A seismic and anti-dislocation structure and construction method for a tunnel crossing an active fault zone

Abstract

The present invention discloses a seismic and anti-dislocation structure and construction method for tunnels crossing active fault zones. The structure comprises a lining for a strongly affected section of the active fault zone and a lining for a generally affected section. Both the strongly affected section and the generally affected section utilize segmental linings, connected by large-deformation waterproof flexible joints. The strongly affected section is shorter than the generally affected section. The strongly affected section utilizes a double-layer off-wall lining, while the generally affected section utilizes a composite lining. The structure of the present invention utilizes different structural types tailored to the seismic damage characteristics of the strongly affected and generally affected sections of the tunnel, effectively resisting near-fault strong earthquakes and fault dislocation, ensuring the safety of tunnels crossing active fault zones.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular to an anti-seismic and anti-dislocation structure of a tunnel crossing an active fault zone and a construction method thereof. Background Art

[0002] Extensive historical data on tunnel earthquake damage indicates that tunnels crossing active fault zones suffer severe structural damage, potentially causing structural failures such as dislocation, cracking, and faulting, resulting in significant casualties and property losses, with significant socioeconomic impacts. Therefore, appropriate seismic mitigation measures are necessary to ensure the safety of tunnels crossing active fault zones.

[0003] At present, there are four main seismic protection measures for tunnels crossing active fault zones, namely: 1) reserving deformation space to optimize the cross-sectional shape and lining segment design; 2) changing the properties of the surrounding rock, such as grouting the surrounding rock or adding anchor rods; 3) improving the lining performance, such as increasing the tunnel structure strength, damping, and stiffness adjustment; 4) setting up shock-absorbing measures, such as setting up shock-absorbing structures between the tunnel and the stratum.

[0004] However, during the fault movement, the interaction between the surrounding rock and the tunnel will generate huge stress, and the frequency components of the near-fault seismic waves are complex, the vibration amplitude is large, and the vertical seismic motion parameters are large. As a result, the current seismic protection measures are difficult to resist the combined effects of strong earthquakes and fault dislocations, and have limited adaptability to large-scale dislocations in active fault zones, making it difficult to ensure the safety of tunnels crossing active fault zones. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides an earthquake-resistant and anti-fault structure and construction method for tunnels crossing active fault zones. Different structural types are adopted according to the earthquake damage characteristics of tunnels in strongly affected sections and generally affected sections. It can effectively resist strong earthquakes near the fault and fault faults, ensure the safety of tunnels crossing active fault zones, and solve the problems mentioned in the above background technology.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solutions: an anti-seismic and anti-dislocation structure for a tunnel crossing an active fault zone, the structure comprising a lining of a strongly affected section of the active fault zone and a lining of a generally affected section, the linings of the strongly affected section and the generally affected section both being segmental linings, the segments being connected by large-deformation waterproof flexible joints, the segment length of the strongly affected section being shorter than that of the generally affected section, the lining of the strongly affected section being a double-layer off-wall lining, and the lining of the generally affected section being a composite lining.

[0007] Preferably, the double-layer off-wall lining includes an inner lining, a middle layer, and an outer lining; the inner lining is a reinforced concrete structure, used to bear the load generated after the outer lining is damaged; the middle layer is a concrete material, used to absorb the energy generated during fault movement and seismic vibration.

[0008] Preferably, the outer lining includes an outer primary support layer, an outer waterproof layer, and an outer secondary lining;

[0009] The outer initial support includes shotcrete, steel frame and anchor rods;

[0010] The outer waterproof layer includes geotextile and waterproof board;

[0011] The outer secondary lining is a reinforced concrete structure.

[0012] Preferably, the inverted arch portion of the intermediate layer is filled with concrete, while the arch wall portion is not filled, and the thickness of the intermediate layer is determined by the maximum offset of the fault.

[0013] Preferably, the composite lining includes initial support, a shock-absorbing layer, a waterproof layer and a secondary lining.

