Combined anti-upheaval reinforcing method for existing large-span operation open-cut tunnel pipe roofs

Abstract

The invention discloses an existing large-span operation open-cut tunnel pipe-roofing combined anti-upheaval reinforcing method. The method comprises the following steps that a site is leveled, and a soil body within the range of an existing tunnel fender post is reinforced; top beams are arranged at the tops of the existing fender posts, and straining beams on the two sides are poured; uplift piles are driven on the outer sides of the fender posts; vertical shafts are constructed on the inner sides of the fender posts, and coping piers are poured to be connected with the fender posts; in the pipe curtain construction area, a drilling machine is used for hole forming, and a concrete pier is poured to the bottom of the pipe curtain; foundation pit slope excavation is conducted, drilling piles are arranged, and then pipe roofs are jacked in and connected with concrete piers; backfilling is conducted in the foundation pit, and a social corridor channel bottom plate structure is constructed and subjected to weight balancing; construction of the channel structure is completed by means of skip excavation and building envelope chiseling, and ballasting is carried out according to monitoring data. According to the method, a stable anti-upheaval structure is formed through the steps, soil deformation is effectively controlled, and normal operation of the existing tunnel is guaranteed.

Description

Technical Field

[0001] The invention relates to the field of rail transit open-cut tunnel engineering, and in particular to a pipe-roof combined anti-uplift reinforcement method for an existing large-span operating open-cut tunnel. Background Art

[0002] With the acceleration of urbanization, limited urban surface land resources can no longer meet people's demand for living space. Urban space is gradually expanding downward, and the development and utilization of underground space has become an important part of urban construction. Although the development plan of urban underground space has been carefully arranged in the early stage of construction, due to the unpredictability of development goals, new underground projects often appear adjacent to existing underground structures. In this case, the impact of the proposed project on the existing underground structure must be considered during the planning and design stage, especially when new underground projects are built near important underground infrastructure such as existing subway tunnels, it is necessary to focus on the possible impact.

[0003] As a key component of modern urban underground transportation, the operational safety of subway tunnels is extremely important. When a new underground project is adjacent to an existing subway tunnel, the tunnel structure may be disturbed during construction, thus affecting the normal operation of the subway. At present, there is a lack of effective anti-uplift reinforcement measures for the construction of ultra-long, close and parallel soil unloading adjacent to large-span open-cut subway tunnels. Existing technologies are difficult to effectively deal with soil deformation problems that may be caused during construction. These problems may lead to safety hazards such as uplift and deformation of the tunnel structure, thereby affecting the stability of the tunnel and the normal operation of the train. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a combined anti-uplift reinforcement method for an existing large-span open-cut tunnel with a pipe curtain. The method forms an overall anti-uplift system by utilizing existing retaining piles and newly constructed structures. The anti-uplift force is sequentially transmitted to the underlying soil layer through the capping pier, concrete pier, pipe curtain, retaining piles, longitudinal connecting beams and anti-pullout piles, thereby effectively controlling the uplift deformation of the large-span open-cut tunnel and ensuring the safe operation of the tunnel. Compared with the traditional anti-floating frame structure, the present invention has significant advantages such as low construction cost and fast construction speed.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel comprises the following steps:

[0007] S1, leveling the site, reinforcing part of the soil within the existing retaining piles of the existing tunnel to form a soil reinforcement area;

[0008] S2, a cap beam is set on the top of the existing retaining piles, and a tension beam is cast between the cap beams on both sides;

[0009] S3, driving anti-pullout piles outside the existing retaining piles;

[0010] S4, construct multiple vertical shafts on the inner side of the existing retaining piles to the existing tunnel roof, cast the top pressure piers and effectively connect them with the existing retaining piles;

[0011] S5: In the section where the pipe curtain is set up, a drilling rig is used to drill holes, and a steel sleeve is used to protect the wall. The drilling is carried out to 0.5m above the tunnel, and then manual excavation is carried out downward to the top plate of the existing tunnel, and concrete piers are poured to the designed elevation of the bottom of the pipe curtain;

