JP5864686B1 - Pile foundation - Google Patents

Abstract

[PROBLEMS] To provide a pile foundation that can be economically designed for a footing that connects a pile head in a pile foundation that supports a single pile with a plurality of piles, and that does not differ in resistance, rigidity, and pile head fixing degree depending on the direction. provide. SOLUTION: In a pile foundation that supports a vertical load of a single pillar or a single seismic isolation device of a seismic isolation structure or a seismic structure with a plurality of piles, the distance between the pile tips of adjacent piles in the support layer of the ground around the pile Secures more than the necessary separation distance determined according to the pile diameter or the pile tip diameter, and the pile head is Dtc as the distance between each pile core of adjacent piles, and the pile head diameter is Do , 1.0Do <Dtc ≦ 1.5Do, and the pile is in the range of 0 <θ ≦ 1/10 (rad), where θ is the inclination angle of the pile axis with respect to the vertical axis. Among them, it is a finely inclined pile that is slightly inclined near the vertical axis. [Selection] Figure 4

Description

  The present invention relates to a pile foundation that supports a base-isolated structure and a building that can dramatically improve seismic safety performance.

  The seismic isolation structure is based on the principle of reducing the seismic response by placing seismic isolation devices on the foundation or intermediate floor of the structure and extending the natural period of the structure. Initially, it started on the premise of building on solid ground, avoiding soft ground where the periodic characteristics of input ground motion would be longer.

  The application of seismic isolation structures to actual structures in Japan began about 30 years ago, around 1985, but with the widespread use of seismic isolation structures and with some seismic experiences, seismic isolation structures It can be said that it is natural that the excellent seismic performance has been recognized and the number of application examples to buildings in urban areas where many building structures are concentrated has increased.

  Not to mention Tokyo, Osaka, Nagoya and other major metropolitan areas, almost all major cities in Japan are developed in plains, and most of them are alluvial plains. Most of them have to be supported by pile foundations. Furthermore, recently, there are increasing cases where construction is required in the coastal area as a location condition of the planned site, and there are increasing cases of building seismic isolation structures even in soft ground with deep support layers.

  On the other hand, due to recent social and economic demands, building structures tend to be higher and larger. As a result, seismic isolation buildings tend to require very large and heavy buildings, and the weight supported by one pillar or one seismic isolation device is very large, and the support weight of one pillar is 2000 tons. Some of which are close to several thousand tons.

  In order to support this heavy weight, technological development to increase the allowable support load is progressing for both ready-made piles, steel pipe piles and cast-in-place piles, but from conditions such as economy and workability, The number of cases in which the supporting load of one pillar or one seismic isolation device (hereinafter referred to as “one pillar”) must be supported by a plurality of piles is increasing.

As a method of supporting one pillar with a plurality of piles, there are the following two methods A and B.
Method A consists of placing a plurality of vertical piles at predetermined horizontal intervals, constructing a footing that connects the pile heads of the piles, and placing a column or seismic isolation device at the upper center of the plane It is a method to do.
Method B is to construct a slant pile that inclines a plurality of piles, and to construct a footing that integrates the pile heads of the slant piles, and to a column or seismic isolation device on the top. It is a method of arrangement. In this case, there are two or more pile heads where a plurality of oblique piles gather, and the pillars or seismic isolation devices may be placed by connecting them with footings.
The above-mentioned method A is a method that has been generally performed for a long time in the design of buildings, and is not a method that is particularly specified in patents, so prior patent documents 1 to 6 relating to method B are exemplified below. .

JP 2001-32570 A Japanese Patent Laid-Open No. 11-117276 JP 2000-17461 A JP 2000-17642 A Japanese Patent Laid-Open No. 2000-17643 JP 10-299005 A

FIG. 1 shows a general configuration method of piles and footings in the case of the above-described method A, that is, one pillar conventionally supported in the design of a building by a plurality of piles. FIG. 1 (1) shows a case where a plurality of cast-in-place piles 2 are connected by a footing 3, and a column 62 is placed on the central portion thereon.
FIG. 1 (2) shows an example in which a plurality of ready-made concrete piles 2 are connected by a footing 3 and a seismic isolation device 5 is arranged in the center portion above the piles.
Since FIG. 1 is expressed as an elevation view or a longitudinal sectional view, two piles 2 are shown, but the same applies to the case where the number of piles is three, four, or more.
First, the building pile 2 is basically driven vertically on the ground (pile surrounding ground) 1, and the pile tip 23 is spaced a predetermined distance in order to avoid stress overlap in the support ground 11. It is necessary. Specifically, both cast-in-place piles and ready-made concrete piles usually have a distance between pile centers of at least twice the pile head diameter, more precisely D1 + D2 or more, and D2 + 1m or more (D1 is the pile shaft diameter, D2 is The diameter of the pile tip enlarged portion is shown.) The pile head 21 is connected with the footing 3 and the column 62 of the upper frame or the seismic isolation device 5 is placed thereon. Reference numeral 7 denotes a vertical load acting on the entire pile foundation from above, and 71 denotes a vertical load borne by each pile.

  In this case, as shown in FIG. 1, the pile head upper footing 3 that connects the pile heads 21 distributes and transmits the vertical load 7 of the column to two (or more) piles as a beam. 3 has a large bending moment and shearing force. Since the shear strength of concrete is not so high, a very large footing cross-section is required, and steel members may be embedded in the concrete, but the amount of excavated soil in the ground will also be large, which will be a very large burden economically Have a problem.

Moreover, as shown in FIG. 1, when the heads of two piles are connected and integrated by the pile head upper footing 3, the pile head 21 and the pile head upper footing 3 are rigidly joined to each other, so that a rigid frame (rigidly joined frame) is obtained. Therefore, when a horizontal load is applied during an earthquake, a large bending moment is generated in the pile head 21. In order to balance the pile head moment, a bending moment having the same value is generated in the footing, and a vertical shearing force corresponding to the moment gradient is applied to the pile head upper footing 3.
On the other hand, for example, when the number of piles is two, the ramen direction connected by the footing is a condition for fixing the head of the pile, whereas the orthogonal direction remains in a self-supported pile state, The rotation of the pile head 21 is not constrained in the direction, and the pile head 21 can be freely rotated (pile head pin). As a result, the constraint condition of the pile head 21 is significantly different depending on the direction of the pile, so that the problem is that the generated stress and the horizontal rigidity at the time of the earthquake differ greatly depending on the direction.

