Tunnel two-stage energy dissipation support structure and construction method thereof

Abstract

The application belongs to the technical field of tunnel supporting, and specifically discloses a two-stage energy consumption supporting structure for a tunnel and a construction method thereof. The two-stage energy consumption supporting structure for the tunnel comprises an air bag compression layer, primary support and secondary lining. The air bag compression layer comprises a rubber air bag, an inflation joint, a one-way air guide pipe, a two-way air guide pipe and a partition belt. The air bag compression layer can transfer and release the internal pressure, and has the ability to quantitatively control the surrounding rock pressure and uniformly conduct the pressure to the primary support. The supporting structure effectively releases the pressure of the surrounding rock through two-stage deformation based on the setting of the air bag compression layer, can reduce the stress concentration and uneven deformation of the primary support of the tunnel, and ensures the safe tunneling of the tunnel. In addition, the stress form of the supporting structure is simple, the construction method is coordinated with the traditional construction method, and the supporting structure can be applied to tunnels in different geological environments.

Description

Technical Field

[0001] This invention relates to the field of tunnel support technology, specifically to a two-stage energy-dissipating support structure for tunnels and its construction method. Background Technology

[0002] As the length of tunnels built in my country continues to increase, various construction challenges have been encountered during the tunnel construction process. Problems such as fault fracture zones, large deformation of soft rock, and expansion of surrounding rock have caused excessive rock pressure and prolonged deformation duration, which have directly led to disasters such as tunnel collapse, steel arch twisting, concrete cracking, and lining exceeding limits. These issues have seriously affected the construction progress and resulted in frequent dismantling and replacement of arches during tunnel construction, which in severe cases can even endanger the lives of construction workers.

[0003] Currently, the principles for controlling the deformation of surrounding rock in tunnel construction support structures are largely the same: first, the surrounding rock deforms and converges after tunnel excavation; then, the deformation pressure is transmitted to the support structure; finally, the support structure plays its role in resisting the deformation and pressure of the surrounding rock. However, traditional support structures cannot effectively control the deformation development of high-stress soft rock tunnels or tunnels under biased pressure, nor can they adequately adjust the distribution and magnitude of pressure acting on the initial support, making them prone to large-scale deformation disasters in the surrounding rock. Therefore, during tunnel construction, it is necessary to fully consider the form and construction method of the support structure to ensure the safety and stability of the tunnel. Summary of the Invention

[0004] To address the aforementioned problems, one objective of this invention is to provide a two-stage energy-dissipating support structure for tunnels. The advantages of this support structure are that it can effectively adjust the distribution of surrounding rock pressure and quantitatively control its magnitude, thereby reducing the uneven pressure on the tunnel support structure. This reduces tunnel deformation and internal forces within the support structure, ensuring the tunnel's safety and stability. Furthermore, the support structure has a simple stress distribution, its construction method is compatible with traditional methods, and it is applicable to tunnels in various geological environments.

[0005] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0006] A two-stage energy-dissipating support structure for tunnels includes an airbag compression layer, which is installed on the rock wall after tunnel excavation and fixed with positioning steel bars (the airbag compression layer is suitable for both bench excavation and full-ring excavation).

[0007] The airbag compression layer includes:

[0008] Rubber airbags have a hollow inner cavity and multiple airbags are arranged side by side (the number of rubber airbags is selected according to the length of the tunnel excavation outline).

[0009] A partition strip is provided between two adjacent rubber airbags to connect them;

[0010] An inflation connector is provided on the surface of the rubber air bladder and is used to connect an inflation device to inflate the inner cavity of the rubber air bladder.

[0011] A bidirectional air duct is located inside the partition strip, connecting two adjacent rubber airbags. It transmits and balances pressure between the adjacent rubber airbags through exhaust ports at both ends.

[0012] A one-way air duct is provided on the surface of the rubber airbag, with an air inlet at its inner end communicating with the inner cavity of the rubber airbag, and an air outlet at its outer end communicating with the outside to depressurize the rubber airbag.

