Reinforcement structure of existing shield tunnel and reinforcement method of existing shield tunnel

Abstract

To provide a reinforcement structure of an existing shield tunnel and a reinforcement method of the existing shield tunnel, which can suppress falling of concrete of the existing shield tunnel in the tunnel during a large scale earthquake at low cost by efficiently reinforcing a portion of a tunnel cross section, at which generated sectional force becomes strong.SOLUTION: A reinforcement structure of an existing shield tunnel 1 is provided on the existing shield tunnel 1 having a circular cross section built with segments 10 and reinforces by coating a portion of a concrete C exposed to a tunnel inner surface. A coating reinforcement member 11 is provided so as to cover at least a portion of tunnel inner surface 10a in at least either one of first reinforcement ranges D1 of 30° to 60° and -30° to -60° from a tunnel top portion P0 in a tunnel circumferential direction X1.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a reinforcement structure for an existing shield tunnel and a reinforcement method for an existing shield tunnel. [Background technology]

[0002] Conventionally, in shield tunnels with an approximately circular cross-section in which concrete is exposed on the inner surface of the tunnel, when a large earthquake occurs, cracks or damage occur in the concrete on the inner surface of the segments, and there is a risk that the concrete will spall off (see, for example, Patent Document 1).

[0003] Specifically, when an earthquake occurs, a shear force acts on the tunnel cross section in the cross-sectional direction, causing it to deform into an oblique ellipse. At this time, a large negative bending moment is generated by the seismic force in addition to the axial compression force at the diagonally upward and downward diagonal parts of the tunnel. The negative (positive) bending moment is compression (tension) on the inner side of the tunnel and tension (compression) on the outer side of the tunnel. In shield tunnels constructed with segments such as RC segments and five-sided steel shell type composite segments, the concrete is exposed on the inner side of the tunnel, so as the seismic load increases, the negative bending moment and the axial compression force in the circumferential direction of the tunnel become dominant in this area, and the compression of the concrete on the inner side of the tunnel becomes dominant. On the other hand, the diagonally upward and downward diagonal parts of the tunnel are subjected to axial compression force and positive bending moment due to seismic force, and although cracks occur in the concrete in these parts, the part where the negative bending moment acts is the most severe condition. In addition, since the seismic load is a repeated load, positive and negative bending are repeatedly applied to the diagonally upward and downward diagonal parts of the tunnel on the left and right. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 7-23098 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional existing shield tunnels described above, in which concrete is exposed on the inner surface, have the following problems. As mentioned above, when a large seismic force acts on an existing shield tunnel, axial force and bending moment act in the direction transverse to the tunnel. In the case of RC segments and composite segments, concrete is exposed on the inner surface of the tunnel, but since concrete has poor deformation performance, it may be destroyed by seismic force (compressive failure (hereinafter referred to as crushing) or splitting failure) and fall into the tunnel, which is an event that must be avoided. As a result of research, the inventors found that concrete is particularly susceptible to destruction by crushing and splitting cracks at diagonal upward and downward angles on the left and right sides of the tunnel (near ±45° and ±135° from the top of the tunnel cross section) due to repeated loads caused by earthquakes, and that there is a particular risk of concrete falling into the tunnel on a large scale at an upward diagonal angle.

[0006] In addition, while it is possible to improve earthquake resistance by using segments made of high-strength materials, this has the problem of being expensive, and it is not possible to reliably prevent the concrete in the segments from falling, so there is room for improvement in this regard.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a reinforcement structure for an existing shield tunnel and a reinforcement method for an existing shield tunnel that can efficiently reinforce parts of the tunnel cross section where the cross-sectional stress generated is severe, thereby preventing a large amount of concrete from falling into the tunnel during a large-scale earthquake at low cost. [Means for solving the problem]

[0008] (1) A first aspect of the reinforcement structure for an existing shield tunnel according to the present invention is a reinforcement structure for an existing shield tunnel that is provided in an existing shield tunnel with a circular cross-section constructed of segments and reinforces the existing shield tunnel by covering a portion of the concrete exposed on the inner surface of the tunnel, and is characterized in that it is provided with a covering reinforcement member that covers at least a portion of the inner surface of the tunnel in a first reinforcement range of at least one of 30° to 60° and -30° to -60° from the tunnel crown in the circumferential direction of the tunnel.

[0009] In the present invention, when a large-scale earthquake acts on an existing shield tunnel, axial force and bending moment act in the circumferential direction of the tunnel across the tunnel, and a covering reinforcement member such as a steel plate, an FRP plate, a carbon fiber sheet, a resin mortar, or a fiber-reinforced concrete is provided to cover the inner surface of the tunnel, which is the first reinforcement range including the diagonally upper part of the tunnel where the axial force and bending moment are dominant. Therefore, since the covering reinforcement member improves the strength and the deformation performance, it is possible to prevent the concrete in the first reinforcement range from collapsing or splitting. In addition, even if the concrete collapses or splitting, it is supported by the covering reinforcement member, so that it is possible to prevent the concrete of the segments in the first reinforcement range from falling into the tunnel interior on a large scale.

[0010] Furthermore, in the present invention, a covering reinforcement member is provided on at least a part of the inner surface of the tunnel in a first reinforcement range that is at least one of 30° to 60° and -30° to -60° from the tunnel top in the circumferential direction of the tunnel, and since reinforcement is not provided around the entire circumference of the tunnel in the circumferential direction, material costs can be reduced. In this way, the present invention makes it possible to prevent concrete from falling in existing shield tunnels, thereby achieving earthquake-resistance reinforcement at reduced cost.

