Method of pouring concrete for tunnel lining

Abstract

To provide a method for placing lining concrete for a tunnel, by which high-quality lining concrete can be placed by discharging surplus water during concrete placement although a formwork installation work is easy without a complicated mechanism.SOLUTION: A formwork 20 is installed with a mesh-like shell 30 formed with a plurality of holes 31 lined up fixed to an outer surface of the formwork 20. Excess water from filled fresh concrete is discharged through each hole 31 of the shell 30 to a water passage 40 between the formwork 20 and the shell 30. Fluidization of the concrete is stopped by discharging surplus water to temporarily solidify the concrete, and after the temporarily solidified concrete is hardened together with the shell 30, the formwork 20 is removed from the inner surface of the hardened concrete.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for placing lining concrete of a tunnel.

Background Art

[0002] As tunnel construction methods, a shield method, a TBM method, a NATM method, an excavation method, etc. are known. The shield method is widely used in urban areas and is suitable for excavating strata with high ground pressure such as alluvial layers and silt layers. In the shield method, after the earth and sand are removed as slurry by a shield machine, precast segments are laid as lining concrete, and the jacks of the shield machine are extended using the segments as a reaction force to form a tunnel. The TBM method is used for so-called mountain tunnels, and the rock mass is cut by a huge cutter head, and the tunnel is dug while discharging the cut rock backward. Also, the NATM method is used for so-called mountain tunnels, and excavation is carried out while reinforcing the ground with rock bolts, and concrete is continuously placed along the axial direction of the tunnel using a centor (formwork). Even in the shield method and the TBM method, a method has been developed in which a mechanized formwork is used to continuously place lining concrete without using segments. Also, a composite method that uses the NATM method for ground reinforcement in the shield method has been developed.

[0003] As a method for placing tunnel lining concrete using a formwork, a method has been proposed in which the formwork is composed of an upper form, a middle form, and a lower form, and a water-permeable formwork is installed on the outer surface of the lower form (see Patent Document 1). In the technique described in Patent Document 1, the water-permeable formwork is composed of a baffle plate, a water retention layer, and a water-permeable sheet, and the outer surface (the surface on the ground side) is flush with the outer surface of the middle form. The water retention layer of the water-permeable formwork includes a core material and facing materials laminated on both sides of the core material. An internal space is formed in the core material, and a plurality of through holes are formed in the core material and the facing materials.

[0004] The permeable sheet is placed on the contact surface with the concrete and is intended to absorb excess water (including bleeding water) generated after concrete placement, as well as supply moisture (curing water) to the concrete surface during curing. Specifically, once the concrete has reached the required strength, the formwork is removed and moved while the permeable formwork remains on the concrete surface. After the concrete has finished curing, the permeable formwork is removed from the concrete surface. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2019-85784 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, in the concrete casting method described in Patent Document 1, it is necessary to position the permeable formwork so that it is flush with the outer surface of the central form, which makes the mechanism of the lower formwork, permeable formwork, and the device that supports them complex, and the installation work of the permeable formwork becomes extremely complicated.

[0007] This invention has been made in view of the above problems, and aims to provide a method for pouring tunnel lining concrete that does not require a complex mechanism, simplifies the formwork installation work, and allows for the drainage of excess water during concrete pouring, thereby enabling the pouring of high-quality lining concrete. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides: A method for pouring lining concrete using formwork whose outer surface faces the inner wall of the tunnel, A formwork installation step involves installing the formwork in such a state that a mesh-like shell, formed by a series of holes arranged in a row, is fixed to the outer surface of the formwork, such that a drainage channel for draining excess concrete water is formed between the formwork and the shell due to the uneven shape formed on at least one of the outer surface and inner surface of the formwork. A concrete filling step in which fresh concrete is filled into the installed formwork, A process of draining excess water from the concrete to the water channel through the holes in the shell to stop fluidization and temporarily solidify the concrete, A concrete hardening step is performed to drain the excess water and harden the partially solidified concrete integrally with the shell, The present invention provides a formwork removal step of removing the formwork from the inner surface of the hardened concrete while the shell is integrated with the concrete, and a method for pouring lining concrete for a tunnel.

[0009] In the method for pouring the lining concrete of the tunnel described above, the water channel may be formed by the uneven shape that is formed on the inner surface of the shell and extends in the cross-sectional direction of the tunnel.

[0010] In the method for pouring the lining concrete of the above-mentioned tunnel, The water channel is formed by the uneven shape formed on the outer surface of the formwork and extending in the cross-sectional direction of the tunnel, The cross-section of the convex portion having the aforementioned uneven shape may be formed in a tapered shape that becomes smaller towards the outside of the tunnel's cross-section.

