Tunnel portal post-pouring ring beam construction method for shield tunneling

Abstract

The invention discloses a tunnel portal post-pouring ring beam construction method for shield tunneling, which comprises the following steps of: constructing a shield segment, and when the last segment is constructed, enabling the last segment to protrude out of a tunnel opening to form an annular extension section; wall back grouting is carried out on at least five final segments; a reinforcement cage of the post-cast ring beam is bound on the periphery of the annular extension section, so that the reinforcement cage is connected with a pre-embedded steel ring on the periphery of the hole; and the post-pouring ring beam is poured on the periphery of the reinforcement cage in a formwork erecting mode, the end face of the post-pouring ring beam is flush with the end face of the annular extension section, the embedded steel ring is poured in the post-pouring ring beam, and through the arrangement of the construction method, the construction efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a method for constructing a post-cast ring beam for a tunnel portal of a shield tunnel. Background Technology

[0002] Before the tunnel boring machine (TBM) enters and exits the tunnel, steel rings are pre-embedded at the connection between the open-cut end wall and the tunnel section. After the completion of the entire shield tunnel section, the portal structure is constructed. There is a significant difference in stiffness between the open-cut structure and the shield tunnel structure. Soil reinforcement is carried out around the portal to minimize uneven settlement. Expansion joint reinforcement rings are installed during TBM entry and exit. The portal structure is designed as a reinforced concrete structure, i.e., a post-cast ring beam, with C40 concrete and P10 impermeability. By pre-embedding steel rings at the portal, which are connected to the post-cast ring beam, the open-cut structure and the shield tunnel structure are integrated, increasing the overall integrity of the portal structure.

[0003] When constructing the post-cast ring beam at the portal of the receiving end, the end of the last ring segment is flush with the portal, making it impossible to form a reliable connection with the post-cast ring beam. It also occupies the pouring space of the post-cast ring beam. Therefore, the current practice is to first remove the entire last ring segment before constructing the post-cast ring beam. This practice is time-consuming and inefficient. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a construction method for the post-cast ring beam of the tunnel portal for shield tunneling. By making the last ring segment protrude from the tunnel portal during the construction of the last ring segment, a connection foundation is provided for the post-cast ring beam, which facilitates the construction of the post-cast ring beam and improves the connection stability.

[0005] To achieve the above objectives, the technical solution adopted by this invention is a method for constructing a post-cast ring beam for a tunnel portal during shield tunneling, comprising the following steps: Step 1: Shield tunnel segment construction, and when constructing the last ring segment, make the last ring segment protrude from the tunnel opening to form a ring extension section; Step 2: Grout the last 5 rings of segments behind the wall; Step 3: Tie the reinforcing cage of the cast-in-place ring beam around the outer periphery of the annular extension section, so that the reinforcing cage is connected to the pre-embedded steel ring around the outer periphery of the opening. Step 4: Cast the post-cast ring beam by supporting formwork around the outer periphery of the reinforcing cage, making the end face of the post-cast ring beam flush with the end face of the annular extension section, and cast the pre-embedded steel ring inside.

[0006] A further improvement of the present invention for the construction method of the post-cast ring beam of the tunnel portal of a shield tunnel is that, after performing step 2 above and before performing step 3 above, the grouting residue that has spilled onto the outer periphery of the annular extension section is cleaned up.

[0007] A further improvement of the present invention for the construction method of the post-cast ring beam of the tunnel portal of the shield tunnel is that, after performing step 2 above and before performing step 3 above, a water-swellable rubber strip is set on the outer periphery of the annular extension section, and a water-swellable rubber strip is set on the end wall covered by the designed position of the post-cast ring beam.

[0008] A further improvement of the present invention for the construction method of the post-cast ring beam of the tunnel portal of a shield tunnel is that, when performing step 3 above, the steel cage and the pre-embedded steel ring are connected by anchor bars, so that one end of the anchor bar is welded and fixed to the pre-embedded steel ring, and the other end is tied to the steel cage.

[0009] A further improvement of the present invention for the construction method of the post-cast ring beam of the tunnel portal of a shield tunnel is that, when performing step 3 above, the end wall covered by the designed position of the post-cast ring beam is reinforced with steel bars, and when binding the steel cage, the implanted steel bars are connected to the steel cage.

