Construction method for reducing size of tunnel portal and structure thereof

Abstract

The present application relates to the technical field of rail transit shield tunnel portal reconstruction, and particularly relates to a construction method for reducing the size of a tunnel portal and a structure thereof. The construction method comprises a station enclosure structure, an existing portal steel ring back plate, a newly-added portal steel ring back plate, a newly-added portal steel ring plate, and a reinforced concrete ring beam structure located in the enclosed space of the station enclosure structure, the existing portal steel ring back plate, the newly-added portal steel ring back plate and the newly-added portal steel ring plate. The structure and method for reducing the size of a shield tunnel portal are beneficial to the control of the construction posture when a shield machine is launched or received, and reduce the risk of groundwater leakage and gushing when the shield machine is launched or received. The existing portal steel ring of the station is not removed, thereby avoiding damage to the existing structure, realizing electrical communication with the existing structure, and reducing the electrochemical corrosion effect of stray current on the existing station structure.

Description

Technical Field

[0001] This invention relates to the field of tunnel portal modification technology for rail transit shield tunneling, specifically to a construction method and structure for reducing the size of tunnel portals. Background Technology

[0002] Subway stations are important nodes in the urban public transportation network. Due to changes in functional requirements, the dimensions of the tunnel portals for future subway stations, which are reserved at the locations of subway transfer stations and transportation hubs built in the early stages, are often adjusted.

[0003] For example, the "Construction Method for Enlarging the Diameter of a Shield Tunnel Portal" disclosed in Chinese Invention Patent Publication No. CN112228084A involves chiseling away part of the existing wall, installing reinforcing bars to fix the enlarged tunnel rim, and then pouring concrete to achieve the tunnel portal diameter expansion. This method, which involves chiseling away the original tunnel portal and installing reinforcing bars to fix the new portal, disrupts the electrical connection between the anchoring reinforcing bars of the subway station portal and the existing structural steel mesh. The resulting stray currents cause electrochemical corrosion to the subway station structure, affecting its durability. Similarly, Chinese Utility Model Patent Publication No. CN217176629U... The patented "Structure for Enlarging and Upgrading the Launch Portal of a Shield Tunnel" uses a steel component fixed to the end wall of the existing portal as a portal ring. A new portal is formed by chiseling away the portion of the end wall between the launch portal and the reinforcing steel component, and also by chiseling away the portion of the end wall within the reinforcing steel component. This method uses expansion bolts and ropes to fix the new portal, but the lack of electrical connection with the existing steel reinforcement mesh of the station results in stray currents that cause electrochemical corrosion. Furthermore, it makes it impossible to install a permanent closed ring beam on the portal enlargement structure, affecting structural safety and station boundary dimensions, thus limiting its use. All of the above patents apply to portal enlargement and upgrading. For cases where the future portal size is smaller than the reserved portal size, maintaining the original reserved portal size without adjustment results in a large gap between the tunnel boring machine (TBM) and the portal, increasing the difficulty of controlling the TBM's launch and receiving attitudes, compromising construction quality, and increasing the risk of groundwater leakage and sudden surges. The method of partially removing existing station portals and then installing reinforcing bars and stirrups in the Chinese invention patent (CN112228084A) cannot solve the problems of stray currents affecting structural electrochemical corrosion, the risk of damage to existing station structures from the removal method, and the impact of vibration and noise. The method in the Chinese utility model patent (CN217176629U) involves attaching and fixing the steel component serving as the portal to the existing portal end wall, which is not suitable for situations where the steel component is smaller than the original portal size. There is an urgent need for a construction method that avoids removing existing station portals and eliminates the risk of damage to the existing structure from removal methods. Summary of the Invention

[0004] This invention provides a structure and method for reducing the size of the tunnel portal in a shield tunneling method. When the required diameter of the portal is smaller than the original portal diameter, a structure and method for reducing the size of the tunnel portal in a shield tunneling method is formed to be electrically connected to the existing structure without removing the existing portal of the station.

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

[0006] A construction method for reducing the size of a tunnel portal includes the following steps:

[0007] Positioning and layout: The center of the modified shield tunnel portal is positioned and laid out, and steel bars are temporarily installed on the station retaining structure to mark the center line of the modified shield tunnel portal.

