JP7708805B2 - PCa concrete block for invert structure - Google Patents

Description

The present invention relates to an invert structure, and in particular to a PCa concrete block for an invert structure that is installed in the invert of a mountain tunnel to form an invert lining.

A mountain tunnel is a tunnel formed by excavating a self-supporting and relatively stable foundation such as bedrock, and the excavated inner wall surface is covered with a primary lining and a secondary lining made of concrete or mortar. That is, after the inner wall surface of a mountain tunnel is excavated while performing, for example, blasting, etc., a protective layer is formed on the inner wall surface of the mountain tunnel by spraying mortar or concrete, preferably by forming a primary lining, and then, for example, a known tunnel lining formwork is installed inside the protective layer formed by the primary lining, and a lining body of a predetermined thickness made of concrete is formed as a secondary lining from the side wall part of the tunnel to the upper arch-shaped part. Furthermore, in the lining body formed previously from the both side walls of the tunnel to the upper arch-shaped part, a lining body of the bottom invert part is formed integrally with a predetermined thickness using concrete in the transverse direction of the tunnel in the part between the receiving parts of the lower end of the pair of side walls. The entire circumference of the inner wall surface of the mountain tunnel is continuously covered with the secondary lining.

Mountain tunnels are formed by excavating relatively stable ground, so some tunnels built several decades ago, for example, omit the invert lining and only form a lining in the area from the tunnel's side wall to the upper arch-shaped part, forming a secondary lining. For mountain tunnels like this where the invert lining is omitted, consideration is being given to forming a new invert lining, for example to prevent future effects such as swelling of the base slab.

Conventionally, the method of forming the invert lining at the bottom of the tunnel, continuing from the lining installed earlier from the side wall to the upper arch-shaped part of the tunnel, has generally been to use cast-in-place concrete (see, for example, Patent Document 1), but finishing the top surface of the invert lining to give it a curved shape requires a high level of skill. Furthermore, when using cast-in-place concrete, it takes a considerable amount of time for the poured concrete to harden and undergo a specified curing period, so that when a new invert lining is formed on the lining from the side wall to the upper arch-shaped part without the invert lining, traffic through the tunnel will be blocked for a long period of time, and it is therefore desirable to be able to complete the construction as quickly as possible.

For this reason, it is being considered to shorten the construction period by forming the invert section covering using precast concrete members manufactured in advance in a factory or the like (see, for example, Patent Documents 2 and 3).

JP 2020-159060 A JP 2013-28898 A JP 2018-123528 A

However, in conventional construction methods for invert sections in mountain tunnels using precast concrete members, these concrete members are formed in advance in a factory or the like to cover the entire transverse width of the invert section, or to a length that divides the invert section into two or three transverse sections. This results in large weight and shape, and requires a lot of work to assemble the formwork in a factory or the like and to accurately form joints, etc. Furthermore, it also requires a lot of work to transport and assemble the members at the construction site, and in particular, 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 concrete members used are bulky, which makes the work difficult.

In response to the above issues, constructing the invert section using precast concrete blocks (PCa concrete blocks) of appropriate weight and size that can be easily manufactured in factories, etc., is preferable because it is easy to work with and can be easily formed, and because it can be installed more quickly as a component part of the invert section lining that is continuous with the lining of the arch-shaped part at the top from the side wall of the tunnel.

On the other hand, when using PCa concrete blocks, the top surface of the invert is required to be a flush curved surface, but gaps may occur between the base and each PCa concrete block, the height of which has been adjusted to ensure a flush surface, and these gaps must be filled with a filling solidification material. In particular, if there are a large number of PCa concrete blocks, it becomes difficult to fill the gaps between each block and the base with a filling solidification material.

The present invention aims to provide a PCa concrete block for invert structures that allows easy filling of the gap between the PCa concrete block and the base with a filling solidification material.

The present invention relates to a PCa concrete block used in forming an invert structure, which is provided in at least one side region of the invert section of a mountain tunnel in the transverse direction of the tunnel to constitute an invert section lining, and which is arranged in series in the transverse direction of the tunnel while maintaining gaps between the support base of the lower end of the adjacent side wall section lining body and between the adjacent PCa concrete blocks, into which a filling solidification material is filled, and which is also arranged in series in the axial direction of the tunnel while maintaining gaps between the adjacent PCa concrete blocks, into which a filling solidification material is filled, and which is installed in the invert section lined up vertically and horizontally. The block has curved upper and lower surfaces with a curved shape that follows the cross-sectional shape of the invert section lining body, and is formed as a hexahedral block having a pair of front and rear flat axially opposing surfaces and a pair of left and right flat transversely opposing surfaces, and the upper surface portion of the hexahedral shape The above-mentioned objective has been achieved by providing a PCa concrete block for an inverted section structure in which a bolt box or female screw anchor is embedded and fixed on each of the four sides to connect adjacent PCa concrete blocks using bolt members, and a bolt insertion screw hole that penetrates the hexahedral shape in the vertical direction is formed at three locations arranged at each corner of an isosceles triangle, and a filler injection hole that penetrates the hexahedral shape in the vertical direction is formed, and a female screw member to which the male screw portion of an opening/closing valve member is screwed is fixed to the middle part in the vertical direction of the filler injection hole, and an upper side trumpet-shaped recess is formed that expands in diameter upward from the part where the female screw member is fixed and opens on the upper surface of the PCa concrete block, and a lower side trumpet-shaped recess is formed that expands in diameter downward from the part where the female screw member is fixed and opens on the lower surface of the PCa concrete block.

The PCa concrete block for invert structure of the present invention is preferably formed so that the filler injection hole that penetrates the hexahedron shape in the vertical direction is disposed in the center of the upper surface.

In addition, the PCa concrete block for invert section structures of the present invention preferably has a spacer jig attached to each of the pair of flat axially opposing surfaces at the front and rear of the hexahedron shape and the pair of flat transversely opposing surfaces at the left and right, which maintains a gap of a predetermined width between the opposing surfaces.

Furthermore, it is preferable that the PCa concrete block for the invert section structure of the present invention has a plurality of lifting jigs embedded and fixed to the upper surface of the hexahedral shape, which are used to lift each of the PCa concrete blocks.

The PCa concrete block for invert structure of the present invention makes it easy to fill the gap between the block and the base with a filling solidification material.

This is a schematic cross-sectional view illustrating a mountain tunnel in which an invert structure according to a preferred embodiment of the present invention is formed on both sides of the invert in the transverse direction of the tunnel. This is a diagram illustrating the state in which an invert section structure according to a preferred embodiment of the present invention is formed on both sides across the entire width of the invert section in the transverse direction of the tunnel, and is a schematic top view of Figure 1 viewed from the A-A direction. This is a schematic top view of an invert section structure according to a preferred embodiment of the present invention, provided in one side region of the invert section in the transverse direction of the tunnel. 4 is a schematic cross-sectional view taken along the line BB in FIG. 3 before the filling solidification material is filled. FIG. This is an oblique view of the PCa concrete block that constitutes the invert structure. (a) is a top view of the PCa concrete block that constitutes 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. 2 is a schematic cross-sectional view illustrating a PCa concrete block along a portion in which a bolt insertion screw hole is formed, illustrating the bolt insertion screw hole. FIG. 1A is a perspective view illustrating a ground adjuster attached to a lower end of a height adjustment bolt, and FIG. 1B is a schematic cross-sectional view illustrating another preferred embodiment of a small trumpet-shaped recess. (a) is a conceptual diagram explaining the situation in which PCa concrete blocks are connected and arranged in a state aligned with the tunnel line curved in the horizontal direction, and (b) is a conceptual diagram explaining the situation in which PCa concrete blocks are connected and arranged in a state aligned with the tunnel line curved in the vertical direction. 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 lower surface of the hexahedral shape. 2 is a schematic cross-sectional view in the transverse direction of a PCa concrete block along a portion in which a filler injection hole is formed, illustrating a filler injection hole and an opening and closing valve. FIG. 1 is a schematic top view of an invert structure illustrating the injection status of filling solidification material. FIG. 1 is an explanatory diagram of an upper surface band plate-shaped formwork that closes gaps in the upper surface of a PCa concrete block. An explanatory diagram of a gable band plate-shaped formwork that closes the gap at the gable end surface. 1 is an explanatory diagram of the unevenness formed on the surface of the central portion of a PCa concrete block. FIG.

