Construction method for shield launching in narrow space

Abstract

The invention discloses a construction method for shield launching in a narrow space. The construction method comprises the following steps that a main machine of a shield tunneling machine is placed in a shield launching well; a hole is reserved in the rear end of the shield launching well, and the hole serves as a channel for the spiral conveyor to enter the shield launching well and a channel for subsequent unearthing and duct piece transportation; an open groove is excavated behind the hole, the open groove serves as an extension section of the shield launching well, and the extension section is used for installing a spiral conveyor, unearthing and transporting duct pieces; a step slope is arranged on the periphery of the open groove, and the gradient of the step slope is 1: 1; a circle of retention wall is arranged on the periphery of the top of the open groove and used for preventing surface accumulated water from flowing into the open groove. A whole-course split tunneling scheme is adopted, all rear matched trolleys of the shield tunneling machine are placed on the ground, and the rear matched trolleys are connected with a main machine of the shield tunneling machine through pipelines. According to the method, the requirement for the size of the starting well can be lowered, the limitation of a narrow space is systematically overcome through the whole set of method, and remarkable safety, economical efficiency and operability are achieved.

Description

Technical Field

[0001] This invention relates to the technical field of tunnel construction, and in particular to a construction method for launching a tunnel boring machine in a narrow space. Background Technology

[0002] Shield tunneling, as an advanced mechanized tunneling technology, has been widely used in underground engineering fields such as urban subways, integrated utility tunnels, and highway tunnels due to its advantages of minimal impact on the surrounding environment, construction safety, and high efficiency. In conventional shield tunneling, the initial launch is the first critical step.

[0003] Conventional tunnel boring machine (TBM) launches require a launch shaft of sufficient size. Typically, after the TBM main unit is hoisted, lowered, and positioned within the shaft, subsequent trolley equipment, such as the screw conveyor, segment assembly machine hydraulic system trolley, electrical control trolley, and grouting system trolley, are sequentially installed and connected behind it, forming a complete TBM tunneling system. Simultaneously, the launch shaft must have sufficient space to accommodate the vertical removal of excavated soil during the initial tunneling phase, as well as the lowering and horizontal transport of materials such as tunnel segments.

[0004] However, with the continuous development of urban underground space, the construction environment faced by tunnel boring machines (TBMs) is becoming increasingly complex and demanding. In some special engineering scenarios, such as constructing short-distance connecting tunnels and pedestrian crossings in the city center, or crossing existing buildings and critical infrastructure at close range, TBMs face increasingly complex and demanding challenges.

[0005] These conditions often result in abnormally narrow planar dimensions of the shield tunneling launch shaft, especially a severe deficiency in length along the tunnel axis. Within this confined launch space, existing conventional shield tunneling launch processes reveal the following pressing technical challenges that need to be addressed: 1. Subsequent equipment cannot be installed inside the shaft: After the tunnel boring machine (TBM) is lowered into the shaft and positioned, its tail end is very close to the rear wall or support structure of the launching shaft, leaving extremely limited longitudinal space. This makes it impossible to complete the conventional hoisting, connection, and commissioning work for long and critical downstream equipment, especially the screw conveyor, inside the shaft.

[0006] 2. Material transport channels are blocked: The narrow space of the starting shaft cannot accommodate conventional horizontal and vertical transport systems. The limited space behind the main unit is insufficient to lay a complete track system, nor can it provide the necessary length for the marshalling and shunting of battery-powered vehicles or dump trucks, resulting in the inability to transport materials such as tunnel segments and slurry, and the inability to transport excavated soil in a timely manner. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a construction method for shield tunneling in narrow spaces, which can reduce the requirements for the size of the launching shaft. The entire method systematically overcomes the limitations of narrow spaces and has significant safety, economy and operability.

[0008] A method for launching a tunnel boring machine (TBM) in a narrow space according to an embodiment of the present invention includes the following steps: S100, the TBM main unit is placed inside the TBM launching shaft; S200, an opening is reserved at the rear end of the TBM launching shaft, the opening serving as a channel for the screw conveyor to enter the TBM launching shaft and a channel for subsequent excavation and segment transportation; S300, a trench is excavated behind the opening, the trench serving as an extension of the TBM launching shaft, the extension being used for installing the screw conveyor, excavation, and segment transportation; S400, a slope is set around the trench, the slope being 1:1; S500, a retaining wall is set around the top perimeter of the trench, the retaining wall being used to prevent surface water from flowing into the trench; S600, a fully separate tunneling scheme is adopted, all the rear auxiliary trolleys of the TBM are placed on the ground, the rear auxiliary trolleys being connected to the TBM main unit through pipelines.

