Improved Construction Method for Non-standard High-strength Composite Steel Rings for Tunnel Reinforcement During Subway Tracking Window

Abstract

This invention belongs to the field of shield tunnel reinforcement construction technology, and particularly relates to an improved construction method for non-standard high-strength composite steel rings used in subway tunnel reinforcement during the operation window. It includes the following steps: S1, Fabrication process: Surveying, mapping, and designing the tunnel segments, and prefabricating composite steel ring components; S2, Preparation process: Determining the installation position of the composite steel ring components; S3, Installation process: During the subway operation window, installing the composite steel ring components with added fiber reinforcement inside the pipe at the determined position according to the installation process, and injecting grout or concrete into the cavity of the assembled improved composite steel ring. This invention, by embedding fiber reinforcement inside the composite steel ring components, forms a four-layer composite force-bearing system of "fiber cloth and steel pipe bundle + grout / concrete + fiber reinforcement" working synergistically, significantly improving the overall elastic modulus, strength, and stiffness of the composite steel ring, and significantly broadening the range of selectable mechanical properties required for tunnel structure reinforcement.

Description

Technical Field

[0001] This invention belongs to the field of shield tunnel reinforcement construction technology, and particularly relates to an improved construction method for non-standard high-strength composite steel rings used for reinforcement of subway tunnels during the track maintenance window. Background Technology

[0002] As urban subways age, tunnel segments are prone to defects such as cracks, deformation, and water leakage, seriously threatening operational safety. Traditional tunnel reinforcement methods suffer from long construction periods, require welding operations, and cause significant disruption to operations, making them unsuitable for the strict time constraints of subway operation windows (usually 3-4 hours at night).

[0003] In the prior art, patent CN115898452B discloses a "construction method for non-standard high-strength composite steel rings for tunnel reinforcement during subway operation windows." This method employs a step-by-step construction approach using composite steel rings and high-strength grouting material, effectively solving the construction challenges during operation windows. However, this technology still has the following shortcomings: (1) There is a lack of available thresholds for elastic modulus, strength and stiffness: Existing composite steel rings mainly rely on the external fiber layer, steel pipe and internal grout to provide elastic modulus, strength and stiffness. When subjected to excessive deformation of the tunnel or worse environmental conditions, the composite steel rings need to have a larger threshold for resisting external loads. (2) Weak node connection structure: The original technology uses joint plates to connect each ring segment with bolts. The joint plates and square steel pipes are lap welded, with a large number of connecting bolts and limited insertion depth; (3) Unreasonable arrangement of bolt holes: The original technology set bolt holes in each pipe of the composite steel ring made of multiple pipes, which weakened the integrity of the cross section and required a large number of holes and complicated construction. This invention proposes an improved construction method for non-standard high-strength composite steel rings used in subway tunnel reinforcement during the track maintenance window period to solve the above-mentioned problems. Summary of the Invention

[0004] To achieve the above objectives, the present invention employs the following technical solutions: An improved construction method for non-standard high-strength composite steel rings used in subway tunnel reinforcement during track maintenance windows includes: S1. Manufacturing process: Survey and map the tunnel segments, design composite steel ring components based on the survey and mapping data and the need for tunnel structure reinforcement, and prefabricate composite steel ring components. Composite steel ring components include top ring, joint pipe, fiber reinforcement, support group, left ring, and right ring. S2. Preparation process: Based on the data obtained from the survey and mapping in step S1, the installation position of the composite steel ring component is determined by the designer. S3. Installation process: During the subway operation window, the composite steel ring component prepared in step S1 is coated with structural adhesive according to the design requirements and installed at the installation position determined in step S2. Then, dense grout or concrete is poured into all the cavities of the completed improved composite steel ring assembly. Step S3 also includes the following steps: S3.1 Installation of the top ring: First, install the two connector pipes at both ends of the top ring, then move the top ring to the installation position, apply structural adhesive to the outer arc surface of the top ring, then make the adhesive-coated outer arc surface of the top ring contact with the tunnel segment, and fix the top ring to the tunnel segment with bolts and fasteners. S3.2 Inserting the fiber reinforcement: First, install the support assembly on the fiber reinforcement, then insert the fiber reinforcement from one end of the top ring opening. The fiber reinforcement passes through the top ring, and both ends of the fiber reinforcement extend to the outer sides of both ends of the top ring to form reserved sections. The length of the reserved section on the left side meets the installation length requirements of the left ring, and the length of the reserved section on the right side meets the installation length requirements of the right ring. S3.3 Installation of left and right rings and brackets: Along the reserved section of the fiber reinforcement, insert the upper end of the left ring into the left joint pipe to form a socket connection, and insert the upper end of the right ring into the right joint pipe to form a socket connection. Install brackets for support at the bottom of the left and right ring components to complete the assembly of the overall steel ring. S3.4. Fill each cavity of the composite steel ring component with dense grout or concrete.

