Composite sealing construction method for tunnel portal

Abstract

The invention discloses a composite sealing construction method for a tunnel portal. The composite sealing construction method comprises the following steps that an annular grout stopping panel is installed and fixed at the position of the tunnel portal; an annular pressure-bearing panel is installed and fixed at the position of a tunnel portal; a plurality of reinforcing grouting pipes are arranged on the pressure-bearing panel in a penetrating mode; concrete is poured into a cavity between the grout stopping panel and the pressure bearing panel through the pouring opening; and primary grouting is conducted on the space between the shield tail and the tunnel wall through the main grouting pipe, after primary grouting is completed, drilling is conducted from the outer side to the reinforcing grouting pipe, secondary pressure grouting is conducted on the periphery through the reinforcing grouting pipe, and pressure reinforcing is conducted on a pea gravel layer and a construction joint. The composite pressure bearing body has the beneficial effects that the composite pressure bearing body formed by the steel ring and the concrete has a clear stress path and excellent integrity, high grouting pressure and stratum water and soil pressure can be effectively resisted, and the problem that a traditional brick masonry structure is insufficient in strength and stability is solved.

Description

Technical Field

[0001] This application belongs to the field of tunnel and underground engineering technology, specifically relating to a composite sealing construction method for tunnel portals, used for the construction of tunnel portals at the launching and receiving ends of shield tunneling machines / TBMs. Background Technology

[0002] Tunnel portal sealing is a crucial step in tunnel construction, especially when using tunnel boring machines (TBMs). The sealing process directly impacts construction progress and watertightness. Existing portal sealing technologies mainly rely on brick masonry, concrete grouting, or steel structure sealing, but these traditional methods generally have some significant technical problems.

[0003] Traditional brick masonry sealing structures typically involve brick wall construction, mortar finishing, and subsequent grouting sealing, and are widely used for portal sealing in shield tunnels. However, this structure has the following drawbacks: Poor shear and compressive strength: The brick masonry structure has poor rigidity and insufficient tensile and shear strength, making it prone to cracking or deformation under high-pressure grouting and water pressure, leading to sealing failure; Difficulty in controlling leakage: Multiple micro-permeability channels exist between the brick masonry and the mortar finishing, which easily lead to water leakage, especially under high water pressure, resulting in repeated repairs in the later stages of construction; Long construction cycle: The construction process of brick masonry is relatively complicated, usually requiring a long time for construction, curing, and finishing, which affects the overall progress of tunnel construction, especially in TBM construction where rapid advancement is required, where the traditional method has low construction efficiency.

[0004] In addition, some sealing structures using steel rings and concrete may also have the following limitations due to improper design or construction: the force transmission path is unclear, which may lead to local stress concentration; similar to traditional brick masonry, the construction gaps formed between it and the gravel layer are also difficult to seal effectively; and the construction process is still relatively complicated, failing to give full play to the advantages of prefabrication and assembly.

[0005] Existing grouting sealing technologies typically rely on pressure injection through grouting pipes to fill construction gaps. However, this grouting technology still has the following shortcomings: uneven grouting: due to issues with the arrangement of grouting pipes and control of grouting pressure, grout often fails to penetrate evenly into all cracks, resulting in some areas not being effectively sealed and creating potential leakage risks; structural damage due to excessive pressure: during high-pressure grouting, if the pressure is not effectively controlled, it may damage the surrounding structure, leading to grouting failure or structural damage; in water-rich sand layers or high water pressure environments, conventional grouting methods often cannot fully control the flow of water and grout, resulting in unsatisfactory grouting effects or even grout leakage.

[0006] In summary, existing tunnel portal sealing technologies generally suffer from insufficient compressive strength, long construction periods, and uneven grouting effects. Especially under complex conditions such as high water pressure and water-rich strata, traditional technologies struggle to meet stringent sealing requirements. To address these issues, a new tunnel portal sealing technology is urgently needed that can improve construction efficiency, reduce leakage, and meet the demands of construction under complex geological conditions while ensuring structural strength. Summary of the Invention

[0007] The purpose of this application is to address the shortcomings of traditional brick masonry sealing structures in existing technologies. These structures suffer from insufficient rigidity, poor shear resistance, and susceptibility to damage under high water or grouting pressure, leading to sealing failure. Furthermore, the presence of multiple interfaces increases the risk of leakage, complicates construction procedures, extends the construction period, and results in poor reinforcement in concealed areas such as construction joints between the gravel layer and the structural body. This application provides a composite sealing construction method for tunnel portals. By employing a novel combination structure of steel rings and wooden boards, along with innovative grouting and sealing technologies, it effectively improves the sealing effect of tunnel portals and solves various problems inherent in traditional technologies.

