A prestressed sleeve lining reinforcing structure for an existing tunnel and a construction method thereof

Abstract

The application discloses a kind of existing tunnel prestressed sleeve lining reinforcing structure and construction method, including one or more along the length direction of tunnel sequentially arranged sleeve lining unit, each sleeve lining unit includes two L-shaped steel plates, two steel arches, corrugated steel plate and multiple prestressed cables;Wherein: corrugated steel plate is arc, for setting in tunnel chamber;L-shaped steel plate and steel arch are arc, one L-shaped steel plate and one steel arch are a group;L-shaped steel plate outer wall is closely attached to existing tunnel lining, enclosed space is enclosed between two existing tunnel linings;Each prestressed cable is connected with two groups of L-shaped steel plate and steel arch, and multiple prestressed cables are arranged at intervals around L-shaped steel plate and steel arch;Each prestressed cable is used to provide pre-pressure to concrete.Prestressed cable is used to apply prestress, and sleeve lining unit is stronger in bending and tensile resistance;And after concrete pouring, formwork does not need to be dismantled, and construction efficiency is higher.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tunnel repair and reinforcement, and particularly relates to a prestressed lining reinforcement structure for an existing tunnel and a construction method. BACKGROUND

[0002] A tunnel lining is a reinforced concrete structure arranged along the length of the tunnel to prevent deformation of the rock and soil. However, due to complex geological environment, poor construction quality, aging of material properties and other reasons, after the tunnel is put into use, problems such as lining water seepage and spalling often occur, which seriously affects 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 a layer of lining on the basis of an existing tunnel is a common tunnel repair and reinforcement strategy. However, due to the need to meet the traffic demand, the window period for tunnel repair and reinforcement construction is extremely short. The traditional reinforced concrete construction is complicated due to steel bar binding, formwork pouring and formwork dismantling, involves the in-and-out of multiple materials and equipment, has low construction efficiency and affects the tunnel passing function. At the same time, the ordinary reinforced concrete has low strength, and it is difficult to ensure that the newly constructed lining will not crack, spall and seep water again. SUMMARY

[0004] The purpose of the present application is to provide a prestressed lining reinforcement structure for an existing tunnel and a construction method, which uses prestressed cables to apply prestress, and the lining unit has stronger bending and tensile resistance, and does not need to be removed after concrete pouring, thereby having higher construction efficiency.

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

[0006] The corrugated steel plate is in the shape of a circular arc and consistent with the shape of the tunnel chamber, and is arranged in the tunnel chamber;

[0007] The L-shaped steel plate and the steel arch are in the shape of a circular arc and consistent with the shape of the tunnel chamber, one L-shaped steel plate and one steel arch form a group, and two groups of L-shaped steel plates and steel arches are located at the front and rear ends of the corrugated steel plate, and in each group of L-shaped steel plates and steel arches, the steel arch is located close to the corrugated steel plate side; the outer wall of the L-shaped steel plate is tightly attached to the existing tunnel lining, and an enclosed space is formed between the two existing tunnel linings; the enclosed space is used for pouring concrete;

[0008] Each prestressed cable is connected with the two groups of L-shaped steel plates and steel arches, and a plurality of prestressed cables are arranged at intervals around the L-shaped steel plate and the steel arch; each prestressed cable is used to provide pre-pressure to the concrete.

[0009] Further, the prestressed cable comprises a corrugated pipe and two anchor rings, each of which is cylindrical, and both of which are horizontally arranged and fixed to the L-shaped steel plates at both ends;

[0010] The corrugated pipe is a hollow pipe, the two ends of which pass through the two groups of L-shaped steel plates and the steel arch, and are connected; the two ends of the corrugated pipe are connected with the anchor rings;

[0011] In each anchor ring and in the radial space of the corrugated pipe, a grouting hole and a plurality of cable passing holes are arranged, the grouting hole and each cable passing hole are arranged along the axial direction of the anchor ring and axially penetrate the anchor ring to communicate with the corrugated pipe; the positions of the cable passing holes on the two anchor rings correspond to each other; the grouting hole is used for pouring cement slurry into the corrugated pipe;

[0012] A plurality of steel strands are coaxially sleeved in the corrugated pipe, the number of the steel strands is the same as the number of the cable passing holes on one anchor ring, and the two ends of each steel strand pass out of the two cable passing holes at the 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 along the axial direction and towards both ends, and are released after tensioning, to provide pre-pressure to the concrete.