[0014] Preferably, the initial support comprises anchor rods, shotcrete, and steel frames;

[0015] The shock-absorbing layer is made of flexible material and is used to absorb the energy generated during ground shaking;

[0016] The waterproof layer includes geotextile and waterproof board;

[0017] The secondary lining is a reinforced concrete structure.

[0018] Preferably, the deformable waterproof flexible joint is composed of a steel plate, a rubber waterstop and a nut; the rubber waterstop is fixed to the end of the lining by the steel plate and the nut, and the length of the rubber waterstop is determined by the maximum offset of the fault.

[0019] In addition, to achieve the above-mentioned purpose, the present invention also provides the following technical solution: a construction method of an earthquake-resistant and anti-fault structure of a tunnel crossing an active fault zone, comprising the following steps:

[0020] S1. Based on the influence of the displacement of the active fault zone and the strong earthquake force on the tunnel, the tunnel crossing the active fault zone is divided into two sections: the section with strong influence of the active fault zone and the section with general influence;

[0021] S2. Double-layer off-wall lining is used for sections with strong influence from the active fault zone, and composite lining is used for sections with general influence;

[0022] S3. When double-layer off-wall lining is used, the cross section includes the following:

[0023] 1) Determine the inner profile dimensions of the tunnel inner lining according to the tunnel clearance dimension requirements of the engineering specifications; preliminarily determine the structural parameters of the tunnel inner lining, then use the load-structure method to analyze the internal forces of the tunnel inner lining under load, calculate the safety factor, and once the safety factor meets the requirements, determine the final structural parameters of the inner lining and begin construction of the inner lining;

[0024] 2) Determine the width of the middle layer d according to the maximum displacement of the fault, d = dmax, and then construct the middle layer;

[0025] 3) Based on the outer contour dimensions of the tunnel inner lining and the width of the middle layer, determine the inner contour dimensions of the tunnel outer lining and preliminarily determine the structural parameters of the tunnel outer lining. Then, use the load-structure method to analyze the internal forces of the tunnel outer lining under load and calculate the safety factor. Once the safety factor meets the requirements, determine the final structural parameters of the outer lining and begin construction of the outer lining, which includes the outer primary support, outer waterproof layer, and outer secondary lining.

[0026] S4. When double-layer off-wall lining is used, the longitudinal section shall include the following:

[0027] The longitudinal segment length of the double-layer off-wall lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established, taking into account the influence of fault movement. The internal forces of the tunnel longitudinal section after fault movement are calculated. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final longitudinal segment length of the double-layer off-wall lining is determined, and construction begins based on the final longitudinal segment length.

[0028] S5. When composite lining is used, the cross section shall include the following:

[0029] Determine the tunnel's internal dimensions based on the tunnel clearance requirements of the engineering specifications. Preliminarily determine the tunnel's composite lining structural parameters. Then, use the reaction-displacement method to analyze the tunnel lining's internal forces under strong earthquake forces and calculate the safety factor. Once the safety factor meets the requirements, determine the final inner lining structural parameters and begin construction of the composite lining, including the initial support, shock-absorbing layer, waterproof layer, and secondary lining.

[0030] S6. When composite lining is used, the longitudinal section shall include the following:

[0031] The length of the longitudinal segment of the composite lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established to consider the influence of strong earthquake motion. The internal forces of the longitudinal section of the tunnel under strong earthquake motion are solved. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final length of the longitudinal segment of the composite lining is determined, and construction begins based on the final determined longitudinal segment length.

[0032] Preferably, in step S1, the strongly affected section of the active fault zone refers to the fault zone and the section on both sides of the fault zone that is severely damaged by the earthquake. This section is affected by both the displacement of the fault of the active fault zone and the strong earthquake force; the generally affected section refers to the section from the edge of the strongly affected section of the active fault zone to the outside that is gradually affected by the earthquake damage, and this section is affected by the strong earthquake force.