[0005] As a preferred embodiment, the support group consists of several elastic supports, which are fixed on the surface of the fiber reinforcement. The elastic supports are made of bent spring steel wire and have arc-shaped grooves. The elastic supports are clamped to the surface of the fiber reinforcement through the arc-shaped grooves. The diameter of the arc-shaped grooves is adapted to the diameter of the fiber reinforcement. The outer dimensions of the elastic supports are slightly smaller than the inner diameter of a single steel pipe in the steel pipe bundle.

[0006] As a preferred option, the fiber reinforcement uses basalt fiber reinforcement with a diameter of 4mm-8mm, and the elastic modulus of the fiber reinforcement is 90-110GPa and the tensile strength is 4100-4800MPa.

[0007] As a preferred option, the length of the fiber reinforcement is about 10mm shorter than the total length of the composite steel ring component.

[0008] As a preferred option, the top ring, left ring, and right ring are prepared using the same method, each consisting of a cluster of n square steel tubes with equal wall thickness arranged side by side, where n≥3.

[0009] As a preferred option, fiber reinforcement is placed inside the square steel tubes except for the one located in the middle of a cluster of embryos, and the number of fiber reinforcements implanted in the square steel tubes is greater than or equal to one according to the design requirements.

[0010] As a preferred embodiment, no fewer than four bolt holes are made on the square steel tube located in the middle of a cluster of blanks. The bolt holes are used for connection and installation with tunnel segments, and the bolt holes are evenly distributed on the square steel tube.

[0011] As a preferred option, the inner dimension of the joint pipe is slightly larger than the outer dimension of the top ring square pipe to meet the installation tolerance requirements. The joint pipe and the top ring form a socket connection relationship. The length of the joint pipe is not less than 360mm, and it is inserted into both ends of the top ring at half the size. Full welding is performed on the outer connection side of the top ring and the joint pipe.

[0012] As a preferred option, an exhaust hole is provided at the top of the top ring, and an exhaust valve is installed at the exhaust hole.

[0013] As a preferred option, the grouting material in step S3.4 is high-strength grouting material, high-strength concrete with aggregate, or concrete mixed with short fibers. The strength grade of the grouting material is not lower than C60. The grouting method adopts pressure grouting process, and the grouting pressure is controlled at 0.2 to 0.4 MPa. Two pumps simultaneously grout into the grout inlets at the lower ends of the left and right rings, respectively. When the vent valve has completely returned the grouting material, the vent valve is closed and grouting is stopped.

[0014] Compared with existing technologies, the advantages of this invention are: 1. This invention forms a four-layer composite synergistic force system of "fiber cloth (outer surface) + steel pipe bundle + grouting material / concrete + fiber reinforcement" by embedding fiber reinforcement in the composite steel ring component. This significantly improves the elastic modulus, strength and stiffness of the high-strength composite steel ring, and further provides a wider range of selectable mechanical index thresholds for effectively suppressing tunnel deformation.

[0015] 2. The present invention uses an elastic bracket fixed on the surface of the fiber reinforcement. The elastic bracket assists the fiber reinforcement in supporting the steel tube bundle. During the grouting or concrete pouring process, it can also maintain the stability of the fiber reinforcement position, preventing grouting or concrete pouring blockage. This keeps the fiber reinforcement in a relatively central position, forming a uniform bond with the pouring material and avoiding stress concentration.