[0014] Further, the two ends of each steel strand are coaxially sleeved with a clamp, each clamp is a circular truncated cone shell, and the small end is directed towards the anchor ring, the diameter of the small end of each clamp is smaller than the diameter of the cable passing hole, and the diameter of the large end is greater than the diameter of the cable passing hole; after the steel strand is released, the small end of the clamp is inserted into and fixed in the corresponding cable passing hole, to fix the steel strand.

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

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

[0017] Further, the longitudinal section of the L-shaped steel plate is inverted L-shaped, and the enclosed space of the L-shaped steel plate is directed towards the steel arch, the horizontal plate of the L-shaped steel plate covers the outer wall of the steel arch, and is closely attached to the wall surface of the existing tunnel lining; the vertical plate is attached to the side wall of the steel arch.

[0018] Further, a steel reinforcement cage is covered outside the corrugated steel plate, the front and rear ends of the steel reinforcement cage are respectively connected with the corresponding end of the steel arch.

[0019] Further, in the tunnel hole, and adhere to each L-shaped steel plate or steel arch foot arching concrete pedestal, concrete pedestal is also connected with the existing tunnel lining through the connecting steel bar in turn.

[0020] The application further discloses a construction method of the existing tunnel prestressed sleeve lining reinforcing structure.

[0021] Step S1, skeleton assembly:

[0022] The steel reinforcement cage is assembled, and the two ends of the steel reinforcement cage are connected with the steel arch.

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

[0024] The steel strand is coaxially sleeved into each corrugated pipe, and the two ends of the steel strand are respectively passed out of the corresponding end passing hole; a fixed clamp is sleeved on the passing-out end of each steel strand.

[0025] Step S2, concrete pouring:

[0026] The corrugated steel plate is installed on the steel reinforcement cage, the corrugated steel plate, the two groups of L-shaped steel plates at the two ends and the steel arch and the existing tunnel lining form an enclosed space.

[0027] The concrete is poured into the enclosed space through the corrugated steel plate pouring hole on the corrugated steel plate.

[0028] Step S3, prestress application:

[0029] After the concrete strength reaches the first design strength, the steel strand at the two ends is tensioned, and after tensioning, the steel strand drives the clamp to be inserted into the passing hole and is locked with the anchor ring, then grouting is performed on the corrugated pipe through the grouting hole to be closed, and after grouting and closing, the cover box is sleeved on the anchor ring and is sealed.

[0030] Step S4, sleeve lining unit fixing:

[0031] The lining connecting steel bar is planted in the existing tunnel lining with the hook end of the lining connecting steel bar being fixed to the L-shaped steel plate.

[0032] The application has the following beneficial effects: 1. The prestressed cable is used to apply pre-pressure to the sleeve lining unit after pouring the concrete, so that the tensile stress generated by the bending of the sleeve lining unit is offset, and the bending and tensile resistance of the sleeve lining unit is greatly improved. 2. The sleeve lining unit serves as a supporting structure and a concrete pouring formwork, and after pouring the concrete, the formwork does not need to be removed, and the construction efficiency is higher. 3. The sleeve lining unit is modularized, and is flexible in repair and reinforcement, that is, the sleeve lining unit can be used for reinforcement in a local area of the existing tunnel where cracks and water leakage occur, or can be used in the whole area of the tunnel. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The overall structure of the lining unit is shown in the figure;

[0034] Figure 2 The exploded view of the lining unit is shown in the figure;

[0035] Figure 3 The figure shows the lining unit of the present application installed in an existing tunnel;

[0036] Figure 4 The figure shows Figure 1 The figure shows the enlarged exploded view of the local structure at A;

[0037] Figure 5 The figure shows the exploded view of the prestressed cable structure;

[0038] Figure 6 The figure shows the profiled steel arch structure;

[0039] Figure 7 The figure shows the corrugated steel plate structure;

[0040] Figure 8 The figure shows Figure 1 The figure shows the enlarged exploded view of the local structure of the steel reinforcement cage at B;

[0041] 1, lining connecting steel; 2, L-shaped steel plate; 3, profiled steel arch; 4, corrugated steel plate; 5, prestressed cable; 6, steel reinforcement cage; 7, existing tunnel lining; 31, vault section; 32, haunch section; 33, sidewall section; 34, connecting steel plate; 41, corrugated steel plate concave ring; 42, corrugated steel plate convex ring; 43, corrugated steel plate pouring hole; 51, cover box; 52, steel strand; 53, clamp; 54, anchor ring; 541, grouting hole; 542, cable passing hole; 55, corrugated pipe; 61, ring steel; 62, longitudinal steel; 63, stirrup. DETAILED DESCRIPTION

[0042] The present application will be described in detail below in conjunction with the drawings and specific embodiments.

