Renewal tunnel and its construction method

Abstract

To provide a renewal tunnel that can be constructed with good workability and shorten a construction period as much as possible when constructing a renewal tunnel by pouring concrete into an existing tunnel, and a construction method for the renewal tunnel.SOLUTION: In a renewal tunnel 100, a precast formwork 20 is placed inside an existing tunnel 10 with a gap 15 and an in-situ cast concrete body 30 is formed in the gap 15, and the precast formwork 20 is formed by a plurality of segment rings 20A divided in the axial direction of the existing tunnel 10 and connected each other, a support body 40 supporting the segment ring 20A is fixed to a floor 13 of the existing tunnel 10, the precast formwork 20 is fixed to the support body 40, and the in-situ cast concrete body 30 is formed around the entire circumference of the precast formwork 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a renewal tunnel and a construction method thereof.

Background Art

[0002] As a reinforcement measure against the aging of an existing tunnel that has already been constructed, or as a measure for using the existing tunnel for other purposes, there are cases where a renewal tunnel is constructed by placing concrete inside the existing tunnel. As an example, when constructing or renewing a dam embankment, after the completion of the embankment construction, new concrete is placed and reinforced inside a diversion tunnel (temporary drainage tunnel) constructed to connect the upstream and downstream sides of the dam, and an example of making it a renewal tunnel can be cited. In addition, in the construction of renewing such a diversion tunnel, in order to ensure the safety of the renewal construction, the most upstream section of the tunnel may be blocked, and new concrete may be placed in other sections to make it a renewal tunnel. By constructing such that the blocked section in such a diversion tunnel and the curtain grouting of the reservoir form a series of water stop surfaces, the water tightness of the dam itself can be enhanced, and thus such a series of construction can be referred to as a blocking work.

[0003] In the method of constructing a renewal tunnel by placing concrete inside an existing tunnel, concrete for the invert is placed, and after passing through a curing period until a predetermined strength is developed, a formwork for the upper half tunnel is installed in a state having a gap between the invert and the side wall of the existing tunnel, and a method of placing concrete in the gap is applied. When placing this concrete, shortening the construction period may be achieved by using a slide centering in some cases. However, ensuring the curing period after placing the concrete for the invert, performing the concrete placement for the invert and the upper half tunnel separately, installing the formwork for the upper half tunnel, and further, placing the concrete for the upper half tunnel and demolding after passing through the curing period often result in a longer construction period. Furthermore, if the cross-sectional dimensions of the existing tunnel are small, the space available for construction becomes limited, which can lead to an even more pronounced increase in the construction period and a significant decrease in constructability. Therefore, in construction methods for constructing a renewed tunnel by pouring concrete into the interior of an existing tunnel, a construction method that offers good workability and can shorten the construction period as much as possible is desirable.

[0004] Here, Patent Document 1 proposes a method for repairing and restoring existing buried pipes. This repair and restoration method involves inserting a cage-shaped frame equipped with an arc-shaped ring seam and side seams connecting multiple ring seams into the inside of a buried pipe that is deteriorating underground, inserting an arc-shaped segment into the frame, fitting the front and rear flange portions of the segment into the grooves of the ring seam, fitting the side flange portions on both sides of the segment into the side seams, filling the space between the side flange portions and the grooves of the side seams with epoxy resin and allowing it to harden, and injecting a filler material such as mortar between the inner pipe formed by the segment and the buried pipe. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 61-126223 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] According to the repair and restoration method for existing buried pipes described in Patent Document 1, although the use of an inner pipe formed from segments eliminates the need for formwork installation and demolding as described above, the construction is complex because a frame is inserted into the buried pipe and then the segments are fitted onto the frame afterward. Furthermore, it is uncertain whether the construction period can be shortened because a filler material such as mortar is injected between the inner pipe and the buried pipe after the joint between the frame and segments is hardened with epoxy resin.

[0007] The present invention aims to provide a renewal tunnel and a construction method that allows for construction under good workability and shortens the construction period as much as possible when constructing a renewal tunnel by pouring concrete into the interior of an existing tunnel. [Means for solving the problem]

[0008] To achieve the aforementioned objective, one embodiment of the renewal tunnel according to the present invention is: In a renovated tunnel, precast formwork is installed inside the existing tunnel with gaps, and cast-in-place concrete is formed in these gaps. The precast formwork is formed by connecting multiple segment rings, which are divided in the axial direction of the existing tunnel, Supports for the segment rings are fixed to the floor surface of the existing tunnel. The precast formwork is fixed to the support, and the cast-in-place concrete body is formed around the entire circumference of the precast formwork.

