Disassembling method in shield low-net cavity

Abstract

The invention discloses a method for disassembling a shield in a low-net cavity. The method comprises the following steps: (1) disassembling an oil cylinder, a cutterhead motor and a speed reducer; (2) a trolley 8-2 is dismantled; (3) a reduction gearbox of the first-stage screw conveyor and double gates of the screw conveyor are dismounted; (4) the connecting bridge, the second-stage screw conveyor and the first trolley are dismantled; (5) the first-stage screw conveyor is dismantled; (6) the erector and the joist are dismantled; (7) the shield body is pushed, and the middle shield and the hinge ring are separated; (8) a shield tail is dismantled; (9) the middle shield and the hinged ring left sub-block as well as the middle shield and the hinged ring right sub-block are disassembled; (10) the H beam is dismantled; (11) a human bin and a central rotary joint are dismantled; the disassembling method in the shield low-clean cavity comprises the following steps of (1) disassembling a middle shield and a hinged ring, (2) disassembling the middle shield and the hinged ring, (3) disassembling the middle shield and the hinged ring, (4) disassembling the middle shield and the hinged ring, (5) disassembling the front shield and the hinged ring, (6) disassembling a driving part, (7) disassembling the front shield and the hinged ring, and (18) turning over the center block of the cutter.According to the disassembling method in the shield low-clean cavity, efficient disassembling in the shield low-clean cavity is achieved, and the safety of disassembling the machine in the cavity is improved.

Description

Technical Field

[0001] This invention belongs to the field of shield tunneling equipment dismantling and construction technology, and particularly relates to a method for dismantling shield tunnels with low clearance. Background Technology

[0002] "Disassembly within a low-clearance tunnel" refers to the process of disassembling, breaking down, and transporting a large tunnel boring machine (TBM) after it has completed its tunneling task in an underground environment with limited space.

[0003] The core challenges of dismantling a shield tunnel in a low-clearance tunnel are: limited space, complex structure, and concentrated safety risks, which can be understood from the following aspects.

[0004] Technical challenges arising from extremely limited space: ① Difficult equipment layout: Tunnel inner diameter is typically only a few meters, making it difficult for conventional lifting equipment to enter or operate normally within it; equipment must be arranged within a limited cross-section, with very limited space for cranes, lifting tools, dismantling platforms, transport trolleys, and personnel operations. ② Restricted lifting posture: Lifting points are often close to the top or sidewalls, with a very small radius of motion, preventing free swinging as in open areas; if a component's center of gravity shifts, it is highly susceptible to collision with the tunnel lining and segments, leading to equipment or structural damage. ③ Large components cannot be transported as a whole: the dimensions of cutterheads, front shields, etc., are often close to or exceed the tunnel clearance, requiring multiple cutting and disassembly into sections; too many sections lead to problems such as chaotic on-site management, increased precision control, and more lifting operations.

[0005] The tunnel boring machine (TBM) has a complex structure and a high degree of process coupling: ① The components are large, heavy, and irregularly shaped. Components such as the cutterhead, main bearing housing, and screw conveyor are both heavy and bulky, requiring specially designed lifting tools and lifting schemes. The irregular shape makes it difficult to estimate the center of gravity and results in poor stability, demanding extremely high precision in lifting command and operation. ② Multiple systems are interdependent. Hydraulic pipelines, electrical control lines, and lubrication systems are often intertwined. Failure to dismantle or isolate one component can affect the safe dismantling of other components. ③ The dismantling sequence is highly sensitive. An incorrect sequence can lead to loss of center of gravity control, structural instability, blocked critical connection points that have not yet been dismantled by dismantled components, and stress concentration or even localized deformation of the remaining structure after the supports have been removed.

[0006] Safety risks are highly concentrated: ① Risks of confined space operations: Poor air circulation poses risks of oxygen deficiency and accumulation of toxic and harmful gases. ② Risks of lifting and mechanical injuries: Under low clearance conditions, lifting blind spots increase, making it easy for oblique lifting, swaying impacts, and falling objects to occur; the probability of suspended objects contacting tunnel walls and pipelines is much higher than in open areas. ③ Structural instability and secondary disasters: After the shield tunnel body is cut and lifted into sections, if the temporary support is not reasonable, it may cause the remaining shell to tilt or slip; abnormal stress on the tunnel segments may lead to local cracking or leakage.

[0007] Increased difficulty in construction organization and management: ① Reduced construction efficiency: Due to space constraints, the work area that can be carried out at the same time is limited, and frequent cross-interference between personnel and equipment forces a slowdown in the work pace. Limited hoisting paths require repeated adjustments, consuming significant time and space resources. ② High complexity of on-site coordination: Multiple positions, including crane operators, signalmen, mechanical repairmen, electrical maintenance personnel, and safety managers, need to be coordinated simultaneously. In confined spaces, any delay in communication can lead to work stoppages or accidents. ③ Difficulty in managing materials and waste: Disassembled parts and materials are piled up in limited spaces, requiring both passage requirements and prevention of loss and damage. Numerous small parts such as bolts, gaskets, and seals are easily confused, affecting subsequent reassembly or quality traceability.

[0008] Equipment selection and adaptation are challenging: ① The requirements for lifting equipment are stringent, demanding small dimensions, large lifting capacity, wide working radius, and good mobility; conventional models have low compatibility. ② Specialized tooling is costly and time-consuming; to adapt to low headroom conditions, customized lifting beams, lifting tools, and specially made segmented cutting fixtures or tilting platforms are required.

[0009] Uncertainties in the environment and surrounding conditions: ① Existing facilities face significant protection pressure, as the tunnel already contains cables, fire-fighting pipelines, communication lines, ventilation ducts, etc., and even slight deviations in the movement path of the suspended load could result in snagging or damage. ② The geological and structural conditions are unknown; after long-term operation, micro-cracks and leaks may appear at the joints of the tunnel segments, and vibrations during dismantling may induce new problems. Summary of the Invention

[0010] The purpose of this invention is to provide a method for dismantling a shield tunnel with low clearance, which enables efficient dismantling within the tunnel and improves the safety of dismantling the machine inside the tunnel.

