JP2002047640A - Liquefaction prevention structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefaction prevention structure extremely effective for liquefaction prevention. SOLUTION: A continuous underground wall 1 is prepared so as to surround the fixed range within a liquefaction foundation A and a plurality of underground foundation improving bodies 2 of prescribed widths and prescribed thickness are prepared so as to exist without being connected one another in the foundation A in the inside region. The underground foundation improving bodies 2 directing in different directions are prepared in dispersedly existing states so as to cope with stress of different directions. Both of the continuous underground wall 1 and the underground foundation improving bodies 2 are prepared by soil cement made of excavated soil and a caking material. H-steel as a reinforcing core member 3 is driven at prescribed intervals in the continuous underground wall 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquefaction-preventing structure that can prevent liquefaction particularly during an earthquake.

[0002]

2. Description of the Related Art Hitherto, as a method for preventing liquefaction of the ground, there has been known a liquefied ground (hereinafter referred to as "liquefied ground").
For example, a method of injecting a cement-based solidifying material into the solidified material and forcibly mixing and mixing the solidified material and excavated soil to form a two-way continuous ground improvement wall in a lattice shape is known, for example. This is known from Japanese Patent Publication No. Hei 4-54004.

[0003]

However, when such a ground improvement wall is formed in two directions to form a grid, the two-way ground improvement wall is formed before and after in time, and Since the ground improvement body created from is hardened after the previously improved ground improvement wall, it is built across the previous ground improvement body, so discontinuous parts, poor adhesion parts, etc. In some cases, a so-called cold joint may be formed, and therefore, there has been a problem that liquefaction cannot be reliably prevented, for example, the inflow of excess pore water due to liquefaction of the outer ground cannot be prevented.

[0004] In addition, since the liquefaction prevention measures are not taken in the area outside the area where the liquefaction prevention measures have been taken, a large moving earth pressure due to liquefaction generated during an earthquake occurs on the ground improvement wall in contact with the outside area. It acts in the horizontal direction, which may damage the ground renovation wall, and as a countermeasure, the outer ground improvement wall must be thickened or densely arranged to increase costs. Was a factor.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is intended to surely prevent the occurrence of liquefaction and eliminate the possibility of cold joints so that the surrounding liquid which has not been subjected to liquefaction prevention measures has been taken. It is an object of the present invention to provide a liquefaction prevention structure capable of reliably blocking the influence of liquefaction.

[0006]

As a means for solving the above problems, a liquefaction-preventing structure according to the present invention is characterized in that, in a ground where liquefaction is likely to occur, a continuous structure reinforced with a stress material is used. A plurality of underground ground improvement bodies having a predetermined width and a predetermined thickness are formed without being connected to each other in an inner region blocked from the outer periphery by an underground wall, and the underground ground improvement bodies are subjected to stresses in different directions. In order to cope with the problem, the underground ground improvement body facing in different directions is formed.

For example, a continuous underground wall is formed in a ground which may be liquefied so as to surround a predetermined area thereof, and a plurality of underground ground improvement bodies having a predetermined width and a predetermined thickness are formed in the ground in an inner area thereof. The underground soil improvement bodies or a plurality of underground ground improvement bodies are separated and formed in a state where they are oriented in different directions from each other.

Here, the construction method of the continuous underground wall is as follows.
In addition to the soil cement column method consisting of excavated soil and solidified material, it is possible to adopt construction methods commonly used so far, such as the underground continuous wall method using cast-in-place concrete, or the method using PC sheet pile or RC sheet pile. it can.

[0009] The method of constructing the underground ground improvement body may be a construction method in which soil cement columns are wrapped with each other, or may be a construction method in which a straight continuous underground wall is constructed. A method of forming an underground continuous wall made of concrete may be used.

According to a second aspect of the present invention, in the liquefaction prevention structure according to the first aspect, the ground in the inner region of the continuous ground wall is rooted to a predetermined depth, and the ground under the ground is formed below the root. The body is created.

According to a third aspect, in the liquefaction prevention structure according to the first or second aspect, some of the underground ground improvement bodies are formed so as to be connected to the continuous ground wall and substantially perpendicular to the continuous ground wall.

According to a fourth aspect, in the liquefaction-preventing structure of the first, second or third aspect, both the continuous underground wall and the underground ground improvement body are formed of soil cemet comprising excavated soil and solidified material.

