Slurry balance shield model test system and settlement monitoring method

Abstract

The invention discloses a slurry balance shield model test system and a settlement monitoring method, and the system comprises a model soil box mechanism which is filled with an in-situ soil body, accommodates a slurry balance shield model mechanism, and is used for simulating a ground surface environment; the slurry balance shield model mechanism is provided with a cutterhead, the back side of the cutterhead is provided with a slurry cabin and an air pressure cabin which are separated through a partition plate and communicate with each other, and the cutterhead is connected with a thrust system. The mud circulating mechanism comprises a mud inlet pipe facing the cutter disc face side and connected to the mud groove and a mud outlet pipe facing the cutter disc face side and connected to the measuring cylinder, and a mud pump and a flow meter are arranged on the mud inlet pipe. And the monitoring mechanism comprises a sensor and a data acquisition instrument which are connected with each other. Through a model test, the double-cabin slurry shield balance system maintains the stability of an excavation surface; through orthogonal test design, an engineering site is helped to know a forming mechanism of a mud film in the slurry shield and a matching mechanism of the slurry shield and stratum characteristics, so that a theoretical basis is provided for land subsidence control in actual engineering.

Description

Technical Field

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

[0002] The shield method has become the mainstream construction method for urban rail transit tunnels due to its advantages such as high excavation efficiency and safe construction process. The slurry shield involved in the shield method uses mud pressurization to support and balance the excavation face, that is, the pressure chamber is filled with mud, and the water and soil pressure of the excavation face is balanced by pressurizing the mud. The mud can be adjusted according to the formation conditions, and the pressure can also be controlled manually. Therefore, the slurry shield has active balance and pressure stability, and is given priority when crossing large sections, water bodies and other complex geological conditions.

[0003] However, in the process of slurry shield tunneling, improper mud pressure setting can easily cause excavation face instability, surface subsidence, ground uplift and even slurry leakage, which seriously threatens the safety of people's lives and property. In addition to the common problems of shallow cover construction, crossing dams and shield cutter head posture control, other major engineering difficulties will be encountered in slurry shield tunnel construction: (1) When crossing the full-section clay layer (or silty soil layer), the mud is difficult to separate; (2) When crossing the high-permeability sand and gravel layer, the mud seepage and mud film formation are difficult; (3) When crossing the composite layer, the tool wear is too large; (4) The problem of opening the chamber under pressure to change the tool, etc. Among them, the ground subsidence caused by the instability of the excavation face has a significant impact on the surrounding environment and construction progress, and is likely to cause serious social impacts. It is necessary to effectively control the ground subsidence to ensure construction safety.

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

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

[0006] In order to solve the problems existing in the background technology, the present invention provides a slurry shield model test system and a settlement monitoring method. Through the model test, the formation state under different pressure states is intuitively observed, and a double-chamber slurry shield balance system is designed to maintain the stability of the excavation face; through orthogonal experimental design, the change law between factors such as mud film thickness (mud penetration distance), mud filtration loss, mud water pressure, pore water pressure on the excavation face, soil pressure and surface settlement is obtained to help the engineering site understand the formation mechanism of the mud film in the slurry shield and the matching mechanism of the slurry shield and the formation characteristics, thereby providing a theoretical basis for ground settlement control in actual engineering.

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

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

[0009] A slurry balance shield 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 accommodate a slurry shield model mechanism, the slurry shield model mechanism has an in-situ soil body inside, and the slurry shield model mechanism is used to simulate the surface environment; the slurry shield model mechanism is provided with a cutterhead, and a slurry chamber and an air pressure chamber separated and connected by a partition are provided on the back side of the cutterhead, and the cutterhead is connected to a thrust system;

[0011] The mud circulation mechanism comprises a mud inlet pipe facing the cutter head surface and connected to the mud tank, and a mud outlet pipe facing the cutter head surface and connected to the measuring cylinder, wherein a mud pump and a flow meter are arranged on the mud inlet pipe;

[0012] The monitoring mechanism includes a sensor and a data acquisition device connected to each other.

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

[0014] Furthermore, the upper surface of the in-situ soil body is covered with shallow covering soil, in which a dynamic water source and shallow buried heavy objects are arranged according to test requirements to simulate the surface environment.

[0015] Furthermore, a soil pressure gauge is provided in the mud and water tank to measure the pressure of the mud and water tank.

