JPH11241336A - Ground hardening injection material, and ground injection construction method using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground hardening injection material suitable for hardening the ground, especially the sand ground having a lot of underground water, for example, to require measures to liquefaction, and a ground injection construction method, in which the ground can be hardened uniformly in a wide range and at a high strength, and in which high strength hardening can be maintained for a long period. SOLUTION: This ground hardening injection material contains an aqueous solution or colloidal liquid of a silica-based compound, and a thickener, and it is especially suitable for hardening the ground requiring measures to liquefaction or the ground having underground water. In this ground injection construction method, the ground hardening injection material is injected to the ground requiring measures to liquefaction, or the ground having ground water to harden the ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a ground, especially a sand ground, a lot of groundwater which needs measures against liquefaction,
The present invention relates to a ground consolidation injection material suitable for consolidation of flowing ground and the like and a ground injection method using the injection material. The present invention relates to an injectable material for ground consolidation capable of being consolidated and maintaining high-strength consolidation for a long period of time, and a ground injecting method using the injectable material.

[0002]

2. Description of the Related Art In Japan, where earthquakes frequently occur, various measures are taken to prevent ground liquefaction during an earthquake. Among them, in recent years, in particular, a method of injecting an injectable material for ground consolidation into the ground to consolidate the ground has been attracting attention as a powerful means because it is simple and can provide a great effect. The reason is, for example, to prevent the liquefaction phenomenon of the ground, it is necessary to prevent the rise of the pore water pressure of the water existing between the sand particles of the ground, and for this purpose, the gel space is filled with the sand particles. Is effective.

Conventionally, as an injection material for forming the gelled material, for example, a suspension-type injection material such as cement milk, a water glass-cement injection material, a silica injection material and the like have been used.

By the way, in order to prevent the liquefaction phenomenon from occurring, in order to fill the gelled material between the sand particles, it is necessary not only to carry out the process economically, but also to make the gelled material durable. is necessary.

[0005] In order to satisfy the durability of the gelled product, it is necessary that all the silica content contained in the injection material is involved in the gelation, and after the gelation, there is no elution of the silica content, and the gel is excellent over a long period of time. It is necessary to maintain a proper gel structure. In addition, in order to obtain economical efficiency, it is necessary that the injection material has a low silica content, and can penetrate and consolidate a sufficiently wide area even if the interval between the injection holes is large while maintaining a long gelation time. .

[0006] However, the suspension type injection material such as the above-mentioned cement milk has poor permeability, and the water glass-cement type injection material has poor durability of the gel.

On the other hand, a silica-based injection material has good permeability and excellent durability, and thus is effective as an injection material for forming a gelled substance in the gap between sand particles. Therefore, this silica-based injection material has a consolidated ground strength of 1 kgf /
Since about ² cm is sufficient, it is injected into the ground at a relatively low concentration. However, at the time of this injection, the silica-based injection material is diluted by the groundwater, and the ground cannot be consolidated with uniform compaction strength.

Therefore, a method of injecting a high-concentration injection material in the initial stage of injection and gradually reducing the concentration of the injection material can be considered. However, this method is complicated in the control of the concentration of the injection material, and is suitable for the site. is not. It is possible to increase the viscosity of the silica-based compound injection material by adding an inorganic salt or the like, but it is difficult to maintain a constant viscosity for a long period of time.

[0009]

The requirements for an injecting material for preventing the liquefaction phenomenon of the ground include good permeability and minimal dilution with groundwater when injected into the ground. It is necessary to have a high consolidation strength and to consolidate uniformly over a wide range, and it is necessary to maintain the strength and water stopping property for a long period of time. The injection material having such a requirement is suitable not only for preventing liquefaction of the sand ground, but also for consolidating the ground where a large amount of groundwater exists or flows.

[0010] Therefore, an object of the present invention is to have good permeability, to be thickened and difficult to be diluted by groundwater,
The solidified material exhibits high strength and also retains durability, so that the ground, especially sand ground where liquefaction countermeasures are required, or ground where a lot of groundwater exists or flows,
In addition, it can be compacted over a wide area and even with high strength, and this high-strength compaction is maintained for a long period of time and has durability. And a ground injection method using the injected material.

[0011]

According to the present invention, there is provided a ground consolidation injection material comprising an aqueous solution or colloidal solution of a silica-based compound, and a thickening agent. In particular, it is characterized by being suitable for consolidation of ground requiring liquefaction countermeasures or ground with groundwater.

