Construction method and structure for reducing size of tunnel portal

Abstract

The invention relates to the technical field of rail transit shield tunnel portal reconstruction, in particular to a construction method for reducing the size of a tunnel portal and a structure of the tunnel portal. Comprising a station enclosure structure, an existing tunnel portal steel ring back plate, a newly-added tunnel portal steel ring back plate, a newly-added tunnel portal steel ring plate and a reinforced concrete ring beam structure located in a space defined by the station enclosure structure, the existing tunnel portal steel ring back plate, the newly-added tunnel portal steel ring back plate and the newly-added tunnel portal steel ring plate. According to the structure and method for reducing the size of the shield tunnel portal, control over the construction posture during starting or receiving of a shield tunneling machine is facilitated, and the underground water leakage and inrush risks during starting or receiving of the shield tunneling machine are reduced; the existing portal steel ring of the station is not chiseled away, damage to the existing structure is avoided, electrical communication with the existing structure is achieved, and the electrochemical corrosion effect of stray current on the existing station structure is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of rail transit shield tunnel portal reconstruction, and in particular to a construction method for reducing the size of a tunnel portal and a structure thereof. Background Art

[0002] Subway stations are important nodes in a city's public transportation network. For future subway stations that are reserved simultaneously at early-stage subway transfer stations, transportation hubs, and other locations, the sizes of reserved shield tunnel portals are often adjusted due to changes in functional requirements.

[0003] For example, the "shield tunnel portal expansion and reconstruction construction method" disclosed in the Chinese invention patent with announcement number CN112228084A adopts the method of chiseling out part of the existing wall, planting steel bars to fix the expanded tunnel ring, and pouring concrete to achieve the tunnel portal expansion and reconstruction. This method adopts the method of chiseling out the original tunnel portal and planting steel bars to fix the new tunnel portal, which destroys the electrical connectivity between the anchor steel bars of the subway station tunnel portal and the existing structural steel mesh. The stray current generated thereby produces electrochemical corrosion to the subway station structure, affecting the durability of the structure; for example, the Chinese utility model patent with announcement number CN217176629U discloses a method for expanding the tunnel portal diameter by embedding steel bars to fix the expanded tunnel ring, and then pouring concrete. The "structure for the expansion and reconstruction of the shield tunneling starting portal" developed by the patent uses a steel member attached to the end wall where the existing portal is located as a tunnel ring, and the new portal is formed by chiseling the part of the end wall between the shield tunneling starting portal and the reinforced steel member, and the part of the end wall located inside the reinforced steel member is chiseled. This method uses expansion bolts and ropes to fix the new portal. The stray current generated by the lack of electrical connection with the existing structural steel mesh of the station produces electrochemical corrosion to the structure. It is impossible to set a permanent closed ring beam on the structure of the portal expansion and reconstruction, which affects the structural safety and affects the boundary size of the station, limiting the conditions of use. The above patents are all applied to the expansion and reconstruction of the portal. For the situation where the future portal size is smaller than the reserved portal size, if the original reserved portal size is maintained without adjustment, the gap between the shield machine and the portal is large, the difficulty of controlling the starting and receiving posture of the shield machine increases, the construction quality is difficult to guarantee, and the risk of groundwater leakage and sudden surge increases. The method of partially chiseling out and then planting reinforcement and stirrups in a new hole ring in the Chinese invention patent with announcement number CN112228084A cannot solve the impact of stray current on the electrochemical corrosion of the structure, the risk of damage to the existing station structure caused by the chiseling scheme, and the impact of vibration and noise. The method in the Chinese utility model patent with announcement number CN217176629U fixes the steel member serving as the tunnel door to the end wall where the existing tunnel door is located, which is not suitable for the case where the size of the steel member is smaller than the original tunnel door size. There is an urgent need for a construction method that does not chisel out the existing tunnel door of the station and avoids the risk of damage to the existing structure caused by the chiseling scheme. Summary of the invention

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

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

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

[0007] Positioning and setting out: Positioning and setting out the center of the modified shield tunnel portal, and temporarily planting steel bars on the station enclosure structure to mark the center line of the modified shield tunnel portal;

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

[0009] Spot welding fixation: After setting out as required, the first connecting steel bar and the first lining plate are spot welded and fixed respectively;

[0010] Welding installation: welding and installing the first connecting steel bar and an edge parallel to the surface of the existing tunnel door steel ring back plate, as well as the first lining plate, on the existing tunnel door steel ring back plate;

[0011] Fabricate the steel cage: fabricate and place the steel cage of the reinforced concrete ring beam, and ensure that the steel cage avoids the first connecting steel bar;