FIG. 2 shows the above-mentioned method B, that is, the case where a plurality of slant piles 24 are used. In addition, the same code | symbol is attached | subjected to the part which is common in FIG.
In this case, the inclination angle of the pile 24 is often driven around 20 ° to 30 ° with respect to the vertical axis. When tilted to 45 ° or more, the efficiency of the resistance force against the horizontal force increases, but the resistance efficiency of the vertical support force decreases, and the length of the pile shaft body 22 also increases, reducing the practicality in terms of economy and workability. . Conversely, when the inclination angle is less than 15 °, the resistance efficiency against the horizontal force is extremely lowered, and the effect of the horizontal resistance force and the horizontal rigidity is not obtained, so the original purpose of using the slant pile is lost. .

  Since the pile piles 22 are driven diagonally, the slant pile 24 resists the horizontal force with its axial force, like the brace material in a building. And can resist the horizontal force very effectively. Therefore, even when the resistance force of the surrounding ground 1 of the pile is extremely low, such as soft ground, or when the surrounding resistance force cannot be expected at all, such as an offshore structure or a floating structure, horizontal rigidity and proof stress It has been proposed as a method that can efficiently realize a high foundation.

The slant pile 24, which has been considered to be extremely effective as a horizontal resistance mechanism, has the following major problems because of its high resistance efficiency.
First of all, the first problem with diagonal piles is that when a horizontal force acts on the pile head 21, a large axial resistance force is generated by the horizontal force, and the axial force is compressed according to the horizontal force and the inclination direction of the pile. It acts as a force and a tensile force. When the pile shaft 22 has a concrete cross section, the bending strength of the cross section is significantly reduced under the action of the tensile axial force. Conversely, if the acting compressive force is excessive, the length of the pile is too long. Sex occurs.

The problem second point is that, at this time, a very large shearing force acts in the vertical direction on the footing where the upper end portion of the diagonal pile is close. That is, since an upward force is applied from the upper end portion of the inclined pile 24 to which the compression axial force acts, and a downward force is applied from the upper end portion of the inclined pile 24 to which the tensile force is applied, the footing 3 corresponding to the boundary portion between the two piles is applied. An extremely severe shear force acts on the vertical direction.
In addition, as shown in FIG. 2, a large horizontal component force is generated in the footing 3 of the slant pile head 21 due to the vertical load acting from the upper column, so the design for the horizontal component force is forgotten in the footing design. must not.

FIG. 3 shows a serious problem of the inclined pile against the horizontal seismic force. That is, the third problem of the diagonal pile is that the horizontal force sharing ratio at the time of the earthquake is greatly different and the horizontal resistance rigidity is greatly different depending on the direction. In addition, the same code | symbol is attached | subjected to the part which is common in FIG.
FIG. 3 (1) shows a plan view of the pile head 21 when three oblique piles are driven in a 120 ° direction. The left view of FIG. 3A is a vector display of the load ratio of the horizontal force 8 of each pile when the horizontal force 8 in the X direction is applied to the pile head 21 with an arrow. Since the resistance stiffness in the axial direction of the diagonal pile is significantly higher than the direction perpendicular to the axis, the horizontal force 8 is resisted by the two on the lower side of the figure, and the horizontal force load on the pile on the upper side of the figure is extremely small. The resistance is not balanced. At this time, since only two of the three piles are effective against the horizontal force 8 acting on the pile head 21, the efficiency is economical and the rigidity of the horizontal resistance is greatly different. There is also a problem that a rotational (torsion) force at 21 is generated. The code | symbol 81 has shown the magnitude | size of the horizontal force (and horizontal rigidity) which a pile bears.

  The right side view of FIG. 3 (1) is a case where the horizontal force 8 in the Y direction acts on the heads of the three diagonal piles. At this time, the pile in which the direction of action of the horizontal force 8 coincides with the oblique pile axis bears a large horizontal force, and no great resistance force acts on the other two piles. If the design is based on the assumption that the pile head horizontal force 8 is equally divided by three piles, an axial force more than twice the design value will be applied to only one pile. If subsidence occurs in the ground at 23, the balance of the three piles may be lost after the earthquake, and the pile head 21 may be inclined.

FIG. 3 (2) shows the resistance force against the horizontal force 8 in the case of two diagonal piles. The figure on the left shows the case where the direction of the pile head horizontal force coincides with the direction of inclination of the diagonal pile 24. At this time, the pile resists with axial rigidity, so it resists the horizontal force very efficiently. Since the axial force becomes a compressive force and a tensile force, a vertical shearing force acts on the footing of the pile head 21.
The right side view of FIG. 3 (2) shows the case where horizontal force 8 in the orthogonal (Y) direction acts on the two diagonal piles. In this case, the horizontal rigidity is extremely low, and the effective resistance element against the horizontal force is not.
When there are many pillars in one building, and two slant piles are arranged under different orientations, the resistance force and resistance rigidity of the piles differ greatly depending on the position of the pillars. Therefore, it is necessary to give sufficient consideration to the setting of the sharing ratio of the horizontal force and torsional deformation of the entire foundation surface.

Furthermore, when a sloping pile foundation is used for soft ground, there is a problem that it induces a large problem with respect to propagation of ground motion and seismic response of structures due to seismic design. In other words, it has been generally understood that the use of diagonal piles on soft ground is an advantageous solution in terms of seismic design because the horizontal rigidity and proof strength of the entire pile foundation are increased. It is an interpretation that neglects the dynamical problems related to propagation.
In soft stratified ground, the short-period component of the ground motion is filtered and removed in the process of propagating through the formation, so that the acceleration input to the structure (input of the short-period component) is reduced. However, in the structure in which the inclined pile 24 is laid, the high axial rigidity of the inclined pile 24 allows a short period component of the earthquake motion to be transmitted directly from the hard support layer 11 of the pile tip 23 to the foundation of the structure. The effect of removing short-period components is lost, and strong strong ground motion with short-period components is input to the structure. Therefore, it cannot be said that it is advantageous in terms of seismic design, and in some cases, extremely severe ground motion input. Will be introduced. Since the rigidity and proof stress of the pile foundation itself are increased, the conventional explanation that the seismic safety is improved is a shallow understanding focusing only on the strength of the pile foundation.