[0033] The beneficial effects of the present invention are:

[0034] 1) This invention addresses the technical challenges of seismic fortification of tunnels crossing active fault zones by providing a seismic-resistant and anti-slip structure. This structure comprises two components: a lining for the strongly affected section of the active fault zone and a lining for the generally affected section. A double-layer off-wall segmental lining is employed for the strongly affected section, while a composite segmental lining is employed for the generally affected section.

[0035] 2) In the strongly affected section of the tunnel, strong earthquakes near the fault and fault shearing are combined. The double-layer free-standing lining can absorb the energy generated by strong earthquakes and fault shearing through flexible joints and intermediate layers between segments, preventing damage to the lining under these conditions.

[0036] 3) Generally, the affected section is subject to strong earthquake motion. The composite lining can absorb the energy generated by the strong earthquake through the shock-absorbing layer, thus preventing the secondary lining from being damaged under the influence of the strong earthquake. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Schematic diagram of the seismic and anti-dislocation structural system of a tunnel crossing an active fault zone according to the present invention;

[0038] Figure 2 This is a schematic diagram of a double-layer off-wall lining structure;

[0039] Figure 3 This is a schematic diagram of the composite lining structure;

[0040] Figure 4 This is a schematic diagram of the inner contour dimensions of the tunnel lining in Example 3;

[0041] Figure 5 This is a schematic diagram of the inner contour dimensions of the tunnel lining in Example 3;

[0042] Figure 6 Schematic diagram of the safety factor of the tunnel longitudinal section in Example 3;

[0043] In the figure, 1-inner lining; 2-middle layer; 3-outer primary support; 4-outer waterproof layer; 5-outer secondary lining; 6-primary support; 7-shock absorption layer; 8-waterproof layer; 9-secondary lining. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0045] Example 1

[0046] Tunnels crossing active fault zones are divided into two sections based on the degree of damage and the factors causing it: the section strongly affected by active fault zone dislocation and the section generally affected. The section strongly affected by active fault zone dislocation refers to the fault zone and the section extending from the fault zone edge to either side that has suffered severe earthquake damage. In this section, affected by both the displacement of the active fault zone and the strong earthquake forces, the tunnel structure experiences both lateral and axial deformation under strong earthquakes, resulting in damage such as uplift and dislocation of the sub-track structure, dislocation, collapse, cracking, and large-scale delamination of the lining structure.

[0047] The general affected section refers to the section where the impact of earthquake damage gradually decreases from the edge of the strongly affected section of the active fault zone. This section is close to the earthquake source, has complex seismic wave frequency components, large vibration amplitude, large vertical seismic motion parameters, and is significantly affected by strong earthquake forces, resulting in earthquake damage such as lining cracks, local spalling, and roadbed cracks.

[0048] Therefore, it is necessary to design defenses based on the earthquake damage characteristics of the strongly affected section and the generally affected section. The strongly affected section should consider near-fault strong earthquakes and fault dislocation, while the generally affected section should consider near-fault strong earthquakes.

[0049] See also Figure 1-Figure 3 The present invention provides a technical solution: an anti-seismic and anti-fault structure for a tunnel crossing an active fault zone, the structure including a lining of a section strongly affected by the fault zone and a lining of a section generally affected by the fault zone, such as Figure 1 shown.

[0050] The lining of the strongly affected section and the general affected section both adopts segmental lining, and the segments are connected by large deformation waterproof flexible joints. The segment length of the strongly affected section is shorter than that of the general affected section. The lining of the strongly affected section adopts double-layer off-wall lining, and the lining of the general affected section adopts composite lining.

[0051] Further, such as Figure 2 As shown, the double-layer off-wall lining includes an inner lining 1, an intermediate layer 2, and an outer lining; the inner lining is a reinforced concrete structure 1, which is used to bear the load generated after the outer lining is damaged; the intermediate layer 2 is a concrete material, which is used to absorb the energy generated during fault movement and seismic vibration.

