A slurry balance shield model test system and a settlement monitoring method

Abstract

The present application discloses a slurry balance shield model test system and a settlement monitoring method, which comprises a model soil box mechanism filled with in-situ soil and accommodating a slurry balance shield model mechanism for simulating the surface environment; the slurry balance shield model mechanism has a cutter head, the back side of the cutter head is provided with a slurry tank and a gas tank separated by a partition plate and connected to each other, and the cutter head is connected to a thrust system; the slurry circulating mechanism comprises a slurry inlet pipe facing the cutter head side and connected to a slurry tank, a slurry outlet pipe facing the cutter head side and connected to a measuring cylinder, and a slurry pump and a flow meter arranged on the slurry inlet pipe; the monitoring mechanism comprises a sensor and a data acquisition instrument connected to each other. Through the model test, the double-tank slurry shield balance system maintains the stability of the excavation face; through the orthogonal test design, the formation mechanism of the mud film in the slurry shield and the matching mechanism of the slurry shield and the stratum characteristics are understood by the engineering site, thereby providing a theoretical basis for ground settlement control in actual engineering.

Description

Technical Field

[0001] This invention relates to the field of urban underground space engineering technology, and in particular to a slurry balance shield tunneling model test system and a settlement monitoring method. Background Technology

[0002] Shield tunneling has become the mainstream construction method for urban rail transit tunnels due to its advantages such as high tunneling efficiency and safe construction process. The slurry-balanced shield tunneling method involves using pressurized slurry to support and balance the excavation face. This involves filling the pressure chamber with slurry and pressurizing it to balance the water and soil pressure at the excavation face. The slurry can be adjusted according to geological conditions, and the pressure can also be manually controlled. Therefore, slurry shield tunneling has active balancing and pressure stability, making it a preferred method when traversing large sections, water bodies, and other complex geological conditions.

[0003] However, during the tunneling process of slurry shield tunneling, improper slurry pressure settings can easily lead to instability of the excavation face, ground subsidence, ground heave, and even slurry leakage, seriously threatening the safety of people's lives and property. In response to the above-mentioned problems in slurry shield tunnel construction, in addition to the common problems of shallow overburden construction, crossing dams, and shield cutterhead posture control, other major engineering difficulties will also be encountered: (1) the problem of slurry separation when crossing full-section clay strata (or silty soil strata); (2) the problem of slurry seepage and mud film formation difficulties when crossing highly permeable sand and gravel strata; (3) the problem of excessive cutter wear when crossing composite strata; (4) the problem of pressurized cutterhead replacement, etc. Among them, the ground subsidence caused by excavation face instability has a significant impact on the surrounding environment and construction progress, and is likely to cause serious social impact. It is necessary to effectively control ground subsidence to ensure construction safety.

[0004] Model testing is a good way to solve engineering problems. However, current model testing cannot help engineering sites understand the formation mechanism of mud film in slurry shield tunnels, nor can it clarify the matching mechanism between slurry shield tunnels and geological characteristics.

[0005] Based on the above, this invention proposes a slurry balance shield tunneling model test system and a settlement monitoring method to effectively solve the above problems. Summary of the Invention

[0006] To address the problems existing in the background technology, this invention provides a slurry-balanced shield tunneling model test system and a settlement monitoring method. Through model tests, the geological conditions under different pressure states can be observed intuitively. The designed dual-chamber slurry shield tunneling balance system maintains the stability of the excavation face. Through orthogonal experimental design, the variation law between factors such as mud film thickness (slurry penetration distance), mud filtration loss, slurry pressure, pore water pressure at the excavation face, and soil pressure and surface settlement is obtained. This helps to understand the formation mechanism of mud film in slurry shield tunneling and the matching mechanism between slurry shield tunneling and geological characteristics in engineering sites, thereby providing a theoretical basis for ground settlement control in actual engineering.

[0007] The present invention adopts the following technical solution:

[0008] The pre-prepared mud required for the experiment is injected into the cutterhead side through the mud tank of the mud pump. By observing the difference in mud volume between the flow meter and the measuring cylinder at the same time scale, the change law of mud filtration loss in the formation and the total filtration loss are obtained, so as to achieve a qualitative evaluation of mud film quality.

