Existing tunnel prestress sleeve lining reinforcing structure and construction method

Abstract

The invention discloses an existing tunnel prestress sleeve lining reinforcing structure and a construction method, the existing tunnel prestress sleeve lining reinforcing structure comprises one or more sleeve lining units which are sequentially arranged in the length direction of a tunnel, and each sleeve lining unit comprises two L-shaped steel plates, two profile steel lagging jacks, a corrugated steel plate and a plurality of prestress cables; wherein the corrugated steel plate is arc-shaped and is used for being arranged in a tunnel cavern; the L-shaped steel plates and the profile steel lagging jacks are arc-shaped, and one L-shaped steel plate and one profile steel lagging jack form a group; the outer walls of the L-shaped steel plates are tightly attached to existing tunnel linings, and a closed space is defined between the two existing tunnel linings. The prestressed cables are connected with the two groups of L-shaped steel plates and the profile steel lagging jacks, and the plurality of prestressed cable rings are arranged around the L-shaped steel plates and the profile steel lagging jacks at intervals; and the prestressed cables are used for providing pre-pressure for the concrete. The prestressed cable is used for applying prestress, so that the bending resistance and the tensile resistance of the sleeve lining unit are higher; and formwork removal is not needed after concrete pouring, and the construction efficiency is higher.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel repair and reinforcement, and specifically relates to a prestressed lining reinforcement structure of an existing tunnel and a construction method. Background Art

[0002] Tunnel lining is a reinforced concrete structure set along the length of the tunnel to prevent rock and soil deformation. However, due to the complex geological environment, poor construction quality, aging of material properties and other reasons, after the tunnel is put into use, problems such as lining seepage and block falling often occur, seriously affecting the driving safety in the tunnel. In order to solve the above problems, it is necessary to repair and reinforce the existing lining.

[0003] Setting up another layer of casing on the foundation of an existing tunnel is a common tunnel repair and reinforcement strategy. However, in order to meet the needs of traffic, the window period left for tunnel repair and reinforcement construction is extremely short. Traditional reinforced concrete construction has complicated processes such as steel bar binding, formwork casting, and formwork removal, and involves the entry and exit of multiple materials and equipment. The construction efficiency is low and affects the tunnel's traffic function. At the same time, ordinary reinforced concrete has low strength, and it is difficult to ensure that the newly constructed casing will not crack, fall off, and leak water again. Summary of the invention

[0004] The purpose of the present invention is to provide a prestressed casing lining reinforcement structure and construction method for an existing tunnel, which uses prestressed cables to apply prestress, and the casing lining unit has stronger bending and tensile resistance; and there is no need to remove the formwork after concrete pouring, so the construction efficiency is higher.

[0005] The present invention adopts the following technical scheme: an existing tunnel prestressed lining reinforcement structure, comprising one or more lining units arranged in sequence along the length direction of the tunnel, each lining unit comprising two L-shaped steel plates, two steel arch frames, corrugated steel plates and a plurality of prestressed cables; wherein:

[0006] The corrugated steel plate is arc-shaped and consistent with the shape of the tunnel chamber; it is used to be set in the tunnel chamber;

[0007] Both the L-shaped steel plate and the steel arch frame are arc-shaped, consistent with the shape of the tunnel chamber. One L-shaped steel plate and one steel arch frame form a group. The two groups of L-shaped steel plates and steel arch frames are located at the front and rear ends of the corrugated steel plate respectively. In each group of L-shaped steel plates and steel arch frames, the steel arch frame is located close to the corrugated steel plate. The outer wall of the L-shaped steel plate is closely attached to the existing tunnel lining, and a closed space is enclosed between the two existing tunnel linings. The closed space is used for pouring concrete.

[0008] Each prestressed cable is connected to two groups of L-shaped steel plates and steel arch frames, and a plurality of prestressed cable rings are arranged at intervals around the L-shaped steel plates and the steel arch frames; each prestressed cable is used to provide prestress to the concrete.