[0052] Furthermore, the outer lining includes an outer primary support layer 3, an outer waterproof layer 4, and an outer secondary lining 5.

[0053] The outer primary support 3 includes shotcrete, steel frame and anchor rods.

[0054] The outer waterproof layer 4 includes geotextile and waterproof board.

[0055] The outer secondary lining 5 is a reinforced concrete structure.

[0056] Furthermore, the inverted arch portion of the middle layer is filled with concrete, while the arch wall portion is not filled, and the thickness of the middle layer is determined by the maximum offset of the fault.

[0057] Further, such as Figure 3 As shown, the composite lining includes an initial support 6, a shock-absorbing layer 7, a waterproof layer 8 and a secondary lining 9.

[0058] Initial support 6 includes anchor rods, shotcrete, and steel frame;

[0059] The shock-absorbing layer 7 is made of flexible material and is used to absorb the energy generated during ground shaking;

[0060] The waterproof layer 8 includes a geotextile and a waterproof board;

[0061] The secondary lining 9 is a reinforced concrete structure.

[0062] Furthermore, the deformable waterproof flexible joint is composed of a steel plate, a rubber waterstop and a nut; the rubber waterstop is fixed to the end of the lining by the steel plate and the nut, and the length of the rubber waterstop is determined by the maximum offset of the fault.

[0063] The structure of the present invention adopts different structural types according to the earthquake damage characteristics of the tunnel in the strongly affected section and the generally affected section, which can effectively resist strong earthquakes near the fault and fault dislocation, and ensure the safety of tunnels crossing active fault zones.

[0064] Example 2

[0065] A construction method for a seismic and anti-dislocation structure of a tunnel crossing an active fault zone comprises the following steps:

[0066] S1. Based on the influence of the displacement of the active fault zone and the strong earthquake force on the tunnel, the tunnel crossing the active fault zone is divided into two sections: the section with strong influence of the active fault zone and the section with general influence;

[0067] S2. Double-layer off-wall lining is used for sections with strong influence from the active fault zone, and composite lining is used for sections with general influence;

[0068] S3. When double-layer off-wall lining is used, the cross section includes the following:

[0069] 1) Determine the inner contour dimensions of the tunnel inner lining according to the tunnel clearance dimension requirements of the engineering specifications; preliminarily determine the structural parameters of the tunnel inner lining, then use the load-structure method to analyze the internal forces of the tunnel inner lining under load, calculate the safety factor, and once the safety factor meets the requirements, determine the final structural parameters of the inner lining and begin construction of the inner lining 1;

[0070] 2) Determine the width of the intermediate layer d according to the maximum displacement of the fault dmax, d=dmax, and then construct the intermediate layer 2;

[0071] 3) Based on the outer contour dimensions of the tunnel inner lining and the width of the middle layer, determine the inner contour dimensions of the tunnel outer lining, preliminarily determine the structural parameters of the tunnel outer lining, then use the load-structure method to analyze the internal forces of the tunnel outer lining under load, calculate the safety factor, and after the safety factor meets the requirements, determine the final structural parameters of the outer lining and begin construction of the outer lining, specifically including the outer primary support 3, the outer waterproof layer 4, and the outer secondary lining 5;

[0072] S4. When double-layer off-wall lining is used, the longitudinal section shall include the following:

[0073] The longitudinal segment length of the double-layer off-wall lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established, taking into account the influence of fault movement. The internal forces of the tunnel longitudinal section after fault movement are calculated. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final longitudinal segment length of the double-layer off-wall lining is determined, and construction begins based on the final longitudinal segment length.

