Flexible connecting mechanism for connecting a shield tunnel and a vertical shaft and design method thereof

Abstract

The present application relates to the technical field of railway engineering, and particularly provides a flexible connecting mechanism for the connection between a shield tunnel and a vertical shaft and a design method thereof, which comprises a tunnel segment, a water-stopping pressure-bearing assembly, a flexible filling layer, an SMA damping assembly and a limiting and restraining assembly, the water-stopping pressure-bearing assembly comprises a water-stopping steel plate, the water-stopping steel plate is sleeved outside the end of the tunnel segment, the flexible filling layer is arranged between the water-stopping steel plate and the tunnel segment and the vertical shaft, the SMA damping assembly is embedded in the flexible filling layer, the two ends of the SMA damping assembly are anchored in the tunnel segment and the vertical shaft respectively, and the limiting and restraining assembly is used for connecting the SMA damping assembly and the water-stopping steel plate, the shape memory alloy rod has a certain ability to restore to the original shape after deformation, the flexible filling layer ensures a certain design allowable deformation amount after an earthquake, the connection node of the tunnel segment and the vertical shaft is protected from damage, the memory alloy rod restores a certain deformation after the earthquake, the recoverability of the structure is realized, and the toughness of the tunnel is enhanced.

Description

Technical Field

[0001] This invention relates to the field of railway engineering technology, and in particular to a flexible connection mechanism and its design method at the connection between a shield tunnel and a vertical shaft. Background Technology

[0002] With the deepening development of underground space, the construction of large-diameter shield tunnels is increasing. The connection node between the shield tunnel and the vertical shaft (or working shaft) is a key part of the underground structural system, and its structural safety and waterproof performance are directly related to the operational safety of the entire tunnel.

[0003] Because shaft structures typically have extremely high stiffness, while shield tunnel segments have relatively low stiffness, a significant abrupt change in stiffness occurs at the connection point. Under seismic loading, this stiffness difference leads to significant differential displacement and stress concentration at the connection, creating a complex spatial "end effect." Both theoretical analysis and disaster investigations indicate that this node is one of the weakest points in the seismic resistance of shield tunnels. It is highly susceptible to excessive relative displacement, which can cause the connection between the shield tunnel and the shaft to open, the concrete to crack, or even the structure to fracture, leading to serious problems such as water leakage.

[0004] To address these challenges, flexible joints are commonly used in engineering projects, but all have significant drawbacks: Flexible filling layers such as cork rubber sheets or foamed concrete are used between the tunnel segments and the shaft to buffer deformation. While this method can alleviate stress concentration to some extent, ordinary flexible materials have extremely low stiffness and weak constraint on differential deformation, easily leading to excessive misalignment at the connection point between the tunnel segments and the shaft, and failing to meet long-term stable waterproofing requirements. Some joints use flexible damping and tensile devices composed of water-stop rubber and steel strands. However, these traditional devices are complex in construction, separating water-stopping and tensile functions, and lack the ability to dissipate seismic energy. After a strong earthquake, the connection point between the shield tunnel and the shaft often experiences significant permanent residual deformation. Summary of the Invention

[0005] To address the issue of significant stiffness abrupt changes and stress concentration at the connection between shaft structures, which typically exhibit extremely high stiffness, and shield tunnel segments, which have relatively low stiffness, this invention provides a flexible connection mechanism and its design method for the connection between shield tunnels and shafts.

[0006] The technical solution adopted by this invention to solve its technical problem is: a flexible connection mechanism and its design method at the connection between a shield tunnel and a shaft, including tunnel segments, and further including a water-stopping and pressure-bearing component, a flexible filling layer, an SMA damping component, and a limiting constraint component disposed between the tunnel segments and the shaft. The water-stopping and pressure-bearing component includes a water-stopping steel plate, which is sleeved on the outer side of the end of the tunnel segment. Multiple flexible filling layers are disposed in the annular gap between the water-stopping steel plate, the tunnel segment, and the shaft. The SMA damping component is pre-embedded in the flexible filling layer along the circumferential direction of the tunnel segment. The two ends of the SMA damping component are respectively anchored in the tunnel segment and the shaft. The limiting constraint component is used to connect the SMA damping component and the water-stopping steel plate.