[0009] Furthermore, the prestressed cable comprises a corrugated tube and two anchor rings, each anchor ring is cylindrical, and the two anchor rings are arranged horizontally and fixed to L-shaped steel plates at both ends respectively;

[0010] The bellows is a hollow tube, and its two ends pass through two sets of L-shaped steel plates and steel arch frames and are connected; the two ends of the bellows are connected to the anchor rings;

[0011] A grouting hole and a plurality of cable holes are provided in each anchor ring and in the radial space of the corrugated pipe. The grouting hole and the cable holes are arranged along the axial direction of the anchor ring and axially penetrate the anchor ring to be connected with the corrugated pipe. The positions of the cable holes on the two anchor rings correspond to each other. The grouting hole is used to pour cement slurry into the corrugated pipe.

[0012] A plurality of steel strands are coaxially sleeved in the corrugated tube, the number of which is the same as the number of cable holes on an anchor ring, and both ends of each steel strand pass through two cable holes at corresponding positions; the length of the steel strand is greater than the length of the sleeve unit.

[0013] When the strength of the concrete in the closed space reaches the first design strength, the steel strands are tensioned axially and toward both ends and released after tensioning to provide pre-pressure to the concrete.

[0014] Furthermore, both ends of each steel strand are coaxially sleeved with clamps, each clamp is a truncated cone-shaped shell, and the small end faces the anchor ring. The diameter of the small end of each clamp is smaller than the diameter of the cable hole, and the diameter of the large end is larger than the diameter of the cable hole; after the steel strand is released, the small end of the clamp is inserted into and fixed in the corresponding cable hole to fix each steel strand.

[0015] Furthermore, a cover box is sleeved and fixedly connected on each anchor ring, and the cover box is used to cover the end of each steel strand and the clamp.

[0016] Furthermore, the L-shaped steel plate and the existing tunnel lining are connected with a plurality of lining connecting steel bars, and the plurality of lining connecting steel bars are arranged at intervals around the L-shaped steel plate. Each lining connecting steel bar includes a vertical section, and one end of the vertical section is in the shape of a chamfered hook; wherein the chamfered hook end is implanted in the existing tunnel lining, and the other end is connected to the L-shaped steel plate.

[0017] Furthermore, the longitudinal section of the L-shaped steel plate is an inverted L-shape, and the space enclosed by the L-shaped steel plate faces the steel arch frame. Its horizontal plate covers the outer wall of the steel arch frame and fits tightly with the existing tunnel lining wall; its vertical plate fits with the side wall of the steel arch frame.

[0018] Furthermore, a steel cage is covered outside the corrugated steel plate, and the front and rear ends of the steel cage are respectively connected to the steel arch frames at the corresponding ends.

[0019] Furthermore, a concrete base is cast in the tunnel and attached to the arch foot of each L-shaped steel plate or steel arch frame. The concrete base is also connected to the existing tunnel lining in turn through connecting steel bars.

[0020] The present invention also discloses a construction method of the above-mentioned existing tunnel prestressed lining reinforcement structure, comprising the following steps:

[0021] Step S1: Skeleton assembly:

[0022] Assemble the steel arch frame, cover the L-shaped steel plate on the steel arch frame; connect the two ends of the steel cage with the steel arch frame;

[0023] The two ends of the corrugated pipe are passed through two sets of L-shaped steel plates and steel arch frames respectively, and connected with the L-shaped steel plates and steel arch frames; an anchor ring is fixedly connected to the two passing ends of each corrugated pipe;

[0024] The steel strands are coaxially inserted into each corrugated tube, and the two ends of the steel strands are respectively passed through the corresponding ends of the cable holes, and a fixing clamp is set on the passing end of each steel strand;

[0025] Step S2: concrete pouring:

[0026] Corrugated steel plates are installed on the steel cage, and the corrugated steel plates, two sets of L-shaped steel plates at both ends and the steel arch frames, as well as the existing tunnel lining, form a closed space;

[0027] pouring concrete into the enclosed space through the corrugated steel plate casting holes on the corrugated steel plate;

[0028] Step S3, applying prestress:

[0029] After the concrete strength reaches the first design strength, the steel strands are tensioned at both ends and released after tensioning. The steel strands drive the clamps to insert into the cable holes. After being locked with the anchor rings, the bellows are grout-injected through the grouting holes to seal them. After grouting and sealing, the cover box is put on the anchor ring and sealed.