[0011] To achieve the above objectives, the technical solution of the present invention is to design a method for dismantling a shield tunnel with low clearance, comprising the following steps: Step 1: Dismantle the hydraulic cylinder, cutter head motor, and reducer. Use an assembly machine to install a gantry frame fixture. Use the forward and backward movement function of the assembly machine and a hand-operated hoist to fix and dismantle the push hydraulic cylinder. Dismantle the cutter head motor and reducer in advance to expand the internal space, and then dismantle the articulated hydraulic cylinder. Step 2: There are 1 to n trolleys, where n is a positive integer greater than or equal to 2. Remove 2 to n trolleys. Step 3: Remove the first-stage screw conveyor gearbox and the screw conveyor double gate; Step 4: Dismantle the connecting bridge, secondary spiral conveyor, and No. 1 trolley; Before dismantling, remove the walkway panels on both sides of the connecting bridge to reduce the clearance on both sides, and transport it out by connecting the connecting bridge and No. 1 trolley; The traction process during horizontal transportation is as follows: lifting the secondary spiral conveyor of the connecting bridge out of the well; dismantling the left and right sliding platforms of the connecting bridge; lifting the connecting bridge out of the well; retracting No. 1 trolley to the well opening; lifting No. 1 trolley out of the well; Step 5: Dismantling of the primary spiral compressor; dismantling is carried out by welding a portal frame to the upper part of the assembly machine's support beam and installing supports at the bottom; during dismantling, the two sides are used for the main force pulling, and the middle is used as an auxiliary pulling point for slow pulling out; one portal frame is set on each side of the front and rear of the assembly machine, and two lifting points are welded at the H-beam inside the ring to assist in pulling out; during the hoisting process of the spiral compressor, additional lifting points are added to meet the pulling requirements; after the spiral compressor is lowered to the horizontal position, a flatbed truck is used to fix the primary spiral compressor. In order to reduce the overall height of the spiral compressor, a heavy-duty flatbed truck is used for transportation. The primary spiral compressor needs to be fixed in the center position in the heavy-duty flatbed truck; Step Six: Dismantle the Assembly Machine and Support Beams; Dismantle the circular platform and suction cups in advance. Weld lifting lugs to the top of the shield tail to assist in dismantling. Install rails and stirrups at the shield tail. Drive the heavy-duty flatbed truck to the bottom of the assembly machine and support beams. Secure the flatbed truck with iron shoes. Use welding fixtures to fix the flatbed truck and the assembly machine support beams to achieve a state where the lower part supports the assembly machine support beams and the upper part assists in hoisting, preventing the assembly machine from tipping over after dismantling due to displacement. Suspend several hand-operated hoists at the upper lifting points for auxiliary use. Step 7: Shield body jacking, separation of the middle shield and articulated ring; after the dismantling of the supporting trolley, assembly machine, auger, and connecting bridge, the shield body is jacked to near the edge of the station platform, leaving space between the front of the cutterhead and the station platform for subsequent dismantling of the cutterhead side blocks; before jacking, the bracket is extended to the edge of the station platform and reinforced with steel sections before jacking; during the dismantling of the shield body in sections, the articulated ring is separated from the middle shield in advance, the seal is removed before jacking, and the top is welded on the left and right sides of the articulated ring seam. The push plate and hydraulic cylinder are used to push the ring seam horizontally until it separates from the circumferential seam. Guide columns are welded at the circumferential seam. Pushing is stopped after both seals are completely exposed. After the middle shield separates from the hinge ring, the mounting plates are welded on both sides for fixation. The seal is cut at the joint between the middle shield and the hinge ring using a utility knife. The weld is removed and separated at the finishing surface using a carbon planer. After the separation is completed, the seal is pressed back into the groove using a pressure plate. After the hinge ring is separated, the mounting plates are welded on both sides of the bracket to push the hinge ring back to its original position. Step 8: Shield tail dismantling, including the left, right, and lower shield tail sections; a multi-point lifting operation is employed, using several hand-operated hoists, tightening them simultaneously. First, tighten the cross-type hand-operated hoists until the entire shield tail is balanced and lifted upwards. Then, simultaneously adjust the main load-bearing hand-operated hoists until the shield tail is detached. Use detachable jacks for complete separation. Tighten the hand-operated hoists until the upper part is detached, then tighten the lower part, pulling the thick shield tail transverse seam into the inner side of the shield tail ring. The gantry frame is slowly moved backwards to the lifting and loading area for transport. The left tail section uses a gantry frame with double lifting points as cross lifting points to fix the shield tail. When the shield tail rotates, a hand-operated hoist is suspended from the center point lifting lug of the gantry frame. The hoist has a built-in rotation function and uses the shield tail lifting points for rotation and loading. During loading, a flatbed is welded to the heavy-duty flatbed truck for fixed horizontal transport. The right section has lifting lugs welded on both the inside and outside of the shield tail. The outer side is mainly stressed, and the inner side lifting points are used for oblique lifting and tightening for dismantling. The lower section has symmetrical lifting lugs welded inside the shield tail. The hand-operated hoist is tightened upwards, and it is only required to meet the conditions for rotation and loading. Step Nine: Dismantling of the central shield and the left and right sections of the articulated ring; The central shield and the left section of the articulated ring are partially lifted using a cross-hoisting system, with some hoists carrying the load; during the lifting process, the cross-hoisting system is used to slowly lift the section, causing the flange of the central shield to completely detach from the upper and lower openings of the flange surface. A gantry crane is then used to slowly move it backward to the loading area. The rails in the loading area need to be temporarily removed to avoid interference with the lowering of the central shield. After the central shield section is lifted, the rails are extended to the lowering position of the central shield; after being placed horizontally on the steel platform, hoists suspended at the front and rear sides of the center of the gantry crane are used to rotate the left section of the central shield. The gantry frame is assisted in rotation by using lifting lugs at the center of the central shield. Removable lifting lugs can be used to suspend the upper lifting point hoist at the flange face of the central shield and the right segment of the hinge ring. After the right segment separates from the flange face of the lower segment, the gantry frame is slowly moved to the rear steel platform. The lower part of the right segment is lifted using the left lifting point to achieve a horizontal state. Rotation is achieved through the hoist and the steel wire rope. When loading the central shield and the left and right segments of the hinge ring, multiple layers of solid square timber are required at the corners of the central shield segment to maintain the balance of the central shield during horizontal transportation. The internal steel structure is welded and fixed to the heavy-duty flatbed truck. Step 10: H-beam dismantling; Move the shield back to leave enough space for the cutterhead to be dismantled in sections. Use several hoists and shackles to dismantle the H-beam by suspending it from the lifting points to the inside of the H-beam; First, dismantle the H-beam by using the original lifting points, move the gantry frame to the rear, and then use the original lifting points and the flipping lifting points to flip the H-beam over. Step 11: Dismantle the manhole and central slewing joint; During the hoisting process, add lifting lugs on both sides of the manhole to ensure balance and left and right leveling, and use hoists to adjust the manhole forward and backward while it is suspended in the air; The central slewing joint is dismantled using slings and a top hoist. Step 12: Dismantle the upper and lower sections of the cutterhead; use the outermost lifting point of the gantry frame to dismantle the upper section of the cutterhead. During dismantling, use a water drill to create a lifting point directly opposite the center of the cutterhead on the station platform to allow the upper section to be placed on the platform. After the upper section is dismantled, move the gantry frame to the platform position and use a hoist suspended from the center anchor point of the platform to pull the upper section to the platform. When dismantling the lower section of the cutterhead, weld symmetrical lifting lugs at the opening and use a hoist. Use slings to assist in lifting at the center lifting point. After the hand-operated hoist is under force, cut off the fixed plates on both sides and let it fall naturally. Then use the gantry frame to move the lower section of the cutterhead to its limit position. For the remaining distance, use the station center anchor point, hoist, and wire rope to press the side block tightly against the platform and use the fixed plates to fix the outer arc surface of the cutterhead on both sides. Step 13: Remove the center block of the cutterhead. After removing the positioning pin, use a hoist and jack to remove the center block. When removing the center block of the cutterhead, rely on the left and right lifting lugs at the center of the gantry frame as the main lifting points. Step Fourteen: Dismantle the lower section of the middle shield and the articulated ring; the lower section of the middle shield, the lower section of the tail shield, and the right section of the middle shield and the articulated ring shall be dismantled in the same way; Step 15: Remove the upper block of the front shield; After separating the upper block from the lower block, place it directly behind the center block of the cutterhead. After the drive unit and the lower block of the front shield have all exited the well, proceed with the exit from the hole. Step 16: Dismantle the drive unit; The upper lifting lugs of the drive unit need to be increased by at least two main lifting lugs at their center distance, and at least two additional lifting points should be added in the middle for auxiliary lifting. At least two additional lifting points should be added on the left and right sides of the drive partition ring for front-to-back adjustment. During dismantling, all hoists should be in a tightened state. First, tighten the main lifting point hoists, then use the hand-operated hoists to apply force evenly until the lower part of the drive unit opens. Then tighten the main lifting points again and use the hand-operated hoists to adjust the front-to-back and left-to-right distances. Before the drive unit is rolled over, place the rolling over fixture at the entrance. Once the drive unit is dismantled, place it directly into the rolling over fixture. Use the four lifting lugs around the drive unit to lift it to the heavy-duty flatbed truck. Use a platform to fix and weld the partition ring component to the heavy-duty flatbed truck. Step 17: Dismantle the lower section of the front shield; the lower section of the front shield, the lower section of the tail shield, the middle shield, and the right section of the hinged ring shall be dismantled in the same way; Step 18: Turning the cutterhead center block over; Place the cutterhead center block horizontally in a heavy-duty flatbed truck for transport outside the tunnel. Before turning it over, remove the seals on the inner and outer circumferences of the cutterhead and roll it over, following the same procedure as when removing the cutterhead center block. After tightening all hoists, remove all anti-tipping fixtures from the cutterhead and slowly move the gantry frame towards the tunnel entrance. Place solid square timber under the bracket to protect the flange lip from damage. When turning it halfway, use steel wire ropes to hold the cutter box at the bottom for leveling. After turning, use steel columns for reinforcement and support. When loading, adjust the direction of the cutterhead according to the distance on both sides to prevent it from being unable to pass through the tunnel. After loading, use steel columns for reinforcement and support against the heavy-duty flatbed truck. After transporting the cutterhead center block, hoist and load the other two smaller blocks using the same method as during dismantling, completing all the dismantling procedures inside the tunnel.