[0016] Furthermore, the pressure cabin is connected to the air pipe through the air bag, the air pipe is connected to the air pressure pump, and through the adjustment of the air pressure pump, the air bag in the pressure cabin balances the mud and water cabin and the pressure cabin to form a double cabin structure.

[0017] Furthermore, the thrust system includes a hydraulic device and a pneumatic pump, which together provide power for the cutter disc to propel.

[0018] Furthermore, the sensor includes an earth pressure box, a resistive piezometer and a multi-point displacement meter.

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

[0020] Step 1: The mud-water balance shield model is pushed through the hole to the predetermined position, and the mud is sent to the mud-water tank to form a mud film. The air pressure pump is used to maintain the balance between the air pressure tank and the mud-water tank, and the value of the mud through the mud outlet pipe to the measuring cylinder is recorded. According to the difference between the flow meter and the measuring cylinder mud volume, the change law of the mud loss is obtained;

[0021] Step 2: Adjust the air pressure step by step, monitor the dynamic changes of the sensor values ​​in the mud and water tank, determine the type of mud film formation state based on the obtained permeation flow curve, record the range of mud pressure and surface settlement range under multiple groups of mud film states, and determine the optimal mud film state;

[0022] Step 3: Within the obtained mud pressure range and surface settlement range, the corresponding gas pressure, propulsion speed and hydraulic pressure are set, and the variation law among mud film thickness, mud filtration loss, mud water pressure, excavation surface pore water pressure, soil pressure and surface settlement is obtained according to the various working condition results obtained by orthogonal test design;

[0023] Step 4: After each test, the soil in the model soil box structure is cut and layered for sampling to observe the mud penetration range, path and stratum settlement state, and the mud film is sampled for geotechnical testing to obtain and preserve the physical and mechanical properties.

[0024] Furthermore, in the in-situ soil, multiple groups of resistive piezometers are arranged in a vertical plane at a set distance from the simulated excavation surface to form corresponding multiple groups of monitoring sections; in the in-situ soil, a group of soil pressure sensors are arranged in a vertical plane at a set distance from the simulated excavation surface to form a monitoring section to monitor the changes in soil pressure and pore water pressure of the excavation surface soil.

[0025] Furthermore, in the shallow overburden, multiple groups of multi-point displacement meters are arranged along the traveling direction of the slurry shield model mechanism.

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

[0027] 1. The model test has a simple structure. The mud and water chamber and the air pressure chamber form a double-chamber slurry shield balance system. The balance state of the double-chamber system is adjusted by hydraulic and air pressure, which can effectively maintain the stability of the excavation surface and help control the experimental parameters.

[0028] 2. The model soil box is transparent, which enables intuitive observation of the state of the strata under different pressure conditions.

[0029] 3. Through orthogonal experimental design, the variation patterns between factors such as mud film thickness (mud penetration distance), mud filtration loss, mud water pressure, pore water pressure on the excavation surface, soil pressure and surface settlement are obtained, which can help the engineering site understand the formation mechanism of mud film in the slurry shield and the matching mechanism between the slurry shield and the formation characteristics, thereby providing a theoretical basis for ground settlement control in actual engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of the surface simulation environment provided by the present invention;

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

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

[0033] Figure 4 A schematic diagram of the distribution of soil pressure monitoring points on the excavation surface provided by the present invention;

[0034] Figure 5 A schematic diagram of the distribution of pore water pressure monitoring points on the excavation surface provided by the present invention;

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

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

[0037] The serial numbers marked in the figure represent the following in turn: 1. dynamic water source, 2. shallow buried heavy object, 3. model soil box mechanism, 4. mud and water chamber, 5. air pressure chamber, 6. partition, 7. cutter head, 8. hydraulic device, 9. air pressure 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 meter, 19. data acquisition instrument, 20. air bag, 21. sealing layer, 22. surface displacement monitoring section, 23. soil pressure monitoring section, 24. pore water pressure monitoring section. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Refer to the attached Figure 1-7 It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

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

[0041] As described in the background technology, in addition to conventional problems, other major engineering difficulties will be encountered in the construction of slurry shield tunnels: ① When crossing the full-section clay layer (or silty soil layer), it is difficult to separate the mud; ② When crossing the high-permeability sand and gravel layer, the mud seepage and mud film formation are difficult; ③ When crossing the composite layer, the tool wear is too large; ④ The problem of opening the chamber under pressure to change the tool, etc. Among them, the ground subsidence caused by the instability of the excavation face has a significant impact on the surrounding environment and construction progress, and is likely to cause serious social impacts. The ground subsidence must be effectively controlled to ensure construction safety.

