JP2022171931A - Joint structure for pile and superstructure, and structural body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint structure for piles and superstructures, and a structural body that can reduce the horizontal displacement of a pile head even if external force that displaces the pile head horizontally is applied.

SOLUTION: A joint structure for piles and superstructures includes: piles that are installed in the ground; a superstructure that is built above the piles; joints that join the piles and the lower section of the superstructure; and a solidified body formed around the piles and the joints and formed by filling a filler into a pit excavation formed in the ground. The joints are installed inside the pit excavation. The solidified body is embedded in the ground in a state where a side face of the solidified body is in contact with the ground, and is formed of a filler excluding concrete that has a uniaxial compressive strength higher than that of the ground and less than 18000[N/mm²].

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2023,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a joint structure between a superstructure used in a structure and piles embedded in the ground, and a structure constructed using these structures.

Conventionally, in structures such as building structures or civil engineering structures, a structure in which a footing is provided at the top of the pile is known as a structure of the joint part between the pile embedded in the ground and the column erected on the pile. It is A foundation beam is fixed to the footing in the horizontal direction, and a column is fixed in the vertical direction. In this case, the foundation beams are installed in a grid pattern in the horizontal direction of the ground, and connect the heads of a plurality of piles (hereinafter referred to as pile heads). Therefore, horizontal displacement of one pile head is strongly supported by the foundation beam and other pile heads. Therefore, horizontal displacement of the base of the column erected on the pile is suppressed. Therefore, the structure is stable even when subjected to horizontal external forces such as seismic loads and wind loads.

On the other hand, since a structure has foundation beams, it requires the steps of excavation, reinforcing bars, formwork, concrete placement, formwork removal, and backfilling during its construction. Therefore, when constructing a structure, many materials were required, and the construction took a long period of time, resulting in a problem of high cost.

In order to solve the above problems, a joint structure between a pile and an upper structure as disclosed in Patent Document 1, for example, is used. This joint structure directly joins the head of the pile and the column, and can transmit the vertical force, horizontal force, and bending moment transmitted from the column to the pile, eliminating the need for the foundation beams of the above-mentioned conventional structures. is. The joint structure disclosed in Patent Document 1 has a structure capable of efficiently adjusting the positions of the piles and the columns against horizontal and vertical positional deviations, and fixing the columns and the piles. This allows the structure to reduce costs, steps, materials and labor associated with constructing foundation beams.

JP-A-2007-9438

In the joint structure between the pile and the superstructure disclosed in Patent Document 1, since no foundation beam is provided between the two piles, there is no structure for supporting the pile head in the horizontal direction. Therefore, there is a problem that the pile head tends to move horizontally due to the horizontal force and bending moment applied to the column. Furthermore, the structure having the joint structure of the pile and the superstructure disclosed in Patent Document 1 analyzes the superstructure, the pile and the ground integrally at the design stage, so that the pile head is It is necessary to calculate the amount of deformation and the load applied to the pile head, and determine the safe material and cross section of each member according to the calculation results. Therefore, in a structure that employs a joint structure of piles without foundation beams and superstructures, there is a problem that at least one of the scale of the superstructure and the ground conditions has its application limit. In addition, even if the joint structure of piles and superstructures can be applied to structures, there is a problem that the cross sections of piles, columns, and beams increase compared to conventional structures having underground beams. rice field.

For example, the joint structure between the pile and the superstructure disclosed in Patent Document 1 is difficult to apply to structures with three stories or more as the superstructure, and it is not applicable in areas with soft ground such as clay. There was a problem of difficulty.

The present invention was made to solve the above problems, and in a joint structure between a pile having no foundation beam between the pile heads and an upper structure, even if an external force that displaces the pile heads in the horizontal direction is applied, It is an object of the present invention to provide a joint structure and structure between a pile and a superstructure that can reduce the horizontal displacement of the pile head.

A joint structure between a pile and a superstructure according to the present invention includes a joint that joins a pile installed in the ground, a superstructure built above the pile, and a lower end of the pile and the superstructure. and a solidified body that is formed around the pile and the joint and is formed by filling a root cutting formed in the ground with a filler, and the joint is inside the root cutting The solidified body is embedded in the ground with the side surface of the solidified body in contact with the ground, and the uniaxial compressive strength is higher than that of the ground and less than 18000 [N/mm ² ] concrete. It is formed by the above filler except for

A structure according to the present invention includes the joint structure between the pile and the superstructure.

According to the present invention, the pile head can be enlarged by installing the solidified body around the pile and embedding the solidified body using a filler other than concrete in the ground. As a result, even when the pile head receives a force that displaces it in the horizontal direction, the ground receives the force from the embedded solidified body, so the area of the ground that receives the force increases. Therefore, when the pile head is displaced in the horizontal direction, the ground is less likely to be deformed, and the horizontal displacement of the pile head on which the solidified body is installed is reduced. Therefore, the structure provided with the joint structure of the pile and the superstructure can be made larger than before, and the range of application to soft ground is widened.

