JP4462608B2 - Silicate soil stabilization chemical and ground stabilization method using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a silicate-based soil stabilization chemical for ground improvement and a ground stabilization method using the same.

  Conventionally, a ground stabilization method is known in which various chemicals are injected into the ground in order to strengthen the soft ground or to stop the water leaking ground, and gel in the ground. The so-called silicate-based soil stabilization chemical solution, which is composed of a chemical solution combined with a hardener component, is now widely used because it is inexpensive and less likely to cause pollution compared to other soil stabilization chemical solutions. Has been.

  As a basic property in this silicate-based soil stabilization chemical solution, when the gel time is adjusted to be long by reducing the amount of curing agent component used in the sodium silicate aqueous solution, the strength of the cured product decreases as the gel time is adjusted to be longer. This is one of the well-known matters. Various methods are also known for injecting the silicate-based soil stabilization chemical into the ground. As an example of this, Non-Patent Document 1 introduces a double-pipe double packer injection method, which describes that this injection method aims at uniform penetration by an injection material having a long gel time. And in the implementation factory surface by the double pipe double packer injection method, the gel time of the chemical solution for stabilizing silicate soil is usually adjusted from 40 minutes to 1 hour and 40 minutes, preferably from 1 hour to 1 hour and 30 minutes. ing.

On the other hand, the present applicant, in Patent Document 1, has sodium silicate containing 3.8 to 4.2 moles of SiO ₂ per mole of Na ₂ O as a main agent, and is blended with bicarbonate as a curing agent. A soil stabilization method was proposed in which chemicals were injected into the soil and hardened in the soil.

  The silicate-based soil stabilization chemical described in this publication is cured by increasing the concentration of sodium silicate in the case of this gel time for a so-called slow-release chemical solution whose gel time is about 1 to 5 minutes. The purpose is to increase the strength of the body and to reduce the fluctuation of the gel time of the drug solution.

  However, as described above, the silicate-based soil stabilization chemical solution proposed in Patent Document 1 is used because of the basic properties of the silicate-based soil stabilization chemical solution that the strength of the cured body decreases as the gel time is adjusted longer. In order to apply to construction by the double pipe double packer injection method, when the amount of bicarbonate used as the curing agent component is adjusted and the gel time of the chemical solution is changed from 40 minutes to 1 hour 40 minutes, It was still difficult to say that it was enough.

  In addition, Patent Document 2 discloses that in order to improve the strength and environment of the stabilized ground, a magnesium salt compound is added to a hydrogen carbonate compound with a molar ratio of sodium silicate to silicic acid of 0.05 or less, and bicarbonates. A soil treatment agent having a molar ratio to the compound in the range of 0.05 to 1.00 has been proposed.

  The soil treatment agent described in this publication has a high compressive strength of the treated soil by using sodium silicate as the main agent and a soil treatment agent using a curing agent composed of bicarbonates and magnesium salts. And it is water-impermeable, and since it uses no acid, there is no corrosion, it is easy to set the curing time, and it is intended to obtain a gel with uniform and high water-stopping properties. .

However, if a mixture of a bicarbonate and a magnesium salt is stored, the following reaction may occur, and since the produced magnesium carbonate is insoluble in water, the performance as a soil stabilization chemical is poor. There were cases where it could not be demonstrated.

(M is alkali metal, A is sulfate ion, chloride ion, etc.)
On the other hand, the gel produced by the reaction between the aqueous solution of sodium silicate and the gelling agent generally reduces or disappears the stable effect of the treated ground, such as a decrease in strength and a decrease in water-stopping effect over time. It was an established theory.

  As described above, the silicate-based soil stabilization chemical solution proposed in Patent Document 1 is applied to the construction by the double-pipe double packer injection method. Therefore, when the gel time of the chemical solution is about 40 minutes to 1 hour 40 minutes, it is cured. It is difficult to say that the strength of the body is still sufficient, and there has been a demand for a chemical solution that exhibits higher strength even when adjusted to such a gel time.

  Further, as described above, there has been a demand for a chemical solution having good storage stability of a curing agent for obtaining a soil treatment agent proposed in Patent Document 2.