[0007] Preferably, an end face annular plate is vertically fixed to the inner side of the water-stop steel plate. One side of the end face annular plate abuts against the end face of the tunnel segment, and the other side of the end face annular plate abuts against the flexible filling layer.

[0008] Preferably, the SMA damping component includes shape memory alloy rods, with multiple shape memory alloy rods pre-embedded in the flexible filling layer between the end face annular plate and the shaft along the circumferential direction, and the two ends of the shape memory alloy rods being anchored to the tunnel segment and the shaft, respectively.

[0009] Preferably, the limiting constraint assembly includes multiple arc-shaped limiting buffer rods and multiple limiting blocks. The two ends of each arc-shaped limiting buffer rod are respectively sleeved on two shape memory alloy rods and rotatably connected to the shape memory alloy rods. The multiple shape memory alloy rods are connected by multiple arc-shaped limiting buffer rods to form a ring-shaped integral structure. The ends of the multiple limiting blocks are sleeved on the multiple shape memory alloy rods at intervals and abut against the sides of the arc-shaped limiting buffer rods. The bottom of each limiting block is fixedly connected to the inner ring of the water-stop steel plate.

[0010] Preferably, the bottom of the limiting block is provided with an arc-shaped bracket, the direction of the notch of the arc-shaped bracket is consistent with the direction of the notch of the arc-shaped limiting buffer rod, and the direction of the notch of the arc-shaped bracket is set towards the outside of the circumference of the waterstop steel plate, and the arc-shaped bracket is fixedly connected to the waterstop steel plate.

[0011] Preferably, the shape memory alloy rod, the arc-shaped limiting buffer rod, and the arc-shaped bracket are all made of shape memory alloy, and the arc-shaped bracket is welded to the limiting block to form an integral structure.

[0012] Preferably, a water-stop groove is fixed on the end face annular plate, and a water-swellable rubber ring is snapped into the water-stop groove. The two sides of the water-swellable rubber ring abut against the end face annular plate and the flexible filling layer, respectively.

[0013] Preferably, the water-stop groove is a closed, wave-shaped annular structure, and the width of the water-stop groove is greater than the diameter of the water-swellable rubber ring.

[0014] A design method for a flexible connection mechanism at the connection between a shield tunnel and a shaft, applicable to the flexible connection mechanism at the connection between a shield tunnel and a shaft as described above, further includes: The flexible joint design method employs dynamic time history analysis to establish a three-dimensional nonlinear dynamic numerical model of the "strata-shaft-shield tunnel". The design seismic motion parameters of the engineering site are input, including but not limited to artificial earthquake response spectrum time histories. The response of the tunnel-shaft connection under design seismic loading is calculated as follows: 1. Longitudinal relative displacement response Δu; 2. Joint rotation response θ; 3. Circumferential opening distribution response Δd(φ), where φ is the circumferential angle; 4. Joint misalignment Δs. For the flexible joint parameter design, based on the joint design displacement response determined in the above numerical simulation steps, the cross-sectional area and number of shape memory alloy rods are determined using the following method: I. Axial bearing capacity control: The axial restoring force F of the shape memory alloy rod under the design displacement Δu should satisfy: F = n × A × σ(ε); Where n is the number of flexible joint components, A is the cross-sectional area of ​​the shape memory alloy rod, and σ(ε) is the stress of the shape memory alloy rod under the corresponding strain ε=Δu / L (L is the effective length of the shape memory alloy rod). It is required that F is not less than 1.2 times the design value of the longitudinal seismic force at the joint, and not greater than the design value of the bearing capacity of the shaft end anchoring ring and the tunnel end reinforcing segment; II. Strain Control: The maximum strain ε of the shape memory alloy rod under the design seismic displacement should satisfy: εL≤ε_max≤0.7εmax_recoverable, where εL is the strain at the beginning of the austenite-to-martensite phase transformation (approximately 0.8%), and εmax_recoverable is the maximum recoverable strain (approximately 6% to 8%). III. Self-resetting capability verification: The residual strain of the shape memory alloy rod after the earthquake should not be greater than 0.5%, and the corresponding residual longitudinal displacement of the joint should not be greater than 1mm, so as to meet the requirements of rapid resumption of operation of high-speed railway ballastless track after the earthquake. IV. Energy dissipation capacity verification: The energy dissipated by the shape memory alloy rod joint in a complete loading and unloading cycle, Wd, should be no less than 3 times the elastic strain energy of the traditional rigid joint under the same displacement, and the equivalent damping ratio should be no less than 0.08.