1 is a perspective view of a structure 100 including a joint structure 10 for piles and superstructures according to Embodiment 1. FIG. 1 is a cross-sectional view of a joint structure 10 of a pile and an upper structure according to Embodiment 1. FIG. FIG. 2 is a schematic diagram showing a reaction force generated in a pile 50 and a solidified body 40 when a horizontal load P is applied to the upper structure 30 of FIG. 1; FIG. 5 is an explanatory view of the action of the joint structure 10 between the pile and the superstructure when a material having sufficiently high strength is used for the solidified body 40; FIG. 5 is an explanatory view of the action of the joint structure 10 between the pile and the superstructure when using a material with low strength for the solidified body 40; FIG. 5 is an explanatory view of the action of the joint structure 10 between the pile and the upper structure when the same soil as the ground 90 is backfilled as the solidified body 40; FIG. 5 is a diagram showing experimental results of measuring a horizontal displacement amount y when a horizontal load P is applied to the joint structure 10 between the pile and the superstructure according to Embodiment 1; FIG. 4 is a cross-sectional view when the ground 90 around the pile-superstructure joint structure 10 according to Embodiment 1 subsides; FIG. 4 is a cross-sectional view of a joint structure 10a between a pile and an upper structure according to a modification of Embodiment 1; FIG. 4 is a cross-sectional view of a joint structure 10b between a pile and an upper structure according to a modification of Embodiment 1; FIG. 4 is a cross-sectional view of a joint structure 10c between a pile and an upper structure according to a modification of Embodiment 1; FIG. 10 is a cross-sectional view of a joint structure 10d between a pile and an upper structure according to a modification of the first embodiment; FIG. 4 is a cross-sectional view of a joint structure 10e between a pile and an upper structure according to a modification of Embodiment 1; 10 is a cross-sectional view of a joint structure 10f between a pile and an upper structure according to a modification of Embodiment 1. FIG. FIG. 4 is a cross-sectional view of a joint structure 10g between a pile and an upper structure according to a modification of Embodiment 1;

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below based on the drawings. Parts with the same reference numerals in each figure represent the same or corresponding parts, which are common throughout the specification. Moreover, the forms of the constituent elements appearing in the entire specification are merely examples, and the present invention is not limited only to the descriptions in the specification. In particular, the combination of components is not limited only to the combinations in each embodiment, and the components described in other embodiments can be applied to other embodiments. Furthermore, when there is no particular need to distinguish or specify a plurality of parts of the same type that are distinguished by subscripts, the subscripts may be omitted. Also, in the drawings, the size relationship of each component may differ from the actual size.

Embodiment 1.
FIG. 1 is a perspective view of a structure 100 having a joint structure 10 between a pile and an upper structure according to Embodiment 1. FIG. FIG. 2 is a sectional view of the joint structure 10 of the pile and superstructure according to the first embodiment. 1 and 2 schematically show a joint structure 10 between a pile and a superstructure and a structure 100. FIG. The structure 100 means the whole thing formed by joining the pile 50 and the superstructure 30, and comprises at least one joining structure 10 between the pile and the superstructure shown in FIG. In addition, the structure 100 does not include a member that connects the joint structure 10 between the pile and the superstructure and other structures that constitute the structure 100 in the horizontal direction.

For example, the structure 100 is an architectural structure or a civil engineering structure that does not have structures such as foundation beams (underground beams) that connect the joint structures 10 of piles and superstructures. That is, the structure 100 has a one-pillar-one-pile structure in which one pile is connected to one pillar 31 . Note that the structure 100 shown in FIG. 1 is an example, and the upper structure 30 may be provided with other structural members.

The pile-superstructure joint structure 10 shown in FIG. 2 is the structure of the part that joins the pile 50 installed in the ground 90 and the column 31 that constitutes the lower end of the superstructure 30. A connector 60 is joined to the lower end of the pillar 31 , and the connector 60 covers the pile head 51 that is the upper end of the pile 50 to form the joint 20 . A solidified body 40 is installed around the joint 20 . The solidified body 40 is surrounded by the ground 90 and is in contact with the solidified body 40 . In the structure 100, only the ground 90 or only members extending in a direction intersecting the imaginary line connecting the ground 90 and the solidified bodies are arranged between the joint structures 10 between the adjacent piles and the superstructure. ing. That is, the structure 100 does not have a structure or member such as a foundation beam that connects between the solidified bodies of the joining structure 10 of the adjacent piles and superstructures.

The upper structure 30 is mainly composed of columns 31 and beams 32 connecting the columns 31 . The column 31 constitutes the lower end of the upper structure 30 and is made of material such as H-section steel or steel pipe. A connector 60 is joined to the lower end of the column 31 by joining means such as welding or bolting. In FIG. 2, the connector 60 is configured by joining a cylindrical portion 62 and a top plate 61 by joining means such as welding. constitutes

The piles 50 are, for example, steel pipe piles or concrete piles installed in the ground 90 and form a pile foundation that supports the superstructure 30 . The pile 50 is installed such that its longitudinal direction is oriented vertically and the lower end 52 reaches the support layer of the ground 90 . The cross-sectional area and length of the pile 50 are appropriately set according to the scale of the upper structure 30 .