[0009] A slurry balance shield tunneling model test system includes a model soil box mechanism, a slurry circulation mechanism, and a monitoring mechanism.

[0010] The model soil box mechanism is used to house the slurry balance shield tunneling model mechanism. The slurry balance shield tunneling model mechanism has in-situ soil inside and is used to simulate the surface environment. The slurry balance shield tunneling model mechanism is equipped with a cutterhead. The back side of the cutterhead is equipped with a slurry chamber and a pressure chamber that are separated by a partition and connected to each other. The cutterhead is connected to the thrust system.

[0011] The mud circulation mechanism includes a mud inlet pipe facing the cutter head side and connected to the mud tank, and a mud outlet pipe facing the cutter head side and connected to the measuring cylinder. The mud inlet pipe is equipped with a mud pump and a flow meter.

[0012] The monitoring device includes connected sensors and data acquisition instruments.

[0013] Furthermore, the model soil box mechanism is made of transparent material, and the upper surface and side of the model soil box mechanism are open. The slurry balance shield model mechanism is installed into the model soil box mechanism through the side opening.

[0014] Furthermore, the surface of the in-situ soil is covered with a shallow overburden. A dynamic water source and shallowly buried weights are placed within the shallow overburden to simulate the surface environment, according to experimental requirements.

[0015] Furthermore, a soil pressure gauge is installed inside the mud and water chamber to measure the pressure within the chamber.

[0016] Furthermore, the pressure chamber is connected to an air bladder and an air pipe, which is connected to a pressure pump. By adjusting the pressure pump, the air bladder in the pressure chamber balances the mud and water chamber, forming a dual-chamber structure with the pressure chamber.

[0017] Furthermore, the thrust system includes a hydraulic device to provide power for the cutterhead propulsion.

[0018] Furthermore, the sensors include a soil pressure gauge, a resistance piezometer, and a multi-point displacement gauge.

[0019] Furthermore, a settlement monitoring method for a slurry balance shield tunneling model test system includes the following steps:

[0020] Step 1: The slurry balance shield model is advanced to the predetermined position through the hole. The slurry is sent to the slurry chamber to form a slurry film. The air pressure pump is used to maintain the balance between the air pressure chamber and the slurry chamber. The value of the slurry from the mud outlet pipe to the measuring cylinder is recorded. The change law of slurry filtration loss is obtained based on the difference between the flow meter and the slurry volume in the measuring cylinder.

[0021] Step 2: Gradually adjust the air pressure, monitor the dynamic changes of sensor values ​​in the mud-water chamber, determine the mud film formation state category based on the obtained permeate flow curve, record the range of mud pressure and surface subsidence range under multiple mud film states, and determine the optimal mud film state.

[0022] Step 3: Within the obtained range of mud pressure and surface settlement, set the corresponding air pressure, propulsion speed and hydraulic pressure. Based on the results of various working conditions obtained from the orthogonal experimental design, obtain the variation law between mud film thickness, mud filtration loss, mud-water pressure, pore water pressure in the excavation hole, earth pressure and surface settlement.

[0023] Step 4: After each test, the soil inside the model soil box is cut and sampled in layers to observe the mud penetration range, path and stratum settlement state. The mud film is also sampled for geotechnical tests to obtain physical and mechanical properties and preserve them.

[0024] Furthermore, in the in-situ soil, multiple sets of resistance piezometers are arranged in a vertical plane at a set distance from the simulated excavation face to form multiple monitoring sections; in the in-situ soil, a set of earth pressure gauges is arranged in a vertical plane at a set distance from the simulated excavation face to form a monitoring section, so as to monitor the changes in earth pressure and pore water pressure of the excavation face soil.

[0025] Furthermore, in the shallow overburden, multiple sets of multi-point displacement gauges are deployed along the travel direction of the slurry balance shield tunneling model mechanism.

[0026] This invention provides a slurry balance shield tunneling model test system and a settlement monitoring method:

[0027] The model test has a simple structure. The slurry chamber and the air pressure chamber form a dual-chamber slurry shield tunneling balance system. The balance of the dual-chamber system can be adjusted by both hydraulic and air pressure, which can effectively maintain the stability of the excavation face and help control the experimental parameters.