[0009] According to this embodiment, precast formwork is installed inside the existing tunnel with a gap, and cast-in-place concrete is formed in the gap. As a result, the precast formwork does not need to be removed and becomes a component of the renewed tunnel as is. Furthermore, because the precast formwork does not have a complex structure, the renewed tunnel can be constructed with good workability, and the construction period can be shortened as much as possible. Furthermore, since the precast formwork is formed by multiple segment rings divided in the axial direction of the existing tunnel, it is only necessary to sequentially transport each segment ring to its installation position within the existing tunnel and install it. Therefore, even if the interior of the existing tunnel is narrow or the existing tunnel has curved sections, each segment ring can be smoothly transported and installed, and the ring joint surfaces of multiple segment rings can be connected. Furthermore, since the support structure for the segment ring is fixed to the floor surface of the existing tunnel, and the precast formwork is fixed to the support structure, and a cast-in-place concrete body is formed around the entire circumference of the precast formwork, the cast-in-place concrete body can be constructed all around the entire circumference of the precast formwork at once. This improves the workability of the cast-in-place concrete body and eliminates the occurrence of construction joints where watertightness is a problem, such as when concrete placement is divided between the invert and the upper half of the tunnel.

[0010] Here, "a cast-in-place concrete body is formed around the entire circumference of the precast formwork" means that a cast-in-place concrete body exists around the entire circumference of a precast formwork (segment ring) with a circular or horseshoe-shaped cross-section. For example, if the segment ring is supported by a pair of supports in one or two rows extending in the axial direction of the existing tunnel, when cast-in-place concrete is poured below the segment ring supported by the supports, it becomes possible to continuously pour cast-in-place concrete on the sides of the upper half of the segment ring as well.

[0011] Thus, since concrete is poured around the entire circumference of the segment ring, an uplift force may occur on the segment ring during concrete pouring. However, because the segment ring and the support are fixed to each other, the segment ring can be prevented from lifting. Furthermore, although lateral pressure is generated on the segment ring during concrete pouring, the fixed relationship between the segment ring and the support prevents the segment ring from shifting laterally due to the acting lateral pressure.

[0012] Furthermore, the term "segment ring" includes forms such as a single continuous ring with a circular or horseshoe-shaped cross-section, or a form in which multiple segment rings are connected to each other at their respective segment joint surfaces in the circumferential direction to form a single segment ring.

[0013] Furthermore, in another embodiment of the renewal tunnel according to the present invention, The segment ring comprises an upper half segment that is arch-shaped in front view and opens downward, and a lower half segment that is U-shaped in front view and opens upward. The ring joint surfaces of the upper and lower segments are each fitted with a split seal that forms an endless seal when the joint surfaces of both segments are connected.

[0014] According to this embodiment, the segment ring has an upper half-segment and a lower half-segment, which further improves the transportability of the segments. Furthermore, since a split seal is attached to the ring joint surface of the upper half-segment and the lower half-segment, forming an endless seal when the two segment joint surfaces are connected, an endless seal is interposed between the ring joint surfaces when multiple segment rings are connected in the axial direction of an existing tunnel, thereby enabling the formation of a renovated tunnel with high watertightness. In this embodiment, since the segment ring is formed by an upper half segment that is arched in shape when viewed from the front and open downwards, and a lower half segment that is U-shaped when viewed from the front and open upwards, the front view shape of this segment ring is horseshoe-shaped.

[0015] Furthermore, in another embodiment of the renewal tunnel according to the present invention, The aforementioned support is A pair of rails extending in the axial direction, It is characterized by having a plurality of bases that are arranged at intervals in the axial direction, fixed to the floor surface via anchor bars, and supporting each rail.

[0016] According to this embodiment, the support for the segment ring has a pair of rails extending in the axial direction and a plurality of bases arranged at intervals in the axial direction and fixed to the floor surface via anchor bars to support each rail, thereby enabling stable support of the axially continuous precast formwork of the existing tunnel by the pair of rails. Furthermore, a plurality of pedestals are arranged and fixed to the floor surface with a gap thereunderneath the rail, so that the concrete placed from, for example, the lower inside of the segment ring can flow to the upper half side of the segment ring through this gap, and continuous concrete placement without a joint surface for the entire circumference of the segment ring can be achieved.

[0017] Also, in another aspect of the renewal tunnel according to the present invention, At least a part of the outer periphery below the precast formwork has a metal piece exposed, and the metal piece is welded and joined to the metal rail.

[0018] According to this aspect, since a metal piece is exposed at least in part of the outer periphery below the precast formwork and the metal piece is welded and joined to the metal rail, the rail and the precast formwork constituting the support can be firmly connected at the site. Here, the segment ring constituting the precast formwork may be any of a concrete segment, a steel segment, and a composite segment of concrete and steel. However, in the case of a steel segment, since the whole is made of metal, the contact portion with the rail becomes a "metal piece". On the other hand, in the case of a concrete segment, the metal piece is embedded in a state where it is exposed to the outside at the contact portion with the rail.

