stabilizing solution after decay that did not contain (b) an acrylic polymer and contained (d) a cellulose polymer was used. (a) Bentonite: Sodium bentonite Product name: Kunigel VA (manufactured by Kunimine Industries Co., Ltd.) Bentonite content: 4.0% by weight (b) Acrylic polymer: Water-soluble acrylic polymer Acrylic polymer content: 0.4% by weight (c) Coagulant sequestering agent: sodium bicarbonate Amount of coagulant sequestering agent: 0.4% by weight (g) Added pollutant: putrid muddy water Amount of added contaminants: 5.0% by weight

[0090] The stabilizing solution of Test Example 52 was prepared in the same manner as Test Example 51, except that the (g) added contaminant was changed to cellulase, a cellulose-degrading enzyme, and the amount of added contaminant was changed to 0.02% by weight.

[0091] [Combination of Test Examples 53 and 54] The following components (a) to (d) and (g) were added to water to prepare a stabilizing solution of Test Example 53. (a) Bentonite: Sodium bentonite Product name: TB-250 (manufactured by Tachibana Material Co., Ltd.) Bentonite content: 4.0% by weight (b) Acrylic polymer content: 0.0% by weight (c) Amount of coagulant sequestering agent: 0.0% by weight (d) Cellulosic polymer: carboxymethyl cellulose Product name: DKS-280 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Cellulosic polymer content: 0.2% by weight (g) Added pollutant: putrid muddy water Amount of added contaminants: 5.0% by weight

[0092] The stabilizing solution of Test Example 54 was prepared in the same manner as Test Example 53, except that the (g) added contaminant was changed to cellulase, a cellulose-degrading enzyme, and the amount of added contaminant was changed to 0.02% by weight.

[0093] [Results of heat-induced spoilage test] For the stabilizing solutions of Test Examples 51 to 54, the funnel viscosity and the amount of water removed were measured from immediately after the preparation of the stabilizing solutions until 14 days had passed.

[0094] As shown in Figure 2, the stabilizing solution composed of (a) sodium bentonite, (b) acrylic polymer, and (c) coagulant ion sequestering agent as in Test Examples 51 and 52 was found to have high decay resistance, as shown by stabilizing the funnel viscosity for 14 days. On the other hand, the stabilizing solution composed of (a) sodium bentonite and (d) cellulose polymer as in Test Examples 53 and 54 was found to have no decay resistance, as shown by a decrease in the funnel viscosity over time from immediately after preparation.

[0095] As shown in Figure 3, the stabilizing solution composed of (a) sodium bentonite, (b) acrylic polymer, and (c) coagulant ion sequestering agent as in Test Examples 51 and 52 was found to have high putrefaction resistance, as shown by stabilizing the dehydration amount to 15 ml or less over a period of 14 days. On the other hand, the stabilizing solution composed of (a) sodium bentonite and (d) cellulose polymer as in Test Examples 53 and 54 was found to have no putrefaction resistance, as shown by increasing the dehydration amount to 30 ml or more over time from immediately after preparation.

[0096] [Effects of the embodiment] As described above, the following effects can be obtained. (1) A stabilizing liquid containing sodium bentonite and an acrylic polymer can suppress the increase in viscosity in cast-in-place concrete pile construction using the earth drill method in ground containing liquefied treated soil or improved soil.

[0097] (2) The stabilizing liquid containing sodium bentonite and acrylic polymer can suppress the increase in the amount of dehydration in cast-in-place concrete pile construction using the earth drill method in ground containing liquefied soil or improved soil.

[0098] Due to the effects equivalent to those of (1) and (2), the above-mentioned stabilizing liquid can suppress the deterioration of wall construction properties in cast-in-place concrete pile construction by the earth drill method in ground containing liquefied treated soil, improved soil, etc. Furthermore, the above-mentioned stabilizing liquid can increase the number of times the stabilizing liquid can be reused in cast-in-place concrete pile construction by the earth drill method in ground containing liquefied treated soil, improved soil, etc. Therefore, the above-mentioned stabilizing liquid can reduce the plant capacity and the amount of waste liquid.

[0099] (3) Cellulosic polymers break down into smaller molecules through biodegradation. For this reason, it is difficult to control whether the amount of cellulose polymer used is effective when constructing cast-in-place concrete piles using the earth drill method. In contrast, if the stabilizing liquid contains sodium bentonite and an acrylic polymer, the acrylic polymer does not break down into smaller molecules through biodegradation, so by measuring the concentration of the acrylic polymer, it is possible to determine the degree of consumption of the active ingredient during excavation. For this reason, it is easy to control whether the amount used is effective for ensuring quality.

[0100] [Note] The technical ideas derived from the above embodiment are described below. [Appendix 1] A stabilizing liquid used in cast-in-place concrete pile construction using the earth drill method for ground backfilled with liquefied soil or improved soil, Sodium bentonite, A water-soluble acrylic polymer, A stabilizing liquid characterized in that, in the sodium-type bentonite, the proportion of sodium among the cations contributing to the CEC of the montmorillonite is 70% or more, and the proportion of powder particle sizes of 63 μm or less is 80% or more.

[0101] [Appendix 2] The amount of the sodium bentonite is 2.0% by weight or more and 8.0% by weight or less, The blending amount of the water-soluble acrylic polymer is 0.2% by weight or more and 1.2% by weight or less, The stabilizing solution described in Appendix 1.

[0102] [Appendix 3] Further comprising a cohesive sequestering agent, The amount of the sodium bentonite blended is 2.0% by weight or more and 6.0% by weight or less, The blending amount of the water-soluble acrylic polymer is 0.2% by weight or more and 1.0% by weight or less, The amount of the coagulant sequestering agent is 0.2% by weight or more and 0.6% by weight or less. The stabilizing solution described in Appendix 1.

Claims

1. A stabilizing liquid used in cast-in-place concrete pile construction using the earth drill method for ground backfilled with liquefied soil or improved soil, Bentonite which is sodium bentonite or activated bentonite; An acrylic polymer, A stabilizing solution characterized by:

2. Further comprising a cohesive sequestering agent, The stabilizing solution according to claim 1.

3. Does not contain cellulosic polymers The stabilizing solution according to claim 1 or 2.

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