JP7535429B2 - Foundation structure, steel segment used in foundation structure, and construction method for foundation structure - Google Patents

Description

The present invention relates to a foundation structure, a steel segment used in the foundation structure, and a construction method for the foundation structure.

A segment press-in method is known in which multiple steel segments are used to construct buried vertical structures such as shafts. In this method, the segments are connected circumferentially at the sinking point, a ring body is assembled, and the ring body is pressed into the ground using a press-in device. After the ring body is pressed in, the inside of the ring body is excavated and soil is removed, and additional segment rings are added on top of it. This work process is repeated to a specified depth to construct buried structures such as shafts and retaining walls for reinforcing bridge piers in the ground (see, for example, Patent Document 1).

The bottom of a buried structure constructed by the above-mentioned method can be used as a foundation structure. The bottom is constructed by placing a reinforcing bar cage assembled above ground or inside the structure inside the buried structure composed of segment rings, and pouring concrete including the reinforcing bar cage. The reinforcing bar cage has a number of main bars extending vertically and arranged at a predetermined interval in the circumferential direction, and a number of tie bars connecting the main bars in the circumferential direction. The tie bars are arranged at a predetermined interval in the vertical direction.

JP 2017-214722 A

When using the bottom of a conventional buried structure as a foundation structure, the part considered effective as a foundation is from the central axis to the inner diameter of the segment ring, including the concrete part. The buried structure located radially outside the reinforcing bar cage is not included in the effective diameter of the foundation, even though it is constructed from segments using a large amount of steel. Therefore, even after the foundation structure is completed, it is not treated as a foundation structure, and there is room for improvement from an economic standpoint.

The present invention was made in consideration of the above problems, and aims to provide a technology that expands the portion that can be considered as the effective cross section of a foundation structure when the foundation structure is constructed using steel segments.

In order to solve the above problems, the foundation structure according to the present invention is characterized by comprising a cylindrical segment structure in which multiple steel segments are connected in the longitudinal and lateral directions, a filler section provided inside the segment structure, and multiple main reinforcements that extend along the axis of the segment structure, are arranged at predetermined intervals in the circumferential direction around the axis, and are integrated with the segment structure and the filler section.

The steel segment may also include a plate forming the wall surface of the segment structure and a main girder erected along the edge of the plate extending in the circumferential direction, and the main girder may have an engagement portion for engaging the main reinforcement.

The steel segment may also include a support section that supports the main reinforcement by sandwiching the main reinforcement between the steel segment.

The support portion may also have a receiving portion that receives the main reinforcement.

The support portion may also be connected to the steel segment.

The main girder may also be formed with a hole for venting air when filling the filled portion into the space defined by the plate and the main girder.

The steel segment may also have a plurality of stiffeners extending between the main girders and spaced at predetermined intervals in the circumferential direction, and the holes may be formed at positions on the main girders that correspond to the corners formed by the plates and the stiffeners.

Furthermore, in order to achieve the above object, the foundation structure according to the present invention comprises a cylindrical segment structure extending along an axis extending in the embedment direction, and a plurality of main reinforcements extending along the axis and arranged at predetermined intervals in the circumferential direction around the axis, engaging with the segment structure, the segment structure being formed of a plurality of steel segments continuously connected in the embedment direction and the circumferential direction to form a wall surface, the steel segments having an outer piece forming the outer wall of the segment structure and an inner piece forming the inner wall of the segment structure, a filler section being provided between the outer piece and the inner piece, and the main reinforcements, the steel segments, and the filler section being integrated with each other.

The outer piece may have a plate forming an outer wall surface and a main girder erected along the edge of the plate extending in the circumferential direction, and the inner piece may have a plate forming an inner wall surface and a main girder erected along the edge of the plate extending in the circumferential direction, and the main girder of at least one of the outer piece and the inner piece may have an engagement portion that engages the main reinforcement.

The steel segment may also have a connecting piece that connects the outer piece and the inner piece.

Furthermore, in order to solve the above problems, the steel segment used in the foundation structure according to the present invention is a steel segment used in a foundation structure having a cylindrical segment structure extending along an axis extending in the embedment direction, a filler section provided inside the segment structure, and a plurality of main reinforcements extending along the axis and arranged at predetermined intervals in the circumferential direction around the axis, and integrated with the segment structure and the filler section, characterized in that the steel segment is provided with a plate forming the outer wall surface of the foundation structure, and a main girder erected along the edge of the plate extending in the circumferential direction, and the main girder has an engagement section for engaging the main reinforcements.

Furthermore, in order to solve the above problem, the steel segment used in the foundation structure according to the present invention has a cylindrical segment structure extending along an axis extending in the embedding direction, a plurality of main reinforcements extending along the axis and arranged at a predetermined interval in the circumferential direction around the axis, engaging with the segment structure, and a filler section, and is characterized in that it comprises an outer piece forming an outer wall, and an inner piece connected to the outer piece and forming the inner wall of the foundation structure, the outer piece having a plate forming the outer wall surface of the foundation structure and a main girder erected along the edge of the plate extending in the circumferential direction, the inner piece having a plate forming the inner wall surface of the foundation structure and a main girder erected along the edge of the plate extending in the circumferential direction, the main girder of at least one of the outer piece and the inner piece has an engagement section for engaging the main reinforcement, and the filler section is provided between the outer piece and the inner piece.

Furthermore, in order to solve the above problems, the construction method for foundation structures according to the present invention is characterized by having a step of constructing a segment structure by connecting multiple steel segments in the longitudinal and lateral directions, a step of constructing main reinforcement along the axial direction of the segment structure, and a step of pouring filler material inside the segment structure to integrate it with the segment structure and the main reinforcement.

This invention makes it possible to expand the area that can be considered as the effective cross section when constructing a foundation structure using steel segments.

FIG. 2 is a schematic diagram showing a bridge pier and deck based on the foundation structure according to the present invention. FIG. FIG. FIG. 4 is a front view of the steel segment as seen from the inside. FIG. FIG. 4 is a perspective view illustrating a configuration of a connecting mechanism. FIG. 2 is a partial cross-sectional view illustrating a configuration of a foundation structure. 13A and 13B are diagrams illustrating a construction method for constructing a foundation structure after constructing a segment structure. FIG. 1 is a diagram comparing the effective cross section of a conventional foundation structure with the effective cross section of a foundation structure. FIG. 11 is a partial cross-sectional perspective view of a substructure according to a second embodiment. FIG. 13 is a plan view of a steel segment according to a third embodiment. 13A to 13C are diagrams illustrating a construction method for constructing a foundation structure after constructing a segment structure in the third embodiment. FIG. 13 is a diagram showing the relationship between the steel segments and the support portion in the fourth embodiment. FIG. 13 is a plan view of a support portion according to the fourth embodiment. 13A to 13C are diagrams illustrating a construction method for constructing a foundation structure after constructing a segment structure in the fourth embodiment. FIG. 13 is a plan view of a substructure in a fourth embodiment. FIG. 11 is a perspective view of a steel segment according to a modified example. FIG. 11 is a schematic diagram showing a state in which steel segments according to a modified example are stacked one on top of the other.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The foundation structure according to the present invention is a foundation for a building on the ground, for example, a foundation (base) for a bridge pier. The foundation structure is buried in the ground as a reinforced concrete structure. Note that the building for which the foundation structure according to the present invention is applied as a foundation is not limited to a bridge pier, and may be a high-rise building or an apartment building, and is not particularly limited.

