Green low-carbon variable space earth pressure balance shield and construction method

Abstract

The invention discloses a green low-carbon variable space earth pressure balance shield and a construction method. A front partition plate is arranged in a front shield, a soil bin is formed in the space between a cutter head and the front partition plate, and an air cushion bin is formed between the front partition plate and a rear partition plate; an air inlet and an air outlet are formed in the upper part of the air cushion bin, and a variable gas space is formed in the air cushion bin by adjusting the gas quantity, so that an adjustable volume is provided for the muck, and the liquid level of the muck is maintained between the first soil liquid level meter and the third soil liquid level meter; gas pressure on the upper portion of the air cushion bin is transmitted to an excavation face in front of the cutter head through muck in a plastic flow state. The air pressure in the air cushion bin is accurately adjusted through the air adjusting device, the air pressure in the air cushion bin is transmitted into the soil bin through the plastic flow state muck to form stable soil bin pressure, and an excavation face is accurately supported. A muck capacity variable space is formed in the air cushion bin, and the problem that the pressure of the soil bin is unstable due to the fact that no muck compression space exists in an original earth pressure balance shield is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of shield tunneling construction, and in particular to a green, low-carbon, variable-space earth pressure balance shield tunnel and its construction method. Background Technology

[0002] As one of the most advanced tunnel construction technologies internationally, shield tunneling has become a core method for urban underground space development due to its superior engineering performance and high level of mechanization and automation. Compared to traditional mining or cut-and-cover methods, shield tunneling offers significant advantages: the operation is completed within a sealed mechanical shell, greatly reducing personnel safety risks; the resulting tunnel has a regular structure, good waterproofing, and high surface quality; it boasts high tunneling efficiency, enabling continuous and rapid advancement and effectively shortening the construction period; and it causes minimal disruption to surface traffic and the surrounding environment, making it particularly suitable for densely populated urban centers with numerous buildings. For these reasons, shield tunneling technology has been widely applied in urban rail transit and infrastructure construction, such as subways, integrated utility tunnels, and municipal tunnels, becoming the mainstream choice for modern urban underground engineering construction.

[0003] Among the main types of tunnel boring machines (TBMs), earth pressure balance (EPB) TBMs and slurry balance (SBP) TBMs each have their own characteristics and are suitable for different geological and engineering needs. EPB TBMs dominate conventional projects such as urban subways due to their advantages such as small working shaft footprint, lower equipment purchase and construction / operation costs, and fast tunneling speed. However, this method also has significant drawbacks: it is highly dependent on the fluidity of the excavated soil, easily forming mud cakes in clay strata or experiencing gushing in water-rich sand layers; the cutterhead cutting resistance is high, resulting in high torque; and traditional excavated soil improvement often relies on chemical foaming agents, which may cause certain environmental pollution problems and is not conducive to green construction. In contrast, SBP TBMs precisely control the excavation face pressure through a slurry circulation system, offering significant advantages such as high accuracy in surface settlement control, stable construction process, and virtually no risk of gushing. Therefore, they are prioritized for high-risk projects with extremely strict deformation control requirements, such as crossing rivers, lakes, and seas, and tunneling under important buildings and structures. Patent publication number CN116220706B discloses a dual-chamber slurry balance shield tunneling test device and method. By dividing the working chamber of the slurry balance shield tunneling test device into an air cushion chamber and a slurry chamber, and utilizing pressure-maintaining equipment to regulate gas and slurry pressure, it solves the problem of controlling support pressure in single-chamber devices, improving the accuracy and stability of the test, and simulating the shield tunneling process under deep burial and high water pressure. However, its cost is a complex equipment system, large land requirement, and high slurry treatment costs, resulting in relatively weaker overall economic efficiency. The complementary advantages and disadvantages of the above two methods together constitute the diversified development pattern of modern shield tunneling technology.

[0004] Currently, most tunnel boring machine (TBM) construction for urban rail transit is located in densely populated main urban areas, requiring the tunneling through numerous buildings and structures. This necessitates stringent settlement control measures and limited construction space, while also creating a demand for a green, environmentally friendly, and low-noise living environment for nearby residents. To address these challenges, there is an urgent need to invent a TBM that offers advantages such as minimal surface and building settlement during TBM construction, a small construction area, low construction costs, and environmental friendliness, striving to achieve harmonious coexistence between TBM construction for urban rail transit and nearby residential areas. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing earth pressure balance (EPB) shield tunneling equipment and methods, and to provide a green, low-carbon, variable-space EPB shield tunneling system and its construction method. The EPB shield tunneling system precisely regulates gas pressure through a variable-space gas chamber, thereby accurately controlling the pressure in the soil chamber and consequently controlling surface and building settlement. The excavated soil from the shield tunneling process is improved and reused, with no added chemicals, resulting in no pollution. The excavated soil is in a fluid state, leading to low energy consumption and making the system green, low-carbon, and environmentally friendly.

[0006] The objective of this invention is achieved through the following technical solution: A green, low-carbon, variable space earth pressure balance shield tunneling machine includes a cutterhead, front shield, middle shield, propulsion cylinder, shield tail, assembly machine, screw conveyor, crusher, screw pump, main drive, support arm, and rear-mounted trolley. The front shield is equipped with a front partition, the space between the cutter head and the front partition forms a soil chamber, and the space between the front partition and the rear partition forms an air cushion chamber. The upper part of the air cushion chamber is equipped with an air inlet and an air outlet. By adjusting the amount of gas, a variable gas space and gas pressure are formed inside the air cushion chamber, thereby providing an adjustable volume for the slag and keeping the slag liquid level between the first and third soil level gauges. The gas pressure at the top of the air cushion chamber is transferred to the excavation face in front of the cutterhead through the fluidized soil to support the original soil mass.