The invert structure 10 according to a preferred embodiment of the present invention is provided as a structure that constitutes the invert lining 32, which is constructed on each side of the transverse center line C of the tunnel as shown in Figure 2 and Figure 3, and integrated 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, when the invert lining 32 is newly formed on the base portion 30a of the mountain tunnel 30.

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 tunnel inner wall surface 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.

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 work in as short a time as possible. The invert structure 10 of this embodiment uses multiple precast concrete blocks (PCa concrete blocks) of an appropriate weight and size that are easy to handle and are manufactured in advance in a factory, etc., so that it can be easily formed one side at a time without much effort, and the invert lining 32, which is continuous with the lining 31 extending from the side wall 31a of the tunnel to the upper arch-shaped portion 31b, can be installed in a shorter time.

In this embodiment, the invert section structure 10 is a structure of the invert section 33 using PCa concrete blocks 20, which is provided in at least one side region in the transverse direction of the invert section 33 of a mountain tunnel 30 as shown in Figures 1 to 4, and constitutes the invert section lining body 32. As shown in Figures 5 and 6 (a) to (c), the PCa concrete blocks 20 are formed as hexahedral blocks having curved upper surface portions 20a and lower surface portions 20b so as to have a curved shape that follows the cross-sectional shape of the invert section lining body 32. More specifically, in the cross-sectional view of the PCa concrete block 20, the upper surface portion 20a and the lower surface portion 20b have a curved shape that is convex downward. The upper surface portion 20a and the lower surface portion 20b in the cross-sectional view can be gently curved with a curvature radius of, for example, about 14,000 to 14,500 mm.

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 between the support 31c at the lower end of the adjacent side wall lining body 31a and between the adjacent PCa concrete blocks 20, and are also arranged in a row in the axial direction of the tunnel with gaps 21b between the adjacent PCa concrete blocks (see Figures 1 to 4). As shown in Figure 10, the multiple PCa concrete blocks 20 arranged in a row vertically and horizontally are integrated through the filling and solidifying material 22 that is filled and hardened in the gaps 21a between the adjacent support 31c, the gaps 21b between the adjacent PCa concrete blocks 20, and the gaps 21c below the hexahedral lower surface that communicates with these gaps 21a and 21b, and constitute one side of the invert lining body 32 as at least a part of the invert lining body 32.

In this embodiment, the multiple PCa concrete blocks 20 are preferably formed to have a similar hexahedral shape with the same width x in the transverse direction of the tunnel, the same vertical width y in the axial direction of the tunnel, and the same height z (see Figures 5 and 6 (a) to (c)). The multiple PCa concrete blocks 20 arranged in a row are arranged in a row and are installed in the invert section 33 in such a way that the gaps 21b extending in the axial direction between the PCa concrete blocks 20 adjacent to each other in the transverse direction of the tunnel, which are filled with the filling solidification material 22, and the gaps 21b extending in the transverse direction between the PCa concrete blocks adjacent to each other in the axial direction of the tunnel, are preferably arranged in a potato shape that is linearly continuous (see Figures 2 and 3). The gaps 21a between the adjacent receiving base parts 31c filled with the filling solidification material 22 and the gaps 21b between the adjacent PCa concrete blocks are preferably gaps with a spacing width of about 15 to 30 mm.

In this embodiment, the multiple PCa concrete blocks 20 constituting the invert section structure 10 are arranged in a row in the transverse direction of the tunnel with the gaps 21a, 21b between the receiving base 31c at the lower end of the adjacent side wall lining body 31a and between the adjacent PCa concrete blocks 20, in which the filling solidification material 22 is filled, as described above. Also, the PCa concrete blocks 20 are arranged in a row in the axial direction of the tunnel with the gaps 21b between the adjacent PCa concrete blocks, in which the filling solidification material 22 is filled, and are installed in the invert section 33 in a row vertically and horizontally. In addition, as shown in Figures 5 and 6 (a) to (c), the PCa concrete blocks 20 have curved upper surface portions 20a and lower surface portions 20b that have a curved shape that follows the cross-sectional shape of the invert section lining body 32, and are formed as hexahedral blocks having a pair of flat axially opposing surfaces 20c in the front and rear and a pair of flat transversely opposing surfaces 20d in the left and right.

Furthermore, each of these PCa concrete blocks 20 has bolt boxes 23 or female thread anchors 24 embedded and fixed to the four sides of the hexahedral top surface portion for connecting adjacent PCa concrete blocks 20 using bolt members (not shown). The four sides are the periphery of the top surface portion 20a of the PCa concrete block 20, and are composed of opposing surfaces 20c, 20d that face other PCa concrete blocks 20 in the axial or transverse direction.

The bolt box 23 is provided at the upper end of one of the transverse facing surfaces 20d in the transverse direction and one of the axial facing surfaces 20c in the axial direction of the PCa concrete block 20, and opens to the upper surface 20a. The bolt box 23 has openings (bolt holes) in these facing surfaces 20d, 20c through which bolt members are inserted, and the openings face the transverse facing surface 20d or the axial facing surface 20c of another PCa concrete block 20.

The female thread anchor 24 is provided at the upper end of the other transverse facing surface 20d in the transverse direction of the PCa concrete block 20 and the other axial facing surface 20c in the axial direction, and these facing surfaces 20d, 20c have openings (anchor holes) through which the bolt members are inserted.

When the PCa concrete block 20 is arranged adjacent to another PCa concrete block 20 in the transverse or axial direction with the transverse opposing faces 20d or the axial opposing faces 20c facing each other, the positions of the bolt boxes 23 and the female thread anchors 24 on the opposing faces of the adjacent blocks 20 are made to be approximately aligned in the transverse or axial direction. In the PCa concrete block 20 of this embodiment, the bolt box 23 is provided at the center of the width direction (axial direction) of one of the transverse opposing faces 20d, and the female thread anchor 24 is provided at the center of the width direction (axial direction) of the other transverse opposing face 20d. In addition, the bolt boxes 23 are provided at two locations on one of the axial opposing faces 20c, and the female thread anchors 24 are provided at two locations on the other axial opposing face 20c. On the axial opposing faces 20c, the two bolt boxes 23 or the two female thread anchors 24 are provided at intervals in the transverse direction.

When viewed from above from the top surface 20a, the central block 20B and the intermediate block 20C have two transverse opposing surfaces 20d, and the opposing surfaces 20d on which the bolt boxes 23 are provided are the opposing surfaces 20d on the same side between the multiple PCa concrete blocks 20B and 20C. On the other hand, the opposing surfaces 20d on which the female thread anchors 24 are provided are the opposing surfaces 20d on the opposite side of the bolt boxes 23 between the multiple PCa concrete blocks 20B and 20C. Similarly, the opposing surfaces 20c on which the bolt boxes 23 are provided are the opposing surfaces 20c on the same side between the multiple PCa concrete blocks 20B and 20C. On the other hand, the opposing surfaces 20c on which the female thread anchors 24 are provided are the opposing surfaces 20c on the opposite side of the bolt boxes 23 between the multiple PCa concrete blocks 20B and 20C. As a result, when connecting the center block 20B or the intermediate block 20C, the direction of connection in the transverse direction or the direction of connection in the axial direction becomes a predetermined direction. In this embodiment, the center block 20B and the intermediate block 20C in one side region have a female thread anchor 24 on the transverse facing surface 20d on the side of the receiving base 31c in the transverse direction of the tunnel, and a bolt box 23 on the transverse facing surface 20d on the center side in the transverse direction.

