A gas-soil combined balanced shield machine and its face balance control method

Abstract

The purpose of the present invention is to provide a gas-soil combined balanced shield machine and a method for controlling the balance of the tunnel face thereof, so as to improve the efficiency of the gas-soil combined balanced shield machine construction. The gas-soil combined balanced shield machine includes a cutter head, an air supply assembly, a soil bin, and a screw conveyor. The air supply assembly includes: a gas pipeline for supplying gas to the soil bin, including an air inlet pipe and an air outlet pipe, the air inlet pipe is equipped with a switch valve and a pressure reducing valve, the air outlet pipe is equipped with a switch valve and a pressure relief valve, the air inlet pipe is connected to the air outlet pipe at the front end and connected to the air hole of the soil bin partition, the tail end of the air inlet pipe is connected to the air compressor for pressurization, and the tail end of the air outlet pipe is connected to the atmosphere for pressure relief; and a foam pipeline for providing foam for cutting soil, including a foam pump, a foam agent box, a foam generator, and a water tank. The foam pump presses water and foam agent from the water tank into the foam generator, and mixes them with the gas pressed by the air compressor in the foam generator.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering, and relates to a gas-soil combined balanced shield tunneling control method and tunneling equipment. Background Art

[0002] With the continuous development of science and technology, the shield method has become the mainstream method for the construction of rail transit tunnels and highway tunnels, especially in the construction of urban rail transit. Due to its small disturbance to the ground environment, it is more widely used. According to the excavation face balance mode, the shield machine can be divided into an earth pressure balance shield and a slurry balance shield, which are suitable for different strata and environmental conditions respectively. Among them, the earth pressure balance shield is more widely used due to its low cost and relatively simple facilities. However, when encountering water-rich soft and hard rock composite strata, the conventional full earth pressure excavation mode will cause the shield load to increase, the tool wear to accelerate, and gushing accidents often occur, which greatly reduces the construction efficiency and reduces the quality of the project.

[0003] In response to this problem, the combined gas-soil balanced shield tunneling technology has gradually developed, with the Guangzhou Metro construction being the most typical example. The two sections of Guangzhou Metro Line 1, Martyrs Cemetery Station-Nongjiangso Station-Parkfront Station, were the first in China (1996) to attempt to use a combined gas-soil balanced shield for construction, and achieved good results. This technology uses air pressure to assist in tunneling, using gas pipelines or foam pipelines to press natural air into the upper part of the soil bin, while the lower part still retains the slag, achieving the goal of reducing the torque of the cutter head and accelerating the construction progress. In the following twenty years, this technology has made great progress and development, bringing good engineering benefits to the practice of similar strata. However, the current combined gas-soil balanced shield still has the following problems:

[0004] (1) The gas pipeline cannot be depressurized, and the air pressure in the soil bin is difficult to control accurately. It can only be adjusted by reducing the inlet pressure. When depressurizing, the slag is easy to flow back and block the pipeline;

[0005] (2) The foam pipeline is a single pump with multiple pipes, which may cause insufficient pressure to inject the foam into the cutter head;

[0006] (3) The air pressure and soil pressure in the soil bin are not clearly distinguished, and the traditional soil pressure control method is still used to control the air pressure and soil pressure. When the pressure in the bin is too high, it is easy to cause misjudgment of the soil bin pressure. If the excavation is accelerated, the empty bin rate will increase and the risk of the tunnel face will increase; if the air pressure is reduced, it will take a long time and the effect may not be significant, which will cause the surface to rise or even break through.

[0007] The existence of these problems brings great inconvenience to the construction of gas-soil combined balanced shield, which reduces the construction efficiency and quality, and more importantly, increases the risk of accidents. Therefore, it is objectively necessary to invent a face balancing method that can effectively control the soil bin pressure to solve the above problems. Summary of the invention

[0008] The object of the present invention is to provide a gas-soil combined balanced shield machine and a tunnel face balance control method thereof, so as to improve the efficiency of the gas-soil combined balanced shield construction.