  Furthermore, when attention is paid to the horizontal displacement of the soft soft ground during the earthquake, a large horizontal displacement occurs in the formation during the earthquake. At this time, the pile head of the diagonal pile with high horizontal rigidity has a small horizontal displacement. At the part level, a large relative displacement occurs between the pile body and the ground, and the diagonal pile bears a very large horizontal load (forced displacement stress) due to the horizontal displacement of the surrounding ground. In the past, because it was not possible to understand the problem of forced displacement stress due to the surrounding ground, it was generally understood that slant piles were advantageous in terms of earthquake resistance. It should be understood that there are serious problems in seismic design.

As described above, the problems in the case where the load of one pillar of a building or one seismic isolation device is supported by a plurality of piles are summarized as follows.
First, as a method A, when placing a plurality of vertical piles with a necessary separation distance, a large footing is required, which is an economic burden, and the horizontal rigidity depends on the presence or absence of the frame structure due to the footing. There arises a problem that a large difference occurs in each direction.
Further, when the oblique pile is adopted as the method B, an excessive axial force is generated at the time of an earthquake, and a very large shear force in the vertical direction is generated in the footing that joins the pile heads. In addition, depending on whether or not the direction of horizontal seismic force acting on the pile head coincides with the axial direction of the oblique pile, there is a possibility that a significant difference occurs in the pile's seismic force load, resulting in the torsional force of the pile head 21. is there. In addition, because of the high axial rigidity of the inclined pile, a short period component of strong acceleration is transmitted directly from the hard ground of the pile tip 23 to the foundation of the structure, which invites input seismic motion that is disadvantageous in terms of the earthquake response of the structure. In addition, the slant pile itself has an important problem in terms of seismic design for both the pile and the structure, such as bearing a very large forced displacement stress due to the horizontal displacement of the surface soft ground.

The present invention adopts the following configuration in order to solve the above problems.
<Configuration 1>
It is a pile foundation that supports the vertical load of one pillar or one seismic isolation device of seismic isolation structure or earthquake resistant structure with multiple piles,
The distance between the pile head and the adjacent pile at the support layer ground is more than the necessary separation distance determined according to the pile shaft diameter or pile tip diameter,
The pile heads are arranged within a range of 1.0 Do <Dtc ≦ 1.5 Do, where Dtc is the distance between each pile core of adjacent piles and Do is the pile head diameter.
And, when the pile has an inclination angle of the pile axis with respect to the vertical axis as θ,
Within the range of 0 <θ ≦ 1/10 (rad) and within the range of both the conditions of the above-mentioned pile tip and pile head, it is a slightly inclined finely inclined pile that is as close to the vertical axis as possible. Pile foundation characterized by that.

<Configuration 2>
In the pile foundation described in Configuration 1,
The pile head horizontal connection members that connect and integrate the horizontal positions of adjacent pile heads so that the pile head displacement during an earthquake is the same horizontal displacement, and that do not restrict the rotational deformation of the pile heads. Located near the top of the head,
A pile head joining device that allows rotational deformation of the pile head is arranged at the top of each pile head,
A pile head upper footing that integrates the plurality of piles at the top is configured,
A pile foundation characterized in that the pile head upper footing is connected to and integrated with an upper frame or the seismic isolation device.

<Configuration 3>
In the pile foundation described in Configuration 1 or Configuration 2,
The pile head joining device can absorb the rotational deformation of the pile head by incorporating a rubber layer alone or a laminated rubber body,
The pile head joining device is disposed on the top surface of the pile head that is slightly inclined and is repaired horizontally with either high strength mortar, high strength concrete, or high strength self-leveling material. A featured pile foundation.

<Configuration 4>
In the pile foundation described in Configuration 1 or Configuration 2,
As the pile head joining device, a cylindrical horizontal stopper fixed to the outer peripheral portion of a horizontal steel plate placed on the upper surface of the pile head and surrounding with a slight gap around the outer peripheral surface of the pile head, or A pile foundation characterized by using a thin steel plate pile head cap shaped into an inverted concave shape on the top surface of the pile head or a headband shaped ring-shaped joining member fitted around the pile head.

<Configuration 5>
In the pile foundation described in Configuration 3 or Configuration 4,
The pile head joining apparatus has a PBL dowel plate provided with a steel plate having a number of holes in two directions in two directions,
A pile foundation in which a pile head and a pile head upper footing are connected and integrated by the pile head joining device.

  The first effect of the present invention is that the pile heads of a plurality of piles supporting one column or one seismic isolation device are arranged close to each other, so that the vertical load from the column or the seismic isolation device is directly below it. It is transmitted as a compressive force directly to each pile through concrete of the pile head footing. When the footing transmits a vertical load to the pile as a beam connecting the tops of multiple piles, the footing generates bending stress and shear stress, so a large cross section is required to withstand it, but the load is transmitted as compressive stress. In this case, the most efficient load transmission is possible and the footing member cross section can be reduced. The concrete section of the footing and the amount of reinforcing bars can be greatly reduced, and at the same time the amount of excavated soil in the ground can be reduced, so the construction cost of the foundation can be greatly reduced and the foundation can be designed economically. .

The second effect of the present invention is that although the slightly inclined pile of the present invention is slightly inclined, the inclination is slight and almost the same as that of a vertical pile. Therefore, it does not generate a large axial resistance force like a slanted pile against the horizontal force acting on the pile head, and large axial force fluctuations due to compression and tension due to the horizontal force do not occur. Sex is not threatened.
Specifically, since this finely inclined pile restricts the inclination angle θ of the pile with respect to the vertical axis to θ = 1/10 (rad) or less at the maximum, the axial force applied to the pile is applied to the pile head. It will not be more than 1/10 of the applied horizontal force. The inclination angle of this finely inclined pile is typically about 1/30 to 1/40 (rad), and it can be said that the axial force fluctuation due to the pile inclination is negligible.

