How to install PCa blocks in the invert section

Abstract

To provide a method for installing PCa blocks so that an invert part lining body formed of PCa concrete blocks can be efficiently and quickly formed in a stable state.SOLUTION: A plurality of PCa concrete blocks 20 are horizontally and vertically arranged and installed on an invert part 33. The plurality of PCa concrete blocks 20A, 20B, 20C of block rows in a transverse direction 20D, which are connected in the transverse direction of a tunnel, are installed on the invert part 33 by installing the block 20A on a pedestal section side so as to be adjacent to a pedestal section 31c and temporarily fixing it by a temporary fixing means 36, and subsequently installing the block 20C at an intermediate part and the block 20B on a central part side so as to be adjacent to the temporarily fixed block 20A on the pedestal section side sequentially.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for installing PCa blocks in an invert section, and in particular to a method for installing PCa blocks used when constructing an invert section structure that is provided in the invert section of a mountain tunnel and constitutes an invert section lining. [Background technology]

[0002] A mountain tunnel is formed by excavating a free-standing, relatively stable foundation, such as bedrock. The excavated interior wall surface is covered with a primary lining and a secondary lining, typically made of concrete or mortar. Specifically, after excavating the tunnel using blasting or other methods, a protective layer is formed on the interior wall surface of the mountain tunnel, preferably by spraying mortar or concrete. Then, a known tunnel lining formwork is installed inside the protective layer formed by the primary lining, and a concrete lining of a predetermined thickness is formed as a secondary lining from the side walls to the arch-shaped upper portion of the tunnel. Furthermore, a bottom invert lining of a predetermined thickness is integrally formed in the transverse direction of the tunnel between the lower end supports of the pair of side walls of the previously formed lining extending from both side walls to the arch-shaped upper portion of the tunnel, thereby continuously covering the entire interior wall surface of the mountain tunnel with a secondary lining.

[0003] Furthermore, because mountain tunnels are formed by excavating relatively stable ground, some tunnels constructed more than several decades ago, for example, omit the invert lining and form a secondary lining only in the area from the tunnel's side wall to the upper arch-shaped part. For such mountain tunnels that omit the invert lining, it is being considered to form a new invert lining to prevent future effects such as swelling of the base of the tunnel.

[0004] Cast-in-place concrete has traditionally been used as a method for forming an invert lining at the bottom of a tunnel, connecting it to a lining that has been installed earlier from the side walls to the upper arch-shaped portion of the tunnel (see, for example, Patent Document 1). However, finishing the top surface of the invert lining to create a curved shape requires a high level of skill. Furthermore, when using cast-in-place concrete, the poured concrete takes a considerable amount of time to harden and then undergo a predetermined curing period. Therefore, particularly when forming a new invert lining on the lining from the side walls to the upper arch-shaped portion without the invert lining, traffic inside the tunnel will be blocked for a long period of time, so it is desirable to complete the construction as quickly as possible.

[0005] For this reason, it is being considered to shorten the construction period by forming the invert section covering body using precast concrete members manufactured in advance in a factory, etc. (see, for example, Patent Document 2 and Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-159060 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-28898 [Patent Document 3] Japanese Patent Application Publication No. 2018-123528 Summary of the Invention [Problem to be solved by the invention]

[0007] However, according to the conventional construction method of the invert section of a mountain tunnel using precast concrete members, these concrete members are formed in advance in a factory or the like to a length that spans the entire width of the invert section in the transverse direction, or to a length that divides the invert section into two or three sections in the transverse direction, which results in a large weight and shape, and requires a lot of effort to assemble the formwork in the factory and accurately form the joints, etc. Furthermore, not only does transporting and assembling the members at the construction site require a lot of effort, but particularly in the case of a multi-lane road tunnel, for example, when construction is to be carried out for each lane while maintaining traffic in the other lane, the use of bulky concrete members results in difficult work.

[0008] The present invention aims to provide a method for installing PCa blocks in an invert section that enables efficient and rapid formation of an invert section structure that is formed as a component part of an invert section lining and is installed continuously from the side wall of a tunnel to the lining of the upper arch-shaped section, in a stable state, by using precast concrete blocks (PCa concrete blocks) of an appropriate weight and size that can be easily manufactured in a factory, etc., without requiring much labor. [Means for solving the problem]

[0009] The present invention relates to a method for installing PCa blocks in an invert section of a mountain tunnel, which is used when constructing an invert section structure using a plurality of PCa concrete blocks that are provided in at least one side region in the transverse direction of the tunnel in the invert section of a mountain tunnel and that constitutes an invert section lining, wherein the PCa concrete blocks are formed as hexahedral blocks having curved upper and lower surfaces so as to have a curved shape that follows the cross-sectional shape of the invert section lining, and the plurality of PCa concrete blocks include a base section side block that is arranged adjacent to a base section at the lower end of the side wall section lining, a central section side block that is arranged on the central side in the transverse direction of the invert section, and one or more intermediate section blocks that are arranged between these, and the plurality of PCa concrete blocks are arranged between adjacent base sections and between adjacent The PCa concrete blocks are arranged in series in the transverse direction of the tunnel, with gaps maintained between them, and are also arranged in series in the axial direction of the tunnel, with gaps maintained between adjacent PCa concrete blocks, and are installed in the invert section lined up vertically and horizontally.The PCa concrete blocks in each row arranged in series in the transverse direction of the tunnel are installed in the invert section by installing the base side blocks adjacent to the base and temporarily fixing them by temporary fixing means, and then installing the intermediate blocks and the central side blocks adjacent to the temporarily fixed base side blocks.This achieves the above-mentioned object by providing a method for installing PCa blocks in an invert section, in which the PCa concrete blocks in each row arranged in series in the transverse direction of the tunnel are installed in the invert section.

[0010] Furthermore, the method of installing PC blocks in the invert section of the present invention preferably involves installing the base side block adjacent to the base and temporarily fixing it using a temporary fixing means, then installing the intermediate block and the central side block adjacent to the temporarily fixed base side block, and temporarily fixing them at adjacent locations of each of these installed blocks with bolt members via bolt boxes arranged on the upper surface of at least one of the PCa concrete blocks close to the opposing transverse surface, and then adjusting the height and position of each of the PCa concrete blocks, and then finally tightening the bolt members, thereby installing the multiple PCa concrete blocks in each row connected in the transverse direction of the tunnel in the invert section.

[0011] Furthermore, in the method of installing the PC blocks in the invert section of the present invention, the base-side blocks are installed adjacent to the base and temporarily fixed by temporary fixing means, then the intermediate blocks are installed adjacent to the temporarily fixed base-side blocks, and the installed intermediate blocks are temporarily fixed with bolt members via bolt boxes arranged on the upper surface of at least one of the PCa concrete blocks adjacent to the base-side blocks at a location adjacent to the installed intermediate blocks and the base-side blocks, and the height and position of each PCa concrete block are adjusted and then the bolt members are finally tightened, and then the central blocks are installed adjacent to the intermediate blocks, and the installed central blocks are temporarily fixed with bolt members via bolt boxes arranged on the upper surface of at least one of the PCa concrete blocks adjacent to the intermediate blocks and the installed central blocks are

[0012] Furthermore, in the method of installing PC blocks in the invert section of the present invention, it is preferable that the temporary fixing means is a cable such as a wire or chain member, both ends of which are engaged with a locking member attached to a hole-in anchor buried in the receiving base section and a locking member attached to a bolt box or a lifting jig provided on the receiving base section side block.

[0013] Furthermore, in the method of installing PC blocks in the invert section of the present invention, it is preferable that the temporary fixing means is a cable such as a wire or chain member, both ends of which are engaged with a locking member attached to a hole-in anchor buried in the receiving section and a locking member attached to a bolt box or a lifting jig provided on the receiving section side block. [Effects of the Invention]

[0014] According to the method of installing PC blocks in the invert section of the present invention, by using precast concrete blocks (PCa concrete blocks) of appropriate weight and size that can be easily manufactured in a factory, etc., it is possible to efficiently and quickly form an invert section structure that is formed as a constituent part of the invert section lining, which is installed without much effort and is continuous from the side wall section of the tunnel to the lining section of the upper arch-shaped section, in a stable and efficient manner. [Brief explanation of the drawings]