[0009] A method for launching a tunnel boring machine in a confined space according to an embodiment of the present invention has at least the following beneficial effects: This invention solves two major technical challenges by setting up reserved openings and excavating extension sections. These openings allow materials to move between the extension section and the shield tunneling launch shaft, enabling the installation of screw conveyors in narrow launch shafts and blocking material transport channels. This solution cleverly transfers operations that would otherwise need to be performed inside the shaft to the extended section space, making shield tunneling launch possible under extremely limited conditions. Simultaneously, the use of a fully split-section tunneling scheme avoids the huge space required for lowering the rear auxiliary trolley into the shaft, further reducing the size requirements for the launch shaft. The entire method systematically overcomes the limitations of narrow spaces, exhibiting significant safety, economy, and operability. Furthermore, the installation of slopes and retaining walls provides a safe and stable environment for personnel and equipment operations within the extension section.

[0010] According to an embodiment of the present invention, a method for launching a tunnel boring machine (TBM) in a narrow space includes step S300, in which the main structure is provided with a TBM launching shaft, the rear end of which is connected to a top plate, and backfill soil is placed on top of the top plate. On this basis, a trench is excavated, and the trench is excavated in two layers.

[0011] The advantages are: by excavating in the backfill soil above the existing structure's top slab and adopting a layered excavation method, the soil disturbance during the excavation process is effectively controlled, ensuring the stability of the existing structure below (such as the top slab) and the slope of the trench itself, and ensuring construction safety.

[0012] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space includes, in step S400: spraying a layer of C20 concrete after slope excavation, wherein the thickness of the C20 concrete is 150mm. Reinforcing bars are inserted into the concrete. The reinforcing bars are made of steel bars with a diameter of φ22 and a spacing of 1500mm between them. The length of the reinforcing bars is 5m. After the reinforcing bars are inserted, a steel mesh is tied. The steel mesh is made of steel bars with a diameter of φ8 and a spacing of 150mm between them. Finally, a layer of C20 concrete is sprayed, with a thickness of 150mm.

[0013] The benefits are that by actively supporting the slope with reinforcement bars, wire mesh, and shotcrete, the integrity and stability of the extended slope are significantly enhanced, preventing landslides or soil erosion during construction and providing a safe and stable environment for personnel and equipment operations within the extended section.

[0014] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space, in step S500, the retaining wall is constructed of C20 concrete, the retaining wall has vertical steel bars, the vertical steel bars are anchored into the ground, and tie bars are connected between adjacent vertical steel bars.

[0015] The benefits are that by setting up C20 concrete retaining walls and configuring steel reinforcement frames, a reliable flood barrier is constructed for the extended section of open-pit excavation. This effectively blocks surface rainwater and runoff from entering, prevents the work area from being flooded, and provides safety protection. At the same time, its structure is solid and durable.

[0016] According to an embodiment of the present invention, a method for launching a tunnel boring machine (TBM) in a narrow space includes step S200, in which an end wall is provided behind the TBM main unit at the TBM launch shaft, a hole is drilled in the end wall, a reaction frame is fixed to the bottom plate of the TBM launch shaft and connected to the end wall through a steel pipe, a bracket is fixed to the bottom plate of the TBM launch shaft, the reaction frame provides a pushing reaction force to the jacks at the rear of the TBM main unit, and the bracket is used to support and position the TBM main unit.

[0017] The advantage is that, within the narrow launching shaft, the two key temporary structures, the reaction frame and the support frame, work together. The support frame precisely supports and positions the front end of the main machine, while the reaction frame provides a strong recoil reaction force for the jacks. This structural system ensures that the tunnel boring machine receives stable support and accurate direction of advance during the launching phase, which is the foundation for a successful launch.

[0018] According to an embodiment of the present invention, a method for launching a tunnel boring machine (TBM) in a narrow space includes a reaction frame composed of a steel ring, a rear shield frame, and steel pipes. The surface flatness of the steel ring is 5mm to ensure uniform stress on the tunnel segments. The rear shield frame is installed at the rear of the steel ring. The steel ring and the rear shield frame are welded and fixed together and supported by steel pipes. The rear reaction force generated by the TBM during tunneling is transmitted to the bottom plate and end walls of the main structure through the steel pipes, which are welded to pre-embedded steel plates.