Further, in order to achieve the above-mentioned object, according to the ground injection method of the present invention, the above-mentioned injection material for solidifying the ground is injected into the ground requiring liquefaction countermeasures or the ground with groundwater. It is characterized by consolidating the ground.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

As described above, the injection material for ground consolidation according to the present invention comprises: an aqueous solution or a colloid solution of a silica compound;
And a thickener.

15. As the aqueous solution or colloidal solution of the silica-based compound, active silica, colloidal silica, or an acidic or neutral silica sol having a pH of about 5 to 9 is used.

Activated silica is an aqueous solution of activated silica which is dealkalized by passing water glass through an ion-exchange resin. In the case of acidic, it is gradually polymerized by itself to be gelled, and is weakly alkaline. In the case of the above, gelation is caused by addition of an acid or the like.

The acidic active silica is stabilized by adding and mixing an acid such as hydrochloric acid, phosphoric acid, sulfuric acid, acidic sodium phosphate, aluminum chloride or a salt thereof as a modifier immediately after production or at the time of compounding the injection material. In addition, the gelation time in the soil can be prolonged.

The silica concentration of the activated silica is 2 to 10% by weight.
Is preferable. When this concentration is low, colloidal silica, water glass, or the like may be appropriately added at the time of compounding the injection material.

Such activated silica not only can prolong the gelation time but also has excellent durability after consolidation, and is suitable for use in the present invention. The viscosity is almost the same as water and is less than 2 cps.

The colloidal silica is obtained by increasing the particle size of the above-mentioned activated silica by heating, stabilizing, and then concentrating. The colloidal silica obtained at this time had a silica concentration of 10%.
As described above, it is usually about 30% or more. This colloidal silica is used at a silica concentration of about 10% in the composition liquid of the present invention. At this concentration, the particle size is 2 cps or less, and it is necessary to increase the viscosity.

The silica sol is an aqueous solution of neutral silica having a pH of about 5 to 9 obtained by mixing water glass with an excess or substantially equivalent amount of an acid and neutralizing an alkali component in the water glass. It is usually prepared at the site of the injection. When used for liquefaction countermeasures, silica concentration is 3 to 10%
It is preferred that Since this silica sol also has alkali removed, gel depolymerization does not occur once it has been consolidated. Thus, although it has good durability, it has almost the same viscosity as water, less than 2 cps.

When the above-mentioned aqueous solution or colloidal solution of the silica-based compound exhibits a pH close to alkaline, a thickener described later is easily dissolved or diluted to form a uniform solution. It is preferable to dissolve the thickener by forcibly stirring it with a mixer or the like, and it is easier to obtain a more uniform solution when the thickener is in a low-concentration aqueous solution.

The thickener is one that does not adversely affect the solidification property and the solidification strength of the obtained injection material, and is, for example, an organic polymer-based thickener. Or derivatives thereof, natural gums, and water-soluble synthetic high-molecular substances.

Examples of the polysaccharide or a derivative thereof include alkali metal salts such as sodium carboxymethylcellulose (cmc), hydroxyethylcellulose, sodium starch glycolate, sodium starch phosphate, sodium alginate, propylene glycol alginate, and sodium caseinate. Natural gums include gum arabic, alginic acid, casein, guar gum, gluten, roasted bean gum, and the like, and water-soluble synthetic polymer substances include polyvinyl alcohol, sodium polyacrylate, and the like.

The amount of such a thickening agent is determined by the silica concentration and pH value of the aqueous solution or colloidal solution of the silica-based compound, the type of the thickening agent, the solidified strength of the obtained injection material mixing solution, the strength of the ground to be injected. It is determined by the permeability, the presence or absence of groundwater, and the strength of the flow, etc.
s, preferably such that it exhibits a viscosity of 2 to 20 cps. Specifically, this amount is preferably in the range of 0.1 to 5% by weight in the mixture of the injection material.

When the above-mentioned thickener is blended with an aqueous solution or colloidal solution of a silica-based compound, it is preferable to dissolve it in water beforehand and blend it as an aqueous solution. At this time, the viscosity of the aqueous solution is in the range of 500 to 5000 cps. The reason for this is that when the thickener aqueous solution of this viscosity is mixed with an aqueous solution or colloidal solution of a silica compound to prepare an injection material mixture solution, the viscosity of the obtained injection material mixture solution is 2 to 40 cps, preferably 2 to 40 cps. It is necessary to increase the viscosity to 20 cps. If the injection material mixture is thickened to this viscosity, even if it is injected into the ground, dilution with groundwater is prevented, and as a result, the injection material mixture becomes 0.5 to 2.0 kgf / cm ² , Preferably, the silica concentration is maintained so as to give a consolidated strength of 1 kgf / cm ² .

