Super-long seabed shield tunneling and secondary lining synchronous construction method

Abstract

The invention relates to the field of subsea tunnel construction, in particular to a super-long subsea shield tunneling and secondary lining synchronous construction method which mainly comprises the steps that S1, shield tunneling is conducted; s2, duct piece installation; s3, placing the box culvert in place; s4, box culvert splicing; s5, a secondary lining trolley is in place; s6, continuous construction is conducted along the tunnel design axis; the method comprises six main steps in total, in the shield construction process of the subsea tunnel, especially the ultra-long subsea tunnel, field staff only need to conduct construction according to the construction steps, continuous, efficient and safe construction of the ultra-long subsea tunnel can be achieved, the construction steps and logic are clearly defined in the whole process, and the construction efficiency is improved. According to the construction method, the construction process can be effectively guided, meanwhile, the technical method adopted in the construction method is combined with various parameters in the construction process for construction, risks caused by hydrogeology in the construction process of the super-long subsea tunnel can be reduced to a certain degree, and safe construction and operation of the super-long subsea tunnel are ensured.

Description

Technical Field

[0001] This application relates to the field of submarine tunnel construction, and in particular to a method for simultaneous excavation and secondary lining construction of ultra-long submarine shield tunnels. Background Technology

[0002] With the rapid development of my country's economy, infrastructure construction has also progressed rapidly. The expansion of highway and railway networks has spurred the construction of numerous highway and railway tunnels. Currently, China has become the country with the largest scale, the most tunnels, and the fastest development speed in the world. The construction of high-speed rail networks, urban subways, and highways has spurred a large number of tunnel projects. In the process of tunnel construction, crossing rivers and seas is inevitable, meaning that the construction of undersea tunnels is unavoidable.

[0003] As mega-projects traversing waterways, undersea tunnels face far greater challenges than land-based tunnels. The main problems include: geological and hydrological difficulties, construction technology bottlenecks, operational risks, the vulnerability of lifeline systems, and immense ecological and cost pressures. Therefore, solving these various challenges has always been a hot and difficult issue in the field of tunnel construction.

[0004] In related technologies, the operational and cost risks of subsea tunnels have been largely resolved. However, due to the highly variable hydrogeological conditions, subsea tunnels simultaneously encounter problems such as fault zones, unfavorable geological formations, bias pressure, seabed caves, ultra-high water pressure environments, and seawater corrosivity. Especially for ultra-long subsea tunnels, the likelihood of encountering these geological problems simultaneously is far greater than for ordinary subsea tunnels, significantly increasing the construction risks. Therefore, there is an urgent need for a construction method to mitigate the hydrogeological risks posed during the construction of ultra-long subsea tunnels, ensuring their safe construction and operation. Summary of the Invention

[0005] To reduce the risks posed by hydrogeology during the construction of ultra-long undersea tunnels and to ensure the safe construction and operation of ultra-long undersea tunnels, this application provides a method for simultaneous construction of tunneling and secondary lining of ultra-long undersea shield tunnels.

[0006] This application provides a method for simultaneous excavation and secondary lining construction of ultra-long undersea shield tunnels, employing the following technical solution: A method for simultaneous excavation and secondary lining construction of an ultra-long undersea shield tunnel includes the following steps: S1. Shield tunneling: using a tunnel boring machine to excavate a tunnel; S2. Segment installation: During tunnel boring machine (TBM) excavation, segment installation is carried out under the protection of the tail of the TBM. S3. Box culvert in place: transport the prefabricated box culvert to the location where the secondary lining is to be constructed, and then construct it simultaneously with the secondary lining. S4. Box culvert splicing: As the tunnel is steadily constructed, adjacent box culverts are spliced ​​together. S5. The secondary lining trolley is positioned. After the distance from the shield tunnel face meets the safety distance requirements, the secondary lining trolley is positioned. S6. Continue construction along the tunnel design axis, repeating steps S1-S5 above, until the tunnel is completed.

