JP2000248561A - Base isolation construction of pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a pile top from breaking down due to shearing force or bending moment at an earthquake, while effectively utilizing the shearing proof stress of a pile main body. SOLUTION: In this base isolation construction, an outer pipe 2 is projectingly provided from the base plate 3 as the base part of an upper structure into the ground so as to surround a pile main body 1. A base side slide member 4 is provided on the underside of the base plate 3, and the upper face of a pile top cap 8 covering a pile top 6 is slidably brought in contact with the underside of a slide plate 9 constituting the base side slide member 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile, particularly a seismic isolation structure at a pile head.

[0002]

2. Description of the Related Art There are two types of pile foundations: a support pile type and a friction pile type. In the former, when a good quality support layer is deep underground, an upper structure is constructed on a pile driven into the support layer. Accordingly, the structure is a type in which the weight of the structure is stably supported by the support layer, and the latter is a basic type in which the upper structure is supported by the frictional force with the surrounding ground when there is no high-quality support layer.

[0003] Naturally, these piles must be able to reliably support the weight of the superstructure, but in the event of an earthquake, a large shear force or bending moment acts on the pile head due to the horizontal force from the superstructure. Therefore, when designing and constructing, it is necessary to give due consideration to earthquake safety.

[0004]

Conventionally, as a method of joining a pile and a foundation slab, a pile head of a cast-in-place concrete pile is embedded in the foundation slab by about 10 cm, and a main bar of the pile previously set is fixed to the foundation slab. There was a method of making the pile head of the ready-made pile into the foundation slab by the pile diameter length, but in these joining methods, the degree of fixation α was 1.0, that is, almost rigid, and in the case of a huge earthquake, Excessive shearing force and bending moment act on the pile head, which may lead to unexpected situations such as breakage of the pile and collapse of the superstructure.

In addition, the pile head of a PC pile or a PHC pile is set to 10 cm.
PC steel wires and steel rods embedded in the foundation slab and left at the time of pile cutting are anchored to the foundation slab, and the joint reinforcement is welded to the pile head of a steel pipe pile or a ready-made concrete pile with an outer shell steel pipe. There have been methods of fixing to the slab or reinforcing the inside of the pile by filling the hollow part with reinforced concrete with a length of about twice the diameter of the pile. Experiments have shown that a significant bending moment is generated at the pile head under the action of the axial force, though it is smaller than that.

On the other hand, there has been proposed a structure in which a seismic isolation bearing using seismic isolation rubber is interposed between a pile head and a foundation slab. In such a joining method, a horizontal force from an upper structure is cut off. While it is possible to prevent the generation of a shearing force at the pile head, the shearing strength inherent in the pile body is not used at all, and there is a lack of economy.

The present invention has been made in view of the above-mentioned circumstances, and has a pile excavator capable of preventing a breakage at a pile head due to a shear force or a bending moment during an earthquake while effectively utilizing the shear strength of the pile body. The purpose is to provide a seismic structure.

[0008]

According to a first aspect of the present invention, there is provided a seismic isolation structure for a pile according to the present invention. At the bottom of the base, projecting from the base of the base into the ground and attaching a predetermined base-side sliding member to the outer tube so that a skirt-like tubular portion provided on the periphery of the base-side sliding member is fitted into the outer tube, A pile head cap provided with a rotation deformation absorbing member for absorbing rotation deformation at the pile head of the pile body is placed on the pile head, and the upper surface thereof is slidably contacted with the lower surface of the foundation side sliding member. It is.

Further, in the seismic isolation structure for a pile according to the present invention, as described in claim 2, a predetermined foundation side sliding member is mounted on the lower surface of the base of the upper structure and the pile body has a rotational deformation at the pile head. The cap is provided with a pile head cap provided with a rotation deformation absorbing member that absorbs the above, and the upper surface thereof is slidably abutted against the lower surface of the foundation side sliding member.

In the seismic isolation structure for a pile according to the first aspect of the present invention, when the horizontal force at the time of the earthquake is small, the static horizontal frictional force between the upper surface of the pile head cap and the lower surface of the foundation side sliding member causes the relative horizontal force between the two. No displacement occurs, and the horizontal force from the superstructure directly acts on the pile head as a shear force corresponding to the static friction force.