[0042] Therefore, the following embodiments provide a slurry shield model test system and a settlement monitoring method. Through the model test, the formation state under different pressure states is intuitively observed, and a double-chamber slurry shield balance system is designed. The balance state of the double-chamber system is adjusted by 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 (mud penetration distance), mud filtration loss, mud water pressure, pore water pressure on the excavation face, soil pressure and surface settlement is obtained to help the engineering site understand the formation mechanism of mud film in the slurry shield and the matching mechanism of the slurry shield and formation characteristics, thereby providing a theoretical basis for ground settlement control in actual engineering.

[0043] Embodiment 1:

[0044] like Figure 1-7 As shown in the figure, the slurry shield model test system includes a model soil box mechanism, a slurry circulation mechanism and a monitoring mechanism.

[0045] The model soil box mechanism is used to accommodate a slurry shield model mechanism, the slurry shield model mechanism has an in-situ soil body inside, and the slurry shield model mechanism is used to simulate the surface environment; the slurry shield model mechanism is provided with a cutterhead, and a slurry chamber and an air pressure chamber separated and connected by a partition are provided on the back side of the cutterhead, and the cutterhead is connected to a thrust system;

[0046] The mud circulation mechanism comprises a mud inlet pipe facing the cutter head surface and connected to the mud tank, and a mud outlet pipe facing the cutter head surface and connected to the measuring cylinder, wherein a mud pump and a flow meter are arranged on the mud inlet pipe;

[0047] The monitoring mechanism includes a sensor and a data acquisition device connected to each other.

[0048] The model soil box mechanism is made of transparent material, with openings on the upper surface and the side surfaces, and the slurry balance shield model mechanism is loaded into the model soil box mechanism through the side openings.

[0049] The upper surface of the in-situ soil is covered with shallow cover soil, in which dynamic water sources and shallowly buried heavy objects are set according to test requirements to simulate the surface environment.

[0050] An earth pressure gauge is installed in the mud water tank to measure the mud water tank pressure.

[0051] The pressure cabin is connected to the air pipe through the air bag, the air pipe is connected to the air pressure pump, and through the adjustment of the air pressure pump, the air bag in the pressure cabin balances the mud and water tank and the pressure cabin to form a double cabin structure.

[0052] The thrust system includes a hydraulic device and a pneumatic pump, which together provide power for the cutterhead propulsion.

[0053] The pre-configured mud required for the experiment is injected into the cutterhead surface through the mud pump mud tank. By observing the difference in the mud volume in the flow meter and the measuring cylinder at the same time scale, the change law of the mud loss in the formation and the total loss are obtained to achieve a qualitative evaluation of the mud film quality.

[0054] The sensors include earth pressure cells, resistive piezometers and multi-point displacement meters.

[0055] In the in-situ soil, multiple groups of resistive piezometers are arranged in the vertical plane at a set distance from the simulated excavation surface to form corresponding multiple groups of monitoring sections. In the in-situ soil, a group of soil pressure sensors are arranged in the vertical plane at a set distance from the simulated excavation surface to form a monitoring section to monitor the changes in soil pressure and pore water pressure of the excavation surface soil; in the shallow overburden, multiple groups of multi-point displacement meters are arranged along the travel direction of the slurry balance shield model mechanism.

[0056] Specific:

[0057] like Figure 1As shown, the test system is located in a simulated surface environment. Specifically, the slurry shield model mechanism is located in a shield tunnel in the in-situ soil. A shallow covering soil of a certain thickness is provided on the upper surface of the in-situ soil. Shallow buried weights 2 and a dynamic water source 1 are provided on the shallow covering soil. The positions of the shallow buried weights 2 and the dynamic water source 1 are set according to the test requirements.

[0058] like Figure 2 As shown, the slurry shield model test system includes a model soil box mechanism, a slurry shield model mechanism, a slurry circulation mechanism, and a monitoring mechanism;

[0059] The model soil box mechanism 3 is welded from 15mm thick organic glass plates to form a box-type structure with an upper opening and closed surroundings and bottom. Triangular steel with transverse or longitudinal steel ribs is provided at the connection of the glass plates to ensure that it has sufficient rigidity. The inner cavity size of the model soil box is 0.5m×0.5m×0.5m (length×width×height), and a 20cm×20cm hole is reserved on the side of the model soil box, so that the slurry shield model mechanism can enter the soil layer in advance to facilitate the test.

