Composite segments and earth retaining structures

Abstract

To provide a synthetic segment capable of suppressing the abdominal pressure that arises on concrete while maintaining the strength and rigidity of a steel shell, and an earth-retaining structure.SOLUTION: A disclosed synthetic segment is used for constructing an earth-retaining structure by connecting multiple segments in the circumferential direction and the axial direction of the earth-retaining structure, which includes a steel shell, and concrete filled inside the steel shell. The steel shell includes: a pair of main girders spaced apart in the axial direction; a skin plate joined to the outer peripheral side of the pair of main girders; a pair of joint plates joined to both circumferential ends of the pair of main girders; and a shape-retaining material joined between the pair of main girders. The shape-retaining material is formed by providing a notch in the center of a rectangular steel plate in the axial direction.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a synthetic segment for forming an earth retaining structure buried in the ground.

Background Art

[0002] Conventionally, as a jacking method for an earth retaining structure for constructing a vertical underground structure, the Urban Ring method (registered trademark) is known. In the Urban Ring method, earth retaining panels are assembled into a ring-shaped structure at the sinking site, and the ring-shaped structure is jacked into the ground by a jacking device. Then, after the ring-shaped structure is jacked into the ground, the inside of the ring-shaped structure is excavated and the soil is discharged, and a new ring-shaped structure is added on top of it. By repeating such work steps to a predetermined depth, an underground structure such as a shaft is constructed.

[0003] Also, one of the tunnel construction methods is the shield method. The shield method is a method in which, every time a tunneling machine installed in a shaft is advanced by a certain length, an arc-shaped synthetic segment is assembled into a ring shape at the rear to construct a segment ring, and this is sequentially extended to form a cylindrical lining to construct a shield tunnel.

[0004] The synthetic segment used for a shaft or a tunnel as described above has a filling material such as concrete filled inside a steel shell having a main girder forming an axial end face of the earth retaining structure, a joint plate forming a circumferential end face, and a skin plate forming an outer peripheral surface. The synthetic segment can withstand the earth pressure from the surrounding ground by integrally forming the steel shell and the filled concrete to ensure strength and rigidity. Further, since a tensile stress or a compressive stress is applied in the axial direction of the earth retaining direction to the synthetic segment, a shape retaining member is provided inside the steel shell in the direction along the axial direction of the earth retaining structure, and is joined between the main girders arranged opposite to each other. The dimensions between the main girders are stably held by the shape retaining member in the steel shell.

[0005] When shape-retaining members are provided in the composite segment, although the strength and rigidity of the steel shell itself can be ensured, the concrete filling between the shape-retaining members and inside the retaining structure beyond the shape-retaining members will be displaced by the circumferential load on the retaining structure, causing it to bulge inward. Therefore, in Patent Document 1, flanges are made to protrude in opposing directions from each of the pair of main girders to prevent the filled concrete from shearing, and the concrete is reinforced by placing circumferentially extending reinforcing bars inside the filled concrete located inside the shape-retaining members (see Patent Document 1). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2009-74291 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the concrete filling on the outer perimeter of the earth retaining structure had a problem: because the shape-retaining material was placed in the steel shell, the reinforcing bars were arranged around the circumferential direction, avoiding the shape-retaining material, resulting in relatively low concrete strength. In addition, tensile stress acting on the reinforcing bars located inside the shape-retaining material caused the bars to displace, making it impossible to suppress the internal pressure generated in the concrete.

[0008] The present invention solves the above-mentioned problems and provides a composite segment and earth retaining structure that can suppress the internal pressure generated in concrete while maintaining the strength and rigidity of the steel shell. [Means for solving the problem]

[0009] The composite segment according to the present invention is a composite segment that constructs an earth retaining structure by connecting a plurality of such segments in the circumferential and axial directions of the earth retaining structure, comprising a steel shell and concrete filled inside the steel shell, wherein the steel shell comprises a pair of main girders spaced apart in the axial direction, a skin plate joined to the outer periphery of the pair of main girders, a pair of joint plates joined to both ends of the pair of main girders in the circumferential direction, a shape-retaining member joined between the pair of main girders, and reinforcing bars having main reinforcement extending in the circumferential direction and distribution reinforcement extending in the axial direction, wherein the shape-retaining member is a rectangular steel plate with the axial center portion Rectangular The structure is formed by providing a notch, and at least a portion of the reinforcing bar is positioned inside the notch and fixed to the shape-retaining material, comprising outer reinforcing bars positioned on the outside in the radial direction of the earth retaining structure and inner reinforcing bars positioned on the inside, wherein the main reinforcing bars and the distribution reinforcing bars of the inner reinforcing bars are joined to each other, and the axial ends of the distribution reinforcing bars are joined to the plate surface of the shape-retaining material. Furthermore, the shape-retaining material has a notch whose axial dimension is 6 / 7 of the axial dimension of the steel plate, the outer end dimension of the notch is equal to the radial dimension of the pair of main girders, and the radial dimension of the notch is 1 / 4 of the radial dimension of the pair of main girders. That is the case.