1. First embodiment Fig. 1 is a schematic diagram showing a pier 100 and a deck 110 based on a foundation 1 according to a first embodiment of the present invention. The deck 110 supported by the pier 100 is a portion on which vehicles such as automobiles and trains run and on which the load of the vehicles is directly applied. For convenience of explanation, the center line of the foundation 1 will be referred to as the axis x in the following description. The direction in which the foundation 1 is embedded along the axis x will be referred to as the embedding direction A, and the direction around the axis x will be referred to as the circumferential direction C.

<Foundation structure>
The foundation 1 is constructed below the pier 100. The foundation 1 is formed, for example, in a cylindrical shape. The foundation 1 includes a segment structure 10 formed in a cylindrical shape, a filler portion 20, and main reinforcement bars 30.

[Segment structure]
The segment structure 10 extends along an axis x that extends along an embedding direction A. The segment structure 10 is formed of a plurality of steel segments 40 that are continuously connected in the embedding direction A and the circumferential direction C and form an earth retaining wall when constructing the foundation structure 1, and also form a concrete formwork when constructing the filled portion 20.

2 is a plan view of the substructure 1. The segment structure 10 of the substructure 1 has a plurality of ring bodies (annular bodies) 11 connected in the embedding direction A along the axis x. That is, the direction along the axis x of the segment structure 10 coincides with the embedding direction A. In the substructure 1, the ring bodies 11 have a plurality of steel segments 40 connected to each other in an annular shape in the circumferential direction C, and function as tie bar substitutes that substitute for the tie bars of the substructure 1. That is, the ring bodies 11 constitute the substructure 1 by being connected in the embedding direction A in multiple numbers, and also substitute for the tie bars originally provided in each ring body 11. Therefore, the ring bodies 11 that substitute for the tie bars are arranged along a direction that intersects with the main reinforcement 30 (the cross-sectional direction of the substructure 1 that is perpendicular to the embedding direction A). In the ring bodies 11 adjacent to each other in the vertical direction (embedding direction A) along the axis x, the steel segments 40 of the upper ring body 11 and the steel segments 40 of the lower ring body 11 are arranged in a staggered pattern with their ends in the circumferential direction C shifted in the circumferential direction C. The number of steel segments 40 connected in the circumferential direction C is changed appropriately based on the size (outer diameter) of the foundation structure 1 to be constructed.

Figure 3 is a plan view of the steel segments 40 that make up the ring body 11. Figure 4 is a front view of the steel segments 40 as seen from the inside. Figure 5 is a perspective view of the steel segments 40. Figure 6 is a perspective view explaining the configuration of the connecting mechanism. The ring body 11, which replaces the hoops, comprises multiple steel segments 40 and a connecting mechanism 50.

(Steel segments)
The steel segment 40 is formed of steel material. The steel segment 40 has a plate 41, a main girder 42, a joint portion 43, and a rib (stiffener) 44. In the steel segment 40, a filling space S into which concrete that forms the core portion 20 is filled is defined by the plate 41, the main girder 42, and the joint portion 43. Note that the main girder 42, the joint portion 43, and the rib 44 may all be joined to the plate 41 by welding, or a portion of each of them may be formed integrally with the plate 41.

The plate 41 forms the outer wall surface of the substructure 1, specifically the segment structure 10. The plate 41 is formed in a rectangular shape when viewed from above. The plate 41 is formed to be curved in an arc. The curvature of the plate 41 is determined based on the size of the substructure 1 to be constructed.

The main girders 42 are erected on two edges (short edges) of the plate 41 extending along the circumferential direction C. The main girders 42 are curved along the plate 41. The main girders 42 are approximately perpendicular to the plate 41 and erected on the inner surface of the plate 41. When the ring bodies 11 are stacked in the vertical direction, the main girders 42 face the steel segments 40 of the ring bodies 11 in the vertical direction. One main girder 42 is provided on the edge located on the aboveground side. The other main girder 42 is provided on the edge located underground.

Each main girder 42 has a plurality of holes 42a, 42b, and 42c formed therein.
The hole 42a is a connecting hole through which a connecting tool (not shown) such as a bolt for connecting to other steel segments 40 adjacent above and below is inserted. The hole 42a is formed, for example, in a circular shape and penetrates the main girder 42 in the thickness direction (direction along the axis x). The hole 42a is formed to have a diameter slightly larger than the cross section of the connecting tool (approximately the outermost diameter of the connecting tool + 3 to 6 mm), but it is not necessary to form it in a size that allows the concrete to be poured to pass through. Of course, the hole 42a may be formed to have a size that allows the aggregate contained in the concrete to pass through the gap between the hole 42a and the connecting tool. The hole 42a is not limited to a circular shape, and may be formed in an elliptical, oval, or rectangular shape, and the shape and size of the hole 42a can be freely changed within a range that satisfies the design strength of the main girder 42.
The holes 42a are provided on the connection side between the plate 41 and the main girder 42. The holes 42a are provided at predetermined intervals in the extension direction of the main girder 42 from one end to the other end in the circumferential direction C. The holes 42a of each main girder 42 facing the axis x are provided so as to be coaxial with each other.

The hole 42b is an air vent hole for venting air from the filling space S when filling the concrete, and also a hole for flowing the concrete. The hole 42b is formed, for example, in a circular shape and penetrates the main girder 42 in the thickness direction (direction along the axis x). The hole 42b is formed to have a size that allows not only air but also aggregate contained in the concrete to pass through. The hole 42b is not limited to a circular shape, and may be formed in an elliptical, oval, or rectangular shape, and the shape and size can be freely changed within a range that satisfies the design strength of the main girder 42. Specifically, from the viewpoint of the inflowability of concrete, it is preferable that the minimum diameter of the hole 42b is larger than 10 mm, which is the maximum size of fine aggregate contained in concrete, and the maximum diameter is 1/3 or less of the main girder width from the viewpoint of the influence on the strength of the main girder 42.
The hole 42b is provided on the connecting side between the plate 41 and the main girder 42. The holes 42a and 42b are formed on the same imaginary circle centered on the axis x. The holes 42b are formed between the holes 42a and 42a in the vicinity of both sides of the rib 44, from one end to the other end in the circumferential direction C of the main girder 42. That is, the holes 42b are formed in the vicinity of the connecting position of the main girder 42 with the rib 44. Furthermore, the holes 42b are formed in the vicinity of both ends in the circumferential direction C of the main girder 42. More specifically, some of the holes 42b are formed at a position sandwiched between the connecting position of the main girder 42 with the joint portion 43 and the connecting position of the second joint portion 52 (described later). The holes 42b in the main girder 42 facing the axis x are provided coaxially with each other.

The holes 42c are holes for a plurality of main reinforcements through which the plurality of main reinforcements 30 are inserted, and function as locking portions for locking the main reinforcements 30. The holes 42c are formed, for example, in a circular shape and penetrate the main girder 42 in the thickness direction (direction along the axis x). The holes 42c are formed to have a diameter slightly larger than the cross section of the main reinforcements. Specifically, from the viewpoint of workability, the minimum diameter of the holes 42c is preferably the outermost diameter of the main reinforcements 30 (nominal diameter + rib height on both sides) + 1 mm (margin) or more on one side, and the maximum diameter of the holes 42c is preferably the outermost diameter of the main reinforcements 30 + 10 mm on one side (allowable error of cover ±10 mm, allowable error of assembly work for the center spacing of the reinforcing bars ±20 mm) from the viewpoint of accuracy of the main reinforcement arrangement position. In addition, the main reinforcement 30 was set to D19 (nominal diameter 19.1 mm) and 1,300 mm in length, and the hole 42c was set to the minimum diameter of 25.1 mm (maximum rib height on one side 2 mm, margin on one side 1 mm). Insertion tests were conducted within a range of up to 1,200 mm, which is the maximum distance between the actual-size main girders 42, and it was confirmed that insertion could be performed without any problems.
However, the holes 42c do not need to be formed to a size that allows the concrete to pass through. Of course, the holes 42c may be formed to a size that allows the aggregate contained in the concrete to pass through the gap between the holes 42c and the main reinforcement. The holes 42c are not limited to a circular shape, and may be formed to an elliptical, oval, or rectangular shape, and the shape and size can be freely changed within a range that satisfies the design strength of the main girder 42.
The holes 42c are provided on the side opposite to the side where the holes 42a and 42b are formed, i.e., on the edge of the main girder 42 on the axis x side (opposite the connection portion with the plate 41). The holes 42c are provided at predetermined intervals from one end to the other end in the circumferential direction C of the main girder 42. The holes 42c in the main girder 42 facing the axis x are provided coaxially with each other. The holes 42c and the holes 42a and 42b are formed on different imaginary circles centered on the axis x.

