Double-chamber slurry shield tunneling test device and method under simulated hypergravity

Abstract

The present invention discloses a double-chamber slurry shield excavation test device and method for simulating supergravity. The shield body and the slurry inlet and outlet system are fixed by a bottom plate and placed on a geotechnical centrifuge. The soil box and the shield power system are connected by the shield body. The shield body is also connected to the slurry inlet and outlet system. The front partition divides the working chamber into a slurry chamber and an air cushion chamber. The shield power system is used to drive the cutter head to rotate and drive the main shaft to advance forward. The slurry inlet and outlet system is used to transport slurry into the slurry chamber and the air cushion chamber and discharge debris. The present invention uses the gas pressure in the air cushion chamber to press the slurry in the slurry chamber out and penetrate into a film to simulate the entire process of slurry shield excavation under great burial depth and high water pressure, simulate the actual shield cutter head cutting and forward excavation movements, and accurately control the slurry pressure in the slurry chamber and the slurry inlet and outlet flow rate.

Description

Technical Field

[0001] The invention belongs to the field of slurry shield model testing, and in particular relates to a double-chamber slurry shield excavation testing device and method under simulated hypergravity. Background Art

[0002] Slurry shields, a common method for constructing river and sea tunnels, use pressurized slurry to penetrate the ground, forming a mud film in front of the excavation face. The slurry pressure acts on the film in the form of a surface force, balancing the lateral water and soil pressure in front of the excavation face and maintaining its stability. The support pressure of a double-compartment slurry shield is dominated by gas pressure and is not subject to significant fluctuations due to factors such as changes in slurry density. Therefore, compared with a single-compartment slurry shield, the support pressure of a double-compartment slurry shield is easier to control during excavation.

[0003] Currently, most excavation tests for slurry shields are conducted under normal gravity. However, since tests under normal gravity cannot reproduce the true stress levels of the strata and the actual size of the shield, the simulated excavation process and excavation face instability patterns cannot be confirmed to conform to actual working conditions. Geotechnical centrifuge physical simulation, as an effective means of reproducing the stress levels of large-scale media under normal gravity in small-scale media, addresses the problem of stress field dissimilarity. The generated hypergravity environment can reproduce the actual soil stress levels and water pressure outside the slurry chamber, as well as the gradient distribution of slurry pressure within the slurry chamber, providing the possibility of simulating the actual slurry shield excavation process and excavation face instability patterns. However, since the slurry is composed of two substances with different densities, bentonite and water, increasing the gravity field strength through a hypergravity centrifuge intensifies the relative driving force between the two substances, thereby accelerating phase separation between the two substances, resulting in uneven slurry density and failing to simulate actual slurry permeability patterns and mud film formation patterns. Excessive gravity can exacerbate the sedimentation and pipe clogging of shield excavation debris, making it difficult to control slurry flow and accurately control slurry pressure. Therefore, addressing these issues, recreating the excavation process of a slurry shield, and understanding the support pressure control mechanism of a double-compartment slurry shield are pressing challenges in research involving complex strata with deep burial depths and high water pressure. Summary of the Invention

[0004] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a double-chamber slurry balance shield excavation test device and method under simulated hypergravity, so as to solve the problem that hypergravity aggravates the deposition of shield excavation debris and blocks the pipeline, resulting in difficulty in controlling the slurry discharge flow and inability to accurately control the mud pressure.

[0005] The scheme adopted by the present invention is as follows:

[0006] 1. A double-chamber slurry shield tunneling test device simulating hypergravity:

[0007] It includes a soil box, a shield body, a shield power system and a slurry feeding and discharge system. The soil box stores soil. The soil box and the shield power system are connected through the shield body. The shield power system is used to drive the shield body to move forward and backward along the excavation direction, so that the shield body can excavate the soil in the soil box. The shield body is connected to the slurry feeding and discharge system. The shield body is equipped with a pressure maintaining system for balancing the air pressure inside the shield body. The soil box, shield power system and slurry feeding and discharge system are all fixed on the bottom plate, and the bottom plate is placed in the basket of the geotechnical centrifuge.

[0008] The shield body includes a hull with a working cabin inside, a cutterhead, an annular front bulkhead and a main shaft; the front bulkhead is located inside the hull and divides the working cabin into a mud and water cabin and an air cushion cabin, the cutterhead is located on the side close to the mud and water cabin, one end of the main shaft is connected to the shield power system, and the other end of the main shaft passes through the air cushion cabin, the front bulkhead and the mud and water cabin in sequence and is coaxially connected to the cutterhead; one end of the hull with the mud and water cabin is movably connected to the opening of the soil box so as to be movable forward and backward, and one end of the hull with the air cushion cabin is fixedly connected to the shield power system, the shield power system is used to drive the cutterhead to rotate and at the same time drive the main shaft to excavate forward along its own axis, the mud and water cabin and the cutterhead are both arranged at the opening position of the soil box; a connecting pipe is connected to the front bulkhead, the connecting pipe is used to transmit the pressure in the air cushion cabin to the mud and water cabin, and the shield power system realizes closed-loop control through a servo valve.

[0009] The slurry inlet and discharge system includes a mud water tank, a mud pump, a slag box, a separation box and a screw conveying device; the mud pump is connected to the output end of the mud water tank, the mud pump is communicated with the mud water tank through a first slurry inlet pipe, and the mud pump is communicated with the air cushion tank through a second slurry inlet pipe, the first slurry inlet pipe and the second slurry inlet pipe are respectively provided with a first electromagnetic ball valve and a second electromagnetic ball valve, one end of the first overflow pipe passes through the air cushion tank and the opening on the front bulkhead and extends into the mud water tank, the other end of the first overflow pipe is connected to the atmosphere, one end of the second overflow pipe extends into the air cushion tank, the other end of the second overflow pipe is connected to the atmosphere, a third electromagnetic ball valve and a fourth electromagnetic ball valve are respectively provided on the first overflow pipe and the second overflow pipe, a bypass pipe is also provided between the mud water tank and the mud pump, one end of the bypass pipe is connected to the mud water tank, and the other end is communicated with the mud pump, the first slurry inlet pipe and the second slurry inlet pipe respectively, and a bypass ball valve is provided on the bypass pipe;

[0010] One end of the screw conveying equipment extends into the mud and water tank, and the other end is connected to the slag box through a pipe. The sixth solenoid valve, separation box and switching valve group are arranged in sequence on the pipe from the screw conveying equipment to the slag box. The mud pump is powered by the hydraulic pressure of the geotechnical centrifuge.

