JP2929352B2 - Chemical solution for soil stabilization and ground stabilization method using it - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chemical for stabilizing soil and a method for stabilizing a ground using the same.

[0002]

2. Description of the Related Art A kneaded product of hydraulic cement excluding alumina cement and water is referred to as a main material liquid (hereinafter referred to as A liquid), and a kneaded product of alumina cement and water is referred to as a hardening material liquid (hereinafter referred to as B liquid). It is known that when these are combined and injected into the ground, the mixed liquid of the liquid A and the liquid B hardens in several minutes to several tens of minutes.

Japanese Patent Application Laid-Open No. 50-16717 discloses a method for applying a hardened cement in which a mixture of soluble aluminum and an inorganic sulfate is mixed with cement as a cement hardening agent,
The soluble aluminum is a crystalline and / or amorphous calcium aluminate and a calcium haloaluminate in which a halogen element is dissolved as a solid,
Particularly preferred minerals are 12CaO.7Al ₂ O ₃ or amorphous materials in which a halogen element is dissolved in solid form. As inorganic sulfates, anhydrous, hemihydrate, gypsum and the like can be used. Is described as anhydrous gypsum. Further, it is described that a cement to which a mixture of alumina cement and gypsum is added is already known as a rapidly hardening cement.

[0004]

As described in Japanese Patent Application Laid-Open No. 50-16717, rapid-hardening cement generally has the property of developing strength in a short time,
Since the setting time is short, there is a problem that the setting hardens during handling, which hinders the construction. As a countermeasure, it is generally indispensable to add a setting retarder such as an organic carboxylic acid such as gluconic acid or citric acid or a salt thereof to the rapid-hardening cement in order to delay the setting and hardening. However, even when a setting retarder is added, its effect varies depending on the type and amount of the added setting retarder, and is further affected by various incidental conditions in the practical work such as temperature and kneading time.

[0005] A mixture of alumina cement and gypsum as a cement hardening agent for hydraulic cement or the soluble aluminum and inorganic sulfate disclosed in Japanese Patent Application Laid-Open No. 50-16717 is used. The same problem as described above also occurs in a ground stabilization method in which a kneaded product of a mixture and water is used as a hardening material liquid (liquid B) and these are combined and injected into the ground.

That is, as the soluble aluminum,
12CaO · 7, which is a crystalline or amorphous calcium aluminate or a calcium haloaluminate in which a halogen element is dissolved in the same, disclosed in Japanese Patent No. 50-16717.
Al ₂ O ₃ , 3CaO · Al ₂ O ₃ or 11CaO · 7Al ₂ O ₃
・ When B liquid is prepared using CaF ₂ as a hardener, the B liquid itself will set and harden within 30 minutes at the longest. A cured product may be generated in the liquid tank or in a pipe or pump for pressure-feeding the liquid B, and the work may not be able to be continued.

[0007] B required for construction by delaying the setting and hardening of B liquid
In order to ensure the stability of the solution, it is necessary to add a setting retarder such as an organic carboxylic acid such as gluconic acid or citric acid or a salt thereof when preparing the solution B. Even if it is added, its effect varies depending on the type and amount of the setting retarder added, and is further affected by various incidental conditions in the implementation work such as temperature and kneading time, and during construction, before injection into the ground. There is a problem that unexpected hardening occurs, so that the solution B cannot be pumped and cannot be applied. Also, the setting retarder for delaying the hardening of the liquid B needs to be dissolved in the kneading water for the liquid B before kneading the cement rapidly hardened material with water to prepare the liquid B. In addition, there is a problem that work on the construction site is complicated.

The solution B using CaO.Al ₂ O ₃ as calcium aluminate as a curing agent does not cure for 3 hours or more, depending on the ratio of water to the curing agent at the time of preparation. The hardening time of B liquid using alumina cement as a hardening agent is about 7 hours, and all of them have sufficient B for construction.
Although the stability of the liquid can be ensured, there is a problem that the cured product formed by mixing the liquid A and the liquid B has a low compressive strength.

In the conventionally known method, the stability of the solution B is poor even if a setting retarder is added, or even if the stability of the solution B can be ensured, the compression strength of the cured product formed is developed. Is low, and the bleeding that occurs after mixing the liquid A and the liquid B causes a vulnerable portion to be formed in the upper layer portion of the formed cured product, so that the bleeding is preferably as small as possible. unknown. As described above, the conventionally known construction method has a practical difficulty as a ground stabilization method, and improvement has been desired.