[0015] [Figure 1] This is a schematic cross-sectional view illustrating a mountain tunnel in which invert structures are formed integrally on both sides of the invert in the transverse direction of the tunnel using a PCa block installation method according to a preferred embodiment of the present invention. [Figure 2] This is a schematic top view of Figure 1 viewed from the AA direction, illustrating an invert section structure formed integrally on both sides of the invert section in the transverse direction of the tunnel using a PCa block installation method according to a preferred embodiment of the present invention. [Figure 3]This is a schematic top view illustrating an invert section structure formed in one side region of the invert section in the transverse direction of the tunnel using a PCa block installation method according to a preferred embodiment of the present invention. [Figure 4] 4 is a schematic cross-sectional view taken along the line BB in FIG. 3 before the filling solidification material is filled. FIG. [Figure 5] This is an oblique view of the PCa concrete blocks that make up the invert structure. [Figure 6] (a) is a top view of the PCa concrete blocks that make up the invert structure, (b) is a transverse side view of (a) seen from the right side, and (c) is an axial side view of (a) seen from the front side. [Figure 7] 1 is a schematic cross-sectional view of a PCa concrete block taken along a portion where a bolt insertion hole is formed, illustrating the bolt insertion hole. FIG. [Figure 8] 10(a) is a perspective view illustrating a grounding adjuster attached to the lower end of a height adjusting bolt, and FIG. 10(b) is a schematic cross-sectional view illustrating another preferred form of a small trumpet-shaped recess. [Figure 9] (a) is a conceptual diagram illustrating the situation in which PCa concrete blocks are connected and arranged in a manner that aligns them with the tunnel line, which curves in the horizontal direction, and (b) is a conceptual diagram illustrating the situation in which PCa concrete blocks are connected and arranged in a manner that aligns them with the tunnel line, which curves in the vertical direction. [Figure 10] This is a simplified cross-sectional view illustrating the state in which filling solidification material has been filled into the gaps between the receiving base, the gaps between adjacent PCa concrete blocks, and the gaps below the bottom surface of the hexahedron shape. [Figure 11] 1 is a schematic cross-sectional view of a PCa concrete block taken along the portion where a filler injection hole is formed, illustrating the filler injection hole and the opening / closing valve. FIG. [Figure 12] This is a schematic top view of the invert structure explaining the injection status of the filling solidification material. [Figure 13] This is an explanatory diagram of an upper surface band plate-shaped formwork that closes gaps on the upper surface of a PCa concrete block. [Figure 14] An explanatory diagram of a gable band plate-shaped formwork that closes the gap at the gable end surface. [Figure 15] This is an explanatory diagram of the unevenness formed on the surface of the center side of the PCa concrete block. DETAILED DESCRIPTION OF THE INVENTION

[0016] The invert structure 10 formed using the PCa block installation method according to a preferred embodiment of the present invention is constructed as a component part of the invert structure 32, which is continuous with the lining 31 in the area extending from the side wall portions 31a on both sides to the upper arch-shaped portion 31b, which was previously formed to cover the inner wall surface of the mountain tunnel 30 shown in Figure 1, and is constructed as a single unit on each side of the transverse center line C of the tunnel, as shown in Figures 2 and 3, when a new invert structure 32 is formed on the base portion 30a of the mountain tunnel 30.The invert structure 10 is constructed as a component part of the invert structure 32, which is continuous with the lining 31 in the area extending from the side wall portions 31a on both sides to the upper arch-shaped portion 31b, as shown in Figures 2 and 3.

[0017] In this embodiment, the mountain tunnel 30 is a tunnel that was constructed, for example, several decades ago, and the ground to be excavated was stable, so at the time of construction, the lining 31 covering the inner wall surface of the tunnel was formed only from the side wall portions 31a on both sides to the upper arch-shaped portion 31b.However, as time passed, concerns arose about the effects of swelling of the base portion 30a, so a new invert lining 32 was formed using invert structures 10 on both the left and right sides.

[0018] Furthermore, when forming a new invert lining 32 in an existing mountain tunnel 30, it is necessary to block traffic through the tunnel, so it is desirable to complete the construction in as short a period as possible. In this embodiment, the invert structure 10 uses a plurality of precast concrete blocks (PCa concrete blocks) that are easy to handle and have an appropriate weight and size, which are manufactured in advance in a factory or the like, so that it can be easily formed one side at a time without requiring much effort, and the invert lining 32, which is continuous with the lining 31 extending from the tunnel side wall 31a to the upper arch-shaped portion 31b, can be installed in a shorter period of time.

[0019] That is, in this embodiment, the invert section structure 10 is a structure of the invert section 33 using PCa concrete blocks 20 that is provided in at least one side region of the invert section 33 of a mountain tunnel 30 in the transverse direction of the tunnel, as shown in Figures 1 to 4, and constitutes the invert section lining body 32, and the PCa concrete blocks 20 are formed as hexahedral blocks having curved upper surface portions 20a and lower surface portions 20b so that they each have a curved shape that follows the cross-sectional shape of the invert section lining body 32, as shown in Figures 5 and 6(a) to (c). These multiple PCa concrete blocks 20 are arranged in a row in the transverse direction of the tunnel and installed in the invert section 33, with gaps 21a and 21b maintained between the receiving portions 31c at the lower ends of adjacent side wall lining bodies 31a and between adjacent PCa concrete blocks 20, and are also arranged in a row in the axial direction of the tunnel and installed in the invert section 33, with gaps 21b maintained between adjacent PCa concrete blocks (see FIGS. 1 to 4). As shown in FIG. 10, these multiple PCa concrete blocks 20 arranged in a row in the vertical and horizontal directions are integrated via filled solidification material 22 that has been filled and hardened in the gaps 21a between adjacent receiving portions 31c, the gaps 21b between adjacent PCa concrete blocks 20, and the gaps 21c below the hexahedral lower surface that communicates with these gaps 21a and 21b, and constitute at least one side of the invert lining body 32.

[0020] In this embodiment, the multiple PCa concrete blocks 20 are preferably formed to have similar hexahedral shapes with the same width x in the tunnel transverse direction, the same vertical width y in the tunnel axial direction, and the same height z (see FIGS. 5 and 6(a)-(c)). The multiple PCa concrete blocks 20 are arranged in a row and column, and are installed in the invert section 33 (see FIGS. 2 and 3). The gaps 21b between adjacent PCa concrete blocks 20 in the transverse direction of the tunnel, which are filled with filling solidification material 22, and extending in the axial direction, and the gaps 21b between adjacent PCa concrete blocks in the axial direction of the tunnel, are preferably arranged in a potato-like shape that is linearly continuous (see FIGS. 2 and 3). The gaps 21a between adjacent receiving sections 31c and the gaps 21b between adjacent PCa concrete blocks, which are filled with filling solidification material 22, are preferably spaced apart by approximately 15 to 30 mm.

[0021] In this embodiment, the PCa concrete blocks 20 constituting the invert structure 10 are arranged in series in the transverse direction of the tunnel, with gaps 21a, 21b filled with the filling solidification material 22 between the receiving bases 31c at the lower ends of adjacent side wall linings 31a and between adjacent PCa concrete blocks 20, as described above. The PCa concrete blocks 20 are also arranged in series in the axial direction of the tunnel, with gaps 21b filled with the filling solidification material 22 between adjacent PCa concrete blocks, and are installed in the invert section 33 in a row. As shown in FIGS. 5 and 6(a)-(c), the PCa concrete blocks 20 are formed as hexahedral blocks having curved upper and lower surfaces 20a, 20b that are curved along the cross-sectional shape of the invert section lining 32, and having a pair of flat axially opposing surfaces 20c at the front and rear and a pair of flat laterally opposing surfaces 20d at the left and right. The upper surface portion 20a and the lower surface portion 20b in cross section can be gently curved with a radius of curvature of, for example, about 14000 mm to 14500 mm.

[0022] Furthermore, bolt boxes 23 or female screw anchors 24 are embedded and fixed to the four sides of the hexahedral top surface of each PCa concrete block 20 to connect adjacent PCa concrete blocks 20 using bolt members (not shown). The bolt boxes 23 open to the top surface 20a of the PCa concrete block 20, and the female screw anchors 24 open to the upper end of the axially opposing surface 20c or the transversely opposing surface 20d of the side surface. As shown in FIG. 7, the PCa concrete block 20 has three bolt insertion holes 25 that penetrate the hexahedral shape in the vertical direction, located at each corner of an isosceles triangle (see FIG. 6(a)). A female screw member 25a, into which a height adjustment bolt 26 is screwed, is fixed to each bolt insertion hole 25 below the vertical middle. A large trumpet-shaped recess 25b is formed from the portion where the female screw member 25a of each bolt insertion hole 25 is fixed, expanding in diameter upward and opening onto the upper surface 20a of the PCa concrete block 20, and a small trumpet-shaped recess 25c is formed from the portion where the female screw member 25a is fixed, expanding in diameter downward and opening onto the lower surface 20b of the PCa concrete block 20. Height adjustment bolts 26 are inserted into these bolt insertion holes 25 and screwed into the female screw members 25a, so that the height adjustment bolts 26 are attached with their lower ends 26a protruding movably from the lower surface 20b of the PCa concrete block 20. Furthermore, since the large trumpet-shaped recess 25b and the small trumpet-shaped recess 25c have a trumpet shape that tapers toward the upper and lower openings, the box punching members attached to the box formwork for concrete pouring to form these trumpet-shaped recesses 25b, 25c can be smoothly removed after the concrete has hardened. From this perspective, it is preferable that the taper gradient of the large trumpet-shaped recess 25b and the small trumpet-shaped recess 25c, which have a tapered trumpet shape that tapers toward the upper and lower openings, be 10% or more inclined with respect to the central axis of the bolt insertion and threaded hole 25.

[0023] As shown in Figure 6(a), the three bolt insertion screw holes 25 are formed on the upper surface 20a of the PCa concrete block 20, preferably at each corner of an imaginary isosceles triangle (see dotted line) with the base positioned parallel to one axially opposing surface 20c and the apex positioned on the other axially opposing surface 20c (see Figure 6(a)).

[0024] In this embodiment, it is preferable that the center of gravity of the PCa concrete block 20 be located inside the imaginary isosceles triangle when viewed from the top side of the PCa concrete block 20, and it is particularly preferable that the center of gravity of the PCa concrete block 20 be located at the centroid of the imaginary isosceles triangle. This makes it possible to adjust the height and inclination of the PCa concrete block 20 with the three height adjustment bolts 26 in a more stable and accurate manner, and also makes it possible to support the PCa concrete block 20, whose height and inclination have been accurately adjusted, in a more stable manner by the three height adjustment bolts 26.