[0012] Further, in step one, a gantry frame is welded at the center of the steel structure of the assembly machine. First, the bolts fixing the hydraulic cylinders are removed. Then, the assembly machine's traveling function is used to pull the cylinders out halfway. After the cylinders are fixed in their front and rear positions, the entire cylinder is pulled out. The assembly machine's rotation function is used to lower the cylinders to their lowest point. A double-beam crane is used to transport the cylinders out of the opening one by one. The dismantling sequence proceeds from simple to complex, starting from the bottom and extending outwards to both sides, finally dismantling the upper pushing cylinder. When dismantling the cutter head motor or reducer, manual assistance is used. The hoist is used to drag and dismantle the machine from behind the motor or reducer. During the lowering process, the lifting point near the assembly machine is used to move the machine backward. When dismantling the articulated cylinder, both the front and rear pin seats are fixed by pins. After fixing the articulated cylinder in place, the pin near the cutterhead is removed using a hand-operated hoist. Then, the rear pin is removed using the lifting strap installed on the top of the shield. The cylinder is then moved to the middle shield platform using a hand-operated hoist. The lowest point of the tunnel below the articulated cylinder is then moved out using the lifting lugs welded in the shield.

[0013] Furthermore, in step two, two dump trucks are used, and cross braces are welded to the front and rear columns of the dump truck each time. During transportation, after the dump truck derails, the wheels of the dump truck are removed and added to the lighter side of the dump truck to maintain the balance of the dump truck during transportation.

[0014] Furthermore, in step three, the connecting bridge is first reinforced and used as a lifting point for removing the gearbox; the single gate connecting the first and second stage screw conveyors and the double gate at the bottom of the first stage screw conveyor are removed; the ball joint connecting the first and second stage screw conveyors and the short cylinder are removed, the second stage screw conveyor is pushed backward towards the trolley, and the sides of the screw conveyor are reinforced with structural steel; windows are opened on the upper part and left side of the screw conveyor cylinder, the screw conveyor gearbox and the gearbox pin are removed, and lifting lugs are welded to both sides of the screw conveyor gearbox for fixation; the bolts connecting the gearbox and the first stage screw conveyor are removed, and the hexagonal head is pushed out of the screw conveyor shaft with the assistance of separate jacks on both sides, and anti-falling plates are welded into the blades; the screw conveyor gearbox is lowered, the flatbed truck is parked below, and after the gearbox is reinforced, it is transported horizontally.

[0015] Furthermore, in step six, when the assembly machine beam is lowered, several sets of steel supports are welded to both ends of the beam; a limit baffle is installed at the beam flange; when all the beam bolts are removed and the safety is cut off, if the beam and the sub-beam are not separated, a top bracket is welded to the sub-beam flange, and split jacks are used on both sides to separate the beam.

[0016] Furthermore, in step seven, a steel plate is laid at the rear of the shield tail. One component is removed and a steel plate is laid to facilitate the subsequent dismantling of the shield body, the cutting head segmentation, and the use of the drive to turn over.

[0017] Furthermore, in step thirteen, the downward force is released the instant the center block is removed. During the process, the center block is fixed by adding a support plate on both sides, and a support stirrup is added at the lower flange of the center block and the cutterhead flange.

[0018] Furthermore, in step sixteen, before removing the main drive, the center slewing joint should be fixed in advance to prevent it from slipping during the overturning process. Pay attention to whether there is any deformation at the positions of the gantry column and diagonal brace.

[0019] The advantages and beneficial effects of this invention are as follows: 1) It reduces the risk of construction inside the tunnel and greatly improves the safety of dismantling the shield tunnel inside the tunnel.

[0020] 2) Optimize the dismantling process in the low-clearance tunnel of the shield, greatly improve dismantling efficiency, and reduce damage to the shield and dismantling tools during the dismantling process. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] Example: I. Construction Overview (Dismantling Project of 8-meter-class Shield Tunnel with Low Clearance in Guangzhou Fangbai Intercity Railway): Section: Man-machine shield tunneling shaft / interval shield tunneling shaft, divided into two lines, left and right, with a distance of 15m between the left and right lines. The thickness of the soil cover on the arch is 20.6m~31.6m. The total length of the left line is 3048.6272m and the total length of the right line is 3080.4844m.

[0024] II. Overview of the Cave: The dimensions of the right-line receiving shaft of the tunnel boring machine are 17.5m (length) × 13.1m (width) × 10.77m (depth). All components for transportation within the tunnel are transported from the receiving shaft to the tunnel and then to the launching shaft. The space inside the tunnel is relatively small, with 7 connecting passage support beams inside the tunnel, each occupying 20cm of space on one side of the tunnel. All equipment is transported to the outside of the tunnel using battery-powered vehicles, flatbed trucks, and dump trucks.

[0025] III. Shield Tunneling Equipment Parameters The equipment is a composite earth pressure balance shield machine with a diameter of Ф8840mm. The main components of the shield machine include the cutterhead, drive unit, front shield, middle shield / articulated ring (T1), shield tail (T2 / T3), primary spiral machine, secondary spiral machine, assembly machine, vacuum suction cup, personnel gate, longitudinal beam, connecting bridge, transport beam, and trolleys No. 1 to No. 8.

[0026] The gantry frame fixture is 10150mm high, 10780mm wide, and 4500mm long. It is mainly composed of columns, drive wheels, drive motors, crossbeams, and lifting lugs. The heaviest component during disassembly is the main drive, weighing approximately 90t.

[0027] The transport vehicle was pulled out of the tunnel by a combination of a heavy-duty air-brake flatbed truck and a 55t battery-powered truck. The dimensions were 9650mm long * 1600mm wide * 1200mm high, and the weight was 15.25 tons.

[0028] Dismantling steps inside the tunnel Step 1: Removal of the hydraulic cylinder, cutter head motor, and reducer. ① Removal of the hydraulic cylinders: There are 38 hydraulic cylinders. The assembly machine is used to install the gantry frame tooling. The assembly machine's forward and backward movement function and a 2t hand chain hoist are used to fix and remove them.

[0029] Weld a gantry frame at the center of the steel structure of the assembly machine. First, remove the four M36 bolts that fix the hydraulic cylinder. Then, use the traveling function of the assembly machine to pull out half of the hydraulic cylinder. After the front and rear positions of the hydraulic cylinder are fixed, pull out the individual hydraulic cylinders as a whole. Use the rotation function of the assembly machine to lower the hydraulic cylinder to the lowest point. Use a double beam crane to transport the hydraulic cylinders out of the hole one by one. The dismantling sequence is from simple to difficult. Start dismantling from the bottom and extend to both sides. Finally, dismantle the upper pushing hydraulic cylinder.

[0030] ② Removal of articulated cylinder, cutter head reducer, and motor: To ensure sufficient internal space for removing the articulated cylinder, the cutter head motor and reducer must be removed beforehand to expand the internal space. The removal process is the same as that for the articulated cylinder. Note that when removing the cutter head motor or reducer, a hand chain hoist is needed to drag it from the rear of the motor or reducer. During the lowering process, the lifting points near the assembly machine should also be used to move it backward. When removing the articulated cylinder, both the front and rear pin seats are fixed by pins. After fixing the articulated cylinder in place, use a 2t hand chain hoist to remove the pins near the cutterhead. Then, use a 2t sling installed on the top of the shield to remove the rear pins. Use a hand chain hoist to move the cylinder to the middle shield platform. Use the lifting lugs welded in the shield to move the lowest point of the tunnel below the articulated cylinder out.

[0031] Step 2: Dismantle trolleys 8-2 During the dismantling of the trolleys, the heaviest trolleys were No. 2 and No. 3, with one side being heavier than the other. To ensure the efficiency and safety of the dismantling process, two 18m3 dump trucks were used. Each time, cross braces were welded to the front and rear columns of the trolleys and inserted into the dump trucks to ensure stability. Small triangular plates were used to firmly hold the cross braces in place.

[0032] During transportation, attention must be paid to the tunnel clearance and the issue of uneven weight distribution. After the trolley is derailed, the wheels of the trolley must be removed and added to the lighter side of the trolley to maintain the balance of the trolley during transportation. Due to the weight of the trolley, the cross braces need to be made of 400 steel.