[0009] A gas-soil combined balanced shield machine comprises a cutter disc, an air supply component, a soil bin, and a screw conveyor. The air supply component comprises a gas pipeline and a foam pipeline, wherein the gas pipeline supplies air to the soil bin and comprises an air inlet pipe and an air outlet pipe, the air inlet pipe is provided with a switch valve and a pressure reducing valve, the air outlet pipe is provided with a switch valve and a pressure relief valve, the air inlet pipe is connected to the air outlet pipe at the front end and connected to the air holes of the soil bin partition, the tail end of the air inlet pipe is connected to an air compressor for pressurization, and the tail end of the air outlet pipe is connected to the atmosphere for pressure relief; and the foam pipeline provides foam for cutting soil, comprises a foam pump, a foam agent box, a foam generator, and a water tank, the foam pump presses water and foam agent from the water tank into the foam generator, and mixes them with the gas pressed by the air compressor in the foam generator.

[0010] In one embodiment, six pressure sensors are arranged on the soil bin partition, wherein one pressure sensor is respectively arranged on the interface between gas and slag, on the horizontal central axis, above the interface, and between the interface and the horizontal central axis, and two pressure sensors are arranged below the horizontal central axis, wherein the setting positions of the last four pressure sensors are adjustable.

[0011] In one embodiment, an anti-clogging porous material is added to the air hole where the soil bin partition is connected to the gas pipeline.

[0012] In one embodiment, one gas pipeline corresponds to one gas injection hole on the soil bin partition, the gas injection hole is arranged near the gas-soil interface of the soil bin partition, and one foam pipeline corresponds to two foam injection holes, the foam injection holes are evenly arranged along the cutter disc.

[0013] In one embodiment, the air flow rate V of the air intake pipe and the speed r of the screw conveyor are maintained to satisfy:

[0014]

[0015] Where: P——gas pressure in soil bin;

[0016] A——cross-sectional area of ​​the shield machine;

[0017] P0——gas pressure in the air compressor;

[0018] f(r)——The relationship function between excavation speed and screw conveyor speed v=f(r).

[0019] A method for controlling the balance of the shield face in the combined air and soil balance shield tunneling, using the combined air and soil balance shield machine. Among them, the value of the pressure sensor above the interface is P1, the value of the pressure sensor on the interface is P2, the value of the pressure sensor on the horizontal central axis is P4, the value of the pressure sensor between the interface and the horizontal central axis is P3, and the values of the two pressure sensors arranged below the horizontal central axis are P5 and P6 respectively;

[0020] During tunneling, ensure that the empty bin rate is less than 1 / 2, and the height of the muck in the soil bin cannot be lower than the horizontal central axis;

[0021] If P1 = P2 < P3, the empty bin rate is normal;

[0022] If P1 = P2 = P3, the empty bin rate increases, the air-soil interface drops, and in combination with the changes in the cutter head torque and thrust, slow down the soil discharge of the screw conveyor and reduce the air intake;

[0023] If P1 < P2, the empty bin rate decreases, the air-soil interface rises, and in combination with the changes in the cutter head torque and thrust, speed up the soil discharge of the screw conveyor and increase the air intake;

[0024] If the values of P1 to P4 are close, the empty bin rate is close to 1 / 2, and immediately slow down the soil discharge of the screw conveyor.

[0025] In one embodiment, if the values of the six pressure sensors are generally greater than the empirical value and the theoretical calculated value, the overall soil bin pressure is too large, mainly reduce the air pressure and supplemented by accelerating the soil discharge;

[0026] If the values of the six sensors are generally less than the empirical value and the theoretical calculated value, the overall soil bin pressure is too small, mainly slow down the soil excavation and supplemented by increasing the intake air pressure.

