Construction method for underneath passing of operating railway through shield

Abstract

The invention relates to the field of subway construction, in particular to a construction method for underneath passing of a shield through an operating railway. The construction method for underneath passing the operating railway through the shield comprises the four steps of S1, S2, S3 and S4 to guide construction, when a subway line is constructed to pass through the existing operating railway, the shield is controlled and adjusted through the step S1, then tunneling is conducted, meanwhile, a main station building and an elevated waiting building in the railway are reinforced under the guidance of the step S2, and the construction process is completed. The railway track is reinforced under the guidance of S3, and in the whole process, the whole process is monitored through 24-hour construction monitoring in S4, so that normal operation of an existing operating railway and normal construction of a subway line are ensured, precious experience is provided for subsequent engineering, and the construction efficiency is improved. The method has the effect that the probability of occurrence of the problems such as cracking deformation of an original station building, platform settlement and railway line settlement which endanger safe operation of an operating railway can be reduced in the process that the subway line passes through the existing operating railway during construction.

Description

Technical Field

[0001] This application relates to the field of subway construction, and particularly to a construction method for a shield tunneling under an operating railway. Background Art

[0002] Nowadays, subway construction has become an important means to meet the needs of urban planning and transportation development. As the core transportation hub of a city, the surrounding areas of existing operating railways are often included in the construction scope of subway lines. Laying subway lines at the location of operating railways can not only effectively optimize the urban traffic network, but also improve the transfer efficiency and overall travel conditions.

[0003] In the planning of the main rail transit lines in some large and medium-sized cities, the relevant lines often undertake the responsibility of connecting the main administrative regions and important railway hubs, and build an efficient urban comprehensive transportation system through connection with multiple existing railway stations. However, many existing railway stations were built earlier and have undergone multiple expansions or repairs, and their foundation structures have limited anti-deformation capabilities. When traditional shield tunneling method is used for subway construction to cross such areas, problems such as cracking of the station building structure, settlement of the platform, and deformation of the track are likely to occur. In severe cases, it may even affect the safety and continuity of railway operation.

[0004] Especially in the sections of old railway hubs and areas where existing transportation arteries densely converge, the problems of structural disturbance control and deformation risk management faced during the shield tunnel crossing construction have become an important bottleneck restricting the progress of urban rail transit construction. Therefore, there is an urgent need to provide a construction method for a shield tunneling under an operating railway with strong adaptability, controllable construction risks, and minimized influence of structural disturbance to ensure construction safety and achieve efficient connection between the new and old transportation systems. Summary of the Invention

[0005] In order to reduce the probability of occurrence of problems that endanger the safe operation of the operating railway, such as cracking and deformation of the original station building, settlement of the platform, and settlement of the railway line, during the process of subway line construction crossing an existing operating railway, this application provides a construction method for a shield tunneling under an operating railway.

[0006] A construction method for a shield tunneling under an operating railway of this application adopts the following technical solutions: A construction method for a shield tunneling under an operating railway includes the following steps: S1. Conduct shield control and shield tunneling. The shield control includes equipment selection, muck improvement, tunneling pressure control, and muck output control to adapt to the geological conditions of the strata where the operating railway is located, and various grouting methods are also included during the process of S1; S2. Reinforce the main station building and the elevated waiting hall. The reinforcement of the main station building includes setting a connecting beam with a size of 0.8m×0.5m between the existing foundations of the main station building. The reinforcement of the elevated waiting hall includes setting a connecting beam between the pile tops of the existing pile foundations of the elevated waiting hall, and pouring a concrete raft in the middle range of the connecting beam to form an integral structure of the connecting beam plus the concrete raft. S3. Reinforce the railway tracks. The reinforcement of the railway tracks includes grouting the subgrade of the arrival and departure tracks and setting 3-5-3 rail fastening for the passing tracks. In the 3-5-3 rail fastening for the passing tracks, the rail joints need to be staggered by more than 1m. The rail fastening is connected to the sleepers below with U-shaped bolts, and the rail fastening uses rails with a weight of 50kg / m. S4. Conduct 24-hour construction monitoring. The monitoring process runs through S1-S3. The 24-hour construction monitoring includes Beidou GNSS monitoring, static level monitoring, and manual inspection monitoring.