[0011] In the method for pouring the lining concrete of the above-mentioned tunnel, The formwork may have a drainage channel formed on the bottom side of the tunnel, with its top open, into which the excess water is collected.

[0012] In the method for pouring the lining concrete of the above-mentioned tunnel, The formwork has a flat section for walking on the bottom side of the tunnel. The water collecting groove may be formed in the flat part.

[0013] In the method for placing the covering concrete of the tunnel, in the formwork installation step, the shell may be fixed to the part of the water collecting groove of the formwork so as to have a predetermined tension.

Advantages of the Invention

[0014] According to the method for placing the covering concrete of the tunnel of the present invention, without a complicated mechanism, the formwork installation work is simple, and surplus water during concrete placement can be discharged, enabling high-quality covering concrete to be placed.

Brief Description of the Drawings

[0015] [Figure 1] It is a flowchart of a method for placing the covering concrete of a tunnel showing an embodiment of the present invention. [Figure 2] It is a longitudinal section explanatory view of a tunnel. [Figure 3] It is a cross-section explanatory view of a tunnel before concrete filling. [Figure 4] It is a partial development view of a shell. [Figure 5] It is a partial cross-section view of a formwork and a shell. [Figure 6] It is a cross-section explanatory view of a tunnel before concrete filling showing a modification. [Figure 7] It is a partial cross-section view of a formwork and a shell showing a modification.

[0016] Figures 1 to 6 show an embodiment of the present invention. Figure 1 is a flowchart of a method for placing the covering concrete of a tunnel, Figure 2 is a longitudinal section explanatory view of a tunnel, Figure 3 is a cross-section explanatory view of a tunnel before concrete filling, Figure 4 is a partial development view of a shell, and Figure 5 is a partial cross-section view of a formwork and a shell.

[0017] As shown in Fig. 1, the method for placing the lining concrete of this tunnel includes an excavation process S1, a formwork installation process S2, a concrete filling process S3, an excess water drainage process S4, a concrete hardening process S5, and a formwork removal process S6. In this embodiment, as shown in Fig. 2, the shield machine 10 is used to place the lining concrete 90 of the tunnel 80. The lining concrete 90 is placed using a formwork 20 whose outer surface faces the inner wall side of the tunnel 80.

[0018] The shield machine 10 has a cylindrical machine body 11, a cutter head 12 disposed at the front end of the machine body 11, a bulkhead 13 provided behind the cutter head 12, a jack 14 provided at the rear end of the machine body 11 and capable of telescoping back and forth, a partition plate 15 extending in the cross-sectional direction of the tunnel 80 provided at the rear end of the jack 14, and a pressure-resistant plate 16 extending rearward from the outer edge of the machine body 11 and receiving the pressure from the ground. The partition plate 15 is formed corresponding to the cross-sectional shape of the lining concrete 90.

[0019] As shown in Fig. 3, a placement hole 17 for concrete filling is formed in the upper part of the partition plate 15. Note that Fig. 3 shows the state before the concrete is filled. In this embodiment, the placement holes 17 are provided in a pair on the left and right in the upper part of the partition plate 15. Also, as shown in Fig. 2, a drain port 18 for discharging excess water described later is formed in the lower part of the partition plate 15. Concavities and convexities are formed on the contact surface of the partition plate 15 with the concrete to increase the contact area with the concrete.

[0020] Regarding the method for placing the lining concrete 90 using the shield machine 1 configured as described above, it will be described while referring to the flowchart of Fig. 1. First, while extending the jack 14, the cutter head 12 is rotated to excavate the ground by a predetermined distance (excavation process S1). At this time, in the work area adjacent to the rear, the concrete hardening process S5 has been completed, and the lining concrete 90 adjacent to the rear of the partition plate 15 has already hardened.

[0021] Next, the formwork 20 is installed (formwork installation step S2) with the mesh-like shell 30, which has multiple holes 31 arranged in a row, fixed to the outer surface of the formwork 20 so that a drainage channel 40 for draining excess concrete water is formed between the formwork 20 and the shell 30 by the uneven shape formed on at least one of the outer surface of the formwork 20 and the inner surface of the shell 30. The outer surface of the formwork 20 faces the inner wall side of the tunnel 80. The material of the formwork 20 is arbitrary, but in this embodiment it is made of steel plate. The formwork 20 has a flat section 21 for walking on the bottom side of the tunnel 80, and a water collection channel 22 is formed in the excavation direction, with the top open and for collecting excess water, which will be described later. The dimensions of the water collection channel 22 are arbitrary, but for example it can be 450 mm to 750 mm in width and 100 mm to 300 mm in depth. In this embodiment, since the formwork 20 remains in place on the lining concrete 90 adjacent to the rear of the partition plate 15, the drainage channel 22 of the newly installed formwork 20 is connected to the drainage channel 22 of the formwork 20 adjacent to the rear.