An object of the present invention is to solve the problems in the conventional method, and to knead a main material liquid (liquid A), which is a kneaded product of hydraulic cement excluding alumina cement and water, and knead alumina cement and water. The hardening material liquid (liquid B) is prepared separately, and both liquids are mixed at the time of construction and a soil retardant is added to the ground and a setting retarder is added to the ground stabilization method. Solution B, ensuring sufficient stability, eliminating the risk of coagulation and hardening before the chemical solution is injected into the ground, and the mixture of solution A and solution B hardening in several minutes to several tens of minutes. And a soil solution stabilizing chemical solution and a ground stabilization method, which exhibit good compressive strength of the formed hardened body, and which hardly cause fragile portions in the upper layer portion of the hardened body formed with less breathing. To provide.

In the soil stabilizing chemical solution of the present invention, the stability of the solution B, the gel time breathing rate of the mixture of the solution A and the solution B, and the compressive strength of the formed hardened material are respectively described as the performance. The purpose is to satisfy the following rules. -Stability of liquid B: not cured in less than 3 hours when left alone after preparation (curing time of liquid B alone is 3 hours or more after preparation). -Gel time: The liquid mixture of liquid A and liquid B hardens within 15 minutes after mixing.・ Breathing rate: When using liquid A containing 160 kg of ordinary Portland cement per 200 L, the value of the breathing rate of the mixed liquid after one day has passed after mixing liquid A and liquid B must be 20% or less. . -Compressive strength of hardened body: When using liquid A containing 160 kg of ordinary Portland cement per 200 L, the unconfined compressive strength value per day of the hardened body formed by mixing liquid A and liquid B is 1 day. , 10kg / cm ² or more.

[0012]

Means for Solving the Problems The present inventors diligently studied to improve the above problems and solve the problems, and used a kneaded product of hydraulic cement and water excluding alumina cement as A liquid, In the chemical solution for soil stabilization and the ground stabilization method in which the kneaded product with water is mixed as liquid B and injected into the ground, the type B anhydrous gypsum adjusted to a specific range of Blaine value is added to the alumina cement for the liquid B. B liquid obtained by blending in a specific range of the amount ratio
Without the addition of a setting retarder, it is possible to ensure the stability that it will not cure alone for more than 3 hours, to eliminate the risk of forming a cured product before injection and making it impossible to work. Further, when mixing the A liquid and the B liquid, Is mixed so that the total weight of alumina cement and type II anhydrous gypsum with respect to the weight of hydraulic cement excluding alumina cement in the mixture is in a specific range, so that the mixture of solution A and solution B becomes 15%. It hardens within minutes, and exhibits good compressive strength of the formed hardened material, and has less bleeding that causes a fragile portion in the upper layer of the hardened material. Further, the present inventor has found that the present invention exhibits a performance that cannot be realized by the ground stabilization method, and thus completed the present invention.

[0013] The first invention of the present invention relates to a method for stabilizing soil which is injected into the ground by combining a main material liquid containing hydraulic cement excluding alumina cement and a hardening material liquid containing alumina cement. A chemical solution having a Blaine value of 3000 with respect to 1 part by weight of alumina cement in the hardening material liquid.
0.5-1.5 parts by weight of type II anhydrous gypsum that is at least cm ² / g, and the main material liquid and the hardening material liquid are mixed with 100 parts by weight of hydraulic cement excluding alumina cement in a mixture of both liquids. The total amount of alumina cement and type II anhydrous gypsum is 20
The chemical liquid for soil stabilization characterized by being mixed and used so that the amount is not less than part by weight ".

[0014] A second invention provides a method for stabilizing a ground by injecting into a ground a combination of a main material liquid containing hydraulic cement except alumina cement and a hardening material liquid containing alumina cement. , The Blaine value is 3000 cm per 1 part by weight of alumina cement in the hardening material liquid
² / g or more of 0.5 to 1.5 parts by weight of type II anhydrous gypsum, and mixing the main material liquid and the hardening material liquid with respect to 100 parts by weight of hydraulic cement excluding alumina cement in a mixture of both liquids A ground stabilization method characterized by mixing alumina cement and type II anhydrous gypsum so that the total amount is 20 parts by weight or more and injecting into the ground.

