A safe and fast evaluation method for railway tunnel cracking lining structure

Abstract

The present application provides a kind of railway tunnel cracking lining structure safety fast evaluation method, first, the prefabricated table corresponding to the same railway line of same period one-off construction is formulated, i.e. the method for calculating the lining structure steel bar tensile stress by assuming crack width, the steel stress state of lining type corresponding to different crack widths is calculated, and the data table is formulated, so as to obtain the steel reinforced concrete lining type and the assumed crack width of the whole railway;When the safety inspection of railway tunnel is carried out, if the crack of tunnel lining is found, the lining type is determined and the crack width is measured, the staff compares the prefabricated table, the cracking condition of crack, the stress state of steel bar can be judged in time, the safety of tunnel is judged in time, the whole process is simple in operation, short in period, high in accuracy, low in professional requirement for evaluation personnel, and convenient for popularization and application.

Description

Technical Field

[0001] This invention relates to the field of evaluation methods for cracked tunnel lining structures, and specifically to a rapid safety evaluation method for cracked railway tunnel lining structures. Background Technology

[0002] With the rapid growth in the number of railway construction projects and the continuous expansion of operational scale in my country, the safety inspection and maintenance of railway tunnels in the later stages have received increasing attention.

[0003] Currently, as many railway tunnels age, their lining structures begin to crack due to complex geological conditions and unpredictable geological disasters. Cracks vary in width; some cracks do not affect the stress on the reinforcing steel, while others may alter the stress distribution. If cracks are not addressed promptly, they may eventually intersect and connect, significantly altering the stress distribution at the cracked areas. Over time, this accumulation and compression can lead to spalling, water leakage, or affect the structural integrity of the tunnel, posing a significant threat to tunnel traffic safety.

[0004] In the daily operation of railway tunnels, safety inspections can generally detect tunnel cracks in a timely manner. Cracks with a width within 0.2mm are generally within the design allowable range and do not require treatment. However, cracks exceeding 0.2mm cannot be directly assessed to determine whether the stress changes on the tunnel reinforcement exceed the design tolerances, making it impossible to make a timely judgment on-site. Inspection personnel can only report the data, and then professional calculation personnel will subsequently create models to simulate the stress and deformation state of the reinforcement under different load conditions. This method is cumbersome, time-consuming, has poor accuracy, and requires specialized personnel to complete the analysis, making it impossible to make a timely judgment on the safety of the tunnel lining structure.

[0005] Therefore, it is of great significance to develop a fast, accurate and simple evaluation method for the safety of cracked lining structures in railway tunnels. Summary of the Invention

[0006] The purpose of this invention is to address the problems of existing technologies in which timely and accurate assessment of the safety of cracked tunnel lining structures is impossible, and the assessment process is cumbersome and time-consuming. This invention provides a rapid safety assessment method for cracked lining structures in railway tunnels. During safety inspections of railway tunnels, if cracks are found in the tunnel lining, staff can quickly determine the extent of the cracking and the impact on the reinforcing steel by referring to prefabricated tables, thus promptly assessing the tunnel's safety. The entire process is simple to operate, has a short cycle time, high accuracy, low professional requirements for assessment personnel, and is easy to promote and apply.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A rapid safety evaluation method for cracked lining structures in railway tunnels includes the following steps:

[0009] Step 1: Calculate the prefabrication table corresponding to the same railway line constructed in the same period; the prefabrication table includes test data corresponding to various lining structure types existing in the same railway line constructed in the same period;

[0010] Step 2: Measure the crack width (m) of the lining structure of a tunnel on the same railway line constructed in the same phase.

[0011] Step 3: Identify the type of tunnel lining with cracks; based on the crack width and tunnel lining type, find the prefabrication table to determine the steel stress state corresponding to the measured crack width value.

[0012] Step 4: Determine the safety status of the lining structure and corresponding measures based on the stress state of the reinforcing steel.

[0013] This invention provides a rapid safety evaluation method for cracked lining structures in railway tunnels. First, a prefabrication table is created for the same railway line constructed concurrently. This involves calculating the tensile stress of the reinforcing steel in the lining structure using an assumed crack width. The stress state of the reinforcing steel for different crack widths is calculated and compiled into a data table, thereby obtaining the reinforced concrete lining types and assumed crack widths for the entire railway line. During safety inspections of railway tunnels, if cracks are found in the tunnel lining, the lining type is identified and the crack width is measured. By referring to the prefabrication table, staff can promptly determine the cracking situation, the stress state of the reinforcing steel, and the tunnel's safety. The entire process is simple to operate, has a short cycle time, high accuracy, low professional requirements for evaluation personnel, and is easy to promote and apply.

