A model test device and method for simulating the floating of subway tunnel segments during operation

Abstract

The present invention relates to the technical field of underground engineering visualization and provides a model test device and method for simulating the floating of subway tunnel segments during operation. The device comprises a groundwater seepage system, a test chamber, and a drainage recovery system, which are connected in sequence along the direction of water flow. The test chamber has an open top and is filled with a simulated stratum, in which a simulated segment structure is pre-embedded, and to which displacement and pressure monitoring devices are connected. The open top area of ​​the test chamber is covered with a rainfall distribution mechanism. The groundwater seepage system includes an inlet tank connected to the test chamber via an inlet pipeline. The drainage recovery system includes a water storage tank connected to the test chamber via an outlet pipeline. This solution can simulate tunnel segment floating scenarios under various hydrogeological conditions, providing experimental support for subway disaster prevention design and safe operation and maintenance.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel segment models, and in particular to a model test device and method for simulating the floating of a subway tunnel segment during operation. Background Art

[0002] The safety and reliability of urban subway networks are core safeguards of urban transportation systems. However, in complex hydrogeological regions, particularly those with abundant groundwater systems, operational subway tunnels face significant challenges from extreme weather events. Extreme rainfall can dramatically alter the hydrological dynamics of the strata surrounding the tunnels in a short period of time, causing a sudden rise in groundwater levels and hydraulic gradients. This can impose continuous and unpredictable additional loads on operational tunnel structures, posing significant safety risks.

[0003] Among these, the uplift, cracking, and water leakage hazards caused by extreme rainfall-induced groundwater flow fluctuations in tunnel segments are particularly prominent. The surge in groundwater recharge caused by heavy rain infiltration rapidly raises water pressure at the tunnel bottom and lateral levels, disrupting the existing stress equilibrium in the tunnel-surrounding rock system. When tunnels pass through water-rich, fractured strata, these transient hydraulic changes can easily drive abnormal uplift of the tunnel lining (segments), leading to secondary hazards such as segment ring joint opening, localized structural damage, leakage, and even water inrush, seriously threatening subway safety and the structural durability of infrastructure. Engineering practice has demonstrated that such hazards are a significant potential risk to the long-term safe operation of subways.

[0004] Currently, there is a lack of physical testing systems capable of effectively simulating the effects of different seepage paths (such as groundwater flow direction) and rainfall conditions (such as rainstorm intensity) on the seepage field in operational subway tunnels under the coupled effects of rainfall and groundwater flow. In particular, there is a lack of active control methods and high-precision monitoring technologies for these multiple factors. Therefore, there is an urgent need to develop a model test device specifically designed to simulate the operational tunnel environment, actively control rainfall infiltration conditions and groundwater dynamics, and accurately measure segment displacement responses and structural damage. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the present invention proposes a model test device and method for simulating the floating of subway tunnel segments during operation. It can simulate the floating scenarios of tunnel segments under various hydrogeological conditions, and provide experimental support for subway disaster prevention design and safe operation and maintenance.

[0006] To achieve the above object, the present invention adopts the following scheme:

[0007] A model test device for simulating the floating of a subway tunnel segment during operation, comprising a groundwater seepage system, a test chamber, and a drainage recovery system connected in sequence along the water flow direction;

[0008] The top of the test box is open and the interior is filled with a simulated stratum. A simulated segment structure is pre-buried in the simulated stratum. The simulated segment structure is connected to a displacement and pressure monitoring device. The side wall of the test box is provided with a segment identification port, and the segment identification port corresponds to the simulated segment structure area.

[0009] The top open area of ​​the test box is covered with a rainfall water distribution mechanism; the groundwater seepage system includes a water inlet tank, which is connected to the test box through an inlet pipe, and the outlet end of the inlet pipe is located in the simulated stratum above the pipe segment identification port; the drainage recovery system includes a water storage tank, which is connected to the test box through an outlet pipe, and the inlet end of the outlet pipe is located in the simulated stratum below the pipe segment identification port;

[0010] The water outlet end of the water inlet pipeline is divided into several first branch pipes, each of which is connected to an independent first valve, and the water inlet pipeline is connected in sequence with a first flow meter and a first water pump along the water flow direction; the water outlet end of each first branch pipe is connected to multiple first seepage branch pipes along different heights and directions of the test box, and the water outlet ends of multiple first seepage branch pipes are connected to the test box and are located in the simulated formation above the pipe segment identification port.

