JP2020094421A - Joint structure for pile and superstructure, construction method for joint structure, and structural body - Google Patents

Abstract

To provide a joint structure for piles and superstructures, a construction method for a joint structure, and a structural body that can reduce the horizontal displacement of a pile head if external forces that displace the pile head horizontally are applied.SOLUTION: The joint structure for piles and superstructures, a construction method for a joint structure, and a structural body according to the present invention include: 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 that is installed around at least one of the piles, the joints and the lower section of the superstructure. The solidified body is embedded in the ground.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a joint structure between an upper structure used for a structure and a pile embedded in the ground, a method for constructing the joint structure, and a structure constructed using these.

Conventionally, in a structure such as a building structure or a civil engineering structure, a structure in which a footing is provided on a head of a pile is known as a structure of a joint portion between a pile embedded in the ground and a pillar built on the pile. Has been. Then, with respect to the footing, the foundation beams are fixed in the horizontal direction and the columns are fixed in the vertical direction. In this case, foundation beams are installed in a grid pattern in the horizontal direction of the ground to connect the heads of a plurality of piles (hereinafter referred to as pile heads). Therefore, the horizontal displacement of one pile head is firmly supported by the foundation beam and the other pile head. Therefore, the horizontal displacement of the base of the pillar built on the pile is suppressed. Therefore, the structure is stable even if an external force applied in the horizontal direction due to an earthquake load or a wind load is applied.

On the other hand, since the structure has a foundation beam, the steps of excavation, rebar, formwork, concrete placing, formwork removal, and backfilling are necessary when constructing the structure. Therefore, there is a problem that a lot of materials are required for constructing the structure, a long construction period is required, and a great cost is required.

In order to solve the above problems, for example, a joint structure of a pile and an upper structure as disclosed in Patent Document 1 is used. In this joint structure, the head of the pile and the pillar are directly joined, and the vertical force, horizontal force, and bending moment transmitted from the pillar can be transmitted to the pile, and the foundation beam of the above conventional structure is unnecessary. Is. The joint structure disclosed in Patent Document 1 has a structure in which the position of the pile and the pillar can be efficiently adjusted with respect to the positional deviation in the horizontal direction and the vertical direction, and the pillar and the pile can be fixed. This allows the structure to reduce the costs, processes, materials, and labor associated with building the foundation beams.

JP, 2007-9438, A

In the joint structure between the pile and the upper structure disclosed in Patent Document 1, since the foundation beam is not 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 easily moves in the horizontal direction due to the horizontal force and the bending moment applied to the column. Further, the structure having the joint structure between the pile and the upper structure disclosed in Patent Document 1 is designed so that the upper structure, the pile, and the ground are integrally analyzed at the designing stage, thereby 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 result. Therefore, there is a problem that there is an application limit in at least one of the scale of the upper structure and the ground condition in the structure adopting the joint structure of the pile and the upper structure without the foundation beam. Further, even if the joint structure of the pile and the upper structure can be applied to the structure, there is a problem that the cross section of the pile, the pillar, and the beam is increased as compared with the conventional structure having the underground beam. It was

For example, the joint structure between a pile and an upper structure disclosed in Patent Document 1 is difficult to apply to a structure having three or more stories as an upper structure, and is not applicable to a soft ground area such as clay. There was a problem that it was difficult.

The present invention has been made in order to solve the above problems, in a joint structure of a pile and a superstructure having no foundation beam between the pile heads, even if an external force for horizontally displacing the pile heads is applied, An object of the present invention is to provide a joint structure of a pile and an upper structure capable of reducing the horizontal displacement of the pile head, a construction method of the joint structure, and a structure.

A joint structure of a pile and an upper structure according to the present invention is a joint that joins a pile installed in the ground, an upper structure built above the pile, and the lower end of the pile and the upper structure. And a solidified body installed around at least one of the pile, the joint, and the lower end of the upper structure, the solidified body being embedded in the ground.

The method for constructing a joint structure according to the present invention includes a step of installing a pile in the ground, a step of forming a root cutting in the ground around the pile head of the pile, and an upper structure above the pile. It comprises a superstructure installing step of installing and a filling step of filling the root cutting with a filler.

A structure according to the present invention includes the above-described joint structure of the pile and the upper structure.