[0013] The inflation pressure of the inflation connector is P1, the deflation pressure of the bidirectional vent tube is P2, and the deflation pressure of the unidirectional vent tube is P3, where P1 < P2 < P3. This ensures that when the pressure difference between two adjacent rubber airbags is greater than P2, gas is transferred from the airbag with higher pressure to the airbag with lower pressure through the bidirectional vent tube, thus maintaining a balanced pressure within the airbag compression layer. When the pressure within the airbag compression layer is greater than P3, the rubber airbag deflates to the outside through the unidirectional vent tube, maintaining the internal pressure of the rubber airbag at a constant P3.

[0014] Preferably, the one-way airway includes:

[0015] Hollow cylindrical steel pipe A;

[0016] There are two end plates A, which are respectively set at the inner end and the outer end of the hollow cylindrical steel pipe A; and the inner end plate A has an air inlet and the outer end plate A has an exhaust outlet.

[0017] Piston A is disposed inside the hollow cylindrical steel tube A and can slide along its axial direction;

[0018] Spring A is installed inside the hollow cylindrical steel tube A, with its two ends fixedly connected to the end plate A and piston A at the inner end, respectively; the pre-set exhaust pressure P2 of the one-way vent pipe is controlled by the type of spring A.

[0019] Furthermore, in the unidirectional air guide tube, the air inlet is a circular hole in the middle of the end plate A at the inner end, and the exhaust port is two symmetrically distributed semi-circular holes that are drilled along the inner wall of the hollow cylindrical steel tube A towards the bottom and penetrate the end plate A at the outer end; the hollow cylindrical steel tube A is divided into a compression section A and an exhaust section A, the exhaust section A is the section where the exhaust port is located, and the inner diameter of the compression section A is the same as the diameter of the piston A.

[0020] Preferably, the bidirectional airway includes:

[0021] Hollow cylindrical steel pipe B,

[0022] There are two end plates B, which are respectively disposed at both ends of the hollow cylindrical steel pipe B; and each of the two end plates B has an exhaust port.

[0023] Piston B is disposed inside the hollow cylindrical steel tube B and can slide along its axial direction;

[0024] Two springs, B, are disposed inside the hollow cylindrical steel tube B, with their ends fixedly connected to the end plate B and the piston B, respectively. The pre-set exhaust pressure P3 of the bidirectional vent pipe is controlled by the type of spring B.

[0025] Furthermore, in the bidirectional venting pipe, the exhaust ports at both ends are two symmetrically distributed semi-circular holes that are drilled along the inner wall of the hollow cylindrical steel pipe B towards the end and penetrate the end plate B; the hollow cylindrical steel pipe B is divided into a middle compression section B and exhaust sections B at both ends, the exhaust section B is the section where the exhaust port is located, and the inner diameter of the compression section B is the same as the diameter of the piston B.

[0026] Preferably, the partition strip has positioning holes for the positioning steel bars to pass through.

[0027] Preferably, the inflation connector and the one-way air guide tube are installed on the side of the rubber airbag.

[0028] Preferably, the width b of the airbag compression layer is the same as the length of a single tunnel excavation, the thickness h is 10-15cm, and the length l is the same as the circumferential length of the inner contour line of the tunnel excavation; the width of the partition strip is 3-5cm, and the distance between the partition strips is 2-3m.

[0029] Preferably, the two-stage energy-dissipating support structure for the tunnel further includes:

[0030] The initial support, which is closely attached to the inner side of the airbag compression layer, includes a steel arch frame, a steel mesh welded to the inner and outer sides of the steel arch frame, and sprayed concrete sprayed around the steel arch frame and inside the airbag compression layer.

[0031] The secondary lining, located inside the initial support, is constructed using a cast-in-place method and includes a steel reinforcement cage and fine aggregate concrete enclosing the steel reinforcement cage.

[0032] The second objective of this invention is to provide a construction method for the aforementioned two-stage energy-dissipating support structure for tunnels, specifically including the following steps:

[0033] S1. Determine the thickness h of the airbag compression layer based on the deformation and convergence of the tunnel, determine the length l of the airbag compression layer based on the length of the tunnel excavation outline, determine the width b of the airbag compression layer based on the depth of the tunnel excavation, and further determine the exhaust value of the unidirectional and bidirectional air ducts based on the pressure on the initial support of the tunnel.

