JP3650892B2 - High earthquake-resistant pile foundation structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
This invention belongs to the technical field of piled raft foundations that support normal vertical force of structures with piles and resist piles against horizontal forces during earthquakes and piled raft foundations that use piles directly on the foundation. .
[0002]
[Prior art]
In the case of a pile foundation structure, the normal vertical force is designed to be supported only by the pile. And since it resists only with a pile also at the time of an earthquake, it resists a horizontal force and an incremental vertical force at the time of an earthquake with a pile. Therefore, it is necessary to design piles to match the horizontal force and vertical force at the time of the earthquake, which is an uneconomical design.
[0003]
That is, as illustrated in FIG. 7, the conventional general pile foundation structure is a pile having a diameter of which the tip 1 reaches the support layer 2 and the shaft diameter of the tip is enlarged. ing. The base bottom surface 4 of the structure 3 is constructed in a substantially horizontal shape (horizontal plane) and in contact with the ground. Accordingly, 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 deformation axial front (in the figure) is caused by the changing axial force due to the overturning moment M of the structure 3. On the pile 1 on the right side, the vertical force further increases as in (+ V1), (+ V2), (+ V3) (so-called incremental vertical force). On the contrary, the pulling force acts on the pile 1 on the rear side in the deformation direction (left side in the figure) as in (−V1) and (−V2). Therefore, it is necessary to perform a cross-sectional design so that any pile can ensure resistance to each of the acting forces (horizontal force H and variable axial force). Therefore, for the pile near the end of the structure 3 where the variable axial force is large, the cross-sectional area of 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 the horizontal force It is determined by the vertical force superior to H and the bending moment. Moreover, about the pile of the position near the center of the structure 3, the cross-sectional area of the shaft portion is determined by the horizontal force H and the magnitude of the bending moment that are superior to the vertical force. It is known that the design is uneconomical because it is often determined by the size of.
[0005]
As a conventional technique of a pile foundation, Patent Document 1 discloses a seismic pile foundation structure in which a ground anchor supporting both ends of a footing is installed and tensioned in a structure in which a footing of a structure is supported by a pile.
Patent Document 2 discloses an earthquake-resistant foundation structure in which a pile head has a pin structure, a pile tip also has a pin structure, and an oblique anchor cable is arranged on the foundation ground.
Patent Document 3 discloses a pile foundation structure in which an elastic-plastic material is interposed at a joint between the foundation frame and the pile head to prevent the pile from being damaged.
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 Documents 5 and 6 disclose a basic structure that generates a frictional force that resists a horizontal force between the bottom surface of the structure and the ground.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-82057 [Patent Document 2]
JP-A-10-237881 [Patent Document 3]
JP 2000-178981 A [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 recognized as inventions that have been devastated in how to effectively exert the bearing capacity of the piles. Research is not allowed.
On the other hand, although the foundation structure disclosed by patent documents 5 and 6 can evaluate the point which asks the frictional force of the ground for the resistance to the horizontal force which acts on a structure, it is not a pile foundation.
[0009]
The purpose of the present invention is to support the normal vertical force only by the pile, but the vertical force and horizontal force at the time of the earthquake are borne by the resistance of the ground, thereby reducing the load on the pile and economical design of the pile. It is 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 horizontal and vertical forces in the ground resistance as a boat shape that can expect ground resistance during horizontal deformation due to earthquakes, etc. It is to provide a high seismic pile foundation structure that is configured to perform.
A further object of the present invention is to directly classify a piled raft foundation with a pile, which is classified as a direct foundation. 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-described problems, the high earthquake-resistant pile foundation structure according to the invention described in claim 1 is:
In the pile foundation structure that supports the normal vertical force of the structure with the pile and resists the horizontal force during the earthquake with the pile,
The vertical cross-sectional shape of the foundation bottom of the structure is constructed in a boat shape with both inclined surfaces that receive the resistance of the ground during horizontal deformation, and when the structure foundation is horizontally deformed due to an earthquake, etc. The friction resistance force and the upward force in the vertical direction are generated to reduce the load on the pile, and the rear side is configured to reduce the ground resistance.