[0015] The beneficial effects of this invention are as follows: First, the shape memory alloy rod has a certain ability to recover its original shape after deformation. After an earthquake, the flexible filling layer ensures a certain amount of design allowable deformation, protecting the tunnel segments and shaft structure from damage. After an earthquake, the shape memory alloy rod recovers a certain amount of deformation, realizing the recoverability of the structure and enhancing the toughness of the tunnel. Combined with the compression water-stopping of the flexible filling layer and the active water-stopping of the water-swellable rubber ring, the leakage problem under large deformation conditions is solved.

[0016] Secondly, when the arc-shaped limiting buffer rod is under stress, its arc-shaped structure can support the shape memory alloy rod and evenly distribute part of the force on the shape memory alloy rod to the limiting block. Then, the limiting block distributes the force to the more robust water-stop steel plate to avoid excessive stress on the shape memory alloy rod. This ensures that the shape memory alloy rod can return to its original shape after the earthquake and also limits the maximum tensile displacement of the shape memory alloy rod under extreme loads, thus preventing the overall overload failure of the SMA damping assembly. After the above components are deformed due to the earthquake, they can return to their original shape to improve the connection stability between the tunnel segment and the wellhead, ensure the integrity of the joint under strong earthquakes, prevent the segment from falling off, and improve the robustness of the structure.

[0017] Thirdly, by installing SMA flexible joints at the points of abrupt change in stiffness between the tunnel and the shaft, the low stiffness characteristic of SMA's superelasticity is utilized to concentrate and confine seismic deformation at the joint, reducing the bending deformation and internal forces of the tunnel segments on both sides of the joint, thereby reducing the amount of deformation transmitted to the track structure. Numerical analysis shows that under the same seismic load, the longitudinal deformation of the tunnel structure using the shape memory alloy rod joint of this invention can be reduced by 30% to 50%, and the track surface unevenness can be controlled within the limits for high-speed railways. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in 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 merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the optimal embodiment of the flexible connection mechanism and its design method at the connection between a shield tunnel and a vertical shaft according to the present invention. Figure 2 yes Figure 1 Enlarged view of point A in the middle; Figure 3 This is a schematic diagram of the water-stop steel plate of a flexible connection mechanism and its design method at the connection between a shield tunnel and a vertical shaft according to the present invention. Figure 4This is a schematic diagram of the arc-shaped limiting buffer rod of the flexible connection mechanism and its design method at the connection between the shield tunnel and the vertical shaft of the present invention. Figure 5 This is a schematic diagram of the water-stop groove of a flexible connection mechanism and its design method at the connection between a shield tunnel and a vertical shaft according to the present invention. Figure 6 This is a flowchart illustrating the design method of a flexible connection mechanism at the connection between a shield tunnel and a vertical shaft according to the present invention.

