A method of reinforcing a tunnel lining

Abstract

The present application relates to the technical field of tunnel, and provides a reinforcing method for tunnel lining, which comprises the following steps: obtaining the deterioration detection information of the existing tunnel lining, judging whether the existing tunnel lining needs to be reinforced according to the deterioration detection information, establishing a separate stress simulation model of the existing tunnel lining when the existing tunnel lining needs to be reinforced, extracting the most unfavorable position of the existing tunnel lining according to the separate stress simulation model, determining the lining reinforcing area according to the most unfavorable position, removing the surface failure layer of the lining reinforcing area, installing a steel band on the inner wall of the lining reinforcing area, and pouring an ultra-high performance concrete layer in the lining reinforcing area. The present application can precisely restore the structure bearing capacity through the existing tunnel lining + ultra-high performance concrete layer + steel band collaborative bearing system, effectively repair the defects such as lining cracking and interface peeling, and avoid the safety hazards such as tunnel collapse, water seepage and track / pavement erosion caused by lining failure from the root.

Description

Technical Field

[0001] This application relates to the field of tunnel technology, and in particular to a method for reinforcing tunnel lining. Background Technology

[0002] Early-operation tunnels in my country suffered from long-term service, and the lining concrete was affected by material aging, continuous load, and environmental erosion. This resulted in problems such as strength reduction and structural integrity decline, often accompanied by lining cracks, interface peeling, and other derivative defects, leading to insufficient load-bearing capacity and difficulty in resisting the long-term effects of surrounding rock pressure and water pressure.

[0003] Existing lining reinforcement technologies mostly rely on single materials (such as bonded steel or carbon fiber cloth). While current reinforcement technologies for deteriorated linings in operating tunnels can address individual defects, they lack a systematic and synergistic approach, exhibiting three main shortcomings: First, load and bearing capacity assessments are often crude, relying heavily on empirical estimations of the lining's load without accurately calculating the overall axial compression-bending moment response at the most unfavorable point based on tunnel cross-sectional characteristics. Furthermore, the lining's load-bearing capacity is not verified according to specifications, leading to ambiguous reinforcement goals and frequent instances of over- or under-reinforcement. Second, there is insufficient synergy among core materials. Reinforcement using single bonded steel or ultra-high-performance concrete fails to achieve mechanical division based on the overall stress logic of the bending members and does not reference the mature system of shotcrete bearing pressure and I-beams bearing tension and bending in initial tunnel support. This prevents the formation of a synergistic load-bearing structure, making it difficult to cope with the complex stress state of the lining. Third, there are temporal and spatial conflicts in the measures. Crack repair, waterproofing, and foundation treatment are simply superimposed, failing to break the chain of seepage-cracking-strength decay, resulting in a high recurrence rate after treatment and hindering long-term tunnel safety.

[0004] Therefore, it is necessary to propose a method for reinforcing tunnel linings to solve or at least alleviate the aforementioned defects. Summary of the Invention

[0005] The main objective of this application is to provide a method for reinforcing tunnel linings, in order to solve the technical problem that existing lining deterioration reinforcement schemes rely on traditional experience and are difficult to cope with the complex stress state of the linings.

[0006] To achieve the above objectives, this application provides a method for reinforcing tunnel lining, comprising the following steps:

[0007] S1, Obtain the deterioration detection information of the existing tunnel lining, and determine whether the existing tunnel lining needs to be reinforced based on the deterioration detection information;

[0008] S2, when the existing tunnel lining needs to be reinforced, establish a separate stress simulation model of the existing tunnel lining, and extract the most unfavorable position of the existing tunnel lining based on the separate stress simulation model.

[0009] S3, determine the lining reinforcement area based on the most unfavorable location, and remove the surface failure layer of the lining reinforcement area;

[0010] S4, install steel strips on the inner wall of the lining reinforcement area, and then pour an ultra-high performance concrete layer in the lining reinforcement area.

[0011] Preferably, step S1 specifically includes the following steps:

[0012] Obtain the axial compressive strength test value of the lining concrete of the existing tunnel lining obtained by core drilling method, and calculate the reduction of the axial compressive strength test value relative to the axial compressive strength design value;

[0013] Obtain the number of cracks per meter in the longitudinal direction of the existing tunnel lining, and obtain the proportion of cracks with a width greater than a first preset value for each crack.

[0014] The peeling information of the lining interface of the existing tunnel lining obtained by the ultrasonic rebound combined method is obtained, and the peeling area ratio is obtained based on the peeling information.

[0015] When at least two of the following conditions are met: the decrease is greater than the second preset value, the number of cracks per meter is greater than the third preset value, the proportion of cracks is greater than the fourth preset value, and the proportion of peeling area is greater than the fifth preset value, it is determined that the existing tunnel lining needs to be reinforced.

[0016] Preferably, step S2 specifically includes the following steps:

[0017] S21, when the existing tunnel lining needs to be reinforced, a separate stress simulation model of the existing tunnel lining is established; wherein, the separate stress simulation model is a two-dimensional finite element model, the existing tunnel lining is simulated by beam elements to simulate bending and axial deformation, and the constraint of the surrounding rock on the existing tunnel lining is simulated by elastic spring elements, and the spring stiffness is determined according to the surrounding rock level.

[0018] S22, input the surrounding rock geological parameters, lining structure parameters, and load parameters into the two-dimensional finite element model to obtain the bending moment data and axial compression data of the entire cross-section of the existing tunnel lining; wherein, the surrounding rock geological parameters include the surrounding rock unit weight, the surrounding rock internal friction angle, the surrounding rock cohesion, and the surrounding rock elastic resistance coefficient; the lining structure parameters include the geometric dimensions of the existing tunnel lining and the performance data of the deteriorated tunnel lining material; the load parameters include the vertical surrounding rock pressure, the horizontal surrounding rock pressure, the self-weight of the existing tunnel lining, and the additional operating load;

[0019] S23. Based on the bending moment data and axial compression data of the entire cross section, extract the bending moment and / or axial compression at the most unfavorable position of the existing tunnel lining.

[0020] Preferably, the removal of the surface failure layer in the lining reinforcement area in step S3 specifically includes the following steps:

[0021] Use a pneumatic pick to remove the deteriorated concrete in the lining reinforcement area, controlling the depth to 3-5cm, until fresh concrete aggregate is exposed. After removal, the surface flatness error should be ≤5mm. Then, use a high-pressure water gun to wash the surface of the existing tunnel lining and then use a hot air blower to dry it.