[0012] Welding steel bars and linings: Spot weld and fix the second connecting steel bars and the second lining plate on the newly added portal steel ring back plate, and perform corresponding welding installation;

[0013] Segment fixing and welding: temporarily fix and install the newly added portal steel ring back plate in segments, pair and parallelly overlap and weld the first connecting steel bars and the second connecting steel bars one by one, weld the second liner plate and the newly added portal steel ring plate at the same time;

[0014] Sealing gaps: The gaps between the newly added tunnel gate steel ring back plate and the station enclosure structure are sealed with quick-hardening cement, and concrete pouring holes and exhaust holes are opened at the top of the newly added tunnel gate steel ring back plate;

[0015] Pouring concrete: 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 transformation of the shield tunnel portal structure with reduced size.

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

[0017] Furthermore, a new tunnel gate steel ring plate is provided between the end of the new tunnel gate steel ring back plate away from the station enclosure structure and the end of the existing tunnel gate steel ring back plate away from the station enclosure structure.

[0018] Furthermore, concrete is poured in 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 plate and the station enclosure structure to form a reinforced concrete ring beam.

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

[0020] Furthermore, the first connecting steel bars are evenly distributed at equal angles along the existing steel ring back plate of the tunnel portal with the center line of the newly added tunnel portal steel ring back plate as the reference, one edge of which is parallel to the surface of the existing tunnel portal steel ring back plate, and the other edge points to the center line of the newly added tunnel portal steel ring back plate; the second connecting steel bars are evenly distributed at equal angles along the new tunnel portal steel ring back plate with the center line of the newly added tunnel portal steel ring back plate as the reference, one edge of which is parallel to the surface of the new tunnel portal steel ring back plate, and the other edge points to the center line of the new tunnel portal steel ring back plate.

[0021] Furthermore, the first connecting steel bar and the second connecting steel bar have the same distribution starting angle and angle interval based on the center line of the newly added portal steel ring back plate; an edge of the first connecting steel bar pointing to the center line and an edge of the second connecting steel bar pointing to the center line are fixed by overlapping welds.

[0022] Furthermore, the embedded nuts of the first connecting steel bars, the second connecting steel bars 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 setting out steps, the center of the modified shield tunnel portal is located, and the center line of the circle is marked on the station enclosure structure to provide an accurate benchmark for subsequent construction. The steps of marking the position, spot welding fixation, welding installation, etc. enable the first connecting steel bar and the first liner plate, as well as the second connecting steel bar and the second liner plate to be accurately set and connected. The cast reinforced concrete ring beam enhances the integrity and stability of the newly added portal structure, which is conducive to bearing the starting and receiving loads of the shield machine.

[0025] Reducing the size of the tunnel portal reduces the difficulty of controlling the starting and receiving postures of the shield machine, reduces the risk of groundwater leakage and sudden surges at the portal location, and thus reduces the risk of construction quality and safety.

[0026] Not removing the existing tunnel gate of the station can avoid damage to the existing structure, ensure the integrity of the station structure, and avoid the vibration and noise caused by the removal.

[0027] The reasonable arrangement and connection of the first connecting steel bar, the second connecting steel bar, etc., and the reasonable avoidance of the steel cage ensure electrical connectivity with the existing structure. The above electrical connectivity reduces the electrochemical corrosion effect of stray current on the existing station structure and prolongs the durability of the station structure. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 A cross-sectional view of a specific implementation of the present invention;

[0030] In the figure: 11. Station enclosure structure; 12. Existing steel ring plate of tunnel gate; 13. Existing steel ring back plate of tunnel gate; 14. Existing side wall of station; 21. New steel ring back plate of tunnel gate; 22. New steel ring plate of tunnel gate; 23. Embedded nuts; 24. First lining plate (lining plate on existing steel ring back plate of tunnel gate); 25. Second lining plate (lining plate on new steel ring back plate of tunnel gate); 26. Center line; 31. Reinforced concrete ring beam; 32. First connecting steel bar; 33. Second connecting steel bar; 34. Weld between connecting steel bar and existing steel ring back plate of tunnel gate; 35. Weld between connecting steel bar and new steel ring back plate of tunnel gate; 36. Weld between connecting steel bar; 37. Steel cage. DETAILED DESCRIPTION

[0031] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0032] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0033] like Figure 1 and Figure 2 As shown, a structure for reducing the size of a shield tunnel portal comprises a station enclosure structure 11, an existing portal steel ring back plate 13, a newly added portal steel ring back plate 21, a newly added portal steel ring plate 22, and a reinforced concrete ring beam 31 located within the space enclosed by the station enclosure structure 11, the existing portal steel ring back plate 13, the newly added portal steel ring back plate 21, and the newly added portal steel ring plate 22.