[0020] Reference numerals: 1. Tunnel segment; 2. Shaft; 3. Water-stop steel plate; 4. Flexible filling layer; 5. End face annular plate; 6. Shape memory alloy rod; 7. Arc-shaped limiting buffer rod; 8. Limiting block; 9. Arc-shaped bracket; 10. Water-stop groove. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The concepts involved in this application will first be described with reference to the accompanying drawings. It should be noted that the following descriptions of various concepts are only for the purpose of making the content of this application easier to understand and do not constitute a limitation on the scope of protection of this application; furthermore, the embodiments and features in the embodiments of this application can be combined with each other unless otherwise specified. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] like Figures 1 to 5 As shown, this invention provides an embodiment of a flexible connection mechanism and its design method at the connection between a shield tunnel and a shaft. The mechanism includes a tunnel segment 1, a water-stopping and pressure-bearing component, a flexible filling layer 4, an SMA damping component, and a limiting constraint component disposed between the tunnel segment 1 and the shaft 2. The water-stopping and pressure-bearing component includes a water-stopping steel plate 3, which is sleeved on the outer side of the end of the tunnel segment 1. Multiple flexible filling layers 4 are disposed within the annular gap between the water-stopping steel plate 3 and the tunnel segment 1 and the shaft 2. The flexible filling layer 4 is made of a viscoelastic material with a low elastic modulus, such as neoprene rubber or polyurethane elastomer, to accommodate differential settlement between the tunnel segment 1 and the shaft 2 and to initially soften the contact surface.

[0024] The SMA damping component is pre-embedded in the flexible filling layer 4 along the circumference of the tunnel segment 1. Through the synergistic effect of the flexible filling layer and the shape memory alloy rod 6, a smooth stiffness transition is achieved from the rigid shaft 2 to the flexible tunnel segment 1, effectively eliminating stress concentration. The two ends of the SMA damping component are anchored in the tunnel segment 1 and the shaft 2 respectively. The limiting constraint component is used to connect the SMA damping component and the waterstop steel plate 3.

[0025] An end face annular plate 5 is also vertically fixed to the inner side of the water-stop steel plate 3. One side of the end face annular plate 5 abuts against the end face of the tunnel segment 1, and the other side of the end face annular plate 5 abuts against the flexible filling layer 4.

[0026] The SMA damping component includes shape memory alloy rods 6. Multiple shape memory alloy rods 6 are pre-embedded in the flexible filling layer 4 between the end face annular plate 5 and the shaft 2 along the circumferential direction and penetrate the end face annular plate 5. The two ends of the shape memory alloy rods 6 are respectively anchored in the tunnel segment 1 and the shaft 2. In this embodiment, the SMA damping component uses shape memory alloy rods 6. In some other embodiments, the SMA damping component can also be made of stranded wire. The superelastic hysteresis characteristics of the shape memory alloy rods 6 or stranded wires are used to dissipate seismic energy and provide restoring force after the earthquake, so as to realize the self-resetting of the joint position between the tunnel segment 1 and the shaft 2 and significantly reduce residual deformation.

[0027] A water-stop groove 10 is also fixed on the end face annular plate 5. A water-swellable rubber ring is snapped into the water-stop groove 10. The two sides of the water-swellable rubber ring abut against the end face annular plate 5 and the flexible filling layer 4, respectively. The water-stop groove 10 is a closed wavy annular structure. When the water-stop groove 10 is subjected to radial force, the wavy annular structure can produce a large elastic deformation, so that the water-stop groove 10 can play a certain buffering role and prevent the water-swellable rubber ring inside the water-stop groove 10 from bearing a large load. When the instantaneous force on the water-stop groove 10 disappears, the wavy annular structure of the water-stop groove 10 can also self-clean. The water-swellable rubber ring is restored to its original shape and reset, improving its sealing effect and service life. The width of the water-swellable rubber ring is greater than the diameter of the water-swellable rubber ring. In this embodiment, the water-swellable rubber ring is used to maintain dynamic sealing when the joint undergoes misalignment and deformation. Combined with the compression water-stopping of the flexible filling layer 4 and the active water-stopping of the water-swellable rubber ring, the problem of easy leakage in the traditional connection method at the connection between the shield tunnel and the shaft under large deformation conditions is solved. In other embodiments, the water-swellable rubber ring can also be replaced by a compression water-stop strip.

[0028] The limiting constraint assembly includes multiple arc-shaped limiting buffer rods 7 and multiple limiting blocks 8. The two ends of each arc-shaped limiting buffer rod 7 are respectively sleeved on two shape memory alloy rods 6 and rotatably connected to the shape memory alloy rods 6. Multiple shape memory alloy rods 6 are connected by multiple arc-shaped limiting buffer rods 7 to form a ring-shaped integral structure. The ends of multiple limiting blocks 8 are sleeved on multiple shape memory alloy rods 6 at intervals and abut against the sides of the arc-shaped limiting buffer rods 7. The bottom of each limiting block 8 is fixedly connected to the inner ring of the water-stop steel plate 3.