[0016] 3. This invention improves the original design of the joint plate into a socket-type joint pipe with a socket length of not less than 360mm, forming a reliable mechanical interlocking and friction connection, improving the load-bearing capacity of the joint, effectively avoiding fatigue damage, and meeting the requirements for rapid installation during the skylight period. It also has the advantage of optimizing the joint connection structure.

[0017] 4. In this invention, the bolt holes for installation and connection in the top ring, left ring, and right ring are only set on the middle square steel tube, and the other square steel tubes are not provided with bolt holes. This reduces the weakening of the cross section, makes it possible to realize the built-in fiber reinforcement, and simplifies the construction process and improves construction efficiency.

[0018] 5. This invention adopts the sequence of "top ring installation → fiber reinforcement insertion → side ring installation → bracket installation". Using the top ring as a positioning reference, the fiber reinforcement is inserted smoothly. The left and right rings are installed accurately and quickly along the reserved fiber reinforcement. Application examples have confirmed that the installation time of a single composite steel ring can be controlled within 2.0 hours, which is about 0.5 hours shorter than the installation time of the patent mentioned in the background technology, and fully adapts to the strict time constraints of the skylight period.

[0019] 6. The basalt fiber reinforcement of this invention has excellent corrosion resistance and fatigue resistance. It forms a multi-layer anti-corrosion system with high-strength grouting materials, and its design service life can reach more than 50 years. Moreover, the thermal expansion coefficient of the fiber reinforcement matches that of concrete, and its bond strength is better than that of steel bars and other fiber reinforcements. It has stable long-term performance and greatly improves structural durability. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in further detail below with reference to the examples. These examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] An improved construction method for non-standard high-strength composite steel rings used in subway tunnel reinforcement during track maintenance windows includes: S1. Manufacturing process: Survey, map and design the tunnel segments. Based on the survey and mapping data and the need for tunnel structure reinforcement, design composite steel ring components and prefabricate composite steel ring components. Composite steel ring components include top ring, joint pipe, fiber reinforcement, support group, left ring and right ring. S2. Preparation process: Based on the data obtained from the survey and mapping in step S1, the installation position of the composite steel ring component is determined by the designer, and the surface defects of the segments are treated and cleaned. S3. Installation process: During the subway operation window, the composite steel ring component prepared in step S1 is coated with structural adhesive according to the design requirements and installed at the installation position determined in step S2. Then, dense grout or concrete is poured into all the cavities of the completed improved composite steel ring assembly. Step S3 also includes the following steps: S3.1 Installation of the top ring: First, install the two connector pipes at both ends of the top ring, then move the top ring to the installation position, apply structural adhesive to the outer arc surface of the top ring, then make the adhesive-coated outer arc surface of the top ring contact with the tunnel segment, and fix the top ring to the tunnel segment with bolts and fasteners. S3.2 Inserting the fiber reinforcement: First, install the support assembly on the fiber reinforcement, then insert the fiber reinforcement from one end of the top ring opening. The fiber reinforcement passes through the top ring, and both ends of the fiber reinforcement extend to the outer sides of both ends of the top ring to form reserved sections. The length of the reserved section on the left side meets the installation length requirements of the left ring, and the length of the reserved section on the right side meets the installation length requirements of the right ring. S3.3 Installation of joint pipes, left ring, right ring and brackets: Along the reserved section of the fiber reinforcement, install the two joint pipes at both ends of the top ring respectively. Insert the upper end of the left ring into the left joint pipe to form a socket connection. Insert the upper end of the right ring into the right joint pipe to form a socket connection. Install brackets for support at the bottom of the left and right ring components to complete the assembly of the whole steel ring. S3.4. Fill each cavity of the composite steel ring component with dense grout or concrete.