Hereinafter, the present invention will be described. The main material liquid (Solution A) in the chemical liquid for soil stabilization of the present invention is obtained by kneading hydraulic cement (excluding alumina cement) with water. Examples of hydraulic cement that can be used as a main material include various types of Portland cements such as ordinary / early strong / very early strong / medium heat / white, and mixed cements such as blast furnace cement / silica cement / fly ash cement. One or more of these cements can be used.

The amount ratio of hydraulic cement to water in the liquid A is usually 20 to 400 k per 200 L of the liquid A.
g, preferably 40-300 kg, more preferably 60-240 kg
Range. The amount of hydraulic cement per 200L of liquid A
If it is less than 20 kg, the compressive strength of the consolidated sediment formed when the chemical solution is injected into the ground and hardened is low, and the ground is not sufficiently stabilized. On the other hand, when the amount of hydraulic cement per 200 L of the liquid A exceeds 400 kg, the compressive strength of the formed sediment compacts is increased, but the viscosity of the liquid A is greatly increased and the pumping by the pump becomes difficult, and Liquid A and B
The permeability of the mixed liquid with the liquid in the ground is reduced, and the volume of the formed solidified body is reduced.

The hardening material liquid (solution B) in the soil stabilizing chemical solution of the present invention is obtained by kneading the hardening material for the hydraulic cement with water. Alumina cement used as hardening material is JIS-R2511 "Alumina cement for refractories"
This is an alumina cement having one to five types of alumina cement specified in the standard or a quality equivalent to this. Of these, it is preferable to use three to four alumina cements or those having a quality equivalent thereto.

The alumina cement is CaO.Al ₂ O ₃ , Ca
Calcium aluminate such as O · 2Al ₂ O ₃ as a main _{component, 4CaO · Al 2 O 3 ·} Fe calcium alumino ferrites, such as ₂ O _3, calcium silicate and 2CaO · Al ₂ O ₃ · SiO such as 2CaO · SiO ₂ It is a cement composed of compounds such as calcium aluminosilicate such as ₂ . As described above, the alumina cement behaves differently from the soluble aluminum disclosed in Japanese Patent Application Laid-Open No. 50-16717. That is, 12CaO · 7 is a crystalline or amorphous calcium aluminate or a calcium haloaluminate in which a halogen element is dissolved in solid form.
Al ₂ O ₃ , 3CaO · Al ₂ O ₃ or 11CaO · 7Al ₂ O ₃
· The CaF ₂ when B was prepared solution as the curing material, B solution itself would condense cured within 3 hours after preparation. In contrast, B using alumina cement as a hardening material
The setting and hardening time of the liquid is about 7 hours.
The stability of the liquid can be ensured.

The solution B in the soil stabilizing solution of the present invention further uses type II anhydrous gypsum together with alumina cement. The amount ratio of alumina cement and type II anhydrous gypsum in the liquid B is in the range of 0.5 to 1.5 parts by weight of type II anhydrous gypsum per 1 part by weight of alumina cement. When the amount of type II anhydrous gypsum per 1 part by weight of alumina cement is less than 0.5 part by weight, or more than 1.5 parts by weight, both are formed when the chemical is injected into the ground and hardened. The compacted soil has low compressive strength, and the object of the present invention cannot be achieved.

As gypsum used in combination with alumina cement in solution B, gypsum other than type II anhydrous gypsum, for example, α-hemihydrate gypsum, β-hemihydrate gypsum, dihydrate gypsum, type III anhydrous gypsum, etc. In any case, the compacted soil formed has a low compressive strength, and the object of the present invention cannot be achieved. In addition, it is permissible that gypsum in a form other than the type II anhydrous gypsum is mixed as impurities into the type II anhydrous gypsum used.

The type II anhydrous gypsum used in combination with the alumina cement has a Blaine value of 3000 cm ² / g or more, preferably
One having a range of 5000 to 8000 cm ² / g is used. If the Blaine value is less than 3000 cm ² / g, the compressive strength of the sediment compact formed when the chemical is injected into the ground and hardened is low, and the object of the present invention cannot be achieved. It should be noted that the use of a material having a Blaine value exceeding 8000 cm ² / g is uneconomical because the effect is not improved.