[0030] Step S4: Fixing the bushing unit:

[0031] One end of the lining connection steel bar with a hook is implanted into the existing tunnel lining, and the other end is fixed to the L-shaped steel plate.

[0032] The beneficial effects of the present invention are: 1. Prestress is applied to the lining unit after concrete pouring by prestressed cables, which can offset the tensile stress caused by the bending of the lining unit, greatly improving the bending and tensile resistance of the lining unit. 2. The lining unit serves as a supporting structure and also as a concrete pouring template. There is no need to remove the template after concrete pouring, which increases construction efficiency. 3. The lining unit is modular and flexible in repair and reinforcement. It can be used to reinforce local areas of cracks and water leakage in existing tunnels, or it can be used in all areas of the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the overall structure of the bushing unit;

[0034] Figure 2 It is an exploded schematic diagram of the bushing unit;

[0035] Figure 3 A schematic diagram of installing the sleeve lining unit of the present invention in an existing tunnel;

[0036] Figure 4 for Figure 1 A local structure enlarged exploded diagram;

[0037] Figure 5 It is a schematic diagram of the decomposition of the prestressed cable structure;

[0038] Figure 6 This is a schematic diagram of the steel arch structure;

[0039] Figure 7 It is a schematic diagram of the corrugated steel plate structure;

[0040] Figure 8 for Figure 1 The enlarged exploded diagram of the local structure of the steel cage at B in the middle;

[0041] Among them: 1. Lining connecting steel bars; 2. L-shaped steel plate; 3. Steel arch frame; 4. Corrugated steel plate; 5. Prestressed cable; 6. Steel cage; 7. Existing tunnel lining; 31. Arch section; 32. Arch waist section; 33. Side wall section; 34. Connecting steel plate; 41. Corrugated steel plate recessed ring; 42. Corrugated steel plate raised ring; 43. Corrugated steel plate casting hole; 51. Cover box; 52. Steel strand; 53. Clamp; 54. Anchor ring; 541. Grouting hole; 542. Cable hole; 55. Corrugated pipe; 61. Annular steel bars; 62. Longitudinal steel bars; 63. Stirrups. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The present invention discloses a prestressed lining reinforcement structure for an existing tunnel, such as Figure 1 and 2 As shown, it includes one or more lining units arranged in sequence along the length direction of the tunnel, each lining unit includes two L-shaped steel plates 2, two steel arch frames 3, corrugated steel plates 4 and multiple prestressed cables 5, and the length of each lining unit is not more than 4m, wherein:

[0044] The corrugated steel plate 4 is arc-shaped and consistent with the shape of the tunnel chamber; it is used to be arranged in the tunnel chamber, and there is a space between it and the existing tunnel lining 7;

[0045] like Figure 3 As shown, the L-shaped steel plate 2 and the steel arch frame 3 are both arc-shaped, which are consistent with the shape of the tunnel chamber, that is, consistent with the shape of the existing tunnel lining 7; one L-shaped steel plate 2 and one steel arch frame 3 form a group, and the two groups of L-shaped steel plates 2 and steel arch frames 3 are respectively located at the front and rear ends of the corrugated steel plate 4, and in each group of L-shaped steel plates 2 and steel arch frames 3, the steel arch frame 3 is located close to the corrugated steel plate 4; the outer wall of the L-shaped steel plate 2 is tightly fitted to the existing tunnel lining 7, and a closed space is enclosed between the two existing tunnel linings 7; the closed space is used for pouring concrete; the steel arch frame 3 plays a supporting role; on the side wall of each L-shaped steel plate 2, a plurality of first circular holes are provided at intervals around it.