  Furthermore, since the chemical solution for stabilizing silicate soil is applied to the construction by the double pipe double packer injection method, even when the gel time of the chemical solution is about 40 minutes to 1 hour 40 minutes, the treated soil is longer than before. In particular, a chemical solution that can suppress a decrease in strength has been desired.

A chemical solution that satisfies all of these requirements at the same time has been desired.
Soil and foundation series 9 for site builder, from survey and design of chemical injection method to construction, 4th printing, published by the Geotechnical Society, Chapter 5 Types and features of injection method JP 54-31906 A JP-A-51-140311

  The object of the present invention is to improve the cured body strength of the silicate-based soil stabilization chemical solution proposed in Patent Document 1, and the cured body strength is well expressed even when the gel time of the chemical solution is changed from 40 minutes to 1 hour 40 minutes. A silicate-based soil stabilization chemical solution that has good storage stability of the curing agent to obtain a chemical solution, and injects the chemical solution into the ground, and the treated soil can suppress a decrease in strength over a longer period of time than before. It is to provide.

  In finding the silicate-based soil stabilization chemical solution and the ground stabilization method of the present invention, the performance criteria of the target chemical solution are as follows, and when all of these performance criteria are satisfied, the object of the present invention is achieved. It was said that it was done.

(1) Storage stability of the curing agent: 450 g of the curing agent was put into a 15 cm × 18 cm polyethylene vinyl bag (with φ0.5 mm × 12 pinholes), and the sealed sample was 0.2 N / Under a load of mm ² , it was stored for 6 months in a constant temperature and humidity room at 35 ° C. and a humidity of 65%. Then, water at 20 ° C. is added so that the sample and the curing agent solution become 13 liters, and the mixture is stirred using a mixer (three-one motor) to completely dissolve the curing agent.

A chemical obtained by adding a curing agent component to a sodium silicate aqueous solution containing 26 kg of SiO 2 per 400 liters at a temperature of 20 ° C .;
(2) Gel time of chemical solution: Curing (gelation) within 40 minutes or more and 1 hour or 40 minutes or less.

(3) Hardened body (homogel body) strength: The uniaxial compressive strength value of the formed cured body (homogel body) after gelation for 1 day is 0.003 N / mm ² or more.

(4) Hardened body (sand gel body) strength: A hardened body (diameter: 3 cm, height: about 6 cm) which was prepared so as to be a close-packed hardened body using a chemical solution and Toyoura silica sand and passed after 1 day. Is immersed in 1 liter of ion-exchanged water, and the uniaxial compressive strength value of the cured body after 28 days has passed is 0.10 N / mm ² or more.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention set the molar ratio of SiO ₂ / Na ₂ O in the aqueous solution of sodium silicate to a specific range, and to this, hydrogen carbonate as a curing agent component is added to sodium silicate. Surprisingly, it was found that all of the above performance criteria were satisfied by using a specific range of quantitative ratios, and the present invention was completed.

That is, according to the first invention of the present invention, “sodium silicate aqueous solution having a SiO ₂ / Na ₂ O molar ratio of 3.3 or more and 4.0 or less is mixed with magnesium sulfate per 100 parts by mass of hydrogen carbonate and magnesium sulfate. A silicate-based soil stabilization chemical solution comprising a curing agent containing 5 parts by mass or more and 18 parts by mass or less in a proportion of 23% by mass or more and 29% by mass or less with respect to SiO _{2 of} sodium silicate. Is the gist.

  In addition, the second invention of the present invention is “in order to stabilize the ground by injecting the soil stabilization chemical to the ground and curing in the ground, the soil stabilization chemical of the first invention is used as the soil stabilization chemical. "Ground stabilization method characterized by that" is the gist.

  With the silicate soil stabilization chemical solution of the present invention, an effect that was not obtained with conventional silicate soil stabilization chemical solutions, that is, when the gel time of the chemical solution was optimized from 40 minutes to about 1 hour 40 minutes for the double packer injection method However, the compressive strength of the cured product is good, the storage stability of the curing agent for obtaining the chemical solution is good, and the treated soil is injected with the chemical solution into the ground and the treated soil has a longer-lasting strength than before. It has the effect of being able to suppress the decline, and has the feature that the ground can be stabilized safely, reliably and efficiently. In addition, as for the hydrogen carbonate as a hardening | curing agent component in the chemical | medical solution for silicate type | system | group soil stabilization of this invention, sodium hydrogencarbonate and / or potassium hydrogencarbonate are preferable.