[0011] (2) A second aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel of the first aspect, the tunnel segments are staggered, and a first segment joint connecting the segment ends is arranged in the first reinforcement range in the tunnel circumferential direction, and the covering reinforcement member is provided in at least a range that includes the first segment joint in the tunnel circumferential direction and a range that is connected to the segment body of a ring adjacent in the tunnel axial direction to the range that includes the first segment joint.

[0012] In this case, the area including the first segment joint and the area of ​​the adjacent ring can be reliably reinforced by the covering reinforcement member.

[0013] (3) A third aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel of the first aspect, the tunnel segments are staggered, and a first segment joint connecting the segment ends is arranged in the first reinforcement range in the tunnel circumferential direction, and the covering reinforcement member is provided on only the segment body of the ring adjacent in the tunnel axial direction to the first segment joint arranged in the first reinforcement range.

[0014] In this case, by staggering the segments, the bending moment that the segment joint should bear is reduced, and the bending moment of the segment body of the adjacent ring is increased (this is called the splice effect). In other words, the bending rigidity of the first segment joint (as well as general segment joints) is smaller than that of the segment body, so force tends to flow to the side with the larger bending rigidity. Therefore, by providing a covering reinforcement member in the reinforcement area of ​​one ring adjacent to the segment joint surface of the other ring, reinforcement can be efficiently achieved while reducing the covering reinforcement member. In other words, the covering reinforcement member can be arranged efficiently and effectively.

[0015] (4) A fourth aspect of the reinforcement structure for an existing shield tunnel according to the present invention is a reinforcement structure for an existing shield tunnel that is provided in an existing shield tunnel with a circular cross-section constructed of segments and reinforces a portion of the concrete exposed on the inner surface of the tunnel by covering it, and is characterized in that it is provided with a covering reinforcement member that covers at least a portion of the inner surface of the tunnel in at least one of a second reinforcement ranges of 120° to 150° and -120° to -150° from the tunnel crown in the circumferential direction of the tunnel.

[0016] In the present invention, when a large-scale earthquake acts on an existing shield tunnel, axial force and bending moment act in the circumferential direction of the tunnel across the tunnel, and a covering reinforcement member such as a steel plate, an FRP plate, a carbon fiber sheet, a resin mortar, or a fiber-reinforced concrete is provided to cover the inner surface of the segment in the second reinforcement range including the diagonally downward part of the tunnel where the axial force and bending moment are dominant. Therefore, since the covering reinforcement member improves the strength and the deformation performance, it is possible to prevent the concrete in the second reinforcement range from collapsing or splitting. In addition, even if the concrete collapses or splitting, it is possible to prevent the concrete of the segment in the second reinforcement range from falling into the tunnel interior on a large scale because it is supported by the covering reinforcement member.

[0017] Furthermore, in the present invention, a covering reinforcement member is provided on at least a part of the inner surface of the tunnel in at least one of the second reinforcement ranges of 120° to 150° and -120° to -150° from the tunnel top in the circumferential direction of the tunnel, and since reinforcement is not provided around the entire circumference of the tunnel in the circumferential direction, material costs can be reduced. In this way, the present invention makes it possible to prevent concrete from falling in existing shield tunnels, thereby achieving earthquake-resistance reinforcement at reduced cost.

[0018] (5) A fifth aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel of the fourth aspect, the tunnel segments are staggered, and a second segment joint connecting the segment ends is arranged in the second reinforcement range in the tunnel circumferential direction, and the covering reinforcement member is provided in at least a range including the second segment joint in the tunnel circumferential direction and a range connected to the segment body of a ring adjacent in the tunnel axial direction to the range including the second segment joint.

[0019] In this case, the area including the second segment joint and the area of ​​the adjacent ring can be reliably reinforced by the reinforcing member.

[0020] (6) A sixth aspect of the present invention may be characterized in that, in the reinforcement structure of an existing shield tunnel of the fourth aspect, the tunnel segments are staggered, and second segment joints connecting the segment ends are arranged in the second reinforcement range in the tunnel circumferential direction, and the covering reinforcement member is provided on only the segment body of the ring adjacent in the tunnel axial direction to the second segment joint arranged in the second reinforcement range.

[0021] In this case, by staggering the segments, the bending moment that the segment joint should bear is reduced, and the bending moment of the segment body of the adjacent ring is increased (this is called the splice effect). In other words, the second segment joint (as well as general segment joints) has a lower bending rigidity than the segment body, so force tends to flow to the side with the greater bending rigidity. Therefore, by providing a covering reinforcement member in the reinforcement area of ​​one ring adjacent to the segment joint surface of the other ring, reinforcement can be achieved efficiently while reducing the covering reinforcement member. In other words, the covering reinforcement member can be arranged efficiently and effectively.

[0022] (7) A seventh aspect of the present invention may be characterized in that, in the reinforcement structure of an existing shield tunnel of any one of the first to sixth aspects, the reinforcement length extending in the circumferential direction of the tunnel in the covering reinforcement member is equal to or greater than the segment girder height and is at an angle of 30° or less in the circumferential direction of the tunnel.

[0023] In this case, by setting the reinforcement length to such dimensions, the tunnel can be reinforced efficiently and effectively. In other words, since the same cross-sectional forces are generated within a range of at most 30° in the tunnel circumferential direction X1, centered on ±45° from the tunnel zenith, it is preferable to reinforce this range. For example, when reinforcing the area around +45° from the zenith of the tunnel cross section, it is preferable to reinforce the range from +30° to +60°. On the other hand, it is preferable that the minimum reinforcement range in the circumferential direction of the tunnel be the same as the girder height of the segment. This is because the range of collapse when a negative bending moment that compresses the empty side of the tunnel is applied is minimized and is approximately equal to the segment girder height, and by doing so, collapse of the concrete on the empty side of the tunnel can be efficiently prevented.

