JPS5826382B2 - Ground improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ground improvement method for the purpose of strengthening soft ground and water-stopping permeable strata.

More specifically, the present invention provides the above-mentioned ground improvement method,
Adjustment can be made by adding and mixing a curing agent that has a buffering effect in an alkaline region to an acidic water glass aqueous solution that contains or does not contain a component that has a buffering effect in an acidic or neutral region. A ground characterized by an easy and stable gelation time, and also by slow pH fluctuations due to buffering action, making it easy to form a gel in a neutral range (pH range of 5 to 9). Concerning consolidation methods.

Various injection methods have been used to improve soft ground.

As an example, a practical method is to prepare a water glass aqueous solution as liquid A, use a reactant as liquid B, combine these using a Y-shaped pipe during injection, and then inject the combined liquid into the ground and solidify it. It is served to.

As examples of the reactants used in this method, acidic reactants such as mineral acids, acid salts, organic acids, etc. are known.

However, these methods have large variations in gelation time, and it is extremely difficult to obtain gel in the neutral range, which is required from the viewpoint of pollution prevention, especially water quality preservation, and alkali syneresis, for the following reasons. be.

Firstly, the water glass aqueous solution exhibits strong alkalinity, and the molar ratio of silicic acid and alkali (for example, S i O2 and Na 20
It exhibits a buffering effect in the strongly alkaline region (pH 11 to 12), depending on the concentration of water glass (corresponding to the ratio of pH 11 to 12) or the concentration of water glass.

The gelation time of water glass is fastest near neutrality, and this buffering effect causes rapid pH fluctuations around neutrality in the reaction with acidic reactants, so the gelation time is extremely unstable and If the water glass is injected into the ground and solidified without sufficient gelation time, the water glass may not solidify due to the influence of groundwater, etc.

Furthermore, it is extremely difficult to obtain a gel in the neutral region.

Second, in order to carry out the ground improvement method, the water glass stock solution is diluted with water to prepare a water glass aqueous solution of a predetermined concentration as a mixing method for liquid A, and the acidic reactant is added to a predetermined concentration for liquid B. However, the variation in concentration at the time of blending is actually large, and the range of variation from both A and B increases further, resulting in I)H change near neutrality. It is difficult not only to obtain a gel in the neutral region, but also to maintain a uniform and stable gelation time.

Thirdly, the quality of commercially available water glass is actually very high due to variations in raw material composition during production, production equipment, impurities, etc., such as variations in alkalinity and loft-to-loft molar ratios of silicic acid and alkali. It fluctuates greatly.

Furthermore, commercially available water glass inevitably contains a small amount of metal ions, and even a small amount of these metal ions have a large effect on the gelation time of the water glass.

From these points as well, the difficulty of obtaining gels in the neutral region,
There is also the difficulty of stabilizing the gelation time uniformly.

The present invention has been developed to solve this problem, and the present invention has been developed to solve this problem by adding an acidic water glass aqueous solution containing or not containing a component that has a buffering effect in an acidic to neutral region to an alkaline region. A curing agent that combines an acid or base that has a buffering effect with these and a salt that has a common ion, or a salt that becomes acidic or alkaline upon hydrolysis and another salt that exhibits a buffering effect when coexisting with an iron salt. A ground improvement method that aims to gel the mixture in the vicinity of a neutral region by adding and mixing a combination of curing agents, making it easy to adjust the gelation time and obtaining a stable gelation time. We aim to provide the following.

Note that the expression "neutral" or "neutral region" used in the present invention means a region in which the pH ranges from 5 or more to 9 or less.

The acidic water glass aqueous solution used in the present invention is obtained by mixing water glass or a water glass aqueous solution with an acidic liquid such as sulfuric acid, nitric acid, phosphoric acid, acetic acid, etc. with vigorous stirring, and has a pH of less than 5. The amount of acidic water glass in the acidic water glass aqueous solution is preferably 2 wt % or more in 5i02 minutes.

If the amount of 5i02 in the acidic water glass aqueous solution is less than this, the strength of the gel obtained by mixing an alkaline agent with the acidic water glass aqueous solution will be weak and the gel will easily form creases.