[0033] Step 3: Dismantle the primary screw conveyor gearbox and the screw conveyor double gate. ① First, reinforce the connecting bridge with 200-type steel and use it as a lifting point for removing the gearbox; ② Remove the single gate connecting the first and second stage screw conveyors and the double gate at the bottom of the first stage screw conveyor; ③ Remove the ball joint and short cylinder of the first and second spiral machines, push the second spiral machine backward (100mm) towards the trolley, and reinforce both sides of the spiral machine with structural steel. ④ Open windows (400mm*300mm) on the upper part and left side of the screw conveyor cylinder, remove the screw conveyor gearbox and gearbox pin, and weld lifting lugs on both sides of the screw conveyor gearbox for fixation; ⑤ Remove the bolts (M36) connecting the gearbox and the first-stage screw conveyor. Use a split jack (50t) on both sides to help push the hexagonal head out of the screw conveyor shaft, and weld anti-falling plates into the blades. ⑥ Lower the screw conveyor gearbox, place the flatbed truck below it, and after the gearbox is reinforced, proceed with horizontal transportation.

[0034] During the dismantling process, the screw conveyor gearbox had no motor maintenance port, making it impossible to remove the gearbox motor. The connecting bridge crossbeam column was removed to allow for the removal of the gearbox.

[0035] Step 4: Dismantle the connecting bridge, secondary spiral conveyor, and No. 1 trolley. During the dismantling of the connecting bridge, due to the long distance of the tunnel, the long longitudinal distance of the connecting bridge, and the combined weight of the secondary spiral conveyor and the connecting bridge (74 tons) and the No. 1 trolley (57 tons), the connecting bridge and the No. 1 trolley were used for transport. This eliminated one step of the connecting bridge installation and support equipment process. During the reinforcement period, two 18m³ dump truck hoppers and one dump truck were used for front and rear reinforcement. The trolley reinforcement method was the same as that of other trolleys. The front of the connecting bridge was reinforced with 300-type steel welded support columns and diagonal braces to ensure the stability of the connecting bridge during transportation.

[0036] Before the demolition, considering that the turning radius of the long section of the tunnel is small, it is necessary to remove the walkway slabs on both sides of the connecting bridge in advance to reduce the clearance on both sides and ensure that there is no interference with the tunnel segments when turning.

[0037] During horizontal transport, due to the long longitudinal distance and heavy weight of the traction components, the 55t electric vehicle locomotive operates at a speed of less than 1km / h throughout the entire process.

[0038] The procedure for pulling the object to the opening: ①The connecting bridge is removed from the well by a secondary spiral hoist; ② Remove the left and right sliding platforms of the connecting bridge; ③ The connecting bridge is hoisted out of the well; ④ Car No. 1 moves back to the wellhead; ⑤ The No. 1 trolley was hoisted out of the well.

[0039] Step 5: Dismantle the primary screw conveyor The first-stage spiral machine is dismantled by welding a gantry frame to the upper part of the assembly machine support beam and installing a support at the lower part. During dismantling, two 30-ton electric hoists, two 20-ton manual hoists, three 10-ton manual hoists, and two 5-ton auxiliary hoists are suspended. During dismantling, the two sides are used for the main force pulling, and the middle is used as an auxiliary pulling point for slow pulling out. One gantry frame is installed on each side of the front and rear of the assembly machine, and two lifting points are welded at the H-beam inside the ring to assist in the pulling.

[0040] During the hoisting process of the screw conveyor, additional lifting points are needed to meet the pulling requirements, especially at the center of the cylinder. The gantry frame is about 1m away from the cylinder, so an additional central lifting point is required.

[0041] After the screw conveyor is lowered to the horizontal position, two flatbed trucks are used to secure the first-stage screw conveyor. To reduce the overall height of the screw conveyor, it is also necessary to switch to a 100-ton heavy-duty flatbed truck for transport. The first-stage screw conveyor must be fixed in the center position in the heavy-duty flatbed truck.

[0042] Step Six: Dismantling of the Assembly Machine and Support Beams The total weight of the assembly machine and supporting beam is 66t, plus a 6-ton vacuum suction cup. Before dismantling the assembly machine, the ring platform and suction cup must be removed in advance. Lifting lugs need to be welded to the top of the shield tail to assist in dismantling. Rails and stirrups are installed at the shield tail. The heavy-duty flatbed truck is driven to the bottom of the assembly machine and supporting beam. The flatbed truck is fixed with iron shoes. The flatbed truck and the assembly machine supporting beam are fixed with 200-type steel welded fixtures to achieve the state of the lower part supporting the assembly machine supporting beam and the upper part assisting in the lifting, so as to prevent the assembly machine from tipping over after dismantling due to displacement. Four 30t hand chain hoists are suspended at the upper lifting points for auxiliary use.

[0043] Finite element analysis was performed on the assembly machine. The assembly machine needs to be moved to the middle position of the support beam. Due to concerns that the shield tail is made of 70mm thick steel plate, finite element analysis was performed on the shield tail to calculate the force. Based on the calculation that the shield tail has 4 lifting lugs welded to the top and each lifting point bears 20t, a total force of 98t is applied. The maximum deformation is 1.05mm.

[0044] Key Issues and Solutions During Assembly Machine and Support Beam Disassembly ① During the lowering of the assembly machine's support beam, there were concerns about excessive downward force. Two sets of 400mm steel supports were welded to both ends of the support beam to support it and prevent uneven force distribution during lowering, which could cause deformation of the shield tail at the lifting point. The degree of deformation of the shield tail was constantly monitored during dismantling.

[0045] ② When removing the bolts of the supporting beam, prevent it from moving towards the tunnel. Install a limit baffle at the flange of the supporting beam to ensure that the position of the supporting beam is fixed during the bolt removal process, and avoid displacement due to inertia or external force. This will protect the shield tail structure from additional stress and ensure the safety of the workers.

[0046] ③ After all the bolts on the supporting beam have been removed and the safety devices cut off, the supporting beam and the sub-beam are still not separated. Weld a top bracket to the flange of the sub-beam, and use two 50-ton split jacks on each side to separate the supporting beam.

[0047] Step 7: Shield body pushing, separation of the middle shield and articulated ring. After the dismantling of the supporting trolley, assembly machine, spiral machine, and connecting bridge, in order to ensure sufficient space for dismantling the shield tail (8072mm long * 3920mm wide * 2709mm high), the shield body needs to be pushed to the vicinity of the station platform. The receiving well is 17.5 meters long. Finally, the front of the shield body topped with the cutterhead leaves an 80cm space with the station platform for subsequent dismantling of the cutterhead in sections.

[0048] In addition, before jacking, the bracket needs to be extended to the edge of the station platform and reinforced with 200 steel before jacking.

[0049] When dismantling the shield in sections, since the hinge seal is a complete ring fitted into the hinge ring, the hinge ring needs to be separated from the middle shield in advance. After removing the seal, the jacking is carried out. The jacking is stopped after reaching 4.5m. Jacking plates are welded on the left and right sides of the hinge ring seam, and 100-ton hydraulic jacking cylinders are installed to jack horizontally until the seam is separated. Guide columns are welded at the seam to prevent displacement during separation. The jacking is stopped after both seals are completely exposed.

[0050] After the middle shield and the hinge ring are separated, since the hinge ring only has a 90cm contact surface with the track, it is necessary to weld the mounting plates on both sides to fix it and prevent it from tipping over. The seal is cut at the joint between the middle shield and the hinge ring using a utility knife, with the cutting positions being position 1, position 4, and position 8. The weld seam is removed and separated using a carbon planer at the finishing surface. After the separation is completed, the seal is pressed back into the groove using a pressure plate.

[0051] After the hinge ring is divided, the bracket is welded to both sides to push the hinge ring back to its original position.

[0052] During the operation, as a through-type bracket extending to the station platform, the aerial work platform and battery vehicle could not operate, and personnel could not walk. According to the site conditions, steel plates were laid at the rear of the shield tail. One steel plate was laid after each component was removed, which facilitated the subsequent dismantling of the shield body, the cutting head segmentation, and the use of the drive to turn it over.