[0022] In this embodiment, during the formwork installation process S2, a water collection pipe 50 is placed at the bottom of the tunnel below the flat section 21, extending in the excavation direction and collecting excess water, which will be described later. The dimensions and cross-sectional shape of the water collection pipe 50 are arbitrary, but for example, the cross-sectional shape can be a circle with a diameter of 200 mm to 400 mm. The water collection pipe 50 is embedded in the lining concrete 90 adjacent to the rear of the partition plate 15, and the new water collection pipe 50 is positioned to connect the front end of the embedded water collection pipe 50 to the drainage port 18 of the partition plate 15. The formwork 20 is constructed in sections and assembled during the formwork installation process S2. The method of dividing the formwork 20 is arbitrary, and if it is relatively small, for example, it can be 2 m in the excavation direction and 1 m in the cross-sectional direction. Also, if it is possible to transport and assemble it using large machinery, the formwork 20 can be divided into, for example, 2 m in the excavation direction and 3 in the cross-sectional direction.

[0023] As shown in Figure 4, the shell 30 has a plurality of holes 31 for draining excess concrete water, which will be described later. The material of the shell 30 is arbitrary, but can be plastic, metal, etc. In this embodiment, the shell 30 is made of engineering plastic. In this embodiment, the shell 30 is formed in a mesh shape, and each square-shaped hole 31 is formed aligned in the vertical and horizontal directions. The shape and size of each hole 31 are arbitrary, and can be rhombic, circular, polygonal, etc. Also, the size of each hole 31 is arbitrary, and can be, for example, the inscribed circle of each hole 31 can have a diameter of 5 mm or more and 50 mm or less. The shape and size of each hole are set appropriately according to the required performance, etc.

[0024] Furthermore, multiple ribs 32 extending in the cross-sectional direction of the tunnel 80 are formed on the inner surface of the shell 30. This creates the aforementioned uneven shape on the inner surface of the shell 30. Each rib 32 is formed at a predetermined interval in the excavation direction of the tunnel 80. The shell 30 is reinforced by each rib 32. As shown in Figure 5, since the outer surface of the formwork 20 is flat, when the shell 30 is placed on the outer surface, a water channel 40 extending in the cross-sectional direction of the tunnel is formed between each rib 32. The dimensions of the water channel 40 are arbitrary, but for example, it can be 10 mm to 50 mm in width and 5 mm to 20 mm in depth. The shell 30 is composed of multiple panels, each having connecting recesses and protrusions (not shown) formed on its outer edge, and adjacent panels are connected by the fitting of the recesses and protrusions. Each panel is processed in a factory or the like to correspond to the outer surface shape of the formwork 20 and then transported to the excavation site for use. Alternatively, the shell 30 may be processed into a mesh-like structure and formed into a long length, which can then be transported to the excavation site in roll form.

[0025] The shell 30 is wrapped around the formwork 20 and fixed to the water collection channel 22 with a predetermined tension. Alternatively, a separate fixing point for the shell 30 may be provided on the formwork 20 in a location other than the water collection channel 22. The method of fixing the formwork 20 and the shell 30 is arbitrary; in this embodiment, they are fixed by screwing with bolts, but they can also be fixed by welding, adhesive, etc.

[0026] Once the formwork 20 and shell 30 are installed, fresh concrete is filled into each of the pouring holes 17 of the partition plate 15 (concrete filling process S3). In this embodiment, a flexible pipe is lowered to the bottom of the tunnel 80 from each pouring hole 17, and the flexible pipe is pulled up while checking the filling state with a sensor or visually. After the concrete filling is complete, each pouring hole 17 is covered. The method of supplying fresh concrete is arbitrary; for example, ready-mix concrete may be transported into the tunnel by a concrete mixer truck, or it may be supplied by a pressure pump from a small, mobile batching plant inside the tunnel. In this embodiment, soft ground is assumed, and various types of rapid-hardening cements are used to rapidly harden the lining concrete 90 that forms a cylindrical protective material for the ground. In this embodiment, since there are no materials that corrode by carbonation, such as reinforcing bars, in the concrete filling space, rapid-hardening agents that may corrode reinforcing bars may be used.

