JP2004257135A - Highly aseismatic pile foundation structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile foundation structure enhancing earthquake resistance while reducing the burden of piles. <P>SOLUTION: In this pile foundation structure which supports the constant vertical force of a structure by the piles and resists horizontal force or the like in case of an earthquake by the piles, the vertical cross-section of a foundation bottom face of the structure is constructed in a boat shape with both inclined faces which receive the resistance of the ground when horizontally deformed. When the structure foundation is horizontally deformed by the earthquake or the like, horizontal frictional resistance and vertically upward force are generated to the front side in a deforming direction by the resistance of the ground to reduce the burden of the piles, and the resistance of the ground is reduced on the rear side. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention belongs to the technical field of a pile foundation structure in which a normal vertical force of a structure is supported by a pile and the pile also resists a horizontal force or the like during an earthquake, and a pile is used in combination with a direct foundation. .
[0002]
[Prior art]
In the case of a pile foundation structure, it is designed so that the normal vertical force is supported only by the pile. In addition, since the pile only resists during an earthquake, the pile also resists horizontal force and incremental vertical force during an earthquake. Therefore, it is necessary to design the pile to match the horizontal force and vertical force during the earthquake, which is uneconomical design.
[0003]
That is, in the conventional general pile foundation structure, as illustrated in FIG. 7, each of the piles 1 is a support pile whose tip reaches the support layer 2 and is an enlarged pile in which the axial diameter of the tip is enlarged. ing. The base bottom surface 4 of the structure 3 has a substantially horizontal shape (horizontal plane) and is configured to be in contact with the ground. Therefore, the support piles 1... Are designed to bear all the normal vertical force W due to the weight of the structure 3, and the foundation bottom surface 4 is in contact with the ground but does not bear the vertical force.
[0004]
In short, as shown in FIGS. 7 and 8, when the horizontal force H and the overturning moment M of the structure 3 act during an earthquake, the fluctuating axial force caused by the overturning moment M of the structure 3 causes the front side in the deformation direction (in FIG. The vertical force acts on the pile 1 on the right side as shown by (+ V1), (+ V2), and (+ V3) (so-called incremental vertical force). Conversely, a pulling force acts on the pile 1 on the rear side (the left side in the drawing) in the deformation direction as shown in (−V1) and (−V2). Therefore, it is necessary to design the cross section of each of the piles so as to secure a resistance to each of the acting forces (the horizontal force H and the fluctuating axial force). Therefore, for a pile near the end of the structure 3 having a large fluctuating axial force, the cross-sectional area at the tip is determined by the vertical force at the time of the earthquake (normal vertical force ± variable axial force), and the shaft diameter is also horizontal force. It is determined by H and the vertical force which is superior to the bending moment. In addition, for the pile near the center of the structure 3, the cross-sectional area of the shaft is determined by the magnitude of the horizontal force H and the bending moment that are superior to the vertical force. It is known that the design is often uneconomical due to the size of the design.
[0005]
As a conventional technique of a pile foundation, Patent Literature 1 discloses an earthquake-resistant pile foundation structure in which a ground anchor that supports both ends of a footing is installed and tensioned in a structure that supports a footing of a structure with a pile.
Patent Literature 2 discloses an earthquake-resistant foundation structure in which a pile head has a pin structure, a tip of a pile has a pin structure, and further, an oblique anchor cable is arranged on the foundation ground.
Patent Literature 3 discloses a pile foundation structure in which an elastic-plastic material is interposed at a joint between a foundation frame and a pile head to prevent breakage of the pile.
Patent Document 4 discloses a pile foundation structure in which vibration absorbing means is installed at a joint between a footing and a pile.
[0006]
Next, Patent Literatures 5 and 6 disclose a basic structure that generates a frictional force that resists a horizontal force between a bottom surface of a structure and the ground.
[0007]
[Patent Document 1]
JP 10-82057 A [Patent Document 2]
Japanese Patent Application Laid-open No. Hei 10-237881 [Patent Document 3]
Japanese Patent Application Laid-Open No. 2000-178981 [Patent Document 4]
JP 2001-303590 A [Patent Document 5]
JP-A-4-85408 [Patent Document 6]
JP-A-7-119164
[Problems to be solved by the invention]
The pile foundation structures disclosed in the above-mentioned Patent Documents 1 to 4 are all considered to be a devastating invention on how to effectively exert the supporting force of the pile, No studies are allowed.
