Double-chamber slurry shield tunneling test device and method suitable for supergravity

Abstract

The present invention discloses a double-chamber slurry shield excavation test device and method suitable for supergravity. The model box is fixed on a base, and is used to place the foundation soil required for the experiment; the shield body realizes the rotary excavation and shield propulsion process of the slurry shield through the cutter head and the shield driving device; the slurry inlet and outlet system simulates the slurry penetration and film forming process of the slurry shield excavation surface and the slag discharge process of the slurry chamber through the circulation of slurry; the pressure maintaining system is divided into a slurry inlet pressure maintaining system and a slurry discharge pressure maintaining system, which are respectively placed in the air cushion chamber and the slag box, and can effectively control the slurry pressure in the slurry chamber and the ratio of the slag discharge amount to the slurry inlet amount per unit time. The present invention can continuously collect real-time data of each sensor in the model box during the test, and monitor the operation status of the experimental device in real time, providing an experimental basis for exploring the interaction between water-soil-shield machine and the instability mechanism of the shield excavation surface.

Description

Technical Field

[0001] The invention belongs to the field of slurry shield model test, and in particular relates to a double-chamber slurry shield excavation test device and method suitable for supergravity. Background Art

[0002] As an efficient tunnel excavation method, slurry shield technology is widely used in the construction of various cross-river and cross-sea tunnels. The slurry shield supports the front stratum by pressurizing mud. The mud forms a mud film on the excavation surface, and then the mud pressure can effectively support the stratum in the form of surface force. The support effect of the mud on the shield excavation surface directly affects the success or failure of the construction, so it is very important to carry out relevant slurry shield physical model tests. Most of the existing related studies have carried out scaled tests on shield machines and foundation soils under normal gravity conditions. However, the existing slurry shield excavation test devices are often designed to be relatively simple and cannot truly and comprehensively simulate the shield excavation process. For example, the shield model proposed in the invention patent 201910648692.3 is difficult to control the amount of slag discharge during the shield excavation process, the pressure stability of the mud in the mud water tank is poor, and the slag in the mud water tank is difficult to be discharged in time. The shield model proposed in invention patent CN201910060410.8 uses a rigid plate with a hole as the cutterhead, which makes it difficult to simulate the shield's excavation process of the foundation soil. At the same time, the stress level of the soil in the 1g scale test is very different from that of the actual project. The relevant conclusions and laws obtained through the scale test are less credible and difficult to directly guide the actual project. The geotechnical centrifuge forms a hypergravity field through high-speed rotation, which can provide the same stress conditions as the prototype foundation soil for the physical model test. Therefore, it is necessary to carry out relevant research on slurry shield excavation in a geotechnical centrifuge. Summary of the invention

[0003] In order to solve the problems existing in the background technology, the purpose of the present invention is to provide a double-chamber slurry shield tunneling test device and method suitable for supergravity.

[0004] The technical solution adopted by the present invention is as follows:

[0005] 1. A double-chamber slurry shield tunneling test device suitable for supergravity:

[0006] It comprises a shield tunneling module, a geotechnical centrifuge and a remote control console; the shield tunneling module is placed on the geotechnical centrifuge, the shield tunneling module is connected to the remote control console, the shield tunneling module comprises a model box, a shield body, a shield drive system and a slurry inlet and outlet system, the model box and the shield drive system are connected through the shield body, the shield body is also connected to the slurry inlet and outlet system, the model box, the shield drive system and the slurry inlet and outlet system are all fixedly connected to a base, the model box is used to place soil, and the base is placed on the hanging basket of the geotechnical centrifuge.

[0007] The shield body comprises a shield shell with a working cabin inside, a cutter disc, an annular front baffle and a main shaft; the front baffle is located inside the shield shell and divides the working cabin into a mud and water cabin and an air cushion cabin, the cutter disc is located on the side close to the mud and water cabin, one end of the main shaft is connected to the shield drive system, and the other end of the main shaft passes through the air cushion cabin, the front baffle and the mud and water cabin in sequence and is coaxially connected to the cutter disc; one end of the shield shell with the mud and water cabin is movably connected to the opening of the model box so as to be movable forward and backward, and one end of the shield shell with the air cushion cabin is fixedly connected to the shield drive system, the shield drive system is used to drive the cutter disc to rotate, and at the same time drive the main shaft to excavate forward along its own axial direction, and the mud and water cabin and the cutter disc are both arranged at the opening position of the model box; a slurry feeding pressure maintaining system is arranged inside the shield shell, and the slurry feeding pressure maintaining system is used to control and adjust the gas pressure in the air cushion cabin.

[0008] The two sides of the knife disc are respectively provided with a knife and a transmission flange, and the knife is located on the side close to the model box. Eight "L"-shaped stirring rods are arranged on the back of the knife disc, and the stirring rods are connected to the transmission flange on the back of the knife disc. The knife includes a shell knife and a cutting knife. The knife height of the shell knife and the cutting knife is set according to the following formula:

[0009] H1=T+P+h+d

[0010] P = xd 50

[0011] H2=max{d,P}

[0012] Where H1 and H2 are the knife heights of the shell knife and the cutting knife respectively; T is the height of the soil pack between adjacent knives; P is the penetration; x is the preset penetration coefficient; d 50 is the average particle size of foundation soil; h is the limit wear value of shell cutter; d is the flow space of slag soil; max{} represents the maximum value function.

[0013] A shield starting hole is provided on the side wall of the model box close to the shield body, and the size of the shield starting hole matches the outer diameter of the shield shell, so that one end of the shield shell can be moved forward and backward to extend into the shield starting hole position of the model box. A soil sample is installed in the model box, and a shield mud cake is arranged between the soil sample and the cutter head of the model box. Side wall openings are provided on the other three side walls of the model box. A soil pressure gauge, a pore pressure sensor, a time domain reflectometer TDR and a displacement sensor are arranged inside the model box, and the soil pressure gauge, the pore pressure sensor, the time domain reflectometer TDR and the displacement sensor are all connected to the remote control console.