[0008] Marking positions: On one side of the existing portal steel ring back plate, which is located on the reinforced concrete ring beam, mark the positions of the first lining plate and the first connecting steel bar at equal angles, with the center line of the modified shield tunnel portal as the reference.

[0009] Spot welding fixation: After the layout is completed as required, the first connecting steel bar and the first backing plate are spot welded and fixed respectively.

[0010] Welding and installation: Weld and install the first connecting steel bar on one side parallel to the surface of the existing portal steel ring back plate, as well as the first lining plate, onto the existing portal steel ring back plate.

[0011] Fabrication of the reinforcing cage: Fabricate and place the reinforcing cage for the reinforced concrete ring beam, ensuring that the reinforcing cage avoids the first connecting reinforcing bar;

[0012] Welding of reinforcing bars and lining: Spot weld the second connecting reinforcing bar and the second lining plate onto the back plate of the newly added portal steel ring, and perform the corresponding welding installation;

[0013] Segmented fixing and welding: The newly added portal steel ring back plate is temporarily fixed and installed in segments. The first connecting steel bar and the second connecting steel bar are paired and welded in parallel lap joints one by one. At the same time, the second lining plate is welded and the newly added portal steel ring plate is welded.

[0014] Sealing gaps: The gaps between the steel ring back plate of the new tunnel portal and the station enclosure structure are sealed with quick-hardening cement, and concrete pouring holes and vent holes are opened at the top of the steel ring back plate of the new tunnel portal.

[0015] Concrete pouring: Self-compacting concrete is poured through the concrete pouring holes on the newly added portal steel ring back plate to form a reinforced concrete ring beam, thereby completing the structural modification of the portal of the shield tunnel with reduced size.

[0016] Correspondingly, this scheme also proposes a structure for reducing the size of the tunnel portal using the above-described method, specifically including: a station retaining structure, an existing portal steel ring back plate, a new portal steel ring back plate, a new portal steel ring ring plate, and a reinforced concrete ring beam located within the space enclosed by the station retaining structure, the existing portal steel ring back plate, the new portal steel ring back plate, and the new portal steel ring ring plate.

[0017] Furthermore, a new portal steel ring plate is provided between the end of the newly added portal steel ring back plate that is far from the station enclosure structure and the end of the existing portal steel ring back plate that is far from the station enclosure structure.

[0018] Furthermore, reinforced concrete ring beams are formed by pouring concrete within the enclosed space of the existing portal steel ring back plate, the newly added portal steel ring back plate, the newly added portal steel ring ring plate, and the station enclosure structure.

[0019] Furthermore, an "L"-shaped first connecting steel bar and a first liner are provided on one side of the existing portal steel ring back plate; an "L"-shaped second connecting steel bar and a second liner are provided on one side of the newly added portal steel ring back plate.

[0020] Furthermore, the first connecting steel bar is evenly distributed at equal angles along the existing portal steel ring back plate with the center line of the newly added portal steel ring back plate as the reference, with one side parallel to the surface of the existing portal steel ring back plate and the other side pointing to the center line of the newly added portal steel ring back plate; the second connecting steel bar is evenly distributed at equal angles along the newly added portal steel ring back plate with the center line of the newly added portal steel ring back plate as the reference, with one side parallel to the surface of the newly added portal steel ring back plate and the other side pointing to the center line of the newly added portal steel ring back plate.

[0021] Furthermore, the first connecting steel bar and the second connecting steel bar have the same starting angle and angle interval based on the center line of the newly added portal steel ring back plate; one side of the first connecting steel bar pointing to the center line and one side of the second connecting steel bar pointing to the center line are fixed by weld lap joint.

[0022] Furthermore, the pre-embedded nuts of the first connecting steel bar, the second connecting steel bar, and the newly added portal steel ring plate all avoid the steel cage of the reinforced concrete ring beam.

[0023] The present invention has the following beneficial technical solutions:

[0024] Through the positioning and layout process, the center of the modified shield tunnel portal was located, and the center line was marked by reinforcing bars on the station retaining structure, providing an accurate benchmark for subsequent construction. Marking positions, spot welding, and welding installation ensured the accurate placement and connection of the first connecting reinforcing bar and the first lining plate, as well as the second connecting reinforcing bar and the second lining plate. The cast reinforced concrete ring beam enhanced the integrity and stability of the newly added portal structure, facilitating the bearing of the shield machine's starting and receiving loads.