[0011] The water inlet end of the outlet pipe is divided into several second branch pipes, each of which is connected to an independent second valve, and the water outlet pipe is connected to a second flow meter; the water inlet end of each second branch pipe is connected to multiple second seepage branch pipes along different heights and directions of the test box, and the water inlet ends of multiple second seepage branch pipes are connected to the test box and are located in the simulated formation below the pipe segment identification port.

[0012] Optionally, the rainfall distribution mechanism includes a continuous U-shaped rainfall pipe, which is connected to the lower part of the water inlet tank through a rainfall pipeline. Several nozzles are evenly distributed at the bottom of the U-shaped rainfall pipe. The rainfall pipeline is connected to the test box through a hose. A rainfall valve, a rainfall flow meter, and a rainfall water pump are sequentially connected to the upper side of the rainfall pipeline in the direction of water flow.

[0013] Optionally, the number and positions of the first seepage branch pipes and the second seepage branch pipes correspond to each other, and the pipe sections of the first seepage branch pipes and the second seepage branch pipes located in the test box are evenly distributed with seepage holes.

[0014] Optionally, the test box is a transparent box, a water level rising space is provided in the transparent box above the simulated stratum, and openable sealing covers are provided on the tops of the water inlet tank and the water storage tank.

[0015] A model test method for simulating the floating of a subway tunnel segment during operation includes the following steps:

[0016] Step 1: Lay the simulated stratum in layers in the test chamber to the height of the segment marking port, install the simulated segment structure and deploy displacement and pressure monitoring devices, continue filling the simulated stratum to the preset height, and compact to the designed density;

[0017] Step 2: After the simulated formation has been allowed to stabilize for at least 24 hours, the first valve on each first branch pipe is opened, and a target flow rate is set for the first water pump. Simultaneously, the second valve on each second branch pipe is opened until the readings of the first flow meter and the second flow meter are stable.

[0018] Step 3: Perform at least one seepage simulation, using displacement and pressure monitoring devices to collect the displacement and pore pressure of the simulated segment structure in real time to study the effects of different seepage paths and rainfall on the seepage field;

[0019] Step 4: Close the first valve on the first branch pipe and drain the water in the test box into the water storage tank until the second flow meter reads zero, thus ending the test.

[0020] Optionally, in step 3, the seepage simulation includes unilateral seepage simulation, vertical seepage dominant simulation, reverse coupling simulation of rainstorm period and underground seepage, and spatial non-uniform seepage simulation, wherein,

[0021] When performing unilateral seepage simulation, close the first valve and the second valve in the non-target area, and only open the first valve and the second valve corresponding to the two sides of the test box to form a directional horizontal seepage field;

[0022] When conducting vertical seepage-dominated simulation, the flow rate of the first water pump is adjusted so that the reading of the first flow meter is greater than that of the second flow meter, forming a vertical seepage field from shallow to deep;

[0023] When conducting reverse coupling simulation of rainstorm period and underground seepage, based on the vertical seepage field, the rainfall distribution mechanism is activated to the rainstorm intensity, so that the surface infiltration flow and the underground vertical seepage flow act in the opposite direction;

[0024] When performing spatial non-uniform seepage simulation, the first valve and the second valve are adjusted differentially to control the flow of the first seepage branch and the second seepage branch at different positions, thereby constructing a non-uniform seepage field with sudden changes in spatial head gradient.