[0012] S6, symmetrical slope excavation of the foundation pits on both sides of the existing subway tunnel is carried out. After the foundation pit is excavated to the bottom, bored piles are first driven into the foundation pit on one side to provide reaction force for the subsequent pipe curtain jacking. Then the pipe curtain jacking construction is carried out. Holes are opened in advance on the pipe curtain steel pipe according to the position of the concrete pier below. After the pipe curtain jacking is completed, concrete is poured into the pipe curtain steel pipe to fill it densely and fully solidify it, and then it is connected with the concrete pier below to form an overall reinforcement structure;

[0013] S7, backfill the small foundation pit below the bottom slab of the social corridor in the foundation pit on both sides of the open-cut tunnel with plain concrete, then construct the bottom slab structure of the social corridor, and balance the weight in time after the bottom slab structure reaches the design strength;

[0014] S8, the foundation pit of the social corridor is excavated symmetrically in sections. After the foundation pit is excavated to the bottom, the bottom plate structure is constructed immediately, and a counterweight is placed on top of the bottom plate structure to control the deformation of the existing tunnel;

[0015] S9. After the bottom plate structure and counterweight of the social corridor on both sides of the existing retaining piles are completed, the soil between the existing retaining piles is excavated as a whole to provide a skip excavation working surface; then the foundation pit between the existing retaining piles is excavated in sections along the longitudinal direction of the existing subway tunnel and the retaining structure is chiseled out, and the channel structure is constructed in time to connect with the channels on both sides, and weight is applied at the same time according to the monitoring data.

[0016] Preferably, in step S1, the soil reinforcement is performed by grouting.

[0017] Preferably, in step S4, the vertical shaft is constructed using an inverted shaft wall method.

[0018] Preferably, in step S4, the node connection between the capping pier and the existing retaining piles is performed by embedding reinforcement, and the contact surface is roughened and coated with an interface agent layer.

[0019] Preferably, the step S6 further comprises casting a connecting beam outside the existing retaining piles, wherein the connecting beam is effectively connected to the existing retaining piles, and the connecting beam is used to connect a plurality of pull-out piles together.

[0020] Preferably, the node connections between the existing retaining piles and the connecting beams are made by embedding reinforcement, and the contact surfaces are roughened and coated with an interface agent layer.

[0021] Preferably, the length direction of the connecting beam is along the extension direction of the existing tunnel.

[0022] Preferably, in step S6, the pipe curtain and the connecting beam are constructed simultaneously, and the steel pipes of the pipe curtain pass through the existing retaining piles during the construction process, and both ends are accurately positioned inside the connecting beam to form a stable overall reinforcement structure.

[0023] Preferably, in step S6, while pouring concrete in the tube-roof steel tube, the connecting beam is also poured, and a synchronous pouring technology is adopted to coordinate and control the flow and curing rate of concrete to ensure that the tube-roof steel tube and the connecting beam are connected as a whole.

[0024] Preferably, in step S6, an automated monitoring system is used to perform real-time monitoring during the pipe-roof jacking construction process, and the monitoring data includes the propulsion force, position and pressure of the pipe-roof, and the construction parameters are adjusted in real time to ensure the jacking accuracy.

[0025] The beneficial effects of the present invention are as follows: The pipe-roof combined anti-uplift reinforcement method for existing large-span open-cut tunnels provided by the present invention adopts a method of combining pipe-roofs with existing retaining piles to form a combined integral anti-uplift structure, which effectively transmits the anti-uplift force to the lower soil layer through the capping pier, concrete pier, pipe-roof, retaining piles, longitudinal connecting beams and anti-pulling piles, thereby effectively controlling the uplift deformation of the large-span open-cut tunnel and ensuring the stability of the tunnel structure and the normal operation of the train. The reinforcement method is particularly suitable for the reinforcement of large-span open-cut tunnels. The combined anti-uplift structure reduces the construction cost while increasing the construction speed. Compared with the traditional anti-floating frame structure, the present invention has higher economy and practicality while ensuring the safety of the tunnel. The reinforcement method provided by the present invention can effectively cope with engineering challenges such as foundation pit excavation encountered in the process of urban underground space development, especially when crossing over an existing open-cut subway tunnel in operation, it can ensure that the tunnel is not disturbed during the construction process and maintains normal operation. With the continuous development of urban underground space, there will be more large foundation pits crossing over existing open-cut subway tunnels in the future. The combined anti-uplift reinforcement method of the present invention can effectively cope with this complex construction environment, has high practicality and economic value, and provides a reliable technical solution for the safe development of underground space. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Attached Figure 1 It is a cross-sectional schematic diagram of the existing large-span open-cut tunnel pipe-roof combined anti-uplift structure of the present invention.