The joint portions 43 are provided on edges (longitudinal edges) extending along the axis x at each end of the plate 41 in the circumferential direction C. The joint portions 43 extend along the axis x between the main girders 42 at the ends of the main girders 42 in the circumferential direction C. The joint portions 43 come into contact with and are connected to the joint portions 43 of other steel segments 40 adjacent in the circumferential direction C.
The joint portion 43 is erected on the inner surface of the plate 41 so as to extend from the plate 41 toward the axis x. One end of the joint portion 43 extending along the axis x is connected to the plate 41, and the other end extends to just before the inner edge of the main girder 42. The edges of the joint portion 43 extending toward the axis x are each connected to the main girder 42.
The joint portion 43 has a plurality of holes 43a formed in two rows along the axis x at predetermined intervals, through which the connecting portions 51 (see FIG. 2) are inserted.

A plurality of ribs 44 are provided on the inner surface of the plate 41 so as to extend between the two main girders 42 along the axis x. The ribs 44 are provided at predetermined intervals between the joint portions 43 provided at each end of the steel segment 40 in the circumferential direction C. The ribs 44 are erected so as to extend from the plate 41 toward the axis x. One end of the rib 44 extending along the axis x is connected to the plate 41, and the other end extends to just before the inner edge of the main girder 42. The edges of the rib 44 extending toward the axis x are each connected to the main girders 42.
In the main girder 42, holes 42b are formed on both sides of each rib 44 in the circumferential direction C. The holes 42b are formed near corners formed by the ribs 44 and the plates 41. The hole 42b located on the outermost side in the circumferential direction C is formed between the joint portion 43 and a second joint portion 52 (described later).

(Connecting mechanism)
As shown in FIG. 6 , the connecting mechanism 50 includes a connecting portion 51 , a second joint portion 52 , a joint rib 53 , and a filling portion 54 .
The connecting portion 51 is inserted through the joint portion 43 and the second joint portion 52, and connects the steel segments 40 adjacent in the circumferential direction (longitudinal direction) to each other. The connecting portion 51 is composed of, for example, a bolt 51a and a nut 51b. The connecting portion 51 is inserted through a hole 43a formed in the joint portion 43 and a hole 52a formed in the second joint portion 52.
The second joint portions 52 are provided in the vicinity of both ends in the circumferential direction C of the steel segment 40, at a predetermined interval in the circumferential direction C from each joint portion 43, and parallel to each other. The second joint portions 52 are provided on the inner surface of the plate 41 and stand so as to extend from the inner surface toward the axis x. One end of the second joint portion 52 extending along the axis x is connected to the plate 41, and the other end extends to just before the inner edge of the main girder 42. Both end edges of the second joint portion 52 extending toward the axis x are each connected to the main girder 42.

In the second joint portion 52, a plurality of holes 52a through which the bolts 51a of the connecting portion 51 are inserted are formed at predetermined intervals along the axis x. For example, six holes 52a are formed, and three holes 52a aligned along the short direction (embedding direction A) of the steel segment 40 are formed in two rows along the thickness direction of the steel segment 40. The hole 43a of the joint portion 43 and the hole 52a of the second joint portion 52 are provided at positions facing each other in the circumferential direction C. Therefore, six bolts 51a are also provided to be inserted into both holes 43a, 52a, and adjacent steel segments 40 are connected by these six bolts 51a and nuts 51b.

When connecting adjacent steel segments 40 in the circumferential direction C, the bolts 51a of the connecting portion 51 are inserted into the holes 43a, 52a of the four joint portions 43, 52, respectively, and nuts 51b are screwed onto the ends of the bolts 51a from the outside of the second joint portions 52. At this time, the nuts 51b are in contact with the second joint portions 52. In this way, the steel segments 40 are connected to each other in the circumferential direction C.
When the bolt 51a having a head is used, the head of the bolt 51a abuts against one of the second joint parts 52, and the nut 51b abuts against the other second joint part 52 and is screwed onto the bolt 51a. In this way, the steel segments 40 are connected to each other in the circumferential direction C.

The joint rib 53 is provided between the joint portion 43 and the second joint portion 52 adjacent to each other in the circumferential direction C. The joint rib 53 is provided parallel to the main girder 42 so as to intersect with the axis x. The joint ribs 53 are provided parallel to each other at a predetermined interval along the axis x. More specifically, the joint ribs 53 are provided between the bolts 51a of the connecting portion 51 along the axial direction of the bolts 51a. The joint ribs 53 are provided on the inner surface of the plate 41 and stand so as to extend from the inner surface toward the axis x. One end of each joint rib 53 in a direction intersecting the axis x is connected to the joint portion 43, and the other end is connected to the second joint portion 52.
As a result, each joint rib 53 divides the space V surrounded by the joint portion 43 and the second joint portion 52 .

The filling section 54 is provided in the space V surrounded by the plate 41, the main girder 42, the joint section 43, and the second joint section 52, and is integrated with the bolt 51a of the connecting section 51. Specifically, the filling section 54 is made of concrete, and is integrated with the steel segment 40 and the connecting mechanism 50 by being poured into the space V and solidifying. Here, the space V is partitioned by the joint ribs 53, and the space V is divided into multiple spaces. The filling section 54 is formed by filling the space V with concrete poured when constructing the infill section 20.

Here, the positions of the adjacent holes 43a, 52a are determined so that the pitch of the bolts 51a inserted through these holes 43a, 52a is equal to or smaller than the pitch required for the hoops in design. Specifically, in a general foundation, in other words, in a case where the segment structure 10 cannot be used as part of a foundation, the spacing of the bolts 51a is also determined so as to be equal to or smaller than the pitch of the hoops wound around the main reinforcement, which is designed based on the size and required strength of the foundation. For example, if the designed pitch of the hoops is 150 mm, the spacing between the centers of the bolts 51a connecting the steel segments 40 is also set to be equal to or smaller than 150 mm.
The diameter and the number of bolts 51a are selected so that the sum of the cross-sectional areas of the bolts 51a per height of the steel segment 40 is equal to or greater than the sum of the cross-sectional areas of the hoops per height. For example, when the sum of the cross-sectional areas of the D41 (cross-sectional area 1340 ^mm2 ) hoops per given length is 5360 ^mm2 , if bolts 51a conforming to the M33 (effective cross-sectional area 694 ^mm2 ) standard are used, it is necessary to connect the steel segments 40 using at least eight bolts 51a.

