JP4090982B2 - Ground injection agent and ground injection method - Google Patents

Description

  The present invention relates to a ground injecting agent used in ground improvement work and water stop work in various civil engineering works. In the present invention, “parts” and “%” are based on mass unless otherwise specified.

  Conventionally, the ground injecting agent has been widely used for ground improvement work, water stop work and the like. Here, ground improvement works are works such as dams, power plants, and ground grouts for reinforcement of foundation ground for large special structures such as oil and LPG storage bases and ground reinforcement works by injecting chemicals before construction work. Water stoppage works by injecting an injecting agent to prevent the spring water generated during excavation work of underground structures below the groundwater level, under the seabed, and in the aquifer ground, and to prevent the water tightness of the ground. It is a work to inject an injectant to raise. In addition to these, the ground injecting agent is also used for preventing the collapse of the ground in the improvement of the ground of ordinary houses and condominiums in poorly drained ground and liquefied ground, and in infrastructure development such as water supply and sewerage.

 In this way, various materials are used as a chemical in the ground injecting agent used for the purpose of consolidating the ground by injecting or strengthening the ground by compacting dehydration, and in the old days, bentonite etc. Non-chemical injections such as clay and ordinary Portland cement have been used, but since then, sodium silicate (water glass) injections and polymer injections such as acrylamide and urethane have also been used. It was.

  However, due to pollution problems caused by the inflow of chemicals into the well water, the former Ministry of Construction issued a “provisional guideline for construction work by the chemical injection method” in 1974. The possible materials are broadly divided into two types of materials, cement-type injection and water glass-type injection. There has been a desire for a safer and better performing infusate.

  Here, the cement-based injecting agent is a general term for an injecting agent that uses ordinary Portland cement or blast furnace cement as a main material and only cement, or as an additive combined with bentonite or an inorganic quick-hardening material, Recently, in place of ordinary Portland cement, fine particle cement and ultrafine particle cement in which ordinary Portland cement and slag are mixed and pulverized to increase the permeation effect have been used.

  In general, cement-based injections are alkaline, but have relatively high safety, and have high durability due to the high strength of the cured product. However, on the other hand, the time until curing, that is, the gel time is long, so it is unsuitable for water stoppage, and the powder is suspended in water, so the permeation performance is greatly inferior compared with solution type injections. There are such properties.

  In addition, water glass-based injection is a generic term for injections that use water silicate, which is sodium silicate as the main material. Among them, depending on the type of material that is used in combination as a hardening agent for water glass, solution injection And suspension type injection.

Here, the solution-type injection agent is a type in which an inorganic salt, an organic solution, an acid, and an alkaline solution in which a curing agent is dissolved in water are used alone or in combination. For example, as an inorganic salt, a carbonate is used. , Chlorides, sulfates, borates and phosphates, and organic solutions include esters such as monoether glycol acetate, aldehydes such as formaldehyde, propylene carbonate, methyl formate and glyoxal As the acid, sulfuric acid is generally used (Patent Documents 1 to 5).
In this way, solution-type injections have excellent permeability due to the absence of particles in the solution, but they have low consolidation strength and therefore poor durability, and depending on the type of curing agent, care must be taken. Some things require.

  On the other hand, a suspension type injection is a material that is insoluble as a curing agent, mainly using an inorganic substance. For example, the most commonly used is Portland cement, which is generally called LW. Widely used. In addition, materials such as slaked lime and quicklime lime, anhydrous, semi-water and dihydrate gypsum, slag, and the like are used (Patent Documents 6 and 7).

Suspension type injection is a powder in which the curing agent is insoluble, but the main material is water glass, so the permeability is better than cement-based injection, and the caking strength also depends on the type of curing agent. However, it is generally higher than the solution type injection and lower than the cement type injection. In addition, many curing agents are relatively safe.
JP 52-11505 A JP 52-087807 A Japanese Patent Laid-Open No. 51-082913 JP-A-52-120507 JP-A-57-195786 Japanese Patent Laid-Open No. 55-078084 JP-A-56-090884

  Among the above-mentioned injections, the water glass suspension type injection has the highest solidified strength and good permeability, so it is the most suitable for the ground composed of various geological features. It is an infusion that has a wide range of applications. Among them, LW using ordinary Portland cement as the curing agent is most often used, but a curing agent with good initial strength development and high safety has been desired.

  As a result of repeated investigations, the present inventor has a high initial caking strength among water glass suspension type injections by using a specific curing agent, good durability, and improved safety. The present invention was completed by obtaining the knowledge that an injectable was obtained. The present invention includes the following inventions:

(1) and the aqueous solution of sodium silicate, calcium aluminum Natick preparative and calcium sulfate corresponding to the Blaine value 4,000 cm ² / g or more 12CaO · _7Al 2 _{O 3} composition as a curing agent, and an organic San及 beauty as Cure Modifier / or soil improvement for injection that contains an organic acid salt.