[0046] Each prestressed cable 5 is connected to two groups of L-shaped steel plates 2 and steel arch frames 3, and a plurality of prestressed cables 5 are arranged around the L-shaped steel plates 2 and the steel arch frames 3 at intervals; each prestressed cable 5 is used to provide prestress to the concrete.

[0047] like Figure 4 and 5 As shown, each prestressed cable 5 includes a bellows 55 and two anchor rings 54. Each anchor ring 54 is cylindrical. The two anchor rings 54 are horizontally arranged and are respectively welded and fixed to the L-shaped steel plates 2 at both ends.

[0048] The bellows 55 is a hollow tube, and its two ends pass through the two groups of L-shaped steel plates 2 and the steel arch frame 3. Specifically, its two ends pass through the first and second circular holes at corresponding positions and are connected to the L-shaped steel plates 2 and the steel arch frame 3. Anchor rings 54 are connected to the two ends of the bellows 55 passing through the L-shaped steel plates 2 and the steel arch frame 3. Each anchor ring 54 is welded to the side wall of the corresponding L-shaped steel plate 2.

[0049] A grouting hole 541 and a plurality of cable holes 542 are provided in each anchor ring 54 and in the radial space of the bellows 55. The grouting hole 541 and the cable holes 542 are arranged along the axial direction of the anchor ring 54, and axially penetrate the anchor ring 54 to be connected with the bellows 55. The positions of the cable holes 542 on the two anchor rings 54 correspond to each other. The grouting hole 541 is used for pouring cement slurry into the bellows 55. As a specific embodiment, four cable holes 542 can be provided.

[0050] A plurality of steel strands 52 are coaxially sleeved in the bellows 55. The number of the steel strands 52 is the same as the number of the cable holes 542 on one anchor ring 54. The two ends of each steel strand 52 pass through two cable holes 542 at corresponding positions. The steel strands 52 are seven-wire galvanized steel strands. The bellows 55 is arranged in a corrugated shape to increase its contact area with concrete.

[0051] When the strength of the concrete in the closed space reaches the first design strength, the steel strands 52 are tensioned axially and toward both ends and released after tensioning, so as to provide pre-stress to the concrete, prevent the concrete from cracking, and enhance the bending and compression resistance of the concrete.

[0052] Cement slurry is poured in the corrugated pipe 55, and the cement slurry covers the steel strands 52 and solidifies, thereby preventing the steel strands 52 from being corroded in the hollow space and ensuring that the stress thereof does not decrease.

[0053] Both ends of each steel strand 52 are coaxially sleeved with a clamp 53, each clamp 53 is a truncated cone-shaped shell, and the small end faces the anchor ring 54, the diameter of the small end of each clamp 53 is smaller than the diameter of the cable hole 542, and the diameter of the large end is larger than the diameter of the cable hole 542; after the steel strand 52 is released, the small end of the clamp 53 is inserted into and fixed in the corresponding cable hole 542, so as to fix each steel strand 52.

[0054] A cover box 51 is sleeved and fixedly connected on each anchor ring 54 . The cover box 51 is used to cover the end of each steel strand 52 and the clamp 53 . The cover box 51 and the anchor ring 54 are welded and sealed.

[0055] Since the steel arch frame 3 is heavy, it is composed of multiple sections for easy transportation and installation, such as Figure 6 As shown, it includes an arch section 31, which is located at the top of the tunnel chamber. An arch waist section 32 is connected to the left and right of the arch section 31, and the ends of each arch waist section 32 are connected to a side wall section 33. Each adjacent segment is fixed by a connecting steel plate 34. The connecting steel plate 34 is a long plate body, and there are multiple connecting steel plates 34. Two connecting steel plates 34 are used between each adjacent segment, which are respectively located in front and behind the steel arch frame 3, and the two ends of each connecting steel plate 34 are respectively welded to connect two adjacent segments.

[0056] A plurality of second circular holes are provided on the web of the steel arch frame 3 and are spaced apart along the circumferential direction, and the positions of the second circular holes correspond to the positions of the first circular holes. The first and second circular holes are used to insert the corrugated pipe 55 .