[0053] The platform is constructed using a 70cm long column at the center of the bracket, ensuring it is flush with the rails on both sides of the bracket. Then, a 2m wide and 5cm thick steel plate is laid on top, which facilitates the passage of people and electric vehicles.

[0054] Step 8: Shield Tail Removal (Left Block Shield Tail) (Right Block, Lower Block) During the dismantling of the shield tail, the upper left shield tail was difficult to dismantle due to the limited space above. The theoretical weight of the left section is 22.5t. During the dismantling process, a total of 5 lifting points were used for hoisting operations. Three hand-operated hoists (20t) and 17-ton shackles were used in a cross manner to support the balance and prevent it from shifting inward or outward. The other two hoists (two 30-ton hoists) and 17-ton shackles were used for load-bearing.

[0055] Five chain hoists are tightened simultaneously. First, the cross chain hoists are tightened. Once the overall shield tail is balanced and lifted upwards, the main load-bearing chain hoist on the left is adjusted simultaneously. Once the chain hoists are pulled until the shield tail separates, the separation is completed using a split jack. Tighten the chain hoists. When the upper part separates by about 10cm, the lower part is tightened to enter the inner side of the shield tail ring through the thick shield tail transverse seam. The gantry frame is then slowly moved backwards to the hoisting and loading area for transport.

[0056] The left section of the shield tail is equipped with two sets of lifting points corresponding to two sets of lifting lugs on the gantry. Due to the insufficient top space of only 40cm, the hand-operated hoist cannot be directly suspended. The gantry frame lifting points 1 and 2 are used as cross lifting points to fix the shield tail.

[0057] When the shield tail rotates, a 30t hand-operated hoist is suspended from the center point lug of the gantry frame. The hoist has a built-in rotation function. The shield tail lifting point 3 is used for rotation and loading.

[0058] During loading, 150mm long and 100mm wide planks are welded onto the heavy-duty flatbed truck for fixed horizontal transport.

[0059] The theoretical weight of the right section is 18.5t, and the lower section is 22t. The right section is heavier during dismantling and is relatively easier to dismantle than the left section. The right section requires simultaneous welding of lifting lugs on the inside and outside of the shield tail. The dismantling is carried out by the main force on the outside and the inclined lifting point on the inside. Two 30t hand chain hoists are suspended on the outside in conjunction with 17-ton shackles. The inside is equipped with one 30t hand chain hoist, two 17-ton shackles, and a 4-meter 56mm ring steel wire rope for hoisting.

[0060] Four symmetrical lifting lugs are welded inside the lower segment tail shield. A hand-operated hoist is used to tighten them upwards, and the process is complete once the conditions for rotation and loading are met. The rotation and loading methods are the same as those for the left tail shield.

[0061] Step Nine: Removal of the left and right sections of the central shield and hinged ring. After the removal of the articulation and propulsion cylinders, the weight of the middle shield was reduced. According to the theoretical value, the left section of the middle shield and articulation ring weighs 58.4t, which is also one of the key and difficult points of the dismantling in the tunnel. In order to ensure the smooth dismantling of the left section, a total of four 30-ton hand chain hoists with 55-ton shackles, two 20-ton hand chain hoists with 55-ton shackles, and two 10-ton hand chain hoists were used for auxiliary hoisting. Because all hoists were used for lifting due to insufficient space above, a cross hoisting method was adopted, and the remaining hand chain hoists were used for load carrying.

[0062] During the hoisting process, a cross hoist was used to slowly lift the shield section flange, causing it to separate from the upper and lower openings of the flange by 5cm. A gantry crane was then used to slowly move it backward to the loading area. The rails in the loading area needed to be temporarily removed to avoid interference with the lowering of the shield. After the shield section was lifted, the rails were extended to the lowering position of the shield.

[0063] After being placed horizontally on the steel platform, a 50-ton electric hoist is suspended on the front and rear sides of the center of the gantry frame to rotate the left section of the middle shield, and a lifting lug at the center of the middle shield assists in the rotation.

[0064] Eight lifting points are set at the left section of the central shield for dismantling and rotation.

[0065] ①The left section of the central shield is hoisted by a 30-ton hand-operated hoist at the section hoisting point 1 of the gantry frame; ② A 30-ton hand-operated hoist is suspended at the cross-lifting point 1 of the gantry frame and at the middle shield block lifting point 2. A 20-ton hand-operated hoist is suspended at the cross-lifting point 2 of the gantry frame to form a cross-lifting point for hoisting and lowering. During rotation, two 50-ton electric hoists are suspended between rotation points 1 and 2 on the gantry frame, while the remaining points 3 and 4 serve as auxiliary load-bearing points to achieve the purpose of rotating the left segment.

[0066] When loading, multiple layers of solid square timber are needed at the corners of the middle shield to keep it balanced during horizontal transport. The internal structure uses 200H steel and is welded and fixed to the heavy-duty flatbed truck.

[0067] The theoretical weight of the right segment of the central shield and articulated ring is 53.4 tons. Compared with the left segment, the difficulty of dismantling is reduced. The flange face can be suspended by the upper hoist using detachable lifting lugs (using two 30t hand hoists with two 55t shackles). After the right segment is separated from the flange face of the lower segment, the gantry frame is slowly moved to the rear steel platform. The lower part of the right segment is lifted using the left lifting point (using two 30t hand hoists and 55t shackles for lifting on the left side) to achieve a horizontal state for the right segment. During rotation, a 50t electric hoist is used in conjunction with a 6-meter steel wire rope. When loading, it is transported horizontally in the same way as the left segment.

[0068] Challenges and solutions during the dismantling of the central shield: ① During the dismantling of the shield in sections, four 30-ton manual chain hoists encountered a problem with the lifting points, which prevented them from directly lifting and separating the shield. After on-site verification, it was found that the uneven force distribution at the original lifting points caused a deviation in the synchronous lifting. The lifting point connection method was then optimized, and a double lifting point interlocking structure was adopted to ensure that the four manual chain hoists worked together to achieve the smooth separation of the shield.

[0069] ② During the dismantling of the right section of the central shield, the 50-ton electric hoist's stroke was insufficient, making lifting impossible. The on-site adjustment plan was to add a 50-ton lifting lug welded below the original lifting point, that is, at the flange above the crossbeam, to extend the lifting height of the electric hoist and ensure sufficient lifting space during the rotation of the right section. At the same time, the welding strength and positional accuracy of the lifting lug were checked to ensure lifting safety.

[0070] ③ During the hoisting of the right segment of the gantry, an off-center load was found between the lifting lug and the center point. Lifting lugs were welded to the second support on the right side of the gantry, and the center of gravity was corrected by adding lateral adjusting hoists, using two 10-ton hand-operated hoists. This ensured balanced force during hoisting. After on-site measurement and adjustment, the off-center load problem was completely resolved, and the right segment could be lifted smoothly and smoothly entered the rotation mode, ensuring the continuity and safety of the overall dismantling process.

[0071] ④ To address the issues of insufficient load-bearing capacity and lateral swaying of the gantry frame during the middle shield lifting operation, two sets of support wheels were added to each side of the gantry to ensure a support point for protection in case of eccentricity during shield lifting. Structural calculations and load verification confirmed that the load-bearing capacity of the gantry main beam and leg connection nodes met the 53.4-ton lifting requirement. In actual construction, structural stability was verified through graded loading and real-time monitoring of deformation data. The lifting sequence was optimized based on site conditions to ensure even load distribution, ultimately achieving safe disassembly of the middle shield in sections.

[0072] Step 10: H-beam removal The theoretical weight of the H-beam is 17 tons. During dismantling, the rear part needs to be 4.7m long. The shield body needs to be moved back to leave enough space for the cutterhead to be dismantled in sections. The lifting points are suspended to the inside of the H-beam and two 20-ton hand chain hoists are used in conjunction with 17-ton shackles for dismantling.

[0073] The H-beam was first disassembled using the original lifting points, the gantry frame was moved to the rear, and then the H-beam was flipped over using two original lifting points and two flipping lifting points.

