JPH03103534A - Countermeasure structure for liquefaction of building - Google Patents

Abstract

PURPOSE:To control a liquefied phenomenon in the event of an earthquake to stabilize the subsoil by providing an underground wall used as a retaining wall by connecting steel pipes penetrated into a hard subsoil continuously and, at the same time, holding the upper part of the underground wall and a building together as a unit. CONSTITUTION:Steel pipes 8 are driven up to a hard bed 4 in the subsoil 1 around a building 5 to be constructed by continuously connecting them, and an underground wall 7 used as a retaining wall is provided. A driven depth lto the bed 4 increases more than five times as long as a steel pipe diameter (d). After that, a circumferential wall 10 of a building 5 constructed on the foundation piles 6 and the upper parts of the steel pipes forming the underground wall 7 are held together as a unit through studs 11. Then, a construction subsoil of the building 5 is separated from an outside liquefaction dangerous layer 3 through the underground wall 7, and the shearing deformation in the inside subsoil of the underground wall 7 is prevented. According to the constitution, a liquefied phenomenon in the event of an earthquake can be efficiently controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquefaction countermeasure structure for buildings in ground areas where there is a risk of liquefaction due to earthquakes.

(Prior Art) Generally, it is known that in sandy ground containing a lot of water, when an external force due to an earthquake is applied, the ground becomes liquid-like, a so-called liquefaction phenomenon. This phenomenon occurs when the pore water pressure of the sandy ground rapidly increases due to local shear deformation of the sandy ground, creating water currents that cause sand particles to flow.

Conventionally, countermeasures against ground liquefaction have included compaction methods such as sand compaction, mixed treatment methods that mix cement or soil solidifying agents, replacement methods that replace soil with soil that is less likely to liquefy, and the use of crushed stones or other materials in the ground. Drainage construction methods that involve installing a large number of pillars are known, but not only do they require large-scale construction, but they are often subject to restrictions on the construction site.

Therefore, as a construction method different from the above, there is a construction method in which a perforated steel pipe filled with crushed stone, etc. is used as the foundation pile of a building, and the excess water pressure is released upward through the pile.
Construction methods have been proposed in which porous walls are buried in the ground around buildings to dissipate excess pore water pressure.

(Problem to be Solved by the Invention) However, the former type of perforated steel pipe piles not only has problems with the strength of the pile, but also has many holes that cause lateral flow, resulting in excessive gaps. There is a problem that water pressure is not sufficiently dissipated. Moreover, even in the latter case where the porous wall body is buried, excessive pore water pressure cannot be sufficiently alleviated. Moreover, although these construction methods have some effect in releasing excess pore water pressure upward, they are not sufficient to suppress the lateral movement of the ground that occurs during an earthquake.

Furthermore, in areas where there is a risk of liquefaction, the bearing capacity of the ground itself is weak, so special measures to increase the bearing capacity are required, such as requiring longer foundation piles or increasing the number of foundation piles. However, the construction cost was troublesome and required a large amount of money.

In view of the above-mentioned conventional problems, the present invention utilizes an underground wall installed as earth retaining for construction of the basement of a building, and connects the wall and the building integrally to the building construction ground. The aim is to suppress the spread of liquefaction caused by earthquakes, and to create structures with high earthquake resistance and supporting capacity.

(Means for Solving the Problems) The structure of the present invention for achieving the above object will be described with reference to embodiments and corresponding drawings.
In the ground surrounding the building 5 to be constructed, an underground wall 7 is constructed by continuously connecting steel pipes 8 and 8, the lower part of which is embedded in a hard stratum 4 with a low possibility of liquefaction. The structure is characterized in that the upper part of the structure 7 and the structure 5 are integrally connected.

(Function) The present invention is configured as described above, and the constructed ground of the building 5 is separated from the outside ground by the underground wall 7. Therefore, the influence of excessive pore water pressure from the outer ground caused by an earthquake is suppressed, and the lateral flow of the ground is suppressed, and shear deformation of the inner ground of the underground wall 7 is prevented.