[0028] The model soil box is transparent, allowing for direct observation of the formation state under different pressure conditions.

[0029] By using orthogonal experimental design, the variation law between factors such as mud film thickness (mud penetration distance), mud filtration loss, slurry pressure, pore water pressure in the excavation hole, and soil pressure and surface settlement can be obtained. This can help to understand the formation mechanism of mud film in slurry shield tunneling and the matching mechanism between slurry shield tunneling and stratum characteristics on the engineering site, thus providing a theoretical basis for ground settlement control in actual engineering. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the simulated surface environment provided by the present invention;

[0031] Figure 2 A schematic diagram of the slurry balance shield tunneling model test system provided by the present invention;

[0032] Figure 3 This is a schematic diagram of the distribution of surface subsidence monitoring points provided by the present invention;

[0033] Figure 4 This is a schematic diagram showing the distribution of earth pressure monitoring points at the excavation face provided by the present invention.

[0034] Figure 5 This is a schematic diagram showing the distribution of interstitial water pressure monitoring points in the excavation face provided by the present invention.

[0035] Figure 6 This is a schematic diagram of the monitoring section distribution provided by the present invention;

[0036] Figure 7 This is a schematic diagram of an orthogonal experiment provided by the present invention.

[0037] The numbers marked in the figure represent the following in order: 1. Dynamic water source, 2. Shallow buried heavy object, 3. Model soil box mechanism, 4. Mud and water chamber, 5. Pressure chamber, 6. Baffle, 7. Cutterhead, 8. Hydraulic device, 9. Pneumatic pump, 10. Mud tank, 11. Mud pump, 12. Flow meter, 13. Mud inlet pipe, 14. Mud outlet pipe, 15. Measuring cylinder, 16. Soil pressure gauge, 17. Piezometer, 18. Displacement gauge, 19. Data acquisition instrument, 20. Airbag, 21. Sealing layer, 22. Surface displacement monitoring section, 23. Soil pressure monitoring section, 24. Pore water pressure monitoring section. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0039] See attached document Figure 1-7 It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] As described in the background section, in addition to conventional problems, other major engineering challenges arise during slurry shield tunnel construction: ① difficulty in separating slurry when traversing full-section clay (or silty soil) strata; ② difficulty in slurry seepage and mud film formation when traversing highly permeable gravel strata; ③ excessive cutter wear when traversing composite strata; ④ the problem of pressurized cutterhead replacement, etc. Among these, ground settlement caused by excavation face instability has a significant impact on the surrounding environment and construction progress, and can easily cause serious social impacts. Therefore, effective control of ground settlement is essential to ensure construction safety.

[0042] Therefore, the following embodiments provide a slurry balance shield tunneling model test system and settlement monitoring method. Through model tests, the stratum state under different pressure conditions can be observed intuitively. A dual-chamber slurry shield tunneling balance system was designed. The balance state of the dual-chamber system can be adjusted by both hydraulic and pneumatic methods, which can effectively maintain the stability of the excavation face. Through orthogonal experimental design, the variation law between factors such as mud film thickness (slurry penetration distance), mud filtration loss, slurry pressure, pore water pressure at the excavation face, and soil pressure and the surface settlement was obtained. This helps to understand the formation mechanism of mud film in slurry shield tunneling and the matching mechanism between slurry shield tunneling and stratum characteristics on the engineering site, thereby providing a theoretical basis for ground settlement control in actual engineering. Example

[0043] like Figure 1-7 As shown, the slurry balance shield tunneling model test system includes a model soil box mechanism, a slurry circulation mechanism, and a monitoring mechanism.

[0044] The model soil box mechanism is used to house the slurry balance shield tunneling model mechanism. The slurry balance shield tunneling model mechanism has in-situ soil inside and is used to simulate the surface environment. The slurry balance shield tunneling model mechanism is equipped with a cutterhead. The back side of the cutterhead is equipped with a slurry chamber and a pressure chamber that are separated by a partition and connected to each other. The cutterhead is connected to the thrust system.

