Shield tunneling construction method under ultra-close distance of existing structure

Abstract

The application discloses a kind of structure super-close distance under shield tunneling construction method, to solve the technical problems of prior art cannot be realized structure super-close distance under shield tunneling construction.The method is in the upper part of transverse passage inverted arch binding double-layer reinforcement net, and carries out concrete integral pouring, to prevent the transverse passage inverted arch from being destroyed in the process of tunneling due to excessive soil pressure uplift;After the above pouring concrete solidifies, sand bag is piled up above concrete, further improve the protection measures for the transverse passage inverted arch;Support structure is arranged at the end wall of the position of existing structure shield, to resist end wall deformation;Shield tunneling parameters are controlled to ensure the safety of shield tunneling.The application sets double-layer reinforcement net in the upper part of transverse passage inverted arch and pours concrete, and piles up sand bag after concrete solidifies, to avoid the transverse passage inverted arch from being destroyed due to excessive soil pressure uplift deformation, to realize the synchronization of station construction and shield construction.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, specifically to a safety protection construction method for ultra-close-distance excavation within a station using the arch cover method. Background Technology

[0002] When the tunnel boring machine (TBM) has completed the tunneling of the upper section and passes through the station, the station has already started normal construction. During the subsequent TBM tunneling, the existing structures already constructed in the station are close to the TBM section. If the TBM tunnels normally, it will cause significant disturbance to the surrounding bottom layer of the existing structures, and may even cause the existing structures to crack or collapse. Furthermore, due to the influence of earth pressure, the invert arch of the cross passage may bulge and be damaged. The existing TBM tunneling method can only be implemented after the station construction is completed. It is not possible to carry out TBM tunneling simultaneously when the existing structure of the arch-covered station is only a temporary construction cross passage with initial support and no secondary lining. Therefore, it is necessary to protect the existing structure to ensure the safety of the TBM tunneling work when the existing structure is extremely close to the TBM tunneling section.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The inventors discovered through research that shield tunneling can damage the temporary construction cross passages within ultra-close-range under-arch method stations, which are only initially supported and have not undergone secondary lining. If shield tunneling is carried out after the station construction is completed, it will delay the shield tunneling schedule. However, if temporary safety protection construction is carried out on the existing structure within the station, shield tunneling can be carried out simultaneously with the temporary construction cross passages where the existing structure is only initially supported and has not undergone secondary lining.

[0005] In view of at least one of the above technical problems, this disclosure provides a method for shield tunneling construction under ultra-close distance to existing structures. By implementing counter-pressure measures on the arch of the existing structure in the arch-type station, supporting the end wall of the cross passage, and controlling the shield tunneling parameters, the shield tunneling work under ultra-close distance to existing structures can be completed.

[0006] According to one aspect of this disclosure, a method for tunneling with a shield in ultra-close proximity to an existing structure is provided, comprising the following steps:

[0007] (1) Bind a double-layer steel mesh to the upper part of the cross passage invert at the location where the existing shield tunnel passes under, and pour concrete as a whole to prevent the cross passage invert from being damaged by excessive soil pressure during the tunneling process.

[0008] (2) After the concrete poured in step (1) has solidified, sandbags are piled on top of the concrete to further improve the protection of the transverse arch.

[0009] (3) A supporting structure is installed at the end wall of the existing shield tunneling location to resist the deformation of the end wall;

[0010] (4) Control the shield tunneling parameters to ensure the safety of shield tunneling.

[0011] In some embodiments of this disclosure, in step (1), the size of the double-layer steel mesh is Φ20@150*150 or Φ20@200*200.

[0012] In some embodiments of this disclosure, in step (1), the concrete is C30 concrete with moderate strength and low cost, and the pouring thickness is 25-35cm.

[0013] In some embodiments of this disclosure, in step (2), the strength grade of the concrete should be ensured to reach 30 MPa before sandbags are piled on top of the concrete.

[0014] In some embodiments of this disclosure, in step (2), the height of the sandbags stacked should be greater than 100cm.

[0015] In some embodiments of this disclosure, in step (3), the support structure is a triangular structure made of 18H steel, which includes multiple support units welded together. The support unit includes diagonal braces and vertical braces. The spacing between each support unit is 90-110cm and the height is 300-330cm.

[0016] In some embodiments of this disclosure, the vertical brace of the support structure corresponds to the vertical wall of the end wall, and its bottom is welded to the pre-embedded steel plate at the bottom of the end wall.