[0022] The support assembly consists of several elastic supports fixed to the surface of the fiber reinforcement. The elastic supports are made of bent spring steel wire and have arc-shaped grooves. The elastic supports are clamped to the surface of the fiber reinforcement through these grooves, with the diameter of the grooves matching the radius of the fiber reinforcement. The shape of the elastic supports can be ω-shaped, double Ω-shaped, or an open ∞-shaped structure. The diameter of the spring steel wire is 0.5–1 mm. One elastic support is tied to the surface of the fiber reinforcement every 1 m. The outer contour dimension of the elastic support is slightly smaller than the inner diameter of a single steel pipe in the steel pipe bundle, with a difference ≤1 mm. This is to ensure that the distance between the fiber reinforcement and the inner wall of the steel pipe remains relatively uniform and that the thickness of the fiber reinforcement protective layer is relatively uniform, ensuring easy installation without causing blockage during grouting or concrete pouring.

[0023] The elastic support not only assists the fiber reinforcement in passing through the top ring in step S3.1, but also keeps the fiber reinforcement in a stable position in step S3.4, ensuring that the fiber reinforcement is evenly wrapped with the grouting material.

[0024] The fiber reinforcement uses basalt fiber reinforcement with a diameter of 4mm-8mm. The elastic modulus of the fiber reinforcement is 90-110GPa and the tensile strength is 4100-4800MPa. The length of the fiber reinforcement is 10mm shorter than the total length of the composite steel ring component.

[0025] The top ring, left ring, and right ring are prepared using the same method. Each ring consists of n square steel tubes of equal thickness arranged side-by-side to form a cluster of preforms. The square steel tubes are arranged front-to-back, with their adjacent front and rear end faces in contact and fixedly connected. n ≥ 3. The square steel tubes within the cluster are bonded together using structural adhesive. The gaps in the bonding surfaces are intermittently welded. After the welding cools, high-strength basalt fiber is coated with adhesive and wrapped around the outer surface of the preform. A vacuum high-pressure composite process is then used to bond the high-strength basalt fiber layer onto the preform to create a semi-finished product.

[0026] Fiber ribs are placed inside all square steel tubes except those located in the middle of a cluster of preforms. No fiber ribs are placed inside the middle square steel tube. The number of fiber ribs implanted in each square steel tube is at least one, as required by design specifications. The specific number of fiber ribs is determined based on the structural stiffness, strength, and modulus of elasticity design requirements. At least four bolt holes are made on the middle square steel tube in the cluster of preforms. These bolt holes are used for connection and installation with tunnel segments, and are evenly distributed throughout the square steel tube. Examples of bolt holes used for connection to joint pipes or tunnel segments are at least four. The diameter of these bolt holes is 16–18 mm. No bolt holes are made on the remaining square steel tubes to maintain the integrity of their cross-sections.

[0027] The joint pipe is a rectangular steel pipe with the same wall thickness as the top ring. The inner dimension of the joint pipe is slightly larger than the outer dimension of the square tube of the top ring to meet the installation tolerance requirements. The joint pipe and the top ring form a socket connection. The length of the joint pipe is not less than 360mm, and it is inserted into both ends of the top ring at half the size. Full welding is performed on the outer connection side of the top ring and the joint pipe.

[0028] The joint pipe is at least three times the length of the short side of the top ring. Half of the joint pipe's length is inserted into the top ring, while the other half is reserved for installation in the tunnel, specifically for the side rings. The section of the joint pipe located on the left side of the top ring is reserved for the left ring, and the section on the right side is reserved for the right ring. The joint pipe is fully welded to the top ring after connection. The total length of the joint pipe is 360–400 mm, with 180–200 mm of the welded section inserted into the top ring and 180–200 mm of the exposed socket section. The upper ends of the left and right rings are inserted into the joint pipe to a depth of 180–200 mm. After insertion, the joint pipe is tightened using bolts on the brackets and structural adhesive is applied to ensure the reliability of the socket connection.

[0029] The joint pipe is installed at the intersection of tensile and compressive stresses of the composite steel ring component. The contact surfaces between the left and right rings and the joint pipe are coated with adhesive for sealing function in step S3.4 to prevent leakage, but not for airtightness.

[0030] Both the left and right rings have a sealed base welded to their bottoms. The lower inner sides of both the left and right rings are provided with slurry inlets and bolt holes for installation and fixing. Valves are installed at the slurry inlets, and vent holes are provided at the top of the top ring, with vent valves installed at the vent holes.