According to the present invention, the solidified body is installed around the pile, and the solidified body is embedded in the ground, so that the pile head is enlarged. As a result, even if the pile head receives a force that displaces in the horizontal direction, the ground receives the force from the embedded solidified body, so that the area of the ground receiving the force increases. Therefore, when the pile head is displaced in the horizontal direction, the ground is not easily deformed, and the horizontal displacement of the pile head on which the solidified body is installed is reduced. Therefore, the structure provided with the above-described joint structure of the pile and the upper structure can be made larger in scale than before, and the range of application to the soft ground is widened.

1 is a perspective view of a structure 100 including a joint structure 10 between a pile and an upper structure according to Embodiment 1. FIG. FIG. 3 is a cross-sectional view of a joint structure 10 of a pile and an upper structure according to the first embodiment. It is a schematic diagram which shows the reaction force which arises in the pile 50 and the solidification body 40, when the horizontal load P is applied to the upper structure 30 of FIG. It is explanatory drawing of the effect|action of the joint structure 10 of a pile and an upper structure when the solidified body 40 uses the material with high enough strength. It is explanatory drawing of the effect|action of the joint structure 10 of a pile and an upper structure when the material with low intensity|strength is used for the solidified body 40. It is explanatory drawing of the effect|action of the joint structure 10 of a pile and an upper structure when the same soil as the ground 90 is backfilled as the solidified body 40. It is a figure which shows the experimental result which measured the horizontal displacement amount y when the horizontal load P is applied to the joint structure 10 of the pile and superstructure which concerns on Embodiment 1. It is sectional drawing when the ground 90 around the joint structure 10 of the pile and superstructure which concerns on Embodiment 1 sinked. FIG. 7 is a cross-sectional view of a joint structure 10a between a pile and a superstructure according to a modified example of the first embodiment. 7 is a cross-sectional view of a joint structure 10b between a pile and a superstructure according to a modified example of Embodiment 1. FIG. 7 is a cross-sectional view of a joint structure 10c between a pile and a superstructure according to a modified example of Embodiment 1. FIG. FIG. 8 is a cross-sectional view of a joint structure 10d between a pile and an upper structure according to a modified example of the first embodiment. FIG. 8 is a cross-sectional view of a joint structure 10e between a pile and a superstructure according to a modified example of the first embodiment. FIG. 7 is a cross-sectional view of a joint structure 10f of a pile and an upper structure of a modified example of the first embodiment. FIG. 9 is a cross-sectional view of a joint structure 10g of a pile and an upper structure of a modified example of the first embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each of the drawings, the parts denoted by the same reference numerals represent the same or corresponding parts, which are common to all the texts of the specification. Further, the forms of the constituent elements appearing in the entire text of the specification are merely examples, and the present invention is not limited to the description in the specification. In particular, the combination of components is not limited to the combination in each embodiment, and the components described in other embodiments can be applied to another embodiment. Further, when it is not necessary to specifically distinguish or specify a plurality of similar parts that are distinguished by subscripts, the subscripts may be omitted. Further, in the drawings, the size relationship of each component may be different from the actual one.

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

For example, the structure 100 is a building structure or a civil engineering structure that does not include a structure such as a foundation beam (underground beam) that connects the joint structures 10 of the pile and the upper structure. That is, the structure 100 has a one-pillar-one-pile structure in which one pile is connected to one pillar 31. The structure 100 shown in FIG. 1 is an example, and the upper structure 30 may include other structural members.

The joint structure 10 of the pile and the upper structure shown in FIG. 2 is a structure of a portion that joins the pile 50 installed in the ground 90 and the pillar 31 that constitutes the lower end of the upper structure 30. The joining tool 60 is joined to the lower end of the column 31, and the joining tool 60 covers the pile head 51, which is the upper end portion of the pile 50, to form the joining portion 20. A solidified body 40 is installed around the joint portion 20. Around the solidified body 40 is 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 a virtual line connecting the ground 90 and the solidified bodies are arranged between the adjacent joint structures 10 of the pile and the upper structure. 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 joint structure 10 of the adjacent pile and the upper structure.

The upper structure 30 mainly includes columns 31 and beams 32 that connect the columns 31. The column 31 constitutes the lower end of the upper structure 30, and is made of a material such as H-section steel or a steel pipe. The lower end of the column 31 is joined to the joining tool 60 by a joining means such as welding and bolting. In FIG. 2, the joining tool 60 is configured by joining a cylindrical portion 62 and a top plate 61 by joining means such as welding, and has a bottomed tubular shape in which the upper end of the cylindrical portion 62 is closed by the top plate 61. Is done.