[0008] The objective of this application is achieved through the following technical solution: A method for constructing a composite seal for a tunnel portal includes the following steps: S01, Install and fix an annular grout-stopping panel at the tunnel entrance. The outer periphery of the grout-stopping panel is sealed and fitted to the tunnel wall. Several main grouting pipes extending into the tunnel are threaded through the grout-stopping panel. S02, Install and fix an annular pressure-bearing panel at the tunnel entrance. The outer periphery of the pressure-bearing panel is sealed and fitted to the tunnel wall. The pressure-bearing panel is arranged relative to the grout-stopping panel outside the tunnel and a cavity is formed between the two. The main grouting pipe is passed through the pressure-bearing panel. A grouting port is reserved at the top of the pressure-bearing panel. S03, Several reinforcing grouting pipes are installed on the pressure-bearing panel, with the inner end of the reinforcing grouting pipes extending to the outer periphery of the cavity, and then the reinforcing grouting pipes are sealed. S04, concrete is poured into the cavity between the grout-stop panel and the pressure-bearing panel through the injection port, so that the concrete fills the cavity, and then the concrete is cured. The concrete, together with the grout-stop panel and the pressure-bearing panel, forms an integral structure. S05, during the tunnel boring machine's excavation process, the first grouting is carried out in the space between the shield tail and the tunnel wall through the main grouting pipe. After the first grouting is completed, it is drilled from the outside to the reinforcement grouting pipe. Secondary pressure grouting is carried out on the outer periphery through the reinforcement grouting pipe to reinforce the gravel layer and construction joints. S06, the main grouting pipe, grouting port and reinforcement grouting pipe are sealed to complete the tunnel portal sealing operation.

[0009] Furthermore, in S01, the grout-stopping panel is made of wood; several first pipe perforations are pre-drilled along the circumference of the grout-stopping panel, and the main grouting pipe is screwed into the first pipe perforations. A sealing gasket is provided between the first pipe perforations and the main grouting pipe; a check valve is installed inside the main grouting pipe; the inner extension length of the main grouting pipe is arranged alternately at different distances; a first sealing strip is provided between the outer periphery of the grout-stopping panel and the tunnel wall, and a secondary seal is performed using water-resistant sealant.

[0010] Furthermore, in S02, the pressure-bearing panel is made of steel plate and is assembled from several fan-shaped steel rings. Bolt holes are reserved at the ends of the steel rings. Adjacent steel rings are fixed by bolts passing through the bolt holes. The outer side of the joint between adjacent steel rings is welded for reinforcement. Several second pipe perforations are reserved along the circumferential direction on the pressure-bearing panel. The main grouting pipe is screwed into the second pipe perforations. A sealing gasket is provided between the second pipe perforations and the main grouting pipe. A sealing groove is provided on the outer periphery of the pressure-bearing panel. A second sealing strip that fits against the cavity wall is provided in the sealing groove.

[0011] Furthermore, in S02, the pressure-bearing panel is composed of six 60° fan-shaped steel rings spliced ​​together. The steel rings are prefabricated in the factory and pre-assembled off-site to check the roundness and hole positions.

[0012] Furthermore, in S01 and S02, several brackets are arranged circumferentially. The brackets are H-shaped steels and support the grout-stopping panel and the pressure-bearing panel. The base plate of the bracket is fixed to the tunnel wall by chemical anchors. The inner end of the bracket provides positioning support for the grout-stopping panel, and the outer end of the bracket provides fixed support for the pressure-bearing panel. The connecting seat plate of the bracket is fixed to the connecting seat plate of the pressure-bearing panel by bolts. An elongated hole for slight adjustment of position is opened on the connecting seat plate.

