A construction method of a large-section tunnel exit section by a mid-partition wall method

Abstract

The application belongs to the field of underground engineering tunnel excavation construction method, and particularly relates to a large-section tunnel exit section middle partition wall method construction method. The method comprises the following steps: S1, weak blasting excavation of a tunnel section 1; S2, lagging a tunnel section 1 by a certain distance to excavate a tunnel section 2; S3, after synchronous construction of the tunnel section 1 and the tunnel section 2 for a distance, staggered weak blasting excavation of a tunnel section 3 and a tunnel section 4; S4, under the advanced support, staggered excavation of a tunnel section 5 from the lagging tunnel section 1, weak blasting excavation of a tunnel section 6 from the lagging tunnel section 5, weak blasting excavation of a tunnel section 7 and a tunnel section 8; S5, lagging a certain distance to excavate a inverted arch, complete initial support of the inverted arch, lengthen temporary vertical supports to make the inverted arch closed into a ring; S6, segmented removal of the temporary vertical supports; construction of a side wall foundation and the inverted arch in a removal area; after initial setting of inverted arch concrete, perform inverted arch pouring and filling; S7, synchronous completion of a waterproof and drainage engineering, and one-time pouring and building of an arch wall lining.

Description

Technical Field

[0001] This invention pertains to underground engineering tunnel excavation and construction methods, specifically a method for constructing a large-section tunnel exit section using the partition wall method. Background Technology

[0002] Large-span composite section tunnels face challenges in conditions such as weak surrounding rock, shallow burial with biased pressure, and water abundance. These challenges include low rock bearing capacity, a large plastic zone, and complex and time-sensitive initial support stress. Improper handling of the spatial and temporal relationships during excavation, support, and closure can easily lead to dangerous situations such as crown subsidence, excessive peripheral convergence, arch over-arching, and local instability, inducing risks of collapse and both over- and under-excavation. In railway engineering scenarios, there are also management challenges related to blasting safety, ventilation and smoke extraction, traffic organization, and the interference of multiple construction processes. While existing projects typically establish management frameworks for quality and safety objectives and risk identification and grading, these frameworks still face limitations in adaptability and operability when applied to the diaphragm wall method in large-span sections.

[0003] Existing large-span tunnels often employ the three-stage method or the double-sidewall pilot tunnel method. However, when facing wide spans, high burial depths, or weak surrounding rock, these methods present challenges such as complex support transitions, difficulty in controlling arch and perimeter deformation, and temporary supports occupying the working face. For large-span sections, the lack of coordinated process organization and information-based dismantling control with advanced central pipe roof and arch anchor cables can easily lead to conflicts between schedule and risk control. Therefore, this paper proposes a construction method for the central diaphragm wall method at the exit section of large-span tunnels. This method combines the central diaphragm wall method with temporary cross bracing, cross-construction of central pipe roof and anchor cables, and monitoring-triggered dismantling to achieve safe, controllable, and highly efficient construction. Summary of the Invention

[0004] The purpose of this invention is to provide a construction method for the exit section of a large-section tunnel. This method utilizes a central partition wall construction system, which involves staggered construction of left and right pilot tunnels, coordinated construction of advanced central pipe roof and arch anchor cables, and monitoring and feedback to guide the timing of support removal and secondary lining. This system enables full control over the arch crown settlement, peripheral convergence, and invert arch arching.