[0057] like Figure 7 As shown, the corrugated steel plate 4 is a 50 mm thick glass wool composite plate, and has an interval concave-convex structure along the length direction of the tunnel, that is, the corrugated steel plate concave rings 41 and the corrugated steel plate convex rings 42 are arranged at intervals, and a corrugated steel plate casting hole 43 is opened on each corrugated steel plate concave ring 41 and located at the arch.

[0058] like Figure 8As shown, a steel cage 6 is covered on the outside of the corrugated steel plate 4, and the front and rear ends of the steel cage 6 extend to the steel arch frame 3 and are welded to the steel arch frame 3. The steel cage 6 includes staggered longitudinal steel bars 62 and annular steel bars 61, and the longitudinal steel bars 62 run along the length of the tunnel. Stirrups 63 are arranged at the connection between the longitudinal steel bars 62 and the annular steel bars 61, and between two annular steel bars 61 in the same group, to enhance the firmness and strength of the steel cage 6. The longitudinal steel bars 62 and the annular steel bars 61 are connected by binding.

[0059] The L-shaped steel plate 2 and the existing tunnel lining 7 are connected with a plurality of lining connecting steel bars 1, which are arranged at intervals around the L-shaped steel plate 2. Each lining connecting steel bar 1 includes a vertical section, one end of which is in the shape of a chamfered hook; the bending angle of the chamfer is 45°; wherein, the chamfered hook end is implanted in the existing tunnel lining 7, and the other end is connected to the L-shaped steel plate 2.

[0060] The longitudinal section of the L-shaped steel plate 2 is in an inverted L shape, and the space enclosed by the L-shaped steel plate 2 faces the steel arch frame 3. Its horizontal plate covers the outer wall of the steel arch frame 3 and fits tightly with the wall surface of the existing tunnel lining 7; its vertical plate fits with the side wall of the steel arch frame 3.

[0061] A steel cage 6 is covered on the outside of the corrugated steel plate 4 , and the front and rear ends of the steel cage 6 are respectively connected to the corresponding ends of the steel arch frame 3 .

[0062] In the tunnel, a concrete foundation is cast at the arch foot of each L-shaped steel plate 2 or steel arch frame 3, and the concrete foundation is also connected to the existing tunnel lining 7 in sequence through connecting steel bars.

[0063] In some preferred embodiments, a locking anchor rod may be provided at the arch foot position of the L-shaped steel plate 2 or the steel arch frame 3, one end of the locking anchor rod passes through the existing tunnel lining and is inserted into the rock and soil, and the other end is welded to the L-shaped steel plate 2 or the steel arch frame 3.

[0064] The present invention also discloses a construction method of the above-mentioned existing tunnel prestressed lining reinforcement structure, comprising the following steps:

[0065] Step S1: Skeleton assembly:

[0066] Assemble the steel arch frame 3, cover the L-shaped steel plate 2 on the steel arch frame 3; connect the two ends of the steel cage 6 to the steel arch frame 3;

[0067] The two ends of the bellows 55 are passed through the two sets of L-shaped steel plates 2 and the steel arch frame 3 respectively, and connected with the L-shaped steel plates 2 and the steel arch frame 3; an anchor ring 54 is fixedly connected to the two passing ends of each bellows 55;

[0068] The steel strand 52 is coaxially inserted into each corrugated tube 55, and the two ends of the steel strand 52 are respectively passed through the corresponding end through the cable holes 542, and a fixing clamp 53 is set on the passing end of each steel strand 52;

[0069] Step S2: concrete pouring:

[0070] A corrugated steel plate 4 is installed on the steel cage 6, and the corrugated steel plate 4, two groups of L-shaped steel plates 2 at both ends and the steel arch frame 3, and the existing tunnel lining 7 are enclosed to form a closed space;

[0071] Pouring concrete into the enclosed space through the grouting holes on the corrugated steel plate 4;