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

As shown in FIG. 2, the pile head 51 of the pile 50 is covered with the joining tool 60, and the upper structure 30 and the pile 50 are joined. In FIG. 2, there is no gap between the pile head 51 of the pile 50 and the joint tool 60, and they are displayed so as to be in contact with each other, but a gap may actually be provided. The top plate 61 forming the upper surface of the joining tool 60 is provided with, for example, a hole (not shown), and is formed so that the filler can be injected from the hole. The filler filled from the holes fills the gap between the joint tool 60 and the pile head 51 of the pile 50 and solidifies. The load applied to the upper structure 30 is transmitted to the pile 50 via the solidified filler filled in the gap between the connector 60 and the pile head 51 of the pile 50. The filler may be a material such as concrete. In the first embodiment, concrete is used as the filler, and the superstructure 30 and the pile 50 are concrete-filled and joined. The portion where the pillar 31 of the upper structure 30 and the pile head 51 of the pile 50 are joined together is referred to as a joint portion 20.

As shown in FIG. 2, a solidified body 40 is installed around the joint portion 20. The solidified body 40 is arranged so as to surround the side surface of the joint portion 20 and is in contact with the joint portion 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. The side surface 43 of the solidified body 40 is a surface that inclines so as to approach the bonding portion 20 side from the upper surface 41 toward the lower surface 42.

The width of 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 larger than the width including the joint portion 20. When an external force is applied to the upper structure 30 and a horizontal load is applied to the pile head 51, the ground 90 receives a load from the joint 20 via the solidified body 40. At this time, the ground 90 can receive a load in a larger area than that directly applied by the joint 20. Therefore, the horizontal displacement of the pile head 51 is suppressed.

The solidified body 40 is installed by excavating the ground 90 around the joint portion 20, forming a root cutting 92 opening to the surface 91, and injecting a filler into the root cutting 92. That is, the solidified body 40 is formed by solidifying the filler material filled in the root cutting 92. The filler is, for example, concrete, mortar, solidified steel slag, cement-improved ground improvement, 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 arranging the ground 90 such as soil at a predetermined distance from the side surface 21 of the joint 20 around the joint 20. 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, extra work is required to form the root cutting 92 by the embankment, which may increase costs and prolong the construction period. Therefore, the root cutting 92 is preferably formed by excavating the surface 91 of the ground 90, and further, the surface 91 of the ground 90 may be ground and compacted before the 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.

(Operation of the solidified body 40 of the joint structure 10 between the pile and the upper structure)
FIG. 3 is a schematic diagram showing a reaction force generated in the pile 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 the pile 50. When the horizontal load P is applied to the upper structure 30, the load is transmitted from the column 31 to the joint portion 20, and the load is transmitted from the joint portion 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 a 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 a 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 around the lower end 52 of the pile 50 or a point between the pile head 51 and the lower end 52. Therefore, the solidified body 40 receives the reaction force f1 from the horizontal soil 90 on the side surface 43 and the reaction force f3 on the lower surface 42 from the lower soil 90. Further, the pile 50 receives a horizontal reaction force f2 from the ground 90 on the pile side surface 53 located below the lower surface 42 of the solidified body 40. Although the reaction force f2 depends on the rigidity and the length of the pile 50, the reaction force f2 is distributed so that it is generally large on the pile head 51 side and decreases toward the lower end 52.

Further, the side surface 43 of the solidified body 40, which is parallel to the horizontal load P, is in contact with the ground 90 and therefore receives the reaction force f5 due to friction. Similarly, the lower surface 42 of the solidified body 40 also receives a reaction force f4 due to friction in the horizontal direction. The solidified body 40 and the pile 50 receive the reaction forces indicated by f1 to f5, so that the displacement is suppressed. In particular, the solidified body 40 is located at the upper end of the pile 50 and is supported from the horizontal direction by the ground 90 that is in contact with the side surface 43, so that the displacement can be suppressed.

4 to 6 are explanatory views of the operation of the joint structure 10 between the pile and the upper structure when the horizontal load P is applied to the upper structure 30 of FIG. 1. 4 to 6, (b) displayed on the lower side shows the same cross section as that of FIG. 1, and (a) displayed on the upper side is a plan view of the joint structure 10 of the pile and the upper structure. It is a figure. 4 to 6, of the reaction forces f1 to f5 in FIG. 3, the resistance force that the solidified body 40 receives in the horizontal direction will be described by considering only the reaction force f1.