[0011] The switching valve group is mainly composed of two branch pipes, a slag inlet pipe and a slag discharge pipe. One end of the slag inlet pipe is connected to the separation box, and the other end of the slag inlet pipe is connected to the input end of the two branch pipes respectively. The output ends of the two branch pipes are connected to one end of the slag discharge pipe, and the other end of the slag discharge pipe is connected to the slag box. The two branch pipes are both provided with a seventh solenoid valve and a damper, and the slag discharge pipe is provided with a second electromagnetic flowmeter;

[0012] The slurry discharge flow rate in the slag discharge pipe is obtained according to the following formula:

[0013]

[0014] Where, Q is the slurry discharge flow rate; C d is the damping coefficient; A is the cross-sectional area of the slag discharge pipe; ΔP is the pressure drop; ρ d The density of mud mixed with slag.

[0015] Three layers of filters with different apertures are arranged inside the separation box. The axial direction of the filter is perpendicular to the mud flow direction. The mud output by the spiral conveying equipment flows into the input end of the separation box, is filtered by the three layers of filter screens in sequence, and then flows out of the separation box. The apertures of the three layers of filter screens decrease in sequence from the inlet to the outlet of the separation box. The aperture of the third layer of filter screen is smaller than the maximum particle size that can pass through the second electromagnetic flowmeter.

[0016] The relationship between the slurry pressure and soil-water pressure at the shield excavation surface satisfies the following expression:

[0017] P g +ρ s g(h-D+z)≥γ w (H+z)+K a γ'(H+z)

[0018] P g +ρ s g(h-D+z)≤γ w (H+z)+K p γ'(H+z)

[0019] Where, P g is the gas pressure; ρ s is the slurry density; g is the acceleration of gravity; h is the liquid level of the air cushion cabin; D is the diameter of the shield; z is the vertical coordinate of the excavation surface; γ w is the density of water; H is the depth of shield top; γ' is the effective density of soil; K a is the active earth pressure coefficient; K p is the passive earth pressure coefficient.

[0020] The thrust F provided by the shield power system dAnd torque T is obtained according to the following formula:

[0021]

[0022] Where F1 is the frontal thrust resistance during shield tunneling; F2 is the friction between the shield shell and the surrounding soil; K is the lateral earth pressure coefficient; γ is the density of the soil; f is the friction coefficient between the shield shell and the surrounding soil; L is the length of the shield machine; W is the weight of the shield machine per unit length; T1 is the friction torque between the cutterhead and the soil; T2 is the formation resistance torque when the cutterhead cuts the soil; η is the cutterhead opening ratio; P0 is the mud pressure in the mud water tank; and p is the penetration rate.

[0023] The expression of the cutter head speed is as follows:

[0024]

[0025] where λ(n) is the ratio of the cutterhead speed under hypergravity to the cutterhead speed under normal gravity; λ(v) is the ratio of the tunneling speed under hypergravity to the tunneling speed under normal gravity; λ(s) is the ratio of the tunneling distance under hypergravity to the tunneling distance under normal gravity; λ(t) is the ratio of the test time under hypergravity to the tunneling time under normal gravity; and λ(p) is the ratio of the penetration under hypergravity to the penetration under normal gravity.

[0026] The pressure maintaining system includes an air inlet pipe, an exhaust pipe, a pressure transmitter, an exhaust valve and an air inlet valve; an air inlet and an air outlet are provided on the front partition, one end of the air inlet pipe is connected to the mud and water tank after passing through the air inlet, and the other end of the air inlet pipe is connected to the air outlet of the geotechnical centrifuge, one end of the exhaust pipe is connected to the mud and water tank after passing through the exhaust port, and the other end of the exhaust pipe is connected to the atmosphere; an air inlet valve and an exhaust valve are respectively provided on the air inlet pipe and the exhaust pipe, the pressure transmitter is connected to the front partition, and the air inlet valve, the exhaust valve and the pressure transmitter are all connected to the control system.

[0027] 2. A double-compartment slurry shield tunneling test method simulating hypergravity comprises the following steps:

[0028] Step 1: Prepare slurry with a preset ratio of bentonite and water, inject the slurry into the mud-water tank, remove the soil tank from the base plate, prepare soil samples in layers in the soil tank, and bury earth pressure sensors in the soil samples;

[0029] Step 2: Use the saturation box to saturate the soil sample in the soil box. When the soil sample is saturated, hoist the soil box as a whole into the geotechnical centrifuge and push the shield into the soil box hole;

[0030] Step 3: Turn on the mud pump to fill the mud and water tank with mud, so that the mud reaches 2 / 3 of the liquid level of the air cushion tank. When mud seeps out of the first overflow pipe and the second overflow pipe, close the third and fourth electromagnetic ball valves and stop the slurry feeding.

[0031] Step 4: Start the geotechnical centrifuge and gradually increase the centrifugal acceleration of the geotechnical centrifuge to the preset Ng. When the geotechnical centrifuge reaches the target Ng value, control the air inlet valve of the pressure maintaining system to intake air and open the sixth solenoid valve to control the liquid level of the air cushion chamber to be maintained at 2 / 3 of the height;

[0032] Step 5: Control the shield to advance forward. After the shield has advanced stably for a preset period of time, use the shield power system to control the shield to stop advancing. Control the pressure-maintaining system to adjust the gas pressure in the air cushion cabin. At the same time, observe the damage to the contact surface between the shield and the soil sample to simulate the actual working conditions when the slurry shield excavation face undergoes active and passive damage, thereby obtaining the stability law of the slurry shield excavation face.

[0033] The technical solution principle of the present invention is as follows:

[0034] For prototype soil sample: σ=ρgh'

[0035] For the 1 / N scale model: σ1=ρ·g·h' / N

[0036] For a 1 / N-fold scale model under N-fold hypergravity: σ2=ρ·Ng·h' / N=ρg h'

[0037] Wherein, σ represents the stress of the prototype soil sample, ρ represents the natural density of the soil, g represents the acceleration of gravity, h' represents the depth of the formation, σ1 represents the stress of the 1 / N times scaled model, σ2 represents the stress of the 1 / N times scaled model under N times hypergravity, and N represents the ratio of the centrifugal acceleration of the geotechnical centrifuge to the acceleration of gravity.

