TBM disassembly working condition tunnel collapse section processing method

Abstract

This application discloses a method for handling tunnel collapse sections during TBM dismantling, aiming to solve the problems of large interference from sequential processes, high risk of construction collapse, and poor structural stability after treatment in traditional methods. This method adopts a split-type step-by-step dismantling approach, decoupling and separating the TBM main unit and its supporting equipment in stable tunnel sections. The main unit is dismantled first, and the interference section is treated later, thus enabling the two operations to proceed in parallel, significantly shortening the total construction period, and avoiding the safety risks of TBM equipment being left in adverse geological sections for a long time. Through a closed-loop treatment process of pre-reinforcement and arch stabilization, grouting arch formation, and arch replacement frame by frame, the process first stops debris removal and completes the arch frame pre-reinforcement, then forms a stable load-bearing arch through double-liquid grouting, and finally replaces the encroaching arch frame frame by frame, achieving stable control of the surrounding rock throughout the construction process and fundamentally improving the safety of the operation. The combination of lightweight backfill material layered gradient backfilling, overall reinforcement of the entire arch frame, and priority lining of adverse geological sections effectively controls the secondary deformation of the initial support, forming a permanent support closed loop, and significantly improving the long-term stability and operational safety of the tunnel structure.

Description

Technical Field

[0001] This invention relates to the field of TBM construction technology in tunnel engineering, specifically to a method for handling tunnel collapse sections during TBM dismantling. Background Technology

[0002] With the rapid development of long-distance water conveyance tunnel construction in my country, open-face TBMs have been widely used in long-distance tunnel construction due to their advantages of high tunneling efficiency and minimal disturbance to the surrounding rock. After the TBM completes the tunnel breakthrough, it needs to proceed to the pre-designated receiving shaft for dismantling. The dismantling path often passes through shallow-buried, fractured surrounding rock sections with poor geological conditions that have been treated during the tunneling phase. These sections are prone to problems such as initial support arch collapse and steel arch deformation encroachment, directly affecting the normal progress of TBM dismantling operations. For this situation, the traditional treatment techniques in the industry mostly follow the methods used for treating poor geological conditions during the TBM tunneling phase. The core approach is to first completely stop dismantling operations, complete the entire process of treating the collapsed section, and then proceed with the continuous construction mode of TBM dismantling. During the treatment process, the conventional methods include slag removal and arch replacement, and grouting reinforcement behind the tunnel walls. For the collapsed arch cavity, a one-time method of backfilling and compacting with plain concrete is often used. After the treatment is completed, secondary lining construction is carried out simultaneously on the poor geological section and the rest of the tunnel.

[0003] However, the inventors discovered the following technical defects when constructing the tunnel using traditional methods: First, addressing the issues of crown collapse and steel arch deformation before dismantling the machine caused interference between the two processes, resulting in severe delays and prolonged burial of the TBM equipment in unfavorable geological conditions, posing a safety risk of the equipment being buried. Second, the slag removal operation easily disturbed the loose surrounding rock at the crown, which could easily trigger a secondary collapse. The heavy concrete backfilling could also exacerbate the structural deformation of the damaged initial support, resulting in high construction safety risks. Third, the timing of the synchronous lining could not effectively constrain the long-term deformation of the surrounding rock, leaving potential safety hazards for the later operation of the tunnel.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the background technology of this disclosure and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, this disclosure provides a method for handling tunnel collapse sections during TBM dismantling, aiming to solve the problems of large interference in the sequence of procedures, high risk of construction collapse, and poor structural stability after treatment in traditional methods.

[0006] According to one aspect of this disclosure, a method for handling tunnel collapse sections during TBM dismantling is provided, comprising the following steps: S1. A split-type step-by-step dismantling scheme is adopted, in which the TBM main unit and the supporting equipment are disconnected in a stable tunnel section without encroachment. The main unit is dismantled first by stepping to the receiving shaft, and the trailer of the supporting equipment that interferes with the encroaching arch frame is dismantled and transported later after the treatment is completed. S2. Stop the slag removal work in the section encroaching on the arch frame, temporarily support and reinforce the deformed arch frame, and add denser arch frames between the arch frames in the deformed section to form an overall stress system before shotcreting and sealing. S3. Grouting is performed to reinforce the loose material in the collapsed cavity on the back of the arch frame, so that the loose material forms a stable load-bearing arch structure; S4. Lightweight backfill material is used to backfill the collapsed cavity in layers; S5. After the backfill material strength stabilizes, replace and reinforce the arch frames that have been damaged by the deformation one by one. After each frame is replaced, spray grouting is carried out to seal it. After the S6.TBM was dismantled, the initial support arch of the entire tunnel section with poor geological conditions was reinforced as a whole. S7. After all treatment work is completed, prioritize the construction of the full-circle lining of the section with poor geological conditions, and then construct the lining of the remaining tunnel sections.