[0029] During an earthquake, the tunnel segment 1 and shaft 2 become misaligned, causing the shape memory alloy rod 6 to undergo elastic deformation. The spacing between multiple shape memory alloy rods 6 changes, and the radial force on the shape memory alloy rod 6 is transmitted to the arc-shaped limiting buffer rod 7. When the arc-shaped limiting buffer rod 7 is under stress, its arc-shaped structure can support the shape memory alloy rod 6 and evenly distribute part of the force on the shape memory alloy rod 6 to the limiting block 8. The limiting block 8 then distributes the force to the more robust water-stop steel plate to prevent the shape memory alloy rod 6 from bearing excessive stress, so that the shape memory alloy rod 6 can return to its original shape after the earthquake. At the same time, the arc-shaped limiting buffer rod 7 and the limiting block 8 can also limit the maximum tensile displacement of the shape memory alloy rod 6 under extreme loads to prevent the overall overload failure of the SMA damping assembly, ensuring the integrity of the joint under strong earthquakes, preventing the segment from falling off, and improving the robustness of the structure.

[0030] The bottom of the limiting block 8 is provided with an arc-shaped bracket 9. The direction of the notch of the arc-shaped bracket 9 is consistent with the direction of the notch of the arc-shaped limiting buffer rod 7, and the notch of the arc-shaped bracket 9 is set towards the outside of the circumference of the waterstop steel plate 3. The arc-shaped bracket 9 is fixedly connected to the waterstop steel plate 3. The arc-shaped bracket 9 at the bottom of the limiting block 8 can improve the support strength of the limiting block 8. In addition, the limiting block 8 and the arc-shaped bracket 9 can also limit the multiple arc-shaped limiting buffer rods 7, so that the arc-shaped limiting buffer rods 7 can maintain their original position after reset.

[0031] The shape memory alloy rod 6, the arc-shaped limiting buffer rod 7, and the arc-shaped bracket 9 are all made of shape memory alloy. The arc-shaped bracket 9 is welded to the limiting block 8 to form an integrated structure. After the above components are deformed due to an earthquake, they can return to their original shape to improve the connection stability between the tunnel segment 1 and the shaft 2.

[0032] like Figure 6 As shown, the present invention provides a design method for a flexible connection mechanism at the connection between a shield tunnel and a shaft, applicable to a flexible connection mechanism at the connection between a shield tunnel and a shaft as described above, and further includes: The flexible joint design method employs dynamic time history analysis to establish a three-dimensional nonlinear dynamic numerical model of "strata-shaft-shield tunnel". The design seismic motion parameters of the engineering site are input, including but not limited to artificial earthquake response spectrum time histories. The response of the tunnel-shaft 2 connection under design seismic loading is calculated as follows: 1. Longitudinal relative displacement response Δu; 2. Joint rotation response θ; 3. Circumferential opening distribution response Δd(φ), where φ is the circumferential angle; 4. Joint misalignment Δs. For the flexible joint parameter design, based on the joint design displacement response determined in the above numerical simulation steps, the cross-sectional area and quantity of the shape memory alloy rods 6 are determined using the following method: I. Axial bearing capacity control: The axial restoring force F of the shape memory alloy rod 6 under the design displacement Δu should satisfy: F = n × A × σ(ε) Where n is the number of flexible joint components, A is the cross-sectional area of ​​shape memory alloy rod 6, and σ(ε) is the stress of shape memory alloy rod 6 under the corresponding strain ε=Δu / L (L is the effective length of shape memory alloy rod 6). It is required that F is not less than 1.2 times the design value of the longitudinal seismic force at the joint, and not greater than the design value of the bearing capacity of the shaft end anchoring ring and the tunnel end reinforcing segment.