In addition, the material of the bolts 51a is selected so that the strength of the bolts 51a (yield stress of the material) is equal to or greater than the strength of the hoops (yield stress). For example, when using D41 (yield stress 345 N/ ^mm2 ) for the hoops, if the bolts 51a comply with the M33 (yield stress 480 N/ ^mm2 ) standard, there is no problem in terms of strength.
It is possible to reduce the number of bolts 51a used by using bolts with a larger standard than M33, but as the bolts 51a become larger, the torque required to tighten them also increases, reducing workability. Therefore, a structure in which multiple bolts 51a are arranged in the thickness direction of the segment, as shown in Figure 6, is preferable. This makes it possible to determine the size and number of bolts 51a to be used by taking into consideration the balance between the effort required to tighten the bolts 51a and the required tightening torque.
In addition, in parts other than the joint part 43, the thickness and material are determined so that the sum of the cross-sectional areas and strength of the plate 41 and the main girder 42 are greater than or equal to the sum of the cross-sectional areas and strength of the designed tie reinforcement.

[Main reinforcement]
The main reinforcement 30 is, for example, a reinforcing bar made of steel. The main reinforcement 30 is provided on a predetermined imaginary circle centered on the axis x. The main reinforcement 30 extends along the embedding direction A and is provided at a predetermined interval in the circumferential direction C. The main reinforcement 30 provided at the same location in the segment structure 10 may be a single reinforcing bar extending along the axis x, or may be formed of a plurality of reinforcing bars having a predetermined length. The main reinforcement 30 extends at least from the upper end of the segment structure 10 on the aboveground side to the other end on the underground side. The main reinforcement 30 is inserted through the hole 42c in each steel segment 40 along the axis x. The main reinforcement 30 is formed integrally with the steel segment 40 by solidifying the filler portion 20 cast inside the segment structure 10.

[Middle packing section]
The filler portion 20 is provided inside the cylindrical segment structure 10 formed by connecting the ring bodies 11 in the height direction. In the foundation structure 1, the inside of the steel segments 40 is filled with the filler portion 20 and is formed integrally with the steel segments 40.

<Method of constructing foundation structure>
Next, a description will be given of a method for constructing the foundation 1. An installation device (not shown) constituted by, for example, a hydraulic jack or the like is installed at a location where the foundation 1 is to be constructed. The installation devices are provided at a plurality of locations in the circumferential direction C of the annular foundation 1.

Then, inside the sinking device, the steel segments 40 are connected in the circumferential direction C (longitudinal direction) to form the annular ring body 11. When forming the ring body 11, the bolt 51a is inserted through the joint portion 43 and the second joint portion 52, and fastened with the nut 51b. Furthermore, another ring body 11 is formed on the ring body 11 to connect the two. Another ring body 11 is formed on this other ring body 11 to connect the two. The ground inside the ring body 11 is excavated using a clamshell (not shown). When the excavation is completed to the depth required to sink the ring body 11 into the ground, the excavation is stopped, and the sinking device is used to press the top surface of the ring body 11 toward the ground, pressing the ring body 11 into the ground.

Next, multiple other ring bodies 11 are assembled on top of the sunk ring body 11. The ground inside the ring body 11 is excavated to the required depth using a clamshell, and the ring body 11 is pressed into the ground using a sinking device to sink the ring body 11 into the ground. This process is repeated to the specified depth. In this way, a cylindrical segment structure 10 is constructed in which multiple ring bodies 11 are connected in the ground along the axis x. The joints 43 of the steel segments 40 of the vertically adjacent ring bodies 11 are offset from each other in the circumferential direction C, and the steel segments 40 are arranged in a staggered pattern.

Next, the groundwater filling the inside of the segment structure 10 is discharged to the outside by an underwater pump (not shown). Next, the main reinforcement 30 is inserted along the axis x into each steel segment 40 of the ring body 11 on the aboveground side. The method of forcing the ring body 11 into the ground by pressing it in the height direction is extremely accurate in the height direction along the axis x, and the holes 42c of the steel segments 40 of the ring bodies 11 stacked one on top of the other are highly consistent. Note that the main reinforcement 30 may be multiple reinforcing bars of a specified length inserted through the same holes 42c of the uppermost ring body 11 of the segment structure 10 and connected along the way as appropriate.

Figure 7 is a partial cross-sectional view explaining the configuration of the foundation structure 1. In Figure 7, the foundation structure 1 is drawn so that the degree of completion increases from the left half to the right half. After the segment structure 10 is constructed to the designed height, as shown in Figure 8 (a), a predetermined number of main reinforcements 30 (reinforcing bars) are inserted into the same holes 42c in the circumferential direction C (see the right side of Figure 7). If one main reinforcement 30 is insufficient for the height of the segment structure 10, multiple main reinforcements 30 are inserted and the ends are connected by welding or the like.

After the main reinforcement bars 30 have been installed around the entire periphery, concrete that will form the filled portion 20 is poured in stages inside the segment structure 10, as shown in Fig. 8(b). The poured concrete spreads toward the plate 41. The concrete that is gradually poured increases in volume toward the ground. The concrete fills the filled space S while pushing out the air in the filled space S through the holes 42b. This makes it possible to reliably prevent air pockets from forming in the foundation structure 1.
The concrete also flows into the space V surrounded by the plate 41, the main girder 42, the joint 43, and the second joint 52, which are open to the inside of the segment structure 10, and after the concrete hardens, it is integrated with the bolt 51a of the connecting portion 51 as the filling portion 54. This strengthens the connection between adjacent steel segments 40.

As shown in FIG. 8(c), the main reinforcement 30 is inserted into the hole 42c and concrete is poured repeatedly until the concrete reaches the top end of the segment structure 10, forming the infilled section 20. As a result, the main reinforcement 30 and the steel segment 40 are integrated with each other via the infilled section 20, and the foundation structure 1 is constructed. At this time, the main reinforcement 30 functions as the main reinforcement of the foundation structure 1 (reinforced concrete structure), and the ring body 11 to which the steel segment 40 is connected by the connecting mechanism 50 functions as a tie bar of the foundation structure 1 (reinforced concrete structure).

The method of constructing the foundation structure 1 by pressing in the steel segments 40 is extremely suitable, for example, when repairing the bridge piers 100 of an elevated road. The space in the vertical direction is limited under an elevated road. The method of constructing the ring body 11 and pressing it into the ground is less subject to spatial restrictions in the vertical direction. The main reinforcement 30 may be inserted each time multiple stages of the ring body 11 are sunk into the ground.

According to the foundation structure 1 as described above, the main reinforcement bars 30 are directly engaged with the steel segments 40 and are integrated via the filled portions 20, so that the segment structure 10, which could not be used as a foundation structure in the past, can be used as part of the foundation structure.
In addition, because the steel segments 40 are connected to the ring body 11 by the connecting mechanism 50, the ring body 11 to which the steel segments 40 are connected can be used in place of the hoops of a reinforced concrete structure, and the strength of the joints of the segment structure 10 can be significantly increased. This allows the segment structure 10, which could not be used as part of a foundation because the joint strength was not sufficient in the past, to be used as part of a foundation structure.
Furthermore, since the connection of the steel segments 40 constitutes the installation of alternative hoop reinforcement sections, the time-consuming process of providing hoop reinforcement to the main reinforcement can be omitted, and the time required to construct the foundation structure 1 can be shortened.

In addition, the smaller the deformation amount of the connecting mechanism 50 when subjected to a tensile force, the higher the restraining force, and the greater the function of the hoop reinforcement. Here, concrete is filled into the space V surrounded by the members of the plate 41, the main girder 42, the joint portion 43, and the second joint portion 52. The concrete filled into this space V is restrained from deformation by the restraint of each member, and exhibits high strength. On the other hand, the rigidity of the concrete filled into the space V can minimize the deformation amount of the connecting mechanism 50. In other words, the filling portion 54 formed by the concrete is integrated with the connecting mechanism 50, and the deformation amount of the connecting mechanism 50 when a tensile force is applied can be minimized.
In addition, by forming a space V in the connecting mechanism 50 and filling it with concrete, and then restraining the concrete, the connecting strength of the steel segments 40 can be increased.