[0007] As a preferred embodiment, multiple active stirring rods are welded behind the cutter head to fully stir the slag in the soil chamber, ensuring that the slag is uniform and in a fluid state, and preventing mud cakes from forming in the soil chamber and air cushion chamber.

[0008] As a preferred embodiment, the front end of the screw conveyor is located at the slag inlet on the front partition at the bottom of the slag bin, which can directly and continuously discharge slag from the bottom of the slag bin, avoiding stagnation.

[0009] As a preferred embodiment, the front partition is equipped with multiple earth pressure sensors for real-time measurement of the earth pressure at different locations within the earth chamber; the front partition is connected to the outer stationary component of the main drive, and the internal rotating component of the main drive is connected to the cutterhead via a support arm to drive the cutterhead to rotate and cut the undisturbed soil in front of the excavation face.

[0010] As a preferred embodiment, the front partition is not a closed structure, but has an upper opening line and a lower opening line. The slag flow channel is formed between the upper opening line, the lower opening line, the outer contour of the main drive and the inner wall of the front shield, so as to allow bidirectional flow of slag between the soil bin and the air cushion bin.

[0011] As a preferred embodiment, the rear partition is provided with an exhaust port, an air inlet, a pressure sensor, a first ranging sensor, a second ranging sensor, a camera, a first soil level gauge, a second soil level gauge, and a third soil level gauge.

[0012] As a preferred method, during tunnel boring machine (TBM) excavation or when the machine is stopped, the control system compares the set value of the soil chamber pressure with the measured value of the soil pressure sensor: when the measured value of the soil pressure sensor is greater than the set value of the soil chamber pressure, the exhaust port is opened to release air, the gas pressure in the air cushion chamber decreases, and the soil chamber pressure decreases accordingly; when the measured value of the soil pressure sensor is less than the set value of the soil chamber pressure, the air inlet is opened to allow air in (note: the exhaust port and the air inlet cannot be opened at the same time), the gas pressure in the air cushion chamber increases, and the soil chamber pressure increases accordingly; when the measured value of the soil pressure sensor is equal to the set value of the soil chamber pressure, both the air inlet and the exhaust port are closed to keep the actual pressure in the soil chamber consistent with the set value, ensuring that the excavation face is in a state of pressure balance.

[0013] A green, low-carbon, variable-space earth pressure balance shield tunneling method includes the following: Start the slag improvement system, inject the thin mud in the mud tank into the front of the cutter head through the pipeline, mix it with the slag cut off, and form a fluidized slag. Start the cutterhead to rotate and advance the tunnel boring machine. Open the rear gate of the screw conveyor to allow the fluidized slag to enter the soil bin and air cushion bin, and then discharge it to the slag truck through the screw conveyor, crusher and screw pump. During the tunneling process, based on the comparison between the set earth pressure value and the measured value of the earth pressure sensor, the air inlet or outlet of the air cushion chamber is automatically controlled to adjust the gas pressure inside the air cushion chamber so that the measured value of the earth pressure sensor is equal to the set value. The first and second distance sensors measure the soil level on the left and right sides of the air cushion chamber in real time, take the average value and compare it with the middle position between the first and third soil level gauges, and automatically adjust the speed of the screw conveyor and the pumping speed of the screw pump to stabilize the soil level near the second soil level gauge. After completing one ring of tunneling distance, the following steps are taken in sequence: stop the propulsion cylinder, close the rear gate of the screw conveyor, stop the cutterhead rotation, and stop the muck soil improvement system. The tubular segments are assembled into a ring inside the tail of the shield using an assembly machine; Repeat the above construction steps in a cyclical manner.

[0014] As a preferred method, the mud injection rate and the injection volume ratio of each pipeline are determined based on the previous soil improvement test. The target injection volume of each pipeline is automatically calculated based on the real-time tunneling speed of the shield. The output flow of the corresponding mud pump is adjusted in real time through the feedback of the flow sensor to achieve closed-loop matching of the injection volume and ensure that the soil reaches a fluid plastic state without forming mud cakes.

[0015] As a preferred approach, safety interlock control is also included: When the first or second ranging sensor detects that the slag liquid level has reached the preset maximum soil level, the tunnel boring machine will automatically stop. When the slag level drops to the preset minimum soil level, the screw conveyor and screw pump will automatically stop discharging slag. The highest point of the soil is located between the exhaust port or air inlet and the first soil level gauge, and the lowest point of the soil is located between the third soil level gauge and the upper opening line of the front partition; this prevents the soil chamber from being not filled with slag and causing the soil pressure balance to fail.

[0016] As a preferred embodiment, the second soil level gauge is positioned in the middle between the first and third soil level gauges, and the stability of the soil level within the target range is determined by the alternating on and off of its signal.

[0017] This invention offers at least the following advantages: The earth pressure balance shield tunneling machine is designed with a soil chamber and an air cushion chamber. The gas pressure within the air cushion chamber is precisely regulated by a gas regulating device. This air pressure is transferred to the soil chamber through the fluidized excavated soil, forming a stable soil chamber pressure that precisely supports the excavation face. The air cushion chamber has variable excavated soil capacity, effectively solving the problem of unstable soil chamber pressure caused by the lack of compressible space in traditional earth pressure balance shield tunneling machines. This original invention ensures continuous and stable support pressure at the excavation face, controlling surface and building settlement. Furthermore, the innovative excavated soil improvement utilizes diluted slurry separated from the excavated soil, eliminating the addition of potentially polluting chemical materials (such as foaming agents and polymers). The slurry in the excavated soil is reused multiple times, offering green and environmentally friendly advantages. The use of distance sensors and program control automatically adjusts the screw conveyor speed and screw pump pumping speed for excavation, preventing the earth pressure balance shield tunneling machine from gushing and improving the automation level of the tunnel boring machine. Attached Figure Description

[0018] To reveal the technical details of the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. It should be emphasized that these drawings only present several embodiments of the present invention and should not be considered as defining the scope of the invention. For those skilled in the art, other related drawings can still be derived based on these drawings without inventive effort.