[0022] Preferably, step S4 specifically includes the following steps:

[0023] S41, determine the reinforcement construction parameters for the steel strip and the reinforcement construction parameters for the ultra-high performance concrete layer;

[0024] S42, determine the longitudinal spacing of the steel strip according to the reinforcement construction parameters of the steel strip, and mark the installation position of the steel strip and the anchor bolt hole position along the tunnel circumference;

[0025] S43, remove rust from the surface of the steel strip with sandpaper, wipe off oil stains with acetone, then attach the steel strip coated with adhesive to the existing tunnel lining at the marked line position, and fix it to the inner wall of the existing tunnel lining with anchor bolts.

[0026] S44 uses steel formwork assembled along the tunnel circumference. The gap between the steel formwork and the existing tunnel lining is sealed with sealant, and then the ultra-high performance concrete layer is poured according to the reinforcement construction parameters of the ultra-high performance concrete layer.

[0027] Preferably, step S41 specifically includes the following steps:

[0028] S411, the current construction parameters of the ultra-high performance concrete layer and the current construction parameters of the steel strip are initially determined; wherein, the current construction parameters of the ultra-high performance concrete layer include concrete thickness and concrete strength grade, and the current construction parameters of the steel strip include steel strip thickness, steel strip width, longitudinal spacing of steel strips, and steel strip strength grade.

[0029] S412, Based on the current construction parameters of the ultra-high performance concrete layer and the current construction parameters of the steel strip, the load distribution is obtained to obtain the axial compression borne by the existing tunnel lining, the axial compression borne by the ultra-high performance concrete layer and the axial compression borne by the steel strip, as well as the bending moment borne by the existing tunnel lining, the bending moment borne by the ultra-high performance concrete layer and the bending moment borne by the steel strip.

[0030] S413, Perform load-bearing capacity calculations on the existing tunnel lining, ultra-high performance concrete layer and steel strip respectively, and determine whether the existing tunnel lining meets the first calculation qualification condition, whether the ultra-high performance concrete layer meets the second calculation qualification condition, and whether the steel strip meets the third calculation qualification condition.

[0031] S4141, when three of the following conditions are met simultaneously: the existing tunnel lining meets the first verification qualification condition, the ultra-high performance concrete layer meets the second verification qualification condition, and the steel strip meets the third verification qualification condition, the current construction parameters of the ultra-high performance concrete layer shall be used as the reinforcement construction parameters of the ultra-high performance concrete layer, and the current construction parameters of the steel strip shall be used as the reinforcement construction parameters of the steel strip.

[0032] S4142, if at least one of the following conditions is not met: the existing tunnel lining meets the first verification qualification condition, the ultra-high performance concrete layer meets the second verification qualification condition, or the steel strip meets the third verification qualification condition, adjust the current construction parameters of the ultra-high performance concrete layer and / or the current construction parameters of the steel strip, and then repeat steps S412 to S413 until the judgment condition of step S4141 is met.

[0033] Preferably, the first verification condition is: ;in, This refers to the actual effective thickness of the existing tunnel lining. The axial pressure borne by the existing tunnel lining. This is the design value of the axial compressive strength of the existing tunnel lining. The bending moment borne by the existing tunnel lining.

[0034] Preferably, the second verification condition is: ;in, This is the calculated thickness of the ultra-high performance concrete layer. The axial compression borne by the ultra-high performance concrete layer. This represents the design value of the axial compressive strength of the ultra-high performance concrete layer. The bending moment borne by the ultra-high performance concrete layer; This refers to the design value of the axial tensile strength of the ultra-high performance concrete layer. The tensile stress borne by the ultra-high performance concrete layer.

[0035] Preferably, the third verification condition is: ;in, This is the calculated value of the cross-sectional area of ​​the steel strip. The bending moment borne by the steel strip. This is the design value for the axial tensile strength of the steel strip. The effective thickness of the steel strip. The axial compression borne by the steel strip. The tensile stress borne by the steel strip.

[0036] Preferably, the following steps are included before step S1:

[0037] Grouting is performed on the foundation of the tunnel;

[0038] For non-water-permeable cracks, chisel a dovetail groove along the crack, clean the debris in the dovetail groove, insert a water-swellable waterstop strip, then inject polyurethane grout, and level the surface with repair mortar.

[0039] For construction joints with seepage, a semi-circular drainage pipe is embedded after the groove is cut; the semi-circular drainage pipe is connected to the tunnel side ditch.

[0040] For seepage settlement joints, stainless steel water collection boxes are embedded after the groove is cut, and the water collection boxes are connected to the tunnel side ditch.

[0041] Drainage pipes are installed in the tunnel lining; one end of the drainage pipe is inserted into the surrounding rock fissure behind the tunnel lining, and the other end is connected to the tunnel side ditch.

[0042] Compared with the prior art, this application has the following beneficial effects:

[0043] This invention provides a method for reinforcing tunnel linings. This application utilizes a synergistic load-bearing system of existing tunnel lining, ultra-high performance concrete layer, and steel strip to precisely restore the structural load-bearing capacity. It effectively repairs defects such as lining cracking and interface peeling, fundamentally avoiding safety hazards such as tunnel collapse and water seepage erosion of tracks / road surfaces caused by lining failure. This ensures the continuous operation of highways, railways, and other major transportation arteries and maintains the stable operation of regional transportation networks. The recurrence rate of defects after treatment is significantly reduced, minimizing traffic closure losses and maintenance costs associated with frequent repairs during the operational period. Furthermore, compared to tunnel reconstruction projects, this solution has a shorter construction period and less traffic disruption, further reducing indirect economic losses caused by construction and achieving the goal of reasonable and sustainable investment in transportation infrastructure operation and maintenance. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0045] Figure 1 This is a flowchart illustrating one embodiment of the present application;

[0046] Figure 2 This is one of the application scenario diagrams in one embodiment of this application;

[0047] Figure 3 This is the second application scenario diagram in one embodiment of this application.

[0048] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings.