Here, since the rotation deformation absorbing member for absorbing the rotation deformation is provided inside the pile head cap, the rotation deformation at the pile head caused by the horizontal force from the upper structure acts. It will be absorbed by the deformation absorbing member,
Separation between the upper surface of the pile head cap and the lower surface of the foundation side sliding member is prevented. As a result, the vertical load and shear force as designed are reliably transmitted to the pile body,
It is also possible to prevent stress concentration from occurring at the pile head and leading to breakage. In addition, by permitting rotational deformation at the pile head, the joint state between the pile head and the upper structure is in a so-called pin state, so that no bending moment is generated at the pile head.

On the other hand, if the horizontal force at the time of the earthquake exceeds a certain level, the upper surface of the pile head cap and the lower surface of the foundation side sliding member relatively slide, so that only the amount corresponding to the dynamic friction force at that time is obtained. The horizontal force at the time of the earthquake acts on the pile head as a shear force.

[0013] Even in such a case, the rotational deformation at the pile head due to the horizontal force from the upper structure acts on the pile deformation absorbing member. Separation from the lower surface of the member is prevented, and the designed shear force acts on the pile body,
By allowing rotation deformation at the pile head, generation of a bending moment at the pile head is prevented.

That is, in the seismic isolation structure for a pile according to the present invention, in the event of a small or medium-sized earthquake, the horizontal force from the upper structure acts on the pile body as a shear force by an amount corresponding to the static friction force, and the large earthquake Even at times, the shear force is transmitted to the pile body with the limit of the dynamic friction force, so it is possible to clearly grasp the upper limit of the shear force acting on the pile body and consider the shear strength of the pile body Thus, a reasonable design can be achieved.

In addition, since bending deformation of the pile head is allowed regardless of the magnitude of the earthquake, no bending moment is generated at the pile head due to horizontal force from the upper structure.

An outer tube projects from the base into the ground so as to surround the pile body, and a skirt-like tubular portion provided on the peripheral edge of the foundation side sliding member is fitted into the outer tube. Therefore, in the event of a small or medium-sized earthquake, the horizontal force from the upper structure during the earthquake should be within the range where the frictional force generated between the upper surface of the pile head cap and the lower surface of the foundation side sliding member does not exceed the static frictional force. And is distributed to the pile and the outer pipe according to their rigidity ratio.

On the other hand, in the case of a large earthquake in which the horizontal force from the upper structure exceeds the above-mentioned static friction force, the pile head
Only the horizontal force corresponding to the dynamic friction force acts, and all the remaining horizontal force is distributed to the outer tube.

That is, in the case of a small-to-medium-sized earthquake, only the horizontal force corresponding to the rigidity ratio with the outer pipe is transmitted to the head of the pile supporting the vertical load of the upper structure in the case of a small-to-medium-sized earthquake. ,
In the case of a large earthquake, no horizontal force greater than the dynamic friction force acts. Therefore, it is possible to secure higher earthquake resistance in combination with the shear strength of the outer pipe while effectively utilizing the shear strength of the pile body.

Since the skirt-shaped tubular portion provided on the peripheral edge of the sliding member on the foundation side is configured to be fitted into the outer tube, it is possible to absorb a construction error in the height of the top of the pile head. Become.

The pile may be of any type, such as a PHC pile, a PC pile, a steel pipe pile, and a cast-in-place concrete pile. It is conceivable to use, for example, a disc spring as the rotation deformation absorbing member.

In the seismic isolation structure for a pile according to the second aspect of the present invention, the operation relating to the sliding between the upper surface of the pile head cap and the lower surface of the foundation side sliding member and the operation relating to the rotational deformation absorbing member are the same as in the first embodiment. Since it is the same, the description is omitted here. In addition, the description of the pile and the rotational deformation absorbing member is the same as that of the first aspect, and thus the description thereof is also omitted.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a seismic isolation structure for a pile according to the present invention will be described below with reference to the accompanying drawings.
It is to be noted that the same reference numerals are given to components and the like that are substantially the same as those in the conventional technology, and description thereof is omitted.