The sodium silicate aqueous solution as the main component of the silicate-based soil stabilization chemical solution of the present invention includes, for example, the manufacturing method described in “13901 Chemical Products, Chemical Industry Daily, Type 2 Soda Industrial Chemicals, Sodium Silicate”, etc. Based on a conventionally known production method of soda, the molar ratio of SiO ₂ and Na ₂ O is 3.3 or less, preferably 3.5 or less, while the upper limit is 4.0 or less, preferably 3 .Many products prepared and manufactured to be in the range of less than 8.

  In addition, “Nanolock base agent” (trade name, manufactured by Ryokan Co., Ltd.) can also be used.

When the SiO ₂ / Na ₂ O molar ratio of the aqueous sodium silicate solution is smaller than the lower limit value 3.3 defined in the present invention and larger than the upper limit value 4.0 defined in the present invention, a cured body (homogel body) ) Regarding the strength, the intended performance of the present invention cannot be obtained. And / or the effect which suppresses the intensity | strength fall over time of a hardening body (sand gel body) is low, and the objective of this invention cannot be achieved. These sodium silicate aqueous solutions can be appropriately diluted with water in order to obtain a concentration suitable for soil stabilization during construction.

For example, in a normal construction method in which a sodium silicate aqueous solution (hereinafter also referred to as “A liquid”) and a curing agent aqueous solution (hereinafter also referred to as “B liquid”) are mixed in equal amounts and poured into the ground, liquid 200 during liter SiO ₂ is less than the lower limit 20 kg, preferably not less than the lower limit value 25 kg, whereas the upper limit 40kg or less, preferably those prepared to be equal to or less than 35 kg, for use as the a solution.

The strength of the treated ground can be increased as the concentration of SiO _{2 in} the liquid A is increased. On the other hand, when the concentration of SiO ₂ becomes too high, the viscosity of the chemical solution increases, and the equipment load increases when pumping by the pump, or the permeability of the chemical solution in the ground tends to decrease. The hardening | curing agent of the chemical | medical solution for silicate type | system | group soil stabilization of this invention consists of hydrogen carbonate and magnesium sulfate.

  Examples of the hydrogen carbonate of the present invention include sodium hydrogen carbonate, potassium hydrogen carbonate, and ammonium hydrogen carbonate. For example, commercially available chemicals such as industrial chemicals can be used. These bicarbonates may be used alone or in a mixed state.

  Of these, sodium hydrogen carbonate and / or potassium hydrogen carbonate are preferred because they are excellent in the development of the strength of the cured product or are easily obtained and handled on site.

  As magnesium sulfate of this invention, what is generally marketed, such as an industrial product, can be used. Magnesium sulfate is commercially available in a form containing crystal water such as heptahydrate, trihydrate, 2.5 hydrate, and 1.5 hydrate, and any of the magnesium sulfate can be used. It is preferable to use a trihydrate from the viewpoint of consolidation, on-site handling and economic efficiency.

  As a ratio of magnesium sulfate in the curing agent of the present invention, the lower limit value is 5 parts by mass or more, and preferably the lower limit value is 10 parts by mass or more per 100 parts by mass of the total of hydrogen carbonate and magnesium sulfate. On the other hand, the upper limit value is 18 parts by mass or less, and preferably the curing agent composition is blended so that the lower limit value is 15 parts by mass or less. In addition, the mass of magnesium sulfate here is a ratio when it is set as the anhydride which does not contain crystal water.

  When the magnesium sulfate is less than 5 parts by mass of the lower limit of the range defined in the present invention with respect to the specific range defined as the composition of the curing agent, the effect of suppressing the strength deterioration of the cured body (sand gel body) over time is obtained. The object of the present invention cannot be achieved at a low level. On the other hand, when exceeding the upper limit of 18 parts by mass of the range defined in the present invention, when the storage stability as a curing agent is poor, and / or the chemical liquid obtained when the A liquid and the B liquid are mixed is cloudy, Alternatively, gelation occurs partially, and the effect of suppressing the strength reduction of the cured body (sand gel body) over time is so low that the object of the present invention cannot be achieved.