The third effect of the present invention is that, for the same reason as the second point, the horizontal force acting on the pile head does not resist with high axial rigidity like a slant pile. Is almost the same as a vertical pile. As a result, the problem that the horizontal rigidity and resistance force of the pile greatly differ depending on the direction in which the horizontal force acts as in the case of the oblique pile does not occur.
In addition, even when a vertical single pile foundation and multiple pile (slightly inclined) foundations are mixed in one building, the resistance force and rigidity of each pile will vary depending on the direction of the pile foundation and seismic force. There is no unbalanced design or complicated problems, and it is possible to design a seismic design that is reasonably balanced, with all piles resisting horizontal loads almost equally.

  The fourth effect of the present invention is that the short-period component of the ground motion on the supporting ground is not directly transmitted to the foundation by the high axial rigidity of the slant pile, so that the filtering (removal) effect of the short-period component by the soft ground is obstructed. Without the negative effect of sloping piles that increase the acceleration input to the structure. Therefore, adverse effects that adversely affect the seismic safety of the structure can be avoided.

In addition to the above, all the problems pointed out as the problem of inclined piles, for example, the difference between the horizontal displacement of the surface soft ground where the pile foundation is placed during earthquake and the horizontal displacement of the inclined pile with high horizontal rigidity, There is no problem of carrying an extremely large horizontal load due to forced displacement.
In addition, the fixing degree of the pile head can be controlled to be constant regardless of the direction, and an appropriate pile head rigidity can be realized.

Furthermore, since the pile shaft body of the present invention has a substantially vertical pile shaft body, the pile length does not become longer as in the case of a slanted pile, which is highly inclined. Since it is not necessary, it has the effect and advantage of being excellent in workability.

It is explanatory drawing which shows the basic composition of the conventional 1 foundation multiple pile foundation, (1) The longitudinal cross-sectional view of the pile head upper footing which connects the vertical cast-in-place concrete pile and the pile head, (2) Vertical ready-made pile and It is the longitudinal cross-sectional view of the pile head upper footing which connects the pile head. It is a longitudinal cross-sectional view which shows the basic composition of the conventional pile head upper footing which connects a diagonal pile and a pile head. It is explanatory drawing which showed the magnitude of the horizontal force which each slant pile shares in the case of a horizontal force acting on the pile head of the conventional slant pile, (1 left) Pile head of three slant pile When X direction horizontal force is applied to (1 right) When Y direction horizontal force is applied to the pile head of three diagonal piles, (2 left) X direction (pile axis (Parallel direction) When horizontal force is applied (2 right) Y direction (pile axis orthogonal direction) horizontal force is applied to the pile head of the two diagonal piles. It is a figure which shows the Example of 1 foundation 2 piles of this invention, (1) When the 2 pile standing surface is seen from the front direction, (2) When the 2 pile standing surface is seen from the side direction, (A) Pile head plan view, (B) Elevation configuration diagram, (C) Pile tip plan view. It is a figure which shows the Example of 1 foundation 3 pile of this invention, (1) When 3 pile standing surfaces are seen from a front direction, (2) 3 pile pile surfaces are seen from the orthogonal direction of (1) They are (A) pile top plan view, (B) elevation configuration diagram, and (C) pile tip plan view. It is explanatory drawing which shows the positional relationship of the plane of the pile head and pile front-end | tip part in 1 foundation multiple pile of this invention, (2T) The pile head top view of 1 foundation 2 pile, (2B) 1 foundation 2 pile (3T) Pile head plan view of three foundation piles, (3B) Pile tip plan view of one foundation three piles, (4T) Pile head plan view of one foundation four piles Fig. (4B) is a plan view of the tip of a pile of four foundation piles. It is a figure which shows the detailed structure of the pile head vicinity of the Example of this invention, (1) It is a longitudinal cross-sectional view which shows the structure which installed the sliding bearing with a rotation mechanism and the upper frame on the pile head upper footing. (2) The longitudinal cross-sectional view which shows the structure which installed the laminated rubber support and the upper frame on the pile head upper footing. (3) Horizontal sectional view at the position indicated by the arrow A in (1) and (2) above (4) Horizontal sectional view at the position indicated by the arrow B in (1) and (2) above (5) Upper figure (1) It is a horizontal sectional view of the position of arrow C in (2). BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the Example of the "pile head joining apparatus" installed in the pile head of this invention, (1A) The top view seen from the upper part of the joining apparatus which incorporates the rubber layer for rotational displacement absorption of a pile head (1B) Longitudinal sectional view showing the relationship between the above-mentioned joining device and the pile head, (2A) A plan view seen from the top of the pile head joining device that does not incorporate a rubber layer, (2B) The relationship between the above-mentioned joining device and the pile head It is a longitudinal cross-sectional view shown. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the Example of the "pile head joining apparatus" installed in the pile head of this invention, (1A) The top view seen from the upper part of the simple type pile head cap type pile head joining apparatus of reverse concave shape (1B) ) Longitudinal sectional view showing the relationship between the same joining device and the pile head, (2A) Plan view from the top of the ring-shaped pile head joining device around the headband shape, (2B) Relationship between the joining device and the pile head FIG. It is a figure which shows the Example of the "pile head position horizontal connection member" arrange | positioned at the pile head of this invention, (1A) The plane at the time of comprising the pile head position horizontal connection member of 1 foundation 2 piles with a steel plate Fig., (1B) Longitudinal sectional view showing the positional relationship between the same member and pile head, (2A) Plan view when the pile head position horizontal connecting member of two foundation piles is made of reinforced concrete, (2B) Same member A vertical cross-sectional view showing the positional relationship between the pile head and (3A) a plan view when the horizontal connection member of the pile head position of the three foundation piles is made of steel plate, (3B) the positional relationship between the same member and the pile head FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part which is common in each Example.