[0027] The construction of one ring of segments in this method includes three stages:

[0028] Stage I: The preparation stage before the shield machine starts tunneling. The shield machine maintains the assembly mode, the cutter head is stationary, the transport vehicle for storing and transporting muck is in place, the screw conveyor gradually discharges soil outward, maintains the air-soil balance, and the height of the muck in the soil bin gradually decreases. When the empty bin rate reaches the set value, enter the next stage;

[0029] Phase II is the normal excavation phase. The shield machine first changes from the assembly mode to the excavation mode, and excavates according to the construction parameters including the set cutter head speed, propulsion speed, screw conveyor speed, and soil bin air inlet flow rate. During the excavation process, the soil bin pressure state is judged by observing the value and change of the soil bin pressure sensor. In addition to the soil bin pressure, key construction parameters including propulsion pressure and cutter head torque are also paid attention to. Whether the flow performance of the slag affects the entry and exit of the earth is checked, and whether the surface settlement control effect is ideal is observed. According to the actual situation, countermeasures are taken to improve the excavation state; when the propulsion jack stroke reaches the control value, it enters the next phase;

[0030] Phase III, the preparation stage for assembling the segments, increases the height of the soil in the soil bin, reduces the effect of air pressure, and reduces the risk of instability of the tunnel face during segment assembly. While excavating forward, the screw conveyor slows down the excavation, and the air compressor reduces the air intake. It is also necessary to maintain the air-soil balance.

[0031] After the slag bin is full and the jack stroke meets the assembly requirements, the segments are transported into place and the shield machine is switched to assembly mode to assemble the segments. At this point, the construction of one ring of segments is completed and the next ring of segments is started. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other features, properties and advantages of the present invention will become more apparent through the following description in conjunction with the accompanying drawings and embodiments, in which:

[0033] Figure 1 It is a structural schematic diagram of a gas-soil combined balanced shield machine;

[0034] Figure 2 This is a schematic diagram of the arrangement of pressure sensors on the soil bin partition;

[0035] Figure 3 This is a flow chart of the balance control method for the gas-soil combined balanced shield tunnel face;

[0036] Figure 4 This is a schematic diagram of the gas supply assembly of the gas-soil combined balanced shield machine;

[0037] Figure 5 This is a schematic diagram of the location of the pipeline injection hole;

[0038] Figure 6 This is a schematic diagram of the location of the pressure sensor on the soil bin partition;

[0039] Figure 7 This is a schematic diagram of the pressure balance mode of the gas-soil combined balanced shield tunnel face;

[0040] In the figure, 1-gas pipeline, 2-foam pipeline, 3-pressure reducing valve, 4-pressure relief valve, 5-switch valve, 6-air compressor, 7-foam generator, 8-mixed liquid, 9-foam agent box, 10-foam pump, 11-air, 12-slag, 13-air-soil interface, 14-water tank, 15-anti-clogging porous material, 16-horizontal neutral axis, 17-soil bin partition, 18-knife disc, 19-screw conveyor, 20-pressure sensor (P1~P6) DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with specific embodiments and drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in a variety of other ways different from the description herein. Those skilled in the art can make similar generalizations and deductions based on actual application situations without violating the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0042] It should be noted that these and other subsequent drawings are only examples and are not drawn to scale, and should not be used to limit the actual scope of protection required by the present invention.

[0043] In one embodiment of the present invention, the shield machine is adaptively modified on the basis of the existing shield machine. The gas supply component, as a part of the control basic equipment, is mainly composed of a gas pipeline 1 and a foam pipeline 2; the gas pipeline 1 supplies gas to the soil bin and is the main gas source, and the foam pipeline 2 provides foam for cutting soil, which plays a role in improving the slag. After the foam bursts, the gas will enter the soil bin and play a role in adding gas.

[0044] The gas pipeline 1 is composed of an air inlet pipe and an air outlet pipe. The air inlet pipe is equipped with a switch valve 5 and a pressure reducing valve 3, and the air outlet pipe is equipped with a switch valve 5 and a pressure relief valve 4. When the pipeline is idle, the switch valve 5 is used to ensure that the pipeline is airtight. When the pipeline is working, the air intake and air release are controlled by adjusting the control parts of the pressure reducing valve 3 and the pressure relief valve 4. The air inlet pipe and the air outlet pipe are connected at the front end and connected to the air holes on the soil bin partition 17. The tail end of the air inlet pipe is connected to the air compressor 6 for pressurization, and the tail end of the air outlet pipe is connected to the atmosphere for pressure relief. Anti-blocking porous material 15 is added at the air holes of the soil bin partition 17 to prevent the slag from reflux and blocking the gas pipeline.