[0045] The mud circulation mechanism includes a mud inlet pipe facing the cutter head side and connected to the mud tank, and a mud outlet pipe facing the cutter head side and connected to the measuring cylinder. The mud inlet pipe is equipped with a mud pump and a flow meter.

[0046] The monitoring device includes connected sensors and data acquisition instruments.

[0047] The model soil box mechanism is made of transparent material with openings on the top surface and sides. The slurry balance shield model mechanism is inserted into the model soil box mechanism through the side opening.

[0048] The surface of the in-situ soil was covered with a shallow overburden, and a dynamic water source and shallowly buried heavy objects were set in the overburden to simulate the surface environment according to the experimental requirements.

[0049] The mud chamber is equipped with a soil pressure gauge to measure the pressure inside the mud chamber.

[0050] The pressure chamber is connected to an air bladder and an air tube, which in turn is connected to a pressure pump. By adjusting the pressure pump, the air bladder in the pressure chamber balances the mud and water chamber, forming a dual-chamber structure.

[0051] The thrust system includes a hydraulic system that provides power for the propulsion of the cutterhead.

[0052] The pre-prepared mud required for the experiment is injected into the cutterhead side through the mud tank of the mud pump. By observing the difference in mud volume between the flow meter and the measuring cylinder at the same time scale, the change law of mud filtration loss in the formation and the total filtration loss are obtained, so as to achieve a qualitative evaluation of mud film quality.

[0053] The sensors include soil pressure gauges, resistance piezometers, and multi-point displacement gauges.

[0054] In the in-situ soil, multiple sets of resistance piezometers are arranged in a vertical plane at a set distance from the simulated excavation face to form multiple monitoring sections. In the in-situ soil, a set of earth pressure gauges is arranged in a vertical plane at a set distance from the simulated excavation face to form a monitoring section, so as to monitor the changes in earth pressure and pore water pressure in the excavation face soil. In the shallow overburden, multiple sets of multi-point displacement gauges are arranged along the travel direction of the slurry balance shield tunneling model mechanism.

[0055] Specifically:

[0056] like Figure 1As shown, the test system is located in a simulated surface environment. Specifically, the slurry balance shield model is located in the shield tunnel in the in-situ soil. The upper surface of the in-situ soil is covered with a certain thickness of shallow overburden. Shallow buried weight 2 and dynamic water source 1 are placed on the shallow overburden. The positions of shallow buried weight 2 and dynamic water source 1 are set according to the test requirements.

[0057] like Figure 2 As shown, the slurry balance shield tunneling model test system includes a model soil box mechanism, a slurry balance shield tunneling model mechanism, a slurry circulation mechanism, and a monitoring mechanism.

[0058] The model soil box mechanism 3 is welded from 15mm thick plexiglass plates, forming a box-shaped structure with an open top and closed sides and bottom. Triangular steel with horizontal or longitudinal steel ribs is installed at the joints of the glass plates to ensure sufficient rigidity. The inner cavity of the model soil box has dimensions of 0.5m × 0.5m × 0.5m (length × width × height). A 20cm × 20cm hole is reserved on the side of the model soil box to allow the slurry shield tunneling model mechanism to be pre-entered into the soil layer for testing.

[0059] The slurry balance shield tunneling model consists of a slurry chamber 4, a pressure chamber 5, a cutterhead 7, and a thrust system. The slurry chamber 4 and the pressure chamber 5 are separated by a 20mm partition 6, with sufficient openings at the bottom of the partition to connect them, forming a double-chamber structure. The thrust system consists of a hydraulic device 8 and a pneumatic pump 9, which together provide power for the propulsion of the cutterhead 7. The cutterhead 7 is a 10cm diameter metal disc that only serves to transmit pressure and provide support.

[0060] The mud circulation mechanism consists of a mud tank 10, a mud pump 11, a flow meter 12, a mud inlet pipe 13, a mud outlet pipe 14, and a measuring cylinder 15. The mud-water chamber 4 is connected to the mud inlet pipe 13 and the mud outlet pipe 14, which have an inner diameter of 20 mm.

[0061] The monitoring unit consists of sensors and a data acquisition device 19. The sensors include soil pressure gauges 16, resistance piezometers 17, multi-point displacement gauges 18, etc. The data acquisition device 19 can realize dynamic real-time data acquisition.