[0025] Furthermore, as shown in FIGS. 10 and 11, some of these PCa concrete blocks 20, specifically PCa concrete blocks 20′ (see FIG. 3), are formed with filler injection holes 27 that penetrate the hexahedron in the vertical direction. A female screw member 27a, to which the male screw portion of an on-off valve 28 is threaded, is fixed to the vertical middle portion of each filler injection hole 27. An upper horn-shaped recess 27b is formed, which expands in diameter upward from the portion where the female screw member 27a of each filler injection hole 27 is fixed and opens onto the upper surface 20a of the PCa concrete block 20′, and a lower horn-shaped recess 27c is formed, which expands in diameter downward from the portion where the female screw member 27a is fixed and opens onto the lower surface 20b of the PCa concrete block 20′. The male threads of the on-off valve 28 are threaded into the female threads 27a of the filler injection holes 27, and the handle 28a is positioned above the upper surface 20a of the PCa concrete block 20'. The on-off valve 28 is detachably attached to the PCa concrete block 20' while the handle 28a can be opened and closed by working on the upper surface 20a of the PCa concrete block 20'. Furthermore, the upper and lower trumpet-shaped recesses 27b and 27c have a trumpet shape that tapers toward the upper and lower openings. This allows the box punching tool attached to the box-shaped formwork for concrete pouring to form these trumpet-shaped recesses 27b and 27c to be easily removed after the concrete has hardened. From this perspective, the taper gradient of the trumpet-shaped recesses 27b and 27c is preferably at least 10% with respect to the central axis of the filler injection hole 27.

[0026] In this embodiment, the filler injection holes 27 that penetrate the hexahedral PCa concrete block 20' in the vertical direction can be preferably formed by being disposed in the center of the upper surface 20a of the PCa concrete block 20' (see FIG. 6(a)). In particular, it is preferable that the filler injection holes 27 are formed by being disposed in the center of the center-side block 20B that is located at the lowest position.

[0027] In this embodiment, spacer jigs 29a, 29b can be attached to each of the pair of flat axially opposing surfaces 20c and the pair of flat transversely opposing surfaces 20d of the hexahedron-shaped PCa concrete blocks 20 (20') to maintain a predetermined gap 21b between the opposing surfaces 20c, 20d (see Figs. 5, 6(b), and 6(c)). A plurality of lifting jigs 29c are embedded and fixed in the upper surface 20a of the hexahedron-shaped PCa concrete blocks 20 (see Fig. 6(a)).

[0028] In this embodiment, the PCa concrete blocks 20 are formed by pouring concrete into a box-shaped formwork assembled in a factory to conform to the predetermined hexahedral shape, allowing it to harden, and then demolding after a predetermined curing period. The resulting blocks are then formed into a hexahedral shape with a curved upper surface 20a and lower surface 20b, preferably measuring approximately 1385-1435 mm in width x, approximately 730 mm in length y, and approximately 500 mm in height z, and weighing approximately 1300 kg. For example, by placing and supporting reinforcement bars inside the box-shaped formwork, the bolt boxes 23, female thread anchors 24, and box-punching members for the bolt insertion and threaded holes 25 and filler injection holes 27 can be attached and embedded in the PCa concrete block 20 or temporarily fixed thereto. In this embodiment, the size, shape, weight, etc. of the PCa concrete blocks 20 used as invert blocks can be designed appropriately according to the capacity of a lifting machine or the like that can be used in the work yard 71 of one side area 55A without affecting the traffic of vehicles in the other side area 55B. For example, the weight of the PCa concrete blocks 20 can preferably be set to 1000 to 1500 kg.

[0029] In this embodiment, the multiple PCa concrete blocks 20 are formed to have similar hexahedral shapes, which allows for efficient production by limiting the type of box-shaped formwork used, and because the blocks are of similar weight, workability during lifting and transportation is improved, and they can be handled in the same way when lifting or installing, making it easy to accurately install each PCa concrete block 20 in a predetermined position, for example, in a potato-like arrangement, and also reduces manufacturing costs.

[0030] In this embodiment, the invert structure 10 is constructed in each of a pair of half-side regions, each of which is located on either side of the tunnel's transverse center (see FIGS. 1 and 2). In the center of the tunnel transverse direction of the invert section 33, a plurality of H-shaped steel beams 35 supporting earth retaining plates and protective fences, etc., can be installed at a predetermined interval along the tunnel axis by driving them into the ground of the invert section 33 with their flanges aligned along the tunnel axis. Therefore, at the positions where the H-shaped steel beams 35 are installed, a pair of PCa concrete blocks (center-side blocks) 20B adjacent in the tunnel axial direction at the center of the tunnel transverse direction can have notched recesses 20e with rectangular cross sections formed at the corners on both sides of the gap 21b between them (see FIG. 3). The notched recesses 20e at the corner portions on both sides allow a flange arrangement recess 10a for arranging one flange portion of the H-shaped steel 35 to be provided at the end face portion (central end face portion) 10B of each invert structure 10 on the central side in the transverse direction of the tunnel, in the portion where the H-shaped steel 35 is erected.

[0031] That is, in the block groups 20X, 20Y (see Figure 1) consisting of a plurality of PCa concrete blocks 20 constituting the invert structure 10 of each side region, the PCa concrete block 20 (central side block 20B) arranged in the portion where the H-shaped steel 35 is installed has a curved upper surface portion 20a and a lower surface portion 20b with a curved shape that follows the cross-sectional shape of the invert section covering body 32, and is formed as a hexahedral block having a pair of flat axial opposing surfaces 20c at the front and rear and a pair of flat transverse opposing surfaces 20d at the left and right (see Figures 6(a) to (c)), and at the corner portion between any one of the axial opposing surfaces 20c and the transverse opposing surfaces 20d, as shown in Figure 3, a notched recess 20e having a rectangular cross-sectional shape is cut out so as to have a side portion with a width of at least half the width of the flange portion of the H-shaped steel 35, and is provided continuously from the upper surface portion 20a to the lower surface portion 20b. As a result, at the central ends of a pair of central side blocks 20B that are adjacent in the axial direction of the tunnel at the section where the H-shaped steel 35 is erected, these notched recesses 20e form flange arrangement recesses 10a that can avoid the flange portion of the H-shaped steel 35.

[0032] In this embodiment, as shown in Figures 3 and 4, the multiple PCa concrete blocks 20 that make up the invert section structure 10 have multiple transverse block rows 20D that include a receiving section side block 20A arranged adjacent to the receiving section 31c at the lower end of the side wall lining body 31a, a central section side block 20B arranged on the transverse central side of the invert section, and one or more intermediate blocks 20C (in this embodiment, one intermediate block 20C) arranged between them. These PCa concrete blocks 20A, 20B, 20C are arranged in a row in the transverse direction of the tunnel, with gaps 21a, 21b maintained between adjacent receiving sections 31c and between adjacent PCa concrete blocks 20A, 20B, 20C, and also in the axial direction of the tunnel, with gaps 21b maintained between adjacent PCa concrete blocks 20A, 20B, 20C (transverse block rows 20D), and are installed in the invert section 33 lined up vertically and horizontally. These multiple PCa concrete blocks 20A, 20B, 20C used when constructing the invert structure 10 are constructed using the PCa block installation method according to a preferred embodiment of the present invention, as described below, and are each installed smoothly and precisely in a stable state at the predetermined positions for forming the invert structure 10.

[0033] In other words, the method of installing PCa blocks in the invert section of this embodiment is an installation method used when constructing an invert section structure 10 using a plurality of PCa concrete blocks 20 that are provided in at least one side region of the invert section 33 of a mountain tunnel 30 in the transverse direction of the tunnel and that constitutes the invert section lining body 32, and as described above, the PCa concrete block 20 is formed as a hexahedral block having a curved upper surface 20a and lower surface 20b so as to have a curved shape that follows the cross-sectional shape of the invert section lining body 32, and the plurality of PCa concrete blocks 20 include a receiving base side block 20A arranged adjacent to the receiving base portion 31c at the lower end of the side wall lining body 31a, a central side block 20B arranged on the central side of the transverse direction of the invert section 33, and an intermediate block 20C arranged between these. The multiple PCa concrete blocks 20A, 20B, 20C are arranged in a row in the transverse direction of the tunnel, with gaps 21a, 21b maintained between adjacent receiving portions 31c and between adjacent PCa concrete blocks 20A, 20B, 20C, and are also arranged in a row in the axial direction of the tunnel, with gaps 21b maintained between adjacent PCa concrete blocks 21A, 21B, so that they are installed in the invert portion 33 lined up vertically and horizontally. As shown in Figure 4, the multiple PCa concrete blocks 20A, 20B, 20C in each row (transverse block row) 20D arranged in the transverse direction of the tunnel are installed in the invert section 33 by installing the base side block 20A adjacent to the base section 31c and temporarily fixing it using temporary fixing means 36, and then installing the intermediate block 20C and the central side block 20B adjacent to the temporarily fixed base side block 20A.