The base block 20A has a bolt box 23 and a female thread anchor 24 on the axially facing surface 20c in the same manner as the center block 20B and the intermediate block 20C, except that a bolt box 23 is provided on each of the two transversely facing surfaces 20d.

As shown in Figure 7, the PCa concrete block 20 has three bolt insertion screw holes 25 that penetrate the hexahedral shape in the vertical direction, arranged at each corner of an imaginary isosceles triangle (see Figure 6(a)). That is, in a plan view of the block 20 seen from the top surface 20a, the three bolt insertion screw holes 25 are each formed to be located at the vertices of an imaginary isosceles triangle. This allows the PCa concrete block 20 to be stably supported by the height adjustment bolts 26 inserted into the bolt insertion screw holes 25.

As shown in FIG. 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 a virtual isosceles triangle (see dashed line) with the base positioned parallel to one axially opposing surface 20c and the apex positioned on the other axially opposing surface 20c (see FIG. 6(a)). The angle between the two equal sides of the isosceles triangle formed by the three bolt insertion screw holes 25 is preferably 80° to 90°. In addition, the two bolt insertion screw holes 25 located at both ends of the base of the isosceles triangle are formed so that their transverse positions are approximately the same as those of the bolt box 23 in a plan view (see FIG. 6(a)).

In this embodiment, it is preferable that the center of gravity of the PCa concrete block 20 is 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 is 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 more stably and precisely using the three height adjustment bolts 26, and also makes it possible to support the PCa concrete block 20, whose height and inclination have been precisely adjusted, in a more stably manner using the three height adjustment bolts 26.

A female screw member 25a into which a height adjustment bolt 26 is screwed is fixed to each bolt insertion screw hole 25 below the vertical middle portion (see Figure 7). When the total height of the PCa concrete block 20 is 100%, the position of the bottom surface 20b of the block 20 in the vertical direction is 0%, and the position of the top surface 20a is 100%, it is preferable that the upper edge of the female screw member 25a is located within a range of 24 to 28% of the block in the vertical direction.

In addition, a large trumpet-shaped recess 25b is formed from the portion where the female screw member 25a of each bolt insertion screw 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 screw 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. In addition, 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-shaped formwork for pouring concrete to form these trumpet-shaped recesses 25b and 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, is 10% or more inclined with respect to the central axis of the bolt insertion screw hole 25.

Furthermore, as shown in Figs. 10 and 11, some of the PCa concrete blocks 20' (see Fig. 3) have a filler injection hole 27 that penetrates the hexahedron in the vertical direction. A female screw member 27a is fixed to the vertical middle of each filler injection hole 27, to which the male screw portion of the opening and closing valve 28 is screwed. An upper trumpet-shaped recess 27b is formed from the portion where the female screw member 27a of each filler injection hole 27 is fixed, expanding upward and opening on the upper surface portion 20a of the PCa concrete block 20', and a lower trumpet-shaped recess 27c is formed from the portion where the female screw member 27a is fixed, expanding downward and opening on the lower surface portion 20b of the PCa concrete block 20'. In these filler injection holes 27, the male threaded portion of the opening/closing valve 28 is screwed into the female threaded member 27a, and the handle portion 28a is positioned above the upper surface portion 20a of the PCa concrete block 20', so that the opening/closing valve 28 is detachably attached to the PCa concrete block 20' in a state in which the handle portion 28a can be opened and closed by working on the upper surface portion 20a of the PCa concrete block 20'.

Some of the PCa concrete blocks 20' have filler injection holes 27, so that the filling solidification material 22 can be easily filled from the upper surface 20a of the PCa concrete block 20' into the gap 21c between the lower surface 20b of each block 20 and the filling bottom surface 26c. The gap 21c is the gap between the lower surface 20b of the PCa concrete block 20 and the filling bottom surface 26c, which is the base (ground).

In addition, since filling is possible while the opening and closing valve 28 is fixed to the female screw member 27a of the filling material injection hole 27, the injection hose for injecting the filling solidification material 22 can be prevented from being pushed upward by the filling pressure. The injection hose is connected to the opening and closing valve 28 when in use.

The upper trumpet-shaped recess 27b and the lower trumpet-shaped recess 27c in the filler injection hole 27 preferably have a height from the opening in the upper surface 20a or the lower surface 20b of these trumpet-shaped recesses 27b, 27c to the end of the female screw member 27a of approximately 210 to 230 mm, and the opening diameter of these trumpet-shaped recesses 27b, 27c in the upper surface 20a or the lower surface 20b is approximately 118 to 123 mm.

In this embodiment, the filler injection hole 27 that penetrates the hexahedral PCa concrete block 20' in the vertical direction can be preferably formed 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 hole 27 is formed in the center of the central block 20B that is located at the lowest position.

In this embodiment, the PCa concrete blocks 20 (20') are preferably hexahedron-shaped, and each of the pair of flat axially opposing faces 20c and the pair of flat transversely opposing faces 20d can be fitted with spacer jigs 29a, 29b to maintain a predetermined gap width 21b between the opposing faces 20c, 20d (see Figures 5, 6(b), and (c)). Preferably, a plurality of lifting jigs 29c used for lifting each PCa concrete block 20 are embedded and fixed in the upper surface 20a of the hexahedron (see Figure 6(a)).

In this embodiment, the PCa concrete blocks 20 are formed by pouring concrete into the box-shaped formwork assembled in a manufacturing factory in a shape that conforms to the above-mentioned predetermined hexahedral shape, allowing it to harden, and then removing it after a predetermined curing period. The blocks are then formed into a hexahedral shape with a curved upper surface 20a and lower surface 20b, preferably with a width x of about 1385 to 1435 mm, a vertical width y of about 730 mm, and a height z of about 500 mm, and weighing about 1300 kg. For example, by arranging and supporting a brace inside the box-shaped formwork, the above-mentioned bolt box 23, female thread anchor 24, and box-removing members for the bolt insertion screw holes 25 and filler injection holes 27 can be attached and embedded in the PCa concrete block 20 or temporarily fixed thereto. As described above, the bolt insertion screw hole 25 and the filler injection hole 27 have two trumpet-shaped recesses that expand outward in the vertical direction, so that the box punch member of the trumpet-shaped recess can be easily punched out. In this embodiment, the receiving block 20A, the center block 20B, and the intermediate block 20C can be manufactured by varying the attachment or attachment position of the box punch member. In this embodiment, the size, shape, weight, etc. of the PCa concrete block 20 used as the invert block can be appropriately designed 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 block 20 can be preferably 1000 to 1500 kg.

In addition, in this embodiment, the multiple PCa concrete blocks 20 are formed to have similar hexahedral shapes, so it is possible to limit the type of box-shaped formwork used and manufacture them efficiently. In addition, because the blocks are of similar weight, workability during lifting and transportation is improved, and they can be handled in the same way when hoisting and installing. This makes it easy to precisely install each PCa concrete block 20 in a predetermined position, for example, so that they are arranged in a potato-like shape. It also makes it possible to reduce manufacturing costs.

