JP2004316410A - Pile head structure and foundation structure using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To practically reduce a pile head restraining moment from the viewpoints of workability, material, construction cost, etc., and to make a cross section of a pile or a foundation concrete member economically excellent in a pile head structure. I will provide a.
SOLUTION: A wound member 12 made of at least one of a viscous body, an elastic body, and an elasto-plastic body is provided on a peripheral surface of a pile head embedded in a foundation concrete part 19. A perforated disk 12 made of an elastic body or an elasto-plastic body having a substantially circular hole 12a formed substantially at the center is provided on the upper end face of the foundation pile 11 as necessary.
[Selection] Figure 2

Description

  The present invention relates to a joint structure between a foundation pile and foundation concrete, and relates to a pile head structure applicable to a PC pile, a steel pipe pile, a cast-in-place pile, and the like, and a foundation structure using the same.

  When a horizontal load is applied to the joint between the foundation pile and the foundation concrete, that is, the pile head, the distribution of the moment generated in the pile differs greatly depending on the constraint condition of the pile head. In many cases, the pile is used with the pile head embedded in the foundation concrete of the structure, so the moment distribution is calculated as the fixed pile head. According to such a calculation, the moment of the pile head reaches several times the maximum moment in the ground, and the cross-sectional inspection of the pile is performed using the bending moment of the pile head. There is.

Regarding the joint structure of the pile head as described above, techniques for reducing the restraining bending moment of the pile head by placing a ball seat on the pile head are described in, for example, Patent Documents 1 and 2 and Non-Patent Document 1.
For example, in Patent Literature 1, a spherical member bulging upward is provided on the top of a foundation pile, and an upper structure-side spherical member having a concave curved surface complementary to the spherical member is stacked on the spherical member. A pile head structure is described in which both members are combined and pivotally connected with a stopper pin passing therethrough. This pile head structure is expected to have a rigid connection strength for small and medium-scale earthquakes, and causes slip at the contact interface between the spherical member and the spherical member on the upper structure side for large-scale earthquakes. It is expected that a large bending moment will not be generated in the foundation pile or foundation concrete.

Certainly, since the structures described in Patent Documents 1 and 2 and Non-Patent Document 1 are configured so that the condition as a hinge is satisfied at the pile head, the restraining bending moment of the pile head is reduced. It is possible to do.
However, as a result, the maximum bending moment in the underground part becomes large on the contrary, so the design check of the pile section is performed based on this underground part, and there is a disadvantage that the number of excessively designed places in the member cross section increases. is there. In addition, since the pile head is not embedded in the foundation concrete, the displacement and horizontal displacement of the pile head increase, and there is concern about the stability during an earthquake. Further, there are problems in workability and material costs, and there is a practical problem.

  In addition, vertical and horizontal loads are applied to the foundation pile, but in actual use, many piles are struck in a limited area, on which the foundation concrete and superstructure concrete are poured. . In this state, a horizontal load acts on the pile during an earthquake, and this horizontal force causes a difference of about twice between the pile at the outer periphery of the foundation and the pile at the center.

  In addition, as a prior art regarding a pile head structure, Patent Literature 3 and Patent Literature 4 can be cited, but a detailed description thereof is omitted.

JP 2001-73390 A JP-A-10-227040 JP 2001-64982 A JP 2001-140266 A "Basic Engineering", Public Works Research Institute, Ltd., December 15, 2001, pp. 76-80

  An object of the present invention is to provide a pile head structure that makes the cross section of a pile or a foundation concrete member excellent in economical efficiency while securing the stability of the foundation practically from the viewpoint of workability, material, construction cost, and the like. It is in.

  Another object of the present invention is to provide a foundation structure capable of equalizing a bending moment generated in a group pile foundation.

