JP3342000B2 - Liquefaction prevention method for sandy ground by injection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for preventing liquefaction of sandy ground by an injection method.

[0002]

2. Description of the Related Art As a method of preventing liquefaction of sandy ground due to an earthquake, a method of injecting cement or a chemical solution having excellent durability and solidifying it is known. There is also known a method of stirring and mixing the solidified material and excavated soil, or forming a grid-like wall in the ground with a sheet pile or the like.

[0003]

For example, FIG. 1 shows a case where a sandy ground 11 on which a structure 10 such as a storage tank is built on the ground liquefies during an earthquake or the like. This is considered to be due to the fact that as shown in the figure, excessive pore water pressure is generated by the shear stress that repeatedly acts on the loose sandy ground 11 under the groundwater surface due to the earthquake, while the effective stress decreases and the bearing capacity decreases. I have.

Various liquefaction-preventing methods including the above-mentioned methods have been considered so far. However, any of the methods is as far as possible under the condition of ground improvement of the already constructed structure 1. Construction is extremely difficult because it must be done economically.

[0005] However, the injection method is not applicable to the structure 1 already built.
Drilling and injecting diagonally into the ground under the foundation from the outside (periphery) of the building, if it can penetrate and consolidate widely from small injection holes, especially for liquefaction measures near existing structures It can be a very excellent liquefaction prevention method.

In other words, as shown in FIG. 2, if the gap between the sand particles of the loose sandy ground 11 where negative dilatancy occurs due to the earthquake can be sufficiently filled with the gelled material by the injection method, the soil effect can be improved. The movement of the particles is prevented, so that negative dilatancy does not occur, and liquefaction can be prevented by the injection method.

The problem in this case is that the ground where liquefaction is liable to occur is fine sand, and especially in the case of a ground where a large structure is built, it is difficult for the injection liquid to penetrate immediately below the structure. If the effect is insufficient, liquefaction tends to occur because the amount of the gelled material filled in the gaps between the sand particles is insufficient.

In general, measures against liquefaction target very large structures and large-capacity structures, structures or facilities such as foundations such as storage tanks, airport runways, underground pipes and railway tunnels. Therefore, workability and economy of drilling in the presence of the structure are required.

In order to improve these grounds by the injection method,
Keep the gap between the injection holes wide and do not leave holes for injection in the structure itself, and prevent the uplift of the ground, and ensure that the injection liquid with excellent durability and permeability is not penetrated to the ground under the foundation must not.

As an injection liquid (injection material) having good permeability and excellent durability, for example, a silica injection liquid, a cement slag, or a clay injection liquid made from water glass is suitable. In particular, a silica-based injection material in which the alkali of water glass, which is a deterioration factor, is neutralized and removed with an acid, or the alkali of water glass is removed or reduced by electrodialysis using an ion exchange resin or an ion exchange membrane, has excellent permeability. ing.

Further, in order to improve the permeability, the concentration of the injection solution must be reduced and the consolidation time must be increased to form a large consolidation zone. For example, when the injection interval is set to 2 m in the forward direction, the filling interval of the injection pipe is set to P = 2 m × 2 m in the forward direction, the injection rate is f = 20 liter / min, and the improved plane area per injection pipe hole is Ap = 2m × 2m = 4m ² , Improved soil (m ³ ) per stage is V = 2m (improved height) × 4m ² = 8m ³ , Injection amount per stage (k liter) Q = V × ( ^{0.35~0.04) = 2.8m 3 ~3.2m 3 =} 3.0m 3 ( average) (0.35 to 0.04: infusion rate) 1 stage per injection time t ₁ = 3k liter ÷ 0 .02 kL / min = 150 min = 2.5 hours (injection continuation time) Infusion must be performed for a long time.