[0013] Furthermore, in S03, the pressure-bearing panel is provided with an ear plate, and the reinforcing grouting pipe is embedded in the ear plate at a 45° angle and welded and fixed; the outer end of the reinforcing grouting pipe is filled with compressed foam, and the outer end of the reinforcing grouting pipe is sealed with a threaded end cap, and a gap of 20~50mm is reserved between the inner end of the reinforcing grouting pipe and the outer surface of the cavity.

[0014] Furthermore, in S04, C40 self-compacting concrete is used. During pouring, it is ensured that the concrete completely fills the cavity between the grout-stopping panel and the bearing panel, and that the main grouting pipe is unobstructed. After the concrete is poured, it needs to be cured to ensure that the concrete reaches more than 70% of the design strength. The concrete curing period is 7 days. During the curing period, the quality of the concrete is checked regularly to ensure that there are no defects such as cracks or air bubbles.

[0015] Furthermore, in S05, the tunnel boring machine excavates, and when the three rings of segments are assembled, gravel is blown in to fill the gap between the shield tail and the tunnel wall. After the fifteen rings of segments are assembled, the first grouting is carried out through the main grouting pipe. The grouting pressure is controlled at 0.3 to 0.5 MPa, and the pressure-time curve and the change in grout return volume are used as the final grouting criteria.

[0016] Furthermore, in S05, the protective layer is drilled from the outside to the reinforcing grouting pipe, the threaded end cap on the reinforcing grouting pipe and the compressed foam inserted inside are removed to form a complete grouting channel. Then, secondary grouting is carried out through the reinforcing grouting pipe until the grout return is clean, the pressure is stable and the grout suction rate is lower than the control threshold.

[0017] Furthermore, in S06, the main grouting pipe and the reinforcing grouting pipe are sealed with blind flanges or welded, and the injection port, shoulder observation port and low-position port are permanently sealed or sealed with maintainable seals.

[0018] The functions achieved by this application are as follows: The core of this application is to provide a steel ring-concrete-wood composite sealing technology, which uses a steel ring as the main load-bearing component and is reliably connected to the concrete structure of the tunnel portal through an anchoring system. A wooden board is set on the side of the steel ring facing the soil as a permanent grout-stopping panel. Concrete is poured between the steel ring and the wooden board to form an integral pressure-bearing structure. A through-board grouting joint is pre-embedded in the wooden board to form the initial grouting system. A reinforcing grouting pipe is pre-embedded obliquely in the concrete layer. The outer end is provided with an openable and closable sealing structure, and the inner end is reserved with a non-penetrating layer near the outer surface of the structure for subsequent secondary pressure grouting. An expandable sealing strip is set on the outer edge of the steel ring, which can expand and tighten to seal the contact interface after installation. First, install and fix the steel ring and wooden plank, ensuring the perimeter of the cavity between them and the steel ring is sealed. Then, pour concrete and cure it to form a composite structure. After the tunneling machine advances and completes the assembly of several ring segments, gravel is blown in. Then, the first grouting is carried out through the through-slab grouting system. Finally, drill through the non-penetrating layer reserved by the inclined reinforcing grouting pipe, and implement secondary pressure reinforcing grouting through this pipe to achieve a comprehensive and effective seal.

[0019] The beneficial effects of this application are: (1) The composite pressure-bearing body composed of steel ring and concrete has a clear force path and excellent integrity, which can effectively resist high grouting pressure and soil and water pressure in the stratum, thus avoiding the problem of insufficient strength and stability of traditional brick masonry structure.

[0020] (2) The multiple sealing system formed by combining the initial sealing of the expandable sealing strip, the double sealing around the wooden board, the precision sealing of the through-board grouting joint, and the secondary reinforcement grouting of the inclined pipe greatly improves the sealing reliability and reduces the risk of leakage.

[0021] (3) The core components of the device can be prefabricated in the factory, and the on-site assembly construction is highly automated. This eliminates a large amount of wet work such as bricklaying and plastering, significantly shortens the construction cycle, and meets the requirements of TBM rapid construction.

[0022] (4) The pioneering sequential grouting process ensures the uniformity and integrity of grouting, effectively solving the problem of insufficient grouting in concealed areas by traditional processes.

[0023] (5) The device also has good maintainability and adaptability, and is particularly suitable for complex geological conditions such as high water pressure and water-rich sand layers, and has broad engineering application prospects.