[0019] Also, the width of the rail serves as an adjustment allowance for the movement of the segment ring in the direction orthogonal to the axial direction of the existing tunnel, and it becomes possible to adjust the position of the segment ring as desired within the range of the width of the rail.

[0020] Also, another aspect of the renewal tunnel according to the present invention is that the lower half segment is provided with an air vent hole and a first placement hole, a second placement hole is provided at the top or near the top of the upper half segment, and a blowing pipe is attached at a position corresponding to the second placement hole on the outer peripheral surface of the upper half segment. The concrete is characterized in that it is poured into the gap from inside the precast formwork through the first pouring hole, the second pouring hole, and the blowing pipe.

[0021] According to this embodiment, since the lower half-segment is provided with air vents and a first concrete pouring hole, concrete can be poured below the lower half-segment while effectively performing air venting. Furthermore, the air vents also function as pouring confirmation holes to confirm the dense filling of the concrete by observing the concrete blowing out into the segment ring, and also have the function of vibrating and compacting the concrete by inserting a vibrator below the lower half-segment.

[0022] On the other hand, concrete is poured onto the back of the upper half-segment through a second pouring hole located at the top of the upper half-segment and a blowpipe connected thereto. This allows for efficient concrete pouring onto the back of the upper half-segment, and the presence of the blowpipe makes it easier to pour concrete at the top, especially when the thickness of the cast-in-place concrete body is large. More specifically, even when filling with concrete with poor fluidity (hard concrete), it becomes possible to stably pour concrete up to the height level of the blowpipe at the top of the upper half-segment. In the gap above the top of the upper half-segment, a small area of ​​unpoured concrete may occur between it and the existing tunnel wall. Grout is injected into this unpoured area via grout piping or the like, which is pre-installed in the existing tunnel wall. In this case, it is preferable to set the height level of the blowpipe as close as possible to the existing tunnel wall, as this reduces the amount of expensive grout that needs to be filled.

[0023] Furthermore, other embodiments of the renewal tunnel according to the present invention include: Of the aforementioned precast formwork, the end face of the segment ring that constitutes the precast formwork that forms the end portion during concrete pouring is fitted with end formwork. The aforementioned end formwork is, A strip-shaped metal plate that extends laterally and in the circumferential direction of the segment ring, A water-stopping plate fixed to the aforementioned metal plate and extending in the circumferential direction, A strip of expanded metal connects the water-stopping plate and the wall surface of the existing tunnel, The expanded metal is characterized by having bracing members that fix it to the wall surface of the existing tunnel.

[0024] According to this embodiment, in the precast formwork, the end formwork is attached to the end face of the segment ring which becomes the end of the concrete when the concrete is poured. The end formwork has a strip-shaped metal plate that extends laterally and circumferentially, a water-stopping plate fixed to the metal plate and extending circumferentially, a strip-shaped expanded metal that connects the water-stopping plate to the wall surface of the existing tunnel, and a bracing member that fixes the expanded metal to the wall surface of the existing tunnel, thereby ensuring high water-stopping performance at the end of the tunnel.

[0025] Furthermore, one embodiment of the construction method for a refurbished tunnel according to the present invention is: A method for constructing a renovated tunnel, comprising: arranging precast formwork inside an existing tunnel with a gap in between; pouring at least concrete into the gap; and constructing the renovated tunnel by allowing the concrete to harden; The precast formwork is formed by a plurality of segment rings divided in the axial direction of the existing tunnel, Step A involves installing a support structure for the precast formwork on the floor surface of the existing tunnel, Step B involves transporting the segment rings by forklift, installing and fixing them on the support, repeating this process, and connecting adjacent segment rings to form the precast formwork with the gap between it and the existing tunnel. The method is characterized by having step C, in which concrete is poured from inside the precast formwork into the gap, and a renewed tunnel having a cast-in-place concrete body formed by the hardening of the concrete and the precast formwork is constructed.

[0026] According to this embodiment, a support structure for supporting precast formwork is installed on the floor surface of the existing tunnel, segment rings are transported by forklift and placed on the support structure, and this is repeated to connect adjacent segment rings and form precast formwork. Concrete is then poured from the inside of the precast formwork into the gap at the back to construct the cast-in-place concrete body. As a result, the precast formwork does not need to be removed and becomes a component of the renewed tunnel as is, and because the precast formwork does not have a complex structure, the renewed tunnel can be constructed with good workability and the construction period can be shortened as much as possible. Furthermore, since the segment rings are transported by forklift, each segment ring can be smoothly transported to its installation position even if the interior of the existing tunnel is narrow or if the existing tunnel has curved sections. However, when constructing an existing tunnel with such curved sections, it is extremely difficult to smoothly feed the segment rings in accordance with the axial alignment of the existing tunnel when using the tunnel jacking method to sequentially feed them out.