[0014] The slurry inlet and discharge system comprises a mud pump, a mud water tank, an overflow pipe, a slurry discharge pipe, a slag box, a first slurry inlet pipe and a second slurry inlet pipe; the mud pump, the mud water tank and the slag box are all placed on a base, a stirring motor is arranged on the upper part of the mud water tank, and the stirring blades in the stirring motor extend into the mud water tank to stir the mud to prevent the segregation and precipitation of the mud in a hypergravity environment, the mud pump is connected to the output end of the mud water tank, the mud pump is connected to the mud water tank through the first slurry inlet pipe, the mud pump is connected to the air cushion cabin through the second slurry inlet pipe, and the first slurry inlet pipe and the second slurry inlet pipe are respectively A second electromagnetic ball valve and a third electromagnetic ball valve are provided, one end of the overflow pipe passes through the openings on the air cushion cabin and the front bulkhead and then extends into the mud water tank, the other end of the overflow pipe is connected to the atmosphere, a first electromagnetic ball valve is provided on the overflow pipe, a connecting pipe is provided at a position of 1 / 2 of the height of the mud water tank, the two ends of the connecting pipe are respectively connected to the mud water tank and the air cushion cabin, a bypass pipe is also provided between the mud pump and the mud water tank, one end of the bypass pipe is connected to the mud water tank, and the other end is respectively connected to the mud pump, the first slurry inlet pipe and the second slurry inlet pipe, and a bypass ball valve is provided on the bypass pipe;

[0015] A slurry discharge pipe opening is provided at the bottom of the front partition, one end of the slurry discharge pipe passes through the slurry discharge pipe opening and is connected to the mud and water tank, the other end of the slurry discharge pipe is connected to the slag box through a pipeline, and a tuning fork density meter, a fourth electromagnetic ball valve and an electromagnetic flowmeter are provided on the pipeline from the slurry discharge pipe to the slag box.

[0016] The slurry feeding pressure-maintaining system is arranged in the air cushion cabin of the shield shell, and the pressure in the mud-water cabin can be kept balanced with the water-soil pressure in front of the cutter disc by changing the pressure in the air cushion cabin; the top of the slag box is provided with a slurry discharge pressure-maintaining system, and the slurry discharge pressure-maintaining system adjusts the slag discharge flow in the slurry discharge pipe by changing the pressure in the slag box; the slurry feeding pressure-maintaining system and the slurry discharge pressure-maintaining system are mainly composed of an air intake pipe, an air exhaust pipe, a pressure transmitter, an air intake regulating valve, an air exhaust regulating valve and an electronic control system;

[0017] An air inlet and an air outlet are provided at the end of the shield shell close to the shield drive system, and an air inlet and an air outlet are provided on the top of the slag box. One end of the air inlet pipe and the exhaust pipe are connected to the air inlet, and the other end of the air inlet pipe and the exhaust pipe are connected to the atmosphere. An air inlet regulating valve and an exhaust regulating valve are respectively provided on the air inlet pipe and the exhaust pipe. Pressure transmitters are installed in the air cushion cabin and the slag box. The pressure transmitter, the air inlet regulating valve and the exhaust regulating valve are all connected to the electronic control system.

[0018] 2. A double-chamber slurry shield tunneling test method suitable for supergravity, comprising the following steps:

[0019] Step 1: Prepare Bentonite Slurry

[0020] The bentonite particles, sodium carboxymethyl cellulose (CMC) and water are mixed in a preset ratio and stirred thoroughly. After stirring, the mixture is allowed to stand for more than 24 hours to obtain a bentonite slurry. When no precipitation is observed in the bentonite slurry, the density of the bentonite slurry is measured.

[0021] Step 2: Prepare Hengdun Mud Cake

[0022] Mix the Kling powder, water, clay and water glass evenly according to the preset proportion, and let it stand for more than 24 hours to obtain the Hengdun mud cake;

[0023] Step 3: Prepare foundation soil samples in the model box and inject slurry into the shield;

[0024] Step 4: Install the entire device in the No. 1 hanging basket of the geotechnical centrifuge, place the counterweight on the No. 2 hanging basket, and ensure the stability of the device installation; start the geotechnical centrifuge, and during the increase of the centrifugal acceleration Ng, open the bypass ball valve in the bypass pipe and the stirring motor in the mud water tank; control the output pressure of the slurry pressure maintenance system to adjust according to the set pressure curve, and at the same time turn on the frequency conversion motor to control the cutter head to reach the set speed;

[0025] Step 5: When the geotechnical centrifuge reaches the target Ng value, close the bypass ball valve, open the second electromagnetic ball valve, the third electromagnetic ball valve and the fourth electromagnetic ball valve, and start the slurry discharge pressure maintenance system to the set pressure value; start the static pressure support hydraulic cylinder to control the shield to move forward at the set speed; the cutter head first cuts the shield mud cake in the starting hole of the shield; according to the density of the mud in the slurry discharge pipe and the mud pressure at the bottom of the mud tank, the slurry discharge pressure maintenance system is controlled to make the pressure in the slag box reach the set pressure value;

[0026] Step 6: When the shield body advances 300 mm into the soil sample layer, close the static pressure support hydraulic cylinder, and close the second electromagnetic ball valve, the third electromagnetic ball valve and the fourth electromagnetic ball valve; at the same time, observe the damage of the contact surface between the shield body and the soil sample to simulate the working conditions when the slurry shield excavation face undergoes active and passive damage under real working conditions, and then obtain the stability law of the slurry shield excavation face.

[0027] The step 3 is specifically as follows:

[0028] Step 3.1: First, insert the shield mud cake into the shield starting hole from the inside of the model box, and smooth the back of the shield mud cake from the outside of the model box. Use silicone grease to strengthen the seal at the interface between the inner wall of the shield starting hole and the shield mud cake; prepare the foundation soil sample in layers in the model box, and inject water into the model box to saturate the foundation soil sample;

[0029] Step 3.2, start the hydrostatic support hydraulic cylinder, push the shield into the shield starting hole of the model box, so that the front end of the tool just touches the shield mud cake, and add a sufficient amount of bentonite mud into the mud water tank;

[0030] Step 3.3, start the slurry pressure maintenance system until the pressure reaches the set pressure value and remains stable; start the mud pump, open the first electromagnetic ball valve, the second electromagnetic ball valve and the third electromagnetic ball valve, and inject grout into the mud and water tank and the air cushion tank through the first slurry inlet pipe and the second slurry inlet pipe respectively. When mud overflows from the overflow pipe on the upper part of the mud and water tank, close the first electromagnetic ball valve. When the liquid level in the air cushion tank reaches the middle position, close the second electromagnetic ball valve and the third electromagnetic ball valve.

[0031] In step 3.3, the pressure provided by the slurry pressure-maintaining system must ensure that the slurry pressure in the mud-water tank is balanced with the water-soil pressure of the foundation soil sample in front of the cutterhead. The pressure P1 provided by the slurry pressure-maintaining system is set using the following formula:

[0032] P1=N·(K0γ′ soil h soil +γ slurry h soil -γ slurry h1)

[0033] Where N is the gravity magnification of the supergravity test; K0 is the lateral earth pressure coefficient; γ′ soil is the dry weight of soil; h soil is the height from the soil surface to the center of the model box opening; γ slurry is the density of the mud liquid; h1 is the height difference between the liquid surface in the air cushion tank and the center of the mud tank.