According to the present invention, there is provided a pile head structure characterized in that at least one of a viscous body, an elastic body, and an elasto-plastic body is provided on a peripheral surface of a pile head embedded in foundation concrete.
In the present invention, since it is only necessary to provide at least one of a viscous body, an elastic body, and an elasto-plastic body on the peripheral surface of the pile head, the construction is easy, and the material cost can be suppressed relatively inexpensively. It has excellent properties. In addition, due to the viscous, elastic, and elasto-plastic materials provided on the periphery of the pile head, the constraint of the pile head by the foundation concrete is larger than the hinge and weaker than the complete fixation. It is possible to rotate moderately inside and functions as an elastic hinge in a semi-fixed state. As a result, an excessive bending moment is prevented from being generated in one of the pile head and the underground portion, and the standard for designing the pile cross section can be relatively low, so that the pile member and the foundation can be formed. The concrete member can be excellent in economic efficiency.

According to the present invention, at least one of a viscous body, an elastic body, and an elasto-plastic body is provided on the entire peripheral surface of the pile head embedded in the base concrete, and a viscous body having a substantially circular hole formed in a substantially central portion thereof. A pile head structure is provided, wherein a perforated disk made of at least one of a body and an elastic-plastic body is arranged on an upper end surface of the foundation pile.
In this pile head structure, the perforated disk may be formed from a plate of the same thickness, or a plate whose outer edge is thicker than the periphery of the hole. it can. In addition, a flat plate or a spherical plate having a spherical surface on the upper side can be disposed in a hole portion of the perforated disk disposed on the upper end surface of the pile.
According to the present invention, when the horizontal force acting on the pile head during an earthquake increases, a member angle occurs between the pile head and the foundation concrete due to the elastic material of the pile head and the like, and the restrained bending moment of the pile head is reduced. Act like so. Also, by reducing the bearing area between the pile concrete and the foundation concrete or by making it spherical, the restraining force against the horizontal load of the pile head is further reduced, and the state can be made closer to the state of the pile head hinge.

  Further, in the present invention, it is possible to use an old tire to constitute both the elastic body covering the entire peripheral surface of the pile head and the elastic body covering the edge portion of the upper end surface of the pile head. It is. As described above, even when an old tire is used, the restrained bending moment of the pile head can be relaxed, and an effect of approaching the state of the pile head hinge can be obtained.

According to the present invention, at least one of a viscous body, an elastic body, and an elasto-plastic body is provided on a peripheral surface of a pile head embedded in the foundation concrete, and a seismic isolation member is provided at an upper end of the foundation pile. A pile head structure is provided, wherein the pile head is covered with a covering member to isolate the seismic member from the foundation concrete.
In the present invention, since the pile head can rotate moderately in the foundation concrete, in addition to functioning as a semi-fixed elastic hinge, a seismic isolation member is provided at the upper end of the foundation pile. Therefore, the bending moment of the pile head is reduced and the seismic isolation effect is obtained. In addition, fixing of the covering member and the seismic isolation member is optional, but if not fixed, even when an extremely large horizontal load is applied during a large earthquake, slippage occurs at the contact portion between the covering member and the seismic isolation member. As a result, the horizontal load transmitted to the seismic isolation member is reduced, a large damping effect is obtained, and the effect of reducing the pile head bending moment is also large.

According to the present invention, in a foundation structure having a plurality of rows of pile groups, a pile head of a pile arranged on an outer peripheral portion is embedded in a foundation concrete in a semi-fixed state as an elastic hinge like the pile head structure. A substructure is provided.
When a horizontal load is transmitted to a pile during an earthquake, a horizontal force approximately twice that of a pile placed inside acts on the head of the pile on the outer periphery of the foundation. When the head of the part pile is configured as an elastic hinge, the horizontal force acting on the pile head of the outer peripheral part is reduced, and the pile arranged inside simply embeds the head in the foundation concrete, The horizontal force acting on the pile can be equalized at the outer peripheral portion and the inner portion.