[0027] Furthermore, in another embodiment of the construction method for a renewed tunnel according to the present invention, The segment ring comprises an upper half segment that is arch-shaped in front view and opens downward, and a lower half segment that is U-shaped in front view and opens upward. In step B, A transport jig equipped with an insertion part into which the forks of a forklift are inserted is attached to each of the lower and upper segments. The method is characterized by inserting the forks of the forklift into the insertion section to transport the lower half segment and place it on the support, transporting the upper half segment and placing it on the lower half segment, connecting the lower half segment and the upper half segment to form the segment ring with the gap inside the existing tunnel, and connecting a plurality of the segment rings to each other to form the precast formwork.

[0028] According to this embodiment, the segment ring comprises an upper half segment and a lower half segment, and a transport jig is attached to each segment, which has an insertion part into which the forks of a forklift are inserted. By transporting each segment with the forklift forks inserted into the insertion part, the transportability of the segments is further improved.

[0029] Furthermore, other embodiments of the construction method for a renewed tunnel according to the present invention include: Of the segment rings, the outer surface facing the existing tunnel is made a roughened surface. The method is characterized by keeping the roughened surface wet when pouring concrete.

[0030] According to this embodiment, the outer surface of the segment ring facing the existing tunnel is pre-roughened, and by wetting the roughened surface by watering or the like when placing concrete, adhesion with the placed concrete is improved, and the bonding strength at the interface between the segment ring and the cast-in-place concrete body can be increased.

[0031] Furthermore, other embodiments of the construction method for a renewed tunnel according to the present invention include: The construction section of the aforementioned renovated tunnel includes multiple concrete pouring sections. In step B, a plurality of the segment rings are connected over the pouring section to form a precast formwork division, and a metal plate is installed on the end face of the segment ring that will serve as the end formwork when concrete is poured, extending laterally and in the circumferential direction of the segment ring, a water-stopping plate is installed on the metal plate and in the circumferential direction of the precast formwork division, a strip of expanded metal is installed connecting the water-stopping plate and the wall surface of the existing tunnel, and the expanded metal is fixed to the wall surface of the existing tunnel with bracing, and then concrete is poured into the gap in the pouring section in step C. The method is characterized by having the aforementioned steps B and C as a set process, and repeating the set process multiple times over the construction section.

[0032] According to this embodiment, in the precast formwork divisions that constitute the concrete pouring section, the end face of the segment ring which becomes the end formwork when concrete is poured is provided with a strip-shaped metal plate that extends laterally and circumferentially, a water-stopping plate fixed to the metal plate and extending circumferentially, a strip-shaped expanded metal connecting the water-stopping plate to the wall surface of the existing tunnel, and a bracing member that fixes the expanded metal to the wall surface of the existing tunnel, thereby ensuring high water-stopping performance at the end section. [Effects of the Invention]

[0033] According to the present invention, when constructing a renewed tunnel by pouring concrete into the interior of an existing tunnel, the construction can be carried out with good workability, and the construction period can be shortened as much as possible. [Brief explanation of the drawing]

[0034] [Figure 1] This is a longitudinal cross-sectional view of an example of a refurbished tunnel according to the embodiment, and a process diagram of an example of a construction method for the refurbished tunnel according to the embodiment. [Figure 2] This diagram shows an example of a construction process for a renewed tunnel according to the embodiment, and is a diagram showing an example of a support structure. [Figure 3] Following Figure 2, the next figure shows a process diagram of an example of a construction method for a renewed tunnel according to the embodiment, and is a diagram showing an example of the lower half segment. [Figure 4] Following Figure 3, this is a process diagram of an example of a construction method for a renewed tunnel according to the embodiment, showing the fixing part of the lower half segment and the support. [Figure 5] Following Figure 4, this figure shows a process diagram of an example of a construction method for a renewed tunnel according to the embodiment, and is a diagram showing an example of the upper half segment. [Figure 6] Following Figure 5, this is a process diagram of an example of the construction method for a renewed tunnel according to the embodiment. [Figure 7]This is a front view of the end section of the precast formwork during concrete pouring. [Figure 8] This is an enlarged view of section VIII in Figure 7. [Figure 9] This is a view from the line IX-IX in Figure 7. [Modes for carrying out the invention]

[0035] The renewal tunnel and its construction method according to the embodiment will be described below with reference to the attached drawings. In this specification and the drawings, substantially identical components may be denoted by the same reference numerals to avoid redundant explanations.

[0036] [Renewal tunnel according to an embodiment and its construction method] An example of a refurbished tunnel and its construction method according to the embodiment will be described with reference to Figures 1 to 9. Here, Figure 1 is a longitudinal cross-sectional view of an example of a refurbished tunnel according to the embodiment. Figures 2 to 6 and Figure 1 are, in order, process diagrams of an example of the construction method of the refurbished tunnel according to the embodiment. Furthermore, Figure 7 is a front view of the end section of the precast formwork during concrete pouring, and Figures 8 and 9 are enlarged views of section VIII and IX-IX of Figure 7, respectively.