[0045] The foam pipeline 2 is composed of a foam pump 10, a foam agent tank 9, a foam generator 7, and a water tank 14. The foam pump 10 presses water and foam agent into the foam generator 7, and mixes with the gas 11 pressed into the generator 7 by the air compressor 6 to form fine tooth-shaped bubbles of 30 mm to 400 mm. Then, the bubbles are injected into the cutter head 18 through the pipeline. In order to ensure the injection pressure, one foam pump 10 is preferably configured for one pipeline.

[0046] The number of gas pipelines 1 and foam pipelines 2 can be configured according to actual needs and space conditions, and the positions of injection holes should be designed and arranged in the same way. One gas pipeline corresponds to one injection hole, which is set near the gas-soil interface of the soil bin partition 17, and one foam pipeline corresponds to two injection holes, which should be evenly arranged along the cutter head.

[0047] The working pressure of pressure reducing valve 3 and pressure relief valve 4 should be 0~1.0MPa, and the gas flow rate per unit time of pressure reducing valve should meet 2m 3 / min. The air pressure setting is determined based on actual conditions and experience, and changes dynamically during excavation.

[0048] In one embodiment, the empty bin ratio is set to 1 / 4 based on previous tests and engineering experience, that is, the ratio of the height of the slag to the height of the gas in the soil bin is 3 / 1. Figure 1 and Figure 4 , Figure 5 As shown, two gas pipelines 1 are provided. Figure 4 , Figure 5 1 shows the gas injection holes a1 and a2 on the soil bin partition 17 corresponding to the two gas pipelines. Four foam pipelines 2 are also provided. Figure 4 , Figure 5 The foam pipeline injection holes f1, f2, f3 and f4 on the soil bin partition 17 corresponding to the four foam pipelines are shown. One gas pipeline corresponds to one gas injection hole, and one foam pipeline corresponds to two foam pipeline injection holes. Figure 6 As shown, a total of 6 pressure sensors P1, P2, P3, P4, P5 and P6 are arranged on the soil bin partition 17, and 6 pressure sensors are arranged on the soil bin partition (numbered 1 to 6 from top to bottom according to the position), and pressure sensors must be installed at the interface between gas and slag (for a certain project, the gas-soil height ratio (or empty bin rate) of the gas-soil combined balanced shield is usually fixed) and the horizontal center axis. One sensor is respectively arranged above the interface and between the interface and the center axis, and two sensors are arranged below the center axis. The positions of the last 4 sensors are adjustable. Generally, there is 1 working gas pipeline and 1 spare, and 2 working foam pipelines and 2 spare. The working pressure of the pressure reducing valve 3 and the pressure relief valve 4 can be 0 to 1.0 MPa, and the maximum gas flow rate per unit time of the pressure reducing valve 3 is 2m 3 / min.

[0049] During construction, first control the soil discharge rate of the screw conveyor to make the soil bin full of slag and balance the tunnel face, then use the gas pipeline 1 to inject compressed gas into the soil bin, and at the same time speed up the soil discharge of the screw conveyor 19, and observe the values ​​of each sensor. When the slag height drops to the set gas-soil interface 13, stabilize the flow of the gas pipeline 1 and the screw conveyor 19 to achieve "gas-soil joint balance" and steadily advance. Figure 7 As shown, P T is the soil pressure, P Qis the gas pressure, P W is the water pressure at the tunnel face, P S is the soil pressure at the tunnel face.

[0050] During construction, the control method of the present invention is used to control the excavation, stabilize the tunnel face, give full play to the advantages of gas-soil combined balance, reduce the excavation load of the shield machine, and improve the assembly quality and construction efficiency of the pipe segments. From the on-site construction situation, practice has proved the advantages of the present invention.