In the pile head structure of the present invention, since it is only necessary to provide at least one of a viscous body, an elastic body, and an elasto-plastic body on the peripheral surface of the pile head, the construction is easy and the material cost is relatively low. Can be.
Also, unlike the prior art in such a technical field, according to the present invention, the pile head is embedded in the foundation concrete, and there is no excessive displacement between the pile and the foundation concrete. It is a practical structure as a stress reduction structure for piles and foundation concrete at the time.
Also, by providing a viscous, elastic or elasto-plastic body on the periphery of the pile head, the constraint of the pile head by the foundation concrete is larger than the hinge and weaker than the complete fixation. It is possible to rotate moderately inside and functions as an elastic hinge in a semi-fixed state. As a result, an excessive bending moment is prevented from being generated, and a cross-sectional design of a pile excellent in economy can be realized.
By reducing the bearing area between the pile head and the foundation concrete or making it spherical, the restraining force of the pile head is further reduced, so that even when the axial force is large, the pile head restraining bending moment can be reduced.
As an industrial waste, it is possible to obtain an opportunity to use a large amount of old tires, which are in trouble for disposal, with simple processing and installation work, and to reduce the construction cost.

Hereinafter, a preferred embodiment will be described with reference to the accompanying drawings, but the present invention is not limited to this embodiment.
FIG. 1 is a diagram comparing bending moment distributions of piles having different constraint conditions.
In a pile with a pile head in the ground, when a horizontal load is applied to the pile head, the moment distribution generated in the pile differs greatly depending on the constraint condition of the pile head. The dotted line (1) in FIG. 1 shows the moment distribution when the pile head is fixed, for example, a pile with the pile head embedded and fixed in the foundation concrete. The dashed line (3) in FIG. 1 is a moment distribution in the case of a pile head hinge, which is shown, for example, by the piles described in Patent Documents 1 and 2 and Non-Patent Document 1. As can be seen from FIG. 1, the moment of the pile head reaches several times the maximum moment of the underground part when the pile head is fixed, and the maximum bending moment of the underground part increases with the pile head hinge. Would.
Therefore, as shown in the solid line (2), the present invention sets the pile head so that the maximum bending moment in the underground portion and the pile head moment are substantially the same, and there is no place where the moment protrudes and increases. The pile head elastic hinge is set in a semi-fixed state, and an embodiment of the pile head structure will be described below.

2A and 2B are sectional views of the pile head structures 10A and 10B of the present invention.
In the pile head structure 10A, a ready-made pile 11 made of precast concrete or steel pipe is cast on the ground 18, crushed stone 17 is laid on the ground 18 around the pile 11, and a viscous material is formed on the periphery of the pile head. A perforated disk 12 made of a viscous, elastic, or elasto-plastic body having a substantially circular hole 12a formed at the center, if necessary, is provided with a winding member 13 made of an elastic body or an elasto-plastic body. Is placed on the top of the pile head. Then, leveling concrete 16 is laid on the crushed stone 17, and concrete is cast so as to bury the pile head, thereby forming a foundation concrete portion 19.
Further, a pile head structure 10B of FIG. 2 (b) is different from the pile head structure 10A of FIG. 2 (a) in that a hoop bar 15 and a reinforcing bar 14 are provided in a foundation concrete portion 19 around a pile head. .
As described above, by making the perforated disk 12 a viscous body, an elastic body, or an elasto-plastic body placed on the upper surface of the pile head, the constraint condition of the pile head becomes closer to the hinge, and the constraint of the pile head is restricted. The moment can be reduced.
Here, as the viscous body, for example, silicone resin, asphalt, etc. are used, and as the elastic body, for example, rubber, urethane resin, polyvinyl chloride resin, silicone resin, polyethylene resin, polypropylene resin, etc. are used. As the elasto-plastic body, asphalt, urethane foam resin, styrene foam resin and the like can be used.

In the pile head structures 10A and 10B described above, since the wound member 13 made of a viscous body, an elastic body, or an elasto-plastic body is provided on the peripheral surface of the pile head, the constraint of the pile head by the foundation concrete 19 is a hinge. Larger, and weaker than fully fixed, allowing the pile head to rotate moderately within the foundation concrete 19 and function as a semi-fixed elastic hinge. Therefore, even if a horizontal load acts on the pile 11, an excessive bending moment does not occur in either the pile head or the underground part. It is possible to make not only the pile section but also the foundation concrete member such as the underground beam into a structure excellent in economic efficiency.
In addition, in the pile head structures 10A and 10B, since it is only necessary to provide the winding member 13 on the peripheral surface of the pile head, the pile head structures can be compared with the conventional pile head structures described in Patent Documents 1 and 2 and Non-Patent Document 1. The construction is easy and the material cost can be kept relatively low.

