JP2000178984A - Liquefaction preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefaction preventing method which can effectively and economically suppress liquefaction of the ground immediately below a structure with the minimum number of construction procedures by a simple method. SOLUTION: There is provided a construction method for preventing liquefaction of the ground below a structure. Soil improvement walls 1 are constructed in the depth direction under the ground until they reach a non-liquefied layer 4. Then, a predetermined zone of the ground is substantially enclosed by the soil improvement wall 1, to thereby form a closed block 2. Further, the periphery of the closed block 2 is substantially enclosed by another closed block 2, or alternatively a similar closed block 2 is formed in the vicinity of the closed block 2. In this manner, the construction method is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing liquefaction occurring on the ground during an earthquake.

[0002]

2. Description of the Related Art As a liquefaction countermeasure method, there is the following method. Improve the entire ground immediately below the structure. Improve the ground directly under the structure in a grid pattern. Drain materials are cast on the premises. Lower the groundwater level in the ground.

However, these methods have the following problems. The construction quantity for ground improvement is large, which is extremely uneconomical. Depending on the ground improvement method, a large number of wrapped portions are generated within the improved range, and if the improved range is wide, construction of the wrapped portion is extra and uneconomical. Since the excess pore water pressure in the ground generated at the time of liquefaction is dissipated by draining, the drain material may be clogged and may not function in the future. Management of the groundwater level must be performed at all times, which is difficult.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and effectively liquefies the ground immediately below a structure by a simple method with a minimum number of works. Another object of the present invention is to provide a method that can be economically suppressed.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for preventing liquefaction of the lower ground of a structure, and comprises a method for preventing non-liquefaction in the depth direction of the ground. Forming a closed section by constructing a ground improvement wall leading to the layer and substantially surrounding a certain area of the ground with the improvement wall;
This is a liquefaction prevention method in which the outer periphery of the closed section is further substantially surrounded by the closed section.

Further, the present invention relates to a construction method for preventing liquefaction of the ground below a structure. The method comprises constructing a ground improvement wall extending to a non-liquefaction layer in the depth direction of the ground. Thereby substantially encircling a certain area of the ground, forming a closed section that is substantially circular in plan, and near this closed section,
This is a liquefaction prevention method in which a similar closed section is formed, and thereafter, an adjacent closed section is similarly formed and performed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

<A> Construction of ground improvement wall. The present invention is a construction method for preventing the occurrence of a liquefaction phenomenon in the liquefaction layer 3 on the ground under the structure 5. Therefore, the ground improvement wall 1 reaching the non-liquefied layer 4 in the depth direction of the ground
To build. For the construction of the ground improvement wall 1, a conventionally known method can be used. For example, a method of injecting a solidifying material and stirring the mixture is employed. The column-shaped improved portions are sequentially adjacent to each other and constructed in the ground to form the wall-shaped improved wall 1.

<B> Formation of a first closed section. This modified wall 1 forms a closed section 2 surrounding a certain area of the ground. The inside of the closed section 2 surrounded by the improved wall 1 reaching the non-liquefied layer 4 is in a state where the ground improvement is not performed, but the shear deformation generated in the ground during the earthquake substantially improves the surroundings. It will be suppressed by the wall 1. At the same time, it is possible to suppress the rise of the excess pore water pressure generated in the ground during an earthquake and to suppress the settlement of the structure in order to prevent the liquefied ground from flowing out of the improved wall. When a certain area is surrounded by the improved wall 1, it is not always necessary to strictly and completely close the area. There is no problem if there is some misalignment or opening. That is, the object of the present invention can be achieved by forming the closed section 2 which substantially surrounds a certain area of the ground. This closed section 2 is temporarily referred to as a first closed section 2.

<C> Formation of the second closed section 2 On the outer periphery of the first closed section 2, an improved wall 1 reaching the non-liquefied layer 4 is constructed while being surrounded by the first closed section 2. This is formed as a second closed section 2. Also in this case, there is no problem not only when the first closed section 2 is completely surrounded, but also when there is some misalignment or an opening.
The interior surrounded by the closed section 2 and the new closed section 2 is in a state in which the ground improvement has not been performed, but the shear deformation generated in the ground during the earthquake is suppressed by the improved wall 1 which substantially surrounds the periphery. Will be. Again, in this case,
At the same time, it is possible to suppress the rise of the excess pore water pressure generated in the ground during an earthquake and to suppress the settlement of the structure in order to prevent the liquefied ground from flowing out of the improved wall. Similarly, on the outer periphery of the substantially closed section 2 formed last time,
Further, a substantially closed section 2 is formed.

<D> Planar arrangement of the improved wall 1. The improved wall 1, which forms a substantially closed section 2, can be constructed in a circular shape in a plane, i.e. in a cylindrical shape. Alternatively, the improved wall 1 forming the substantially closed section 2 can be constructed in a polygonal manner in a plane, i.e. a bottomless polygonal cylinder. In that case, the arrangement of the plurality of improved walls 1 can be constructed by being arranged concentrically in a plane with the same center point.

<E> Relationship with buildings. For example, when the planar figure is a rectangular structure 5, the plurality of improved walls 1 are constructed circularly and concentrically in a plane. (FIG. 3) Then, the perimeter surrounding the given improvement range becomes the shortest, and the ground improvement for preventing liquefaction can be constructed economically.