[0007] By adopting the above technical solutions, the subway line effectively and safely crosses the existing special-class operating railway. The smooth implementation of the construction method of this application shows that under the guidance of S1, S2, S3, and S4, the shield tunnel can pass under the existing old station building and track lines at a short distance. At the same time, the settlement of the station building foundation and track can be controlled within a safe range, and it also provides valuable experience for subsequent projects. This application has the effect of reducing the probability of problems that endanger the safe operation of the operating railway, such as the cracking and deformation of the original station building, the settlement of the platform, and the settlement of the railway line, during the construction of the subway line crossing the existing operating railway.

[0008] Optionally, the equipment selection includes the selection of the cutter head and cutters of the shield machine, and the selection of the cutter head and cutters is based on the formation conditions. The muck improvement includes adding dispersed foam, and the dispersed foam needs to be added in front of the cutter head. The control of the tunneling pressure and the muck output is to adjust the shield tunneling pressure and the muck output in real time by combining theoretical calculations with the actual situation on site.

[0009] By adopting the above technical solutions, the equipment selection can make the equipment more in line with the construction requirements, ensuring the stability during the construction process. The muck improvement ensures the fluidity of the muck, making it more convenient for the shield. The control of the tunneling pressure can effectively control the settlement during the shield tunneling process.

[0010] Optionally, the various grouting methods in S1 during shield tunneling include Claymore grouting, synchronous grouting, and secondary grouting, and the grouting sequence is strictly controlled according to the construction organization design process.

[0011] By adopting the above technical solutions, the Kerr effect grouting enables the shield tunneling process to have fluidity. At the same time, the Kerr effect slurry has a certain bearing capacity after filling, which can effectively provide support. The synchronous grouting ensures the effective filling of the construction voids, and at the same time can ensure that the segment structure will not be deformed or damaged due to grouting. The secondary grouting can effectively control the settlement caused by material shrinkage.

[0012] Optionally, in the Kerr effect grouting in S1, the Kerr effect is composed of calcium-based clay minerals, cellulose derivatives, colloid stabilizers and dispersants. The Kerr effect grouting is to pump the Kerr effect slurry and the plastic strength conditioner to a designated position through a pipe, and then mix the two liquids into a high-viscosity plastic colloid, and then inject it through the radial holes.

[0013] By adopting the above technical solutions, the specially formulated Kerr effect can ensure that the slurry is not easily diluted by water, and the viscosity does not change with time, thus effectively controlling the settlement during the shield tunneling process.

[0014] Optionally, the slurry ratio used in the synchronous grouting in S1 is water:cement:yellow sand:fly ash:bentonite = 40:23:80:35:7. The secondary grouting in S1 uses a double-fluid slurry, and the double-fluid slurry is injected deeply 8 rings behind the segment shield tail of the shield machine to reinforce the soil within 3 m of the shield. And the slurry is centered on controlling the slump, and the amount of water used in the slurry ratio is adjusted in real time according to the moisture content of the sand.

[0015] By adopting the above technical solutions, it effectively ensures the effective filling of the construction voids, and at the same time can ensure that the segment structure will not be deformed or damaged due to grouting.

[0016] Optionally, in S2, the outer diameter of the shield of the interval tunnel is 6.2 m, the center distance is 17.2 m, and the top of the interval tunnel is about 16 m away from the bottom of the foundation of the station building. The foundation forms include independent foundations and strip foundations. A connecting beam with a size of 0.8 m × 0.5 m is set between independent foundations, and a connecting beam with a size of 0.8 m × 0.5 m is set between strip foundations to disperse stress.

[0017] By adopting the above technical solutions, the stress concentration phenomenon of the original foundations of the main station building and the elevated waiting hall is effectively reduced, and further the settlement of the pile foundation after being disturbed is reduced.

[0018] Optionally, in S2, the elevated waiting hall adopts a column-expanded base pile foundation. The pile diameter is 1.3 - 2.3 m, the expanded base diameter is 2 - 3.4 m, the pile length is 15 m, and the minimum distance between the top of the shield tunnel and the bottom of the pile foundation is about 4 m. The elevated waiting hall adopts an enlarged head pile foundation, and the closest distance between the pile foundation and the tunnel is only 4 m. A connecting beam with a relatively large stiffness is added to the pile top, and a concrete raft is poured in the middle range of the connecting beam to form a way of connecting the structural columns as a whole by the strengthened beam plus the raft to disperse stress.

[0019] By adopting the above technical solution, the structural columns are connected as a whole in the form of a reinforced beam plus a raft slab. After being disturbed in a local area, the stress is dispersed in a timely manner, effectively controlling the settlement of local points.

