Large-split starting and safe tunneling method for stacked line small-clear-distance tunnel TBM (Tunnel Boring Machine)

Abstract

The invention belongs to the technical field of tunnel engineering construction, and provides a large-split launching and safe tunneling method for a stacked-line small-clear-distance tunnel TBM (Tunnel Boring Machine), which comprises the following steps of: constructing a launching pilot tunnel and a launching well; dividing the TBM into a core operation unit and a to-be-accessed unit; a main machine and a trolley contained in the TBM core operation unit are sequentially hoisted through the vertical shaft and pushed to the starting hole to be assembled, and debugging is completed; an interface of a TBM core operation unit is transformed; after a TBM main engine is pushed into a tunnel, a rock anchor type reaction frame is installed, and horizontal transportation marshalling configuration is conducted in the TBM large split starting stage; after the TBM core operation unit is assembled and debugged, starting tunneling and complete machine connection are carried out; for the initial tunneling of the stacked line small-clear-distance tunnel, the TBM firstly performs initial tunneling on the downlink line and then performs initial tunneling on the uplink line, and an inner support is arranged in the hole of the downlink line during the tunneling of the uplink line, so that the initial tunneling of the TBM is safely and efficiently completed in the limited space, and the construction risk and cost are reduced.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering construction technology, and in particular relates to a method for the large-scale starting and safe excavation of a TBM in a tunnel with overlapping lines and small clearance. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Full-face tunnel boring machines (TBMs) are widely used in subway and railway tunnel projects due to their advantages such as high tunneling efficiency, stable construction quality, and minimal disturbance to the surrounding environment. However, TBMs are large in size, and traditional launching methods typically require long launching pilot tunnels (generally exceeding 130 meters) and end launching shafts to meet the needs of machine assembly, equipment layout, and construction transportation. In tunnel construction in densely packed structures such as urban subways, there are situations where the TBM tunnel has a small clearance with existing structures or adjacent tunnels. In such scenarios, long-distance cut-and-cover excavation can easily lead to risks such as surrounding rock instability and excessive settlement of surrounding structures. It is impossible to excavate long pilot tunnels sufficient for TBM launching, making traditional TBM launching methods unsuitable, severely restricting construction progress, and even affecting project safety.

[0004] Alongside TBMs, another mainstream type of tunnel boring machine (TBM) is the shield tunneling machine. Although both are full-face tunneling equipment, their applicable scenarios and launching processes differ significantly. TBMs, widely used in urban soft soil engineering, are modular and highly flexible, and have long since developed flexible solutions such as split-unit launching for space-constrained environments. In contrast, the traditional design and launching process of TBMs originated from the relatively relaxed conditions of mountain tunnels. TBMs are characterized by high rigidity and integration, and their split-unit launching technology and related experience are severely lacking. This prevents TBMs from leveraging their advantages in sensitive urban areas, and traditional launching methods are completely unsuitable due to excessively long pilot tunnel requirements, severely hindering project progress and directly threatening project safety. Therefore, there is an urgent need for a TBM launching technology suitable for tunnels with small clearances and without the need for long-distance underground excavation, addressing the technical bottleneck of excessively long pilot tunnel requirements in existing processes. Summary of the Invention

[0005] To address the technical problems mentioned above, this invention provides a method for the safe and efficient launching and excavation of a TBM in a tunnel with a small clearance between overlapping lines. This method involves rationally arranging the TBM main unit and some trolleys within a short pilot tunnel, optimizing equipment modification and transportation organization, setting up a dedicated rock-anchored reaction frame, and separately launching and excavating the up and down lines with internal supports. This enables the safe and efficient completion of the TBM launching and excavation within a confined space, reducing construction risks and costs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for the large-segment launching and safe tunneling of a TBM with overlapping lines and small clearances, comprising: Construction of the initial pilot tunnel and starting shaft, and adaptation to TBM passage and installation, tunnel geology and the spacing between the two tunnels; Based on the limitations of the initial pilot tunnel length and the correlation of equipment functions, the TBM is divided into the core working unit and the unit to be connected. The core working unit meets the basic functions of tunneling, support and muck removal in the initial stage. The unit to be connected is temporarily stored on the ground or in the section behind the shaft tail, and will be connected after subsequent tunneling to the preset distance. According to the TBM large-scale split launching method, the main unit and trolley of the TBM core working unit are sequentially hoisted through the vertical shaft and pushed to the launching tunnel for assembly and commissioning. The interfaces of the core operating units of the TBM are modified to enable unloading, slag transportation, and pipeline extension. After the TBM main unit is pushed into the tunnel, a rock-anchored reaction frame is installed. During the initial stage of the TBM large-section launch, a horizontal transport train is configured to complete the removal of excavated soil and the lowering of tunnel segments in the launch shaft. After the TBM core working unit is assembled and debugged, the initial excavation and segment assembly within the main unit range will be carried out. When the excavation reaches the set distance, the temporarily stored unit to be connected will be connected to the core working unit and the whole machine will be connected to restore the TBM to the working state and switch to normal tunneling mode. For tunnels with small clearance between overlapping lines, the TBM will start excavating the down line first, followed by the up line. During the excavation of the up line, internal supports will be installed inside the down line tunnel.