When the injection interval is set to 4 m in the forward direction, the improvement area per injection pipe hole is: Ap = 4 m × 4 m = 16 m ^{2 The} amount of improved soil per stage is V = 2 m (improved height) ) × 16 m ² = 32 m ³ One stage injection amount (kl) is: Q = V × (0.35 to 0.4) = 32 × (0.35 to 0.4) = 11.2 to 12.8 kL ≒ Assuming that the injection rate is f = 20 l / min and the injection time per stage is t = 12 kL / 0.02 kL = 600 min = 10 hours, injection must be performed for 10 hours.

That is, in consideration of economy, it is necessary to increase the interval between the injection holes. For this purpose, an injection liquid (consolidating material) having excellent permeability and being economical and having excellent durability is used. Must-have.

In order to obtain such a permeability with a silica-based injection solution, a long gelation time and a low viscosity are required so that the silica concentration can be reduced to allow the silica particles to penetrate between the soil particles for a long period of time and allow continuous injection. Need to be maintained.

The silica-based grout comes in contact with the surface of a large amount of soil particles during a long period of infiltration in the ground to prevent liquefaction, so that the gel time tends to be shortened due to the reaction with the minute metal contained in the soil particles. Therefore, it is necessary to reduce the silica concentration to maintain the gel time and low viscosity.

However, when the silica concentration is reduced, the fluidity is too good, so that the silica deviates from the target area of the ground to be improved through the ground surface or a weak portion of the ground, and as a result, the ground should be improved. The consolidation in the target area of the ground is insufficient, and the injection purpose is not sufficiently achieved.

On the other hand, when an injection solution having a high strength is used, the gelation time is short and the viscosity is high. Also, a suspension of cement or the like is similarly poor in permeability, so that pulse injection is likely to occur. Also in this case, negative dilatancy is generated in a portion where penetration is insufficient.

In addition, a region that cannot be fully penetrated is easily formed in the ground under the foundation, and the gap between the soil particles is difficult to be sufficiently filled with the gelled material. Therefore, a negative dilatancy is generated due to the repeated shear stress during the earthquake. Liquefaction is likely to occur.

In this case, even if the injection material (consolidation material) is simply injected near the foundation of the structure 10 as shown in FIG. 2, it is difficult to sufficiently obtain the injection effect for preventing liquefaction. On the other hand, there is known a method in which soil walls are formed into a plane lattice by mixing cement to prevent liquefaction. This method has the effect of preventing the liquefaction by supporting the load of the structure with a strong underground wall (consolidation wall) and blocking the shear stress due to the earthquake by the consolidation wall.

However, such an effect depends on the width (L) of the grating.
And the height (H) ratio, and it is known that L / H = 0.5-0.8. That is, the width of the grating must be smaller than the height. Therefore, in order to prevent liquefaction of the foundation of a large structure such as a tank foundation, there is a problem that the foundation is in the way and a solidified wall cannot be formed at a narrow interval.

FIG. 3 illustrates a case where a part of the ground is solidified in a plane lattice shape. Generally, the lattice-like solidified wall 12 increases the rigidity of the ground, restrains the internal ground, and Reduces shear stress caused by earthquakes and suppresses excessive pore water pressure.

However, in the case of the injection method, since the strength of the consolidation wall 12 is lower than that of the cement mixing method, it is necessary to form the consolidation wall 12 densely (at a small interval) or to increase the wall thickness. is there. However, it is impossible for injection work to form the consolidation wall 12 densely or thickly under the foundation of a large-scale structure such as a storage tank, and it is economically difficult.

As described above, in order to effectively prevent the liquefaction of the sandy ground at the foundation of a large structure by the injection method, the development of a technique utilizing the characteristics of the injection method and the characteristics of the injection consolidated body. Needed. In addition, in FIGS.
Reference numeral 3 denotes a non-liquefied layer, which is a support layer.

Accordingly, an object of the present invention is to provide a method for effectively preventing the foundation of a large structure from being liquefied by an injection method.

