JP2002302933A - Grout injection strengthening construction method for structure foundation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grout injection strengthening construction method for a structure foundation in which grout can be strongly united with the structure foundation to be strongly integrated with it by stepwise injecting grout of high adhesion and chemical grout. SOLUTION: In this grout injection strengthening construction method for a structure foundation, foundation grout 5 mainly comprising hardening material and bentonite cohesive liquid is primarily injected into a cavity 3 generated around the structure foundation 1, and after the cavity 3 is filled with the foundation grout 5, the chemical grout 6 is secondarily injected to ground around the foundation grout. Concretely, the hardening material is composed of cement, cement with slag, or slag with lime, or it is composed of water glass to mainly comprise chemical grout.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grout injection strengthening method for a structural foundation, and in particular, grouting a grout and a chemical grout having a high adhesive force stepwise into a cavity formed around the structural foundation. The present invention relates to a grout injection strengthening method for a structural foundation that strengthens the ground around the structural foundation.

[0002]

2. Description of the Related Art Existing structures, such as buildings, bridges, seawalls, and the like, have been deteriorated for many years as the time has passed since the time of construction. In many cases, cavities are generated in the ground around the structure foundation due to soil erosion due to changes in groundwater level due to ebb and flow, and ground changes due to earthquakes and the like.

[0005] As shown in the conventional example of FIG. 5, the foundation 2 of the existing pier 1 often forms a cavity 3 below the foundation 2 as time passes. Since it may cause problems, reinforcement measures for the foundation are required.

[0004] However, as a conventional countermeasure against cavities, a method has been adopted in which a structural grout is reinforced by injecting and solidifying a chemical grout into the cavities around the foundation and the ground around the cavities.

[0005] The chemical grout used in the method is generally a water-glass suspension type having a high consolidation strength of 300 to 400 N / cm ² or a solution type having good permeability to this suspension type. Suspension grout used in combination.

In the chemical grouting method, the suspension type chemical grout is injected into a cavity formed around the foundation of an existing structure and the surrounding ground and solidified. It has been pointed out that a strong adhesion and a firm integration with a material base cannot be expected.

[0007] In other words, the suspension type chemical grout has a low viscosity because it is intended to penetrate and solidify into the gaps between the soil particles in the ground, and has a long gel time of 1 to 60 minutes. The resulting grout causes material separation due to sedimentation of the particles before gelation, resulting in non-uniform consolidation strength, and the suspended chemical grout after consolidation becomes wet. This is because it has a characteristic that the adhesive force to a structure is weakened in order to cause a shrinkage phenomenon of the grout due to a decrease in the volume in a state of water or underwater.

[0008] However, the cavity of the existing structure described above is
Since most of them are generated at the bottom of the foundation and its side surfaces, the above-mentioned characteristics of the suspended-type chemical grout cannot achieve this even for the purpose of strengthening the foundation of the underground structure.

[0009] The problem is that when the suspension-type chemical grout is injected into the cavity of the existing structure, the particles of the hardening material having the gel time and simultaneously constituting the grout cause a sedimentation phenomenon. For this reason, the grout filling in the cavity of the existing structure has been developed to form a consolidated body with reduced strength that does not contain much hardening material particles at the upper part, and the non-uniformity of the consolidated strength This is because the adhesive strength to the object base is weakened.

Further, the shrinkage phenomenon of the filled grout weakens the adhesiveness between the consolidated grout and the structural foundation,
The filled grout and the foundation of the structure have not yet formed a strong integrated state.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and proposes a solution therefor, in which grout having high adhesion and chemical grout are injected stepwise. This provides a grout injection strengthening method for structural foundations that can be expected to have strong adhesion and strong integration with the structural foundation.

[0012]

The grout injection strengthening method for a structural foundation according to the present invention is basically a method of reinforcing a ground around a structural foundation by grouting, and the cavity generated around the structural foundation in the method. The base grout mainly composed of a hardening material and a bentonite adhesive liquid is mainly injected into the part, and after the hollow part is filled with the base grout, the chemical grout is secondarily injected into the outer ground of the base grout, Specifically, it is characterized in that the hardening material is composed of any of cement, cement and slag, slag and lime, or mainly composed of water glass with chemical grout as a main component.