[0031] The grouting material in step S3.4 is high-strength grouting material, high-strength concrete with aggregate, or concrete mixed with short fibers. The strength grade of the grouting material is not lower than C60. The grouting method adopts pressure grouting process. The grouting pressure is controlled at 0.2-0.4MPa. Two pumps simultaneously grout into the grout inlets at the lower ends of the left and right rings, respectively. When the vent valve has completely returned the grouting material, the vent valve is closed and grouting is stopped.

[0032] The top ring, connector tube, left ring, right ring, bracket, and bolts used during installation can be made of stainless steel.

[0033] Brackets are installed at the bottom of the left and right ring components between the tunnel segments or the track bed. The brackets are adjustable brackets. The adjustable brackets adopt existing technology and can use ready-made bracket devices sold on the market or the bracket structure in the published patent CN115898452B.

[0034] In addition, the composite steel ring component can adopt not only the overall structure of the large semi-circular ring mentioned above, but also the overall structure of the full ring. The bracket and empty areas are replaced by top rings and connection pipes. That is, the composite steel ring component of the full ring is a structure with two top rings, and the left and right rings are the left and right rings respectively. The left and right rings are connected to the top rings through connection pipes. The specific connection and fixing method is the same as the original method.

[0035] The improved construction method is applicable to construction during the track maintenance window of an operational subway. The actual installation process has proven that the construction time for a single composite steel ring reinforcement can be completely controlled within 2.0 hours, meeting the requirements for nighttime track maintenance windows of 3-4 hours.

[0036] 1) Examples of improved construction methods under standard working conditions: S1. Precast composite steel ring component: Preparation of the top ring: Three 304 stainless steel square tubes with outer dimensions of 30mm × 60mm × 1.5mm (inner dimensions of 27mm × 57mm) are arranged side by side and bonded together using structural adhesive to form a cluster. Intermittent welding is performed at the joints between the three square tubes, with weld lengths of 30mm and spacing of 300mm. After welding and cooling, high-strength basalt fiber coated with adhesive is laid and wrapped around the outer surface of the cluster, forming a 1.5mm thick fiber composite layer through a vacuum high-pressure composite process.

[0037] Preparation of fiber reinforcement: An elastic support is tied to the fiber reinforcement at 1-meter intervals. The elastic support is made of 0.8mm diameter spring steel wire bent into an Ω shape, with an outer contour dimension of 25mm × 55mm (1mm smaller than the inner cavity of the tube on one side). A 4mm arc-shaped groove is provided at the contact point between the elastic support and the fiber reinforcement. One 8mm diameter basalt fiber reinforcement is implanted into each of the square steel tubes on the front and rear sides. The fiber reinforcement has an elastic modulus of 100GPa and a tensile strength of 4500MPa.

[0038] Preparation of the joint pipes: Rectangular steel pipes with a wall thickness of 1.5mm are selected as the joint pipes, with an inner cavity size of 31mm × 61mm (1mm larger than the outer dimensions of the top ring, left ring, and right ring), and a total length of not less than 360mm (basically consistent with the total width of the steel pipe cluster assembly). The two joint pipes are inserted 180mm into each end of the top ring, and the outer surface joint is fully welded for fixation. The inner mating gap is filled with adhesive. A 180mm exposed length is reserved for the insertion and insertion sections of the left and right rings.

[0039] Preparation of the left and right rings: The same method as the top ring is used for preparation. The length is determined according to the tunnel cross-section. The upper end is 180mm as the insertion end, and the lower end is welded to the closed base. Two grouting and return ports with a diameter of 25mm are set on the lower inner side of each ring.

[0040] Preparation of adjustable brackets: stainless steel is selected, and it is composed of a top plate, a sloping groove plate and a bottom plate. The top plate is provided with two M16 adjusting bolt holes, and the slope of the sloping groove plate matches the inclination angle of the tube segment and is pre-set with four M20 bolt holes.