FIG. 4 shows Example 1 in which Configuration 1 and Configuration 2 of the present invention are applied to two 1 foundation piles. 4 (1) shows the case where the two pile erection surfaces are viewed from the front direction, and FIG. 4 (2) shows the case where the two pile erection surfaces are viewed from the side surface direction (orthogonal direction of FIG. 4 (1)). These are (A) a plan view of the pile head 21, (B) an elevational configuration diagram, and (C) a plan view of the pile tip 23.
The seismic isolation device 5 of FIG. 4 illustrates the case of a sliding bearing with a rotating mechanism, but the same is true if it is replaced with a laminated rubber bearing.

First, as shown in FIGS. 4A and 4A, the two pile heads 21 are driven close to each other, and the distance Dtc between the pile cores of the two adjacent pile heads 21 is as follows. The pile head diameter Do is limited to a range of 1.0 Do <Dtc ≦ 1.5 Do, and is typically arranged at about Dtc≈1.2 Do.
Since the two pile heads 21 are close to each other, the vertical load from the seismic isolation device 5 can be directly transmitted to the two piles as a compressive stress via the pile head upper footing 3. A large bending moment and shearing force are not generated unlike the head top footing, and the pile head top footing 3 can be designed compactly and economically.

4 (1) and (B) in FIG. 4 show a vertical longitudinal section (elevation) configuration from the seismic isolation device upper footing 61 to the pile tip 23 reaching the support layer 11 of the ground 1. ing. The weight of the upper building is first transmitted to the seismic isolation device upper footing 61, which is supported by one seismic isolation device 5. A pile head upper footing 3 that connects the pile head 21 is provided directly below the seismic isolation device 5, and is supported by two pile shaft bodies 25. The pile shaft body 25 is a “slightly inclined pile” that is slightly inclined as close to the vertical axis as possible. The pile tip 23 reaches the support layer 11 of the ground 1, and a necessary depth penetrates into the support layer 11.
The inclination angle θ of the finely inclined pile 25 with respect to the vertical axis is limited to a range of 0 <θ ≦ 1/10 (rad). Typically, as shown in the present embodiment, it is placed in a state of approximately θ in the vicinity of θ≈ 1/30 to 1/40 (rad). The inclination angle of the pile is determined by the difference in the distance between the pile cores at the pile head 21 and the pile tip 23 and the pile length (depth of the support layer 11).

  FIGS. 4C and 4C are plan views of the pile tip 23. FIG. As shown in the figure, in the present invention, the pile separation distance at the pile tip 23 reaching the support ground is placed adjacent to the minimum distance between the pile cores necessary for securing the support force. This is a prerequisite. This is because it is an important condition that the inclination angle of the pile is as close to vertical as possible.

FIG. 5 shows Example 2 in which Configurations 1 and 2 of the present invention are applied to a three-stake foundation. FIG. 5 (1) shows a case where three pile erection surfaces are viewed from the front direction, and FIG. 5 (2) shows a case where they are viewed from the orthogonal direction. FIG. 4 is an elevation configuration diagram, and FIG.
The seismic isolation device 5 of FIG. 5 illustrates the case of a sliding bearing with a rotating mechanism, but the same is true if it is replaced with a laminated rubber bearing.

First, as shown in FIGS. 5 (1) and (2) (A), since the three pile heads 21 are driven in close proximity, the vertical load from the seismic isolation device 5 is applied to the pile head upper footing. 3 can be directly transmitted to the three piles 25 by compressive stress. For this reason, the pile head upper footing 3 can be designed extremely economically and economically.
The pile core distance Dtc of each pile head 21 is the same as that of the two piles of the first embodiment.

(B) of FIG. 5 (1) and (2) has shown the vertical longitudinal cross-section (elevation) structure from the seismic isolation apparatus upper footing 61 to the pile tip 23, A pile head upper footing 3 for connecting the pile heads 21 is provided and supported by three pile shafts. Similar to Example 1, these pile shaft bodies 25 are “slightly inclined piles” that are slightly inclined, and the pile tips 23 reach the support layer 11 of the ground, and the necessary depth is the support layer 11. It penetrates inside.
The limit value of the inclination θ with respect to the vertical axis and the actual inclination of the finely inclined pile 25 are the same as those in the first embodiment, and are placed close to the vertical pile.

  (C) of FIGS. 5 (1) and (2) is a plan view of the pile tip 23. As shown in the drawing, the distance between the piles at the pile tip 23 is the distance between the pile cores that is necessary for securing the supporting force. The piles are adjacent to each other at a distance close to the minimum value of the distance, and the pile shaft has a slight inclination angle and is almost a vertical pile.

FIG. 6 is a view of pile arrangement at a pile head level and a pile tip level for each of the case of a slightly inclined pile 25 of the present invention, which is a 1 foundation 2 pile, 1 foundation 3 pile, 1 foundation 4 pile. A plan view is shown.
In any number of piles, pile placement at the height level of the pile head 21 is close, so the pile head footing can be designed compactly and economically. In each figure of the pile head positions, that is, FIGS. 6 (2T), (3T), and (4T), the outline of the broken line surrounding the outer periphery of the pile head 21 indicates the size of the planar shape of the pile head upper footing 3. On the other hand, in the conventional vertical pile, the planar shape of the magnitude | size surrounding the pile front-end | tip 23 is required, and it turns out that the very big planar shape pile head upper footing was required. As the planar shape increases, the bending moment generated in the footing also increases, so it is necessary to increase the height (depth) of the footing. The conventional pile head upper footing of multiple vertical piles is the upper part of the pile head of the present invention. It had to be much larger than Footing 3.
On the other hand, the planar arrangement at the position of the pile tip 23 penetrating into the support layer of the ground secures the distance between the pile cores between adjacent piles necessary for the bearing force as in the case of the conventional vertical pile, so the tip bearing capacity of the pile Is sufficiently secured.

  In the present invention, although the pile is slightly inclined, the inclination angle is typically about 1/30 to 1/40 (rad) and is almost vertical, so the pile head is horizontal like a conventional inclined pile. The axial resistance force of the pile is not generated by the force, and the problem of fluctuation of the pile axial force due to the horizontal load and increase of the pile tip load does not occur.

  Moreover, since the conventional inclined pile has a large inclination angle, the length of the pile shaft body is considerably longer than that of the vertical pile (the inclination angle is 30 ° to 45 ° and the pile length is increased by 15% to 40%). However, since the slightly inclined pile 25 of the present invention is almost vertical, the length of the pile shaft body is almost the same as that of the vertical pile, which is economically more advantageous than the conventional oblique pile. .