[0049] Explanation of icon numbers:

[0050] 10. Existing tunnel lining; 20. Steel strip; 210. Anchor bolt; 30. Ultra-high performance concrete layer; 40. Drainage pipe; 50. Steel perforated pipe; 610. Waterproof crack; 620. Waterproof construction joint; 630. Waterproof settlement joint. Detailed Implementation

[0051] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0052] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0053] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0054] Furthermore, the descriptions of "right side," "middle side," etc., in this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined as "right side" or "middle side" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0055] Please see the appendix Figures 1 to 3 A method for reinforcing tunnel lining according to one embodiment of this application includes the following steps:

[0056] S1. Obtain the deterioration detection information of the existing tunnel lining 10 (i.e., the old lining), and determine whether the existing tunnel lining 10 needs to be reinforced based on the deterioration detection information; specifically, the deterioration detection information can be obtained by collecting geological parameters such as the tunnel surrounding rock grade, stratum unit weight, and internal friction angle, as well as dynamic data of groundwater level; retrieve the original tunnel design drawings to clarify parameters such as lining thickness and concrete strength grade; and summarize monitoring data such as arch settlement, perimeter convergence, and lining stress during operation.

[0057] Before inspection, the tunnel can be divided into independent segments of 10-20m each along its longitudinal direction, based on the continuity of the surrounding rock, the distribution characteristics of operational defects, and the convenience of construction. When dividing the segments, care should be taken to avoid the tunnel entrance, and the segment boundaries should coincide with the construction joints to facilitate the connection of subsequent procedures and ensure that the structural stress and defect characteristics within each segment are relatively uniform.

[0058] In a preferred embodiment, step S1 specifically includes the following steps:

[0059] The axial compressive strength test value of the lining concrete of the existing tunnel lining 10 obtained by core drilling method is obtained, and the decrease of the axial compressive strength test value relative to the axial compressive strength design value is calculated. Usually, the axial compressive strength of the lining concrete of the existing tunnel lining 10 will decrease after deterioration. The decrease can reflect the degree of deterioration of the existing tunnel lining 10.

[0060] The number of cracks per meter in the longitudinal direction of the existing tunnel lining 10 is obtained, as well as the proportion of cracks with a width greater than a first preset value. Preferably, a crack width meter and a depth sounder are used to set up a detection section every 5m along the longitudinal direction of the tunnel, record the number, length, width and depth of cracks, calculate the crack density and the proportion of width cracks, and set the first preset value to 0.2mm.

[0061] The existing tunnel lining 10 is obtained from the ultrasonic rebound combined method by acquiring the lining interface peeling information, and the peeling area ratio is obtained according to the lining interface peeling information; preferably, the key parts such as the arch crown, arch foot, and sidewall can be fully covered by scanning, the peeling area is marked and the peeling area ratio is calculated.

[0062] When at least two of the following conditions are met: the decrease is greater than the second preset value, the number of cracks per meter is greater than the third preset value, the proportion of cracks is greater than the fourth preset value, and the proportion of peeling area is greater than the fifth preset value, it is determined that the existing tunnel lining 10 needs to be reinforced.

[0063] Specifically, when at least two of the following conditions are met: the reduction rate is greater than the second preset value, the number of cracks per meter is greater than the third preset value, the crack ratio is greater than the fourth preset value, and the peeling area ratio is greater than the fifth preset value, it indicates that the existing tunnel lining 10 has deteriorated to a certain extent and needs reinforcement. The process then proceeds to step S2 for precise finite element modeling and analysis. In other embodiments, those skilled in the art can also adaptively set the threshold conditions for each judgment according to the tunnel requirements. As a preferred example, the second preset value is set to 20%, the third preset value is set to 3 cracks / m, the fourth preset value is set to 50%, and the fifth preset value is set to 10%.

[0064] S2, when the existing tunnel lining 10 needs reinforcement, a separate stress simulation model of the existing tunnel lining 10 is established, and the most unfavorable position of the existing tunnel lining 10 is extracted based on the separate stress simulation model. The core objective of this application is to accurately restore the mechanical response of the existing tunnel lining 10 under actual load in a deteriorated state by establishing a separate stress simulation model of the existing tunnel lining 10, and to extract the most unfavorable position, such as bending moment and / or axial compression. This provides benchmark internal force data for the calculation of reinforcement construction parameters of the subsequent ultra-high performance concrete layer 30-steel strip 20, avoids the actual stress of the existing tunnel lining 10 being obscured due to the direct superposition of reinforcement structures, and ensures that the reinforcement design conforms to the actual bearing requirements of the existing tunnel lining 10.

[0065] In a preferred embodiment, step S2 specifically includes the following steps:

[0066] S21, when the existing tunnel lining 10 needs reinforcement, a separate stress simulation model of the existing tunnel lining 10 is established; wherein, the separate stress simulation model is a two-dimensional finite element model, the existing tunnel lining 10 uses beam elements to simulate bending and axial deformation, and the constraint of the surrounding rock on the existing tunnel lining 10 uses elastic spring elements, the spring stiffness is determined according to the surrounding rock grade, and the spring stiffness corresponds to the elastic resistance coefficient of the surrounding rock in tunnel mechanics, characterizing the ability of the surrounding rock to constrain the deformation of the lining. The method for determining the spring stiffness can be the lookup table method or the experimental method, which will not be elaborated here.

[0067] S22, input the surrounding rock geological parameters, lining structure parameters, and load parameters into the two-dimensional finite element model to obtain the bending moment data and axial compression data of the entire cross-section of the existing tunnel lining 10; wherein, the surrounding rock geological parameters include the surrounding rock unit weight, the surrounding rock internal friction angle, the surrounding rock cohesion, and the surrounding rock elastic resistance coefficient; the lining structure parameters include the geometric dimensions of the existing tunnel lining 10 and the performance data of the deteriorated tunnel lining material; the load parameters include the vertical surrounding rock pressure, the horizontal surrounding rock pressure, the self-weight of the existing tunnel lining 10, and the additional operational load; preferably, the tunnel lining material performance data includes the axial compressive strength, elastic modulus, unit weight, and Poisson's ratio of the concrete of the existing tunnel lining 10.

[0068] S23, based on the bending moment data and axial compression data of the entire cross section, extract the bending moment and / or axial compression at the most unfavorable position of the existing tunnel lining 10.

