Method for preventing tunnel heave at the end of a tunnel excavated through a passage

Abstract

A method for preventing tunnel heave when excavating a passage through the end of a tunnel, comprising the following steps: S1. When constructing a pipe shed steel pipe, a horizontal pipe shed is set up at the station layer station end and the station hall layer air duct part; S2. A profile steel is inserted into the pipe section; S3. The gap between the pipe section and the H-shaped steel is filled with high-density mortar; S4. The ground wall inside the steel bar is firmly welded to the outer surface of the near end of the pipe shed steel pipe, and then the end is sealed; S5. The above steps are repeated to construct an underground connecting passage or an overpass passage outside the station; S6. The CRD method which is beneficial to controlling the displacement of the ground surface and the upper soil is used to construct the underground connecting passage or the overpass passage; the invention reduces the tunnel heave by increasing the weight on the top of the tunnel and strengthening the vertical bending stiffness of the top, and can fully exert the rigid constraint of the large stiffness pipe shed in the ground wall and the vertical constraint of the overburden on the pipe shed, effectively controlling the tunnel heave effect caused by excavation unloading.

Description

Technical Field

[0001] This invention relates to the field of trenchless tunneling technology, and more particularly to a method for preventing tunnel uplift when a tunnel passes over the end of a tunnel. Background Technology

[0002] In areas with deep groundwater, connecting passages or underground pedestrian crossings between different subway lines are constructed on the outer side of station ends. To avoid traffic disruptions or pipeline relocation issues on the upper roads, the cut-and-cover method is used to construct these underground pedestrian crossings, achieving normal surface traffic without requiring pipeline relocation. Since the pedestrian crossings traverse tunnel segments, soil unloading during excavation can cause segment uplift. To reduce the amount of segment uplift, protective measures are needed to minimize the adverse effects of underground passage excavation on the tunnel. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for reducing tunnel segment uplift during construction inside subway stations. This method eliminates the need to occupy surface space, avoids traffic diversion and pipeline relocation, saves time, and reduces costs.

[0004] The technical solution adopted in this invention:

[0005] A method for preventing tunnel uplift when a cut-and-cover tunnel passes over the end of a tunnel, the steps of which are as follows:

[0006] S1. When constructing the steel pipe shed, during the subway shutdown period, horizontal pipe sheds are installed at the station end of the platform level and the ventilation duct of the station hall level. When installing the pipe shed, the internal structural beams of the station that are close to the ground diaphragm wall at the shield shaft are avoided. The length of the pipe section driven into the pipe shed in one go is determined according to the size of the operating space. The steel pipe sections are connected by threaded connections.

[0007] S2. Insert the H-beam into the pipe section to ensure that the web of the H-beam is in the vertical plane. Weld the H-beam to the steel pipe at the near end to ensure the stability of the H-beam position. After one section of H-beam is inserted into the steel pipe, the next section is connected to the previous section by welding until the length of the H-beam is equal to that of the pipe section.

[0008] S3. Fill the gap between the pipe section and the H-beam with high-density mortar to ensure a tight filling.

[0009] S4. After firmly welding the inner reinforcing bars of the diaphragm wall to the outer surface of the near end of the pipe shed steel pipe, seal the end to ensure the stability of the pipe shed within the diaphragm wall and repair the internal structure of the station.

[0010] S5. Repeat the above steps to form a reliable pipe roof structure parallel to the longitudinal direction of the tunnel on the top of the existing tunnel during the construction process of the platform level and the concourse level. After the mortar strength in the pipe roof reaches the design requirements, carry out the construction of the underground connecting passage or pedestrian crossing outside the station.

[0011] S6. When the cross-sectional area of ​​underground connecting passages or pedestrian crossings is large, the CRD construction method, which is beneficial to controlling the displacement of the ground surface and the upper soil, shall be adopted for the construction of underground connecting passages or pedestrian crossings.