[0024] (8) An eighth aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel of the seventh aspect, the reinforcement length of the covering reinforcement member is greater than or equal to two times and less than or equal to four times the height of the segment girder.

[0025] In this case, by setting the reinforcement length to such dimensions, the tunnel can be reinforced more efficiently and effectively. In other words, because alternating positive and negative loads act on tunnels during earthquakes, there is a risk that positive and negative bending moments will act repeatedly on the tunnel at angles of ±45° and ±135° from the zenith of the cross section, along with axial force (axial compression force). Damage is likely to accumulate on the interior side of the tunnel due to the repeated stresses, and the damage range of the concrete in the circumferential direction of the tunnel will also increase, and this range will generally be more than two times and less than four times the girder height of the segment. Therefore, it is effective and economical to reinforce the range in the circumferential direction of the tunnel within a range that is more than two times and less than four times the girder height of the segment.

[0026] (9) A ninth aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel of any one of aspects 1 to 6, the inner surface of the covering reinforcement member is flush with the inner surface.

[0027] In this case, the inner peripheral surface of the covering reinforcement member does not protrude from the inner surface of the tunnel, which makes it possible to prevent the space inside the tunnel from being insufficient.

[0028] (10) A tenth aspect of the present invention may be characterized in that, in the reinforcement structure for an existing shield tunnel according to any one of the first to sixth aspects, the covering reinforcement member is arranged across a plurality of segment rings.

[0029] In this case, even if concrete falls from some of the segment rings, the reinforcing effect can be enhanced because the covering reinforcing members are fixed across the adjacent segment rings.

[0030] (11) An eleventh aspect of the present invention may be characterized in that, in the reinforcement structure of an existing shield tunnel of any one of aspects 1 to 6, the covering reinforcement member penetrates the segment and is fixed to the ground on the back surface of the segment.

[0031] In this case, the covering reinforcement member fixed to the inner surface of the tunnel is firmly fixed to the ground, for example by anchor bolts, thereby further enhancing the reinforcing effect.

[0032] (12) A twelfth aspect of the method for reinforcing an existing shield tunnel according to the present invention is a method for reinforcing an existing shield tunnel having a circular cross-section constructed by segments, which is provided with a covering member for covering a portion of the concrete exposed on the inner surface of the tunnel, and is characterized by including a step of covering at least a portion of the inner surface of the tunnel with a covering reinforcement member in a first reinforcement range of at least one of 30° to 60° and -30° to -60° from the tunnel ceiling in the circumferential direction of the tunnel.

[0033] (13) A thirteenth aspect of the method for reinforcing an existing shield tunnel according to the present invention is a method for reinforcing an existing shield tunnel having a circular cross-section constructed by segments, which is provided in the existing shield tunnel and reinforces the tunnel by covering a portion of the concrete exposed on the inner surface of the tunnel, and is characterized by including a step of covering at least a portion of the tunnel inner surface with a covering reinforcement member in at least one of a second reinforcement ranges of 120° to 150° and -120° to -150° from the tunnel crown in the circumferential direction of the tunnel.

[0034] In the present invention, when a large-scale earthquake acts on an existing shield tunnel, axial force and bending moment act in the circumferential direction of the tunnel across the tunnel, and a covering reinforcement member such as a steel plate, an FRP plate, a carbon fiber sheet, a resin mortar, or a fiber-reinforced concrete is provided to cover the inner surface of the tunnel, which is the first reinforcement range including the diagonally upward side of the tunnel where the axial force and bending moment are predominant, or the second reinforcement range including the diagonally downward side. Therefore, since the covering reinforcement member improves the strength and improves the deformation performance, it is possible to prevent the concrete in the reinforcement range (the first reinforcement range and the second reinforcement range) from collapsing or splitting. In addition, even if the concrete collapses or splitting is caused, it is possible to prevent the concrete of the segment in the reinforcement range from falling into the tunnel interior on a large scale because it is supported by the covering reinforcement member. Effect of the Invention

[0035] According to the reinforcement structure for an existing shield tunnel and the reinforcement method for an existing shield tunnel of the present invention, by efficiently reinforcing the parts of the tunnel cross section where the cross-sectional stress generated is severe, it is possible to prevent concrete in the existing shield tunnel from falling into the tunnel during a large-scale earthquake at low cost. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 is a perspective view showing a tunnel according to a first embodiment of the present invention. [Diagram 2] A cross-sectional view showing the reinforced area of ​​the tunnel. [Diagram 3] FIG. 2 is an exploded view of the upper half of the tunnel, showing the inner surface of the tunnel. [Figure 4] FIG. 2 is a partial oblique view of a segment that constitutes an existing shield tunnel equipped with a covering reinforcement member when the segment is extracted. [Diagram 5] FIG. 2 is a partial oblique view of a segment that constitutes an existing shield tunnel equipped with a covering reinforcement member when the segment is extracted. [Figure 6] FIG. 4 is a cross-sectional view of a tunnel showing an example of a fixed state of a covering reinforcing member. [Figure 7] FIG. 13 is an exploded view of the upper half of a tunnel showing another example of the arrangement of covering reinforcement members, illustrating the inner surface of the tunnel. [Figure 8] FIG. 11 is a development view of the upper half of a tunnel according to a second embodiment, showing the inner surface of the tunnel. [Figure 9] FIG. 11 is a development view of the upper half of a tunnel according to a third embodiment, showing the inner surface of the tunnel. [Figure 10] 10 is a cross-sectional view taken along line XX shown in FIG. [Figure 11] FIG. 13 is a partial oblique view of a composite segment when a segment constituting an existing shield tunnel equipped with a modified covering reinforcement member is extracted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Hereinafter, a reinforcement structure for an existing shield tunnel and a reinforcement method for an existing shield tunnel according to an embodiment of the present invention will be described with reference to the drawings.