According to a fifth aspect of the present invention, in the liquefaction prevention structure according to the first, second, third or fourth aspect, a reinforcing core material is provided at predetermined intervals on the continuous underground wall as a stress material. As the reinforcing core material, a metal material such as a shape steel such as an H-section steel or a steel pipe, or a concrete material such as a concrete plate reinforced with a reinforcing bar is preferable.

[0014]

With this construction, a continuous underground wall reinforced with a stress material is formed around the periphery, and the ground is blocked from the outer periphery. Therefore, even if lateral fluidization occurs, the ground in the inner region of the continuous underground wall is not affected, and excess pore water due to liquefaction of the outer ground does not flow.

Further, a plurality of underground ground improvement bodies having a predetermined width and a predetermined thickness are dispersedly formed in the ground inside the continuous ground wall, so that the shear rigidity of the liquefied ground is increased. Since the shear deformation is suppressed, the generated shear strain is reduced and liquefaction is prevented.

That is, the liquefaction of the ground in the inner region of the continuous ground wall is prevented by the operation of the plurality of distributed ground improvement bodies, and the outer surface of the ground is prevented by the operation of the surrounding continuous ground wall. Liquefaction on unliquefied ground is blocked.

The principle that the underground ground improvement body dispersedly arranged in the ground inside the continuous ground wall prevents the liquefaction is, for example, as shown in FIGS. 6 (a) and 6 (b). Since the presence of the underground ground improvement body 2 reduces the shear strain generated in the surrounding ground a surrounding the middle ground improvement body 2, the underground ground improvement bodies 2 are dispersed and arranged so that the ground a overlaps with each other. By doing so, liquefaction of the entire ground (site) inside the continuous ground wall is prevented.

[0018]

1 (a) and 1 (b) show an example of a liquefaction prevention structure according to the present invention, in which a liquefied ground A is surrounded in a substantially rectangular plane over a certain range. The continuous underground wall 1 is formed. Also, a plurality of underground ground improvement bodies 2 are formed in a dispersed state in the ground inside the continuous ground wall 1.

In the drawing, the surrounding ground surrounding the underground ground improvement body 2 shown in FIG. 6 is shown by broken lines for reference.

Both the continuous underground wall 1 and the underground ground improvement body 2 excavate the ground while discharging the solidified material into the ground, and forcibly mix and mix the solidified material and the excavated soil. In this way, a plurality of soil cement columns are formed in a continuous wall shape, and in particular, the continuous underground wall 1 is made of a shape steel such as an H-section steel or a steel pipe,
A reinforcing core material 3 made of a concrete plate or the like is driven in as a stress material and reinforced.

Therefore, even if the liquefied ground D in the outer region of the continuous underground wall 1 liquefies and the earth pressure from the outside rises, the continuous underground wall 1 is reinforced by the plurality of reinforcing cores 3. This makes it possible to resist the earth pressure.

Further, the continuous underground wall 1 penetrates the liquefied ground A and is continuously formed at least up to the intermediate support ground B. In some places, the continuous underground wall 1 extends through the intermediate support ground B to the deep support ground C. And the tip 1a is a deep supporting ground C
May be formed continuously at a predetermined depth.

The underground ground improvement body 2 is continuously formed with a predetermined width and a predetermined thickness up to the lower end portion of the liquefied ground A, and is formed so as to exist without being connected to each other. 2 are formed so as to face different directions and to be dispersed so as to be able to cope with (resist) stresses caused by earthquakes in different directions.

An underground ground improvement body 2 as shown in FIG.
May penetrate the liquefied ground A and may be continuously formed at a predetermined depth to the inside of the intermediate support ground B at the tip end.

In any case, as the solidifying material, a cement milk-like material obtained by mixing a cement solidifying material with water is used.

FIGS. 2 (a) and 2 (b) show another example of the liquefaction prevention structure according to the present invention. In FIG. 2 (a), particularly, a certain area of the liquefied ground A is formed so as to surround a substantially rectangular plane. The inside ground of the continuous underground wall 1 is cut to a predetermined depth, and a plurality of underground ground improvement bodies 2 having the above-described structure are dispersed and formed below the cut bottom.

At the time of root cutting, the surrounding continuous underground wall 1 is used as a dike for stopping the collapse of the ground due to the root cutting.

Also in this example, the continuous underground wall 1 penetrates the liquefied ground A, is continuously formed at least up to the intermediate support ground B, and penetrates the intermediate support ground B in some places, and the deep support ground C And the tip portion 1a may be continuously formed at a predetermined depth in the deep support ground C.