[0025] The beneficial effects of the present invention are as follows: This solution constructs a device that can reproduce the complex hydrogeological environment of the subway tunnel during the operation period in a test environment through the groundwater seepage system, the test box and the drainage recovery system. Compared with the traditional single seepage field device, a directional horizontal seepage field, a vertical seepage field from shallow to deep and a non-uniform seepage field can be formed by adjusting the first valve, the second valve and the first water pump. Moreover, on the basis of the vertical seepage field, the rainfall distribution mechanism is started to the intensity of heavy rain, so that the surface infiltration water flow and the underground vertical seepage flow act in opposite directions, and reverse coupling simulation with underground seepage during heavy rain can be carried out. The entire device does not need to disassemble the pipeline, and the test conditions can be switched by opening and closing the valves and water pumps, which improves the test efficiency and provides a reliable model test basis for studying the floating mechanism of tunnel segments during operation.

[0026] Moreover, the experimental method of this scheme reproduced four typical disaster conditions: unilateral seepage, vertical seepage dominance, reverse coupling with underground seepage during heavy rain, and spatially non-uniform seepage, further verifying the reliability of the simulation test device and providing quantifiable experimental data support for the disaster prevention design and safe operation and maintenance of subway projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The overall structure of the model test device of the present invention is shown in FIG. Figure 1 ;

[0028] Figure 2 The overall structure of the model test device of the present invention is shown in FIG. Figure 2 ;

[0029] Figure 3 Schematic diagram of the layout of the displacement and pressure monitoring device on the simulated segment structure in an embodiment of the present invention;

[0030] Figure 4 Schematic diagram of the layout of the first seepage branch pipe in the test box in an embodiment of the present invention;

[0031] Figure 5 Schematic diagram of the structure of the first seepage branch pipe or the second seepage branch pipe in the test box in an embodiment of the present invention.

[0032] Numbers in the figure: 1. Test chamber; 101. Simulated stratum; 102. Simulated segment structure; 103. Segment identification port; 2. Rainfall pipeline; 201. Hose; 202. Rainfall valve; 203. Rainfall flow meter; 204. Rainfall pump; 3. Water inlet pipeline; 301. First branch pipe; 302. First valve; 303. First flow meter; 304. First water pump; 305. First seepage branch pipe; 4. Water outlet pipeline; 401. Second branch pipe; 402. Second valve; 403. Second flow meter; 404. Second seepage branch pipe; 5. Water inlet tank; 6. U-shaped rainfall pipe; 7. Water storage tank; 8. Seepage hole; 9. Water level rising space; 10. Sealing cover; 11. Pressure sensor; 12. Displacement sensor. DETAILED DESCRIPTION

[0033] In order to make the present invention clearer and more understandable, the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiment given is only one implementation method and does not represent all embodiments.

[0034] Example 1

[0035] Combine Figure 1-Figure 4 This embodiment provides a model test apparatus for simulating the floating of subway tunnel segments during operation. The apparatus comprises a groundwater seepage system, a test chamber 1, and a drainage recovery system, which are sequentially connected along the water flow direction. The test chamber 1 has an open top and is filled with a simulated stratum 101. A simulated segment structure 102 is embedded in the simulated stratum 101. Displacement and pressure monitoring devices are connected to the simulated segment structure 102. The sidewalls of the test chamber 1 are provided with segment identification openings 103 corresponding to the areas of the simulated segment structure 102. The top open area of ​​the test box 1 is covered with a rainfall water distribution mechanism; the groundwater seepage system includes an inlet tank 5, which is connected to the test box 1 through an inlet pipe 3, and the outlet end of the inlet pipe 3 is located in the simulated stratum 101 above the pipe segment identification port 103; the drainage recovery system includes a water storage tank 7, which is connected to the test box 1 through an outlet pipe 4, and the inlet end of the outlet pipe 4 is located in the simulated stratum 101 below the pipe segment identification port 103.

[0036] This embodiment uses a groundwater seepage system, a test box 1 and a drainage recovery system to construct a system that can simulate tunnel segment floating scenarios under various hydrogeological conditions in a test environment by adjusting the water inflow, rainfall intensity and seepage path.