[0005] This invention adopts the following technical solution: a method for constructing a diaphragm wall in the exit section of a large-section tunnel, comprising: S1: Construct an advanced central pipe shed and establish a monitoring and measurement system to monitor the settlement of the arch crown, the convergence of the perimeter and the stress of the steel frame. Under the reinforcement and protection of the advanced central pipe shed, excavate one section of the tunnel section with weak blasting, and complete the initial shotcrete, the construction of arch anchors and locking foot anchors, the laying of steel mesh, the erection of steel arch frame and the re-shotcrete in sequence. S2: Destroy two tunnel sections at a certain distance from the first section of the delayed tunnel section and set temporary vertical supports at the bottom of them, complete the locking anchor rods, extend the temporary vertical supports and set temporary horizontal supports; S3: After the tunnel sections 1 and 2 are constructed simultaneously for a certain distance, the left face is closed and the arch advance pipe roof and anchor cables are constructed; after the anchor cables are completed, the temporary cross bracing is dismantled in sections according to the monitored arch settlement, perimeter convergence and steel frame stress data. During the construction, the tunnel sections 3 and 4 are excavated by staggered weak blasting; the locking anchor rods are completed and the temporary vertical bracing is extended. S4: Under advanced support, 1 section of the lagging tunnel section is excavated with staggered steps, 5 sections of the lagging tunnel section are excavated with weak blasting, and 6 sections of the tunnel section are excavated with weak blasting. After a certain distance of synchronous construction, the working face is closed, and advanced pipe roof and anchor cables are installed. 7 sections of the tunnel section and 8 sections of the tunnel are excavated with weak blasting; the locking anchor rods are completed, and the temporary vertical supports are extended. S5: Delay the excavation of the invert arch by a certain distance, complete the initial support of the invert arch, and extend the temporary vertical bracing to close the invert arch into a ring. S6: Based on the monitored arch settlement, perimeter convergence and steel frame stress indicators, the temporary vertical supports are dismantled in sections; the side wall foundations and invert arch are constructed in the dismantled area; after the invert arch concrete has initially set, the invert arch is filled with concrete. S7: Analyze and monitor the arch settlement, perimeter convergence, and steel frame stress indicators to determine the timing of secondary lining construction; simultaneously complete the drainage and waterproofing works, and pour the arch wall lining in one go.

[0006] In some embodiments, the advancement of the left and right pilot tunnels in S3 and S4 adopts staggered advance control. When the advance length of one pilot tunnel exceeds the preset control length, the other pilot tunnel must be constructed in order to maintain the overall force symmetry.

[0007] In some embodiments, temporary horizontal and vertical braces are made of steel sections or steel pipes and welded or bolted to the steel arch frame, and are arranged continuously along the longitudinal direction to form a spatial truss or frame to improve lateral stiffness.

[0008] In some embodiments, prior to S4, the arch crown is constructed with advanced pipe roof and anchor cables and grouting reinforcement under the condition of closed left and right working faces. The installation is carried out in an alternating manner, from top to bottom and from inside to outside, in order to improve the overall rigidity of the arch and reduce the disturbance of excavation to the existing support, so that subsequent excavation is always within the protection range of advanced reinforcement.

[0009] In some embodiments, in S5, the invert arch construction adopts a short-segment sequential closing method, so that the invert arch concrete and the anchor bolts form a local closed loop, gradually improving the overall structure.

[0010] In some embodiments, the weak blasting drilling and blasting design satisfies the requirements of precise control of the peripheral eye layout error and a deeper cut hole depth than other holes; the arrangement and detonation sequence are executed according to the principle of "cutting first, then peripheral, then auxiliary".

[0011] In some embodiments, before removing the temporary horizontal bracing in S3 and the temporary vertical bracing in S6 in stages, the monitoring indicators of arch crown settlement, perimeter convergence, and steel frame stress are used as the entry conditions for dismantling. Before dismantling, it should be confirmed that the cumulative value of arch crown settlement and the cumulative value of perimeter convergence are both controlled within the allowable range, and the deformation rate has obviously converged for 3 consecutive days or more. The stress of the steel frame does not exceed the design allowable value and tends to stabilize. On this basis, the dismantling is carried out in the order of first restoring the arch wall force system and then unloading the temporary components in stages. If any indicator exceeds the limit or the trend of change is not stable, the corresponding temporary vertical bracing shall not be dismantled.

[0012] In some embodiments, in S7, an integral steel formwork trolley or a crawler formwork trolley is used for continuous pouring to reduce secondary disturbance to the initial support.