[0007] By adopting the above technical solution, when constructing an ultra-long undersea shield tunnel, the process of shield tunneling → segment installation → box culvert transportation and placement → box culvert splicing → secondary lining trolley placement (after safety distance) → repeating until breakthrough can achieve continuous, efficient and safe construction of ultra-long undersea tunnels. The process of this application clearly defines the construction steps and logic, which can effectively guide the construction. At the same time, the setting of synchronous construction can effectively shorten the overall construction period of ultra-long tunnels and effectively avoid the long-cycle serial construction mode of traditional methods, which first completes the shield tunneling, then the secondary lining, and finally the internal structure. Furthermore, the use of prefabricated box culverts for transportation and placement and splicing in the tunnel improves construction efficiency, ensures component quality, and realizes the assembly line operation of internal structure construction, tunnel excavation, and secondary lining construction. The construction method of this application reduces the risks brought by hydrogeology during the construction of ultra-long undersea tunnels to a certain extent, ensuring the safe construction and operation of ultra-long undersea tunnels.

[0008] Optionally, in step S5, the safety distance is no less than 200m from the shield tunnel face. At the same time, before the secondary lining construction, a three-dimensional scanner is used to check the tunnel clearance. By matching the line and checking the ellipticity, the minimum point of each secondary lining thickness is found to ensure that the secondary lining thickness is no less than 30cm.

[0009] By adopting the above technical solutions, a safe distance threshold of 200m was clearly defined, providing specific and operable safety standards for construction and balancing construction efficiency and safety risks. At the same time, the introduction of three-dimensional scanning technology for tunnel clearance verification and alignment fitting greatly improved the efficiency and accuracy of tunnel forming precision measurement. Furthermore, by verifying the ellipticity, the potential thinnest point of each lining layer was identified, ensuring that even the weakest point of the lining concrete could meet the design thickness requirement of ≥30cm. This significantly improved the overall waterproofness, load-bearing capacity, and durability of the lining structure, which is crucial for undersea tunnels.

[0010] Optionally, step S4 includes: S401. Clean up debris. Workers remove debris from the assembly area and the bottom of the connecting surface of the previous box culvert. S402, Box Culvert Treatment: Workers attach a 1cm thick nitrile cork rubber sheet to one side of the box culvert along the large curve direction to achieve a fit with the axis of the formed tunnel. S403. Horizontal lifting of box culvert: Drive the flatbed truck carrying the box culvert to a suitable position, adjust the height of the flatbed truck so that the box culvert crane can grab the box culvert. After the height adjustment is completed, lower and move the spreader to below the box culvert. After initial alignment, raise the spreader so that it is just locked onto the box culvert. After it is in place, the proximity switch will give a signal. The staff can tighten the clamps and lift the box culvert. After the box culvert touches the limit switch, the box culvert can be moved horizontally. S404. Move the box culvert crane forward. After grabbing the box culvert, move the box culvert crane forward to the assembly position and confirm that there is enough space for the box culvert to be erected. S405. Connect the box culverts, adjust the height of the box culverts and the spacing between them and the previous box culvert, and then connect and assemble them.

[0011] By adopting the above technical solution, the steps for assembling box culverts are given in detail, enabling standardized and streamlined operations during the box culvert assembly process.

[0012] Optionally, after step S405, once the secondary lining construction begins, grouting is performed on the grouting holes of the box culvert top slab. Before grouting, the joints of the box culvert are sealed with sealing material. Grout is injected from one end until it overflows from the other end of the hole, at which point grouting is stopped.

[0013] By adopting the above technical solution, the gap between the top slab and the secondary lining of the box culvert can be effectively filled with grout, eliminating voids, ensuring the stability of the structure, and forming an important waterproof barrier.

[0014] Optionally, the bottom of the box culvert is fixed with mortar, and the top joint is filled with polysulfide sealant.

[0015] By adopting the above technical solution, mortar fills the gap at the bottom of the box culvert, providing a uniform and stable supporting foundation for the box culvert, preventing settlement and uneven stress. Polysulfide sealant has excellent elasticity, adhesion, water resistance and durability, providing a long-term reliable flexible waterproof seal for the top joint of the box culvert, and adapting to minor deformation of the structure.

[0016] Optionally, during the assembly of the box culvert, every 10m, a 50cm long PE foam strip needs to be inserted into the longitudinal joint of the two ring segments, and then a 20cm wide geotextile is laid at the joint. A single-component chloroprene-phenolic adhesive is used as the adhesive to form a circumferential drainage channel for the segments.

