A shield type TBM and a tunneling method suitable for micro-pressure tunneling in a water-rich broken stratum

Abstract

This invention relates to the field of tunnel boring machine (TBM) construction equipment technology, and discloses a shield-type TBM and tunneling method suitable for low-pressure tunneling in water-rich and fractured strata. A movable belt conveyor driven by a hydraulic cylinder moves the slag collection bucket backward. The slag collection bucket's built-in baffles tightly seal the slag outlet on the cutterhead backplate, transforming the originally open shield-type TBM slag bin into a pressurized, sealed cavity. Simultaneously, a modifier is injected directionally into the bin through several first grouting holes arranged on the backplate. This fills the free space within the bin, improves the workability of the slag, and establishes a stable, preset low pressure. This actively pressurizes and balances the water and soil pressure at the tunnel face, suppressing the instability and collapse of water-rich and fractured surrounding rock after softening upon contact with water, preventing a sudden surge in pressure caused by a large influx of slag into the bin. It also improves slag flowability, reduces slag discharge resistance, effectively avoids the risk of the cutterhead becoming stuck due to instantaneous overload, ensures continuous tunneling of the shield-type TBM in adverse geological sections, and significantly improves construction efficiency.

Description

Technical Field

[0001] This invention relates to the field of tunnel boring machine construction equipment technology, and discloses a shield-type TBM and tunneling method suitable for low-pressure tunneling in water-rich and fractured strata. Background Technology

[0002] Shield tunneling machines (TBMs) are primarily designed for hard rock formations. Their muck chambers are typically open, lacking effective sealing and pressurization capabilities. When a TBM is tunneling in water-rich, fractured strata, the surrounding rock at the tunnel face softens upon contact with water, making it prone to instability and collapse. This can cause excessive instantaneous pressure within the TBM's muck chamber, trapping the cutterhead and preventing it from rotating. This increases the risk of the TBM becoming trapped and reduces construction efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a shield-type TBM and tunneling method suitable for low-pressure tunneling in water-rich and fractured strata. When tunneling in water-rich and fractured strata, the shield-type TBM can tunnel continuously, reducing the risk of being trapped due to face collapse and improving construction efficiency.

[0004] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0005] A shield-type TBM suitable for low-pressure tunneling in water-rich and fractured strata includes a shield body, a cutterhead, a slag hopper, and a movable belt conveyor; the back of the cutterhead is provided with a back plate, the back plate is connected to the front shield in the shield body, a slag bin is formed between the cutterhead and the back plate, and the movable belt conveyor is installed in the shield body by a hydraulic cylinder, and the front end of the movable belt conveyor extends from the upper slag outlet of the slag bin into the slag bin; The slag collection hopper is installed at the front end of the movable belt conveyor and located inside the slag bin. The slag collection hopper is equipped with a partition to seal the upper slag outlet after the hydraulic cylinder drives the movable belt conveyor and the slag collection hopper to move a preset distance away from the cutterhead during micro-pressure tunneling. The back plate is provided with several first grouting holes for injecting a modifier into the slag bin so that the soil pressure in the slag bin reaches the preset pressure.

[0006] Furthermore, the modifier includes bentonite and a foaming agent.

[0007] Furthermore, the shield body also includes a middle shield and a tail shield. The front shield, middle shield and tail shield are each provided with a second grouting hole for injecting foamed chemical grout into the gap between the shield body and the external rock wall, so as to fill the fractured rock mass outside the shield body and the gap between the shield body and the rock wall tightly.

[0008] Furthermore, the tail shield is equipped with at least one sealing steel brush with sealing grease, used to seal the gap between the assembled ring segment and the tail shield.

[0009] Furthermore, a long spiral conveyor is also provided, which is installed inside the shield body, and the inlet of the long spiral conveyor extends to the lower outlet of the slag bin, for transporting the slag inside the slag bin to the outside of the bin.

[0010] A shield tunneling method for low-pressure tunneling in water-rich fractured strata, utilizing the aforementioned shield tunneling method for low-pressure tunneling in water-rich fractured strata, includes the following steps: By combining geophysical exploration and advanced drilling, the location of unfavorable rock masses and the distribution of water-rich structures in front of the tunnel were determined, and the type of unfavorable geology in front of the tunnel was identified. When the geological conditions ahead of the tunnel are of the low-pressure tunneling type, the slag hopper and movable belt conveyor are removed from the slag bin, the upper slag outlet of the slag bin is sealed, and then an amendment is injected into the slag bin to make the soil pressure in the slag bin reach the preset pressure. The shield-type TBM is started for low-pressure tunneling. The lower outlet of the slag bin is opened, and the slag in the slag bin is discharged using a long screw conveyor. Meanwhile, the soil conditioner is continuously injected into the slag bin. By controlling the speed of the long screw conveyor, the soil pressure in the slag bin is kept constant at the preset pressure.