[0025]

The liquefaction prevention method according to claim 1 is a method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A is formed on a ground near a structure and a ground around the structure. And a consolidation zone B are respectively formed by an injection method, and the consolidation zone A uses an injection solution having a long gelation time.
Forming Te, the consolidated zone B is rigid than said consolidating zone A using the silica-based injection solution using water glass as a raw material, prior
It is characterized in that it is formed in a substantially vertical or obliquely downward direction so as to have more water blocking property than the consolidation zone A and to wrap around the consolidation zone A.

The liquefaction prevention method according to claim 2 is a method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A and a consolidation zone B are formed on the ground near the structure and the surrounding ground. Each is formed by the injection method and the consolidation zone
A is formed using an injection liquid having a long gelation time, and the consolidation zone B is formed in a substantially vertical or diagonal direction using a silica-based injection liquid made of water glass as a raw material. The zone A is formed more coarsely than the consolidation zone B.

The liquefaction prevention method of claim 3, wherein the claim
In the liquefaction prevention method described in 2, the inside of the consolidation zone B
To form a combination of the consolidated and unconsolidated parts
It is a feature.

The liquefaction prevention method according to claim 4 is a method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A is formed on the ground near a structure by an injection method. A plurality of consolidation zones B according to claim 1, 2 or 3 are formed as partition walls in A. The liquefaction prevention method according to claim 5 is based on claim 1,
In the liquefaction prevention method described in 2, 3 or 4, as a silica-based injection liquid made of water glass, an alkali of water glass is neutralized and removed with an acid, or electrodialysis using an ion exchange resin or an ion exchange membrane. To remove or reduce alkali of water glass by slag, cement , or
Is characterized by using a fine particle slag or a suspension based on fine particle cement and solution silica.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present invention will be described with reference to FIGS. In FIG. 4, in the consolidation zone (low-strength consolidation) A and the consolidation zone (high-strength consolidation) B, the former has relatively low strength and the latter has high strength.

Here, as an example of a combination of low strength and high strength, low strength generally means that the axial compression strength of consolidated soil is 0.1 to 3 kg / cm ² , and high strength is about 1 kg / cm ^2. c
The strength is not less than m ^{2 and} higher than the low strength, and the combination is relative and not limited. In addition, how to combine low strength and high strength may be determined by arbitrarily considering ground conditions, construction conditions, characteristics of the injected material, and the like.

The consolidation zone A includes a structure 1 such as a storage tank.
Is formed in the ground near the building, and the consolidation zone B is formed in the ground around the consolidation zone A more hardly than the consolidation zone A and around the consolidation zone A substantially vertically or obliquely downward. It is formed so as to enclose it.

In the present invention, the ground near the structure 1 refers to the foundation ground of the structure 1 or the ground close to the structure. Further, both the consolidation zones A and B are formed by an injection method in which an injection material (consolidation material) is injected into the ground.

At this time, in order to form the consolidation zone A and the consolidation zone B, respectively, combinations of large and small consolidation strengths depending on the type and composition of the solution type silica grout injected into the ground, and the silica content High strength grout and low strength grout are injected into the ground near the structure 1 by a combination of a large grout and a grout with a small amount of silica. Are formed respectively.

At this time, the consolidation zone A of the grout having a small strength is wrapped around the consolidation zone B of the grout having a high strength, which is formed substantially vertically or diagonally downward in the surrounding ground. I do.

The consolidation zone A is formed by a combination of a grout based on a suspension of slag or cement (or fine particle slag or fine particle cement) and a solution silica and a grout based on a solution silica. Then, the consolidation zone B is formed by the former.

Further, a grout based on the above-mentioned suspension, wherein a consolidation zone A is formed by the combination of a grout having a high concentration of suspension and a grout having a low concentration of suspension, and the consolidation zone is formed by the former. Form B. In addition, bentonite or the like may be further added to the suspension or the solution silica.