[0034] For example, the base section side block 20A is placed adjacent to the base section 31c and temporarily fixed using the temporary fixing means 36, and then the intermediate section block 20C and the central section side block 20B are placed adjacent to the temporarily fixed base section side block 20A, and at the adjacent locations of each of these installed blocks 20A, 20B, 20C, they are temporarily fixed using bolt members (not shown) via bolt boxes 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, 20C near the transverse opposing surface 20d.The height and position of each PCa concrete block 20A, 20B, 20C can then be adjusted, and the bolt members can then be fully tightened, allowing the multiple PCa concrete blocks 20A, 20B, 20C of each transverse block row 20D, which are connected in the transverse direction of the tunnel, to be installed in the invert section 33.

[0035] Also, for example, the receiving base side block 20A is installed adjacent to the receiving base 31c and temporarily fixed using the temporary fixing means 36, and then the intermediate block 20C is installed adjacent to the temporarily fixed receiving base side block 20A, and at the adjacent location between the installed intermediate block 20C and the receiving base side block 20A, they are temporarily fixed using bolt members (not shown) via a bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20C that is close to the transverse opposing surface 20d, and then the height and position of each PCa concrete block 20A, 20C are adjusted and the bolt members are then fully tightened. Next, a central side block 20B is installed adjacent to the intermediate block 20C, and at the adjacent location between the installed central side block 20B and the intermediate block 20C, they are temporarily fixed with bolt members via a bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20C, 20B that is close to the transverse opposing surface 20d.After adjusting the height and position of the central side block 20B, the bolt members are finally tightened, and the multiple PCa concrete blocks 20A, 20B, 20C of each transverse block row 20D that are connected in the transverse direction of the tunnel can be installed in the invert section 33.

[0036] In this embodiment, the temporary fixing means 36 for temporarily fixing the pedestal-side block 20A adjacent to the pedestal 31c preferably comprises a cable 36b such as a wire or chain, both ends of which are secured to a locking member attached to a hole-in anchor 36a embedded in the pedestal 31c and to a locking member attached to a bolt box 23 or a lifting jig 29c provided on the pedestal-side block 20A. The cable 36b such as a wire or chain may be provided with an extension / retraction adjustment means 36c, such as a turnbuckle, that adjusts the length between the locked ends. This makes it possible to adjust the width of the gap 21a maintained between the pedestal 31c and the adjacent pedestal-side block 20A.

[0037] 6(a) and 7, the height of each of the PCa concrete blocks 20A, 20B, and 20C can be adjusted using three height-adjusting bolts 26 threaded into the bolt insertion holes 25 formed in the three locations. That is, each of the PCa concrete blocks 20A, 20B, and 20C has three bolt insertion holes 25 formed in the vertical direction, and a height-adjusting bolt 26 is attached to each of the bolt insertion holes 25 in a state in which its lower end 26a can protrude downward from the lower surface 20b of the PCa concrete block 20A, 20B, and 20C. Prior to the process of filling the gaps 21a between adjacent receiving base portions 31c of a plurality of PCa concrete blocks 20A, 20B, 20C arranged in a row vertically and horizontally, the gaps 21b between adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexahedral undersides 20b that communicate with these gaps 21a, 21b with filling solidification material 22 (see Figure 10), the PCa concrete blocks 20A, 20B, 20C are rotated from above to change the protruding lengths of the three height adjustment bolts 26 in each of the PCa concrete blocks 20A, 20B, 20C from the undersides 20b of the PCa concrete blocks 20A, 20B, 20C, thereby adjusting the height and inclination of each of the PCa concrete blocks 20A, 20B, 20C.

[0038] As described above, in this embodiment, a nut member, preferably a female thread member 25a, is fixed to each bolt insertion hole 25 below the vertical center. The height adjustment bolt 26 is threadedly attached to the nut member 25a, allowing the lower end 26a of the height adjustment bolt 26 to protrude downward from the lower surface 20b of the PCa concrete block 20A, 20B, or 20C. A tiltable ground adjuster 26b can be attached to the lower end 26a of the height adjustment bolt 26 (see FIG. 8(a)). By tilting the ground adjuster 26b relative to the lower end 26a of the height adjustment bolt 26, the adjuster 26b can be tilted along the filling bottom surface 26c, e.g., the ground surface. This allows the lower end 26a of the height adjustment bolt 26 to stably ground against the filling bottom surface 26c below the lower surface 20b.

[0039] The grounding adjuster 26b is preferably configured to be accommodated in the small horn-shaped recess 25c, which expands downward when the height adjustment bolt 26 is retracted upward. For example, as shown in FIG. 8(b), the small horn-shaped recess 25c is configured to be a horn-shaped recess that expands downward and conforms to the outer periphery of the grounding adjuster 26b, but is slightly larger than the outer periphery. This allows the grounding adjuster 26b, which has a similar shape to the small horn-shaped recess 25c, to be easily accommodated inside the small horn-shaped recess 25c without protruding downward from the bottom surface 20b of the PCa concrete block 20. This allows the adjuster 26b to be placed in contact with the bottom surface 26c, allowing fine adjustment of the height of the PCa concrete block 20, even if the gap 21c between the bottom surface 20b and the filling bottom surface 26c of the PCa concrete block 20 is less than the height of the grounding adjuster 26b. Furthermore, since the height position of the filled bottom surface 26c after leveling is the same height as the designed position of the lower surface 20b of the PCa concrete block 20, even if there is no room for error, the entire grounding adjuster 26b can be accommodated in the small trumpet-shaped recess 25c, and each PCa concrete block 20 can be installed in a predetermined position with these lower surface portions 20b abutting against the filled bottom surface 26c.

[0040] The small horn-shaped recess 25c preferably has a height from the opening in the underside 20b of the PCa concrete block 20 to the lower end of the female screw member 25a of about 60 to 80 mm, and an opening diameter in the underside 20b of about 65 to 70 mm. The taper gradient of the small horn-shaped recess 25c is preferably inclined by 10% or more with respect to the central axis of the bolt insertion and threaded hole 25, from the viewpoint of facilitating removal of the box punch member after the concrete has hardened.

[0041] In this embodiment, the upper end 26d of the height adjustment bolt 26 is preferably formed to have a rectangular cross section, and by engaging an insert extension bar, for example, as a rotation jig, with this upper end 26d and rotating the height adjustment bolt 26, the length of protrusion of the lower end 26a of the height adjustment bolt 26 from the lower surface 20b of the PCa concrete block 20A, 20B, 20C can be easily changed by working above the upper surface 20a of the PCa concrete block 20A, 20B, 20C. As described above, the bolt insertion hole 25 is formed with a large trumpet-shaped recess 25b that expands upward from the portion where the nut member 25a, which is a female thread member, is fixed and opens to the upper surface 20a of the PCa concrete block 20A, 20B, 20C. If the upper end 26d of the height-adjusting bolt 26, after being adjusted so that its lower end 26a contacts the filling bottom 26c, protrudes from or is close to the upper surface 20a of the PCa concrete block 20A, 20B, or 20C, preventing a sufficient covering thickness above the upper end 26d when the large trumpet-shaped recess 25b is filled with a finishing filler, the upper end 26d of the height-adjusting bolt 26 can be appropriately cut to the required length in the large trumpet-shaped recess 25b. This ensures a desired covering thickness of the finishing filler, such as mortar, filled in the bolt insertion hole 25, preventing corrosion of the height-adjusting bolt 26. The work of cutting the upper end 26d of the height-adjusting bolt 26 can be performed smoothly because sufficient working space is secured in the large trumpet-shaped recess 25b, which expands in diameter upward.

[0042] The large trumpet-shaped recess 25b preferably has a height from the opening in the upper surface 20a of the PCa concrete block 20 to the upper end of the female screw member 25a of approximately 360 to 380 mm, and an opening diameter in the upper surface 20a of approximately 106 to 110 mm. The taper gradient of the large trumpet-shaped recess 25b is preferably inclined by 10% or more with respect to the central axis of the bolt insertion and threaded hole 25, from the viewpoint of making it easier to remove the box punch member after the concrete has hardened.

[0043] In this embodiment, as described above, each of the PCa concrete blocks 20A, 20B, 20C has three bolt insertion holes 25 formed therethrough in the vertical direction, and a height adjustment bolt 26 is attached to each of the bolt insertion holes 25 in a state in which the protruding length of the lower end portion 26a protruding downward from the lower surface portion 20b of the PCa concrete block 20A, 20B, 20C can be adjusted. As a result, prior to the step of filling the filling solidification material 22 into the gaps 21a between the adjacent receiving portions 31c of the multiple PCa concrete blocks 20A, 20B, 20C arranged vertically and horizontally, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexahedral lower surface portion 20b that communicate with these gaps 21a, 21b, The gap width b (see FIGS. 7 and 10) of the gap 21c below the hexahedral lower surface 20b of each PCa concrete block 20A, 20B, and 20C is measured from the protruding length of the lower end 26a of the height adjustment bolt 26 protruding from the lower surface 20b of each PCa concrete block 20A, 20B, and 20C, and the planned amount of filling solidification material 22 to be filled in the gap 21c below the hexahedral lower surface 20b can be calculated in advance based on this and the area of ​​the lower surface 20b of each PCa concrete block 20A, 20B, and 20C. In the process of filling the filling solidification material 22, a predetermined amount of filling solidification material 22 is injected into the gap 21c below the hexahedral lower surface 20b, taking into consideration the calculated planned filling amount, and allowed to fill and harden.