3 (a) and 3 (b) also show another example of the liquefaction prevention structure according to the present invention. In the figure, the underground ground improvement body 2a immediately inside the continuous ground wall 1 is particularly continuous. Underground wall 1
And is formed substantially at right angles to the continuous underground wall 1 and at predetermined intervals in a continuous direction of the continuous underground wall 1.

By forming a part of the underground ground improvement body 2, that is, the underground ground improvement body 2a in this way, the liquefied ground D in the outer region of the continuous underground wall 1 is liquefied and externally. Even if the earth pressure increases, the resistance of the continuous underground wall 1 to the earth pressure in the outer region is significantly increased.

FIG. 4 also shows another example of the liquefaction preventing structure according to the present invention. In particular, the underground ground improvement body 2 is formed as a set of three underground layers having a predetermined width, a predetermined thickness and a predetermined distance in the same direction. The underground ground improvement bodies 2 in a set of three pieces are dispersedly formed in a state where they face in different directions. Note that the number of the set of underground ground improvement bodies 2 may be arbitrarily increased or decreased as needed.

In any of the examples shown in FIGS. 2 to 4, the underground ground improvement body 2 is continuously formed with a predetermined width and a predetermined thickness up to the lower end of the liquefied ground A, and is not connected to each other. It is built to exist, and the underground ground improvement body 2 is
In order to be able to cope with (resist) the stress of earthquakes in different directions, they are created in a state where they are dispersed in different directions.

The underground ground improvement body 2 may be arranged in any manner as long as it is arranged as described above.
May be arranged as shown in FIG.

Although not particularly shown, a pile for supporting the load of the superstructure may be installed in the inner area of the continuous underground wall 1.

For example, the continuous underground wall 1 and the underground ground improvement body 2
Is constructed in the continuous underground wall 1 at a position where the underground ground improvement body 2 is not formed in the continuous underground wall 1 as a support pile for supporting a superstructure to be constructed later, such as a PC pile. Piles or cast-in-place concrete piles may be constructed. Of course, even if such a pile is formed, it does not hinder the liquefaction prevention effect of the present invention. Example 1 Next, an embodiment of the liquefaction prevention structure according to the present invention will be described.
As shown in the figure, soil cement and excavated soil are agitated and mixed to form a soil cement column wall, and H-section steel is erected at predetermined intervals as a reinforcing core material 3 in the soil cement column wall. I have.

The underground ground improvement body 2 is dispersed and formed by overlapping and connecting columnar soil cement columns in the ground inside the continuous ground wall 1.

The underground ground improvement body 2 is formed continuously with a predetermined width and a predetermined thickness, and is formed so as to exist without being connected to each other. In order to be able to cope with (resist) stress, it is formed in a state of being dispersed in different directions.

As a method for constructing the continuous underground wall 1, for example, JP-A-10-159084 and JP-A-10-168
No. 873, an endless chain having a cutting blade is circulated around the cutter post while traversing the ground, and at the same time, the cement milk is discharged from the lower end of the cutter post or near the ground surface. ,
The soil cement column wall is formed by stirring and mixing with the excavated soil, and an H-shaped steel is inserted as a reinforcing core before the soil cement hardens.

As a method of constructing the underground ground improvement body 2, for example, a rod having at least a drilling wing at its tip and a number of stirring blades at the top thereof is used. A solidified material such as milk is injected, and the two are stirred and mixed to form a column-shaped soil cement column by overlapping and connecting. Embodiment 2. FIG.
As another construction method of the continuous underground wall 1 as shown in FIG. 3, as in the underground ground improvement body 2, a rod having at least a drilling wing at the tip and a large number of stirring blades at the top thereof is used,
The ground is excavated while rotating the rod, and a solidifying material such as cement milk is injected, and the two are stirred and mixed to form a column-shaped soil cement column by overlapping and connecting. Then, before the soil cement hardens, the reinforcing core members 3 made of H-shaped steel are erected at predetermined intervals.

The construction method of the underground ground improvement body 2 is the same as that of the first embodiment, and the underground ground improvement body 2 is continuously formed at a position as shown in FIG. , And are formed apart from each other so as not to be connected to each other,
And it is formed in mutually different directions. Further, the surrounding underground ground improvement body 2a is connected to the continuous underground wall 1 as shown in FIG.

After completing the formation of the underground continuous wall structure 1 and the underground ground improvement body 2 in this manner, the surface layer is cut off to a predetermined depth as shown in FIG.