[0038] It is easy to see that σ=σ2, that is, the stress level of the prototype soil sample is equal to that of the 1 / N times scaled model under N times hypergravity, that is, the stress field of the prototype can be replicated under hypergravity, thereby greatly improving the similarity of the slurry shield tunneling test.

[0039] The shield body and slurry inlet and discharge system of the present invention are fixed by a bottom plate and placed on a geotechnical centrifuge. A supergravity field is created by centrifugal rotation to restore the real shield excavation process. A variety of pipeline installation interfaces are set on the front partition to realize functions such as slurry inlet and discharge, pressure transmission and monitoring equipment connection. Considering that the mud circulates in the pipeline during the g-lift process, the cutter head is connected to a ring-shaped stirring rod, and a blade-type stirring rod is designed in the mud water tank to avoid separation and precipitation of the mud under supergravity. A separation box is set on the slurry discharge pipeline, intending to retain large particles in the separation box under supergravity to avoid particles clogging the electromagnetic flowmeter and pipeline. After the g value stabilizes, the stratum soil samples in the excavation box are excavated by controlling the slurry shield tunneling. During the process, the monitoring data of the sensors are collected in real time to simulate the dynamic cutting process of the mud film and the soil disturbance during the actual shield tunneling process. After the shield body has steadily advanced forward for a preset period of time, in order to simulate the working condition of instability of the shield excavation face, the shield power system is used to control the shield body to stop excavation, and the pressure maintaining system is used to adjust the gas pressure. Through the pressure transmission method, the mud pressure is accurately controlled, and then the ultimate support pressure and the excavation face stability law are obtained.

[0040] The slurry shield's working chamber is divided by a front bulkhead into an air cushion chamber and a slurry chamber. This means that the excavation face support pressure is divided into gas pressure and the pressure generated by the slurry's own weight. The gas pressure is regulated by a pressure-maintaining system, while the slurry's own weight pressure is regulated by the slurry inlet and outlet flow rates. This invention utilizes the hypergravity environment created by a geotechnical centrifuge. Based on similar scale relationships, the shield can be restored to the true scale of the slurry shield, with the stress level of the formation and the slurry gradient pressure restored to their true conditions. This allows the slurry shield to reproduce the working conditions of actual engineering excavation.

[0041] The beneficial effects of the present invention are:

[0042] 1. The present invention has a high degree of mechanization and restoration, and can simulate the actual shield cutter head cutting and forward excavation actions and accurately control the mud pressure and mud inlet and outlet flow in the mud and water chamber.

[0043] 2. Using an N-fold hypergravity environment to conduct 1 / N-fold slurry shield tunneling excavation and excavation face stability tests greatly improved the similarity of the model test.

[0044] 3. The present invention avoids the influence of hypergravity effect on mud segregation and sedimentation by designing different types of stirring rods on the cutter head and in the mud water tank and designing a method for circulating mud in the pipeline during the g-lift process.

[0045] 4. This invention designs a separation box and damping for the slurry discharge pipeline. By designing a combination of different damping devices, the slurry discharge pressure in the pipeline is regulated, thereby controlling the slurry discharge flow rate. The separation box is designed to filter large particles to prevent large particles from clogging the electromagnetic flowmeter and pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a structural diagram of the device of the present invention;

[0047] Figure 2 Schematic diagram of the internal structure of the device of the present invention;

[0048] Figure 3 Schematic diagram of the internal structure of the shield body of the present invention;

[0049] Figure 4 It is a schematic diagram of the slurry inlet and outlet system;

[0050] Figure 5 is a schematic diagram of the separation box;

[0051] Figure 6 It is a schematic diagram of the hydraulic system;

[0052] Figure 7 It is a schematic diagram of the pressure holding system;

[0053] Figure 8 This is the structural diagram of the cutter head;

[0054] Figure 9 It is a structural diagram of the screw conveying equipment;

[0055] Figure 10 This is a schematic diagram of the mud water tank;

[0056] Figure 11 Schematic diagram of a geotechnical centrifuge.

[0057] Figure: 1. Soil box; 2. Shield; 3. Mud and water tank; 4. Muck box; 5. Power box; 6. Drive motor; 7. Mud pump; 8. Separation box; 9. Screw conveyor; 10. Bottom plate; 11. Cutter head; 12. Mud and water tank; 13. Front partition; 14. Air cushion cabin; 15. Spindle; 16. Torque sensor; 17. First slurry inlet pipe; 18. Second slurry inlet pipe; 19. First electromagnetic flowmeter; 20. Pressure maintaining system; 21. Ball guide rail; 22. Oil cylinder; 23. 2. Second electromagnetic flowmeter; 24. Seventh solenoid valve; 25. Geotechnical centrifuge; 26. Control system; 27. Thin aluminum plate; 28. First overflow pipe; 29. First overflow pipe; 30. Connecting pipe; 31. Third solenoid ball valve; 32. First solenoid ball valve; 33. Fourth solenoid ball valve; 34. Fifth solenoid ball valve; 35. Second solenoid ball valve; 36. Bypass ball valve; 37. Sixth solenoid valve; 38. Mud tank; 39. Third slurry inlet pipe; 40. Switching valve group; 41 , damping; 201, pressure transmitter; 202, exhaust valve; 203, intake valve; 301, stirring motor; 302, stirring blade; 701, gear flowmeter; 702, first proportional speed regulating valve; 703, second proportional speed regulating valve; 704, reversing valve; 705, pressure reducing valve; 706, two-position two-way electromagnetic ball valve; 707, second ball valve; 708, third rotary joint; 709, fourth rotary joint; 801, filter screen; 901, hard tube cylinder; 9 02. Hose barrel; 903. Dynamic torque sensor; 904. Reducer; 905. Servo motor; 111. Stirring rod; 221. Servo valve; 222. One-way valve; 223. Filter; 224. First rotary joint; 225. First ball valve; 251. First hanging basket; 252. Counterweight; 253. Second hanging basket; 254. Rotating arm; 255. Air outlet; 256. Oil outlet; 257. Camera; 258. Cable; 259. Oil return port. DETAILED DESCRIPTION

[0058] The present invention will be further described below with reference to the accompanying drawings and examples.