[0007] As one implementation method, the construction includes a starting shaft, a starting guide tunnel, and a guide platform. The size of the starting guide tunnel is adapted to the passage and installation of the TBM core operating unit. The starting shaft is reserved with slag discharge and material unloading ports to meet the needs of slag discharge and material transfer during construction.

[0008] As one implementation method, the excavation length of the initial pilot tunnel is determined by the length of the TBM core working unit, the tunnel geology, and the small clearance between overlapping lines.

[0009] As one implementation method, the main structure of the launching shaft is completed before the TBM starts, and the net space reserved on the top plate of the main structure meets the requirements of dual-line TBM equipment, slag discharge and material unloading.

[0010] In one implementation, the core TBM operating unit includes a main unit and trolleys #1 to #5; the unit to be connected includes trolleys #6 to #13.

[0011] As one implementation method, the assembly sequence of the TBM core working unit is as follows: First, the main unit is assembled by lowering the middle shield, front shield, cutterhead and tail shield into the shaft in sequence using a crawler crane. Then, the hoisting connecting bridge is lowered into the shaft and connected to the main unit. After that, trolleys #1 to #5 are lowered into the shaft in sequence and connected to trolleys #1 to #5 via the connecting bridge.

[0012] As one implementation method, the process of modifying the interface of the TBM core working unit is as follows: A rear-mounted belt conveyor unloading port was added to the rear of trolley #4, and the gravel tank transfer belt was modified to meet the needs of slag unloading and material transfer; the space behind trolley #5 was used for hoisting tunnel segments and temporary slag trucks; extension systems such as grouting pipelines, water pipes, cables and air pipes were added to connect with subsequent equipment.

[0013] As one implementation method, to ensure the safe construction of the dual-track tunnel, the left and right TBMs are started separately. After the TBM of the first track has completed the overall trolley assembly, the TBM of the other track is started to begin excavation.

[0014] As one implementation method, during the excavation of the uplink line, the TBM main unit always excavates within the support range of the downlink tunnel.

[0015] As one implementation method, the rock-anchored reaction frame consists of a ring plate, a support, and a diagonal brace. The ring plate is pre-embedded in the starting tunnel and is firmly connected to the rock wall of the pilot tunnel by mortar anchor rods. The angle between the diagonal brace and the support is set at 60°, and the angle between the diagonal brace and the tunnel wall is set at 30°.

[0016] The beneficial effects of this invention are: This invention addresses the construction of the launching pilot tunnel and launching shaft. Based on the length limitations of the launching pilot tunnel and the functional correlation of the equipment, the TBM is divided into a core TBM operating unit and a unit to be connected. Following a large-scale split-unit launching method, the main unit and trolley of the core TBM operating unit are sequentially hoisted through the shaft and pushed to the launching tunnel for assembly and commissioning. Once the tunnel has advanced to a set distance, the temporarily stored unit to be connected is integrated into the core operating unit for overall machine connection. This solves the problems of limited space in tunnels with small clearances, which prevent the overall launching of the TBM and the high risks of long-distance underground excavation. It employs a combination of short pilot tunnels, split-unit TBM launching, and internal support, requiring only the installation of the TBM... The core working unit can initiate tunneling, followed by the connection of the remaining trolleys, effectively overcoming the dual limitations of space and construction risks. Through the modification of the core working unit and the configuration of double-track transport, key functions such as tunneling, muck removal, and grouting are fully retained. A dedicated reaction frame ensures axial accuracy and construction stability, solving the problem of equipment installation in confined spaces while preserving the advantages of TBM construction in terms of construction time and aesthetic appearance. Simultaneously, by separately initiating tunneling and erecting internal supports on the up and down lines, dual-line coordinated advancement and dynamic load control are achieved, further optimizing the stress distribution and construction sequence of the tunnel structure. This creates an efficient and controllable construction cycle under complex geological and spatial constraints. Compared to traditional cut-and-cover construction, this significantly saves time and reduces costs, while achieving significant improvements in safety, quality, and efficiency.