Next, the pile head structures 20A and 20B shown in FIGS. 3A and 3B differ from the pile head structures 10A and 10B shown in FIG. 2 in that the present invention is applied to a pile 21 made of cast-in-place concrete. is there.
That is, in the pile head structure 20A, a pile 21 is formed on the ground 18 by cast-in-place concrete, a steel pipe 22 is fitted to the head of the pile 21, and a filler such as mortar is injected into a gap between the pile 21 and the steel pipe 22. A winding member 23 made of a viscous body, an elastic body or an elasto-plastic body is provided on the outer peripheral surface of the steel pipe 22, and a sliding material (not shown) such as asphalt is applied to the upper surface of the pile head as needed. ing. Then, leveling concrete 26 is laid on the ground 18 around the pile head, and concrete is cast so as to bury the pile head to form the foundation concrete portion 19.
Further, the pile head structure 20B of FIG. 3B is different from the pile head structure 20A of FIG. 3A in that a perforated disk 24 made of an elastic body or an elasto-plastic body having a substantially circular hole 24a formed substantially at the center. Is provided on the upper surface of the pile head, and the PC steel wire 25 is provided so as to extend upward from the pile head. Since the PC steel wire 25 has a large tension and can be extended, the PC steel wire 25 has a force for restraining the pile head. It can be kept relatively small, and can also secure sufficient proof stress even when a pulling load acts on the pile head.
Note that the thickness of the wound member 23 may be set so that the pile head can be rotated by about ± 5 ° in practical use according to the material.

Next, the pile head structures 30A and 30B shown in FIGS. 4A and 4B are different from FIGS. 1 and 2 in that cylindrical bodies 32 and 33 including an elastic body are installed on the pile head.
That is, in the pile head structure 30A, a cast-in-place pile or a ready-made pile 31 is driven into the ground 18, the crushed stone 17 is laid on the ground 18 around the pile 31, and a cylinder having a rectangular cross section around the pile head. A body 32 is fitted, a sliding material such as asphalt or an edge-cutting material (not shown) is fixed to the upper surface of the pile head as necessary, a leveling concrete 16 is laid on the crushed stone 17, and the pile head is Concrete is cast so as to be embedded, and a basic concrete portion 19 is formed.
Here, the cylindrical body 32 includes an elastic-plastic body 32b such as a rubber chip, sand, gravel, soil cement, urethane foam, foam mortar, asphalt, or the like inside a hollow ring member 32a made of an elastic body such as rubber or soft vinyl chloride. Are filled.
The pile head structure 30B in FIG. 4B is provided with a cylindrical body 33 different from the cylindrical body 32 in FIG. 4A, and this cylindrical body 33 has the same elasto-plasticity inside the rubber tire 33a. It is formed by filling the body 33b. For example, discarded used tires can be used as the rubber tires 33a, so that used tires that are waste can be recycled.