[0044] That is, in this embodiment, a nut member 25a is fixed as a female screw member below the vertical middle of each bolt insertion screw hole 25, and a height adjustment bolt 26 is screwed into the nut member 25a, so that the protruding length of the lower end 26a of the height adjustment bolt 26 from the lower surface 20b of the PCa concrete block 20A, 20B, 20C can be adjusted.Therefore, for example, when the lower end 26a of the height adjustment bolt 26 is grounded on the filling bottom surface 26c below the hexahedral lower surface 20b, the gap width b of the gap 21c below the hexahedral lower surface 20b can be easily measured from the length of the height adjustment bolt 26 above the nut member 25a.

[0045] In addition, in this embodiment, a tiltable grounding adjuster 26b is preferably attached to the lower end 26a of the height adjustment bolt 26, so that when the grounding adjuster 26b is grounded on the filling bottom surface 26c below the hexahedral lower surface 20b, the gap width b of the gap 21c below the hexahedral lower surface 20b can be easily measured in a more stable state from the length of the height adjustment bolt 26 above the nut member 25a.

[0046] The planned amount of filling solidification material 22 can be calculated in advance by calculating the amount of filling material to be filled in the gaps 21c below the hexahedral lower surface 20b of each PCa concrete block 20A, 20B, 20C based on the average gap width b of the gaps 21c below the hexahedral lower surface 20b measured by three height adjustment bolts 26 attached to the three bolt insertion and threaded holes 25 of each PCa concrete block 20A, 20B, 20C.

[0047] In addition, the planned amount of filling solidification material 22 can also be calculated in advance by calculating the amount of filling to be filled in the gaps below the hexahedral lower surface portions 20b of the PCa concrete blocks 20A, 20B, and 20C throughout the entire invert structure 10 based on the overall average of the gap width b of the gaps 21c below the hexahedral lower surface portions 20b, each measured by three height adjustment bolts 26 attached to three bolt insertion and threaded holes 25 of all of the PCa concrete blocks 20A, 20B, and 20C that make up the invert structure 10.

[0048] Furthermore, in this embodiment, in the invert section structure 10 using the above-mentioned PCa concrete blocks 20A, 20B, 20C, a PCa block connection structure 37 in the invert section structure described below can be adopted as the connection section structure for connecting and arranging multiple PCa concrete blocks 20A, 20B, 20C vertically and horizontally while maintaining gaps 21b of a predetermined spacing width between adjacent PCa concrete blocks 20A, 20B, 20C and installing them as a single unit in the invert section 33.

[0049] That is, in this embodiment, as shown in Figures 3, 4, and 6(a) to (c), the PCa concrete block connection structure 37 in the invert structure has transverse spacer jigs 29a (see Figure 6(b)) fixed to one of the transversely facing surfaces 20d of the PCa concrete blocks 20A, 20B, and 20C adjacent to each other in the transverse direction of the tunnel, preferably at least three of which are interposed between the transversely facing surfaces 20d, and each pair of PCa concrete blocks 20A, 20B, and 20C adjacent to each other in the transverse direction of the tunnel is connected by the fastening force of bolt members (not shown) fastened in bolt boxes 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, and 20C adjacent to the transversely facing surfaces 20d, while maintaining a gap 21b of a predetermined interval between the transversely facing surfaces 20d. Between each pair of axially opposing faces 20c of adjacent PCa concrete blocks 20A, 20B, and 20C in the tunnel axial direction, axial spacer jigs 29b (see FIG. 6(c)) are fixed to one of the axially opposing faces 20c, preferably at least three positions. The bolt boxes 23 are provided on the upper surfaces 20a of at least one of the PCa concrete blocks 20A, 20B, and 20C adjacent to the axially opposing faces 20c. The bolts (not shown) fasten the pair of PCa concrete blocks 20A, 20B, and 20C in the tunnel axial direction, maintaining a predetermined gap 21b between the axially opposing faces 20c. The transverse spacer jigs 29a and axial spacer jigs 29b can also be attached to the transversely opposing faces 20d and the axially opposing faces 20c at the positions where the bolt boxes 23 are provided.

[0050] In this embodiment, the transverse spacer jigs 29a and / or the axial spacer jigs 29b may be made of mortar blocks, preferably attached and fixed to either one of the opposing surfaces 20c, 20d. The mortar block spacer jigs 29a, 29b may be removably attached to the opposing surfaces 20c, 20d and removed after the PCa concrete blocks 20A, 20B, 20C are fully tightened and connected. The transverse spacer jigs 29a and / or the axial spacer jigs 29b may also be made of male threaded members, preferably screwed into female threaded inserts embedded in either one of the opposing surfaces 10c, 10d, so that the protruding length can be adjusted.

[0051] The transverse spacer jigs 29a and the axial spacer jigs 29b, which are preferably arranged at at least three locations and fixed to either one of the transverse opposing surfaces 20d or the axial opposing surface 20c, are preferably fixed to at least two locations in the region below the center of gravity of the PCa concrete blocks 20A, 20B, and 20C. This makes it possible to stably and accurately form the gaps 21a and 21b of the predetermined intervals in the region below the center of gravity, where it is difficult to confirm that the gaps 21a and 21b have been formed accurately, without using any special equipment when installing the PCa concrete blocks 20A, 20B, and 20C.

[0052] The bolt members fastened in the bolt boxes 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, 20C adjacent to the lateral opposing surface 20d, or the bolt members fastened in the bolt boxes 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, 20C adjacent to the axial opposing surface 20c, may preferably be fastened across the bolt boxes 23 arranged on the upper surface 20a adjacent to the axial opposing surface 20c or lateral opposing surface 20d of one of the PCa concrete blocks 20A, 20B, 20C, and the female thread anchors 24 embedded in the axial opposing surface 20c or lateral opposing surface 20d of the other PCa concrete block 20A, 20B, 20C. Preferably, the bolt box 23 may be fastened across the bolt box 23 arranged on the upper surface 20a adjacent to the axially opposing surface 20c or the transversely opposing surface 20d of one PCa concrete block 20A, 20B, 20C, and the bolt box 23 arranged on the upper surface 20a adjacent to the axially opposing surface 20c or the transversely opposing surface 20d of the other PCa concrete block 20A, 20B, 20C.

[0053] In this embodiment, when a mountain tunnel includes a section with a tunnel line shape that curves horizontally, multiple PCa concrete blocks 20A, 20B, 20C can be connected vertically and horizontally and installed as a single unit in the invert section 33, while maintaining gaps 21b of a predetermined spacing width between adjacent PCa concrete blocks 20A, 20B, 20C and aligning them along the tunnel line shape that curves horizontally.

[0054] That is, in this embodiment, between each pair of transversely opposing surfaces 20d of adjacent PCa concrete blocks 20A, 20B, 20C that face each other in the transverse direction of the tunnel, transverse spacer jigs 29a (see Figure 6(b)) fixed to one of the transversely opposing surfaces 20d are arranged in at least three locations, and each pair of PCa concrete blocks 20A, 20B, 20C adjacent in the transverse direction of the tunnel are connected by the fastening force of bolt members (not shown) while maintaining a gap 21b of a predetermined spacing width between the transversely opposing surfaces 20d, thereby forming a transverse block row 20D made up of a plurality of PCa concrete blocks 20A, 20B, 20C (see Figure 3). Between each pair of axially opposing surfaces 20c of adjacent PCa concrete blocks 20A, 20B, 20C in the axial direction of the tunnel, axial spacer jigs 29b (see Figure 6(c)) fixed to one of the axially opposing surfaces 20c are arranged in at least three locations, and each pair of PCa concrete blocks 20A, 20B, 20C adjacent in the axial direction of the tunnel is connected by the fastening force of bolt members (not shown) while maintaining a gap 21b of a predetermined spacing width between the axially opposing surfaces 20c (see Figure 3). 9(a), at one or more axial connection portions 20f between multiple transverse block rows 20D arranged in the tunnel axial direction, axial spacer jigs 29b interposed between a pair of axially opposing surfaces 20c in the tunnel axial direction are fixed to the axially opposing surfaces 20c with the width of the outer gap 21b maintained by the axial spacer jigs 29b fixed to the outer PCa concrete block 20E located on the outside of the horizontally curved tunnel alignment in the transverse direction of the tunnel adjusted to be larger than the width of the inner gap 21b maintained by the axial spacer jigs 29b fixed to the inner PCa concrete block 20F located on the inside of the horizontally curved tunnel alignment. This allows multiple PCa concrete blocks 20A, 20B, 20C to be connected vertically and horizontally and installed as a unit in the invert section 33 along the horizontally curved tunnel alignment.This also makes it possible to use rectangular parallelepiped PCa concrete blocks 20A, 20B, 20C to accommodate tunnel alignments that curve in the horizontal direction, without using tapered blocks.

[0055] Here, when the axial spacer jig 29b is made of a mortar block that is attached and fixed to one of the axial opposing surfaces 20c, the spacing width can be adjusted so that the spacing width of the outer gap 21b is larger than the spacing width of the inner gap 21b by fixing mortar blocks of different sizes to the outer PCa concrete block 20E and the inner PCa concrete block 20F at the connecting portion 20f where the spacing width is different.