[0014] Among them, the same railway line constructed at the same time refers to railway lines that implement the same standards, such as railway lines with consistent lining thickness, lining size and concrete usage parameters; for example, the Zhengzhou-Wanzhou Railway.

[0015] Furthermore, the lining structure types existing in the same railway line constructed at the same time include at least two of the following: IVa2 lining, IVb lining, IVc lining, Va lining, Vb lining, and Vc lining. Among them, IVa2 lining is suitable for lining sections with deep-buried soft rock of Class IV surrounding rock; IVb lining is suitable for lining sections with shallow-buried Class IV surrounding rock; IVc lining is suitable for lining sections with biased pressure, faults, karst development, or other special sections of Class IV surrounding rock; Va lining is suitable for lining sections with deep-buried Class V surrounding rock; Vb lining is suitable for lining sections with shallow-buried Class V surrounding rock; and Vc lining is suitable for lining sections with biased pressure, faults, karst development, or other special sections of Class V surrounding rock.

[0016] Furthermore, in step 1, the test data corresponding to each type of lining structure in the prefabrication table includes the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement, the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement, and the allowable crack width n3 corresponding to the tensile ultimate strength of the tunnel reinforcement.

[0017] Furthermore, the allowable stress for tunnel reinforcement is 210 MPa; the yield strength of tunnel reinforcement is 400 MPa; and the ultimate tensile strength of tunnel reinforcement is 540 MPa.

[0018] Furthermore, in the prefabrication table, the test data corresponding to each type of lining structure is calculated by the following method: assuming the maximum crack width ω of the lining structure;

[0019] (1) Calculate the tensile stress σ of the steel reinforcement in the tension zone according to Equations 1 to 3. s ;

[0020]

[0021]

[0022]

[0023] In the formula σ s —Tensile stress in the reinforcement of the tension zone (MPa);

[0024] ω—Maximum crack width of the lining structure (mm);

[0025] E s —The elastic modulus of the reinforcing steel;

[0026] α cr —The stress characteristic coefficient of the component is taken as 1.9 for eccentrically compressed components;

[0027] c s —The distance from the outermost longitudinal tensile reinforcement to the bottom edge of the tension reinforcement, when c s When <20, take c. s =20; when c s When >65, take c. s =65;

[0028] d—Equivalent diameter of the longitudinal reinforcement under tension;

[0029] ρ te —The longitudinal tensile reinforcement ratio calculated based on the effective tensile concrete cross-sectional area, ρ te =A s / A te , ρ te When <0.01, take ρ te =0.01; where As A is the cross-sectional area of ​​the longitudinal reinforcement in the tension zone. te For the effective tensile concrete cross-sectional area, A te =0.5bh (b and h are the width and height of the calculated section, respectively);

[0030] f tk —Standard value of axial tensile strength of concrete;

[0031] —Coefficient of non-uniformity of strain in longitudinal tensile reinforcement, when At that time, take when At that time, take

[0032] (2) Calculate the strain non-uniformity coefficient of longitudinal tensile reinforcement according to Equation 4.

[0033]

[0034] (3) The strain non-uniformity coefficient of the longitudinal tensile reinforcement calculated according to step (2) For the corresponding interval, determine which of equations 1 to 3 should be the tensile stress σ of the steel reinforcement in the tension zone. s ;

[0035] When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the stress is not equal to the design allowable stress, re-assume the maximum crack width ω of the lining structure and repeat steps (1)-(3) until the tensile stress σ of the tensile reinforcement in the tension zone calculated in step (3) is obtained. s Equal to the design allowable stress, the assumed maximum crack width of the lining structure is the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement;

[0036] Similarly, when the tensile stress σ of the steel reinforcement in the tension zone calculated in step (3) is... s When the value is not equal to the yield strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σ of the tension zone reinforcement obtained in step (3) is obtained. s It is equal to the yield strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement.