[0007] In some embodiments of this disclosure, in step S1, the TBM main unit and its supporting trailers are disconnected at a stable rock section in the track-connecting area of ​​the trapped trailer. After the main unit is disconnected from the main beam, it is moved to the receiving shaft for dismantling. The remaining supporting trailers are disconnected section by section and transported by locomotive to a nearby branch tunnel and then out of the tunnel.

[0008] In some embodiments of this disclosure, in step S2, jacks are used in conjunction with vertical I-beams to temporarily support the deformed arch frame. The jack foundations are set on the TBM, and the I-beams are welded and fixed to the deformed arch frame. The reinforced arch frame is a fully enclosed I-beam arch frame, which is welded and fixed to the original arch frame in a circumferential manner, while restoring the original structure's steel bar rows and transverse connecting bars.

[0009] In some embodiments of this disclosure, in step S3, the grouting reinforcement uses cement-water glass dual-liquid grout, which is injected through a perforated steel pipe installed in the loose body. The grouting sequence follows the principle of first the left and right sides and then the top, and first the short and then the long. Grouting is stopped when the grouting pressure reaches the set final pressure.

[0010] In some embodiments of this disclosure, before layered backfilling, backfill pipes and vent pipes are pre-embedded in the collapse cavity. The backfill pipes and vent pipes are arranged at intervals along the longitudinal direction of the tunnel and are set in multiple sets in a staggered manner in the transverse direction. After each layer of backfilling is completed and the strength of the backfill material reaches the set standard, the next layer of backfilling is carried out until the collapse cavity is filled.

[0011] In some embodiments of this disclosure, the backfill pipe and the exhaust pipe are arranged longitudinally along the tunnel, and three backfill pipes are arranged laterally. The angle between the backfill pipes on both sides and the middle backfill pipe gradually changes from 45° to 20° as the backfill layer height increases. The backfill pipes and exhaust pipes are staggered between layers, with the backfill pipe openings higher than the corresponding backfill layers, the exhaust pipe openings flush with the top surface of the corresponding backfill layers, and a safe distance is left between the exhaust pipe opening at the top layer and the top surface of the collapsed cavity.

[0012] In some embodiments of this disclosure, the collapsed cavity is backfilled in multiple layers in a gradient manner. The upper layer of backfill can only be backfilled after the compressive strength of the lower layer of backfill material reaches a set value.

[0013] In some embodiments of this disclosure, in step S5, temporary supports are set up at the bottom of the arch frame before replacement. During replacement, the arch frames that encroach on the deformation are removed one by one and replaced with brand new fully enclosed I-beam arch frames and sealed into a ring. After replacement, the arch frames, steel bar rows, and connecting bars are welded and reinforced. I-beams are used to connect adjacent arch frames in a circumferential manner at equal intervals.

[0014] In some embodiments of this disclosure, in step S6, the overall reinforcement uses I-beams to connect the arch frames of the entire section of the tunnel with poor geological conditions in a circumferential transverse direction, and adds additional densified arch frames to the deformed and offset sections of the arch frames. After the reinforcement is completed, anchor spraying support and closure are carried out.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. By adopting a split-type step-by-step dismantling method, the TBM main unit and its supporting equipment are decoupled and separated in the stable tunnel section. The main unit is dismantled first, and the interference section is dealt with later. This solves the problem of the dismantling and collapse treatment processes being sequential and interfering with each other in traditional construction. This allows the two operations to be carried out in parallel, greatly shortening the total construction period, while avoiding the safety risks of TBM equipment being left in adverse geological sections for a long time.