[0020] Optionally, in step S3, a three-dimensional finite element model needs to be established first to simulate and analyze the shield tunnel passing under a group of railway lines, and then reinforcement measures are carried out. During the reinforcement process, the number of splicing joints should be minimized as much as possible, and the joints should be far away from the lines.

[0021] By adopting the above technical solution, a three-dimensional finite element model is established to simulate and analyze the shield tunnel passing under a group of railway lines and the setting of rail fastening reinforcement, effectively improving the stability of the railway tracks.

[0022] Optionally, in step S4, the Beidou GNSS monitoring includes installing a Beidou GNSS monitoring system at the corresponding roof position of the load-bearing columns on the roof of the main station building to monitor the displacement changes in real time. One reference station is arranged in the Beidou monitoring network, and the point is selected at a straight-line distance of more than 610 meters. The GNSS reference station point uses an expansion bolt to fix a forced centering base, and a Beidou GNSS base station antenna is installed on the base. An antenna protection cover is fixed above the support base, and a Beidou receiver and a Beidou antenna device are integrated in the protection cover.

[0023] By adopting the above technical solution, the normal operation of the operating railway is further ensured.

[0024] Optionally, during the static level monitoring in step S4, a static level system needs to be used. The static level system includes a liquid storage tank and a collection box. A liquid connection pipe is connected to the bottom of the liquid storage tank, and a ventilation pipe is arranged at one end of the liquid storage tank away from the liquid connection pipe. The other ends of the liquid connection pipe and the ventilation pipe are both connected to the observation points, and a communication power line is also connected to the observation points, and the other end of the communication power line is connected to the collection box, and multiple observation points are arranged.

[0025] By adopting the above technical solution, the effective monitoring of the entire construction process can be realized, thereby ensuring that the subway line can effectively cross the existing operating railway.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. Guide the construction through the four steps of S1, S2, S3, and S4. When the subway line needs to cross an existing operating railway, first, it can effectively adjust and control the shield machine. Secondly, by cooperating with the reinforcement of the main station building and the elevated waiting hall, and the reinforcement of the railway tracks, it can minimize the settlement of the existing operating railway during the shield tunneling process. At the same time, construction monitoring is carried out 24 hours a day, which can effectively ensure the safety of the shield process and also ensure the normal operation of the operating railway, providing valuable experience for subsequent projects. This application has the effect of reducing the probability of problems that endanger the safe operation of the operating railway, such as cracking and deformation of the original station building, platform settlement, and railway line settlement, during the construction of the subway line crossing the existing operating railway; 2. The combined action of KnitCote grouting, synchronous grouting, and secondary grouting effectively guarantees the bearing capacity during the shield tunneling process and can also effectively reduce the settlement of the existing operating railway building complex; 3. The setting of the connecting beam and the concrete raft slab poured in the middle range of the connecting beam effectively disperses the stress generated by local disturbances, and thus effectively controls the settlement of local points. Description of the Drawings

[0027] Figure 1 It is a design schematic diagram for strengthening the independent foundation of the main station building in step S2 of a shield tunneling method under an operating railway in an embodiment of the present application.

[0028] Figure 2 It is a design schematic diagram for strengthening the pile foundation of the elevated waiting hall in step S2 of a shield tunneling method under an operating railway in an embodiment of the present application.

[0029] Figure 3 It is a schematic diagram of the 3-5-3 rail fastening setting for the passing track in step S3 of a shield tunneling method under an operating railway in an embodiment of the present application. Detailed Embodiments

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the present invention.

[0031] In addition, the described features, structures, or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present application. However, those skilled in the art will realize that the technical solutions of the present application can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. may be adopted. In other cases, well-known methods, devices, implementations, or operations are not shown or described in detail to avoid obscuring aspects of the present application.

[0032] As Figures 1-3 , the present application provides a construction method for a shield tunneling under an operating railway, including: a total of four steps, namely S1, S2, S3, and S4, to guide the construction. When the subway line is constructed through the existing operating railway, first, the shield is controlled and adjusted through the steps of S1, and then tunneling is carried out. At the same time, under the guidance of S2, the main station building and the elevated waiting hall are reinforced, and under the guidance of S3, the railway tracks are reinforced simultaneously. Throughout the process, the entire process is monitored through the 24-hour construction monitoring of S4, thereby ensuring the normal operation of the existing operating railway and the normal construction of the subway line, and providing valuable experience for subsequent projects. The present application has the effect of reducing the probability of problems such as cracking and deformation of the original station building, settlement of the platform, and settlement of the railway line, which endanger the safe operation of the operating railway, during the process of the subway line construction passing through the existing operating railway.