[0034] S2. After the tunnel is excavated, the airbag compression layer is first installed on the rock wall and fixed with positioning steel bars. Then, air is injected into the air inlet, and the inflation pressure P1 is set to 0.1-0.3 MPa.

[0035] S3. Immediately after the airbag compression layer is inflated, the initial support construction shall be carried out. First, install the steel arch frame according to the construction requirements, leaving a 2-3cm gap between the steel arch frame and the airbag compression layer; then weld the steel mesh between the steel arch frames, and then spray concrete to fill the gaps completely without leaving any voids.

[0036] S4. First Stage: As the surrounding rock deforms and converges after tunnel excavation, the airbag compression layer is squeezed by the rock wall and begins to compress and deform. At this time, each rubber airbag provides uniform pressure on the initial support and rock wall. When the internal pressure difference between two adjacent rubber airbags exceeds the predetermined pressure P2 of the bidirectional venting pipe, the rubber airbag with higher internal pressure will release air into the rubber airbag with lower internal pressure, making the overall pressure in the airbag compression layer more balanced. At this time, the pressure acting on the initial support is also more uniform. As the airbag compression layer continues to compress and deform, the internal pressure continues to increase, and the pressure acting on the initial support and rock wall also continues to increase. This stage is the stage of increased resistance deformation of the surrounding rock.

[0037] S5. Second stage: As the airbag compression layer continues to deform and the internal pressure continues to increase, it exceeds the pressure transfer capacity of the two-way venting tube. When the internal pressure of the rubber airbag exceeds the predetermined pressure P3 of the one-way venting tube, the airbag compression layer begins to release air to the outside, so that its internal pressure remains constant at a value equal to P3. This prevents the pressure acting on the initial support and rock wall from continuing to rise. The deformation of the surrounding rock in this stage is the constant resistance deformation stage.

[0038] S6. Once the compression deformation of the airbag compression layer remains essentially unchanged and the internal pressure stabilizes, the secondary lining can be constructed as the deformation of the initial support stabilizes.

[0039] The present invention has the following beneficial effects:

[0040] This invention divides the airbag compression layer into multiple rubber airbags via partitions and installs bidirectional air guide tubes between adjacent airbags. When the pressure difference between two adjacent airbags exceeds P2, gas is transferred through the bidirectional air guide tubes from the higher-pressure airbag to the lower-pressure airbag, maintaining a balanced pressure within the airbag compression layer. This ensures that the pressure at any point in the initial support and on the rock wall does not become excessive. Furthermore, if one airbag ruptures and leaks air, the remaining airbags can maintain a pressure of P2 and continue operating, preventing tunnel instability and damage caused by a sudden depressurization of the entire airbag compression layer.

[0041] This invention features a two-stage graded compression. In the first stage, when the pressure inside the airbag compression layer is less than P3, the gas inside the airbag compression layer automatically adjusts according to the different pressures inside each rubber airbag. In this stage, as the airbag compression layer is continuously compressed, the internal pressure continuously increases, and the surrounding rock is in the stage of increased resistance deformation. In the second stage, when the pressure inside the airbag compression layer is greater than P3, the rubber airbags exhaust gas to the outside through one-way venting tubes, maintaining the internal pressure of the rubber airbags at a constant value of P3. At this time, the pressure acting on the initial support can be kept constant, avoiding the initial support from being subjected to excessive pressure and causing damage. The deformation of the surrounding rock in this stage can be regarded as the constant resistance deformation stage.

[0042] This invention effectively prevents large deformation damage to the tunnel by installing an airbag compression layer on the rock wall, immediately applying initial support, and then applying secondary lining after the deformation has stabilized. This improves the tunnel's ability to cope with uneven surrounding rock pressure and reduces the possibility of tunnel failure. Attached Figure Description

[0043] Figure 1 A schematic diagram of a tunnel cross-section of a two-stage energy-dissipating support structure for tunnels is provided for this embodiment.