(First Embodiment)

FIG. 1 is a sectional view showing a seismic isolation structure for a pile according to this embodiment. As can be seen from the figure, in the seismic isolation structure for a pile according to the present embodiment, the outer pipe 2 is projected from the base plate 3 which is the base of the upper structure into the ground so as to surround the pile main body 1. The foundation side sliding member 4 is installed on the lower surface of the foundation plate 3, and the upper surface of the pile head cap 8 covered on the pile head 6 is slidably abutted on the lower surface of the sliding plate 9 constituting the foundation side sliding member. It is composed.

The pile body 1 supports the vertical load of the upper structure through the foundation side sliding member 4 and the pile head cap 8, and includes pre-made piles such as steel pipe piles, RC piles, and PHC piles. It can be composed of any material such as a cast-in-place RC pile.

FIG. 2 is an exploded perspective view of the pile main body 1, outer tube 2, pile head cap 8, and foundation side sliding member 4. As can be seen from the figure, the outer pipe 2 is formed of a cylindrical body, for example, a steel pipe, and is disposed so that the pile main body 1 penetrates inside. Here, the horizontal rigidity of the outer pipe 2 is appropriately set so that a predetermined ratio of the horizontal force at the time of the earthquake from the base plate 3 of the upper structure flows to the outer pipe. The horizontal rigidity of the outer pipe 2 means the magnitude of the resistance force received from the ground with respect to the unit horizontal movement distance, and the size is appropriately changed by changing the wall thickness, the pipe diameter, the height, and the like. Can be changed.

The base side sliding member 4 is provided with a skirt-shaped cylindrical portion 5 on the peripheral edge thereof. For example, the outer diameter of the cylindrical portion 5 is adjusted so that the cylindrical portion 5 can be fitted into the outer tube 2 in a height-adjustable manner. Correspond to the inner diameter of the outer tube 2.

On the other hand, the pile head cap 8 has a cap body 10 whose upper surface is in contact with the sliding plate 9 of the foundation side sliding member 4,
Belleville spring 11 housed in the cap body, and load distribution washer 1 sandwiched between the Belleville spring and pile head 6
2, the disc spring 11 is adapted to fit its upper opening into a projection 13 formed on the inner surface of the top of the cap body 10. Here, the disc spring 11 functions as a rotational deformation absorbing member that absorbs rotational deformation at the pile head 6 of the pile main body 1.

The cap body 10 is mounted on the top of the pile head 6 so that the horizontal force can be transmitted to the pile head 6 as a shearing force without being detached from the pile head 6 when a horizontal force acts on the upper surface thereof. From the inner surface of the pile head 6 and the peripheral surface of the pile head 6, so that the rotation deformation of the pile head is not restrained by an appropriate horizontal clearance. d is provided as appropriate.

The cap body 1 constituting the pile head cap 8
The cap body 10 and the sliding plate 9 themselves are formed of, for example, a clad steel plate (having a friction coefficient of about 0.3) and the sliding surface of the sliding surface 9 constitutes the basic sliding member 4. By adhering or interposing a composite material such as Somalite (trade name, coefficient of friction μ about 0.2) having properties and durability, both can be configured to be slidable.

In addition, the pile head cap 8 and the foundation side sliding member 4
From which point (how much seismic force) the horizontal displacement of the two can be allowed to occur depends on the size of the upper structure, the importance of the structure during the earthquake, the nature of the ground, etc. The shear force may be transmitted within a range where the long-term structural integrity of the pile body 1 is not impaired (specifically, for example, an elastic range), while taking into account various design items.

As an example of a procedure for constructing the pile seismic isolation structure according to the present embodiment, first, the outer pipe 2 is driven into the ground,
Thereafter, the earth and sand in the outer pipe is excavated and discharged. Next, the pile main body 1 is driven into the outer pipe 2 so as to penetrate the outer pipe 2.

When the driving of the pile body 1 is completed, the pile head cap 8 containing the washer 12 and the disc spring 11 in the cap body 10 is put on the pile head 6, and the foundation side sliding member 4 is removed from above. It is dropped into the outer tube so as to fit into the tube 2. In addition, the installation error in the height direction of the pile main body 1 can be automatically absorbed by such fitting.

Next, in this state, the base plate 3 of the upper structure
To build.