In this embodiment, the invert structure 10 is constructed in each of the pair of half-side regions, with the regions on both sides sandwiching the center in the transverse direction of the tunnel being regarded as a pair of half-side regions (see Figs. 1 and 2). In the center of the transverse direction of the tunnel in the invert section 33, a plurality of H-shaped steels 35 supporting retaining plate members and protective fences, etc., for preventing the other half-side region from being affected when constructing the invert structure 10 in each half-side region can be erected at a predetermined interval in the axial direction of the tunnel by driving the flanges into the ground of the invert section 33 with the flanges aligned in the axial direction of the tunnel. For this reason, at the center end of a pair of PCa concrete blocks (center side blocks) 20B adjacent in the axial direction of the tunnel at the center side of the transverse direction of the tunnel at the position where these H-shaped steels 35 are erected, a notch recess 20e having a rectangular cross-sectional shape can be formed at the corners on both sides sandwiching the gap 21b between them (see Fig. 3). The notched recesses 20e at the corners on both sides allow a flange mounting recess 10a for mounting one flange of the H-shaped steel 35 to the end face (center end face) 10B on the central side of the tunnel crossing direction of each invert structure 10, in the portion where the H-shaped steel 35 is erected.

That is, in the block group 20X, 20Y (see FIG. 1) consisting of a plurality of PCa concrete blocks 20 constituting the invert structure 10 of each side region, the PCa concrete block 20 (center side block 20B) arranged in the portion where the H-shaped steel 35 is erected 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 covering body 32, and is formed as a hexahedral block having a pair of front and rear flat axial opposing surfaces 20c and a pair of left and right flat transverse opposing surfaces 20d (see FIGS. 6(a) to (c)). At the corner portion between the axial opposing surfaces 20c and the transverse opposing surfaces 20d at any one location, as shown in FIG. 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 1/2 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 blocks 20B that are adjacent in the axial direction of the tunnel at the portion 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.

In this embodiment, the multiple PCa concrete blocks 20 constituting the invert structure 10 have multiple transverse block rows 20D including a support side block 20A arranged adjacent to the support portion 31c at the lower end of the side wall covering body 31a, a central side block 20B arranged on the transverse central side of the invert, and one or more intermediate blocks 20C (in this embodiment, one intermediate block 20C) arranged between them, as shown in Figures 3 and 4. 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 support 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 20A, 20B, 20C (transverse block rows 20D), and are arranged vertically and horizontally in the invert section 33. The multiple PCa concrete blocks 20A, 20B, and 20C used in constructing the invert structure 10 can be constructed using the following method for installing PCa blocks in the invert.

In other words, in the method of installing PCa blocks in the invert section according to this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C of each transverse block row 20D arranged in a row 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 31c and temporarily fixing it with the temporary fixing means 36, as shown in FIG. 4, and then installing the intermediate block 20C and the central block 20B adjacent to the temporarily fixed base side block 20A in sequence.

For example, the base block 20A is installed adjacent to the base 31c and temporarily fixed by the temporary fixing means 36, and then the intermediate block 20C and the central block 20B are installed adjacent to the temporarily fixed base block 20A, and the adjacent locations of the installed blocks 20A, 20B, and 20C are temporarily fixed by bolt members (not shown) through the bolt boxes 23 that are opened and disposed on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, and 20C close to the transverse opposing surface 20d. For temporary fixing at the adjacent locations, the bolt members are inserted into the female thread anchors 24 that face the bolt boxes 23 through the openings on the upper surface 20a of the bolt boxes 23 and temporarily fastened. Then, by adjusting the height and position of each PCa concrete block 20A, 20B, 20C and then fully tightening the bolt members, 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.

For example, the receiving base block 20A is installed adjacent to the receiving base 31c and temporarily fixed by the temporary fixing means 36, and then the intermediate block 20C is installed adjacent to the temporarily fixed receiving base block 20A, and the adjacent area between the installed intermediate block 20C and the receiving base block 20A is temporarily fixed by 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 adjacent to the transverse facing surface 20d. Then, after adjusting the height and position of each PCa concrete block 20A, 20C, the bolt members are permanently tightened. Next, the central block 20B is installed adjacent to the intermediate block 20C, and at the adjacent location between the installed central block 20B and the intermediate block 20C, the bolt members are temporarily fixed via the bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20C, 20B adjacent to the transverse facing surface 20d, and then the height and position of the central block 20B are adjusted, and the bolt members are finally tightened, so that the multiple PCa concrete blocks 20A, 20B, 20C of each transverse block row 20D connected in the transverse direction of the tunnel can be installed in the invert section 33.

Here, in this embodiment, the temporary fixing means 36 for temporarily fixing the receiving base side block 20A adjacent to the receiving base 31c can be preferably a wire, chain, or other such rope 36b, both ends of which are engaged with a locking member attached to a hole-in anchor 36a embedded in the receiving base 31c and a locking member attached to a bolt box 23 or a hanging jig 29c provided on the receiving base side block 20A. The wire, chain, or other such rope 36b can be provided with an expansion and contraction adjustment means 36c, such as a turnbuckle, that can adjust the length between the two engaged ends. This makes it possible to adjust the width of the gap 21a maintained between the receiving base 31c and the adjacent receiving base side block 20A.

In this embodiment, the height of each of the PCa concrete blocks 20A, 20B, and 20C can be adjusted using three height adjustment bolts 26 screwed into the bolt insertion screw holes 25 formed in the three locations as shown in Figures 6(a) and 7. That is, each of the PCa concrete blocks 20A, 20B, and 20C has three bolt insertion screw holes 25 formed in the vertical direction, and the height adjustment bolts 26 are attached to each of the bolt insertion screw holes 25 in a state in which the lower end 26a can protrude downward from the lower surface portion 20b of the PCa concrete blocks 20A, 20B, and 20C. Prior to the process of filling 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 bottom surface portion 20b that communicates with these gaps 21a and 21b with the filling solidification material 22 (see FIG. 10), the PCa concrete blocks 20A, 20B, 20C are rotated from above to change the protruding length of the three height adjustment bolts 26 from the bottom surface portion 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.

As described above, in this embodiment, a nut member is preferably fixed as a female screw member 25a to the lower part of each bolt insertion screw hole 25 below the vertical middle part, and the height adjustment bolt 26 is screwed into this nut member 25a, so that the height adjustment bolt 26 is attached in a state in which the lower end 26a can protrude downward from the lower surface part 20b of the PCa concrete block 20A, 20B, 20C. In addition, 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 part 26c, for example, the ground surface. This allows the lower end 26a of the height adjustment bolt 26 to be grounded on the filling bottom surface part 26c below the lower surface part 20b in a stable state.

It is preferable that the ground adjuster 26b can be accommodated in the small trumpet-shaped recess 25c, which expands downward when the height adjustment bolt 26 is retracted upward. For example, as shown in FIG. 8(b), by making the small trumpet-shaped recess 25c a trumpet-shaped recess that expands downward and conforms to the outer circumferential shape of the ground adjuster 26b and is slightly larger than the small trumpet-shaped recess 25c, the ground adjuster 26b having a shape similar to the small trumpet-shaped recess 25c can be easily accommodated inside the small trumpet-shaped recess 25c without protruding downward from the lower surface 20b of the PCa concrete block 20. As a result, even if the gap 21c between the lower surface 20b and the filling bottom surface 26c of the PCa concrete block 20 is not sufficient to meet the height of the ground adjuster 26b, the adjuster 26b can be grounded on the filling bottom surface 26c to fine-tune the height of the PCa concrete block 20. In addition, the height position of the filled bottom surface 26c after leveling is the same height as the design position of the bottom surface 20b of the PCa concrete block 20, so even if there is no room, the entire ground adjuster 26b can be accommodated in the small trumpet-shaped recess 25c, and each PCa concrete block 20 can be installed in a specified position with the bottom surface 20b abutting against the filled bottom surface 26c.