[0019] Figure 1 This is a schematic diagram of the earth pressure balance shield tunneling structure of the present invention; Figure 2 This is a schematic diagram of the front partition. Figure 3 This is a structural schematic diagram of the rear partition. Figure 4 Diagram of the waste soil improvement system; Figure 5 This is a schematic diagram of the vertical cross-sectional area of ​​the air cushion chamber.

[0020] In the diagram, 1-Cutterhead, 2-Active mixing rod, 3-Front shield, 4-Soil chamber, 5-Front partition, 6-Air cushion chamber, 7-Rear partition, 8-Middle shield, 9-Propulsion cylinder, 10-Shield tail, 11-Segment, 12-Assembly machine, 13-Shield tail brush, 14-Screw conveyor, 15-Hydraulic motor, 16-Screw conveyor rear gate, 17-Crusher, 18-Support arm, 19-Variable frequency motor, 20-Screw pump, 21-Slag outlet, 22-Earth pressure sensor, 23-Main drive, 24-Upper opening line, 25-Lower opening line, 26-Slag inlet, 27-Exhaust port, 28-First ranging sensor, 29-Camera, 30- Second ranging sensor, 31-Air pressure sensor, 32-Air inlet, 33-Highest soil level, 34-First soil level gauge, 35-Second soil level gauge, 36-Third soil level gauge, 37-Lowest soil level, 38-Bottom of rear partition, 39-Slurry tank, 40-Highest level gauge, 41-Normal level gauge, 42-Lowest level gauge, 43-First shut-off valve, 44-Slurry pump, 45-Overflow valve, 46-First check valve, 47-Flow sensor, 48-Pressure gauge, 49-Pressure sensor, 50-Second check valve, 51-Second shut-off valve, 52-Included angle, 53-Projection direction, 54-Actual slag and soil level. Detailed Implementation

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0022] In the following description, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, it should be understood that the present disclosure is not limited to the specific forms shown herein. Rather, it should be understood to encompass various variations, equivalents, and / or alternatives to the embodiments of the present disclosure. In illustrating the drawings, the same reference numerals will be used to denote similar components.

[0023] In the various embodiments of this disclosure, the terms "first," "second," "the first," or "the second" are intended to modify different components and not to indicate order and / or importance, nor do they constitute a limitation on the respective components. For example, a first user equipment and a second user equipment represent different user equipments, although they both fall under the category of user equipment. Similarly, a first component may be named a second component, and a second component may be named a first component, without changing their essential attributes within the scope of this disclosure.

[0024] In this disclosure, terminology is used to describe specific embodiments and does not constitute a limitation thereof. In this context, the use of the singular form also encompasses the plural form, unless otherwise expressly stated herein. In the course of description, terms such as “comprising” or “having” are intended to indicate the presence of features, quantities, steps, operations, structural components, parts, or combinations thereof, and do not preclude the possibility or addition of one or more other features, quantities, steps, operations, structural components, parts, or combinations thereof.

[0025] It should be clarified that while the following description provides detailed specific information to aid in a comprehensive understanding of the exemplary embodiments, those skilled in the art will recognize that the exemplary embodiments can be implemented even without these specific details. For example, the system may be illustrated using block diagrams to avoid excessive detail that could obscure the clarity of the example. In other cases, to maintain the clarity of the example, unnecessary details of well-known processes, structures, and techniques may be omitted.

[0026] like Figure 1 As shown, a green, low-carbon, variable space earth pressure balance shield tunneling machine includes a cutterhead 1, a front shield 3, a middle shield 8, a propulsion cylinder 9, a shield tail 10, an assembly machine 12, a screw conveyor 14, a crusher 17, a screw pump 20, a main drive 23, a support arm 18, and a rear-mounted trolley. The front shield 3 is provided with a front partition 5, the space between the cutter head 1 and the front partition 5 forms a soil chamber 4, and the space between the front partition 5 and the rear partition 7 forms an air cushion chamber 6. The air cushion chamber 6 is provided with an air inlet 32 ​​and an exhaust outlet 27 at the top. By adjusting the amount of gas, a variable gas space is formed inside the air cushion chamber 6, thereby providing an adjustable volume for the slag and keeping the slag liquid level between the first soil level gauge 34 and the third soil level gauge 36. The gas pressure at the top of the air cushion chamber 6 is transferred to the excavation face in front of the cutterhead 1 through the fluidized soil to support the original soil mass.

[0027] In a preferred embodiment, a plurality of active stirring rods 2 are welded behind the cutter head 1 to fully stir the slag in the soil chamber 4, ensuring that the slag is uniform and in a fluid state, and preventing mud cakes from forming in the soil chamber 4 and the air cushion chamber 6.

[0028] In a preferred embodiment, see Figure 2 The front end of the screw conveyor 14 is located at the slag inlet 26 on the front partition 5 at the bottom of the soil bin 4, which can directly and continuously discharge slag from the bottom of the soil bin 4 to avoid stagnation.

[0029] In a preferred embodiment, the screw conveyor 14 is driven to rotate by a hydraulic motor 15, and a screw conveyor rear gate 16 is provided between its rear opening and the crusher 17; when the tunnel boring machine stops tunneling or the crusher 17 is repaired, the screw conveyor rear gate 16 is closed.