[0059] like Figure 1As shown, the device includes a soil box 1, a shield body 2, a shield power system and a slurry feeding and discharge system. Soil is stored in the soil box 1. The soil box 1 and the shield power system are connected through the shield body 2. The shield power system is used to drive the shield body 2 to move forward and backward along the excavation direction, so that the shield body 2 excavates the soil in the soil box 1. The shield body 2 is connected to the slurry feeding and discharge system. The slurry stored in the slurry feeding and discharge system is injected into the shield body 2 through a pipeline. The slag generated during the excavation of the device is discharged from the shield body 2 through a pipeline to the slurry feeding and discharge system. A pressure maintaining system 20 for balancing the internal air pressure of the shield body 2 is provided in the shield body 2. The pressure maintaining system 20 is used to control and adjust the gas pressure in the air cushion cabin 14. The soil box 1, the shield power system and the slurry feeding and discharge system are all fixed on the base plate 10, and the base plate 10 is placed in the hanging basket of the geotechnical centrifuge 25. The pressure maintaining system 20, the shield power system and the slurry feeding and discharge system are all electrically connected to the external control system 26.

[0060] like Figure 11 As shown, the geotechnical centrifuge 25 includes a first hanging basket 251, a second hanging basket 253 and a centrifuge base; the first hanging basket 251 and the second hanging basket 253 are fixedly mounted on both sides of the centrifuge base through a rotating arm 254, a counterweight 252 is placed inside the first hanging basket 251, and the bottom plate 10 is fixedly mounted on the second hanging basket 253. A camera 257 is installed on the rotating arm 254 connecting the second hanging basket 253 and the centrifuge base, and an air outlet 255, an oil outlet 256 and an oil return port 259 are provided on the rotating arm 254.

[0061] like Figure 2-Figure 3 As shown, the shield body 2 includes a hull with a working cabin inside, a cutter head 11, an annular front baffle 13 and a main shaft 15; the front baffle 13 is located inside the hull and divides the working cabin into a mud and water cabin 12 and an air cushion cabin 14, the cutter head 11 is located on the side close to the mud and water cabin 12, one end of the main shaft 15 is connected to the shield power system, and the other end of the main shaft 15 passes through the air cushion cabin 14, the front baffle 13 and the mud and water cabin 12 in sequence and is coaxially connected to the cutter head 11; the end of the hull with the mud and water cabin 12 can be moved forward and backward between the opening of the soil box 1 The shield power system is used to drive the cutter head 11 to rotate and drive the main shaft 15 to advance forward along its own axis. The mud and water tank 12 and the cutter head 11 are both arranged at the opening position of the soil box 1; a connecting pipe 30 is connected to the front partition 13, and the connecting pipe 30 is used to transfer the pressure in the air cushion cabin 14 to the mud and water tank 12. The oil cylinder 22 in the shield power system realizes closed-loop control through the servo valve 221 in the control system 26.

[0062] A pressure sensor is located on one side of the front bulkhead 13, near the mud and water compartment 12. This pressure sensor transmits the collected mud pressure signal to the control system 26. A connecting pipe opening is provided on the front bulkhead 13 for mounting a connecting pipe 30. The two ends of the connecting pipe 30 communicate with the mud and water compartment 12 and the air cushion compartment 14, respectively. The installation of the connecting pipe 30 ensures gas flow between the air cushion compartment 14 and the mud and water compartment 12.

[0063] The shield power system includes a power box 5, a drive motor 6, a ball guide rail 21 and a cylinder 22; the ball guide rail 21 is fixed on the base plate 10, and the cylinder 22 can be installed on the ball guide rail 21 for reciprocating movement along the extension direction of the ball guide rail 21. The power box 5 is fixedly installed on the cylinder 22, and the drive motor 6 is arranged inside the power box 5. The side wall of the power box 5 is fixedly connected to one end of the cabin shell. An opening is provided on the side wall of the power box 5 close to the shield body 2 as a power box outlet. One end of the main shaft 15 passes through the power box outlet and is connected to the output shaft of the drive motor 6. A torque sensor 16 is provided on the outer surface of the main shaft 15 close to the drive motor 6; the torque sensor 16 transmits the collected torque signal to the control system 26, and the cylinder 22 is connected to the oil outlet 256 of the geotechnical centrifuge 25. Drive motor 6 drives spindle 15 to a set torque value based on the electrical signal from torque sensor 16. This torque is then transmitted to cutterhead 11 via spindle 15. Cylinder 22 propels power box 5 forward, which in turn transmits the thrust to cutterhead 11 via spindle 15. Cylinder 22 is connected to oil outlet 256 and oil return port 259 via pipelines.

[0064] like Figure 4-Figure 6 As shown, the slurry inlet and outlet system includes a mud water tank 3, a mud pump 7, a slag box 4, a separation box 8 and a screw conveying device 9; the mud pump 7 is connected to the output end of the mud water tank 3, the mud pump 7 is communicated with the mud water tank 12 through a first slurry inlet pipe 17, and the mud pump 7 is communicated with the air cushion cabin 14 through a second slurry inlet pipe 18. The first slurry inlet pipe 17 and the second slurry inlet pipe 18 are respectively provided with a first electromagnetic ball valve 32 and a second electromagnetic ball valve 35. The second slurry inlet pipe 18 is also provided with a first electromagnetic flowmeter 19. One end of the first overflow pipe 28 passes through the opening on the air cushion cabin 14 and the front partition 13 and then extends into the mud water tank 12. The other end of the first overflow pipe 28 The first overflow pipe 28 and the second overflow pipe 29 are respectively provided with a third electromagnetic ball valve 31 and a fourth electromagnetic ball valve 33. A bypass pipe is also provided between the mud water tank 3 and the mud pump 7. One end of the bypass pipe is connected to the mud water tank 3, and the other end is respectively connected to the mud pump 7, the first slurry inlet pipe 17 and the second slurry inlet pipe 18. A bypass ball valve 36 is provided on the bypass pipe. The mud water tank 12 is also connected to the external mud tank 38 through the third slurry inlet pipe 39, and the third slurry inlet pipe 39 is provided with a fifth electromagnetic ball valve 34.

[0065] One end of the screw conveying device 9 extends into the mud and water tank 12, and the other end is connected to the slag box 4 through a pipe. The sixth solenoid valve 37, the separation box 8 and the switching valve group 40 are sequentially arranged on the pipe from the screw conveying device 9 to the slag box 4. The mud pump 7 is powered by the hydraulic pressure of the geotechnical centrifuge 25.