[0034] In step 5, the pressure in the slag box makes the flow rate in the slurry discharge pipe per unit time Q=Q1+Q2, wherein Q1 is the slurry inlet flow rate, which is controlled by the mud pump in the slurry inlet pipe, and the setting value of the mud flow rate in the first slurry inlet pipe and the second slurry inlet pipe is not less than 3.25m / s to prevent the mud from settling in the slurry inlet pipe under the supergravity environment; Q2 is the slag discharge flow rate, and in the experiment, the ratio of the slag discharge amount per unit time to the slurry inlet amount per unit time is 1:11.7.

[0035] The principle of the present invention is as follows:

[0036] Slurry feeding and discharging control technology under N times hypergravity conditions:

[0037] The lateral pressure of soil and water at the center of the model box opening is: σ1=NK0γ′ soil h soil +Nγ slurry h soil

[0038] Mud pressure at the center of the mud tank: σ2=Nγ slurry h1+P1

[0039] Mud pressure at the bottom of the mud tank: σ3 = Nγ slurry h2+P1

[0040] Pressure in the model box: σ4 = P2

[0041] Slurry discharge pipe flow

[0042] Where K0 is the lateral earth pressure coefficient; γ′ soil is the dry weight of soil; h soil is the height from the soil surface to the center of the model box opening; γ slurry is the weight of the mud; h1 is the height difference between the liquid surface in the air cushion tank and the center of the mud tank; h2 is the height difference between the liquid surface in the air cushion tank and the bottom of the mud tank; P1 is the air pressure provided by the slurry inlet pressure maintenance system; P2 is the air pressure provided by the slurry discharge pressure maintenance system; A is the cross-sectional area of ​​the slurry discharge pipe; ΔP is the pressure difference between the pressure in the slag box and the bottom of the mud tank, ΔP = σ3-σ4; ρ l is the density of the slurry in the slurry discharge pipe; Δh is the height difference between the inlet and outlet of the slurry discharge pipe; h 损 It is the pressure loss in the discharge pipe.

[0043] σ1=σ2 is maintained by adjusting the size of P1 of the slurry inlet and pressure maintenance system in the air cushion chamber.

[0044] The flow in the slurry discharge pipe is regulated by adjusting the size of P2 of the slurry discharge pressure maintaining system 2 in the slag box. During the excavation process, the ratio of the slurry input volume to the slag discharge volume per unit time needs to be controlled to be 1:11.7.

[0045] The double-chamber slurry shield excavation test device and method of the present invention can fully restore the actions of grouting, excavation surface film formation, cutter head rotation excavation, slag discharge, mud pressure control in the air cushion cabin, etc. during the excavation process of the prototype slurry shield. At the same time, the super gravity environment of the geotechnical centrifuge is used to restore the actual stratum stress and strength of the foundation soil. It has unique advantages in the research under different working conditions in the slurry shield model test. The power of the shield body forward and the rotation of the cutter head is provided by the static pressure support hydraulic cylinder and the variable frequency motor in the excavation and support system to simulate the excavation process of the slurry shield. The power of the mud circulation and the balance of the excavation surface pressure are controlled by the slurry feeding and discharging system and the pressure maintaining system, so as to realize the generation of the excavation surface mud film and the timely removal of the cut slag. At the same time, during the shield excavation process, the real-time data of each sensor in the model box is continuously collected, which provides an experimental basis for exploring the interaction between water, soil and shield machine and the instability mechanism of the shield excavation surface.

[0046] The beneficial effects of the present invention are:

[0047] 1. When preparing the foundation soil in the model box, the method of the present invention uses the Hengdun mud cake to block the opening of the model box, and no longer uses the rigid plate to block the opening of the model box. Therefore, there is no need to remove the rigid plate after the foundation soil is prepared. In the slurry shield excavation test, the cutter head first cuts the Hengdun mud cake, which reduces the disturbance of the foundation soil during the foundation soil preparation process.

[0048] 2. The present invention sets a slurry discharge and pressure maintaining system in the slag box to accurately control the pressure in the slag box, and can actively control the slurry discharge flow in the slurry discharge pipe, instead of relying on the height difference at both ends of the slurry discharge pipe to control the slurry discharge volume. This is beneficial to improving the stability of the pressure in the mud and water tank, and can discharge the slag in the mud and water tank in a timely and smooth manner.

[0049] 3. In the slurry shield excavation test carried out in the geotechnical centrifuge, the model foundation soil is the same as the prototype soil, but the model shield is scaled down by N times. When the scale factor N is high, the cutting of soil particles by the model shield may reach the particle scale, resulting in the cutting mode of the model shield being different from that of the prototype. Based on the prototype tool size, the present invention combines the existing scaled-down cutter diameter with a non-direct proportional reduction design to meet the requirements of cutter penetration, tool wear, and slag fluidity, so as to cut the soil more effectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a side view of the model box in the present invention;

[0051] Figure 2 A side view of the tunneling and support system of the present invention;

[0052] Figure 3 is a cross-sectional view of the device of the present invention;

[0053] Figure 4 A top view of the device of the present invention;

[0054] Figure 5 The internal structure diagram of the shield body in the present invention;

[0055] Figure 6 It is a front view of the cutter disc in the present invention;

[0056] Figure 7 It is an internal schematic diagram of the mud water system in the present invention;

[0057] Figure 8 is a schematic diagram of a pressure-maintaining system in the present invention;

[0058] Fig. 9 is a schematic diagram of a geotechnical centrifuge in the present invention;

[0059] In the figure: 1. Model box; 2. Shield starting hole; 3. Side wall opening; 4. Base; 5. Cutter head; 6. Shield shell; 7. Main shaft; 8. Front bulkhead; 9. Mud and water tank; 10. Air cushion tank; 11. Connecting pipe; 13. Stirring rod; 14. Transmission flange; 15. Rolling guide; 16. Hydrostatic support hydraulic cylinder; 17. Frequency conversion motor; 18. Torque sensor; 19. Main shaft support; 20. Power box; 21. Lifting lug; 22. Shell knife; 23. Cutter; 24. Mud pump; 25. Mud and water tank; 26. Overflow pipe; 27. Slurry discharge pipe; 28. Muck box; 29. ​​First slurry inlet pipe; 30. Second slurry inlet pipe; 31. First electromagnetic ball valve; 32. Second electromagnetic ball valve; 33. Third electromagnetic ball valve; 34. The fourth electromagnetic ball valve; 35. The bypass ball valve; 36. The tuning fork density meter; 37. The electromagnetic flowmeter; 38. The sealing ring; 39. The guide ring; 40. The Gley ring; 41. The filler; 42. The slurry inlet pressure maintaining system; 43. The slurry discharge pressure maintaining system; 44. The pressure transmitter; 45. The electronic control system; 46. The air inlet regulating valve; 47. The air exhaust regulating valve; 48. The high-pressure reducing valve; 49. The low-pressure reducing valve; 50. The geotechnical centrifuge; 51. The No. 1 hanging basket; 52. The No. 2 hanging basket; 53. The counterweight; 54. The swing arm; 55. The waterway; 56. The electric circuit; 57. The oilway; 58. The remote control console; 59. The power distribution room; 60. The bypass pipe; 61. The Hengdun mud cake; 62. The stirring motor; 63. The stirring blade. DETAILED DESCRIPTION