[0044] Figure 2 An enlarged perspective view of tunnel section J, provided as an embodiment, of a two-stage energy-dissipating support structure for tunnels;

[0045] Figure 3 A three-dimensional view of an airbag compression layer structure of a two-stage energy-dissipating support structure for tunnels, provided as an embodiment;

[0046] Figure 4 A cross-sectional view of an airbag compression layer structure of a two-stage energy-dissipating support structure for tunnels, provided as an embodiment;

[0047] Figure 5 A perspective view, a cross-sectional view, a top view, and a bottom view of a bidirectional air duct in the airbag compression layer of a two-stage energy-dissipating support structure for a tunnel provided as an embodiment;

[0048] Figure 6A perspective view, a cross-sectional view, a top view, and a bottom view of a one-way air duct in the airbag compression layer of a two-stage energy-dissipating support structure for a tunnel provided for an embodiment;

[0049] Labels in the diagram: 1—Airbag compression layer; 11—Rubber airbag; 12—Inflation connector; 13—One-way air guide tube; 131—Hollow cylindrical steel pipe A; 1311—Compression section A; 1312—Exhaust section A; 132—End plate A; 133—Piston A; 134—Spring A; 14—Two-way air guide tube; 141—Hollow cylindrical steel pipe B; 1411—Compression section B; 1412—Exhaust section B; 142—End plate B; 143—Piston B; 144—Spring B; 15—Positioning hole; 16—Divider strip; 2—Initial support; 21—Shotcrete; 22—Steel arch frame; 23—Reinforcing mesh; 3—Secondary lining; 31—Reinforcing steel skeleton; 32—Fine aggregate concrete; 4—Rock wall; 5—Positioning reinforcing bars. Detailed Implementation

[0050] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other. Please refer to the accompanying drawings. Figures 1 to 6 The present invention will now describe a two-stage energy-dissipating support structure for tunnels and its construction method.

[0051] A two-stage energy-dissipating support structure for tunnels, such as Figure 1-4 As shown, the tunnel includes an airbag compression layer 1, an initial support 2, and a secondary lining 3. The airbag compression layer 1 is installed on the rock wall 4 after tunnel excavation and fixed with positioning steel bars 5. The initial support 2 is constructed close to the inner side of the airbag compression layer 1. The secondary lining 3 is constructed inside the initial support 2 after the overall deformation of the tunnel has stabilized. The airbag compression layer 1 includes a rubber airbag 11, an inflation joint 12, a one-way air guide pipe 13, a two-way air guide pipe 14, a positioning hole 15, and a partition strip 16. The initial support 2 includes shotcrete 21, a steel arch frame 22, and a steel mesh 23. The secondary lining 3 includes a steel reinforcement skeleton 31 and fine stone concrete 32.

[0052] In the airbag compression layer 1, multiple rubber airbags 11 with hollow inner cavities are arranged side by side; a partition strip 16 is disposed between two adjacent rubber airbags 11 to connect them; an inflation connector 12 is disposed on the surface of the rubber airbag 11 for connecting an inflation device to inflate the inner cavity of the rubber airbag 11; a bidirectional air guide tube 14 is disposed inside the partition strip 16, connecting two adjacent rubber airbags 11 for pressure transmission and balance between adjacent rubber airbags 11; a unidirectional air guide tube 13 is disposed on the surface of the rubber airbag 11 for venting and depressurizing the rubber airbag 11 to the outside. In the initial support 2, the steel mesh 23 is welded to the inner and outer sides of the steel arch frame 22, and the shotcrete 21 is sprayed around the steel arch frame 22 and inside the airbag compression layer 1. In the secondary lining 3, the fine stone concrete 32 encases the steel reinforcement skeleton 31.