[0010] A further improvement of the present invention for the construction method of the post-cast ring beam of the tunnel portal of a shield tunnel is that, after performing step 4 above, a waterproofing agent is applied to the gap between the post-cast ring beam and the end wall.

[0011] Compared with the prior art, the advantages of the present invention are: By making the last ring segment protrude beyond the opening during construction, a connection foundation is provided for the subsequent ring beam, facilitating the construction of the subsequent ring beam and avoiding the need to remove the last ring segment, thus improving construction efficiency. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a flowchart of the construction method for the post-cast ring beam of the tunnel portal used in the present invention for shield tunneling.

[0014] Figure 2 This is a schematic diagram of the post-cast ring beam of the present invention.

[0015] In the diagram: 1. The last ring segment; 2. The post-cast ring beam. Detailed Implementation

[0016] 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 also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0017] The following detailed description of the construction method for the post-cast ring beam of the tunnel portal for shield tunneling is provided in conjunction with the accompanying drawings and specific embodiments.

[0018] Please see Figures 1-2 As shown, the construction method for the post-cast ring beam of the tunnel portal used for shield tunneling includes the following steps: Step 1: Shield tunnel segment construction, and when constructing the last ring segment 1, make the last ring segment 1 protrude from the tunnel opening to form a ring extension section; Step 2: Grout the last 5 rings of segments behind the wall; Step 3: Tie the reinforcing cage of the post-cast ring beam 2 around the outer periphery of the annular extension section, so that the reinforcing cage is connected to the pre-embedded steel ring around the outer periphery of the opening. Step 4: Cast the post-cast ring beam 2 around the outer perimeter of the reinforcing cage, making the end face of the post-cast ring beam 2 flush with the end face of the annular extension section, and then cast the pre-embedded steel ring inside.

[0019] By making the last ring segment 1 protrude from the tunnel opening during the construction of the shield tunnel segments to form the annular extension section, a connection foundation is provided for the post-cast ring beam 2, so that the post-cast ring beam 2 can be connected with the last ring segment 1 to form an integral whole.

[0020] By grouting the last 5 ring segments behind the tunnel wall, the waterproof performance between the segments and the tunnel wall was ensured, and water seepage in the tunnel was prevented from affecting the post-cast ring beam 2.

[0021] Preferably, after performing step 2 above and before performing step 3 above, the grouting residue that has spilled onto the outer periphery of the annular extension section is cleaned up.

[0022] When grouting is performed on the last at least 5 ring segments, the grout will inevitably overflow onto the ring extension. By cleaning up the grout residue, space will be provided for the subsequent reinforcement cage to be tied.

[0023] Specifically, after performing step 2 above and before performing step 3 above, the outer periphery of the annular extension is roughened.

[0024] By roughening the outer periphery of the annular extension, the tightness of the connection between the subsequent cast ring beam 2 and the annular extension is ensured.

[0025] Preferably, after performing step 2 above and before performing step 3 above, a water-swellable rubber strip is provided on the outer periphery of the annular extension section, and a water-swellable rubber strip is provided on the end wall covered by the designed position of the post-cast ring beam 2.

[0026] By setting up the rainwater-expanding rubber strip to block the water between the post-cast ring beam 2 and the end wall, and between the post-cast ring beam 2 and the annular extension section, the waterproof performance is improved.

[0027] Specifically, after performing step 2 above and before performing step 3 above, scaffolding is erected on the outside of the opening to tie the steel cage and also to serve as a formwork support. The scaffolding is erected using Φ48 disc-lock scaffolding steel pipes, with a longitudinal spacing of 1m, a transverse spacing of 0.9m, and a step distance of 1m.

[0028] Preferably, when performing step 3 above, the reinforcing cage and the embedded steel ring are connected by anchor bars, so that one end of the anchor bar is welded and fixed to the embedded steel ring, and the other end is tied to the reinforcing cage.

[0029] By setting this anchoring bar, it is ensured that the post-cast ring beam 2 is connected with the pre-embedded steel ring to form an integral whole after the post-cast ring beam 2 is poured, which further enhances the stability of the opening.

[0030] Preferably, when performing step 3 above, the end wall covered by the designed position of the post-cast ring beam 2 is reinforced with steel bars, and the implanted steel bars are connected to the steel cage when the steel cage is tied.