The foundation structure 1 also has greater strength than a conventional structure in which reinforcing bars are crossed to provide tie bars. Furthermore, by using the steel segments 40, it is no longer necessary to attach tie bars to the main reinforcement bars 30 at a specified interval along the axis, as was the case in the past, and the work time required to construct the foundation structure 1 can be significantly reduced.

The foundation 1 allows the effective cross section to be expanded to the outer diameter of the ring body 11. FIG. 9 is a diagram comparing the effective cross section of a conventional foundation with that of the foundation 1. In the conventional foundation 200, a reinforcement structure 220 is arranged inside the segments 210 connected in an annular shape. The reinforcement structure 220 has a plurality of main reinforcements 221 extending along the axis x and arranged at a predetermined interval from each other in the circumferential direction, and hoops 222 surrounding all the main reinforcements 221 and assembled at a predetermined interval along the axis x. The segments 210 and the reinforcement structure 220 are not directly engaged with each other, and the effective diameter r of the foundation cannot include the segments 210. Therefore, the portion of the segments 210 cannot be considered as the effective cross section of the foundation. In other words, in the conventional foundation 200, the effective cross section can only be considered up to the reinforcement structure 220.
When attempting to construct a foundation of the same diameter (cross-section), the outer diameter of the conventional foundation 200 is larger by the amount of the segments 210, and the cost of materials (segments, concrete) for the parts not considered as the foundation 200 was extremely high.

In contrast, with the foundation structure 1, the outer diameter of the ring body 11 made of the steel segments 40 can be considered as the effective diameter R of the foundation. Therefore, for example, to ensure an effective cross-section of the same size as that of the conventional foundation structure 200, it is sufficient to form a segment structure 10 with the same diameter as the reinforcement structure 220 (r = R), and the materials and construction area required to construct the foundation structure 1 can be made smaller than those of the conventional foundation structure 200.

Furthermore, in the foundation 1, the main girders 42 and joints 43 of the steel segments 40 can also be considered as hoops, so that the entire foundation 1 can be used as a foundation with extremely high strength.
Furthermore, since the steel segments 40 and the connecting mechanisms 50 can replace the tie bars that are normally provided, the amount of steel used can be significantly reduced without reducing the strength of the foundation structure 1.

In addition, the hole 42c is secured in the main girder 42 at a position a predetermined distance inward from the plate 41. In general, since the position of the main reinforcement cannot be visually confirmed in a foundation structure, a large amount of main reinforcement cover is secured with a margin. In contrast, since the hole 42c through which the main reinforcement 30 is inserted is formed in the main girder 42, the position of the main reinforcement 30 can be uniquely determined in the design. This allows the main reinforcement cover to be small, and for example, a foundation structure with a smaller diameter than that of a general foundation structure can be constructed, even for the same building. Furthermore, by inserting the main reinforcement 30 into the hole 42c, the reliability of alignment can be improved.

In addition, holes 42b are formed in the main girder 42. Conventionally, air pockets tended to form near the corners formed by the plates and ribs. Due to the air pockets, the filling space S in the steel segment 40 was not completely filled with concrete. Since holes 42b are formed in the main girder 42 at the positions corresponding to the corners formed by the plates 41 and ribs 44, air pushed toward the plate 41 during concrete pouring is reliably discharged to the outside of the steel segment 40 through the holes 42b. This allows the entire steel segment 40 to be considered as the effective cross section of the foundation.

In addition, in the connection mechanism 50, the connection between the steel segments 40 can be strengthened by directing the concrete poured to form the filled section 20 into the space V, so there is no need to fill the space V with a filler material in advance.

2. Second embodiment Next, a second embodiment of the foundation structure will be described. FIG. 10 is a partial cross-sectional perspective view of the foundation structure 1A. The foundation structure 1A includes a cylindrical segment structure 10A and a plurality of main reinforcements 30A. The segment structure 10A extends along an axis x extending in the embedding direction A. The main reinforcements 30A extend along the axis x and are arranged at predetermined intervals in the circumferential direction C around the axis x, and engage with the segment structure 10A. The segment structure 10A is formed of a plurality of steel segments 40A that are continuously connected in the embedding direction A and the circumferential direction C to form a wall surface. The steel segments 40A have an outer piece 60 that forms the outer wall of the segment structure 10A, and an inner piece 65 that forms the inner wall of the segment structure 10A. A filler portion 80 is provided between the outer piece 60 and the inner piece 65. The main reinforcements 30A, the steel segments 40A, and the filler portion 80 are integrated with each other. The configuration of the substructure 1A will be specifically described below.

The foundation structure 1A comprises a segment structure 10A, a filler section 80, and main reinforcement 30A. The segment structure 10A has a number of ring bodies (only some of which are shown) 11A that connect a number of steel segments 40A in the circumferential direction C and function as hoop replacement sections that replace the hoop reinforcement. The steel segments 40A have an outer piece 60, an inner piece 65, and a connecting piece 70. The outer piece 60 forms the outer wall of the foundation structure 1A. The inner piece 65 forms the inner wall of the foundation structure 1A. The connecting piece 70 connects the outer piece 60 and the inner piece 65 to each other.

The outer piece 60 has a plate 61, a main girder 62, a joint section 63, and a rib (stiffener) 64. In the outer piece 60, the plate 61 and the main girder 62 define a filling space S1 when filling with concrete that forms the filled section 80 described below. The plate 61 forms the outer wall surface of the foundation structure 1A.

The main girders 62 are erected along the edge of the plate 61 extending in the circumferential direction C. Each main girder 62 has a plurality of holes 62a, 62b, and 62c formed therein. The holes 62a, 62b, and 62c have the same structure and function as the holes 62a, 62b, and 62c of the steel segment 40A. The main girders 62, joint parts 63, and ribs 64 have the same structure as the main girders 62, joint parts 63, and ribs 64 of the steel segment 40A.

The inner piece 65 has a plate 66, a main girder 67, a joint 68, and a rib (stiffener) not shown in the drawing. In the inner piece 65, the plate 66 and the main girder 67 define a filling space (not shown) when filling with concrete that forms the infill section 80. The plate 66 forms the inner wall surface of the foundation structure 1A. In the inner piece 65, the plate 66 is provided along the edge of the main girder 67 on the opposite side to the outer piece 60.

The main girders 67 are erected along the edge of the plate 66 extending in the circumferential direction C. Each main girder 67 has a plurality of holes 67a, 67b, and 67c formed therein. The holes 67a, 67b, and 67c have the same structure and function as the holes 67a, 62b, and 62c of the steel segment 40A. The main girders 67, joint parts 68, and ribs have the same structure as the main girders 42, joint parts 43, and ribs 44 of the steel segment 40.

The steel segments 40A in the circumferential direction C are connected to each other by a connecting mechanism (not shown). The configuration of the connecting mechanism in the foundation structure 1A is the same as the configuration of the connecting mechanism 50 in the foundation structure 1.

The connecting pieces 70 increase the shear strength of the steel segments 40A. Multiple connecting pieces 70 are provided between the outer piece 60 and the inner piece 65. The connecting pieces 70 are joined to the filling portion 80 to increase the unity between the outer piece 60 and the inner piece 65.

The connecting piece 70 is formed of a steel bar. The connecting piece 70 connects the outer piece 60 and the inner piece 65 between both ends of the outer piece 60 and the inner piece 65 in the circumferential direction C. The connecting piece 70 is bridged over the rib 64 of the outer piece 60 and the rib of the inner piece 65. The connecting piece 70 is fixed to the upper end and the lower end of the rib 64 of the outer piece 60 and the rib of the inner piece 65, respectively, in the height direction of the steel segment 40A along the axis x.

