JPH093871A - Ground injection method - Google Patents

Abstract

PURPOSE: To continue high consolidation strength for a long time by a method wherein a gelation time indicated by a specified value is provided and chemicals for ground injection containing colloidal silica as a main agent are injected in a ground as the chemicals are kept at temperature of a specified value. CONSTITUTION: Sulfuric acid is added to colloidal silica to prepare A1 . Further, magnesium sulfate water salt and sodium bicarbonate are dissolved in water to prepare B1 liquid. A1 liquid and B1 liquid are mixed together to prepare chemicals for ground injection having a gelation time of 2 minutes - 24 hours at 25 deg.C. Further, the chemicals for ground injection are injected with a pressure in a ground as temperature of 35-70 deg.C. Thus, since the chemicals for ground injection gelates in a short time and to develop a high strength immediately after gelation, a work is easily executed and high consolidation strength is maintained for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of injecting a chemical solution containing colloidal silica as a main ingredient into the ground.

[0002]

2. Description of the Related Art Conventionally, to strengthen soft ground,
For the purpose of stopping the outflow of groundwater from the ground, a chemical solution is injected into these grounds to form a gel of the chemical solution in the ground. Such a chemical solution is also called a ground injection agent or a grout agent, and various kinds thereof are already known. As a ground injection agent that is frequently used, water glass as a main agent, various acids as a curing agent, a so-called water glass-based injection agent that uses a combination of salts, etc., but as an improved ground injection agent, colloidal silica is used. Used as the main agent,
A ground injection agent has been proposed in which an acid, salt or the like is also used as a gelling agent.

For example, Japanese Unexamined Patent Publication (Kokai) No. 54-73407 discloses a ground injection using a neutral silica sol having a SiO ₂ / Na ₂ O molar ratio of 50 or more as a main agent and an inorganic salt of a polyvalent metal as a curing agent. Agents are disclosed. Japanese Examined Patent Publication No. 6-62953 discloses 5 to 20 nm
Colloidal silica having a particle diameter of 0.1 to
0.4% NaCl or KCl / SiO ₂ weight ratio sodium chloride and /
Alternatively, a ground injection agent using potassium chloride as a curing agent is disclosed.

[0004]

The above-mentioned water glass-based injecting agent is advantageous in that not only can it be adjusted so as to show a short gelling time, but also its gelation product shows a high consolidation strength. , In order to diffuse a large amount of sodium salt contained in this injectant and the acid used as a curing agent from the gelled product of this injectant, and to diffuse into the ground or soil outside the injection area of this injectant, The problem often arises that soils and groundwater around the injection area of the infusate are contaminated by the hardener. Furthermore, the strength of the ground once reinforced by the gelation of the above-mentioned water glass-based injecting agent tends to decrease with the lapse of time after the gelation, and the reinforced ground using the water glass-based injecting agent has poor durability.

On the other hand, the ground injection agents containing silica sol, colloidal silica, etc. as the main ingredients disclosed in JP-A-54-73407, JP-B-6-62953 and the like are as follows.
The amount of pollutant contained is much smaller than that of water-glass type injecting agent, so it does not cause serious pollution problem to soil and groundwater around the injecting agent injecting area, and gives durability to reinforced ground. There are some problems. For example, in the case of an injecting agent having a composition that causes gelation in a short time, high strength cannot be obtained immediately after gelation, or a nonuniform gelation product is likely to be formed. Further, the ground injection agent containing silica sol, colloidal silica or the like as a main agent has a drawback that the gelation time thereof is easily affected by the liquid temperature, and is difficult to handle during construction.

The present invention is an improvement of the ground pouring method using a ground pouring agent composed of colloidal silica as a main agent and a hardening agent thereof. The ground pouring agent is prepared within 1 second to 2 minutes after preparation. It is possible to cause the injectable agent to gel, to form a gelled product having a high consolidation strength immediately after the gelation, and further to make it possible to maintain the high consolidation strength for a long period of time. It is intended to provide a ground injection method.