[0038] (First embodiment) 1 and 2, the reinforcement structure for an existing shield tunnel 1 according to the first embodiment is a structure that is provided in an existing shield tunnel 1 with a circular cross section constructed from segments 10, and reinforces the tunnel by covering a part of the concrete C exposed on the inner surface of the tunnel. In this embodiment, a shield tunnel made of RC segments (reinforced concrete segments) will be described as an example.

[0039] The segments 10 constituting the existing shield tunnel 1 are connected in multiples in the tunnel circumferential direction X1 and the tunnel axial direction X2 along the inner wall of the excavation hole of the existing shield tunnel 1 excavated in the natural ground in the shield construction method, for example, to construct a cylindrical wall body. The segments 10 are formed in an arc plate shape with a radius of curvature approximately equal to the radius of curvature of the inner surface of the excavation hole of the existing shield tunnel 1. In other words, the segments 10 form a quadrangular frame shape curved on an arc on the tunnel outer circumferential surface side.

[0040] The segments 10 are assembled in a staggered arrangement in which the joining positions of adjacent rings in the tunnel circumferential direction X1 in the tunnel axial direction X2 are shifted in the tunnel circumferential direction X1 (this is called a staggered set). Hereinafter, one of the adjacent rings will be referred to as the first ring R1, and the other as the second ring R2. The first ring R1 and the second ring R2 are alternately arranged in the tunnel axial direction X2.

[0041] Inside the concrete of the segment 10, a plurality of main reinforcing bars are arranged on the inner space side and the natural ground side, extending in an arc shape in the tunnel circumferential direction X1. The segment 10 has an arc-shaped tunnel inner surface 10a and a tunnel outer surface 10b, a pair of arc-shaped ring joint surfaces 10d arranged opposite each other at a predetermined interval in the tunnel axial direction X2, and a pair of segment joint surfaces 10c arranged opposite each other at a predetermined interval in the tunnel circumferential direction X1. The tunnel inner surface 10a and the tunnel outer surface 10b are located on the inner and outer circumferential sides of the pair of ring joint surfaces 10d and the pair of segment joint surfaces 10c, respectively. The ring joint surfaces 10d and the segment joint surfaces 10c are segment end surfaces that include joints such as bolts (not shown).

[0042] The size of the segment 10 can be appropriately changed depending on the ease of transport, assembly, etc. In other words, the arcuate curvature of the segment 10 is appropriately determined depending on the cross section of the tunnel to be excavated. Also, for example, in Figures 1 and 2, a so-called K segment (symbol 10K in the figures) is used in which the installation angle of the segment joint and the length dimension in the tunnel circumferential direction X1 are appropriately changed so that the segment 10 can be fitted last when assembling the segment 10.

[0043] The segments 10 in the tunnel circumferential direction X1 and the tunnel axial direction X2 are fixed to each other by fastening means (not shown) such as bolts.

[0044] As shown in Figs. 1 to 3, the existing shield tunnel 1 is provided with covering reinforcement members 11 and 12 (the covering reinforcement member denoted by reference numeral 12 is omitted in Fig. 3) that cover at least a part of the tunnel inner surface 10a. The covering reinforcement members 11 and 12 are arranged in at least a part of a first reinforcement range D1 (in this embodiment, the entire region of the first reinforcement range D1 shown in Fig. 3) that is at least one of 30° to 60° and -30° to -60° from the tunnel vertex P0 in the tunnel circumferential direction X1, and at least a part of a second reinforcement range D2 (in this embodiment, the entire region of the second reinforcement range D2) that is at least one of 120° to 150° and -120° to -150° from the tunnel vertex P0 in the tunnel circumferential direction X1. Therefore, the covering reinforcement members 11 and 12 provided in each segment 10 have different reinforcement ranges depending on the positions in the tunnel circumferential direction X1 of one ring. The thickness of the covering reinforcement members 11, 12 varies depending on the material used, but it is preferable that they are provided flush with the tunnel inner surface 10a. Note that "flush" here does not mean that the covering reinforcement members 11, 12 do not protrude at all from the tunnel inner surface 10a, but includes cases where they protrude into the tunnel interior by a millimeter or less, such as by attaching a thin material such as a sheet or thin steel plate.

[0045] The first reinforcement area D1 is provided with a first covering reinforcement member 11 that covers at least a part of the tunnel inner surface 10a. The first covering reinforcement member 11 is provided at least in an area including the first segment joint (a joint provided on the segment joint surface 10c) in the tunnel circumferential direction X1, and in an area connected to the segment body of the ring adjacent in the tunnel axial direction X2 to the area including the first segment joint.

[0046] In the second reinforcement area D2, a second covering reinforcement member 12 is provided at least in a part of the tunnel inner surface side. The second covering reinforcement member 12 is provided at least in an area including the second segment joint (a joint provided on the segment joint surface 10c) in the tunnel circumferential direction X1, and in an area connected to the segment body of the ring adjacent in the tunnel circumferential direction X1 to the area including the second segment joint. Note that the above-mentioned first segment joint and second segment joint generally have the same configuration.

[0047] The covering reinforcement members 11 and 12 are curved members that fit the tunnel inner surface 10a. Examples of the covering reinforcement members 11 and 12 include steel plates, FRP plates, carbon fiber sheets, mesh, resin mortar, fiber-reinforced concrete, etc. The covering reinforcement members 11 and 12 are fixed to the segment main body by fastening means such as adhesion, welding, bolts / nuts, hooks, etc. In this embodiment, the segment body is filled with concrete C or steel materials such as reinforcing bars and steel plates. The covering reinforcing members 11, 12 are preferably fixed to the steel materials in the segment body so as not to fall together with the concrete C.