As shown in FIG. 2, the pile head 51 of the pile 50 is covered with a connector 60 to join the superstructure 30 and the pile 50 together. In FIG. 2, there is no gap between the pile head 51 of the pile 50 and the connector 60, so that they are in contact with each other, but a gap may be provided in practice. A top plate 61 forming the upper surface of the connector 60 is provided with, for example, a hole (not shown), and is formed so that a filler can be injected through the hole. The filler filled from the hole fills the gap between the connector 60 and the pile head 51 of the pile 50 and solidifies. The load applied to the superstructure 30 is transmitted to the pile 50 through the solidified filler filling the gap between the connector 60 and the pile head 51 of the pile 50 . In addition, materials, such as concrete, can be used for a filler, for example. In Embodiment 1, concrete is used as the filler, and superstructure 30 and pile 50 are jointed by concrete filling. A portion where the column 31 of the upper structure 30 and the pile head portion 51 of the pile 50 are joined is called a joint portion 20 .

As shown in FIG. 2 , a solidified body 40 is installed around the joint 20 . The solidified body 40 is arranged to surround the side surface of the joint 20 and is in contact with the joint 20 . The solidified body 40 has a trapezoidal outer shape in cross section. That is, the upper surface 41 of the solidified body 40 is formed wider than the lower surface 42, and this is the same in the horizontal direction orthogonal to the viewpoint shown in FIG. A side surface 43 of the solidified body 40 is a surface that slopes toward the joint portion 20 side from the upper surface 41 toward the lower surface 42 .

The solidified body 40 is wider in the horizontal direction than the pile head 51 which is the upper end of the pile 50, and is wider than the joint 20 as well. When an external force is applied to the upper structure 30 and a horizontal load is applied to the pile head 51 , the load is applied to the ground 90 from the joint 20 via the solidified body 40 . At this time, the ground 90 can receive the load over a wider area than when the load is directly applied from the joint 20 . Therefore, horizontal displacement of the pile head 51 is suppressed.

The solidified body 40 is installed by excavating the ground 90 around the joint 20 , forming a root cut 92 opening to the surface 91 , and injecting a filling material into the root cut 92 . That is, the solidified body 40 is formed by solidifying the filling material filled in the root cutting 92 . The filler is, for example, concrete, mortar, solidified steel slag, soil improvement material mixed with cement, or solidified soil cement.

The root cutting 92 is formed by excavating the ground 90 . That is, the root cutting 92 is not formed by placing a predetermined distance from the side surface 21 of the joint portion 20 around the joint portion 20 and piling up what constitutes the ground 90 such as soil. When the root cutting 92 is formed by holding soil or the like on the ground 90, the side surface 93 of the root cutting 92 requires a process for increasing the strength of the ground 90 such as compaction. Therefore, there is a concern that unnecessary work is increased in forming the root cutting 92 by embankment, increasing the cost and prolonging the construction period. Therefore, the excavation 92 is preferably formed by excavating the surface 91 of the ground 90, and the surface 91 of the ground 90 may be leveled and compacted before excavation. By doing so, the strength of the ground 90 around the solidified body 40 is increased, and the horizontal displacement of the pile head 51 is further suppressed.

(Action of Solidified Body 40 of Joint Structure 10 Between Pile and Superstructure)
FIG. 3 is a schematic diagram showing reaction forces generated in the piles 50 and the solidified body 40 when a horizontal load P is applied to the upper structure 30 of FIG. FIG. 3 shows a cross section including the central axis of pile 50 . When a horizontal load P is applied to the upper structure 30 , the load is transmitted from the column 31 to the joint 20 , and from the joint 20 to the pile head 51 and the solidified body 40 . The load transmitted to the pile head 51 and the solidified body 40 is transmitted to the ground 90 in contact with the pile 50 and the solidified body 40 and receives reaction force from the ground 90 .

When a horizontal load is applied to the pile head 51 , the pile 50 is displaced so as to rotate about the lower end 52 of the pile 50 or a point between the pile head 51 and the lower end 52 . Similarly, the solidified body 40 is also displaced so as to rotate about the lower end 52 of the pile 50 or the point between the pile head 51 and the lower end 52 . Therefore, the solidified body 40 receives a reaction force f1 from the ground 90 in the horizontal direction to the side surface 43 and a reaction force f3 to the lower surface 42 from the ground 90 on the lower side. In addition, the pile 50 receives a reaction force f2 in the horizontal direction from the ground 90 to the pile side surface 53 located below the bottom surface 42 of the solidified body 40 . Although the reaction force f2 depends on the rigidity and length of the pile 50, it is generally distributed such that it is large at the pile head 51 side and becomes smaller toward the lower end 52. As shown in FIG.

Moreover, since the side surface 43 of the solidified body 40 parallel to the horizontal load P is in contact with the ground 90, it receives a reaction force f5 due to friction. Similarly, the lower surface 42 of the solidified body 40 also receives the reaction force f4 due to friction in the horizontal direction. Displacement of the solidified body 40 and pile 50 is suppressed by receiving reaction forces indicated by f1 to f5. In particular, the solidified body 40 is positioned at the upper end of the pile 50 and is horizontally supported by the ground 90 in contact with the side surface 43, thereby suppressing displacement.