[0060] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0061] like Figure 3 As shown, the device includes a shield tunneling module, a geotechnical centrifuge 50 and a remote control console 58; the shield tunneling module is placed on the geotechnical centrifuge 50, and the shield tunneling module is connected to the remote control console 58. The shield tunneling module includes a model box 1, a shield body, a shield drive system and a slurry inlet and outlet system. The model box 1 and the shield drive system are connected through the shield body, and the shield body is also connected to the slurry inlet and outlet system. The model box 1, the shield drive system and the slurry inlet and outlet system are all fixedly connected to the base 4. The model box 1 is used to place soil, and the base 4 is placed on the hanging basket of the geotechnical centrifuge 50.

[0062] The shield body realizes the excavation and advancement process of the slurry balance shield through the cutter head 5 and the shield driving device; the slurry feeding and discharging system is connected to the shield body, and the slurry circulation is used to simulate the slurry penetration and film formation process of the excavation face of the slurry balance shield and the slag discharge process of the slurry tank 9; two sets of pressure maintaining systems are respectively placed in the air cushion cabin 10 and the slag box 28, which can effectively control the slurry pressure in the slurry tank 9 and the ratio of the slag discharge volume to the slurry feeding volume per unit time; the monitoring system is connected to the remote control console 58, and the data changes of the foundation soil in the model box 1 and the operation status of the experimental device are collected in real time through various sensors in the monitoring system.

[0063] like Fig. 9 As shown, the geotechnical centrifuge 50 includes a No. 1 hanging basket 51, a No. 2 hanging basket 52, a counterweight 53 and a rotating arm 54. The shield excavation module is placed in the No. 1 hanging basket 51, and the No. 2 hanging basket 52 is placed with a counterweight 53 to maintain the balance of the geotechnical centrifuge 50; the rotating arm 54 is provided with a waterway 55, an electric circuit 56 and an oilway 57, which are used for water, electricity and oil respectively; the remote control console 58 includes a control console 58 and a distribution room 59; the control console 58 is arranged on the ground, responsible for the human-machine interaction, including a display interface, operation buttons, and controls the distribution room 59 through remote communication; the distribution room 59 is arranged on the geotechnical centrifuge 50, responsible for the power distribution of the entire system, sensor data collection, and equipment signal output control;

[0064] The shield body includes a shield shell 6 with a working cabin inside, a cutter head 5, an annular front baffle 8 and a main shaft 7; the front baffle 8 is located inside the shield shell 6 and divides the working cabin into a mud and water cabin 9 and an air cushion cabin 10, the cutter head 5 is located on the side close to the mud and water cabin 9, one end of the main shaft 7 is connected to the shield drive system, and the other end of the main shaft 7 passes through the air cushion cabin 10, the front baffle 8 and the mud and water cabin 9 in sequence and is coaxially connected to the transmission flange 14 in the cutter head 5; one end of the shield shell 6 with the mud and water cabin 9 is movably connected to the opening of the model box 1 so as to be movable forward and backward, and one end of the shield shell 6 with the air cushion cabin 10 is fixedly connected to the shield drive system, and the shield drive system is used to drive the cutter head 5 to rotate and drive the main shaft 7 to advance forward along its own axial direction at the same time. The mud and water cabin 9 and the cutter head 5 are both arranged at the opening position of the model box 1; a slurry feeding pressure maintaining system 42 is arranged inside the shield shell 6, and the slurry feeding pressure maintaining system 42 is used to control and adjust the gas pressure in the air cushion cabin 10. A liquid level sensor for measuring the liquid level is arranged in the air cushion cabin 10 , and the liquid level sensor is connected to the remote control console 58 .

[0065] like Figure 2 As shown, the shield drive system includes a variable frequency motor 17, a torque sensor 18, a power box 20, a hydrostatic support hydraulic cylinder 16 and a ball guide 15; the ball guide 15 is fixed on the upper surface of the base 4, the hydrostatic support hydraulic cylinder 16 can be installed on the ball guide 15 for reciprocating motion along the extension direction of the ball guide 15, the power box 20 is fixedly installed on the hydrostatic support hydraulic cylinder 16 through a lifting lug 21, the variable frequency motor 17 and the torque sensor 18 are both arranged inside the power box 20, the side wall of the power box 20 is fixedly connected to one end of the shield shell 6, an opening is provided on the side wall of the power box 20 close to the shield body as a power box outlet, one end of the main shaft 7 is passed through the power box outlet and connected to the output shaft of the variable frequency motor 17, and a torque sensor 18 is provided on the outer surface of the main shaft 7 close to the variable frequency motor 17; the torque sensor 18 is connected to the remote control console 58, and the torque sensor 18 transmits the collected torque signal to the remote control console 58.

[0066] The spindle support 19 is fixed at the bottom of the power box 20 and connected to the spindle 7 through a flange. The hydrostatic support hydraulic cylinder 16 has a built-in displacement sensor and a force sensor, and the closed-loop control of the speed and output force of the hydrostatic support hydraulic cylinder 16 can be achieved through the remote control console 58; the variable frequency motor 17 makes the spindle 7 reach the set torque value according to the electrical signal of the torque sensor 18, and the torque is transmitted to the cutter head 5 through the spindle 7; the hydrostatic support hydraulic cylinder 16 pushes the power box 20 forward, and the power box 20 transmits the thrust to the cutter head 5 through the spindle 7.

[0067] like Figure 5 and Figure 6 As shown, the two sides of the cutter disc 5 are provided with cutters and transmission flanges 14, and the cutters are located on the side close to the model box 1. Eight "L"-shaped stirring rods 13 are provided on the back of the cutter disc 5, and the stirring rods 13 are connected to the transmission flange 14 on the back of the cutter disc 5. The cutters include shell cutters 22 and cutters 23. A sealing ring 38 and a guide ring 39 for sealing are provided between the shield body and the inner wall of the hole of the model box 1. The connection between the front partition 8 and the main shaft 7 is sealed with a Gly ring 40 and a packing 41.