[0066] The mud water tank 3, mud pump 7, slag box 4 and separation box 8 are all placed on the bottom plate 10. Figure 10 As shown, a stirring motor 301 is installed at the top of the mud tank 3. The output shaft of the stirring motor 301 is connected to a stirring blade 302. The stirring blade 302 is located in the mud tank 3 and is used to stir the mud to prevent the mud from segregating and settling in the hypergravity environment. The oil outlet 256 of the geocentrifuge 25 is connected to the input end of the mud pump 7 via a pipeline. The mud pump 7 is used to transport the mud from the mud tank 3 to the mud tank 12 and the air cushion chamber 14. Electromagnetic flowmeters for real-time flow monitoring are installed on the slurry inlet pipes 17 and 18. The first electromagnetic flowmeter 19 transmits the signal to the control system 26 via cable 258. A slurry discharge port is opened at the bottom of the front partition 13. One end of the screw conveyor 9 passes through the slurry discharge port and connects to the mud tank 12. The other end of the screw conveyor 9 is connected to the input end of the separation tank 8 and is controlled by a sixth solenoid valve 37. The first overflow pipe 28 is arranged at the top of the mud and water tank 12, and the second overflow pipe 29 is arranged at a liquid level 2 / 3 of the distance from the bottom of the air cushion tank 14. The electromagnetic ball valve in the slurry discharge system is connected to the control system 26.

[0067] The switching valve group 40 is mainly composed of two branch pipes, a slag inlet pipe and a slag discharge pipe. One end of the slag inlet pipe is connected to the separation box 8, and the other end of the slag inlet pipe is connected to the input end of the two branch pipes respectively. The output ends of the two branch pipes are connected to one end of the slag discharge pipe, and the other end of the slag discharge pipe is connected to the slag box 4. The two branch pipes are both provided with a seventh solenoid valve 24 and a damper 41. The slag discharge pipe is provided with a second electromagnetic flowmeter 23. The flow resistance of the damper 41 realizes the regulation of the slurry discharge flow rate.

[0068] The slurry discharge flow rate in the slag discharge pipe is obtained according to the following formula:

[0069]

[0070] Where, Q is the slurry discharge flow rate; C d is the damping coefficient of damping 41; A is the cross-sectional area of the slag discharge pipe; ΔP is the pressure drop; ρ d The density of mud mixed with slag.

[0071] like Figure 5As shown, separation box 8 is internally provided with three layers of filter screens 801 of varying pore sizes. The axial direction of filter screens 801 is perpendicular to the slurry flow direction. Slurry output by screw conveyor 9 flows into separation box 8 from its input end, is filtered sequentially through the three layers of filter screens, and then flows out of separation box 8. The pore sizes of the three layers of filter screens 801 decrease from the inlet to the outlet of separation box 8. The pore size of the third layer of filter screen 801 (i.e., the filter screen 801 with the smallest pore size) is smaller than the maximum particle size that can pass through second electromagnetic flowmeter 23. The height of the input / output end of separation box 8 is consistent with the height of screw conveyor 9.

[0072] To ensure the stability of the excavation face in front of the cutterhead and prevent active and passive damage, the gas pressure adjusted by the pressure-maintaining system should be such that the relationship between the mud pressure and soil-water pressure at any vertical position z on the excavation face satisfies the following equation.

[0073] The relationship between the mud pressure and soil-water pressure at the excavation surface of shield 2 satisfies the following expression:

[0074] P g +ρ s g(h-D+z)≥γ w (H+z)+K a γ'(H+z)

[0075] P g +ρ s g(h-D+z)≤γ w (H+z)+K p γ'(H+z)

[0076] Where, P g is the gas pressure; ρ s is the slurry density; g is the acceleration of gravity; h is the liquid level of the air cushion cabin; D is the diameter of the shield; z is the vertical coordinate of the excavation surface; γ w is the density of water; H is the depth of shield top; γ' is the effective density of soil; K a is the active earth pressure coefficient; K p is the passive earth pressure coefficient.

[0077] By γ w +K a γ'-ρ s g>0、γ w +K p γ'-ρ s g>0, we know that:

[0078] (γ w +K a γ')(H+D)-ρ s gh≤P g ≤(γ w +Kp γ')H+ρ s g(Dh)

[0079] The thrust F provided by the hydraulic cylinder 22 in the shield power system d The torque T provided by the drive motor 6 is obtained by the following formula:

[0080]

[0081] Where, F d is the thrust provided by the shield power system; F1 is the front propulsion resistance during shield excavation; F2 is the friction between the shield shell and the surrounding soil; K is the lateral earth pressure coefficient; γ is the weight of the soil; f is the friction coefficient between the shield shell and the surrounding soil; L is the length of the shield machine; W is the weight of the shield machine per unit length; T is the torque provided by the shield power system; T1 is the friction torque between the front and side of the cutterhead and the soil; T2 is the formation resistance torque when the cutterhead cuts the soil; η is the cutterhead opening rate; P0 is the mud pressure in the mud water tank; p is the penetration rate.

[0082]

[0083]

[0084] Among them, λ(F d ) is the ratio of the thrust under hypergravity to the thrust under normal gravity; N is the gravity magnification factor of the hypergravity test; λ(T1) is the ratio of the friction torque under hypergravity to the friction torque under normal gravity; λ(T2) is the ratio of the formation resistance torque under hypergravity to the formation resistance torque under normal gravity; λ(p) is the ratio of the penetration under hypergravity to the penetration under normal gravity. The height of the cutterhead 11 is greater than or equal to the penetration of the cutterhead 11. Since the foundation soil actually cut by the shield is a continuous medium, the cutterhead penetration is considered to be a certain multiple of the average particle size d of the foundation soil. 50 , such as 20d 50 , 30d 50 or 40d 50 .

[0085] like Figure 8 As shown, a stirring rod 111 is fixedly connected to the side of the cutterhead 11 near the mud and water chamber 12. There are two types of stirring rod arrangements: one is flat and mounted on the panel of the cutterhead 11, and the other is hook-shaped and arranged circumferentially along the main shaft 15. The stirring rod is driven by the rotation of the main shaft 15. Considering that the shield tunneling parameters under high gravity and normal gravity have a similar scale relationship, the expression for the speed of the cutterhead 11 under high gravity is as follows:

[0086]

[0087] Where λ(n) is the ratio of the cutterhead speed under hypergravity to the cutterhead speed under normal gravity; λ(v) is the ratio of the tunneling speed under hypergravity to the tunneling speed under normal gravity; λ(s) is the ratio of the tunneling distance under hypergravity to the tunneling distance under normal gravity; and λ(t) is the ratio of the test time under hypergravity to the tunneling time under normal gravity.