[0043] The present application discloses a prestressed lining reinforcement structure for an existing tunnel, as shown in Figure 1 and 2 , which comprises one or more lining units arranged sequentially along the length direction of the tunnel, each lining unit comprising two L-shaped steel plates 2, two profiled steel arches 3, a corrugated steel plate 4, and a plurality of prestressed cables 5, and the length of each lining unit is not greater than 4m, wherein:

[0044] The corrugated steel plate 4 is in the shape of a circular arc and consistent with the shape of the tunnel chamber; it is arranged in the tunnel chamber and has a space with the existing tunnel lining 7;

[0045] AsFigure 3 As shown, the L-shaped steel plates 2 and the steel arches 3 are in the shape of a circular arc, which is 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 3 form a group, and two groups of L-shaped steel plates 2 and steel arches 3 are 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 arches 3, the steel arch 3 is located close to the side of the corrugated steel plate 4; the outer wall of the L-shaped steel plate 2 is closely attached to the existing tunnel lining 7, and the two existing tunnel linings 7 are enclosed to form a closed space; the closed space is used for pouring concrete; the steel arch 3 plays a supporting role; a plurality of first circular holes are provided on the side wall of each L-shaped steel plate 2 and are spaced apart around the L-shaped steel plate 2.

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

[0047] As shown in Figure 4 and 5 Each prestressed cable 5 includes a corrugated pipe 55 and two anchor rings 54, each anchor ring 54 is in the shape of a cylinder, and the two anchor rings 54 are horizontally arranged and respectively welded and fixed to the L-shaped steel plates 2 at both ends;

[0048] The corrugated pipe 55 is a hollow pipe, and its two ends pass through the two groups of L-shaped steel plates 2 and steel arches 3, specifically, its two ends pass through the first circular hole and the second circular hole at the corresponding positions and are connected to the L-shaped steel plate 2 and the steel arch 3; the two ends of the corrugated pipe 55 passing through the L-shaped steel plate 2 and the steel arch 3 are connected to the anchor ring 54. Each anchor ring 54 is welded to the side wall of the corresponding L-shaped steel plate 2.

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

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

[0051] When the strength of the concrete in the enclosed space reaches the first design strength, the steel strands 52 are tensioned in the axial direction and towards both ends and released after tensioning, for providing pre-pressure to the concrete, preventing the concrete from cracking and enhancing the performance of the concrete against bending and compression.

[0052] The cement slurry is cast in the bellows 55, the cement slurry coats the steel strands 52 and solidifies, preventing the steel strands 52 from being corroded in the hollow space and ensuring that the stress thereof does not decrease.

[0053] The two ends of each steel strand 52 are coaxially sleeved with a clamp 53, each clamp 53 is a circular truncated cone shell, and the small end is towards the anchor ring 54, the diameter of the small end of each clamp 53 is smaller than the diameter of the rope hole 542, and the diameter of the large end is larger than the diameter of the rope hole 542; after the steel strand 52 is released, the small end of the clamp 53 is inserted into and fixed in the corresponding rope hole 542, for fixing each steel strand 52.

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

[0055] Since the steel arch 3 is heavy, it is composed of multiple segments for the convenience of transportation and installation, as shown in Figure 6 The arch top segment 31 is located at the top of the tunnel chamber, and each arch waist segment 32 is connected to the left and right of the arch top segment 31, and each arch waist segment 32 is connected to the end of each side wall segment 33, and each adjacent segment is fixed by the connecting steel plate 34. The connecting steel plate 34 is a long strip plate body, and there are multiple connecting steel plates 34, two connecting steel plates 34 are used between each adjacent segment and are located at the front and rear of the steel arch 3, and the two ends of each connecting steel plate 34 are welded to connect the adjacent two segments.

[0056] A plurality of second circular holes are arranged on the web of the steel arch 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 circular holes and the second circular holes are used for penetrating the bellows 55.

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

[0058] As shown in Figure 8As shown, the corrugated steel plate 4 is covered with a steel cage 6, and the front and rear ends of the steel cage 6 extend to the steel arch 3 and are welded to the steel arch 3. The steel cage 6 comprises longitudinally arranged longitudinal steel bars 62 and annular steel bars 61, and 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, a stirrup 63 is arranged for enhancing 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 is connected with a plurality of lining connecting steel bars 1, the plurality of lining connecting steel bars 1 are arranged around the L-shaped steel plate 2 at intervals, each lining connecting steel bar 1 comprises a vertical section, one end of the vertical section is 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 with the L-shaped steel plate 2.