4 to 6 are explanatory views of the operation of the pile-superstructure joint structure 10 when a horizontal load P is applied to the superstructure 30 of FIG. 4 to 6, (b) displayed on the lower side shows the same cross section as in FIG. 1, and (a) displayed on the upper side is a plan view of the joint structure 10 between the pile and the superstructure. It is a diagram. 4 to 6, the resistance force that the solidified body 40 receives in the horizontal direction will be described by considering only the reaction force f1 among the reaction forces f1 to f5 in FIG.

FIG. 4 is an explanatory view of the action of the joint structure 10 between the pile and the superstructure when a material having sufficiently high strength is used for the solidified body 40. As shown in FIG. The behavior of the joint structure 10 between the pile and the superstructure changes with respect to the horizontal load P applied to the superstructure 30 depending on the strength of the material used for the solidified body 40 . That is, if the strength of the material forming the solidified body 40 is high, the solidified body 40 receives the horizontal load from the joint 20 without breaking, and the ground 90 receives the horizontal load from the solidified body 40 . As a result, the horizontal displacement of the pile head portion 51 is suppressed depending on the strength of the ground 90 and the horizontal projected area of the solidified body 40 .

Here, as shown in FIG. 3, P is the horizontal component of the external force applied to the upper structure 30, B1 is the horizontal width of the upper surface 41 of the solidified body 40, and B2 is the horizontal width of the lower surface 42 of the solidified body 40. , H is the height from the lower surface 42 to the upper surface 41 of the solidified body 40 , and D is the diameter of the joint 20 . The diameter D of the joint 20 is the cross-sectional diameter of the cylindrical portion 62 of the joint 60 . In Embodiment 1, the upper end of connector 60 is aligned with upper surface 41 of solidified body 40 , and the lower end of connector 60 is aligned with lower surface 42 of solidified body 40 . Further, let A1 be the projected area of the internal structure 70 inside the solidified body 40 in the horizontal direction parallel to the surface of the ground, and let A2 be the projected area of the solidified body 40 horizontally projected.

When an external force is applied to the upper structure 30 , the horizontal load P is transmitted from the column 31 to the joint 20 and further transmitted to the pile head 51 and the solidified body 40 . A horizontal load P is supported by the ground 90 on the side surface 43 of the solidified body 40 . Therefore, the horizontal resistance force that the solidified body 40 receives is the ground reaction force corresponding to the projected area of the solidified body 40 in the horizontal direction. At this time, the pressure receiving area of the ground 90 that receives the force from the solidified body 40 is represented by A2=(B1+B2)H/2. Assuming that the uniaxial compressive strength of the ground 90 is qu, the ultimate load Pu1 that the ground 90 can receive in the horizontal direction in the state of FIG.
Pu1=qu·A2 (1)
can be expressed as

FIG. 5 is an explanatory view of the operation of the joint structure 10 between the pile and the superstructure when a material having a low strength is used for the solidified body 40. As shown in FIG. When the ultimate shear stress τ of the solidified body 40 is sufficiently high, the horizontal load P is supported by the ground 90 in contact with the side surface 43 of the solidified body 40, as shown in FIG. However, when the ultimate shear stress τ of the solidified body 40 is low, the solidified body 40 undergoes shear failure when the load is transmitted from the joint 20 to the solidified body 40 . Specifically, as shown in FIG. 5(a), the solidified body 40 undergoes shear fracture at the boundary L between the portion receiving the load from the joint 20 and the portion not receiving the load. Therefore, the area of the ground 90 that receives the horizontal load P after the solidified body 40 shear fractures is the area A1=D·H of the joint 20 projected in the horizontal direction. That is, when the strength of the solidified body 40 is low, the ground 90 for the entire projected area of the solidified body 40 cannot receive the horizontal load P. 5, the dimensions of the solidified body 40 are the same as in FIG.

Therefore, in FIG. 5, the horizontal load P is supported by the shear strength S of the solidified body 40 and the ground 90 corresponding to the area of the joint 20 projected in the horizontal direction. Assuming that the compressive strength of the material of the solidified body 40 is the compressive strength K, the ultimate shear stress τ of the solidified body 40 is expressed by τ=K/10. Further, since the shear cross-sectional area _AK of the solidified body 40 is the cross-sectional area of the boundary L in FIG.
A _K =2(B1/2+B2/2)H/2=(B1+B2)H/2=A2
is represented by Therefore, the shear strength S of the solidified body 40 is
S = τA2
is represented by

In addition, in FIG. ₅ , the ultimate load P0 that the ground 90 can receive in the horizontal direction is
P ₀ = qu·A1
is represented by Therefore, when the ultimate shear stress τ of the solidified body 40 is low as shown in FIG.
Pu2 ₌ P0+S=qu·A1+τA2 (2)
is represented by

4 and 5, the compressive strength K Ask for Then, the horizontal ultimate load Pu2 that the ground 90 can receive when the solidified body 40 undergoes shear failure as shown in FIG. If the ultimate load Pu1 or more, the solidified body 40 does not break and behaves integrally with the pile 50 . Such a condition is represented by Pu2≧Pu1, but from the above formulas (1), (2), and τ=K/10, the compressive strength K required for the solidified body 40 is
K≧10·qu(1−A1/A2) (3)
is represented.