On the other hand, the foundation structures disclosed in Patent Literatures 5 and 6 can evaluate that the resistance to the horizontal force acting on the structure is obtained from the frictional force of the ground, but is not a pile foundation.
[0009]
The purpose of the present invention is to support the vertical force at all times only with piles, but to bear part of the vertical force and horizontal force during the earthquake with the resistance of the ground, thereby reducing the load on the piles and reducing the economical design of the piles. It is an object of the present invention to provide a highly seismic pile foundation structure that has been made possible.
[0010]
The next object of the present invention is to reduce the burden on piles by generating a horizontal force and a vertical force in the resistance of the ground, as a boat shape that can expect the resistance of the ground when horizontal deformation due to earthquake etc. It is an object of the present invention to provide a highly seismic pile foundation structure having such a configuration.
A further object of the present invention is to form a vertical cross section of the bottom of the foundation slab, which can be expected to have resistance to the ground during horizontal deformation due to an earthquake, etc. An object of the present invention is to provide a high-seismic piled-raft foundation structure with improved seismic resistance by generating horizontal and vertical forces in the ground resistance.
[0011]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, a high-seismic pile foundation structure according to the invention described in claim 1 is:
In a pile foundation structure in which the normal vertical force of the structure is supported by piles and the piles also resist horizontal forces during earthquakes, etc.
The vertical cross-sectional shape of the foundation of the structure is constructed in a boat shape with both slopes receiving the resistance of the ground during horizontal deformation, and the horizontal direction of the deformation direction due to the resistance of the ground during horizontal deformation of the structure foundation due to earthquakes etc. And a vertical upward force to reduce the load on the pile and reduce the resistance of the ground on the rear side.
[0012]
The invention described in claim 2 is the high-seismic pile foundation structure described in claim 1,
Piles are constructed vertically, and the vertical cross-sectional shape of the base of the foundation of the structure is constructed in a boat shape that is equally inclined to the left and right in the horizontal direction. Increased resistance to generate horizontal frictional resistance and vertical upward force to reduce the load on piles to reduce the fluctuating axial force, and to reduce the ground resistance on the rear side. And
[0013]
The invention described in claim 3 is the highly earthquake-resistant pile foundation structure described in claim 1 or 2,
The vertical cross-sectional shape of the bottom surface of the foundation of the structure is characterized in that it is formed in a boat shape that changes stepwise along both inclined surfaces that receive resistance of the ground when the structure foundation is horizontally deformed due to an earthquake or the like.
[0014]
The high-seismic piled raft foundation structure according to the invention described in claim 4 is a piled raft foundation in which a pile is used in combination with a direct foundation,
The vertical cross section of the bottom surface of the base slab is constructed in a boat shape with both slopes receiving the resistance of the ground during horizontal deformation, and when the base slab is horizontally deformed due to an earthquake or the like, the horizontal friction due to the ground resistance due to the resistance of the ground It is characterized in that a resistance force and a vertically upward force are generated, and the rear side is configured to reduce the resistance of the ground.
[0015]
Embodiments and Examples of the Invention
Next, an embodiment of a highly seismic pile foundation structure according to the first to third aspects of the present invention will be described with reference to the drawings.
First, in the pile foundation structure shown in FIG. 1, the normal vertical force W of the structure 3 is supported by the support piles 1 reaching the support layer 2, and the horizontal pile H and the overturning moment M at the time of the earthquake are also supported. 1. The pile foundation structure resisting at 1 ..., characterized in that the vertical cross-sectional shape of the foundation bottom surface 5 of the structure 3 is constructed in a boat shape with both inclined surfaces receiving the resistance of the ground 6 at the time of horizontal deformation. . Although not shown in the drawings, it is preferable that the vertical cross-section taken along the line II passing through the center of the structure 3 be constructed in a similar boat shape as shown in FIG. Therefore, the base bottom surface 5 of the structure 3 has a pyramid shape. However, if the structure 3 is sufficiently long in the direction perpendicular to the plane of the paper of FIG. 1, it is not necessary to dare to form a boat because the earthquake resistance in the same direction is large.