[0034] Depend on Figure 2 It can be seen that a newly added 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 in the space surrounded 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, thereby forming a reinforced concrete ring beam 31.

[0035] Also in Figure 2 It can be seen that an "L"-shaped first connecting steel bar 32 and a first lining plate 24 are arranged on one side of the existing tunnel portal steel ring back plate 13; and an "L"-shaped second connecting steel bar 33 and a second lining plate 25 are arranged on one side of the newly added tunnel portal steel ring back plate 21. Among them, the first connecting steel bar 32 is uniformly distributed at equal angles along the existing tunnel portal steel ring back plate 13 with the center line 26 of the newly added tunnel portal steel ring back plate 21 as the reference, one side of which is parallel to the surface of the existing tunnel portal steel ring back plate 13, and the other side points to the center line 26 of the newly added tunnel portal steel ring back plate 21; the second connecting steel bar 33 is uniformly distributed at equal angles along the newly added tunnel portal steel ring back plate 21 with the center line 26 of the newly added tunnel portal steel ring back plate 21 as the reference, one side of which is parallel to the surface of the newly added tunnel portal steel ring back plate 21, and the other side points to the center line 26 of the newly added tunnel portal steel ring back plate 21.

[0036] In addition, the first connecting steel bar 32 and the second connecting steel bar 33 are based on the center line 26 of the newly added portal steel ring back plate 21, and have the same distribution starting angle and angle interval; 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 and one side of the second connecting steel bar 33 pointing to the center line 26 of the newly added portal steel ring back plate 21 are matched and overlapped 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 avoid the steel cage 37 of the reinforced concrete ring beam 31.

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

[0038] Step 1: Positioning and setting out the center of the shield tunnel portal after the transformation, and temporarily planting steel bars on the station enclosure structure 11 to mark the center line 26 of the shield tunnel portal after the transformation.

[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 center line 26 of the modified shield tunnel portal as the reference, mark the setting positions of the first liner plate 24 and the "L"-shaped first connecting steel bar 32 at equal angles.

[0040] Step 3: The "L"-shaped first connecting steel bar 32 is laid out with one side parallel to the surface of the existing portal steel ring back plate 13 and the other side pointing to the center line 26 of the back ring plate 21 of the newly added portal steel ring, and then spot welded and fixed.

[0041] Step 4: The first liner plate 24 is positioned according to its position requirements, that is, the newly added tunnel gate steel ring plate 22 is closely attached to the first liner plate 24 and vertically aligned with the existing tunnel gate steel ring plate 12, and is spot welded and fixed after layout.

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

[0043] Step 6: Make and place the steel cage 37 of the reinforced concrete ring beam 31 , and the steel cage 37 needs to avoid the first connecting steel bars 32 .

[0044] Step seven: Fix the "L"-shaped second connecting steel bar 33 by spot welding on the reinforced concrete ring beam 31 of the newly added tunnel portal steel ring back plate 21, so that one edge of the second connecting steel bar 33 is parallel to the surface of the existing tunnel portal steel ring back plate 13, and the other edge can be matched one by one with an edge of the first connecting steel bar 32 pointing to the center line 26 of the newly added tunnel portal steel ring back plate 21, and parallel lap welded.

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

[0046] Step nine: Weld and install one side of the “L”-shaped second connecting steel bar 33 parallel to the surface of the newly added tunnel gate steel ring back plate 21 on the newly added tunnel gate steel ring back plate 21, and weld and install the first lining plate 24 on the newly added tunnel gate steel ring back plate 13 at the same time.

[0047] Step 10: temporarily fix and install the newly added portal steel ring back plate 21 in sections, parallelly overlap and weld the first connecting steel bars 32 and the second connecting steel bars 33 one by one, weld the second liner plate 25 and the newly added portal steel ring plate 22 at the same time.

[0048] Step 11: The gap between the newly added tunnel portal steel ring back plate 21 and the station enclosure structure 11 is sealed with rapid-hardening cement, and a concrete pouring hole and an exhaust hole are opened at the top of the newly added tunnel portal steel ring back plate 21.

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

[0050] The present embodiment provides a construction method for reducing the size of a shield tunnel portal structure. By reducing the size of a shield tunnel portal, it is helpful to control the construction posture of a shield machine when it is started or received, thereby reducing the risk of groundwater leakage and sudden surge when the shield machine is started or received. At the same time, the existing portal steel ring of the station is not removed to avoid damage to the existing structure. In addition, electrical connectivity with the existing structure is achieved to reduce the electrochemical corrosion effect of stray current on the existing station structure.