[0048] If the compressive strain generated in a tunnel by bending moment and compressive axial force during an earthquake exceeds the limit value of the concrete material, collapse will occur, and the maximum compressive strain will occur on the tunnel inner surface 10a or the tunnel outer surface 10b, causing the concrete to collapse. If the tunnel inner surface 10a collapses, the concrete will fall into the tunnel. Therefore, in order to prevent the concrete from falling, it is effective to at least reinforce the concrete on the tunnel inner surface side.

[0049] When carbon fiber sheets are used as the covering reinforcement members 11, 12, for example, as shown in Fig. 4, the carbon fiber sheets may be placed on the tunnel inner surface 10a of the segment 10 and fixed by adhering to the concrete C. In this case, the thickness of the covering reinforcement members 11, 12 can be set to be extremely thin. This makes it possible to reinforce the tunnel without invading the space inside the tunnel, without impeding the flow of compressive strain and compressive stress generated on the tunnel inner surface 10a, and without causing local stress concentration, and thus makes it possible to efficiently reinforce the tunnel while preventing localized collapse of the concrete.

[0050] Furthermore, when a resin mortar plate or fiber-reinforced concrete is used as the covering reinforcement members 11, 12, for example as shown in FIG. 5, the resin mortar plate or fiber-reinforced concrete may be directly poured onto the tunnel inner surface 10a side of the segment 10, or a prefabricated plate may be glued or fixed to the concrete C with bolts, hooks, or the like.

[0051] When the covering reinforcement members 11, 12 are steel plates or FRP plates, they can be adhered to the tunnel inner surface 10a. Alternatively, nuts can be embedded in the concrete C of the segment and the members can be joined to the nuts by joining means (bolts, etc.). Alternatively, the steel plates may be arranged on the tunnel inner surface 10a by being fixed to the reinforcing bars in the concrete C by welding, hooks, etc. The inner surfaces of the covering reinforcement members 11, 12 protrude slightly from the tunnel inner surface 10a of the segment 10. In this case, the covering reinforcement members 11, 12 can be more firmly connected to the segment body, and the concrete C can be more reliably prevented from falling.

[0052] 6, the covering reinforcement members 11, 12 may be fixed to the ground G on the back surface of the segment 10 by having a portion of the covering reinforcement members 11, 12 penetrate the segment 10 in the thickness direction. In the reinforcement structure shown in Fig. 6, the covering reinforcement members 11, 12 fixed to the tunnel inner surface 10a are provided with anchor bolts 13 (anchoring members). In this case, by fixing the anchor bolts 13 to the ground G, the covering reinforcement members 11, 12 are firmly supported by the tunnel inner surface 10a, thereby improving the reinforcing effect.

[0053] 2 and 3, the reinforcement length L of the covering reinforcement members 11, 12 extending in the tunnel circumferential direction X1 is equal to or greater than the segment girder height H and is in the range of a reinforcement angle θ in the tunnel circumferential direction X1 of 30° or less. More preferably, the reinforcement length L of the covering reinforcement members 11, 12 is equal to or greater than two times and equal to or less than four times the segment girder height H.

[0054] The inventors have found through research that the range in which the cross-sectional force generated in the tunnel by an earthquake is the largest, i.e., the range in which the maximum cross-sectional force occurs, particularly the range in which the cross-sectional force as a result of the axial force (axial compression force) and bending moment (negative bending moment in which the tunnel interior side is compressed) is the largest, is approximately ±45° and / or ±135° from the tunnel apex P0. Therefore, by arranging the covering reinforcement members 11 and 12 in this manner, the strength of this vicinity is improved and the deformation performance is enhanced, so that the concrete can be prevented from collapsing or splitting. Or, even if the concrete does collapse or split, it can be prevented from falling into the tunnel because it is supported by the covering reinforcement members 11 and 12.

[0055] In other words, since the same cross-sectional forces are generated within a range of at most 30° in the tunnel circumferential direction X1 centered on ±45° and / or ±135° from the tunnel zenith P0, it is preferable to reinforce this range. For example, when reinforcing the vicinity of +45° and / or +135° from the zenith of the tunnel cross section, it is preferable to reinforce the range of +30° to +60° and / or +120° to +150°.

[0056] On the other hand, it is preferable that the minimum reinforcement range in the circumferential direction of the tunnel be the same as the girder height of the segment. This is because the range of collapse when a negative bending moment that compresses the empty side of the tunnel is applied is minimized and is approximately equal to the segment girder height, and by doing so, collapse of the concrete on the empty side of the tunnel can be efficiently prevented.

[0057] Furthermore, because alternating positive and negative loads act on tunnels during earthquakes, there is a risk that positive and negative bending moments act repeatedly on the tunnel at an angle of ±45° and / or ±135° from the zenith of the cross section, along with axial force (axial compression force). Damage is likely to accumulate on the inner side of the tunnel due to the repeated stresses, and the damage range of the concrete in the tunnel circumferential direction X1 also becomes large, and this range is generally more than two times and less than four times the girder height of the segment. Therefore, it is effective and economical to reinforce the range of the tunnel circumferential direction X1 within the range of more than two times and less than four times the girder height of the segment.