[0017] By adopting the above technical solutions, an orderly drainage system can be constructed, thereby effectively diverting and draining leaking water.

[0018] Optionally, between steps S3 and S4, the internal structure is constructed using a synchronous construction method, which includes: The construction of the precast integral box culvert, the bottom filling of the curved slab with cement mortar, the bottom backfill layer of cast-in-place reinforced concrete, the cast-in-place secondary lining, the cast-in-place leveling layer, the cast-in-place trench, the stairs above the cast-in-place invert arch, the evacuation opening of the box culvert, the stairs below the cast-in-place invert arch, the steps at the maintenance door, and the steps of the track surface layer shall be carried out in the above order.

[0019] By adopting the above technical solutions, the internal structure of the tunnel (box culvert, stairs, trenches, leveling layer, etc.) and the secondary lining construction are closely connected and carried out in time and space, which greatly optimizes the construction organization and significantly reduces the construction period of the internal structure of ultra-long tunnels.

[0020] Optionally, the secondary lining is poured using a window-type formwork pouring system. In this system, a feed pump pipe is installed at the center line of the top platform of the lining trolley, along with a movable main hopper and multiple diversion pump pipes. The diversion pump pipes are arranged sequentially on both sides of the unloading trolley track at the center line of the top platform of the trolley. The discharge pipe of the main hopper and the diversion pump pipes are connected by a quick connection method. The main hopper is connected to the pump pipes from bottom to top for pouring.

[0021] By adopting the above technical solution, the problem of large-section secondary lining casting is effectively solved, and multi-point material distribution and uniform casting can be achieved.

[0022] Optionally, the secondary lining arch wall also needs to be poured. The secondary lining arch wall is poured using a step-by-step pouring method. During the pouring process, the concrete is poured from the lower end to the upper end in a step-by-step pouring manner. The concrete is poured in through the formwork window, from the lower end to the upper end, and in symmetrical layers. During the pouring process, the height difference between the concrete on both sides is less than 1m.

[0023] By adopting the above technical solutions, it is possible to control the pouring speed and lateral pressure, thereby effectively preventing formwork bulging and slippage. The skip-window pouring combined with layered operation can effectively utilize heat dissipation, reduce temperature cracks, and allow each layer of concrete sufficient time to settle, thereby reducing the generation of shrinkage cracks.

[0024] Optionally, the secondary lining arch is constructed using radial formwork. Multiple grouting holes are set along the longitudinal direction of the lining trolley at the center line of the arch. Fixed flanges for grouting are installed. Active powder concrete grouting pipes are pre-embedded before concrete pouring. Grouting is carried out from the pre-embedded grouting pipes in a timely manner after the concrete pouring is completed.

[0025] By adopting the above technical solutions, the problem of voids caused by bleeding, shrinkage, and insufficient compaction of the tunnel secondary lining arch concrete can be effectively solved.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. When constructing an ultra-long undersea shield tunnel, following the S1→S2→S3→S4→S5→S6 of this application to guide construction enables continuous, efficient, and safe construction of the ultra-long undersea tunnel. The process of this application clearly defines the construction steps and logic, which can effectively guide construction. At the same time, the synchronous construction setting can effectively shorten the overall construction period of the ultra-long tunnel and effectively avoid the long-cycle serial construction mode of the traditional method of completing the shield tunnel first, then the secondary lining, and finally the internal structure. Furthermore, the use of prefabricated box culverts for transportation and placement, and splicing within the tunnel, improves construction efficiency, ensures component quality, and realizes the assembly line operation of internal structure construction, tunnel excavation, and secondary lining construction. The construction method of this application reduces the risks brought by hydrogeology during the construction of ultra-long undersea tunnels to a certain extent, ensuring the safe construction and operation of ultra-long undersea tunnels. 2. By refining step S4 into five more detailed steps, such as S401, clearing debris, S402, box culvert processing, S403, horizontally lifting the box culvert, S404, moving the box culvert crane forward, and S405, connecting the box culvert, the operation can be standardized and streamlined during the box culvert splicing process. 3. The window-type casting system effectively solves the problem of casting large-section secondary linings, enabling multi-point material distribution and uniform casting. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the construction process of a method for simultaneous excavation and secondary lining of an ultra-long undersea shield tunnel according to an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the precast box culvert in a method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to an embodiment of this application.