[0012] The pipe roof installation in step S1 needs to be carried out during the off-peak period when the subway is not in operation at night.

[0013] In step S1, the length of the steel pipe driven in each time needs to be determined based on the size of the operating space at the end of the platform level and the concourse level. If the operating space is limited, it needs to be carried out according to the principle of driving in short pipes multiple times, and the connection between pipe sections must be reliable.

[0014] In step S1, before installing the horizontal pipe shed, a horizontal borehole is drilled at the top of the tunnel, and a steel pipe is inserted into the horizontal borehole.

[0015] In step S1, the steel pipe must be moved vertically to avoid obstacles, but cannot be moved left or right to avoid obstacles, in order to ensure the formation of a vertical protective pipe shed at the top of the tunnel.

[0016] The beneficial effects of this invention are as follows: This invention reduces tunnel heave by increasing the weight on the top of the tunnel and strengthening the vertical bending stiffness of the top. It also fully utilizes the rigid constraint of the high-rigidity pipe roof within the diaphragm wall and the vertical constraint of the overburden above the pipe roof at the far end, effectively controlling the tunnel heave effect caused by excavation unloading. This method does not occupy surface space, does not affect traffic flow above, and does not require pipeline relocation. It is particularly beneficial for the construction of connecting passages between new and existing subway lines. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure constructed using the present invention.

[0018] Figure 2 The front view is for construction using the present invention.

[0019] Figure 3 This is a schematic diagram of a longitudinal section during construction using the present invention.

[0020] Among them: 1-internal structural beam; 2-diaphragm wall; 3-existing tunnel; 4-underground connecting passage or pedestrian crossing; 5-pipe shed. Detailed Implementation

[0021] A method for preventing tunnel uplift when a cut-and-cover tunnel passes over the end of a tunnel, the steps of which are as follows:

[0022] S1. When constructing the steel pipe shed 5, during the subway's nighttime shutdown period, horizontal holes are drilled at the station end of the platform level and the ventilation duct of the station hall level. When drilling, it is necessary to avoid the main structural components such as beams and slabs. The φ325×7mm steel pipe shed 5 is inserted into the horizontal hole. The far end of the steel pipe extends 10m beyond the outer wall of the side wall of the newly built connecting passage. A sealing plate is set at the far end of the steel pipe. When drilling the steel pipe shed 5, it avoids the internal structural beam 1 of the station that is close to the diaphragm wall 2 at the shield shaft. The length of the single pipe section is determined according to the size of the operating space. The steel pipe sections are connected by threaded connections. The steel pipe wall is perforated in a quincunx pattern so that the soil near the pipe shed 5 can be effectively reinforced by grouting later. The near end of the steel pipe is fixed within the wall body of the diaphragm wall 2 and reliably connected to the inner reinforcement of the diaphragm wall 2.

[0023] S2. Insert H175×175×7.5×11 steel into the φ325×7mm pipe section. Use the steel with the largest cross-section possible to maximize vertical stiffness and ensure that the web of the H-beam is in the vertical plane. Weld the steel to the steel pipe firmly near the end to ensure the stability of the steel position. The length of the steel inserted at one time needs to be determined according to the size of the operating space. After one section of steel is inserted into the steel pipe, the next section is connected to the previous section by welding until the length of the H-beam is equal to that of the pipe section.

[0024] S3. The gap between the pipe section and the H-beam is filled with high-density mortar to ensure a dense filling and to appropriately increase the weight on the top of the tunnel to improve its ability to prevent tunnel uplift.

[0025] S4. After firmly welding the inner steel bars of the diaphragm wall 2 to the outer surface of the near end of the steel pipe of the pipe shed 5, the end is sealed to ensure the stability of the position of the pipe shed 5 within the diaphragm wall 2, thereby ensuring the constraint effect of the rigid support of the diaphragm wall 2, and repairing the internal structure of the station. After repairing the connection parts, the original structural wall is restored to minimize the adverse effects on the internal structure.