[0074] S5. When composite lining is used, the cross section shall include the following:

[0075] Determine the tunnel's internal dimensions based on the tunnel clearance requirements of the engineering specifications; preliminarily determine the tunnel's composite lining structural parameters; then use the reaction-displacement method to analyze the tunnel lining's internal forces under strong earthquake forces and calculate the safety factor. Once the safety factor meets the requirements, determine the final inner lining structural parameters and begin construction of the composite lining, including the primary support layer 6, the shock-absorbing layer 7, the waterproof layer 8, and the secondary lining 9.

[0076] S6. When composite lining is used, the longitudinal section shall include the following:

[0077] The length of the longitudinal segment of the composite lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established to consider the influence of strong earthquake motion. The internal forces of the longitudinal section of the tunnel under strong earthquake motion are solved. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final length of the longitudinal segment of the composite lining is determined, and construction begins based on the final determined longitudinal segment length.

[0078] Furthermore, in step S1, the strongly affected section of the active fault zone refers to the fault zone and the section on both sides of the fault zone that is severely damaged by the earthquake. This section is affected by both the displacement of the fault of the active fault zone and the strong earthquake force; the generally affected section refers to the section from the edge of the strongly affected section of the active fault zone to the outside that is gradually affected by the earthquake damage. This section is affected by the strong earthquake force.

[0079] Example 3

[0080] Taking a 350km / h double-track high-speed railway tunnel in my country as an example, the design method described in the present invention is explained, and the double-layer off-wall lining in the section strongly affected by the active fault zone is taken as an example.

[0081] The cross-section design steps are as follows:

[0082] (1) According to the tunnel clearance size requirements of relevant engineering specifications, determine the inner contour dimensions of the tunnel lining; according to the Railway Tunnel Design Code (TB 10003), determine the inner contour dimensions of the tunnel lining as follows: Figure 4 shown.

[0083] (2) Preliminary determination of tunnel lining structural parameters based on relevant engineering specifications and engineering experience, including concrete grade, concrete thickness, steel grade, steel bar spacing, etc.;

[0084] The tunnel lining structural parameters are determined according to the Railway Tunnel Design Code (TB 10003) as shown in Table 1.

[0085] Table 1 Tunnel lining structural parameters

[0086] Arch wall thickness (cm) Invert / base plate thickness (cm) Steel bar number Steel bar diameter (mm) Rebar spacing (m) 55 65 HRB400 22 0.25

[0087] (3) Determine the width of the intermediate layer d according to the maximum displacement of the fault, d = dmax;

[0088] The maximum displacement of the fault that the tunnel passes through is 1m, so the width of the middle layer is 1m.

[0089] (4) Determine the inner contour dimensions of the tunnel lining based on the outer contour dimensions of the tunnel lining and the width of the intermediate layer;

[0090] According to the outer contour size of the tunnel lining and the width of the middle layer, the inner contour size of the tunnel lining is determined as follows: Figure 5 shown.

[0091] (5) Preliminary determination of tunnel lining structural parameters based on relevant engineering specifications and engineering experience, including: initial support shotcrete grade of the outer lining, shotcrete thickness, steel frame type, steel frame spacing, secondary lining concrete grade, concrete thickness, steel bar grade, steel bar spacing, etc.;

[0092] The tunnel lining structural parameters are determined according to the Railway Tunnel Design Code (TB 10003) and engineering experience, as shown in Table 2.

[0093] Table 2 Tunnel lining structural parameters

[0094]

[0095]

[0096] (6) The load-structure method is used to analyze the internal forces of the tunnel lining under load.

[0097] Finite element software is used to establish a load structure model and calculate the axial force and bending moment of the tunnel cross section.

[0098] (7) Calculate the safety factor of the tunnel lining according to relevant engineering specifications. If the safety factor meets the requirements, use this parameter as the lining parameter. If it does not meet the requirements, further strengthen the lining structure parameters until the safety factor meets the design requirements.

[0099] The safety factor of the tunnel lining is calculated according to the Code for Design of Railway Tunnels (TB 10003), as shown in Table 3.