[0062] An earth pressure gauge 16 is installed inside the mud and water chamber 4 to measure the pressure in the mud and water chamber, and can monitor the dynamic mud and water pressure in the mud and water chamber 4 in real time.

[0063] The air pressure chamber 5 is connected to the air pipe via the air bag 20. With the adjustment of the air pressure pump 9, the air bag 20 can effectively balance the water and soil pressure of the dual-chamber structure in the air pressure chamber 5. At the same time, there is a sealing layer 21 outside the air pressure chamber 5 and the mud and water chamber 4 to prevent mud and air leakage.

[0064] The hydraulic device 8 has two propulsion modes: constant speed and constant pressure. The changes in the mud film formation state and the stress state of the excavation face can be observed in the two modes through preset methods.

[0065] The mud pump 11 can inject the pre-prepared mud from the mud tank 10 into the excavation face by adjusting the flow rate 12 and the change in the amount of mud in the measuring cylinder 15 at the same time scale. This allows for the determination of the change in the filtration loss of mud in the formation and the total filtration loss, thus enabling a qualitative evaluation of the mud film quality.

[0066] Sensor deployment methods as follows Figure 3-6 Three sets of resistance piezometers 17 (spaced 5cm apart) were installed in a vertical plane approximately 2cm from the simulated excavation surface, forming three soil pressure monitoring sections 23. One set of earth pressure gauges 16 was also installed in a vertical plane approximately 2cm from the simulated excavation surface, forming one earth pressure monitoring section 23, to monitor changes in soil pressure and pore water pressure at the excavation surface. Six surface displacement monitoring sections 22 and 29 measuring points were established using multi-point displacement gauges 18. Section 24 in the figure shows the pore water pressure monitoring section.

[0067] The data acquisition instrument 19 has real-time monitoring and storage functions, which facilitates data processing in the later stages of the experiment.

[0068] The system is simple to operate and highly practical. It can effectively reveal the formation law of mud film in slurry balance shield tunneling and its impact on ground settlement, providing a reliable basis for guiding construction. Example

[0069] The method for implementing settlement monitoring based on the above system includes the following steps:

[0070] Slurry preparation; simulation of the surface environment; installation of the slurry shield tunneling model into the simulated surface environment;

[0071] The slurry balance shield model is advanced to the predetermined position through the hole. The slurry is sent to the slurry chamber to form a mud film. The balance between the air pressure chamber and the slurry chamber is maintained by the air pressure pump. The value of the slurry from the mud outlet pipe to the measuring cylinder is recorded. The change law of slurry filtration loss is obtained based on the difference between the flow meter and the slurry volume in the measuring cylinder.

[0072] The air pressure is adjusted step by step, and the dynamic changes of the sensor values ​​in the mud-water chamber are monitored. Based on the obtained permeation flow curve, the mud film formation state is determined. The range of mud pressure and the range of surface subsidence under multiple mud film states are recorded to determine the optimal mud film state.

[0073] Within the range of mud pressure and surface settlement, corresponding air pressure, propulsion speed and hydraulic pressure are set. Based on the results of various working conditions obtained from orthogonal experimental design, the variation law between mud film thickness, mud filtration loss, mud-water pressure, pore water pressure in the excavation hole, earth pressure and surface settlement is obtained.

[0074] After each test, the soil inside the model soil box was cut and sampled in layers to observe the mud penetration range, path and stratum settlement state. The mud film was also sampled for geotechnical tests to obtain physical and mechanical properties and to preserve them.

[0075] Specifically:

[0076] A. Before starting the experiment, prepare a suitable proportion of mud according to the formation conditions, expand it for 12 hours, then use pigment to dye the mud red and place it in mud tank 10;

[0077] B. The original soil is thoroughly mixed beforehand, and sand is added to the model soil box 3 in layers according to the stratum conditions. Pore water pressure sensors 17 and earth pressure gauges 16 are installed at the corresponding points. Then, the layers are compacted. The uniformity of the soil layers is tested using a miniature vane shear tester and Protodyakonov penetration test. Then, water is added for saturation and consolidation for 48 hours. Subsequently, a 0.2m×0.1m×0.2m (length×width×height) cavity is pre-excavated at the reserved hole so that the slurry balance shield model can enter the model soil box 3.