[0088] like Figure 7 As shown, the pressure maintaining system 20 includes an air inlet pipe, an exhaust pipe, a pressure transmitter 201, an exhaust valve 202 and an air inlet valve 203; an air inlet and an air outlet are provided on the front partition 13, one end of the air inlet pipe passes through the air inlet and is connected to the mud and water tank 12, and the other end of the air inlet pipe is connected to the air outlet 255 of the geotechnical centrifuge 25, one end of the exhaust pipe passes through the exhaust port and is connected to the mud and water tank 12, and the other end of the exhaust pipe is connected to the atmosphere; an air inlet valve 203 and an exhaust valve 202 are respectively provided on the air inlet pipe and the exhaust pipe, and the pressure transmitter 201 is connected to the front partition 13 for measuring the gas pressure in the air cushion cabin 14, the air inlet valve 203, the exhaust valve 202 and the pressure transmitter 201 are all connected to the control system 26 through a cable 258, and the control system 26 is used to control the opening and closing degree of the exhaust valve 202 and the air inlet valve 203, thereby controlling the inlet and outlet flow rates of the gas in the air inlet pipe and the exhaust pipe.

[0089] Cylinder 22 utilizes closed-loop control using a servo valve 221. The oil outlet 256 of the geotechnical centrifuge 25 is connected to the input of a ball valve 225. The output of the first ball valve 225 is connected to the oil inlet P of the servo valve 221 via a pipeline. The pipeline from the first ball valve 225 to the servo valve 221 is sequentially provided with a first rotary joint 224, a filter 223, and a check valve 222. The oil return port T of the servo valve 221 is connected to the oil return port 259 via a second rotary joint 226. The oil outlet B of the servo valve 221 is connected to the cylinder 22. The filter 223 prevents metal debris generated by the rotary joint from damaging the servo valve 221 in the control system 26. The three-position, four-way servo valve 221 can also perform a reversing function.

[0090] The mud pump 7 is powered by the hydraulic pressure of the geotechnical centrifuge 25. The oil outlet 256 of the geotechnical centrifuge 25 is connected to the input of a second ball valve 707 via a pipeline. The output of the second ball valve 707 is also connected to the oil inlet of the mud pump 7 via a pipeline. The pipeline from the second ball valve 707 to the mud pump 7 is sequentially provided with a third rotary joint 708, a two-position, two-way solenoid ball valve 706, a pressure reducing valve 705, a reversing valve 704, proportional speed regulating valves 702 and 703, and a gear flowmeter 701. The oil return port of the mud pump 7 is connected to the oil return port 259 of the geotechnical centrifuge 25 via a fourth rotary joint 709. The pressure reducing valve 705 is used to balance the rated operating pressures of the mud pump 7 and the oil cylinder 22. The oil return port of the pressure reducing valve 705 is connected to the input of the fourth rotary joint 709.

[0091] like Figure 9 As shown, the screw conveying device 9 includes a hard tube barrel 901, a soft tube barrel 902 and a servo motor 905; the hard tube barrel 901 extends into the mud and water tank 12, and the soft tube barrel 902 is arranged inside the air cushion cabin 14 and communicates with the separation box 8; the hard tube barrel 901 is mainly composed of a first barrel wall and a first spiral blade, and the first spiral blade is rotatably arranged inside the first barrel wall, and the soft tube barrel 902 is mainly composed of a second barrel wall and a second spiral blade, and the second spiral blade is rotatably arranged inside the second barrel wall. The first barrel wall and the second barrel wall are coaxially fixedly connected, and one end of the first spiral blade and the second spiral blade are coaxially fixedly connected. The output shaft of the servo motor 905 is coaxially fixedly connected to the other end of the second spiral blade through a coupling and a reducer 904. The servo motor 905 is used to drive the first spiral blade and the second spiral blade to rotate, thereby preventing the screw conveying device 9 from being blocked. A dynamic torque sensor 903 for monitoring the torque of the screw conveying device 9 is provided on the coupling connected to the servo motor 905.

[0092] The embodiment of the present invention includes the following steps:

[0093] Preliminary preparation: Determine the shield parameters, including shield diameter, shield burial depth, excavation speed, and cutterhead speed. Based on the shield diameter, shield burial depth, and foundation soil and water pressure, determine the target Ng value that the geotechnical centrifuge 25 needs to provide, and then determine the gas pressure of the air cushion cabin 14. Based on the ratio of the volume of slag cut by the cutterhead 11 per unit time to the slurry flow rate of 1:11.7, the slurry flow rate is determined in combination with the excavation speed. Based on the conservation relationship of inlet and outlet mass, determine the slurry discharge flow rate. Calculate the slurry discharge flow rate based on the mud pressure in the mud and water tank 12, compare the calculated value with the preset value, and determine the damping 41.

[0094] Step 1: Prepare slurry with a preset ratio of bentonite and water, and inject the slurry into the mud and water tank 3 of the slurry inlet and outlet system. Remove the soil box 1 from the bottom plate 10, seal the opening of the soil box side wall with a thin aluminum plate 27, and then prepare soil samples in layers in the soil box 1 and bury the earth pressure sensor in the soil sample.

[0095] In the specific implementation, bending element sensors, micro soil pressure gauges, micro pore pressure sensors and TDR sensors are also buried in the soil sample, and a wire brush is used to polish the top of the foundation soil to a thickness of 2 mm.

[0096] Step 2: Use a saturation box to saturate the soil sample in the soil box 1. When the soil sample is saturated, hoist the soil box 20 as a whole into the geotechnical centrifuge 25, and push the shield 2 into the hole of the soil box 1. The cutter head 11 is pressed against the thin aluminum plate 27, and the slurry discharge pipe is closed.

[0097] Specifically, the soil box 1 is placed in the saturation box, and the airless water in the saturation box is pumped into the soil box 1 by vacuuming. After the airless water is extracted, the soil box 1 is re-fixed on the base plate 10, the counterweight block 252 is hoisted into the first hanging basket 251, and the base plate 10 is hoisted into the second hanging basket 253.