[0030] In a preferred embodiment, the screw pump 20 is driven by the variable frequency motor 19, which can steplessly adjust the slag discharge speed within the range of 0 to the slag volume corresponding to the highest tunneling speed of the shield; the fluidized slag in the soil chamber 4 is sequentially pumped to the slag car below the rear supporting trolley via the screw conveyor 14, crusher 17, screw pump 20, slag outlet 21 and pipeline pump, effectively preventing gushing during the tunneling process.

[0031] In a preferred embodiment, multiple rows of annular shield tail brushes 13 are welded to the rear of the shield tail 10, and shield tail sealing grease is injected between adjacent shield tail brushes 13 to seal the sliding surface between the inside of the shield tail 10 and the outside of the segment 11, preventing synchronous slurry or mud from entering the shield tail 10.

[0032] In a preferred embodiment, a plurality of earth pressure sensors 22 are arranged on the front partition 5 for real-time measurement of the earth pressure at different locations within the soil chamber 4; the front partition 5 is connected to the outer stationary part of the main drive 23, and the internal rotating part of the main drive 23 is connected to the cutter head 1 via the support arm 18 to drive the cutter head 1 to rotate and cut the undisturbed soil in front of the excavation face.

[0033] In a preferred embodiment, the front partition 5 is not a closed structure, and it is provided with an upper opening line 24 and a lower opening line 25. The slag flow channel is formed between the upper opening line 24, the lower opening line 25, the outer contour of the main drive 23 and the inner wall of the front shield 3, so as to allow bidirectional flow of slag between the soil chamber 4 and the air cushion chamber 6.

[0034] In a preferred embodiment, see Figure 3 The rear partition 7 is equipped with an exhaust port 27, an air inlet 32, a pressure sensor 31, a first ranging sensor 28, a second ranging sensor 30, a camera 29, a first soil level gauge 34, a second soil level gauge 35, and a third soil level gauge 36.

[0035] In a preferred embodiment, during shield tunneling or when the machine is stopped, the control system compares the set value of the soil chamber pressure with the measured value of the soil pressure sensor 22: when the measured value of the soil pressure sensor 22 is greater than the set value of the soil chamber pressure, the control system opens the exhaust port 27 to exhaust gas, the gas pressure in the air cushion chamber 6 decreases, and the pressure in the soil chamber 4 decreases accordingly; when the measured value of the soil pressure sensor 22 is less than the set value of the soil chamber pressure, the control system opens the air inlet 32 ​​to allow air to enter, the gas pressure in the air cushion chamber 6 increases, and the pressure in the soil chamber 4 increases accordingly; when the measured value of the soil pressure sensor 22 is equal to the set value of the soil chamber pressure, both the air inlet 32 ​​and the exhaust port 27 are closed, so that the actual pressure in the soil chamber 4 is consistent with the set value, ensuring that the excavation face is in a pressure balance state.

[0036] In one embodiment, to improve the accuracy and response speed of pressure control, this invention further introduces a dynamic control model based on the gas state equation. Traditional on / off control is prone to pressure overshoot or lag, while this solution achieves continuous and smooth pressure closed-loop by quantitatively calculating the required gas adjustment amount. Let the current volume occupied by the gas in the air cushion chamber 6 be... (unit, The gas pressure is (Unit: Pa), the set target pressure for the earthwork chamber is (Unit: Pa), the actual pressure measured by earth pressure sensor 22 is... (Unit: Pa), then the required gas volume correction amount for injection or discharge. (unit: It is determined by the following formula: ; In the formula, This indicates that air inlet 32 ​​needs to be opened to inject gas. This indicates that exhaust port 27 needs to be opened to release the gas. Among other things, The pressure can be calculated using the geometry of the air cushion chamber and the real-time slag level (measured by the first ranging sensor 28 and the second ranging sensor 30). This model is suitable for rapid compensation scenarios involving small pressure fluctuations during tunnel boring machine (TBM) excavation. Through this model, the control system can predict the gas adjustment amount in advance, avoiding pressure oscillations caused by frequent valve starts and stops, significantly improving the stability of the excavation face support pressure, and thus effectively suppressing settlement and deformation of the ground surface and adjacent buildings / structures. This method upgrades the previously discrete control, which relied on empirical thresholds, to continuous quantitative regulation based on physical mechanisms, providing core technical support for achieving precise pressure management in "variable spaces."

[0037] In a preferred embodiment, the volume occupied by the gas inside the air cushion chamber 6 It can be obtained through joint calculation of the shield structure's geometric parameters and real-time liquid level measurement data. Let the inner diameter of the front shield 3 be... (Unit: m), the diameter of the outer contour of the main drive 23 is (Unit: m), the axial distance between the front partition 5 and the rear partition 7 (i.e., the effective length of the air cushion) is: (Unit: m) The first distance sensor 28 and the second distance sensor 30, mounted on the rear partition 7, respectively measure the distance to the actual slag liquid level 54. and (Unit: m), see Figure 5 The angle 52 between the projection direction 53 of the ranging sensor and the vertical downward direction is both... Vertical height from the sensor mounting reference surface to the top of the air cushion chamber (Unit: m) can be used to calculate the average liquid level height of the slag. (Unit: m). According to or Calculate the vertical cross-sectional area S of the gas inside the air cushion chamber 6 (unit: m²) based on one of the two actual scenarios. 2 Ultimately, the gas volume... (Unit: m) 3 It is determined by the following formula: ; The calculation results provide key state variables for the pressure closed-loop control system, supporting the accurate solution of gas regulation and ensuring stable pressure at the excavation face.