[0024] The aforementioned main solution and its various further alternatives can be freely combined to form multiple solutions, all of which are solutions that can be adopted and are claimed in this application; furthermore, the (non-conflicting alternatives) can also be freely combined with each other and with other alternatives. Those skilled in the art, after understanding the solution of this application, will realize from the prior art and common general knowledge that there are many combinations, all of which are technical solutions to be protected by this application, and will not be exhaustively listed here. Attached Figure Description

[0025] Figure 1 This is a structural cross-sectional view of this application.

[0026] Figure 2 This is a schematic diagram of the inner structure of the grout-stopping panel of this application.

[0027] Figure 3 This is a schematic diagram of the outer structure of the grout-stopping panel of this application.

[0028] Figure 4 This is a schematic diagram of the outer structure of the pressure-bearing panel in this application.

[0029] Figure 5 This is a schematic diagram of the inner structure of the pressure-bearing panel in this application.

[0030] Figure 6 This is a structural schematic diagram of the grouting pipe used in this application.

[0031] In the diagram: 1-Grouting stop panel, 2-Pressure bearing panel, 3-First pipe perforation, 4-First sealing strip, 5-Second pipe perforation, 6-Sealing groove, 7-Second sealing strip, 8-Main grouting pipe, 9-Injection port, 10-Bracket, 11-Chemical anchor, 12-Reinforcing grouting pipe, 13-Ear plate, 14-Compressed foam, 15-Threaded end cap, 16-Steel ring, 17-Bolt hole, 18-Assembly bolt, 19-Filling concrete, 20-Process opening. Detailed Implementation

[0032] The following non-limiting embodiments are used to illustrate this application.

[0033] Example 1 refer to Figures 1-6 As shown, a method for constructing a composite seal for a tunnel portal includes the following steps: S01, installing and fixing an annular grout-stopping panel 1 at the portal, the outer periphery of the grout-stopping panel 1 being sealed and fitted to the tunnel wall, and several main grouting pipes 8 extending to the inside of the tunnel being threaded through the grout-stopping panel 1.

[0034] The grout-stopping panel 1 is made of wooden boards. First, the opening of the tunnel portal is measured and laid out. A wooden board ring is installed on the soil-facing side as the front grout-stopping surface. The outer diameter of the wooden board matches the opening of the tunnel portal. The wooden board is positioned and fixed by steel brackets, chemical anchors, and temporary supports. A first sealing strip 4 is provided between the outer periphery of the grout-stopping panel 1 and the tunnel wall. Water-resistant sealant is used for secondary sealing to ensure the formation of the first grout-stopping seal.

[0035] The grout-stopping panel 1 has several pre-drilled first pipe perforations 3 evenly spaced around its circumference. The main grouting pipe 8 (specifically, the connector at this location) is screwed into the first pipe perforations 3 for secure installation. A sealing gasket is provided between the first pipe perforations 3 and the main grouting pipe 8 to prevent grout or liquid leakage from the first pipe perforations 3. A check valve is installed inside the main grouting pipe 8 to ensure unidirectional grout flow and prevent backflow. The inner extension length of the main grouting pipe 8 is arranged alternately at near and far distances, with alternating extension lengths of 0.3m and 1.0m, forming a complementary coverage range for near-field and far-field grouting.

[0036] S02, an annular pressure-bearing panel 2 is installed and fixed at the tunnel entrance. The outer periphery of the pressure-bearing panel 2 is sealed and fitted to the tunnel wall. The pressure-bearing panel 2 is arranged relative to the grout-stopping panel 1 outside the tunnel and a cavity is formed between the two. The main grouting pipe 8 is installed on the pressure-bearing panel 2. A grouting port 9 is reserved at the top of the pressure-bearing panel 2.

[0037] The pressure-bearing panel 2 is made of steel plate and is assembled from several fan-shaped steel ring pieces 16. Preferably, the pressure-bearing panel 2 is composed of six 60° fan-shaped steel ring pieces 16. The steel ring pieces 16 are prefabricated in the factory and pre-assembled off-site, with roundness and hole positions checked. Bolt holes 17 are pre-drilled at the ends of the steel ring pieces 16. During assembly, the holes are aligned, and adjacent steel ring pieces 16 are fixed together by assembly bolts 18 inserted into the bolt holes 17. The outer side of the joint between adjacent steel ring pieces 16 is reinforced by welding, specifically by applying continuous fillet welds to the outer side of the joint to form a closed annular pressure-bearing component. During factory prefabrication, a concrete pouring port is opened at the crown of the steel ring.