The amount of the curing agent of silicate soil-stabilizing drug solution of the present invention, the lower limit value 23% by mass or more with respect to SiO ₂ in the chemical solution, the upper limit is blended so that the range of less than 29 wt%. When the blending amount of the curing agent with respect to SiO ₂ in the chemical solution is less than the lower limit of 23% by mass or more of the range specified in the present invention, the gel time, the cured product (homogen) strength and the cured product (sand gel product) of the chemical solution The effect of suppressing the decrease in strength over time is low, and the target performance of the present invention cannot be obtained in any aspect. On the other hand, when the amount exceeds 29% by mass or less of the upper limit of the range defined in the present invention, the performance intended by the present invention cannot be obtained with respect to the gel time of the chemical solution.

Note here, disengaging the purposes of the present invention, the ratio of the bicarbonate salt to SiO ₂ in the chemical solution, by adjusting the amount thereof appropriately large range outside the range defined in the present invention, conventionally For example, it can be used as a so-called instantaneous solution having a gel time of about 10 seconds or less, or as a so-called slow solution having a gel time of about several minutes.

When the silicate-based soil stabilization chemical solution of the present invention is used in the ground stabilization method, an alkali silicate aqueous solution having a SiO ₂ / Na ₂ O molar ratio in the range specified in the present invention is further appropriately diluted with water to prepare solution A. Moreover, the B salt is prepared by dissolving the hydrogen carbonate as the curing agent component in water, and the prepared A and B solutions are added to the SiO _{2 in} the mixed solution of the A and B solutions. Illustrates a method of stabilizing the ground by injecting and curing the chemical obtained by mixing so that the quantity ratio of the bicarbonate as the curing agent component is the quantity ratio specified in the present invention. be able to.

  When injecting the chemical solution thus prepared, various injection tubes such as a single tube type, a double tube type, and a multi-tube type can be used. In addition, the A solution and the B solution are mixed in advance into the injection tube. A method of introducing, a method of mixing and injecting A liquid and B liquid in a mixing part provided at the base of the injection tube, for example, a Y-shaped mixing part, and A liquid and B liquid are independently introduced into the injection pipe An appropriate method such as mixing in the ground while injecting into the ground from the injection pipe can be adopted according to the workability.

  Next, the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited to these examples.

Examples and Comparative Examples Sodium silicates having various SiO ₂ / Na ₂ O molar ratios prepared by the method described in “Chemical Products of 13901, Issuance of Chemical Industry Daily, Type 2 Soda Industrial Chemicals, Sodium Silicate” Using the chemical solution obtained by dissolving a predetermined amount of bicarbonate as a curing agent component in a sodium silicate aqueous solution prepared by adding water appropriately so that the SiO ₂ content per 400 liters is 26 kg, the performance of the following items Was evaluated. Reagent grade 1 was used for bicarbonate and magnesium sulfate (anhydrous). Test methods and evaluation criteria for each evaluation item of chemical performance are as follows.

・ Evaluation items, evaluation methods, and evaluation criteria (1) Storage stability of curing agent: 450 g of curing agent is put into a 15 cm × 18 cm polyethylene vinyl bag (with 0.5 mm × 12 pinholes) and sealed. This was used as a test specimen and stored for 6 months in a constant temperature and humidity room at 35 ° C. and a humidity of 65% under a load of 0.2 N / mm ² . Thereafter, water at 20 ° C. was added so that the sample and the curing agent solution were 13 liters, and the mixture was stirred using a mixer (three-one motor), and the state of the curing agent solution was visually observed.

  Evaluation ○: The curing agent was completely dissolved in water.

  Evaluation x: The curing agent was not completely dissolved in water, and insoluble matters were observed.

  (2) Gel time of chemical liquid: At a liquid temperature of 20 ° C., the chemical liquid was allowed to stand in the container, and the time required until the fluidity of the chemical liquid disappeared was defined as gel time.

  Evaluation (circle): The gel time of the chemical | medical solution was 40 minutes or more and 1 hour 40 minutes or less.

  Evaluation x: The gel time of the chemical solution was less than 40 minutes. Or the gel time of the chemical | medical solution was long exceeding 1 hour 40 minutes.

  (3) Hardened body (homogel body) strength: At a liquid temperature of 20 ° C., the chemical solution was poured into a cylindrical mold, and the uniaxial compressive strength of the formed cured body was measured for one day.