[0025] Reducing the size of the tunnel portal lowers the difficulty of controlling the attitude of the tunnel boring machine during launch and reception, and reduces the risk of groundwater leakage and sudden surge at the portal location, thereby reducing construction quality and safety risks.

[0026] By not removing the existing station entrances, damage to the existing structure was avoided, ensuring the integrity of the station structure, and also avoiding the vibration and noise caused by removal.

[0027] The proper placement and connection of the first and second connecting reinforcing bars, as well as the reasonable avoidance of the reinforcing cage, ensured electrical connectivity with the existing structure. This electrical connectivity reduced the electrochemical corrosion of the existing station structure by stray currents, thus extending the durability of the station structure. Attached Figure Description

[0028] Figure 1 This is an elevation view of a specific embodiment of the present invention;

[0029] Figure 2 This is a cross-sectional view of a specific embodiment of the present invention;

[0030] In the diagram: 11. Station enclosure structure; 12. Existing portal steel ring plate; 13. Existing portal steel ring back plate; 14. Existing station side wall; 21. New portal steel ring back plate; 22. New portal steel ring plate; 23. Embedded nut; 24. First liner plate (liner plate on the existing portal steel ring back plate); 25. Second liner plate (liner plate on the new portal steel ring back plate); 26. Center line; 31. Reinforced concrete ring beam; 32. First connecting reinforcement; 33. Second connecting reinforcement; 34. Weld between connecting reinforcement and existing portal steel ring back plate; 35. Weld between connecting reinforcement and new portal steel ring back plate; 36. Weld between connecting reinforcement; 37. Reinforcing cage. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] like Figure 1 and Figure 2 As shown, a structure for reducing the size of the tunnel portal in shield tunneling includes a station retaining structure 11, an existing portal steel ring back plate 13, a new portal steel ring back plate 21, a new portal steel ring ring plate 22, and a reinforced concrete ring beam 31 located inside the space enclosed by the station retaining structure 11, the existing portal steel ring back plate 13, the new portal steel ring back plate 21, and the new portal steel ring ring plate 22.

[0034] Depend on Figure 2 It is known that a new portal steel ring plate 22 is provided between the end of the newly added portal steel ring back plate 21 away from the station enclosure structure 11 and the end of the existing portal steel ring back plate 13 away from the station enclosure structure 11. Furthermore, concrete is poured within the space enclosed by the existing portal steel ring back plate 13, the newly added portal steel ring back plate 21, the newly added portal steel ring plate 22, and the station enclosure structure 11 to form a reinforced concrete ring beam 31.

[0035] Also in Figure 2 As can be seen, an "L"-shaped first connecting steel bar 32 and a first pad plate 24 are provided on one side of the existing portal steel ring back plate 13; an "L"-shaped second connecting steel bar 33 and a second pad plate 25 are provided on one side of the newly added portal steel ring back plate 21. The first connecting steel bar 32 is evenly distributed at equal angles along the existing portal steel ring back plate 13, with one side parallel to the surface of the existing portal steel ring back plate 13 and the other side pointing towards the center line 26 of the newly added portal steel ring back plate 21. The second connecting steel bar 33 is evenly distributed at equal angles along the newly added portal steel ring back plate 21, with one side parallel to the surface of the newly added portal steel ring back plate 21 and the other side pointing towards the center line 26 of the newly added portal steel ring back plate 21.

[0036] Furthermore, the first connecting steel bar 32 and the second connecting steel bar 33 have the same starting angle and angle interval, based on the center line 26 of the newly added portal steel ring back plate 21. One side of the first connecting steel bar 32 pointing towards the center line 26 of the newly added portal steel ring back plate 21 and one side of the second connecting steel bar 33 pointing towards the center line 26 of the newly added portal steel ring back plate 21 are lapped and fixed by a weld 36. In addition, the first connecting steel bar 32, the second connecting steel bar 33 and the embedded nuts 23 of the newly added portal steel ring plate 22 must all avoid the steel cage 37 of the reinforced concrete ring beam 31.

[0037] An embodiment of the present invention also provides a construction method for reducing the size of the tunnel portal structure using the shield tunneling method, the specific steps of which are as follows:

[0038] Step 1: Positioning and layout operation is carried out for the center of the modified shield tunnel portal. Temporary steel bars are installed on the station retaining structure 11 to mark the center line 26 of the modified shield tunnel portal.