[0053] In one embodiment, the one-way air guide tube 13 includes a hollow cylindrical steel tube A131, an end plate A132, a piston A133, and a spring A134 (e.g., Figure 6 (as shown); the end plate A132 has two parts, which are respectively disposed at the inner end and the outer end of the hollow cylindrical steel tube A131; the piston A133 and the spring A134 are disposed inside the hollow cylindrical steel tube A131. The spring A134 is welded firmly to the inner end plate A132 at one end and to the piston A133 at the other end. The piston A133 can slide along the axial direction of the hollow cylindrical steel tube A131. The inner end plate A132 has a circular air inlet in the middle and an outer end plate A132 has an exhaust port. Specifically, the outer end plate A132 has two symmetrically distributed semi-circular holes that are chiseled along the inner wall of the hollow cylindrical steel tube A131 towards the bottom and penetrate the outer end plate A132. The hollow cylindrical steel tube A131 is divided into a compression section A1311 and an exhaust section A1312. The exhaust section A1312 is the section where the exhaust port is located. The inner diameter of the compression section A1311 is the same as the diameter of the piston A133. This design ensures that when the pressure difference between the two ends of piston A133 is less than the preset exhaust pressure P3 of the one-way vent pipe 13, piston A133 will not leak air in the compression section A1311. When the pressure difference is greater than P3, piston A133 will be in the exhaust section A1312 and begin to exhaust air to the outside, thereby keeping the internal pressure of the airbag compression layer 1 constant.

[0054] In one embodiment, the bidirectional air guide tube 14 includes a hollow cylindrical steel tube B141, an end plate B142, a piston B143, and a spring B144 (e.g., ...). Figure 5(As shown); there are two end plates B142, respectively disposed at both ends of the hollow cylindrical steel tube A131; the piston B143 and the spring B144 are disposed inside the hollow cylindrical steel tube B141. One end of the spring B144 is firmly welded to the end plate B142, and the other end is welded to the piston B143; the piston B143 can slide along the axial direction of the hollow cylindrical steel tube B141; both end plates B142 are provided with exhaust ports, specifically two symmetrically distributed semi-circular holes are drilled along the inner wall of the hollow cylindrical steel tube B141 towards the end and penetrate the end plate B142; the hollow cylindrical steel tube B141 is divided into a middle compression section B1411 and exhaust sections B1412 at both ends, the exhaust section B1412 being the section where the exhaust ports are located, and the inner diameter of the compression section B1411 being the same as the diameter of the piston B143. This design ensures that when the pressure difference between the two ends of piston B143 is less than the preset exhaust pressure P2 of the bidirectional air guide tube 14, piston B143 will not leak air in the compression section B1411. When the pressure difference is greater than P2, piston B143 will be in the exhaust section B1412 and will begin to exhaust air into the lower pressure rubber bladder 11. This maintains that the pressure difference inside each rubber bladder 11 is not too large. It also ensures that when one rubber bladder 11 breaks and leaks air, the remaining rubber bladders 11 can still maintain the pressure of P2 and continue to work.

[0055] In one embodiment, the initial pressure P1 of the inflation connector 12 is less than the preset exhaust pressure P2 of the bidirectional air guide tube 14, and the preset exhaust pressure P2 of the bidirectional air guide tube 14 is less than the preset exhaust pressure P3 of the unidirectional air guide tube 13. The preset exhaust pressure P2 of the unidirectional air guide tube 13 and the preset exhaust pressure P3 of the bidirectional air guide tube 14 are controlled by the models of spring A134 and spring B144, respectively. This design ensures that when the pressure difference between adjacent rubber airbags 11 is less than P2, the airbag compression layer 1 performs internal pressure transfer; when the pressure in the airbag compression layer 1 is greater than P3, it begins to exhaust to the outside, keeping the internal pressure P3 constant, thereby keeping the pressure acting on the initial support 2 constant.

[0056] In one embodiment, positioning holes 15 are drilled in the partition strip 16, and positioning steel bars 5 are passed through the positioning holes 15 and fixed to the rock wall 4 during the installation of the airbag compression layer 1. This design ensures that the airbag compression layer 1 is firmly installed, so as not to affect the construction of the initial support 2.

[0057] In one embodiment, the inflation connector 12 and the one-way venting tube 13 are installed on the side of the rubber airbag 11, and the two-way venting tube 14 is installed inside the partition strip 16 to connect the two rubber airbags 11, with the length of the two-way venting tube 14 being the same as the width of the partition strip 16. This design ensures that the inflation connector 12 and the one-way venting tube 13 will not be blocked by sprayed concrete, affecting the exhaust effect; the two-way venting tube 14, being the same length as the partition strip 16, ensures smooth gas flow within adjacent rubber airbags 11.