Accordingly, the grout injection strengthening method is
In the cavities generated in the ground around the structure foundation, strong adhesion between the structure foundation and the filling grout is ensured, and strong integration is established to ensure the strengthening of the structure foundation.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The grouting and strengthening method for a structural foundation according to the present invention is a method for strengthening the ground around the structural foundation by grouting. The primary grout mainly composed of a bentonite adhesive liquid is primarily injected, and after the hollow portion is filled with the basic grout, the chemical grout is secondarily injected into the outer ground of the basic grout.

Hereinafter, an embodiment in which the present invention is applied to a structural foundation will be described in detail based on drawings and experimental results for verification. To facilitate understanding, members similar to those of the related art are denoted by the same reference numerals.

FIG. 1 shows a pier 1 as an example of an existing structure. The foundation 2 of the pier 1 is built inside the sandy ground 4, but a cavity 3 is formed around the bottom of the foundation over the years.

For this purpose, it is necessary to reinforce the foundation 2 of the pier 1, and according to the present invention, grout injection into the cavity 3 is strengthened.

In the present embodiment, as shown in FIG. 1 (a), a basic grout 5 is injected as a primary injection into the cavity 3 generated around the pier foundation 2 to fill the interior of the cavity 3. I have.

As will be described in detail later, the basic grout 5 is composed mainly of a hardening material and a bentonite adhesive liquid, and is formed of a bentonite adhesive liquid which swells remarkably when exposed to water to obtain a high viscosity. When the suspension of the hardening material is added, the alkali component and the bentonite in the hardening material undergo a gelling reaction almost instantaneously and become very thick.

Therefore, the foundation grout 5 secures a strong adhesion to the foundation 2 while filling the cavity 3.

Next, as shown in FIG. 1 (b), after the basic grout of the cavity 3 has hardened to a certain compaction strength,
The ground is strengthened by injecting and solidifying a suspended chemical grout 6 as a secondary injection into the outer ground 4 between the foundation 2 and the foundation grout 5.

The chemical grout 6 is a grout whose gel time can be adjusted. As will be described in detail later, a suspension type and a solution type mainly composed of water glass can be used.

As a result, the foundation 2, the foundation grout 5 and the outer ground 4 are firmly integrated, and the structural foundation such as a pier is reliably strengthened.

Next, an injection grout used in the grout injection reinforcement method for a structural foundation according to the present invention will be described.

The basic grout used for the primary injection is composed of a hardening material, bentonite, other additives, and an aggregate as an extender, and the hardening material and bentonite develop hardening over time even after mixing. At the same time, by utilizing the property that the bentonite component gradually expands, the adhesive force with the structural foundation or the like is improved.

The characteristics of the basic grout vary depending on the amount of each compound. However, it is the bentonite that basically adjusts the properties of the basic grout, and the properties of the basic grout vary greatly depending on the increase or decrease.

When the amount of bentonite is large,
It becomes a non-flowable plastic mold and is suitable as a basic grout used in the grout injection strengthening method of the present invention.

However, even if the amount of bentonite is relatively small, as long as the fluidizing type is such that the breathing is adjusted to the range of 2 to 5%, the ground around the cavity is made of a permeable ground such as sandy soil. If it is, it can be used as a basic grout.

That is, even if there is a slight breathing at the time of blending, the basic grout in which the amount of bentonite is adjusted in the range of the above-mentioned fluid type is pressurized at the time of injection so that excess water is deposited in the surrounding ground. This is because penetration occurs and the breathing becomes close to 0% and is converted into a non-flowable plastic mold.

The bentonite used in the basic grout is mainly composed of a montmorillonite clay mineral, and can be used either alone or with an additive added or processed.

The bentonite is used in accordance with the properties of the basic grout in the range of different degrees of swelling. In the case of the plastic type basic grout, particularly, super clay (trade name in the United States) is high. This is preferable because of its quality.

As the hardening material used for the basic grout, any hardening material that can be hardened by adding water can be used, but typically, cement, cement-slag, slag-lime can be used. There is no particular limitation on the particle diameter, but the particle diameter is preferably about the same as that of ordinary cement, since it fills the cavities.

Further, the basic grout is, besides only bentonite, a hardening material and water, a primary mineral fine powder such as sand, fly ash, lime, rock, quartz, limestone, dolomite, etc. It is selected from clay minerals such as pottery clay and the like, and one kind or a combination of two or more kinds is used.

In addition, even in the suspension of the basic grout, it is possible to add a dispersing agent, a retarding agent, a thickening agent, an early strength developing agent, a foaming agent and the like conventionally used conventionally according to the purpose. Obtaining the initial effect is naturally considered.