[0011] Furthermore, it also includes: injecting sealing grease into the sealing steel brush at the tail of the shield to seal the gap between the assembled ring segments and the tail shield, so that a sealed cavity is formed inside the slag bin.

[0012] Furthermore, it also includes: injecting foamed chemical grout into the gap between the shield body and the external rock wall through the second grouting holes on the front shield, middle shield and tail shield, so as to fill the fractured rock mass outside the shield body and the gap between the shield body and the rock wall tightly.

[0013] Furthermore, during the low-pressure tunneling process of the shield-type TBM, in order to maintain a constant soil pressure within the spoil bin at a preset pressure, the injection flow rate of the amendment into the spoil bin is determined by the following formula: ; in: The infusion flow rate of the modifier; The tunneling speed of a shield-type TBM; The rotational speed of the cutter head; The diameter of the spiral blades in a long spiral conveyor; The pitch of the helical blades in a long helical conveyor; The rotational speed of the screw shaft of the long screw conveyor; The filling rate of the long screw conveyor; The bulk density of the material in the long screw conveyor; This is the correction factor for inclined conveying of the long screw conveyor; This represents the number of the first grouting holes; This refers to the tunneling time of a shield-type TBM.

[0014] Compared with the prior art, the beneficial effects of this invention are: The shield-type TBM of this invention uses a hydraulic cylinder to drive a movable belt conveyor to move the slag collection bucket backward. The slag collection bucket's built-in baffles tightly seal against the slag outlet on the cutterhead back plate, transforming the originally open slag bin into a pressurized, sealed cavity. Simultaneously, a modifier is injected directionally into the bin through several first grouting holes on the back plate. This fills the free space within the bin, improves the workability of the slag, and establishes a stable, preset micro-pressure. This actively pressurizes the face water and soil pressure, suppressing the instability and collapse of water-rich, fractured surrounding rock after softening upon contact with water, preventing a sudden surge in pressure caused by a large influx of slag into the bin. It also improves slag flowability and reduces slag discharge resistance, effectively avoiding the risk of the cutterhead becoming stuck due to instantaneous overload. This ensures continuous tunneling of the shield-type TBM in adverse geological conditions and significantly improves construction efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the shield-type TBM used for low-pressure tunneling in water-rich and fractured strata in the embodiment. Figure 2 This is a schematic diagram of the front shield, middle shield, tail shield, and second grouting hole in the embodiment. Figure 3 This is a schematic diagram of the slag collection hopper in the embodiment; Figure 4 This is a schematic diagram of the structure of the first grouting hole on the back plate in the embodiment; Figure 5 This is a flowchart of a shield TBM tunneling method applicable to low-pressure tunneling in water-rich fractured strata in the embodiments. Among them, 1-cutter head, 2-front shield, 3-middle shield, 4-tail shield, 5-back plate, 51-first grouting hole, 6-slag bin, 61-upper slag outlet, 62-lower slag outlet, 71-movable belt conveyor, 72-slag collection hopper, 73-partition plate, 8-second grouting hole, 9-sealing steel brush, 10-long screw conveyor, 11-segment. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0017] See Figures 1 to 4The present invention provides a shield-type TBM suitable for low-pressure tunneling in water-rich and fractured strata, including a shield body, a cutterhead 1, a slag collection bucket 72 and a movable belt conveyor 71; the back of the cutterhead 1 is provided with a back plate 5, the back plate 5 is connected to the front shield 2 in the shield body, and a slag bin 6 is formed between the cutterhead 1 and the back plate 5. The movable belt conveyor 71 is installed in the shield body by a hydraulic cylinder, and the front end of the movable belt conveyor 71 extends from the upper slag outlet 61 of the slag bin 6 into the slag bin 6. The slag collection hopper 72 is installed at the front end of the movable belt conveyor 71 and located in the slag bin 6. The slag collection hopper 72 is provided with a partition 73, which is used to seal the upper slag outlet 61 after the hydraulic cylinder drives the movable belt conveyor 71 and the slag collection hopper to move a preset distance away from the cutter head 1 during micro-pressure tunneling. The back plate 5 is provided with a plurality of first grouting holes 51 for injecting a modifier into the slag bin 6 so that the soil pressure in the slag bin 6 reaches the preset pressure.