In the seismic isolation structure of the pile according to the present embodiment, when the horizontal force at the time of the earthquake is small, the static horizontal frictional force between the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4 causes the relative horizontal force between them. No displacement occurs, and the horizontal force from the upper structure directly acts on the pile head 6 as a shear force corresponding to the static friction force.

Here, since the conical spring 11 as a rotational deformation absorbing member for absorbing rotational deformation is provided inside the pile head cap 8, the pile head 6 is acted upon by horizontal force from the upper structure. The rotation deformation at the point is absorbed by the disc spring, and the upper surface of the pile head cap 8 and the foundation side sliding member 4
Is prevented from separating from the lower surface. In addition, since rotational deformation at the pile head 6 is allowed, the joining state between the pile head 6 and the foundation plate 3 of the upper structure is in a so-called pin state.

On the other hand, when the horizontal force at the time of the earthquake exceeds a certain level, as shown in FIG. 3, the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4 relatively slide, and at that time, The horizontal force at the time of the earthquake acts on the pile head 6 as a shear force by an amount corresponding to the dynamic friction force. Further, as in the case of a small-to-medium-sized earthquake, the rotational deformation of the pile head 6 due to the horizontal force from the upper structure is absorbed by the disc spring 11 as shown in FIG. 8 is prevented from separating from the upper surface of the foundation-side sliding member 4, a shear force as designed acts on the pile body 1, and the pile head 6 is allowed to rotate and deform. No bending moment is generated.

In the seismic isolation structure for a pile according to the present embodiment, an outer pipe 2 projects from the base plate 3 into the ground so as to surround the pile main body 1 and is provided on the periphery of the base-side sliding member 4. Because the skirt-shaped tubular portion 5 is fitted into the outer tube, the horizontal force from the upper structure during an earthquake is limited to the upper surface of the pile head cap 8 and the foundation in the case of a small-to-medium-sized earthquake. The pile body 1 and the outer pipe 2 are distributed to the pile body 1 and the outer pipe 2 in accordance with their rigidity ratio within a range in which the frictional force generated between the lower surface of the side sliding member 4 and the frictional force does not exceed the static frictional force.

On the other hand, in the case of a large earthquake in which the horizontal force from the upper structure exceeds the above-mentioned static friction force, only the horizontal force corresponding to the dynamic friction force acts on the pile head 6, All remaining horizontal forces are distributed to the outer tube 2.

As described above, according to the seismic isolation structure of the pile according to the present embodiment, since the rotational deformation of the pile head 6 during the earthquake is absorbed by the disc spring 11, the upper surface of the pile head cap 8 can be absorbed. Separation from the lower surface of the foundation side sliding member 4 is prevented.

Accordingly, the vertical load and the designed shearing force can be reliably transmitted to the pile body 1, and
It is possible to prevent the pile head 6 from being damaged due to stress concentration. In addition, since the pile head 6 is allowed to be rotationally deformed, no bending moment is generated at the pile head 6, and the pile head 6 and thus the pile body 1 are prevented from being broken by an excessive bending moment as in the related art. can do.

Further, according to the seismic isolation structure of the pile according to the present embodiment, when the horizontal force during an earthquake is small, the pile head cap 8
When the horizontal force from the upper structure acts as a shearing force on the pile head 6 by the static friction force between the upper surface of the base member and the lower surface of the foundation-side sliding member 4, and when the horizontal force during an earthquake exceeds a certain scale, The upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4 relatively slide, and the horizontal force at the time of the earthquake acts on the pile head 6 as a shear force by an amount corresponding to the dynamic friction force at that time. .

Therefore, the upper limit of the shearing force acting on the pile main body 1 can be clearly grasped, and a rational design in consideration of the shear strength of the pile main body 1 becomes possible.

In addition, according to the pile seismic isolation structure of the present embodiment, the outer pipe 2 is surrounded by the base plate 3 so as to surround the pile body 1.
And the skirt-like tubular portion 5 provided on the periphery of the foundation side sliding member 4 is fitted into the outer tube, so that the horizontal force from the upper structure during an earthquake In the case of a small-to-medium-sized earthquake, the pile body 1 and the outer pipe 2 are connected to the pile body 1 and the outer pipe 2 within a range where the frictional force generated between the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4 does not exceed the static frictional force. In addition to the distribution according to the stiffness ratio, in the case of a large earthquake, only the horizontal force corresponding to the dynamic frictional force acts on the pile head 6, and all the remaining horizontal forces are distributed to the outer pipe 2. .