In Embodiment 1, since the horizontal projected area A2 of the solidified body 40 is larger than the horizontal projected area A1 of the joint 20 inside the solidified body 40, A1/A2 in Equation (3) is 0 to Varies in the range of 1. Therefore, regardless of the size of the solidified body 40 (horizontal projected area A2), the solidified body 40 behaves integrally with the pile 50 without shear failure, ensuring horizontal resistance from the ground 90. A sufficient condition for this is that K≧10·qu.

From the above description, in the joint structure 10 of the pile and the upper structure having the solidified body 40 according to Embodiment 1, by setting the compressive strength of the solidified body 40 to be K≧10·qu, the solidified body 40 can be 50, it is possible to suppress the horizontal displacement of the joint structure 10 between the pile and the superstructure due to the horizontal load P. In other words, it is sufficient that the compressive strength K of the solidified body 40 is at least ten times the uniaxial compressive strength qu of the ground 90 .

FIG. 6 is an explanatory view of the action of the joint structure 10 between the pile and the superstructure when the same soil as the ground 90 is backfilled as the solidified body 40. As shown in FIG. When the root cutting 92 is backfilled with the soil of the ground 90, the strength of the solidified body 40 is the same as the strength of the surrounding ground 90. - 特許庁Therefore, in the state of FIG. 6, the ultimate load Pu3 that the ground 90 can receive in the horizontal direction is given by:
Pu3=qu·A1 (4)
is represented as

FIG. 7 is a graph showing experimental results of measuring a horizontal displacement amount y when a horizontal load P is applied to the joint structure 10 between the pile and the superstructure according to the first embodiment. The experiment was carried out by changing the material of the solidified body 40, and No. in FIG. The experimental result indicated by No. 1 was obtained by using backfill soil as the solidified material 40, and No. 2 and No. The experimental result of No. 4 was obtained by using improved soil as the solidified body 40 . 3 uses concrete as the solidified body 40 . In addition, No. 1 to No. 4, the diameters D of the joints 20 were all set under the same conditions, that is, the areas A1 of the joints 20 projected in the horizontal direction were all set to the same value. Also, No. 1 to No. Experimental result No. 3 was carried out by setting the projected area A2 of the solidified body 40 projected in the horizontal direction to the same value.

No. in FIG. 1 to No. 3 with the same horizontal displacement amount y, No. 3, which uses concrete as the solidified body 40, shows that the experimental results shown in FIG. The horizontal load P of No. 3 was the highest, followed by No. 3 using improved soil. 2, No. using backfill soil. followed by 1. Concrete generally has a compressive strength of 18000 [kN/m ² ], and even when the N value of the standard penetration test is 3, the unconfined compressive strength of the ground 90 is 75 [kN/m ² ]. Therefore, the compressive strength of concrete is ten times or more the uniaxial compressive strength of the ground 90 . Therefore, No. in FIG. Under experimental conditions 3, the solidified body 40 does not undergo shear failure, and the ground 90 can receive the horizontal load P over the entire horizontal projected area A2 of the solidified body 40 . Therefore, the joint structure 10 between the pile and the superstructure has a high effect of suppressing the displacement even if the load P in the horizontal direction is applied. Also, No. The experimental result of No. 3 is for the joint structure 10 between the pile and the superstructure having the solidified body 40 having a predetermined horizontal projected area A2. The horizontal displacement amount y with respect to the horizontal load P becomes smaller.

Moreover, No. in FIG. In the experimental condition No. 2, improved soil is used as the solidified body 40 . This improved soil has a compressive strength K of 100 [kN/m ² ]. The improved soil has a higher compressive strength than the unconfined compressive strength of the ground 90, which is about 1.3 times. As shown in FIG. 5, the solidified body 40 made of improved soil is shear fractured. Therefore, in FIG. 2 and No. The horizontal displacement amount y with respect to a predetermined horizontal load P in the experimental results of No. 1 is the same as that of No. 1 using concrete. This is a large result compared with the experimental result of No. 3.

Note that No. in FIG. 2 and No. 4, the relationship between the horizontal load P and the horizontal displacement y is almost the same. These two experimental results are considered to be because the same improved soil is used as the solidified body 40, but when compared with the same horizontal displacement amount y, the shear area A _k (horizontal projected area No. with large A2). 4 results in a slightly higher horizontal load P.

As the solidified body 40, not only concrete but also mortar, steel slag solidified body, cement-mixed soil improvement body, soil cement solidified body, or the like can be used. These materials generally have a compressive strength ten times or more as large as the uniaxial compressive strength qu of the ground 90, and can suppress the horizontal displacement of the pile head 51.

(Construction method of joint structure 10 between pile and superstructure)
As described above, the horizontal displacement of the pile head portion 51 can be suppressed by applying a material having a high compressive strength to the solidified body 40 . As an example, the construction method of the joint structure 10 between the pile and the upper structure when concrete is applied to the solidified body 40 will be described below.