[0027] When fresh concrete is filled into the formwork 20, the consolidation due to the concrete's own weight causes excess water to be discharged from the concrete into the water channel 40 through each hole 31 of the shell 30 (excess water discharge process S4). At this time, air is also discharged from the concrete along with the excess water. In this way, excess water is discharged from the concrete, which reduces the pressure applied to the formwork 20 from the concrete. Also, when excess water is discharged from the concrete, the fluidization stops before the concrete begins to harden, and the concrete is temporarily solidified. This makes it possible to omit various ground reinforcement works using shoring, sprayed concrete, rock bolts, chemical grouting, etc. The excess water seeping out from the formwork 20 is discharged from the water channel 40 into the water collection ditch 22 and water collection pipe 50.

[0028] After this, the concrete from which excess water and air have been discharged is hardened integrally with the shell 30 (concrete hardening process S5). The discharge of excess water and air improves the density of the hardened concrete. As a result, the occurrence of cracks in the concrete is suppressed and the waterproofing effect is improved. In addition, the discharge of excess water and air promotes the development of concrete strength. In this embodiment, the development of strength is further promoted by the use of high-early-strength cement. The formwork 20, shell 30 and hardened lining concrete 90 function as tubular protective materials for the ground and contribute to the stabilization of the stress balance of the ground. That is, the stress balance of the ground is quickly stabilized by the pre-hardening of the concrete and the use of high-early-strength cement.

[0029] After the concrete hardens, the jack 14 is extended while the cutter head 12 is rotated to excavate the ground again by a predetermined distance (excavation process S1). After the lining concrete 90 has developed its strength, the shell 30 does not buckle, and the reaction force necessary for propelling the shield machine 1 can be obtained from the side of the hardened lining concrete 200, which has become one with the formwork 20 and pressure plate 16, via the partition plate 15. In this way, the excavation process S1, formwork installation process S2, concrete filling process S3, excess water discharge process S4, and concrete hardening process S5 are repeated in the excavation direction of the tunnel 100 to proceed with the placement of the lining concrete 90.

[0030] After confirming the stability of the ground stress using stress sensors, strain gauges, etc., the formwork 20 is removed from the inner surface of the hardened concrete with the shell 30 integrated with the concrete (formwork removal process S6). Subsequently, the lining concrete 200 is cured with the shell 30 remaining on the lining concrete 200 side. In other words, the shell 30 acts as formwork during the concrete curing period. Then, with the shell 30 remaining on the lining concrete 200 side, the tunnel 80 is put into use.

[0031] The dismantled formwork 20 is transported to the next work section and reused. Since the inner surface of the shell 30 has irregularities formed by each reinforcing rib 32, the formwork 20 can be peeled off relatively easily from the lining concrete 90 side. If the peelability of the formwork 20 from the lining concrete 90 side is to be considered, it is preferable to use a material or finish that provides high peelability for the surface of the formwork 20. If a void is found in the lining concrete 90 after the formwork 20 has been removed, the concrete can be repaired by injecting non-shrink mortar through each hole 31. The grooves formed in the lining concrete 90 by the water collection grooves 22 of the formwork 20 are used as drainage grooves.

[0032] According to the concrete lining concrete placement method of this embodiment described above, high-quality concrete lining concrete 90 can be placed without complex mechanisms, with simple formwork installation, and by draining excess water during concrete placement. Furthermore, since the concrete strength can be developed quickly, the construction period required for placing the concrete lining concrete 90 of the tunnel 80 can be shortened. In addition, high-speed construction is possible by eliminating various ground reinforcement work using shoring, sprayed concrete, rock bolts, chemical grouting, etc. Moreover, segments required in conventional shield tunneling methods are unnecessary, eliminating the need for vast backyards such as segment factories. Furthermore, reinforcing steel and joint steel are also unnecessary, eliminating the need to consider their durability and waterproofing performance.

[0033] As carbon dioxide from the outside air is supplied to the lining concrete 90 through each pore 31 of the shell 30, carbonation progresses from the surface inward, and the concrete is transformed into stone material with coarse and fine aggregates as gravel. As a result, the strength and durability of the lining concrete 90 are improved. The lining concrete 90, which has been transformed into a petrified portion, is endowed with a durability of over 1,000 years, similar to stone structures such as archaeological sites.