[0060] The longitudinal section of the L-shaped steel plate 2 is inverted L-shaped, and the enclosed space of the L-shaped steel plate 2 faces the steel arch 3, the horizontal plate of the L-shaped steel plate 2 covers the outer wall of the steel arch 3, and is closely attached to the wall of the existing tunnel lining 7; the vertical plate of the L-shaped steel plate 2 is attached to the side wall of the steel arch 3.

[0061] The corrugated steel plate 4 is covered with a steel cage 6, and the front and rear ends of the steel cage 6 are connected with the corresponding end of the steel arch 3.

[0062] In the tunnel hole, and the concrete base is poured at the arch foot of each L-shaped steel plate 2 or steel arch 3, and the concrete base is connected with the existing tunnel lining 7 in sequence through the connecting steel bars.

[0063] In some preferred modes, a lock foot anchor rod can be arranged at the arch foot position of the L-shaped steel plate 2 or the steel arch 3, one end of the lock foot anchor rod penetrates the existing tunnel lining and is inserted into the rock-soil body, and the other end is welded with the L-shaped steel plate 2 or the steel arch 3.

[0064] The application also discloses a construction method of the existing tunnel prestressed sleeve lining reinforcing structure.

[0065] Step S1, skeleton assembly:

[0066] Assembling the steel arch 3, covering the L-shaped steel plate 2 on the steel arch 3, and connecting the two ends of the steel cage 6 with the steel arch 3;

[0067] The two ends of the corrugated pipe 55 are respectively penetrated through the two groups of L-shaped steel plates 2 and the steel arch 3, and are connected with the L-shaped steel plate 2 and the steel arch 3; an anchor ring 54 is fixedly connected to each of the two penetrating ends of the corrugated pipe 55;

[0068] The steel strand 52 is coaxially sleeved into each corrugated pipe 55, and the two ends of the steel strand 52 are respectively sleeved out of the corresponding end of the through hole 542, and the fixed clamp 53 is sleeved at the through-out end of each steel strand 52;

[0069] Step S2, concrete pouring:

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

[0071] The concrete is poured into the closed space through the grouting hole on the corrugated steel plate 4;

[0072] Step S3, prestress application:

[0073] After the concrete strength reaches the first design strength, the steel strand 52 at both ends is tensioned, and after tensioning, the steel strand 52 drives the clamp 53 to be inserted into the through hole 542, and after being locked with the anchor ring 54, the grouting hole 541 is used to grout and close the corrugated pipe 55, and after grouting and closing, the cover box 51 is sleeved on the anchor ring 54 and sealed, realizing the prestress application process. The size of the prestress is determined by the design. If the exposed length of the steel strand 52 passing through the through hole 542 is too long, it can be cut short to facilitate the cover box 51 to be sleeved on the anchor ring 54. The first design strength is 70% of the final design strength.

[0074] Step S4, sleeve lining unit fixation:

[0075] The lining connecting steel bar 1 is planted in the existing tunnel lining 7 with a hook at one end, and the other end is welded and fixed with the L-shaped steel plate 2.

Claims

1. A prestressed lining reinforcement structure for existing tunnels, characterized in that, It includes one or more lining units arranged sequentially along the tunnel length direction, each lining unit comprising two L-shaped steel plates (2), two steel arch frames (3), a corrugated steel plate (4), and multiple prestressed cables (5); wherein: The corrugated steel plate (4) is arc-shaped and conforms to the shape of the tunnel chamber; it is used to be installed inside 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 located at the front and rear ends of the corrugated steel plate (4), respectively. In each group of L-shaped steel plates (2) and steel arch frames (3), the steel arch frame (3) is located on the side close to the corrugated steel plate (4). The outer wall of the L-shaped steel plate (2) is tightly attached to the existing tunnel lining (7), forming a closed space 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 sets of L-shaped steel plates (2) and steel arch frames (3), and multiple prestressed cables (5) are arranged at intervals around the L-shaped steel plates (2) and steel arch frames (3); each of the prestressed cables (5) is used to provide prestress to the concrete; Each of the prestressed cables (5) includes a corrugated pipe (55) and two anchor rings (54). Each anchor ring (54) is cylindrical. The two anchor rings (54) are horizontally arranged and fixed to the L-shaped steel plates (2) at both ends respectively. The corrugated pipe (55) is a hollow pipe, with its two ends passing through two sets of L-shaped steel plates (2) and steel arch frames (3) and connected to each other; the two ends of the corrugated pipe (55) are connected to anchor rings (54); Grouting holes (541) and multiple cable-passing holes (542) are provided within each anchor ring (54) and within the radial space of the corrugated pipe (55). The grouting holes (541) and each cable-passing hole (542) are arranged along the axial direction of the anchor ring (54) and axially penetrate the anchor ring (54), communicating with the corrugated pipe (55). The cable-passing holes (542) on the two anchor rings (54) are positioned correspondingly. The grouting holes (541) are used to pour cement grout into the corrugated pipe (55). Multiple steel strands (52) are coaxially sleeved inside the corrugated pipe (55). The number of steel strands (52) is the same as the number of cable-passing holes (542) on one of the anchor rings (54). The two ends of each steel strand (52) are passed through two cable-passing holes (542) at corresponding positions. The length of the steel strand (52) is greater than the length of the bushing unit. When the concrete in the enclosed space reaches the first design strength, the steel strand (52) is tensioned axially and toward both ends, and then released after tensioning to provide pre-stress to the concrete.