[0098] Step 3: Turn on the mud pump 7 and fill the mud and water tank 12 with mud through the mud inlet pipes 17 and 18 until the mud reaches 2 / 3 of the liquid level of the air cushion tank 14. When mud seeps out of the first overflow pipe 28 and the second overflow pipe 29 of the mud inlet and discharge system, close the third electromagnetic ball valve 31 and the fourth electromagnetic ball valve 33 and stop the mud inlet. At this time, the mud pressure in the shield body 2 is 0-2.5kPa.

[0099] Install the mud tank 38 and the third slurry inlet pipe 39, open the fifth electromagnetic ball valve 34 on the third slurry inlet pipe 39, control the height and liquid level of the mud tank 38 so that the pressure in the mud and water tank 12 is slightly higher than the lateral water and soil pressure of the soil sample in the soil box 1, lift the thin aluminum plate 27 to allow the pressurized mud in the mud and water tank 14 to penetrate the soil layer, close the fifth electromagnetic ball valve 34 when a mud film is formed, and remove the mud tank 38 and the third slurry inlet pipe 39;

[0100] Step 4: Start the geotechnical centrifuge 25 and gradually increase the centrifugal acceleration of the geotechnical centrifuge 25 to the preset Ng. During the centrifugal acceleration increase process, close all the electromagnetic ball valves (the first electromagnetic ball valve 32, the second electromagnetic ball valve 35, the third electromagnetic ball valve 31, the fourth electromagnetic ball valve 33, and the sixth electromagnetic valve 37) to keep the mud filled in the mud and water tank 12 and the air cushion tank 14. The mud pressure in the mud and water tank 12 increases continuously with the increase of the acceleration Ng value; during the centrifugal acceleration increase process, the cutter head 11 idles to prevent the mud in the mud and water tank 12 from segregating and settling. At the same time, the stirring rod 302 in the mud water tank 3 continues to stir to prevent the mud in the mud water tank 3 from segregating and settling. The mud pump 7 and the bypass ball valve 36 are opened to allow the mud to circulate in the pipeline connected to the mud water tank 3 to prevent segregation and sedimentation in the pipeline. When the geotechnical centrifuge 25 reaches the target Ng value, the air inlet valve 203 of the pressure maintaining system 20 is controlled to intake air and the sixth solenoid valve 37 is opened to control the liquid level of the air cushion cabin 14 to be maintained at 2 / 3 of the height of the air cushion cabin 14. The damping 41 is set according to the change in the liquid level height of the air cushion cabin 14 and the theoretical value of the mud pressure.

[0101] Step 5: Control the shield body 2 to advance forward. After the shield body 2 has advanced stably for a preset period of time, use the shield power system to control the shield body 2 to stop advancing, close all valves on the pipeline, and control the pressure maintaining system 20 to control the gas pressure in the air cushion cabin 14. At the same time, observe the damage of the contact surface between the shield body 2 and the soil sample to simulate the working conditions when the slurry shield excavation surface undergoes active and passive damage under real working conditions, and then obtain the stability law of the slurry shield excavation surface.

Claims

1. A double-chamber slurry shield tunneling test device under simulated hypergravity, characterized by: The invention comprises a soil box (1), a shield body (2), a shield power system and a slurry feeding and discharging system. Soil is stored in the soil box (1). The soil box (1) and the shield power system are connected via the shield body (2). The shield power system is used to drive the shield body (2) to move forward and backward along the excavation direction, thereby enabling the shield body (2) to excavate the soil in the soil box (1). The shield body (2) is connected to the slurry feeding and discharging system. A pressure maintaining system (20) for balancing the internal air pressure of the shield body (2) is provided in the shield body (2). The soil box (1), the shield power system and the slurry feeding and discharging system are all fixed on a bottom plate (10). The bottom plate (10) is placed in the hanging basket of a geotechnical centrifuge (25). The slurry inlet and outlet system comprises a mud water tank (3), a mud pump (7), a slag box (4), a separation box (8) and a screw conveying device (9); the mud pump (7) is connected to the output end of the mud water tank (3), the mud pump (7) is communicated with the mud water tank (12) through a first slurry inlet pipe (17), and the mud pump (7) is communicated with the air cushion cabin (14) through a second slurry inlet pipe (18). A first electromagnetic ball valve (32) and a second electromagnetic ball valve (35) are respectively provided on the first slurry inlet pipe (17) and the second slurry inlet pipe (18), and one end of the first overflow pipe (28) passes through the opening on the air cushion cabin (14) and the front partition (13) and then extends into the In the mud and water tank (12), the other end of the first overflow pipe (28) is connected to the atmosphere, one end of the second overflow pipe (29) extends into the air cushion tank (14), and the other end of the second overflow pipe (29) is connected to the atmosphere. The first overflow pipe (28) and the second overflow pipe (29) are respectively provided with a third electromagnetic ball valve (31) and a fourth electromagnetic ball valve (33). A bypass pipe is also provided between the mud and water tank (3) and the mud pump (7). One end of the bypass pipe is connected to the mud and water tank (3), and the other end is respectively communicated with the mud pump (7), the first slurry inlet pipe (17) and the second slurry inlet pipe (18). A bypass ball valve (36) is provided on the bypass pipe. One end of the screw conveying device (9) extends into the mud and water tank (12), and the other end is connected to the slag box (4) through a pipeline. A sixth solenoid valve (37), a separation box (8) and a switching valve group (40) are sequentially provided on the pipeline from the screw conveying device (9) to the slag box (4). The mud pump (7) is powered by the hydraulic pressure of the geotechnical centrifuge (25). The switching valve group (40) is mainly composed of two branch pipes, a slag inlet pipe and a slag outlet pipe. One end of the slag inlet pipe is connected to the separation box (8), and the other end of the slag inlet pipe is respectively connected to the input ends of the two branch pipes. The output ends of the two branch pipes are connected to one end of the slag outlet pipe, and the other end of the slag outlet pipe is connected to the slag box (4). The two branch pipes are both provided with a seventh electromagnetic valve (24) and a damper (41), and the slag outlet pipe is provided with a second electromagnetic flowmeter (23); The slurry discharge flow rate in the slag discharge pipe is obtained according to the following formula: Where, Q is the slurry discharge flow rate; C d is the damping coefficient of the damping (41); A is the cross-sectional area of the slag discharge pipe; ΔP is the pressure drop; ρ d The density of mud mixed with slag.

2. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 1, characterized in that: The shield body (2) comprises a hull with a working cabin provided therein, a cutterhead (11), an annular front baffle (13) and a main shaft (15); the front baffle (13) is located inside the hull and divides the working cabin into a mud and water cabin (12) and an air cushion cabin (14); the cutterhead (11) is located on a side close to the mud and water cabin (12); one end of the main shaft (15) is connected to the shield power system; the other end of the main shaft (15) passes through the air cushion cabin (14), the front baffle (13) and the mud and water cabin (12) in sequence and is coaxially connected to the cutterhead (11); one end of the mud and water cabin (12) provided in the hull is connected to the soil box The openings of the soil box (1) are movably connected to each other in a forward and backward manner. One end of the air cushion cabin (14) is fixedly connected to the shield power system in the cabin shell. The shield power system is used to drive the cutter head (11) to rotate and drive the main shaft (15) to dig forward along its own axis. The mud and water cabin (12) and the cutter head (11) are both arranged at the opening position of the soil box (1); a connecting pipe (30) is connected to the front partition (13), and the connecting pipe (30) is used to transmit the pressure in the air cushion cabin (14) to the mud and water cabin (12). The shield power system realizes closed-loop control through a servo valve (221).

3. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 1, characterized in that: Three layers of filter screens (801) with different apertures are provided inside the separation box (8). The axial direction of the filter screens (801) is perpendicular to the flow direction of the mud. The mud output by the spiral conveying device (9) flows into the input end of the separation box (8), is filtered by the three layers of filter screens in sequence, and then flows out of the separation box (8). The apertures of the three layers of filter screens (801) decrease in sequence from the inlet to the outlet of the separation box (8). The aperture of the third layer of filter screen (801) is smaller than the maximum particle size that can pass through the second electromagnetic flowmeter (23).

4. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 1, characterized in that: The relationship between the mud pressure and the soil-water pressure at the excavation surface of the shield (2) satisfies the following expression: P g +ρ s g(h-D+z)≥γ w (H+z)+K a γ'(H+z) P g +ρ s g(h-D+z)≤γ w (H+z)+K p γ'(H+z) Where, P g is the gas pressure; ρ s is the slurry density; g is the acceleration of gravity; h is the liquid level of the air cushion cabin; D is the diameter of the shield; z is the vertical coordinate of the excavation surface; γ w is the density of water; H is the depth of shield top; γ' is the effective density of soil; K a is the active earth pressure coefficient; K p is the passive earth pressure coefficient.

5. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 1, characterized in that: The thrust F provided by the shield power system d And torque T is obtained according to the following formula: Where F1 is the frontal thrust resistance during shield tunneling; F2 is the friction between the shield shell and the surrounding soil; K is the lateral earth pressure coefficient; γ is the density of the soil; f is the friction coefficient between the shield shell and the surrounding soil; L is the length of the shield machine; W is the weight of the shield machine per unit length; T1 is the friction torque between the cutterhead and the soil; T2 is the formation resistance torque when the cutterhead cuts the soil; η is the cutterhead opening ratio; P0 is the mud pressure in the mud water tank; and p is the penetration rate.

6. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 2, characterized in that: The expression of the rotation speed of the cutter head (11) is as follows: Where λ(n) is the ratio of the cutterhead speed under hypergravity to the cutterhead speed under normal gravity; λ(v) is the ratio of the excavation speed under hypergravity to the excavation speed under normal gravity; λ(s) is the ratio of the excavation distance under hypergravity to the excavation distance under normal gravity; λ(t) is the ratio of the test time under hypergravity to the excavation time under normal gravity. λ(p) is the ratio of penetration under high gravity to penetration under normal gravity.

7. The double-chamber slurry shield tunneling test device under simulated hypergravity according to claim 1, characterized in that: The pressure maintaining system (20) includes an air inlet pipe, an air outlet pipe, a pressure transmitter (201), an exhaust valve (202) and an air inlet valve (203); an air inlet and an air outlet are provided on the front baffle (13); one end of the air inlet pipe passes through the air inlet and is connected to the mud and water tank (12); the other end of the air inlet pipe is connected to the air outlet (255) of the geotechnical centrifuge (25); one end of the exhaust pipe passes through the exhaust port and is connected to the mud and water tank (12); the other end of the exhaust pipe is connected to the atmosphere; an air inlet valve (203) and an exhaust valve (202) are respectively provided on the air inlet pipe and the exhaust pipe; the pressure transmitter (201) is connected to the front baffle (13); the air inlet valve (203), the exhaust valve (202) and the pressure transmitter (201) are all connected to the control system (26).

8. A double-chamber slurry shield tunneling test method under simulated hypergravity applied to the apparatus according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Prepare slurry with bentonite and water in a preset ratio, inject the slurry into the mud-water tank (3), remove the soil box (1) from the base plate (10), prepare soil samples in layers in the soil box (1), and bury soil pressure sensors in the soil samples; Step 2: Using a saturation box to saturate the soil sample in the soil box (1), after the soil sample is saturated, the soil box (20) is hoisted as a whole into the geotechnical centrifuge (25), and the shield (2) is pushed into the hole of the soil box (1); Step 3: Turn on the mud pump (7) to fill the mud and water tank (12) with mud, and make the mud reach 2 / 3 of the liquid level of the air cushion tank (14). When mud seeps out of the first overflow pipe (28) and the second overflow pipe (29), close the third electromagnetic ball valve (31) and the fourth electromagnetic ball valve (33), and stop the slurry feeding; Step 4: Start the geotechnical centrifuge (25), gradually increase the centrifugal acceleration of the geotechnical centrifuge (25) to a preset Ng, and when the geotechnical centrifuge (25) reaches the target Ng value, control the air inlet valve (203) of the pressure maintaining system (20) to allow air to enter and open the sixth solenoid valve (37), so as to control the liquid level of the air cushion cabin (14) to be maintained at 2 / 3 of the height; Step 5: Control the shield body (2) to advance forward. After the shield body (2) advances forward stably for a preset period of time, the shield power system is used to control the shield body (2) to stop advancing. The gas pressure in the air cushion cabin (14) is controlled by controlling the pressure maintaining system (20). At the same time, the damage of the contact surface between the shield body (2) and the soil sample is observed to simulate the working conditions when the active and passive damage occurs on the excavation surface of the slurry shield under real working conditions, thereby obtaining the stability law of the excavation surface of the slurry shield under real working conditions.

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