(2) wherein the curing agent, characterized by containing 30 to 70 wt% of 30 to 70 wt% and calcium sulfate the calcium aluminate Natick preparative (1) soil improvement for injection agent according to claim.

(3) The ground improvement injecting agent according to (1), wherein the curing regulator is composed of one or two organic acids .

(4) Prepared by adding the curing modifier used in the ground improvement injecting agent according to any one of items (1) to (3) in kneaded water, and also adding the curing agent to this. The hardener slurry thus prepared is liquid A, and the liquid prepared by adding water glass to kneaded water is liquid B. After kneading each of liquid A and liquid B, they are pumped separately and before or after ground injection. A ground improvement method characterized by mixing or mixing in the ground.

According to the present invention, since the curing agent itself is cured by a hydration reaction as compared with the curing agent of the conventional water glass suspension type injection, it is possible to provide an injection with high initial strength and high long-term durability. It becomes possible.

Hereinafter, the present invention will be described in more detail.
As the water glass (sodium silicate) used in the present invention, among the commercially available water glasses, there is a slight difference in molar ratio depending on the manufacturer, but silicon dioxide (SiO ₂ ) and sodium oxide (Na ₂ O). No. 1 sodium silicate having a molar ratio (Na ₂ O / SiO ₂ ) of 2.1 to 2.3, and No. 2 sodium silicate having a ratio of 2.4 to 2.6, 3.0 to 3.3 Certain No. 3 sodium silicate can be used, and No. 3 sodium silicate is particularly preferable.
In addition, other special water glass or colloidal silica can be used in combination with the curing agent of the present invention.

  20-200 parts are preferable with respect to 100 parts of water, and, as for the quantity of the water glass in water glass aqueous solution, 30-100 parts is more preferable. If the amount is less than 20 parts, the concentration may be thin and may not solidify due to poor setting. In some cases, the shrinkage of the cured body increases and the durability significantly decreases.

  As the curing agent used in the present invention, a calcium aluminate and calcium sulfate content is kneaded with water and used as a slurry. At this time, a curing regulator is previously dissolved in the kneading water and used.

The calcium aluminate used in the present invention is a mixture of a raw material containing calcia and a raw material containing alumina, and is obtained by heat treatment such as firing in a kiln or melting in an electric furnace. ₂ O ₃ is a generic name for substances having hydration activity as a main component, and a part of CaO and / or Al ₂ O ₃ is an alkali metal oxide, an alkaline earth metal oxide, silicon oxide, titanium oxide, To compounds containing iron oxide, alkali metal halides, alkaline earth metal halides, alkali metal sulfates, alkaline earth metal sulfates, etc., or those containing CaO and Al ₂ O ₃ as main components, These are substances dissolved in a small amount. The mineral form may be either crystalline or amorphous.

Among these, amorphous calcium aluminate obtained by quenching a heat-treated product corresponding to a composition of 12CaO · 7Al ₂ O ₃ (hereinafter referred to as C ₁₂ A ₇ ) is preferable in terms of reaction activity.
The particle size of the calcium aluminate is in terms of permeability to the initial strength development and ground, preferably 4,000 cm ² / g or more in Blaine value, 6,000 ² / g or more is more preferable. If it is less than 4,000 cm < ² > / g, initial strength development property may fall, or the osmosis | permeation performance may deteriorate remarkably.

Examples of the calcium sulfate used in the present invention include gypsum. Among the gypsum, type II anhydrous gypsum and natural gypsum are preferable in terms of high strength development. The particle size of the calcium sulfate is preferably 4,000 cm ² / g or more in Blaine value, 6,000 ² / g or more is more preferable. If it is less than 4,000 cm ² / g, the initial strength development may be lowered.
The amount of calcium sulfate used is preferably 70 to 150 parts, more preferably 90 to 110 parts, relative to 100 parts of calcium aluminate. If it is less than 70 parts, the initial strength development may be lowered, and if it exceeds 150 parts, the short-term strength development may be deteriorated.

20-300 parts are preferable with respect to 100 parts of water, and, as for the hardening | curing agent used by this invention, 50-200 parts are more preferable. If it is less than 20 parts, the curing time is long, the desired gel time cannot be obtained, and the strength expression of the cured product may be insufficient. If it exceeds 300 parts, it becomes difficult to slurry the curing agent. Even if it is changed, it may be difficult to construct with ordinary construction machines.
10-200 parts is preferable with respect to 100 parts of water glass aqueous solution, and, as for the usage-amount of the hardening | curing agent slurry in this invention, 50-150 parts is more preferable. If it is less than 10 parts, there is no effect of addition, and there is a case where condensation or initial strength developability may be reduced. If it exceeds 200 parts, the dispersibility of the slurry is poor and kneading becomes difficult, and the slurry cannot be pumped. It may become impossible.

  The curing modifier used in the present invention has a role of adjusting the curing time of the curing agent because the curing agent itself becomes a hydration reaction and solidifies when the curing agent is made into a slurry. Therefore, there is an effect of stabilizing the reaction time when the curing agent is mixed.