[0068] The knife heights of the shell knife (22) and the cutting knife (23) are set according to the following formula:

[0069] H1=T+P+h+d

[0070] P = xd 50

[0071] H2=max{d,P}

[0072] Wherein, H1 and H2 are the knife heights of the shell knife (22) and the cutting knife (23), respectively; T is the height of the soil pack between adjacent knives; P is the penetration, and considering that the foundation soil cut by the actual shield machine belongs to a continuous medium, the value of the penetration P is taken as xd 50 , x is the preset penetration coefficient; d 50 is the average particle size of foundation soil; h is the limit wear value of shell cutter, considering the maximum wear amount; d is the flow space of slag, ensuring that the slag has good fluidity between the openings on the cutter head; max{} represents the maximum value function.

[0073] The selection of x must satisfy the following conditions: P 实际 is the actual shield penetration.

[0074] like Figure 1As shown, a shield starting hole 2 is opened on the side wall close to the shield body in the model box 1, and the size of the shield starting hole 2 is consistent with the outer diameter of the shield shell 6, so that one end of the shield shell 6 can be moved forward and backward to extend into the position of the shield starting hole 2 of the model box 1, and a soil sample is installed in the model box 1, and a shield balance mud cake 61 is arranged between the soil sample of the model box 1 and the cutter head 5. The shield balance mud cake 61 is used to block the shield starting hole 2, and the outer diameter of the shield shell 6 and the size of the shield balance mud cake 61 are consistent with the size of the shield starting hole 2. The other three side walls of the model box 1 are opened with side wall openings 3 with a diameter of 36 mm, and the side wall openings 3 are used for sensor wiring and the arrangement of the air and water intake pipes of the model box 1. An earth pressure gauge, a pore pressure sensor, a time domain reflectometer TDR and a displacement sensor are arranged inside the model box 1, and the earth pressure gauge, the pore pressure sensor, the time domain reflectometer TDR and the displacement sensor are all connected to the remote control console 58.

[0075] like Figure 4 and Figure 7 As shown, the slurry inlet and discharge system includes a slurry pump 24, a slurry water tank 25, an overflow pipe 26, a slurry discharge pipe 27, a slag box 28, a first slurry inlet pipe 29 and a second slurry inlet pipe 30; the slurry pump 24, the slurry water tank 25 and the slag box 28 are all placed on the base 4, a stirring motor 62 is arranged on the upper part of the slurry water tank 25, and a stirring blade 63 in the stirring motor 62 extends into the slurry water tank 25 to stir the slurry to prevent the segregation and precipitation of the slurry in the hypergravity environment. The output ends of the slurry pump 24 and the slurry water tank 25 are connected, the slurry pump 24 is communicated with the slurry water tank 9 through the first slurry inlet pipe 29, the slurry pump 24 is communicated with the air cushion cabin 10 through the second slurry inlet pipe 30, and the first slurry inlet pipe 29 and the second slurry inlet pipe 30 are respectively provided with a second electromagnetic ball valve 3 2 and a third electromagnetic ball valve 33, one end of the overflow pipe 26 passes through the openings on the air cushion cabin 10 and the front bulkhead 8 and then extends into the mud water tank 9, the other end of the overflow pipe 26 is connected to the atmosphere, the other end of the overflow pipe 26 faces upward to prevent bubbles from existing in the overflow pipe 26, a first electromagnetic ball valve 31 is arranged on the overflow pipe 26, a connecting pipe 11 is arranged at a position of 1 / 2 of the height of the mud water tank 9, the two ends of the connecting pipe 11 are respectively connected to the mud water tank 9 and the air cushion cabin 10, a bypass pipe 60 is also arranged between the mud pump 24 and the mud water tank 25, one end of the bypass pipe 60 is connected to the mud water tank 25, and the other end is respectively connected to the mud pump 24, the first slurry inlet pipe 29 and the second slurry inlet pipe 30, and a bypass ball valve 35 is arranged on the bypass pipe 60;

[0076] A slurry discharge pipe opening is provided at the bottom of the front partition 8, one end of the slurry discharge pipe 27 passes through the slurry discharge pipe opening and is connected to the mud and water tank 9, the other end of the slurry discharge pipe 27 is connected to the slag box 28 through a pipeline, and a tuning fork density meter 36, a fourth electromagnetic ball valve 34 and an electromagnetic flowmeter 37 are provided on the pipeline from the slurry discharge pipe 27 to the slag box 28.

[0077] like Figure 8As shown, the slurry feeding pressure maintaining system 42 is arranged in the air cushion cabin 10 of the shield shell 6, and the slurry pressure in the mud and water tank 9 can be balanced with the water and soil pressure in front of the cutter head 5 by changing the pressure in the air cushion cabin 10; the slurry discharge pressure maintaining system 43 is arranged on the top of the slag box 28, and the slurry discharge pressure maintaining system 43 adjusts the slag discharge flow in the slurry discharge pipe 27 by changing the pressure in the slag box 28; the slurry feeding pressure maintaining system 42 and the slurry discharge pressure maintaining system 43 are mainly composed of an air intake pipe, an exhaust pipe, a pressure transmitter 44, an air intake regulating valve 46, an exhaust regulating valve 47 and an electronic control system 45;

[0078] An air inlet and an air outlet are provided at the end of the shield shell 6 near the shield drive system, and an air inlet and an air outlet are provided at the top of the slag box 28. One end of the air inlet pipe and the exhaust pipe are connected to the air inlet of the shield shell 6 / slag box 28, and the other ends of the air inlet pipe and the exhaust pipe are connected to the atmosphere. An air inlet regulating valve 46 and an exhaust regulating valve 47 are respectively provided on the air inlet pipe and the exhaust pipe. A pressure transmitter 44 is installed in the air cushion cabin 10 and the slag box 28. The pressure transmitter 44, the air inlet regulating valve 46 and the exhaust regulating valve 47 are all connected to the electronic control system 45.

[0079] The pressure transmitter 44 transmits the gas pressure signal collected in real time to the electronic control system 45. The electronic control system 45 adjusts the air intake regulating valve 46 and the exhaust regulating valve 47 by comparing the preset air pressure value with the actual air pressure value collected, so that the gas pressure in the air cushion cabin 10 / slag box 28 is maintained at the preset air pressure value. The slurry inlet pressure maintaining system 42 and the slurry discharge pressure maintaining system 43 are simultaneously provided with a high-pressure reducing valve 48 and a low-pressure reducing valve 49. The gas source is connected to the inlet of the high-pressure reducing valve 48 through a pipeline, and the outlet of the high-pressure reducing valve 48 is connected to the inlet of the low-pressure reducing valve 49, and the outlet of the low-pressure reducing valve is connected to the air intake regulating valve 46 and the exhaust regulating valve 47. Through multi-stage pressure reduction and precise control of the intake and exhaust flow rates, the pressure maintaining systems 42 and 43 have good pressure regulation capabilities.

[0080] The two sets of pressure maintaining systems 42 and 43 are placed in the air cushion cabin 10 and the slag box 28 respectively, which can effectively control the mud pressure in the mud and water tank 9 and the ratio of the slag discharge amount to the mud intake amount per unit time.