In the conventional vertical pile, when the position of the vertical load P acting on the pile head 21 is deviated by δ from the pile core, the P-δ moment acts on the pile head 21 and the pile alone (underground beam) None) has an unstable structural framework, such as a large horizontal displacement of the pile, and there is a problem that it cannot be a stable pile foundation without an underground beam connecting the pile head 21.
On the other hand, the foundation of the slightly inclined pile 25 of the present invention has a plurality of piles which are driven in a stable shape with a widening end with the tips widened outward, and the pile head 21 at the top is the pile head upper footing. 3 because it is integrated with the vertical load, it forms a stable frame shape against the vertical load. Even if there is a deviation of the vertical load acting position due to construction errors, etc., the pile foundation itself It is possible to cope with pile core misalignment by automatically adjusting the load axial force, realizing a highly safe pile foundation that constitutes a stable structural system (framework) without underground beams. .

  FIG. 7 shows the configuration in the vicinity of the pile head 21 of the present invention in detail. FIG. 7 (1) shows a sliding bearing 51 with a rotation mechanism on the pile head 21 and the pile head upper footing 3. FIG. 7B is a longitudinal cross-sectional view showing a configuration in which the laminated rubber support 52 and the upper housing 6 are installed on the pile head 21 and the pile head upper footing 3. 7 (3) is a horizontal sectional view at the position indicated by the arrow A in FIGS. 7 (1) and 7 (2), FIG. 7 (4) is a horizontal sectional view at the position indicated by the arrow B, and FIG. The horizontal sectional view of a position is shown.

As shown in FIGS. 7 (1) and (2), in order to keep the horizontal position of the pile head 21 evenly below the upper end of the pile head placed in close proximity and to keep the horizontal displacement at the time of an earthquake the same. The pile head position horizontal connection member 31 is arranged. The portion of the pile head position horizontal connecting member 31 that contacts the side surface of the pile head 21 is tapered so as to transmit a horizontal force but does not restrain the rotational deformation of the pile head 21 (see FIG. 10 (2B) enlarged portion). Is provided.
Moreover, the pile head joining apparatus 4 is arrange | positioned on the upper surface of the pile head 21, The fixed degree of joining of the pile head 21 and the pile head upper footing 3 is adjustable with the rotational performance, and the pile head joining apparatus 4 The pile head pin or the pile head semi-rigid joint is realized by the rotational performance of
The pile head upper footing 3 is arranged on the upper part of the pile head 21, but since the two pile heads 21 are close to each other, the sliding bearing isolator 51 with rotating mechanism or the laminated rubber bearing isolator The vertical load from 52 is transmitted to the two pile heads as compressive stress in the pile head upper footing 3, and the pile head upper footing 3 does not generate a large bending moment or shearing force. Designed extremely compact.
Furthermore, the upper part of the seismic isolation device 51 or 52 is integrated with the upper housing 6 via the seismic isolation device upper footing 61.

FIGS. 7 (3) to 7 (5) show horizontal sectional views taken along arrows A, B, and C in FIGS. 7 (1) and 7 (2). In particular, as clearly shown in FIG. 7 (5), since the horizontal section of the seismic isolation device 5 and the planes of the two pile heads located below are closely overlapping, the vertical of the seismic isolation device 5 It can be seen that the load is transmitted to the two piles without difficulty.
Further, since the pile head joining device 4 is arranged on the upper surface of the pile head 21, the rotational rigidity of the pile head 21 is kept constant regardless of the direction due to the effect (rotational rigidity) of this device. I'm leaning. Therefore, the load ratio of the horizontal load of all the piles becomes equal regardless of the direction, and all the piles evenly resist the horizontal force of the entire building, and the seismic design of the piles is rationalized.

FIG. 8 shows an embodiment of the pile head joining devices 4A and 4B installed on the pile head 21 of the present invention.
FIG. 8 (1A) is a plan view seen from the top of the pile head joining device 4A incorporating the rubber body 41 for absorbing pile head rotational displacement, and FIG. 8 (1B) shows the pile head joining device 4A and the pile head. 3 is a longitudinal sectional view showing a positional relationship of a part 21.
Although the present Example has shown the case where a ready-made pile is employ | adopted, the cavity part 210 of the plane center part of a ready-made pile head is filled with high-strength mortar or high-strength concrete. Since the upper end of the pile head is slightly inclined according to the slight inclination of the pile body, the upper surface is finished horizontally and flatly with either high-strength mortar, high-strength concrete, or high-strength self-leveling material, On top of that, the pile head joining device 4A is installed. A high-strength self-leveling material is a gypsum-based self-leveling material, a high-performance AE damping agent or a high-performance AE damping agent having a flow value of 250 mm or more as a flow value at the time of construction before curing, and a compressive strength of 30 N / mm 2 or more after curing. It is filled with a fluidizing agent, has a high fluidity of a slump flow of 500 mm or more, and includes high-strength concrete or high-strength mortar with a compressive strength of 30 N / mm 2 or more after curing.
In this pile head joining device 4A, a horizontal stopper 42 has a slight gap and surrounds the outer peripheral surface of the pile head 21. When horizontal deformation occurs in the rubber body 41, it comes into contact with the outer peripheral surface of the pile head 21. As a result, the horizontal displacement beyond this gap is constrained and the rotational deformation of the rubber body is not disturbed.
Due to the function of the rubber body 41, the short-period component of the ground motion is removed by a filter, so that a certain amount of seismic isolation effect is also exhibited.