[0069] S3, determine the lining reinforcement area based on the most unfavorable location, and remove the surface failure layer of the lining reinforcement area;

[0070] It is worth noting that determining the lining reinforcement area based on the most unfavorable location can also be based on a three-layer logic of disease severity detection + accurate mechanical risk assessment + structural integrity adaptation, as follows:

[0071] First, on-site inspections are used to identify areas with visible defects, which forms the basis for reinforcement. The tunnel is divided into equal-length segments of 10-20m. Then, core drilling, crack detection, and ultrasonic rebound methods are used to systematically inspect the entire tunnel cross-section. Sections or local areas with lining concrete strength degradation exceeding 20%, crack density ≥3 cracks / m with a width ≥0.2mm accounting for more than 50% of the total, and interface peeling area >10% are directly identified as priority reinforcement areas. These stages, due to significant material performance degradation, can no longer meet basic load-bearing requirements and are the core trigger points of the defect chain. Furthermore, for areas with severe water seepage, related reinforcement areas should be delineated based on crack distribution to prevent further water seepage from exacerbating structural deterioration and ensure that reinforcement covers all visible defect risk points.

[0072] Secondly, the most unfavorable points (i.e., mechanically weak areas) can be extracted through finite element modeling, overcoming the limitations of relying solely on visual inspection. A load-structure model is established using the load method, inputting geological and load parameters to calculate the bending moment, axial compression, and stress distribution across the entire lining section. The most unfavorable internal force section is included in the reinforcement range. Even if these areas show minor visual defects, their mechanical response is close to or exceeds the bearing capacity limit of the deteriorated lining. Without reinforcement, these areas will become the point of structural failure and need to be superimposed with areas of obvious defects to form a core reinforcement section.

[0073] Finally, considering both tunnel operation requirements and structural integrity, the boundaries and scope of the reinforcement area are determined. The continuity of the reinforcement area must be ensured, and the length of each reinforcement stage should not be too short to avoid abrupt changes in lining stiffness due to localized reinforcement. Furthermore, construction feasibility (such as clearance limitations and traffic diversion section lengths) must be considered to integrate scattered small-scale defect areas into continuous reinforcement units, ensuring uniform stress distribution across the reinforced lining, covering all risk points while avoiding resource waste caused by excessive construction.

[0074] The main purpose of removing the surface failure layer in the lining reinforcement area is to increase the interface roughness, increase the adhesive bonding area, reduce the bonding failure between the existing tunnel lining 10 and the bonding stop, provide a reliable bonding substrate for the interface connection medium, and enable the subsequent existing tunnel lining 10 to form a continuous stress interface with the steel strip 20 and the ultra-high performance concrete layer 30.

[0075] Preferably, the step S3 of removing the surface failure layer of the lining reinforcement area specifically includes the following steps: using a pneumatic pick (or a milling machine for finer areas) to remove the deteriorated concrete in the lining reinforcement area, with a depth controlled at 3-5cm, until fresh concrete aggregate is exposed, and the surface flatness error after removal is ≤5mm; then using a high-pressure water gun to wash the surface of the existing tunnel lining 10, and after repair, the surface is flush with the surrounding lining; using a high-pressure water gun to wash away surface dust and debris, and then using a hot air blower to dry it.

[0076] Furthermore, the step between step S3 and step S4 includes the following step:

[0077] Apply adhesive to the inner wall of the existing tunnel lining 10. Specifically, the first application is to evenly apply a 2-3 mm thick layer of adhesive to the treated surface of the existing tunnel lining 10 and let it stand for 10-15 minutes (surface dry, not sticky to the touch). If there are air bubbles on the surface, they should be scraped off with a scraper. The second application is to apply a 2-3 mm thick layer of adhesive to both sides of the steel strip 20 (the side in contact with the existing tunnel lining 10 and the ultra-high performance concrete layer 30), ensuring a total thickness of 5 mm.

[0078] This embodiment utilizes an epoxy resin adhesive with a shear strength ≥1.5MPa to transfer the load borne by the existing tunnel lining 10 to the steel strip 20 and the ultra-high performance concrete layer 30, preventing the reinforcement layer from bearing stress alone. Simultaneously, it seals the interface pores of the existing tunnel lining 10, preventing water and oxygen intrusion and delaying carbonization of the existing tunnel lining 10 and corrosion of the steel strip 20. A multi-layer bonding system of existing tunnel lining 10-adhesive-steel strip 20-adhesive-ultra-high performance concrete layer 30 can be constructed, ensuring uniform load transfer between layers and eliminating localized stress concentrations.

[0079] S4, install steel strip 20 on the inner wall of the lining reinforcement area, and then pour ultra-high performance concrete layer 30 (i.e. UHPC layer) in the lining reinforcement area.

[0080] In a preferred embodiment, step S4 specifically includes the following steps:

[0081] S41, determine the reinforcement construction parameters of steel strip 20 and ultra-high performance concrete layer 30;

[0082] S42, determine the longitudinal spacing of steel strip 20 according to the reinforcement construction parameters of steel strip 20, mark the installation position of steel strip 20 and anchor bolt 210 hole position along the tunnel circumference;

[0083] S43, remove rust from the surface of the steel strip 20 with sandpaper, wipe off the oil stains with acetone, then attach the steel strip 20 with adhesive to the marked position of the existing tunnel lining 10, and fix it to the inner wall of the existing tunnel lining 10 with anchor bolts 210.

[0084] As a preferred example, based on the reinforcement construction parameters of the steel strip 20, the longitudinal spacing of the steel strip 20 is determined, and a line is drawn along the tunnel circumference to mark the position of the steel strip 20 and the hole position of the anchor bolt 210. The surface of the Q355 grade steel strip 20 is derusted with sandpaper (rust removal grade Sa2.5), and then the oil stains are wiped off with acetone. The steel strip 20 with adhesive is attached to the existing tunnel lining 10 at the marked position and fixed with M22 high-strength chemical anchor bolts 210 (anchor bolt 210 spacing 50cm / bolt, 2 bolts per meter of steel strip 20, anchored into the existing tunnel lining 10 to a depth ≥220mm, i.e. 10d, where d is the diameter of the anchor bolt 210).

[0085] After the above steps are completed, tap the surface of the steel strip 20 lightly with a small hammer. If the sound is crisp, the bond is tight (without voids). If the sound is dull, it needs to be chiseled open and the adhesive applied.