The filling section 80 is provided between the outer piece 60 and the inner piece 65.

The method for constructing the foundation structure 1A using steel segments 40A will be described. The method for constructing the foundation structure 1A is almost the same as the method for constructing the foundation structure 1.

The steel segments 40A are connected in the circumferential direction C to form an annular ring body 11A. After stacking and connecting multiple ring bodies 11A in the vertical direction, the ground inside the ring body 11A is excavated using a clamshell (not shown). When the excavation is completed to the depth required to sink the ring body 11A into the ground, the excavation is stopped and the upper surface of the ring body 11A is pressed into the ground by the sinking device, pressing the ring body 11A into the ground.

This process is repeated until the segment structure 10A reaches its designed height, and then the groundwater filling the inside of the segment structure 10A is discharged to the outside using a submersible pump (not shown). After that, a predetermined number of main reinforcements 30A (reinforcing bars) are inserted into the same holes 62c in the circumferential direction C (see Figure 10).

After the main reinforcement 30A is installed around the entire circumference, concrete is poured between the outer piece 60 and the inner piece 65 of the segment structure 10A. The poured concrete spreads between the outer piece 60 and the inner piece 65. This creates a foundation structure 1A in which multiple ring bodies 11A are connected underground along the axis x. The foundation structure 1A is a cylindrical structure with a hollow inside the inner piece 65.

The concrete may also be poured in stages. Specifically, after multiple ring bodies 11A stacked to a predetermined height are pressed into the ground, the main reinforcement 30 is inserted into the holes 62c, 67c of the outer piece 60 and the inner piece 65 of the pressed-in ring body 11A. After the main reinforcement 30 is inserted, concrete is filled between the outer piece 60 and the inner piece 65. After the concrete has solidified, multiple other ring bodies 11A are assembled on top of the sunken ring body 11A. The ground inside the ring body 11A is excavated to the required depth using a clamshell, and the ring body 11A is pressed into the ground using a sinking device, and the ring body 11A is further sunken into the ground.

After sinking, the main reinforcement 30 is inserted into the steel segment 40A, and the lower end of the main reinforcement 30 is connected to the upper end of the main reinforcement 30 inserted into the steel segment 40A that was previously buried in the ground. Next, concrete is filled between the outer piece 60 and the inner piece 65. This process is repeated to a specified depth. This completes the construction of the foundation structure 1A in which multiple ring bodies 11A are connected in the ground along the axis x.

The foundation structure 1A described above provides the same effects as the foundation structure 1 according to the above embodiment, and the main reinforcement 30 directly engages with the steel segments 40A and is integrated via the filled section 80, allowing the steel segment portions that could not previously be used as part of the foundation to be used as part of the foundation.

The steel segment 40A is suitable for construction of a large cross-section foundation 1A because it has an outer piece 60 and an inner piece 65. The outer piece 60 and the inner piece 65 of the steel segment 40A are connected to each other via a connecting piece 70, and the main reinforcement 30 and the steel segment 40A are engaged with each other. Therefore, a large amount of steel material is used in the foundation 1A, and the strength of the foundation 1A is increased.

3. Third embodiment Next, a third embodiment of the foundation will be described. A foundation 1B in the third embodiment differs from the foundation 1 in the first embodiment in that the holes 42c in the main girders 42 for engaging the main reinforcements 30 are eliminated, and the main reinforcements 30 are engaged in the cutouts. Therefore, the following description will focus on the main girders, and the other components will be given the same reference numerals and will not be described. Figure 11 is a plan view of a steel segment in the third embodiment.

11 , the main girder 42B of the steel segment 40B is formed to have a width shorter than that of the main girder 42 in the first embodiment. Specifically, the main girder 42B is formed to have the same width as the joint portion 43 and does not protrude inward beyond the joint portion 43.
The inner (shorter) edge of the main girder 42B along the circumferential direction (longitudinal direction) C has cutouts 42Bc cut out at predetermined intervals, which function as locking sections for locking the main reinforcements 30. The cutouts 42Bc are formed in the main girder 42B, for example, at intervals equal to the arrangement intervals of the main reinforcements 30. The cutouts 42Bc are formed, for example, in a semicircular shape, and are formed to a size such that about half of the main reinforcements 30 to be used can be fitted into them. Therefore, the main reinforcements 30 are not inserted into the main girder 42B, but only a portion of the main reinforcements 30 is fitted into them.

When constructing the foundation structure 1B, after constructing the segment structure 10 to the design height, a predetermined number of main reinforcements 30 (reinforcing bars) are fitted into the cutouts 42Bc in the circumferential direction C as shown in FIG. 12(a), and the main reinforcements 30 are fixed to the main girder 42B by a method such as clips or welding. If one main reinforcement 30 is insufficient for the height of the segment structure 10, multiple main reinforcements 30 are fitted into the cutouts 42Bc and the ends are connected together by welding or the like.

After the main reinforcement 30 has been installed around the entire periphery, as shown in Fig. 12(b), concrete that constitutes the filled portion 20 is poured stepwise inside the segment structure 10. The poured concrete fills the filling space S while pushing out the air in the filling space S through the holes 42b.
In addition, the concrete also flows into the space V, and after the concrete hardens, it is integrated with the bolts 51a of the connecting portions 51 as the filled portions 54. This strengthens the connection between the adjacent steel segments 40B.

As shown in FIG. 12(c), the main reinforcement 30 is inserted and fixed into the cutout 42Bc, and concrete is poured repeatedly until the concrete reaches the top of the segment structure 10 to form the infilled section 20. As a result, the main reinforcement 30 and the steel segment 40 are integrated with each other via the infilled section 20, and the foundation structure 1B is constructed. At this time, the main reinforcement 30 functions as the main reinforcement of the foundation structure 1B (reinforced concrete structure), and the ring body 11 to which the steel segment 40 is connected by the connecting mechanism 50 functions as a tie bar of the foundation structure 1B (reinforced concrete structure).

As described above, with the foundation structure 1B, when placing the main reinforcement 30, it is a simple task of fitting a part of the main reinforcement 30 into the cutout 42Bc and fastening it with a clip or the like. This eliminates the time-consuming task of sequentially inserting the main reinforcement 30 into the holes 42c of the main girder 42 as in the first embodiment, and significantly improves work efficiency. This makes it possible to shorten the construction period compared to the foundation structure 1 in the first embodiment. In addition, since the position of the main reinforcement 30 is fixed at the stage of filling the concrete, the reliability of the alignment of the main reinforcement 30 can be improved simply by fitting the main reinforcement 30 into the cutout 42Bc.

4. Fourth embodiment Next, a fourth embodiment of the foundation will be described. A foundation 1C in the fourth embodiment differs from the foundation 1B in the third embodiment in that the notch 42Bc in the main girder 42B is eliminated and the main reinforcement 30 is fixed by a support part separate from the steel segment. Therefore, the following will describe the difference, and other components will be given the same reference numerals and will not be described. Figure 13 is a diagram showing the relationship between the steel segments and the support parts in the fourth embodiment. Figure 14 is a plan view of the support parts in the fourth embodiment.

As shown in FIG. 13, the main girder 42C, like the main girder 42B in the third embodiment, is formed with a width shorter than the main girder 42 in the first embodiment. Specifically, the main girder 42C is formed with the same width as the joint part 43 and does not protrude inward beyond the joint part 43. The main girder 42C does not have holes or notches for engaging the main reinforcement 30, but has a connection hole 42a used to connect to adjacent steel segments and an air vent hole 42b.