[0037] The renewed tunnel 100 shown in Figure 1 is formed by constructing a new concrete structure inside the existing tunnel 10, which has already been constructed in the natural ground G. The existing tunnel 10 is, for example, a diversion tunnel constructed to connect the upstream and downstream sides of a dam.

[0038] The existing tunnel 10 in the illustrated example has a horseshoe-shaped longitudinal cross-section, but tunnels with various longitudinal cross-sectional shapes, such as circular or rectangular, can also be subject to renewal. Precast formwork 20 is placed inside the existing tunnel 10 with a gap 15, and cast-in-place concrete 30 is poured into the gap 15 to form the renewed tunnel 100.

[0039] The precast formwork 20 is formed by connecting multiple segment rings 20A that are divided in the axial direction of the existing tunnel 10. Each segment ring 20A has an upper half segment 21A that is arch-shaped in front view and open downwards, and a lower half segment 21B that is U-shaped in front view and open upwards. The segment joint surfaces 22a and 22b of the upper half segment 21A and the lower half segment 21B are in contact and connected by joint bolts 23.

[0040] Both the upper segment 21A and the lower segment 21B are reinforced concrete segments. Here, each segment may be a steel segment or a composite segment.

[0041] The outer circumferential surface 22a of the upper half-segment 21A and the outer circumferential surface 22b of the lower half-segment 21B are both roughened surfaces, and a portion of the cast-in-place concrete body 30 fits into the recesses of each roughened surface 22a and 22b, thereby increasing the joint strength at the interface between the segment ring 20A and the cast-in-place concrete body 30.

[0042] A support structure 40 is fixed to the floor surface 13 of the existing tunnel 10, supporting a precast formwork 20 formed by multiple segment rings 20A. The support structure 40 has rails 45 that extend in the axial direction of the existing tunnel 10, and multiple bases 41 that are spaced apart in the axial direction and fixed to the floor surface 13 via anchor bars 43 to support the rails 45.

[0043] As shown in Figure 1, a pair of support members 40 are fixed to the left and right positions of the floor surface 13 of the existing tunnel 10, and a pair of rails 45 forming the pair of support members 40 support the lower end of the precast formwork 20. Angle steel 29 (an example of a metal piece) is embedded in the left and right lower end corners of the lower half segment 21B so as to be exposed to the outside and is resting on the rails 45.

[0044] The rail 45 is formed from channel steel, and a corresponding metal piece 29 is placed on the upper flange of the rail 45. The two pieces are welded together, thereby fixing the segment ring 20A to the pair of rails 45.

[0045] Next, the construction method for the renewed tunnel will be explained with reference to Figures 1 to 9.

[0046] First, as shown in Figure 2, a support structure 40 for supporting the precast formwork 20 is installed on the floor surface 13 of the existing tunnel 10. More specifically, multiple anchor bars 43 are driven into the ground on the left and right sides of the floor surface 13 of the existing tunnel 10 at intervals in the axial direction of the existing tunnel 10, and a base 41 made of steel is fixed to each anchor bar 43 via a welded joint 47 (see Figure 4) (this is step A).

[0047] Next, as shown in Figure 3, the lower half-segment 21B is transported by a forklift (not shown) and installed on a pair of rails 45, for example, starting from the far side of the existing tunnel 10. Here, as shown in Figure 3, a split seal 25b is attached to the ring joint surface 21b of the lower half-segment 21B. This split seal 25b is a linear, fixed-shape seal that forms an endless seal when the segment joint surfaces 22b and 22a of both the lower half-segment 21B and the upper half-segment 21A are connected.

[0048] A joint fitting 24 is further attached to the ring joint surface 21b of the lower half segment 21B, and is bolted to the ring joint surface of the other axially adjacent segment ring.

[0049] When transporting the lower half segment 21B with a forklift, the transport jig 70A is attached to span both segment joint surfaces 22b, with the two left and right segment joint surfaces 22b of the lower half segment 21B facing upwards.

[0050] Here, the transport jig 70A has a steel horizontal member 71 that spans the left and right segment joint surfaces 22b, and a plurality of insertion parts 73, 72 attached to the upper and lower surfaces of the horizontal member 71.

[0051] The left and right ends of the horizontal member 71 are temporarily fixed to the left and right segment joint surfaces 22b via fixing bolts 74. For example, the forks F of a forklift are inserted into two insertion parts 72 attached to the lower surface of the horizontal member 71, and the member is lifted by the forklift and transported inside the existing tunnel 10.

[0052] In this way, since the lower half-segments 21B are transported by forklift, each lower half-segment 21B can be smoothly transported to its installation position even if the interior of the existing tunnel 10 is narrow or if the existing tunnel 10 has a curved alignment. Here, in addition to forklifts, various heavy machines equipped with lifting equipment such as truck cranes can be used to transport the lower half-segments 21B and upper half-segments 21A.