[0029] Figure 3 This is a layout diagram (along the tunneling direction) before pipeline relocation in a method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to an embodiment of this application.

[0030] Figure 4 This is a diagram showing the layout of the inner pipes of the secondary lining trolley in a method for simultaneous excavation and secondary lining construction of an ultra-long undersea shield tunnel according to an embodiment of this application (along the excavation direction). Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention belong to the present invention.

[0032] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this application. However, those skilled in the art will recognize that the technical solutions of this application can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this application.

[0033] like Figures 1-4 This application discloses a method for simultaneous construction of tunneling and secondary lining of an ultra-long undersea shield tunnel, mainly including six main steps: S1, shield tunneling; S2, segment installation; S3, box culvert positioning; S4, box culvert splicing; S5, secondary lining trolley positioning; and S6, continuous construction along the tunnel design axis. In the process of shield tunneling for undersea tunnels, especially ultra-long undersea tunnels, on-site personnel only need to follow the construction steps outlined in this application to achieve continuous, efficient, and safe construction of ultra-long undersea tunnels. The entire process clearly defines the construction steps and logic, effectively guiding the construction process. Furthermore, the technological methods used in this application, combined with various parameters during construction, can reduce the risks posed by hydrogeology during the construction of ultra-long undersea tunnels to a certain extent, ensuring the safe construction and operation of ultra-long undersea tunnels.

[0034] Specifically, S1, shield tunneling, involves using a tunnel boring machine (TBM) to excavate the tunnel. Furthermore, in this embodiment, the TBM needs to excavate over 6,000 meters cumulatively, traversing weakly weathered tuff, weakly weathered tuff, composite strata of soft upper and hard lower layers, silt, silty clay, and fine sand. For those skilled in the art, how to implement the shield tunneling, and how to construct the remaining structures within the tunnel after the shield tunneling, are all unimaginable.

[0035] Specifically, S2, segment installation: During tunnel boring machine (TBM) excavation, segment installation is carried out under the protection of the TBM's tail section. In this embodiment, 10 equal-sized TBM segments with an outer diameter of 14m, an inner diameter of 12.8m, a thickness of 60cm, and a strength of C60P15 are used as tunnel support.

[0036] Specifically, S3 and the box culvert are in place, and the prefabricated box culvert is transported to the location where the secondary lining is to be constructed, so that it can be constructed simultaneously with the secondary lining.

[0037] Furthermore, in this embodiment, the prefabricated box culvert is prefabricated in the factory and then transported to the construction site for construction. In other embodiments, depending on different production environments, on-site prefabrication can also be carried out according to design requirements, which is also a preferred embodiment of this application.

[0038] Meanwhile, between steps S3 and S4, the internal structure is constructed using a synchronous construction method, which includes: The construction of the precast integral box culvert, the bottom filling of the curved slab with cement mortar, the bottom backfill layer of cast-in-place reinforced concrete, the cast-in-place secondary lining, the cast-in-place leveling layer, the cast-in-place trench, the stairs above the cast-in-place invert arch, the evacuation opening of the box culvert, the stairs below the cast-in-place invert arch, the steps at the maintenance door, and the steps of the track surface layer shall be carried out in the above order.

[0039] This simultaneous construction method tightly integrates and overlaps the construction of internal tunnel structures, such as box culverts, staircases, trenches, and leveling layers, with the secondary lining construction in both time and space. This greatly optimizes construction organization and significantly reduces the construction period for the internal structures of ultra-long tunnels. Furthermore, the approach, from bottom filling to secondary lining, and then to the superstructure and details, conforms to the objective laws and spatial logic of structural construction, ensuring that the lower structure provides support for the upper structure and avoiding interference. This effectively improves space utilization efficiency, allowing for the orderly and simultaneous construction of multiple internal structures within the limited space of the tunnel, maximizing the use of working faces and construction time.