[0027] Attached Figure 2It is a schematic diagram of the soil jump excavation above the subway tunnel of the present invention;

[0028] Attached Figure 3 It is a schematic diagram of the arrangement of the pull-out piles and the capping piers of the present invention;

[0029] Attached Figure 4 It is a cross-sectional view of the social corridor and anti-uplift structure of the present invention;

[0030] Figure numerals: 1-cap beam; 2-tension beam; 3-soil reinforcement area; 4-connecting beam; 5-pipe curtain; 6-existing tunnel; 7-existing retaining piles; 8-pull-out piles; 9-capping pier; 10-concrete pier. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention belong to the present invention.

[0032] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present application. However, those skilled in the art will appreciate that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps, etc. can be adopted. In other cases, known methods, devices, realizations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0033] See also Figure 1-4 This embodiment provides a combined anti-uplift reinforcement method for an existing large-span open-cut tunnel, specifically comprising the following steps:

[0034] S1, leveling the site, reinforcing part of the soil within the existing retaining piles 7 of the existing tunnel 6, and forming a soil reinforcement area 3.

[0035] In this step, the soil around the existing tunnel 6 is reinforced by leveling the construction site and using grouting technology. Grouting reinforcement can effectively enhance the overall stability of the soil, fill the voids in the soil, and improve the density of the soil layer, thereby preventing the soil from loosening or settling during the construction process and ensuring the safety of the tunnel structure.

[0036] S2, a cap beam 1 is arranged on the top of the existing retaining pile 7, and a tension beam 2 is cast between the cap beams 1 on both sides.

[0037] In this step, the connection between the cap beam 1 and the tension beam 2 can effectively share the load of the soil and the structure and improve the anti-uplift capability.

[0038] S3, driving anti-pullout piles 8 outside the existing retaining piles 7.

[0039] In this step, by driving anti-pullout piles 8 outside the existing retaining piles 7, the anti-pullout capacity of the structure is increased to prevent the tunnel and the surrounding soil from floating and deforming. A plurality of anti-pullout piles 8 are evenly arranged outside the existing retaining piles 7 on both sides of the existing tunnel 6. The anti-pullout piles 8 are close to the existing retaining piles 7 and are constructed using fully-rotating bored casing to minimize disturbance to the surrounding strata.

[0040] S4, construct multiple vertical shafts on the inner side of the existing retaining piles 7 to the top plate of the existing tunnel 6, cast the top pressure pier 9 and effectively connect it with the existing retaining piles 7.

[0041] In this step, piles are attached to the inner side of the existing retaining piles 7 and multiple vertical shafts are constructed. The vertical shafts penetrate to the top plate of the existing tunnel 6. The top piers 9 are cast through the construction of these vertical shafts, thereby effectively strengthening the connection between the retaining piles 7 and the underground structure and improving the overall structural strength against uplift. In order to construct multiple vertical shafts and ensure the stability of the vertical shaft wall, the inverted shaft wall method can be used for construction. The inverted shaft wall method first installs the shaft wall support structure and then excavates during the construction of the shaft, avoiding the risk of shaft wall collapse due to excessive excavation during the conventional shaft construction process.

[0042] S5, in the section where the pipe curtain 5 is set, a drilling rig is used to drill holes, and a steel sleeve is used to protect the wall. The drilling is carried out to 0.5m above the tunnel, and then manual excavation is carried out downward to the existing tunnel roof, and concrete piers 10 are poured to the designed elevation of the bottom of the pipe curtain.