[0016] 2. By adopting a closed-loop treatment process of pre-reinforcement and stabilization of the arch, grouting to form the arch, and replacing the arch frame one by one, the cleaning of debris is stopped and the arch frame is pre-reinforced. Then, a stable load-bearing arch is formed by grouting with two liquids. Finally, the encroaching arch frames are replaced one by one. This solves the problem of high risk of secondary collapse caused by the disturbance of the surrounding rock during cleaning of debris and the lack of effective protection during arch replacement in the traditional process. As a result, the stability control of the surrounding rock is achieved throughout the construction process, which fundamentally improves the safety of the operation.

[0017] 3. By adopting a combination of lightweight backfill material in layered gradient backfill, overall reinforcement of the arch frame throughout the entire section, and priority lining in sections with adverse geological conditions, the problems of poor structural stability caused by large backfill load, uneven support stress, and unrestrained long-term deformation of surrounding rock in traditional methods were solved. This effectively controlled the secondary deformation of the initial support, formed a permanent support closed loop, and significantly improved the long-term stability and operational safety of the tunnel structure. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for handling tunnel collapse sections during TBM dismantling operations, as described in one embodiment of this application. Figure 2 This is a schematic diagram of temporary reinforcement of deformable arch frame in one embodiment of this application; Figure 3 This is a schematic diagram of the arch replacement reinforcement structure in one embodiment of this application; Figure 4 This is a schematic diagram of the pre-embedded pipe arrangement for layered backfilling of collapsed cavities in one embodiment of this application; Figure 5 This is a schematic diagram of the cavity layered backfilling steps in one embodiment of this application.

[0019] In the above figures, 1 is the excavation face, 2 is the arch frame, 21 is the deformed arch frame, 22 is the original arch frame, 23 is the reinforced arch frame, 3 is the TBM, 31 is the I-beam support, 32 is the jack, 4 is the I-beam connection, 5 is the steel pipe, 511 is the first layer of backfill pipe, 512 is the second layer of backfill pipe, 513 is the third layer of backfill pipe, 514 is the fourth layer of backfill pipe, 515 is the fifth layer of backfill pipe, 516 is the sixth layer of backfill pipe, 521 is the first layer of exhaust pipe, 522 is the second layer of exhaust pipe, 523 is the third layer of exhaust pipe, 524 is the fourth layer of exhaust pipe, 525 is the fifth layer of exhaust pipe, 526 is the sixth layer of exhaust pipe, 61 is cement mortar backfill, and 62 is loose muck. Detailed Implementation

[0020] In the description of this application, it should be understood that the terms "upper," "lower," "front," "rear," "top," "bottom," "inner," "outer," "vertical," and "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," etc., used in this application are used to distinguish the described objects and do not have any sequential or technical meaning. Unless otherwise specified, the terms "connection" and "linkage" used in this application include both direct and indirect connections (linkages).

[0021] Unless otherwise specified, all devices and other components involved in the following embodiments are commercially available products.

[0022] This application provides a construction method for treating adverse geological sections during the dismantling phase of an open-type TBM (Tunnel Boring Machine) system. By decoupling and separating the TBM main unit and its supporting equipment in a stable tunnel section, the main unit is dismantled first, and the interference section is treated later. A closed-loop treatment process is adopted, which includes pre-reinforcement and arch stabilization, grouting arch formation, and arch replacement frame by frame. The method also addresses the problems of large-scale interference in the sequence of procedures, high risk of construction collapse, and poor structural stability after treatment in traditional methods by using a combination of lightweight backfill material in a layered gradient, overall reinforcement of the entire arch frame, and priority lining of adverse geological sections.

[0023] To better understand the technical solution of this application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific embodiments. Example

[0024] This embodiment discloses a method for handling tunnel collapse sections under TBM dismantling conditions, specifically applied to the No. 5 tunnel project of the fourth section of the Yinchuo-Jiliao water conveyance project.

[0025] After the TBM completed its tunneling breakthrough, it needed to be dismantled by advancing towards the temporary receiving shaft. The dismantling path passed through a section of shallowly buried, strongly weathered tuff with fractured surrounding rock. This section was 30-50 meters deep, and the surrounding rock was strongly weathered tuff with highly developed joints and a fragmented, blocky structure, exhibiting extremely poor self-stability. During the TBM's dismantling process, an arch collapse occurred in this section. The collapse caused the steel arch frame 2 to deform beyond its limits, interfering with the No. 1 trailer truck attached to the TBM, preventing the TBM from advancing and forcing it to stop.