[0053] After placing the lower half-segment 21B on a predetermined position on a pair of rails 45, as shown in Figure 4, the installation position of the lower half-segment 21B can be adjusted in the X1 direction, which is perpendicular to the axial direction of the existing tunnel 10, within the width t1 of the upper flange 45a of the rails 45.

[0054] After the installation position of the lower half-segment 21B relative to the pair of rails 45 is set, the metal piece 29 exposed to the outside at the corner of the lower half-segment 21B and the rail 45 are fixed together via a welded joint 48, such as a fillet weld. Here, the metal piece 29 and the rail 45 may also be fixed together with bolts or the like.

[0055] In the construction method for the renewal tunnel shown in the illustration, concrete is continuously poured around the entire circumference of the segment ring 20A, as explained below. As a result, the segment ring 20A may experience uplift forces and lateral pressure during concrete pouring. However, because the lower half-segments 21B and the support 40 that constitute the segment ring 20A are fixed to each other, both uplift and lateral displacement of the segment ring 20A caused by the acting uplift forces and lateral pressure can be prevented.

[0056] Next, as shown in Figure 5, the upper half segment 21A is transported by a forklift (not shown) and placed on top of the lower half segment 21B which is fixed to the support 40. Here, as shown in Figure 5, a split seal 25a is attached to the ring joint surface 21a of the upper half segment 21A. This split seal 25a is a linear, fixed-shape seal that forms an endless seal when the segment joint surfaces 22a and 22b of both the upper half segment 21A and the lower half segment 21B are connected.

[0057] A joint fitting 24 is further attached to the ring joint surface 21a of the upper half segment 21A, and is bolted together with the ring joint surface of the other axially adjacent segment ring.

[0058] When transporting the upper half segment 21A by forklift, a transport jig 70B is attached to the inside of the upper half segment 21A.

[0059] Here, the transport jig 70B has a steel horizontal member 75, a plurality of vertical members 76 attached to the upper surface of the horizontal member 75, and a plurality of insertion parts 72 attached to the lower surface of the horizontal member 75. Cushioning material 77 is attached to the end faces of the horizontal member 75 and the vertical members 76 that come into contact with the upper half segment 21A, thereby suppressing damage to the upper half segment 21A that may occur when the end faces of the horizontal member 75 and the vertical members 76 come into direct contact with the upper half segment 21A.

[0060] After placing the transport jig 70B inside the upper half segment 21A, the forks F of the forklift are inserted into the two insertion parts 72, and the upper half segment 21A is lifted by the forklift and transported inside the existing tunnel 10.

[0061] As shown in Figure 6, a segment ring 20A is formed by placing the segment joint surface 22a of the upper half segment 21A on the segment joint surface 22b of the lower half segment 21B and connecting the two via joint bolts 22c.

[0062] The construction section of the renewed tunnel 100 includes multiple concrete pouring sections (it is divided into multiple pouring sections), and therefore, for each pouring section, multiple segment rings 20A are connected to each other's ring joint surfaces to construct a precast formwork segment (a precast formwork 20 formed in the entire construction section is divided into segments for each pouring section).

[0063] As shown in Figure 6, an annular gap 15 is provided between the tunnel wall of the existing tunnel 10 and the segment ring 20A.

[0064] As shown in Figure 6, the lower half-segment 21B is provided with multiple air vent holes 26 and a first pouring hole 27. On the other hand, a second pouring hole 28 is provided at the top of the upper half-segment 21A, and a blowing pipe 50 is attached to the outer surface 23a at a position corresponding to the second pouring hole 28. Here, the first pouring hole 27 and the second pouring hole 28 can be set to holes of approximately φ200 mm, and the air vent holes 26 can be set to holes of approximately φ50 mm. In addition, multiple grout pipes 18 are attached to the tunnel wall of the existing tunnel 10 near the top (this is step B).

[0065] Concrete is poured in the Y1 direction into the gap 15 below the segment ring 20A through the first pouring hole 27 provided in the lower half segment 21B of the segment ring 20A from inside the precast formwork segment that spans the pouring section. During concrete pouring, the air present in the lower gap 15 is released into the precast formwork 20A through each air vent hole 26 while the concrete pouring continues. Furthermore, when the concrete is blown upward from each air vent hole 26 in the Y2 direction, it can be confirmed that sufficient concrete has been poured into the gap 15 below the lower half segment 21B.

[0066] Here, a vibrator (not shown) can be inserted into the concrete poured below the lower half-segment 21B through the air vent hole 26 to perform vibration compaction of the concrete.