[0038] In a preferred embodiment, although the air pressure sensor 31 does not directly participate in the main control closed loop of intake / exhaust, its measured value is used to monitor the actual air pressure inside the air cushion chamber 6 and compare it with the reading of the earth pressure sensor 22 to assess the degree of attenuation of gas pressure transmission in the slag. Based on this attenuation data, the operator or control system can preset a slightly higher target air pressure in the initial setting stage. For example, if the required earth pressure is 1.5 bar, but the measured air pressure needs to be 2.0 bar to reach it, the target air pressure can be set to 2.1 to 2.4 bar in the future, thereby improving the response speed and stability of pressure regulation.

[0039] In a preferred embodiment, the first soil level gauge 34 is used to monitor the highest soil level in the air cushion chamber 6, the second soil level gauge 35 is used to monitor the normal soil level, and the third soil level gauge 36 is used to monitor the lowest soil level. When the soil level reaches the first soil level gauge 34, the tunnel boring machine automatically stops tunneling. When the soil level drops to the third soil level gauge 36, the tunnel boring machine automatically stops slag removal. When the soil level is between the first soil level gauge 34 and the third soil level gauge 36, the tunnel boring machine continues to tunnel and remove slag normally.

[0040] In a preferred embodiment, the camera 29 is an infrared camera, and the first ranging sensor 28 and the second ranging sensor 30 are ultrasonic ranging sensors, used to assist in monitoring the liquid level of the slag in the humid and dark environment of the air cushion chamber 6.

[0041] In a preferred embodiment, see Figure 4 It also includes a slag improvement system, which includes a mud tank 39, a first shut-off valve 43, a mud pump 44, an overflow valve 45, a first check valve 46, a flow sensor 47, a pressure gauge 48, a pressure sensor 49, a second check valve 50, a second shut-off valve 51, and connecting pipelines; the mud tank 39 is equipped with a maximum liquid level gauge 40, a normal liquid level gauge 41, and a minimum liquid level gauge 42.

[0042] In a preferred embodiment, the slag improvement system employs multiple improved pipelines, each corresponding to a continuously variable frequency mud pump 44, to achieve single-pipe single-pump slurry supply and prevent blockage of the injection port in front of the cutterhead; the mud pump 44 can steplessly adjust the injection speed.

[0043] In a preferred embodiment, after the fluidized soil is separated by screening equipment outside the tunnel, the resulting thin mud slurry composed of fine particles and water is reused and pumped back to the mud tank 39; when the liquid level in the mud tank 39 reaches the highest liquid level gauge 40, an audible and visual alarm is triggered to prohibit further pumping; when the liquid level is lower than the lowest liquid level gauge 42, an audible and visual alarm is triggered to indicate that the mud has been exhausted.

[0044] In a preferred embodiment, the slurry contains no chemical foaming agents or polymers, and consists only of natural fine particles and water, fundamentally avoiding the environmental pollution problems caused by traditional slag and soil improvement, and embodying the concept of green and low-carbon construction.

[0045] To further ensure the quantifiable and predictable effectiveness of slag soil improvement under chemical-free conditions, this invention proposes a fluidity criterion based on natural components. Extensive engineering practice and laboratory tests have shown that when the fine particle content and moisture content of the slag soil meet a specific combination relationship, even without the addition of foaming agents or polymers, a fluidized soil with good flowability, low internal friction angle, and minimal segregation can be formed. The mass fraction of fine particles with a particle size less than 75 micrometers in the slag soil is defined as... (No unit), natural moisture content is (Unitless, i.e., the ratio of water mass to solid particle mass), then the necessary condition for slag to exhibit good fluidity and plasticity is: ; In the formula, This is the critical fluid plasticity coefficient, and its value depends on the properties of the strata and soil: for highly cohesive strata (such as silty clay and silty soil), it is recommended to take [value missing]. For sandy or gravelly strata, the following can be taken: Before construction, a small amount of slag sample can be screened and tested for moisture content to quickly obtain the necessary information. and If the above criteria are not met, optimization can be achieved by adjusting the proportion of recycled thin mud slurry or supplementing with fine particles (such as using excess mud slurry from the pre-ring screening). This criterion not only provides a scientific design basis for "green and low-carbon" improvements but also realizes the transformation from "experience-based trial and error" to "parameter-driven" approaches. More importantly, since the thin mud slurry originates from the recycling of slag and soil from this project, the entire improvement process is free from external pollution and chemical residues, fully meeting the stringent requirements of the urban core area for environmental protection, low noise, and sustainable construction.

[0046] A green, low-carbon, variable-space earth pressure balance shield tunneling method includes the following: (1) Start the slag improvement system and inject the thin mud in the mud tank 39 into the front of the cutter head 1 through the pipeline to mix with the slag cut off and form a fluid plastic state slag. (2) Start the cutterhead 1 to rotate and advance the shield, open the rear gate 16 of the screw conveyor to allow the plastic slag to enter the soil chamber 4 and the air cushion chamber 6, and be discharged to the slag car through the screw conveyor 14, crusher 17 and screw pump 20. (3) During the tunneling process, based on the comparison between the set earth pressure value and the measured value of the earth pressure sensor 22, the air inlet 32 ​​or the exhaust port 27 of the air cushion chamber 6 is automatically controlled to open or close, and the gas pressure inside the air cushion chamber 6 is adjusted so that the measured value of the earth pressure sensor 22 is equal to the set value. (4) The soil liquid level on the left and right sides of the air cushion chamber 6 is measured in real time by the first distance sensor 28 and the second distance sensor 30. The average value is taken and compared with the middle position between the first soil liquid level gauge 34 and the third soil liquid level gauge 36. The speed of the screw conveyor 14 and the pumping speed of the screw pump 20 are automatically adjusted to stabilize the soil liquid level near the second soil liquid level gauge 35. (5) After completing one ring of tunneling distance, stop the propulsion of the propulsion cylinder 9, close the screw conveyor gate 16, stop the rotation of the cutter head 1, and stop the slag improvement system in sequence; (6) Use assembly machine 12 to assemble the segments 11 into a ring inside the shield tail 10; (7) Repeat steps (1) to (6) to form a tunnel through cyclical construction.