[0037] When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the tensile strength is not equal to the ultimate tensile strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σ of the reinforcement in the tension zone calculated in step (3) is obtained. sIt is equal to the ultimate tensile strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n3 corresponding to the ultimate tensile strength of the tunnel reinforcement.

[0038] Furthermore, in step 2, the measured crack width m of the tunnel lining structure is greater than 0.2 mm. When the measured crack width of the tunnel lining structure is ≤ 0.2 mm, it is within the design allowable range and no further processing is required; it is judged to be in a safe state. When m > 0.2 mm, the method provided in this application is used for safety assessment.

[0039] Furthermore, in step 4, the specific method for determining the safety status of the lining structure based on the stress state of the reinforcing bars is as follows:

[0040] When the measured crack width m of the tunnel lining structure is less than or equal to n1, the safety level is Class I.

[0041] When the measured crack width m of the tunnel lining structure is greater than n1 and m ≤ n2, the safety level is Class II.

[0042] When the measured crack width m of the tunnel lining structure is greater than n2 and m≤n3, the safety level is III.

[0043] When the measured crack width m of the tunnel lining structure is greater than n3, the safety level is IV.

[0044] The safety levels of Level I, Level II, Level III, and Level IV decrease progressively.

[0045] Furthermore, in step 4, when the safety level is Level I, the lining structure meets the requirements for normal use and can maintain normal operation.

[0046] When the safety level is II, the safety of the lining structure decreases and the internal force of the lining exceeds the design state, but the lining reinforcement can still continue to bear the load within the elastic range. Measures such as increasing the monitoring frequency and issuing early warnings are taken.

[0047] When the safety level is III, the lining reinforcement undergoes irreversible plastic deformation. Crack changes should be continuously monitored, and the lining structure should be repaired and reinforced according to the crack changes.

[0048] When the safety level is IV, the stress on the reinforcing steel exceeds the ultimate strength, the lining structure is damaged, the reinforcing steel at the crack no longer has the load-bearing capacity, the train speed should be limited, and if the cracks continue to increase and multiply, the line should be closed, the lining should be removed and the lining structure should be reconstructed.

[0049] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0050] This invention provides a rapid safety evaluation method for cracked lining structures in railway tunnels. First, a prefabrication table is created for the same railway line constructed concurrently. This involves calculating the tensile stress of the reinforcing steel in the lining structure using an assumed crack width. The stress state of the reinforcing steel for different crack widths is calculated and compiled into a data table, thereby obtaining the reinforced concrete lining types and assumed crack widths for the entire railway line. During safety inspections of railway tunnels, if cracks are found in the tunnel lining, the lining type is identified and the crack width is measured. By referring to the prefabrication table, staff can promptly determine the cracking situation, the stress state of the reinforcing steel, and the tunnel's safety. The entire process is simple to operate, has a short cycle time, high accuracy, low professional requirements for evaluation personnel, and is easy to promote and apply. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0052] Example 1

[0053] A rapid safety evaluation method for cracked lining structures in railway tunnels includes the following steps:

[0054] Step 1: Calculate the prefabrication table corresponding to the same railway line constructed in the same period; the prefabrication table includes test data corresponding to various lining structure types existing in the same railway line constructed in the same period.

[0055] The same railway line constructed at the same time refers to a railway line that follows the same standards, such as the thickness of the lining, the size of the lining, and the parameters for using the concrete.

[0056] The railway line constructed at the same time and in one phase may have at least two of the following lining structure types: IVa2 lining, IVb lining, IVc lining, Va lining, Vb lining, and Vc lining. Among them, IVa2 lining is suitable for linings in deeply buried soft rock sections of Class IV surrounding rock; IVb lining is suitable for linings in shallowly buried sections of Class IV surrounding rock; IVc lining is suitable for linings in sections of Class IV surrounding rock with bias pressure, faults, karst development, or other special sections; Va lining is suitable for linings in deeply buried sections of Class V surrounding rock; Vb lining is suitable for linings in shallowly buried sections of Class V surrounding rock; and Vc lining is suitable for linings in sections of Class V surrounding rock with bias pressure, faults, karst development, or other special sections.

[0057] The test data corresponding to each type of lining structure in the prefabrication table include the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement, the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement, and the allowable crack width n3 corresponding to the tensile ultimate strength of the tunnel reinforcement.