In particular, the use of metal aluminum powder as a foaming agent further enhances the expansion of the basic grout, and is effective as a function capable of adding adhesion to the structural foundation.

Next, the chemical grout used for the secondary injection will be described. Chemical grout is a hardening material,
It is blended from water glass, other additives and aggregates as fillers, and its properties differ depending on the blending amount, but it is water glass that basically adjusts the properties of chemical grout, The properties of chemical grout vary greatly depending on the increase or decrease.

Since the chemical grout is used to solidify the ground, a cement or the like having high consolidation strength is used as a hardening material.

That is, examples of the hardening material include cement, cement-slag, and slag-lime as in the primary injection.

The hardening material particles are selected according to the size of the gap between the soil particles on the ground. The ordinary cement class is applied to gravel or coarse sand having a large gap. Has a Brain value of 6,000-
Fine particles of 15,000 cm ² / g are used.

The chemical grout is a grout whose gelation time can be adjusted, and a suspension type having water glass as a main component and a solution type can be used. It is a grout in which material components are combined, and the purpose of which is to set the consolidation strength to a high value such as 200 to 400 N / cm ² with a homogel and to penetrate as much as possible into the gaps between the soil particles.

The water glass used for the chemical grout is not particularly limited, but preferably has a molar ratio of 2.0.
~ 4.0 can be applied, and more preferably, the molar ratio is in the range of 2.8 ~ 3.5.

However, since the suspension type usually uses fine particles, there is a limit to permeation. For this reason, in the case where the chemical grout cannot sufficiently penetrate into the gaps between the soil particles, a solution type grout is used together to strengthen the surrounding ground of the structural foundation.

As the curing agent used for the solution type grout,
Many hardeners can be cited in pursuit of permeability. Although there is no particular limitation on the selection, for example, calcium hydroxide or the like, which has good compatibility, is a preferable degree in consideration of the compatibility with the hardening material.

As additives, dispersants, gelling accelerators, retarders, early strength developing materials and the like are used according to the purpose, and it is sufficient to deal with them as usual.

As the grouting method, various types of well-known grouting methods can be adopted, and the following examples are preferred embodiments.

As the method of injecting the basic grout for the primary injection, one-pack and two-pack properties are to be considered. Depending on the respective properties of the basic grout and the construction environment, they will be used properly. When the basic grout is of a fluid type, one-component is suitable mainly. In the case of a plastic type, it is preferable to select a two-component injection form, although not particularly limited.

In the case of a one-pack type, after mixing water, bentonite, a hardening material and the like at once in a mixing tank such as a mixer, the mixture is injected and filled by one injection pump. In the case of the above, a suspension containing a hardening material as a main component is a solution A, and an adhesive liquid containing a bentonite as a main component is B
Liquids A and B are pumped by separate injection pumps as liquids. In the case of a single tube lot, they are mixed and mixed in front of the injection tube, and in the case of a double tube lot, they are mixed and mixed at the tip and injected and filled. become.

The installation of the injection pipe is not particularly limited. As in the case of a general example, the injection pipe is pierced to a predetermined position by a boring machine or the like while corresponding to the depth. The grouting method is adopted.

The injection of the chemical grout for secondary injection is as follows:
This is the same as ordinary ground injection, and is generally performed appropriately in one-pack or two-pack.

The installation of the injection pipe is not particularly limited, but a double strainer method in which the injection pipe is previously installed is preferable in the case of one-liquid type, and in the case of two-liquid type,
It is good to inject grout by mainly piercing the double tube lot and using the double tube lot as the injection tube as it is.

As described above, the embodiments of the present invention have been described in detail. Next, the basic grout to be primary injected and the chemical grout to be secondary injected exhibit desired characteristics, and the object of the present invention is as follows. Is verified in the following experiment.

In this experiment, the plastic-type basic grout used for the primary injection was, as Example 1, a cement made of ordinary cement as a hardening material and a super clay (trade name of bentonite, manufactured by the United States) as a plasticizer. The conventional suspension-type chemical grout for Comparative Example 1
Normal cement as hardening material, water glass as plasticizer (J
IS3 product).

The first verification experiment confirms changes in the volume and the weight of the compact injected and filled in the cavity. Examples 1 in Table 1 shown in FIG. 2 and Table 2 shown in FIG. The measured values are recorded in the comparative example-1.