[0051] It should be noted that the above content is only a description of a specific embodiment of the present invention in conjunction with the accompanying drawings, and this specific embodiment is only illustrative and not restrictive. Without departing from the scope of protection of the claims of the present invention, any form of modification, replacement, improvement and other operations are within the scope of protection of the present invention.

Claims

1. A construction method for reducing the size of a tunnel portal, characterized in that: The following steps are involved: Positioning and setting out: Positioning and setting out the center of the modified shield tunnel portal, and temporarily planting steel bars on the station enclosure structure (11) to mark the center line of the modified shield tunnel portal (26); Marking position: On one side of the existing portal steel ring back plate (13) located on the reinforced concrete ring beam (31), the center line (26) of the modified shield tunnel portal is used as a reference, and the setting positions of the first lining plate (24) and the first connecting steel bar (32) are marked at equal angles; Spot welding fixation: after setting out as required, the first connecting steel bar (32) and the first lining plate (24) are spot welded and fixed respectively; Welding installation: welding and installing a first connecting steel bar (32) and an edge parallel to the surface of the existing tunnel door steel ring back plate (13), as well as a first lining plate (24) on the existing tunnel door steel ring back plate (13); Making a steel cage: making and placing a steel cage (37) of the reinforced concrete ring beam (31), and ensuring that the steel cage (37) avoids the first connecting steel bar (32); Welding the steel bars and the liner: spot welding and fixing the second connecting steel bars (33) and the second liner plate (25) on the newly added portal steel ring back plate (21), and performing corresponding welding and installation; Segmented fixing and welding: temporarily fixing and installing the newly added portal steel ring back plate (21) in segments, pairing and parallel-lap welding the first connecting steel bars (32) and the second connecting steel bars (33) one by one, welding the second lining plate (25) and the newly added portal steel ring plate (22) at the same time; Sealing the gap: The gap between the newly added tunnel door steel ring back plate (21) and the station enclosure structure (11) is sealed with rapid hardening cement, and a concrete pouring hole and an exhaust hole are opened at the top of the newly added tunnel door steel ring back plate (21); Pouring concrete: pouring self-compacting concrete through the concrete pouring holes on the newly added portal steel ring back plate (21) to form a reinforced concrete ring beam (31), thereby completing the transformation of the shield tunnel portal structure with reduced size.

2. A structure for reducing the size of a tunnel portal, constructed using the method of claim 1, comprising: A station enclosure structure (11), an existing tunnel gate steel ring back plate (13), a newly added tunnel gate steel ring back plate (21), a newly added tunnel gate steel ring plate (22), and a reinforced concrete ring beam (31) located in a space enclosed by the station enclosure structure (11), the existing tunnel gate steel ring back plate (13), the newly added tunnel gate steel ring back plate (21), and the newly added tunnel gate steel ring plate (22).

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

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

5. The structure for reducing the size of a tunnel portal according to claim 4 is characterized in that: An "L"-shaped first connecting steel bar (32) and a first lining plate (24) are arranged on one side of the existing tunnel portal steel ring back plate (13); and an "L"-shaped second connecting steel bar (33) and a second lining plate (25) are arranged on one side of the newly added tunnel portal steel ring back plate (21).

6. The structure for reducing the size of a tunnel portal according to claim 5, characterized in that: The first connecting steel bar (32) is evenly distributed along the existing tunnel gate steel ring back plate (13) at equal angles with the center line (26) of the newly added tunnel gate steel ring back plate (21) as a reference, one side of which is parallel to the surface of the existing tunnel gate steel ring back plate (13), and the other side points to the center line (26) of the newly added tunnel gate steel ring back plate (21); the second connecting steel bar (33) is evenly distributed along the newly added tunnel gate steel ring back plate (21) at equal angles with the center line (26) of the newly added tunnel gate steel ring back plate (21) as a reference, one side of which is parallel to the surface of the newly added tunnel gate steel ring back plate (21), and the other side points to the center line (26) of the newly added tunnel gate steel ring back plate (21).

7. The structure for reducing the size of a tunnel portal according to claim 6, characterized in that: The first connecting steel bar (32) and the second connecting steel bar (33) have the same distribution starting angle and angle interval based on the center line (26) of the newly added portal steel ring back plate (21); an edge of the first connecting steel bar (32) pointing to the center line (26) and an edge of the second connecting steel bar (33) pointing to the center line (26) are overlapped and fixed by a weld (36).

8. The structure for reducing the size of a tunnel portal according to claim 7, characterized in that: 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) all avoid the steel cage (37) of the reinforced concrete ring beam (31).

Images