The present invention forms the high-strength consolidation zone B around the consolidation zone A in a substantially vertical or obliquely downward direction, thereby increasing the acceleration transmitted to the ground due to the repeatedly acting earthquake. The strength can be reduced by the consolidation zone B. For this reason, the shear stress at the time of the earthquake generated in the consolidation zone A via the consolidation zone B is greatly reduced.

[0038] For this reason, even if the strength of the gel filled between the soil particles in the consolidation zone A is low, the gel structure is not destroyed, so that negative dilatancy is unlikely to occur, and therefore excessive pore water pressure Liquefaction can be prevented without increasing the rise of the ground or the effective stress of the ground.

Although the consolidation zone B has a higher strength than the consolidation zone A, it has a lower strength than cement-mixed soil, sheet pile, or the like. However, the presence of the consolidation zone A suffices.

FIG. 5 shows a strength characteristic model of the consolidated ground according to the present invention. Even if liquefaction occurs outside the foundation due to the ground, the consolidation zone B blocks changes in pore water pressure around the foundation and acceleration due to earthquake, so the acceleration in the consolidation zone A is reduced and the strength of the consolidation zone A Even if the height is low, the negative dilatancy caused by the earthquake is unlikely to occur.

In general, a consolidated body obtained by injection has a high strength and a small breaking strain, and a low strength body has a large breaking strain. Therefore, if the shearing stress is reduced by the consolidation zone B, the consolidation zone A can easily withstand a break even if the strength is low.

The effect of the present invention is considered to correspond to the strength similar to an egg in hot water as shown in FIG. Egg shells alone or egg contents are easily destroyed by external forces. However, in the whole egg, the shell of the egg and its contents combine to exhibit structurally excellent strength against external force. Probably, the whole egg has a higher shear strength than the consolidation zone B of FIG. 5B and is hard to break even with a large strain, and keeps the strength even if the strength is reduced.

That is, the consolidation zone A and the consolidation zone B are combined with each other to prevent an increase in excess pore water pressure due to an earthquake, a reduction in an increase in shear stress, and a prevention of liquefaction factors such as interruption of fluidity of groundwater and soil particles. Enable measures simultaneously and economically. Such a principle can be similarly considered in the inventions of claims 2 and 3.

For this reason, as shown in FIG.
Distance between ₁ and B ₂ can be widened, and since the thickness of the consolidated zone B ₁ and B ₂ can be thin, the workability and economy can be obtained.

The consolidation zone A can be formed by injecting an injection solution having a long gelling time of, for example, several hours to several tens of hours, by using an injection pipe 2 provided at a large interval between injection holes. For this reason, even if the injection pipe 2 is installed obliquely, it becomes possible to allow the injection liquid to penetrate directly below the structure 1 due to the constraint of the consolidation zone B.

Accordingly, it is not necessary to bore the injection hole by directly drilling the foundation of the structure 1, and it is not necessary to drill the injection hole densely through the foundation of the structure 1. There is no need to make zone B thicker.

[0047] Figures 7-9 show another example, FIG. 7 in the consolidated zone formed between both sides of the consolidation zone B ₁ and B ₂ A, to form a consolidated zone B ₃ as a partition wall It is an example. FIG. 8 shows an example in which a consolidation zone B is formed around the entire consolidation zone A formed in the ground near the structure.

Further, FIG. 9 shows that the consolidation zone B is formed around the consolidation zone A so as to wrap the entire circumference of the consolidation zone A almost vertically, and the consolidation zone A is formed inside the consolidation zone A. consolidating zone B ₃ as a partition which is continuous with B is an example of forming a planar grid pattern.

FIG. 10A shows a case where a railway, an airfield, and other structures 1 are constructed on the ground and drilling and injection from the ground cannot be performed. A vertical shaft (not shown) is excavated, a horizontal hole is drilled in the ground near the structure 1 from the vertical shaft, and the injection material is formed in the ground near the structure 1 and in the surrounding ground. Is shown in which the consolidation zones A and B are respectively formed by injecting the liquid.