The foundation structure 1C includes a support section 90 that supports the main reinforcement 30 by sandwiching the main reinforcement 30 between the steel segment 40C and the support section 90. The support section 90 is formed from a curved plate material that fits along the inner edge of the main girder 42C in the circumferential direction C. The support section 90 is disposed inside the main girder 42C and is connected to the main girder 42C of the steel segment 40C using fasteners (e.g., bolts and nuts). Note that the support section 90 is not limited to being connected to the main girder 42C, and may also be connected to the plate 41, the joint section 43, the rib 44, etc.

As shown in FIG. 14 , the support portion 90 supports the main reinforcement 30 by sandwiching the main reinforcement 30 between the steel segment 40</b>C and the support portion 90 , and has a main body portion 91 , a receiving portion 92 , and a connecting portion 93 .
The main body 91 is formed to have approximately the same curvature as the main girder 42C so as to follow the circumferential direction C of the main girder 42C, and its length along the circumferential direction C (longitudinal direction) is formed to be approximately the same length as the main girder 42C of one steel segment 40C.
The receiving portions 92 are cutouts that receive and lock the main reinforcements 30, and are formed at predetermined intervals on the outer (longer bulging side) edge of the main body portion 91 along the circumferential direction (longitudinal direction) C. The receiving portions 92 are formed in the main body portion 91, for example, at intervals equal to the arrangement intervals of the main reinforcements 30. The receiving portions 92 are formed, for example, in a semicircular shape, and are formed in a size such that about half of the main reinforcements 30 to be used can be fitted into them. Therefore, the main reinforcements 30 are not inserted into the support portion 90, but rather a part of the main reinforcements 30 is simply fitted into them, and the main reinforcements 30 are fixed to the support portion 90 by clips, welding, or the like.
The connecting portion 93 is provided on the main body portion 91, and is formed so as to protrude and extend toward the outside (the bulging side having the longer length) along the circumferential direction (longitudinal direction) C of the main body portion 91. A hole through which a fastener is inserted is formed at the tip of the connecting portion 93, and the fastener can be inserted through the hole of the connecting portion 93 and the hole of the main girder 42C and fastened to connect the support portion 90 to the main girder 42C. A connecting portion 93a for connecting to the adjacent support portion 90 is provided at one end of the main body portion 91. The connecting portions 93, 93a may be formed integrally with the main body portion 91, or may be formed from a member separate from the main body portion 91.

When constructing the foundation structure 1C, after constructing the segment structure 10 to the design height, as shown in FIG. 15(a), the support part 90 to which the multiple main reinforcements 30 are attached is connected to the main girder 42C of the steel segment 40C using fasteners. Here, it is preferable to attach the main reinforcements 30 to each receiving part 92 of the support part 90 in advance at a factory or the like. When attaching the main reinforcements 30 to the receiving parts 92, the main reinforcements 30 are fitted into the receiving parts 92 and fixed to the support part 90 by a method such as a clip or welding. It is preferable to attach the support part 90 to both ends of the main reinforcements 30, but the support part 90 may be attached to three or more places depending on the length of the main reinforcements 30. It is also possible to simply sandwich the main reinforcements 30 between the main girder 42C and the support part 90 without attaching the main reinforcements 30 to the support part 90.

After the main reinforcement 30 has been installed around the entire periphery, as shown in Fig. 15(b), concrete that constitutes the filled portion 20 is poured stepwise inside the segment structure 10. The poured concrete fills the filling space S while pushing out the air in the filling space S through the holes 42b.
In addition, the concrete also flows into the space V, and after the concrete hardens, it is integrated with the bolts 51a of the connecting portions 51 as the filled portions 54. This strengthens the connection between the adjacent steel segments 40C.

As shown in FIG. 15(c), the support section 90 to which the main reinforcement 30 is attached is connected to the main girder 42C, and concrete is poured repeatedly until the concrete reaches the top end of the segment structure 10 to form the infill section 20. As a result, the main reinforcement 30 and the steel segment 40C are integrated with each other via the infill section 20, and the foundation structure 1C as shown in FIG. 16 is constructed. At this time, the main reinforcement 30 functions as the main reinforcement of the foundation structure 1C (reinforced concrete structure), and the ring body 11 to which the steel segment 40C is connected by the connecting mechanism 50 functions as a tie bar of the foundation structure 1C (reinforced concrete structure).

According to the foundation 1C as described above, when arranging the main reinforcements 30, a plurality of main reinforcements 30 can be arranged along the main girders 42C at once by a simple operation of attaching the plurality of main reinforcements 30 to the support parts 90 in advance and fastening the support parts 90 to the main girders 42C with clips or the like. This eliminates the need for a time-consuming operation of sequentially inserting the main reinforcements 30 into the holes 42c of the main girders 42 as in the first embodiment, and significantly improves the work efficiency. This allows the construction period to be shorter than that of the foundation 1 in the first embodiment. In addition, there is no need to fit and fix the main reinforcements 30 one by one into the notches 42Bc as in the foundation 1B in the third embodiment, so that the construction period can be shorter than that of the foundation 1B in the third embodiment.
Furthermore, since there is no need to process the steel segments 40C such as the main girders 42C themselves, it is possible to accommodate post-construction. Even if there are design changes during construction, the number and size of the main reinforcements 30 to be placed can be flexibly changed by changing the number and size of the receiving portions 92 of the support portions 90.
Furthermore, by forming multiple receiving portions 92 in the support portion 90, multiple main reinforcements 30 can be attached to the support portion 90 to form a unit, and by connecting the unit to the main girder 42C, many main reinforcements 30 can be placed at once, thereby greatly improving work efficiency.

Although the preferred embodiment and other embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiment and other embodiments, and includes all aspects included in the concept of the present invention and the scope of the claims. In addition, the configurations of the above-mentioned embodiment and other embodiments may be appropriately and selectively combined so as to achieve at least a part of the above-mentioned problems and effects. In addition, for example, the shape, material, arrangement, size, etc. of each component in the above-mentioned embodiment and other embodiments may be appropriately changed depending on the specific usage mode of the present invention. Figure 17 is a perspective view of a steel segment 40D relating to a modified example.

The steel segment 40D has a plate 41D, a main girder 42D, a joint 43D, a rib (stiffener) 44D, and a second joint 52D. In the steel segment 40D, one (lower) of the pair of main girders 42D has a recess 45D recessed toward the plate 41D, except for the connection points with the joint 43D and the second joint 52D. In the steel segment 40D, the holes 42Dc through which the main reinforcement 30 is inserted are formed along the circumferential direction C in the upper main girder 42D, but are formed only at the ends in the circumferential direction C in the lower main girder 42D.

Figure 18 is a schematic diagram showing a state where steel segments 40D according to a modified example are stacked one on top of the other. When a ring body is formed using steel segments 40D, the main reinforcement 30 is inserted only in the upper main girder 42D of one ring body stacked on top of the other ring body of each steel segment 40D. The upper main girder 42D of the steel segment 40D in the lower ring body is located at the position of the recess 45D of the lower main girder 42D. The steel segment 40D can achieve the same effect as the steel segment 40, while significantly reducing the amount of steel material used. In addition, the number of holes 42Dc through which the main reinforcement 30 is inserted can be reduced, improving work efficiency. The steel segment 40D can also be applied to the foundation structure 1A.

In the above embodiment, the holes 42c in the main girder 42 of the steel segment 40 are provided on one imaginary circle, but the main girder 42 may be provided with another imaginary circle with a different diameter from the one imaginary circle. In this case, the main reinforcement 30 is provided in double with the axis x as the center.