[0037] The groundwater seepage system, the test box 1 and the drainage recovery system form a closed-loop water cycle to achieve the reuse of water resources. The segment identification port 103 serves as an external identifier of the simulated segment structure 102 area, which facilitates the test personnel to locate the position of the simulated segment structure 102. Therefore, the outlet end of the water inlet pipe 3 is located above the simulated segment structure 102, and the water is transported to the simulated stratum 101 above the simulated segment structure 102, forming a seepage path from top to bottom to simulate the buoyancy effect of groundwater infiltration on the tunnel segment. The water inlet end of the water outlet pipe 4 is located below the simulated segment structure 102, and the water in the stratum below the simulated segment structure 102 is discharged to form a seepage channel to simulate the drainage process of groundwater. It should be noted that there is a seal between the simulated stratum 101 and the box body in the test box 1, so that water will not overflow from the segment identification port 103 during the test. On the other hand, the segment identification port 103 can facilitate the connection of the displacement and pressure monitoring device with an external monitoring system. The displacement and pressure monitoring device includes a displacement sensor 12 and a pressure sensor 11 .

[0038] The rainfall distribution mechanism is used to simulate rainfall. Water is evenly supplied to the top of the test chamber 1 through the water distribution device, increasing the moisture content of the stratum and the groundwater level. Combined with the groundwater seepage system, it reproduces the working conditions of extreme weather such as heavy rain, where rainwater infiltration causes stratum softening and a sudden increase in water buoyancy. This allows a comprehensive study of the risk of tunnel segment floating under the coupling of multiple factors.

[0039] Specifically, the rainfall distribution mechanism comprises a continuous U-shaped rain pipe 6, connected to the lower portion of the water inlet tank 5 via a rain pipe 2. Several nozzles are evenly distributed across the bottom of the U-shaped rain pipe 6. The rain pipe 2 is connected to the test chamber 1 via a hose 201. Connected to the rain pipe 2 along the water flow direction are a rain valve 202, a rainfall flow meter 203, and a rain pump 204. The U-shaped layout expands the coverage area and allows for more even distribution of the nozzles, ensuring consistent rainfall across the top of the test chamber 1 and avoiding uneven ground moisture caused by localized water volume differences. The nozzles disperse the water into droplets, simulating the splashing effect of natural rainfall. This prevents the pipes from directly scouring the ground surface and ensures that the ground infiltration process is consistent with actual conditions. In this embodiment, by replacing nozzles with different apertures or adjusting the flow rate of the rain pump 204, various rainfall intensities, such as light rain and heavy rain, can be simulated to meet the needs of multiple operating conditions. The flexible connection of the hose 201 provides flexible adjustment space, facilitating debugging of the rainfall distribution mechanism.

[0040] Specifically, the outlet end of the water inlet pipeline 3 is divided into several first branch pipes 301, each of which is connected to an independent first valve 302. The water inlet pipeline 3 is connected to a first flowmeter 303 and a first water pump 304 in sequence along the direction of water flow. The outlet end of each first branch pipe 301 is connected to multiple first seepage branch pipes 305 at different heights and directions of the test box 1. The outlet ends of multiple first seepage branch pipes 305 are connected to the test box 1 and are located in the simulated stratum 101 above the segment identification port 103. The water inlet pipeline 3 achieves accurate simulation of the multi-dimensional seepage field of groundwater through the layered design of the first branch pipes 301 and the directional design of the seepage branch pipes. Each first branch pipe 301 corresponds to multiple first seepage branch pipes 305, and the flow rate of each first branch pipe 301 can be adjusted by the first water pump 304 to simulate the water pressure gradient at different depths of the stratum and restore the layered seepage characteristics of groundwater in the actual stratum. As a preferred solution, three first branch pipes 301 are provided in the embodiment, each first branch pipe 301 is connected to four first seepage branch pipes 305 respectively, and connected to the test box 1 in two groups at different heights, wherein the two first seepage branch pipes 305 in each group are located at the same height.