[0060] The slurry shield model consists of a slurry tank 4, an air pressure tank 5, a cutter head 7 and a thrust system. The slurry tank 4 and the air pressure tank 5 are separated by a 20 mm partition 6, and a sufficient gap is left at the bottom of the partition to connect them, forming a double-cabin structure; the thrust system consists of a hydraulic device 8 and an air pressure pump 9, and the two parts together provide power for the cutter head 7 to propel; the cutter head 7 is a metal disk with a diameter of 10 cm, which only plays the role of transmitting pressure and supporting.

[0061] The mud circulation mechanism is composed 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 with an inner diameter of 20 mm.

[0062] The monitoring mechanism is composed of sensors and a data acquisition device 19. The sensors include an earth pressure gauge 16, a resistive piezometer 17, a multi-point displacement meter 18, etc. The data acquisition device 19 can realize dynamic and real-time data acquisition.

[0063] A soil pressure gauge 16 is installed in the mud and water tank 4 to measure the pressure of the mud and water tank, and the dynamic mud and water pressure of the mud and water tank 4 can be monitored in real time.

[0064] The pressure cabin 5 is connected to the air pipe through the air bag 20. Through the adjustment of the air pressure pump 9, the air bag 20 can effectively balance the water and soil pressure of the double-cabin structure in the pressure cabin 5. At the same time, there is a sealing layer 21 outside the pressure cabin 5 and the mud and water cabin 4 to prevent mud and air leakage.

[0065] 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 surface under the two modes can be observed in a pre-set manner.

[0066] The mud pump 11 can be adjusted to inject the pre-configured mud in the mud tank 10 into the excavation face. By observing the difference in the amount of mud in the flow meter 12 and the measuring cylinder 15 at the same time scale, the change pattern of the filtration loss of the mud in the formation and the total filtration loss can be obtained, thereby achieving a qualitative evaluation of the mud film quality.

[0067] Sensor layout method Figure 3-6 : Three groups of resistance piezometers 17 (5 cm apart) are arranged on a vertical plane about 2 cm away from the simulated excavation surface, with a total of three soil pressure monitoring sections 23, and a group of soil pressure sensors 16 are arranged on a vertical plane about 2 cm away from the simulated excavation surface, with a total of one soil pressure monitoring section 23, to monitor the soil pressure and pore water pressure changes of the excavation surface soil. The multi-point displacement meter 18 is arranged in a total of 6 surface displacement monitoring sections 22 and 29 measuring points. 24 in the figure is a pore water pressure monitoring section.

[0068] The data acquisition device 19 has the functions of real-time monitoring and storage, which is convenient for data processing in the later stage of the test.

[0069] The system is easy to operate and highly practical. It can effectively reveal the formation rules of mud film in slurry balance shield and its influence on ground settlement, providing a reliable basis for guiding construction.

[0070] Embodiment 2:

[0071] The method for realizing settlement monitoring based on the above system comprises the following steps:

[0072] Mud preparation; simulated surface environment; the slurry shield model mechanism is installed in the simulated surface environment;

[0073] The mud-water balance shield model is pushed through the hole to the predetermined position, and the mud is sent to the mud-water tank to form a mud film. The air pressure pump is used to maintain the balance between the air pressure tank and the mud-water tank. The value of the mud through the mud outlet pipe to the measuring cylinder is recorded. According to the difference between the flow meter and the measuring cylinder mud volume, the change law of the mud loss is obtained.

[0074] Adjust the air pressure step by step, monitor the dynamic changes of the sensor values ​​in the mud and water tank, determine the type of mud film formation state based on the obtained seepage flow curve, record the range of mud pressure and surface settlement range under multiple groups of mud film states, and determine the optimal mud film state;

[0075] In the obtained mud pressure range and surface settlement range, the corresponding gas pressure, propulsion speed and hydraulic pressure are set, and the variation law between mud film thickness, mud filtration loss, mud water pressure, excavation surface pore water pressure, soil pressure and surface settlement is obtained according to the various working condition results obtained by orthogonal test design;

[0076] After each test, the soil in the model soil box structure was cut and layered for sampling to observe the mud penetration range, path and stratum settlement state, and the mud film was sampled for geotechnical tests to obtain and preserve the physical and mechanical properties.