[0058] The specific calculation process for the prefabricated table is as follows:

[0059] Assume the maximum crack width ω in the lining structure;

[0060] (1) Calculate the tensile stress σ of the steel reinforcement in the tension zone according to Equations 1 to 3. s ;

[0061]

[0062]

[0063]

[0064] In the formula σ s —Tensile stress in the reinforcement of the tension zone (MPa);

[0065] ω—Maximum crack width of the lining structure (mm);

[0066] E s —The elastic modulus of the reinforcing steel;

[0067] α cr —The stress characteristic coefficient of the component is taken as 1.9 for eccentrically compressed components;

[0068] c s —The distance from the outermost longitudinal tensile reinforcement to the bottom edge of the tension reinforcement, when c s When <20, take c. s =20; when c s When >65, take c. s =65;

[0069] d—Equivalent diameter of the longitudinal reinforcement under tension;

[0070] ρ te —The longitudinal tensile reinforcement ratio calculated based on the effective tensile concrete cross-sectional area, ρ te =A s / A te , ρ te When <0.01, take ρ te =0.01; where A s A is the cross-sectional area of ​​the longitudinal reinforcement in the tension zone. te For the effective tensile concrete cross-sectional area, A te =0.5bh (b and h are the width and height of the calculated section, respectively);

[0071] f tk —Standard value of axial tensile strength of concrete;

[0072] —Coefficient of non-uniformity of strain in longitudinal tensile reinforcement, when At that time, take when hour,

[0073] Pick

[0074] (2) Calculate the strain non-uniformity coefficient of longitudinal tensile reinforcement according to Equation 4.

[0075]

[0076] (3) The strain non-uniformity coefficient of the longitudinal tensile reinforcement calculated according to step (2) For the corresponding interval, determine which of equations 1 to 3 should be the tensile stress σ of the steel reinforcement in the tension zone. s ;

[0077] When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the stress is not equal to the design allowable stress, re-assume the maximum crack width ω of the lining structure and repeat steps (1)-(3) until the tensile stress σ of the tensile reinforcement in the tension zone calculated in step (3) is obtained. s Equal to the design allowable stress, the assumed maximum crack width of the lining structure is the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement;

[0078] Similarly, when the tensile stress σ of the steel reinforcement in the tension zone calculated in step (3) is... s When the value is not equal to the yield strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σ of the tension zone reinforcement obtained in step (3) is obtained. s It is equal to the yield strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement.

[0079] When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the tensile strength is not equal to the ultimate tensile strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σ of the reinforcement in the tension zone calculated in step (3) is obtained. s It is equal to the ultimate tensile strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n3 corresponding to the ultimate tensile strength of the tunnel reinforcement.

[0080] For example, a railway line constructed in the same phase at one time may include six types of lining. IV a2 Type IV b Type IV c Type, V a Type, V b Type, V c type.

[0081] The test results are shown below.

[0082] Table 1. Stress variation of reinforcing steel in type IVa2 lining with crack width

[0083]

[0084]

[0085] Table 2IV b V a Stress variation of reinforcing steel in lining with crack width

[0086]

[0087]

[0088] Table 3IV c V b Stress variation of reinforcing steel in lining with crack width

[0089]

[0090]

[0091] Table 4V c Stress variation of reinforcing steel in lining with crack width

[0092]

[0093]

[0094] Based on the calculation results in Tables 1-4, Table 5 summarizes the crack widths of various types of reinforced concrete lining structures when the steel reinforcement stress reaches the design allowable stress, yield strength, and tensile ultimate strength, respectively, thus obtaining the prefabrication table.

[0095] Table 5. Crack width data corresponding to reinforcement stress in various types of reinforced concrete linings.

[0096]

[0097] Step 2: Measure the crack width (m) of the lining structure of a tunnel on the same railway line constructed in the same phase.

[0098] Step 3: Identify the type of tunnel lining with cracks; based on the crack width and tunnel lining type, find the prefabrication table to determine the steel stress state corresponding to the measured crack width value.

[0099] Step 4: Determine the safety status of the lining structure and corresponding measures based on the stress state of the reinforcing steel.

[0100] When the measured crack width m of the tunnel lining structure is less than or equal to n1, the safety level is Class I; the lining structure meets the requirements for normal use and can maintain normal operation.