[0051] The control method of the tunnel face balance of the gas-soil combined balanced shield machine can be divided into three stages:

[0052] Phase I:

[0053] This stage is the preparation stage before the shield machine starts excavation. The shield machine remains in assembly mode, the cutterhead is stationary, the battery vehicle for storing and transporting slag is in place, and the screw conveyor gradually discharges the slag outward, but at the same time it needs to maintain a balance with the air injected into the soil bin, which can be controlled according to claim 10. In this stage, the height of the slag in the soil bin gradually decreases, and when the empty bin rate reaches the set value, it enters the next stage.

[0054] Phase II:

[0055] This stage is the normal excavation stage. The shield machine first changes from assembly mode to excavation mode, and sets construction parameters such as cutter head speed, propulsion speed, screw conveyor speed, and soil bin air intake flow.

[0056] During the excavation process, the pressure state of the soil bin is determined by observing the value and changes of the soil bin pressure sensor. Generally, it can be divided into two categories: changes in the air-soil interface and overall changes. The air-soil interface will rise or fall. The former can be dealt with by accelerating excavation and increasing air intake, while the latter requires slowing down excavation and reducing air intake. Overall changes refer to the overall decrease or increase of the pressure in the bin relative to the theoretical value or empirical value. From the perspective of face stability, when the overall decrease occurs, the main approach should be to slow down excavation and increase air intake pressure; when the overall increase occurs, the main approach should be to slowly reduce air pressure and accelerate soil discharge.

[0057] In addition to the soil bin pressure, key construction parameters such as propulsion pressure and cutter head torque should also be considered to check whether the flow performance of the slag affects the entry and exit of the soil, and whether the surface settlement control effect is ideal. Take countermeasures according to the actual situation to improve the excavation status.

[0058] When the battery truck filled with slag is fully loaded, it needs to drive away to dump the slag. At this time, the shield machine stops excavating, and the soil bin remains in its current state until the battery truck is reset, and then the construction parameters are reset for excavation. When the thrust jack stroke reaches the control value (this value can be calculated based on the empty bin rate and the speed of the screw conveyor in stage III and other related parameters), it is necessary to enter stage III to prepare for the assembly of the segments.

[0059] Phase Ⅲ:

[0060] This stage is the preparatory stage for segment erection. The purpose is to increase the height of the muck in the soil bin, reduce the effect of air pressure, and reduce the risk of face instability during segment erection. The specific method is exactly the opposite of that in Phase Ⅰ. While advancing forward, the screw conveyor slows down the muck discharge, and the air compressor reduces the air intake. The two also need to maintain balance.

[0061] After the muck fills the bin and the jack stroke meets the erection requirements, use a battery-powered vehicle to transport the segments into position. The shield machine switches to the erection mode and performs segment erection.至此,一环管片施工完成,进入下一环管片施工,重复上述三阶段。

[0062] In one embodiment, the sensor arrangement according to the foregoing embodiment can better reflect the soil bin pressure value and its changes, enabling the operator to determine the construction risks and take timely countermeasures. The specific method is as follows:

[0063] If P1 = P2 < P3, it indicates that the empty bin rate is normal;

[0064] If P1 = P2 = P3, it indicates that the empty bin rate increases and the air-soil interface descends. The screw conveyor muck discharge should be slowed down and the air intake reduced in combination with the changes in cutter head torque and thrust;

[0065] If P1 < P2, it indicates that the empty bin rate decreases and the air-soil interface ascends. The screw conveyor muck discharge should be accelerated and the air intake increased in combination with the changes in cutter head torque and thrust;

[0066] If the values of P1 to P4 are close, it indicates that the empty bin rate is close to 1 / 2, and the screw conveyor muck discharge should be immediately slowed down.

[0067] If the measured values of the 6 sensors are generally greater than the empirical value and the theoretical calculated value, it indicates that the overall soil bin pressure is relatively large. The main measure should be to slowly reduce the air pressure, supplemented by accelerating the muck discharge.

[0068] If the measured values of the 6 sensors are generally less than the empirical value and the theoretical calculated value, it indicates that the overall soil bin pressure is relatively small. The main measure should be to slow down the muck discharge, supplemented by increasing the intake air pressure.