[0077] Specific:

[0078] A. Before starting the test, prepare the mud in appropriate proportions according to the formation conditions, swell for 12 hours, and then dye the mud red with pigment and place it in the mud tank 10;

[0079] B. The original soil is fully mixed in advance, and sand is filled into the model soil box 3 in layers according to the state of the stratum. The pore water pressure sensor 17 and the soil pressure sensor 16 are buried at the corresponding points, and then the soil is compacted in layers. The soil uniformity test is carried out using a micro cross-plate shear instrument and Proctor penetration test, and then water is added for saturation consolidation for 48 hours. Subsequently, a 0.2m×0.1m×0.2m (length×width×height) cavity is pre-dug at the reserved hole to allow the slurry shield model to enter the model soil box 3;

[0080] C. Set up the surface environment at the simulated surface, such as setting up a water source 1 to simulate the shield tunneling through the water area, setting up a shallow buried heavy object 2 to simulate the shield tunneling through the residential area, and setting up a displacement meter 18 to monitor the surface settlement according to the monitoring plan;

[0081] D. Start the test. Push the slurry shield model through the hole to the predetermined position through the hydraulic device 8. Use the pressure switch of the mud pump 11 to pump the pre-configured mud into the mud and water tank 4 through the mud inlet pipe 13 to form a mud film in the formation. At this time, adjust the air pressure pump 9 to transfer it to the air pressure tank 5 through the air pipe to maintain the balance state of the double-cabin structure. At this time, record the value of the mud through the mud outlet pipe 14 to the measuring cylinder 15. According to the difference between the mud amount of the flow meter 12 and the measuring cylinder 15, the change law of the mud loss is obtained;

[0082] E. By adjusting the air pressure step by step, the dynamic changes of the values ​​of the earth pressure box in the mud and water tank, the earth pressure box 16 on the excavation surface, the piezometer 17, and the multi-point displacement meter 18 are monitored. According to the seepage flow curve obtained from the data acquisition instrument 19, the type of mud film formation state is determined, and the approximate range of mud pressure and surface settlement range under the three mud film states are recorded to determine the optimal mud film state;

[0083] F. Within this range, three air pressures, three propulsion speeds, and three hydraulic pressures are set. According to the orthogonal test design, 27 working condition results can be obtained, and finally the variation law between mud film thickness (mud penetration distance), mud filtration loss, mud water pressure, excavation surface pore water pressure, soil pressure and surface settlement is obtained;

[0084] In this embodiment, Figure 7 As shown in Table 1, according to the orthogonal test principle, the following test combinations can be obtained:

[0085] Test No. Advance speed Hydraulic jack thrust Air pump pressure Formation 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 1KPa Ordinary sand 5 2mm / min 5KN 2KPa Ordinary sand 6 2mm / min 15KN 1KPa Ordinary sand 7 1mm / min 10KN 2KPa Ordinary sand 8 1mm / min 15KN 3KPa Ordinary sand 9 1.5mm / min 10KN 1KPa Ordinary sand

[0086] Table 1: Test parameter combinations

[0087] According to Table 1, the most intuitive thing is the influence of propulsion speed, hydraulic jack pressure, and air pressure changes on ground settlement. Furthermore, based on the test monitoring data, further settlement rules can be obtained.

[0088] The thickness of the mud film is measured with a ruler after the test, the mud loss is obtained based on the flow difference between the inlet and outlet of the mud pipe, the mud water pressure is measured by the earth pressure box pre-buried in the mud and water tank (wireless signal transmission), the pore water pressure of the excavation surface is measured by a piezometer, the earth pressure is measured by an earth pressure box, and the surface settlement is measured by a displacement meter. When other excavation parameters remain unchanged, a regression equation is established between the change data of each parameter in different test combinations and the ground settlement value, and finally the influence of each parameter on the settlement is obtained.

[0089] G. After each test, the soil in the model box is cut and layered for sampling to observe the mud penetration range, path and stratum settlement state, and the mud film is sampled for relevant geotechnical tests to test its physical and mechanical properties and record them.

[0090] The model test has a simple structure. The slurry chamber and the air pressure chamber form a double-chamber slurry shield balance system. The balance state of the double-chamber system is adjusted by hydraulic and air pressure methods, which can effectively maintain the stability of the excavation face and help control the experimental parameters.

[0091] The model soil box is transparent, and the state of the strata under different pressure conditions can be observed intuitively.