[0074] Step 11: Dismantle the personnel compartment and central rotary joint. The theoretical weight of the personnel compartment during dismantling is 3 tons. Although the weight is relatively light, one side is suspended in the air during dismantling, while the other side is in contact with the front shield flange, making dismantling more difficult. Leveling is required during dismantling. During the hoisting process, lifting lugs are added on both sides, left rear and right front, to ensure balance and left and right leveling. Hoists are suspended in the suspended position of the personnel compartment for front and back adjustments.

[0075] The central slewing joint is relatively lightweight, with a theoretical weight of 1.4 tons. It was dismantled using a 2-ton sling and a 10-ton hand-operated hoist at the top.

[0076] Step 12: Remove the upper and lower sections of the cutter head. According to the dismantling sequence, the theoretical weight of both the upper and lower sections is 20 tons. During the dismantling process, due to the lack of space in the upper section, the outermost lifting point of the gantry frame needs to be used for dismantling. The lifting points are set with 20-ton hand chain hoists on both sides with 35-ton shackles, and 10-ton hand chain hoists in the middle with 17-ton shackles for hoisting. During hoisting, due to the insufficient length of the receiving well, the upper section needs to be moved to the station platform to accommodate the placement of the remaining components.

[0077] During the dismantling process, a water drill was used to create a lifting point directly opposite the center of the cutterhead on the station platform to allow the upper section to be placed on the platform. After the upper section was dismantled, the gantry frame was moved to the platform position, and a 10-ton hand-operated hoist was used to pull the upper section to the platform by suspending it through the center anchor point of the platform.

[0078] When dismantling the lower section, symmetrical lifting lugs need to be welded at the opening and used in conjunction with a 20-ton hand chain hoist. The central lifting point is assisted by 10-ton and 5-ton slings for hoisting. After the hand chain hoist is under load, the fixed support plates on both sides are cut off and the section falls naturally. Then, a gantry frame is used to move the lower section of the cutterhead to its limit position. The remaining distance is used to anchor the section to the platform through the station center anchor point, with the help of a 10-ton hoist and a 6-meter steel wire rope. The support plates are then used to fix the outer arc surfaces of the cutterhead on both sides.

[0079] Step 13: Removal of the cutter head center block The cutterhead center block was one of the most challenging parts of the dismantling process inside the tunnel. Due to its heavy weight and large size, after removing all the bolts, eight locating pins remained. The center block was removed using a hoist and jack. During dismantling, the center block would release a downward force at the moment of removal. To reduce the downward force of the entire cutterhead during dismantling, stirrups were added to both sides of the center block for fixation, and stirrups were added to the lower flange of the center block and the flange of the cutterhead. This helped to alleviate the greater load on the gantry frame.

[0080] When dismantling the cutterhead center block, the left and right lifting lugs at the center of the gantry frame are used as the main lifting points. A 50T electric hoist is used in conjunction with a 55-ton shackle, and three 30-ton manual hoists are added in sequence at the center of the gantry frame to assist in the lifting. All shackles are 55 tons.

[0081] To ensure that the cutter head center block can be easily removed and the gantry frame does not have to bear the force of being dragged back and forth, a support plate is welded at the cutting ring, and a steel support is welded to the cutter head center block. The cutter head center block is then pushed out with the help of a 30-ton split jack. After the cutter head flange is separated from the drive, the cutter head center block is placed in place and fixed under the bracket.

[0082] The center block of the cutter head is reinforced with 200H steel. Two diagonal braces are used to support the back of both sides. The bottom of the center of the cutter head is reinforced with a plate connected to the bracket. The front of the cutter head is reinforced with four steel sections, two long and two short, for diagonal bracing. The bottom left and right side brackets are reinforced with two 200 steel sections, for a total of 14 reinforcements.

[0083] The key difficulties encountered during cutterhead removal and their solutions.

[0084] ① During the removal of the cutterhead, limited space makes it difficult to operate large lifting equipment, and the large weight of the central block easily leads to the risk of uneven loading. To address this issue, the coordinated operation rhythm of the manual hoist and electric hoist was optimized to ensure stable lifting. Simultaneously, during the disassembly of the locating pins, a symmetrical loosening and gradual stress release method was adopted to avoid sudden instability.

[0085] ② To address the issue of concentrated load on the gantry crane, temporary support columns were added and the structure at the welded bracket flange connection was reinforced to improve overall stability, ultimately ensuring the safe and precise lowering of the cutterhead center block to the designated position. Real-time monitoring of stress changes and fine-tuning of the hoist's load ensured the smooth detachment of the center block.

[0086] ③ During the flipping of the cutterhead center block, an interference risk was discovered between the cutterhead flange lip and the bracket. Operations were immediately stopped, and personnel were organized to recheck the cutterhead's posture on-site. The distance between the interference points was measured, confirming a 15mm interference. An emergency on-site meeting was held, and it was decided to make a partial cut to avoid the interference at the corresponding position on the bracket, and to add a 25cm*100cm square timber. At the same time, the flipping angle was adjusted to the optimal stress position.

[0087] Step Fourteen: Removal of the middle shield and lower section of the hinged ring The removal methods for the lower section of the middle shield, the lower section of the tail shield, the middle shield, and the right section of the hinged ring are the same.

[0088] Step 15: Removal of the front shield sections The front shield consists of two sections, upper and lower, and a drive unit. The theoretical weight is 55 tons for the upper section and 64 tons for the lower section. During dismantling, four 30-ton and two 20-ton hand-operated hoists are made for the upper section, which are used in conjunction with a 55-ton shackle for hoisting. During the dismantling process, the upper section needs to be separated from the lower section and placed directly behind the center block of the cutterhead. The drive unit and the lower section of the front shield will be completely removed from the well before the tunnel is opened.

[0089] Step Sixteen: Dismantle the drive unit The main drive is a core component of the dismantling process inside the tunnel and is also the heaviest piece of equipment. The drive has a diameter of 4800mm. A total of 12 reducers and motors were removed, reducing the weight to 90 tons with the upper lifting lugs and the lower turning tool. During the dismantling process, the center distance between the upper lifting lugs of the drive unit needs to be increased by two main lifting lugs, and two additional lifting points need to be added in the middle position for auxiliary lifting. Two additional lifting points also need to be added on the left and right sides of the drive partition ring for front and back adjustment.

[0090] During dismantling, a total of two 50-ton electric hoists with 80-ton shackles, two 30-ton manual hoists, and two 20-ton manual hoists with 55-ton shackles were used to dismantle and lower the drive unit. During dismantling, all hoists were in the tightened state. First, the two 50-ton electric hoists at the main lifting point were tightened, and then the two 30-ton manual hoists and two 20-ton manual hoists were used to evenly distribute the force until the lower part of the drive unit opened. Then the main lifting point was tightened again, and the 20-ton and 30-ton manual hoists were used to adjust the front, back, left and right distances.

[0091] To facilitate the turning of the drive unit's rolling turning fixture during the turning process, the rolling turning fixture was specially modified to increase the rolling arc, so as not to cause the gantry frame to bear the drag force.

[0092] Before the drive unit is rolled over, the rolling over fixture needs to be placed at the tunnel entrance in advance. After the drive unit is dismantled, it can be directly placed into the rolling over fixture. Because the length of the drive unit, upper lifting lug, and rolling over fixture can reach 6.7m during dismantling, and because the length of the receiving shaft is limited, the drive unit needs to be moved to the extreme position towards the tunnel entrance before the drive unit starts to turn over to ensure the turning over.

[0093] It is also important to note that before dismantling the main drive, since the center slewing joint has already been removed, it is necessary to fix the center slewing joint in advance to prevent it from slipping during the overturning process. It is also necessary to pay attention to whether there is any deformation at the position of the gantry column and diagonal brace, and to continuously observe them.

[0094] During horizontal transport, the four lifting lugs around the drive unit are used to lift the vehicle onto the heavy-duty flatbed truck. The speed must be controlled while the vehicle is moving, with a speed limit of 1 km / h. Additionally, a support plate is used to securely weld the partition ring components to the heavy-duty flatbed truck.

[0095] Key challenges and solutions encountered during the disassembly of the drive unit.

[0096] ① The drive unit is heavy and has a high center of gravity, limiting the dismantling space and making it difficult to adjust the lifting posture. To address this issue, auxiliary lifting points were added, and multiple hoists were used in coordination to achieve precise leveling and positioning. Meanwhile, due to frequent cross-operations on site and high safety risks, a special warning area was set up, and dedicated personnel were assigned to direct the process, ensuring a smooth and controllable dismantling process.