[0039] Step 2: On the existing portal steel ring back plate 13 and on one side of the reinforced concrete ring beam 31, with the modified shield tunnel portal centerline 26 as the reference benchmark, mark the positions of the first lining plate 24 and the "L"-shaped first connecting steel bar 32 at equal angles.

[0040] Step 3: The first connecting steel bar 32 of the "L" shape is laid out according to the requirement that one side of it is parallel to the surface of the existing portal steel ring back plate 13 and the other side points to the center line 26 of the new portal steel ring back plate 21, and then spot welded to fix it.

[0041] Step 4: The first lining plate 24 is fixed by spot welding after the layout is completed, according to its position requirements, that is, the newly added portal steel ring plate 22 is closely attached to the first lining plate 24 and vertically aligned with the existing portal steel ring plate 12.

[0042] Step 5: Weld and install one side of the "L"-shaped first connecting steel bar 32 parallel to the surface of the existing portal steel ring back plate 13 on the existing portal steel ring back plate 13, and at the same time weld and install the first liner plate 24 on the existing portal steel ring back plate 13.

[0043] Step 6: Fabricate and place the reinforcing cage 37 of the reinforced concrete ring beam 31, and the reinforcing cage 37 must avoid the first connecting reinforcing bar 32.

[0044] Step 7: Spot weld an "L"-shaped second connecting steel bar 33 to the newly added portal steel ring back plate 21 located on the reinforced concrete ring beam 31, so that one side of the second connecting steel bar 33 is parallel to the surface of the existing portal steel ring back plate 13, and the other side can be paired and lapped with one side of the first connecting steel bar 32 pointing to the center line 26 of the newly added portal steel ring back plate 21.

[0045] Step 8: Spot weld the second liner plate 25 to one side of the newly added portal steel ring back plate 21 located on the reinforced concrete ring beam 31. The position is determined according to the requirement that the newly added portal steel ring plate 22 is closely attached to the second liner plate 25 and vertically aligned with the existing portal steel ring plate 12.

[0046] Step 9: Weld and install one side of the "L"-shaped second connecting steel bar 33 parallel to the surface of the new tunnel portal steel ring back plate 21 on the new tunnel portal steel ring back plate 21. At the same time, weld and install the first liner plate 24 on the new tunnel portal steel ring back plate 13.

[0047] Step 10: Temporarily fix and install the new portal steel ring back plate 21 in sections, and weld the first connecting steel bar 32 and the second connecting steel bar 33 in parallel lap joints one by one. At the same time, weld the second lining plate 25 and weld the new portal steel ring plate 22.

[0048] Step 11: Seal the gap between the newly added portal steel ring back plate 21 and the station enclosure structure 11 with quick-hardening cement, and open a concrete pouring hole and a vent hole at the top of the newly added portal steel ring back plate 21.

[0049] Step 12: Pour self-compacting concrete through the concrete pouring hole on the newly added portal steel ring back plate 21 to form a reinforced concrete ring beam 31, thereby completing the modification of the portal structure to reduce the size of the shield tunnel.

[0050] This embodiment provides a construction method for reducing the size of the tunnel portal structure in shield tunneling. By reducing the size of the tunnel portal, it is helpful to control the construction posture during the launch or reception of the shield machine, and reduce the risk of groundwater leakage and sudden surge during the launch or reception of the shield machine. At the same time, it avoids the removal of the existing portal steel ring of the station, thus avoiding damage to the existing structure. Furthermore, it achieves electrical connection with the existing structure, reducing the electrochemical corrosion effect of stray current on the existing station structure.

[0051] It should be noted that the above description is merely a specific embodiment of the present invention in conjunction with the accompanying drawings. This specific embodiment is only illustrative and not restrictive. Any modifications, substitutions, improvements, etc., without departing from the scope of protection of the claims of the present invention shall fall within the protection scope of the present invention.