[0041] S2. Preparation process: Three-dimensional laser scanning was used to acquire cross-sectional data of tunnel segments, and a BIM model was established to determine the installation positions of each ring. Installation positions were marked on the tunnel segments, avoiding structures such as manholes, grouting holes, and main reinforcing bars. Defect treatment was performed on the surface of the tunnel segments: cracks were sealed with epoxy resin grout, water stains were dried with a hot air gun, oil stains were cleaned with industrial cleaning agents, and finally, the segments were polished with an angle grinder to remove surface dust.

[0042] S3. Installation process (to be completed within the maintenance window): S3.1 Installation of the top ring: Apply adhesive to the outer arc surface of the top ring, transport it to the installation position and lift it into place. The outer arc surface is attached to the tunnel segment. Drill holes through the four bolt holes of the intermediate pipe and insert M16 mechanical and chemical anchors for fixation.

[0043] S3.2 Inserting the fiber reinforcement: Insert the fiber reinforcement, which has been fixed to the elastic support, from one side of the top ring, through the entire length, leaving a length on each side that is about 5mm shorter than the left and right rings (the total length of the fiber reinforcement is 10mm shorter than the total length of the composite steel ring) to facilitate the installation of the left and right rings.

[0044] S3.3 Installation of the left and right rings: Following the reserved basalt fiber reinforcement, insert the upper ends of the left and right rings into the exposed socket section of the joint pipe to a depth of 180mm. Install the adjustable bracket at the bottom and adjust the bolts to make the left and right rings fit tightly with the top ring, while making the entire steel ring fit tightly against the inner surface of the pipe segment.

[0045] S3.4 Grouting or Concrete Injection: Use C60 high-strength grout at a pressure of 0.3 MPa, pumping it in through the inlets of the left and right rings until the grout is fully discharged from the vent at the top of the top ring. Stop pumping then close the valves of the left and right rings, as well as the vent valve of the jacking pipe. During the grouting process, the elastic support should keep the fiber reinforcement centered to ensure uniform bonding.

[0046] In this embodiment, a total of 31 composite steel rings were installed, with the construction time for each composite steel ring reinforced within 2.0 hours, meeting the construction requirements during the skylight period. After reinforcement, the mechanical properties of the composite steel rings, such as the elastic modulus and bending strength, are significantly improved compared to the original technology, and the joint bearing capacity is also improved.

[0047] 2) Examples of high-stiffness reinforcement under large deformation conditions: The difference from Option 1) is that, Three basalt fiber optic tendons with a diameter of 8mm were implanted into each square steel tube where fiber optic tendons were to be placed, and the elastic supports on the fiber optic tendons were spaced 800mm apart. The total length of the joint pipe is extended to 400mm, with a 200mm welding section inserted into the top ring and a 200mm exposed socket section. The intermediate pipe has 4 bolt holes and uses M16 mechanical and chemical anchors; The grouting material is C80 high-strength concrete with aggregate, with a maximum aggregate particle size of 4mm; 3) Examples of efficient construction in rapid repair situations: The difference from Option 1) is that, Three basalt fiber reinforcements with a diameter of 8mm were inserted into each square steel pipe that needed to be fitted with fiber reinforcements, simplifying the reinforcement installation process. The flexible support uses simple U-shaped steel wire clips with a spacing of 800mm; The socket section of the connector is equipped with a guide bevel for easy and quick insertion; The grouting material used is an early-strength, micro-expansion, high-strength grout, with a strength of 30MPa or higher after 2 hours; the rest of the fabrication and installation process is the same as in scheme 1).

[0048] 27 units were installed, with each unit taking less than 2.0 hours to install.