[0016]
The state of horizontal deformation during the earthquake is exaggerated in FIG. When the structure foundation is horizontally deformed, the resistance of the ground 6 acts on the foundation bottom surface 5 of the structure 3. That is, as shown in the vector diagram in FIG. 3, the ground 6 causes the bottom surface 5 (the inclined surface) on the front side (the right side in FIG. 2) in the deformation direction of the structural foundation due to the inclination angle θ of the foundation bottom surface 5. A horizontal component (−ΔH) and a vertical upward component (−ΔV) of the horizontal frictional resistance R are generated. On the rear side in the deformation direction (the left side in FIG. 2), the base bottom surface 5 of the structure 3 is separated from the ground 6 and does not cause any resistance.
[0017]
In short, when the structure 3 is horizontally deformed due to an earthquake or the like, in addition to the resistance (−H ′) of the pile head that resists the horizontal force H, the ground 6 Since the horizontal component (−ΔH) of the resistance R functions as a resistance, the horizontal force of the earthquake can be reduced.
At the same time, an upward vertical component (−ΔV) of the resistance R of the ground 6 is also generated, and the vertical force V acting on the pile 1 is reduced.
[0018]
As a result, the horizontal force burden of the pile is reduced in the form of offsetting with the horizontal component (-ΔH) of the resistance R of the ground 6 acting on the front side in the deformation direction (about the right half of the foundation bottom surface 5), and the shaft section of the pile is reduced. Can be designed economically. At the same time, the vertical force burden on the pile is reduced by offsetting the resistance force R of the ground 6 with the upward vertical component (−ΔV), thereby achieving a reduction in the fluctuating axial force and an economical design in which the shaft tip diameter is reduced. . As a result, the smaller the pile diameter, the more labor can be saved in the construction work. In particular, the effect is great for a pile near the center of the structure 3.
[0019]
As means for utilizing the resistance R of the ground 6 more positively, the strength, rigidity, surface pressure, etc. of the ground immediately below the foundation bottom surface 5 are increased by ground improvement or the like. In some cases, the vertical cross-sectional shape of the base bottom surface 5 of the structure 3 is not limited to the bilaterally symmetrical boat-like shape shown in FIG. It can be similarly implemented by constructing it into an asymmetrical boat shape with different sizes.
[0020]
Next, FIGS. 4 to 6 show different variations of the boat shape in which the vertical cross-sectional shape of the base bottom surface 5 of the structure 3 increases the ground resistance on the front side in the deformation direction and decreases the ground resistance on the rear side. Is shown.
First, FIG. 4 shows an example in which a boat shape is formed while connecting adjacent piles 1 with a straight line (a straight plane). FIG. 5 shows an example in which a boat shape is formed while connecting adjacent piles 1 with a chevron line (a chevron surface). FIG. 6 shows an example in which a boat shape is formed in a step shape (the invention described in claim 3). The height and width of the stairs are not limited to those in the illustrated example.
[0021]
Although illustration is omitted, in the so-called direct foundation typified by a footing foundation and a solid foundation, the above-described technical idea of the present invention is also applied to a piled raft foundation using a pile (friction pile) in combination. It can be applied, and a similar effect can be obtained.
That is, if the vertical cross-sectional shape of the bottom of the foundation plate of the direct foundation is constructed in a boat shape with both slopes receiving the resistance of the ground when the foundation plate is horizontally deformed, the deformation direction due to the resistance of the ground during the horizontal deformation of the foundation plate due to an earthquake etc. A horizontal frictional resistance and a vertical upward force are generated on the front side of the stake, thereby reducing the burden on the pile. Of course, the resistance of the ground can be reduced on the rear side (the invention described in claim 4).
[0022]
[Effects of the Invention]
The high earthquake-resistant pile foundation structure according to the invention described in claims 1 to 3, the normal vertical force is supported only by the pile, but part of the vertical force and horizontal force during an earthquake is borne by the resistance of the ground, The burden on piles was reduced by that much, and economic design of piles became possible.