The small trumpet-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. From the viewpoint of making it easier to remove the box punch member after the concrete has hardened, the taper gradient of the small trumpet-shaped recess 25c is preferably inclined by 10% or more with respect to the central axis of the bolt insertion screw hole 25.

In this embodiment, the upper end 26d of the height adjustment bolt 26 is preferably formed to have a square cross section, and by engaging an insert extension bar as a rotation operation tool with the upper end 26d and rotating the height adjustment bolt 26, 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 easily changed by working above the upper surface 20a of the PCa concrete block 20A, 20B, 20C. As described above, the bolt insertion screw hole 25 has a large trumpet-shaped recess 25b that expands upward from the portion where the nut member 25a, which is a female screw 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 adjustment bolt 26 after the lower end 26a is adjusted to be in contact with the filling bottom surface 26c protrudes from or is close to the upper surface 20a of the PCa concrete block 20A, 20B, 20C, and a sufficient covering thickness cannot be secured above the upper end 26d when the large trumpet-shaped recess 25b is filled with the finishing filler, the upper end 26d of the height adjustment bolt 26 can be appropriately cut to the required length in the large trumpet-shaped recess 25b. This makes it possible to secure the desired covering thickness by the finishing filler such as mortar filled in the bolt insertion screw hole 25, and to prevent the height adjustment bolt 26 from corroding. The work of cutting the upper end 26d of the height adjustment bolt 26 can be performed smoothly because a sufficient working space can be secured in the large trumpet-shaped recess 25b, which expands in diameter toward the top.

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 about 360 to 380 mm, and an opening diameter in the upper surface 20a of about 106 to 110 mm. From the viewpoint of making it easier to remove the box punch member after the concrete has hardened, it is preferable that the taper gradient of the large trumpet-shaped recess 25b is inclined by 10% or more with respect to the central axis of the bolt insertion screw hole 25.

In this embodiment, as described above, each of the PCa concrete blocks 20A, 20B, and 20C has three bolt insertion holes 25 formed 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 26a protruding downward from the lower surface portion 20b of the PCa concrete block 20A, 20B, and 20C can be adjusted. As a result, prior to the process 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, and 20C arranged in a row vertically and horizontally, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, and 20C, and the gaps 21c below the hexahedral lower surface portion 20b that communicate with these gaps 21a and 21b, the gaps 21c between the adjacent receiving portions 31c of the multiple PCa concrete blocks 20A, 20B, and 20C arranged in a row vertically and horizontally, and the gaps 21c below the hexahedral lower surface portion 20b that communicate with these gaps 21a and 21b, the gaps 21a between the adjacent receiving portions 31c of the multiple PCa concrete blocks 20A, 20B, and 20C are adjusted. The gap width b (see Figures 7 and 10) of the gap 21c below the hexagonal bottom surface 20b of the PCa concrete blocks 20A, 20B, and 20C is measured from the protruding length of the lower end 26a of the height adjustment bolt 26 protruding from the bottom surface 20b of the PCa concrete blocks 20A, 20B, and 20C, and the planned amount of filling solidification material 22 to be filled in the gap 21c below the hexagonal bottom surface 20b can be calculated in advance based on this and the area of the bottom surface 20b of the PCa concrete blocks 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 hexagonal bottom surface 20b, taking into account the calculated planned filling amount, and is filled and hardened.

In other words, in this embodiment, the nut member 25a is fixed as a female screw member to the lower part of each bolt insertion screw hole 25 below the vertical middle part, and the 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. 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.

In addition, in this embodiment, a tiltable ground adjuster 26b is preferably attached to the lower end 26a of the height adjustment bolt 26, so that 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 when the ground adjuster 26b is grounded to the filling bottom surface 26c below the hexahedral lower surface 20b.

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

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 widths b of the gaps 21c below the hexahedral lower surface portions 20b measured by the three height adjustment bolts 26 attached to the three bolt insertion and screw holes 25 of each of the PCa concrete blocks 20A, 20B, and 20C that make up the invert structure 10.

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

That is, in this embodiment, as shown in Figures 3, 4, and 6 (a) to (c), the connection structure 37 of the PCa concrete blocks in the invert structure has a transverse spacer jig 29a (see Figure 6 (b)) fixed to one of the opposing surfaces between each pair of transverse opposing 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 locations, and is connected by the fastening force of a bolt member (not shown) fastened by a bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, and 20C adjacent to these transverse opposing surfaces 20d, while maintaining a gap 21b of a predetermined interval between the transverse opposing surfaces 20d. In addition, between each pair of axially opposing surfaces 20c of the PCa concrete blocks 20A, 20B, and 20C adjacent to each other in the axial direction of the tunnel, axial spacer jigs 29b (see FIG. 6(c)) fixed to one of the axially opposing surfaces 20c are arranged, preferably at least in three places, and are interposed. The pair of PCa concrete blocks 20A, 20B, and 20C adjacent to each other in the axial direction of the tunnel are connected with a predetermined gap 21b between the axially opposing surfaces 20c by the fastening force of a bolt member (not shown) fastened by a bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, and 20C adjacent to the axially opposing surfaces 20c. The transverse spacer jigs 29a and the axial spacer jigs 29b can also be attached to the transversely opposing surfaces 20d and the axially opposing surfaces 20c at the position where the bolt box 23 is provided.

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

The transverse spacer jigs 29a and axial spacer jigs 29b, which are preferably arranged at at least three locations and fixed to either one of the transverse facing surfaces 20d or the axial facing surfaces 20c, are preferably fixed to at least two locations in the area below the center of gravity of the PCa concrete blocks 20A, 20B, and 20C. This makes it possible to accurately and appropriately form gaps 21a and 21b of a predetermined distance in a stable state in the area 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.

The bolt member fastened in the bolt box 23 arranged on the upper surface 20a of at least one of the PCa concrete blocks 20A, 20B, 20C adjacent to the transverse opposing surface 20d, or the bolt member fastened in the bolt box 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 box 23 arranged on the upper surface 20a adjacent to the axial opposing surface 20c or transverse opposing surface 20d of one of the PCa concrete blocks 20A, 20B, 20C and the female thread anchor 24 embedded in the axial opposing surface 20c or transverse opposing surface 20d of the other PCa concrete block 20A, 20B, 20C. Preferably, the bolt box 23 arranged on the upper surface 20a adjacent to the axially facing surface 20c or the transversely facing surface 20d of one PCa concrete block 20A, 20B, 20C may be fastened across the bolt box 23 arranged on the upper surface 20a adjacent to the axially facing surface 20c or the transversely facing surface 20d of the other PCa concrete block 20A, 20B, 20C.

In this embodiment, when the mountain tunnel includes a portion with a tunnel line curved in the horizontal direction, the 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 a gap 21b of a predetermined spacing width between adjacent PCa concrete blocks 20A, 20B, 20C and aligning them along the tunnel line curved in the horizontal direction.