[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An improved construction method for non-standard high-strength composite steel rings used in tunnel reinforcement during subway track maintenance windows, characterized in that... Includes the following steps: S1. Manufacturing process: Survey and map the tunnel segments, design composite steel ring components based on the survey and mapping data and the need for tunnel structure reinforcement, and prefabricate the composite steel ring components, which include a top ring, joint pipe, fiber reinforcement, support group, left ring, and right ring. S2. Preparation process: Based on the data obtained from the survey and mapping in step S1, the installation position of the composite steel ring component is determined by the designer. S3. Installation process: During the subway operation window, the composite steel ring component prepared in step S1 is coated with structural adhesive according to the design requirements and installed at the installation position determined in step S2. Then, dense grout or concrete is poured into all the cavities of the completed improved composite steel ring assembly. Step S3 also includes the following steps: S3.1 Install the top ring: First, install the two connection pipes at both ends of the top ring respectively, then move the top ring to the installation position, apply structural adhesive to the outer arc surface of the top ring, then make the adhesive-coated outer arc surface of the top ring contact with the tunnel segment, and fix the top ring to the tunnel segment with bolts and fasteners. S3.2 Inserting the fiber reinforcement: First, install the support assembly on the fiber reinforcement, and then insert the fiber reinforcement from one end of the top ring opening. The fiber reinforcement passes through the top ring, and both ends of the fiber reinforcement extend to the outer sides of both ends of the top ring to form reserved sections. The length of the reserved section on the left side meets the installation length requirements of the left ring, and the length of the reserved section on the right side meets the installation length requirements of the right ring. S3.3 Install the left ring, right ring and bracket: Along the reserved section of the fiber reinforcement, insert the upper end of the left ring into the joint pipe on the left side to form a socket connection, and insert the upper end of the right ring into the joint pipe on the right side to form a socket connection. Install brackets for support at the bottom of the left ring and right ring components to complete the assembly of the overall steel ring. S3.

4. Fill each cavity of the composite steel ring component with dense grout or concrete.

2. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1, is characterized in that: The support group consists of several elastic supports, which are fixed on the surface of the fiber reinforcement. The elastic supports are made of bent spring steel wire and have arc-shaped grooves. The elastic supports are clamped on the surface of the fiber reinforcement through the arc-shaped grooves. The diameter of the arc-shaped grooves is adapted to the diameter of the fiber reinforcement. The outer dimensions of the elastic supports are slightly smaller than the inner diameter of a single steel pipe in the steel pipe bundle.

3. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1 or 2, is characterized in that: The fiber reinforcement is made of basalt fiber reinforcement with a diameter of 4mm-8mm, and the elastic modulus of the fiber reinforcement is 90-110GPa and the tensile strength is 4100-4800MPa.

4. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1, is characterized in that: The length of the fiber reinforcement is about 10 mm shorter than the total length of the composite steel ring component.

5. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1, is characterized in that: The top ring, left ring, and right ring are prepared using the same method, each consisting of a cluster of n square steel tubes of equal wall thickness arranged side by side, where n ≥ 3.

6. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 5, is characterized in that: Fiber ribs are placed inside square steel tubes (excluding those located in the middle) within a cluster of embryos. The number of fiber ribs implanted inside the square steel tubes is greater than or equal to one, according to design requirements.

7. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 5, is characterized in that: No fewer than four bolt holes are made on the square steel tube located in the middle of a cluster of embryos. The bolt holes are used for connection and installation with tunnel segments, and the bolt holes are evenly distributed on the square steel tube.

8. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1, is characterized in that: The inner dimension of the joint tube is slightly larger than the outer dimension of the top ring square tube to meet the installation tolerance requirements. The joint tube and the top ring form a socket connection. The length of the node tube is not less than 360mm, and it is inserted into both ends of the top ring at half the size. Full welding is performed on the outer connection side of the top ring and the node tube.

9. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 1, is characterized in that: The top of the top ring is provided with an exhaust hole, and an exhaust valve is installed at the exhaust hole.

10. The improved construction method for non-standard high-strength composite steel rings used for tunnel reinforcement during subway track maintenance windows, as described in claim 9, is characterized in that: The grouting material in step S3.4 is high-strength grouting material, high-strength concrete with aggregate, or concrete mixed with short fibers. The strength grade of the grouting material is not lower than C60. The grouting method adopts pressure grouting process, and the grouting pressure is controlled at 0.2-0.4MPa. Two pumps simultaneously grout into the grout inlets at the lower ends of the left and right rings, respectively. When the vent valve has completely returned the grouting material, the vent valve is closed and grouting is stopped.