In addition, in the steel segment 40A according to another embodiment, the main reinforcement 30A is inserted through each of the outer piece 60 and the inner piece 65, but may be inserted through either the outer piece 60 or the inner piece 65.

The main reinforcements 30 may also be attached in advance to the main girders 42, 62, 67 of the steel segments 40, 40A themselves. The main reinforcements 30 of the steel segments 40, 40A adjacent in the height direction may be joined together when they are connected to each other in the height direction.

The support portion 90 in the fourth embodiment may also be used to hold down the main reinforcement 30 fitted into the notch portion 42Bc in the third embodiment.

1 Foundation structure 10 Segment structure 11 Ring body (replacement for tie bar)
20 Filling section 30 Main reinforcement 40 Steel segment 41 Plate 42 Main girder 42c Hole (hole through which each main reinforcement is inserted)
43 Joint portion 44 Rib (stiffener)
50 Connection mechanism 51 Connection portion 52 Second joint portion 53 Joint rib 54 Filling portion 1A Foundation structure 10A Segment structure 11A Ring body (replacement for tie bar)
30A Main reinforcement 40A Steel segment 60 Outer piece 61 Plate 62 Main girder 62c Hole 65 Inner piece 66 Plate 67 Main girder 67c Hole 70 Connecting piece 80 Filled portion 1B Foundation structure 40B Steel segment 42B Main girder 42Bc Cutout portion 1C Foundation structure 40C Steel segment 42C Main girder 90 Support portion 91 Main body portion 92 Receptacle portion 93, 93a Connecting portion A Buried direction C Circumferential direction S, S1 Filling space (space)
x-axis

Claims (18)

A cylindrical segment structure in which a plurality of steel segments are connected in a longitudinal direction and a transverse direction;
a filler portion provided inside the segment structure;
A plurality of main reinforcements extending along the axis of the segment structure and arranged at predetermined intervals in the circumferential direction around the axis, and integrated with the segment structure and the fill portion ,
The steel segment is
A plate forming a wall surface of the segment structure;
A main girder erected along an edge of the plate extending in the circumferential direction,
The main girder has an engagement portion that engages the main reinforcement,
A foundation structure, characterized in that the engaging portion is provided on the edge of the main girder on the opposite side to the connection portion between the plate and the main girder . The foundation structure according to claim 1 , wherein the engaging portion is a hole through which the main reinforcement is inserted. The locking portion is a notch portion that is formed on an inner edge portion of the main girder along the circumferential direction and is cut out at a predetermined interval,
The foundation structure according to claim 1, wherein a part of the main reinforcement is fitted into the notch. The substructure according to claim 3 , wherein the cutout portion is formed in a semicircular shape. A cylindrical segment structure in which a plurality of steel segments are connected in a longitudinal direction and a transverse direction;
a filler portion provided inside the segment structure;
A plurality of main reinforcements extending along the axis of the segment structure and arranged at predetermined intervals in the circumferential direction around the axis, and integrated with the segment structure and the fill portion,
A foundation structure comprising a support section that supports the main reinforcement by sandwiching the main reinforcement between the steel segment and the support section. The foundation structure according to claim 5 , wherein the support portion has a receiving portion for receiving the main reinforcement. 7. The foundation structure according to claim 5 or 6 , wherein the supporting portion is connected to the steel segment. The steel segment is
A plate forming a wall surface of the segment structure;
A main girder erected along an edge of the plate extending in the circumferential direction,
8. The foundation structure according to claim 5, wherein the main reinforcement is supported by being sandwiched between the main girder and the support portion. 9. The foundation structure according to claim 1, wherein the main girder is formed with a hole for venting air when the filled portion is filled into the space defined by the plate and the main girder. The foundation structure according to claim 9 , wherein the holes are provided on a connection side between the plate and the main girder. The steel segment extends between the main girders and has a plurality of stiffeners provided at predetermined intervals in the circumferential direction,
11. The foundation structure according to claim 9 , wherein the holes are formed in the main girders at positions corresponding to corners formed by the plates and the stiffeners. A cylindrical segment structure extending along an axis extending in the embedding direction;
A plurality of main reinforcements extending along the axis and arranged at predetermined intervals in a circumferential direction around the axis , and engaging with the segment structure;
The segment structure is formed of a plurality of steel segments that are continuously connected in the embedding direction and the circumferential direction to form a wall surface,
The steel segment has an outer piece forming an outer wall of the segment structure and an inner piece forming an inner wall of the segment structure,
A filling portion is provided between the outer piece and the inner piece,
The main reinforcement, the steel segment, and the filled portion are integrated with each other ,
The outer piece has a plate forming an outer wall surface and a main girder erected along an edge of the plate extending in the circumferential direction,
The inner piece has a plate forming an inner wall surface and a main girder erected along an edge of the plate extending in the circumferential direction,
A foundation structure, characterized in that the main girder of at least one of the outer piece and the inner piece has an anchoring portion that anchors the main reinforcement . The foundation structure according to claim 12 , wherein the steel segment has a connecting piece connecting the outer piece and the inner piece. A steel segment for use in a foundation structure, the steel segment having a cylindrical segment structure extending along an axis extending in an embedding direction, a filler section provided inside the segment structure, and a plurality of main reinforcements extending along the axis, arranged at predetermined intervals in a circumferential direction around the axis, and integrated with the segment structure and the filler section,
A plate forming an outer wall surface of the foundation structure;
A main girder erected along an edge of the plate extending in the circumferential direction,
The main girder has an engagement portion that engages the main reinforcement,
A steel segment used in a foundation structure, characterized in that the engaging portion is provided on the edge of the main girder on the opposite side to the connection portion between the plate and the main girder . A steel segment for use in a foundation structure, the steel segment having a cylindrical segment structure extending along an axis extending in an embedding direction, a plurality of main reinforcements extending along the axis and arranged at predetermined intervals in a circumferential direction around the axis and engaging with the segment structure, and a fill portion,
an outer piece forming an outer wall;
an inner piece connected to the outer piece and forming an inner wall of the substructure;
the outer piece has a plate forming an outer wall surface of the foundation structure and a main girder erected along an edge of the plate extending in the circumferential direction,
the inner piece includes a plate forming an inner wall surface of the foundation structure and a main girder erected along an edge of the plate extending in the circumferential direction,
At least one of the main girders of the outer piece and the inner piece has a locking portion that locks the main reinforcement,
13. A steel segment for use in a foundation structure, wherein the filler portion is provided between the outer piece and the inner piece. A construction method for a foundation structure according to claim 1,
A step of connecting a plurality of steel segments in a longitudinal direction and a transverse direction to construct a segment structure;
a step of fastening the main reinforcement to the fastening portion and fastening the main reinforcement along the axial direction of the segment structure;
A step of pouring a filler into the inside of the segment structure to integrate it with the segment structure and the main reinforcement;
A foundation structure construction method comprising the steps of: The construction method for a foundation structure according to claim 5,
A step of connecting a plurality of steel segments in a longitudinal direction and a transverse direction to construct a segment structure;
a step of supporting the main reinforcement by sandwiching it between the steel segment and the support portion and locking the main reinforcement along the axial direction of the segment structure;
A step of pouring a filler into the inside of the segment structure to integrate it with the segment structure and the main reinforcement;
A foundation structure construction method comprising the steps of: A construction method for a foundation structure according to claim 12, comprising the steps of:
A step of connecting a plurality of steel segments in a longitudinal direction and a transverse direction to construct a segment structure;
A step of fastening a main reinforcement to the fastening portion along an axial direction of the segment structure;
A step of placing a filler between the outer piece and the inner piece to integrate the filler with the segment structure and the main reinforcement;
A foundation structure construction method comprising the steps of:

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