First, the pile 50 is installed in the ground 90 . The installation method of the pile 50 is not particularly limited. The pile 50 is, for example, a steel pipe pile.

Next, an excavation step of excavating the periphery of the pile head portion 51 of the pile 50 to form the root cutting 92 is performed. In the excavation step, the ground 90 is excavated to a predetermined depth and width around the pile head 51 to form a root cut 92 having a predetermined dimension. The root cutting 92 may be formed by, for example, tamping the side surface 93 and the bottom surface 94 after excavation. In addition, since the side surface 93 of the root cutting 92 is likely to collapse if formed vertically, for example, it is formed on a slope having an inclination angle of 30° with respect to a plane perpendicular to the surface of the ground 90 (an inclination angle of 60° with respect to the horizontal plane). It would be nice to be.

Also, after the excavation step, the bottom surface 94 of the root cut 92 may be provided with dump concrete (not shown) and level mortar (not shown). As shown in FIG. 1, when the structure of the joint 20 is such that the joint 60 is placed over the pile head 51 and jointed, by placing the joint 60 on the scrap concrete and level mortar, position can be determined accurately.

After the excavation process, the superstructure 30 is installed above the piles 50 . That is, in Embodiment 1, the pile head 51 of the pile 50 is covered with the joint 60, and the filler is injected into the gap between the joint 60 and the pile head 51 to form the joint 20. be. Note that the pillars 31 of the superstructure 30 may be joined after the connectors 60 are joined to the piles 50 . This step is called the superstructure installation step.

After the upper structure installation step, a filling material that solidifies into the root cutting 92 and becomes the solidified body 40 is injected. This step is called a filling step. In Embodiment 1, the filler is concrete. Since the root cutting 92 is filled with the filling material, the solidified body 40 is placed in contact with the surrounding ground 90 . Further, the solidified body 40 is molded according to the shape of the root cutting 92 . In Embodiment 1, as shown in FIG. 1, the cross-sectional shape is trapezoidal and rectangular in plan view, but the shape is not limited to this. For example, the solidified body 40 has a rectangular cross-sectional shape, and if the root cut 92 is formed so as to be rectangular in plan view, the area occupied by the solidified body 40 in plan view can be reduced, and the surrounding area such as wiring pits can be reduced. interference with other structures can be avoided. Note that the plan view of the solidified body 40 refers to a state in which the solidified body 40 is viewed from the axial direction of the pile 50 .

The construction method of the joint structure 10 between the pile and the superstructure comprises the steps described above. When the concrete filled in the root cutting 92 solidifies, it becomes the solidified body 40 . The ground 90 around the solidified body 40 is not backfilled or mounded, but is composed of soil in an initial compacted state. Therefore, the ground 90 with which the solidified body 40 is in contact has high strength in a state where the lower surface 42 and the side surfaces 43 are compacted. Therefore, since the joint structure 10 between the pile and the superstructure is formed in contact with the inner surface of the root cut 92 formed in the ground 90 where the solidified body 40 is compacted without any gap, it receives the horizontal load P. Also, the displacement of the solidified body 40 is minimized.

FIG. 8 is a cross-sectional view when the ground 90 around the joint structure 10 between the pile and the superstructure according to Embodiment 1 subsides. The pile-superstructure joint structure 10 has the solidified body 40 formed around the joint 20, and the solidified body 40 may be configured to be movable downward. In Embodiment 1, the solidified body 40 is formed by solidifying concrete, for example, so the solidified body 40 and the side surface 21 of the joint portion 20 are in contact with each other. By constructing so that the side surface 21 of the joint 20 does not have a structure in which the solidified body 40 is caught, the solidified body 40 can move downward only by a frictional force acting between the solidified body 40 and the side face 21. Can be configured. With this configuration, the solidified body 40 can follow the subsidence of the ground 90 when the ground 90 subsides.

When the ground 90 subsides, the surface 91 of the ground 90, the side surface 93 of the root cutting 92, and the bottom surface 94 move downward substantially in parallel. If the solidified body 40 were configured so that it could not move downward, the solidified body 40 would remain fixed at the initial position, and a gap w shown in FIG. put away. Therefore, since the joint structure 10 between the pile and the upper structure is not supported by the ground 90 in the horizontal direction, when the upper structure 30 receives the horizontal load P, the horizontal displacement increases. However, since the solidified body 40 is configured to be able to move downward with respect to the internal structure 70 such as the joint 20 , the solidified body 40 moves following the subsidence of the ground 90 and is in contact with the ground 90 . Therefore, the effect of suppressing horizontal displacement can be maintained.

(Modification)
FIG. 9 is a cross-sectional view of a joint structure 10a between a pile and a superstructure according to a modification. The pile-superstructure joint structure 10 according to the first embodiment may be modified in each part as follows. For example, in the joint structure 10 between the pile and the superstructure shown in FIG. . However, as shown in FIG. 9 , in the pile-superstructure joint structure 10 a according to the modification, the connector 60 may be installed so as to protrude from the upper surface 41 of the solidified body 40 . In this case, the horizontal projected area A1 is the area obtained by horizontally projecting the portions of the connector 60 and the pile 50 inside the solidified body 40 . The lower end of the upper structure 30 and the portion of the pile 50 inside the solidified body 40 are referred to as the inner structure 70 .