[0026] S5. Repeat the above steps to form a reliable pipe roof 5 structure parallel to the longitudinal direction of the tunnel on the top of the existing tunnel 3 during the construction process of the platform level and the concourse level. This will form a hard dome with a large self-weight and strong rigidity in the tunnel top, which will prevent the excavation of the connecting passage above the tunnel from having an adverse effect on the road surface and buried pipelines above the tunnel. After the mortar strength in the pipe roof 5 reaches the design requirements, the construction of the underground connecting passage or pedestrian crossing 4 outside the station will be carried out.

[0027] S6. When the cross-sectional area of ​​the underground connecting passage or pedestrian crossing 4 is large, the CRD construction method, which is beneficial to controlling the displacement of the ground surface and the upper soil, shall be adopted for the construction of the underground connecting passage or pedestrian crossing 4.

[0028] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used 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. Therefore, they should not be construed as limitations on this invention.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0031] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preventing tunnel uplift when a mined tunnel passes over the end of a tunnel, characterized in that, The steps are as follows: S1. When constructing the steel pipe shed (5), during the subway shutdown period, horizontal pipe sheds (5) are installed at the station end of the platform level and the ventilation duct of the station hall level. When installing the pipe shed (5), the internal structural beam (1) of the station close to the ground diaphragm wall (2) of the shield shaft is avoided. The length of the pipe section driven into the pipe shed in one go is determined according to the size of the operating space. The steel pipe sections are connected by threaded connections. S2. Insert the H-beam into the pipe section to ensure that the web of the H-beam is in the vertical plane. Weld the H-beam to the steel pipe at the near end to ensure the stability of the H-beam position. After one section of H-beam is inserted into the steel pipe, the next section is connected to the previous section by welding until the length of the H-beam is equal to that of the pipe section. S3. Fill the gap between the pipe section and the H-beam with high-density mortar to ensure a tight filling. S4. After firmly welding the inner steel bars of the diaphragm wall (2) to the outer surface of the near end of the steel pipe of the pipe shed (5), seal the end to ensure the stability of the position of the pipe shed (5) within the diaphragm wall (2) and repair the internal structure of the station. S5. Repeat the above steps to form a reliable pipe roof (5) structure parallel to the longitudinal direction of the tunnel on the top of the existing tunnel (3) during the construction process of the platform level and the concourse level. After the mortar strength in the pipe roof (5) reaches the design requirements, the construction of the underground connecting passage or pedestrian crossing (4) outside the station will be carried out. S6. When the cross-sectional area of ​​the underground connecting passage or pedestrian crossing (4) is large, the CRD construction method, which is beneficial to controlling the displacement of the ground surface and the upper soil, shall be adopted for the construction of the underground connecting passage or pedestrian crossing (4).

2. The method for preventing tunnel uplift when a mined tunnel passes over the end of a tunnel according to claim 1, characterized in that, The pipe shed (5) in step S1 needs to be installed during the off-peak period when the subway is not in operation at night.

3. The method for preventing tunnel uplift when a mined tunnel passes over the end of a tunnel according to claim 2, characterized in that, In step S1, the length of the steel pipe driven in each time needs to be determined based on the size of the operating space at the end of the platform level and the concourse level. If the operating space is limited, it needs to be carried out according to the principle of driving in short pipes multiple times, and the connection between pipe sections must be reliable.

4. The method for preventing tunnel uplift when a mined tunnel passes over the end of a tunnel according to claim 3, characterized in that, In step S1, before installing the horizontal pipe shed, a horizontal borehole is drilled at the top of the tunnel, and a steel pipe is inserted into the horizontal borehole.

5. The method for preventing tunnel uplift when a mined tunnel passes over the end of a tunnel according to claim 4, characterized in that, In step S1, the steel pipe must be moved vertically to avoid obstacles, but cannot be moved left or right to avoid obstacles, in order to ensure the formation of a vertical protective pipe shed at the top of the tunnel.

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