Anti-floating structure of shallow-buried tunnel

Abstract

This invention relates to the field of tunnel engineering technology. It discloses an anti-buoyancy structure for shallow-buried tunnels, comprising a bidirectional open-cut structure with a bend on one side of the open-cut end wall connected to bidirectional shield tunnel segments via a portal ring beam. Vertical anti-uplift piles are embedded below steel segments in the inner wall of the shield tunnel segments. The tops of the anti-uplift piles pass through the steel segments and connect to an anti-buoyancy longitudinal beam laid continuously at the lowest point within the shield tunnel segments. One end of the anti-buoyancy longitudinal beam extends to and connects with the minimum inner contour of the portal ring beam. This invention achieves anti-buoyancy by connecting the anti-buoyancy longitudinal beam inside the tunnel to the lower anti-uplift piles, and by connecting the anti-buoyancy longitudinal beam to the portal ring beam and the bidirectional open-cut structure. This structure eliminates the need for surface excavation to construct anti-buoyancy pressure plates, does not affect surface traffic or the surrounding environment, and saves on engineering costs caused by surface excavation, pipeline relocation, and traffic diversion. Furthermore, the anti-buoyancy structure does not require advance construction, allowing the shield tunneling schedule to be unrestricted by the construction period of the anti-buoyancy structure.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to an anti-buoyancy structure for shallow-buried tunnels. Background Technology

[0002] In sections of tunnels near open-cut structures, the soil thickness above the tunnel is often insufficient, causing the tunnel structure's anti-buoyancy to fail to meet design specifications. One existing technology typically involves installing tension piles on both sides of the tunnel and an anti-buoyancy plate above the tunnel, with the pile tops connected to the anti-buoyancy plate, thus forming an anti-buoyancy structure of tension piles + anti-buoyancy plate. Another existing anti-buoyancy technology involves installing anti-buoyancy anchors inside the tunnel, extending downwards and outwards.

[0003] As attached Figure 1 As shown, the first existing technology requires the construction of anti-uplift piles and anti-buoyancy plates to be completed before tunnel construction. The construction of anti-buoyancy plates requires large-scale soil excavation. If there are existing pipelines above the tunnel, the pipelines need to be relocated first. This increases the construction period, cost, and difficulty of project implementation. At the same time, soil excavation also has a certain impact on the surrounding environment and affects the normal operation of road traffic.

[0004] As attached Figure 2 As shown, the shortcomings of the second type of existing anti-buoyancy technology are that the anti-buoyancy anchor has a small diameter and a shallow installation depth, resulting in low structural reliability. Furthermore, it requires the installation of many anti-buoyancy anchors to meet the anti-buoyancy requirements, which results in too many holes in the tunnel structure, which is detrimental to the stress on the tunnel segment structure. In addition, since tunnels are century-long projects, the durability of the anti-buoyancy anchors is relatively short, which cannot meet the anti-buoyancy requirements of the entire life cycle of subway tunnels.

[0005] In summary, the present invention aims to solve the technical problem of achieving high anti-buoyancy requirements and not affecting the ground traffic environment by carrying out small-scale construction on existing shallow-buoyancy tunnels under construction without pre-constructing anti-buoyancy structures or affecting the overall structure of the shallow-buoyancy tunnel. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a shallow-buried tunnel anti-buoyancy structure that can shorten the construction period, reduce the impact of construction on the surrounding environment, and lower the project cost, thereby solving the technical problems mentioned in the background art. To achieve the above objective, the present invention provides the following technical solution: a shallow-buried tunnel anti-buoyancy structure, comprising a bidirectional open-cut structure, wherein the end wall of the open-cut structure bent on one side of the bidirectional open-cut structure is connected to the bidirectional shield tunnel segments through a portal ring beam, and anti-uplift piles are vertically embedded below the steel pipe segments embedded in the inner wall of the shield tunnel segments. The top of the anti-uplift piles passes through the steel pipe segments and is connected to an anti-buoyancy longitudinal beam laid continuously at the lowest point inside the shield tunnel segments, and one end of the anti-buoyancy longitudinal beam is laid to the end of the minimum inner contour of the portal ring beam.