[0033] II. Strain Control: The maximum strain ε of the shape memory alloy rod 6 under the design seismic displacement should satisfy: εL≤ε_max≤0.7εmax_recoverable, where εL is the strain at the beginning of the austenite-to-martensite phase transformation (approximately 0.8%), and εmax_recoverable is the maximum recoverable strain (approximately 6% to 8%).

[0034] III. Self-resetting capability verification: The residual strain of the shape memory alloy rod 6 after the earthquake should not exceed 0.5%, and the corresponding residual longitudinal displacement of the joint should not exceed 1mm, so as to meet the requirements of rapid resumption of operation of high-speed railway ballastless track after the earthquake.

[0035] IV. Energy dissipation capacity verification: The energy dissipated by the shape memory alloy rod 6 joint in a complete loading and unloading cycle, Wd, should not be less than 3 times the elastic strain energy of the traditional rigid joint under the same displacement, and the equivalent damping ratio should not be less than 0.08.

[0036] In this embodiment, the following case is used for calculation: The tunnel is a single-bore, double-track section with a shield excavation diameter of 12.2 meters, a segment thickness of 55 centimeters, and a ring width of 2 meters. The shaft is a circular reinforced concrete structure with an inner diameter of 8 meters and a depth of 65 meters. The site has a seismic fortification intensity of 8 degrees (design basic seismic acceleration of 0.20g), a design seismic group of Group 2, and a site category of Class II. CRTSⅢ type slab track is laid inside the tunnel.

[0037] Implementation Step 1: A three-dimensional model was established using general-purpose finite element software. The soil layers were linearized using an equivalent method to consider the changes in modulus ratio and damping ratio with shear strain. Axial, rotational, and shear springs were installed between the segment rings. Dynamic time-history analysis was performed using two natural strong earthquake records and one artificial wave with a fitted design response spectrum. The results showed that the peak longitudinal relative displacement at the joint section was 12 mm, the maximum section rotation angle was 0.15 degrees, the circumferential opening at the arch crown was 6 mm, and the radial misalignment was 4 mm. On the other hand, based on the 350 km / h ballastless track elevation deviation limit of 3.6 mm, the allowable longitudinal displacement of the joint was approximately 15 mm. Taking the smaller value, the design control longitudinal displacement was determined to be 12 mm.

[0038] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A flexible connection mechanism at the connection between a shield tunnel and a shaft, comprising tunnel segments (1), characterized in that: It also includes a water-stop pressure-bearing component, a flexible filling layer (4), an SMA damping component, and a limiting constraint component disposed between the tunnel segment (1) and the shaft (2). The water-stop pressure-bearing component includes a water-stop steel plate (3), which is sleeved on the outer side of the end of the tunnel segment (1). Multiple flexible filling layers (4) are disposed in the annular gap between the water-stop steel plate (3) and the tunnel segment (1) and the shaft (2). The SMA damping component is pre-embedded in the flexible filling layer (4) along the circumferential direction of the tunnel segment (1). The two ends of the SMA damping component are respectively Anchored within the tunnel segment (1) and shaft (2), the limiting constraint assembly is used to connect the SMA damping assembly and the water-stop steel plate (3); the SMA damping assembly includes shape memory alloy rods (6); the limiting constraint assembly includes multiple arc-shaped limiting buffer rods (7) and multiple limiting blocks (8), the two ends of each arc-shaped limiting buffer rod (7) are respectively sleeved on two shape memory alloy rods (6) and rotatably connected to the shape memory alloy rods (6), and multiple shape memory alloy rods (6) are connected through multiple arc-shaped limiting buffer rods (7) to form a ring-shaped integral structure.

2. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 1, characterized in that: The inner side of the water-stop steel plate (3) is also vertically fixed with an end face annular plate (5). One side of the end face annular plate (5) abuts against the end face of the tunnel segment (1), and the other side of the end face annular plate (5) abuts against the flexible filling layer (4).

3. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 2, characterized in that: Multiple shape memory alloy rods (6) are pre-embedded in the flexible filling layer (4) between the end face annular plate (5) and the vertical shaft (2) along the circumferential direction. The two ends of the shape memory alloy rods (6) are respectively anchored in the tunnel segment (1) and the vertical shaft (2).

4. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 3, characterized in that: Multiple limiting blocks (8) are spaced apart and fitted onto multiple shape memory alloy rods (6) and abut against the side of the arc-shaped limiting buffer rod (7). The bottom of each limiting block (8) is fixedly connected to the inner ring of the water-stop steel plate (3).

5. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 4, characterized in that: The bottom of the limiting block (8) is provided with an arc-shaped bracket (9). The direction of the notch of the arc-shaped bracket (9) is consistent with the direction of the notch of the arc-shaped limiting buffer rod (7), and the direction of the notch of the arc-shaped bracket (9) is set towards the outside of the circumference of the water-stop steel plate (3). The arc-shaped bracket (9) is fixedly connected to the water-stop steel plate (3).

6. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 5, characterized in that: The shape memory alloy rod (6), the arc-shaped limiting buffer rod (7) and the arc-shaped bracket (9) are all made of shape memory alloy. The arc-shaped bracket (9) is welded to the limiting block (8) to form an integral structure.

7. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 6, characterized in that: A water-stop groove (10) is also fixed on the end face annular plate (5). A water-swellable rubber ring is snapped into the water-stop groove (10). The two sides of the water-swellable rubber ring abut against the end face annular plate (5) and the flexible filling layer (4) respectively.

8. The flexible connection mechanism at the connection between a shield tunnel and a shaft as described in claim 7, characterized in that: The water-stop groove (10) is a closed wave-shaped ring structure, and the width of the water-stop groove (10) is greater than the diameter of the water-swellable rubber ring.

9. A design method for a flexible connection mechanism at the connection between a shield tunnel and a vertical shaft, characterized in that, The flexible connection mechanism applicable to the connection between a shield tunnel and a shaft as described in any one of claims 1 to 8 further includes: The flexible joint design method adopts the dynamic time history analysis method to establish a three-dimensional nonlinear dynamic numerical model of "strata-shaft-shield tunnel". The design ground motion parameters of the engineering site are input, including but not limited to the artificial earthquake response spectrum time history. The response of the tunnel and shaft (2) connection part under the design earthquake is calculated:

1. Longitudinal relative displacement response of the joint Δu; 2. Joint rotation response θ; 3. Circumferential opening distribution response of the joint Δd(φ), where φ is the circumferential angle; 4. Joint misalignment Δs; The parameters of the flexible joint are designed based on the joint design displacement response determined by the above numerical simulation steps. The cross-sectional area and number of shape memory alloy rods (6) are determined by the following method: I. Axial bearing capacity control: The axial restoring force F of the shape memory alloy rod (6) under the design displacement Δu should satisfy: F = n × A × σ(ε); Where n is the number of flexible joint components, A is the cross-sectional area of ​​the shape memory alloy rod (6), σ(ε) is the stress of the shape memory alloy rod (6) under the corresponding strain ε=Δu / L, and L is the effective length of the shape memory alloy rod (6). It is required that F is not less than 1.2 times the longitudinal seismic force design value at the joint, and not greater than the bearing capacity design value of the shaft end anchoring ring and the tunnel end reinforcing segment; II. Strain control: The maximum strain ε of the shape memory alloy rod (6) under the design seismic displacement should satisfy: εL≤ε_max≤0.7εmax_recoverable where εL is the strain at the beginning of the austenite to martensite phase transformation and εmax_recoverable is the maximum recoverable strain; III. Self-resetting capability verification: The residual strain of the memory alloy rod (6) after the earthquake should not be greater than 0.5%, and the corresponding residual longitudinal displacement of the joint should not be greater than 1mm, so as to meet the requirements of rapid resumption of operation of the ballastless track of high-speed railway after the earthquake. IV. Energy dissipation capacity verification: The energy dissipated by the shape memory alloy rod (6) joint in a complete loading and unloading cycle, Wd, should not be less than 3 times the elastic strain energy of the traditional rigid joint under the same displacement, and the equivalent damping ratio should not be less than 0.08.

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