[0019] The advantages are: by setting up steel rings, rear shield frames, and steel pipe supports, the reaction frame is ensured to have sufficient rigidity and strength, which can safely distribute the thousands of tons of thrust of the tunnel boring machine to the main structure, prevent the reaction frame itself from deforming or being damaged, and ensure the smooth and controllable start-up process.

[0020] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space involves using a segment assembly machine to install negative ring segments. The negative ring segments are installed using a closed-ring method. The negative ring segments are assembled sequentially by the shield lifting arm inside the shield shell to form a negative ring tube. After the negative ring tube is securely connected using circumferential bolts and longitudinal bolts, the negative ring tube is pushed to the required rear seat position.

[0021] The advantage is that by installing the negative ring segments using a closed-ring method and advancing them ring by ring to the rear seat position, a complete and uniform stress ring can be formed, thereby effectively transferring the thrust of the tunnel boring machine to the reaction frame. This method ensures the flatness of the negative ring segment surface and avoids stress concentration, which is a key step in establishing a reliable reaction system.

[0022] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space involves using a 7-shaped hook welded to the reaction frame to secure the negative ring pipe segments during installation. Simultaneously, two steel wire ropes are wrapped around the assembled negative ring pipe, with tensioners threaded onto the rope ends to tighten the ropes, resulting in a tighter connection between the pipe segments.

[0023] The benefits are: by using the rigid connection of the welded figure-eight hook to constrain the axis of the ring pipe, and by using the steel wire rope to bind and tighten the radial constraint of the ring pipe, the overall stability of the negative ring segment is greatly enhanced. This effectively prevents the segments from sliding, misaligning, or elliptical on the slope due to their own weight and thrust, ensuring the safety and reliability of the reaction force system in the initial stage of launch.

[0024] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space includes an extension section equipped with a horizontal transport track, which serves as a transport channel for a screw conveyor, a segment assembler, and excavated soil.

[0025] The benefits are that by setting up horizontal transport tracks in the extended section, the material transport system in the conventional starting shaft was successfully recreated, solving the core logistics problems of transporting materials such as segments and slurry into the shaft and transporting excavated soil out of the shaft, thus ensuring the continuous progress of tunneling work.

[0026] According to an embodiment of the present invention, a method for launching a tunnel boring machine in a narrow space is provided, wherein a crane and a construction access road are provided on one side of the extension section, and a segment storage yard, supporting equipment and warehouse are arranged on both sides of the construction access road.

[0027] The benefits are: by scientifically planning and zoning the limited construction site, the cranes, material storage yards and construction access roads are rationally arranged, the construction flow is optimized, and mutual interference of on-site transportation is reduced. As a result, efficient and orderly construction organization is achieved in the narrow space, ensuring the progress of the project.

[0028] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a plan view of a method for launching a tunnel boring machine in a narrow space, according to an embodiment of the present invention. Figure 2 for Figure 1 A schematic diagram of the shield launching shaft is shown, illustrating a construction method for launching a shield tunnel in a narrow space. Figure 3 for Figure 1 A schematic diagram of a retaining wall for a construction method of shield tunneling initiation in a narrow space is shown. Figure 4 for Figure 1 A schematic diagram of the slope protection structure for a construction method of launching a tunnel boring machine in a narrow space is shown. Figure 5 for Figure 1A schematic diagram of the reaction wall structure for a construction method of shield tunneling initiation in a narrow space is shown. Figure 6 for Figure 1 The flowchart illustrates a construction method for launching a tunnel boring machine in a confined space.

[0031] Attached reference numerals: 100-Shield tunneling machine main unit, 110-Shield launching shaft, 120-Entrance, 130-Extension section, 140-Slope protection, 150-Retaining wall, 160-Main structure, 170-Reinforcing bar, 180-Steel mesh, 190-Vertical reinforcement, 200-Tie bar, 210-Reaction frame, 220-Steel ring, 230-Rear shield frame, 240-Tunnel, 250-Cranial, 260-Construction access road. Detailed Implementation

[0032] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0033] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0034] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. If "first" and "second" are mentioned, this is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation, connection, and linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The following describes, with reference to the accompanying drawings, a construction method for launching a tunnel boring machine in a narrow space according to an embodiment of the present invention.

[0037] Reference Figure 1 The present invention aims to provide an embodiment of a construction method for launching a tunnel boring machine in a narrow space.