[0007] Preferably, the inner wall of the portal ring beam is annular stepped, the inner step of the portal ring beam is connected to the end of the shield tunnel segment, and the shield tunnel segment is flush with the minimum inner contour of the portal ring beam in the horizontal direction, so that the portal ring beam fits around the outer periphery of the shield tunnel segment.

[0008] Preferably, the bidirectional open-cut structure includes an open-cut structure base slab, the internal structure of which is a two-stage stepped structure, and the external structure of the open-cut structure base slab corresponding to the two-stage stepped structure is provided with a slope that is set in the opposite direction to the shield tunnel segments to strengthen the connection strength with the shield tunnel segments; open-cut structure side walls are provided on both sides of the open-cut structure base slab, and an open-cut structure central partition wall of the same height as the open-cut structure side walls is provided in the middle of the open-cut structure base slab; multiple support structures are provided opposite to the open-cut structure side walls and the open-cut structure central partition wall.

[0009] Preferably, an opening is provided above the bidirectional open-cut structure, the length of which corresponds to the length of the middle step of the bottom plate of the open-cut structure, and vertical support plates are provided on both sides of the opening, with the highest point of the vertical support plates being above the ground.

[0010] Preferably, the net distance between the side wall of the open-cut structure and the central partition wall of the open-cut structure is greater than 1 times the outer diameter of the shield segment, and not more than 2 times; the distance by which the top of the anti-uplift pile extends into the shield segment is greater than 0.5 times the length of the anti-uplift pile diameter, and the diameter of the anti-uplift pile is set not more than 2.0m.

[0011] Preferably, the anti-uplift pile is a cast-in-place pile, with the pile body located directly below the steel segment. The pile length and the distance between the anti-uplift pile and the end wall of the open-cut structure are determined by the results of the current anti-buoyancy calculation. At the same time, before construction, a distance of more than 0.5m needs to be reserved between the top of the anti-uplift pile and the bottom of the shield segment.

[0012] Preferably, a track bed is provided above the anti-buoyancy longitudinal beam, the track bed is nested around the anti-buoyancy longitudinal beam, and is connected to the inner wall of the shield tunnel segment by fasteners.

[0013] Preferably, the radial reinforcing bars of the portal ring beam extend into the anti-buoyancy longitudinal beam, and the portal ring beam and the anti-buoyancy longitudinal beam are reliably connected by a reinforcing bar connector. The outer perimeter of the portal ring beam is connected to the end wall of the open-cut structure by a reinforcing bar connector and radial reinforcing bars.

[0014] Preferably, the anti-buoyancy longitudinal beam is formed by pouring reinforced concrete on site after the shield tunnel segments are constructed.

[0015] Preferably, the steel pipe segment has an arc-shaped mesh structure, and the steel pipe segment is embedded directly below the shield tunnel segment. The height of both ends of the steel pipe segment does not exceed the connection between the track bed and the shield tunnel segment.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] This patent differs from existing technologies that implement anti-buoyancy structures from outside the tunnel. Instead, it achieves the anti-buoyancy effect by connecting the anti-buoyancy longitudinal beam inside the tunnel to the anti-uplift piles below, and by connecting the anti-buoyancy longitudinal beam to the tunnel portal ring beam + bidirectional open-cut structure. This structure does not require ground excavation to construct the anti-buoyancy pressure plate, does not affect ground traffic and the surrounding environment, and saves engineering costs caused by ground excavation, pipeline relocation and traffic diversion. At the same time, the anti-buoyancy structure does not need to be constructed in advance, so the tunnel boring machine schedule is not limited by the construction period of the anti-buoyancy structure. Attached Figure Description

[0018] Figure 1 This is a diagram of an anti-buoyancy structure, which is an existing technology.

[0019] Figure 2 This is a diagram of another anti-buoyancy structure in the prior art.

[0020] Figure 3 This is a plan view of the anti-buoyancy structure of the present invention.

[0021] Figure 4 This is a longitudinal cross-sectional view of the anti-buoyancy structure of the present invention.