[0010] The earth retaining structure of the present invention is formed by combining a plurality of the above-mentioned composite segments in the circumferential and axial directions. [Effects of the Invention]

[0011] The composite segment of the present invention has a notch in the center of the shape-retaining member joined between a pair of main girders. Since it is configured so that, for example, reinforcing bars can be placed inside the notch of the shape-retaining member, the distance between the main girders is maintained by the shape-retaining member, while the degree of freedom in placing the reinforcing bars that reinforce the concrete is improved. As a result, the degree of freedom in placing reinforcing bars inside the concrete is improved, and it becomes possible to place reinforcing bars that are advantageous to the internal pressure generated in the concrete installed inside the steel shell. [Brief explanation of the drawing]

[0012] [Figure 1] This is a conceptual diagram of the earth retaining structure 200 according to Embodiment 1. [Figure 2]This is a conceptual diagram of the segment ring 150 according to Embodiment 1, viewed in the direction AD of the hole axis. [Figure 3] This is a perspective view showing an example of a synthetic segment 100 according to Embodiment 1. [Figure 4] This is a perspective view showing an example of the internal structure of the synthetic segment 100 according to Embodiment 1. [Figure 5] Figure 3 is a perspective view of the composite segment 100 as seen from the outer perimeter of the retaining wall structure 200. [Figure 6] This is a schematic diagram of the cross-sectional structure of the composite segment 100 according to Embodiment 1. [Figure 7] This is a schematic diagram of synthetic segment 1000, which is a comparative example of synthetic segment 100 according to Embodiment 1. [Figure 8] This is a schematic diagram of the composite segment 100 according to Embodiment 1. [Figure 9] This is a schematic diagram of the cross-sectional structure of the composite segment 101 according to Embodiment 2. [Figure 10] This is a schematic diagram of the cross-sectional structure of the composite segment 102 according to Embodiment 3. [Modes for carrying out the invention]

[0013] The earth-retaining structure according to the embodiment will be described below with reference to the drawings. Note that in the following drawings, including Figure 1, the relative dimensions and shapes of each component may differ from those of the actual components. Also, in the following drawings, components with the same reference numerals are the same or equivalent, and this is consistent throughout the entire specification. In addition, terms indicating direction (e.g., up, down, left, right, front, back, front and back, etc.) will be used as appropriate to facilitate understanding, but these notations are for the convenience of explanation and do not limit the arrangement, direction, and orientation of devices, equipment, or parts.

[0014] Embodiment 1. [Earth retaining structure 200] FIG. 1 is a conceptual diagram of the earth retaining structure 200 according to Embodiment 1. In FIG. 1, the hole axis direction AD indicates the axial direction of the earth retaining structure 200, the circumferential direction CD indicates the circumferential direction of the earth retaining structure 200, the radial direction RD indicates the radial direction of the earth retaining structure 200, the Y1 side represents the inner circumferential side of the earth retaining structure 200, and the Y2 side represents the outer circumferential side of the earth retaining structure 200.

[0015] The earth retaining structure 200 is used, for example, for the lining of a tunnel and is installed along the wall surface of an excavation hole formed by excavating the ground. The earth retaining structure 200 is installed in the ground 90 and is used, for example, for tunnels, shafts that constitute subways, road tunnels, sewers, power lines, communication ducts, utility tunnels, etc. The earth retaining structure 200 is a cylindrical body and has a hollow portion. The earth retaining structure 200 has at least one segment ring 150 or is formed by continuously connecting a plurality of segment rings 15 in the direction in which the tunnel extends.

[0016] Further, the earth retaining structure 200 may be a structure used as an earth retaining wall by the jacked caisson method. The earth retaining structure 200 is a structure that covers the excavation surface in the ground in a construction method such as the jacking method. The earth retaining structure 200 is sunk in the ground 90. The earth retaining structure 200 is a cylindrical body and forms a space 91 that is a hollow portion. When the earth retaining structure 200 is used for a shaft, it is arranged in the ground so that the cylindrical hole axis direction AD is in the vertical direction.

[0017] The earth retaining structure 200 is formed in a circular shape when viewed in the hole axis direction AD and is formed in a cylindrical shape as a whole, but is not limited to the cylindrical shape. As long as the earth retaining structure 200 is formed in a cylindrical shape, it may be formed in other shapes such as an oval shape or an oval shape when viewed in the hole axis direction AD.

[0018] [Segment Ring 150] Figure 2 is a conceptual diagram of the segment ring 150 according to Embodiment 1, viewed in the direction of the borehole axis AD. The segment ring 150 is a structure that covers the excavated surface underground. The segment ring 150 is formed in an annular shape when viewed in the direction of the borehole axis AD, and is formed in a cylindrical shape overall. The segment ring 150 is formed in a cylindrical shape, for example, but is not limited to a cylindrical shape.

[0019] The earth retaining structure 200 is constructed by connecting multiple segment rings 150 along the direction in which the earth retaining structure 200 extends, that is, along the bore axis direction AD. When the earth retaining structure 200 is used, for example, in the shield tunneling method, the earth retaining structure 200 is constructed by arranging the segment rings 150 around the entire circumference (1 ring) of the tunnel cross-section. Therefore, in the earth retaining structure 200, the segment rings 150 constitute one unit in the direction in which the tunnel extends.

[0020] The segment ring 150 is divided into multiple composite segments 100 in the circumferential direction CD. That is, multiple composite segments 100 are arranged in a ring, and adjacent composite segments 100 are connected to each other to form the segment ring 150. In Figure 2, the segment ring 150 is shown with composite segments 100 of approximately equal size in the circumferential direction CD, but the size of the composite segments 100 may be different depending on their installation position in the circumferential direction CD.