[0043] This step mainly involves drilling holes in the area where the pipe curtain 5 is set, and using steel sleeves to protect the wall to ensure the stability of the tunnel. After drilling to 0.5m above the tunnel, manual excavation is used until the tunnel roof, and concrete piers 10 are poured at the same time to ensure the stability of the bottom of the pipe curtain and the installation accuracy of the pipe curtain.

[0044] S6, symmetrical slope excavation is carried out on both sides of the existing subway tunnel. After the foundation pit is excavated to the bottom, bored piles are first driven into the foundation pit on one side to provide reaction force for the subsequent jacking of the pipe curtain 5. Then the jacking construction of the pipe curtain 5 is carried out. Holes are opened in advance on the steel pipe of the pipe curtain according to the position of the concrete pier 10 below. After the jacking of the pipe curtain 5 is completed, concrete is poured into the steel pipe of the pipe curtain to fill it densely and fully solidify it, and then it is connected with the concrete pier 10 below to form an overall reinforcement structure.

[0045] In this step, the foundation pit is first excavated symmetrically to ensure the stability of the foundation pit. After excavation to the bottom, bored piles are driven on one side of the foundation pit to provide reaction force for the jacking of the pipe curtain 5, and then the jacking construction of the pipe curtain is carried out. Holes are opened on the steel pipe of the pipe curtain and concrete is poured to fill it tightly. The connection between the pipe curtain 5 and the concrete pier 10 ensures the stability of the reinforcement effect and forms a stable overall reinforcement structure.

[0046] S7, backfill the small foundation pit below the bottom slab of the social corridor in the foundation pit on both sides of the open-cut tunnel with plain concrete, and then construct the bottom slab structure of the social corridor, and balance the weight in time after the bottom slab structure reaches the design strength.

[0047] In this step, the small foundation pit under the floor of the social corridor is first backfilled with plain concrete to provide a foundation for subsequent construction. After the floor structure reaches the designed strength, the deformation of the subway tunnel is controlled by timely counterweighting to ensure the stability of the tunnel structure below. The social corridor is located in the underground space and is used to connect underground passages in different areas of the city. It is usually used to facilitate the passage of pedestrians or small vehicles, effectively reducing the pressure on ground traffic.

[0048] S8, the foundation pit of the social corridor is excavated symmetrically in sections. After the foundation pit is excavated to the bottom, the bottom plate structure is constructed immediately, and counterweights are placed above the bottom plate structure to control the deformation of the existing tunnel 6.

[0049] In this step, a symmetrical segmented excavation method is used to construct the foundation pit of the social corridor. After the foundation pit is excavated to the bottom, the bottom plate structure is constructed immediately, and counterweights are placed on top of the bottom plate structure to effectively control the deformation of the existing tunnel 6 below, ensuring that the subway tunnel is stable and not affected during the construction process.

[0050] S9, after the bottom plate structure and counterweight of the social corridor on both sides of the existing retaining piles 7 are completed, the soil between the existing retaining piles 7 is excavated as a whole to provide a skip excavation working surface; then the foundation pit between the existing retaining piles 7 is excavated in sections along the longitudinal direction of the existing subway tunnel 6 and the retaining structure is chiseled out, and the channel structure is constructed in time to connect with the channels on both sides, and weight is applied at the same time according to the monitoring data.

[0051] In the last step, after completing the bottom plate structure and counterweight of the social corridor, the soil between the existing retaining piles 7 was excavated as a whole to provide a working surface for skipping excavation. The foundation pit was excavated by longitudinal segmented skipping and the retaining structure was removed to ensure the smooth construction of the channel structure. The weight was then applied according to the real-time monitoring data to ensure the safety and stability of the existing tunnel.

[0052] Through these steps, the reinforcement method provided in this embodiment effectively improves the structural stability of the existing large-span open-cut tunnel, prevents the influence of soil deformation on the tunnel during the construction process, and ensures the safe operation of the subway tunnel.