[0022] Figure 5 This is a cross-sectional view (AA) of the anti-buoyancy structure of the present invention.

[0023] Figure 6 This is a BB cross-sectional view of the flight suit structure of the present invention.

[0024] In the diagram: 1. Two-way open-cut structure; 1-1. Side wall of open-cut structure; 1-2. End wall of open-cut structure; 1-3. Bottom slab of open-cut structure; 1-4. Central partition wall of open-cut structure; 1-5. Intermediate step; 1-6. Opening; 1-7. Vertical support plate; 2. Portal ring beam; 2-1. Inner contour of portal ring beam; 2-2. Outer contour of portal ring beam; 3. Anti-uplift pile; 4. Anti-buoyancy longitudinal beam; 5. Shield segment; 5-1. Outer contour of shield segment; 5-2. Inner contour of shield segment; 6. Steel segment; 7. Track bed. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The following describes embodiments of the invention based on its overall structure.

[0027] Please see Figures 3-6 This invention provides a technical solution: a shallow-buried tunnel anti-buoyancy structure, comprising a bidirectional open-cut structure 1, wherein the bidirectional shield tunnel segments 5 are connected to the end wall 1-2 of the open-cut structure 1, which is bent on one side, via a portal ring beam 2. The shield tunnel segments 5 and steel pipe segments 6 form a tunnel structure. Anti-uplift piles 3 are vertically embedded below the steel pipe segments 6 embedded in the inner wall of the shield tunnel segments 5. The tops of the anti-uplift piles 3 pass through the steel pipe segments 6 and connect to an anti-buoyancy longitudinal beam 4 laid continuously at the lowest point inside the shield tunnel segments 5. One end of the anti-buoyancy longitudinal beam 4 is laid to the end of the minimum inner contour of the portal ring beam 2 and connected to the portal ring beam 2. The annular structure of the shield tunnel segments 5... Steel segments 6 are installed inside the tunnel structure. The steel segments 6 have an arc-shaped mesh structure and are embedded directly below the shield segments 5. The height of the two ends of the steel segments 6 does not exceed the connection between the track bed 7 and the shield segments 5. The steel segments 6 are used to strengthen the resistance to the upward buoyancy of the pull-out piles 3 below. The tunnel structure can be equipped with steel segments 6 at the pull-out piles 3. Other sections of the tunnel structure can use shield segments 5 composed of reinforced concrete. Alternatively, the overall tunnel structure strength can be strengthened by laying steel segments 6 throughout the structure of the shield segments 5, which enhances the stability of the tunnel section or the entire tunnel structure at the pull-out piles 3.

[0028] like Figures 3-5The bidirectional open-cut structure 1 includes an open-cut structure base slab 1-3. The internal structure of the open-cut structure base slab 1-3 is a two-stage stepped structure, and the external structure of the open-cut structure base slab 1-3 corresponding to the two-stage stepped structure is provided with a ramp that is set in the opposite direction to the shield tunnel segment 5 to strengthen the connection strength with the shield tunnel segment 5. Open-cut structure sidewalls 1-1 are provided on both sides of the open-cut structure base slab 1-3. The net distance from the open-cut structure sidewall 1-1 to the open-cut structure partition wall 1-4 is greater than 1 times the outer diameter of the shield tunnel segment 5, and the maximum distance is not more than 1 / 3 of the outer diameter of the shield tunnel segment 5. The height of the open-cut structure is twice that of the base slab 1-3; a central partition wall 1-4 of the open-cut structure is set at the middle of the base slab 1-3, with the same height as the side wall 1-1. Multiple support structures are set opposite to the side wall 1-1 and the central partition wall 1-4. At the same time, an opening 1-6 is set above the bidirectional open-cut structure 1. The length of the opening 1-6 corresponds to the length of the middle step 1-5 of the base slab 1-3. Vertical support plates 1-7 are set on both sides of the opening 1-6, and the highest point of the vertical support plates 1-7 is higher than the ground level. This invention achieves the anti-buoyancy effect by connecting the anti-buoyancy longitudinal beam 4 to the lower anti-uplift pile 3, and connecting the anti-buoyancy longitudinal beam 4 to the portal ring beam 2 + bidirectional open-cut structure 1.