[0072] Step S3, applying prestress:

[0073] After the concrete strength reaches the first design strength, the steel strand 52 is tensioned at both ends and released after tensioning. The steel strand 52 drives the clamp 53 to insert into the cable hole 542. After being locked with the anchor ring 54, the bellows 55 is grout-injected through the grouting hole 541 to seal it. After the grouting is sealed, the cover box 51 is put on the anchor ring 54 and sealed to realize the prestressing process. The size of the prestress is determined by the design. If the exposed length of the steel strand 52 passing through the cable hole 542 is too long, it can be shortened to facilitate the cover box 51 to be put on the anchor ring 54. The first design strength is 70% of the final design strength.

[0074] Step S4: Fixing the bushing unit:

[0075] One end of the lining connecting steel bar 1 with a hook is implanted into the existing tunnel lining 7, and the other end is welded and fixed to the L-shaped steel plate 2.

Claims

1. An existing tunnel prestressed lining reinforcement structure, characterized in that: It comprises one or more lining units arranged in sequence along the length direction of the tunnel, each of the lining units comprising two L-shaped steel plates (2), two steel arch frames (3), a corrugated steel plate (4) and a plurality of prestressed cables (5); wherein: The corrugated steel plate (4) is arc-shaped and consistent with the shape of the tunnel chamber; it is used to be arranged in the tunnel chamber; The L-shaped steel plate (2) and the steel arch frame (3) are both arc-shaped, consistent with the shape of the tunnel chamber; one L-shaped steel plate (2) and one steel arch frame (3) form a group; two groups of L-shaped steel plates (2) and steel arch frames (3) are respectively located at the front and rear ends of the corrugated steel plate (4); in each group of L-shaped steel plates (2) and steel arch frames (3), the steel arch frame (3) is located close to the corrugated steel plate (4); the outer wall of the L-shaped steel plate (2) is tightly fitted to the existing tunnel lining (7), and a closed space is enclosed between the two existing tunnel linings (7); the closed space is used for pouring concrete; Each of the prestressed cables (5) is connected to two groups of the L-shaped steel plates (2) and the steel arch frames (3), and a plurality of the prestressed cables (5) are arranged at intervals around the L-shaped steel plates (2) and the steel arch frames (3); each of the prestressed cables (5) is used to provide prestress to the concrete.

2. The existing tunnel prestressed lining reinforcement structure according to claim 1, characterized in that: Each of the prestressed cables (5) comprises a corrugated tube (55) and two anchor rings (54), each of the anchor rings (54) is cylindrical, and the two anchor rings (54) are arranged horizontally and are respectively fixed on the L-shaped steel plates (2) at both ends; The bellows (55) is a hollow tube, and its two ends pass through the two groups of L-shaped steel plates (2) and the steel arch frame (3) and are connected to each other; the two ends of the bellows (55) are connected to the anchor ring (54); A grouting hole (541) and a plurality of cable holes (542) are provided in each anchor ring (54) and in the radial space of the corrugated pipe (55); the grouting hole (541) and each of the cable holes (542) are arranged along the axial direction of the anchor ring (54), and axially penetrate the anchor ring (54) and are connected to the corrugated pipe (55); the positions of the cable holes (542) on the two anchor rings (54) correspond to each other; the grouting hole (541) is used to pour cement slurry into the corrugated pipe (55); A plurality of steel strands (52) are coaxially sleeved in the corrugated tube (55), the number of the steel strands (52) being the same as the number of the cable holes (542) on one anchor ring (54), and the two ends of each steel strand (52) passing through two cable holes (542) at corresponding positions; the length of the steel strand (52) is greater than the length of the sleeve unit. When the strength of the concrete in the closed space reaches a first design strength, the steel strand (52) is tensioned axially and toward both ends, and is released after tensioning to provide pre-pressure to the concrete.