[0038] An embodiment of the present invention provides a method for launching a tunnel boring machine (TBM) in a confined space, referring to... Figure 1 , Figure 2 and Figure 6 This includes the following steps: S100, the main shield machine 100 is installed inside the shield launching shaft 110; S200, a reserved opening 120 is made at the rear end of the shield tunneling starting shaft 110. The opening 120 serves as the channel for the screw conveyor to enter the shield tunneling starting shaft, as well as the channel for subsequent excavation and segment transportation. S300, a trench is excavated behind the tunnel entrance 120. The trench serves as an extension section 130 of the shield tunneling starting shaft 110. The extension section 130 is used for installing the screw conveyor, excavating soil, and transporting tunnel segments. S400, a slope of 140 is set around the groove, and the slope of the 140 slope is 1:1; S500, a water-retaining wall 150 is provided around the top perimeter of the groove, the water-retaining wall 150 is used to prevent ground water from flowing into the groove; The S600 adopts a fully split tunneling scheme, placing all the rear auxiliary trolleys of the tunnel boring machine on the ground. The rear auxiliary trolleys are connected to the main tunnel boring machine 100 through pipelines.

[0039] Understandably, this invention solves two major technical challenges—the inability to install a screw conveyor in a narrow launching shaft and the obstruction of material transport channels—by setting up a reserved opening 120 and an extension section 130. The opening 120 allows materials to move between the extension section 130 and the shield launching shaft 110. This solution cleverly transfers operations that would otherwise need to be performed inside the shaft to the space of the extension section 130, making shield launching possible under extremely limited conditions. Simultaneously, the adoption of a fully split-section tunneling scheme avoids the huge space required for lowering the rear auxiliary trolley into the shaft, further reducing the size requirements for the launching shaft. The entire method systematically overcomes the limitations of narrow spaces, exhibiting significant safety, economy, and operability. Furthermore, by setting up a slope 140 and a water retaining wall 150, a safe and stable environment is provided for personnel and equipment operations within the extension section 130.

[0040] It should be noted that there are two shield launching shafts 110, each housing a shield machine host 100. The center-to-center distance between the two shafts is approximately 1 meter, thus enabling the construction of two tunnels 240.

[0041] In some embodiments of the present invention, reference is made to... Figure 5 In step S200, the shield launching shaft 110 is provided with an end wall behind the shield machine host. Holes are drilled in the end wall. The reaction frame 210 is fixed to the bottom plate of the shield launching shaft 110 and connected to the end wall through steel pipes. The bracket is fixed to the bottom plate of the shield launching shaft. The reaction frame 210 provides propulsion reaction force for the jacks at the rear of the shield machine host 100. The bracket is used to support and position the shield machine host 100.

[0042] Understandably, within the narrow launching shaft, the reaction frame 210 and the support frame, two key temporary structures, work together. The support frame precisely supports and positions the front end of the main machine, while the reaction frame provides a powerful recoil reaction force for the jacks. This structural system ensures that the tunnel boring machine receives stable support and accurate direction of advance during the launching phase, which is the foundation for a successful launch.

[0043] In some embodiments of the present invention, the reaction frame 210 is composed of a steel ring 220, a rear shield frame 230 and a steel pipe. The flatness of the ring surface of the steel ring 220 is 5mm, so that the segments are subjected to uniform force. The rear shield frame 230 is set at the rear of the steel ring 220. The steel ring 220 and the rear shield frame 230 are welded and fixed together and supported by steel pipes. The rear reaction force generated when the shield machine host 100 is excavating is transmitted to the bottom plate and end wall of the main structure 160 through the steel pipes. The steel pipes are welded to the pre-embedded steel plates.

[0044] Understandably, by setting up steel rings 220, rear shield frames 230, and steel pipe supports, and welding steel rings 220 and rear shield frames 230 together, and fixing steel rings 220 and rear shield frames 230 to pre-embedded steel plates via steel pipes, the reaction frame is ensured to have sufficient rigidity and strength, which can safely distribute the thousands of tons of thrust of the tunnel boring machine to the main structure 160, prevent the reaction frame itself from deforming or being damaged, and ensure the smooth and controllable start-up and propulsion process.

[0045] In some embodiments of the present invention, a segment assembly machine is used to install negative ring segments. The negative ring segments adopt a closed ring installation method. The negative ring segments are assembled sequentially by the shield lifting arm inside the shield shell to form a negative ring tube. After the negative ring tube is firmly connected with circumferential bolts and longitudinal bolts, the negative ring tube is pushed to the required rear seat position.