[0067] Next, the first pouring hole 27 is sealed with a rubber plug or the like, and the outer surface of the precast formwork 20A is moistened by spraying water on it. Then, concrete is poured in the Y3 direction through the second pouring hole 28 of the upper half segment 21A and the blowing pipe 50, thereby filling the gaps 15 on the sides and top of the precast formwork 20A. Here, a slide centerer (not shown) may be used for concrete pouring.

[0068] By pouring concrete through a blowpipe 50 that communicates with the second pouring hole 28 at the top of the upper half segment 21A, concrete can be efficiently poured into the gap 15 on the back of the upper half segment 21A. Furthermore, when the width of the gap 15 in the direction perpendicular to the axial direction (thickness of the cast-in-place concrete body 30) is large, it becomes easier to pour concrete at the top.

[0069] Therefore, even when low-flow concrete (hard concrete) is used for filling, concrete can be stably poured up to the height level of the blowing pipe 50 at the top of the upper half-segment 21A. In the gap 15 above the top of the upper half-segment 21A, a small area of ​​unfilled concrete may occur between it and the tunnel wall of the existing tunnel 10. This unfilled area is filled by injecting grout through the grout pipe 18 to close it. At this time, by setting the height level of the blowing pipe 50 as close as possible to the tunnel wall of the existing tunnel 10, the amount of expensive grout to be filled can be reduced (C process).

[0070] Steps B and C described above are performed for each concrete pouring section, and this is treated as a set process. By repeating this set process multiple times (as many times as there are pouring sections) across the entire construction section, the renewed tunnel 100 shown in Figure 1 is constructed.

[0071] Next, with reference to Figures 7 to 9, the end formwork for the end sections in each concrete pouring section will be described. In step B, end formwork 60 is attached to the end face of the end section of the concrete pouring section of the precast formwork 20A. Here, the end formwork 60 has a strip-shaped metal plate 61 that extends laterally and in the circumferential direction of the segment ring 20A, a water-stopping plate 62 fixed to the metal plate 61 and extending in the circumferential direction, a strip-shaped expanded metal 63 that connects the water-stopping plate 62 to the wall surface of the existing tunnel 10, and a bracing member 68 that fixes the expanded metal 63 to the wall surface of the existing tunnel 10. Here, the metal plate 61 is made of, for example, stainless steel.

[0072] The circumferentially extending water-stopping plate 62 is fixed to the metal plate 61 via multiple water-stopping plate fasteners 64. After concrete pouring is completed in the section to be poured, the multiple water-stopping plate fasteners 64 are removed from the end and reused at the end of the next section to be poured.

[0073] The expanded metal 63 is supported by circumferential separators 66 formed from reinforcing bars, etc., and radial separators 67 similarly formed from reinforcing bars, etc., so as to be able to withstand lateral pressure from the concrete, and the intersections of the circumferential separators 66 and radial separators 67 are fixed to each other via welding hardware (not shown).

[0074] In this way, the strip-shaped expanded metal 63 is fixed to the wall surface of the existing tunnel 10 via bracing members 68, and the watertight plate 62 extending in the circumferential direction is connected to the metal plate 61 fixed to the end face of the segment ring 20A. This makes it possible to construct a renewed tunnel 100 in which each cast section is interconnected via a joint with guaranteed watertightness.

[0075] According to the construction method for the renovated tunnel 100 shown in the diagram, a support 40 for supporting the precast formwork 20 is installed on the floor surface 13 of the existing tunnel 10, segment rings 20A are transported by forklift and placed on the support 40, and this is repeated to connect adjacent segment rings 20A to form the precast formwork 20, and concrete is poured from the inside of the precast formwork 20 into the gap 15 at the back to construct the cast-in-place concrete body 30. As a result, the precast formwork 20 does not need to be removed and becomes a component of the renovated tunnel 100 as is, and because the precast formwork 20 does not have a complex structure, the renovated tunnel 100 can be constructed with good workability and the construction period can be shortened as much as possible.

[0076] Furthermore, other embodiments may be used in which other components are combined with the configurations listed in the above embodiments, and the present invention is not limited in any way to the configurations shown herein. In this regard, modifications can be made without departing from the spirit of the present invention, and can be appropriately determined according to the application form. [Explanation of Symbols]

[0077] 10: Existing tunnels 13: Floor 15: Gap 18: Grout pipe 20: Precast formwork 20A: Segment ring 21A: Upper half segment 21B: Lower half segment 21a, 21b: Ring joint surface 22a:22b:Segment joint surface 22c: Joint bolt 23a, 23b: Outer surface (roughened surface) 24: Fittings 25a, 25b: Half-cut seals 26: Air vent hole 27: 1st pouring hole 28:Second pouring hole 29: Metal piece (angle steel) 30: Cast-in-place concrete body 40:Support 41: Pedestal 43: Anchor muscle 45: Rail 45a: Flange 47,48: Welded section 50: Blowing pipe 60: Gable formwork 61:Metal plate 62: Water stop plate 63: Expanded Metal 64: Water stop plate fastening material 66: Circumferential separator 67: Radial separator 68: Support material 70A, 70B: Conveying fixtures 71: Horizontal structural members 72,73: Insertion section 74: Fixing bolts 75: Horizontal structural members 76: Vertical members 77: Cushioning material 100: Renewed Tunnel G: Natural ground F: Forklift forks