[0026] like Figure 1 To address the aforementioned engineering problems, the specific construction steps in this embodiment are as follows: S1: A split-type step-by-step dismantling scheme is adopted. The TBM main unit and the supporting equipment are disconnected in a stable tunnel section without encroachment. The main unit is dismantled first by stepping to the receiving shaft. The trailers of the supporting equipment that interfere with the encroaching arch 2 are dismantled and transported later after the treatment is completed. The disconnection position between the TBM main unit and the supporting equipment is selected in a stable surrounding rock tunnel section in the track connection area of ​​the trapped trailer. After the main unit is disconnected from the main beam, it is stepped to the receiving shaft for dismantling. The remaining supporting trailers are disconnected section by section and transported by locomotive to the adjacent branch tunnel and transported out of the tunnel.

[0027] Before construction, technical communication and confirmation were completed with the TBM manufacturer. The overall plan of split-type stepping dismantling was adopted. The disconnection point was selected in the No. 1 trailer connection area where there was no arch frame encroachment and the surrounding rock was stable. The TBM main unit and main beam were separated from the supporting system at this point. After separation, the main unit and main beam were first stepped to the temporary receiving shaft to complete the dismantling operation. Except for the No. 1 trailer which interfered with the deformed arch frame 21, the other supporting trailers were disconnected section by section. They were towed by a 25t locomotive in the tunnel to the 5-1# branch tunnel and transported out of the tunnel. The No. 1 trailer which interfered with the deformed arch frame 21 was parked in the original position in the stable tunnel section. After the arch frame encroachment section was dealt with and the tunnel clearance met the passage requirements, the dismantling and transportation out of the tunnel was carried out.

[0028] This step solves the problem of severe delays caused by the complete sequential and mutually interfering operation of dismantling and landslide handling in the traditional serial construction mode. At the same time, it avoids the risk of equipment being buried due to the TBM being left in the bad geological section for a long time. It realizes the decoupling and parallel construction of dismantling and landslide handling, which greatly shortens the total construction period and provides sufficient operating space for subsequent landslide handling operations, avoiding damage to the TBM equipment during the handling operations.

[0029] S2: As Figure 2 , Figure 3 As shown, the slag removal work on the encroaching section of the arch frame is stopped, the deformed arch frame 21 is temporarily supported and reinforced, and a denser arch frame 2323 is added between the arch frames in the deformed section to form an overall load-bearing system before shotcreting and sealing. Jacks 32 are used in conjunction with vertical I-beams to temporarily support the deformed arch frame 21. The foundation of jacks 32 is set on the TBM, and the I-beams are welded and fixed to the deformed arch frame 21. The denser arch frame 2323 is a fully enclosed I-beam arch frame, which is circumferentially welded and fixed to the original arch frame 22. At the same time, the original steel bar row and transverse connecting bars are restored.

[0030] Before commencing work, immediately stop the slag discharge and cleaning operations in the arch frame encroachment section. Any work that may disturb the loose material in the collapsed arch cavity is strictly prohibited. Use jack 32 in conjunction with vertical I-beams to temporarily support and reinforce the deformed arch frame 21. The bottom of jack 32 is placed on the hardened concrete foundation of the tunnel floor to ensure that the support foundation is stable and reliable. The top of the vertical I-beams is tightly attached to and welded to the deformed arch frame 21. Each deformed arch frame 21 is equipped with no less than two sets of symmetrical supports. Then restore the original connecting steel bar row and transverse connecting structure of the deformed section. Add a complete fully enclosed I16 I-beam arch frame between every two adjacent deformed arch frames 21. The densified arch frames 2323 are welded and fixed to the original arch frame 22 through circumferential connecting plates to form a complete overall force system. Finally, the reinforced arch frame is fully sealed with shotcrete.

[0031] This step solves the problems in traditional treatment processes where slag removal operations disturb the loose surrounding rock at the arch crown, easily leading to secondary collapses, and the lack of pre-reinforcement of the deformed arch frame 21, which can easily cause continuous deformation or even collapse. It eliminates the disturbance of the surrounding rock by slag removal operations from the source, effectively curbs the continued deformation of the deformed arch frame 21, and forms an integrated support system by densifying the arch frame 2323 and sealing it with shotcrete, which greatly improves the load-bearing capacity of the support structure and provides a safe working environment for subsequent grouting and backfilling operations.