[0046] Understandably, installing the negative ring segments using a closed-ring method and advancing each negative ring segment to the rear seat position one by one can form a complete and uniform stress ring, thereby effectively transferring the thrust of the tunnel boring machine to the reaction frame. This method ensures the flatness of the negative ring segment surface and avoids stress concentration, which is a key step in establishing a reliable reaction system.

[0047] In some embodiments of the present invention, when installing the negative ring pipe, a 7-shaped hook welded to the reaction frame is used to hook the negative ring pipe segments, so that the negative ring pipe is fixed to the reaction frame. At the same time, the assembled negative ring pipe is wrapped around the negative ring pipe with two steel wire ropes, and a tensioner is threaded through the rope ends. The steel wire ropes are tightened by the tensioner, so that the segments are more tightly connected.

[0048] Understandably, the rigid connection of the welded figure-eight hook constrains the axis of the ring pipe, and the radial constraint of the ring pipe is achieved by binding and tightening with steel wire ropes. This greatly enhances the overall stability of the negative ring segments, effectively preventing the segments from sliding, misaligning, or elliptical due to their own weight and thrust on the slope, thus ensuring the safety and reliability of the reaction force system in the initial stage of launch.

[0049] In some embodiments of the present invention, reference is made to... Figure 1 and Figure 2 In step S300, the main structure 160 is provided with a shield launching shaft 110. The rear end of the shield launching shaft 110 is connected to a top plate. Backfill soil is placed on top of the top plate, and a trench is excavated on this basis. The trench is excavated in two layers.

[0050] Understandably, by excavating in the backfill soil above the existing structure's top slab and adopting a layered excavation method, soil disturbance during the excavation process was effectively controlled, ensuring the stability of the existing structure below (such as the top slab) and the slope of the trench itself, thus ensuring construction safety.

[0051] In some embodiments of the present invention, the extension section 130 is provided with a horizontal transport track, which serves as a transport channel for the screw conveyor, the segment assembler, and the excavated soil.

[0052] Understandably, by setting up a horizontal transport track within the 130-meter extension section, the material transport system within the conventional starting shaft was successfully recreated, solving the core logistics problems of transporting materials such as segments and slurry into the shaft and transporting excavated soil out, thus ensuring the continuous progress of tunneling work.

[0053] In some embodiments of the present invention, a crane 250 and a construction access road 260 are provided on one side of the extension section 130, and a segment storage yard, supporting equipment and warehouse are arranged on both sides of the construction access road.

[0054] Understandably, by scientifically planning and zoning the limited construction site, the crane 250, material storage yard and construction access road 260 were rationally arranged, the construction flow was optimized, and mutual interference of on-site transportation was reduced. As a result, efficient and orderly construction organization was achieved in the narrow site, ensuring the progress of the project.

[0055] It should be noted that the crane 250 is used for transporting vehicles and materials.

[0056] In some embodiments of the present invention, reference is made to... Figure 4 In step S400, the following is included: Step S410: After slope excavation, spray a layer of C20 concrete with a thickness of 150mm. Step S420: Drill holes in the concrete and insert reinforcing bars into the holes. The reinforcing bars are made of steel bars with a diameter of φ22, a spacing of 1500mm between the reinforcing bars, and a length of 5m. Step S430: After inserting the reinforcing bars, tie the reinforcing mesh. The reinforcing mesh is made of φ8 diameter steel bars, with a spacing of 150mm between the bars. Step S440: Finally, spray a layer of C20 concrete, with a thickness of 150mm.

[0057] Understandably, by carrying out active support treatment on slope 140 by sequentially laying concrete, inserting reinforcing bars, tying steel mesh, and laying concrete, the integrity and stability of the slope of extension section 130 were significantly enhanced, preventing slope collapse or soil erosion during construction and providing a safe and stable environment for personnel and equipment operations within extension section 130.

[0058] In some embodiments of the present invention, reference is made to... Figure 3 In step S500, the retaining wall 150 is constructed with C20 concrete and has vertical steel bars 190. The vertical steel bars 190 are anchored into the ground and tie bars 200 are connected between adjacent vertical steel bars 190.

[0059] By setting up a C20 concrete retaining wall 150 and configuring a steel reinforcement frame, a reliable flood barrier is constructed for the open-pit excavation extension section 130. It can effectively block surface rainwater and runoff from flowing in, prevent the work area from being flooded, and play a safety protection role. At the same time, its structure is solid and has good durability.

[0060] Specifically, vertical reinforcing bars 190 are inserted into the soil, and then tie bars 200 are placed between adjacent vertical reinforcing bars 190, followed by pouring C20 concrete.