The underground wall 7 is integrally connected with steel pipes, and the building 5
Furthermore, each steel pipe 8.8 has its lower part rooted in a hard stratum, and its upper part integrally connected to the structure 5, so it is highly rigid and large. Not only will a horizontal counterforce be exerted, but a large supporting force for the structure 5 will be obtained.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In Figures 1 and 2, ■ indicates the ground that is at risk of liquefaction due to an earthquake, and generally a soft liquefaction risk layer (saturated layer) 3 is formed at a considerable depth under the topsoil layer 2. Below that is hard stratum 3.

5 is a structure built on the above ground 1, hard ground layer 4
It is supported by foundation piles 6.6 that are deeply rooted and sunk inside. It is an underground wall formed by continuously connecting steel pipes surrounding the building 5, as in steel pipe sheet piles.
It is formed into a wall shape by connecting a large number of steel pipes 8.8 with joints 9.9, and each steel pipe 8 has its lower part rooted to a considerable depth in the hard stratum 4 below the liquefaction danger layer 3. It is sunk into the ground. It is preferable that the depth of penetration Q be five times or more the diameter d of the steel pipe.

Furthermore, studs 11 and 11 are protruded from the upper part of each steel pipe 8 so as to be in contact with the peripheral wall 10 of the building 5, and are embedded in the concrete of the peripheral wall 10 as connectors to the peripheral wall 10. As shown in FIG. 3, this stud 11.11 is attached to a triangular stud base piece 12 fixed to the steel pipe 8.
It will be installed in the field by arc stud welding and will project diagonally upward and downward.

The building is constructed by excavating the ground surrounded by the underground wall 7 which is continuous with the above-mentioned pipe, and after sinking the foundation pit 6.6, including the ground part f on top of it. At this time, the underground part of the peripheral wall 10 is in contact with the underground wall 7, and the protruding studs 11, 11 of each cast pipe 8 forming the underground wall 7 are buried in the concrete cast in the underground part, and As a result, the upper part of the underground wall 7 and the building 5 become an integral rigid connection.

(Effects of the Invention) As explained above, the present invention provides a hard stratum with a low possibility of liquefaction at the bottom of the ground surrounding the building to be constructed. An underground wall is constructed by continuously connecting steel pipes embedded inside the building, and the upper part of this underground wall is integrally connected to the building, resulting in many excellent effects as follows. It is.

(1) The underground wall made of continuous steel pipes surrounding the building divides and isolates the strata at risk of liquefaction inside and outside the building, and the ground inside the underground wall is placed on the outside. It is possible to suppress the effects of shear strain and excess pore water pressure on the ground that is at risk of liquefaction during an earthquake, and it is possible to stabilize the ground on which buildings are built.

(2) An underground wall is a connected body of steel pipes, the lower part of which is rooted in a hard stratum, and the upper part integrally connected to a building, so it has great rigidity and can withstand external forces. Deformation of the wall itself is suppressed, and the underground wall also exerts a large supporting capacity for the building, making it possible to greatly reduce the burden on the supporting capacity of the foundation piles.

(3) Conventionally, when constructing the underground part of a building, sheet pile walls, etc. for earth retention were temporarily installed and buried.
The underground wall of the present invention can be used as an earth retaining wall, and costs can be reduced accordingly.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing one embodiment of the present invention, FIG. 2 is a plan cross-sectional view thereof, and FIG. 3 is an enlarged vertical cross-sectional view showing a state in which a steel pipe and a building are connected. 1... Ground 2... Topsoil layer

Claims (1)

[Claims] In the ground surrounding the building to be constructed, an underground wall is constructed by continuously connecting steel pipes with the lower part embedded in a hard stratum with low possibility of liquefaction, and the upper part of this underground wall is connected to the building. A liquefaction countermeasure structure for a building, characterized by integrally combining the following.