[0033] Specifically, regarding S1, shield control and shield tunneling are carried out.

[0034] The shield control in S1 includes equipment selection, muck improvement, tunneling pressure control, and muck output control to adapt to the geological conditions of the formation where the operating railway is located.

[0035] Equipment selection can make the equipment more in line with the construction requirements, ensuring the stability during the construction process. Muck improvement ensures the fluidity of the muck, making it more convenient to control the shield and the tunneling pressure, and effectively controlling the settlement during the shield tunneling process.

[0036] Here, a specific explanation needs to be made for equipment selection. In the present application, the strata to be traversed are mainly Quaternary silt and clay, and a composite earth pressure balance shield machine can meet the construction requirements. To ensure the reliability of the equipment during the crossing process, it is required to use a relatively new shield machine. The cutter head of the shield machine should be selected as a highly wear-resistant and strengthened cutter head and cutters according to the formation conditions, and the cutter head opening ratio should be reasonably determined to avoid the occurrence of cutter head mud cake and cause large formation deformation. Before the shield starts, a comprehensive inspection of the shield cutter head and cutters should be carried out, and the starting operation can be carried out only after confirming good performance, and a targeted emergency plan should be formulated.

[0037] Specific explanations need to be made for muck improvement, tunneling pressure control, and muck output control. In this application, the main strata passed through in the scope of crossing the operating railway are the Quaternary silty clay strata. The most important problem in shield tunneling in such strata is the formation of mud cakes in front of the cutter head. After the formation of mud cakes on the cutter head, the soil mass in front of the excavation face cannot be discharged in time, and the shield jacking pressure increases, which has a great impact on controlling the uplift and settlement of the strata. To ensure that the muck has good fluidity, when the shield machine is tunneling in the full-section clay strata, dispersed foam and water need to be added in front of the cutter head for muck improvement to ensure the fluidity of the muck. The greater the shield cutting pressure, the smaller the settlement of the ground surface and the upper structure. However, if the cutting pressure is too small, the soil mass on the shield excavation face will become unstable and collapse, resulting in excessive settlement of the ground surface above and damage to the upper structure; if the cutting pressure is too large, the ground surface in front of the upper part of the excavation face will bulge, and the final settlement will be large, which will also damage the upper structure and affect the safety and stability of the structure. Therefore, the tunneling pressure suitable for this project should be calculated through formulas in combination with the actual engineering situation. In actual construction, a shield tunneling test section is set up, and the shield tunneling pressure and muck output are adjusted in real time by combining theoretical calculations with the actual situation on site. This measure can effectively control the settlement generated in the first and second stages during the shield tunneling process.

[0038] In S1, shield tunneling includes Knife-Clay Effect grouting, synchronous grouting, and secondary grouting.

[0039] Specific explanations need to be made for the Knife-Clay Effect grouting process adopted during the shield tunneling. The main reason for the settlement generated in the third stage of shield tunneling construction is that the excavation diameter of the cutter head is larger than the diameter of the shield body, resulting in gaps during the construction process outside the shield body. The soil mass is prone to subsidence under its own weight. To reduce the disturbance of shield construction to the soil mass above the shield body, filling materials in the gaps outside the shield body in time can effectively control the settlement. The filling materials need to have the following characteristics: (1) The materials have good fluidity and can effectively wrap the outer shell of the shield body; (2) After the materials are filled, they have a certain bearing capacity to support the subsidence of the soil mass; (3) The materials have a certain waterproof property and are not easily diluted by water; (4) The materials need to have a certain lubricity to reduce the frictional resistance between the shield machine shell and the soil mass and ensure the smooth tunneling of the shield.

[0040] The Knife-Clay Effect grouting makes the tunneling process of the shield have fluidity, and at the same time, the Knife-Clay Effect slurry has a certain bearing capacity after being filled, which can effectively provide support. Synchronous grouting ensures the effective filling of the construction gap and can also ensure that the segment structure will not be deformed and damaged due to grouting. Secondary grouting can effectively control the settlement caused by material shrinkage.

[0041] In the Knife-Clay Effect grouting in S1, the Knife-Clay Effect is composed of calcium-based clay minerals, cellulose derivatives, colloid stabilizers, and dispersants.