[0061] In the description of this specification, the references to terms such as "an embodiment, some embodiments, illustrative embodiments, example, specific example, or examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method of construction for launching a shield machine in a narrow space, characterized in that, The method comprises the following steps: S100, placing a shield machine main machine in a shield starting shaft; S200, reserving a hole opening at the rear end of the shield starting shaft, the hole opening serving as a channel for a spiral conveyor to enter the shield starting shaft and a channel for subsequent soil removal and segment transportation; S300, excavating a slot behind the hole opening, the slot serving as an extension of the shield starting shaft, and the extension being used for installing the spiral conveyor, soil removal and segment transportation; S400, setting a slope around the slot, the slope having a slope of 1:1; S500, providing a water retaining wall around the top periphery of the slot, the water retaining wall being used for preventing ground surface water from flowing into the slot; S600, adopting a full-length split tunneling scheme, and placing all rear supporting trolleys of the shield machine on the ground, the rear supporting trolleys being connected to the shield machine main machine through pipelines.

2. The construction method for launching a shield machine in a narrow space according to claim 1, characterized in that In the step S300, the main body structure is provided with the shield starting shaft, the rear end of the shield starting shaft is connected to a top plate, the top plate is backfilled with earth on top, and the slot is excavated on this basis, and the slot is excavated in two layers.

3. The construction method of claim 1, wherein, In the step S400, the following steps are included: C20 concrete is sprayed after the slope is excavated, and the thickness of the C20 concrete is 150 mm; Reinforcing bars are inserted on the concrete, the reinforcing bars are made of steel bars, the diameter of the reinforcing bars is φ22, the spacing between the steel bars is 1500 mm, and the length of the reinforcing bars is 5 m; After the reinforcing bars are inserted, a steel mesh is bound, the steel mesh is bound by steel bars with a diameter of φ8, and the spacing between the steel bars is 150 mm; Finally, C20 concrete is sprayed, and the thickness of the C20 concrete is 150 mm.

4. The construction method of initiating a shield from a narrow space according to claim 1, wherein In the step S500, the water retaining wall is made of C20 concrete, the water retaining wall is provided with vertical steel bars, the vertical steel bars are anchored into the ground, and pull bars are connected between adjacent vertical steel bars.

5. The method of claim 1, wherein the method further comprises: In the step S200, the shield starting shaft is provided with an end wall behind the shield machine main machine, the hole is drilled in the end wall, a reaction frame is fixed to the bottom plate of the shield starting shaft and connected to the end wall through a steel pipe, and a bracket is fixed to the bottom plate of the shield starting shaft, the reaction frame provides a propelling reaction force for the jacks at the rear of the shield machine main machine, and the bracket is used for supporting and positioning the shield machine main machine.

6. The construction method of initiating a shield from a narrow space according to claim 5, wherein The reaction frame is composed of a steel ring, a rear shield frame and a steel pipe, the ring surface flatness of the steel ring is 5 mm, the pipe segment is uniformly stressed, the rear shield frame is arranged at the rear of the steel ring, the steel ring and the rear shield frame are fixed by welding and supported by the steel pipe, and the reverse force of the recoil produced by the shield machine main machine during tunneling is transmitted to the bottom plate of the main body structure and the end wall through the steel pipe, and the steel pipe is welded to the embedded steel plate.

7. The method according to claim 6, wherein, A segment assembling machine is used to install a negative ring segment, the negative ring segment is installed in a closed ring manner, the negative ring segment is sequentially assembled into a negative ring pipe by a shield lifting arm in a shield shell, and the negative ring pipe is connected firmly by using circumferential bolts and longitudinal bolts, and then the negative ring pipe is pushed to a required recoil position.

8. The construction method of initiating a shield from a narrow space according to claim 7, wherein In the installation of the negative ring pipe, the negative ring pipe piece is hooked by the 7-shaped hook fixed on the counterforce frame by welding, so that the negative ring pipe is fixed on the counterforce frame, and meanwhile, the assembled negative ring pipe is wound by two steel wires for one round, a tightener is worn on the wire head, and the steel wire is pulled tight through the tightener, so that the combination between the pipe pieces is more tight.

9. The method of claim 1, wherein the method further comprises: The horizontal transportation track is provided on the extension section and serves as a transportation channel for the spiral conveyor, the pipe piece assembling machine and the excavated earth.

10. The method of claim 1, wherein the method is characterized by: The extension section is provided with a crane and a construction access road on one side, and pipe piece yards, rear supporting equipment and warehouses are arranged on both sides of the construction access road.

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