[0029] like Figure 3 and Figure 5 As shown, the inner wall of the portal ring beam 2 is annular stepped. The inner stepped part of the portal ring beam 2 connects with the end of the shield segment 5. The shield segment 5 and the minimum inner contour of the portal ring beam 2 are horizontally aligned, so that the portal ring beam 2 fits over the outer periphery of the shield segment 5. The radial steel bars of the portal ring beam 2 extend into the anti-buoyancy longitudinal beam 4. The portal ring beam 2 and the anti-buoyancy longitudinal beam 4 are reliably connected by steel bar connectors. The outer periphery of the portal ring beam 2 is connected to the open-cut structure end wall 1-2 by steel bar connectors and radial steel bars. The connection of the two parts through the connecting components of the portal ring beam 2 further strengthens the overall structural strength.

[0030] like Figure 3 and Figure 6 As shown, an anti-buoyancy longitudinal beam 4 is laid at the lowest point inside the shield tunnel segment 5. The anti-buoyancy longitudinal beam 4 is formed by pouring reinforced concrete on site after the shield tunnel segment 5 is constructed. A track bed 7 is set above the anti-buoyancy longitudinal beam 4. The track bed 7 is nested around the anti-buoyancy longitudinal beam 4 and connected to the inner wall of the shield tunnel segment 5 by fasteners. The fasteners can be steel bars, large screws and other fasteners. The whole construction is convenient and not subject to additional restrictions.

[0031] like Figure 3 and Figure 6As shown, the anti-buoyancy longitudinal beam 4 is fixedly connected to the anti-tension pile 3 passing through the steel pipe segment 6. The anti-tension pile 3 is a cast-in-place pile. The anti-tension pile 3 is first poured to the bottom of the shield pipe segment 5, leaving a certain space. When it needs to be combined with the steel pipe segment 6 in the shield pipe segment 5, a second pour is carried out by drilling holes at the corresponding steel pipe segment 6 above the anti-tension pile 3, and finally the anti-tension pile 3 is formed. The pile body of the anti-tension pile 3 is located directly below the steel pipe segment 6. The pile length of the anti-tension pile 3 and the distance of the anti-tension pile 3 from the open-cut structure end wall 1-2 are determined by the results of the current anti-buoyancy calculation. At the same time, before the shield construction, the top of the anti-tension pile 3 needs to be more than 0.5m away from the bottom of the steel pipe segment 6. The distance of the top of the anti-tension pile 3 extending into the steel pipe segment 6 is more than 0.5 times the length of the anti-tension pile 3 diameter. The diameter of the anti-tension pile 3 is set not to exceed 2.0m. The anti-uplift piles 3 are set vertically and buried below the steel pipe segments 6, which not only strengthens the anti-buoyancy ability but also reduces the construction difficulty.

[0032] The anti-buoyancy structure of the present invention does not require ground excavation to construct the anti-buoyancy pressure plate, does not affect ground traffic and the surrounding environment, and saves engineering costs caused by ground excavation, pipeline relocation and traffic diversion. At the same time, the anti-buoyancy structure does not need to be constructed in advance, so the tunnel boring machine schedule is not limited by the construction period of the anti-buoyancy structure.

[0033] Construction process flow:

[0034] (1) Construction of bidirectional open-cut structure 1, the preset position and overall shape of anti-tension pile 3 can be calculated at the same time;

[0035] (2) The tunnel structure (shield segment 5 + steel segment 6) is generally laid with reinforced concrete. At the same time, an area of ​​the same size as the steel segment 6 is opened directly below the inner wall of the shield segment 5 at the proposed anti-uplift pile 3, and the steel segment 6 is embedded and concrete is poured until it solidifies.