[0047] In a preferred embodiment, the thin mud is obtained by separating the fluidized soil from the excavated material using an external screening device. It consists of fine particles and water, contains no chemical additives, and is pumped back to the mud tank 39 for recycling.

[0048] In a preferred embodiment, in step (1), the mud injection rate and the injection volume ratio of each pipeline are determined based on the previous soil improvement test. The target injection volume of each pipeline is automatically calculated based on the real-time tunneling speed of the shield. The output flow of the corresponding mud pump 44 is adjusted in real time through the feedback of the flow sensor 47 to achieve closed-loop matching of the injection volume and ensure that the soil reaches the state of fluid plastic without forming mud cake.

[0049] In a preferred embodiment, in step (2), if the slag contains large-diameter particles or is located in a pebble stratum, the crusher 17 is turned on to crush the slag to ensure that the particle size of the slag meets the conveying requirements of the screw pump 20.

[0050] In a preferred embodiment, the crusher 17 is installed in the pipeline between the outlet of the screw conveyor 14 and the inlet of the screw pump 20, for secondary crushing of large pieces of slag or pebbles, to prevent blockage of the screw pump (20) or interruption of the conveying process.

[0051] In a preferred embodiment, in step (4), the pumping speed of the screw pump 20 is set to be slightly greater than the slag discharge speed of the screw conveyor 14, so as to prevent the slag pressure inside the screw conveyor 14 from accumulating and causing the shaft to jam.

[0052] In a preferred embodiment, "slightly greater than" means that the instantaneous discharge capacity of the screw pump 20 is 5% to 15% higher than the slag discharge capacity of the screw conveyor 14. This difference is sufficient to maintain a slightly negative pressure or low pressure state inside the screw conveyor and avoid back pressure accumulation of slag.

[0053] In a preferred embodiment, a safety interlock control is also included: If the first soil level gauge 34 or the third soil level gauge 36 is inaccurate or malfunctions, an early warning can also be issued through the first distance sensor 28 and the second distance sensor 30. When the first ranging sensor 28 or the second ranging sensor 30 detects that the slag liquid level has reached the preset maximum soil level 33, the tunnel boring machine will automatically stop. When the slag level drops to the preset minimum soil level of 37, the screw conveyor 14 and screw pump 20 automatically stop discharging slag. The highest soil level 33 is located between the exhaust port 27 or the air inlet 32 ​​and the first soil level gauge 34, and the lowest soil level 37 is located between the third soil level gauge 36 and the upper opening line 24 of the front partition 5; this prevents the soil chamber 4 from being not filled with slag and causing the soil pressure balance to fail.

[0054] In a preferred embodiment, the camera 29 captures real-time images of the excavated soil inside the air cushion chamber 6 and transmits them to the shield tunneling operation room, allowing operators to intuitively monitor the liquid level of the excavated soil.

[0055] In a preferred embodiment, the second soil level gauge 35 is positioned at the midpoint between the first soil level gauge 34 and the third soil level gauge 36, and the alternating on / off state of its signal is used to determine whether the soil level is stable within the target range.

[0056] In a preferred embodiment, the present invention introduces a compressible gas space by configuring an air cushion chamber 6, which fundamentally solves the problem of severe pressure fluctuations and difficulty in settlement control caused by the lack of variable space in the soil chamber of traditional earth pressure balance shield tunnels. At the same time, it uses circulating thin mud slurry to achieve green soil improvement and avoid mud cake formation. In conjunction with the screw conveyor 14 and screw pump 20, the slag is pumped out, which effectively prevents gushing. Thus, the invention achieves the synergistic treatment of the three major problems of surface settlement, gushing, and mud cake formation.

[0057] In summary, this invention systematically solves the core technical bottlenecks faced by traditional earth pressure balance shield tunneling machines in complex urban environments through air cushion chamber structural design, green soil improvement technology, and intelligent liquid level-pressure coordinated control strategy. To more clearly illustrate the technical breakthroughs of this invention and its significant advancements compared to existing technologies, the correspondence between the background issues and this solution is explained below: (1) Reasons for the difficulty in controlling settlement of earth pressure balance shield tunnels The original earth pressure balance shield tunneling system uses the cutters on the cutterhead 1 to compress or cut the excavated soil, which is then modified into a plastic state and fills the soil chamber to create pressure to balance the original soil at the excavation face. Although there is a small amount of compressible space in the excavated soil, it is very small. If the shield tunneling speed increases while the excavation speed of the screw conveyor 14 remains constant, and more excavated soil enters the soil chamber, the soil chamber pressure will rise rapidly. Conversely, if the shield tunneling speed decreases while the excavation speed of the screw conveyor remains constant, and less excavated soil enters the soil chamber, the soil chamber pressure will drop rapidly. The reason for this is that there is no compressible space (variable space) within the soil chamber, resulting in inaccurate pressure control and causing deformation (settlement or heave) of the ground surface and buildings during shield tunneling. The slurry balance shield tunneling system is equipped with an air cushion chamber, effectively solving the problem of the lack of variable space in earth pressure balance shield tunneling systems. Furthermore, earth pressure balance shield tunneling systems have very high requirements for excavated soil modification; if the excavated soil is too thin, it will gush out; if it is too dry, it will form mud cakes. Whether it's gushing or mud cake formation, it can easily cause abnormal muck discharge during shield tunneling, leading to ground and building settlement during shield construction. Precise control of the earth pressure chamber pressure during earth pressure balance shield tunneling, while simultaneously preventing gushing and mud cake formation, has always been an unsolvable problem.