[0040] Furthermore, refer to Figure 3 Regarding the synchronous construction method of this application, it possesses a key logistics organization design method. The specific logistics organization design method is as follows: before the short sidewall is poured, the mud pipe and circulating water pipe are fixed to the sidewall of the tunnel segment using supports. A 2m diameter ventilation duct supplies air from inside the box culvert to the working face. At this point, the road width is 7m to meet the passing requirements. Traffic lights are installed at the inclined shaft entrance and intersections. Simultaneously, vehicle collision avoidance facilities, voice announcements, and speed limit signs are installed inside the tunnel to ensure vehicle transportation and personnel safety. The specific pipeline layout is as follows: Figure 3 As shown.

[0041] Furthermore, refer to Figure 4 After the low sidewall is poured, the mud pipe and circulating water pipe will be moved to the top of the box culvert (spare pipes will be laid on the box culvert in advance, and the flanges will be switched from the top of the segment to the bottom via a single bend during shield tunneling shifts). After the pipe relocation, the clear width of the lane will be 7m, with a one-way lane width of 3m and a double-sided pedestrian walkway width of 0.5m. This section meets the requirements for safe transportation and separation of pedestrians and vehicles in both directions. After the secondary lining formwork trolley is installed, the clear space inside the tunnel will be 5.58m. The space is relatively small, and vehicles are strictly prohibited from passing within 30m in front of and behind the secondary lining trolley.

[0042] Specifically, for S4, the box culverts are spliced ​​together as the tunnel is steadily constructed.

[0043] Furthermore, step S4 includes: S401. Clean up debris. Workers remove debris from the assembly area and the bottom of the connecting surface of the previous box culvert. S402, Box Culvert Treatment: Workers attach a 1cm thick nitrile cork rubber sheet to one side of the box culvert along the large curve direction to achieve a fit with the axis of the formed tunnel. S403. Horizontal lifting of the box culvert: Drive the flatbed truck carrying the box culvert to a suitable position, adjust the height of the flatbed truck so that the box culvert crane can grab the box culvert. After the height is adjusted, lower and move the spreader to below the box culvert. After initial alignment, raise the spreader so that it is just locked onto the box culvert. Once in place, the proximity switch will give a signal, and the workers can tighten the clamps and lift the box culvert. After the box culvert touches the limit switch, the box culvert can be moved horizontally. S404. Move the box culvert crane forward. After grabbing the box culvert, move the box culvert crane forward to the assembly position and confirm that there is enough space for the box culvert to be erected. S405. Connect the box culverts, adjust the height of the box culverts and the spacing between them and the previous box culvert, and then connect and assemble them.

[0044] By setting steps S401-S405, firstly, step S401, cleaning debris, ensures the cleanliness of the connection surface, thereby guaranteeing the assembly quality and joint sealing effect; secondly, step S402, box culvert treatment, involves pasting a 1cm thick nitrile cork rubber sheet along the large curve direction, utilizing the material's elastic deformation capability to allow the rigid box culvert to better fit the actual tunnel axis, reducing stress concentration or joint looseness caused by rigid assembly; thirdly, step S403, horizontal lifting of the box culvert, achieves automated and precise lifting, with the application of flatbed truck height adjustment, proximity switches, and limit switches, significantly improving the automation level, positioning accuracy, and operational safety of box culvert lifting, reducing manual intervention and errors; and fourthly, steps S404, moving the box culvert crane forward, and S405, connecting the box culvert, effectively standardize the assembly process, making the box culvert assembly process standardized, orderly, and efficient.

[0045] Furthermore, after step S405, once the secondary lining construction begins, grouting is performed on the grouting holes of the box culvert top slab. Before grouting, the joints of the box culvert are sealed with sealing material. Grout is injected from one end until it overflows from the other end of the hole, at which point grouting is stopped.

[0046] First, grouting fills the gaps between the box culvert top slab and the tunnel segments / secondary lining, eliminating voids, ensuring structural integrity, and forming a crucial waterproof barrier. Second, it is essential to seal the joints before grouting, adhering to the principle of "grouting one end and stopping when the other overflows." This is the most reliable method to ensure the grout completely fills the entire predetermined gap, effectively preventing incomplete grouting or the formation of air pockets. Finally, after the grout hardens, tightly connecting the box culvert to the superstructure effectively improves the structural stress state and enhances overall stability.

[0047] Meanwhile, the bottom of the box culvert was fixed with mortar, and the top joints were filled with polysulfide sealant.