[0038] The pressure-bearing panel 2 has several second pipe perforations 5 evenly pre-drilled along its circumference. The main grouting pipe 8 (specifically, the joint at this location) is screwed into the second pipe perforations 5 to fix the main grouting pipe 8 in place. A sealing gasket is provided between the second pipe perforations 5 and the main grouting pipe 8 to ensure that no grout or liquid leakage occurs. The outer periphery of the pressure-bearing panel 2 is provided with a sealing groove 6, and a second sealing strip 7 that fits against the tunnel wall is provided in the sealing groove 6. Specifically, an expansion sealing strip is installed, and during installation, a 10-20% pre-compression deformation is applied to ensure that it fits tightly against the concrete interface of the tunnel entrance, forming an initial periphery seal.

[0039] In S01 and S02, several brackets 10 are evenly arranged circumferentially. The brackets 10 are H-beams and support the grout-stopping panel 1 and the pressure-bearing panel 2. The base plate of the bracket 10 is fixed to the tunnel wall using chemical anchors 11. The anchor installation employs a process of "drilling-cleaning-injecting adhesive-implanting-curing-re-tightening," with the embedment depth and diameter checked against the design load. The inner end of the bracket 10 provides positioning support for the grout-stopping panel 1.

[0040] The outer end of the bracket 10 provides fixed support for the pressure-bearing panel 2. The connecting seat plate of the bracket 10 is fixed to the connecting seat plate of the pressure-bearing panel 2 by bolts. An elongated hole for fine adjustment is opened on the connecting seat plate. The connecting seat plate is fixed by welding and is provided with an elongated hole for fine adjustment. Through the bracket 10, the steel ring is finally reliably fixed to the doorway and maintains a 300mm clearance from the wooden ring.

[0041] S03, several reinforcing grouting pipes 12 are installed on the pressure-bearing panel 2, with the inner end of the reinforcing grouting pipe 12 extending to the outer periphery of the cavity, and then the reinforcing grouting pipe 12 is sealed.

[0042] Ear plates 13 are provided on the pressure-bearing panel 2. Reinforcing grouting pipes 12 are embedded in the ear plates 13 at a 45° angle and welded in place. Construction workers use the prefabricated process opening 20 of the steel ring to position and install the inclined reinforcing grouting pipes (DN25-DN32) at approximately a 45° design angle. Compressed foam 14 is inserted into the outer end of the reinforcing grouting pipe 12, and a threaded end cap 15 is used to seal the outer end of the reinforcing grouting pipe 12 to prevent concrete from entering the steel pipe and ensure smooth use of the steel pipe during subsequent grouting. A 20-50mm gap is reserved between the inner end of the reinforcing grouting pipe 12 and the outer surface of the cavity. During concrete pouring, ensure that the inclined steel pipes are completely encased to avoid obstruction during later construction. After all inclined pipes are installed, close the process opening 20, leaving only the crown grouting port open.

[0043] S04, concrete is poured into the cavity between the grout-stopping panel 1 and the pressure-bearing panel 2 through the grouting port 9, so that the concrete fills the cavity, and then the concrete is cured. The filling concrete 19, together with the grout-stopping panel 1 and the pressure-bearing panel 2, forms an integral structure.

[0044] The concrete used is C40 self-compacting concrete. During pouring, ensure that the concrete completely fills the cavity between the grout-stopping panel 1 and the bearing panel 2, and ensure that the main grouting pipe 8 is unobstructed. After the concrete is poured, it needs to be cured to ensure that the concrete reaches more than 70% of the design strength. The curing period is 7 days. During the curing period, the quality of the concrete is checked regularly to ensure that there are no defects such as cracks or air bubbles.

[0045] S05, during the tunnel boring machine's excavation process, the first grouting is carried out through the main grouting pipe 8 into the space between the shield tail and the tunnel wall. After the first grouting is completed, it is drilled from the outside to the reinforcement grouting pipe 12. Secondary pressure grouting is carried out through the reinforcement grouting pipe 12 to reinforce the gravel layer and construction joints.