[0081] The embodiment of the present invention comprises the following steps:

[0082] Step 1: Prepare Bentonite Slurry

[0083] The bentonite particles, sodium carboxymethyl cellulose (CMC) and water are mixed in a preset ratio and stirred thoroughly. After stirring, the mixture is allowed to stand for more than 24 hours to obtain a bentonite slurry. When no precipitation is observed in the bentonite slurry, the density of the bentonite slurry is measured.

[0084] Step 2: Preparation of Hengdun Mud Cake 61

[0085] According to the preset proportion, the Kling powder, water, clay and water glass are stirred and mixed evenly, poured into a prefabricated mold with a diameter of 250 mm and a height of 50 mm, and allowed to stand for more than 24 to obtain the Hengdun mud cake 61;

[0086] Assemble the entire device, conduct a power-on self-test on each system and component of the device, and at the same time turn on the variable frequency motor 17 to rotate the cutter head 5 and the static pressure support hydraulic cylinder 16 to slowly push the spindle 7 forward; check whether the various sensor signals and the motion state of each moving part are abnormal. If no abnormality occurs, it is considered that the various systems and components of the device are normal, and all electromagnetic ball valves in the device are closed; if an abnormality occurs, the abnormal system and component are repaired;

[0087] Step 3: Prepare foundation soil samples in the model box 1 and inject slurry into the shield;

[0088] Step 4: Install the entire device in the No. 1 hanging basket 51 of the geotechnical centrifuge 50, place the counterweight 53 on the No. 2 hanging basket 52, and ensure the stability of the device installation; start the geotechnical centrifuge 50, the rotating arm 54 starts to drive the two hanging baskets to rotate, and the water and soil pressure of the foundation soil in the model box 1 and the mud pressure in the mud water tank 9 are passively increased as the Ng value increases; during the centrifugal acceleration Ng increase process, open the bypass ball valve 35 in the bypass pipe 60 and the stirring motor 62 in the mud water tank 25; control the output pressure of the slurry inlet pressure maintaining system 42 to adjust according to the set pressure change curve over time, and turn on the frequency conversion motor 17 at the same time to control the cutter head 5 to reach the set speed;

[0089] Step 5: When the geotechnical centrifuge 50 reaches the target Ng value, close the bypass ball valve 35, open the second electromagnetic ball valve 32, the third electromagnetic ball valve 33 and the fourth electromagnetic ball valve 34, and start the slurry discharge pressure maintaining system 43 to the set pressure value; start the static pressure support hydraulic cylinder 16 to control the shield body to move forward at a set speed; the cutter head 5 first cuts the shield mud cake 61 in the shield starting hole 2; according to the density of the mud in the slurry discharge pipe 27 and the mud pressure at the bottom of the mud and water tank 9, the slurry discharge pressure maintaining system 43 is controlled to make the pressure in the slag box 28 reach the set pressure value;

[0090] Step 6: In order to explore the catastrophic mechanism of active and passive damage during slurry shield excavation, the static pressure support hydraulic cylinder 16 is closed after the shield body excavates 300 mm into the soil sample layer, and the second electromagnetic ball valve 32, the third electromagnetic ball valve 33 and the fourth electromagnetic ball valve 34 are closed; at the same time, the damage of the contact surface between the shield body 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, and then the stability law of the excavation surface of the slurry shield is obtained.

[0091] If active destruction of the soil layer in front of the shield body is to be achieved, the air pressure in the grouting and pressure maintaining system 42 is slowly reduced, and the data in the displacement sensor, earth pressure gauge and pore pressure sensor in the soil layer are observed. If a sudden change in the data in each sensor is observed, it is considered that active destruction has occurred in the stratum in front of the shield body. If passive destruction of the stratum in front of the shield body is to be achieved, the air pressure in the grouting and pressure maintaining system 42 is slowly increased, and the data in the displacement sensor, earth pressure gauge and pore pressure sensor in the stratum are observed. If a sudden change in the data in each sensor is observed, it is considered that passive destruction has occurred in the stratum in front of the shield body.

[0092] Specifically, step 3 is as follows:

[0093] Step 3.1, first, insert the shield mud cake 61 into the shield starting hole 2 from the inside of the model box 1, and smooth the back of the shield mud cake 61 from the outside of the model box 1, and use silicone grease to strengthen the seal at the interface between the inner wall of the shield starting hole 2 and the shield mud cake 61; prepare the foundation soil sample in layers in the model box 1 by using the rain method, and inject water into the model box 1 to saturate the foundation soil sample;

[0094] Step 3.2, start the hydrostatic support hydraulic cylinder 16, push the shield into the shield starting hole 2 of the model box 1, so that the front end of the tool just touches the shield mud cake 61, and add a sufficient amount of bentonite slurry into the mud water tank 25;

[0095] Step 3.3, open the slurry pressure maintaining system 42 until the pressure reaches the set pressure value and remains stable; turn on the mud pump 24, open the first electromagnetic ball valve 31, the second electromagnetic ball valve 32 and the third electromagnetic ball valve 33, and inject grout into the mud and water tank 9 and the air cushion tank 10 through the first slurry inlet pipe 29 and the second slurry inlet pipe 30 respectively, and when the overflow pipe 26 on the upper part of the mud and water tank 9 finds that mud has overflowed, close the first electromagnetic ball valve 31, and when the liquid level of the air cushion tank 10 reaches the middle position, close the second electromagnetic ball valve 32 and the third electromagnetic ball valve 33.

[0096] In step 3.3, the pressure provided by the slurry feeding pressure maintaining system 42 needs to ensure that the slurry pressure in the mud water tank 9 is balanced with the water and soil pressure of the foundation soil sample in front of the cutter head 5. The pressure P1 provided by the slurry feeding pressure maintaining system 42 is set using the following formula:

[0097] P1=N·(K0γ′ soil h soil +γ slurry h soil -γ slurry h1)

[0098] Where N is the gravity magnification of the supergravity test; K0 is the lateral earth pressure coefficient; γ′ soil is the dry weight of soil; h soil is the height from the soil surface to the center of the model box opening; γslurry is the density of the mud liquid; h1 is the height difference between the liquid surface in the air cushion tank and the center of the mud tank.

[0099] In step 5, the pressure in the slag box 28 makes the flow rate in the slurry discharge pipe 27 per unit time Q=Q1+Q2, wherein Q1 is the slurry inlet flow rate, which is controlled by the mud pump 24 in the slurry inlet pipe, and the setting value of the mud flow rate in the first slurry inlet pipe 29 and the second slurry inlet pipe 30 is not less than 3.25m / s to prevent the mud from settling in the slurry inlet pipe under the supergravity environment; Q2 is the slag discharge flow rate. In the experiment, the ratio of the slag discharge amount per unit time to the slurry inlet amount per unit time is 1:11.7, that is, Q2=Q1 / 11.7.