Next, FIG. 5 is a cross-sectional view showing a pile head structure 40 different from FIGS. 2 to 4.
In the pile head structure 40, a cast-in-place pile or a ready-made pile 41 is cast on the ground 18, a concrete pedestal 48 is provided in a ring shape on the ground 18 around the pile 41, and the crushed stone 17 is wrapped around the concrete pedestal 48. Is spread, and the elastic body or the elasto-plastic body 45 is placed on the concrete base 48. A seismic isolation member 42 is fixed on the pile head, and a cover 43 is provided so as to cover the seismic isolation member 42, and leveling concrete 16 is laid around the cover 43 and covered with the cover 43. Concrete is poured so as to bury the pile head thus formed, and the foundation concrete portion 19 is formed.
Here, the seismic isolation member 42 is formed by fixing upper and lower plates 42a and 42c made of a steel plate or the like above and below a seismic isolation rubber 42b. The cover 43 is composed of a top plate 43a and a side plate 43b, and is formed in a box shape capable of accommodating the seismic isolation member 42, the elastic body or the elasto-plastic body 45, and the pile head inside. I have. The cover 43 is provided such that the upper surface plate 43a contacts the upper plate 42a of the seismic isolation member 42 so that a load from above can be transmitted to the seismic isolation member 42. The side plate 43b of the cover 43 is disposed so as to contact the elastic body 45, and the elastic body or the elasto-plastic body 45 is disposed so as to contact the periphery of the pile head. Alternatively, it can be transmitted to the pile head via the elastic-plastic body 45.
The upper plate 43a of the cover 43 and the upper plate 42a of the seismic isolation member 42 may be fixed with bolts or the like, or may be non-fixed so that the two members 43a, 42a can slide in a contact state.

In the pile head structure 40, in addition to the pile head functioning as an elastic hinge in a semi-fixed state, the seismic isolation member 42 is provided at the upper end of the pile 41, so that the pile head bending moment is reduced and the seismic isolation is performed. Both effects can be obtained.
When the upper plate 42a of the seismic isolation member 42 is not fixed to the upper plate 43a of the cover 43, when an extremely large horizontal load is applied during a large earthquake, the upper plate 43a and the upper plate 42a slide. The vibration transmitted to the foundation concrete and structure is greatly attenuated, and the bending moment generated at the pile head is also reduced.
Conversely, when the upper plate 42a of the seismic isolation member 42 is fixed to the upper plate 43a of the cover 43, the foundation structure is formed using ordinary seismic isolation rubber. Since the member 42 behaves integrally, the seismic isolation effect of the seismic isolation member 42 is more effectively exerted. By filling the cover 43 with an appropriate viscous material, the seismic isolation rubber 42b can be protected and a function as a damper can be added. In addition, the elastic body or the elasto-plastic body 45 also serves as a formwork for preventing the concrete from entering.

Next, FIG. 6 is a cross-sectional view showing a pile head structure 50 different from FIGS. 2 to 5.
The pile head structure 50 is one in which the present invention is applied to a pile 51 formed of cast-in-place concrete on the ground 18. A steel pipe 52 is fitted to the head of the pile 51, and a gap between the pile 51 and the steel pipe 52 is formed. A filler such as mortar is injected, a winding member 53 made of a viscous body, an elastic body, or an elasto-plastic body is provided on the outer peripheral surface of the steel pipe 52, and a viscous body or an elastic body having a substantially circular hole formed substantially in the center. Alternatively, a perforated disk 55 made of an elasto-plastic material is placed on the upper surface of the pile head, and a disk 56 made of cast iron or the like is fitted into a central hole of the perforated disk 55. The disk 56 has a convex portion 56a on the lower surface, and an upper surface 56b is formed in a spherical shape bulging upward, while a hole 51a is formed in the center of the upper surface of the pile head in advance. The convex portion 56a of the disk 56 is fitted in the hole 51a. Then, leveling concrete 26 is laid on the ground 18 around the pile head, and concrete is cast so as to bury the pile head to form the foundation concrete portion 19.
As described above, in the pile head structure 50, the bearing area between the pile head upper surface and the foundation concrete is reduced by the perforated disk 55, and the disk 56 having the spherical upper surface 56b is connected to the pile head. By providing on the upper surface, the restraining force of the pile head by the foundation concrete 19 can be reduced, and even when the axial force is large, the restraining bending moment of the pile head can be reduced.