That is, in this embodiment, between each pair of transverse opposing surfaces 20d of adjacent PCa concrete blocks 20A, 20B, 20C facing in the transverse direction of the tunnel, transverse spacer jigs 29a (see Figure 6 (b)) fixed to one of the transverse opposing surfaces 20d are arranged at 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 transverse 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 facing 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 are 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), in one or more axial connection parts 20f between the transverse block rows 20D arranged in a row in the axial direction of the tunnel, the axial spacer jigs 29b interposed between a pair of axially opposed surfaces 20c in the axial direction of the tunnel are fixed to the axially opposed surfaces 20c in a state in which the intervening width is adjusted so that the width of the outer gap 21b held by the axial spacer jigs 29b fixed to the outer PCa concrete block 20E located on the outside of the tunnel linear curve in the horizontal direction in the transverse direction of the tunnel is larger than the width of the inner gap 21b held by the axial spacer jigs 29b fixed to the inner PCa concrete block 20F located on the inside of the tunnel linear curve in the horizontal direction. This makes it possible to install the multiple PCa concrete blocks 20A, 20B, 20C in a connected arrangement vertically and horizontally along the tunnel linear curve in the horizontal direction and integrally in the invert part 33. This also makes it possible to use rectangular PCa concrete blocks 20A, 20B, and 20C to accommodate tunnel linear shapes that curve horizontally, without using tapered blocks.

Here, when the axial spacer jig 29b is made of a mortar block that is attached and fixed to one of the axially opposing surfaces 20c, the gap width can be adjusted so that the gap width of the outer gap 21b is larger than the gap 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 gap width is different.

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

On the other hand, in this embodiment, when the mountain tunnel includes a portion with a tunnel line curved in the vertical direction, the multiple PCa concrete blocks 20A, 20B, 20C can be integrally installed in the invert section 33 by connecting them vertically and horizontally while maintaining a gap 21b of a predetermined interval between adjacent PCa concrete blocks 20A, 20B, 20C and aligning them along the tunnel line curved in the vertical direction.

That is, in this embodiment, between each pair of transverse opposing surfaces 20d of adjacent PCa concrete blocks 20A, 20B, 20C facing in the transverse direction of the tunnel, transverse spacer jigs 29a (see Figure 6 (b)) fixed to one of the transverse opposing surfaces 20d are arranged at 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 transverse 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 facing 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 FIG. 9B, in one or more axial connection parts 20g between the transverse block rows 20D arranged in the axial direction of the tunnel, at least three axial spacer jigs 29b interposed between each pair of axially opposing surfaces 20c facing each other in the axial direction of the tunnel are fixed to the axially opposing surfaces 20c with the intervening width adjusted so that the spacing width of the upper gap 21b held by the axial spacer jigs 29b arranged in the upper stage and the spacing width of the lower gap 21b held by the axial spacer jigs 29b arranged in the lower stage are different. This makes it possible to install multiple PCa concrete blocks 20A, 20B, and 20C as one unit in the invert section 33 by connecting them vertically and horizontally along the tunnel linear curve. This also makes it possible to use rectangular PCa concrete blocks 20A, 20B, and 20C to correspond to the tunnel linear curve in the vertical direction without using tapered blocks.

For example, by adjusting the spacing widths of the upper gap 21b held by the axial spacer jig 29b arranged in the upper tier in the connecting portion 20g having different spacing widths so that the spacing width 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 adjacent transverse block rows 20D along the tunnel linear shape that curves downward in the vertical direction.

In addition, by adjusting the spacing widths of the upper gap 21b held by the axial spacer jig 29b arranged in the upper tier in the connecting portion 20g with different spacing widths so that the spacing width is smaller 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 adjacent transverse block rows 20D along a tunnel line that curves upward in the vertical direction.

Here, when the axial spacer jig 29b is made of mortar blocks that are attached and fixed to one of the axially 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 tiers at the connecting portion 20g, which has different spacing widths.

In addition, when the axial spacer jig 29b is a male screw member that is fixed so that the protruding length can be adjusted by screwing it 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 of the connecting portion 20g, which has different spacing widths, 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.

In this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and column are integrated through the filling solidification material 22 filled and hardened in the gaps 21a between the adjacent receiving bases 31c, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexagonal bottom surface that communicates with these gaps, as shown in FIG. 10, to form at least a part of the invert section covering body 32. In this embodiment, the filling solidification material 22 is filled in the gaps 21a between the adjacent receiving bases 31c, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexagonal bottom surface that communicates with these gaps 21a and 21b by the following construction method.

That is, in this embodiment, in the process of filling the gaps 21a between adjacent receiving portions 31c of multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and column, 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 multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and column are closed. Thereafter, as shown in Figures 10 to 12, the filling solidification material 22 is sequentially injected from the filling material injection hole 27d on the center side, which is provided vertically penetrating one or more of the multiple central side blocks 20B arranged in the axial direction of the tunnel, and from the filling material injection hole 27e on the receiving side, which is provided vertically penetrating one or more of the multiple receiving base side blocks 20A arranged in the axial direction of the tunnel. As shown in Figure 12, preferably, the filling solidification material 22 is injected from the filling material injection hole 27d on the center side, and then the filling material injection hole 27e on the receiving base 31c side is switched to inject the filling solidification material 22 further, and the filling solidification material 22 is confirmed to flow out from the opening of the gap 21a between the receiving base 31c held by the upper surface 20a of the receiving base side block 20A, and the filling of the filling solidification material 22 is completed. 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 when it is confirmed 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.

In this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row are preferably arranged adjacent to the axial direction of the tunnel of the existing invert structure 40 (see Figures 3 and 12) formed in advance. In a state where the opening portion of the gap 21d between the upper surface 20a of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and the existing invert structure 40, which opens at the center end surface 10B, and the upper surface 20a of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row, and the existing invert structure 40, is blocked, the filling solidification material 22 is injected while switching from the filling material injection hole 27d on the center side located on the existing invert structure 40 side to the filling material injection hole 27d on the center side located on the gable side, as shown in Figure 12, and the filling solidification material 22 is injected while switching from the filling material injection hole 27e on the receiving base side located on the existing invert structure 50 side to the filling material injection hole 27e on the receiving base side located on the gable side. It is also possible to switch from the filler injection hole 27d of the central block 20B on the existing invert structure 50 side to the filler injection hole 27d of the central 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 block 20A on the existing invert structure 50 side to the filler injection hole 27e of the receiving block 20A on the gable side to inject the filling solidification material 22.

Furthermore, in this embodiment, the upper surface band plate-shaped formwork 41a is attached to the upper surface 20a of the multiple PCa concrete blocks 20A, 20B, 20C arranged 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 Figures 10 and 13). In the end surface 10A, the end band plate-shaped formwork 41b is attached to the end surface 10A so as to cover the openings of the gaps 21a, 21b, 21c, thereby blocking the openings of the end surface 10A (see Figure 14). Similarly to the end face 10A, the central end face 10B is preferably fitted with a central side band plate-shaped formwork 41c that is overlapped and fixed to the central end face 10B so as to cover the openings of the gaps 21b, 21c, and 21d, thereby blocking the openings of the central end face 10B (see FIG. 10).

The upper surface band plate-shaped formwork 41a, the gable portion band plate-shaped formwork 41b, and the central side band plate-shaped formwork 41c are preferably formed using transparent plate-shaped members. This makes it possible to visually check the filling status of the filling solidification material 22 in each of the gaps 21a, 21b, 21c, and 21d through these transparent band plate-shaped formworks.

Furthermore, it is preferable to attach an air vent hose 42 (see FIG. 10) extending from an appropriate position to the upper surface band plate formwork 41a attached so as to cover the openings of the gaps 21a, 21b, 21d in the upper surface 20a of the multiple PCa concrete blocks 20A, 20B, 20C arranged vertically and horizontally. The air vent hose 42 can effectively vent air from the gaps 21a, 21b, 21d when the filling solidification material 22 is filled, and it is possible to confirm that the filling solidification material 22 has been filled by flowing out of the air vent hose 42.