[0017] In some embodiments of this disclosure, the control of shield tunneling parameters includes the control of soil chamber pressure, cutterhead rotation speed, cutterhead torque, total thrust, tunneling speed, and tunnel muck discharge, and should ensure that the shield tunneling parameters are lower than normal tunneling parameters.

[0018] In some embodiments of this disclosure, the soil chamber pressure should be maintained at 1.4-1.6 bar during tunneling, and at 1.8 bar when the shield tunneling machine stops working; the cutterhead rotation speed should be controlled at 1.3-1.5 rpm to reduce disturbance to the bottom layer; the cutterhead torque should be <1800 kN·m, and the amount of water added to the cutterhead and the amount of foaming agent should be increased during tunneling to prevent the torque from increasing; the total thrust should be ≤1500T; and the tunneling speed should be 10-20 mm / min.

[0019] Strictly control the slag discharge rate, discharging 10-25m of slag as the hydraulic cylinder advances 35cm. 3 The slag discharge rate should be controlled at 60-75m³ per ring. 3 .

[0020] In some embodiments of this disclosure, during the tunnel boring process, air and grout leakage in the tunnel should be addressed promptly. By appropriately reducing the air flow rate in the foam mixture, the excavated soil can be made into a fluid plastic state, thereby reducing air leakage in the tunnel. Grout leakage in the tunnel can be reduced by monitoring changes in grouting pressure and appropriately reducing the amount of synchronous grouting. Furthermore, closed rings should be installed at both ends of the transverse tunnel to prevent grout leakage during secondary grouting.

[0021] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0022] 1. This application involves installing a double-layer steel mesh on the upper part of the inverted arch of the cross passage at the location where the existing structure passes under the station, pouring concrete, and then stacking sandbags after the concrete has solidified. This prevents the inverted arch of the cross passage from being damaged by excessive soil pressure and deformation, thereby ensuring the safe progress of the shield tunneling construction and enabling the station construction and shield tunneling construction to proceed simultaneously.

[0023] 2. This application proposes to install a supporting structure at the end wall of the existing structure under the station to prevent the end wall from collapsing due to the tunnel boring machine.

[0024] 3. This application controls the shield tunneling parameters to minimize damage to existing structures caused by shield tunneling, and takes measures to address air and grout leakage during shield tunneling, thereby further improving the protection of existing structures. Attached Figure Description

[0025] Figure 1 This is a flowchart of a safety protection construction method in one embodiment of this application.

[0026] Figure 2 This is a schematic diagram of the support structure in one embodiment of this application.

[0027] Figure 3 This is a schematic diagram of the structure of the support unit in one embodiment of this application.

[0028] Figure 4 This is a schematic diagram of the installation of the support structure in one embodiment of this application.

[0029] Figure 5 This is a schematic diagram of the overall construction structure in one embodiment of this application.

[0030] In the above figures, 1 is the tunnel segment, 2 is concrete, 3 is sandbag, 4 is end wall, 41 is embedded steel plate, 5 is supporting structure, 51 is vertical brace, 52 is diagonal brace, and 53, 54 and 55 are connecting columns. Detailed Implementation

[0031] In the description of this application, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," "vertical," "horizontal," "clockwise," and "counterclockwise," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this application 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 application. The terms "first," "second," etc., used in this application are used to distinguish the described objects and do not have any sequential or technical meaning. And the terms "connection" and "linkage," unless otherwise specified, include both direct and indirect connections (linkages).

[0032] Unless otherwise specified, the unit modules, components, structures, mechanisms and materials involved in the following embodiments are all conventional commercially available products.

[0033] This application provides a method for tunneling shields at extremely close range to existing structures, which solves the technical problem that existing technologies cannot achieve tunneling shields at extremely close range to existing structures. By taking protective measures for the existing structure, the method ensures that the tunneling shield construction and the construction of the existing structure are carried out simultaneously.

[0034] The technical solution in this application embodiment is to solve the problem that existing structures cannot perform synchronous shield tunneling at extremely close distances. The overall approach is as follows:

[0035] By taking safety protection measures on the existing structure, the synchronous construction of the shield tunneling under ultra-close distance can be ensured. The safety protection measures mainly include taking counter-pressure measures on the invert arch of the cross passage, taking support measures on the end wall at the underpass location, and controlling the shield parameters, so as to avoid damage to the existing structure during the shield tunneling process.