When the above-mentioned thickener is an alkali metal salt, specifically, an alkali metal salt of a polysaccharide or a derivative thereof, the aqueous solution or colloidal solution of the silica compound as the main material is acidic. Since the gelling time of the obtained injection material compounding solution is shortened, it is necessary to add a gelling modifier and a curing agent to the main material to adjust the gelling time.

The gelling agent and the curing agent are not particularly limited, but preferably those which do not precipitate when added in the form of a powder or an aqueous solution.
Specific examples include water-soluble inorganic salts such as potassium chloride, sodium chloride and magnesium chloride, water-soluble glass and poorly soluble or water-soluble alkaline compounds such as magnesium hydroxide, calcium carbonate, calcium hydroxide and sodium bicarbonate. Sequestering agents such as acid soda can also be used.

The ground injection method according to the present invention comprises the step of introducing the ground consolidation material obtained as described above into the ground, particularly into the ground requiring liquefaction countermeasures, for example, the sand ground or ground with groundwater. It is constructed by injecting and solidifying the ground.

The injection material used for the above-mentioned injection has good permeability, and is thickened and difficult to be diluted by the groundwater. Therefore, the injection speed is set to 5 to 50 l / min at the time of the injection, and In addition, the injection can be performed by setting the injection hole interval in the ground to 50 to 400 cm, and the number of injection points per unit area in the ground can be reduced to improve workability.

Further, after the above-described injection material is consolidated, the consolidated material exhibits high strength and also retains durability. Therefore, the above-described injection causes a large amount of sandy ground or groundwater that requires liquefaction countermeasures. Solidify the existing or flowing ground uniformly, widely and with high strength, and maintain the high strength of the solidified material for a long period of time and also maintain the durability and consolidate Can be. In addition, in the injection of the present invention, when the gelation time of the injection material is long, it is convenient to perform injection in one shot.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail using embodiments.

1. Materials Used (1) Aqueous Solution or Colloidal Solution of Silica Compound (Main Material) Three types of main materials shown in Table 1 were used.

[0034]

[Table 1]

In Table 1, the activated silica was prepared by diluting No. 3 water glass with 5 times the volume of water, and then diluting it with an ion exchange resin (Duolit).
e C-20, manufactured by Rohm and Hass). This was stored at about 10 ° C. and used.

As the colloidal silica, Permaloc AT-30 (trade name) manufactured by Asahi Denka Kogyo KK was used.

The acidic to neutral silica sol is No. 3 water glass 27
The mixture was rapidly mixed with 5.6 ml of sulfuric acid (95%) and 67.4 ml of water to obtain an acidic silica sol.

(2) Thickeners Four kinds of thickeners shown in Table 2 were used.

[0039]

[Table 2]

(3) Other Materials The following materials were used as other materials. Hydrochloric acid HCl 35% first grade reagent aluminum chloride AlCl ₃ · 6H ₂ O reagent first grade magnesium MgCl ₂ · 6H ₂ O reagent first grade potassium chloride KCl reagent first grade No. 3 water glass Asahi Denka chloride Co.

2. Measurement and Preparation of Specimen Various measurements were performed as follows, and preparation of santogel as a specimen was performed as follows.

(1) Measurement of Viscosity The specimen was heated to 20 ° C. and measured with a B-type viscometer.

(2) Measurement of gel time (gel time) The gel time was measured by a cup inverted method. The potassium chloride was directly added to the silica compound solution and immediately dissolved by stirring. There is almost no problem because the gel time is long.

(3) Measurement of gel time in soil (gel time) 50 ml of the compounded solution was added to 100 g of Toyoura standard sand, immediately mixed and allowed to stand, and from the time of mixing to the time when it was stabbed with a bamboo skewer and felt firm. The elapsed time was taken as the soil gelation time.

(4) Preparation of Sand Gel The standard sand of Toyoura and the blended liquid were mixed, immediately poured into a mold of 5φ × 10 cm, left at room temperature, and released from the mold after the demolding strength was reached (usually about 1 day). .

Examples 1 to 13 and Comparative Examples 1 to 4 1) Thickening of an aqueous solution or colloidal solution of a silica compound A thickening agent was previously dissolved in water to prepare a 5% aqueous solution. Next, the mixture was added to an aqueous solution or colloidal solution of the silica-based compound, and water was added as needed to adjust the silica concentration. Table 3 shows the silica concentration and viscosity of the obtained liquid.

[0047]

[Table 3]

2) Preparation of injection material Tables 4 and 5 were used for the liquids (injection materials) obtained in Examples 1 to 6.
Was added to obtain an injection material. The silica concentration, viscosity and gel time are shown in Tables 4 and 5. In addition,
The curing agents of Examples 7, 8, and 9 were directly added to the main material and dissolved, and those of Examples 10 and below were dissolved or diluted in water and added.