[0042] The Knit-Crete is composed of synthetic calcium-based clay minerals, cellulose derivatives, colloid stabilizers, and dispersants. The Knit-Crete method is a new method in which two liquids, namely, a high-concentration muddy water material and a plastic strength regulator (i.e., water glass), are respectively pumped to a designated position through pipes, and then the two liquids are mixed in an appropriate proportion into a high-viscosity plastic gel, and then injected through radial holes. The mixed flowing plastic gel is not easily diluted by water, and its viscosity does not change with time. The Knit-Crete meets the above conditions. When the Knit-Crete is injected radially into the shield body during shield tunneling construction, the settlement in the third stage of the shield is effectively controlled.

[0043] In S1, the slurry ratio used for synchronous grouting is water:cement:yellow sand:fly ash:bentonite = 40:23:80:35:7.

[0044] Here, a specific explanation of strengthening synchronous grouting is required. The main reason for the settlement in the fourth stage of shield tunneling construction is that the diameter of the shield body is larger than the diameter of the segment, resulting in a gap around the segment after the shield body is pulled out of the segment, and the soil mass is prone to subsidence under the action of its own weight. During the propulsion process, it is required to carry out synchronous grouting in a timely manner, and the filling material should have the following characteristics: (1) The material has good fluidity and can effectively fill the gaps around the segments; (2) The material has a certain bearing capacity after filling to support the subsidence of the soil mass; (3) The material has a certain waterproof property and is not easily diluted by water, and the shrinkage after consolidation of the material is small. The construction unit extracts on-site formation soil samples based on past project experience and conducts special proportioning tests on the grouting material, and finally selects the "thick slurry" configured with fly ash, bentonite, lime, and sand as the main materials. Using the "thick slurry" for synchronous grouting ensures the effective filling of the construction gap, and at the same time can ensure that the segment structure will not be deformed and damaged due to grouting. By improving the synchronous slurry mix ratio, the spread and viscosity of the "thick slurry" are ensured, and the best construction parameters are determined through tests. The mix ratio parameters of the "thick slurry" here are also water:cement:yellow sand:fly ash:bentonite = 40:23:80:35:7.

[0045] It should be noted here that the slurry is centered on controlling the slump, and the water consumption in the slurry ratio is appropriately adjusted according to the moisture content of the sand.

[0046] The setting of strengthening synchronous grouting effectively ensures the effective filling of the construction gap, and at the same time can ensure that the segment structure will not be deformed and damaged due to grouting.

[0047] Here, a specific explanation of secondary grouting is required. The main reasons for the settlement in the fifth stage of shield tunneling construction are soil consolidation settlement and settlement caused by the shrinkage of the filling material in the segment gap in the fourth stage. During the propulsion process, it is required to carry out secondary grouting in a timely manner to effectively control such settlement. Double-fluid slurry is used for secondary grouting, and double-fluid slurry is injected into deep holes 8 rings after the segment has exited the shield tail to reinforce the soil mass within 3 meters of the shield and control the post-construction settlement.

[0048] Generally speaking, construction carried out under the guidance of S1 above effectively controlled the ground deformation caused by shield construction, laying a solid foundation for the railway crossing project.

[0049] Specifically, referring to Figure 1 and Figure 2 , for S2, the main station building and the elevated waiting hall were strengthened.

[0050] The strengthening of the main station building in S2 includes setting a connecting beam with a size of 0.8m×0.5m between the existing foundations of the main station building.

[0051] Here, specific elaboration on the strengthening measures for the main station building is required. The left line of a certain tunnel is aligned with the central axis of the operating railway, and the right line is located south of the left line. The outer diameter of the shield for the interval tunnel is 6.2m, the center distance is 17.2m, and the top of the interval tunnel is about 16m away from the bottom of the foundation of the station building. Some old railway station buildings were built early, with complex structural forms and having undergone multiple renovations and expansions. Their anti-deformation capabilities are generally weak, mainly including structures such as the awning, grand hall, and middle hall of the old station building. The awning structure uses independent foundations, and the rest of the structures are strip foundations. The structural type is a frame structure, with the highest structural floor height of about 12m, and masonry infill walls are set inside. The structure is extremely sensitive to deformation. In addition to taking shield self-control measures and in-tunnel grouting measures when crossing the old station building, considering that some local columns at the west entrance of the old station building have independent shallow foundations and weak anti-deformation capabilities, new connecting beams are built for strengthening to increase the stability and integrity of the foundation.