In this embodiment, in the process of filling the gaps 21a between the adjacent receiving base portions 31c of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row vertically and horizontally, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the hexahedral bottom surface portions that communicate with the gaps 21a and 21b, as described above, the upper surface portions 20a and With the openings of the gaps 21a, 21b, 21c at the end face 10A and the center face 10B closed, the filling solidification material 22 is sequentially injected from the center side filler injection hole 27d provided vertically penetrating one or more of the multiple center side blocks 20B arranged adjacent to each other in the axial direction of the tunnel, and from the receiving side filler injection hole 27e provided vertically penetrating one or more of the multiple receiving side blocks 20A arranged adjacent to each other in the axial direction of the tunnel. An open/close valve 28 is attached to the center side filler injection hole 27d and the receiving side filler injection hole 27e, respectively. When filling the filling solidification material 22 by sequentially connecting the injection hose to the opening and closing valves 28 of the selected filling material injection holes 27d on the center side or the filling material injection holes 27e on the pedestal side, the opening and closing valves 28 of the filling material injection holes 27d on the center side or the filling material injection holes 27e on the pedestal side are closed after filling is completed. The opening and closing valves 28 of the unused filling material injection holes 27d on the center side or the filling material injection holes 27e on the pedestal side are left open and can be used as air vent members. As described above, in the process of filling the filling solidification material 22, the filling solidification material 22 can be injected using only the filling material injection holes 27d of the center side block 20B without using the filling material injection holes 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 from the opening portion of the gap 21a between the pedestal 31c held on 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 center side, air can be smoothly removed from the gap 21a between the receiving base 31c held on the upper surface 20a of the receiving base side block 20A, effectively preventing air from collecting in the filled filling solidification material 22.

In addition, in this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row are preferably arranged adjacent to each other in the axial direction of the tunnel of the existing invert structure 40 formed in advance, as described above. With the upper surface 20a and the central end surface 10B of the multiple PCa concrete blocks 20A, 20B, 20C arranged in a row and the gap 21d between the existing invert structure 40 and ... As described above, it is also possible to switch from the filler injection hole 27d of the central block 20B on the existing invert structure 50 side to the filler injection hole 27d of the central 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 block 20A on the existing invert structure 50 side to the filler injection hole 27e of the receiving block 20A on the gable side to inject the filling solidification material 22.

In each of the central filler injection holes 27d and the base filler injection holes 27e, the open/close valves 28 can be attached by screwing the male threads 28b into the female thread members 27a fixed to the middle of the central filler injection holes 27d or the base filler injection holes 27e in the penetration direction, as described above, so that they protrude upward from the upper surfaces of the multiple PCa concrete blocks 20A, 20B arranged vertically and horizontally. This makes it possible to easily connect the injection hose detachably by working on the upper surfaces 20a of the PCa concrete blocks 20A, 20B, 20C.

In this embodiment, the invert structure 10 having the above-mentioned configuration is constructed in each of a pair of side regions, each of which is sandwiched between the center of the tunnel in the transverse direction, as shown in Figures 1 and 2. These are integrated to form the invert covering body 32, forming the invert structure 50 over the entire transverse area.

That is, the invert section structure 50 covering the entire transverse area is a structure using PCa concrete blocks 20A, 20B, 20C that is provided throughout the entire transverse area of the tunnel in the invert section 33 of the mountain tunnel and constitutes 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. As shown in Figures 1 and 2, in each of one side region and the other side region in the transverse direction of the tunnel, a plurality of PCa concrete blocks 20A, 20B, 20C are arranged in series in the transverse direction of the tunnel and installed in the invert section 33 with gaps 21a, 21b between the support pedestal 31c at the lower end of the adjacent side wall lining body 31a and between the adjacent PCa concrete blocks, and are also arranged in series in the axial direction of the tunnel with gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, thereby forming a one-side block group 20X and an other-side block group 20Y. In addition, a space portion 51 is maintained between the one-side block group 20X and the other-side block group 20Y in the central portion of the transverse direction of the tunnel. The multiple PCa concrete blocks 20A, 20B, 20C arranged vertically and horizontally in the first block group 20X and the second block group 20Y are integrated together via the filling solidification material 22 that is filled and hardened in the gaps 21a between the adjacent receiving bases 31c, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, the gaps 51 between the first block group 20X and the second block group 20Y, and the gaps 21c below the hexahedral lower surface that communicates with the gaps 21a, 21b and the gaps 51, to form the invert section covering body 32.

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.

Furthermore, in this embodiment, the multiple PCa concrete blocks 20A, 20B, 20C arranged vertically and horizontally in the one side block group 20X and the other side block group 20Y are installed in the invert section 33, with the gaps 21b between the PCa concrete blocks adjacent in the transverse direction of the tunnel, filled with the filling solidification material 22, and the gaps between the PCa concrete blocks adjacent in the axial direction of the tunnel being preferably arranged in a potato shape that is continuous in a straight line.

Furthermore, in this embodiment, it is preferable that the central side surface of the PCa concrete block (central side block) 20B located at the most central side of the 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 at the most central side of the other side block group, have irregularities 52 formed thereon to improve adhesion with the filling solidification material 22, as shown in FIG. 15, for example.

The unevenness 52 for improving the adhesion with the filling solidification material 22 can also be formed on the transverse facing surfaces 20d that face each other across the retained gaps 21a, 21b of each PCa concrete block 20 that is arranged in a row in the transverse direction of the tunnel and installed in the invert section 33, preferably with the gaps 21a, 21b held between the receiving base 31c at the lower end of the adjacent side wall covering body 31a and between the adjacent PCa concrete blocks 20. The unevenness 52 for improving the adhesion with the filling solidification material 22 can also be formed on the axial facing surfaces 20c that face each other across the retained gaps 21b of each PCa concrete block 20 that is arranged in a row in the axial direction of the tunnel and installed in the invert section 33, preferably with the gaps 21b held between the adjacent PCa concrete blocks 20.

In addition, in this embodiment, it is preferable that 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 connected via long bolt members (not shown). This makes it possible to ensure the installation accuracy of the one-side block group 20X and the other-side block group 20Y, and also to ensure the shear strength of the portion between these block groups 20X and 20Y.

In this embodiment, the invert structure 50 in the entire transverse direction of the tunnel described above can be formed by the following construction method. That is, in this embodiment, the construction method of the invert structure 50 is to install a plurality of PCa concrete blocks 20A, 20B, 20C in one side region in the transverse direction of the tunnel in a state in which gaps 21a, 21b are maintained between the support portion 31c of the lower end of the side wall lining body 31a adjacent to the side wall lining body 31a and between the adjacent PCa concrete blocks 20A, 20B, 20C and arrange them in series in the transverse direction of the tunnel and install them in the invert portion 33, while maintaining gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C in the axial direction of the tunnel as well. and forming a block group 20X on one side by arranging the blocks 20A, 20B, 20C in series and installing them on the invert portion 33. Filling and hardening a filling solidification material 22 into the gaps 21a between the adjacent receiving base portions 31c of the plurality of PCa concrete blocks 20A, 20B, 20C of the block group 20X on one side arranged in series vertically and horizontally, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, and the gaps 21c below the lower surface portions of the hexahedrons communicating with the gaps 21a, 21b ..., respectively, of the plurality of PCa concrete blocks 20A, 20B, 20C in the other side region in the transverse direction of the tunnel. 20B, 20C are arranged in series in the transverse direction of the tunnel and installed in the invert section 33 while maintaining gaps 21a, 21b between the adjacent PCa concrete blocks 20A, 20B, 20C and the receiving base section 31c at the lower end of the adjacent side wall covering body 31a and between the adjacent PCa concrete blocks 20A, 20B, 20C, and also in the axial direction of the tunnel while maintaining gaps 21b between the adjacent PCa concrete blocks 20A, 20B, 20C, thereby forming the other side block group 20Y; The process includes a process of filling and hardening the filling solidification material 22 in the gaps 21a between the adjacent receiving portions 31c of the PCa concrete blocks 20A, 20B, and 20C, the gaps 21b between the adjacent PCa concrete blocks 20A, 20B, and 20C, and the gaps 21c below the lower surfaces of the hexahedral shapes that communicate with these, as well as in the gaps 51 between the block group 20X on one side and the block group 20Y on the other side, which makes it easy to form the invert structure 50 that is provided across the entire transverse area of the tunnel and that constitutes the invert covering body 32.