[0041] Similar to the inlet pipe 3, the outlet pipe 4 branches out from its inlet end into several second branch pipes 401. Each second branch pipe 401 is connected to an independent second valve 402. A second flowmeter 403 is also connected to the outlet pipe 4. The inlet end of each second branch pipe 401 is connected to multiple second seepage branch pipes 404 at different heights and directions within the test chamber 1. The inlet ends of these multiple second seepage branch pipes 404 are connected to the test chamber 1 and are located within the simulated stratum 101 below the segment identification port 103.

[0042] Specifically, the number and position of the first seepage branch pipe 305 and the second seepage branch pipe 404 correspond to each other. When performing a unilateral seepage simulation, the first valve 302 and the second valve 402 in the non-target area are closed, and only the first valve 302 and the second valve 402 corresponding to the two sides of the test box 1 are opened to form a directional horizontal seepage field. The pipe sections of the first seepage branch pipe 305 and the second seepage branch pipe 404 located in the test box 1 are evenly distributed with seepage holes 8 to ensure that water flows evenly from the water inlet pipe 3 to the simulated stratum 101 or seeps into the water outlet pipe 4 from the simulated stratum 101 in multiple directions. When the seepage holes 8 of multiple seepage branches at different heights act synchronously, osmotic water pressure can be simultaneously generated at multiple depths throughout the simulated stratum 101, or multiple parallel horizontal seepage channels can be formed, thereby simulating a complex groundwater flow field environment with vertical stratification distribution inside the stratum 101.

[0043] Therefore, the outlet pipe 4 and the inlet pipe cooperate with each other, and by adjusting the first valve 302, the second valve 402 and the first water pump 304, a directional horizontal seepage field, a vertical seepage field from shallow to deep and a non-uniform seepage field can be formed. Moreover, on the basis of the vertical seepage field, the rainfall distribution mechanism is started to the intensity of heavy rain, so that the surface infiltration water flow and the underground vertical seepage flow act in the opposite direction, and a reverse coupling simulation of the heavy rain period and the underground seepage can be performed. In this embodiment, there is no need to disassemble the pipeline, and the test conditions can be switched by opening and closing the valves and water pumps, which improves the test efficiency. The first branch pipe 301 and the second branch pipe 401 in the embodiment are closed structures near the end of the test box 1, and only the first seepage branch pipe 305 and the second seepage branch pipe 404 are deep in the test box 1.

[0044] Specifically, the test chamber 1 is a transparent box, allowing for easy observation of the test status within. A water level rise space 9 is provided within the transparent box, located above the simulated stratum 101, to simulate the reverse coupling process of underground seepage during a rainstorm. The tops of the inlet tank 5 and the water storage tank 7 are equipped with removable sealing covers 10 to facilitate filling and draining.

[0045] Example 2

[0046] This embodiment provides a model test method for simulating the floating of a subway tunnel segment during operation. The method uses the model test apparatus in the first embodiment and includes the following steps:

[0047] Step 1: Lay the simulated stratum 101 in layers in the test box 1 to the height of the segment identification port 103, specifically the horizontal line at the bottom of the segment identification port 103, install the simulated segment structure 102 and arrange the displacement and pressure monitoring device, continue to fill the simulated stratum 101 to the preset height, and compact it to the designed density.

[0048] Step 2: After the simulated formation 101 has been allowed to stabilize for at least 24 hours, the first valve 302 on each first branch pipe 301 is opened, and a target flow rate is set for the first water pump 304. Simultaneously, the second valve 402 on each second branch pipe 401 is opened until the readings of the first and second flow meters stabilize, thereby establishing a steady-state seepage field. This steady-state seepage field provides a constant initial stress environment for the simulated segment structure 102, ensuring that subsequent test data changes are only affected by the preset operating conditions.

[0049] Step 3: Perform a seepage simulation test. The displacement and pore pressure of the simulated segment structure 102 are collected in real time through the displacement and pressure monitoring device to study the effects of different seepage paths and rainfall on the seepage field. In this embodiment, seepage simulations of multiple research directions can be performed, including single-sided seepage simulation, vertical seepage-dominated simulation, reverse coupling simulation of rainstorm period and underground seepage, and spatial non-uniform seepage simulation.