[0034] In the above embodiment, a concrete made with high-early-strength cement was shown, but if the ground conditions are good, there is no problem in using concrete made with ordinary cement instead of high-early-strength cement. In other words, since the concrete is pre-solidified in the excess water discharge process S4, if the ground conditions are good, the stress balance of the ground can be stabilized solely by the effect of pre-solidifying the concrete, making high-speed construction possible without the need for ground reinforcement work such as shoring, sprayed concrete, rock bolts, and chemical grouting.

[0035] Furthermore, although the above embodiment showed an example using a shield machine 1, the present invention can also be applied to the placement of lining concrete for mountain tunnels using the TBM method, NATM method, etc., as shown in Figure 6, as long as it includes an excavation process S1, a formwork installation process S2, a concrete filling process S3, an excess water discharge process S4, a concrete hardening process S5, and a formwork removal process S6. In the above embodiment, a partition plate 15 was provided on the shield machine 1, but in the modified example shown in Figure 6, a partition plate 115 is provided independently. In this modified example, as shown in Figure 6, the lower part of the cross-section of the tunnel 180 is horizontal, and the flat portion 121 of the formwork 120 is formed to be relatively large in the width direction. The water collection channels 122 of the formwork 120 are provided in pairs on the outside in the width direction of the tunnel 180. Furthermore, a drain port 118 and a water collection pipe connected thereto are also provided in pairs in the width direction of the tunnel 180. In this modified example as well, a mesh-like shell 130 is wrapped around the outer surface of the formwork 120.

[0036] Furthermore, although the above embodiment shows that the water passage 40 is formed by an uneven shape formed on the inner surface of the shell 30, it is also possible to form the water passage 240 by an uneven shape formed on the outer surface of the formwork 220, for example, as shown in Figure 7. In Figure 7, the shell 230 is formed in a mesh shape with a plurality of holes 231 arranged in a row. In Figure 7, the cross-section of the convex portion 221 of the formwork 220, which has an uneven shape, is formed in a tapered shape that becomes smaller towards the outside of the tunnel cross-section. This makes it relatively easy to remove the formwork 20 from the concrete side in the formwork removal process S6.

[0037] Although embodiments of the present invention have been described above, the embodiments described above do not limit the invention as defined in the claims. Furthermore, it should be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. [Explanation of Symbols]

[0038] 20 formwork 22 Water collection ditch 30 shell bodies 31 holes 32 Reinforcement Ribs 40 Waterway 50 Water collection pipe 80 Tunnel 90. Lining concrete 120 formwork 122 Water collection ditch 130 Shells 180 Tunnel 190 Lining concrete 220 formwork 221 Convex part 230 shell bodies 231 hole 240 Canal S2 Formwork installation process S3 Concrete filling process S4 Surplus water discharge process S5 Concrete hardening process S6 Formwork removal process

Claims

1. A method for pouring lining concrete using formwork whose outer surface faces the inner wall of the tunnel, A formwork installation step involves installing the formwork in such a state that a mesh-like shell, formed by a series of holes arranged in a row, is fixed to the outer surface of the formwork, such that a drainage channel for draining excess concrete water is formed between the formwork and the shell due to the uneven shape formed on at least one of the outer surface and inner surface of the formwork. A concrete filling step in which fresh concrete is filled into the installed formwork, A process of draining excess water from the concrete to the water channel through the holes in the shell to stop fluidization and temporarily solidify the concrete, A concrete hardening step is performed to drain the excess water and harden the partially solidified concrete integrally with the shell, A method for pouring tunnel lining concrete, comprising a formwork removal step of removing the formwork from the inner surface of the hardened concrete while the shell is integrated with the concrete, and a method for pouring tunnel lining concrete.

2. The method for pouring tunnel lining concrete according to claim 1, wherein the water channel is formed by the uneven shape formed on the inner surface of the shell and extending in the cross-sectional direction of the tunnel.

3. The water channel is formed by the uneven shape formed on the outer surface of the formwork and extending in the cross-sectional direction of the tunnel, The method for pouring tunnel lining concrete according to claim 1, wherein the cross-section of the convex portion having the aforementioned uneven shape is formed in a tapered shape that becomes smaller toward the outside of the tunnel cross-section.

4. The method for pouring tunnel lining concrete according to claim 2 or 3, wherein the formwork is formed on the bottom side of the tunnel and has a drainage channel that is open at the top and collects the excess water.

5. The formwork has a flat section for walking on the bottom side of the tunnel. The method for pouring tunnel lining concrete according to claim 4, wherein the drainage channel is formed in the flat portion.

6. The method for pouring tunnel lining concrete according to claim 5, wherein in the formwork installation step, the shell is fixed to the portion of the formwork in the drainage channel to a predetermined tension.

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