[0021] As shown in Figure 1, in the earth retaining structure 200, the segment rings 150 adjacent to each other in the hole axis direction AD are assembled in a state where the positions of the composite segments 100 constituting the segment rings 150 are shifted in the circumferential direction CD. More specifically, in the earth retaining structure 200, the composite segments 100 constituting the segment rings 150 are constructed in a staggered arrangement.

[0022] [Composite Segment 100] Figure 3 is a perspective view showing an example of a composite segment 100 according to Embodiment 1. Figure 4 is a perspective view showing an example of the internal structure of a composite segment 100 according to Embodiment 1. Figure 5 is a perspective view of the composite segment 100 of Figure 3 as seen from the outer periphery of the earth retaining structure 200. The composite segment 100 will be explained using Figures 3 to 5.

[0023] The composite segments 100 are arranged in a ring and connected to each other in the circumferential direction CD, thereby forming a cylindrical segment ring 150 that covers the excavation surface underground. The composite segment 100 is a box-shaped structure made by combining multiple steel materials. When viewed in the direction AD of the hole axis of the segment ring 150, the composite segment 100 is formed in an arc shape, and the overall shape is curved.

[0024] The composite segment 100 has a steel shell 10 and concrete 80 poured inside the steel shell 10. The composite segment 100 is a composite structure of a box-shaped steel shell 10 and concrete 80 filled inside the steel shell 10 as a filler, with the steel shell 10 and concrete 80 being integrated into one structure. The composite segment 100 also has reinforcing bars 40 and 41 inside the concrete 80. The reinforcing bar 40 is made by joining main reinforcement bars 42 and distribution reinforcement bars 44. The reinforcing bar 41 is made by joining main reinforcement bars 43 and distribution reinforcement bars 45.

[0025] As shown in Figure 4, the steel shell 10 of the composite segment 100 comprises a pair of main girders 11, a pair of joint plates 12, and a skin plate 16. The steel shell 10 is formed in a box shape by welding and fixing these main girders 11, joint plates 12, and skin plate 16 to each other to form a single unit.

[0026] The pair of main girders 11 are the parts where adjacent composite segments 100 abut each other in the hole axis direction AD of the earth retaining structure 200 and the segment ring 150, and constitute the axial connection portion 93 (see Figure 1) where adjacent composite segments 100 are connected. The pair of main girders 11 are located at both ends of the composite segment 100 in the hole axis direction AD of the earth retaining structure 200 and the segment ring 150. That is, the main girders 11 are provided at both ends of the skin plate 16 and joint plate 12 in the hole axis direction AD of the earth retaining structure 200 and the segment ring 150. The main girders 11 form one face and the other face of the composite segment 100 in the hole axis direction AD.

[0027] The main girder 11 is formed in a flat plate shape. The main girder 11 is formed in an arc shape in a plan view taken in the direction AD of the borehole axis, according to the cross-sectional shape of the tunnel, and is formed in an annular fan shape. The main girder 11 is formed to extend in the circumferential direction CD and the radial direction RD.

[0028] In one of the pair of main girders 11, multiple bolt holes 13 are formed for connecting adjacent composite segments 100 stacked vertically in the hole axis direction AD. For example, one bolt hole 13 is formed at each interval partitioned by a shape-retaining material 20. Also, as shown in Figure 3, bolt boxes 81 are provided in the concrete 80 at locations corresponding to the bolt holes 13. The bolt boxes 81 create a space in the composite segment 100 between the concrete 80 and the main girder 11 that exposes the bolt holes 13. The bolt boxes 81 serve as a working space used for fastening bolts to connect the main girders 11 of adjacent composite segments 100 in the hole axis direction AD.

[0029] Of the pair of main girders 11, the other main girder 11 has multiple bosses 14 formed therein for connecting adjacent composite segments 100 stacked vertically in the hole axis direction AD. The bosses 14 have mounting holes 14a (see Figure 6) with female threads for screwing in bolts.

[0030] Adjacent composite segments 100 in the axial direction AD of the hole are connected by butting the main girders 11 together, using bolt boxes 81, and fastening the shafts of the bolts, which are inserted through the bolt holes 13 and fastened with nuts, using bolts provided on the bosses 14. The number of bolt holes 13 and bosses 14 is not limited to the illustrated example and is determined by considering, for example, the size and shape of the composite segments 100. Furthermore, the connection structure of adjacent composite segments 100 is not limited to the above and may be done by bolts and nuts or quick-connect fittings. The composite segments 100 are connected by butting the main girders 11 together to form the axial connection portion 93 of the earth retaining structure 1.

[0031] The pair of joint plates 12 are the parts where adjacent composite segments 100 come into contact with each other in the circumferential direction CD of the earth retaining structure 200 and the segment ring 150, and the adjacent composite segments 100 form a circumferential connecting portion 92 (see Figure 1). The pair of joint plates 12 are members attached to both ends of the composite segment 100 in the circumferential direction CD.

[0032] The joint plate 12 is formed in a plate shape and consists of a rectangular steel plate. The joint plate 12 is formed to extend in the hole axis direction AD and radial direction RD. The joint plate 12 is spanned and fixed between the longitudinal ends of a pair of main girders 11. The longitudinal direction of the main girders 11 is the circumferential direction CD. A joint for connecting the composite segments 100 to form a single segment ring 150 may be attached to the end of the composite segment 100 where the joint plate 12 is located.

[0033] The joint plate 12 is positioned at both ends of the circumferential CD of the composite segment 100 so as to cover the opening formed by the pair of main girders 11 and the skin plate 16 positioned between the pair of main girders 11. The joint plate 12 is provided at both ends of the skin plate 16 in the arc direction and forms the left and right sides of the composite segment 100.