3. The existing tunnel prestressed lining reinforcement structure according to claim 2, characterized in that: Both ends of each of the steel strands (52) are coaxially sleeved with a clamp (53), each of the clamps (53) is a truncated cone-shaped shell, and the small end faces the anchor ring (54), the diameter of the small end of each of the clamps (53) is smaller than the diameter of the cable hole (542), and the diameter of the large end is larger than the diameter of the cable hole (542); after the steel strands (52) are released, the small end of the clamp (53) is inserted into and fixed in the corresponding cable hole (542) to fix each of the steel strands (52).

4. The existing tunnel prestressed lining reinforcement structure according to claim 1, characterized in that: A cover box (51) is sleeved and fixedly connected on each anchor ring (54), and the cover box (51) is used to cover the end of each steel strand (52) and the clamp (53).

5. The existing tunnel prestressed lining reinforcement structure according to claim 1, characterized in that: The L-shaped steel plate (2) and the existing tunnel lining (7) are connected by a plurality of lining connecting steel bars (1), the plurality of lining connecting steel bars (1) are arranged at intervals around the L-shaped steel plate (2), each of the lining connecting steel bars (1) comprises a vertical section, one end of the vertical section is in the shape of a chamfered hook; wherein the chamfered hook end is embedded in the existing tunnel lining (7), and the other end is connected to the L-shaped steel plate (2).

6. The existing tunnel prestressed lining reinforcement structure according to claim 1, characterized in that: The longitudinal section of the L-shaped steel plate (2) is in an inverted L shape, and the space enclosed by the L-shaped steel plate (2) faces the steel arch frame (3), and its horizontal plate covers the outer wall of the steel arch frame (3) and is tightly fitted with the wall surface of the existing tunnel lining (7); and its vertical plate is fitted with the side wall of the steel arch frame (3).

7. The existing tunnel prestressed lining reinforcement structure according to claim 6, characterized in that: A steel cage (6) is covered on the outside of the corrugated steel plate (4), and the front and rear ends of the steel cage (6) are respectively connected to the steel arch frame (3) at the corresponding ends.

8. The existing tunnel prestressed lining reinforcement structure according to claim 7, characterized in that: A concrete base is cast in the tunnel and attached to the arch foot of each L-shaped steel plate (2) or steel arch frame (3). The concrete base is also connected to the existing tunnel lining (7) in sequence through connecting steel bars.

9. A construction method for reinforcing an existing tunnel prestressed lining structure according to any one of claims 1 to 8, characterized in that: The steps include: Step S1: Skeleton assembly: Assembling the steel arch frame (3), covering the L-shaped steel plate (2) on the steel arch frame (3); connecting the two ends of the steel cage (6) to the steel arch frame (3); The two ends of the bellows (55) are passed through two groups of L-shaped steel plates (2) and steel arch frames (3) respectively and connected to the L-shaped steel plates (2) and steel arch frames (3); an anchor ring (54) is fixedly connected to the two passing ends of each bellows (55); The steel strands (52) are coaxially inserted into each corrugated tube (55), and the two ends of the steel strands (52) are respectively passed through the corresponding end through holes (542), and a fixing fixture (53) is set on the passing end of each steel strand (52); Step S2: concrete pouring: A corrugated steel plate (4) is installed on the steel cage (6), and a closed space is formed between the corrugated steel plate (4), the two groups of L-shaped steel plates (2) and the steel arch frame (3) at both ends, and the existing tunnel lining (7); pouring concrete into the enclosed space through the corrugated steel plate pouring holes (43) on the corrugated steel plate (4); Step S3, applying prestress: After the concrete strength reaches the first design strength, the steel strands (52) are tensioned at both ends and released after tensioning, and the steel strands (52) drive the clamps (53) to be inserted into the cable holes (542). After being locked with the anchor ring 54, the corrugated pipe (55) is grout-injected through the grouting holes (541) to seal it. After grouting and sealing, the cover box (51) is put on the anchor ring (54) and sealed; Step S4: Fixing the bushing unit: One end of the lining connecting steel bar (1) with a hook is implanted into the existing tunnel lining (7), and the other end is fixed to the L-shaped steel plate (2).

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