According to the present invention, when the acidic water glass aqueous solution is gelled using a curing agent having a buffering effect in an alkaline region, an unexpected effect is that the gelation time can be easily adjusted; , a predetermined gelling time can be stably obtained without being affected by variations in the quality of the water glass used when preparing the acidic water glass aqueous solution, metal ions contained in the water glass, etc., and further, Unlike the case where water glass has a buffering effect in the strongly alkaline region,
The fluctuation becomes slow near neutrality, and a neutral gel can be easily obtained.

According to the present invention, by using a curing agent that has a buffering effect in an alkaline region, it is possible to eliminate the effects of variations in composition at actual ground improvement construction sites and electrolytes contained in groundwater. , it is possible to stably obtain a gel in an aqueous region, and a certain gelation time can be easily adjusted.

In the present invention, the curing agent that has a buffering effect in the alkaline region has a pH value of 7 when made into an aqueous solution.
．． Those exhibiting a buffering effect in the range of 5 or more and 11 or less are preferred.

These include, for example, sodium hydroxide and sodium tetraborate, sodium hydroxide and dibasic sodium phosphate, sodium hydroxide and glycine and sodium chloride, aqueous ammonia and ammonium chloride, boric acid and sodium borate and chloride. Combinations of acids or bases such as sodium and salts having a common ion with these; hydrolysis such as sodium carbonate and sodium bicarbonate, sodium carbonate and sodium tetraborate, sodium tetraborate and potassium monophosphate, etc. There are combinations of salts that become acidic or alkaline when exposed to iron salts and other salts that coexist with iron salts and exhibit a buffering effect.

The first feature of the present invention is that the curing agent has a buffering effect in the alkaline region, but two or more of the above curing agents may be used in combination within the range where this buffering effect is not extremely impaired. There is no problem in using one or more of the above curing agents together with one or more commonly known alkaline agents.

Such an alkaline agent may be one that exhibits alkalinity when dissolved in water, such as hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, barium hydroxide, etc. sodium carbonate,
Carbonates such as potassium carbonate, etc.: Bicarbonates such as sodium bicarbonate, potassium bicarbonate, etc.; Silicates such as sodium silicate, potassium silicate, etc.; Sodium aluminate, potassium aluminate, etc. Borate salts such as aluminate sodium diborate, potassium borate, etc.; Secondary phosphates such as dibasic sodium phosphate, dibasic potassium phosphate, etc.;
Tertiary phosphates such as dibasic potassium phosphate; tripolyphosphates such as sodium tripolyphosphate; phosphites such as sodium phosphite; acetates such as sodium acetate, potassium acetate, etc. ; Sodium citrate,
Citric acid salts such as potassium citrate: Sulfites such as sodium sulfite, potassium sulfite, etc. Sulfides such as sodium sulfide, potassium sulfide, etc.; Sulfides such as hydrogen sulfide, potassium hydrogen sulfide, etc. Hydrogen sulfide; and water glass.

The amount of curing agent used in the present invention is greatly influenced by the type of acidic liquid agent used when preparing the acidic water glass aqueous solution, the pH of the prepared acidic water glass aqueous solution, and the alkalinity strength of the curing agent used. However, usually 0.0001 parts by weight or more and 50 parts by weight per 100 parts by weight of the acidic water glass aqueous solution.
The amount is suitably less than 0.01 parts by weight and preferably 30 parts by weight or less (pure fractionated material not containing water of crystallization).

If the amount of the alkaline agent is less than this range, the gelation time of the acidic water glass aqueous solution will be too long, and gelation may not occur in some cases.

If the amount of the alkali agent is greater than this range, the amount of alkali will be too excessive and it will be difficult to obtain a gel in the neutral range.

In addition, in the present invention, when a component having a buffering effect in the acidic to neutral range is contained in the acidic water glass aqueous solution, the gelation time can be adjusted even more easily.
It becomes easier to obtain gels in the neutral region.

As a component having a buffering effect in such an acidic or neutral range, a component having a buffering effect in a pH value range of 1 or more and 7 or less is preferable.