[0058] Moreover, the covering reinforcement members 11 and 12 are not limited to being provided for each ring, and may be arranged across a plurality of rings as shown in FIG. 7. The structure shown in FIG. 7 is configured such that one covering reinforcement member 110 is set to a width dimension (length dimension in the tunnel axial direction X2) for three rings. In FIG. 7, four covering reinforcement members 110 (110A, 110B, 110C, 110D) are shown, and each covering reinforcement member 110 is arranged across three rings. These covering reinforcement members 110A, 110B, 110C, 110D are arranged such that the center of each of the tunnel circumferential direction X1 is at a position of ±45° from the tunnel zenith P0, that is, at a position of 30° to 60° and −30° to −60° from the tunnel zenith P0 in the tunnel circumferential direction X1. In this case, even if concrete falls from some rings, the covering reinforcement members 11 and 12 are fixed across adjacent rings, so that the reinforcing effect can be enhanced. Furthermore, the size (width dimension) of the covering reinforcement member 110 is not limited to a size spanning three rings, and there is no limit to the number of rings that the covering reinforcement member 110 spans, for example, two rings, four rings, etc.

[0059] According to the reinforcement structure of the existing shield tunnel described above, when a large-scale earthquake acts on the existing shield tunnel 1, axial force and bending moment act in the tunnel circumferential direction X1 to cross the tunnel, and the covering reinforcement member 11 such as a steel plate, FRP plate, carbon fiber sheet, resin mortar, and fiber reinforced concrete is provided to cover the tunnel inner surface 10a which is the first reinforcement range D1 (at least one of 30° to 60° and -30° to -60° from the tunnel top P0 in the tunnel circumferential direction X1) including the diagonally upward part of the tunnel where the axial force and bending moment are dominant. Therefore, since the covering reinforcement member 11 improves the strength and enhances the deformation performance, it is possible to suppress the crushing and splitting failure of the concrete in the first reinforcement range D1. Furthermore, even if the concrete C should crush or splitting fail, it is supported by the covering reinforcement member 11, so that it is possible to suppress the concrete C of the segment in the first reinforcement range D1 from falling into the tunnel interior on a large scale.

[0060] Moreover, in this embodiment, when a large-scale earthquake acts on the existing shield tunnel 1, the covering reinforcement member 12 is provided so as to cover the tunnel inner surface 10a which is the second reinforcement range D2 (at least one of the ranges of 120° to 150° and -120° to -150° from the tunnel top P0 in the tunnel circumferential direction X1) including the diagonally downward portion of the existing shield tunnel 1. Therefore, since the covering reinforcement member 12 improves the strength and enhances the deformation performance, it is possible to prevent the concrete C in the second reinforcement range D2 from collapsing or splitting failure. Furthermore, even if the concrete C should collapse or splitting failure occur, it is possible to prevent the concrete C of the segment in the second reinforcement range D2 from falling into the tunnel interior space on a large scale because it is supported by the covering reinforcement member 12.

[0061] Furthermore, in this embodiment, the covering reinforcement members 11, 12 are arranged in at least a part of the first reinforcement range D1 and / or the second reinforcement range D2 from the tunnel top P0 in the tunnel circumferential direction X1, and do not provide reinforcement over the entire circumference of the tunnel in the tunnel circumferential direction X1, thereby making it possible to reduce material costs. In this manner, in this embodiment, by preventing the concrete C of the existing shield tunnel 1 from falling, earthquake resistance reinforcement can be achieved while keeping costs down.

[0062] In this embodiment, the reinforcement length L of the covering reinforcement member 11 extending in the tunnel circumferential direction X1 is equal to or greater than the segment girder height H and is in the range of an angle of 30° or less in the tunnel circumferential direction X1. In this case, the tunnel can be reinforced efficiently and effectively by setting the reinforcement length L to such a dimension. That is, since the same cross-sectional force is generated in a range of at most 30° in the tunnel circumferential direction X1 from the tunnel zenith P0 at ±45° as the center, it is preferable to reinforce this range. For example, when reinforcing the vicinity of +45° from the zenith of the tunnel cross section, it is preferable to reinforce the range of +30° to +60°. On the other hand, it is preferable to set the minimum reinforcement range in the tunnel circumferential direction X1 to the same as the segment girder height H, because the range of crushing when a negative bending moment that compresses the tunnel interior side is applied is the smallest and is almost equal to the segment girder height H, and by doing so, the crushing of the concrete C on the interior side of the tunnel can be efficiently suppressed.

[0063] In this embodiment, the reinforcement length L is equal to or greater than two times the segment girder height H and equal to or less than four times the segment girder height H. In this case, by setting the reinforcement length L to such a dimension, the tunnel can be reinforced more efficiently and effectively. That is, since alternating positive and negative loads act on the tunnel during an earthquake, there is a risk that positive and negative bending moments act repeatedly on the tunnel at angles of ±45° and ±135° from the apex of the cross section, along with axial force (axial compression force). Damage is likely to accumulate on the inner side of the tunnel due to the repeated stresses, and the damage range of the concrete in the tunnel circumferential direction X1 also becomes large, and the range is generally two to four times the girder height of the segment. Therefore, it is effective and economical to reinforce the range of the tunnel circumferential direction X1 to two to four times the girder height H.

[0064] As described above, in the reinforcement structure for an existing shield tunnel and the reinforcement method for an existing shield tunnel according to this embodiment, by efficiently reinforcing the parts of the tunnel cross section where the cross-sectional stress generated is severe, it is possible to prevent the concrete of the existing shield tunnel 1 from falling into the existing shield tunnel 1 during a large-scale earthquake at low cost.

[0065] Next, a reinforcement structure for an existing shield tunnel and a reinforcement method for an existing shield tunnel according to another embodiment will be described with reference to the attached drawings. Note that the same reference numerals are used for the same or similar members and parts as those in the first embodiment described above, and the description will be omitted. Only the configurations different from the first embodiment will be described.