[0031] By installing reinforcing bars on the end wall, it is ensured that the post-cast ring beam 2 is connected to the end wall to form an integral whole after the post-cast ring beam 2 is completed, thus ensuring structural stability.

[0032] Specifically, the following requirements must be met when installing rebar in the end wall: the installation depth should not be less than 420mm, Class A rebar adhesive should be used, the corresponding drilling diameter should be 20mm, the design value of the tensile bearing capacity of a single rebar should be 65KN, and the rebar installation process and its technical requirements should meet the relevant specifications.

[0033] Specifically, when performing step 3 above, the rebar is installed on the annular extension section, and when the rebar cage is tied, the installed rebar is connected to the rebar cage.

[0034] By installing rebar in the annular extension section, it is ensured that the post-cast ring beam 2 is connected to the last ring segment 1 to form an integral whole after the post-cast ring beam 2 is completed, thus ensuring structural stability.

[0035] Preferably, after performing step 4 above, a waterproofing agent is applied to the gap between the post-cast ring beam 2 and the end wall.

[0036] By applying this waterproofing agent as the first layer of waterproofing barrier, external rainwater is prevented from seeping in through the gap between the post-cast ring beam 2 and the end wall, thus improving the waterproofing performance.

[0037] Specifically, the following conditions must be met when binding the reinforcing cage: lap welding should be used for rebar splices; the reinforcing cage should be spot welded in a staggered pattern and equipped with a sufficient number and strength of limiting bars to ensure accurate rebar positioning; the steel type, number of bars, diameter, grade, etc. of the reinforcing bars should meet the design requirements; only one splice is allowed on the same reinforcing bar within a range of 30d and <500mm; the distance between the lapped or welded splice and the bending point of the reinforcing bar should not be less than 10 times the diameter of the main bar, and it should not be located at the point of maximum bending moment.

[0038] Specifically, the protective layer thickness of the post-cast ring beam 2 is controlled between 45mm and 55mm. After the steel cage is tied and before the formwork is erected, spacers are connected at intervals around the outer perimeter of the steel cage to control the protective layer thickness.

[0039] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for constructing a post-cast ring beam for a tunnel portal of a shield tunnel, characterized in that, Including the following steps: Step 1: Shield tunnel segment construction, and when constructing the last ring segment, make the last ring segment protrude from the tunnel opening to form a ring extension section; Step 2: Grout the last 5 rings of segments behind the wall; Step 3: Tie the reinforcing cage of the cast-in-place ring beam around the outer periphery of the annular extension section, so that the reinforcing cage is connected to the pre-embedded steel ring around the outer periphery of the opening. Step 4: Cast the post-cast ring beam by supporting formwork around the outer periphery of the reinforcing cage, making the end face of the post-cast ring beam flush with the end face of the annular extension section, and cast the pre-embedded steel ring inside.

2. The construction method for the post-cast ring beam of the tunnel portal for shield tunneling as described in claim 1, characterized in that, After performing step 2 above and before performing step 3 above, clean up the grouting residue that has spilled onto the outer periphery of the annular extension section.

3. The construction method for the post-cast ring beam of the tunnel portal for shield tunneling as described in claim 1, characterized in that, After performing step 2 above and before performing step 3 above, a water-swellable rubber strip is installed on the outer periphery of the annular extension section, and a water-swellable rubber strip is installed on the end wall covered by the design position of the post-cast ring beam.

4. The construction method for the post-cast ring beam of the tunnel portal for shield tunneling as described in claim 1, characterized in that, When performing step 3 above, the steel cage and the pre-embedded steel ring are connected by anchor bars, so that one end of the anchor bar is welded and fixed to the pre-embedded steel ring, and the other end is tied to the steel cage.

5. The construction method for the post-cast ring beam of the tunnel portal for shield tunneling as described in claim 1, characterized in that, When performing step 3 above, reinforcement bars are installed on the end wall covered by the designed location of the post-cast ring beam, and the implanted reinforcement bars are connected to the reinforcement cage when the reinforcement cage is tied.

6. The construction method for the post-cast ring beam of the tunnel portal for shield tunneling as described in claim 1, characterized in that, After completing step 4 above, apply a waterproofing agent to the gap between the post-cast ring beam and the end wall.

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