[0018] Based on the same inventive concept, see [link to inventive concept] Figure 5 The present invention also provides a shield TBM tunneling method suitable for low-pressure tunneling in water-rich fractured strata, which is implemented using the aforementioned shield TBM suitable for low-pressure tunneling in water-rich fractured strata, and includes the following steps: By combining geophysical exploration and advanced drilling, the location of unfavorable rock masses and the distribution of water-rich structures in front of the tunnel were determined, and the type of unfavorable geology in front of the tunnel was identified. When the geological conditions in front of the tunnel are of the low-pressure tunneling type, the slag hopper 72 and the movable belt conveyor 71 are removed from the slag bin 6, the upper slag outlet 61 of the slag bin 6 is sealed, and then the soil conditioner is injected into the slag bin 6 to make the soil pressure in the slag bin 6 reach the preset pressure. The shield-type TBM is started for low-pressure tunneling. The lower discharge port 62 of the slag bin 6 is opened, and the slag in the slag bin 6 is discharged by the long screw conveyor 10. The soil pressure in the slag bin 6 is kept constant by controlling the speed of the long screw conveyor 10.

[0019] The shield-type TBM of this invention uses a hydraulic cylinder to drive a movable belt conveyor 71 to move the slag collection bucket 72 backward. The slag collection bucket 72's own partition 73 is tightly sealed with the slag outlet 61 on the back plate 5 of the cutterhead 1, transforming the originally open shield-type TBM slag bin 6 into a pressurized, sealed cavity. At the same time, a modifier is injected into the bin through several first grouting holes 51 arranged on the back plate 5. While filling the free space inside the bin and improving the workability of the slag, a stable preset micro-pressure is established. This can not only balance the water and soil pressure at the working face through active pressurization, but also suppress the instability and collapse of the water-rich fractured surrounding rock after it softens in water, and avoid the sudden pressure increase caused by a large amount of slag rushing into the bin. It can also improve the fluidity of the slag and reduce the slag discharge resistance, thereby effectively avoiding the risk of the cutterhead 1 getting stuck due to instantaneous overload. This ensures continuous tunneling of the shield-type TBM in adverse geological sections and significantly improves construction efficiency.

[0020] The tunneling method of this invention utilizes the linkage and retraction of the movable belt conveyor 71 and the slag collection hopper 72, along with the sealing of the upper slag outlet 61 by the partition plate 73. Combined with the grease injection by the shield tail sealing steel brush 9 and the grouting of the shield back to fill the surrounding rock gaps, a fully enclosed pressure environment is constructed in the slag bin 6. Bentonite and foaming agent are then precisely injected into the bin through the first grouting hole 51 of the back plate 5 to improve the slag and establish a stable micro-pressure reaching the preset pressure. This balances the water and soil pressure at the tunnel face and inhibits the instability and collapse of the water-rich and fractured surrounding rock after it softens in water. At the same time, relying on the continuous slag discharge of the long spiral conveyor 10 under pressurized conditions, the instantaneous pressure exceeding the limit in the slag bin 6 is avoided, which could cause the cutterhead 1 to become stuck and trapped. Ultimately, the shield-type TBM achieves continuous and steady tunneling in adverse geological sections, effectively reducing the risk of the cutterhead 1 becoming trapped and improving construction efficiency.

[0021] Example This embodiment further elaborates on the detailed structure and tunneling method of the shield-type TBM suitable for low-pressure tunneling in water-rich and fractured strata, as detailed below.

[0022] See Figures 1 to 2 The shield-type TBM suitable for low-pressure tunneling in water-rich and fractured strata includes a shield body, a cutterhead 1, a slag hopper 72, a movable belt conveyor 71, and a long screw conveyor 10.