[0101] When the measured crack width m of the tunnel lining structure is greater than n1 and m ≤ n2, the safety level is II. The safety of the lining structure is reduced and the internal force of the lining exceeds the design state, but the lining reinforcement can still continue to bear the load within the elastic range. Measures such as increasing the monitoring frequency and issuing early warnings are taken.

[0102] When the measured crack width m of the tunnel lining structure is greater than n2 and m≤n3, the safety level is III; when the lining reinforcement undergoes irreversible plastic deformation, the crack changes should be continuously monitored, and the lining structure should be repaired and reinforced according to the crack changes.

[0103] When the measured crack width m of the tunnel lining structure is greater than n3, the safety level is IV; when the stress on the steel bars exceeds the ultimate strength, the lining structure is damaged, and the steel bars at the crack no longer have the load-bearing capacity, the train speed should be limited; if the cracks continue to increase and multiply, the line should be closed, the lining should be removed and the lining structure should be reconstructed.

[0104] This invention provides a rapid safety evaluation method for cracked lining structures in railway tunnels. First, a prefabrication table is created for the same railway line constructed concurrently. This involves calculating the tensile stress of the reinforcing steel in the lining structure using an assumed crack width. The stress state of the reinforcing steel for different crack widths is calculated and compiled into a data table, thereby obtaining the reinforced concrete lining types and assumed crack widths for the entire railway line. During safety inspections of railway tunnels, if cracks are found in the tunnel lining, the lining type is identified and the crack width is measured. By referring to the prefabrication table, staff can promptly determine the cracking situation, the stress state of the reinforcing steel, and the tunnel's safety. The entire process is simple to operate, has a short cycle time, high accuracy, low professional requirements for evaluation personnel, and is easy to promote and apply.

[0105] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rapid safety evaluation method for cracked lining structures in railway tunnels, characterized in that, Includes the following steps: Step 1: Calculate the prefabrication table corresponding to the same railway line constructed in the same period; the prefabrication table includes test data corresponding to various lining structure types existing in the same railway line constructed in the same period; The test data corresponding to each type of lining structure in the prefabrication table include the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement, the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement, and the allowable crack width n3 corresponding to the tensile ultimate strength of the tunnel reinforcement. In the prefabrication table, the test data corresponding to each type of lining structure is calculated using the following method: Assume the maximum crack width ω in the lining structure; (1) Calculate the tensile stress σ of the steel reinforcement in the tension zone according to Equations 1 to 3. s ; Formula 1 Formula 2 Formula 3 In the formula σ s —Tensile stress in the tension zone of the reinforcing steel, MPa; ω—Maximum crack width in the lining structure, mm; E s —The elastic modulus of the reinforcing steel; α cr —The stress characteristic coefficient of the component is taken as 1.9 for eccentrically compressed components; c s —The distance from the outermost longitudinal tensile reinforcement to the bottom edge of the tension reinforcement, when c s When <20, take c. s =20; when c s When >65, take c. s =65; d—Equivalent diameter of the longitudinal reinforcement under tension; ρ te —The longitudinal tensile reinforcement ratio calculated based on the effective tensile concrete cross-sectional area, ρ te =A s / A te,ρ te When <0.01, take ρ te =0.01; where A s A is the cross-sectional area of ​​the longitudinal reinforcement in the tension zone. te For the effective tensile concrete cross-sectional area, A te =0.5bh, where b and h are the width and height of the calculated section, respectively; f tk — Standard value of axial tensile strength of concrete; φ - Coefficient of non-uniform strain of longitudinal tensile reinforcement. When φ < 0.2, take φ = 0.2; when φ > 1.0, take φ = 1.