[0034] As shown in Figure 3, the joint plate 12 has multiple bolt holes 15 formed therein for connecting adjacent composite segments 100 arranged in the circumferential direction CD of the excavated hole. Also as shown in Figure 3, bolt boxes 82 are provided in the concrete 80 at locations corresponding to the bolt holes 15. The bolt boxes 82 form a space in the composite segment 100 between the concrete 80 and the joint plate 12 that exposes the bolt holes 15. The bolt boxes 82 serve as a working space used for fastening bolts to connect the joint plates 12 of adjacent composite segments 100 in the circumferential direction CD. Note that the connection in the circumferential direction CD is not limited to a structure using bolts and nuts; for example, a boss 14 having a bolt and a mounting hole 14a that screws into it may be used, similar to the axial connection part 93, or a one-touch joint may be used.

[0035] Adjacent composite segments 100 in the circumferential direction are connected by butting joint plates 12 together and fastening the shafts of bolts inserted through bolt holes 15 with nuts. The number of bolt holes 15 shown in the figure is just an example and is not limited to this number; it is determined by considering, for example, the size and shape of the composite segments 100.

[0036] The skin plate 16 is a plate-shaped member facing the ground side of the composite segment 100, and is formed by bending a rectangular steel plate into an arc shape in the planar direction. The skin plate 16 is formed in a plate shape with a curved surface. The skin plate 16 is formed to extend in the circumferential direction CD and the hole axis direction AD. The skin plate 16 is formed in an arc shape when viewed in a plan view in the hole axis direction AD, and in a rectangular shape when viewed in a side view in the radial direction RD.

[0037] As shown in Figure 4, the skin plate 16 is joined to close the opening on the ground-side end face of the frame obtained by joining a pair of main girders 11 and a pair of joint plates 12. That is, the skin plate 16 is attached to the outer periphery of the main girders 11 and joint plates 12 that constitute the composite segment 100. When the composite segment 100 is installed in the ground, the skin plate 16 faces the wall of the excavation hole and constitutes the outer periphery wall of the earth retaining structure 200.

[0038] A shape-retaining member 20 is provided inside the composite segment 100, that is, inside the box-shaped steel shell 10. The shape-retaining member 20 is also provided to ensure the dimensions between the main girders 11 during the manufacturing of the composite segment 100.

[0039] The shape-retaining members 20 are members that extend in the direction AD of the hole axis. The shape-retaining members 20 are erected in the direction normal to the surfaces of the main girder 4 and the skin plate 6, and the ends of the shape-retaining members 20 are joined to the main girder 11 in the direction AD of the hole axis. The shape-retaining members 20 are composed of plate-shaped members made of, for example, steel plates as shown in the figure, or rod-shaped members made of reinforcing bars, etc. (not shown). In the illustrated example, six shape-retaining members 20 are arranged at intervals in the circumferential direction CD. The number and arrangement of the shape-retaining members 20 are not limited to the illustrated example and can be determined by considering, for example, the size and shape of the composite segment 100.

[0040] Figure 6 is a schematic diagram of the cross-sectional structure of the composite segment 100 according to Embodiment 1. Figure 6 shows a cross-section of the composite segment 100 including the center C of the earth retaining structure 200, with the center C located at the top of the figure. In Figure 6, the outline of the concrete 80 is shown by a dashed line.

[0041] The shape-retaining material 20 has a rectangular shape with a notch 21 in the center of the hole axis direction AD of the rectangular plate. The notch 21 is a rectangular notch formed by cutting out the edge 22 facing inward of the shape-retaining material 20. The edge 21a corresponding to the bottom of the notch 21 is parallel to the hole axis direction AD of the earth retaining structure 200. Edges 21b rise perpendicularly from both ends of the hole axis direction AD of edge 21a toward the radial direction RD.

[0042] In Embodiment 1, the edge 21a of the shape-retaining material 20 is located outside the center N (see Figure 8) of the width of the steel shell 10 in the radial direction RD. The notch 21 has a right-angled corner, but for example, an R-shape or inclined portion may be provided at the corner.

[0043] Reinforcement bars 40 are the innermost reinforcement bars in the radial direction RD, and reinforcement bars 41 are the outermost reinforcement bars. Reinforcement bars 40 and 41 are embedded inside the concrete 80 to reinforce the concrete 80. Reinforcement bars 40 each consist of main reinforcement bars 42 extending in the circumferential direction CD and distribution reinforcement bars 44 extending in the bore axis direction AD. The main reinforcement bars 42 and distribution reinforcement bars 44 are joined, for example, by welding. Reinforcement bars 41 each consist of main reinforcement bars 43 extending in the circumferential direction CD and distribution reinforcement bars 45 extending in the bore axis direction AD. The main reinforcement bars 43 and distribution reinforcement bars 45 are joined, for example, by welding. The main reinforcement bars 42, 43, distribution reinforcement bars 44 and distribution reinforcement bars 45 are made of, for example, steel bars, deformed steel bars, etc. Reinforcement bar 40 is the innermost reinforcement bar in the radial direction RD and is also called inner reinforcement bar 40. Reinforcement bars 41 are the outermost bars arranged in the radial direction RD, and are also called outer reinforcement bars 41. Note that the main reinforcement bars 42, 43, distribution reinforcement bars 44, and distribution reinforcement bars 45 may be joined by binding them together using binding wires, for example, in addition to welding, and the form of joining is not limited.