The flow values in Table 1 indicate the viscosity, and the inner diameter was 80 mm and the height was 8 mm on an acrylic plate.
After filling the grout in the 0 mm cylinder, the cylinder is gently lifted and the diameter indicating the spread of the grout at that time is measured.

As for the flow value, the measured value is expressed in cm. In the present embodiment, a value of less than about 13 cm is called a plastic type, and a value of about 13 cm or more is called a fluid type. .

Similarly, in the breathing, grout is placed in a 200-ml measuring cylinder, which is sealed, and after 3 hours, syneresis water is measured, and the measured value is shown in%.

Each grout specimen was 4.0 × 4.0 × 1
It is made by filling a grout of each composition shown in Tables 1 and 2 into a 6.0 cm triple formwork, wrapping the surface with Saran wrap, curing in a wet state, and removing the frame after 3 days. The rest is cured underwater.

The underwater curing was carried out in five times the amount of water in the specimen, and the water was replaced on the seventh, 28th and 90th days.

Table 3 shown in FIG. 4 shows the state of volume change and weight change in Example-1 and Comparative Example-1.

The volume change is measured up to four decimal places using a dial gauge on the basis of a length of 16.0 cm, and the measured value is expressed in%.

The change in weight is measured by a weighing machine after blotting moisture on the surface of the test piece with a paper.

As is clear from Table 3, the suspension-type chemical grout of Comparative Example 1 exhibited a wet-cured 4
After a day, the shrinkage has already started to occur, and the shrinkage has progressed even under water curing, reaching 0.8% after 180 days.

Regarding the change in weight, the soluble components other than the insoluble matter in the solidified matter, which are presumed to be sodium hydroxide in the water glass, continuously leached under water curing. As a result, after 180 days, 2.11%
It seems to have decreased.

These phenomena of shrinkage and decrease are properties peculiar to the suspension-type chemical grout, and needless to say, cause a lack of adhesion to the foundation of the structure.

On the other hand, the plastic type basic grout of Example-1 is a grout using bentonite instead of the water glass of Comparative Example-1, as shown in Table 1 in FIG. The characteristics are significantly different, as the measured values of Example-1 in Table 3 show.

That is, the plastic-type basic grout used for the primary injection of the present invention has a volume change that does not change under wet curing, but continues to expand little by little under water curing. 0.07 after 180 days
% Has been reached.

The change in weight is continuously increasing even under water curing, and shows about 1.0% increase in 180 days.

The expansion and increase of the plastic type basic grout are closely related to each other, and it is presumed that the cause is that bentonite in the basic grout has caused a swelling phenomenon over a long period of time. By the phenomenon, the basic grout can be said to adhere well to the structural foundation.

Although the experimental results are not particularly shown for the basic grout used in the present invention, the same results were confirmed for the fluid type basic grout. Cement other than cement
It has been confirmed that slag and slag-lime have the same tendency to increase in volume and increase in weight.

Further, a verification experiment is conducted to confirm whether or not the cavity formed at the bottom of the existing structure has an adhesive force with the structure foundation when the grout is filled with the foundation grout. .

This experiment assumes that the thickness of the cavity is 8 cm. The injection device is a 4x4cm steel detachable
It has a box shape with a corner and a height of 16 cm. An inlet is arranged at the bottom, an outlet is provided at a position 8 cm from the bottom, and a cock is attached to the outlet.

In the upper half of the pouring device, a concrete piece having a surface of 4 × 4 × 8 cm with some irregularities is placed, and the lower half of 8 cm is hollow.

The injection port is connected to an injection hose via a separately prepared compressor and grout pressure vessel.

The injection into the cavity is performed by mixing 1 liter of the plastic type basic grout of the above-mentioned Example 1 and putting it in a grout pressure vessel, sealing it, and then operating the compressor.

The plastic type basic grout is injected and filled into the lower half cavity from the inlet at a pressure of 5 N / cm ² by the operation of the compressor, and when the basic grout comes out from the upper outlet, the upper and lower grouts are obtained. Each cock at the bottom was closed and left as it was.

Next, when it was confirmed that the frame was removed after 7 days, the filled basic grout and the concrete pieces were well adhered.

Although the test method for confirming the adhesive force of the grout has not been clarified, in this verification experiment, the adhesion between the concrete and the foundation grout was measured using a bending plate with a uniaxial compression tester. Measuring the bending strength at
This value was taken as the strength of the adhesive force.