[0100] Personnel in the technical field can easily make various changes and modifications based on the text description, drawings and claims provided by the present invention without departing from the concept and scope of the present invention defined by the claims. Any modification or equivalent change made to the above embodiments based on the technical concept and essence of the present invention shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A double-chamber slurry shield tunneling test device suitable for supergravity, characterized in that: The invention comprises a shield tunneling module, a geotechnical centrifuge (50) and a remote control console (58); the shield tunneling module is placed on the geotechnical centrifuge (50), the shield tunneling module is connected to the remote control console (58), the shield tunneling module comprises a model box (1), a shield body, a shield drive system and a slurry inlet and outlet system, the model box (1) and the shield drive system are connected via the shield body, the shield body is also connected to the slurry inlet and outlet system, the model box (1), the shield drive system and the slurry inlet and outlet system are all fixedly connected to a base (4), the model box (1) is used to place soil, and the base (4) is placed on the hanging basket of the geotechnical centrifuge (50); The shield body comprises a shield shell (6) with a working cabin arranged inside, a cutter disc (5), an annular front baffle (8) and a main shaft (7); the front baffle (8) is located inside the shield shell (6) and divides the working cabin into a mud and water cabin (9) and an air cushion cabin (10); the cutter disc (5) is located on a side close to the mud and water cabin (9); one end of the main shaft (7) is connected to the shield drive system; the other end of the main shaft (7) passes through the air cushion cabin (10), the front baffle (8) and the mud and water cabin (9) in sequence and is coaxially connected to the cutter disc (5); the shield shell (6) is provided with a mud and water cabin (9) One end of the shield (6) is movably connected to the opening of the model box (1) so as to be movable forward and backward; one end of the shield shell (6) is provided with an air cushion cabin (10) and is fixedly connected to the shield driving system; the shield driving system is used to drive the cutter head (5) to rotate and drive the main shaft (7) to excavate forward along its own axis; the mud and water cabin (9) and the cutter head (5) are both arranged at the opening of the model box (1); a slurry feeding pressure maintaining system (42) is arranged inside the shield shell (6), and the slurry feeding pressure maintaining system (42) is used to control and adjust the gas pressure in the air cushion cabin (10); The two sides of the knife disc (5) are respectively provided with a knife and a transmission flange (14), and the knife is located on the side close to the model box (1). Eight "L"-shaped stirring rods (13) are arranged on the back of the knife disc (5), and the stirring rods (13) are connected to the transmission flange (14) on the back of the knife disc (5). The knife comprises a shell knife (22) and a cutting knife (23), and the knife heights of the shell knife (22) and the cutting knife (23) are set according to the following formula: H1=T+P+h+d P=xd 50 H2=max{d,P} Wherein, H1 and H2 are the knife heights of the shell knife (22) and the cutting knife (23) respectively; T is the height of the soil pack between adjacent knives; P is the penetration; x is the preset penetration coefficient; d 50 is the average particle size of foundation soil; h is the limit wear value of shell cutter; d is the flow space of slag soil; max{} represents the maximum value function.

2. A double-chamber slurry shield tunneling test device suitable for supergravity according to claim 1, characterized in that: A shield starting hole (2) is provided on the side wall near the shield body in the model box (1), and the size of the shield starting hole (2) matches the outer diameter of the shield shell (6), so that one end of the shield shell (6) can be moved forward and backward to extend into the position of the shield starting hole (2) in the model box (1). A soil sample is installed in the model box (1), and a shield mud cake (61) is provided between the soil sample and the cutterhead (5) of the model box (1). Side wall openings (3) are provided on the other three side walls of the model box (1). A soil pressure gauge, a pore pressure sensor, a time domain reflectometer TDR and a displacement sensor are provided inside the model box (1), and the soil pressure gauge, the pore pressure sensor, the time domain reflectometer TDR and the displacement sensor are all connected to a remote control console (58).

3. The double-chamber slurry shield tunneling test device suitable for supergravity according to claim 1, characterized in that: The slurry inlet and discharge system comprises a slurry pump (24), a slurry water tank (25), an overflow pipe (26), a slurry discharge pipe (27), a slag box (28), a first slurry inlet pipe (29) and a second slurry inlet pipe (30); the slurry pump (24), the slurry water tank (25) and the slag box (28) are all placed on a base (4); a stirring motor (62) is arranged on the upper part of the slurry water tank (25); a stirring blade (63) in the stirring motor (62) extends into the slurry water tank (25) to stir the slurry to prevent the slurry from being separated and precipitated in a hypergravity environment; the output ends of the slurry pump (24) and the slurry water tank (25) are connected; the slurry pump (24) is communicated with the slurry water tank (9) through the first slurry inlet pipe (29); the slurry pump (24) is communicated with the air cushion cabin (10) through the second slurry inlet pipe (30); the first slurry inlet pipe (29) and the second slurry inlet pipe (31) are connected to each other; 0) are respectively provided with a second electromagnetic ball valve (32) and a third electromagnetic ball valve (33); one end of the overflow pipe (26) passes through the openings on the air cushion cabin (10) and the front bulkhead (8) and then extends into the mud and water tank (9); the other end of the overflow pipe (26) is connected to the atmosphere; a first electromagnetic ball valve (31) is provided on the overflow pipe (26); a connecting pipe (11) is provided at a position 1 / 2 of the height of the mud and water tank (9); the two ends of the connecting pipe (11) are respectively connected to the mud and water tank (9) and the air cushion cabin (10); a bypass pipe (60) is also provided between the mud pump (24) and the mud and water tank (25); one end of the bypass pipe (60) is connected to the mud and water tank (25); the other end is respectively connected to the mud pump (24), the first slurry inlet pipe (29) and the second slurry inlet pipe (30); a bypass ball valve (35) is provided on the bypass pipe (60); A slurry discharge pipe opening is provided at the bottom of the front partition (8); one end of the slurry discharge pipe (27) passes through the slurry discharge pipe opening and is communicated with the mud and water tank (9); the other end of the slurry discharge pipe (27) is connected to the slag box (28) through a pipeline; a tuning fork density meter (36), a fourth electromagnetic ball valve (34) and an electromagnetic flow meter (37) are provided on the pipeline from the slurry discharge pipe (27) to the slag box (28).