[0017] Advantages of additional aspects 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

[0018] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0019] Figure 1 This is a plan view of the launching well and launching tunnel according to an embodiment of the present invention; Figure 2 This is a cross-sectional view of the island platform according to an embodiment of the present invention; Figure 3 This is a cross-sectional view of the rock-anchored reaction frame according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the hoisting of the main unit according to an embodiment of the present invention; Figure 5 These are schematic diagrams of the hoisting of trolleys #1 to #5 in an embodiment of the present invention; Figure 6 This is a schematic diagram of the placement positions of #6-13 in an embodiment of the present invention; Figure 7 This is a schematic diagram of a train formation according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the initial excavation process according to an embodiment of the present invention; Figure 9 This is a schematic diagram of the internal support in an embodiment of the present invention.

[0020] The components include: 1. Main structure of the launching shaft; 2. Top plate openings; 3. TBM launching tunnel; 4. Arc-shaped island platform; 5. Steel rails; 6. Boundary between launching tunnel segments and secondary lining; 7. Steel plate; 8. Mortar anchor bolts; 9. TBM main unit; 10. Cutterhead; 11. Front shield; 12. Middle shield; 13. Tail shield; 14. Connecting bridge; 15. Shield tunnel section after the vertical shaft; 16. Temporary muck truck; 17. Segment; 18. Horizontal transport train formation; 19. Normal train formation; 20. Auxiliary thrust cylinder; 21. Ring plate; 22. Support; 23. Diagonal brace; 24. Internal support. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] The following example illustrates the detailed process of the large-scale split-type starting and safe tunneling method for a double-shield TBM with a total equipment length of 170 meters, using a TBM main unit paired with trolleys #1-13 in a certain section: Step 1: Construction of the pilot tunnel and launching shaft, adapting to the TBM, tunnel geology, and spacing between the two tunnels.

[0025] The construction includes a starting shaft, a starting guide tunnel, and a guide platform. The size of the starting guide tunnel is adapted to the passage and installation of the TBM core operating unit. The starting shaft is reserved with slag discharge and material unloading ports to meet the needs of slag discharge and material transfer during construction.

[0026] The length of the initial pilot tunnel is determined by the length of the TBM core operating unit, the tunnel geology, and the clearance between overlapping lines. For example, the length of the initial pilot tunnel must be at least 50m to meet the starting length requirements of the TBM core equipment.

[0027] Before the TBM launch, the main structure of the launching shaft was completed, and the net space reserved in the top plate of the main structure met the requirements of dual-line TBM equipment, slag removal, and material unloading. The guide platform adopts a C30 reinforced concrete arc-shaped guide platform, with double rows of P43 steel rails pre-embedded in the arc-shaped guide platform. The arc-shaped guide platform is laid on the launching tunnel and the bottom plate of the launching shaft.

[0028] In the specific implementation process, such as Figure 1 As shown, the starting shaft is excavated, and the main structure 1 of the starting shaft is constructed. A pre-drilled hole 2 is constructed in the top slab. The size of the pre-drilled hole 2 should meet the lowering requirements of all TBM equipment. The vertical shaft size should be no less than 31m × 28m. After the starting shaft is constructed, a 50m long TBM starting tunnel 3 is excavated. A C30 arc-shaped island platform 4 and double-row P43 steel rails 5 are pre-embedded within the arc-shaped guide platform at the bottom of the starting tunnel and starting shaft. The rail spacing is 1m. Tracks for the TBM and transport trains are laid on the rails, with the highest point of the arc-shaped guide platform always 840mm from the rail surface. Gantry cranes are installed on both sides of the starting shaft for vertical transport of segments, trolleys, and other materials down the shaft. Figure 2 As shown.

[0029] Step 2: Based on the length limit of the initial pilot tunnel and the functional correlation of the equipment, the TBM is divided into the core TBM operation unit and the unit to be connected. The core TBM operation unit is used to meet the basic functions of tunneling, support and muck removal in the initial stage, and the unit is temporarily stored on the ground or in the section behind the shaft. It will be connected after the subsequent tunneling reaches the preset distance.