[0032] S3: As Figure 4 As shown, the loose body in the collapsed cavity on the back of the arch frame is reinforced by grouting to form a stable load-bearing arch structure. The grouting reinforcement uses cement-water glass double liquid grout, which is injected through a perforated steel pipe installed in the loose body. The grouting sequence follows the principle of first the left and right sides and then the top, and first the short and then the long. Grouting is stopped when the grouting pressure reaches the set final pressure.

[0033] Grouting holes were drilled at the designed intervals on the arch frame. Φ42mm perforated steel pipes were then driven through these holes into the loose rock mass within the collapsed cavity on the back of the arch frame. The driving depth of the perforated steel pipes and the arrangement of the grouting holes were dynamically adjusted according to the actual extent of the loose rock mass within the collapsed cavity, ensuring that the grouting reinforcement completely covered the collapsed cavity and surrounding loose rock. A cement + water glass two-component grout was prepared using P.O42.5 ordinary Portland cement, with the water-cement ratio controlled within the range of 0.5:1 to 1:1, adjusted according to the density of the loose rock mass on site. The grouting process is adjusted in real time, and the grouting operation strictly follows the principle of grouting the left and right sides first and then the top, and grouting the short sections first and then the long sections. The loose material on both sides of the arch waist is grouted first, and then the top of the arch is grouted. Shallow grouting is completed first through short pipes, and deep grouting is completed through long pipes. The grouting pressure is monitored in real time during the grouting process. When the grouting pressure reaches 0.5MPa and remains stable, the grouting operation at that hole is ended and the grouting pipe is sealed. After the double liquid grout has finally set, the loose rock mass in the collapsed cavity forms a complete and stable load-bearing arch structure.

[0034] This step solves the problem in traditional arch replacement processes where the loose rock mass at the arch crown is not reinforced beforehand, leading to instability and collapse of the surrounding rock during replacement operations. By using dual-liquid grouting, the broken and loose rock mass is cemented into a stable load-bearing arch structure. A stable support and protection system is pre-formed in the upper part before the arch replacement operation, ensuring that the subsequent arch replacement operation is in a safe and protected state throughout, fundamentally reducing the risk of collapse during the arch replacement process. The grouting sequence used ensures the uniformity and integrity of the grouting reinforcement, avoids grouting blind spots, and improves the overall load-bearing capacity of the load-bearing arch.

[0035] S4: As Figure 5As shown, lightweight backfill material is used to backfill the collapsed cavity in layers. Before layered backfilling, backfill pipes and vent pipes are pre-embedded in the collapsed cavity. The backfill pipes and vent pipes are arranged at intervals along the longitudinal direction of the tunnel and staggered in multiple sets laterally. After each layer of backfilling is completed and the strength of the backfill material reaches the set standard, the next layer of backfilling is carried out until the collapsed cavity is full. The backfill pipes and vent pipes are arranged along the longitudinal direction of the tunnel, and three backfill pipes are arranged laterally. The angle between the backfill pipes on both sides and the middle backfill pipe gradually changes from 45° to 20° with the height of the backfill layer. The backfill pipes and vent pipes are staggered between layers. The opening of the backfill pipe is higher than the corresponding backfill layer, and the opening of the vent pipe is flush with the top surface of the corresponding backfill layer. A safety distance is left between the opening of the top vent pipe and the top surface of the collapsed cavity. The collapsed cavity is backfilled in multiple layers in a gradient manner. The next layer of backfilling can only be carried out after the compressive strength of the lower layer of backfill material reaches the set value.