[0058] (2) Based on the above-mentioned reasons for the difficulty in controlling the settlement of earth pressure balance shield tunnels, this invention reuses the thin mud in the excavated soil to improve the soil, and improves the soil excavated by the cutter into a fluid plastic state (without forming mud cakes). By configuring an air cushion chamber, the variable space of the excavated soil is greatly increased, and the soil pressure in the soil chamber is precisely controlled, so that the soil pressure in the soil chamber remains stable and supports the excavation face. At the same time, through the distance sensor and program control, the speed of the screw conveyor 14 and the pumping speed of the screw pump 20 (without gushing) are automatically adjusted, so that the position of the excavated soil in the air cushion chamber is at the normal mud liquid level, thus solving the problems of settlement, easy gushing, and easy mud cake formation of earth pressure balance shield tunnels.

[0059] This invention has the following advantages: (1) The variable space of slag and soil in the air cushion chamber 6 of the earth pressure balance shield ensures precise control of the pressure of the earth chamber, greatly reduces ground disturbance, and reduces the probability of surface and building (structure) settlement. (2) The innovative slag soil conditioner uses fine particles separated from slag soil and water to form a thin mud slurry, which allows for the reuse of some slag soil. Furthermore, the slag soil conditioner contains no chemical components, which reduces the cost of slag soil conditioner and is green, environmentally friendly and pollution-free. (3) Numerous active stirring rods 2 behind the cutterhead 1 can fully stir the slag and make it flowable and uniform. The flowable slag reduces the cutterhead torque, reduces power consumption, and reduces carbon emissions compared to the plastic slag that does not gush in the original earth pressure balance shield. The flowable slag has a low pressure reduction rate during pressure transmission and is more stable than the plastic slag. (4) The front end of the screw conveyor 14 is directly connected to the slag inlet 26 at the bottom of the soil bin 4, which avoids the phenomenon of stagnation at the bottom of the soil bin 4. (5) The screw conveyor is connected to the crusher 17 below the rear gate 16, which can crush large pieces of slag to the size that the screw pump 20 can pump, reducing the probability of blockage and failure rate of the screw pump 20. (6) The slag and soil are improved to reach a fluid plastic state to prevent the shield from forming mud cake; the slag is discharged by conveying with a screw conveyor 15 and pumping with a screw pump 20 to prevent gushing. (7) The lower opening line 25 elevation is designed to be lower than the bottom of the rear partition 38 position, so that the slag can enter the soil chamber 4 more easily from the air cushion chamber 6, preventing the slag from accumulating here; (8) The multiple soil level monitoring methods, including camera 29, first ranging sensor 28, second ranging sensor 30, first soil level gauge 34, and third soil level gauge 36, prevented deviations in soil level, failure of soil chamber support for excavation face, and shield tunneling safety accidents.

[0060] In summary, this invention successfully overcomes the technical bottlenecks of traditional earth pressure balance shield tunneling in three major areas: settlement control, gushing risk, and mud cake formation. It organically integrates a variable space pressure regulation mechanism for the air cushion chamber, a green slag recycling improvement technology without chemical additives, and an intelligent slag discharge control strategy based on multi-sensor fusion. This not only achieves high-precision dynamic stability of the excavation face support pressure, significantly improving the safety and environmental friendliness of tunnel construction in densely populated urban areas, but also substantially reduces carbon emissions and construction costs through slag resource utilization and low-energy fluidized bed slag discharge, truly embodying the modern underground engineering construction concept of "green, low-carbon, intelligent, and efficient." This solution combines the pressure stability advantages of slurry balance shield tunneling with the economical and compact characteristics of earth pressure balance shield tunneling, providing a new technical path for shield tunneling construction in complex urban environments that is advanced, practical, and sustainable.

[0061] Although the present invention has been described in detail through preferred embodiments, those skilled in the art, upon understanding its core inventive concept, can make various equivalent substitutions, structural changes, or technical improvements to the above embodiments. Therefore, the claims of the present invention should be understood to cover not only the disclosed preferred embodiments but also all other variations and modifications falling within the essential spirit and scope of protection of the present invention. It should be emphasized that the above content is only a preferred embodiment of the present invention and is not a limitation thereof; any modifications, equivalent substitutions, combinations, adjustments, or optimizations made within the spirit and principles of the present invention should be considered as included within the patent protection scope of the present invention.

Claims

1. A green low-carbon variable space earth pressure balance shield, characterized in that, The shield tunneling machine comprises a cutter head (1), a front shield (3), a middle shield (8), a pushing oil cylinder (9), a shield tail (10), an assembling machine (12), a screw conveyor (14), a crusher (17), a screw pump (20), a main drive (23), a support arm (18) and a rear matching trolley. The front shield (3) is internally provided with a front partition plate (5), and a space between the cutter head (1) and the front partition plate (5) forms a soil bin (4), and the front partition plate (5) and a rear partition plate (7) form an air cushion bin (6). The air cushion bin (6) is provided with an air inlet (32) and an air outlet (27) at the upper portion, and the air cushion bin (6) forms a variable gas space by adjusting the amount of gas, so as to provide an adjustable volume for the muck and maintain the muck level between a first soil level meter (34) and a third soil level meter (36). The gas pressure at the upper portion of the air cushion bin (6) is transmitted to the excavation face in front of the cutter head (1) through the muck in a plastic flow state, so as to support the undisturbed soil body.