[0023] In this embodiment, see Figures 1 to 2The shield body includes a front shield 2, a middle shield 3, and a tail shield 4. A cutterhead 1 is located at the front end of the front shield 2, and a drive device is installed inside the front shield 2. The cutterhead 1 is connected to the drive device, and during tunneling, the cutterhead 1 excavates the rock and soil at the tunnel face. Furthermore, a back plate 5 is provided on the back of the cutterhead 1, which is connected to the front shield 2. A muck bin 6 is formed between the cutterhead 1 and the back plate 5. The muck bin 6 has an upper muck outlet 61 and a lower muck outlet 62. The muck generated during tunneling enters the muck bin 6 and is then transported to the tail of the shield-type TBM through the upper muck outlet 61 or the lower muck outlet 62. In this embodiment, when the shield TBM adopts the normal pressure tunneling mode, the lower muck outlet 62 is sealed by a sealing plate, and the muck is transported to the tail of the shield TBM through the upper muck outlet 61; when the shield TBM adopts the low pressure tunneling mode, the upper muck outlet 61 is sealed, and the muck is transported to the tail of the shield TBM through the lower muck outlet 62.

[0024] In this embodiment, see Figure 4 A plurality of first grouting holes 51 are arrayed on the back plate 5. When the shield-type TBM is tunneling under low pressure in water-rich and fractured strata, a modifier, including bentonite and foaming agent, is injected into the spoil bin 6 through the first grouting holes 51. During injection, some of the first grouting holes 51 are connected to a bentonite pump to inject bentonite slurry into the spoil bin 6, and some of the first grouting holes 51 are connected to a foaming agent pump to inject foaming agent into the spoil bin 6.

[0025] Further, see Figures 1 to 3 The movable belt conveyor 71 is installed in the shield body by a hydraulic cylinder, and the front end of the movable belt conveyor 71 extends from the upper slag outlet 61 of the slag bin 6 into the slag bin 6. The slag collection hopper 72 is installed at the front end of the movable belt conveyor 71 and located inside the slag bin 6. A partition plate 73 is welded onto the slag collection hopper 72. When the shield TBM is tunneling under normal pressure, the movable belt conveyor 71 is moved closer to the cutterhead 1 by a hydraulic cylinder, so that the slag collection hopper 72 is located inside the slag bin 6, so that the slag can smoothly enter the slag collection hopper 72. When the shield TBM is tunneling under low pressure in water-rich and fractured strata, the movable belt conveyor 71 is moved away from the cutterhead 1 by a hydraulic cylinder until the partition plate 73 of the slag collection hopper 72 blocks the upper slag outlet 61 of the slag bin 6. Then, the partition plate 73 is locked to the back plate 5 by bolts. A sealing ring can also be added between the partition plate 73 and the back plate 5 to ensure a tight seal and prevent leakage that could cause unstable soil pressure inside the slag bin 6.

[0026] In this embodiment, when the shield-type TBM is tunneling under low pressure in water-rich and fractured strata, after the upper slag outlet 61 of the slag bin 6 is blocked by the partition 73 of the slag collection hopper 72, bentonite and foaming agent are injected into the slag bin 6 through the first grouting hole 51. This increases the soil pressure in the slag bin 6 to the preset pressure, ensuring that the unstable rock mass at the tunnel face reaches a stable state. At the same time, it improves the slag and increases its workability, which is beneficial for the screw conveyor to discharge slag and reduces the risk of the screw conveyor getting stuck.

[0027] In this embodiment, see Figures 1 to 2 The front shield 2, middle shield 3, and tail shield 4 are all equipped with second grouting holes 8. The front shield 2 has six Φ25mm second grouting holes 8, while the middle shield 3 and tail shield 4 each have five Φ25mm second grouting holes 8. These are connected to a grouting system via pipelines. This grouting system includes a grouting pump and a grout tank. During tunneling in water-rich, fractured strata, foamed chemical grout is injected into the gap between the shield and the external rock wall through the second grouting holes 8. This fills the fractured rock mass outside the shield and the gap between the shield and the rock wall, preventing pressure leakage within the spoil heap 6 along the surrounding rock fissures and the gap between the shield and the rock mass, thus ensuring that the spoil heap 6 does not reach a constant pressure state.

[0028] Further, see Figures 1 to 2 The tail shield 4 is equipped with at least one sealing steel brush 9 with sealing grease, which is used to seal the gap between the assembled ring segment 11 and the tail shield 4, and to prevent groundwater outside the shield from seeping into the slag bin 6 through the gap between the segment 11 and the tail shield 4. Together with the external water-stopping reinforcement ring, it further improves the water-proofing effect of the construction area and ensures the pressure stability of the slag bin 6 during the micro-pressure tunneling process.