[0069] It should be particularly noted that the above "=" all indicates that the values are close, and "<" indicates that the values differ greatly. During tunneling, it is necessary to ensure that the empty bin rate is less than 1 / 2, that is, the height of the muck in the soil bin cannot be lower than the horizontal central axis;

[0070] In one implementation, when adjusting the empty bin rate, the balance between muck discharge and air intake, and between muck intake and air discharge needs to be maintained. In actual construction, this is reflected in that the intake air flow rate V and the screw conveyor rotation speed r need to satisfy:

[0071]

[0072] Where: P——gas pressure in soil bin;

[0073] A——cross-sectional area of ​​the shield machine;

[0074] P0——gas pressure in the air compressor;

[0075] f(r)——The relationship function between excavation speed and screw conveyor speed v=f(r).

[0076] The above control method is applicable to strata with a certain degree of self-stability, and has the function of reducing the shield excavation cutter torque and improving excavation efficiency. The excavation control process has the function of actively adjusting the air pressure in the soil bin, including the functions of active pressurization and active pressure relief regulation, which can better control the balance of the tunnel face, avoid the risk of accelerated soil discharge due to excessive pressure and instability of the tunnel face caused by too little pressure, and effectively prevent blockage caused by soil return pipes.

[0077] Compared with the prior art, the present invention has the following advantages:

[0078] 1. The air pressure supply pipeline of the soil bin of the gas-soil combined balanced shield has been improved, the pressure relief function of the gas pipeline has been supplemented, and the injection capacity of the foam pipeline has been improved; the modified pipeline can also be used for air pressure tool replacement to prevent bentonite backflow from causing system damage.

[0079] 2. The layout of the pressure sensor on the soil bin partition has been optimized to make it easier to judge the interface between air pressure and soil pressure, providing a more reliable basis for the reasonable control of soil bin pressure;

[0080] 3. A combined gas-soil balanced shield tunneling control method was proposed to standardize the construction process, which can effectively avoid misjudgment of pressure and reduce the risk of face instability.

[0081] Although the present invention is disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. Gas-soil combined balanced shield machine, including cutter head, gas supply assembly, soil bin, screw conveyor, It is characterized in that The gas supply assembly comprises: A gas pipeline supplies gas to the soil bin, including an air inlet pipe and an air outlet pipe. The air inlet pipe is provided with a switch valve and a pressure reducing valve, and the air outlet pipe is provided with a switch valve and a pressure relief valve. The air inlet pipe and the air outlet pipe are connected at the front end and connected to the air holes of the soil bin partition. The tail end of the air inlet pipe is connected to the air compressor for pressurization, and the tail end of the air outlet pipe is connected to the atmosphere for pressure relief; and The foam pipeline provides foam for cutting soil, and comprises a foam pump, a foam agent box, a foam generator, and a water tank. The foam pump presses water and foam agent from the water tank into the foam generator, and the water and foam agent are mixed with the gas pressed into the foam generator by the air compressor.

2. The gas-soil combined balanced shield machine according to claim 1, It is characterized in that It includes 6 pressure sensors arranged on the soil bin partition, wherein 1 pressure sensor is respectively arranged on the interface between gas and slag, on the horizontal central axis, above the interface, and between the interface and the horizontal central axis, and 2 pressure sensors are arranged below the horizontal central axis, wherein the setting positions of the last 4 pressure sensors are adjustable.

3. The gas-soil combined balanced shield machine according to claim 1, It is characterized in that Anti-clogging porous material is added to the air hole where the soil bin partition is connected to the gas pipeline.

4. The gas-soil combined balanced shield machine according to claim 1, It is characterized in that One gas pipeline corresponds to one gas injection hole on the soil bin partition, and the gas injection hole is arranged near the gas-soil interface of the soil bin partition. One foam pipeline corresponds to two foam injection holes, and the foam injection holes are evenly arranged along the cutter disc.