0. (2) Calculate the strain non-uniformity coefficient φ of the longitudinal tensile reinforcement according to Equation 4; Formula 4 (3) Based on the corresponding interval of the longitudinal tensile reinforcement strain non-uniformity coefficient calculated in step (2), determine which of Equations 1 to 3 should be the tensile stress σ of the reinforcement in the tensile zone. s ; When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the stress is not equal to the design allowable stress, re-assume the maximum crack width ω of the lining structure and repeat steps (1)-(3) until the tensile stress σ of the tensile reinforcement in the tension zone calculated in step (3) is obtained. s Equal to the design allowable stress, the assumed maximum crack width of the lining structure is the allowable crack width n1 corresponding to the design allowable stress of the tunnel reinforcement; Similarly, when the tensile stress σs of the steel reinforcement in the tension zone calculated in step (3) is not equal to the yield strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σs of the steel reinforcement in the tension zone calculated in step (3) is obtained. s It is equal to the yield strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n2 corresponding to the yield strength of the tunnel reinforcement. When the tensile stress σ of the steel reinforcement in the tension zone is calculated in step (3) s If the tensile strength is not equal to the ultimate tensile strength of the tunnel reinforcement, the maximum crack width ω of the lining structure is re-assumed, and the calculations in steps (1) to (3) are performed again until the tensile stress σ of the reinforcement in the tension zone calculated in step (3) is obtained. s It is equal to the ultimate tensile strength of the tunnel reinforcement. The assumed maximum crack width of the lining structure is the allowable crack width n3 corresponding to the ultimate tensile strength of the tunnel reinforcement. Step 2: Measure the crack width (m) of the lining structure of a tunnel on the same railway line constructed in the same phase. Step 3: Identify the type of tunnel lining with cracks; based on the crack width and tunnel lining type, find the prefabrication table to determine the steel stress state corresponding to the measured crack width value. Step 4: Determine the safety status of the lining structure and corresponding measures based on the stress state of the reinforcing steel.

2. The method for rapid safety evaluation of cracked lining structures in railway tunnels according to claim 1, characterized in that, The railway line constructed at the same time and in one phase may have at least two of the following lining structure types: IVa2 lining, IVb lining, IVc lining, Va lining, Vb lining, and Vc lining. Among them, IVa2 lining is suitable for linings in deeply buried soft rock sections of Class IV surrounding rock; IVb lining is suitable for linings in shallowly buried sections of Class IV surrounding rock; IVc lining is suitable for linings in sections of Class IV surrounding rock with bias pressure, faults, karst development, or other special sections; Va lining is suitable for linings in deeply buried sections of Class V surrounding rock; Vb lining is suitable for linings in shallowly buried sections of Class V surrounding rock; and Vc lining is suitable for linings in sections of Class V surrounding rock with bias pressure, faults, karst development, or other special sections.

3. The method for rapid safety evaluation of cracked lining structures in railway tunnels according to claim 1, characterized in that, The allowable stress for tunnel reinforcement is 210 MPa; the yield strength of tunnel reinforcement is 400 MPa; and the ultimate tensile strength of tunnel reinforcement is 540 MPa.

4. The method for rapid safety evaluation of cracked lining structures in railway tunnels according to claim 1, characterized in that, The In step 2, the measured crack width m of the tunnel lining structure is greater than 0.2 mm.

5. The method for rapid safety evaluation of cracked lining structures in railway tunnels according to any one of claims 1-4, characterized in that, In step 4, the specific method for determining the safety status of the lining structure based on the stress state of the reinforcing steel is as follows: When the measured crack width m of the tunnel lining structure is less than or equal to n1, the safety level is Class I. When the measured crack width m of the tunnel lining structure is greater than n1 and m ≤ n2, the safety level is Class II. When the measured crack width m of the tunnel lining structure is greater than n2 and m≤n3, the safety level is III. When the measured crack width m of the tunnel lining structure is greater than n3, the safety level is IV. The safety levels of Level I, Level II, Level III, and Level IV decrease progressively.

6. The method for rapid safety evaluation of cracked lining structures in railway tunnels according to claim 5, characterized in that, In step 4 When the safety level is I, the lining structure meets the requirements for normal use and can maintain normal operation; When the safety level is II, the safety of the lining structure is reduced and the internal force of the lining exceeds the design state, but the lining reinforcement can still continue to bear the load within the elastic range. Measures such as increasing the monitoring frequency and issuing early warnings are taken. When the safety level is III, the lining reinforcement undergoes irreversible plastic deformation. Crack changes should be continuously monitored, and the lining structure should be repaired and reinforced according to the crack changes. When the safety level is IV, the stress on the reinforcing steel exceeds the ultimate strength, the lining structure is damaged, the reinforcing steel at the crack no longer has the load-bearing capacity, the train speed should be limited, and if the cracks continue to increase and multiply, the line should be closed, the lining should be removed and the lining structure should be reconstructed.

Images