[0044] Main reinforcement bars 42 and 43 are embedded in the concrete 80 as main steel materials and are arranged to extend in the circumferential direction CD of the composite segment 100. In Figure 4, the reinforcement bars 40 and 41 of the composite segment 100 each have four main reinforcement bars 42 or 43 along the hole axis direction AD, but the number of main reinforcement bars 42 and 43 is not limited to these numbers.

[0045] The distribution reinforcement bars 44 and 45 are embedded inside the concrete 80 and are arranged to extend in the axial direction AD of the hole in the composite segment 100. The distribution reinforcement bars 44 are arranged perpendicular to the multiple main reinforcement bars 42 and are joined by welding or the like to connect the multiple main reinforcement bars 42 to each other. The distribution reinforcement bars 45 are similarly joined to connect the multiple main reinforcement bars 43 to each other. In Embodiment 1, the composite segment 100 has eight distribution reinforcement bars 44 and eight distribution reinforcement bars 45 arranged in the circumferential direction CD, but the number of distribution reinforcement bars 44 and 45 is not limited to this number.

[0046] The outer reinforcement bars 41 are positioned in contact with the edge 21a of the notch 21 formed in the shape-retaining material 20. More specifically, of the outer reinforcement bars 41, the main reinforcement bars 43 that are positioned inward in the radial direction RD are positioned in contact with the edge 21a of the notch 21. The edge 21a is the edge facing inward of the notch 21. The main reinforcement bars 43 are joined to the contacting edge 21a by welding. The main reinforcement bars 43 are joined to the shape-retaining material 20 at six locations shown in Figure 4 and are formed integrally with the steel shell 10 before the concrete 80 is filled.

[0047] As shown in Figure 6, the distribution reinforcement bars 44 of the inner reinforcement 40 extend in the hole axis direction AD and are longer than the width of the hole axis direction AD of the notch 21 of the shape-retaining material 20. Both ends 44a of the distribution reinforcement bars 44 in the hole axis direction AD may be welded to the plate surface 23 of the shape-retaining material 20. In other words, in the circumferential direction CD, at least two of the multiple distribution reinforcement bars 44 are positioned adjacent to the plate surface 23 of the shape-retaining material 20 and joined to the plate surface 23 of the shape-retaining material 20. This fixes the reinforcement bars 40 near the inner edge 22 in the radial direction RD of the shape-retaining material 20, determining their position within the composite segment 100. In this case, the arrangement of the multiple shape-retaining materials 20 and the multiple distribution reinforcement bars 44 may be adjusted so that a distribution reinforcement bar 44 is joined to each shape-retaining material 20.

[0048] Similarly, the distribution reinforcement bars 45 of the outer reinforcement bars 41 may also be formed to be longer than the width AD in the axial direction of the notch 21 of the shape-retaining material 20, and may be joined to the plate surface 23 of the shape-retaining material 20. This strengthens the bond between the reinforcement bars 41 and the steel shell 10. The distribution reinforcement bars 44 of the outer reinforcement bars 41 can also be positioned in accordance with the position of the shape-retaining material 20, thereby increasing the number of connection points between the outer reinforcement bars 41 and the shape-retaining material 20.

[0049] [Effect of the synthetic segment 100 according to Embodiment 1] Figure 7 is a schematic diagram of composite segment 1000, which is a comparative example of composite segment 100 according to Embodiment 1. Figure 7 is a view of the earth retaining structure 200 from the hole axis direction AD, and schematically represents the composite segment 1000 that constitutes the earth retaining structure 200. The composite segment 1000 according to the comparative example comprises a steel shell 1010, concrete 80 filled inside the steel shell 1010, and main reinforcement bars 42 arranged inside the concrete 80. Since the composite segment 1000 has a shape-retaining material 1020 on the outside in the radial direction RD, the main reinforcement bars 42 are arranged only in the inner portion of the composite segment 1000. The shape-retaining material 1020 is made of a normal rectangular steel plate and connects the main girders 11.

[0050] When soil pressure is applied, for example, from the ground 90, to the segment ring 150 composed of composite segments 1000, the composite segments 1000 receive the load F shown in Figure 7. Since the load F is received in the center of the composite segment 1000, the entire composite segment 1000 receives a bending moment M. Note that although the load F on the composite segment 1000 is schematically shown in Figure 7, in reality it is distributed and applied to the outer circumference of the composite segment 1000.

[0051] When a bending moment M is applied to the composite segment 1000, the concrete 80 experiences a tummy pressure indicated by arrow f in Figure 7, causing deformation between the shape-retaining members 1020 as shown by the outer shape P. In other words, the concrete 80 deforms so as to bulge inward in the radial direction RD at the center between the shape-retaining members 1020. At this time, the concrete 80 bulges out from the steel shell 1010 in the circumferential direction CD at the center between the two shape-retaining members 1020 and at the center between the shape-retaining member 1020 and the joint plate 12, causing a displacement between the concrete 80 and the steel shell 1010.