[0007]

Means for Solving the Problems The ground injection method of the present invention provides a ground injection chemical solution which exhibits a gelation time of 2 minutes to 24 hours at 25 ° C. and which contains colloidal silica as a main agent.
It is characterized by pouring into the ground while maintaining the temperature at 35 to 70 ° C. The construction method of the present invention can be applied to the ground that has been conventionally constructed, such as clay ground, sand ground, and gravel ground. Usually, these grounds are several tens of cm above the ground surface.
At a depth of tens of meters, the temperature of the ground is usually below 35 ° C and above 0 ° C, except in special areas.

The colloidal silica may be any conventionally known one, but it is preferably used in the form of an aqueous silica sol in which colloidal silica particles are stably dispersed in an aqueous medium. As the aqueous silica sol, it is possible to use an aqueous silica sol containing colloidal silica particles having an average particle diameter of 3 to 20 nm as its SiO _{2 in} a concentration of 10 to 50% by weight and having a pH of 8 to 11. In particular, colloidal silica particles having an average particle diameter of 3 to 10 nm are used as the SiO ₂
Aqueous silica sols having a concentration of 45% by weight and having a pH of 9-11 are preferred. Such a silica sol can be easily produced by a known method, for example, a method described in U.S. Pat.No. 3711419, U.S. Pat.No. 3714064, or Japanese Patent Publication No. 4-55127, or It can also be obtained as a commercial product.

The chemical liquid for ground injection used in the ground injection method of the present invention contains the above colloidal silica as a main agent, and is preferably obtained by adding the above aqueous silica sol. It is preferable that this ground injection liquid is prepared by further adding a curing agent that causes gelation to an aqueous silica sol. Preferred examples of this curing agent include water-soluble inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and sulfamic acid; water-soluble organic acids such as formic acid, acetic acid, oxalic acid and oxalic acid;
Water-soluble acid salts such as sodium acid sulfate, sodium bicarbonate, sodium monophosphate; water-soluble ammonium salts such as ammonium sulfate and ammonium bicarbonate; sodium chloride, calcium chloride, magnesium chloride, aluminum chloride, sodium sulfate, magnesium sulfate, sulfuric acid Aluminum, aluminum phosphate, calcium nitrate, magnesium nitrate,
Examples thereof include water-soluble metal salts such as aluminum nitrate, calcium carbonate and sodium aluminate.

The chemical liquid for ground injection of the present invention may further contain any component as long as the object of the present invention is achieved. The ground injection liquid of the present invention has a SiO ₂ concentration derived from colloidal silica of 10 to 50% by weight, preferably 10 to 35% by weight, and exhibits a gelation time of 2 minutes to 24 hours at 25 ° C. Is mixed with the above-mentioned aqueous silica sol and a curing agent.
This mixing can be easily performed by mixing an aqueous silica sol with an aqueous solution of a curing agent.

The gelation time of the ground injection chemicals can be adjusted by changing the concentration of the curing agent therein. And, this gelation time becomes shorter as the SiO ₂ concentration of the colloidal silica is higher when the particle size of the colloidal silica contained in the ground injection liquid is constant, and the colloid contained in the ground injection liquid is also higher. When the SiO ₂ concentration of the particulate silica is constant, the smaller the particle size of the colloidal silica is, the shorter the particle size of the colloidal silica contained in the ground injection liquid is. It can be adjusted by changing the method.

When the ground injection chemical of the present invention is injected into the ground, the temperature of the injection chemical is maintained at 35 to 70 ° C, preferably 35 to 50 ° C. Usually, it is injected into the ground as a ground injection chemical solution having this temperature before the ground injection. 35-70
Since the ground injection chemical kept at ℃ causes gelation in a short time, preferably 1 second to 2 minutes, it is more preferable than the method of injecting the ground injection chemical obtained by the above-mentioned formulation into the ground after heating. It is preferable to prepare the aqueous silica sol before mixing and the aqueous solution of the curing agent separately, maintain at this temperature, and then inject by a method called 1.5 shot method or 2 shot method.

In the 1.5-shot method, usually, both liquids kept at the above temperature are passed through separate liquid feed pipes to be joined in a mixing zone of the pipes provided in front of the injection ground,
Therefore, a method is used in which after mixing once, the ground injection chemical solution obtained by this mixing is pressed into the ground. In the two-shot method, normally, both liquids kept at the above temperature are passed through separate liquid supply pipes to join each other just before the injection ground, and the ground injection chemical solution obtained by this joining is directly injected into the ground. The method of doing is adopted.