[0046] The tunnel boring machine (TBM) is excavating. When three rings of tunnel segments are assembled, gravel backfilling is carried out to fill the gap between the shield tail and the tunnel wall. After fifteen rings of tunnel segments are assembled, the first grouting is carried out through the main grouting pipe 8. The grouting pressure is controlled at 0.3-0.5 MPa, and the pressure-time curve and the change in grout return volume are used as the final grouting criteria. If local seepage is found, replenishment grouting is carried out immediately until the sealing requirements are met.

[0047] The protective layer is drilled from the outside to the reinforcing grouting pipe 12. The threaded end cap 15 on the reinforcing grouting pipe 12 and the compressed foam 14 inserted inside are removed to form a complete grouting channel. Then, secondary grouting is carried out through the reinforcing grouting pipe 12 until the grout return is clean, the pressure is stable, and the grout suction rate is lower than the control threshold.

[0048] S06. After grouting is completed, the main grouting pipe 8, the injection port 9, the reinforcing grouting pipe 12, and the process opening 20 are sealed to complete the tunnel portal sealing operation. The main grouting pipe 8, the reinforcing grouting pipe 12, and the process opening 20 are sealed with blind flanges or welded. The injection port 9, the shoulder observation port, and the low-level port are permanently sealed or sealed with maintainable seals.

[0049] The foregoing basic examples and their further alternative examples can be freely combined to form multiple embodiments, all of which are embodiments that can be adopted and claimed in this application. In the scheme of this application, each alternative example can be arbitrarily combined with any other basic example and alternative example.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method of constructing a composite seal for a tunnel portal, characterised in that, The method comprises the following steps: S01, installing and fixing a ring-shaped grouting stop panel (1) at the tunnel portal, the outer periphery of the grouting stop panel (1) is sealed and fitted with the tunnel wall, and a plurality of main grouting pipes (8) extending to the inside of the tunnel are arranged on the grouting stop panel (1); S02, installing and fixing a ring-shaped pressure bearing panel (2) at the tunnel portal, the outer periphery of the pressure bearing panel (2) is sealed and fitted with the tunnel wall, the pressure bearing panel (2) is arranged outside the tunnel relative to the grouting stop panel (1) and a cavity is formed between the two, the main grouting pipes (8) are arranged on the pressure bearing panel (2), and a pouring opening (9) is reserved at the top of the pressure bearing panel (2); S03, a plurality of reinforcing grouting pipes (12) are arranged on the pressure bearing panel (2), the inner ends of the reinforcing grouting pipes (12) extend to the outer periphery of the cavity, and then the reinforcing grouting pipes (12) are sealed; S04, pouring concrete into the cavity between the grouting stop panel (1) and the pressure bearing panel (2) through the pouring opening (9), so that the concrete fills the cavity, and then the concrete is maintained, the concrete, the grouting stop panel (1) and the pressure bearing panel (2) together form an integral structure; S05, during the tunneling process of the tunnel boring machine, first grouting is performed on the space between the shield tail and the tunnel wall through the main grouting pipes (8), after the first grouting is completed, the reinforcing grouting pipes (12) are drilled from the outside, and secondary pressure grouting is performed on the outer periphery through the reinforcing grouting pipes (12), so as to reinforce the pressure of the pebble layer and the construction joint; S06, the main grouting pipes (8), the pouring opening (9) and the reinforcing grouting pipes (12) are sealed, and the sealing operation of the tunnel portal is completed.

2. The method of constructing a composite seal for a tunnel portal according to claim 1, wherein: In the S01, the grouting stop panel (1) is made of a wooden board; a plurality of first pipe through holes (3) are reserved on the grouting stop panel (1) in the circumferential direction, the main grouting pipes (8) are screwed into the first pipe through holes (3), sealing gaskets are arranged between the first pipe through holes (3) and the main grouting pipes (8); check valves are installed in the main grouting pipes (8); the inner extension length of the main grouting pipes (8) is arranged alternately in the far and near directions; a first sealing strip (4) is arranged between the outer periphery of the grouting stop panel (1) and the tunnel wall, and a water-resistant sealing glue is used for secondary sealing.