The amount ratio of alumina cement / II type anhydrous gypsum to water in the solution B is usually 20 to 200 kg, preferably 40 to 180 kg, and more preferably 200 to 200 kg of the total weight of alumina cement and type II anhydrous gypsum per 200 L of the solution B. Preferably it is in the range of 60 to 160 kg. When the total weight of alumina cement and type II anhydrous gypsum per 200 L of liquid B is less than 20 kg, the compressive strength of the solidified soil formed when the chemical solution is injected into the ground and hardened is low, Is insufficiently stabilized. On the other hand, liquid B
When the total weight of alumina cement and type II anhydrous gypsum per 200 L exceeds 200 kg, the viscosity of the liquid B increases and the mixing state of the liquid A and the liquid B becomes poor, and the formed soil-solids The variation in the compressive strength becomes large and becomes uneven.

When preparing the liquid B, the alumina cement
There is no particular limitation on the order of mixing of the type II anhydrous gypsum. For example, a method of separately carrying alumina cement and type II anhydrous gypsum into a construction site and kneading a predetermined amount with water, or a method in which alumina cement and type II anhydrous gypsum are previously blended in a predetermined amount ratio, are used in the construction site. And kneading it with water. The latter method is preferred because it can simplify the work on the construction site and is efficient and efficient.

The soil stabilizing solution of the present invention is used by mixing solution A and solution B. The ratio between the A liquid and the B liquid is as follows:
Hydraulic cement except alumina cement in liquid mixture
The alumina cement and the type II anhydrous gypsum are mixed in an amount of 20 parts by weight or more, preferably 25 to 50 parts by weight, based on 100 parts by weight. When the total amount of alumina cement and type II anhydrous gypsum is less than 20 parts by weight with respect to 100 parts by weight of hydraulic cement excluding alumina cement in the liquid mixture of liquid A and liquid B, gel time, breathing and curing With respect to the compressive strength of the body, the desired effect of the present invention cannot be obtained. In addition, even if the total amount of the alumina cement and the type II anhydrous gypsum exceeds 50 parts by weight, the effect is not improved, and it is uneconomical.

In the ground stabilization method using the soil stabilizing chemical liquid of the present invention, the liquid A and the liquid B are mixed at the above-mentioned ratio and injected into the ground. As a method of mixing the liquid A and the liquid B at such a quantitative ratio, for example, when the weight of the hydraulic cement in the unit volume of the liquid A is 100, Solution A and solution B prepared so that the total weight of alumina cement and type II anhydrous gypsum are 20 or more, respectively, using a pump having the same liquid sending volume per unit time, a Y-tube, a stirring device, For example, there is a method in which the mixture is fed under pressure into a mixing chamber (in-pipe mixer / pipe mixer) provided in the injection pipe to be mixed and mixed. In the ground stabilization method of the present invention, a mixed solution of the liquid A and the liquid B is mixed with a single pipe type, a multi-tube type,
The ground is stabilized by injecting into the ground and hardening using various injection pipes such as a multi-tube type. Alternatively, injection and injection can be performed at a pressure of 50 to 1000 kg / cm ² using an injection pipe having an injection nozzle.

If necessary, various commonly used cement admixtures such as a water reducing agent, an antifoaming agent, and a thickening agent can be added to the chemical solution for soil stabilization of the present invention. These cement additives can be used by adding to one or both of the liquid A and the liquid B. Examples of such water reducing agents include lignin sulfonate or a derivative thereof.
Various water reducing agents and dispersants containing oxyorganic acid salts, alkyl allyl sulfonates, polyoxyethylene alkyl ethers, polyol complexes, higher polyhydric alcohol sulfonates, melamine formalin condensate sulfonates, etc. High performance water reducing agents and fluidizers can be mentioned.

Examples of the antifoaming agent include higher alcohols, alkylphenols, diethylene glycols, dibutyl phthalate, water-insoluble alcohols, tributyl phosphates, polyglycols, silicones,
Various antifoaming agents such as ethylene oxide-propylene oxide copolymers can be used.

Examples of the thickener include cellulose ethers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxybutylmethylcellulose, hydroxyethylethylcellulose and carboxymethylcellulose; polyacrylamide, sodium polyacrylate, and the like. Acrylic polymers such as polyacrylamide-sodium polyacrylate copolymer / partially hydrolyzed polyacrylamide; and various thickeners such as water-soluble polymers such as polyvinyl alcohol, polyethylene oxide, sodium alginate, casein, and guar gum. it can.