[0013] In some embodiments, the monitoring and measurement system adopts a deployment and feedback mechanism of "point-area combination and hierarchical early warning": monitoring sections are set up at the center line of the tunnel arch, the left and right side wall shoulders and waist, the top and bottom of the temporary vertical supports, and the middle of the invert arch, with one monitoring section set up every 5m.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention is applicable to the excavation of large-section tunnel exit sections. Through the progressive segmentation and box-forming of the pilot tunnel, arch, and invert, combined with temporary horizontal and vertical bracing, the cross-section maintains multiple stress paths throughout construction, significantly reducing the risk of arch collapse and sidewall instability. Support removal and adjustment are based on monitoring and measurement, effectively controlling surface settlement and tunnel convergence, making it suitable for deformation-sensitive areas. The construction organization is clear and efficient, linking pre-support, pilot tunnel excavation, arch excavation, invert construction, and secondary lining closure in a series, facilitating mechanized and continuous operations, reducing repeated erection and dismantling and unnecessary waiting, and improving construction efficiency. This method allows for flexible adjustment of temporary support density, pre-support form, and support removal rhythm according to different surrounding rock grades, burial depths, and environmental conditions, meeting high safety reserve requirements while avoiding cost waste caused by excessive reinforcement. Therefore, this method has the advantages of ensuring structural stability, easy deformation control, strong adaptability, and reduced construction costs. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the construction process of the method of the present invention; Figure 2 This is a diagram showing the division of tunnel sections in the diaphragm wall construction method applicable to the exit section of large-section tunnels according to the present invention; Figure 3 This invention relates to tunnel lining constructed using the diaphragm wall method in the exit section of large-section tunnels; Figure 4 Diagram showing the excavation and temporary cross bracing method of this invention; Figure 5This is a diagram showing the right half of the excavation process at the closed left face of the excavation site according to the method of the present invention. Figure 6 This is a diagram illustrating the backfilling of the invert arch and the construction of the secondary lining using the method of this invention. In the diagram: 1-Tunnel section 1; 2-Tunnel section 2; 3-Tunnel section 3; 4-Tunnel section 4; 5-Tunnel section 5; 6-Tunnel section 6; 7-Tunnel section 7; 8-Tunnel section 8; 9-Tunnel invert arch; 10-Temporary vertical brace; 11-Temporary horizontal brace; 12-Secondary lining; 13-Anchor cable; 14-Advanced central pipe shed; 15-Arch anchor bolt; 16-Locking foot anchor bolt. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figures 1-3 As shown, the tunnel cross-section is divided into nine parts: tunnel cross-section 1, tunnel cross-section 2, tunnel cross-section 3, tunnel cross-section 4, tunnel cross-section 5, tunnel cross-section 6, tunnel cross-section 7, tunnel cross-section 8, and tunnel invert arch 9. During construction, temporary vertical supports 10, temporary horizontal supports 11, anchor cables 13, advanced central pipe shed 14, arch anchor rods 15, and locking foot anchor rods 16 are applied. Finally, secondary lining 12 is poured.

[0018] like Figure 2 As shown, this invention adopts a 9-part division principle of "left and right tunnels, upper and lower layers, arch first then wall, and invert arch as the finishing section," dividing the cross-section of the large-section tunnel exit section into 8 excavation pilot tunnels + 1 invert arch unit. The spatial location, construction sequence, and stress division of each unit are clearly defined, as follows: Tunnel Section 1: Upper Left Pilot Pit (Left Half of the Arch Crown), located in the upper left quadrant of the tunnel section, covering the area from the left side of the arch crown centerline to the left wall shoulder area. It is the first excavation unit and mainly bears the surrounding rock load on the left half of the arch crown.

[0019] The tunnel has two sections: the left middle pilot tunnel (upper left wall section) is located directly below section 1, from the left wall shoulder to the wall waist area, forming the upper left load-bearing unit with section 1, and bearing the surrounding rock load of the upper left wall section.

[0020] The tunnel has three sections: the lower left pilot tunnel (lower middle part of the left wall), located directly below section 2, in the area from the waist to the upper part of the left wall, bearing the load of the surrounding rock in the lower middle part of the left wall.

[0021] The tunnel cross-section consists of four sections: the left bottom pilot tunnel (left wall foot area), located directly below section 3, is the transition area connecting the left arch foot and the invert arch, bearing the concentrated load of the left arch foot and providing a foundation for the closure of the invert arch.

[0022] The tunnel section consists of five parts: the upper right pilot tunnel (right half of the arch crown), located in the upper right quadrant of the tunnel section, is symmetrically arranged with part 1, covering the area from the right side of the arch crown centerline to the right wall shoulder, and bearing the surrounding rock load on the right half of the arch crown.