Evaluation (circle): The uniaxial compressive strength value of the hardening body (homogel body) after gelatinization 1 day passed was 0.003 N / mm < ² > or more.

Evaluation x: The uniaxial compressive strength value of the cured body (homogel body) after gelation after 1 day was less than 0.003 N / mm ² .

  (4) Hardened body (sand gel body) strength (material age 28 days): At a liquid temperature of 20 ° C., a chemical solution is injected into the closest packed Toyoura cinnabar, and a cured body diameter 3 cm × height formed after 1 day has passed. About 6 cm was immersed in 1 liter of ion-exchanged water, and the uniaxial compressive strength after the lapse of 28 days was measured.

Evaluation ○: The uniaxial compressive strength value of the cured body (sand gel body) after immersion for 28 days was 0.10 N / mm ² or more.

Evaluation x: The uniaxial compressive strength value of the cured body (sand gel body) after immersion for 28 days was less than 0.10 N / mm ² .

In each evaluation, the SiO ₂ / Na ₂ O molar ratio of sodium silicate, the type of hydrogen carbonate in the curing agent composition, the mass of magnesium sulfate per 100 parts by mass of the total of hydrogen carbonate and magnesium sulfate, 400 liters of chemical solution Table 1 shows the composition, the ratio of the amount of the curing agent composition to the SiO ₂ of sodium silicate, the measurement results and evaluations, and the overall evaluation. Moreover, it described together about the uniaxial compressive strength of the hardened | cured body (sand gel body) formed after 1 day after gelatinizing.

  The comprehensive evaluation shows the following.

  Comprehensive evaluation (circle): All of the storage stability of a hardening | curing agent, the gel time of a chemical | medical solution, hardened | cured material (homogel body) intensity | strength, and hardened | cured body (sand gel body) strength evaluation were (circle).

  Overall evaluation x: At least one of the evaluation items was x.

  Moreover, it described together about the uniaxial compressive strength of the formed hardening body (sand gel body) after gelatinization and progress for one day.

  Note that the uniaxial compressive strength of the hardened body (sand gel body) per day is about 3 cm × height of the hardened body formed by injecting a chemical into the closest packed Toyoura sand at a liquid temperature of 20 ° C. The uniaxial compressive strength after 6 days was measured for 6 cm.

As described in Table 1, when the requirements of the present invention are satisfied, the stored curing agent is completely dissolved in water, and the chemical solution is cured (gelled) within a period of 40 minutes or more and 1 hour or 40 minutes or less. The uniaxial compressive strength of the cured body (homogel body) formed after 1 day of curing (gelation) is 0.003 N / mm ² or more, and is formed after 1 day of curing (gelation). Even if the cured body (sand gel body) is immersed in ion-exchanged water for 28 days, the uniaxial compressive strength is ensured to be 0.10 N / mm ² or more, satisfying the performance standard of the chemical solution, and achieving the object of the present invention. In contrast, even when using the blending components defined in the present invention, the SiO ₂ / Na ₂ O molar ratio of the sodium silicate aqueous solution, the amount ratio of magnesium sulfate per 100 parts by mass of the curing agent composition, and the curing agent composition The amount ratio of the sodium silicate aqueous solution to the SiO ₂ is specified by the present invention. If it is outside the range, the storage stability of the curing agent is poor, the gel time of the chemical solution, the strength of the formed cured body (homogen body) and the formed cured body (sand gel body) immersed in ion-exchanged water for 28 days Any one or two or more of the strengths after it does not satisfy the performance standard of the chemical solution, and the object of the present invention cannot be achieved.

Claims (2)

Curing agent containing 5 parts by mass or more and 18 parts by mass or less of magnesium sulfate per 100 parts by mass in total of hydrogen carbonate and magnesium sulfate in a sodium silicate aqueous solution having a SiO ₂ / Na ₂ O molar ratio of 3.3 to 4.0 Is a silicate-based soil-stabilizing chemical solution, characterized in that it is blended at a ratio of 23 mass% to 29 mass% with respect to SiO _{2 of} sodium silicate.   A soil stabilization method according to claim 1, wherein the soil stabilization chemical is used as a soil stabilization chemical when the soil stabilization chemical is poured into the ground and cured in the ground to stabilize the ground.