3. The method of constructing a composite seal for a tunnel portal according to claim 1 or 2, wherein: In the S02, the pressure bearing panel (2) is made of a steel plate, the pressure bearing panel (2) is assembled by a plurality of fan-shaped steel ring pieces (16), bolt holes (17) are reserved at the ends of the steel ring pieces (16), adjacent two steel ring pieces (16) are fixed by assembling bolts (18) arranged in the bolt holes (17), and the outer sides of the joint seams of the adjacent two steel ring pieces (16) are welded and reinforced; a plurality of second pipe through holes (5) are reserved on the pressure bearing panel (2) in the circumferential direction, the main grouting pipes (8) are screwed into the second pipe through holes (5), sealing gaskets are arranged between the second pipe through holes (5) and the main grouting pipes (8); a sealing groove (6) is arranged on the outer periphery of the pressure bearing panel (2), and a second sealing strip (7) is arranged in the sealing groove (6) to be fitted with the tunnel wall.

4. The method of claim 3, wherein: In the S02, the pressure bearing panel (2) is composed of six 60° fan-shaped steel ring pieces (16), the steel ring pieces (16) are prefabricated in the factory, and the roundness and hole position are checked and assembled outside the site.

5. The method of constructing a composite seal for a tunnel portal according to claim 1 or 2, wherein: The S01 and S02 are characterized in that a plurality of brackets (10) are arranged along the ring, the bracket (10) is an H-shaped steel, the bracket (10) supports the stop grouting panel (1) and the pressure bearing panel (2), the bottom plate of the bracket (10) is fixed on the hole wall through chemical anchor bolts (11), the inner end of the bracket (10) positions and supports the stop grouting panel (1), the outer end of the bracket (10) fixedly supports the pressure bearing panel (2), the connecting seat plate of the bracket (10) is fixed with the connecting seat plate of the pressure bearing panel (2) through bolts, and a long circular hole for position fine adjustment is formed on the connecting seat plate.

6. The method of constructing a composite seal for a tunnel portal according to claim 1, wherein: In the S03, the pressure bearing panel (2) is provided with an ear plate (13), and the reinforcing grouting pipe (12) is embedded on the ear plate (13) at an angle of 45° and is welded and fixed; the outer end of the reinforcing grouting pipe (12) is inserted with compressed foam (14), and the outer end of the reinforcing grouting pipe (12) is closed by a threaded end cover (15); and the inner end of the reinforcing grouting pipe (12) is provided with a gap of 20-50 mm with the outer surface of the cavity.

7. The method of constructing a composite seal for a tunnel portal according to claim 1, wherein: In the S04, the concrete is C40 self-compacting concrete, and when pouring, the concrete is ensured to completely fill the cavity between the stop grouting panel (1) and the pressure bearing panel (2), and the passage of the main grouting pipe (8) is ensured to be unobstructed; after the concrete pouring is completed, maintenance is needed to ensure that the concrete reaches more than 70% of the design strength; the concrete curing period is 7 days, and the quality of the concrete is checked regularly during the curing period to ensure that there are no cracks, bubbles and other defects.

8. The method of constructing a composite seal for a tunnel portal according to claim 1, wherein: In the S05, the tunnel boring machine is used for tunneling, and when the pipe piece assembly is completed to three rings, the gravel is filled to fill the gap between the shield tail and the hole wall, and after the pipe piece assembly is completed to fifteen rings, the first grouting is implemented through the main grouting pipe (8), the grouting pressure is controlled to be 0.3-0.5 MPa, and the pressure-time curve and the back grouting amount change are used as the final pouring criterion.

9. The method of claim 1 or 8, wherein: In the S05, the protective layer is drilled from the outside to the reinforcing grouting pipe (12), the threaded end cover (15) and the compressed foam (14) inserted in the reinforcing grouting pipe (12) are removed, a complete grouting passage is formed, and then the second grouting is implemented through the reinforcing grouting pipe (12) until the back grouting is clean, the pressure is stable, and the grouting rate is lower than the control threshold.

10. The method of constructing a composite seal for a tunnel portal according to claim 1, wherein: In the S06, the main grouting pipe (8) and the reinforcing grouting pipe (12) are closed by blind plates or welded, and the pouring port (9), the shoulder observation port and the low port are permanently sealed or closed by a maintainable sealing element.

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