[0053] Furthermore, in step S4, the node connection between the capping pier 9 and the existing retaining pile 7 is performed by embedding reinforcement, and the contact surface is roughened and coated with an interface agent layer. Embedding reinforcement is a technology that enhances the connection strength of steel bars by embedding them into hardened concrete. In order to ensure the firmness of the connection, the contact surface of the node needs to be roughened to increase the contact area and remove loose materials on the surface to enhance the bonding force between the concrete and the steel bars. Then, the contact surface is coated with an interface agent, which helps to improve the interface bonding performance and ensure the stability of the node connection, thereby improving the tensile strength and deformation resistance of the entire structure.

[0054] Furthermore, in step S6, it also includes casting a connecting beam 4 outside the existing retaining pile 7, the connecting beam 4 is effectively connected to the existing retaining pile, the connecting beam 4 is used to connect multiple pull-out piles 8 together, and the length direction of the connecting beam 4 is arranged along the extension direction of the existing tunnel 6. In this process, by casting the connecting beam 4 outside the existing retaining pile 7, the connecting beam 4 is effectively connected to the existing retaining pile 7 to form a stable overall structure. The setting of the connecting beam 4 can not only enhance the deformation resistance of the retaining pile 7, but also connect multiple pull-out piles 8 together to form an pull-out system, further enhancing the stability of the entire reinforced structure. This structure can effectively disperse and transmit external loads and reduce the influence of the deformation of the surrounding soil on the tunnel structure.

[0055] Similarly, the node connection between the existing retaining pile 7 and the connecting beam 4 is carried out by embedding reinforcement, and the contact surface is roughened and coated with an interface agent layer. In this node connection step, the steel bar is implanted into the contact surface between the existing retaining pile 7 and the connecting beam 4 by embedding reinforcement technology to enhance the connection strength between the two. The contact surface is first roughened to remove loose materials on the surface and increase the contact area, thereby improving the bonding force between the concrete and the steel bar, and then the interface agent layer is applied. The interface agent can further enhance the bonding force between the contact surfaces, ensure the stability of the node and the strength of the connection, and make the entire reinforced structure more solid and reliable.

[0056] In step S6 of this embodiment, the pipe curtain 5 and the connecting beam 4 are constructed simultaneously. During the construction process, the pipe curtain steel pipe passes through the existing retaining piles, and the two ends are accurately positioned inside the connecting beam to form a stable integral reinforcement structure. While pouring concrete in the pipe curtain steel pipe, the connecting beam 4 is also poured. The synchronous pouring technology is adopted to coordinate and control the flow and solidification rate of concrete to ensure that the pipe curtain steel pipe and the connecting beam 4 are connected as a whole. This construction method ensures a stable connection between the pipe curtain 5 and the connecting beam 4, forming an integral reinforcement structure, and effectively preventing the soil from being bulged and deformed due to unloading during the tunnel construction process. The pipe curtain 5 is composed of a plurality of pipe curtain steel pipes, which are arranged in parallel and together constitute the main structure of the pipe curtain 5. During the construction process, the pipe curtain steel pipe passes through the existing retaining piles 7 to form a stable connection with the surrounding soil. The two ends of the pipe curtain steel pipe are positioned inside the connecting beam 4. The pipe curtain 5 and the connecting beam 4 work together to increase the stability of the tunnel structure and prevent the impact on the existing subway tunnel. In this step, the concrete in the pipe curtain steel pipe is poured synchronously with the connecting beam 4. Through the synchronous pouring technology, the flow and curing rate of concrete are precisely coordinated and controlled. This technology can ensure a solid connection between the pipe curtain steel pipe and the connecting beam 4, avoiding the joint problem that may occur in traditional pouring methods. Synchronous pouring ensures a tighter connection between the pipe curtain 5 and the connecting beam 4, providing stronger structural stability.