FIG. 4 is an explanatory view of the action of the joint structure 10 between the pile and the upper structure when the solidified body 40 is made of a material having sufficiently high strength. The behavior of the joint structure 10 of the pile and the upper structure with respect to the horizontal load P applied to the upper structure 30 changes depending on the strength of the material used for the solidified body 40. That is, when the strength of the material forming the solidified body 40 is high, the solidified body 40 is not damaged and receives the horizontal load from the joint portion 20, and the ground 90 receives the horizontal load from the solidified body 40. Thereby, the horizontal displacement of the pile head 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 portion 20. The diameter D of the joining portion 20 is the diameter of the cross section of the cylindrical portion 62 of the joining tool 60. In the first embodiment, the upper end of the joining tool 60 matches the upper surface 41 of the solidified body 40, and the lower end of the joining tool 60 matches the lower surface 42 of the solidified body 40. Further, the projected area of the internal structure 70 inside the solidified body 40 projected in the horizontal direction parallel to the surface of the ground is A1, and the projected area of the solidified body 40 projected in the horizontal direction is A2.

When an external force is applied to the upper structure 30, the horizontal load P is transmitted from the column 31 to the joint portion 20 and further to the pile head 51 and the solidified body 40. The horizontal load P is supported by the ground 90 on the side surface 43 of the solidified body 40. Therefore, the horizontal resistance force received by the solidified body 40 is the ground reaction force corresponding to the horizontal projected area of the solidified body 40. 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. When 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 action of the joint structure 10 between the pile and the upper structure when the solidified body 40 is made of a material having low strength. 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. 4. However, when the ultimate shear stress τ of the solidified body 40 is low, the solidified body 40 undergoes shear failure when a load is transmitted from the joint portion 20 to the solidified body 40. Specifically, as shown in FIG. 5A, 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 undergoes shear failure is the area A1=D·H obtained by projecting the joint 20 in the horizontal direction. That is, when the strength of the solidified body 40 is low, the horizontal load P cannot be received by the ground 90 corresponding to the entire projected area of the solidified body 40. In FIG. 5, the size of the solidified body 40 is the same as that 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. The shear strength S of the solidified body 40 is expressed by τ=K/10, where the compressive strength of the material of the solidified body 40 is the compression strength K. Further, since the shear area A _K of the solidified body 40 is the cross-sectional area of the boundary L in FIG. 5,
A _K =2(B1/2+B2/2)H/2=(B1+B2)H/2=A2
It is represented by. Therefore, the shear strength S of the solidified body 40 is
S=τA2
It is represented by.

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

From FIG. 4 and FIG. 5, the compressive strength K of the solidified body 40 for securing the horizontal resistance force from the ground 90 by the solidified body 40 behaving integrally with the pile 50 without shear failure of the solidified body 40. Ask for. Then, as shown in FIG. 5, the horizontal ultimate load Pu2 that the ground 90 receives when the solidified body 40 undergoes shear failure is the horizontal load that the ground 90 can receive when the solidified body 40 does not break as shown in FIG. If the ultimate load is Pu1 or more, the solidified body 40 behaves integrally with the pile 50 without breaking. Such a condition is represented by Pu2≧Pu1, and the compressive strength K required for the solidified body 40 is calculated from the above formulas (1) and (2) and τ=K/10.
K≧10·qu(1-A1/A2) (3)
Is expressed as

In the first embodiment, the horizontal direction projected area A2 of the solidified body 40 is larger than the horizontal direction projected area A1 of the joint portion 20 inside the solidified body 40, and therefore A1/A2 of the formula (3) is 0 to 0. It changes in the range of 1. Therefore, regardless of the size of the solidified body 40 (the projected area A2 in the horizontal direction), the solidified body 40 behaves integrally with the pile 50 without shear failure and secures the horizontal resistance force from the ground 90. A sufficient condition for this is K≧10·qu.

From the above description, in the joint structure 10 of the pile having the solidified body 40 and the upper structure according to the first embodiment, by setting the compressive strength of the solidified body 40 to K≧10·qu, the solidified body 40 becomes the pile. It behaves integrally with 50, and it becomes possible to suppress the horizontal displacement of the joint structure 10 between the pile and the upper structure due to the horizontal load P. That is, the compressive strength K of the solidified body 40 should be at least 10 times the uniaxial compressive strength qu of the ground 90.