Claims

1. A construction method for reducing the size of a tunnel portal, characterized in that, Includes the following steps: Positioning and layout: Positioning and layout of the center of the tunnel portal after the modification, and temporarily install steel bars on the station enclosure structure (11) to mark the center line (26) of the tunnel portal after the modification. Marking positions: On one side of the existing portal steel ring back plate (13) located on the reinforced concrete ring beam (31), the positions of the first lining plate (24) and the first connecting steel bar (32) are marked at equal angles with reference to the center line (26) of the portal of the modified shield tunnel. Spot welding fixation: After the layout is completed as required, the first connecting steel bar (32) and the first pad plate (24) are spot welded and fixed respectively; Welding installation: Weld the first connecting steel bar (32) parallel to one side of the surface of the existing portal steel ring back plate (13) and the first pad plate (24) onto the existing portal steel ring back plate (13). Fabrication of the steel cage: Fabricate and place the steel cage (37) of the reinforced concrete ring beam (31), and ensure that the steel cage (37) avoids the first connecting steel bar (32); Welding of reinforcing bars and lining: Spot weld the second connecting reinforcing bar (33) and the second lining plate (25) onto the newly added portal steel ring back plate (21), and perform the corresponding welding installation; Segmented fixing and welding: The newly added portal steel ring back plate (21) is temporarily fixed and installed in segments. The first connecting steel bar (32) and the second connecting steel bar (33) are welded in parallel lap joints one by one. At the same time, the second lining plate (25) is welded and the newly added portal steel ring plate (22) is welded. Sealing gaps: The gap between the newly added portal steel ring back plate (21) and the station enclosure structure (11) is sealed with quick-hardening cement, and a concrete pouring hole and an exhaust hole are opened at the top of the newly added portal steel ring back plate (21). Concrete pouring: Self-compacting concrete is poured through the concrete pouring hole on the newly added portal steel ring back plate (21) to form a reinforced concrete ring beam (31), thereby completing the transformation of the portal structure of the shield tunnel with reduced size; The structure for reducing the size of the tunnel portal includes: a station retaining structure (11), an existing portal steel ring back plate (13), a new portal steel ring back plate (21), a new portal steel ring ring plate (22), and a reinforced concrete ring beam (31) located within the space enclosed by the station retaining structure (11), the existing portal steel ring back plate (13), the new portal steel ring back plate (21), and the new portal steel ring ring plate (22). An "L"-shaped first connecting steel bar (32) and a first pad plate (24) are provided on one side of the existing portal steel ring back plate (13); an "L"-shaped second connecting steel bar (33) and a second pad plate (25) are provided on one side of the newly added portal steel ring back plate (21). The first connecting steel bar (32) is evenly distributed along the existing portal steel ring back plate (13) at equal angles with the center line (26) of the newly added portal steel ring back plate (21) as the reference. One side of the steel bar is parallel to the surface of the existing portal steel ring back plate (13), and the other side points to the center line (26) of the newly added portal steel ring back plate (21). The second connecting steel bar (33) is evenly distributed along the newly added portal steel ring back plate (21) at equal angles with the center line (26) of the newly added portal steel ring back plate (21) as the reference. One side of the steel bar is parallel to the surface of the newly added portal steel ring back plate (21), and the other side points to the center line (26) of the newly added portal steel ring back plate (21).

2. The construction method for reducing the size of tunnel portals according to claim 1, characterized in that: A new portal steel ring plate (22) is provided between the end of the new portal steel ring back plate (21) away from the station enclosure structure (11) and the end of the existing portal steel ring back plate (13) away from the station enclosure structure (11).

3. The construction method for reducing the size of the tunnel portal according to claim 2, characterized in that: Concrete is poured into the enclosed space of the existing portal steel ring back plate (13), the newly added portal steel ring back plate (21), the newly added portal steel ring ring plate (22), and the station enclosure structure (11) to form a reinforced concrete ring beam (31).

4. The construction method for reducing the size of tunnel portals according to claim 1, characterized in that: The first connecting steel bar (32) and the second connecting steel bar (33) have the same starting angle and angle interval based on the center line (26) of the newly added portal steel ring back plate (21); one side of the first connecting steel bar (32) pointing to the center line (26) and one side of the second connecting steel bar (33) pointing to the center line (26) are fixed by weld (36).

5. The structure for reducing the size of a tunnel portal according to claim 4, characterized in that: The pre-embedded nuts (23) of the first connecting steel bar (32), the second connecting steel bar (33), and the newly added portal steel ring plate (22) all avoid the steel cage (37) of the reinforced concrete ring beam (31).

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