[0100] Table 3 Tunnel lining safety factor

[0101] section Axial force (N) Bending moment (N·m) control Safety factor Security 1 -9.95E+05 65899 pressure 19.62 pass 2 -9.92E+05 2857.7 pressure 15.17 pass 3 -9.93E+05 -250.76 pressure 15.13 pass 4 -9.85E+05 38199 pressure 18.29 pass 5 -9.67E+05 97522 pressure 27.44 pass 6 -9.34E+05 1.49E+05 pressure 53.16 pass 7 -8.89E+05 1.41E+05 pull 9.51 pass 8 -8.37E+05 89774 pressure 39.26 pass 9 -7.85E+05 13903 pressure 23.22 pass 10 -7.41E+05 -66606 pressure 36.07 pass 11 -7.10E+05 -1.34E+05 pull 10.75 pass 12 -6.95E+05 -1.76E+05 pull 7.13 pass 13 -6.97E+05 -1.84E+05 pull 5.81 pass 21 -7.17E+05 -1.56E+05 pull 8.76 pass 22 -7.50E+05 -99034 pressure 63.58 pass 23 -7.92E+05 -22884 pressure 24.39 pass 24 -8.36E+05 56647 pressure 26.93 pass 25 -8.76E+05 1.21E+05 pressure 46.90 pass 26 -9.04E+05 1.52E+05 pull 9.03 pass 27 -9.17E+05 1.33E+05 pressure 46.44 pass 28 -9.14E+05 76687 pressure 26.17 pass 29 -9.00E+05 20455 pressure 18.60 pass 30 -8.86E+05 -13979 pressure 16.80 pass

[0102] (8) Use the load-structure method to analyze the internal forces of the lining structure;

[0103] Finite element software is used to establish a load structure model and calculate the axial force and bending moment of the tunnel cross section.

[0104] (9) Calculate the safety factor of the tunnel lining according to relevant engineering specifications. If the safety factor meets the requirements, use this parameter as the outer lining parameter. If it does not meet the requirements, further strengthen the lining parameters until the safety factor meets the design requirements.

[0105] The steps for longitudinal section design are as follows:

[0106] (1) Preliminary determination of the longitudinal segment length of the double-layer off-wall structure lining based on relevant engineering specifications and engineering experience;

[0107] According to the Railway Tunnel Design Code (TB 10003), the segment length was preliminarily determined to be 9m.

[0108] (2) Establish a three-dimensional numerical finite element calculation model of the tunnel considering the influence of fault dislocation based on the formation parameters and fault parameters;

[0109] The fault dip angle is 76°, the tunnel is perpendicular to the fault, and the formation parameters are shown in Table 4. A tunnel calculation model considering fault movement is established.

[0110] Table 4 Stratigraphic and fault parameters

[0111]

[0112] (3) Determine the internal forces of the tunnel lining longitudinal section after fault displacement.

[0113] (4) Calculate the safety factor of the lining according to the specification. If the safety factor meets the requirements, use this segment length. If not, further reduce the segment length until the safety factor meets the design requirements. Figure 6 shown.

[0114] For the composite lining, the method adopted is basically the same as that in the above embodiment, and will not be described in detail here.

[0115] The anti-seismic and anti-fault structure of the tunnel constructed by the construction method of the present invention can effectively resist strong earthquakes near the fault and fault fault, thereby ensuring the safety of the tunnel crossing the active fault zone.