[0023]
ADVANTAGE OF THE INVENTION According to this invention, the vertical cross-sectional shape of the foundation bottom of a structure is set as a boat shape which can expect the resistance of the ground at the time of horizontal deformation by an earthquake etc., and generates the horizontal force and the vertical force in the resistance of the ground, and reduces the load on the pile. Therefore, it can be easily implemented by the existing technology.
In the case of the piled raft foundation structure according to the invention described in claim 4, even if it is functionally a direct foundation, the vertical cross-sectional shape of the bottom of the foundation plate is expected to have resistance to the ground during horizontal deformation due to an earthquake or the like. As a possible boat shape, it generates horizontal force and vertical force on the resistance of the ground, so it is possible to improve the earthquake resistance.
[0024]
In summary, according to the present invention, the stability of the structure during an earthquake can be achieved, the foundation can resist the horizontal force and the overturning moment during the earthquake, and the fluctuating axial force and the horizontal force acting on the pile can be reduced. Therefore, the shaft diameter of the pile can be reduced, and the pile can be rationalized. Increasing the vertical resistance (surface pressure) of the foundation ground on the front side in the deformation direction increases the ultimate ground resistance of the ground on the front side of the pile, and also has the advantage of increasing the ultimate horizontal resistance of the pile. .
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing an embodiment of a highly earthquake-resistant pile foundation structure according to the present invention.
FIG. 2 is an explanatory view of an operation and effect of the high-seismic pile foundation structure.
FIG. 3 is a diagram illustrating the operation and effect of the high-seismic pile foundation structure.
FIG. 4 is a vertical cross-sectional view showing a different embodiment of the highly earthquake-resistant pile foundation structure according to the present invention.
FIG. 5 is a vertical sectional view showing a different embodiment of the high earthquake-resistant pile foundation structure according to the present invention.
FIG. 6 is a vertical cross-sectional view showing a different embodiment of the high earthquake-resistant pile foundation structure according to the present invention.
FIG. 7 is a vertical sectional view showing an example of a conventional pile foundation structure.
FIG. 8 is an explanatory diagram of the operation and effect of the pile foundation structure.
FIG. 9 is a view for explaining the operation and effect of the pile foundation structure.
[Explanation of symbols]
Reference Signs List 1 pile 3 structure 5 base bottom R ground resistance 6 ground

Claims (4)

In a pile foundation structure in which the normal vertical force of the structure is supported by piles and the piles also resist horizontal forces during earthquakes, etc.
The vertical cross-sectional shape of the foundation of the structure is constructed in a boat shape with both slopes receiving the resistance of the ground during horizontal deformation, and the horizontal direction of the deformation direction due to the resistance of the ground during horizontal deformation of the structure foundation due to earthquakes etc. A high seismic pile base structure, characterized in that it generates a frictional resistance force and a vertical upward force to reduce the load on the pile and reduces the resistance of the ground on the rear side. The piles are constructed vertically, and the vertical cross-sectional shape of the bottom of the foundation of the structure is constructed in a boat shape that is inclined equally to the left and right in the horizontal direction. It is characterized by increasing the resistance to generate horizontal frictional resistance and vertical upward force to reduce the load on the pile and reduce the variable axial force, and to reduce the ground resistance on the rear side. The highly earthquake-resistant pile foundation structure according to claim 1, wherein The vertical cross-sectional shape of the bottom surface of the foundation of the structure is formed in a boat shape that changes stepwise along both inclined surfaces that receive resistance of the ground when the structure foundation is horizontally deformed due to an earthquake or the like. Or the high-strength pile foundation described in 2. In piled raft foundations where piles are also used directly on foundations,
The vertical cross section of the bottom surface of the base slab is constructed in a boat shape with both slopes receiving the resistance of the ground during horizontal deformation, and when the base slab is horizontally deformed due to an earthquake or the like, the horizontal friction due to the ground resistance due to the resistance of the ground Highly earthquake-resistant piled raft foundation structure characterized by generating resistance and vertical upward force, and reducing the ground resistance on the rear side.

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