FIG. 6 is an explanatory diagram 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. When the soil of the ground 90 is backfilled in the root cutting 92, the strength of the solidified body 40 is the same as the strength of the surrounding ground 90. Therefore, in the state of FIG. 6, the ultimate load Pu3 that can be received by the ground 90 in the horizontal direction is as follows:
Pu3=qu·A1 (4)
Expressed as

7: is a figure which shows the experimental result which measured the horizontal displacement amount y when the horizontal load P is applied to the joint structure 10 of the pile and superstructure which concerns on Embodiment 1. FIG. The experiment was carried out by changing the material of the solidified body 40, and the No. 1 of FIG. The experimental result shown by No. 1 uses backfilled soil as the solidified body 40, and No. 2 and No. The experimental results of No. 4 are the results of using the improved soil as the solidified body 40, In the experiment result of No. 3, concrete is used as the solidified body 40. In addition, No. 1-No. In the experiment result of No. 4, the diameter D of the joint portion 20 is all performed under the same condition, that is, the area A1 of the joint portion 20 projected in the horizontal direction is arranged with the same value. In addition, No. 1-No. The experiment result of 3 is performed by aligning the projected areas A2 of the solidified body 40 projected in the horizontal direction to the same value.

No. 1 in FIG. 1-No. Comparing the experimental results shown in FIG. 3 with the same horizontal displacement amount y, No. 3 using concrete as the solidified body 40 was used. 3 has the highest horizontal load P, followed by No. 3 using improved soil. No. 2 using backfill soil Continues with 1. Concrete generally has a compressive strength of 18000 [kN/m ² ], and even if the N value of the standard penetration test is 3, the uniaxial compressive strength of the ground 90 is 75 [kN/m ² ]. Therefore, the compressive strength of concrete is 10 times or more the uniaxial compressive strength of the ground 90. Therefore, No. 1 in FIG. Under the experimental conditions of No. 3, the ground 90 can receive the horizontal load P over the entire horizontal projected area A2 of the solidified body 40 without shear failure of the solidified body 40. Therefore, the joint structure 10 of the pile and the upper structure has a high effect of suppressing the displacement even when the horizontal load P is applied. In addition, No. The experimental result of No. 3 is for the joint structure 10 of the pile and the upper structure having the solidified body 40 having the predetermined horizontal projected area A2, but when the horizontal projected area A2 of the solidified body 40 is increased, The horizontal displacement amount y with respect to the horizontal load P becomes small.

In addition, in FIG. Under the experimental conditions of 2, the 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 compressive strength higher than the uniaxial compressive strength of the ground 90, but is about 1.3 times. As shown in FIG. 5, the solidified body 40 composed of the improved soil has undergone shear failure. Therefore, in FIG. 2 and No. The horizontal displacement amount y with respect to the predetermined horizontal load P in the experimental result of No. 1 is No. 1 using concrete. The result is larger than the experimental result of No. 3.

In addition, in FIG. 2 and No. Comparing the experimental results with No. 4, the relationship between the horizontal load P and the horizontal displacement amount y is almost the same. It is considered that these two experimental results are because the same improved soil is used as the solidified body 40, but when compared with the same horizontal displacement amount y, the sheared area A _k (horizontal projected area of the solidified body 40) is compared. No. A2) is large. In No. 4, the horizontal load P is slightly higher.

As the solidified body 40, not only concrete but also mortar, steel slag solidified body, cement mixed ground improvement body, soil cement solidified body, or the like can be used. These materials generally have a compressive strength that is 10 times or more 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 of pile and superstructure)
As described above, by applying a material having high compressive strength to the solidified body 40, horizontal displacement of the pile head 51 can be suppressed. As an example, a 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 method of installing the pile 50 is not particularly limited. The pile 50 is, for example, a steel pipe pile.

Next, an excavation process of excavating the periphery of the pile head 51 of the pile 50 and forming the root cutting 92 is performed. In the excavation step, the ground 90 is excavated around the pile head 51 with a predetermined depth and width, and a root cut 92 having a predetermined size is formed. The root cutting 92 may be formed by crushing the side surface 93 and the bottom surface 94 after excavation. Further, the side surface 93 of the root cutting 92 is easily collapsed when formed vertically, and thus is formed, for example, on an inclined surface having an inclination angle of 30° with respect to a surface vertical to the surface of the ground 90 (inclination angle of 60° with respect to a horizontal plane). It is good to be done.

Further, after the excavation process, the bottom surface 94 of the root cutting 92 may be provided with waste concrete (not shown) and level mortar (not shown). As shown in FIG. 1, when the structure of the joint 20 is a structure in which the joint 60 is covered on the pile head 51 to be jointed, by placing the joint 60 on waste concrete and level mortar, The position can be set accurately.