A well-shaped two-way shear force (horizontal + vertical) transmission PBL dowel plate 43 is disposed on the top of the pile head joining device 4A. A PBL dowel is a steel plate in which a large number of holes having a diameter of about 40φ to 50φ are arranged in a steel plate. By filling the inside with concrete, a two-surface shearing mechanism is formed at the interface with the concrete. A combination of steel plate thickness and concrete strength can transmit very large shear forces. Moreover, the conventional stud bolt does not exhibit the proof strength unless it is deformed, whereas the PBL gibber has an extremely high rigidity and hardly deforms.
Further, as shown in FIG. 8 (1B), the height of the hole provided in the PBL dowel plate (steel plate) 43 of the present invention is 30 for the X-direction hole 44X and the Y-direction hole 44Y of the PBL dowel. The height is different by about 40 mm, and the rebar of the upper footing is penetrated through this hole and can be arranged by crossing. By penetrating the reinforcing bar through the hole of the PBL dowel plate (steel plate) 43, the plastic deformation performance as the dowel is improved, and at the same time, the integration with the footing can be reasonably performed.

FIG. 8 (2A) is a plan view seen from the top of a pile head joining device 4B of a type that does not contain a rubber body 41, and FIG. 8 (2B) is a longitudinal section showing the positional relationship between the pile head joining device 4B and the pile head 21. FIG. In this apparatus, since the rubber body 41 is omitted, the rotational rigidity of the pile head joining apparatus is increased, the rotational deformation performance is also reduced, and the fixing degree of the pile head is increased. However, when the horizontal load is increased, the pile head is increased. When the part comes out, the fixing degree is lowered and the function as a semi-rigid joint is exhibited. Although the pile head rotation performance is lower than that of the joining device 4A of FIG. 8 (1B), it is a low-cost device, and thus has an advantage in terms of economy.
Moreover, like the joining device 4A of FIG. 8 (1B), it has a PBL dowel plate 43 in the upper part, and it can be rationally integrated with the footing. Since no fixed reinforcing bars are required, on-site welding is also unnecessary, the arrangement of bars is simplified, and the workability of the pile head 21 is extremely excellent. The inner cavity portion 210 of the pile head is filled with high-strength concrete or the like, and the upper surface 201 is horizontally finished, as in the pile head joining device 4A.

FIG. 9 shows an example in which an existing simple pile head joining device is applied to the upper end of the slightly inclined pile 25. FIG. 9 (1A) shows a reverse pile-shaped simple pile head cap 4C as viewed from above. 9B is a longitudinal sectional view showing the positional relationship between the pile head joining device 4C and the pile head 21. FIG.
As in Example 5, the cavity 210 at the center of the plane of the pre-made pile head is filled with high-strength mortar or high-strength concrete, and the upper end of the pile head is leveled with a high-strength self-leveling material or the like. And after finishing flat, the pile head joining apparatus 4C is installed, and the concrete of the pile head upper footing 3 is placed so as to surround the main joining apparatus 4C around and above the pile head joining apparatus 4C.
This pile head joining device is made of a cap-shaped thin steel plate that encloses an extremely simple pile head. The pile head is fixed with a semi-rigid joint with a considerably high degree of fixing, but is excellent in workability and economy.

FIG. 9 (2A) is a plan view of the ring-type pile head joining device 4D that surrounds the periphery of the pile head in a headband shape, and FIG. 9 (2B) is a positional relationship between the pile head joining device 4D and the pile head 21. FIG.
In this embodiment, the cavity 210 at the center of the plane of the ready-made pile head is filled with high-strength mortar or high-strength concrete and the upper surface is finished flat, but the repair of leveling the upper end of the pile head is omitted. doing. The principle of this pile head joining device 4D is that the apparent equivalent rigidity is lowered by the donut-shaped ring which is arranged on the outer periphery of the pile head and integrated with the upper footing of the pile head comes out of the pile head 21. This is because a slight inclination (levelness) of the upper surface of the pile body inside the ring body 4D is not a problem.
Semi-rigid joining with a considerably high pile head fixing degree by this pile head joining device.
Reference numeral 29 indicates a horizontal line in the vicinity of the upper end of the pile head.

  FIG. 10 shows an example of a “pile head position horizontal connecting member” arranged on the pile head 21 of the present invention, and FIGS. 10 (1A) and (1B) are one foundation two piles made of steel plates. Pile head position horizontal connecting member 31, FIGS. 10 (2 A) and (2 B) are pile foundation position horizontal connecting members 32 of two foundations made of reinforced concrete, and FIGS. 10 (3 A) and (3 B) are made of steel plates. The pile head position horizontal connection member 31 of the 1 foundation 3 pile which was done is shown, respectively.

This pile head position horizontal connection member 31, 32 is a role of a holder that holds the position constant so that a plurality of piles within one foundation maintain the same horizontal position, and holds the horizontal force evenly. To fulfill. However, in order to transmit the horizontal force but not restrain the rotational deformation of the pile head 21, the members 31 and 32 are the side surfaces of the pile head 21 as shown in the enlarged portion in a circle of FIG. 10 (2 B). A taper is provided in a portion that contacts the.
Although this pile head position horizontal connection member 31 and 32 may be installed at the time of construction around the pile head 21 after pile driving, if it uses as a template which keeps a pile head position as a target at the time of pile driving It becomes possible to construct the pile head position and the pile head interval with high accuracy. In particular, the pile-head connecting member 31 also serving as a template is effective for positioning the pile head 21 in the case of the three piles shown in FIG. 10 (3A).

  In the case of the pile head position horizontal connection member 32 of 1 foundation 2 piles made of reinforced concrete shown in FIGS. 10 (2A) and (2B), the pile head position horizontal connection member 32 is first constructed on the pile head 21, and then The pile head joining device 4 may be installed, and the pile head footing 3 may be constructed thereon.

As described above, the use of the slightly inclined pile according to the present invention not only greatly reduces the size and rationalizes the pile head footing, but also the horizontal rigidity of the pile compared to the case where a plurality of vertical piles are used on a single foundation. And the conventional unreasonableness that pile head fixing degree varies greatly depending on the direction in which the seismic force acts can be eliminated.
In addition, the conventional slant pile has a large axial force increase / decrease in the pile shaft body due to the horizontal seismic force acting on the pile head, and the horizontal rigidity / resistance force of the pile varies greatly depending on the direction of the seismic force. There was a problem with a large unreasonable structural mechanics such as (especially in the case of two piles) (an unreasonable reason for oblique piles being too effective against horizontal force), but this mechanical problem can only be solved In addition, the economical problem that the pile shaft length becomes long, and the difficulty in construction for tilting the pile at the time of pile driving can be solved.
This construction method can be applied to all building structures, but the effect is particularly remarkable when applied to seismic isolation structures with a very high vertical load per column.