[0066] Second embodiment As shown in Figure 8, the reinforcement structure for an existing shield tunnel 1 according to the second embodiment shows an example applied when multiple segment joint surfaces 10c are arranged in the vicinity of ±45° from the tunnel top P0 in the tunnel circumferential direction X1.

[0067] The covering reinforcement member 11A is provided in the first reinforcement range D1 (at least one of a range of 30° to 60° and -30° to -60° from the tunnel zenith P0) according to the above-mentioned first embodiment and in the second reinforcement range D2 (at least one of a range of 120° to 150° and -120° to -150° from the tunnel zenith P0) not shown, in a first range d1 including the segment joint surface 10c of the upper ring R1, a second range d2 of the second ring R2 adjacent to the first range d1 in the tunnel axis direction X2, a third range d3 including the segment joint surface 10c of the second ring R2, and a fourth range d4 of the upper ring R1 adjacent to the third range d3 in the tunnel axis direction X2.

[0068] In the case where there are a plurality of segment joint surfaces 10c in each of the first reinforcement range D1 and the second reinforcement range D2 as in the second embodiment, the reinforcement length L is set to the same as that of the first embodiment at each segment joint surface 10c. That is, the reinforcement length L extending in the tunnel circumferential direction X1 of the covering reinforcement member 11 at each segment joint surface 10c is in the range of not less than the segment girder height H and not more than 30° at the reinforcement angle θ in the tunnel circumferential direction X1, and more preferably is not less than two times and not more than four times the segment girder height H.

[0069] In this way, it is not necessary to reinforce the entire reinforcement area, and a part of the reinforcement area may be divided into multiple parts and reinforced. In this way, material costs can be reduced, and construction costs can be reduced by downsizing heavy machinery during on-site construction.

[0070] Third embodiment 9, the covering reinforcement member 11C of the segment 10C according to the third embodiment shows an example applied when the segment joint surface 10c is arranged in the vicinity of ±45° from the tunnel zenith P0 in the tunnel circumferential direction X1 in a cross-sectional view. The covering reinforcement member 11C is arranged only in the reinforcement range of the other ring adjacent in the tunnel axial direction X2 to the one ring where the segment joint surface 10c is arranged in the first reinforcement range D1 (at least one of 30° to 60° and -30° to -60° from the tunnel zenith P0) and the second reinforcement range D2 (not shown) (at least one of 120° to 150° and -120° to -150° from the tunnel zenith P0).

[0071] Specifically, the covering reinforcement member 11C is provided in a second area d2 of the second ring R2 adjacent to the segment joint surface 10c of the first ring R1 in the tunnel axis direction X2, and in a fourth area d4 of the first ring R1 adjacent to the segment joint surface 10c of the second ring R2 in the tunnel axis direction X2.

[0072] In the third embodiment, as shown in Fig. 10, the reinforcement length L is set to be the same as that of the first embodiment. That is, the reinforcement length L extending in the tunnel circumferential direction X1 of the covering reinforcement member 11C at each segment joint surface 10c is equal to or greater than the segment girder height H and is in the range of 30° or less at a reinforcement angle θ in the tunnel circumferential direction X1, and more preferably is equal to or greater than two times and equal to or less than four times the segment girder height H.

[0073] The covering reinforcing members 11C provided in the second area d2 and the fourth area d4 as in the third embodiment utilize a splice effect, thereby allowing the covering reinforcing members 11C to be disposed efficiently and effectively. The splice effect means that, as shown in Fig. 9, by staggering the segments 10C, the bending moment that the segment joint at the segment joint surface 10c should bear is reduced, and the bending moment burden of the segment body of the adjacent ring is increased. In other words, since the bending rigidity of the first segment joint is smaller than that of the segment body, the force (symbol F in Fig. 9) tends to flow to the side with the larger bending rigidity. Therefore, by providing the covering reinforcement member 11 on the segment body of the segment 10C in the reinforcement range of the other ring adjacent to the segment joint surface 10c of one ring, the covering reinforcement member 11 can be arranged efficiently and effectively. In this manner, in the third embodiment, the covering reinforcing member 11C is provided in the reinforcement areas (the second area d2 and the fourth area d4) of one ring adjacent to the segment joint surface 10c of the other ring.

[0074] The above describes embodiments of the reinforcement structure for an existing shield tunnel and the tunnel reinforcement method according to the present invention. However, the present invention is not limited to the above embodiments and can be modified as appropriate without departing from the spirit of the present invention.

[0075] For example, in the above-mentioned embodiment, RC segments (reinforced concrete segments) are used as the segments forming the tunnel inner surface 10a on which the covering reinforcement member 11 is provided, but the present invention is not limited to this and may be applied to, for example, a composite segment 20 as shown in Fig. 11. In short, it is sufficient to cover and reinforce a part of the concrete provided in a tunnel with a circular cross section and exposed on the tunnel inner surface including the first reinforcement range D1 (at least one of the ranges of 30° to 60° and -30° to -60° from the tunnel zenith P0) or the second reinforcement range D2 (at least one of the ranges of 120° to 150° and -120° to -150° from the tunnel zenith P0).