[0049]

[Table 4]

[0050]

[Table 5]

1.8 cps of Comparative Example 3 in Table 5 and Table 4
Although there was little difference from Example 11 in viscosity in terms of viscosity, there was a large difference in effect. The reason is presumed to be that a structural net of silica colloid was formed in the injection liquid by adding the thickener, and the injection liquid was difficult to be diluted. For comparison, an injection material mixture was prepared from a material to which no thickener was added, and the viscosity and gel time were measured.

Example 14 and Comparative Example 5 The mixture of Example 7 and Toyoura standard sand were mixed, and then 5φ × 1
It was filled in a 0 cm mold, cured, demolded and sealed and cured after 1 day, and the strength was measured for 7 days. The strength was 1.5 kgf / cm ² .
The gel time in soil measured at the time of making Santogel was 5
It was time.

Further, the influence of water dilution was measured by injecting into sand. The mixed solution of Example 7 was applied to a gravel layer (groundwater level GL-
2m). After installing the single tube to the depth of GL-10m, after injecting 6800l from the tip of the single tube,
The same process is repeated after raising the single pipe by 1.0 m, and
-3 m was injected. As a result of the excavation investigation, a solid body having a diameter of about 350 cm was formed around the injection pipe.

For comparison, a sand gel was prepared under the same conditions as in Example 14 except that no thickener was used. The soil gel time was 8 hours, and the sand gel strength was measured to be 1.7 kgf / cm ² . Further, when injection was performed under the same conditions as in Example 14, the diameter of the consolidated body was only 120 cm.

[0055]

As described above, the present invention can be applied to the case where the injection material of the present invention is injected into sandy ground where liquefaction countermeasures are required, or the case where the injection material of the present invention is injected into the ground having groundwater. Since the injection material is not diluted with water, the strength is not relatively reduced and the ground can be uniformly improved.

Further, even if the injection material of the present invention is thickened,
The ground, especially sand ground, has a sufficiently wide range of penetration and consolidation properties, and the injected and consolidated ground exhibits a sufficient liquefaction prevention effect or is consolidated with a sufficient consolidation strength. Furthermore, the consolidated body of the injection material of the present invention is durable, and the effect of preventing liquefaction is maintained for a long time.

Claims (13)

[Claims] 1. An injection material for soil consolidation, which comprises an aqueous solution or colloidal solution of a silica compound and a thickener, and is particularly suitable for consolidation of ground or ground with groundwater requiring liquefaction countermeasures. . 2. The method according to claim 1, wherein the aqueous solution or colloidal solution of the silica-based compound is activated silica, colloidal silica or silica sol in an acidic or neutral region.
Injection material for soil consolidation described in the above. 3. The injection material for solidifying ground according to claim 1, wherein the thickener is an organic polymer thickener. 4. The injection material for solidifying ground according to claim 3, wherein the organic polymer thickener is a polysaccharide or a derivative thereof, a natural gum or a water-soluble synthetic polymer. 5. The injection material for solidifying ground according to claim 1, wherein the compounding amount of the thickener is such that the obtained injection material exhibits a viscosity of 2 to 40 cps. 6. The injection material for solidifying ground according to claim 5, wherein the compounding amount of the thickener is 0.1 to 5% by weight of the total compounding amount. 7. An injection material containing an aqueous solution or colloidal solution of a silica-based compound and a thickener is injected into a ground requiring liquefaction countermeasures or a ground with groundwater, thereby consolidating the ground. And ground injection method. 8. The method according to claim 7, wherein the aqueous solution or colloidal solution of the silica-based compound is activated silica, colloidal silica, or silica sol in an acidic or neutral region.
Ground injection method described in. 9. The method according to claim 7, wherein the thickener is an organic polymer thickener. 10. The method according to claim 9, wherein the organic polymer thickener is a polysaccharide or a derivative thereof, a natural gum or a water-soluble synthetic polymer. 11. The method according to claim 7, wherein the compounding amount of the thickener is such that the obtained injection material exhibits a viscosity of 2 to 40 cps. 12. The method according to claim 11, wherein the compounding amount of the thickener is 0.1 to 5% by weight of the total compounding amount. 13. The method according to claim 7, wherein the injection material is injected into the ground at an injection speed of 5 to 50 l / min and an injection hole interval of 50 to 400 cm to reduce the number of injection points per unit area in the ground. The ground injection method according to claim 7, wherein the workability is improved.