[0052] The above strengthening measures for the main station building effectively reduced the stress concentration phenomenon in the original foundations of the main station building and the elevated waiting hall, and thus reduced the settlement of the pile foundations after being disturbed.

[0053] The strengthening of the elevated waiting hall in S2 includes setting a connecting beam between the pile tops of the existing pile foundations of the elevated waiting hall and pouring a concrete raft in the middle range of the connecting beam.

[0054] Here, specific elaboration on the strengthening measures for the elevated waiting hall is required. The typical elevated waiting hall structure was formed by later expansion on the existing platform foundation and often uses a steel structure ceiling. It uses under-reamed pile foundations under columns, with a pile diameter of 1.3 - 2.3m, an under-reamed diameter of 2 - 3.4m, and a pile length of 15m. The minimum distance between the top of the shield tunnel and the bottom of the pile foundation is about 4m. The elevated waiting hall uses enlarged-head pile foundations, and the pile foundation is only 4m away from the tunnel at the closest point. It is inevitable that the construction disturbs the pile bottom soil layer, resulting in stress concentration at the pile bottom, and it is difficult to control the settlement of the pile foundation after being disturbed. By adding a connecting beam with greater stiffness at the pile top and pouring a concrete raft in the middle range of the connecting beam, a method of strengthening beam + raft is used to connect the structural columns into a whole. After local areas are disturbed, the stress is dispersed in a timely manner, effectively controlling the settlement of local points.

[0055] Specifically, referring to Figure 3, regarding S3, reinforce the railway tracks.

[0056] The railway track reinforcement measures in S3 include grouting the subgrade of the arrival and departure tracks and setting up 3-5-3 rail fastening on the passing tracks. When setting up 3-5-3 rail fastening on the passing tracks, the rail joints need to be staggered by more than 1 m.

[0057] Here, it is necessary to elaborate on the railway track reinforcement measures in S3. An operating railway has 5 platforms and 12 tracks, all with 60 kg / m rails and ballast beds. Among them, there are 8 station tracks and 4 main lines. Tracks No. 1, 3, 4, 6, 7, 8, and 9 are concrete wide-sleeper tracks, and Tracks No. II, V, X, and XI are ordinary concrete sleeper tracks. The shield tunnel is about 18 m away from the track bed.

[0058] During the design stage, a three-dimensional finite element model was established to simulate and analyze the shield tunnel passing under the railway track group. The analysis results show that only by taking the reinforcement measures inside the shield tunnel, the maximum settlement of the track is about 3.6 mm, and the settlement can meet the deformation control requirements. Considering the lack of experience in shield tunnels passing under existing tracks in this area and the importance of this station, grouting reinforcement measures for the subgrade of the arrival and departure tracks and 3-5-3 rail fastening measures for the passing tracks are taken. It is required that the rail joints be staggered by more than 1 m. The rail fastening is connected to the sleepers below with ∅24-U bolts. The rail fastening uses 50 kg / m rails. The track reinforcement should minimize the number of splicing joints and keep the joints away from the track.

[0059] The setting of rail fastening reinforcement in S3 effectively improves the stability of the railway tracks, and the treatment of the passing tracks further ensures the normal operation of the operating railway.

[0060] Specifically, regarding S4, conduct 24-hour construction monitoring, and the monitoring process runs through S1 - S3. The 24-hour construction monitoring in S4 includes Beidou GNSS monitoring, static level monitoring, and manual inspection monitoring.

[0061] Specific descriptions of construction monitoring measures are required here. During the crossing period, automated monitoring (Beidou satellite, liquid level survey, etc.) is used to conduct 24-hour real-time monitoring on key parts such as the old station building, tracks, platforms, etc., and at the same time, special personnel are continuously arranged for patrol. A Beidou GNSS monitoring system is installed at the corresponding roof position of the load-bearing columns on the main station building roof to monitor displacement changes in real time. One reference station is set up in the Beidou monitoring network. The location is selected 610 meters away in a straight line. The location is far from the construction influence area, with an open view around, no electromagnetic interference, and the location is stable and reliable, capable of long-term preservation. The GNSS reference station uses expansion bolts to fix the forced centering base, and a Beidou GNSS base station antenna is installed on the base. An antenna protection cover is fixed above the support base, and devices such as a Beidou receiver and a Beidou antenna are integrated in the protection cover. The power cord is led out from the reserved hole at the base and connected to the 220V power supply of nearby residents. The fixed support and equipment are installed stably and firmly. Liquid level survey can also be called communicating pipe survey, and the corresponding liquid level survey system is also called communicating pipe level gauge. It is a measurement method that uses the liquid surface in a mutually connected state and in static equilibrium to conduct elevation transfer. The liquid level survey system is a precision instrument for measuring the relative elevation changes between two points or multiple points. It is mainly used for monitoring the vertical displacement and inclination of large buildings. During the level monitoring process, a liquid level survey system is required. The liquid level survey system includes a liquid storage tank and a collection box. A liquid connection pipe is connected to the bottom of the liquid storage tank. One end of the liquid storage tank away from the liquid connection pipe is provided with a ventilation pipe. The other ends of the liquid connection pipe and the ventilation pipe are both connected to the observation points. A communication power cord is also connected to the observation points, and the other end of the communication power cord is connected to the collection box, and multiple observation points are provided.