[0097] ② There is spatial interference between the drive unit and the lower section of the front shield, which can easily cause jamming during the turning process; to address this, the arc design of the rolling turning tool was optimized to improve the smoothness of rolling, and a 10-ton hand-operated hoist was added at the tunnel entrance to assist in pulling back and ensure that the turning is in place.

[0098] ③ After the central slewing joint is removed, there is a risk of slippage at the connection of the drive unit; in order to prevent this, a 2-ton hand-operated hoist with clamps is used to rigidly fix the drive unit to the adjacent structure before turning over to prevent accidental displacement.

[0099] ④ Uneven road surfaces during transportation can easily cause vibrations. To avoid impact damage, the route for heavy-duty flatbed trucks is leveled and compacted in advance, and rubber pads are added to the contact surfaces for lifting to cushion the impact. Horizontal transportation carries a high risk of center of gravity shift; therefore, four-point lifting combined with flatbed securing is employed, and the vehicle speed is strictly controlled to within 1 km / h to ensure smooth and safe transportation.

[0100] Step 17: Removal of the front shield sub-section The removal methods for the lower section of the front shield, the lower section of the tail shield, the middle shield, and the right section of the hinged ring are the same.

[0101] Step 18: Turn the center block of the cutter head over. Turning the cutter head over is one of the key and difficult parts of this disassembly. The center block of the cutter head needs to be placed horizontally in a heavy-duty flatbed truck before being transported outside the hole. Before turning it over, the seals on the inner and outer circumferences of the cutter head need to be removed before it is rolled over. The turning process must be consistent with the previous removal of the center block of the cutter head.

[0102] After all the hoists are tightened, remove all 14 anti-tipping fixtures on the cutterhead and slowly move the gantry frame towards the tunnel entrance. Place solid square timber under the bracket to protect the flange lip from damage. Since the cutterhead is light with a panel and heavy with flanges and brackets, moving the gantry frame is enough to achieve the purpose of turning it over. When it is halfway turned over, use steel wire ropes at the bottom to hold the cutter box and level it. After turning it over, use 200 steel columns to reinforce and support it.

[0103] When loading, the direction of the cutter head needs to be adjusted according to the distance on both sides to prevent the cutter head from being unable to pass through the tunnel. After loading, steel columns need to be made and the heavy-duty flatbed truck needs to be reinforced.

[0104] After the central block of the cutterhead was transported, the other two smaller blocks (20t) were hoisted and loaded onto trucks using the same method as during dismantling, thus completing all the dismantling procedures inside the tunnel.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for dismantling a shield tunnel with low clearance, characterized in that, Includes the following steps: Step 1: Dismantle the hydraulic cylinder, cutter head motor, and reducer. Use an assembly machine to install a gantry frame fixture. Use the forward and backward movement function of the assembly machine and a hand-operated hoist to fix and dismantle the push hydraulic cylinder. Dismantle the cutter head motor and reducer in advance to expand the internal space, and then dismantle the articulated hydraulic cylinder. Step 2: There are 1 to n trolleys, where n is a positive integer greater than or equal to 2. Remove 2 to n trolleys. Step 3: Remove the first-stage screw conveyor gearbox and the screw conveyor double gate; Step 4: Dismantle the connecting bridge, secondary spiral conveyor, and No. 1 trolley; Before dismantling, remove the walkway panels on both sides of the connecting bridge to reduce the clearance on both sides, and transport it out by connecting the connecting bridge and No. 1 trolley; The traction process during horizontal transportation is as follows: lifting the secondary spiral conveyor of the connecting bridge out of the well; dismantling the left and right sliding platforms of the connecting bridge; lifting the connecting bridge out of the well; retracting No. 1 trolley to the well opening; lifting No. 1 trolley out of the well; Step 5: Dismantling of the primary spiral compressor; dismantling is carried out by welding a portal frame to the upper part of the assembly machine's support beam and installing supports at the bottom; during dismantling, the two sides are used for the main force pulling, and the middle is used as an auxiliary pulling point for slow pulling out; one portal frame is set on each side of the front and rear of the assembly machine, and two lifting points are welded at the H-beam inside the ring to assist in pulling out; during the hoisting process of the spiral compressor, additional lifting points are added to meet the pulling requirements; after the spiral compressor is lowered to the horizontal position, a flatbed truck is used to fix the primary spiral compressor. In order to reduce the overall height of the spiral compressor, a heavy-duty flatbed truck is used for transportation. The primary spiral compressor needs to be fixed in the center position in the heavy-duty flatbed truck; Step Six: Dismantle the Assembly Machine and Support Beams; Dismantle the circular platform and suction cups in advance. Weld lifting lugs to the top of the shield tail to assist in dismantling. Install rails and stirrups at the shield tail. Drive the heavy-duty flatbed truck to the bottom of the assembly machine and support beams. Secure the flatbed truck with iron shoes. Use welding fixtures to fix the flatbed truck and the assembly machine support beams to achieve a state where the lower part supports the assembly machine support beams and the upper part assists in hoisting, preventing the assembly machine from tipping over after dismantling due to displacement. Suspend several hand-operated hoists at the upper lifting points for auxiliary use. Step 7: Shield body jacking, separation of the middle shield and articulated ring; after the dismantling of the supporting trolley, assembly machine, auger, and connecting bridge, the shield body is jacked to near the edge of the station platform, leaving space between the front of the cutterhead and the station platform for subsequent dismantling of the cutterhead side blocks; before jacking, the bracket is extended to the edge of the station platform and reinforced with steel sections before jacking; during the dismantling of the shield body in sections, the articulated ring is separated from the middle shield in advance, the seal is removed before jacking, and the top is welded on the left and right sides of the articulated ring seam. The push plate and hydraulic cylinder are used to push the ring seam horizontally until it separates from the circumferential seam. Guide columns are welded at the circumferential seam. Pushing is stopped after both seals are completely exposed. After the middle shield separates from the hinge ring, the mounting plates are welded on both sides for fixation. The seal is cut at the joint between the middle shield and the hinge ring using a utility knife. The weld is removed and separated at the finishing surface using a carbon planer. After the separation is completed, the seal is pressed back into the groove using a pressure plate. After the hinge ring is separated, the mounting plates are welded on both sides of the bracket to push the hinge ring back to its original position. Step 8: Shield tail dismantling, including the left, right, and lower shield tail sections; a multi-point lifting operation is employed, using several hand-operated hoists, tightened simultaneously. First, the cross-type hand-operated hoists are tightened until the entire shield tail is balanced and lifted upwards. Then, the main load-bearing hand-operated hoists are adjusted simultaneously until the shield tail is detached. Separate jacks are then used for complete separation. The hand-operated hoists are tightened until the upper part is detached, and the lower part is tightened to the thick shield tail transverse seam, entering the inner side of the shield tail ring. The gantry frame is slowly moved backwards to the lifting and loading area for transport. The left shield tail section is secured using the gantry frame's double lifting points as cross-type lifting points. When rotating the shield tail, the center point lifting lug of the gantry frame is used to suspend the hand-operated hoist, which has a built-in rotation function. The shield tail lifting points are used for rotation and loading. During loading, a platform is welded onto a heavy-duty flatbed truck for horizontal transport. The right section has lifting lugs welded on both the inside and outside of the shield tail. It is then lifted and tightened by the main force on the outside and the inclined lifting point on the inside. The lower section has symmetrical lifting lugs welded inside the shield tail. It is tightened upward by a hand-operated hoist. It can be removed once the conditions for rotation and loading are met. Step Nine: Dismantling of the central shield and the left and right sections of the articulated ring; The central shield and the left section of the articulated ring are partially lifted using a cross-hoisting system, with some hoists carrying the load; during the lifting process, the cross-hoisting system is used to slowly lift the section, causing the flange of the central shield to completely detach from the upper and lower openings of the flange surface. A gantry crane is then used to slowly move it backward to the loading area. The rails in the loading area need to be temporarily removed to avoid interference with the lowering of the central shield. After the central shield section is lifted, the rails are extended to the lowering position of the central shield; after being placed horizontally on the steel platform, hoists suspended at the front and rear sides of the center of the gantry crane are used to rotate the left section of the central shield. The gantry frame is assisted in rotation by using lifting lugs at the center of the central shield. Removable lifting lugs can be used to suspend the upper lifting point hoist at the flange face of the central shield and the right segment of the hinge ring. After the right segment separates from the flange face of the lower segment, the gantry frame is slowly moved to the rear steel platform. The lower part of the right segment is lifted using the left lifting point to achieve a horizontal state. Rotation is achieved through the hoist and the steel wire rope. When loading the central shield and the left and right segments of the hinge ring, multiple layers of solid square timber are required at the corners of the central shield segment to maintain the balance of the central shield during horizontal transportation. The internal steel structure is welded and fixed to the heavy-duty flatbed truck. Step 10: H-beam dismantling; Move the shield back to leave enough space for the cutterhead to be dismantled in sections. Use several hoists and shackles to dismantle the H-beam by suspending it from the lifting points to the inside of the H-beam; Dismantle the H-beam first by using the original lifting points, move the gantry frame to the rear, and then use the original lifting points and the flipping lifting points to flip the H-beam over. Step 11: Dismantle the manhole and central slewing joint; During the hoisting process, add lifting lugs on both sides of the manhole to ensure balance and left and right leveling, and use hoists to adjust the manhole forward and backward while it is suspended in the air; The central slewing joint is dismantled using slings and a top hoist. Step 12: Dismantle the upper and lower sections of the cutterhead; use the outermost lifting point of the gantry frame to dismantle the upper section of the cutterhead. During dismantling, use a water drill to create a lifting point directly opposite the center of the cutterhead on the station platform to allow the upper section to be placed on the platform. After the upper section is dismantled, move the gantry frame to the platform position and use a hoist suspended from the center anchor point of the platform to pull the upper section to the platform. When dismantling the lower section of the cutterhead, weld symmetrical lifting lugs at the opening and use a hoist. Use slings to assist in lifting at the center lifting point. After the hand-operated hoist is under force, cut off the fixed plates on both sides and let it fall naturally. Then use the gantry frame to move the lower section of the cutterhead to its limit position. For the remaining distance, use the station center anchor point, hoist, and wire rope to press the side block tightly against the platform and use the fixed plates to fix the outer arc surface of the cutterhead on both sides. Step 13: Remove the center block of the cutterhead. After removing the positioning pin, use a hoist and jack to remove the center block. When removing the center block of the cutterhead, rely on the left and right lifting lugs at the center of the gantry frame as the main lifting points. Step Fourteen: Dismantle the lower section of the middle shield and the articulated ring; the lower section of the middle shield, the lower section of the tail shield, and the right section of the middle shield and the articulated ring shall be dismantled in the same way; Step 15: Remove the upper block of the front shield; After separating the upper block from the lower block, place it directly behind the center block of the cutterhead. After the drive unit and the lower block of the front shield have all exited the well, proceed with the exit. Step 16: Dismantle the drive unit; At least two additional main lifting lugs need to be added to the upper part of the drive unit, and at least two additional lifting points need to be added in the middle for auxiliary lifting. At least two additional lifting points need to be added on the left and right sides of the drive partition ring for front and back adjustment. During dismantling, all hoists should be in the tightened state. First, tighten the main lifting point hoists, and then use the hand hoist to apply force evenly until the lower part of the drive unit opens. Then tighten the main lifting points again and use the hand hoist to adjust the front, back, left and right distances. Before the drive unit is rolled over, place the rolling over fixture at the entrance in advance. After the drive unit is dismantled, put it directly into the rolling over fixture. Use the four lifting lugs around the drive unit to lift it to the heavy-duty flatbed truck. Use the jack to fix and weld the partition ring component to the heavy-duty flatbed truck. Step 17: Dismantle the front shield lower section; The front shield lower section, the shield tail lower section, the middle shield, and the right section of the hinged ring shall be dismantled in the same way; Step 18: Turning the cutterhead center block over; Place the cutterhead center block horizontally in a heavy-duty flatbed truck for transport outside the tunnel. Before turning it over, remove the seals on the inner and outer circumferences of the cutterhead and roll it over, following the same procedure as when removing the cutterhead center block. After tightening all hoists, remove all anti-tipping fixtures from the cutterhead and slowly move the gantry frame towards the tunnel entrance. Place solid square timber under the bracket to protect the flange lip from damage. When turning it halfway, use steel wire ropes to hold the cutter box at the bottom for leveling. After turning, use steel columns for reinforcement and support. When loading, adjust the direction of the cutterhead according to the distance on both sides to prevent it from being unable to pass through the tunnel. After loading, use steel columns for reinforcement and support against the heavy-duty flatbed truck. After transporting the cutterhead center block, hoist and load the other two smaller blocks using the same method as during dismantling, completing all the dismantling procedures inside the tunnel.