2. The green low-carbon variable space earth pressure balance shield according to claim 1, wherein, The front end of the screw conveyor (14) is located at a muck inlet (26) on the front partition plate (5) at the lower portion of the soil bin (4), and the muck can be continuously discharged from the bottom of the soil bin (4) directly, so as to avoid stagnation and discharge.

3. The green low-carbon variable space earth pressure balance shield according to claim 1, wherein, A plurality of earth pressure sensors (22) are arranged on the front partition plate (5) for measuring the earth bin pressure at different positions in the soil bin (4) in real time; the front partition plate (5) is connected with the fixed part of the main drive (23) on the outside, and the rotating part of the main drive (23) is connected with the cutter head (1) through the support arm (18) to drive the cutter head (1) to rotate and cut the undisturbed soil in front of the excavation face.

4. The green low-carbon variable space earth pressure balance shield according to claim 3, characterized in that, The front partition plate (5) is not a closed structure, and is provided with an upper opening line (24) and a lower opening line (25), and a muck flow channel is formed between the upper opening line (24), the lower opening line (25), the outer contour of the main drive (23) and the inner wall of the front shield (3) to allow the muck to flow bidirectionally between the soil bin (4) and the air cushion bin (6).

5. The green low-carbon variable space earth pressure balance shield according to any one of claims 1-4, characterized in that, The rear partition plate (7) is provided with an air outlet (27), an air inlet (32), a gas pressure sensor (31), a first distance measuring sensor (28), a second distance measuring sensor (30), a camera (29), a first soil level meter (34), a second soil level meter (35) and a third soil level meter (36).

6. The green low-carbon variable space earth pressure balance shield according to claim 5, characterized in that, During the shield tunneling process or when the machine is stopped, the control system compares the measured value of the earth pressure sensor (22) with the set value of the earth bin pressure: when the measured value of the earth pressure sensor (22) is greater than the set value of the earth bin pressure, the air outlet (27) is controlled to be opened to discharge air, the gas pressure in the air cushion bin (6) is reduced, and the pressure in the soil bin (4) is correspondingly reduced; when the measured value of the earth pressure sensor (22) is less than the set value of the earth bin pressure, the air inlet (32) is controlled to be opened to intake air, the gas pressure in the air cushion bin (6) is increased, and the pressure in the soil bin (4) is correspondingly increased; when the measured value of the earth pressure sensor (22) is equal to the set value of the earth bin pressure, the air inlet (32) and the air outlet (27) are both closed, so that the actual pressure in the soil bin (4) is consistent with the set value, and the excavation face is kept in a pressure balance state.

7. A green low-carbon variable space earth pressure balance shield construction method, characterized in that, The method comprises the following steps: (1) starting the slurry improvement system, and injecting the thin slurry in the slurry tank (39) into the front of the cutter head (1) through pipelines to mix with the cuttings to form flowable slurry; (2) starting the rotation of the cutter head (1) and the advance of the shield, opening the rear gate (16) of the screw conveyor to make the flowable slurry enter the soil bin (4) and the air cushion bin (6), and then being discharged to the slurry car through the screw conveyor (14), the crusher (17) and the screw pump (20); (3) during the tunneling process, based on the comparison between the set soil bin pressure value and the measured value of the soil pressure sensor (22), the air inlet (32) or the air outlet (27) of the air cushion bin (6) is automatically controlled to open or close, the air pressure in the air cushion bin (6) is adjusted, and the measured value of the soil pressure sensor (22) is equal to the set value; (4) the left and right slurry levels in the air cushion bin (6) are measured in real time by the first distance measuring sensor (28) and the second distance measuring sensor (30), the average value is obtained, and the average value is compared with the middle position between the first soil level meter (34) and the third soil level meter (36), the rotation speed of the screw conveyor (14) and the pumping speed of the screw pump (20) are automatically adjusted, and the slurry level is stabilized near the second soil level meter (35); (5) after completing the tunneling distance of one ring, the advance of the push cylinder (9) is stopped, the rear gate (16) of the screw conveyor is closed, the rotation of the cutter head (1) is stopped, and the slurry improvement system is stopped; (6) the pipe segment (11) is assembled into a ring in the shield tail (10) by using the assembling machine (12); (7) the steps (1) to (6) are repeated to circulate the construction.

8. The green low-carbon variable space earth pressure balance shield construction method according to claim 7, characterized in that, In the step (1), the slurry injection rate and the injection amount ratio of each pipeline are determined according to the previous slurry improvement test, the target injection amount of each pipeline is automatically calculated based on the real-time tunneling speed of the shield, the output flow of the corresponding slurry pump (44) is adjusted in real time through the feedback of the flow sensor (47), and the closed-loop matching of the injection amount is realized.

9. The green low-carbon variable space earth pressure balance shield construction method according to claim 7, characterized in that, The safety interlocking control is further included: When the first distance measuring sensor (28) or the second distance measuring sensor (30) detects that the slurry level reaches the preset maximum soil level (33), the shield tunneling is automatically stopped; When it is detected that the slurry level drops to the preset minimum soil level (37), the screw conveyor (14) and the screw pump (20) are automatically stopped to discharge the slurry; The maximum soil level (33) is located between the air outlet (27) or the air inlet (32) and the first soil level meter (34), and the minimum soil level (37) is located between the third soil level meter (36) and the upper opening line (24) of the front partition plate (5).

10. The green low-carbon variable space earth pressure balance shield construction method according to claim 7, characterized in that, The second soil level meter (35) is arranged at the middle position between the first soil level meter (34) and the third soil level meter (36), and whether the slurry level is stable in the target interval is judged by the alternate on-off of the signal of the second soil level meter (35).

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