[0057] Step S6 in this embodiment is the key, which realizes the combined use of the pipe curtain 5, the concrete pier 10 and the connecting beam 4. Through this combined design, not only can the stability of the existing tunnel structure be effectively enhanced, but also an efficient anti-uplift reinforcement system can be formed. During the construction process, the pipe curtain 5 forms a tight connection with the concrete pier 10 below by pouring concrete into the pipe curtain steel pipe. The concrete pier 10 enhances the stability of the pipe curtain, allowing the pipe curtain steel pipe to withstand greater soil pressure during underground construction, preventing the tunnel structure from being affected by soil deformation. In addition, the combination of the pipe curtain 5 and the connecting beam 4, by effectively connecting the pipe curtain steel pipe with the existing retaining piles 7 and the longitudinal connecting beam 4, enhances the overall stability of the structure. This design makes the reinforcement effect more stable, further improves the anti-uplift ability, and reduces the risk of tunnel deformation.

[0058] Furthermore, in step S6, an automated monitoring system is used to monitor the pipe curtain jacking process in real time. The monitoring data includes the pipe curtain propulsion force, position and pressure, and the construction parameters are adjusted in real time to ensure the jacking accuracy. This automated monitoring technology can accurately control the advancement process of the pipe curtain, ensure that the pipe curtain always remains in the correct position during the construction process, avoid the impact of construction errors on the tunnel structure, and further ensure the accuracy and safety of the construction.

[0059] In summary, the present invention proposes a combined anti-uplift reinforcement method for an existing large-span open-cut tunnel pipe curtain. Through multiple structural components such as a capping pier 9, a concrete pier 10, a pipe curtain 5, existing retaining piles 7, a longitudinal connecting beam 4 and an anti-pull pile 8, a combined effective anti-uplift system is formed, which can restrain the deformation of the underlying soil and prevent the tunnel from uplifting or settling, thereby ensuring the safety of the construction process and the normal operation of the existing tunnel. The present invention solves the problem of insufficient anti-uplift reinforcement measures in the construction of an ultra-long, close and parallel soil unloading adjacent to an open-cut subway tunnel in operation. The method effectively utilizes the existing retaining piles in combination with the newly built structure to form a stable overall anti-uplift reinforcement structure, which not only improves the stability of the tunnel, but also significantly reduces the construction risk and difficulty. The synchronous casting technology, the real-time monitoring system and the coordinated construction of the pipe curtain and the connecting beam further ensure the reinforcement effect and construction accuracy. The present invention has the advantages of low project cost, good anti-uplift effect, and low construction risk. In addition, by reinforcing the excavated foundation pit, it can reduce the impact on surface structures and existing tunnel operations and reduce social impact. Compared with conventional reinforcement schemes, the present invention effectively utilizes existing retaining piles, significantly reduces project costs, and ensures construction safety. With the support of the implementation of technical measures, the present invention has a good prospect for promotion and application, and is particularly suitable for the development of urban underground space, involving situations involving close tunnel construction. Its simple, economical and efficient reinforcement method provides a reliable solution for similar projects, and has broad application value and market potential.