[0013]

Embodiment 2 of the present invention

<F> Formation of closed section 2 (FIGS. 4 to 6) In order to prevent liquefaction of the lower ground of the structure, the ground improvement wall 1 reaching the non-liquefied layer 4 is constructed in the depth direction of the ground. This construction method is the same as in the above-described embodiment. The ground improvement wall 1 substantially surrounds a certain area of the ground to form a closed section 2 which is substantially circular in plan. When a certain area is surrounded by the improved wall 1 as in the above-described embodiment, it is not always necessary to strictly and completely close the area. There is no problem if there is some misalignment or opening. That is, the object of the present invention can be achieved by forming the closed section 2 which substantially surrounds a certain area of the ground.

<G> Formation of adjacent closed section 2 In the above embodiment, the second closed section 2 is formed so as to surround the outer periphery of the first closed section 2. In the present embodiment, however, a similar closed section 2 is formed which approaches the outside of the closed section 2 and substantially surrounds a certain area of the ground. Therefore, a large number of substantially ring-shaped improved walls 1 in plan view,
They will be arranged side by side. The close compartment 2 arranged in close proximity may be formed with the outer surface of the improved wall 1 completely abutting. Alternatively, they may be formed in a state where they are not directly in contact with each other but are separated by a certain distance. Similarly, the closed sections 2 are sequentially formed by approaching each other.

<H> Pile driving. The interior surrounded by the closed section 2 remains unmodified, but the shear deformation that occurs in the ground during an earthquake is suppressed by the modified wall 1 that substantially surrounds the periphery. At the same time, it is possible to suppress an increase in excess pore water pressure generated in the ground during an earthquake. A stake 6 can be driven into the closed section 2. Alternatively, the pile 6 can be driven not only inside the closed section 2 but also inside and outside the closed section 2.

[0017]

Since the present invention has been described above,
The following effects can be obtained. <A> Since the improved wall 1 reaching the non-liquefied layer 4 is formed in a state of substantially surrounding a certain area, the number of constructions is small and economical. <B> Alternatively, since a large number of the improved walls 1 reaching the non-liquefied layer 4 are formed in a state of substantially surrounding a certain area in a plane, shear deformation generated in the ground during an earthquake can be suppressed. <C> Since there is no part to wrap within the scope of ground improvement,
It can be economical construction. <D> There is no need to drain the underground excessive pore water pressure generated at the time of liquefaction, so there is no danger of drain material clogging. <E> There is no need for management after construction. <F> Even if a pile body is constructed within the ground improvement area, the influence of liquefaction is suppressed, so that a large horizontal resistance during an earthquake can be expected.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a construction state of a liquefaction prevention method according to the present invention.

FIG. 2 is a longitudinal sectional view of a construction state.

FIG. 3 is a plan view showing a construction range of a ground improvement unit.

FIG. 4 is an explanatory view of a construction state of another embodiment.

FIG. 5 is a plan view thereof.

FIG. 6 is a plan view showing a state in which a pile is cast.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsuyoshi Hirono 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Corporation F-term (reference) 2D046 DA17 2D049 EA06

Claims (10)

[Claims] 1. A construction method for preventing liquefaction of the ground below a structure, comprising: constructing a ground improvement wall extending to a non-liquefaction layer in the depth direction of the ground, and maintaining the ground with the improved wall. A liquefaction prevention method in which a closed section is formed by substantially surrounding an area, and the outer periphery of the closed section is further substantially surrounded by the closed section. 2. A method for preventing liquefaction of the ground below a structure, comprising: constructing a ground improvement wall extending to a non-liquefaction layer in the depth direction of the ground, and fixing the ground with the improved wall. Forming a first closed section by substantially surrounding the area; forming a second closed section substantially surrounding the outer periphery of the first closed section by the improved wall; and so on. The liquefaction-preventing method according to claim 6, wherein the closed section is formed by substantially surrounding the outer periphery of the previously formed closed section with the improved wall. 3. The liquefaction-prevention method according to claim 1, wherein the improved wall forming the substantially closed section is constructed circularly in a plane. 4. The liquefaction prevention method according to claim 1, wherein the improved wall forming the substantially closed section is constructed in a polygonal shape in a plane. 5. The liquefaction prevention method according to claim 1, wherein the improved wall forming the substantially closed section is constructed by being arranged concentrically in a plane. 6. A method for preventing liquefaction of the ground below a structure, comprising: constructing a ground improvement wall extending to a non-liquefaction layer in the depth direction of the ground, and Forming a substantially circular closed section in a plane, substantially forming a closed section near the closed section, and forming an adjacent closed section in the same manner, and so on. Perform the liquefaction prevention method. 7. The liquefaction prevention method according to claim 6, wherein the closed sections formed near one closed section are formed at positions where the improved walls do not contact each other. 8. The liquefaction prevention method according to claim 6, wherein the closed sections formed near one closed section are formed by bringing the improved walls into contact with each other. 9. The liquefaction prevention method according to claim 6, wherein a pile is driven into the closed section. 10. The liquefaction prevention method according to claim 6, wherein piles are driven into and out of the closed section.