[0029] In this embodiment, see Figures 1 to 2 The long spiral conveyor 10 is installed inside the shield body, and the inlet of the long spiral conveyor 10 extends to the lower outlet 62 of the slag bin 6. When the shield TBM is tunneling under low pressure in water-rich and fractured strata, the sealing plate of the lower outlet 62 is removed, and then the slag in the slag bin 6 is transported to the outside of the bin through the long spiral conveyor 10.

[0030] Based on the same inventive concept, see [link to inventive concept] Figure 5 This embodiment also provides a shield TBM tunneling method suitable for low-pressure tunneling in water-rich fractured strata, which is implemented using the aforementioned shield TBM suitable for low-pressure tunneling in water-rich fractured strata, and includes the following steps: Step 1: Using a combination of geophysical exploration and advance drilling, the location of unfavorable rock masses and the distribution of water-rich structures ahead of the tunnel are determined, thus identifying the type of unfavorable geology ahead of the tunnel. These unfavorable types include water-rich fractured strata and hard rock strata. Specifically, in determining the type of unfavorable geology ahead of the tunnel, a comprehensive analysis is conducted using advance drilling, geophysical exploration (3D seismic wave method, induced polarization method), and borehole television. First, the approximate location of unfavorable geological bodies and water bodies ahead of the tunnel is determined through advance geophysical exploration using the 3D seismic wave method and induced polarization method. Then, drilling combined with borehole television confirms the scale of unfavorable geological bodies such as fractured rock and siltstone ahead of the tunnel, providing early warning of TBM construction risks and supporting the selection of the shield-type TBM tunneling mode.

[0031] Step 2: When the geological conditions ahead of the tunnel are of the low-pressure tunneling type, remove the slag hopper 72 and the movable belt conveyor 71 from the slag bin 6, seal the upper slag outlet 61 of the slag bin 6, and then inject an amendment into the slag bin 6 to make the soil pressure in the slag bin 6 reach the preset pressure; at the same time, inject sealing grease into the sealing steel brush 9 of the shield tail to seal the gap between the assembled ring segment 11 and the tail shield 4, so that a sealed cavity is formed in the slag bin 6.

[0032] Specifically, when it is confirmed that the geology ahead of the tunnel is a water-rich and fractured stratum, and the unfavorable geological conditions ahead of the tunnel are determined to be of the low-pressure tunneling type, the tunnel is switched to the shield-type TBM low-pressure tunneling mode. Then, the muck hopper 72 and the movable conveyor belt 71 are removed from the muck bin 6, and the upper muck outlet 61 of the muck bin 6 is sealed by the partition 73 to ensure that the muck bin 6 is in a sealed state. Bentonite and foaming agent are injected into the muck bin 6 through the first grouting hole 51 to bring the bin pressure to the preset pressure of 2 bar. It should be noted that a pressure sensor is installed at the top of the muck bin 6 to detect the soil pressure inside the muck bin 6. Bentonite is mixed evenly outside the tunnel at a ratio of 1000:700 (water:bentonite), transported to the tunnel by tanker truck, and then injected into the slag silo 6 through two grouting holes using two bentonite pumps (injection capacity 28m³ / h). Foaming agent is injected into the slag silo 6 through eight grouting holes using one foam slurry pump (flow rate 550L / h) in conjunction with eight foam mixture pumps. This foaming agent is used to build up pressure in the slag silo 6 and improve the slag, enhance the workability of the slag, facilitate the discharge of slag from the screw conveyor, and reduce the risk of screw conveyor jamming.

[0033] In this step, sealing grease is injected into the sealing steel brush 9 at the tail of the shield to seal the gap between the assembled ring segment 11 and the tail shield 4, creating a sealed cavity inside the spoil heap 6. Furthermore, foamed chemical grout is injected into the gap between the shield and the external rock wall through the second grouting holes 8 on the front shield 2, middle shield 3, and tail shield 4, filling the fractured rock mass outside the shield and the gap between the shield and the rock wall, further enhancing the airtightness of the spoil heap 6.

[0034] Step 3: Start the shield-type TBM for low-pressure tunneling. Remove the sealing plate of the lower muck outlet 62, open the lower muck outlet 62 of the muck bin 6, and use the long screw conveyor 10 to discharge the muck from the muck bin 6. Continue to inject modifier into the muck bin 6, and control the speed of the long screw conveyor 10 to maintain a constant soil pressure within the muck bin 6 at a preset pressure. Specifically, during tunneling, continue to inject modifier into the muck bin 6. After the pressure inside the muck bin 6 rises, gradually open 1-2 pre-drilled holes on the top of the cutterhead 1 panel, connect hoses to guide the mud to the slurry discharge system near the segment 11 trolley, and use this to control the pressure inside the bin to stabilize it and prevent excessive pressure from damaging the sealing system (3 bar). Following the principle of "how much goes in, how much goes out," control the speed of the long screw conveyor 10 to maintain a constant soil pressure of 2 bar within the muck bin 6.