4. The double-chamber slurry shield tunneling test device suitable for supergravity according to claim 3, characterized in that: The slurry feeding pressure-maintaining system (42) is arranged in the air cushion cabin (10) of the shield shell (6), and the pressure in the air cushion cabin (10) is changed so that the slurry pressure in the mud and water cabin (9) can be balanced with the water and soil pressure in front of the cutter disc (5); the top of the slag box (28) is provided with a slurry discharge pressure-maintaining system (43), and the slurry discharge pressure-maintaining system (43) adjusts the slag discharge flow in the slurry discharge pipe (27) by changing the pressure in the slag box (28); the slurry feeding pressure-maintaining system (42) and the slurry discharge pressure-maintaining system (43) are mainly composed of an air intake pipe, an air exhaust pipe, a pressure transmitter (44), an air intake regulating valve (46), an air exhaust regulating valve (47) and an electronic control system (45); An air inlet and an air outlet are provided at the end of the shield shell (6) close to the shield drive system, and an air inlet and an air outlet are provided at the top of the slag box (28). One end of the air inlet pipe and the exhaust pipe are both connected to the air inlet, and the other ends of the air inlet pipe and the exhaust pipe are both connected to the atmosphere. An air inlet regulating valve (46) and an exhaust regulating valve (47) are respectively provided on the air inlet pipe and the exhaust pipe. A pressure transmitter (44) is installed in the air cushion cabin (10) and the slag box (28). The pressure transmitter (44), the air inlet regulating valve (46) and the exhaust regulating valve (47) are all connected to the electronic control system (45).

5. A double-chamber slurry shield tunneling test method suitable for supergravity applied to the device described in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Prepare Bentonite Slurry The bentonite particles, sodium carboxymethyl cellulose (CMC) and water are mixed in a preset ratio and stirred thoroughly. After stirring, the mixture is allowed to stand for more than 24 hours to obtain a bentonite slurry. When no precipitation is observed in the bentonite slurry, the density of the bentonite slurry is measured. Step 2: Prepare Hengdun Mud Cake (61) The clarithromycin powder, water, clay and water glass are mixed evenly according to a preset ratio, and allowed to stand for more than 24 hours to obtain a Hengdun mud cake (61); Step 3: preparing a foundation soil sample in the model box (1) and injecting slurry into the shield; Step 4: Install the entire device in the No. 1 hanging basket (51) of the geotechnical centrifuge (50), place the counterweight (53) on the No. 2 hanging basket (52), and ensure the stability of the device installation; start the geotechnical centrifuge (50), and during the centrifugal acceleration Ng increase process, open the bypass ball valve (35) in the bypass pipe (60) and the stirring motor (62) in the mud water tank (25); control the output pressure of the slurry inlet pressure maintaining system (42) to adjust according to the set pressure curve, and at the same time turn on the variable frequency motor (17) to control the cutter head (5) to reach the set speed; Step 5: When the geotechnical centrifuge (50) reaches the target Ng value, the bypass ball valve (35) is closed, the second electromagnetic ball valve (32), the third electromagnetic ball valve (33) and the fourth electromagnetic ball valve (34) are opened, and the slurry discharge pressure maintaining system (43) is turned on to a set pressure value; the static pressure support hydraulic cylinder (16) is started to control the shield body to move forward at a set speed; the cutter head (5) first cuts the shield mud cake (61) in the shield starting hole (2); the slurry discharge pressure maintaining system (43) is controlled according to the density of the mud in the slurry discharge pipe (27) and the mud pressure at the bottom of the mud and water tank (9) so that the pressure in the slag box (28) reaches the set pressure value; Step 6: After the shield body has excavated 300 mm into the soil sample layer, the static pressure support hydraulic cylinder (16) is closed, and the second electromagnetic ball valve (32), the third electromagnetic ball valve (33) and the fourth electromagnetic ball valve (34) are closed; at the same time, the damage of the contact surface between the shield body and the soil sample is observed to simulate the working conditions when the active and passive damage occurs to the excavation surface of the slurry shield under real working conditions, and then the stability law of the excavation surface of the slurry shield is obtained.

6. A double-chamber slurry shield tunneling test method suitable for supergravity according to claim 5, characterized in that: The step 3 is specifically as follows: Step 3.1, first, insert the shield mud cake (61) into the shield starting hole (2) from the inside of the model box (1), and smooth the back of the shield mud cake (61) from the outside of the model box (1), and use silicone grease to strengthen the seal at the interface between the inner wall of the shield starting hole (2) and the shield mud cake (61); prepare foundation soil samples in layers in the model box (1), and inject water into the model box (1) to saturate the foundation soil samples; Step 3.2, start the hydrostatic support hydraulic cylinder (16), push the shield into the shield starting hole (2) of the model box (1), so that the front end of the tool just touches the shield mud cake (61), and add a sufficient amount of bentonite slurry into the mud water tank (25); Step 3.3, start the slurry inlet pressure maintaining system (42) until the pressure reaches the set pressure value and remains stable; start the mud pump (24), open the first electromagnetic ball valve (31), the second electromagnetic ball valve (32) and the third electromagnetic ball valve (33), and inject grout into the mud water tank (9) and the air cushion tank (10) through the first slurry inlet pipe (29) and the second slurry inlet pipe (30), respectively; when the overflow pipe (26) on the upper part of the mud water tank (9) finds that mud has overflowed, close the first electromagnetic ball valve (31); when the liquid level of the air cushion tank (10) reaches the middle position, close the second electromagnetic ball valve (32) and the third electromagnetic ball valve (33).

7. A double-chamber slurry shield tunneling test method suitable for supergravity according to claim 6, characterized in that: In step 3.3, the pressure provided by the slurry feeding pressure maintaining system (42) needs to ensure that the slurry pressure in the mud water tank (9) is balanced with the water and soil pressure of the foundation soil sample in front of the cutter head (5). The pressure P1 provided by the slurry feeding pressure maintaining system (42) is set using the following formula: P1=N·(K0γ′ soil h soil +g slurry h soil -c slurry h1) Where N is the gravity magnification of the supergravity test; K0 is the lateral earth pressure coefficient; γ ′ soil is the dry weight of soil; h soil is the height from the soil surface to the center of the model box opening; γ slurry is the density of the mud liquid; h1 is the height difference between the liquid surface in the air cushion tank and the center of the mud tank.

8. The double-chamber slurry shield tunneling test method suitable for supergravity according to claim 5, characterized in that: In step 5, the pressure in the slag box (28) makes the flow rate in the slurry discharge pipe (27) per unit time Q=Q1+Q2, wherein Q1 is the slurry inlet flow rate, which is controlled by the mud pump (24) in the slurry inlet pipe, and the setting value of the mud flow rate in the first slurry inlet pipe (29) and the second slurry inlet pipe (30) is not less than 3.25m / s to prevent the mud from settling in the slurry inlet pipe under the supergravity environment; Q2 is the slag discharge flow rate, and in the experiment, the ratio of the slag discharge amount per unit time to the slurry inlet amount per unit time is 1:11.7.

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