[0023] The tunnel has six sections: the right middle pilot tunnel (upper right wall section), located directly below section 5, in the area from the right wall shoulder to the wall waist, is symmetrical to section 2 and bears the surrounding rock load of the upper right wall section.

[0024] The tunnel has 7 sections: the lower right pilot tunnel (lower middle part of the right wall), located directly below section 6, in the area from the waist to the upper part of the right wall, symmetrical to section 3, and bearing the surrounding rock load of the lower middle part of the right wall.

[0025] The tunnel cross-section consists of eight sections: the right bottom pilot tunnel (right wall foot area), located directly below section 7, is the transition area connecting the right arch foot and the invert arch, symmetrical to section 4, and bears the concentrated load of the right arch foot.

[0026] Tunnel invert arch (9 sections): Located at the bottom of the tunnel cross section, it is an arc-shaped structural section that spans the bottom of the left and right walls. It connects to the bottom of sections 4 and 8 above and to the tunnel foundation below. It bears the reaction force of the surrounding rock at the bottom and together with the secondary lining, it forms a closed force ring with the entire cross section.

[0027] like Figure 1 As shown, a method for constructing a diaphragm wall in the exit section of a large-section tunnel includes: S1: Before construction, advance geological forecasting is carried out, advance middle pipe shed 14 is constructed and a corresponding monitoring and measurement system is established to monitor the settlement of the arch crown, the convergence of the perimeter and the stress of the steel frame. Under the reinforcement and protection of advance middle pipe shed 14, the tunnel section 1 is excavated by weak blasting, and the initial shotcrete, arch anchor bolts 15 and foot anchor bolts 16 are completed in sequence, the steel mesh is laid, the steel arch frame is erected and the shotcrete is repeated.

[0028] S2: Demolish tunnel section 1 at a distance of 5m from tunnel section 2 and install temporary vertical supports 11, complete the locking anchor rods 16, extend the temporary vertical supports 10 and install temporary horizontal supports 11.

[0029] S3: After 6m of simultaneous construction of tunnel section 1 and tunnel section 2, the left working face is closed and the arch advance pipe shed 14 and arch anchor cable 13 are constructed; after the anchor cable 13 is completed, the temporary cross bracing 11 is dismantled in sections according to the analysis of monitoring and measurement data. During the construction, tunnel section 3 and tunnel section 4 are excavated by weak blasting at staggered levels; the locking anchor rod 16 is completed and the temporary vertical bracing 10 is extended.

[0030] S4: Similarly, under the advance support, the tunnel section 1 is 10m-15m behind the tunnel section 5, the tunnel section 5 is 5m behind the tunnel section 6, the tunnel section 6 is 5m behind the tunnel section 6, and the tunnel face is closed after 6m of synchronous construction. The advance middle pipe shed 14 and anchor cable 13 are constructed, the tunnel section 7 and tunnel section 8 are 7 and 8 are 8, the tunnel section 7 is 7, and the tunnel section 8 is 8; the locking anchor rod 16 is completed, and the temporary vertical support 10 is extended.

[0031] S5: Delay the excavation of invert arch 9 by a certain distance, complete the initial support of invert arch 9, and extend the temporary vertical brace 10 to close the invert arch into a ring.

[0032] S6: Based on the analysis of monitoring and measurement data, the temporary vertical supports were dismantled in 10 sections; the side wall foundation and invert arch were constructed in the dismantled area; after the invert arch concrete had initially set, the invert arch 9 was filled with concrete.

[0033] S7: Based on monitoring and measurement analysis, determine the timing of secondary lining 12 construction; simultaneously complete the drainage and waterproofing works, and pour the arch wall lining in one go.

[0034] In this embodiment, the monitoring and measurement system adopts a "point-to-surface combined, graded early warning" deployment and feedback mechanism: monitoring sections are set up at the center line of the tunnel arch, the left and right sidewall arch shoulders and waists, the top and bottom of the temporary vertical supports, and the middle of the invert arch, with one monitoring section set up every 5m; the monitoring frequency of arch settlement and surrounding convergence is once every 2 hours for 1-7 days after excavation, once every 6 hours for 7-15 days, and once a day after 15 days; a three-level early warning threshold is set. When the monitoring value reaches the first-level early warning, the monitoring frequency is increased; when the second-level early warning is reached, excavation is suspended and the surrounding support is reinforced; when the third-level early warning is reached, personnel are immediately evacuated and the emergency reinforcement plan is activated.