[0052] Furthermore, main reinforcement bars 42 are arranged inside the concrete 80, and these bars can resist the tensile stress T generated in the concrete 80 by the bending moment M. However, the main reinforcement bars 42, which are formed in an arc shape along the circumferential direction CD, deform in a direction that reduces the overall curvature due to the tensile stress T. In other words, the main reinforcement bars 42 are displaced inward in the radial direction RD at the center of the composite segment 1000. This displacement of the main reinforcement bars 42 becomes the abdominal pressure shown by arrow f in Figure 7. This is one of the reasons why the concrete 80 bulges inward from the steel shell 1010 in the composite segment 1000 of the comparative example. On the other hand, in Figure 7, the concrete 80 is wedge-shaped between the two shape-retaining members 1020, and the deformation of bulging inward is suppressed. That is, the shape-retaining members 1020 act as a shearing stopper between the concrete 80 and the steel shell 1010. However, because the angle formed by the plate surfaces of the two shape-retaining materials 1020 is small, the effect of suppressing deformation that causes the concrete 80 to bulge radially is small. Therefore, in the comparative example composite segment 1000, it is difficult to suppress deformation that causes the concrete 80 to bulge out from the steel shell 1010.

[0053] Thus, if the deformation of the concrete 80 bulging out from the steel shell 1010 cannot be suppressed, and a displacement occurs between the steel shell 1010 and the concrete 80, not only will the integration of the steel shell 1010 and the concrete 80 become impossible, but the concrete 80 will also be unable to bear the compressive force in the circumferential direction of the tunnel, resulting in a problem where the load-bearing capacity of the composite segment 1000 decreases sharply. Therefore, the challenge for the composite segment 1000 in the comparative example is how to suppress the displacement between the steel shell 1010 and the concrete 80.

[0054] Figure 8 is a schematic diagram of the composite segment 100 according to Embodiment 1. Figure 8 is a schematic diagram of the composite segment 100 corresponding to Figure 7, and the structure of the composite segment 100 is partially omitted. Unlike the comparative example, the composite segment 100 according to Embodiment 1 includes main reinforcement bars 43 that are located radially outward RD from the main reinforcement bars 42. The main reinforcement bars 43 are joined to the edge 21a of the notch 21 of the shape-retaining material 20 and are integrated with the steel shell 10. In Figure 8, the joint W shows the location where the main reinforcement bars 43 and the shape-retaining material 20 are fixed. As a result, the composite segment 100 has improved bonding strength between the concrete 80 and the steel shell 10 compared to the comparative example. In other words, the main reinforcement bars 43 are supported by the steel shell 10 at the joint W, and the concrete 80 is supported by a part of the main reinforcement bars 43 between the joint W. The shape-retaining material 20 has a notch 21 and is configured to allow the main reinforcement bars 43 to be placed, but it is placed across a pair of main girders 11 and functions as a shearing stopper for the concrete 80.

[0055] The main reinforcement bars 43 are fixed to the steel shell 10 by the shape-retaining material 20. Therefore, even when the main reinforcement bars 43 are subjected to compressive or tensile stress when a bending moment M acts on the composite segment 100, they are less likely to be displaced inward toward the earth retaining structure 200. This makes it possible to suppress the abdominal pressure generated in the concrete 80. Alternatively, the outer reinforcement bars 41 may be joined to the plate surface 23 of the shape-retaining material 20 by joining the end 45a of the distribution reinforcement bars 45 instead of the main reinforcement bars 43. Even in this case, the main reinforcement bars 43 are indirectly joined to the shape-retaining material 20. Furthermore, the outer reinforcement bars 41 may be joined to the shape-retaining material 20 by joining both the main reinforcement bars 43 and the distribution reinforcement bars 45.

[0056] In the composite segment 100 according to Embodiment 1, the end portion 44a of the distribution reinforcement 44 joined to the main reinforcement 42 can also be joined to the shape-retaining material 20. Even in this case, the inner reinforcement 40 located on the inside in the radial direction RD also becomes integrated with the steel shell 10, and the main reinforcement 42 of the inner reinforcement 40 is indirectly fixed to the steel shell 10. As a result, the displacement of the main reinforcement 42 due to tensile stress T can be suppressed, and thus the intra-abdominal pressure generated in the concrete 80 can also be suppressed.

[0057] Furthermore, when the inner reinforcing bars 40 and outer reinforcing bars 41, which are spaced apart in the radial RD within the concrete 80, are joined to the shape-retaining material 20, the inner reinforcing bars 40 and outer reinforcing bars 41 are connected via the shape-retaining material 20. In other words, the outer main reinforcing bars 43 and the inner main reinforcing bars 42 are constrained, and deformation that causes the concrete 80 to bulge inward in the radial RD is suppressed, thereby reducing internal pressure. The outer main reinforcing bars 43 and the inner main reinforcing bars 42 are positioned with the center N of the radial RD of the steel shell 10 in between, which improves the strength of the concrete 80 against bending moment M.

[0058] The composite segment 100 according to Embodiment 1 ensures the rigidity and strength of the steel shell 10 with the shape-retaining material 20, and allows circumferentially extending main reinforcement bars 42 or 43 to be placed in the notch 21, thereby improving the strength of the concrete 80 and the overall strength. Furthermore, the composite segment 100 can also have additional reinforcement bars placed inside the notch 21; for example, another layer of reinforcement bars consisting of main reinforcement bars and distribution bars may be placed between the inner reinforcement bars 40 and the outer reinforcement bars 41.

[0059] Furthermore, the composite segment 100 according to Embodiment 1 has a notch 21 in the shape-retaining material 20 that faces inward in the radial direction RD, which has the advantage that it is easy to arrange the reinforcing bars 40 and 41 during manufacturing and that the joining workability is also excellent.