[0036] The aforementioned counter-pressure measures involve setting up a double-layer steel mesh on the upper part of the transverse passage invert and pouring concrete. After the concrete has solidified, sandbags are placed on top to further prevent the transverse passage invert from deforming during the tunnel boring machine (TBM) excavation. Additionally, a support structure is set up at the end wall of the underpass location to prevent the end wall from collapsing and to improve the stability of the end wall. This facilitates the synchronous construction of the TBM excavation under the existing structure at extremely close distances.

[0037] Example 1

[0038] This example discloses a method for shield tunneling construction under ultra-close distance conditions on existing structures. (See also...) Figure 1 and Figure 5 The main steps include the following:

[0039] (1) A double-layer steel mesh is tied to the upper part of the cross passage invert at the location where the existing shield tunnel passes. The size of the double-layer steel mesh is Φ20@200*200. Concrete 2 is poured as a whole to prevent the cross passage invert from being damaged by excessive soil pressure during the tunneling process.

[0040] (2) After the concrete 2 poured in step (1) has solidified, sandbags 3 with a height of 100cm are piled up on top of the concrete 2. Before piling up the sandbags 3, the strength grade of the concrete 2 should be ensured to reach 30MPa to further improve the protection measures for the cross passage arch.

[0041] (3) such as Figure 2 and 4 As shown, a support structure 5 is installed at the end wall 4 where the existing shield tunnel passes under it to resist deformation of the end wall 4; the support structure 5 is a triangular structure made of 18H-beams, which includes multiple support units welded together, such as... Figure 3 As shown, the support unit includes diagonal bracing 52 and vertical bracing 51. In a preferred embodiment, the spacing between each support unit is 100cm and the height is 315cm. Each support unit is welded together by multiple connecting columns 53, 54, and 55. The vertical bracing 51 of the support structure 5 corresponds to the vertical wall of the end wall 4, and its bottom is welded to the pre-embedded steel plate 41 at the bottom of the end wall 4.

[0042] (4) Controlling shield tunneling parameters can reduce the disturbance to the soil and existing structures during shield tunneling, reduce construction risks, and ensure the safe progress of shield tunneling. The control of shield tunneling parameters includes the control of soil chamber pressure, cutterhead speed, cutterhead torque, total thrust, tunneling speed, and tunnel muck discharge. The shield tunneling parameters should be lower than the normal tunneling parameters.

[0043] During tunneling, the soil chamber pressure should be maintained at 1.4-1.6 bar. When the shield tunneling machine stops working, the soil chamber pressure should be maintained at 1.8 bar. During tunneling, the soil chamber should be filled to more than 1 / 2 full. When the machine stops, the muck should be filled to more than 2 / 3 full. The cutterhead speed should not be too fast, at 1.3-1.5 rpm, to reduce disturbance to the bottom layer. The cutterhead torque should be less than 1800 kN•m. During tunneling, the amount of water added to the cutterhead and the amount of foaming agent should be increased to increase the fluidity of the muck and prevent the torque from increasing due to clogging of the chamber and sticking to the cutterhead and cutters.

[0044] Based on the previous tunneling situation, the total thrust should not be too large. According to the cutterhead torque and the shield tail articulation, the total thrust should not exceed 1500T; the tunneling speed is 10-20mm / min.

[0045] Shield tunneling mainly traverses sections with poor geological conditions and high settlement requirements. Therefore, the amount of muck removed must be strictly controlled, with a muck removal rate of 10-25m for every 35cm of hydraulic cylinder advance. 3 The slag discharge rate should be controlled at 60-75m³ per ring. 3 .

[0046] In addition, timely responses should be made to air and grout leakage in the cross passages during shield tunneling. When the shield tunnels pass very close to each other in cross passages, effective pressure maintenance is often impossible, typically accompanied by air leakage and unstable earth pressure within 500cm in front of the cutterhead. The following measures should be taken promptly to address air leakage in the cross passages:

[0047] ① Based on the characteristics of the slag discharge, adjust the slag improvement effect appropriately, reduce the air flow rate in the foam mixture, increase the amount of foam mixture, and increase the amount of foaming agent stock solution to make the slag reach a fluid plastic state, thereby avoiding the phenomena of clogging and sticking to the cutter head.

[0048] ② Assign dedicated personnel to monitor the tunnel face and inspect the cross passages. If any air leakage is found, report it promptly and take appropriate measures.