[0029]

Next, the present invention will be described specifically with reference to examples and comparative examples. The present invention is not limited to these examples. Examples and Comparative Examples Liquid A: Ordinary Portland cement as a hydraulic cement (commercially available product) Water was added to 160 kg and kneaded, and the amount of water was adjusted so that the finished volume was 200 L and adjusted. Liquid B: Gypsum prepared by using alumina cement (JIS-R2511, three types) or various calcium aluminates shown in Table 1 for comparison as a hardening material, and adjusting the various Blaine values in the proportions shown in Table 1 for each (Commercial product; type III anhydrous gypsum
After mixing the reagent (grade 1), water was added and kneaded, and the amount of water was adjusted so that the volume of kneading became 200 L, and the mixture was prepared. The calcium aluminate used for the test was Ca
A combination of O, Al ₂ O ₃ and CaF ₂ synthesized in an electric furnace was used.

The following items were tested using the solution A and the solution B prepared as described above. Table 1 shows the type of hardening material, the type and gypsum value of gypsum used in combination with the hardening material and the blending ratio (weight ratio: gypsum / hardening material), the formulation of liquid B,
Mixing ratio of liquid B and liquid B (weight ratio: total amount of hardener and gypsum /
Amount of hydraulic cement excluding alumina cement in the mixture)
showed that.

The test items, test methods, display symbols and evaluation contents are as follows. Solution B stability: Solution B prepared at a temperature of 20 ° C. was allowed to stand in a beaker, and the time required from the preparation to the formation of a cured product was measured. …: It took three hours or more after the preparation to produce a cured product. (Liquid B alone does not cure for more than 3 hours after preparation.) ×: A cured product was formed in less than 3 hours after preparation.

Gel time: Solution A and B at a temperature of 20 ° C.
The solution was mixed well and allowed to stand in the container, and after mixing, the time required until the contents did not move even when the container was tilted was measured and defined as gel time. …: Gel time was within 15 minutes. X: The gel time was longer than 15 minutes.

· Breathing rate: Mixed liquid of liquid A and liquid B 5
00ml into a measuring cylinder (capacity 500ml)
After the passage of days, the amount of breathing (Vml) was measured, and the breathing rate (B,%) was determined by the following equation. B = (V
/ 500) × 100…: The breathing rate was 20% or less. C: The breathing rate was larger than 20%.

Compressive strength of the cured product: A mixture of the liquid A and the liquid B is poured into a cylindrical mold (diameter 5 cm × height 10 cm), and the formed cured product has a uniaxial compressive strength of one day of material age. The value was measured. …: The compressive strength value was 10 kg / cm ² or more. X: The compressive strength value was less than 10 kg / cm ² .

In each test, stability of solution B, solution A and B
Table 1 shows the evaluation results and the overall evaluation of the gel time breathing rate of the liquid mixture and the compressive strength value of the formed cured product.・ Comprehensive evaluation ○: stability of solution B, gel time of mixture of solution A and solution B ・
Both evaluation results of the breathing rate and the compressive strength value of the cured product were ○. ×: stability of solution B, gel time of mixture of solution A and solution B
Any of the evaluation results of the breathing rate and the compressive strength value of the cured product was “X”.

[0036]

[Table 1]

Experiment Nos. 1 to 6 show the effect of the type of hardening material. As a curing material, calcium aluminate such as _{12CaO · 7Al 2 O 3, 3CaO} · Al 2 O 3 of 12CaO · 7Al ₂ O ₃ or crystalline amorphous or _{11CaO · 7Al 2 O 3 · Ca} ,
When the preparation of the solution B using a calcium halophosphate aluminate such as F _2, the cured product produced in B solution in less than 3 hours after preparation, the present invention can not be obtained the stability of the B liquid of interest, Also, the compressive strength value of the cured product was small (Experiment No. 1,
2,4,5). In addition, when CaO.Al ₂ O ₃ was used, the stability of Solution B aimed at by the present invention was obtained, but the compressive strength value of the cured product was small (Experiment No. 3).

Experiments Nos. 6-10 show the effect of the type of gypsum used with Alumina Cement in Liquid B. As gypsum, gypsum in other forms other than type II anhydrous gypsum-α hemihydrate gypsum,
When β-hemihydrate gypsum, dihydrate gypsum or type III anhydrous gypsum was used, the compressive strength value of the cured product intended by the present invention could not be obtained (Experiment Nos. 7 to 10).