1: Ground (Pile surrounding ground)
11: Support layer 2: Pile
201: Horizontal repair part of pile head upper end part 21: Pile head 210: Filling part inside pile head 22: Pile shaft 23: Pile tip 24: Slope pile 25: Slightly inclined pile 29: Horizontal line in the vicinity of pile head upper part

3: Pile head upper footing 31: Pile head position horizontal connecting member (steel)
32: Pile head position horizontal connecting member (made of reinforced concrete)
4: Pile head joining device 4A: Pile head joining device (pile head rotational displacement absorbing rubber body built-in type)
4B: Pile head joining device (4A same type and rubber body omitted type)
4C: Pile head joining device (reverse concave shape simple pile head cap)
4D: Pile head joining device (ring-shaped pile head surrounding ring type)
41: Pile head rotational displacement absorbing rubber body 42: Horizontal stopper 43: Two-direction shearing force (horizontal + vertical) transmission PBL gibber plate 44X: PBL diver X-direction hole 44Y: PBL diver Y-direction hole

5: Seismic isolation device 51: Sliding bearing with rotating mechanism 52: Laminated rubber bearing

6: Upper frame 61: Seismic isolation device upper footing 62: Upper frame-column 63: Upper frame-beam

7: Vertical load acting on the pile foundation (upper part) 71: Vertical load borne by each pile 8: Horizontal force acting on the pile head 81: Magnitude of horizontal force (and horizontal rigidity) borne by the pile

Claims (6)

It is a pile foundation that supports the vertical load of one pillar or one seismic isolation device of seismic isolation structure or earthquake resistant structure with multiple piles,
The distance from the adjacent pile at the tip of the pile in the supporting layer ground is D1 + D2 or more and D2 + 1m or more at each pile core distance when the pile shaft diameter is D1 and the pile tip diameter is D2.
The pile heads are arranged within a range of 1.0 Do <Dtc ≦ 1.5 Do, where Dtc is the distance between each pile core of adjacent piles and Do is the pile head diameter.
And when the inclination of the pile axis with respect to the vertical axis is θ, the pile is θ ≦ 1/10 (rad), and the fine inclination is inclined within the range of both conditions of the pile tip and the pile head. In pile foundations that are considered piles,
The pile head horizontal connection members that connect and integrate the horizontal positions of adjacent pile heads so that the pile head displacement during an earthquake is the same horizontal displacement, and that do not restrict the rotational deformation of the pile heads. A pile foundation characterized by being placed near the top of the head . It is a pile foundation that supports the vertical load of one pillar or one seismic isolation device of seismic isolation structure or earthquake resistant structure with multiple piles,
The distance from the adjacent pile at the tip of the pile in the supporting layer ground is D1 + D2 or more and D2 + 1m or more at each pile core distance when the pile shaft diameter is D1 and the pile tip diameter is D2.
The pile heads are arranged within a range of 1.0 Do <Dtc ≦ 1.5 Do, where Dtc is the distance between each pile core of adjacent piles and Do is the pile head diameter.
And when the inclination of the pile axis with respect to the vertical axis is θ, the pile is θ ≦ 1/10 (rad), and the fine inclination is inclined within the range of both conditions of the pile tip and the pile head. In pile foundations that are considered piles,
A pile head joining device that allows rotational deformation of the pile head is arranged at the top of each pile head,
A pile head upper footing that integrates the plurality of piles at the top is configured,
A pile foundation characterized in that the pile head upper footing is connected to and integrated with an upper frame or the seismic isolation device. It is a pile foundation that supports the vertical load of one pillar or one seismic isolation device of seismic isolation structure or earthquake resistant structure with multiple piles,
The distance from the adjacent pile at the tip of the pile in the supporting layer ground is D1 + D2 or more and D2 + 1m or more at each pile core distance when the pile shaft diameter is D1 and the pile tip diameter is D2.
The pile heads are arranged within a range of 1.0 Do <Dtc ≦ 1.5 Do, where Dtc is the distance between each pile core of adjacent piles and Do is the pile head diameter.
And when the inclination of the pile axis with respect to the vertical axis is θ, the pile is θ ≦ 1/10 (rad), and the fine inclination is inclined within the range of both conditions of the pile tip and the pile head. In pile foundations that are considered piles,
The pile head horizontal connection members that connect and integrate the horizontal positions of adjacent pile heads so that the pile head displacement during an earthquake is the same horizontal displacement, and that do not restrict the rotational deformation of the pile heads. Located near the top of the head,
A pile head joining device that allows rotational deformation of the pile head is arranged at the top of each pile head,
A pile head upper footing that integrates the plurality of piles at the top is configured,
A pile foundation characterized in that the pile head upper footing is connected to and integrated with an upper frame or the seismic isolation device . In the pile foundation according to any one of claims 1 to 3,
On the upper surface of the pile head, a pile head joining device that can absorb rotational deformation of the pile head by incorporating a rubber layer alone or a laminated rubber body is installed,
The pile head joining device is disposed on the top surface of the pile head that is slightly inclined and is repaired horizontally with either high strength mortar, high strength concrete, or high strength self-leveling material. A featured pile foundation. In the pile foundation according to any one of claims 1 to 3,
On the upper surface of the pile head, a pile head joining device that can absorb rotational deformation of the pile head by incorporating a rubber layer alone or a laminated rubber body is installed,
As the pile head joining device, a cylindrical horizontal stopper fixed to the outer peripheral portion of a horizontal steel plate placed on the upper surface of the pile head and surrounding with a slight gap around the outer peripheral surface of the pile head, or A pile foundation characterized by using a thin steel plate pile head cap shaped into an inverted concave shape on the top surface of the pile head or a headband shaped ring-shaped joining member fitted around the pile head . In the pile foundation according to claim 4 or claim 5,
The pile head joining apparatus has a PBL dowel plate provided with a steel plate having a number of holes in two directions in two directions,
A pile foundation in which a pile head and a pile head upper footing are connected and integrated by the pile head joining device .