[0092] Through orthogonal experimental design, the variation patterns between factors such as mud film thickness (mud penetration distance), mud filtration loss, mud water pressure, pore water pressure on the excavation surface, soil pressure and surface settlement are obtained, which can help the engineering site understand the formation mechanism of mud film in slurry shield and the matching mechanism between slurry shield and stratum characteristics, thus providing a theoretical basis for ground settlement control in actual engineering.

[0093] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A slurry shield model test system, characterized in that: Including model soil box mechanism, mud circulation mechanism and monitoring mechanism, The model soil box mechanism is used to accommodate a slurry shield model mechanism, the slurry shield model mechanism has an in-situ soil body inside, and the slurry shield model mechanism is used to simulate the surface environment; the slurry shield model mechanism is provided with a cutterhead, and a slurry chamber and an air pressure chamber separated and connected by a partition are provided on the back side of the cutterhead, and the cutterhead is connected to a thrust system; The mud circulation mechanism comprises a mud inlet pipe facing the cutter head surface and connected to the mud tank, and a mud outlet pipe facing the cutter head surface and connected to the measuring cylinder. The mud inlet pipe is provided with a mud pump and a flow meter. The monitoring mechanism includes a sensor and a data acquisition device connected to each other.

2. A slurry shield model test system according to claim 1, characterized in that: The model soil box mechanism is made of transparent material, and the upper surface and the side of the model soil box mechanism are open. The slurry shield model mechanism is loaded into the model soil box mechanism through the side opening.

3. A slurry shield model test system according to claim 1, characterized in that: The upper surface of the in-situ soil body is covered with shallow covering soil, in which a dynamic water source and shallow buried heavy objects are arranged according to the test requirements to simulate the surface environment.

4. A slurry shield model test system according to claim 1, characterized in that: A soil pressure gauge is provided in the mud and water tank to measure the pressure of the mud and water tank.

5. A slurry shield model test system according to claim 1, characterized in that: The air pressure cabin is connected to the air pipe through the air bag, and the air pipe is connected to the air pressure pump. Through the regulation of the air pressure pump, the air bag in the air pressure cabin balances the mud and water cabin and the air pressure cabin to form a double cabin structure.

6. A slurry shield model test system according to claim 1, characterized in that: The thrust system includes a hydraulic device and a pneumatic pump, which together provide power for the cutter head to propel.

7. A slurry shield model test system according to claim 1, characterized in that: The sensor comprises an earth pressure box, a resistance piezometer and a multi-point displacement meter.

8. The settlement monitoring method of any one of claims 1 to 7 for a slurry shield model test system, characterized in that: The following steps are involved: Step 1: The mud-water balance shield model is pushed through the hole to the predetermined position, and the mud is sent to the mud-water tank to form a mud film. The air pressure pump is used to maintain the balance between the air pressure tank and the mud-water tank, and the value of the mud through the mud outlet pipe to the measuring cylinder is recorded. According to the difference between the flow meter and the measuring cylinder mud volume, the change law of the mud loss is obtained; Step 2: Adjust the air pressure step by step, monitor the dynamic changes of the sensor values ​​in the mud and water tank, determine the type of mud film formation state based on the obtained permeation flow curve, record the range of mud pressure and surface settlement range under multiple groups of mud film states, and determine the optimal mud film state; Step 3: Within the obtained mud pressure range and surface settlement range, the corresponding gas pressure, propulsion speed and hydraulic pressure are set, and the variation law among mud film thickness, mud filtration loss, mud water pressure, excavation surface pore water pressure, soil pressure and surface settlement is obtained according to the various working condition results obtained by orthogonal test design; Step 4: After each test, the soil in the model soil box structure is cut and layered for sampling to observe the mud penetration range, path and stratum settlement state, and the mud film is sampled for geotechnical testing to obtain and preserve the physical and mechanical properties.

9. A method for monitoring the drop of a slurry shield model test according to claim 8, characterized in that: In the in-situ soil, multiple groups of resistive piezometers are arranged in a vertical plane at a set distance from the simulated excavation surface to form corresponding multiple monitoring sections; in the in-situ soil, a group of soil pressure sensors are arranged in a vertical plane at a set distance from the simulated excavation surface to form a monitoring section to monitor the changes in soil pressure and pore water pressure of the excavation surface soil.

10. The method for monitoring the drop of a slurry shield model test according to claim 8, characterized in that: In shallow overburden, multiple groups of multi-point displacement meters are arranged along the traveling direction of the slurry balance shield model mechanism.

Images