[0076] Specifically, an example of a composite segment 20 constituting an existing shield tunnel 1 includes an arc-shaped plate-shaped frame 21 formed of steel covering five faces of the segment other than the inner surface, and concrete 22 poured inside the arc-shaped plate-shaped frame 21. That is, the arc-shaped plate-shaped frame 21 includes a pair of main girders 23 arranged at both ends in the tunnel axial direction X2, a pair of joint plates 24 joined to both ends in the tunnel circumferential direction X1 of the pair of main girders 23, and a skin plate 25 curved into a cylindrical circumferential shape joined to the natural ground side of the tunnel to the main girders 23 and the joint plate 24. A rib material extending in the tunnel axial direction X2 and the tunnel circumferential direction X1 is generally provided on the inside of the arc-shaped plate-shaped frame 21. A covering reinforcement member 26 is provided on the composite segment 20 so as to cover at least a part of the concrete 22 on the inner surface of the tunnel. The configuration and installation concept of the covering reinforcement member 26, such as the reinforcing range, position, members, and shape, are the same as those of the existing shield tunnel 1 composed of the above-mentioned RC segments.

[0077] Furthermore, within the scope of the present invention, the components in the above-described embodiments can be appropriately replaced with well-known components. [Explanation of symbols]

[0078] 1. Tunnel 10, 10A~10C segments 10a Tunnel inner surface 10b Tunnel exterior 10c Segment joint surface 10d Ring joint surface 11, 11A to 11C, 12 Covering reinforcement member 11a Inner surface 13 Anchor bolt (fixing member) 20 Synthetic Segments 22 Concrete 22a Tunnel inner surface 26 Covering reinforcement members C. Concrete P0 Tunnel zenith R1 Instep Ring R2 Otsu Ring X1 Tunnel circumferential direction X2 Tunnel axis direction

Claims

1. A reinforcement structure for an existing shield tunnel that is installed in an existing shield tunnel with a circular cross section constructed by segments and reinforces the tunnel by covering a part of the concrete exposed on the inner surface of the tunnel. A reinforcement structure for an existing shield tunnel, comprising a covering reinforcement member that covers at least a portion of the inner surface of the tunnel in a first reinforcement range of at least one of 30° to 60° and -30° to -60° from the tunnel top in the circumferential direction of the tunnel.

2. The tunnel segments are staggered, and a first segment joint that connects the segment ends to each other is arranged in the first reinforcement range in the tunnel circumferential direction; 2. The reinforcement structure for an existing shield tunnel as described in claim 1, wherein the covering reinforcement member is provided at least in an area including the first segment joint in the tunnel circumferential direction and in an area connected to the segment body of the ring adjacent in the tunnel axial direction to the area including the first segment joint.

3. The tunnel segments are staggered, and a first segment joint that connects the segment ends to each other is arranged in the first reinforcement range in the tunnel circumferential direction; 2. The reinforcement structure for an existing shield tunnel according to claim 1, wherein the covering reinforcement member is provided on only the segment body of a ring that is adjacent in the tunnel axial direction to the first segment joint that is located in the first reinforcement range.

4. A reinforcement structure for an existing shield tunnel that is installed in an existing shield tunnel with a circular cross section constructed by segments and reinforces the tunnel by covering a part of the concrete exposed on the inner surface of the tunnel. A reinforcement structure for an existing shield tunnel, comprising a covering reinforcement member that covers at least a portion of the inner surface of the tunnel in a second reinforcement range of at least one of 120° to 150° and -120° to -150° from the tunnel top in the circumferential direction of the tunnel.

5. The tunnel segments are staggered, and second segment joints that connect the segment ends to each other are arranged in the second reinforcement range in the tunnel circumferential direction; 5. The reinforcement structure for an existing shield tunnel as described in claim 4, wherein the covering reinforcement member is provided in at least an area including the second segment joint in the tunnel circumferential direction and in an area connected to the segment body of the ring adjacent in the tunnel axial direction to the area including the second segment joint.

6. The tunnel segments are staggered, and second segment joints that connect the segment ends to each other are arranged in the second reinforcement range in the tunnel circumferential direction; 5. The reinforcement structure for an existing shield tunnel according to claim 4, wherein the covering reinforcement member is provided on only the segment body of a ring that is adjacent in the tunnel axial direction to the second segment joint that is located in the second reinforcement range.

7. 7. A reinforcement structure for an existing shield tunnel as described in any one of claims 1 to 6, wherein the reinforcement length extending in the tunnel circumferential direction of the covering reinforcement member is equal to or greater than the segment girder height and is in the range of an angle of 30° or less in the tunnel circumferential direction.

8. 8. The reinforcement structure for an existing shield tunnel according to claim 7, wherein the reinforcement length of the covering reinforcement member is between two and four times the segment girder height.

9. 7. A reinforcement structure for an existing shield tunnel according to claim 1, wherein an inner circumferential surface of the covering reinforcement member is flush with the inner surface of the tunnel.

10. The reinforcement structure for an existing shield tunnel according to claim 1 , wherein the covering reinforcement member is arranged across a plurality of segment rings.

11. 7. A reinforcement structure for an existing shield tunnel according to claim 1, wherein the covering reinforcement member penetrates the segment and is fixed to the natural ground on the back surface of the segment.

12. A method for reinforcing an existing shield tunnel with a circular cross section constructed of segments, by covering a portion of the concrete exposed on the inner surface of the tunnel, comprising: A method for reinforcing an existing shield tunnel, comprising the step of covering at least a portion of the inner surface of the tunnel with a covering reinforcement member in a first reinforcement range that is at least one of 30° to 60° and -30° to -60° from the tunnel crown in the circumferential direction of the tunnel.

13. A method for reinforcing an existing shield tunnel with a circular cross section constructed of segments, by covering a portion of the concrete exposed on the inner surface of the tunnel, comprising: A method for reinforcing an existing shield tunnel, comprising the step of covering at least a portion of the inner surface of the tunnel with a covering reinforcement member in a second reinforcement range that is at least one of 120° to 150° and -120° to -150° from the tunnel top in the circumferential direction of the tunnel.

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