2. The prestressed lining reinforcement structure for existing tunnels as described in claim 1, characterized in that, Each of the steel strands (52) is coaxially fitted with a clamp (53) at both ends. Each clamp (53) is a frustum-shaped shell with its small end facing the anchor ring (54). The diameter of the small end of each clamp (53) is smaller than the diameter of the cable-passing hole (542), and the diameter of the large end is larger than the diameter of the cable-passing 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-passing hole (542) to fix each steel strand (52).

3. The prestressed lining reinforcement structure for existing tunnels as described in claim 2, characterized in that, A cover box (51) is fixedly connected to each of the anchor rings (54), and the cover box (51) is used to cover the ends of each of the steel strands (52) and the clamps (53).

4. The prestressed lining reinforcement structure for existing tunnels as described in claim 3, 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 lining connecting steel bar (1) includes a vertical section, one end of which is a chamfered hook. The chamfered hook end is inserted into the existing tunnel lining (7), and the other end is connected to the L-shaped steel plate (2).

5. The prestressed lining reinforcement structure for existing tunnels as described in claim 4, characterized in that, The longitudinal section of the L-shaped steel plate (2) is inverted L-shaped, 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 is closely attached to the wall of the existing tunnel lining (7); its vertical plate is attached to the side wall of the steel arch frame (3).

6. The prestressed lining reinforcement structure for existing tunnels as described in claim 5, 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.

7. The prestressed lining reinforcement structure for existing tunnels as described in claim 6, characterized in that, Inside the tunnel, a concrete base is poured at the arch foot of each L-shaped steel plate (2) or steel arch frame (3), and the concrete base is also connected to the existing tunnel lining (7) in sequence by connecting steel bars.

8. A construction method for a prestressed lining reinforcement structure for existing tunnels as described in any one of claims 6-7, characterized in that, Includes the following steps: Step S1, Frame Assembly: Assemble the steel arch frame (3), cover the steel arch frame (3) with the L-shaped steel plate (2); connect the two ends of the steel cage (6) to the steel arch frame (3); The two ends of the corrugated pipe (55) are respectively passed through two sets of L-shaped steel plates (2) and steel arch frame (3) and connected to the L-shaped steel plates (2) and steel arch frame (3); an anchor ring (54) is fixedly connected to each of the two protruding ends of the corrugated pipe (55). The steel strand (52) is coaxially inserted into each corrugated pipe (55), and the two ends of the steel strand (52) are respectively passed out through the corresponding end through the cable hole (542). A fixing clamp (53) is fitted on the end of each steel strand (52). Step S2, Concrete pouring: A corrugated steel plate (4) is installed on the steel cage (6). The corrugated steel plate (4), the two sets of L-shaped steel plates (2) at both ends and the steel arch frame (3), and the existing tunnel lining (7) form a closed space. Concrete is poured into the enclosed space through the corrugated steel plate pouring hole (43) on the corrugated steel plate (4); Step S3: Apply prestress: After the concrete strength reaches the first design strength, the steel strands (52) are tensioned at both ends and released after tensioning. The steel strands (52) drive the clamps (53) to insert into the cable hole (542). After locking with the anchor ring (54), grout is injected into the corrugated pipe (55) through the grouting hole (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: The hooked end of the lining connecting steel bar (1) is inserted into the existing tunnel lining (7), and the other end is fixed to the L-shaped steel plate (2).

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