[0036] (3) A hole of a certain depth is opened at the bottom of the steel pipe segment 6, and reinforced concrete is continued to be poured into the hole until the structure of the tension pile 3 is formed, so that the top of the tension pile 3 is reserved at a certain distance from the bottom of the shield pipe segment 5. After the concrete solidifies, concrete is poured on the top of the tension pile 3 so that the top of the tension pile 3 extends into the steel pipe segment 6 and is integrated with the overall structure of the shield pipe segment 5.

[0037] (4) Pour the anti-buoyancy longitudinal beam 4 until the radial reinforcement extending from the top of the anti-uplift pile 3 is laid. The anti-buoyancy longitudinal beam 4 is laid until it reaches the portal ring beam 2, and its end is connected to the portal ring beam 2.

[0038] (5) Construction of track bed 7, and subsequent construction process.

[0039] The formation process of the entire system is as follows Figures 3-6 As shown:

[0040] (1) Anti-buoyancy structural system: A section of shield tunnel segment 5 in the shallow buried section is connected to the open-cut structural end wall 1-2. The distance between the anti-uplift pile 3 and the open-cut structural end wall 1-2 is determined based on the anti-buoyancy force provided by the anti-uplift pile 3. The final design is the actual distance between the anti-uplift pile 3 and the open-cut structural end wall 1-2. The top of the anti-uplift pile 3 is connected to the anti-buoyancy longitudinal beam 4 by steel bars and concrete. The anti-buoyancy longitudinal beam 4 is laid along the bottom inner wall of the shield tunnel segment 5 in the tunnel, extending towards the open-cut structural end wall 1-2. The end of the anti-buoyancy longitudinal beam 4 is connected to the portal ring beam 2 (radial steel bars embedded in the portal ring beam 2) by steel bars. Thus, an anti-buoyancy structural system of "anti-uplift pile 3 + portal ring beam 2 + open-cut structural end wall 1-2 + anti-buoyancy longitudinal beam 4" is formed.

[0041] (2) Temporary ground surcharge: Before shield tunneling, a temporary surcharge is placed on the ground directly above the tunnel. The surcharge thickness is determined according to the shield machine's construction needs and the tunnel's anti-buoyancy calculations, thereby providing sufficient backfill thickness to meet the tunnel's anti-buoyancy requirements during shield tunneling. The temporary surcharge can be removed after the anti-buoyancy longitudinal beam 4 is constructed.

[0042] (3) Anti-tension pile 3: Anti-tension pile 3 is a cast-in-place pile, and the pile body is located below the tunnel structure. It is implemented before shield tunneling. The length of the anti-tension pile 3 is determined by anti-buoyancy calculation. A certain safe distance is reserved between the top of the pre-set anti-tension pile 3 and the bottom of the tunnel structure.

[0043] (4) Anti-buoyancy longitudinal beam 4: After the tunnel construction is completed, a reinforced concrete structure is poured on site to form the anti-buoyancy longitudinal beam 4. The radial steel bars extending from the top of the anti-uplift pile 3 are connected to the anti-buoyancy longitudinal beam 4 to play an anchoring role; the radial steel bars of the portal ring beam 2 are connected to the anti-buoyancy longitudinal beam 4, so that the portal ring beam 2 and the anti-buoyancy longitudinal beam 4 are reliably connected. At the same time, the outer contour 2-2 of the portal ring beam is reliably connected to the end wall 1-2 of the open-cut structure with radial steel bars.

[0044] (5) Mechanism of the anti-buoyancy structure system: The tunnel tends to float upward due to the buoyancy of groundwater. This upward buoyancy is transmitted to the anti-buoyancy longitudinal beam 4 through the tunnel structure. On the other hand, the anti-uplift pile 3 and the portal ring beam 2 (also called the portal ring beam) jointly provide anti-buoyancy force. This anti-buoyancy force and the upward buoyancy force cancel each other out, thereby achieving the purpose of anti-buoyancy of the tunnel structure.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention, and no reference numerals in the claims should be regarded as limiting the scope of the claims.