[0042]

As described above, the present invention comprises a continuous underground wall formed around the ground and an underground ground improvement body formed in the ground in the inner region, and is formed in the inner region. The underground ground improvement body is a wall-like body that is not connected to each other, and the wall-like body is formed in a state where the underground ground improvement body facing in different directions exists so as to be able to resist stresses in different directions from each other. Therefore, the shear rigidity of the ground increases in different directions. Therefore, liquefaction of the ground in the inner region is reliably prevented.

Further, since the continuous underground wall is formed so as to block the liquefied ground in a certain area from the ground in the outer area, excess pore water due to liquefaction in the outer area ground is formed in the inner area. Can be prevented.

Further, since a reinforcing core member made of H-section steel, steel pipe, or the like is built in the surrounding continuous underground wall as a stress material, it can be used as a retaining wall, and can be used as a reinforcement. Due to the presence of the core material, it is possible to resist the increased earth pressure due to the liquefaction of the outer region ground.

That is, the static earth pressure coefficient Ka = 0.5 as the earth pressure coefficient before liquefaction rises to 1.0 when liquefied, and almost doubles. The reinforcing core material effectively resists this.

Further, among the underground ground improvement bodies, those arranged near the continuous ground wall are connected to the continuous ground wall and formed substantially perpendicular to the continuous ground wall. Not only can the seismic resistance of the continuous underground wall due to the vibration during the earthquake be remarkably increased, but also the resistance against the increased earth pressure due to the liquefaction of the surrounding ground can be further increased.

[Brief description of the drawings]

FIG. 1 shows an example of a liquefaction prevention structure of the present invention, wherein (a)
2 is a plan view, and FIG. 2B is a cross-sectional view taken along the line II-II of FIG.

FIG. 2 shows an example of the liquefaction prevention structure of the present invention, wherein (a)
FIG. 2B is a plan view, and FIG.

FIG. 3 shows an example of the liquefaction prevention structure of the present invention, wherein (a)
FIG. 2B is a plan view, and FIG. 2B is a sectional view taken along the line C-A of FIG.

FIG. 4 is a plan view showing an example of the liquefaction prevention structure of the present invention.

FIG. 5 is a plan view showing an example of the liquefaction prevention structure of the present invention.

FIGS. 6A and 6B show the principle that an underground ground improvement body can prevent liquefaction, where FIG. 6A is a plan view and FIG. 6B is a cross-sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Continuous underground wall 1a End part of continuous underground wall 2 Underground ground improvement body 2a Underground ground improvement body 3 Reinforcement core material (stress material) A Liquefied ground (ground that may be liquefied) B Intermediate support ground C Deep support ground

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Shinichi Hibino 6-13-7 Akasaka, Minato-ku, Tokyo Tenox Co., Ltd. (72) Naoya Matayoshi 6-13-7 Akasaka, Minato-ku, Tokyo Co., Ltd. Inside Tenox (72) Inventor Eijiro Mizoguchi 6-13-7 Akasaka, Minato-ku, Tokyo Tenox Inside Co., Ltd. (72) Inventor Takashi Motome 6-13-7 Akasaka, Minato-ku, Tokyo Tenoxnai Co., Ltd. (72) Invention Person Hiromasa Huang 6-13-7 Akasaka, Minato-ku, Tokyo Tenox Co., Ltd. F-term (reference) 2D040 AA01 AB03 AB05 BB01 BD03 BD05 CA01 2D049 EA02 EA06 GA12 GA15 GB05 GC11 GE03 GE04 GE09

Claims (5)

[Claims] 1. In a ground that may be liquefied, a plurality of underground ground improvement bodies having a predetermined width and a predetermined thickness are not connected to each other in an inner region blocked from an outer periphery by a continuous ground wall reinforced with a stress material. Characterized in that the underground ground improvement is oriented in different directions so that the underground improvement can cope with stresses in different directions. Liquefaction prevention structure. 2. The underground ground improvement body is formed in the ground below the root of the ground, wherein the ground in the inner region of the continuous ground wall is cut to a predetermined depth. 2. The liquefaction prevention structure according to 1. 3. The liquefaction prevention according to claim 1, wherein some of the underground ground improvement bodies are formed so as to be connected to the continuous ground wall and substantially perpendicular to the continuous ground wall. Construction. 4. The liquefaction-preventing structure according to claim 1, wherein the continuous underground wall and the underground ground improvement body are made of a soil cemet comprising excavated soil and a solidified material. 5. The liquefaction-preventing structure according to claim 1, wherein a metal reinforcing core material such as a shaped steel or a steel pipe is used as a stress material for the underground continuous wall. .