After the excavation process, the superstructure 30 is installed above the pile 50. That is, in the first embodiment, the pile head 51 of the pile 50 is covered with the joining tool 60, and the filler is injected into the gap between the joining tool 60 and the pile head 51 to form the joining portion 20. It The pillar 31 of the upper structure 30 may be joined after the joining tool 60 is joined to the pile 50. This process is called a superstructure installation process.

After the superstructure installation step, the filler that solidifies into the root cutting 92 and becomes the solidified body 40 is injected. This process is called a filling process. In the first embodiment, the filler is concrete. Since the filler is filled in the root cutting 92, the solidified body 40 is installed in contact with the surrounding ground 90. Further, the solidified body 40 is molded in conformity with the shape of the root cutting 92. In the first embodiment, as shown in FIG. 1, the cross-sectional shape is trapezoidal and formed in a rectangular shape in plan view, but the shape is not limited to this. For example, if the solidified body 40 has a rectangular cross-sectional shape and the root cutting 92 is formed so as to have a rectangular shape in a plan view, the area occupied by the solidified body 40 in a plan view can be reduced, for example, a peripheral wiring pit or the like. Interference with the structure of 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 viewpoint of the pile 50.

The method for constructing the joint structure 10 between the pile and the upper structure includes the above steps. When the concrete filled in the root cutting 92 solidifies, it becomes a solidified body 40. The ground 90 around the solidified body 40 is not backfilled or filled with earth, but is composed of soil in an initially compacted state. Therefore, the ground 90 with which the solidified body 40 contacts has high strength in the state where the lower surface 42 and the side surface 43 are compacted. Therefore, since the joint structure 10 of the pile and the upper structure is formed without a gap in a state where the solidified body 40 is in contact with the inner surface of the root cutting 92 formed in the ground 90 where the solidified body 40 is compacted and solidified, it receives the horizontal load P. Also, the displacement of the solidified body 40 is suppressed to the minimum.

FIG. 8 is a cross-sectional view when the ground 90 around the joint structure 10 between the pile and the upper structure according to the first embodiment sinks. In the joint structure 10 of the pile and the upper structure, the solidified body 40 is formed around the joint portion 20, but the solidified body 40 may be configured to be movable downward. In the first embodiment, since the solidified body 40 is formed by solidifying concrete, for example, the solidified body 40 and the side surface 21 of the joint portion 20 are in contact with each other. By configuring so that the solidified body 40 does not have a structure in which the solidified body 40 is hooked on the side surface 21 of the joint portion 20, only a frictional force acts between the solidified body 40 and the side surface 21 so that the solidified body 40 can move downward. Can be configured. With this configuration, when the ground 90 subsides, the solidified body 40 can follow the subsidence of the ground 90.

When the ground 90 sinks, 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 cannot move downward, the solidified body 40 remains fixed at the initial position, and a gap w shown in FIG. 8 is formed between the solidified body 40 and the inner surface of the root cutting 92. I will end up. Therefore, since the joint structure 10 of 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 becomes large. However, since the solidified body 40 is configured to be movable downward with respect to the internal structure 70 such as the joint portion 20, the solidified body 40 moves following the subsidence of the ground 90 and is in contact with the ground 90. Since it can be maintained, the effect of suppressing the horizontal displacement can be maintained.

(Modification)
FIG. 9: is sectional drawing of the joining structure 10a of the pile and upper structure of a modification. In the joint structure 10 of the pile and the upper structure according to the first embodiment, each part may be modified as follows. For example, in the joining structure 10 of the pile and the upper structure shown in FIG. 2, the upper end and the lower end of the joining tool 60 forming the joining portion 20 coincide with the upper surface 41 and the lower surface 42 of the solidified body 40. .. However, as shown in FIG. 9, in the joint structure 10 a of the pile and the upper structure according to the modified example, the connector 60 may be installed so as to extend beyond the upper surface 41 of the solidified body 40. In this case, the horizontal direction projected area A1 is an 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 a part of the pile 50 inside the solidified body 40 are referred to as an internal structure 70.

FIG. 10: is sectional drawing of the joining structure 10b of the pile and upper structure of a modification. In the joint structure 10b of the pile and the upper structure according to the modified example, the joint portion 20 of the upper structure 30 and the pile 50 is located above the upper surface 41 of the solidified body 40. In this case, the horizontal projection area A1 is an area obtained by horizontally projecting a part of the pile 50 located inside the solidified body 40.

FIG. 11: is sectional drawing of the joining structure 10c of the pile and upper structure of a modification. The pile-up joint structure 10c according to the modification is different in the structure of the joint portion 20 between the upper structure 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 bolt-joined. A plurality of bolts 64 for fastening and fixing are provided in the joint structure 10c between the pile and the upper structure.