FIG. 10B shows a case where a railway, an airfield, and other structures 1 are also constructed on the ground, and the consolidation zone B is wrapped around the consolidation zone A in a substantially vertical direction. forming a, and illustrates an example of forming a consolidated zone B ₄ in disk-shaped continuous horizontally from the upper end of the consolidation zone B on the consolidation zone a.

Of course, the consolidation zone B may be formed in an arbitrary layer (a plurality of layers) in a plane, in the consolidation zone A, or at the upper end and lower end of the consolidation zone A. FIG. 11 shows an example in which consolidation zones A and B are formed around the underground pipe 3 used as a common trench to prevent liquefaction.
Is considered to form the improved ground so that the consolidation zone A is wrapped almost vertically in the consolidation zone B, even if the consolidation zone B is formed only on both sides in the opposite extension direction. Can be.

FIG. 12 shows that the consolidation zones A and B are respectively formed in the ground near the structure 1 and in the surrounding ground, and the consolidation zone A is formed obliquely from the upper end of the consolidation zone B. it is an example of forming a consolidated zone B ₅ continuous with.

At this time, the consolidation zone B ₅ may be formed to have a substantially V-shaped cross-section that is continuous in one direction along the consolidation zone B. circular, when formed in a rectangular shape or a polygonal shape, consolidation zone B ₅ in accordance with the shape of the consolidation zone B, reverse conical, or may be formed in an inverted quadrangular pyramid shape or a reverse pyramidal shape.

[0054] Then, Figures 13 and 14, an example of forming a consolidated zone B ₃ as a partition wall at predetermined intervals in the consolidation zone A. FIG. 15 shows that a consolidation zone A is formed in the ground near the structure 1, and a consolidation zone B is formed around the consolidation zone A almost diagonally downward. This is an example in which the binding zone A is wrapped.

At this time, the consolidation zone A may be formed in a substantially inverted triangular cross section continuous in one direction, and the consolidation zone B may be formed in a substantially V-shaped cross section along the outer shape of the consolidation zone A. Alternatively, the consolidation zone A may be formed in an inverted conical shape, an inverted quadrangular pyramid shape, or an inverted polygonal pyramid shape, and the consolidation zone B may be formed in a substantially V-shaped cross section along the outer shape of the consolidation zone A. .

FIG. 16 shows that a consolidation zone A is formed in the ground near the structure 1 and a consolidation zone B is formed around the consolidation zone A in a substantially vertical direction. it is an example of forming a consolidated zone B ₅ so as to wrap the consolidation zone a substantially diagonally downward from the upper end of the B.

At that time, the consolidation zones B on both sides are continuously formed in parallel in one direction, and the consolidation zone A is formed in a substantially inverted triangular cross section continuous in one direction along the consolidation zone B; it may be formed in a substantially V-shaped cross section along the outer shape of the further consolidation zone B ₅ caking zone a.

Alternatively, the consolidation zone B is formed in a plane circular shape, a rectangular shape or a polygonal shape so as to surround the consolidation zone A, and the consolidation zone A is formed into an inverted cone along the plane shape of the consolidation zone B. Shaped, inverted quadrangular pyramid or inverted polygon pyramid,
It may be formed in a substantially V-shaped cross section along the outer shape of the further consolidation zone B ₅ caking zone A.

In each case, the consolidation zones B _{1 to} B ₅ are the same as the consolidation zone B. Next, an example in which a consolidation zone having a higher water stopping property than the consolidation zone A is used as the consolidation zone B will be described. Here, the consolidation zone having a high water-stopping property means an injection zone formed by consolidating with an injection material having a higher permeability than the consolidation zone A to form an excellent water-stopping zone.

For example, the consolidation zone B is a zone in which solution-type silica grout is consolidated mainly by infiltration between soil particles, and the consolidation zone A is based on a suspension of cement, clay, or the like, or on cement, slag, or clay. A suspension grout, a suspension grout to which a gelling agent or solution-type silica is added, or a suspension grout to which solution-type silica is added with clay such as bentonite, or a pulse having a short gelation time. This zone is solidified mainly by injection.