[0030] The core TBM operating unit includes the main unit and trolleys #1 to #5; the units to be connected include trolleys #6 to #13. Specifically, the core TBM operating unit includes trolleys #1 to #5 containing the main unit, connecting bridge and segment crane, main control room, hydraulic pump station, pebble pump and electrical control, etc., which meet the basic functions of tunneling, support and muck removal in the initial stage; the units to be connected include trolleys #6 to #13 containing the remaining equipment, which are temporarily stored on the ground or in the section behind the shaft tail, and will be connected after subsequent tunneling to the preset distance.

[0031] Step 3: Following the TBM large-scale split-type launching method, the main unit and trolley included in the TBM core working unit are sequentially hoisted through the vertical shaft and pushed to the launching tunnel for assembly and commissioning.

[0032] First, the middle shield 12, front shield 11, cutterhead 10, and tail shield 13 of the TBM main unit 9 are sequentially lowered into the well for assembly using a crawler crane. After being secured with bolts, the main unit is then pushed in the air to the face of the TBM starting tunnel via a pre-laid track. Figure 4 As shown. Then, the connecting bridge 14 is hoisted down into the well and connected to the main unit. Afterwards, trolleys #1 to #5 are sequentially lowered into the well and connected to the main unit via the connecting bridge, as shown. Figure 5 As shown.

[0033] In this embodiment, since the vertical shaft and shield tunnel section 15 had been completed before the TBM tunnel excavation, the remaining trolleys #6 to #14 were placed within the completed shield tunnel section 15 for subsequent connection. Figure 6 As shown.

[0034] Step 4: Modify the interface of the TBM core operating unit to enable unloading, slag transportation and pipeline extension.

[0035] The process of modifying the interface of the TBM core work unit is as follows: A rear-mounted belt conveyor unloading port was added to the rear of trolley #4, and the gravel tank transfer belt was modified to meet the needs of slag unloading and material transfer; the space behind trolley #5 was used for hoisting tunnel segments and temporary slag trucks; extension systems such as grouting pipelines, water pipes, cables and air pipes were added to connect with subsequent equipment.

[0036] Once the starting tunnel is ready to accommodate the entire machine, the slag outlet of the rear-mounted belt conveyor will be returned to the No. 8 trolley.

[0037] The space behind trolley #5 is used for hoisting segment 17 and temporary dump truck 16, such as Figure 8 As shown.

[0038] The project includes the addition of extension systems for grouting pipelines, water pipes, cables, and air pipes to connect with subsequent equipment. Temporary supports will be constructed within the shaft and pilot tunnel, and S-shaped coils will be installed vertically or horizontally for temporary pipeline storage. A pipeline length of 150m will be reserved. Specific pipeline modifications are as follows: Dust removal system: Move the dust collector forward to trolley number 5 for dust removal.

[0039] Water system: The internal circulation cooling system is on trolley #9, with the internal circulation pipeline extended and connected manually; the industrial water system is on trolley #10, with the pipeline extended and connected manually; the sewage tank is on trolley #12, with the pipeline extended and connected manually.

[0040] Electrical system: The necessary electrical control system for construction is already on trolleys 3 to 5. The extension cables are directly connected to the high-voltage switch cabinet and other electrical cabinets. Cable supports are prepared in advance, and the cables are laid manually.

[0041] Industrial air systems: Cable supports should be prepared in advance, and pipes should be laid manually.

[0042] Filling system: The pea gravel filling system is already on trolley #5. The pea gravel is temporarily pumped from the ground to trolley #5 via pipeline; the cement silo is temporarily stored on the ground, and the grouting system is a temporary system that is transported to the tunnel wall via pipeline.

[0043] Step 5: After the TBM main unit is pushed into the tunnel, install the rock anchor reaction frame, and configure the horizontal transport train during the initial stage of the TBM large segment launch. Use the horizontal transport train to complete the removal of excavated soil and the lowering of tunnel segments in the launch shaft.

[0044] The rock-anchored reaction frame consists of a ring plate, supports, and diagonal braces. The ring plate is pre-embedded in the launching tunnel and is firmly connected to the tunnel wall via mortar anchors. The angle between the diagonal brace and the support is set at 60°, and the angle between the diagonal brace and the tunnel wall is set at 30°. The support and diagonal brace are made of HW250 steel, and the mortar anchors are Ф22 mortar anchors. No special excavation of the launching tunnel is required for the TBM reaction frame.