[0012]
The invention described in claim 2 is the high earthquake resistant pile foundation structure according to claim 1, wherein the pile is constructed in the vertical direction, and the vertical cross-sectional shape of the foundation bottom of the structure is a boat shape that is equally inclined to the left and right in the horizontal direction. When the structure foundation is horizontally deformed due to an earthquake, etc., the resistance of the ground is increased on the front side in the deformation direction to generate horizontal friction resistance force and vertical upward force to reduce the load on the pile. The variable axial force is reduced, and the rear side is configured to reduce ground resistance.
[0013]
The invention described in claim 3 is the high earthquake-resistant pile foundation structure according to claim 1 or 2,
The vertical cross-sectional shape of the foundation bottom of the structure is characterized in that it is formed in a boat shape that changes stepwise along both inclined surfaces that receive ground resistance when the structure foundation is horizontally deformed due to an earthquake or the like.
[0014]
The highly earthquake-resistant 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-sectional shape of the bottom surface of the foundation slab is constructed in a boat shape with both inclined surfaces that receive ground resistance during horizontal deformation, and when the foundation slab is deformed horizontally due to an earthquake, etc. A resistance force and a vertical 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 the high earthquake-resistant pile foundation structure according to the invention described in claims 1 to 3 will be described with reference to the drawings.
First, the pile foundation structure shown in FIG. 1 supports the normal vertical force W of the structure 3 by the support pile 1 that reaches the support layer 2, and supports the horizontal force H and the overturning moment M during the earthquake. 1 is a pile foundation structure which resists at 1 ..., and the vertical cross-sectional shape of the foundation bottom surface 5 of the structure 3 is constructed in a boat shape of both inclined surfaces that receive the resistance of the ground 6 during horizontal deformation. . Although not shown in the figure, it is preferable that the vertical cross-sectional shape cut along the line II passing through the center of the structure 3 as shown in FIG. Therefore, the base bottom surface 5 of the structure 3 is a pyramid shape. However, when the structure 3 has a shape that is sufficiently long in the direction perpendicular to the paper surface of FIG. 1, it is not necessary to dare to form a boat shape because the earthquake resistance in the same direction is large.
[0016]
The horizontal deformation state during the earthquake is exaggerated in FIG. During horizontal deformation of the structure foundation, the resistance of the ground 6 acts on the foundation bottom surface 5 of the structure 3. That is, the bottom surface 5 (inclined surface) on the front side (right side in FIG. 2) in the deformation direction of the structure foundation is caused by the inclination angle θ of the foundation bottom surface 5 by the ground 6 as shown in the vector diagram of FIG. The horizontal component (−ΔH) and the vertical component (−ΔV) of the horizontal frictional resistance force R are generated. On the rear side in the deformation direction (left side in FIG. 2), the base bottom surface 5 of the structure 3 is separated from the ground 6 and does not generate resistance.
[0017]
In short, at the time of horizontal deformation of the structure 3 due to an earthquake or the like, in addition to the resistance force (−H ′) of the pile head that resists the horizontal force H on the front side in the deformation direction (about half right of the foundation bottom surface 5), the ground 6 Since the horizontal component (−ΔH) of the resistance force R acts as a resistance force, the horizontal force of the earthquake can be reduced.
At the same time, an upward vertical component (−ΔV) of the resistance force R of the ground 6 is also generated, and the vertical force V acting on the pile 1 is reduced.
[0018]
Eventually, the horizontal force burden of the pile is reduced in the form of offsetting with the horizontal component (-ΔH) of the resistance force R of the ground 6 acting on the front side in the deformation direction (about the right half of the foundation bottom surface 5). Can be economically designed. At the same time, the vertical force burden of the pile is reduced as an offset with the upward vertical component (−ΔV) of the resistance force R of the ground 6, thereby achieving an economic design that reduces the variable axial force and reduces the shaft tip diameter. . As a result, the construction work can be saved as much as the pile diameter becomes smaller. In particular, the effect is great for a pile near the center of the structure 3.