[0062] Through the setting of S4, the effective monitoring of the entire construction process can be realized, thereby ensuring that the subway line can effectively cross the existing operating railway.

[0063] It should also be noted that the construction steps S1, S2, S3, and S4 involved in this application do not refer to the construction in sequence, but are the steps in the construction. In the actual construction process, the order is not strictly specified, so it cannot be understood as a limitation to the present invention.

[0064] The implementation principle of the construction method of a shield tunnel under an operating railway in an embodiment of the present application is as follows: during the subway construction process, when crossing an existing operating railway, construction is carried out under the guidance of the methods S1, S2, S3, and S4 of the present application. First, the shield is controlled and adjusted according to the guidance of S1, and excavation is carried out after adjustment. Secondly, the main station building and the elevated terminal are reinforced under the guidance of S2. At the same time, the railway track is reinforced under the guidance of S3, and each of the above processes is monitored 24 hours a day under the guidance of S4. Through S1, S2, S3, and S4, the existing old station building and line track can be passed under the close range, and the settlement of the station building foundation and track can be controlled within a safe range. At the same time, it also provides valuable experience for reference for subsequent projects. The present application has the effect of reducing the probability of problems such as cracking and deformation of the original station building, settlement of the platform, and settlement of the railway line that endanger the safe operation of the operating railway during the construction of the subway line crossing the existing operating railway.

[0065] In some typical urban rail transit projects, subway lines must use shield tunneling to orthogonally pass under operating railway station areas, facing the construction challenges of crossing existing old station buildings, historical buildings, and densely packed trackways, among other high-risk sources. The successful implementation of related projects using this proposed construction method demonstrates that, under the premise of adopting scientific and reasonable construction measures and control methods, shield tunneling can achieve close-range crossings of core operating railway structures and control the settlement of station building foundations and line structures within safe limits, demonstrating good feasibility and engineering safety. Railway-related projects have long been considered one of the technical challenges in urban rail transit construction, involving multiple key aspects such as line section design, ancillary facility layout, settlement control standards for various structures, structural reinforcement strategies, construction risk management, automated monitoring systems, and emergency response mechanisms. The shield tunneling construction method for crossing operating railways, developed based on this complex engineering context, although derived from specific project practices, its summarized key control points, construction organization model, and risk response system possess strong engineering versatility and adaptability. This method is also applicable to rail transit projects in other cities that require crossing complex structures such as old railway stations, high-density track layouts, and elevated waiting halls. It can provide systematic technical support and practical experience for similar complex construction scenarios, and has good promotion value and practical guiding significance.

[0066] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A construction method for a shield tunneling under an operating railway, characterized in that Including the following steps: S1. Conduct shield control and shield tunneling. The shield control includes equipment selection, muck improvement, tunneling pressure control, and muck output control to adapt to the geological conditions of the strata where the operating railway is located. During the process of S1, various grouting methods are also included. S2. Strengthen the main station building and the elevated waiting hall. The strengthening of the main station building includes setting a connecting beam with a size of 0.8m×0.5m between the existing foundations of the main station building. The strengthening of the elevated waiting hall includes setting a connecting beam between the pile tops of the existing pile foundations of the elevated waiting hall and pouring a concrete raft in the middle range of the connecting beam to form an integral structure of the connecting beam plus the concrete raft. S3. Strengthen the railway tracks. The strengthening of the railway tracks includes grouting the subgrade of the arrival and departure tracks and setting a 3-5-3 rail fastening for the passing tracks. In the 3-5-3 rail fastening for the passing tracks, the rail joints need to be staggered by more than 1m. The rail fastening is connected to the sleepers below with U-bolts, and 50kg / m rails are used for the rail fastening. S4. Conduct 24-hour construction monitoring. The monitoring process runs through S1-S3. The 24-hour construction monitoring includes Beidou GNSS monitoring, static level monitoring, and manual inspection monitoring.