FIG. 10 is a cross-sectional view of a joint structure 10b between a pile and a superstructure according to a modification. In the pile/superstructure joint structure 10b according to the modification, the joint portion 20 between the superstructure 30 and the pile 50 is located above the upper surface 41 of the solidified body 40 . In this case, the horizontal projected area A1 is an area obtained by horizontally projecting a portion of the pile 50 located inside the solidified body 40 .

FIG. 11 is a cross-sectional view of a joint structure 10c between a pile and a superstructure according to a modification. The joint structure 10 c between the pile and the superstructure according to the modification differs in the structure of the joint 20 between the superstructure 30 and the pile 50 . In the joint portion 20, a plate 54 joined to the upper end of the pile head 51 and a plate 65 joined to the lower end of the upper structure 30 are bolted. A plurality of bolts 64 for fastening and fixing are provided in the joint structure 10c between the pile and the superstructure.

FIG. 12 is a cross-sectional view of a joint structure 10d between a pile and a superstructure according to a modification. The joint structure 10 d of the pile and the superstructure according to the modification differs in the structure of the joint 20 between the superstructure 30 and the pile 50 . The joint portion 20 is configured by inserting the lower end of the column 31 of the upper structure 30 into the pile 50 from the upper end of the pile head 51 . The column 31 and the pile 50 are fixed by filling and solidifying the filling material between the column 31 and the inner surface of the pile 50 . The filling material used for fixing the pillar 31 and the pile 50 and the filling material for forming the solidified body 40 may be the same. That is, the fixing of the pillar 31 and the pile 50 and the filling process of forming the solidified body 40 may be performed at the same time.

FIG. 13 is a cross-sectional view of a joint structure 10e between a pile and a superstructure according to a modification. A joint structure 10e between a pile and a superstructure according to a modification includes fins 81 attached to the side surface 21 of the joint portion 20 as the internal structure 70 . The fins 81 are provided so as to protrude from the side surfaces 63 of the connector 60 . Therefore, the horizontal projection area A1 increases in the direction orthogonal to the direction in which the fins 81 protrude. The provision of the fins 81 has the effect of dispersing the pressure transmitted from the internal structure 70 to the solidified body 40 and suppressing the destruction of the solidified body 40 even when the strength of the solidified body 40 is low.

FIG. 14 is a cross-sectional view of a joint structure 10f between a pile and a superstructure according to a modification. In the joint structure 10f between the pile and the superstructure according to the modification, a reinforcing bar 82 is arranged inside the solidified body 40. As shown in FIG. Since the reinforcing bar 82 reinforces the shear strength S of the solidified body 40, the horizontal width of the solidified body 40 can be increased, and the horizontal projected area A2 can be further increased, thereby enhancing the effect of suppressing horizontal displacement. It is also possible to Reinforcing bars 82 are installed so as to surround the central internal structure 70 . The number and arrangement of reinforcing bars 82 are not limited to the form shown in FIG.

FIG. 15 is a cross-sectional view of a joint structure 10g between a pile and a superstructure according to a modification. The pile-superstructure joint structure 10g has the same basic structure as the pile-superstructure joint structure 10 shown in FIG. However, it differs in that an intermediate member 80 is arranged between the internal structure 70 arranged inside the solidified body 40 and the solidified body 40 . Intermediate member 80 is positioned adjacent side 63 of connector 60 , which is the side of internal structure 70 . Also, the intermediary member 80 and the connector 60 may be adjacent to each other. Further, the space between the intermediary member 80 and the side surface 63 of the connector 60 or between the intermediary member 80 and the solidified body 40 is configured to be vertically movable.

For example, the intermediary member 80 may be made of a thin metal plate so that the solidified body 40 and the connector 60 are not in direct contact with each other so that the connector 60 and the solidified body 40 can be relatively moved up and down. . Further, the intermediary member 80 may be, for example, an unbonding agent, which is applied to the side surface 63 of the connector 60 to reduce the frictional force between the side surface 63 of the connector 60 and the solidified body 40, thereby 60 and solidified body 40 may be configured to be vertically movable relative to each other.

As shown in FIGS. 9 to 15, the joint 20 between the upper structure 30 and the pile 50 may be changed in position with respect to the solidified body 40, or may be changed in structure for joining. Even if the structure of the joint 20 is changed, since the solidified body 40 has sufficient compressive strength, the solidified body 40 does not break and the effect of suppressing horizontal displacement due to the surrounding ground 90 can be obtained. As in the joint structures 10, 10a to 10g of the pile and the superstructure according to Embodiment 1, the shapes of the superstructure 30 and the piles 50 can take various forms. A joint structure of piles and superstructures can be applied to the structure.