[0036] After grouting reinforcement is completed and the load-bearing arch structure is stable, backfilling of the collapsed cavity is carried out. Before backfilling, the installation of pre-embedded pipes is completed. φ125mm backfill mortar pipes and φ42mm vent pipes are pre-embedded in the collapsed cavity. The vent pipes also serve as overflow pipes. The backfill pipes and vent pipes are arranged in groups at 2m intervals along the longitudinal direction of the tunnel. Each group has 3 backfill pipes arranged transversely. The angle between the backfill pipes on both sides and the middle backfill pipe gradually changes from 45° to 20° as the backfill layer height increases. The last backfill layer has a separate pre-embedded backfill pipe. The backfill pipes and vent pipes between layers are staggered. The pipe opening of the backfill pipe is 10cm higher than the design thickness of the corresponding backfill layer, and the pipe opening of the vent pipe is flush with the design top surface of the corresponding backfill layer. The vent pipe opening of the top layer is 5cm from the top surface of the collapsed cavity. The specific location and number of pre-embedded pipes are ultimately determined based on the actual situation of the collapsed cavity. The backfill material is a lightweight mixture of mortar and fly ash. The backfill material was centrally mixed at an HZS90 mixing plant outside the tunnel and transported to the work face by a 25t locomotive pulling a 12m³ rail-mounted mixer truck. Backfilling was carried out using a pump. The cavities were backfilled in six layers in a gradient manner. The first backfilling height was 0.3m from the top surface of the loose material; the second backfilling height was 0.5m from the top surface of the first layer; the third backfilling height was 0.8m from the top surface of the second layer; the fourth backfilling height was 1.0m from the top surface of the third layer; the fifth backfilling height was 1.0m from the top surface of the fourth layer; and the sixth backfilling completely filled the top surface of the cavities. Each layer of backfilling was injected through the corresponding backfill pipe. When uniform slurry flowed from the bottom of the corresponding layer's vent pipe, the backfilling of that layer was completed, and the corresponding backfill pipe opening was sealed. The next layer of backfilling was carried out only after the compressive strength of the next layer reached over 5MPa and it had the load-bearing capacity, until the cavities were completely filled.

[0037] This step addresses the problems of heavy self-weight of traditional one-time plain concrete backfill, high additional load on the damaged initial support which easily leads to secondary deformation of the initial support, and the tendency of one-time backfill to be incomplete and have cavities. The use of lightweight backfill material of mortar + fly ash significantly reduces the self-weight of the backfill body, reduces the additional load on the initial support, and avoids secondary deformation of the initial support and re-encroachment of the arch frame caused by backfilling. Through layered gradient backfilling, layer-by-layer strength control and gradient staggered arrangement of pre-embedded pipes, the backfill density of the entire collapsed cavity is ensured, backfill blind spots are avoided, the loose area of ​​the surrounding rock is effectively filled, and the long-term stability of the surrounding rock is further improved.

[0038] S5: After the backfill strength stabilizes, the intruding deformation arch frame 21 is replaced and reinforced one by one. After the replacement of a single frame is completed, shotcrete sealing is carried out. Before replacement, temporary support is set at the bottom of the arch frame. During replacement, the intruding deformation arch frame 21 is removed one by one and replaced with a brand new fully enclosed I-beam arch frame and sealed into a ring. After the replacement is completed, the arch frame, steel bar row and connecting bar are welded and reinforced. I-beams are used to connect adjacent arch frames in a circumferential manner at equal intervals.

[0039] After the backfill material in the collapsed cavity has completely set and its strength has stabilized, the replacement of the intruding deformation arch frame 21 will commence. Before replacement, temporary vertical supports will be installed at the bottom of the arch frame to be replaced to ensure the overall stability of the support system during the replacement process. A frame-by-frame replacement method will be adopted, replacing only one intruding deformation arch frame at a time. Simultaneous replacement of multiple arch frames is strictly prohibited. After removing the deformed arch frame 21, a brand new fully enclosed I16 I-beam arch frame will be immediately installed. The arch frame joints will be connected using connecting plates and high-strength bolts, forming a closed loop, according to the site conditions. The spacing between the arch frames was adjusted to be denser based on the surrounding rock conditions. After the new arch frames were installed, the arch frames were immediately reinforced by full welding with the original steel bars and connecting bars. I16 I-beams were used to weld the adjacent arch frames together in a circumferential manner at a spacing of 1m×1m to form an integral load-bearing structure. After the replacement and reinforcement of a single arch frame was completed, the entire section was immediately sealed with shotcrete. After the shotcrete strength reached the design requirements, the replacement of the next arch frame was carried out until all the arch frames 21 that had been infringed upon were replaced.