The consolidation zone A is a consolidation zone having a low water-stopping property due to vein injection or the like, insufficient permeation between soil particles, or insufficient permeation distance. Therefore, the gap between the soil particles cannot be sufficiently filled with the solidified matter.

According to this combination, since the consolidation zone B is excellent in waterproofness, the occurrence of negative dilatency is prevented, the propagation of excessive pore water pressure from the outside is blocked, and the surrounding liquefaction phenomenon is blocked.

While this zone reduces the shear stress caused by the earthquake, the infiltration between the soil particles is insufficient in the consolidation zone A, but the injected liquid is hardly deviated to the periphery due to the restraining effect of the consolidation zone B. Since the portion where the infusate has not completely penetrated is compressed and dense, negative dilatancy is less likely to occur.

That is, since the shearing stress due to the earthquake is reduced in the consolidation zone B, even if the consolidation zone A has insufficient permeation between the soil particles, it does not have to be liquefied. For this reason, in the consolidation zone A, an inexpensive suspension-type injection material having poor permeability or without gelation or an injection material with a short gelation time in which the gap filling rate is reduced can be used. Due to the restraining effect of B, injection can be performed without deviating from the pulse shape, and the effect of preventing liquefaction can be provided extremely economically.

The present invention also includes the size of the gel deionized water as an element indicating the degree of the water stoppage margin. In general, syneresis water in solution-type silica grout often contains a large amount of ions other than silica. For example,
Silica grout obtained by desalting water glass with an ion exchange resin or an ion exchange membrane, or silica grout having a large particle diameter of silica has very little syneresis water.

As a matter of course, the zone solidified with less syneresis water has a higher gel filling rate between soil particles and a lower water permeability. Therefore, the consolidation zone A may be formed with the larger grout of syneresis water, and the consolidation zone B may be formed with the smaller grout of syneresis water. The effect is the same as described above.

Further, the present invention is to form an improved ground excellent in workability and economy by the pouring method, wherein the consolidation zone A is formed by the consolidation zone B which is more excellent in strength and water stopping property. By improving the ground in such a manner that the ground is wrapped in a substantially vertical direction, the space between the frames of the consolidation zone B can be increased, and the consolidation zone A greatly reduces economical material by the restraining effect of the consolidation zone B. The liquefaction can be prevented extremely economically and excellently in operability only by injecting in the pore gap.

For the same reason, an example of the consolidation zone A coarsely formed (ground improvement) by the injection method inside the consolidation zone B densely formed (ground improvement) by the injection method is shown. In the above-mentioned example, an insufficiently consolidated portion is formed by using an infused material that cannot be completely penetrated, but the term “roughly formed” (ground improvement) as used herein means that the degree of ground improvement is small. For example, FIGS. 17 and 18 show that the solidified portion B ₆ and the unsolidified portion A
₂ and FIGS. 19 and 20 show an example in which a consolidated portion B ₆ and an unconsolidated portion A ₂ are intentionally combined in a consolidated zone B.

Also in this case, the liquefaction can be economically prevented by the effect of the consolidation zone B in the presence of the consolidation zone B as described above. In the present invention, as to how to combine the contents of the consolidation zone A and the consolidation zone B,
What is necessary is just to determine in consideration of an effect and economic efficiency according to ground conditions.

In the present invention, when a layer having a high permeability in the horizontal direction is present, it is natural that the suspension can be combined with the grout having a short gelling time in the horizontal direction.

[0071]

The present invention has been described above. In particular, the present invention provides a consolidation zone B in which the shearing stress due to an earthquake is reduced, the excess pore water pressure is blocked, the surrounding liquefaction phenomenon is blocked, and the consolidation is performed. Sharing the constraint of the infusate that solidifies zone A,
The consolidation zone A and the consolidation zone B are assigned to the consolidation zone A to prevent the occurrence of negative dilatancy.
Work together to prevent the rise in pore water pressure and the decrease in effective stress caused by the repeated shear stress increase in the pore water pressure of sandy ground, thereby effectively preventing liquefaction that satisfies workability and economy. It is made possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of a ground where a liquefaction phenomenon occurs.