[0086] S44 uses steel formwork assembled along the tunnel circumference. The gap between the steel formwork and the existing tunnel lining 10 is sealed with sealant. Then, the ultra-high performance concrete layer 30 is poured according to the reinforcement construction parameters of the ultra-high performance concrete layer 30.

[0087] As a preferred example, the concrete can be poured in one continuous motion from the arch foot to the arch crown along the circumferential direction, using an immersion vibrator to ensure proper compaction and avoid missed areas. The formwork should be removed within 24 hours of pouring, and the concrete should be covered with geotextile and plastic film to maintain moisture. It should then be water-cured for 7 days. After curing, the compressive strength of the ultra-high performance concrete should be tested to be ≥120MPa. In this step, the ultra-high performance concrete layer 30 serves as the main load-bearing layer, completely encasing the steel strip 20 to form a rigid constraint, preventing water and oxygen erosion of the steel strip 20 and improving its durability.

[0088] In a preferred embodiment, step S41 specifically includes the following steps:

[0089] S411, the current construction parameters of the ultra-high performance concrete layer 30 and the steel strip 20 are initially determined; wherein, the current construction parameters of the ultra-high performance concrete layer 30 include concrete thickness and concrete strength grade, and the current construction parameters of the steel strip 20 include steel strip thickness, steel strip width, longitudinal spacing of steel strip 20, and steel strip strength grade.

[0090] Specifically, based on the existing tunnel lining's degree of deterioration (strength attenuation rate, crack density), the internal forces at the most unfavorable location (bending moment M, axial compression N), and the performance limits of the core materials, and referring to similar operational tunnel reinforcement projects, material performance indicators, and tunnel cross-sectional dimensions, the initial construction parameters are proposed as follows:

[0091] Ultra-high performance concrete layer 30 parameters: (When the degradation is severe, take the upper limit, such as...) Attenuation exceeding 30% Strength grade C120;

[0092] Parameters of steel strip 20: Thickness of steel strip 20 20mm wide steel strip 20 longitudinal spacing of steel strip (For areas with large bending moments, such as the crown of the arch) ), strength grade Q355.

[0093] It is worth noting that although the strength of the existing tunnel lining 10 decreases due to tunnel deterioration, it still possesses compressive bearing capacity and contributes to some bending resistance. It needs to form a synergistic system with the ultra-high performance concrete layer 30 and the steel strip 20, consisting of the existing tunnel lining 10 bearing pressure, the ultra-high performance concrete layer 30 bearing main pressure, and the steel strip 20 bearing main tension.

[0094] Axial pressure: The existing tunnel lining 10 and the ultra-high performance concrete layer 30 share the axial pressure according to their stiffness ratio. It is necessary to ensure that the axial pressure borne by the existing tunnel lining 10 is less than or equal to its compressive bearing capacity after deterioration.

[0095] Bending moment: The compression zone of the existing tunnel lining 10 (the side away from the steel strip 20) bears part of the compressive stress. In the tension zone (the side closer to the steel strip 20), due to the low tensile strength of the concrete, the tensile stress is mainly borne by the steel strip 20. The remaining compressive stress of the bending moment is borne by the ultra-high performance concrete layer 30.

[0096] Constraints: First, verify the individual bearing capacity of the existing tunnel lining 10 to prevent it from failing before the reinforcing structure, and then derive the parameters of the ultra-high performance concrete layer 30 and the steel strip 20.

[0097] S412, based on the current construction parameters of the ultra-high performance concrete layer 30 and the current construction parameters of the steel strip 20, the load distribution is obtained to obtain the axial compression borne by the existing tunnel lining 10, the axial compression borne by the ultra-high performance concrete layer 30 and the axial compression borne by the steel strip 20, and the bending moment borne by the existing tunnel lining 10, the bending moment borne by the ultra-high performance concrete layer 30 and the bending moment borne by the steel strip 20.

[0098] In a preferred embodiment, the total axial stiffness of the composite section is the sum of the axial stiffness of the existing tunnel lining 10, the ultra-high performance concrete layer 30, and the steel strip 20: ;

[0099] The total bending stiffness of the composite section is the sum of the bending stiffness of the existing tunnel lining (10), the ultra-high performance concrete layer (30), and the steel strip (20): ;

[0100] In the formula, The total elastic modulus of the composite section is expressed in GPa. The effective area of ​​the composite section, in meters. 2 ; The moment of inertia of the composite section is expressed in meters (m). 4; The elastic modulus of existing tunnel lining is 10, in GPa. The effective area of ​​the existing tunnel lining is 10 m². 2 ; The moment of inertia of the existing tunnel lining section 10 is expressed in meters. 4 ; The elastic modulus of ultra-high performance concrete layer 30 is expressed in GPa. The effective area of ​​the ultra-high performance concrete layer 30 is expressed in m². 2 , The moment of inertia of the section of ultra-high performance concrete layer 30 is given in meters. 4 ; The elastic modulus of the steel strip is 20 g / L, in GPa. The effective area of ​​the steel strip is 20m². 2 , The moment of inertia of the 20mm cross section of the steel strip is expressed in meters. 4 .

[0101] The axial pressure is borne jointly by the existing tunnel lining 10, the ultra-high performance concrete layer 30, and the steel strip 20. Therefore, the axial pressure distribution among the existing tunnel lining 10, the ultra-high performance concrete layer 30, and the steel strip 20 is as follows:

[0102] The axial pressure borne by the existing tunnel lining 10 : ;

[0103] The axial compression borne by the ultra-high performance concrete layer 30 : ;

[0104] Axial pressure borne by steel strip 20 : ;

[0105] The bending moment is borne jointly by the existing tunnel lining 10, the ultra-high performance concrete layer 30, and the steel strip 20. Therefore, the bending moment distribution among the existing tunnel lining 10, the ultra-high performance concrete layer 30, and the steel strip 20 is as follows:

[0106] The bending moment borne by the existing tunnel lining 10 : ;

[0107] The bending moment borne by the ultra-high performance concrete layer 30 : ;

[0108] Bending moment borne by steel strip 20 : ;

[0109] The tensile force generated by the bending moment of the existing tunnel lining 10 is jointly borne by the ultra-high performance concrete layer 30 and the steel strip 20. Simultaneously considering that the tensile force generated by the bending moment of the existing tunnel lining 10 is jointly borne by the ultra-high performance concrete layer 30 and the steel strip 20, the tensile stress of the existing tunnel lining 10 at this time... : ;in, The equivalent section modulus of the existing tunnel lining 10 is given in meters. 3 ;

[0110] Distributed according to its axial stiffness:

[0111] The tensile stress borne by the ultra-high performance concrete layer 30 : ;

[0112] The tensile stress borne by steel strip 20 : ;

[0113] S413, the bearing capacity of the existing tunnel lining 10, the ultra-high performance concrete layer 30 and the steel strip 20 are respectively verified, and it is determined whether the existing tunnel lining 10 meets the first verification qualification condition, whether the ultra-high performance concrete layer 30 meets the second verification qualification condition, and whether the steel strip 20 meets the third verification qualification condition.