[0078] C. Set up a simulated surface environment, such as setting up a water source 1 to simulate the shield tunnel passing under a water area, setting up a shallow buried heavy object 2 to simulate the shield tunnel passing through a residential area, and setting up displacement gauge 18 to monitor surface settlement according to the monitoring plan.

[0079] D. Start the test. The slurry balance shield model is pushed to the predetermined position through the hole by the hydraulic device 8. The pre-mixed slurry is pumped into the slurry chamber 4 through the mud inlet pipe 13 using the pressure regulating switch of the slurry pump 11. A mud film is formed in the stratum. At this time, the air pressure pump 9 is adjusted to transmit the air to the air pressure chamber 5 through the air pipe to maintain the balance of the dual chamber structure. At this time, the value of the slurry through the mud outlet pipe 14 to the measuring cylinder 15 is recorded. According to the difference in the amount of slurry in the flow meter 12 and the measuring cylinder 15, the change law of slurry filtration loss is obtained.

[0080] E. By adjusting the air pressure step by step, monitor the dynamic changes of the values ​​of the earth pressure gauge in the mud chamber, the earth pressure gauge 16 at the excavation face, the piezometer 17, and the multi-point displacement gauge 18. Based on the seepage flow curve obtained from the data acquisition instrument 19, determine the mud film formation state category, record the approximate range of mud pressure and the range of surface subsidence under the three mud film states, and determine the optimal mud film state.

[0081] F. Within this range, three air pressures, three propulsion speeds, and three hydraulic pressures are set. Based on orthogonal experimental design, 27 working conditions can be obtained, and the variation law between mud film thickness (mud penetration distance), mud filtration loss, mud-water pressure, pore water pressure in the excavation hole, earth pressure, and surface settlement can be obtained.

[0082] In this embodiment, as Figure 7 As shown, based on the orthogonal experiment principle, the following experimental combinations can be obtained, as shown in Table 1:

[0083] Test number propulsion speed Hydraulic jack thrust air pump pressure Stratigraphic materials 1 1.5mm / min 15KN 2KPa ordinary sand 2 2mm / min 10KN 3KPa ordinary sand 3 1.5mm / min 5KN 3KPa ordinary sand 4 1mm / min 5KN 1 kPa ordinary sand 5 2mm / min 5KN 2KPa ordinary sand 6 2mm / min 15KN 1 kPa ordinary sand 7 1mm / min 10KN 2KPa ordinary sand 8 1mm / min 15KN 3KPa ordinary sand 9 1.5mm / min 10KN 1 kPa ordinary sand

[0084] Table 1: Combinations of Experimental Parameters

[0085] According to Table 1, the most intuitive result is the effect of changes in propulsion speed, hydraulic jack pressure, and air pressure on ground settlement. Furthermore, based on the experimental monitoring data, further settlement patterns can be obtained.

[0086] The mud film thickness was measured by a ruler after the test. The mud filtration loss was obtained by the flow difference between the inlet and outlet mud pipes. The mud-water pressure was measured by an earth pressure gauge (wireless signal transmission) pre-installed in the mud-water chamber. The pore water pressure in the excavation holes was measured by a piezometer. The earth pressure was measured by an earth pressure gauge. The surface settlement was measured by a displacement gauge. With other tunneling parameters unchanged, regression equations were established between the change data of each parameter in different test combinations and the ground settlement values ​​to finally obtain the influence of each parameter on settlement.

[0087] G. After each test, the soil in the model box is cut and sampled in layers to observe the mud penetration range, path and stratum settlement state. The mud film is also sampled and relevant geotechnical tests are conducted to test its physical and mechanical properties and record them.

[0088] The model test has a simple structure. The slurry chamber and the air pressure chamber form a dual-chamber slurry shield tunneling balance system. The balance of the dual-chamber system can be adjusted by both hydraulic and air pressure, which can effectively maintain the stability of the excavation face and help control the experimental parameters.

[0089] The model soil box is transparent, allowing for direct observation of the formation state under different pressure conditions.