[0035] Furthermore, during the low-pressure tunneling process of the shield-type TBM, in order to maintain a constant soil pressure within the spoil bin 6 at a preset pressure, the injection flow rate of the amendment into the spoil bin 6 is determined by the following formula: ; in: The injection flow rate of the modifier is equal to the sum of the injection flow rates of bentonite and foaming agent; The tunneling speed of a shield-type TBM; The rotational speed of the cutter head; For the diameter of the spiral blades in the long spiral conveyor 10, a standard series value must be selected; The pitch of the helical blades in the long helical conveyor 10; The rotational speed of the screw shaft of the long screw conveyor 10; The filling rate (fill factor) of the long screw conveyor 10. The value of depends on the state of the slag: for granular slag, The value range is 0.25~0.35, for silty slag. The value range is 0.2; The bulk density of the slag conveyed by the long screw conveyor 10; This is the correction factor for inclined conveying of the long screw conveyor 10. When the long screw conveyor 10 is conveying horizontally... The value is 1.0. When the long screw conveyor 10 is inclined, taking the horizontal state as the reference, for every 1° increase in the inclination angle of the long screw conveyor 10, then... The value is reduced by 7‰ based on the value in the horizontal state. This refers to the number of the first grouting holes 51; This refers to the tunneling time of a shield-type TBM.

[0036] In this embodiment, to determine the injection flow rate of the modifier, the total amount of excavated soil generated by the TBM tunneling speed, cutterhead speed, and tunneling time is considered. At the same time, the blade diameter, pitch, speed, filling rate, excavated soil bulk density, and inclined conveying correction coefficient of the long screw conveyor 10 are also included to calculate the excavated soil discharge per unit time. The total modifier flow rate is then distributed by combining the number of the first grouting holes 51 on the back plate. This can accurately match the material balance between tunneling excavation and screw discharge, and dynamically calculate the modifier injection flow rate to meet the constant pressure requirements in the silo in real time. This avoids excessive modifier injection causing excessive pressure in the silo and sealing failure, or insufficient injection causing the silo pressure to be lower than the preset value, which can lead to the inability to balance the water and soil pressure at the working face and cause the surrounding rock to collapse. This stabilizes the sealed micro-pressure environment of the excavated soil silo and simultaneously ensures the excavated soil improvement effect and stable operation under continuous tunneling conditions.

[0037] This invention employs the aforementioned shield-type TBM for low-pressure tunneling in water-rich and fractured strata, enabling the TBM's spoil bin 6 to achieve a sealed mode. By adding modifiers (foaming agent and bentonite), the internal space of the spoil bin 6 is reduced, while the internal pressure is increased. This pressure stabilizes the surrounding rock at the tunnel face in the fractured and fractured strata, achieving the conditions for continuous tunneling with the shield-type TBM and reducing the risk of the TBM becoming trapped due to tunnel face collapse.

[0038] In the micro-pressure mode, the shield-type TBM of this invention allows the pressure within the spoil bin 6 to stabilize the surrounding rock at the tunnel face, preventing excessive resistance to the cutterhead 1 due to large amounts of collapsed debris and thus avoiding the risk of the cutterhead 1 becoming trapped. Furthermore, the micro-pressure mode ensures continuous tunneling by the TBM, significantly improving its construction efficiency.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A shield-type TBM suitable for low-pressure tunneling in water-rich and fractured strata, comprising a shield body, a cutterhead (1), a slag hopper (72), and a movable belt conveyor (71); the cutterhead (1) has a back plate (5) on its back, the back plate (5) being connected to the front shield (2) in the shield body, and a slag bin (6) being formed between the cutterhead (1) and the back plate (5), characterized in that: The movable belt conveyor (71) is installed in the shield body by a hydraulic cylinder, and the front end of the movable belt conveyor (71) extends from the upper slag outlet (61) of the slag bin (6) into the slag bin (6). The slag collection hopper (72) is installed at the front end of the movable belt conveyor (71) and located in the slag bin (6). The slag collection hopper (72) is provided with a partition (73) for sealing the upper slag outlet (61) after the hydraulic cylinder drives the movable belt conveyor (71) and the slag collection hopper to move a preset distance away from the cutter head (1) during micro-pressure tunneling. The back plate (5) is provided with a number of first grouting holes (51) for injecting a modifier into the slag bin (6) so that the soil pressure in the slag bin (6) reaches the preset pressure.