[0114] Preferably, the first verification condition is: ;in, The actual effective thickness of the existing tunnel lining is 10m, in meters. This refers to the axial pressure borne by the existing tunnel lining 10, which is positive and measured in kN. The design value of the axial compressive strength of the existing tunnel lining 10 is given in MPa. The bending moment borne by the existing tunnel lining 10, in kN. m; the specific process is as follows:

[0115] The existing tunnel lining 10 is subjected to axial compressive stress plus bending moment compressive stress in its compression zone. To ensure that the existing tunnel lining 10 does not fail alone under the total load, the formula for the total compressive stress of the existing tunnel lining 10 (the combined effect of axial compression and bending moment) is as follows: ;in,

[0116] Will (That is, the calculated width is 1m) Substituting into the above equation, we get: Therefore, the first verification condition is: .

[0117] Preferably, the second verification condition is: ;in, The calculated thickness of the ultra-high performance concrete layer 30 is in meters (m). The axial compression borne by the ultra-high performance concrete layer 30, in kN. The design value of the axial compressive strength of the ultra-high performance concrete layer 30 is given in MPa. The bending moment borne by the ultra-high performance concrete layer 30, in kN. m; The design value of the axial tensile strength of the ultra-high performance concrete layer 30 is given in MPa. The tensile stress borne by the ultra-high performance concrete layer 30 is expressed in kN. The specific steps to obtain this value are as follows:

[0118] Ultra-high performance concrete layer 30 is controlled by both compressive strength and tensile strength:

[0119] Compressive strength verification: ; The equivalent section modulus of ultra-high performance concrete layer 30 is given in meters. 3 ;

[0120] Tensile strength verification: ;

[0121] Will (That is, the calculated width is 1m) Substituting into the above formula, we derive the formula for calculating the thickness of the ultra-high performance concrete layer 30. Considering a safety factor of not less than 2.0, the thickness of the ultra-high performance concrete layer 30 must simultaneously meet the verification indicators for compressive strength and tensile strength:

[0122] ;and ;

[0123] The second verification condition is as follows: ;

[0124] For example, the calculated thickness of ultra-high performance concrete layer 30. If the second verification condition is met, then the proposed thickness of the ultra-high performance concrete layer of 30 mm meets the requirements.

[0125] Preferably, the third verification condition is: ;in, This is the calculated cross-sectional area of ​​steel strip 20, in meters. 2 , The bending moment borne by steel strip 20, in kN. m, The axial tensile strength of steel strip 20 is given in MPa. The effective thickness of the steel strip is 20 mm. The axial compression borne by steel strip 20, in kN. The tensile stress borne by steel strip 20 is expressed in kN; the specific steps to obtain this are as follows:

[0126] The load-bearing capacity of the steel strip 20 was verified: ;in, The equivalent section modulus of steel strip 20 is given in meters. 3 ;

[0127] Will , Substituting into the above formula, where s is the longitudinal spacing of the steel strip (20mm), Let b be the effective thickness of steel strip 20 and b be the width of steel strip 20. Derive the formula for calculating the area of ​​steel strip 20, while considering a safety factor of not less than 2.0: ;

[0128] For example, steel strip 20 , , , If the calculation results meet the requirements of the above formula, then the proposed steel strip 20 meets the requirements.

[0129] S4141, when the existing tunnel lining 10 meets the first verification qualification condition, the ultra-high performance concrete layer 30 meets the second verification qualification condition, and the steel strip 20 meets the third verification qualification condition, the current construction parameters of the ultra-high performance concrete layer 30 shall be used as the reinforcement construction parameters of the ultra-high performance concrete layer 30, and the current construction parameters of the steel strip 20 shall be used as the reinforcement construction parameters of the steel strip 20.

[0130] As a preferred embodiment, the bearing capacity of the existing tunnel lining 10 is tested first, and then the bearing capacity of the ultra-high performance concrete and steel strip 20 is tested simultaneously.

[0131] (1) First verify the bearing capacity of the existing tunnel lining 10. The core reason is that although the existing tunnel lining 10 has deteriorated, it still has residual compressive strength and some bending strength. It is the basic stress unit of the composite reinforcement system. If its bearing capacity is not verified first, the existing tunnel lining 10 may fail before the reinforcement structure (ultra-high performance concrete layer 30, steel strip 20), resulting in the load not being able to be transferred to the reinforcement layer through the existing tunnel lining 10, which in turn causes the entire composite system to fail due to the collapse of the foundation. At the same time, it can also avoid the waste of materials caused by over-reliance on the reinforcement structure and provide the available bearing boundary of the existing tunnel lining 10 for the subsequent reinforcement parameter design.

[0132] (2) The bearing capacity of the ultra-high performance concrete layer 30 and the steel strip 20 needs to be verified simultaneously because they are the core of the composite system: the ultra-high performance concrete layer 30 is mainly responsible for compression, and the steel strip 20 is mainly responsible for tension and bending. The loads (axial compression and bending moment) are distributed according to the stiffness ratio of the three (existing tunnel lining 10 + ultra-high performance concrete layer 30 + steel strip 20). The two are interrelated in terms of stress. Adjusting the thickness of the ultra-high performance concrete layer 30 will change the stiffness of the composite section, which will affect the tensile stress borne by the steel strip 20. Conversely, changes in the size / spacing of the steel strip 20 will also have a reaction effect on the compressive stress distribution of the ultra-high performance concrete layer 30. Verifying any one component alone will ignore this mechanical coupling relationship, which may lead to the stress of one side exceeding the limit (such as the steel strip 20 cracking) or the performance of the other side being idle (such as the ultra-high performance concrete layer 30 being insufficient in bearing capacity). Simultaneous verification ensures that both meet the strength requirements, realizes the precise mechanical division of labor between main compression and main tension and bending, avoids excessive or insufficient reinforcement, and ensures the overall bearing reliability of the composite system.