5. The gas-soil combined balanced shield machine as claimed in claim 2, It is characterized in that Maintain the air flow rate V of the air intake pipe and the speed r of the screw conveyor to meet the following conditions: Where: P——gas pressure in soil bin; A——cross-sectional area of ​​the shield machine; P 0 - Gas pressure in the air compressor; f(r)——The relationship function between excavation speed and screw conveyor speed v=f(r).

6. A method for controlling the balance of a gas-soil combined balanced shield tunnel face. It is characterized in that The gas-soil combined balanced shield machine as claimed in claim 2 is used, wherein: The value of the pressure sensor above the interface is P 1 , the value of the pressure sensor on the interface is P 2 The value of the pressure sensor on the horizontal central axis is P 4 The value of the pressure sensor between the interface and the horizontal center axis is P 3 The values ​​of the two pressure sensors arranged below the horizontal central axis are P 5 , P 6 ; During excavation, the empty bin ratio should be less than 1 / 2, and the height of the slag in the bin should not be lower than the horizontal center axis; If P 1 =P 2 <P 3 , then the short position rate is normal; If P 1 =P 2 =P 3 , the empty bin rate increases, the air-soil interface decreases, and the screw conveyor discharge is slowed down and the air intake is reduced in combination with the change of cutter head torque and thrust; If P 1 <P 2 , the empty bin rate decreases, the air-soil interface rises, and the change of cutter head torque and thrust speeds up the screw conveyor to discharge soil and increase the air intake; If P 1 ~P 4 If the values ​​are close, the empty bin rate is close to 1 / 2, and the screw conveyor discharge is immediately slowed down.

7. The gas-soil combined balanced shield tunnel face balance control method according to claim 6, It is characterized in that If the values ​​of the six pressure sensors are generally greater than the empirical values ​​and theoretical calculation values, the overall pressure in the soil bin is too high, and the main approach is to reduce the air pressure and speed up soil discharge. If the values ​​of the six sensors are generally smaller than the empirical values ​​and theoretical calculated values, the overall soil bin pressure is too small, and the main approach should be to slow down the excavation and increase the intake pressure as a supplement.

8. The gas-soil combined balanced shield tunnel face balance control method as claimed in claim 6, It is characterized in that Maintain the air flow rate V of the air intake pipe and the speed r of the screw conveyor to meet the following conditions: Where: P——gas pressure in soil bin; A——cross-sectional area of ​​the shield machine; P 0 - Gas pressure in the air compressor; f(r)——The relationship function between excavation speed and screw conveyor speed v=f(r).

9. The gas-soil combined balanced shield tunnel face balance control method according to claim 6, It is characterized in that The construction of a ring segment of this method includes three stages: Phase I is the preparation phase before the shield machine starts excavation. The shield machine remains in assembly mode, the cutterhead is stationary, the transport vehicle for storing and transporting the slag is in place, the screw conveyor gradually discharges the soil to maintain the air-soil balance, and the height of the slag in the soil bin gradually decreases. When the empty bin rate reaches the set value, it enters the next phase. Phase II is the normal excavation phase. The shield machine first changes from the assembly mode to the excavation mode, and excavates according to the construction parameters including the set cutter head speed, propulsion speed, screw conveyor speed, and soil bin air inlet flow rate. During the excavation process, the soil bin pressure state is judged by observing the value and change of the soil bin pressure sensor. In addition to the soil bin pressure, key construction parameters including propulsion pressure and cutter head torque are also paid attention to. Whether the flow performance of the slag affects the entry and exit of the earth is checked, and whether the surface settlement control effect is ideal is observed. According to the actual situation, countermeasures are taken to improve the excavation state; when the propulsion jack stroke reaches the control value, it enters the next phase; Phase III, the preparation stage for assembling the segments, increases the height of the soil in the soil bin, reduces the effect of air pressure, and reduces the risk of instability of the tunnel face during segment assembly. While excavating forward, the screw conveyor slows down the excavation, and the air compressor reduces the air intake. It is also necessary to maintain the air-soil balance. After the slag bin is full and the jack stroke meets the assembly requirements, the segments are transported into place and the shield machine is switched to assembly mode to assemble the segments. At this point, the construction of one ring of segments is completed and the next ring of segments is started.

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