Therefore, in the case of a small or medium-sized earthquake, the pile head 6 of the pile body 1 that supports the vertical load of the upper structure has a horizontal force corresponding to the rigidity ratio with the outer pipe 2 up to the static frictional force. Only in the case of a large earthquake, no horizontal force greater than the dynamic friction force acts.

Therefore, the pile main body 1 is not damaged, and in the worst case, the outer pipe 2 is only broken, and the basic function of the pile main body 1 to support the vertical load of the upper structure is maintained even under a large earthquake. In addition to the above, the shear strength of the pile body 1 can be effectively used, and higher earthquake resistance can be secured in combination with the shear strength of the outer pipe 2 and the like.

According to the seismic isolation structure for a pile according to the present embodiment, the skirt-shaped tubular portion 5 provided on the peripheral edge of the foundation-side sliding member 4 is configured to be fitted into the outer tube 2. Head 6
The construction error at the height of the top can be absorbed.

(Second Embodiment)

Next, a second embodiment will be described. Note that components that are substantially the same as those in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 4 is a sectional view showing the seismic isolation structure of the pile according to this embodiment. As can be seen from the figure, the seismic isolation structure for a pile according to the present embodiment is such that a base-side sliding member 4a is installed on the lower surface of a base plate 3, which is the base of an upper structure, and the sliding constituting the base-side sliding member is provided. The upper surface of the pile head cap 8 placed on the pile head 6 is slidably abutted on the lower surface of the plate 9.

Here, regarding the pile head cap 8, the first
The description is omitted here because it is the same as the embodiment, and the cap main body 10 constituting the pile head cap is omitted.
The material and the like of the sliding plate 9 constituting the base-side sliding member 4a are the same as those in the first embodiment, and the description thereof will be omitted.

As an example of a procedure for constructing the seismic isolation structure of the pile according to the present embodiment, a pile head cap 8 is put on the pile head 6 of the driven pile body 1, and the foundation side sliding member 4a is placed thereon.
After fixing the sliding member on the foundation side with an appropriate support, the base plate 3 of the upper structure is constructed.

In the seismic isolation structure of the pile according to the present embodiment, similarly to the first embodiment, when the horizontal force during an earthquake is small,
A relative horizontal displacement does not occur between the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4a due to the static friction force therebetween, and the horizontal force from the upper structure is a shear force corresponding to the static friction force. Acts on the pile head 6 as it is. Also,
Rotational deformation at the pile head 6 is absorbed by the action of the disc spring 11, preventing separation between the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4a, and allowing rotational deformation at the pile head 6 to be allowed. The pile head 6 and the base plate 3 of the superstructure
Is in a pinned state.

On the other hand, if the horizontal force at the time of the earthquake exceeds a certain level, the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4a relatively slide, which corresponds to the dynamic friction force at that time. The horizontal force at the time of the earthquake acts on the pile head 6 as a shearing force. Further, similarly to the case of the small and medium-sized earthquakes, the rotational deformation at the pile head 6 due to the horizontal force from the upper structure acts on the pile head cap 8 so that the disc spring 11 absorbs the rotational deformation.
Is prevented from separating from the upper surface of the base member and the lower surface of the foundation side sliding member 4a, and a shear force as designed acts on the pile body 1 and rotation deformation at the pile head 6 is allowed. No moment is generated.

As described above, according to the seismic isolation structure of the pile according to the present embodiment, as in the first embodiment, the rotational deformation of the pile head 6 during the earthquake is absorbed by the disc spring 11. Therefore, separation between the upper surface of the pile head cap 8 and the lower surface of the foundation side sliding member 4a is prevented, and as a result, the vertical load and the designed shearing force can be reliably transmitted to the pile body 1, It is possible to prevent the pile head 6 from being damaged due to stress concentration. In addition, since the pile head 6 is allowed to be rotationally deformed, no bending moment is generated at the pile head 6, and the pile head 6 and thus the pile body 1 are prevented from being broken by an excessive bending moment as in the related art. can do.