2. The method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step one, a gantry frame is welded to the center of the steel structure of the assembly machine. First, the bolts fixing the hydraulic cylinders are removed. Then, the assembly machine's traveling function is used to pull the cylinders out halfway. After the cylinders are fixed in their front and rear positions, the entire cylinder is pulled out. The assembly machine's rotation function is used to lower the cylinders to their lowest point. A double-beam crane is used to transport the cylinders out of the opening one by one. The dismantling sequence proceeds from simple to complex, starting from the bottom and extending outwards to both sides, finally dismantling the upper pushing cylinder. When dismantling the cutter head motor or reducer, a hand-operated hoist is used. The motor or reducer is towed and dismantled from the rear. During the lowering process, the lifting points near the assembly machine are used to move it backward. When dismantling the articulated cylinder, both the front and rear pin seats are fixed by pins. After fixing the articulated cylinder in place, the pins near the cutterhead are removed using a hand-operated hoist. Then, the rear pins are removed using the lifting straps installed in the top space of the shield. The cylinder is then moved to the middle shield platform using a hand-operated hoist. The lowest point of the tunnel below the articulated cylinder is then moved out using the lifting lugs welded in the shield.

3. The method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step two, two dump trucks are used. Each time, cross braces are welded to the front and rear columns of the dump truck and then to the dump truck. During transportation, after the dump truck derails, the wheels of the dump truck are removed and added to the lighter side of the dump truck to maintain the balance of the dump truck during transportation.

4. The method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step three, the connecting bridge is first reinforced and used as a lifting point for removing the gearbox; the single gate connecting the first and second stage screw conveyors and the double gate at the bottom of the first stage screw conveyor are removed; the ball joint connecting the first and second stage screw conveyors and the short cylinder are removed, the second stage screw conveyor is pushed backward towards the trolley, and the sides of the screw conveyor are reinforced with structural steel; windows are opened on the upper part and left side of the screw conveyor cylinder, the screw conveyor gearbox and the gearbox pin are removed, and lifting lugs are welded to both sides of the screw conveyor gearbox for fixation; the bolts connecting the gearbox and the first stage screw conveyor are removed, and the hexagonal head is pushed out of the screw conveyor shaft with the assistance of separate jacks on both sides, and anti-falling plates are welded into the blades; the screw conveyor gearbox is lowered, the flatbed truck is parked below, and after the gearbox is reinforced, it is transported horizontally.

5. A method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step six, when the assembly machine beam is lowered, several sets of steel supports are welded to both ends of the beam; limit baffles are installed at the beam flange; when all the beam bolts are removed and the safety is cut off, if the beam and the sub-beam are not separated, a top bracket is welded to the sub-beam flange, and split jacks are used on both sides to separate the beam.

6. The method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step seven, a steel plate is laid at the rear of the shield tail. One component is removed and a steel plate is laid to facilitate the subsequent dismantling of the shield body, the cutting head segmentation, and the use of the drive to turn over.

7. The method for dismantling a shield tunnel with low clearance as described in claim 1, characterized in that, In step thirteen, the downward force is released the instant the center block is removed. During the process, the center block is fixed by adding a support plate on both sides, and a support stirrup is added at the lower flange of the center block and the blade flange.

8. A method for dismantling a shield tunnel with low clearance according to claim 1, characterized in that, In step sixteen, before removing the main drive, fix the center slewing joint in advance to prevent it from slipping during the overturning process, and pay attention to whether there is any deformation at the positions of the gantry column and diagonal brace.

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