2. The construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, The equipment selection includes the selection of the cutterhead and cutters of the shield machine, and the selection of the cutterhead and cutters is based on the formation conditions. The muck improvement includes adding dispersed foam, and the dispersed foam needs to be added in front of the cutterhead. The tunneling pressure control and muck output control are to adjust the shield tunneling pressure and muck output in real time by combining theoretical calculations with the actual situation on site.

3. The construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, The various grouting methods in the shield tunneling in S1 include C-knife grouting, synchronous grouting, and secondary grouting, and the grouting sequence is strictly controlled according to the construction organization design process.

4. A construction method for a shield tunneling under an operating railway according to claim 3, characterized in that, In the C-knife grouting in S1, the C-knife is composed of calcium-based clay minerals, cellulose derivatives, colloid stabilizers, and dispersants. The C-knife grouting is to pump the C-knife slurry and the plastic strength regulator to the designated position through a pipe, and then mix the two liquids into a high-viscosity plastic colloid and inject it through the radial holes.

5. A construction method for a shield tunneling under an operating railway according to claim 3, characterized in that, The slurry ratio used in the synchronous grouting in S1 is water:cement:yellow sand:fly ash:bentonite = 40:23:80:35:

7. The secondary grouting in S1 uses a double-fluid slurry. Deep-hole injection of the double-fluid slurry is carried out 8 rings behind the segment shield tail of the shield machine to reinforce the soil within 3m of the shield. The slurry is centered on controlling the slump, and the amount of water used in the slurry ratio is adjusted in real time according to the moisture content of the sand.

6. The construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, In S2, the outer diameter of the shield in the interval tunnel is 6.2m, the center distance is 17.2m, and the top of the interval tunnel is about 16m away from the bottom of the station building foundation. The foundation forms include independent foundations and strip foundations. A connecting beam with a size of 0.8m×0.5m is set between independent foundations, and a connecting beam with a size of 0.8m×0.5m is set between strip foundations to disperse the stress.

7. A construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, In S2, the elevated waiting hall adopts under-reamed pile foundation under columns. The pile diameter is 1.3 - 2.3 m, the under-reamed diameter is 2 - 3.4 m, and the pile length is 15 m. The minimum distance from the top of the shield tunnel to the bottom of the pile foundation is about 4 m. The elevated waiting hall adopts under-reamed pile foundation, and the closest distance between the pile foundation and the tunnel is only 4 m. A tie beam with greater stiffness is added to the pile top, and a concrete raft is poured in the middle range of the tie beam to form a way of combining the strengthened beam and the raft to connect the structural columns into a whole to disperse stress.

8. A shield tunneling method under an operating railway according to claim 1, characterized in that, In S3, a three-dimensional finite element model needs to be established first to simulate and analyze the shield tunnel passing under the railway line group, and then reinforcement measures are carried out. During the reinforcement process, the number of splicing joints should be minimized as much as possible, and the joints should be far away from the line.

9. The construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, In S4, the Beidou GNSS monitoring includes installing a Beidou GNSS monitoring system at the corresponding roof position of the load-bearing columns on the main station building roof to monitor the displacement changes in real time. One reference station is arranged in the Beidou monitoring network, and the point position is selected 610 meters away in a straight line. The GNSS reference station point uses an expansion screw to fix the forced centering base, and a Beidou GNSS base station antenna is installed on the base. An antenna protection cover is fixed above the support base, and a Beidou receiver and Beidou antenna equipment are integrated in the protection cover.

10. The construction method for a shield tunneling under an operating railway according to claim 1, characterized in that, In S4, a static level system needs to be used during the static level monitoring process. The static level system includes a liquid storage tank and a collection box. The bottom of the liquid storage tank is connected with a liquid delivery pipe, and a ventilation pipe is arranged at one end of the liquid storage tank far away from the liquid delivery pipe. The other ends of the liquid delivery pipe and the ventilation pipe are both connected to the observation points, and a communication power line is also connected to the observation points. The other end of the communication power line is connected to the collection box, and multiple observation points are arranged.

Images