[0056] Furthermore, when the axial spacer jig 29b is made of a male screw member that is fixed so that the protruding length can be adjusted by being screwed into a female screw insert embedded in one of the axial opposing surfaces 20c, the male screw member can be screwed in and fixed with different screw-in amounts to the outer PCa concrete block 20E and the inner PCa concrete block 20F at the connecting portion 20f, which has different spacing widths, so that the spacing width of the outer gap 21b is larger than the spacing width of the inner gap 21b.

[0057] On the other hand, in this embodiment, when the mountain tunnel includes a section with a tunnel line that curves in the vertical direction, multiple PCa concrete blocks 20A, 20B, 20C can be installed as a single unit in the invert section 33 by connecting them vertically and horizontally while maintaining gaps 21b of a predetermined spacing width between adjacent PCa concrete blocks 20A, 20B, 20C and aligning them along the tunnel line that curves in the vertical direction.

[0058] That is, in this embodiment, between each pair of transversely opposing surfaces 10d of adjacent PCa concrete blocks 20A, 20B, 20C in the transverse direction of the tunnel, transverse spacer jigs 29a (see Figure 6(b)) fixed to one of the transversely opposing surfaces 10d are arranged in at least three locations, and each pair of PCa concrete blocks 20A, 20B, 20C adjacent in the transverse direction of the tunnel is connected by the fastening force of bolt members (not shown) while maintaining a gap 21b of a predetermined spacing width between the transversely opposing surfaces 10d, thereby forming a transverse block row 20D made up of a plurality of PCa concrete blocks 20A, 20B, 20C (see Figure 3). Between each pair of axially opposing surfaces 20c of adjacent PCa concrete blocks 20A, 20B, 20C in the axial direction of the tunnel, axial spacer jigs 29b (see Figure 6(c)) fixed to one of the axially opposing surfaces 20c are arranged in at least three locations, and each pair of PCa concrete blocks 20A, 20B, 20C adjacent in the axial direction of the tunnel is connected by the fastening force of bolt members (not shown) while maintaining a gap 21b of a predetermined spacing width between the axially opposing surfaces 20c. As shown in Figure 9(b), at least three axial spacer jigs 29b are fixed to the axially opposing surfaces 20c of one or more tunnel axial connection sections 20g between multiple transverse block rows 20D arranged in the tunnel axial direction, with the upper gap 21b maintained by the axial spacer jigs 29b at the upper tier and the lower gap 21b maintained by the axial spacer jigs 29b at the lower tier, with their spacing widths adjusted so that they are different. This allows multiple PCa concrete blocks 20A, 20B, and 20C to be connected vertically and horizontally and installed integrally in the invert section 33 along the vertically curved tunnel alignment. This also makes it possible to use rectangular PCa concrete blocks 20A, 20B, and 20C to accommodate the vertically curved tunnel alignment without using tapered blocks.

[0059] For example, in connecting portions 20g having different spacing widths, by adjusting the spacing widths so that the spacing width of the upper gap 21b held by the axial spacer jig 29b arranged in the upper tier is larger than the spacing width of the lower gap 21b held by the axial spacer jig 29b arranged in the lower tier, it becomes possible to arrange multiple consecutive transverse block rows 20D along the tunnel line shape that curves downward in the vertical direction.

[0060] Furthermore, by adjusting the spacing widths at the connecting portions 20g having different spacing widths so that the spacing width of the upper gap 21b held by the axial spacer jig 29b arranged at the upper level is smaller than the spacing width of the lower gap 21b held by the axial spacer jig 29b arranged at the lower level, it becomes possible to arrange multiple consecutively arranged transverse block rows 20D along the tunnel line shape that curves upward in the vertical direction.

[0061] Here, when the axial spacer jig 29b is made of mortar blocks that are attached and fixed to one of the axial opposing surfaces 20c, the spacing width can be adjusted so that the spacing width of the gap 21b held at the upper part and the spacing width of the gap 21b held at the lower part are different widths by fixing mortar blocks of different sizes to the upper and lower parts at the connecting part 20g where the spacing widths are different.

[0062] Furthermore, when the axial spacer jig 29b is made of a male screw member fixed so that the protruding length can be adjusted by being screwed into a female screw insert embedded in one of the axial opposing surfaces 20c, the male screw member can be screwed and fixed with different screwing amounts in the upper and lower stages at the connecting portion 20g where the spacing width is different, thereby making it possible to adjust the spacing width so that the spacing width of the gap 21b held at the upper part and the spacing width of the gap 21b held at the lower part are different widths.

[0063] In this embodiment, the multiple PCa concrete blocks 20A, 20B, and 20C arranged in a row and column are integrated via the filling solidification material 22 filled and hardened in the gaps 21a between adjacent receiving portions 31c, the gaps 21b between adjacent PCa concrete blocks 20A, 20B, and 20C, and the gaps 21c below the hexahedral undersides that communicate with these gaps, as shown in Fig. 10, to form at least a portion of the invert section lining body 32. In this embodiment, the filling solidification material 22 is filled in the gaps 21a between adjacent receiving portions 31c, the gaps 21b between adjacent PCa concrete blocks 20A, 20B, and 20C, and the gaps 21c below the hexahedral undersides that communicate with these gaps 21a and 21b by the following construction method.

[0064] That is, in this embodiment, in the process of filling the gaps 21a between adjacent receiving base portions 31b of multiple PCa concrete blocks 20A, 20B, 20C arranged in a row vertically and horizontally, the gaps 21b between adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexahedral lower surface portions that communicate with these gaps 21a, 21b, the opening portions of the gaps 21a, 21b that open in the upper surface portions 20a, gable end surface portions 10A (see Figures 3 and 12) and center end surface portions 10B (see Figures 3 and 12) of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row vertically and horizontally are closed. 10 to 12, the filling solidification material 22 is sequentially injected through the center-side filler injection holes 27d provided vertically through one or more of the plurality of center-side blocks 20B arranged in the axial direction of the tunnel, and through the pedestal-side filler injection holes 27e provided vertically through one or more of the plurality of pedestal-side blocks 20A arranged in the axial direction of the tunnel. Preferably, as shown in FIG. 12, the injection of the filling solidification material 22 is started from the center-side filler injection holes 27d, then switched to the pedestal-side filler injection holes 27e, and further injected. After that, the injection of the filling solidification material 22 is completed upon confirmation that the filling solidification material 22 flows out from the opening of the gap 21a between the pedestal 31c held by the upper surface 20a of the pedestal-side block 20A. It is also possible to inject the filling solidification material 22 using only the filling material injection hole 27d of the center side block 20B without using the filling material injection hole 27e of the receiving base side block 20A, and to finish filling the filling solidification material 22 by confirming that the filling solidification material 22 flows out from the opening of the gap 21a between the receiving base 31c held on the upper surface 20a of the receiving base side block 20A.

[0065] In this embodiment, the multiple PCa concrete blocks 20A, 20B, and 20C arranged in a row and column are preferably adjacent to the previously formed existing invert structure 40 (see FIGS. 3 and 12) in the axial direction of the tunnel. With the gaps 21d between the upper surfaces 20a and the central end surfaces 10B of the multiple PCa concrete blocks 20A, 20B, and 20C arranged in a row and column closed, the filling solidification material 22 is injected by switching from the central filler injection hole 27d located on the existing invert structure 40 side to the central filler injection hole 27d located on the gable side, as shown in FIG. 12. At the same time, the filling solidification material 22 is injected by switching from the base filler injection hole 27e located on the existing invert structure 50 side to the base filler injection hole 27e located on the gable side. It is also possible to switch from the filler injection hole 27d of the central side block 20B on the existing invert section structure 50 side to the filler injection hole 27d of the central side block 20B on the gable side and inject the filling solidification material 22 partway, and then switch again from the filler injection hole 27e of the receiving base side block 20A on the existing invert section structure 50 side to the filler injection hole 27e of the receiving base side block 20A on the gable side and inject the filling solidification material 22.

[0066] Furthermore, in this embodiment, the upper surface band plate-shaped formwork 41a is attached by overlapping and fixing to the upper surface 20a of the plurality of PCa concrete blocks 20A, 20B, 20C, which are preferably arranged in a row vertically and horizontally, so as to cover the openings of the gaps 21b in the upper surface 20a, thereby blocking the openings of the upper surface 20a (see Figs. 10 and 13). Similarly, the end side end surface 10A is also blocked by overlapping and fixing to the end side end surface 10A, preferably so as to cover the openings of the gaps 21a, 21b, 21c (see Fig. 14). As with the end face portion 10A, the central end face portion 10B is also preferably closed by overlapping and fixing the central band plate-shaped formwork 41c to the central end face portion 10B so as to cover the openings of the gaps 21b, 21c, and 21d (see Figure 10).

[0067] Furthermore, the upper surface band-shaped formwork 41a, the end band-shaped formwork 41b, and the central side band-shaped formwork 41c are preferably formed using transparent plate-shaped members, which allows the filling status of the filling solidification material 22 into each of the gaps 21a, 21b, 21c, and 21d to be visually observed through these transparent band-shaped formworks.

[0068] Furthermore, it is preferable to attach air-bleeding hoses 42 (see FIG. 10) extending from an appropriate position to the upper surface band-shaped formwork 41a attached so as to cover the openings of the gaps 21a, 21b, 21d in the upper surfaces 20a of the multiple PCa concrete blocks 20A, 20B, 20C arranged vertically and horizontally. This makes it possible to effectively bleed air from the gaps 21a, 21b, 21d via the air-bleeding hoses 42 when filling with the filling solidification material 22, and it is also possible to confirm that the filling solidification material 22 has been filled by the flow of the filling solidification material 22 from these air-bleeding hoses 42.