FIG. 2 is a cross section of the ground in which only the vicinity of the foundation of the structure has been ground-improved by an injection method.

FIG. 3 is a cross-sectional view of the ground obtained by improving the ground into a lattice shape by an injection method.

FIG. 4 is a sectional view of an improved ground by an injection method showing a liquefaction preventing effect of the present invention.

FIG. 5A is a schematic diagram of a plan view of the improved ground, and FIG. 5B is a diagram showing a tendency of shear characteristics of a high-strength consolidation zone and a low-strength consolidation zone.

FIG. 6 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 7 is a cross-sectional view of the improved ground by the pouring method of the present invention.

FIG. 8 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 9 is a cross-sectional view of the improved ground by the pouring method of the present invention.

10 (a) and 10 (b) are cross-sectional views of an improved ground by the injection method of the present invention.

FIG. 11 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 12 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 13 is a sectional view of an improved ground by the pouring method of the present invention.

FIG. 14 is a cross-sectional view of the improved ground by the pouring method of the present invention.

FIG. 15 is a cross-sectional view of the improved ground by the pouring method of the present invention.

FIG. 16 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 17 is a cross-sectional view of an improved ground by the pouring method of the present invention.

FIG. 18 is a cross-sectional view of the improved ground by the pouring method of the present invention.

FIG. 19 is a cross-sectional view of the improved ground by the injection method of the present invention.

FIG. 20 is a cross-sectional view of the improved ground by the injection method of the present invention.

[Explanation of symbols]

A consolidated zone (low intensity Katayuitai) A ₂ Not consolidated portion B consolidation zone (high strength Katayuitai) B ₁ solidification zone (high strength Katayuitai) B ₂ consolidation zone (high strength consolidated body) B ₃ solidification zone (high strength Katayuitai) B ₄ consolidation zone (high strength Katayuitai) B ₅ solidification zone (high strength Katayuitai) B ₆ consolidated portion 1 structure 2 injection pipe 3 Underground pipe

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) E02D 27/34 E02D 3/12 101

Claims (5)

(57) [Claims] 1. A method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A and a consolidation zone B are respectively formed on a ground near a structure and a ground therearound by the injection method. Use the injection solution with long gelation time
The consolidation zone B is harder than the consolidation zone A using a silica-based injection liquid made of water glass,
A liquefaction-preventing method characterized by being formed in a substantially vertical or obliquely downward direction so as to have a more water-blocking property than the consolidation zone A and wrap around the consolidation zone A. 2. A method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A and a consolidation zone B are respectively formed on a ground near a structure and a ground around the structure by the injection method. In the sintering zone A, use an injection solution with a long gelation time.
The consolidation zone B is formed densely in a substantially vertical or oblique direction using a silica-based injection liquid made of water glass, and the consolidation zone A is formed more coarsely than the consolidation zone B. Liquefaction prevention method characterized by performing. 3. An unconsolidated portion inside the consolidation zone B
3. A combination of parts.
Liquefaction prevention method described. 4. A method for preventing liquefaction of sandy ground by an injection method, wherein a consolidation zone A is formed in the ground near a structure by an injection method, and a partition is formed in the consolidation zone A as a partition. 4. A method for preventing liquefaction, comprising forming a plurality of consolidation zones B according to 2 or 3. 5. A silica-based injection liquid made of water glass as a raw material, wherein alkali of water glass is neutralized and removed with an acid, or alkali of water glass is removed by electrodialysis using an ion exchange resin or an ion exchange membrane. Reduced or slag or cement or fine slag or fine cement
5. A liquefaction-preventing method according to claim 1, wherein the suspension is based on a suspension of silica and a solution silica.