[0014]

[Function] It has a gelation time of 2 minutes to 24 hours at 25 ° C, and it is used as a base injection chemical liquid containing colloidal silica as a main ingredient at 35 ° C.
When gelation is caused to occur at a lower temperature, for example, 25 ° C, the gelled product immediately after gelation exhibits normal strength, whereas the ground injection chemical solution is kept at 35 ° C or higher, for example, 40 ° C, Surprisingly, it was found that gelation occurs in a short time of only a few seconds, and a gelled product having a remarkably high strength is formed immediately after the gelation.

At a normal temperature, for example in the ground at 25 ° C, 35 ° C
Similarly, when the ground injection chemical at a higher temperature is injected, gelation similarly occurs in a short time, and the ground strength is remarkably increased immediately after the gelation, because the injected ground injection chemical is in the ground. It is considered that this gelation occurs before it is cooled in. However, a ground injection chemical containing colloidal silica colloidal silica particles having an average particle size of 3 nm or less as a main component is poor in stability and is not preferable. On the contrary, when a ground injection chemical containing, as the main ingredient, colloidal silica particles having an average particle size of more than 20 nm is used, a gelled product having high strength is unlikely to be produced. A ground injection chemical containing colloidal silica in a SiO ₂ concentration of 10 wt% or less also produces a gelled product having low strength.

When injecting into the ground, if the liquid temperature of this injecting chemical is set to 70 ° C. or higher, it is difficult to adjust the gelling time and it is difficult to form a uniform gel. At temperatures below 35 ° C, the gelling time can be shortened by changing the type of curing agent in the liquid chemical for injection, such as the type of acid or salt, its concentration, etc. However, the strength cannot be expressed, or the gelled substance separates into agglomerated parts and solution parts, resulting in non-uniformity.
By maintaining the temperature of the drug solution for injection having a gelation time of 2 minutes to 24 hours at 35 to 70 ° C. for gelation, a gelled product having high strength can be produced within a short time of 2 minutes. The gelation time of the ground injection chemical at 35 to 70 ° C is 25
The longer the gelation time at ° C, the longer the tendency.

[0017]

EXAMPLE Colloidal silica particles having an average particle size of 4 to 9 nm were contained as SiO _{2 in} a concentration of 30% by weight,
The aqueous silica sol having a pH is colloidal silica (S ₁ ), and the colloidal silica particles having an average particle diameter of 4 to 6 nm are contained as SiO _{2 in} a concentration of 15% by weight, and the aqueous silica sol having a pH of 10.0 is colloidal silica. (S ₂₎ and to and the colloidal silica particles having an average particle diameter of 10~20nm contained in a concentration of 30 wt% as SiO _2, an aqueous silica sol having a pH of 10.0 as colloidal silica (S _3), respectively I prepared.

Generally, a ground injection chemical solution exhibiting a gelation time of several seconds to ten and several seconds is also called a quick-setting type ground injection agent, and its gelled product is characterized by exhibiting high strength immediately after gelation. However, the strength of the gelled product also changes with time immediately after gelation. Therefore, it is not possible to measure whether or not the strength of such an instantaneous setting type ground injectable agent immediately after gelation is high by the measuring method of uniaxial compressive strength measured several minutes after gelation. Therefore, as a method suitable for measuring the strength immediately after gelation, a method of measuring a static needle penetration resistance value was adopted.

This static needle penetration resistance value is measured in accordance with the asphalt penetration test method (JIS K 2530-1961), and the needle of the penetration meter used in this test method has a total weight of 10 g. , The tip angle is 30 degrees, the length is 44 mm, and the top diameter is 23 mm. The measuring method is to prepare a chemical liquid for ground injection, align the tip of the needle with the surface, remove the needle support at the time of 30 seconds immediately after this preparation, and measure the length that the needle penetrates due to the weight of the needle. The measurement method was used.