According to the pile seismic isolation structure of the present embodiment, when the horizontal force during an earthquake is small, the pile head cap 8
The horizontal force from the upper structure as a shearing force is the shear force between the pile head 6 and the lower surface of the foundation side sliding member 4a.
When the horizontal force during an earthquake exceeds a certain level, the upper surface of the pile head cap 8 and the foundation side sliding member 4
a slides relatively to the lower surface of the pile head 6 and the horizontal force at the time of the earthquake as a shear force by the amount corresponding to the dynamic friction force at that time.
Act on.

Therefore, it is possible to clearly grasp the upper limit of the shear force acting on the pile main body 1, and it is possible to make a rational design in consideration of the shear strength of the pile main body 1.

[0058]

As described above, according to the seismic isolation structure for a pile according to the first aspect of the present invention, the upper surface of the pile head cap and the lower surface of the foundation side sliding member are separated by the action of the rotational deformation absorbing member. The vertical load and the designed shearing force can be reliably transmitted to the pile body, and the pile head is allowed to rotate and deform. As a result, it is possible to prevent the pile head and the pile body from being broken due to an excessive bending moment.

Further, the sliding action between the upper surface of the pile head cap and the lower surface of the foundation side sliding member makes it possible to clearly grasp the upper limit of the shear force acting on the pile body according to the magnitude of the earthquake. Rational design considering the shear strength of

Further, by using the pile body together with the outer pipe, the pile body will not be damaged. In the worst case, only the outer pipe will be destroyed, and the basic function of the pile body to support the vertical load of the upper structure will be huge. In addition to being able to maintain even under an earthquake, it is also possible to ensure higher seismic resistance in combination with the shear strength of the outer pipe while effectively utilizing the shear strength of the pile body.

Also, since the skirt-shaped tubular portion provided on the peripheral edge of the base side sliding member is fitted into the outer tube,
It is also possible to absorb construction errors at the height of the pile head.

According to the seismic isolation structure of a pile according to the present invention, the upper surface of the pile head cap and the lower surface of the foundation side sliding member are prevented from being separated by the action of the rotational deformation absorbing member, and the vertical load is reduced. And the shear force as designed is reliably transmitted to the pile body, and the pile head is allowed to rotate and deform. It is possible to prevent the pile head and the pile body from being broken by the moment.

Further, the upper limit of the shearing force acting on the pile body according to the magnitude of the earthquake can be clearly grasped by the sliding action between the upper surface of the pile head cap and the lower surface of the foundation side sliding member. Rational design considering the shear strength of

[0064]

[Brief description of the drawings]

FIG. 1 is a sectional view of a seismic isolation structure for a pile according to a first embodiment.

FIG. 2 is an exploded perspective view of a pile head cap used in the pile seismic isolation structure according to the first embodiment.

FIG. 3 is a cross-sectional view illustrating the operation of the seismic isolation structure of the pile according to the first embodiment.

FIG. 4 is a sectional view of a seismic isolation structure for a pile according to a second embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pile main body 2 Outer pipe 3 Basic version of superstructure (base) 4 Foundation side sliding member 5 Tube part 6 Pile head 8 Pile head cap 11 Belleville spring (Rotation deformation absorption member)

Claims (2)

[Claims] 1. A skirt-like structure in which a predetermined outer pipe projects from the base of an upper structure into the ground so as to surround a pile body, and a predetermined foundation-side sliding member is provided on a peripheral edge of the foundation-side sliding member. A pile head cap, in which a rotation deformation absorbing member that absorbs rotation deformation in the pile head of the pile body is provided inside, is attached to the pile head so that the cylindrical portion of A seismic isolation structure for a pile, wherein an upper surface of the pile is slidably abutted on a lower surface of the foundation side sliding member. 2. A pile head cap in which a predetermined foundation side sliding member is attached to a lower surface of a base of an upper structure and a rotation deformation absorbing member for absorbing rotation deformation at a pile head of a pile body is provided inside the pile head. A seismic isolation structure for a pile, wherein the upper surface of the pile is slidably abutted on the lower surface of the base-side sliding member by covering the head.