Although the present invention has been described above based on the embodiments, the present invention is not limited only to the configurations of the above-described embodiments. For example, the joint 20 is not limited to the structure described above. Also, the shape of the solidified body 40 is not limited to a square in a plan view, and may be a circle, a rectangle, or other polygons. Furthermore, the joint structures 10, 10a to 10g between the piles and the superstructure can be used by appropriately combining the respective structures. In short, it should be noted that the gist (technical scope) of the present invention also includes various modifications, applications, and the scope of utilization made as necessary by those skilled in the art.

10 joint structure, 10a joint structure, 10b joint structure, 10c joint structure, 10d joint structure, 10e joint structure, 10f joint structure, 10g joint structure, 20 joint, 21 side surface, 30 upper structure, 31 pillar, 32 beam, 40 Solidified body, 41 upper surface, 42 lower surface, 43 side surface, 50 pile, 51 pile head, 52 lower end, 53 pile side surface, 54 plate, 60 connector, 61 top plate, 62 cylindrical portion, 63 side surface, 64 bolt, 65 plate , 70 internal structure, 80 intermediate member, 81 fin, 82 reinforcing bar, 90 ground, 91 surface, 92 root cutting, 93 side surface, 94 bottom surface, 100 structure, A1 horizontal projected area, A2 horizontal projected area, A _K shear area, K compressive strength, L boundary, P horizontal load, P0 ultimate load, Pu1 ultimate load, Pu2 ultimate load, Pu3 ultimate load, S shear strength, f1 reaction force, f2 reaction force, f3 reaction force, f4 reaction force, f5 reaction force, qu uniaxial compressive strength, w gap, y horizontal displacement, τ ultimate shear stress.

Claims (18)

piles installed in the ground;
a superstructure erected above the piles;
a joint that joins the pile and the lower end of the superstructure;
A solidified body formed around the pile and the joint and formed by filling a root cut formed in the ground with a filler,
The junction is
located inside the root cutting;
The solidified body is
The solidified body is embedded in the ground with the side surface of the solidified body in contact with the ground, and has a uniaxial compressive strength higher than that of the ground and less than 18000 [N/mm ² ]. The joint structure between the pile and the superstructure. The upper surface of the solidified body is
The joint structure of the pile and the superstructure according to claim 1, which is located on the surface of the ground. The lower surface of the solidified body is
The joint structure between the pile and the superstructure according to claim 1 or 2, which is located below the joint portion. The junction is
The joint structure between the pile and the superstructure according to any one of claims 1 to 3, which is located between the upper surface and the lower surface of the solidified body. The upper surface of the solidified body is
The joint structure between the pile and the superstructure according to any one of claims 1 to 3, which is located below the joint portion. The side surface of the solidified body is
The joint structure of the pile and superstructure according to any one of claims 1 to 5, wherein the solidified body is inclined so as to approach the pile as it goes from the upper surface to the lower surface. qu is the uniaxial compressive strength of the ground, A1 is the projected area of the internal structure inside the solidified body projected in the horizontal direction parallel to the surface of the ground, and A1 is the projected area of the solidified body projected in the horizontal direction. A2, when the compressive strength of the solidified body is K,
The joint structure between the pile and the superstructure according to any one of claims 1 to 6, satisfying K≧10·qu·(1−A1/A2). The internal structure inside the solidified body,
8. The pile-to-superstructure joint structure of claim 7, comprising fins projecting outwardly from the sides of the internal structure. The solidified body is
The joint structure between the pile and the superstructure according to any one of claims 1 to 8, which is any one of mortar, steel slag solidification, cement-mixed soil improvement, or soil cement solidification. The junction is
Joining the pile and the superstructure according to any one of claims 1 to 8, wherein the pile and a bottomed cylindrical connector that is joined to the lower end of the superstructure are joined by concrete filling joint. structure. The pile is a steel pipe pile or a concrete pile,
The pile-superstructure joint structure according to any one of claims 1 to 9, wherein the superstructure includes columns made of steel pipes or H-section steel. The solidified body is
The joint structure between the pile and the superstructure according to any one of claims 1 to 11, which is configured to be movable downward in the axial direction of the pile with respect to the internal structure inside the solidified body. further comprising an intermediate member positioned adjacently around at least one of said pile, said joint, and said lower end of said superstructure;
The solidified body is
13. The joint structure between the pile and the superstructure according to claim 12, which is installed adjacently around the intermediate member. The solidified body is
The joint structure between the pile and the superstructure according to any one of claims 1 to 13, which is rectangular when viewed in the axial direction of the pile. The solidified body is
The joint structure between the pile and the superstructure according to any one of claims 1 to 14, wherein the joint structure between the pile and the superstructure according to any one of claims 1 to 14 is provided with a reinforcing bar arranged inside to surround the internal structure inside the solidified body. A structure comprising a joint structure between a pile and a superstructure according to any one of claims 1 to 15. A joint structure between a plurality of piles and a superstructure,
Between the solidified bodies of the joint structure between the two adjacent piles and the superstructure,
17. The structure according to claim 16, wherein only the ground or only members extending in a direction crossing a virtual line connecting the ground and two adjacent solidified bodies are arranged. A joint structure between a plurality of piles and a superstructure,
Between the solidified bodies of the joint structure between the two adjacent piles and the superstructure,
18. The structure according to claim 17, which does not have a member connecting the solidified bodies.

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