[0090] By using orthogonal experimental design, the variation law between factors such as mud film thickness (mud penetration distance), mud filtration loss, slurry pressure, pore water pressure in the excavation hole, and soil pressure and surface settlement can be obtained. This can help to understand the formation mechanism of mud film in slurry shield tunneling and the matching mechanism between slurry shield tunneling and stratum characteristics on the engineering site, thus providing a theoretical basis for ground settlement control in actual engineering.

[0091] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A slurry balance shield tunneling model test system, characterized in that, Includes a model soil box mechanism, a mud circulation mechanism, and a monitoring mechanism. The model soil box mechanism is used to house the slurry balance shield tunneling model mechanism. The slurry balance shield tunneling model mechanism has in-situ soil inside and is used to simulate the surface environment. The slurry balance shield tunneling model mechanism is equipped with a cutterhead. The back side of the cutterhead is equipped with a slurry chamber and a pressure chamber that are separated by a partition and connected to each other. The cutterhead is connected to the thrust system. The mud circulation mechanism includes a mud inlet pipe facing the cutter head side and connected to the mud tank, and a mud outlet pipe facing the cutter head side and connected to the measuring cylinder. The mud inlet pipe is equipped with a mud pump and a flow meter. The monitoring mechanism includes connected sensors and data acquisition devices; The model soil box mechanism is made of transparent material. The model soil box mechanism has openings on its upper surface and sides. The slurry balance shield model mechanism is inserted into the model soil box mechanism through the side opening. The surface of the in-situ soil is covered with a shallow overburden, and a dynamic water source and shallowly buried heavy objects are set in the shallow overburden to simulate the surface environment according to the test requirements. The mud and water chamber is equipped with a soil pressure gauge to measure the pressure in the mud and water chamber. The pressure chamber is connected to an air bladder and an air tube, which is connected to a pressure pump. By adjusting the pressure pump, the air bladder in the pressure chamber balances the mud and water chamber, forming a dual-chamber structure with the pressure chamber. The thrust system includes a hydraulic device that provides power for the propulsion of the cutterhead. The sensors include a soil pressure gauge, a resistance piezometer, and a multi-point displacement gauge.

2. The settlement monitoring method for a slurry balance shield tunneling model test system according to claim 1, characterized in that, Includes the following steps: Step 1: The slurry balance shield model is advanced to the predetermined position through the hole. The slurry is sent to the slurry chamber to form a slurry film. The air pressure pump is used to maintain the balance between the air pressure chamber and the slurry chamber. The value of the slurry from the mud outlet pipe to the measuring cylinder is recorded. The change law of slurry filtration loss is obtained based on the difference between the flow meter and the slurry volume in the measuring cylinder. Step 2: Gradually adjust the air pressure, monitor the dynamic changes of sensor values ​​in the mud-water chamber, determine the mud film formation state category based on the obtained permeate flow curve, record the range of mud pressure and surface subsidence range under multiple mud film states, and determine the optimal mud film state. Step 3: Within the obtained range of mud pressure and surface settlement, set the corresponding air pressure, propulsion speed and hydraulic pressure. Based on the results of various working conditions obtained from the orthogonal experimental design, obtain the variation law between mud film thickness, mud filtration loss, mud-water pressure, pore water pressure in the excavation hole, earth pressure and surface settlement. Step 4: After each test, the soil inside the model soil box is cut and sampled in layers to observe the mud penetration range, path and stratum settlement state. The mud film is also sampled for geotechnical tests to obtain physical and mechanical properties and preserve them.

3. The settlement monitoring method for a slurry balance shield tunneling model test system according to claim 2, characterized in that, In the in-situ soil, multiple sets of resistance piezometers are arranged in a vertical plane at a set distance from the simulated excavation face to form multiple monitoring sections; in the in-situ soil, a set of earth pressure gauges is arranged in a vertical plane at a set distance from the simulated excavation face to form a monitoring section, so as to monitor the changes in earth pressure and pore water pressure in the excavation face soil.

4. The settlement monitoring method for a slurry balance shield tunneling model test system according to claim 2, characterized in that, In shallow overburden, multiple sets of multi-point displacement gauges are deployed along the travel direction of the slurry balance shield tunneling model.

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