[0133] S4142, if at least one of the following conditions is not met: the existing tunnel lining 10 meets the first verification qualification condition, the ultra-high performance concrete layer 30 meets the second verification qualification condition, and the steel strip 20 meets the third verification qualification condition, the current construction parameters of the ultra-high performance concrete layer 30 and / or the current construction parameters of the steel strip 20 are adjusted, and then steps S412 to S413 are repeated until the judgment condition of step S4141 is met.

[0134] It is worth noting that when adjustments are needed, it is preferable to first adjust the longitudinal spacing of the steel strip 20, then adjust the width of the steel strip 20, and finally adjust the thickness of the ultra-high performance concrete layer 30. This way, the project cost can be reduced as much as possible while ensuring the adjustment.

[0135] This embodiment, through the design logic of prioritizing the bearing capacity of the existing tunnel lining 10 and then accurately calculating the reinforcement construction parameters, can make full use of the remaining bearing capacity of the existing tunnel lining 10, avoid the waste of resources caused by blindly increasing the amount of reinforcement materials, and reduce unnecessary material cost input.

[0136] In another preferred embodiment, the following steps are included before step S1:

[0137] Grouting is performed on the tunnel foundation. Specifically, foundation grouting is mainly used to improve the weak surrounding rock at the arch foot, increase the foundation stiffness, avoid additional bending moments in the core structure due to uneven settlement at the arch foot, provide a rigid support foundation for the subsequent ultra-high performance concrete layer 30-steel strip 20 composite structure, and reduce the deformation stress of the core structure.

[0138] Steel perforated pipes 50 are laid circumferentially along the tunnel arch foot line (10-15cm from the arch foot), with longitudinal spacing consistent with the drawings. The steel perforated pipes 50 are made of seamless steel pipes, with one end sharpened and fitted with Φ8mm grouting holes (15cm spacing, quincunx arrangement). A geological drilling rig is used to drill holes at a 30° angle (towards the arch foot surrounding rock), extending 0.2m beyond the length of the steel perforated pipe 50 to ensure anchorage. After inserting the steel perforated pipes 50, ultrafine cement-water glass grout is injected using a dual-liquid grouting machine, with the grouting pressure controlled at 0.5-1.0MPa until the grouting volume reaches the design value or the pressure suddenly increases. Seven days after grouting is completed, a plate load test is used to check the bearing capacity of the arch foot surrounding rock, which must be ≥300kPa.

[0139] For non-permeable cracks 610, chisel a dovetail groove along the crack (preferably 3-5cm wide and 2-3cm deep), clean the debris in the dovetail groove, insert a water-swellable waterstop strip, and then inject polyurethane grout (compressive strength ≥5MPa). The surface is then leveled with repair mortar.

[0140] For the seepage construction joint 620, a semi-circular drainage pipe is embedded after the groove is cut; the semi-circular drainage pipe is connected to the tunnel side ditch; preferably, the semi-circular drainage pipe is Φ75mm with a slope ≥2% to ensure smooth drainage.

[0141] For the seepage settlement joint 630, a stainless steel water collection box is embedded after the groove is cut, wherein the water collection box is connected to the tunnel side ditch; preferably, the width of the water collection box is 20cm and the height is 10cm.

[0142] A drainage pipe 40 is installed in the tunnel lining; one end of the drainage pipe 40 is inserted into the surrounding rock fissure behind the tunnel lining, and the other end is connected to the tunnel side ditch.

[0143] This embodiment also addresses the treatment of lining cracking and water seepage, primarily used to interrupt the "water seepage-cracking-strength decay" disease chain, control the surface humidity of the lining, prevent the decline in adhesive bonding strength and accelerated carbonization of the ultra-high performance concrete layer 30, and provide a dry working environment for the interface bonding medium and the core load-bearing structure. By interrupting the disease development chain through measures such as base grouting and water seepage treatment, combined with the protective effect of the ultra-high performance concrete layer 30 on the steel strip 20, the service life of the tunnel is significantly extended, reducing the long-term occupation of traffic lines and environmental disturbance caused by premature reconstruction, which meets the social demand for long-term operation and maintenance of transportation infrastructure.

[0144] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method of reinforcing a tunnel lining, characterized in that, The method comprises the following steps: S1, obtaining deterioration detection information of an existing tunnel lining, and judging whether the existing tunnel lining needs to be reinforced according to the deterioration detection information; S2, when the existing tunnel lining needs to be reinforced, establishing a separate stress simulation model of the existing tunnel lining, and extracting a most unfavorable position of the existing tunnel lining according to the separate stress simulation model; S3, determining a lining reinforcement area according to the most unfavorable position, and removing a surface failure layer of the lining reinforcement area; S4, installing a steel band on an inner wall of the lining reinforcement area, and pouring an ultra-high performance concrete layer in the lining reinforcement area; The step S4 specifically comprises the following steps: S41, determining reinforcement construction parameters of the steel band and reinforcement construction parameters of the ultra-high performance concrete layer; S42, determining a longitudinal spacing of the steel band according to the reinforcement construction parameters of the steel band, drawing a line along a ring of the tunnel, marking a steel band installation position and an anchor bolt hole position; S43, rusting the surface of the steel band with sandpaper, wiping oil stains with acetone, and then pasting the steel band coated with an adhesive on the line position of the existing tunnel lining, and fixing the steel band on the inner wall of the existing tunnel lining by using an anchor bolt; S44, assembling a steel formwork along the ring of the tunnel, sealing the gap between the steel formwork and the existing tunnel lining with sealant, and then pouring the ultra-high performance concrete layer according to the reinforcement construction parameters of the ultra-high performance concrete layer; The step S41 specifically comprises the following steps: S411, initially determining current construction parameters of the ultra-high performance concrete layer and current construction parameters of the steel band; wherein the current construction parameters of the ultra-high performance concrete layer include a concrete thickness and a concrete strength grade, and the current construction parameters of the steel band include a steel band thickness, a steel band width, a steel band longitudinal spacing, and a steel band strength grade; S412, performing load distribution according to the current construction parameters of the ultra-high performance concrete layer and the current construction parameters of the steel band to obtain an axial pressure borne by the existing tunnel lining, an axial pressure borne by the ultra-high performance concrete layer, and an axial pressure borne by the steel band, and to obtain a bending moment borne by the existing tunnel lining, a bending moment borne by the ultra-high performance concrete layer, and a bending moment borne by the steel band; S413, respectively performing bearing capacity checking on the existing tunnel lining, the ultra-high performance concrete layer, and the steel band, and judging whether the existing tunnel lining satisfies a first checking qualified condition, whether the ultra-high performance concrete layer satisfies a second checking qualified condition, and whether the steel band satisfies a third checking qualified condition; S4141, when all of the three conditions that the existing tunnel lining satisfies the first checking qualified condition, the ultra-high performance concrete layer satisfies the second checking qualified condition, and the steel band satisfies the third checking qualified condition are satisfied, taking the current construction parameters of the ultra-high performance concrete layer as the reinforcement construction parameters of the ultra-high performance concrete layer, and taking the current construction parameters of the steel band as the reinforcement construction parameters of the steel band. S4142, when at least one of the following conditions is not met: the existing tunnel lining meets the first checking eligible condition, the ultra-high performance concrete layer meets the second checking eligible condition, and the steel strip meets the third checking eligible condition, adjusting the current construction parameter of the ultra-high performance concrete layer and / or the current construction parameter of the steel strip, and then repeating steps S412-S413 until the determination condition of step S4141 is met.