[0060] Embodiment 2. The composite segment 101 according to Embodiment 2 will now be described. The composite segment 101 is a modified version of the composite segment 100 according to Embodiment 1, with a change in the fixing structure of the reinforcing bars 40. Components having the same function and operation as those in Embodiment 1 are denoted by the same reference numerals and their descriptions are omitted.

[0061] Figure 9 is a schematic diagram of the cross-sectional structure of the composite segment 101 according to Embodiment 2. The composite segment 101 according to Embodiment 2 includes a radial connecting member 46 joined to the main reinforcement bars 42 constituting the reinforcing bar 40 and the skin plate 16 of the steel shell 10. The radial connecting member 46 is formed in a U-shape and includes a steel shell-side joint portion 46a that is joined to the skin plate 16 at the outer end of the radial RD and a main reinforcement-side joint portion 46b that is joined to the main reinforcement bars 42 at the inner end of the radial RD. The radial connecting member 46 suppresses fluctuations in the distance between the skin plate 16 and the main reinforcement bars 42. The radial connecting member 46 may also be referred to as the radial reinforcement bar.

[0062] In Figure 9, radial connecting members 46 are provided only on the main reinforcement bars 42 located at both ends in the hole axis direction AD, but the configuration is not limited to this. For example, radial connecting members 46 may also be provided on the main reinforcement bars 42 located in the central part, and the number and location of installations can be changed as appropriate.

[0063] By changing the position of the radial connecting member 46, the composite segment 101 can freely set the point where it connects the main reinforcement 42 and the skin plate 16. For example, by installing the radial connecting member 46 in the center of the two shape-retaining members 20, the displacement of the main reinforcement 42 in the radial direction RD inward, as explained in Figure 7, can be effectively suppressed, thereby suppressing abdominal pressure and improving the effect of preventing deformation in which the concrete 80 bulges inward. The abdominal pressure suppression effect can be further improved by installing the radial connecting member 46 between the shape-retaining members 20 in the circumferential direction CD.

[0064] The radial connecting member 46 is made of, for example, a steel bar bent into a U-shape, but its shape and material are not limited. For example, the radial connecting member 46 may be configured such that the steel shell side joint 46a and the main reinforcement side joint 46b face in different directions. Alternatively, the radial connecting member 46 may be formed by bending a steel plate.

[0065] The radial connecting member 46 is not limited to being positioned to extend in the radial direction RD, but may also be installed at an inclination in the circumferential direction CD or the bore axis direction AD with respect to the radial direction RD. Furthermore, a single radial connecting member 46 may be used to connect multiple main reinforcement bars 42 and skin plates 16. The radial connecting member 46 may have multiple steel shell-side joint portions 46a or main reinforcement bar-side joint portions 46b.

[0066] Furthermore, the radial connecting member 46 may be joined to the distribution reinforcement 44 instead of the main reinforcement 42 of the inner reinforcement 40. By suppressing the displacement of the distribution reinforcement 44 in the radial direction RD, the displacement of the main reinforcement 42 can be indirectly suppressed. In this case, the radial connecting member 46 and the distribution reinforcement 44 may be integrally constructed. That is, a part of the distribution reinforcement 44 may be extended radially RD and joined to the steel shell 10.

[0067] The radial connecting member 46 may be joined to the inner reinforcing bar 40 and also to the outer reinforcing bar 41. This allows the inner reinforcing bar 40 and the outer reinforcing bar 41 to be more firmly integrated with the steel shell 10, thereby suppressing the displacement of both the inner reinforcing bar 40 and the outer reinforcing bar 41, and further improving the effect of suppressing abdominal pressure.

[0068] Furthermore, the position of the reinforcing bar 40 in the radial direction RD can be moved further inward. This allows the main reinforcement 42 to reinforce the portion of the concrete 80 where the tensile stress is high due to the bending moment M acting on the composite segment 101, while suppressing the displacement of the main reinforcement 42.

[0069] As described above, according to the composite segment 101 of Embodiment 2, the displacement of the reinforcing bars 40 relative to the steel shell 10 can be suppressed by connecting the reinforcing bars 40 located on the inside to the steel shell 10. Therefore, the composite segment 101 can suppress abdominal pressure. In Embodiment 2, the skin plate 16 and the reinforcing bars 40 are connected, but the steel shell side joint portion 46a of the radial connecting member 46 may be connected to other members constituting the steel shell 10 depending on the structure of the steel shell 10.

[0070] Embodiment 3. The composite segment 102 according to Embodiment 3 will now be described. The composite segment 102 is a modified version of the composite segment 101 according to Embodiment 2, with a change in the target to which it is connected by the radial connecting member 46. Components having the same function and operation as those in Embodiment 1 or Embodiment 2 are denoted by the same reference numerals and their descriptions are omitted.

[0071] Figure 10 is a schematic diagram of the cross-sectional structure of the composite segment 102 according to Embodiment 3. In the composite segment 102 according to Embodiment 3, the inner reinforcing bar 40 and the outer reinforcing bar 41 are connected by a radial connecting member 46. As a result, fluctuations in the distance between the inner reinforcing bar 40 and the outer reinforcing bar 41 are suppressed. The outer reinforcing bar 41 is joined to the edge 21a of the notch 21 provided in the shape-retaining member 20 and fixed to the steel shell 10, so the displacement of the inner reinforcing bar 40 relative to the steel shell 10 can be suppressed indirectly. As a result, the composite segment 102 can suppress abdominal pressure.