[0069] In this embodiment, in the process of filling the gaps 21a between the adjacent receiving base portions 31c of the plurality of PCa concrete blocks 20A, 20B, 20C arranged in a row in the vertical and horizontal directions, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexahedral bottom surfaces communicating with these gaps 21a and 21b, as described above, With the openings of gaps 21a, 21b, and 21c at end face 10A and center face 10B closed, filler solidification material 22 is sequentially injected through center-side filler injection holes 27d provided vertically penetrating one or more of the center-side blocks 20B connected in the axial direction of the tunnel, and through pedestal-side filler injection holes 27e provided vertically penetrating one or more of the base-side blocks 20A connected in the axial direction of the tunnel. Open-close valves 28 are attached to center-side filler injection holes 27d and pedestal-side filler injection holes 27e, respectively. When the filling solidification material 22 is filled by sequentially connecting the injection hose to the valves 28 of the selected center-side filler injection holes 27d or pedestal-side filler injection holes 27e, the valves 28 of the center-side filler injection holes 27d or pedestal-side filler injection holes 27e are closed after filling is completed. The valves 28 of the unused center-side filler injection holes 27d or pedestal-side filler injection holes 27e are left open and can be used as air vents. As described above, in the filling process with the filling solidification material 22, the filling solidification material 22 can be filled only through the filler injection hole 27d of the center-side block 20B, without using the filler injection hole 27e of the pedestal-side block 20A, and the filling of the filling solidification material 22 can be completed by confirming that the filling solidification material 22 flows out of the opening of the gap 21a between the pedestal-side block 31c and the upper surface 20a of the pedestal-side block 20A.By filling the filling solidification material 22 through the filling material injection hole 27d on the central side, air can be smoothly released from the gap 21a between the receiving portion 31c held on the upper surface 20a of the receiving portion side block 20A, making it possible to effectively prevent air from accumulating in the filled filling solidification material 22.

[0070] In addition, in this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and column are preferably arranged adjacent to each other in the axial direction of the tunnel of the existing invert structure 40, as described above. With the openings of the gaps 21d between the upper surface 20a and the central end surface 10B of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and column closed, the filling solidification material 22 is injected by switching from the opening / closing valve 28 of the filler injection hole 27d on the central side located on the existing invert structure 40 side to the opening / closing valve 28 of the filler injection hole 27e on the central side located on the gable side, and the filling solidification material 22 is injected by switching from the opening / closing valve 28 of the filler injection hole 27e on the receiving base side located on the existing invert structure 40 side to the opening / closing valve 28 of the filler injection hole 27e on the receiving base side located on the gable side. As described above, it is also possible to switch from the filler injection hole 27d of the central side block 20B on the existing invert section structure 50 side to the filler injection hole 27d of the central side block 20B on the gable side to inject the filling solidification material 22 partway, and then switch again from the filler injection hole 27e of the receiving base side block 20A on the existing invert section structure 50 side to the filler injection hole 27e of the receiving base side block 20A on the gable side to inject the filling solidification material 22.

[0071] As described above, in each of the central filler injection holes 27d and the base-side filler injection holes 27e, the on-off valves 28 can be attached by threading the male threads 28b into the female thread members 27a fixed to the middle of the central filler injection holes 27d or the base-side filler injection holes 27e in the penetration direction, so that they protrude upward from the top surfaces of the multiple PCa concrete blocks 20A, 20B arranged vertically and horizontally. This makes it easy to detachably connect injection hoses by working on the top surfaces 20a of the PCa concrete blocks 20A, 20B, 20C.

[0072] In this embodiment, the invert section structure 10 having the above-mentioned configuration is constructed in each of a pair of side regions, as shown in Figures 1 and 2, with the regions on both sides of the center of the tunnel in the transverse direction being treated as a pair of side regions, so that these together form the invert section covering body 32, thereby forming the invert section structure 50 over the entire transverse area.

[0073] That is, the invert section structure 50 covering the entire transverse area is a structure using PCa concrete blocks 20A, 20B, 20C that are provided throughout the entire transverse area of ​​the tunnel in the invert section 33 of the mountain tunnel and constitute the invert section lining body 32, and each of the PCa concrete blocks 20A, 20B, 20C is formed as a hexahedral block having curved upper surface portion 20a and lower surface portion 20b so as to have a curved shape that follows the cross-sectional shape of the invert section lining body 32, as described above. 1 and 2, in each of the transversely opposite regions of the tunnel, a plurality of PCa concrete blocks 20A, 20B, and 20C are arranged in series in the transverse direction of the tunnel and installed in an inverted section 33, with gaps 21a and 21b maintained between the support bases 31c at the lower ends of adjacent side wall linings 31a and between adjacent PCa concrete blocks. Also, adjacent PCa concrete blocks 20A, 20B, and 20C are arranged in series in the axial direction of the tunnel and installed in an inverted section 33, with gaps 21b maintained between them. This forms a first-side block group 20X and a second-side block group 20Y. Furthermore, a gap 51 is maintained between the first-side block group 20X and the second-side block group 20Y in the transversely central portion of the tunnel. The multiple PCa concrete blocks 20A, 20B, and 20C arranged vertically and horizontally in the one side block group 20X and the other side block group 20Y are integrated together via the filling solidification material 22 that has been filled and hardened in the gaps 21a between each adjacent receiving portion 31c, the gaps 21b between adjacent PCa concrete blocks 20A, 20B, and 20C, the gap portion 51 between the one side block group 20X and the other side block group 20Y, and the gap 21c below the hexahedral lower surface portion that communicates with these gaps 21a, 21b and the gap portion 51, to form the invert portion covering body 32.

[0074] In addition, in this embodiment, the gaps 21a between adjacent receiving base portions 31c filled with filling solidification material 22 and the gaps 21b between adjacent PCa concrete blocks 20A, 20B, 20C preferably have a spacing width of 15 to 30 mm, and the spacing portion 51 between one side block group 20X and the other side block group 20Y preferably has a spacing width of 100 to 130 mm.

[0075] Furthermore, in this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row vertically and horizontally in the one side block group 20X and the other side block group 20Y are installed in the invert section 33 in a potato-like arrangement, with gaps 21b extending axially between adjacent PCa concrete blocks in the transverse direction of the tunnel and filled with filling solidification material 22, and gaps extending transversely between adjacent PCa concrete blocks in the axial direction of the tunnel, both preferably arranged linearly and continuously.

[0076] Furthermore, in this embodiment, it is preferable that the central side surface of the PCa concrete block (central side block) 20B located closest to the center of one side block group 20X, which faces the gap portion 51, and the central side surface of the PCa concrete block (central side block) 20B located closest to the center of the other side block group, are formed with irregularities 52 to improve adhesion with the filling solidification material 22, as shown in Figure 15, for example.

[0077] The unevenness 52 for improving adhesion with the filling solidification material 22 can also be formed on the lateral opposing surfaces 20d of each PCa concrete block 20, across the maintained gaps 21a, 21b, of the PCa concrete blocks 20 that are arranged in series in the transverse direction of the tunnel and installed in the invert section 33, preferably with gaps 21a, 21b maintained between the receiving base portions 31c at the lower ends of adjacent side wall lining bodies 31a and between adjacent PCa concrete blocks 20. The unevenness 52 for improving adhesion with the filling solidification material 22 can also be formed on the axial opposing surfaces 20c of each PCa concrete block 20, across the maintained gaps 21b, of the PCa concrete blocks 20 that are arranged in series in the axial direction of the tunnel and installed in the invert section 33, preferably with gaps 21b maintained between the PCa concrete blocks 20.

[0078] In this embodiment, the PCa concrete block (center-side block) 20B located most centrally of the one-side block group 20X and the PCa concrete block (center-side block) 20B located most centrally of the other-side block group 20Y are preferably connected via long bolt members (not shown). This ensures installation accuracy of the one-side block group 20X and the other-side block group 20Y, and also ensures shear strength of the portion between these block groups 20X and 20Y.

[0079] In this embodiment, the invert structure 50 across the entire transverse direction of the tunnel can be formed by the following construction method. That is, in this embodiment, the construction method of the invert section structure 50 includes a step of arranging a plurality of PCa concrete blocks 20A, 20B, 20C in a row in the transverse direction of the tunnel and installing them in the invert section 33 in a state where gaps 21a, 21b are maintained between the blocks and the receiving base portions 31c at the lower ends of adjacent side wall lining bodies 31a and between adjacent PCa concrete blocks 20A, 20B, 20C, and also in the axial direction of the tunnel, where gaps 21b are maintained between adjacent PCa concrete blocks 20A, 20B, 20C, to form one side block group 20X; and a process of filling and hardening a filling solidification material 22 into gaps 21c below the lower surface of the hexahedron-shaped block 31a and communicating with the blocks 31a and 31b, and a process of arranging a plurality of PCa concrete blocks 20A, 20B, 20C in a row in the transverse direction of the tunnel and installing them in an invert section 33 in a state where gaps 21a and 21b are maintained between the receiving base 31c at the lower end of the adjacent side wall lining body 31a and between the adjacent PCa concrete blocks 20A, 20B, 20C in the other side region in the transverse direction of the tunnel. and a step of forming the other-side block group 20Y by arranging the PCa concrete blocks 20A, 20B, 20C in a row and installing them in the invert section 33 while maintaining gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C in the axial direction of the tunnel, and by maintaining gaps 21a between the adjacent receiving base sections 31c of the plurality of PCa concrete blocks 20A, 20B, 20C of the other-side block group 20Y that are arranged in a row and horizontally.In addition to the gap 21b between the block group 20C and the gap 21c below the bottom surface of the hexahedron that communicates with these, the process also includes filling and hardening the filling solidification material 22 into the gap 51 between the block group 20X on one side and the block group 20Y on the other side, thereby making it possible to easily form the invert structure 50 that is provided across the entire transverse direction of the tunnel and that constitutes the invert lining body 32.