2. The method of reinforcing a tunnel lining according to claim 1, wherein, The step S1 specifically comprises the following steps: obtaining the axial compressive strength detection value of the lining concrete of the existing tunnel lining detected by the core drilling method, and calculating the drop of the axial compressive strength detection value relative to the axial compressive strength design value; obtaining the number of cracks per meter of the existing tunnel lining in the longitudinal direction of the tunnel, and obtaining the crack proportion of each crack with a crack width greater than a first preset value; obtaining the lining interface peeling information of the existing tunnel lining detected by the ultrasonic rebound comprehensive method, and obtaining the peeling area proportion according to the lining interface peeling information; when at least two of the following conditions are met: the drop is greater than a second preset value, the number of cracks per meter is greater than a third preset value, the crack proportion is greater than a fourth preset value, and the peeling area proportion is greater than a fifth preset value, it is determined that the existing tunnel lining needs to be reinforced.

3. The method of reinforcing a tunnel lining according to claim 1, wherein, The step S2 specifically comprises the following steps: S21, when the existing tunnel lining needs to be reinforced, a separate force simulation model of the existing tunnel lining is established; wherein the separate force simulation model is a two-dimensional finite element model, the existing tunnel lining adopts a beam element to simulate bending and axial deformation, the constraint of surrounding rock on the existing tunnel lining adopts an elastic spring element, and the spring stiffness is determined according to the surrounding rock grade; S22, inputting the surrounding rock geological parameters, lining structure parameters and load parameters into the two-dimensional finite element model to obtain the bending moment data and axial pressure data of the full cross section of the existing tunnel lining; wherein the surrounding rock geological parameters include the unit weight of surrounding rock, the internal friction angle of surrounding rock, the cohesion of surrounding rock, and the elastic resistance coefficient of surrounding rock; the lining structure parameters include the geometric size of the existing tunnel lining and the material performance data of the deteriorated tunnel lining; the load parameters include the vertical surrounding rock pressure, the horizontal surrounding rock pressure, the self weight of the existing tunnel lining and the operation additional load; S23, according to the bending moment data and the axial pressure data of the full cross section, the most unfavorable position of the existing tunnel lining and the bending moment and / or axial pressure of the most unfavorable position are extracted.

4. The method of reinforcing a tunnel lining according to claim 1, wherein, The step S3 of chiseling off the surface failure layer of the lining reinforcement area specifically comprises the following steps: the deteriorated concrete of the lining reinforcement area is chiseled off by using a pneumatic pick, the depth is controlled to 3-5 cm, until the fresh concrete aggregate is exposed, and the flatness error of the chiseled surface is ≤5 mm; then the surface of the existing tunnel lining is washed by using a high-pressure water gun, and then dried by using a hot air blower.

5. The method of reinforcing a tunnel lining according to claim 1, wherein, The first checking qualified condition is: ; wherein, is the actual effective thickness of the existing tunnel lining, is the axial pressure borne by the existing tunnel lining, is the axial compressive strength design value of the existing tunnel lining, is the bending moment borne by the existing tunnel lining.

6. The method of reinforcing a tunnel lining according to claim 1, wherein, The second checking qualified condition is: ; wherein, is a thickness calculated value of the ultra-high performance concrete layer, is an axial compression borne by the ultra-high performance concrete layer, is a design value of axial compressive strength of the ultra-high performance concrete layer, is a bending moment borne by the ultra-high performance concrete layer; is a design value of axial tensile strength of the ultra-high performance concrete layer, is a tensile stress borne by the ultra-high performance concrete layer.

7. The method of reinforcing a tunnel lining according to claim 1, wherein, The third checking qualified condition is: ; wherein, is a cross-sectional area calculation value of the steel strip, is a bending moment borne by the steel strip, is a design value of the axial tensile strength of the steel strip, is an effective thickness of the steel strip, is an axial pressure borne by the steel strip, is a tensile stress borne by the steel strip.

8. The method of reinforcing a tunnel lining according to claim 1, wherein, The step S1 further comprises the following steps before the step S1: grouting the base of the tunnel; for the non-water permeable cracks, a dovetail groove is chiseled along the cracks, after the debris in the dovetail groove is cleaned, a water-swelling sealing strip is embedded, then polyurethane slurry is poured, and the surface is leveled with repair mortar; for the water permeable construction joints, a semicircular drainage pipe is embedded after grooving; wherein the semicircular drainage pipe is connected to the tunnel gutter. For water seepage settlement joint, after slotting, stainless steel water receiving box is embedded, wherein the water receiving box is connected to the tunnel side ditch; Drain pipe is arranged in the tunnel lining; wherein one end of the drain pipe is inserted into the surrounding rock fissure behind the tunnel lining, and the other end is connected to the tunnel side ditch.

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