[0116] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A construction method for a seismic and anti-dislocation structure of a tunnel crossing an active fault zone, characterized by: The steps include: S1. Based on the influence of the displacement of the active fault zone and the strong earthquake force on the tunnel, the tunnel crossing the active fault zone is divided into two sections: the section with strong influence of the active fault zone and the section with general influence; S2. Double-layer off-wall lining is used for sections with strong influence from the active fault zone, and composite lining is used for sections with general influence; S3. When double-layer off-wall lining is used, the cross section includes the following: 1) Determine the inner contour dimensions of the tunnel inner lining according to the tunnel clearance dimension requirements of the engineering specifications; preliminarily determine the structural parameters of the tunnel inner lining, then use the load-structure method to analyze the internal forces of the tunnel inner lining under load, calculate the safety factor, and determine the final structural parameters of the inner lining after the safety factor meets the requirements, and start construction of the inner lining (1); 2) Determine the width of the intermediate layer d according to the maximum displacement of the fault, d = dmax, and then construct the intermediate layer (2); 3) According to the outer contour dimensions of the tunnel inner lining and the width of the middle layer, determine the inner contour dimensions of the tunnel outer lining, preliminarily determine the structural parameters of the tunnel outer lining, then use the load-structure method to analyze the internal forces of the tunnel outer lining under load, calculate the safety factor, and after the safety factor meets the requirements, determine the final structural parameters of the outer lining and start construction of the outer lining, specifically including the outer primary support (3), the outer waterproof layer (4) and the outer secondary lining (5); S4. When double-layer off-wall lining is used, the longitudinal section shall include the following: The longitudinal segment length of the double-layer off-wall lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established, taking into account the influence of fault movement. The internal forces of the tunnel longitudinal section after fault movement are calculated. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final longitudinal segment length of the double-layer off-wall lining is determined, and construction begins based on the final longitudinal segment length. S5. When composite lining is used, the cross section shall include the following: Determine the tunnel's internal dimensions based on the tunnel clearance requirements of the engineering specifications; preliminarily determine the tunnel composite lining structural parameters, then use the reaction displacement method to analyze the tunnel lining's internal forces under strong earthquake forces, calculate the safety factor, and once the safety factor meets the requirements, determine the final inner lining structural parameters and begin construction of the composite lining, including initial support (6), shock-absorbing layer (7), waterproof layer (8), and secondary lining (9); S6. When composite lining is used, the longitudinal section includes the following: The length of the longitudinal segment of the composite lining is preliminarily determined based on engineering specifications and engineering experience. A three-dimensional numerical finite element calculation model of the tunnel is established to consider the influence of strong earthquake motion. The internal forces of the longitudinal section of the tunnel under strong earthquake motion are solved. The safety factor is calculated based on the internal forces of the longitudinal section. Once the safety factor meets the requirements, the final length of the longitudinal segment of the composite lining is determined, and construction begins based on the final determined longitudinal segment length.

2. The construction method according to claim 1, characterized in that: In step S1, the strongly affected section of the active fault zone refers to the fault zone and the section on both sides of the fault zone that is severely damaged by the earthquake. This section is affected by both the displacement of the fault of the active fault zone and the strong earthquake force; the generally affected section refers to the section from the edge of the strongly affected section of the active fault zone to the outside that is gradually affected by the earthquake damage. This section is affected by the strong earthquake force.

3. The construction method according to claim 1, wherein: The inner lining (1) is a reinforced concrete structure, used to bear the load generated after the outer lining is damaged; the middle layer (2) is a concrete material, used to absorb the energy generated during fault movement and earthquake vibration.

4. The construction method according to claim 1, characterized in that: The outer primary support (3) includes sprayed concrete, a steel frame, and anchor rods; the outer waterproof layer (4) includes geotextile and a waterproof board; and the outer secondary lining (5) is a reinforced concrete structure.

5. The construction method according to claim 1, characterized in that: The inverted arch portion of the intermediate layer is filled with concrete, while the arch wall portion is not filled. The thickness of the intermediate layer is determined by the maximum offset of the fault.

6. The construction method according to claim 1, characterized in that: The initial support (6) comprises anchor rods, shotcrete, and steel frames; The shock-absorbing layer (7) is made of a flexible material and is used to absorb the energy generated during ground shaking; The waterproof layer (8) includes a geotextile and a waterproof board; The secondary lining (9) is a reinforced concrete structure.

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