Experiments Nos. 11-15 show the effect of the Blaine value of type II anhydrous gypsum used with Alumina cement in B liquid. When the Blaine value is less than 3000 cm ² / g, the compressive strength value of the cured product intended by the present invention could not be obtained (Experiment No.
11).

Experiment Nos. 16 to 20 show the effect of the blending ratio of alumina cement and type II anhydrous gypsum in solution B (weight ratio: type II anhydrous gypsum / alumina cement). When gypsum was not blended, the breathing rate was large, and the gel time and the compressive strength value of the cured product aimed at by the present invention could not be obtained (Experiment No. 16). When the weight ratio of the gypsum to be blended is less than 0.5 part by weight (Experiment No. 17), and when it exceeds 1.5 parts by weight (Experiment No. 20), the cured product targeted by the present invention is obtained. No compressive strength value was obtained.

Experiment Nos. 21 to 25 show the effect of the mixing ratio of the liquid A and the liquid B-the ratio of the total weight of the alumina cement and the type II anhydrous gypsum to the weight of the hydraulic cement excluding the alumina cement in the mixed liquid. Show. 100 parts by weight of hydraulic cement excluding alumina cement, when the total weight of alumina cement and type II anhydrous gypsum is less than 20 parts by weight, the bleeding rate is large, and the gel time or cured product targeted by the present invention is Could not obtain the compressive strength value of
No. 21).

On the other hand, when the requirements of the present invention are satisfied, the solution B can be used after the preparation without adding a setting retarder.
The hardening does not occur for more than an hour.
It hardens within 15 minutes after mixing, the value of the breathing rate one day after mixing is 20% or less, and the uniaxial compressive strength value of the formed cured product (1 day old) is 10 kg / cm ² or more. The object of the present invention was achieved (Experiment Nos. 6, 12 to 15, 1
8,19,22-25).

[0043]

According to the present invention, a liquid A, which is a kneaded product of hydraulic cement and water, and a liquid B, which is a kneaded product of a hardening agent and water, are separately prepared, and the two liquids are mixed at the time of construction. In the chemical solution for soil stabilization injected into the ground and the ground stabilization method,
The addition of a setting retarder ensures sufficient stability of Solution B to eliminate the risk of setting and hardening before the chemical solution is injected into the ground, and the mixture of Solution A and Solution B takes several minutes. ~
It hardens in more than ten minutes, and the expression of the compressive strength of the formed cured body is good, and furthermore, less fragile parts are formed in the formed cured body upper layer with less breathing,
The chemical solution for soil stabilization and the ground stabilization method can be provided, and the ground can be stabilized more reliably. The chemical solution for soil stabilization of the present invention does not require a setting retarder, and since the basic constituent materials are all inorganic substances, when injected into the ground, compared with a chemical solution containing an organic substance as an essential component. Low degree of water pollution.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-108139 (JP, A) JP-A-5-208853 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) C09K 17/10 C09K 17/06 E02D 3/12

Claims (2)

(57) [Claims] 1. A soil stabilizing chemical liquid, which is injected into the ground by combining a main material liquid containing hydraulic cement except alumina cement and a hardening material liquid containing alumina cement, wherein the hardening material liquid And 0.5 to 1.5 parts by weight of a type II anhydrous gypsum having a Blaine value of 3000 cm ² / g or more with respect to 1 part by weight of the alumina cement in the above, and a main material liquid and a hardening material liquid in a mixed liquid of both liquids A soil stabilizing chemical solution which is mixed and used so that the total amount of alumina cement and type II anhydrous gypsum is at least 20 parts by weight with respect to 100 parts by weight of hydraulic cement excluding alumina cement. 2. A ground stabilization method in which a main material liquid containing hydraulic cement excluding alumina cement and a hardening material liquid containing alumina cement are combined and injected into the ground, Alumina cement in a mixed liquid of a main material liquid and a hardening material liquid in which 0.5 to 1.5 parts by weight of type II anhydrous gypsum having a Blaine value of 3000 cm ² / g or more is blended with respect to 1 part by weight of cement A ground stabilization method characterized by mixing alumina cement and type II anhydrous gypsum in a total amount of 20 parts by weight or more and injecting into the ground with respect to 100 parts by weight of hydraulic cement excluding water.