[0058] In one embodiment, the width b of the airbag compression layer 1 is the same as the length of a single tunnel excavation, the thickness h is 10-15 cm, and the length l is the same as the circumferential length of the inner contour line of the tunnel excavation. A partition strip 16 is provided every 2-3 m in the airbag compression layer 1, and the width of the partition strip 16 is 3-5 cm. This design ensures that the dimensions of the airbag compression layer 1 match the dimensions of the tunnel excavation, facilitating actual construction.

[0059] In one embodiment, the airbag compression layer 1 is suitable for both bench excavation and full-ring excavation of tunnels, and the number of rubber airbags 11 is selected according to the length of the tunnel excavation outline. This design ensures that the tunnel support structure is suitable for different geological conditions and different tunnel excavation methods, and has strong adaptability and scalability.

[0060] The construction method for the two-stage energy-dissipating support structure of the tunnel includes the following steps:

[0061] S1. Determine the thickness h of the airbag compression layer 1 based on the deformation and convergence of the tunnel, determine the length l of the airbag compression layer 1 based on the length of the tunnel excavation outline, determine the width b of the airbag compression layer based on the depth of the tunnel excavation, and further determine the exhaust value of the unidirectional air guide pipe 13 and the bidirectional air guide pipe 14 based on the pressure on the initial support 2 of the tunnel.

[0062] S2. After the tunnel is excavated, the airbag compression layer 1 is first installed on the rock wall 4 and fixed with the positioning steel bar 5. Then, air is injected into the air inlet 12 and the air pressure P1 is set to 0.1-0.3MPa.

[0063] S3. Immediately after the airbag compression layer 1 is inflated, the initial support 2 shall be constructed. First, install the steel arch frame 22 according to the construction requirements, then weld the steel mesh 23 between the steel arch frames 22, and then spray concrete. It is necessary to ensure that the joint between the steel arch frame 22 and the airbag compression layer 1 is tightly sprayed.

[0064] S4. First Stage: As the surrounding rock deforms and converges after tunnel excavation, the airbag compression layer 1 is squeezed by the rock wall 4 and begins to compress and deform. At this time, each rubber airbag 11 provides uniform pressure on the initial support 2 and the rock wall 4. When the internal pressure difference between two adjacent rubber airbags 11 exceeds the predetermined pressure P2 of the bidirectional air guide tube 14, the rubber airbag 11 with higher internal pressure will expel air into the rubber airbag 11 with lower internal pressure, so that the overall pressure in the airbag compression layer 1 is balanced. At this time, the pressure acting on the initial support 2 is also more uniform. As the airbag compression layer 1 continues to compress and deform, the internal pressure continues to increase, and the pressure acting on the initial support 2 and the rock wall 4 also continues to increase. This stage is the stage of increased resistance deformation of the surrounding rock.

[0065] S5. Second stage: As the airbag compression layer 1 continues to deform and the internal pressure continues to increase, it exceeds the pressure transfer capacity of the bidirectional air duct 14 until the internal pressure of the rubber airbag 11 exceeds the predetermined pressure P3 of the unidirectional air duct 13. At this point, the airbag compression layer 1 begins to release air to the outside, so that its internal pressure remains constant at a value equal to P3. This prevents the pressure acting on the initial support 2 and the rock wall 4 from continuing to rise. The deformation of the surrounding rock in this stage is the constant resistance deformation stage.

[0066] S6. Once the compression deformation of the airbag compression layer 1 remains basically unchanged and the internal pressure stabilizes, the secondary lining 3 can be constructed as the deformation of the initial support 2 stabilizes. The secondary lining 3 is constructed by cast-in-place method.

[0067] In one embodiment, when installing the steel arch frame 22 in step S3, a gap of 2-3 cm is reserved between the steel arch frame 22 and the airbag compression layer 1. Then, a steel mesh 23 is welded between the steel arch frames 22, and then concrete is sprayed to fill the reserved gap completely without leaving any voids. This design ensures that the sprayed concrete 21 tightly covers the entire airbag compression layer 1, making the pressure exerted by the airbag compression layer 1 on the initial support 2 more uniform.