FIG. 12 is a cross-sectional view of a joining structure 10d of a modified example of a pile and an upper structure. The pile-up joint structure 10d according to the modification is different in the structure of the joint portion 20 between the top structure 30 and the pile 50. The joint portion 20 is configured by inserting the lower end of the pillar 31 of the superstructure 30 into the pile 50 from the upper end of the pile head 51. Between the pillar 31 and the inner surface of the pile 50, the pillar 31 and the pile 50 are fixed by filling and solidifying the filler. The filler used to fix the pillar 31 and the pile 50 and the filler used to form the solidified body 40 may be the same. That is, the pillar 31 and the pile 50 may be fixed and the filling step of forming the solidified body 40 may be performed at the same time.

FIG. 13: is sectional drawing of the joining structure 10e of the pile and upper structure of a modification. The joint structure 10e between the pile and the upper structure according to the modified example includes the fin 81 attached to the side surface 21 of the joint portion 20 as the internal structure 70. The fin 81 is provided so as to project from the side surface 63 of the connector 60. Therefore, the horizontal projection area A1 increases in the direction orthogonal to the direction in which the fin 81 projects. Since the fins 81 are provided, the pressure transmitted from the internal structure 70 to the solidified body 40 is dispersed, and even if the strength of the solidified body 40 is low, the solidified body 40 is prevented from being broken.

FIG. 14: is sectional drawing of the joining structure 10f of the pile and upper structure of a modification. In the joint structure 10f of the pile and the upper structure according to the modified example, the reinforcing bars 82 are arranged inside the solidified body 40. Since the shear strength S of the solidified body 40 is reinforced by the reinforcing bars 82, the width of the solidified body 40 in the horizontal direction can be increased and the horizontal projected area A2 can be further increased, and the effect of suppressing the horizontal displacement can be enhanced. It is also possible to do. The reinforcing bar 82 is installed so as to surround the internal structure 70 in the center. The number and arrangement of the reinforcing bars 82 are not limited to the form shown in FIG.

FIG. 15 is a cross-sectional view of a joint structure 10g of a modified example of a pile and an upper structure. The joint structure 10g of the pile and the upper structure has the same basic structure as the joint structure 10 of the pile and the upper structure shown in FIG. However, the difference is that the intermediate member 80 is arranged between the internal structure 70 arranged inside the solidified body 40 and the solidified body 40. The intermediary member 80 is disposed adjacent to the side surface 63 of the connector 60, which is the side surface of the internal structure 70. Further, the intermediary member 80 and the joining tool 60 may be adjacent to each other. Further, 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, it is configured to be vertically movable.

For example, the intermediary member 80 may be formed of a thin metal plate, and the solidified body 40 and the joint 60 may not be in direct contact with each other, and the joint 60 and the solidified body 40 may be vertically movable relative to each other. .. Further, the intermediary member 80 may be, for example, an unbonding agent, and is applied to the side surface 63 of the joining tool 60 to reduce the frictional force between the side surface 63 of the joining tool 60 and the solidified body 40. The 60 and the 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 the structure for joining may be changed. Even if the structure of the joint portion 20 is changed, since the solidified body 40 has sufficient compressive strength, the solidified body 40 is not damaged and the horizontal displacement due to the surrounding ground 90 can be suppressed. Like the joint structures 10, 10a to 10g of the pile and the superstructure according to the first embodiment, the shapes of the superstructure 30 and the pile 50 can take various forms, and thus various building structures or civil engineering. A joint structure of a pile and a superstructure can be applied to the structure.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the configurations of the above-described embodiments. For example, the joint portion 20 is not limited to the structure described above. Further, the shape of the solidified body 40 is not limited to a square in plan view, and may be a circle, a rectangle, or another polygon. Furthermore, the above-described joint structures 10, 10a to 10g of the pile and the upper structure can be used by appropriately combining the respective structures. In short, it should be added that the scope of the present invention (technical scope) also includes various modifications, applications, and utilization ranges that are required by those skilled in the art.