[0049] ③ Arrange a monitoring team to monitor the convergence and settlement points of the pilot tunnel in a timely manner, provide timely feedback on the monitoring data, and adjust the tunnel boring parameters in a timely manner based on the monitoring situation.

[0050] During the synchronous and secondary grouting processes of shield tunneling under the cross passage, grout leakage occurred within the cross passage. The following measures should be taken to address this leakage:

[0051] ① When grout leakage occurs, stop grouting immediately and pay attention to changes in grouting pressure. When the grouting pressure is low, the amount of grout can be increased appropriately, and when the grouting pressure is high, the amount of grout can be reduced.

[0052] ② Based on the actual situation, reduce the amount of synchronous grouting in advance, and arrange for dedicated personnel to monitor the cross passage for any abnormal changes in real time. If there is settlement after tunneling, add secondary grouting in time. If there is settlement before tunneling, increase the earth pressure appropriately. If there is bulging during tunneling, reduce the earth pressure and adopt appropriate earth pressure tunneling or reduce the amount of synchronous grouting.

[0053] ③ If leakage occurs during the secondary grouting process, a closed ring should be constructed at both ends of the transverse channel in advance. At the two ring positions at the east and west ends of the transverse channel, the shield hoisting holes should be used to perform secondary double-liquid grouting in the circumferential direction to form a seal behind the segments, thereby preventing leakage. Double-liquid grout should be used for backfilling within the transverse channel area, while single-liquid grout should be used for backfilling in other areas.

[0054] Although some preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0055] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for shield tunneling construction under ultra-close distance conditions in existing structures, characterized in that, Includes the following steps: (1) Bind a double-layer steel mesh to the upper part of the cross passage invert at the location where the existing shield tunnel passes under, and pour concrete as a whole to prevent the cross passage invert from being damaged by excessive soil pressure during the tunneling process. (2) After the concrete poured in step (1) has solidified, sandbags are piled on top of the concrete to further improve the protection of the transverse arch. (3) A supporting structure is installed at the end wall of the existing shield tunneling location to resist the deformation of the end wall; In step (3), the support structure is a triangular structure made of 18H steel, which includes multiple support units welded together. The support unit includes diagonal braces and vertical braces. The spacing between each support unit is 90-110cm and the height is 300-330cm. (4) Control the shield tunneling parameters to ensure shield tunneling safety; In step (4), the control of shield tunneling parameters includes the control of soil chamber pressure, cutterhead speed, cutterhead torque, total thrust, tunneling speed, and tunnel muck discharge. The shield tunneling parameters should be lower than the normal tunneling parameters; the soil chamber pressure should be maintained at 1.4-1.6 bar during tunneling, and at 1.8 bar when the shield stops working; the cutterhead speed should be controlled at 1.3-1.5 rpm to reduce disturbance to the bottom layer; the cutterhead torque should be <1800 KN·m, and the amount of water added to the cutterhead and the amount of foaming agent should be increased during tunneling to prevent the torque from increasing; the total thrust should be ≤1500T; the tunneling speed should be 10-20 mm / min; the muck discharge should be strictly controlled, and the muck discharge should be 10-25 m when the hydraulic cylinder advances 35 cm. 3 The slag discharge rate should be controlled at 60-75m³ per ring. 3 .

2. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, In step (1), the dimensions of the double-layer steel mesh are Φ20@150*150 or Φ20@200*200.

3. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, In step (1), the concrete is C30 concrete with moderate strength and low cost, and the pouring thickness is 25-35cm.

4. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, In step (2), the strength grade of the concrete should be ensured to reach 30 MPa before sandbags are piled on top of the concrete.

5. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, In step (2), the height of the sandbags should be greater than 100cm.

6. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, The vertical brace of the supporting structure corresponds to the vertical wall of the end wall, and its bottom is welded to the pre-embedded steel plate at the bottom of the end wall.

7. The method for shield tunneling under ultra-close distance conditions on existing structures according to claim 1, characterized in that, During the tunnel boring machine (TBM) excavation process, it is also necessary to promptly address any air or grout leakage within the tunnel. By appropriately reducing the air flow rate in the foam mixture, the slag can be made into a fluid plastic state, thereby reducing air leakage in the channel. Grout leakage in the channel can be reduced by monitoring changes in grouting pressure and appropriately reducing the amount of synchronous grouting. In addition, sealing rings should be installed at both ends of the transverse channel to prevent grout leakage during secondary grouting.

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