  The curing modifier used in the present invention comprises one or more selected from organic acids such as gluconic acid, tartaric acid, citric acid, malic acid and lactic acid, and salts of the organic acids. Citric acid and its salts are preferred from the viewpoint of good kneading properties and good initial strength development.

  0.5-30 parts are preferable with respect to 100 parts of water glass aqueous solution, and, as for the usage-amount of a hardening regulator, 5-15 parts are more preferable. If it is less than 0.5 part, it will be difficult to ensure the kneading time of the curing agent slurry, and if it exceeds 30 parts, the kneading time of the curing agent slurry will be long, but the curing time will be extremely short and workability will be reduced. In addition, the durability of the cured product may be reduced.

  As the mixing preparation and use method of the injectable of the present invention, a predetermined curing adjusting agent is previously added to kneading water, and a curing agent slurry prepared by adding a mixture of calcium aluminate and calcium sulfate to this is designated as A liquid. A solution prepared by putting predetermined water glass into water is used as B liquid, and after kneading each, it is separately pumped and used before or after ground injection (1.5 shot injection method) In addition, when the curing time is short, a two-shot injection method in which the liquid A and the liquid B are separately fed in the ground is also possible.

  Hereinafter, the present invention will be described in detail by experimental examples, but the present invention is not limited to these experimental examples.

Experimental example 1
JIS No. 3 sodium silicate was diluted with water to prepare 200 ml of sodium silicate aqueous solutions having various concentrations shown in Table 1, and designated as solution A.
On the other hand, 200 parts of a mixture of 100 parts of calcium aluminate and 100 parts of anhydrous gypsum and 200 parts of a slurry solution prepared by dissolving 5 parts of a hardening modifier in kneading water for diluting the hardening agent in advance were prepared and used as B. Liquid.
Liquid A and liquid B were mixed in a room at 20 ° C. and a relative humidity of 80%, cured at 20 ° C. in water, and the gel time and compressive strength were measured. The results are shown in Table 1.

Experimental example 2
JIS No. 3 sodium silicate was diluted with water to prepare 200 ml of a 50% strength aqueous sodium silicate solution.
On the other hand, a slurry solution 200m1 was prepared by adjusting the curing agent and the curing regulator to the concentrations shown in Table 2, and this was designated as B solution.
Liquid A and liquid B were mixed in a room at 20 ° C. and a relative humidity of 80%, cured at 20 ° C. in water, and the gel time and compressive strength were measured. The results are shown in Table 2.

Experimental example 3
Experiment No. 1 in Table 1 The pH of the injectable slurry having the composition of 1-4 and the elution amount of hexavalent chromium from the cured product were measured. As a comparative example, Experiment No. The case where the same hardening agent as 1-4 was used with normal cement was implemented.

[Materials used]
Water glass: JIS sodium silicate No. 3 calcium aluminate: Main component C ₁₂ A ₇ , amorphous, Blaine value 6,000 cm ² / g
Anhydrous gypsum: type II anhydrous gypsum, brain value 6,050 cm ² / g
Curing modifier: Commercially available powdered citric acid water: Tap water

Measuring method Gel time. : After mixing a water glass aqueous solution and a curing agent, transfer a small amount to a cup, time compressive strength at the time when the cup stops tilting, compressive strength: Measure a cured material of a predetermined age according to JIS A5201 pH measurement: calories Measured with a meter Hexavalent chromium elution amount: Tank leaching test. A 7 day old cured body was immersed in water for 28 days, and the concentration was measured according to JIS K0102.

  The water glass hardener of the present invention is safer than conventional hardeners because of its neutrality, and it has less hexavalent chromium content than ordinary Portland cement, so it is safe for the human body and the environment. Therefore, it is expected to be used at injection sites with severe restrictions on the environment.

Claims (4)

And aqueous solution of sodium silicate, calcium aluminum Natick preparative and calcium sulfate corresponding to the Blaine value 4,000 cm ² / g or more 12CaO · _7Al 2 _{O 3} composition as a curing agent, and an organic San及 beauty / or perforated as a curing control agent A ground improvement injecting agent that contains silicate . Wherein the curing agent, soil improvement for injection agent according to claim 1, characterized in that it contains 30 to 70 wt% of 30 to 70 wt% and calcium sulfate the calcium aluminate Natick bets. 2. The ground improvement injecting agent according to claim 1, wherein the curing adjusting agent comprises one or two organic acids . The said hardening regulator used for the ground improvement injection agent of any one of Claims 1-3 is put into kneading water, and also the hardening agent slurry prepared by putting the said hardening agent into this is made into A liquid. The liquid prepared by adding water glass to the kneading water is used as the B liquid, and after mixing each of the A liquid and the B liquid, they are pumped separately and mixed before or after the ground injection or mixed in the ground. The ground improvement construction method characterized by doing.