[0048] For the bottom of the box culvert, mortar fills the gaps to provide a uniform and stable supporting foundation, preventing settlement and uneven stress. For the top of the box culvert, mortar fills the gaps to provide a uniform and stable supporting foundation, preventing settlement and uneven stress. The rigid mortar fixation at the bottom combined with the flexible sealant at the top forms a complete box culvert fixing and waterproofing system.

[0049] Furthermore, during the assembly of the box culvert, every 10m, a 50cm long PE foam strip needs to be inserted into the longitudinal joint of the two ring segments, and then a 20cm wide geotextile is laid at the joint. A single-component chloroprene-phenolic adhesive is used as the adhesive to form a circumferential drainage channel for the segments.

[0050] This specific design, derived from extensive practical experience, represents a superior implementation. This design constructs an orderly drainage system, explicitly requiring the installation of water-conducting layers at the circumferential and longitudinal joints of the tunnel segments, forming a continuous, circumferential drainage channel behind the lining. This channel effectively collects seepage water behind the lining and systematically guides it to the drainage ditch at the bottom of the tunnel, preventing water pressure buildup and structural erosion—crucial for the long-term waterproofing of the subsea tunnel. Regarding material selection, PE foam strips provide support and water conduction; geotextile is permeable and prevents silt blockage of the channels; and chloroprene-phenolic adhesive provides reliable bonding and durability. Finally, the specific design parameters enable a more systematic and standardized layout of the drainage channels, facilitating future engineering applications.

[0051] Meanwhile, in this embodiment, a special process is also used for the pouring of the secondary lining. Specifically, the secondary lining is poured using a window-type casting system. In this system, a feed pump pipe is installed at the center line of the top platform of the lining trolley, along with a movable main hopper and multiple diversion pump pipes. The diversion pump pipes are arranged sequentially on both sides of the unloading trolley track at the center line of the top platform of the trolley. The discharge pipe of the main hopper and the diversion pump pipes are connected by a quick connection method, and the main hopper is sequentially connected to the pump pipes from bottom to top for pouring.

[0052] The above methods effectively solved the challenges of large-section secondary lining pouring in undersea shield tunnels, addressing issues such as easy segregation and cold joints in the concrete. Simultaneously, multiple branch pump pipes allow concrete to be simultaneously or sequentially fed through multiple windows on the top of the lining trolley formwork, avoiding aggregate segregation and concrete accumulation caused by a single feeding point. The movable main hopper and quick-connect design facilitate rapid switching of the material placement position between different branch pump pipes, improving placement efficiency. Finally, the requirement that "the main hopper be connected sequentially to pump pipes from bottom to top for pouring" ensures that concrete fills from the lower window and gradually advances upwards, facilitating air removal, reducing voids, ensuring the density of the arch concrete, and effectively preventing arch voids.

[0053] Furthermore, it is necessary to pour concrete for the secondary lining arch wall. The secondary lining arch wall is poured using a step-by-step pouring method. During the pouring process, the concrete is poured from the lower end to the upper end in a step-by-step pouring manner. The concrete is poured in through the formwork window, from the lower end to the upper end, and in symmetrical layers. During the pouring process, the height difference between the concrete on both sides is less than 1m.

[0054] In the above methods, layered pouring effectively controls the lateral pressure of concrete on the formwork, preventing bulging or displacement of the formwork. The "skip-window" pouring technique combined with layered pouring facilitates heat dissipation, reducing temperature cracks while allowing each layer of concrete sufficient time to settle, minimizing shrinkage cracks. Specifically, the requirement for symmetrical layered pouring with a height difference of less than 1 meter on both sides strictly controls the concrete pressure difference on both sides of the formwork, greatly reducing the risk of displacement or deformation due to asymmetrical loads and ensuring accurate structural dimensions. Finally, pouring from the lower end to the higher end conforms to the flow characteristics of concrete, facilitating the removal of bleeding water and air bubbles, and ensuring the quality of the pouring.

[0055] Furthermore, special construction methods are required for the arch. The secondary lining arch is constructed using radial formwork. Multiple grouting holes are set along the longitudinal direction of the lining trolley formwork arch centerline, and grouting fixing flanges are installed. Before pouring concrete, active powder concrete grouting pipes are pre-embedded, and grouting is carried out from the pre-embedded grouting pipes in a timely manner after the concrete is poured.