[0068] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. Any changes made by those skilled in the art after reading the specification of the present invention, as long as they are within the scope of the claims of the present invention, will be protected by patent law.

Claims

1. A two-stage energy-dissipating support structure for tunnels, characterized in that: Includes an airbag compression layer (1), which is installed on the rock wall (4) after tunnel excavation and fixed with positioning steel bars (5); the airbag compression layer (1) includes: Rubber airbags (11) have a hollow inner cavity and multiple airbags arranged side by side; A partition strip (16) is provided between two adjacent rubber airbags (11) to connect them; An inflation connector (12) is provided on the surface of the rubber airbag (11) for connecting an inflation device to inflate the inner cavity of the rubber airbag (11); A bidirectional air duct (14) is provided inside the partition strip (16) and connects two adjacent rubber airbags (11). It transmits and balances pressure between adjacent rubber airbags (11) through exhaust ports at both ends. A one-way air duct (13) is provided on the surface of the rubber airbag (11), with an air inlet at its inner end communicating with the inner cavity of the rubber airbag (11) and an exhaust port at its outer end communicating with the outside to depressurize the rubber airbag (11). The inflation pressure of the inflation connector (12) is P1, the exhaust pressure of the bidirectional air guide tube (14) is P2, and the exhaust pressure of the unidirectional air guide tube (13) is P3, where P1 < P2 < P3.

2. The two-stage energy-dissipating support structure for tunnels according to claim 1, characterized in that: The one-way airway (13) includes: Hollow cylindrical steel pipe A(131); There are two end plates A (132), which are respectively set at the inner end and the outer end of the hollow cylindrical steel pipe A (131); and the inner end plate A (132) is provided with an air inlet, and the outer end plate A (132) is provided with an exhaust outlet. Piston A (133) is disposed inside the hollow cylindrical steel tube A (131) and can slide along its axial direction; Spring A (134) is disposed inside the hollow cylindrical steel tube A (131), and its two ends are fixedly connected to the end plate A (132) and piston A (133) at the inner end, respectively.

3. The two-stage energy-dissipating support structure for tunnels according to claim 2, characterized in that: In the one-way air guide tube (13), the air inlet is a circular hole in the middle of the end plate A (132) at the inner end, and the exhaust port is two symmetrically distributed semi-circular holes that are drilled along the inner wall of the hollow cylindrical steel tube A (131) towards the bottom and penetrate the end plate A (132) at the outer end; the hollow cylindrical steel tube A (131) is divided into a compression section A (1311) and an exhaust section A (1312), the exhaust section A (1312) is the section where the exhaust port is located, and the inner diameter of the compression section A (1311) is the same as the diameter of the piston A (133).

4. The two-stage energy-dissipating support structure for tunnels according to claim 1, characterized in that: The bidirectional airway (14) includes: Hollow cylindrical steel pipe B(141), There are two end plates B(142), which are respectively disposed at both ends of the hollow cylindrical steel pipe B(141); and each of the two end plates B(142) has an exhaust port. Piston B (143) is disposed inside the hollow cylindrical steel tube B (141) and can slide along its axial direction; Two springs B (144) are disposed inside the hollow cylindrical steel tube B (141), and their two ends are respectively fixed to the end plate B (142) and the piston B (143).

5. The two-stage energy-dissipating support structure for tunnels according to claim 4, characterized in that: In the bidirectional air guide tube (14), the exhaust ports at both ends are two symmetrically distributed semi-circular holes that are drilled along the inner wall of the hollow cylindrical steel tube B (141) towards the end and penetrate the end plate B (142); the hollow cylindrical steel tube B (141) is divided into a middle compression section B (1411) and exhaust sections B (1412) at both ends, the exhaust section B (1412) is the section where the exhaust port is located, and the inner diameter of the compression section B (1411) is the same as the diameter of the piston B (143).