[0072] Furthermore, the composite segment 102 allows the position of the inner reinforcement bars 40 to be moved inward in the radial direction RD. This makes it possible to reinforce the areas of the concrete 80 where the tensile stress is high due to the bending moment M acting on the composite segment 102 with the main reinforcement bars 42, while suppressing the displacement of the main reinforcement bars 42.

[0073] The radial connecting member 46 in Embodiment 3 may be composed of a portion of the distribution reinforcement 44 or 45 of the inner reinforcement 40 or the outer reinforcement 41. In other words, the distribution reinforcement 44 or 45 may be extended radially RD and joined to the main reinforcement 42 or 43. In this case, the inner reinforcement 40 and the outer reinforcement 41 are formed as a single reinforcement cage.

[0074] As described above, according to the composite segment 102 of Embodiment 3, by connecting the reinforcing bars 40 located on the inside and the reinforcing bars 41 located on the outside, the bonding force between the reinforcing bars 40 and 41 is increased, and the strength of the concrete 80 is also improved. Furthermore, since the reinforcing bars 40 are also fixed to the steel shell 10 via the reinforcing bars 41 fixed to the shape-retaining material 20, the displacement of the reinforcing bars 40 can be suppressed. Therefore, the composite segment 102 can suppress abdominal pressure.

[0075] The configurations shown in the above embodiments are examples only, and the configurations shown in each embodiment can be combined. Furthermore, each embodiment can be combined with other known technologies, and parts of the configuration can be omitted or modified without departing from the gist of the invention. [Explanation of symbols]

[0076] 1 Earth retaining structure, 4 Main girder, 6 Skin plate, 10 Steel shell, 11 Main girder, 12 Joint plate, 13 Bolt hole, 14 Boss, 14a Mounting hole, 15 Bolt hole, 16 Skin plate, 20 Shape retaining material, 21 Notch, 21a Edge, 21b Edge, 22 Edge, 23 Plate surface, 40 (Inside) Reinforcement, 41 (Outside) Reinforcement, 42 Main reinforcement, 43 Main reinforcement, 44 Distribution reinforcement, 44a End, 45 Distribution reinforcement, 45a End, 46 Radial connecting member, 46a Steel shell side joint, 46b Main reinforcement side joint, 80 Concrete, 81 Bolt box, 82 Bolt box, 90 Ground, 91 Space, 92 Circumferential connecting part, 93 Axial connecting part, 100 Composite segment, 101 Composite segment, 102 Composite segment, 150 Segment ring, 200 Earth retaining structure, 1000 Composite segment, 1010 Steel shell, 1020 Shape-retaining material, AD Hole axis direction, C Center, CD Circumferential direction, M Bending moment, P Outer shape, RD Radial direction, T Tensile stress, W Joint.

Claims

1. A composite segment that is connected in multiple ways in the circumferential and axial directions of the earth retaining structure to construct the earth retaining structure, Steel shell and, The steel shell is filled with concrete, The aforementioned steel shell is A pair of main girders spaced apart in the axial direction, A skin plate joined to the outer periphery of the pair of main girders, A pair of joint plates joined to both ends in the circumferential direction of the pair of main girders, A shape-retaining member joined between the pair of main girders, A reinforcing bar having main reinforcement extending in the circumferential direction and distribution reinforcement extending in the axial direction, Equipped with, The shape-retaining material is It is formed by providing a rectangular notch in the axial center of a rectangular steel plate. The aforementioned reinforcing bars are At least a portion of it is positioned inside the notch and fixed to the shape-retaining material, The earth retaining structure comprises outer reinforcement bars arranged radially outward and inner reinforcement bars arranged radially inward, The main reinforcement and the distribution reinforcement of the inner reinforcement are, They are joined together, The axial end of the aforementioned force distribution reinforcement is The shape-retaining material is bonded to the plate surface, The shape-retaining material is The axial dimension of the notch is The dimension of the steel plate in the axial direction is 6 / 7, The dimensions at the outer end of the aforementioned notch are, Equal to the radial dimension of the pair of main girders, The radial dimension of the notch is, A composite segment having a radial dimension of 1 / 4 of the pair of main girders.

2. The aforementioned external reinforcement is, The composite segment according to claim 1, wherein the composite segment is joined to the radial edge of the notch of the shape-retaining material.

3. The radially oriented edge of the notch is The composite segment according to claim 2, which is located outside the center of the radial width of the steel shell.

4. The aforementioned external reinforcement is, The composite segment according to claim 3, which is located outside the center of the radial width of the steel shell.

5. The main reinforcement bars of the outer reinforcement and the inner reinforcement are, The composite segment according to any one of claims 1 to 4, which is connected in the radial direction.

6. The aforementioned reinforcing bars are The aforementioned radially extending radial connecting member is further provided, The radial connecting member is, The composite segment according to claim 5, which connects the main reinforcement bars of the outer reinforcement and the inner reinforcement, respectively.

7. The aforementioned reinforcing bars are The aforementioned radially extending radial connecting member is further provided, The composite segment according to any one of claims 1 to 5, wherein one end of the radial connecting member is connected to the steel shell.

8. The radial connecting member is, The composite segment according to claim 7, which connects the main reinforcement of the inner reinforcement to the skin plate.

9. The radial connecting member is, The composite segment according to claim 7, which connects the distribution reinforcement of the inner reinforcement and the skin plate.

10. A retaining structure formed by combining a plurality of composite segments according to any one of claims 1 to 9 in the circumferential direction and the axial direction.

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