According to the above-mentioned method, when the above-mentioned specimen after being wet-cured for 28 days was measured, its uniaxial compressive strength was 18.4 N / cm ^2, which was about 1 of the uniaxial compressive strength shown in Table 1. It was confirmed that the adhesive strength was / 16.

Next, the suspension-type chemical grout of Comparative Example 1 was placed in a grout pressure vessel in the same manner as in Example 1, and injected and filled at an injection pressure of 5 N / cm ² .

In these settings, it took about 25 seconds from the preparation of the suspension type chemical grout to the completion of the pouring. However, it was confirmed that the frame was unframed after 7 days. The contact surface with the chemical grout peeled off and had no adhesive force.

Then, when the consolidation of the chemical grout was carefully observed, the cement was separated and the cement portion was present at the lower portion and was very hard, but the cement portion was very hard at the contact portion with the upper concrete piece. The gel strength was estimated to be about ² to 4 N / cm ² and it was confirmed that the gel strength was very weak.

Therefore, in the case of the conventional suspension-type chemical grout of Comparative Example 1, an adhesion test could not be carried out.

As verified in the above experiments, the basic grout to be primarily injected in the grout injection strengthening method for a structural foundation according to the present invention is based on the fact that bentonite mixed with the hardening material causes a swelling phenomenon over a long period of time. The volume and weight of the compact injected into the cavity are swelled and increased without reducing or decreasing the volume and weight, ensuring strong adhesion between the structural foundation and the filling grout even at the bottom of the structural foundation. I have.

Although the chemical grout to be injected secondarily has not been specifically verified, the function contributed by the chemical grout by the grout injection strengthening method of the present invention is to improve the consolidation strength by penetrating into the gaps between the soil particles. Therefore, it is clear that the intended purpose can be sufficiently achieved by combining the hardening material and water glass.

As described above, the grout injection strengthening method for a structural foundation according to the present invention involves primary injection of a basic grout,
By secondary injection of chemical grout after generating the prescribed hardening, in the cavity generated in the surrounding ground of the structural foundation, strong adhesion with the structural foundation and strong integration are established This will surely strengthen the material foundation.

Although the present invention has been described in detail based on the embodiments, the grout injection strengthening method for a structural foundation according to the present invention is not limited to the above-described embodiments at all. It is a matter of course that various changes can be made to the material such as bentonite, water glass, and the like, taking into account those already known before filing the application without departing from the spirit of the present invention.

[0087]

The grout injection strengthening method of the structure foundation according to the present invention is a method of strengthening the ground around the structure foundation by grout injection, wherein the hardening material and the bentonite stick to the cavity formed around the structure foundation. The primary grout containing the liquid as the main component is primarily injected, and after the cavity is filled with the basic grout, the chemical grout is secondary injected into the outer ground of the basic grout, and the hardening material is cement, cement and slag. , Slag and lime, or water-glass with chemical grout as the main component. This has the effect of ensuring strong adhesion to the grout, establishing strong integration, and reliably strengthening the foundation of the structure.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment to which a grout injection strengthening method for a structural foundation according to the present invention is applied.

FIG. 2 is a table showing composition of basic grout and experimental results used in the grout injection strengthening method of the present invention.

Fig. 3 Table 2 showing the composition of chemical grout and the experimental results of the conventional method

Fig. 4 Measured values of volume change and weight change of basic grout and chemical grout of conventional method

Fig. 5 Cavity diagram generated around the foundation of an existing structure

[Explanation of symbols]

1 Existing pier, 2 foundation, 3 hollow, 4 sandy ground, 5 foundation grout, 6 chemical grout,

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Asahi Asani Otani 2-F 25, Tenjin-cho, Fuchu-shi, Tokyo 21F term (reference) 2D040 AA06 AB01 AC02 BB03 CA01 CA02 CA03 CA04 CA05 CA09 CA10 CB03 CD01 CD06 DA03 2D046 DA17

Claims (3)

[Claims] 1. A method for reinforcing a ground around a structural foundation by grouting, wherein a primary grout comprising a hardening material and a bentonite adhesive liquid as main components is formed in a cavity formed around the structural foundation. A grouting reinforcement method for a structural foundation, wherein a secondary grouting of a chemical grout is carried out into an outer peripheral ground of the basic grout after the cavity is filled with the basic grout. 2. The method according to claim 1, wherein the hardening material is made of one of cement, cement and slag, and slag and lime. 3. The grout injection strengthening method according to claim 1, wherein the chemical grout is mainly composed of water glass.