6. The two-stage energy-dissipating support structure for tunnels according to claim 1, characterized in that: The partition strip (16) has positioning holes (15) through which the positioning steel bar (5) passes.

7. The two-stage energy-dissipating support structure for tunnels according to claim 1, characterized in that: The inflation connector (12) and the one-way air guide tube (13) are installed on the side of the rubber airbag (11).

8. The two-stage energy-dissipating support structure for tunnels according to claim 1, characterized in that: The width b of the airbag compression layer (1) is the same as the length of a single tunnel excavation, the thickness h is 10-15cm, and the length l is the same as the circumferential length of the inner contour line of the tunnel excavation; the width of the partition strip (16) is 3-5cm, and the distance between the partition strips (16) is 2-3m.

9. The two-stage energy-dissipating support structure for tunnels according to any one of claims 1-8, characterized in that: Also includes: The initial support (2) is closely attached to the inner side of the airbag compression layer (1), including a steel arch frame (22), a steel mesh (23) welded to the inner and outer sides of the steel arch frame (22), and sprayed concrete (21) sprayed around the steel arch frame (22) and inside the airbag compression layer (1). The secondary lining (3) is located inside the initial support (2) and is constructed by cast-in-place method. It includes a steel reinforcement cage (31) and fine stone concrete (32) enclosing the steel reinforcement cage (31).

10. The construction method of the two-stage energy-dissipating support structure for tunnels as described in claim 9, characterized in that: Includes the following steps: S1. Determine the thickness h of the airbag compression layer (1) based on the size of the tunnel deformation convergence, determine the length l of the airbag compression layer (1) based on the length of the tunnel excavation outline, determine the width b of the airbag compression layer based on the depth of the tunnel excavation, and further determine the exhaust value of the unidirectional air guide pipe (13) and the bidirectional air guide pipe (14) based on the pressure on the initial support (2) of the tunnel. S2. After the tunnel is excavated, the airbag compression layer (1) is first installed on the rock wall (4), and the airbag compression layer (1) is fixed with positioning steel bars (5). Then, air is injected into the air inlet (12), and the air pressure P1 is set to 0.1-0.3 MPa. S3. After the airbag compression layer (1) is inflated, the initial support (2) is constructed immediately. First, install the steel arch frame (22) according to the construction requirements. Leave a 2-3cm gap between the steel arch frame (22) and the airbag compression layer (1). Then, weld the steel mesh (23) between the steel arch frames (22) and then spray concrete to fill the gaps and leave no voids. S4. First stage: As the surrounding rock deforms and converges after tunnel excavation, the airbag compression layer (1) is squeezed by the rock wall (4) and begins to compress and deform. At this time, each rubber airbag (11) provides uniform pressure on the initial support (2) and the rock wall (4). When the internal pressure difference between two adjacent rubber airbags (11) exceeds the predetermined pressure P2 of the bidirectional air guide tube (14), the rubber airbag (11) with higher internal pressure will exhaust air into the rubber airbag (11) with lower internal pressure, so that the overall pressure in the airbag compression layer (1) is balanced. At this time, the pressure acting on the initial support (2) is also more uniform. As the airbag compression layer (1) continues to compress and deform, the internal pressure continues to rise, and the pressure acting on the initial support (2) and the rock wall (4) also continues to increase. This stage is the stage of deformation of the surrounding rock into resistance-increasing deformation. S5. The second stage: When the airbag compression layer (1) continues to deform and the internal pressure continues to increase, it exceeds the pressure transfer capacity of the bidirectional air duct (14) until the internal pressure of the rubber airbag (11) exceeds the predetermined pressure P3 of the unidirectional air duct (13). At this time, the airbag compression layer (1) begins to vent to the outside, so that its internal pressure is kept at a constant value equal to P3. This ensures that the pressure acting on the initial support (2) and the rock wall (4) will not continue to increase. The deformation of the surrounding rock in this stage is the constant resistance deformation stage. S6. When the compression deformation of the airbag compression layer (1) remains basically unchanged and the internal pressure stabilizes, the secondary lining (3) can be constructed as the deformation of the initial support (2) stabilizes.

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