[0060] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel, characterized in that: The following steps are involved: S1, leveling the site, reinforcing part of the soil within the existing retaining piles (7) of the existing tunnel (6), and forming a soil reinforcement area (3); S2, setting a cap beam (1) on the top of the existing retaining pile (7), and casting a tension beam (2) between the cap beams (1) on both sides; S3, driving anti-pullout piles (8) outside the existing retaining piles (7); S4, constructing multiple vertical shafts on the inner side of the existing retaining piles (7) to the top plate of the existing tunnel (6), pouring the top pressure pier (9) and effectively connecting it with the existing retaining piles (7); S5, in the section where the pipe curtain (5) is to be set, a drilling machine is used to drill holes, a steel sleeve is used to protect the wall, and the drilling is carried out to 0.5 m above the tunnel. Then, manual excavation is carried out downward to the top plate of the existing tunnel (6), and a concrete pier (10) is poured to the designed elevation of the bottom of the pipe curtain; S6, symmetrical slope excavation of the foundation pits on both sides of the existing subway tunnel (6), after the foundation pits are excavated to the bottom, bored piles are first driven into the foundation pit on one side to provide reaction force for the subsequent jacking of the pipe curtain (5), and then the jacking construction of the pipe curtain (5) is carried out. Holes are opened in advance on the steel pipes of the pipe curtain according to the position of the concrete pier (10) below. After the jacking of the pipe curtain (5) is completed, concrete is poured into the steel pipes of the pipe curtain to fill them densely and fully solidify them, and then connected with the concrete pier (10) below to form an overall reinforcement structure; S7, backfill the small foundation pit below the bottom slab of the social corridor in the foundation pit on both sides of the open-cut tunnel with plain concrete, then construct the bottom slab structure of the social corridor, and balance the weight in time after the bottom slab structure reaches the design strength; S8, the foundation pit of the social corridor is excavated symmetrically in sections. After the foundation pit is excavated to the bottom, the bottom plate structure is constructed immediately, and a counterweight is placed on top of the bottom plate structure to control the deformation of the existing tunnel (6); S9, after the bottom plate structure and counterweight of the social corridor passage on both sides of the existing retaining piles (7) are completed, the soil between the existing retaining piles (7) is excavated as a whole to provide a skip excavation working surface; then, the foundation pit between the existing retaining piles (7) is excavated in sections along the longitudinal direction of the existing subway tunnel (6) and the retaining structure is removed, and the passage structure is constructed in a timely manner to connect with the passages on both sides, and weight is applied at the same time according to the monitoring data.

2. The combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel in operation according to claim 1 is characterized in that: In the step S1, the soil is reinforced by grouting.

3. The combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel in operation according to claim 2 is characterized in that: In step S4, the vertical shaft is constructed by using the inverted shaft wall method.

4. The combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel in operation according to claim 3 is characterized in that: In the step S4, the node connection between the capping pier (9) and the existing retaining pile (7) is performed by embedding reinforcement, and the contact surface is roughened and coated with an interface agent layer.

5. The pipe-roof combined anti-uplift reinforcement method for an existing large-span open-cut tunnel in operation according to any one of claims 1 to 4, characterized in that: The step S6 further comprises casting a coupling beam (4) outside the existing retaining pile (7), wherein the coupling beam (4) is effectively connected to the existing retaining pile (7), and the coupling beam (4) is used to connect a plurality of pull-out piles (8) together.

6. The pipe-roof combined anti-uplift reinforcement method for an existing large-span open-cut tunnel in operation according to claim 5 is characterized in that: The node connection between the existing retaining pile (7) and the connecting beam (4) is performed by embedding reinforcement, and the contact surface is roughened and coated with an interface agent layer.

7. The pipe-roof combined anti-uplift reinforcement method for an existing large-span open-cut tunnel in operation according to claim 6 is characterized in that: The length direction of the connecting beam (4) is along the extension direction of the existing tunnel (6).

8. The pipe-roof combined anti-uplift reinforcement method for an existing large-span open-cut tunnel in operation according to claim 7 is characterized in that: In step S6, the pipe curtain (5) and the connecting beam (4) are constructed simultaneously. During the construction process, the pipe curtain steel pipe passes through the existing retaining piles (7), and both ends are accurately positioned inside the connecting beam (4), forming a stable overall reinforcement structure.

9. The combined anti-uplift reinforcement method for pipe-roof of an existing large-span open-cut tunnel in operation according to claim 8 is characterized in that: In the step S6, while pouring concrete in the tube-roof steel pipe, the connecting beam (4) is also poured, using a synchronous pouring technology to coordinate and control the flow and solidification rate of concrete, thereby ensuring that the tube-roof steel pipe and the connecting beam (4) are connected as a whole.

10. The pipe-roof combined anti-uplift reinforcement method for an existing large-span open-cut tunnel in operation according to claim 9 is characterized in that: In step S6, an automated monitoring system is used to perform real-time monitoring during the jacking construction of the pipe curtain (5). The monitoring data includes the propulsion force, position and pressure of the pipe curtain, and the construction parameters are adjusted in real time to ensure the jacking accuracy.

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