[0040] This step solves the problems of traditional arch replacement processes, such as the risk of overall instability of the support system due to simultaneous replacement of multiple arches, and insufficient load-bearing capacity of the support structure due to failure to seal the arches in time after replacement. It adopts a method of replacing arches one by one and sealing them one by one, which ensures that the overall stress and stability of the support system is maintained throughout the replacement process, avoiding the risk of instability of the support system caused by large-area replacement. Welding reinforcement and shotcrete sealing are carried out immediately after the arch is replaced, so that the new arch frame can quickly form load-bearing capacity, effectively control the deformation of the surrounding rock, and ensure the safety and treatment effect of the arch replacement operation.

[0041] S6: After the TBM is dismantled, the initial support arch frame of the entire section of the tunnel with poor geological conditions is reinforced as a whole. The overall reinforcement uses I-beams to connect the arch frame of the entire section of the tunnel with poor geological conditions in a circumferential and transverse manner. For the arch frame deformation and displacement section, additional densified arch frames 23 are added. After the reinforcement is completed, anchor spraying support and sealing are carried out.

[0042] After all TBM equipment was dismantled and transported out of the tunnel, the initial support arches of the entire section with adverse geological conditions were reinforced. I16 I-beams were used to reinforce the arches in a circumferential and transverse manner. The steel sections were arranged in a circumferential pattern at 1m×1m intervals and welded to each arch to form a unified grid-like stress system for the entire section. For locations where the arches were deformed or shifted within the tunnel section, additional denser arches 23 were added between adjacent arches and welded to reinforce them simultaneously. After all reinforcement work was completed, the entire section was sealed with overall anchor spray support, thus completing the reinforcement of the entire section with adverse geological conditions.

[0043] This step solves the problem that traditional treatments only address the localized sections of the collapsed and encroached area, and the lack of reinforcement in adjacent sections with unfavorable geological conditions can easily lead to inconsistent deformation and localized instability. By reinforcing the entire section as a whole, the support structure of the entire tunnel section with unfavorable geological conditions is made into a unified whole force system, which solves the problem of inconsistent deformation between adjacent sections after local treatment, effectively curbs the continuous deformation of the surrounding rock throughout the entire section, and significantly improves the support bearing capacity and long-term stability of the entire tunnel section.

[0044] S7: After all treatment work is completed, prioritize the construction of the full-circle lining of the section with poor geological conditions, and then construct the lining of the remaining tunnel sections.

[0045] From the start of pre-reinforcement work to the completion of secondary lining construction and complete stabilization of surrounding rock deformation, continuous monitoring and measurement were carried out throughout the entire construction process. During the arch replacement operation, the monitoring and measurement frequency was increased to once every 2 hours. The monitoring range covered both the treated and untreated sections of the tunnel. The monitoring content included tunnel arch settlement, peripheral convergence, and internal deformation of the surrounding rock. The monitoring data was analyzed on-site in real time, and regardless of the deformation amount, it was reported to the on-site duty personnel immediately. A written monitoring report was compiled daily and submitted to the project technical leader. When the monitoring data showed abnormal deformation or exceeded the warning level, the monitoring was initiated. When on duty, construction work should be stopped immediately, personnel and equipment should be evacuated to a safe area, and emergency response measures should be taken until the deformation stabilizes before resuming work. Monitoring work should continue until the secondary lining construction is completed and the surrounding rock deformation has been stable within the allowable range of the specifications for 7 consecutive days. After all the arch frame replacement, reinforcement, backfilling of collapsed sections, and TBM equipment removal work are completed, the secondary lining construction of sections with poor geological conditions should be arranged first. The lining should be formed in one go using a needle beam trolley. After the lining construction of the section with poor geological conditions is completed and the concrete strength reaches the design requirements, the lining construction of the remaining tunnel sections will be carried out.

[0046] This step addresses the problems of traditional construction methods, such as the simultaneous lining of unfavorable geological sections with other tunnel sections, the continuous deformation of the surrounding rock during the waiting period which can easily lead to initial support instability and operational risks, and the inability to predict the risk of surrounding rock deformation due to untimely monitoring and measurement during construction. By conducting high-frequency monitoring and measurement throughout the entire process, real-time control and early warning of surrounding rock deformation are achieved, ensuring the safety and controllability of the entire construction process. By prioritizing the secondary lining of unfavorable geological sections, a permanent support structure is quickly formed, realizing closed-loop control of tunnel structure stability, completely eliminating the operational safety hazards caused by long-term deformation of the surrounding rock, and significantly improving the long-term safety and durability of the tunnel structure.