[0056] The radial formwork construction method described above effectively solves the problem of voids in the tunnel secondary lining arch concrete caused by bleeding, shrinkage, and insufficient compaction. It is a direct and efficient measure. Grouting before formwork removal allows the grout to fill all voids more effectively under the constraint of the formwork, resulting in a significantly better effect than grouting after formwork removal. Pre-embedded grouting pipes, combined with the grouting holes on the fixed flanges of the formwork, provide a reliable and precise grouting channel, ensuring the grout can be injected into the target voids. Furthermore, the timing of grouting is carefully controlled; in this embodiment, it is performed before or after the initial setting of the concrete. At this time, the grout can more easily penetrate and fill tiny voids, resulting in better bonding with the concrete and optimal compaction. This effectively fills the arch, preventing voids and significantly improving the overall load-bearing capacity, compactness, and waterproofing performance of the secondary lining structure.

[0057] Specifically, S5 and the secondary lining trolley are positioned. Once the distance from the shield tunnel face meets the safety distance requirements, the secondary lining trolley is put into place.

[0058] Furthermore, the safe distance referred to in step S5 means a distance of not less than 200m from the tunnel face. Clarifying the 200m safe distance threshold provides a specific and operable safety standard for construction, balancing construction efficiency and safety risks. It should also be noted that, in addition to the safe distance limitation, in this embodiment, the average horizontal convergence over the past 7 days is less than 0.2mm / d, and the arch settlement velocity is less than 0.15mm / d.

[0059] Furthermore, before secondary lining construction, a 3D scanner is used to verify the tunnel clearance. By fitting the alignment and checking the ellipticity, the minimum thickness point for each section of the secondary lining is identified, ensuring a thickness of no less than 30cm. Ellipticity checking identifies the potential thinnest point for each section, ensuring that even the weakest point of the secondary lining concrete meets the design thickness requirement of ≥30cm. This significantly improves the overall waterproofing, load-bearing capacity, and durability of the secondary lining structure, which is crucial for undersea tunnels. Simultaneously, identifying and addressing clearance deviations and ellipticity issues in advance effectively prevents quality accidents such as insufficient secondary lining thickness or even tunnel penetration due to tunnel deformation. It is also important to note that after the tunnel trolley is positioned, timely re-measurement is conducted, ensuring that the maximum allowable deviation of the internal clearance axis and the allowable settlement within the shield tunnel structure is 150mm, as required by the drawings.

[0060] S6. Continue construction along the tunnel design axis, repeating steps S1-S5 above, until the tunnel is completed.

[0061] The implementation principle of the method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining in this application embodiment is as follows: When constructing an ultra-long undersea shield tunnel, the method follows the steps of shield excavation → segment installation → secondary lining trolley positioning → box culvert transportation and positioning → box culvert splicing → repeating until breakthrough. This enables continuous, efficient, and safe construction of ultra-long undersea tunnels. The process of this application clearly defines the construction steps and logic, which can effectively guide construction. At the same time, the simultaneous construction setting can effectively shorten the overall construction period of ultra-long tunnels and effectively avoid the long-cycle serial construction mode of traditional methods, which involves completing the shield first, then the secondary lining, and finally the internal structure. Furthermore, the use of prefabricated box culverts for transportation and positioning, and splicing within the tunnel, improves construction efficiency, ensures component quality, and realizes the streamlined operation of internal structure construction, tunnel excavation, and secondary lining construction. The construction method of this application reduces the risks brought by hydrogeology during the construction of ultra-long undersea tunnels to a certain extent, ensuring the safe construction and operation of ultra-long undersea tunnels.

[0062] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining, characterized in that, Includes the following steps: S1. Shield tunneling: using a tunnel boring machine to excavate a tunnel; S2. Segment installation: During tunnel boring machine (TBM) excavation, segment installation is carried out under the protection of the tail of the TBM. S3. Box culvert in place: transport the prefabricated box culvert to the location where the secondary lining is to be constructed, and then construct it simultaneously with the secondary lining. S4. Box culvert splicing: As the tunnel is steadily constructed, adjacent box culverts are spliced ​​together. S5. The secondary lining trolley is positioned. After the distance from the shield tunnel face meets the safety distance requirements, the secondary lining trolley is positioned. S6. Continue construction along the tunnel design axis, repeating steps S1-S5 above, until the tunnel is completed.

2. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, In step S5, the safe distance is no less than 200m from the shield tunnel face. At the same time, before the secondary lining construction, a 3D scanner is used to check the tunnel clearance. By matching the line and checking the ellipticity, the minimum point of each secondary lining thickness is found to ensure that the secondary lining thickness is no less than 30cm.

3. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, Step S4 includes: S401. Clean up debris. Workers remove debris from the assembly area and the bottom of the connecting surface of the previous box culvert. S402, Box Culvert Treatment: Workers attach a 1cm thick nitrile cork rubber sheet to one side of the box culvert along the large curve direction to achieve a fit with the axis of the formed tunnel. S403. Horizontal lifting of box culvert: Drive the flatbed truck carrying the box culvert to a suitable position, adjust the height of the flatbed truck so that the box culvert crane can grab the box culvert. After the height adjustment is completed, lower and move the spreader to below the box culvert. After initial alignment, raise the spreader so that it is just locked onto the box culvert. After it is in place, the proximity switch will give a signal. The staff can tighten the clamps and lift the box culvert. After the box culvert touches the limit switch, the box culvert can be moved horizontally. S404. Move the box culvert crane forward. After grabbing the box culvert, move the box culvert crane forward to the assembly position and confirm that there is enough space for the box culvert to be erected. S405. Connect the box culverts, adjust the height of the box culverts and the spacing between them and the previous box culvert, and then connect and assemble them.

4. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 3, characterized in that, After step S405, once the secondary lining construction begins, grouting is performed on the grouting holes of the box culvert top slab. Before grouting, the joints of the box culvert are sealed with sealing material. Grout is injected from one end until it overflows from the other end of the hole, at which point grouting is stopped.

5. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 3, characterized in that, The bottom of the box culvert was fixed with mortar, and the top joints were filled with polysulfide sealant.

6. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 3, characterized in that, During the assembly of the box culvert, every 10m, a 50cm long PE foam strip needs to be inserted into the longitudinal joint of the two ring segments, and then a 20cm wide geotextile is laid at the ring joint. A single-component chloroprene-phenolic adhesive is used as the adhesive to form a circumferential drainage channel for the segments.

7. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, Between steps S3 and S4, the internal structure is constructed using a synchronous construction method, which includes: The construction of the precast integral box culvert, the bottom filling of the curved slab with cement mortar, the bottom backfill layer of cast-in-place reinforced concrete, the cast-in-place secondary lining, the cast-in-place leveling layer, the cast-in-place trench, the stairs above the cast-in-place invert arch, the evacuation opening of the box culvert, the stairs below the cast-in-place invert arch, the steps at the maintenance door, and the steps of the track surface layer shall be carried out in the above order.

8. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, The secondary lining is poured using a window-type formwork pouring system. In this system, a feed pump pipe is installed at the center line of the top platform of the lining trolley, along with a movable main hopper and multiple diversion pump pipes. The diversion pump pipes are arranged sequentially on both sides of the unloading trolley track at the center line of the top platform of the trolley. The discharge pipe of the main hopper and the diversion pump pipes are connected by a quick connection method. The main hopper is connected to the pump pipes from bottom to top for pouring.

9. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, The secondary lining arch wall also needs to be poured. The secondary lining arch wall is poured using a step-by-step pouring method. During the pouring process, the concrete is poured from the lower end to the upper end in a step-by-step pouring manner. The concrete is poured in through the formwork window, from the lower end to the upper end, and in symmetrical layers. During the pouring process, the height difference between the concrete on both sides is less than 1m.

10. The method for simultaneous construction of ultra-long undersea shield tunnel excavation and secondary lining according to claim 1, characterized in that, The secondary lining arch is constructed using radial formwork. Multiple grouting holes are set along the longitudinal direction of the lining trolley at the center line of the arch. Fixed flanges for grouting are installed. Active powder concrete grouting pipes are pre-embedded before concrete pouring. Grouting is carried out from the pre-embedded grouting pipes in a timely manner after the concrete is poured.

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