Claims

1. A shallow tunnel anti-floating structure, characterized in that, The application relates to a bidirectional open-cut structure (1), which is connected with bidirectional shield segments (5) through a portal ring beam (2) at a bent open-cut structure end wall (1-2) on one side of the bidirectional open-cut structure (1), a steel segment (6) is embedded in the inner wall of the shield segment (5), a vertical uplift pile (3) is vertically embedded below the steel segment (6), the top of the uplift pile (3) penetrates through the steel segment (6) and is connected with a floating-resistant longitudinal beam (4) at the lowest position in the shield segment (5), and one end of the floating-resistant longitudinal beam (4) is laid to the end of the minimum inner contour of the portal ring beam (2). The bidirectional open-cut structure (1) comprises an open-cut structure bottom plate (1-3), the internal structure of the open-cut structure bottom plate (1-3) is two-section ladder type, and the external structure of the open-cut structure bottom plate (1-3) corresponding to the two-section ladder is provided with a slope which is reversely arranged with the shield segment (5) so as to reinforce the connecting strength with the shield segment (5); open-cut structure side walls (1-1) are arranged on the two sides of the open-cut structure bottom plate (1-3), a open-cut structure middle partition wall (1-4) with the same height as the open-cut structure side walls (1-1) is arranged at the middle of the open-cut structure bottom plate (1-3), and a plurality of supporting structures are oppositely arranged on the open-cut structure side walls (1-1) and the open-cut structure middle partition wall (1-4). An opening (1-6) is arranged above the bidirectional open-cut structure (1), the length of the opening (1-6) corresponds to the length of the middle ladder (1-5) of the open-cut structure bottom plate (1-3), vertical supporting plates (1-7) are arranged on the two sides of the opening (1-6), and the highest position of the vertical supporting plates (1-7) is higher than the ground level. The inner wall of the portal ring beam (2) is annular ladder type, the inner ladder position of the portal ring beam (2) is butted with the end of the shield segment (5), the shield segment (5) is horizontally flush with the minimum inner contour of the portal ring beam (2), and the portal ring beam (2) is sleeved with the periphery of the shield segment (5).

2. The anti-floating structure of a shallow tunnel according to claim 1, wherein, The clear distance of the open-cut structure side walls (1-1) to the open-cut structure middle partition wall (1-4) is greater than 1 times the outer diameter of the shield segment (5) and is not more than 2 times at most; the distance that the top of the uplift pile (3) extends into the shield segment (5) is greater than 0.5 times the pile diameter length of the uplift pile (3), and the pile diameter of the uplift pile (3) is not more than 2.0 m.

3. The anti-floating structure of a shallow tunnel according to claim 1, wherein, The uplift pile (3) is a cast-in-place pile, the pile body of the uplift pile (3) is located directly below the steel segment (6), the length of the uplift pile (3) and the distance of the uplift pile (3) from the open-cut structure end wall (1-2) are determined according to the current anti-floating calculation result, and the distance between the top of the uplift pile (3) and the bottom of the shield segment (5) is more than 0.5 m before construction.

4. The anti-floating structure of a shallow tunnel according to claim 1, wherein, A track bed (7) is arranged above the floating-resistant longitudinal beam (4), the track bed (7) is nested in the periphery of the floating-resistant longitudinal beam (4) and is connected with the inner wall of the shield segment (5) through a fixing piece.

5. The anti-floating structure of a shallow tunnel according to claim 1, wherein, The radial steel bars of the portal ring beam (2) extend into the floating-resistant longitudinal beam (4), the portal ring beam (2) and the floating-resistant longitudinal beam (4) are reliably connected through a steel bar connector, and the periphery of the portal ring beam (2) and the open-cut structure end wall (1-2) are connected through the steel bar connector and the radial steel bars.

6. The anti-floating structure of a shallow tunnel according to claim 1, wherein, The anti-floating longitudinal beam (4) is formed by pouring reinforced concrete on site after the shield segment (5) is constructed.

7. The anti-floating structure of a shallow tunnel according to claim 1, wherein, The steel segment (6) is an arc-shaped net structure, and is embedded directly below the shield segment (5). The height of the two ends of the steel segment (6) does not exceed the connection between the track bed (7) and the shield segment (5).

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