[0020] Separately, the static needle penetration resistance value measured for a practically used instantaneous setting type ground injecting agent showed a penetration length of 25 mm or less according to this measuring method. Chemical liquid for ground injection such as showing a penetration length of 25 mm or less,
Judged as a practical instantaneous injection type ground injection. Example 1 66 ml of colloidal silica (S ₁ ) and 0.22 ml of 75% by weight sulfuric acid
A solution (A ₁ ) was prepared by adding. Next, 1.625 g of magnesium sulfate heptahydrate and 0.25 g of sodium bicarbonate are added to 32 ml of water.
A (B ₁ ) solution was prepared by dissolving in ( ₁ ). A ground injection liquid chemical (G ₁ ) was prepared by mixing the total amount of the (A ₁ ) liquid and the total amount of the (B ₁ ) liquid at 35 ° C. in a beaker. After this preparation, while maintaining the ground injection drug solution at 35 ° C,
The gelation time was determined by measuring the time until the ground injection drug solution showed thickening, and the needle penetration length was measured by the method described above. The results shown in Table 1 were obtained.
The pH of the ground injection liquid (G ₁ ) was 8.0.

Separately, (A ₁ ) solution and (B
₁ ) The liquid was maintained at 40 ° C, 50 ° C or 25 ° C, and the ground injection drug solution (G ₁ ) was prepared by mixing in a beaker as above, and kept at 40 ° C, 50 ° C or 25 ° C. When the gelation time and the needle penetration length at each temperature were measured in the same manner as above, the results shown in Table 1 were obtained. The measurement at 25 ° C. is a comparative example, chemical (G ₁₎ at 30 seconds elapsed time after the preparation, gelation does not occur in this chemical solution (G _1), a needle penetration length was not determined .

Example 2 66 ml of colloidal silica (S ₁ ) and 0.26 ml of 75% by weight sulfuric acid
A solution (A ₂ ) is prepared by adding the following, and then 1.625 g of magnesium sulfate heptahydrate and 0.25 g of sodium bicarbonate are added to 32 m of water.
A (B ₂ ) solution was prepared by dissolving it in 1 l. A ground injection liquid chemical (G ₂ ) was prepared by mixing the total amount of the (A ₂ ) liquid and the total amount of the (B ₂ ) liquid at 50 ° C. in a beaker. While maintaining the ground injection drug solution at 50 ° C even after this preparation, the gelation time was determined by measuring the time until the ground injection drug solution showed thickening, and the needle penetration length was measured by the method described above. The results shown in Table 1 were obtained. The pH of the ground injection liquid (G ₂ ) was 8.1.

Separately, as a comparative control example, the gelling time at 25 ° C. was measured in the same manner as above for the ground injection drug solution (G ₂ ) obtained in the same manner as above, and the results shown in Table 1 were obtained. Was obtained. This chemical solution (G ₂ ) also did not gel at 30 seconds after its preparation at 25 ° C., and the needle penetration length was not measured. Example 3 Solution (A ₃ ) was prepared by adding 0.2 ml of 75 wt% sulfuric acid to 90 ml of colloidal silica (S ₂ ), and then dissolving 5 g of magnesium sulfate heptahydrate in 8 ml of water to give (B) ₃ ) A liquid was prepared. The total amount of this (A ₃ ) liquid and the total amount of (B ₃ ) liquid are respectively
The ground injection chemical solution (G ₃ ) was prepared by mixing in a beaker while maintaining the temperature at 50 ° C. While maintaining the ground injection drug solution at 50 ° C even after this preparation, the gelation time was determined by measuring the time until the ground injection drug solution showed thickening, and the needle penetration length was measured by the method described above. The results shown in Table 1 were obtained. The pH of the above ground injection chemical (G ₃ )
Was 7.7.

Separately, as a comparative example, the gelling time at 25 ° C. was measured in the same manner as above for the ground injection drug solution (G ₃ ) obtained in the same manner as above, and the results shown in Table 1 were obtained. Was obtained. This drug solution (G ₃ ) also did not gel at 30 seconds after its preparation at 25 ° C., and the needle penetration length was not measured. Comparative Example 50 ml of colloidal silica (S ₃ ) and an aqueous calcium chloride solution obtained by dissolving 6 g of calcium chloride in 47.5 ml of water are kept at 25 ° C., and then the total amount of both liquids is mixed in a beaker. Thus, the ground injection chemical solution (G ₄ ) was prepared. The pH of this drug solution was 8.95.