[0045] At position 6, the boundary between the initial tunnel segment and the secondary lining, 15 pre-embedded reaction frame supports and diagonal bracing steel plates 7 are installed along the tunnel ring. Each steel plate is fixed to the initial tunnel using mortar anchor rods 8. The dimensions of the pre-embedded steel plates are 450×450mm and 700×450mm, respectively. The centerline deviation of each steel plate is ±10mm. These are used to fix the reaction frame supports and diagonal bracing, ensuring that the reaction frame is installed firmly and reliably.

[0046] When the TBM starts, it relies on the auxiliary thrust cylinder 20 for power, and the jacking force of the auxiliary thrust cylinder acts on the reaction frame. After normal operation, it relies on the TBM support shoes to provide reaction force against the tunnel wall. A rock-anchored reaction frame is installed after the TBM is pushed into the tunnel. Figure 3 As shown in (a) and (b), the rock-anchored reaction frame consists of ring plates 21, supports 22, and diagonal braces 23. There are 30 ring plates 21; 30 supports 22, made of HW250×250mm steel; and 30 diagonal braces 23, also made of HW250×250mm steel. The angle between the diagonal braces and supports is 60°, and the angle with the tunnel wall is 30°. The allowable horizontal deviation for the reaction frame installation is no more than ±10 mm, and the elevation control is no more than ±15 mm.

[0047] The supports and braces here are used to ensure stable support, accurate guidance, and initial propulsion for the TBM main unit.

[0048] like Figure 7 As shown, the train formation consists of two horizontal transport formations (18) during the initial stage of the split-type launch, each pulled by a 45-ton electric vehicle, and equipped with one slag car and two segment cars. After the TBM enters the launch tunnel as a whole, it will be converted into a normal train formation (19).

[0049] Step 6: After the TBM core working unit is assembled and debugged, start excavation and assemble the tunnel segments within the main unit's range. When the excavation reaches the set distance, connect the temporarily stored unit to the core working unit and connect the whole machine to restore the TBM's overall operating state and switch to normal tunneling mode.

[0050] For example, in the initial stage of the split-type launch, two horizontal transport trains are configured, each train is pulled by a 45-ton battery-powered vehicle, and is equipped with one slag car and two segment cars.

[0051] Initial Excavation: After the TBM core operating unit is assembled and debugged, the horizontal transport train 18 is hoisted down into the shaft, the tunneling system is started, and the initial reaction force is provided by the reaction frame. The tunnel segments in the area where the main unit is located are assembled and fixed simultaneously. During tunneling, the belt conveyor transports the excavated soil to the unloading port at the rear of the No. 4 trolley and drops it into the excavation car of the train; tunnel segments, excavated soil and other materials are loaded and unloaded through the starting shaft.

[0052] Machine Integration: After the TBM has advanced more than 120 meters, there is sufficient space inside the tunnel to connect subsequent trolleys. Trolleys #6-#13, temporarily stored in the tunnel behind the shaft, are towed to the rear of the core unit using a battery-powered vehicle. Mechanical connections are completed sequentially (bolt torque meets specifications), hydraulic lines (pressure maintained without leakage), and electrical lines (insulation qualified). All temporary extension pipelines are removed, and all systems are restored to their factory integrated state. After overall machine testing, tunneling resumes. Simultaneously, the train formation is restored to normal train formation #19.

[0053] Step 7: For tunnels with small clearance between overlapping lines, the TBM will start excavating the down line first, and then start excavating the up line. When the up line is being excavated, internal supports will be installed inside the down line tunnel.

[0054] The internal support in step 7 is a movable support, consisting of a hydraulic cylinder, column, crossbeam, pressure gauge, inward-facing brace, and support wheels. For example... Figure 9 As shown, the pressure gauge can be used to monitor the stress on the downlink tunnel caused by the TBM's uplink tunnel construction.

[0055] For the initial excavation of overlapping tunnels with small clearance, the TBM should begin excavation of the downline first, followed by the upline. After the TBM for the first tunnel has completed its overall connection and excavation, the TBM for the subsequent line will be lowered into the shaft for assembly and begin excavation. To ensure safe construction of the overlapping double-track subway tunnels with small clearance, internal supports 24 should be installed inside the downline tunnel during the upline excavation. Figure 9 As shown.