Examples of these are hydrochloric acid and sodium chloride, hydrochloric acid and potassium chloride, hydrochloric acid and ammonium chloride, hydrochloric acid and aluminum chloride, hydrochloric acid and glycine and sodium chloride, sulfuric acid and sodium sulfate, sulfuric acid and aluminum sulfate, acetic acid and sodium acetate, phosphoric acid and Sodium monophosphate, phosphoric acid and dibasic sodium phosphate, phosphoric acid and dibasic sodium phosphate, phosphoric acid and sodium tripolyphosphate, citric acid and dibasic sodium citrate, citric acid and potassium dibasic citrate, citric acid and dibasic citric acid Combinations of acids or bases with salts having common ions with these, such as potassium, tartaric acid and sodium tartrate, lactic acid and sodium lactate, dibasic sodium citrate and sodium hydroxide, etc.: hydrochloric acid and sodium carbonate, Hydrochloric acid and sodium acetate, hydrochloric acid and primary sodium citrate,
Hydrochloric acid and primary potassium citrate, hydrochloric acid and secondary sodium citrate, hydrochloric acid and secondary potassium citrate, hydrochloric acid and tertiary sodium citrate, hydrochloric acid and tertiary potassium citrate, hydrochloric acid and potassium hydrogen phthalate, hydrochloric acid and tertiary potassium citrate Sodium borate, hydrochloric acid and sodium diethylberbiturate and sodium acetate, sulfuric acid and sodium monophosphate, sulfuric acid and potassium monophosphate, sulfuric acid and dibasic sodium phosphate, sulfuric acid and potassium dibasic phosphate, citric acid and sodium monophosphate acid or Combination of a base and a salt that coexists with these and exhibits a buffering effect; monophosphoric acid 1-IJ
Hydrolyzed into acidic or alkaline substances such as dibasic sodium phosphate, monosodium phosphate, tribasic sodium phosphate, monobasic potassium phosphate and dibasic sodium phosphate, monobasic potassium citrate and sodium tetraborate, etc. Combinations of other salts that coexist with iron salts and exhibit a buffering effect: Formic acid, sodium hydroxide, acid mixtures (mixtures of phosphoric acid, acetic acid, boric acid, or citric acid, monopotassium phosphate, boric acid) , diethylbarbic acid, and hydrochloric acid) and sodium hydroxide.

The amount of the component having a buffering effect in the acidic to neutral range is suitably 0.001 parts by weight or more, preferably 0.01 parts by weight or more per 100 parts by weight of the acidic water glass aqueous solution. Parts by weight or less (pure fractionated material not containing water of crystallization) is appropriate.

If the amount is less than 0.001 part by weight, the buffering effect will be too weak, making it impossible to achieve the object of the present invention.

In the present invention, a corrosion inhibitor may also be included in the grout mixture used in the method of the present invention in order to prevent corrosion of containers, equipment, etc. used in carrying out the method of the present invention.

Examples of anticorrosive agents used for this purpose include:
Inorganic acid salts such as nitrites, phosphates, polyphosphates, silicates, molybdates, tungstates, etc., or aliphatic amines, aromatic amines, aliphatic aldehydes and ketones, thiourea, pyridine There are organic corrosion inhibitors such as , quinoline, etc.

The appropriate amount of these anticorrosive agents to be contained is 0.001 part by weight or more and 1 part by weight or less based on 100 parts by weight of the grout mixture.

If the amount is less than this range, the anti-corrosion performance will be too low, and if the amount is more than this range, the gelling time of the grout mixture will be affected.

As explained above, the ground improvement method of the present invention takes into account variations in the quality of water glass used when preparing an acidic water glass solution, metal ions contained in the water glass, electrolytes contained in groundwater, etc. It is not affected by water, the gelation time can be easily adjusted to a constant level, and gels can be easily obtained in the neutral range.Since it does not contain harmful poisons, there is no need to worry about environmental pollution. The industrial effects are significant.

Next, the effects of the present invention will be specifically explained according to Examples.