Claims

1. In a renovated tunnel, precast formwork is installed inside the existing tunnel with gaps, and cast-in-place concrete is formed in these gaps. The precast formwork is formed by connecting multiple segment rings, which are divided in the axial direction of the existing tunnel, Supports for the segment rings are fixed to the floor surface of the existing tunnel. The precast formwork is fixed to the support, and the cast-in-place concrete body is formed around the entire circumference of the precast formwork. The aforementioned support is A pair of rails extending in the axial direction, A refurbished tunnel characterized by having a plurality of bases arranged at intervals in the axial direction, fixed to the floor surface via anchor bars, and supporting each rail.

2. The segment ring comprises an upper half segment that is arch-shaped in front view and opens downward, and a lower half segment that is U-shaped in front view and opens upward. The renewal tunnel according to claim 1, characterized in that a split seal is attached to the ring joint surface of the upper half segment and the lower half segment, which forms an endless seal when the joint surfaces of both segments are connected.

3. At least a portion of the lower outer circumference of the precast formwork has exposed metal pieces. The renewal tunnel according to claim 1 or 2, characterized in that the metal piece is welded to the metal rail.

4. The lower half-segment is provided with an air vent hole and a first casting hole. A second casting hole is provided at or near the top of the upper half-segment, and a blowing pipe is attached to the outer surface of the upper half-segment at a position corresponding to the second casting hole. The renewal tunnel according to claim 2, characterized in that concrete is poured into the gap from inside the precast formwork via the first pouring hole, the second pouring hole, and the blowing pipe.

5. Of the aforementioned precast formwork, the end face of the segment ring that constitutes the precast formwork that forms the end portion during concrete pouring is fitted with end formwork. The aforementioned end formwork is, A strip-shaped metal plate that extends laterally and in the circumferential direction of the segment ring, A water-stopping plate fixed to the aforementioned metal plate and extending in the circumferential direction, A strip of expanded metal connects the water-stopping plate and the wall surface of the existing tunnel, The renewed tunnel according to claim 2, characterized in that it has bracing members for fixing the expanded metal to the wall surface of the existing tunnel.

6. A method for constructing a renovated tunnel, comprising: arranging precast formwork inside an existing tunnel with a gap in between; pouring at least concrete into the gap; and constructing the renovated tunnel by allowing the concrete to harden; The precast formwork is formed by a plurality of segment rings divided in the axial direction of the existing tunnel, Step A involves installing a support structure for the precast formwork on the floor surface of the existing tunnel, Step B involves transporting the segment rings by forklift, installing and fixing them on the support, repeating this process, and connecting adjacent segment rings to form the precast formwork with the gap between it and the existing tunnel. The process includes step C, in which concrete is poured from inside the precast formwork into the gap, and a renewed tunnel having a cast-in-place concrete body formed by the hardening of the concrete and the precast formwork is constructed. The segment ring comprises an upper half segment that is arch-shaped in front view and opens downward, and a lower half segment that is U-shaped in front view and opens upward. In step B, A transport jig equipped with an insertion part into which the forks of a forklift are inserted is attached to each of the lower and upper segments. A method for constructing a renovated tunnel, characterized by inserting the forks of the forklift into the insertion section to transport the lower half segment and place it on the support, transporting the upper half segment and placing it on the lower half segment, connecting the lower half segment and the upper half segment to form the segment ring with the gap inside the existing tunnel, and connecting a plurality of the segment rings to each other to form the precast formwork.

7. Of the segment rings, the outer surface facing the existing tunnel is made a roughened surface. The method for constructing a renovated tunnel according to claim 6, characterized in that the roughened surface is kept wet when concrete is poured.

8. The construction section of the aforementioned renovated tunnel includes multiple concrete pouring sections. In step B, a plurality of the segment rings are connected over the pouring section to form a precast formwork division, and a metal plate is installed on the end face of the segment ring that will be the end portion when concrete is poured, extending laterally and in the circumferential direction of the segment ring, a water-stopping plate is installed on the metal plate and in the circumferential direction of the precast formwork division, a strip of expanded metal is installed connecting the water-stopping plate and the wall surface of the existing tunnel, and the expanded metal is fixed to the wall surface of the existing tunnel with bracing, and then concrete is poured into the gap in the pouring section in step C. The method for constructing a renewed tunnel according to claim 6 or 7, characterized in that the aforementioned steps B and C are set as a set of steps, and the set of steps is repeated multiple times over the construction section.

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