[0035] In this embodiment, the tunnel cross-section is divided into nine parts from top to bottom: tunnel cross-section 1 to tunnel cross-section 8 and tunnel invert arch 9. Tunnel cross-sections 1 to 4 mainly bear the load of the arch crown and the upper and middle surrounding rock, while tunnel cross-sections 5 to 8 bear the load of the sidewalls and the middle waist area. The invert arch 9 and the secondary lining 12 together form a closed force-bearing system. The various parts are continuously arranged with temporary vertical supports 10 and temporary horizontal supports 11. Advanced central pipe sheds 14, arch anchors 15, and prestressed anchor cables 13 are installed in the arch. Locking anchors 16 are densely installed in the arch foot and sidewall area, thus forming a joint support system of "advanced central pipe shed + anchor cables and anchors + steel arch frame shotcrete + temporary support", which significantly improves the overall stiffness and stability during the construction of large-span cross-sections.

[0036] In this embodiment, the excavation and pouring of the tunnel invert 9 are carried out in a phased, flowing manner with short-segment closure: the invert 9 is excavated in stages after lagging behind the upper section by a certain distance, the initial support of the invert 9 is completed in a timely manner and the temporary vertical bracing 10 is extended, so that the invert 9 and the foundation of the side walls on both sides form a local closed loop as much as possible, shortening the duration of the initial support being subjected to unilateral bending moment; then, based on the monitoring and measurement data, the temporary vertical bracing 10 and the temporary horizontal bracing 11 are removed in stages and grades, and the side wall foundation and invert 9 are filled in the removal area first. After the concrete strength of the invert 9 reaches the requirements and the monitoring indicators such as the settlement of the arch top, the peripheral convergence and the internal force of the steel frame are stable, the timing of the construction of the secondary lining 12 is determined, and the drainage system and the secondary lining of the arch wall are poured together in one go, thereby further improving the structural integrity and durability.

[0037] The layout parameters of the pre-construction pipe roof 14, arch anchor cable 13, anchor bolt 16, and temporary support system can be flexibly adjusted according to different surrounding rock grades, burial depth conditions, and environmental sensitivity. When the surrounding rock grade reaches level III or above, the monitored deformation is less than 70% of the reserved deformation, and the surrounding environment is not sensitive, such as when existing buildings (structures) are more than 3 times the tunnel diameter away from the tunnel and the surface settlement value is less than 70% of the allowable value, the longitudinal spacing of the temporary vertical brace 10 and temporary horizontal brace 11 can be appropriately increased, and local graded dismantling of the support can be implemented in advance to improve construction efficiency. When the surrounding rock is broken, groundwater is abundant, or there are existing buildings or structures nearby, the layout of the pre-construction pipe roof 14 and prestressed anchor cable 13 should be densified, the advance per cycle should be appropriately reduced, and the timing of dismantling the temporary support should be delayed. If necessary, grouting reinforcement or shotcrete thickness can be added to achieve full control of the deformation of the large-section tunnel exit section under the premise of ensuring safety reserves.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for constructing a large-section tunnel exit section using the diaphragm wall method, characterized in that, include: S1: Construct an advanced central pipe shed (14) and establish a monitoring and measurement system to monitor the settlement of the arch, the convergence of the perimeter and the stress of the steel frame. Under the reinforcement and protection of the advanced central pipe shed (14), a section of the tunnel cross-section (1) is excavated by weak blasting. The initial spraying, construction of arch anchor rods (15) and foot anchor rods (16), laying of steel mesh, erection of steel arch frame and re-spraying are completed in sequence. S2: Delayed tunnel section 1 (1) Excavate tunnel section 2 (2) at a certain distance and set temporary vertical support (11) at its bottom, complete the locking anchor rod (16), extend the temporary vertical support (10) and set temporary horizontal support (11). S3: After the tunnel section 1 (1) and tunnel section 2 (2) are constructed simultaneously for a certain distance, the left face is closed and the arch advance pipe shed (14) and anchor cable (13) are constructed. After the anchor cable (13) is completed, the temporary cross bracing (11) is dismantled in sections according to the monitored arch settlement, perimeter convergence and steel frame stress data. During the construction, the tunnel section 3 (3) and tunnel section 4 (4) are excavated by staggered weak blasting. The locking anchor rod (16) is completed and the temporary vertical bracing (10) is extended. S4: Under advanced support, the tunnel section 1 (1) is delayed, the tunnel section 5 (5) is excavated at the staggered platform, the tunnel section 5 (5) is delayed, and the tunnel section 6 (6) is excavated by weak blasting. After a certain distance of synchronous construction, the tunnel face is closed, and the advanced middle pipe shed (14) and anchor cable (13) are constructed. The tunnel section 7 (7) and the tunnel section 8 (8) are excavated by weak blasting. The locking anchor rod (16) is completed, and the temporary vertical support (10) is extended. S5: Delay the excavation of the invert arch (9) by a certain distance, complete the initial support of the invert arch (9), and extend the temporary vertical support (10) to close the invert arch into a ring; S6: Based on the monitored arch settlement, perimeter convergence and steel frame stress index, the temporary vertical support (10) was dismantled in sections; the side wall foundation and invert arch were constructed in the dismantled area; after the invert arch concrete had initially set, the invert arch (9) was poured and filled. S7: Analyze the monitored arch settlement, perimeter convergence and steel frame stress index to determine the timing of secondary lining (12); simultaneously complete the drainage project and pour the arch wall lining in one go.

2. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, characterized in that, The advancement of the left and right guide tunnels in S3 and S4 adopts staggered advance control. When the advance length of one guide tunnel exceeds the preset control length, the other guide tunnel must follow up with the construction to maintain the overall force symmetry.

3. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, characterized in that, The temporary horizontal bracing (10) and vertical bracing (11) are made of steel sections or steel pipes and welded or bolted to the steel arch frame, and are arranged continuously along the longitudinal direction to form a spatial truss or frame to improve the lateral stiffness.

4. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, characterized in that, Before S4, the arch top advanced pipe roof (14) and anchor cable (13) and grouting reinforcement are concentrated under the closed left and right working faces. The alternating arrangement, the order of first up and then down, and first inside and then outside is adopted to improve the overall rigidity of the arch and reduce the disturbance of excavation to the existing support, so that the subsequent excavation is always within the advanced reinforcement protection range.

5. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1 or 4, characterized in that, In S5, the construction of the invert arch (9) adopts a short-segment sequential closing method, so that the invert arch concrete and the anchor bolt (16) form a local closed loop, gradually improving the overall structure.

6. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, characterized in that: The weak blasting drilling and blasting design ensures precise control of the peripheral eye layout error and a deeper cut hole than other holes; the layout and detonation sequence is executed according to the principle of "cutting first, then peripheral, then auxiliary".

7. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, characterized in that: Before removing the temporary horizontal bracing (10) in S3 and the temporary vertical bracing (11) in S6, the monitoring indicators of arch settlement, perimeter convergence and steel frame stress shall be used as the conditions for removal. Before removal, it shall be confirmed that the cumulative value of arch settlement and the cumulative value of perimeter convergence are controlled within the allowable range, and the deformation rate has obviously converged for 3 consecutive days or more. The stress of the steel frame shall not exceed the design allowable value and tend to be stable. On this basis, the removal shall be carried out in the order of first restoring the arch wall force system and then unloading the temporary components in sections. If any indicator exceeds the limit or the trend of change is not stable, the corresponding temporary vertical bracing (11) shall not be removed.

8. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1 or 7, characterized in that: In S7, continuous pouring is carried out using an integral steel formwork trolley or a crawler formwork trolley to reduce secondary disturbance to the initial support.

9. The method for constructing a large-section tunnel exit section using the diaphragm wall method according to claim 1, 7, or 8, characterized in that, The monitoring and measurement system adopts a deployment and feedback mechanism of "point-area combination and hierarchical early warning": monitoring sections are set up at the center line of the tunnel arch, the left and right side wall shoulders and waist, the top and bottom of the temporary vertical supports, and the middle of the invert arch, with one monitoring section set up every 5m.

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