Example 1 A water glass aqueous solution was prepared using commercially available JISB water glass, and the aqueous solution was added to an acidic liquid while stirring vigorously. Using the acidic water glass aqueous solution obtained, grout mixtures of various compositions were prepared. The pH value and gelation time of the mixture were measured.

pf (measurement of the value is based on the grout mixture immediately after preparation,
Alternatively, the pH was measured using a pH meter (Toa Denpa HM-5A) for syneresis water obtained by pressing the gelled product.

The gelation time was measured by placing the grout mixture in a beaker in a thermostatic water bath adjusted to 20° C., and using a stopwatch to measure the time until the mixture no longer flows out even when the beaker was tipped over.

Table 1 summarizes the composition and test results of the grout mixture.
It is shown in Table 4.

In addition, the component that has a buffering effect in the acidic to neutral region in the table refers to a component that coexists with the acid used when preparing the acidic water glass solution and exhibits a buffering effect in the acidic to neutral region. (The same applies to the table below).

Moreover, each measurement value is an average value of 5 repeated measurements.

From Table 1, it can be seen that the grout mixture used in the method of the present invention is less affected by differences in the quality of the water glass used when preparing the acidic water glass aqueous solution and the difference in the quality of the water used.
It can be seen that the value and gelation time are stable, and gel is easily obtained in the neutral region.

Note that the pH of the acidic water glass aqueous solutions having the compositions listed in Table 1 was all within the range of 1.8 to 2.2.

From Table 2, it can be seen that a grout mixture using only a normal alkaline agent as a hardening agent is greatly affected by the amount of acidic liquid added, the pH is outside the neutral range, and the gelation time fluctuates greatly, making it impractical. It can be seen that the grout mixture used in the method of the present invention has a pH value in the neutral range, and a gelation time of several seconds to 10 minutes, which is considered to be practical, is stably obtained.

Example 2 A treated soil specimen was prepared using the grout mixture having the composition obtained in Example 1, and its unconfined compressive strength and hydraulic conductivity were measured.

The treated soil specimen was placed in a cylindrical iron container with an internal size of 110Ox and a height of 150mm, with coarse sand at a thickness of 10mm each at the bottom and top, and Toyoura standard sand (JIS-R) at a thickness of 130mm at the center. -52
01-1964) and moistened with water.

The boundaries between each layer are separated with a wire mesh, and from the center of the upper lid, an iron pipe is used to
．． The grout mixture was injected and fed under pressure using five shots, and the lower lid was used as a perforated plate to relieve pressure and allow distilled water to flow out.

After the grout mixture gelled, the treated soil was taken out of the iron container and cured for 24 hours in a paper mixer, followed by an unconfined compressive strength test (JIS-A-1216) and a soil water permeability test (
JIS-A-1218).

The test results are shown in Table 5.

Note that the experiment numbers in the table are the same as those in Tables 1 to 4.

Table 5 shows that the use of the grout mixture used in the construction method of the present invention improves the unconfined compressive strength and hydraulic permeability of the resulting treated soil specimens.

Example 3 In order to examine the influence of metal ions contained in water glass used when preparing an acidic water glass aqueous solution, a grout mixture with the composition shown in Table 6 was prepared, and the pH value and gelation were measured. The time was measured.

The measurement method is the same as that in Example 1.

The composition of the grout mixture and the test results are summarized in Table 6.

From this table, the grout mixture used in the construction method of the present invention is:
It is extremely useful at ground improvement construction sites because it is not affected by metal ions and can stably obtain the desired gelation time without being affected by electrolytes contained in groundwater. It can be seen that

Claims (1)

[Claims] 1. In a ground consolidation method in which a curing agent is added to an acidic water glass aqueous solution and mixed, the resulting grout mixture is injected into the ground and gelled and solidified underground. A curing agent that is a combination of an acid or base and a salt that has a common ion with these, or a salt that becomes acidic or alkaline upon hydrolysis, and other salts that exhibit a buffering effect in coexistence with an iron salt. A ground improvement method characterized by the use of a hardening agent in combination with. 2. A ground improvement method according to claim 1, wherein the acidic water glass aqueous solution contains a component having a buffering effect in an acidic to neutral range.