2. The shield-type TBM suitable for low-pressure tunneling in water-rich, fractured strata according to claim 1, characterized in that, The modifiers include bentonite and foaming agents.

3. The shield-type TBM suitable for low-pressure tunneling in water-rich, fractured strata according to claim 2, characterized in that, The shield body also includes a middle shield (3) and a tail shield (4). The front shield (2), the middle shield (3) and the tail shield (4) are each provided with a second grouting hole (8) for injecting foamed chemical grout into the gap between the shield body and the external rock wall, so that the fractured rock outside the shield body and the gap between the shield body and the rock wall are filled tightly.

4. The shield-type TBM suitable for low-pressure tunneling in water-rich, fractured strata according to claim 3, characterized in that, The tail shield (4) is provided with at least one sealing steel brush (9) with sealing grease, which is used to seal the gap between the assembled ring segment (11) and the tail shield (4).

5. The shield-type TBM suitable for low-pressure tunneling in water-rich, fractured strata according to claim 1, characterized in that, A long spiral conveyor (10) is also provided. The long spiral conveyor (10) is installed in the shield body, and the inlet of the long spiral conveyor (10) extends to the lower outlet (62) of the slag bin (6) for transporting the slag inside the slag bin (6) to the outside of the bin.

6. A shield TBM tunneling method suitable for low-pressure tunneling in water-rich fractured strata, implemented using the shield TBM for low-pressure tunneling in water-rich fractured strata as described in any one of claims 1-5, characterized in that, Includes the following steps: By combining geophysical exploration and advanced drilling, the location of unfavorable rock masses and the distribution of water-rich structures in front of the tunnel were determined, and the type of unfavorable geology in front of the tunnel was identified. When the geological conditions in front of the tunnel are of the low-pressure tunneling type, the slag collection bucket (72) and the movable belt conveyor (71) are removed from the slag bin (6), the upper slag outlet (61) of the slag bin (6) is sealed, and then the soil conditioner is injected into the slag bin (6) so that the soil pressure in the slag bin (6) reaches the preset pressure. Start the shield-type TBM for micro-pressure tunneling, open the lower slag outlet (62) of the slag bin (6), use the long screw conveyor (10) to discharge the slag in the slag bin (6), and keep injecting the soil conditioner into the slag bin (6). By controlling the speed of the long screw conveyor (10), keep the soil pressure in the slag bin (6) constant at the preset pressure.

7. The shield TBM tunneling method for low-pressure tunneling in water-rich fractured strata according to claim 6, characterized in that, Also includes: Inject sealing grease into the sealing steel brush (9) at the tail of the shield to seal the gap between the assembled ring segment (11) and the tail shield (4), so that a sealed cavity is formed inside the slag bin (6).

8. The shield TBM tunneling method for low-pressure tunneling in water-rich fractured strata according to claim 7, characterized in that, Also includes: Foamed chemical grout is injected into the gap between the shield body and the external rock wall through the second grouting holes (8) on the front shield (2), middle shield (3) and tail shield (4), so that the fractured rock outside the shield body and the gap between the shield body and the rock wall are filled tightly.

9. The shield TBM tunneling method for low-pressure tunneling in water-rich fractured strata according to claim 6, characterized in that, During the low-pressure tunneling process of the shield-type TBM, in order to keep the soil pressure inside the slag bin (6) constant at the preset pressure, the injection flow rate of the amendment into the slag bin (6) is determined by the following formula: ； in: The infusion flow rate of the modifier; The tunneling speed of a shield-type TBM; The rotational speed of the cutter head; The diameter of the spiral blade in the long spiral conveyor (10); The pitch of the helical blades in the long helical conveyor (10); The rotational speed of the screw shaft of the long screw conveyor (10); The filling rate of the long screw conveyor (10); The bulk density of the material in the long screw conveyor (10); For the inclined conveying correction factor of the long screw conveyor (10); The number of the first grouting holes (51); This refers to the tunneling time of a shield-type TBM.

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