[0080] The invert structure 50 for the entire transverse area can be formed by constructing both areas simultaneously, rather than constructing each side area at a time, for example, when construction can be carried out by blocking traffic through the mountain tunnel 30 for an extended period of time.

[0081] Furthermore, according to the method of installing PC blocks in the invert section of this embodiment having the above-mentioned configuration, by using PCa concrete blocks 20 (20A, 20B, 20C) of appropriate weight and size that can be easily manufactured in a factory, etc., it is possible to efficiently and quickly form the invert section structure 10, which is formed as a component part of the invert section lining body 32 and is installed continuously from the tunnel side wall portion 31a to the lining body 31 of the upper arch-shaped portion 31b, in a stable and efficient manner, without much effort.

[0082] That is, according to this embodiment, the invert structure 10 is formed so that the PCa concrete blocks 20 constituting the invert structure have a hexahedral shape with a curved upper surface 20a and lower surface 20b, for example, with a width x of approximately 1385 to 1435 mm, a vertical width y of approximately 730 mm, and a height z of approximately 500 mm, and weigh approximately 1300 kg.Compared to conventional concrete components for inverts made of precast concrete, which are heavy and have complex shapes, the PCa concrete blocks have a moderate weight, size, and shape, which not only allows for efficient manufacturing but also improves workability during lifting and transportation, and makes them easier to handle when lifting and installing, making it possible to precisely install each PCa concrete block 20 at a predetermined interval.

[0083] In addition, in the method of installing PC blocks in the invert section of this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C of each transverse block row 20D arranged in succession in the transverse direction of the tunnel are installed in the invert section 33 by installing the base section side block 20A adjacent to the base section 31c and temporarily fixing it by the temporary fixing means 36, and then installing the intermediate section block 20C and the central section side block 20B adjacent to the temporarily fixed base section side block 20A. By sequentially adjusting the positioning and height of the PCa concrete blocks 20 in 33, from the PCa concrete blocks 20 in the steepest slope (inclination) section to the PCa concrete blocks 20 in the central section with a gentler slope (inclination), it becomes possible to install the multiple PCa concrete blocks 20A, 20B, 20C in each transverse block row 20D in a stable state with greater precision, thereby making it possible to more efficiently and quickly form an invert structure 10 using PCa concrete blocks 20 (20A, 20B, 20C) of appropriate weight and size that can be easily manufactured in a factory, etc.

[0084] The present invention is not limited to the above-described embodiment and can be modified in various ways. For example, the invert section structure using the PC block installation method of the present invention is not limited to construction work in which a lining covering the tunnel inner wall surface is formed only in the region from both side walls to the upper arch-shaped portion, and not in the invert section, but can also be formed in construction work in which a lining is installed around the entire inner wall surface of the tunnel, including the invert section, when building a new mountain tunnel, or in construction work in which an invert section lining already installed in a mountain tunnel is repaired and a new invert section lining is installed. [Explanation of symbols]

[0085] 10 Inverter structure 10a Flange placement recess 10A End face on the side 10B Center side end section 20,20' PCa concrete block 20a Top part 20b Bottom part 20c Axial opposing surface 20d Transverse opposing surface 20e Notched recess 20f, 20g Axial connection part 20A Receiving block 20B Central side block 20C Middle block 20D Transverse Block Row 20E Exterior PCa concrete block 20F Inner PCa concrete block 20X One-Sided Block Group 20Y Other side block group 21a Gap between the base and the 21b Gap between adjacent PCa concrete blocks 21c Lower gap of the underside 21d Gap between the existing invert structure 22 Filling and solidification material 23 Bolt Box 24 Female thread anchor 25 Bolt insertion screw hole 25a Female screw member (nut member) 25b Large trumpet-shaped recess 25c Small trumpet-shaped recess 26 Height adjustment bolt 26a Lower end 26b Grounding adjuster 26c Filled bottom part 26d Upper end 27 Filler injection hole 27a Female thread member 27b Upper trumpet-shaped recess 27c Lower trumpet-shaped recess 27d Filler injection hole on the center side 27e Filler injection hole on the base side 28 Opening and closing valve 28a Handle 29a Transverse spacer jig 29b Axial spacer jig 29c Hanging jig 30 Mountain Tunnel 30a Bottom panel part 31 Lining body 31a Side wall (side wall lining) 31b Arch-shaped part 31c pedestal part 32 Invert lining 33 Inverter 35 H type steel 36 Temporary fixing means 36a Hole in Anchor 36b striae 36c Telescopic adjustment means 37 PCa block connection structure 40 Existing invert structure 41a Upper surface band plate formwork 41b Gable band plate formwork 41c Central side band plate formwork 42 Air bleed hose 50 Invert structure throughout the entire tunnel crossing 51 Interval between one side block group and the other side block group b Gap below the bottom surface

Claims

1. A method for installing PCa blocks in an invert section, which is used when constructing an invert section structure using a plurality of PCa concrete blocks that are provided in at least one side region of the invert section of a mountain tunnel in the transverse direction of the tunnel and that constitutes an invert section lining, The PCa concrete block is formed as a hexahedral block having curved upper and lower surfaces so as to have a curved shape that follows the cross-sectional shape of the invert section covering body, The plurality of PCa concrete blocks include a base portion side block arranged adjacent to the base portion at the lower end of the side wall covering body, a central portion side block arranged on the transverse center side of the invert portion, and one or more intermediate portion blocks arranged between them, The PCa concrete blocks are arranged in a row in the transverse direction of the tunnel, with gaps maintained between adjacent support sections and between adjacent PCa concrete blocks, and are also arranged in a row in the axial direction of the tunnel, with gaps maintained between adjacent PCa concrete blocks, and are installed in the invert section lined up vertically and horizontally, The PCa concrete blocks in each row connected in the transverse direction of the tunnel are installed in the invert section by installing the base section side blocks adjacent to the base section and temporarily fixing them by temporary fixing means, and then installing the intermediate section blocks and the central section side blocks adjacent to the temporarily fixed base section side blocks, Furthermore, the base section side block is installed adjacent to the base section and temporarily fixed by temporary fixing means, and then the intermediate section block and the central section side block are installed adjacent to the temporarily fixed base section side block, and at adjacent locations of each of these installed blocks, they are temporarily fixed with bolt members via bolt boxes arranged on the upper surface of at least one of the PCa concrete blocks close to the opposing transverse surface, and then the height and position of each of the PCa concrete blocks is adjusted, and then the bolt members are finally tightened, thereby installing the multiple PCa concrete blocks in each row connected in the transverse direction of the tunnel in the invert section.

2. A method for installing PCa blocks in an invert section, which is used when constructing an invert section structure using a plurality of PCa concrete blocks that are provided in at least one transverse region of the invert section of a mountain tunnel and that constitutes an invert section covering body, comprising: The PCa concrete block is formed as a hexahedral block having curved upper and lower surfaces so as to have a curved shape that follows the cross-sectional shape of the invert section covering body, The plurality of PCa concrete blocks include a base portion side block arranged adjacent to the base portion at the lower end of the side wall covering body, a central portion side block arranged on the transverse center side of the invert portion, and one or more intermediate portion blocks arranged between them, The PCa concrete blocks are arranged in a row in the transverse direction of the tunnel, with gaps maintained between adjacent support sections and between adjacent PCa concrete blocks, and are also arranged in a row in the axial direction of the tunnel, with gaps maintained between adjacent PCa concrete blocks, and are installed in the invert section lined up vertically and horizontally, The PCa concrete blocks in each row connected in the transverse direction of the tunnel are installed in the invert section by installing the base section side blocks adjacent to the base section and temporarily fixing them by temporary fixing means, and then installing the intermediate section blocks and the central section side blocks adjacent to the temporarily fixed base section side blocks, and a bolt box disposed on an upper surface of at least one of the PCa concrete blocks adjacent to the lateral surface of the PCa concrete block, the bolt box being ...

3. A method for installing PCa blocks in an inverter section as described in claim 1 or 2, wherein the temporary fixing means is a cable such as a wire or chain member, both ends of which are engaged with a locking member attached to a hole-in anchor buried in the receiving section and a locking member attached to a bolt box or a lifting jig provided on the receiving section side block.

4. A method for installing PCa blocks in an inverter section as described in claim 3, wherein the cable member is provided with an expansion / contraction adjustment means that can adjust the length between the two engaged ends, thereby making it possible to adjust the width of the gap maintained between the receiving base section and the adjacent receiving base section side block.

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