[0019]
As a means of more actively utilizing the resistance force R of the above-mentioned ground 6, there is a difference in the strength, rigidity, surface pressure, etc. of the ground directly under the base bottom surface 5 by improving the ground or the hardness and softness of the ground. In some cases, the vertical cross-sectional shape of the foundation bottom surface 5 of the structure 3 is not limited to the bilaterally symmetrical boat shape shown in FIG. 1, but the left and right inclination angles are different or the length of the left and right inclined surfaces is different. It can be constructed in the same way by constructing a boat shape with an asymmetrical shape such as different sizes.
[0020]
Next, FIGS. 4 to 6 show different variations of the boat shape in which the vertical cross-sectional shape of the foundation 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. Indicates.
First, FIG. 4 shows an example in which a boat shape is formed while connecting adjacent piles 1 and 1 with a straight line (straight plane). FIG. 5 shows an example in which a boat shape is formed while connecting adjacent piles 1 and 1 with a mountain-shaped line (mountain curved surface). FIG. 6 shows an example in which a boat shape is formed in a staircase shape (the invention described in claim 3). The height and width dimensions of the stairs are not limited to those shown in the example.
[0021]
Although illustration is omitted, the above technical idea of the present invention is also applied to piled raft foundations that use piles (friction piles) among so-called direct foundations represented by footing foundations and solid foundations. It can be applied and the same effect can be obtained.
That is, if the vertical cross-sectional shape of the bottom of the foundation foundation is constructed in a boat shape with both inclined surfaces that receive the ground resistance when the foundation foundation is deformed horizontally, the deformation direction depends on the resistance of the foundation during horizontal deformation of the foundation foundation due to an earthquake, etc. A horizontal frictional resistance force and a vertical upward force can be generated on the front side of the pile, thereby reducing the burden on the piles. 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]
In 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 some vertical force and horizontal force during the earthquake are borne by the resistance of the ground. The load of the pile was reduced by that much, and the economic design of the pile was made possible.
[0023]
According to the present invention, the vertical cross-sectional shape of the foundation bottom surface of the structure is a boat shape that can be expected to have ground resistance during horizontal deformation due to an earthquake or the like, and horizontal and vertical forces are generated in the ground resistance to reduce the burden on the pile. Therefore, it can be easily implemented by 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 face of the foundation plate is expected to be the resistance of the ground during horizontal deformation due to an earthquake or the like As a boat form that can generate horizontal and vertical forces in the resistance of the ground, it can improve earthquake resistance.
[0024]
In short, according to the present invention, the stability of the structure during an earthquake can be achieved, the foundation resists the horizontal force and overturning moment during the earthquake, and the variable axial force and 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 force (surface pressure) of the foundation foundation on the front side in the direction of deformation increases the ultimate ground resistance of the front ground of the pile and increases the ultimate horizontal resistance of the pile. .
[Brief description of the drawings]
FIG. 1 is a vertical sectional view showing an embodiment of a high earthquake-resistant pile foundation structure according to the present invention.
FIG. 2 is a diagram for explaining the effects of the high earthquake-resistant pile foundation structure.
FIG. 3 is a diagram for explaining the effect of the high earthquake-resistant pile foundation structure.
FIG. 4 is a vertical sectional view showing different embodiments of the high earthquake-resistant pile foundation structure according to the present invention.
FIG. 5 is a vertical sectional view showing different embodiments of the high earthquake-resistant pile foundation structure according to the present invention.
FIG. 6 is a vertical sectional view showing different embodiments 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 a diagram for explaining the effect of the pile foundation structure.
FIG. 9 is a diagram for explaining the effect of the pile foundation structure.
[Explanation of symbols]
1 Pile 3 Structure 5 Base bottom surface R Ground resistance 6 Ground

Claims (4)

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

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