[0047] Although some preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0048] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application is also intended to include such modifications and variations.

Claims

1. A method for handling tunnel collapse sections during TBM dismantling operations, characterized in that, Includes the following steps: S1. A split-type step-by-step dismantling scheme is adopted, in which the TBM main unit and the supporting equipment are disconnected in a stable tunnel section without encroachment. The main unit is dismantled first by stepping to the receiving shaft, and the trailer of the supporting equipment that interferes with the encroaching arch frame is dismantled and transported later after the treatment is completed. S2. Stop the slag removal work in the section encroaching on the arch frame, temporarily support and reinforce the deformed arch frame, and add denser arch frames between the arch frames in the deformed section to form an overall stress system before shotcreting and sealing. S3. Grouting is performed to reinforce the loose material in the collapsed cavity on the back of the arch frame, so that the loose material forms a stable load-bearing arch structure; S4. Lightweight backfill material is used to backfill the collapsed cavity in layers; S5. After the backfill material strength stabilizes, replace and reinforce the arch frames that have been damaged by the deformation one by one. After each frame is replaced, spray grouting is carried out to seal it. After the S6.TBM was dismantled, the initial support arch of the entire tunnel section with poor geological conditions was reinforced as a whole. S7. After all treatment work is completed, prioritize the construction of the full-circle lining of the section with poor geological conditions, and then construct the lining of the remaining tunnel sections.

2. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S1, the TBM main unit and its supporting trailers are disconnected at a stable rock section in the track-connecting area of ​​the trapped trailer. After the main unit is disconnected from the main beam, it is moved to the receiving shaft for dismantling. The remaining supporting trailers are disconnected section by section and transported by locomotive to a nearby branch tunnel and then out of the tunnel.

3. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S2, jacks are used in conjunction with vertical I-beams to temporarily support the deformed arch frame. The jack foundation is set on the TBM, and the I-beams are welded and fixed to the deformed arch frame. The densified arch frame is a fully enclosed I-beam arch frame, which is welded and fixed to the original arch frame in a circumferential manner, while restoring the original structure's steel bar rows and transverse connecting bars.

4. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S3, the grouting reinforcement uses cement-water glass dual-liquid grout, which is injected through a perforated steel pipe installed in the loose body. The grouting sequence follows the principle of first the left and right sides and then the top, and first the short and then the long. Grouting is stopped when the grouting pressure reaches the set final pressure.

5. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S4, before layered backfilling, backfill pipes and vent pipes are pre-embedded in the collapse cavity. The backfill pipes and vent pipes are arranged at intervals along the longitudinal direction of the tunnel and are set in multiple sets in a staggered manner in the transverse direction. After each layer of backfilling is completed and the strength of the backfill material reaches the set standard, the next layer of backfilling is carried out until the collapse cavity is filled.

6. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 5, characterized in that, The backfill pipe and the exhaust pipe are arranged longitudinally along the tunnel. Three backfill pipes are arranged laterally. The angle between the backfill pipes on both sides and the middle backfill pipe gradually changes from 45° to 20° as the backfill layer height increases. The backfill pipes and exhaust pipes are staggered between layers. The opening of the backfill pipe is higher than the corresponding backfill layer, and the opening of the exhaust pipe is flush with the top surface of the corresponding backfill layer. A safe distance is left between the opening of the top exhaust pipe and the top surface of the collapsed cavity.

7. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 5, characterized in that, The cavity is backfilled in multiple layers in a gradient manner. The upper layer of backfill can only be carried out after the compressive strength of the lower layer of backfill material reaches the set value.

8. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S5, temporary supports are set up at the bottom of the arch frame before replacement. During replacement, the arch frames that encroach on the limit and deform are removed one by one and replaced with brand new fully enclosed I-beam arch frames and closed into a ring. After the replacement is completed, the arch frames, steel bars and connecting bars are welded and reinforced. I-beams are used to connect adjacent arch frames in a circumferential manner at equal intervals.

9. The method for handling tunnel collapse sections during TBM dismantling operations according to claim 1, characterized in that, In S6, the overall reinforcement uses I-beams to connect the arch frame of the entire section of the tunnel with poor geological conditions in a circumferential and transverse manner. For the deformed and offset sections of the arch frame, additional densified arch frames are added. After the reinforcement is completed, anchor spraying support and closure are carried out.

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