The invert structure 50 can be formed across the entire transverse area by constructing both sides simultaneously, rather than constructing each side at a time, for example when construction can be carried out with traffic in the mountain tunnel 30 closed for an extended period of time.

The invert structure 10 of this embodiment, which has the above-mentioned configuration, can be easily formed without much effort by using PCa concrete blocks 20 (20A, 20B, 20C) of appropriate weight and size that can be easily manufactured in a factory, etc., and can be installed more quickly as a component part of the invert lining body 32 that is provided continuously from the tunnel side wall portion 31a to the lining body 31 of the upper arch-shaped portion 31b.

That is, according to this embodiment, the invert structure 10 is formed so that the PCa concrete block 20 constituting the invert structure has a hexahedral shape with a width x of about 1385 to 1435 mm, a vertical width y of about 730 mm, and a height z of about 500 mm, with a curved upper surface 20a and a curved lower surface 20b, and has a weight of about 1300 kg. Compared to conventional concrete members for inverts made of precast concrete, which are heavy and complex in shape, the PCa concrete block 20 has a moderate weight, size, and shape, and can be manufactured efficiently. In addition, the workability during lifting and transportation is improved, and the ease of handling when lifting and installing is also improved, making it possible to accurately install each PCa concrete block 20 at a predetermined position and at intervals. In addition, the bolt insertion screw hole 25 having a large trumpet-shaped recess 25b and a small trumpet-shaped recess 25c is formed, so that the height of each PCa concrete block 20 can be accurately and easily adjusted by the height adjustment bolt 26. This allows the invert portion 33 to be formed easily and with high precision so that the upper surface of the invert portion 33 is a downwardly convex, evenly curved surface. Furthermore, the filling solidification material 22 can be easily filled from the upper surface portion 20a of the block 20 through the filling material injection hole 27, which has an upper trumpet-shaped recess 27b and a lower trumpet-shaped recess 27c.

Furthermore, by simply injecting a filling material into the gaps and spaces between adjacent PCa concrete blocks 20 installed vertically and horizontally and allowing it to harden, these PCa concrete blocks 20 can be firmly integrated together, making it easy to form, and therefore it can be installed even more quickly and easily as a component part of the invert lining body 32 that is provided in continuity with the lining body 31 of the tunnel side wall portion 31a and the upper arch-shaped portion 31b.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the invert section structure of the present invention is not limited to construction work for extending the lining to the invert section of a mountain tunnel in which the lining covering the inner wall surface of the tunnel is formed only in the area from both side walls to the upper arch-shaped part, and is not formed in the invert section, but can also be used in construction work for installing a lining around the entire circumference of the inner wall surface of the tunnel, including the invert section, when constructing a new mountain tunnel, or in construction work for repairing the lining of the invert section already installed in the mountain tunnel and reinstalling a new lining of the invert section.

10 Invert part structure 10a Flange arrangement recess 10A Gable side end surface portion 10B Central side end surface portion 20, 20' PCa concrete block 20a Upper surface portion 20b Lower surface portion 20c Axial facing surface 20d Transverse facing surface 20e Notch recess 20f, 20g Axial connection portion 20A Receiving base side block 20B Central side block 20C Middle block 20D Transverse block row 20E Outer PCa concrete block 20F Inner PCa concrete block 20X One side block group 20Y Other side block group 21a Receiving base portion gap 21b Gap between adjacent PCa concrete blocks 21c Gap below the lower surface portion 21d Gap between existing invert part structure 22 Filling solidification material 23 Bolt box 24 Female thread anchor 25 Bolt insertion screw hole 25a Female thread member (nut member)
25b Large trumpet-shaped recess 25c Small trumpet-shaped recess 26 Height adjustment bolt 26a Lower end 26b Grounding adjuster 26c Filling bottom surface 26d Upper end 27 Filling material injection hole 27a Female screw member 27b Upper trumpet-shaped recess 27c Lower trumpet-shaped recess 27d Center side filling material injection hole 27e Receiving base side filling material injection hole 28 Opening and closing valve 28a Handle portion 29a Transverse spacer jig 29b Axial spacer jig 29c Suspension jig 30 Mountain tunnel 30a Base portion 31 Covering body 31a Side wall portion (side wall covering body)
31b Arch-shaped portion 31c Support portion 32 Invert portion covering body 33 Invert portion 35 H-shaped steel 36 Temporary fixing means 36a Hole-in anchor 36b Cable member 36c Expansion adjustment means 37 Connection portion structure of PCa concrete block 40 Existing invert portion structure 41a Upper surface portion band plate-shaped formwork 41b Gable portion band plate-shaped formwork 41c Central side band plate-shaped formwork 42 Air vent hose 50 Invert portion structure 51 throughout the entire transverse direction of the tunnel Spacing portion b between one side block group and the other side block group Gap below the lower surface portion

Claims (4)

A PCa concrete block used to form an invert section structure that is provided in at least one side region of the invert section of a mountain tunnel in the transverse direction of the tunnel and constitutes an invert section covering body,
They are arranged in series in the transverse direction of the tunnel, with gaps maintained between the support base portions of the lower ends of adjacent side wall covering bodies and between adjacent PCa concrete blocks for filling with filling solidification material, and also in series in the axial direction of the tunnel, with gaps maintained between adjacent PCa concrete blocks for filling with filling solidification material, and are installed in the invert section lined up vertically and horizontally.
The invert portion is formed as a hexahedral block having a curved upper surface and a curved lower surface that are curved along the cross-sectional shape of the invert portion covering body, and having a pair of front and rear flat axially opposing surfaces and a pair of left and right flat transversely opposing surfaces.
Bolt boxes or female thread anchors for connecting adjacent PCa concrete blocks using bolt members are embedded and fixed to the four sides of the upper surface portion of the hexahedron shape, and bolt insertion screw holes penetrating the hexahedron shape in the vertical direction are formed in three locations at each corner of an isosceles triangle shape,
A filler injection hole is formed that penetrates the hexahedral shape in the vertical direction, and a female threaded member into which the male threaded portion of an opening/closing valve member is screwed is fixed to the middle portion of the filler injection hole in the vertical direction, and an upper trumpet-shaped recess is formed that expands in diameter upward from the portion where the female threaded member is fixed and opens onto the upper surface of the PCa concrete block, and a lower trumpet-shaped recess is formed that expands in diameter downward from the portion where the female threaded member is fixed and opens onto the lower surface of the PCa concrete block. The PCa concrete block for invert structure according to claim 1, wherein the filler injection hole penetrating the hexahedral shape in the vertical direction is disposed in the center of the upper surface. A PCa concrete block for an invert structure according to claim 1 or 2, in which a spacer jig is attached to each of the pair of flat axially opposing surfaces of the hexahedron shape, front and rear, and the pair of flat transversely opposing surfaces of the hexahedron shape, left and right, to maintain a gap of a predetermined width between the opposing surface and the other opposing surface. The PCa concrete block for invert structure according to claim 1 or 2, in which a plurality of lifting jigs are embedded and fixed to the upper surface of the hexahedral shape, for use in lifting each of the PCa concrete blocks.