Separately, 80 ml of colloidal silica (S ₃ ) and 6
g of calcium chloride was dissolved in 17.5 ml of water and the resulting aqueous solution of calcium chloride was kept at 25 ° C.
A ground injection chemical solution (G ₅ ) was prepared by mixing the total amount of both solutions in a beaker. The pH of this drug solution was 8.9.
Separately, 50 ml of colloidal silica (S ₃ ) and 50 ml of an aqueous solution of magnesium chloride obtained by dissolving 10 g of magnesium chloride and 0.2 g of citric acid in 198 ml of water, respectively.
After maintaining at 25 ° C., the total amount of both solutions was mixed in a beaker to prepare a ground injection chemical solution (G ₆ ). PH of this chemical
Was 9.4.

Next, these ground injection chemicals (G ₄ ) and (G ₅ )
Each of (G ₆ ) and (G ₆ ) was kept at 25 ° C. to cause gelation, but a non-uniform aggregated gel was formed. Table 1 Earth Release Notes inlet for drug solution gelation needle penetration codes pH SiO ₂ concentration (%) Temperature (℃) Time (sec) Length _{(mm) (G 1) 8.0} 21.2 35 8 23.8 (G 1) 8.0 21.2 40 3 16.1 (G ₁ ) 8.0 21.2 50 1 12.3 (G ₁ ) 8.0 21.2 25 300 − (G ₂ ) 8.1 21.2 50 3 9.8 (G ₂ ) 8.1 21.2 25 570 − (G ₃ ) 7.7 13.25 50 4 13.7 (G ₃ ) 7.7 13.25 25 1020- Example 4 A cylindrical mold having a diameter of 8 cm and a height of 25 cm was filled with gravel having a particle size of 10 to 20 mm so that the porosity was 50%, and then the mold was saturated with water. Then, as in Example 1,
Solution (A ₁ ) and solution (B ₁ ) were prepared and kept at 40 ° C. respectively. The solution (A ₁ ) and the solution (B ₁ ) kept at 40 ° C. were poured into the mold saturated with water as the chemical solution (G ₁ ) by the 1.5 shot method. The water in the mold was completely replaced with the chemical solution (G ₁ ). At 1 minute after this injection, when a rising water pressure was sequentially applied to the mold in which the chemical solution (G ₁ ) was injected, it was 6 kg / cm 2.
^When the water pressure of ² was reached, water flow occurred in the mold.

[0027]

According to the present invention, a ground injection chemical containing colloidal silica as a main agent is injected into the ground,
A quick-setting type ground injection work showing a gelation time of 1 second to 2 minutes can be performed. This ground injection work takes 2 minutes at 25 ℃
The ground injection drug solution having a gelation time of 24 hours, since it is only necessary to inject into the ground while maintaining the temperature at 35 ~ 70 ℃, conventional methods, for example, double pipe rod composite injection method,
Alternatively, the double tube double packer injection method can be used.

Particularly, since the injection ground according to the method of the present invention has a high pressure resistance, the double injection rod composite injection method or the double tube double packer injection method, which is widely used, is used for the primary injection. Then, the above-mentioned instant injection work according to the present invention can be performed, and then the loose injection work can be performed as a secondary injection. Furthermore, by adjusting the gelation time,
It shows a gelation time of several minutes to several tens of minutes at 70 ° C., and since a ground injection chemical containing colloidal silica as a main agent can also be obtained, by using this for the slow-injection type injection construction,
Both of the above primary injection and secondary injection, it is possible to perform construction with a chemical solution for ground injection mainly composed of colloidal silica,
The problem of contamination of the surrounding soil and groundwater that occurs when using the conventional water glass-based ground injection chemical does not occur.

Claims (1)

[Claims] 1. A ground injection chemical liquid having a gelation time of 2 minutes to 24 hours at 25 ° C. and containing colloidal silica as a main agent is injected into the ground while maintaining the temperature at 35 to 70 ° C. The characteristic ground injection method.