[0056] The position of the inner support 24 should be dynamically matched with the tunneling speed of the upstream TBM main unit, ensuring that the TBM main unit remains within the range of the movable support. Specifically, to avoid the impact of the rear support shoe of the TBM main unit on the downstream tunnel, after each support adjustment, the tail of the movable support should always be controlled to be 2-3m behind the tail of the TBM main unit. The single-cycle tunneling length of the TBM should not exceed (trolley length - main unit length - 2-3m), and tunneling can only continue after the trolley has been moved into place. This process continues until the downstream TBM completes the overall connection and construction of the tunnel section with overlapping lines and small clearance.

[0057] After completing the above tunneling, the dual-track TBMs entered normal tunneling operation.

[0058] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for starting and safely excavating a large-part TBM in a small-clearance tunnel with overlapping lines, characterized in that, Comprise: Construction of the starting guide hole and the starting well, and adaptation of TBM passing and installation, tunnel geology and double-line tunnel spacing; According to the length limit of the starting guide hole and the relevance of equipment functions, the TBM is divided into a TBM core operation unit and a unit to be connected, the core operation unit meets the basic functions of starting stage excavation, support and slag discharge, and the unit to be connected is temporarily stored in the ground or the tail section of the shaft, and is connected after subsequent excavation to a preset distance; According to the TBM large-part starting mode, the main machine and the trolley included in the TBM core operation unit are sequentially hoisted through the shaft and pushed into the starting hole for assembly and debugging; The interface of the TBM core operation unit is modified to realize unloading, slag transportation and pipeline extension; After the TBM main machine is pushed into the hole, a rock anchor type counterforce frame is installed, and during the TBM large-part starting stage, the horizontal transportation composition is configured, and the horizontal transportation composition is used to complete the slag transportation and segment lowering in the starting well; After the TBM core operation unit is assembled and debugged, starting excavation and segment assembly within the range of the main machine are performed, and when excavation to a set distance is completed, the temporarily stored unit to be connected is connected to the core operation unit and the whole machine is connected, and the TBM whole machine operation state is restored, and the normal excavation mode is entered; For the starting excavation of a small-clearance tunnel, the TBM first starts to excavate the lower line, and then starts to excavate the upper line, and during the excavation of the upper line, an internal support is arranged in the lower line hole.

2. The method of claim 1, wherein the method further comprises: The starting shaft, the starting guide hole and the guide table are constructed, the size of the starting guide hole is adapted to the passing and installation of the TBM core operation unit, and the starting well is reserved with slag and material discharge ports to meet the requirements of slag discharge and material transfer during construction.

3. The method of claim 1, wherein the method further comprises: The length of the starting guide hole is determined by the length of the TBM core operation unit, the tunnel geology and the small-clearance double-line tunnel.

4. The method of claim 1, wherein the method further comprises: The main structure of the starting well is constructed before the TBM starts, and the net space reserved on the top plate of the main structure meets the requirements of double-line TBM equipment, slag discharge and material discharge.

5. The method of claim 1, wherein the method further comprises: The TBM core operation unit includes a main machine and 1-5# trolleys, and the unit to be connected includes 6#-13# trolleys.

6. The method of claim 5, wherein the method further comprises: The assembly sequence of the TBM core operation unit is: Firstly, the middle shield, the front shield, the cutter head and the tail shield are sequentially assembled into a main machine empty push into the starting hole through a crawler crane, then the connecting bridge is hoisted and connected with the main machine, and then 1#-5# trolleys are sequentially hoisted and connected with the main machine through the connecting bridge.

7. The method of claim 1, wherein the method further comprises: The process of modifying the interface of the TBM core operation unit is: A rear supporting belt conveyor discharge port is added at the tail of the 4# trolley, and the pea gravel tank transfer belt is modified to meet the requirements of slag discharge and material transfer; the space behind the 5# trolley is used for hoisting segments and temporary slag cars; and grouting pipelines, water pipes, cables and gas pipes are added to extend the system and connect with subsequent equipment.

8. The method of claim 1, wherein the method further comprises: To ensure the safety of double-line tunnel construction, the left and right lines of the TBM are started respectively, and after the TBM of the first line is excavated to complete the whole trolley assembly, the TBM of the other line is started to excavate.

9. The method of claim 1, wherein the method further comprises: During the excavation of the upper line, the TBM main machine always excavates within the support range of the lower tunnel.

10. The method of claim 1, wherein the method further comprises: The rock anchor counterforce frame is composed of a ring plate, a support and a diagonal brace; the ring plate is pre-buried in the starting hole and is firmly connected with the guide hole rock wall through the mortar anchor rod; the included angle between the diagonal brace and the support is 60°, and the included angle between the diagonal brace and the hole wall is 30°.

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