10 joining structure, 10a joining structure, 10b joining structure, 10c joining structure, 10d joining structure, 10e joining structure, 10f joining structure, 10g joining structure, 20 joining part, 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 joining tool, 61 top plate, 62 cylindrical portion, 63 side surface, 64 bolt, 65 plate , 70 internal structure 80 intermediary member, 81 fin, 82 rebar, 90 soil, 91 surface, 92 Excavation, 93 side, 94 the bottom surface, 100 structures, A1 horizontally projected area, A2 horizontally projected area, _{A K} shear Area, K compressive strength, L boundary, P horizontal load, P0 limit load, Pu1 limit load, Pu2 limit load, Pu3 limit 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 (22)

Piles installed in the ground,
An upper structure built above the pile,
A joint portion that joins the pile and the lower end portion of the upper structure,
A solidified body installed around at least one of the pile, the joint, and the lower end of the superstructure,
The solidified body is
A joint structure of a pile and a superstructure embedded in the ground. The upper surface of the solidified body,
The joint structure between a pile and a superstructure according to claim 1, which is located on the surface of the ground. The lower surface of the solidified body,
The joint structure between a pile and a superstructure according to claim 1 or 2, which is located below the joint portion. The joint is
The joint structure between the pile and the upper structure according to claim 1, wherein the joint structure is located between the upper surface and the lower surface of the solidified body. The upper surface of the solidified body,
The joint structure between the pile and the upper structure 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 a pile and an upper structure according to any one of claims 1 to 5, which is inclined so as to approach the pile from the upper surface of the solidified body toward the lower surface. The uniaxial compressive strength of the ground is qua, at least one of the pile, the upper structure, and the joint portion, and an internal structure inside the solidified body is projected in a horizontal direction parallel to the surface of the ground. Assuming that the projected area is 1, and the projected area of the solidified product projected in the horizontal direction is A2,
The compressive strength K of the solidified body is
The joint structure between a pile and a superstructure according to any one of claims 1 to 6, which satisfies K≧10·qu·(1-A1/A2). The internal structure inside the solidified body,
The joint structure between a pile and a superstructure according to claim 7, further comprising a fin protruding outward from a side surface. The compressive strength K of the solidified body is
The joining structure between the pile and the upper structure according to any one of claims 1 to 8, which has a bonding strength of 18 N/mm ² or more. The solidified body is
The joint structure between a pile and a superstructure according to any one of claims 1 to 9, which is one of concrete, mortar, solidified steel slag, cement-improved ground improvement, and solidified soil cement. The joint is
The joint structure between a pile and a superstructure according to any one of claims 1 to 10, wherein the pile and the superstructure are joined by concrete filling joint, bolt joint, or weld joint. The pile is a steel pipe pile or a concrete pile,
The joint structure between a pile and a superstructure according to any one of claims 1 to 11, wherein the superstructure includes a column made of a steel pipe or H-shaped steel. The solidified body is
The structure, which is at least one of the pile, the upper structure, and the joint and is inside the solidified body, is configured to be movable in the axial direction of the pile. A joint structure between the pile and the upper structure according to any one of claims. Further comprising an intermediary member disposed adjacent to each other around at least one of the pile, the joint, and the lower end of the superstructure,
The solidified body is
The joint structure between a pile and a superstructure according to claim 13, wherein the joint structure is installed adjacent to the periphery of the intermediary member. The solidified body is
The joint structure between the pile and the upper structure according to any one of claims 1 to 14, wherein the pile has a rectangular shape in the axial direction of the pile. The solidified body is
The joint structure of a pile and an upper structure according to any one of claims 1 to 15, further comprising a rebar arranged inside the inner structure to surround the inner structure. The process of installing piles in the ground,
Forming a root cutting in the ground around the pile head of the pile;
A superstructure installation step of installing a superstructure above the pile,
And a filling step of filling the root cutting with a filling material. The step of forming the root cutting includes
The method for constructing a joint structure according to claim 17, which is performed after the step of installing a pile on the ground. Between the superstructure setting step and the filling step, an intermediate member is arranged around the joint between the pile and the pile arranged in the root cutting, adjacent to the side surface of the joint. Further equipped with steps
The filling step is
The method for constructing a joint structure according to claim 17, wherein the filler is filled between the intermediary member and the side surface of the root cutting. A structure comprising the joint structure between the pile according to claim 1 and an upper structure. Comprising a joint structure between a plurality of the piles and the upper structure,
Between each of the solidified bodies that the joint structure of the two adjacent piles and the upper structure has,
21. The structure according to claim 20, wherein only the ground or only members extending in a direction intersecting a virtual line connecting the ground and two adjacent solidified bodies are arranged. Comprising a joint structure between a plurality of the piles and the upper structure,
Between each of the solidified bodies that the joint structure of the two adjacent piles and the upper structure has,
The structure according to claim 21, which does not have a member that connects the solidified bodies to each other.

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