  Next, FIG. 7A is a cross-sectional view showing a pile head structure 60 different from those in FIGS. 2 to 6, and FIG. 7B is a diagram in which one sidewall is cut, and the other sidewall 62 a and a tread. It is a side view of the old tire 62 which left 62b. In the pile head structure 60, the present invention is applied to a cast-in-place pile or a ready-made pile 61, and as shown in FIG. The entire peripheral surface of the pile head is covered with the tread 62b of the old tire 62, and the gap between the bead 62c of the sidewall 62a and the upper surface of the pile head is sealed with the sealing material 63. That is, the sidewall 62a corresponds to the perforated disk 12 in the pile head structure 10A in FIG. 2A, and the tread 62b corresponds to the winding member 13 in FIG. 2A. . Therefore, the pile head structure 60 in FIG. 7A has the same operation and effect as the pile head structure 10A in FIG. 2A. As a further effect, the old tires that are industrial wastes can be easily obtained. This makes it possible to effectively use a large amount of it in complicated processing and installation.

Next, FIG. 8 is a diagram schematically showing a foundation structure 70 having a plurality of rows of pile groups. In this foundation structure 70, a joint portion between a pile 73 and a foundation concrete portion 72 arranged on the outer peripheral portion is provided. While the pile head structure of any one of FIGS. 2 to 7 is applied, the pile head of the pile 71 disposed on the inner side than the outer pile 73 is embedded and fixed in the foundation concrete portion 72. .
As described above, when the pile head of the outer pile 73 is embedded in the base concrete in a semi-fixed state as an elastic hinge, the horizontal force acting on the pile head of the outer peripheral portion is larger than that of the pile head completely fixed inside. Is greatly reduced, so that the horizontal force acting on the pile at the outer peripheral portion and the inner portion can be equalized.

It is a figure which compares the bending moment distribution in a pile head. (A) (b) is sectional drawing of the pile head structure of this invention. (A) (b) is sectional drawing which shows embodiment different from FIG. (A) (b) is sectional drawing which shows embodiment different from FIG.2 and FIG.3. FIG. 5 is a sectional view showing an embodiment different from FIGS. 2 to 4. It is sectional drawing which shows the pile head structure different from FIGS. 2-5. (A) is sectional drawing which shows the pile head structure different from FIG. 2-FIG. 6, (b) is a side view of the old tire used for the pile head structure of (a). It is sectional drawing of the basic structure of this invention.

Explanation of reference numerals

Reference Signs List 10A, 10B pile head structure 11 pile 12 perforated disk 13 wound member 19 foundation concrete part 20A, 20B pile head structure 21 pile 23 wound member 24 perforated disk 30A, 30B pile head structure 31 pile 32, 33 cylinder Body 40 Pile head structure 41 Pile 42 Seismic isolation member 43 Cover (covering member)
45 Elastic body or elastoplastic body 51 Pile 52 Steel pipe 53 Winding member 55 Perforated disk 56 Disk 60 Pile head structure 61 Pile 62 Old tire 63 Seal material 70 Foundation structure 71 Pile placed inside 72 Base concrete part 73 Pile 73A pile head structure arranged on the outer periphery

Claims (6)

  A pile head structure, wherein at least one of a viscous body, an elastic body, and an elasto-plastic body is provided on a peripheral surface of a pile head embedded in basic concrete.   At least one of a viscous, elastic, and elasto-plastic body is provided on the entire circumference of the pile head embedded in the foundation concrete. A pile head structure, wherein at least one perforated disk is arranged on an upper end surface of the foundation pile.   The pile head structure according to claim 2, wherein a flat plate or a spherical plate having a spherical surface on an upper side is disposed in a hole of the perforated disk disposed on an upper end surface of the pile.   A pile head structure in which an old tire is provided as an elastic body covering an entire peripheral surface and an edge portion of an upper end surface of a pile head embedded in basic concrete.   At least one of a viscous body, an elastic body, and an elasto-plastic body is provided on a peripheral surface of a pile head embedded in the foundation concrete, a seismic isolation member is provided at an upper end of the foundation pile, and the seismic isolation member is isolated from the foundation concrete. A pile head structure, wherein the pile head is covered by a covering member.   In a foundation structure having a plurality of rows of pile groups, a part or all of piles arranged on an outer peripheral portion are provided with the pile head structure according to any one of claims 1 to 5. Foundation structure to do.

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