[0050] When conducting unilateral seepage simulation, the first valve 302 and the second valve 402 in the non-target area are closed, and only the first valve 302 and the second valve 402 corresponding to the two sides of the test box 1 are opened to form a directional horizontal seepage field. The influence of horizontal seepage on the lateral pressure and displacement of the tunnel segment is studied, and the working condition of the tunnel passing through the unidirectional aquifer is simulated, which can provide data for the lateral anti-floating design of the tunnel segment.

[0051] When performing vertical seepage-dominated simulation, the flow rate of the first water pump 304 is adjusted so that the reading of the first flow meter 303 is greater than the reading of the second flow meter 403, forming a vertical seepage field from shallow to deep, simulating the vertical buoyancy effect of groundwater infiltration from shallow to deep on the tunnel segments, and analyzing the influence of the vertical hydraulic gradient of the stratum on the buoyancy of the tunnel segments.

[0052] When conducting reverse coupling simulation of rainstorm period and underground seepage, based on the vertical seepage field, the rainfall water distribution mechanism is started, and the flow rate is adjusted to the rainstorm intensity by controlling the rainfall pump 204, so that the surface infiltration water flow and the underground vertical seepage flow act in the opposite direction, reproducing the combined effect of surface infiltration and groundwater seepage on the tunnel segments under extreme rainfall conditions, studying the floating risk under severe or extreme weather conditions, and providing a test basis for the formulation of emergency plans.

[0053] When performing spatially non-uniform seepage simulations, the first valve 302 and the second valve 402 are differentially adjusted to control the flow rates of the first seepage branch 305 and the second seepage branch 404 at different locations, thereby constructing a non-uniform seepage field with a sudden change in spatial head gradient. For example, when simulating a high-permeability stratum area, the corresponding valve opening is increased to increase the flow rate of this branch; when simulating a low-permeability stratum area, the corresponding valve opening is decreased to limit the flow rate of this branch, thereby constructing a non-uniform seepage field with a sudden change in spatial head gradient. This seepage field primarily simulates the asymmetric seepage environment caused by permeability differences in stratum 101 or local water supply, and is used to analyze the non-uniform stress characteristics of the tunnel segments under these complex hydraulic conditions. The spatially non-uniform seepage field primarily simulates the asymmetric seepage field caused by permeability differences in stratum 101 or local water supply, and is used to analyze the stress characteristics of the tunnel segments under these complex hydraulic conditions.

[0054] Step 4: To prevent residual water from affecting subsequent operations, close the first valve 302 on the first branch pipe 301 and drain the water in the test box 1 into the water storage tank 7 until the second flow meter 403 returns to zero, and the test is completed.

[0055] Therefore, the model test device and method of the present invention reproduced four typical disaster conditions: unilateral seepage, vertical seepage dominance, reverse coupling with underground seepage during heavy rain, and spatial non-uniform seepage, providing a reliable model test basis for studying the floating mechanism of tunnel segments during operation and evaluating corresponding protective measures.

[0056] The above detailed description of the specific embodiments of the present invention is provided in conjunction with the drawings, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations of these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. A model test device for simulating the floating of subway tunnel segments during operation, characterized by: It includes a groundwater seepage system, a test chamber (1) and a drainage recovery system connected in sequence along the water flow direction; The top of the test box (1) is open and the interior is filled with a simulated stratum (101), a simulated segment structure (102) is pre-buried in the simulated stratum (101), a displacement and pressure monitoring device is connected to the simulated segment structure (102), and a segment identification port (103) is provided on the side wall of the test box (1), and the segment identification port (103) corresponds to the area of ​​the simulated segment structure (102); The top open area of ​​the test box (1) is covered with a rainfall water distribution mechanism; the groundwater seepage system includes a water inlet tank (5), the water inlet tank (5) is connected to the test box (1) through a water inlet pipe (3), and the water outlet end of the water inlet pipe (3) is located in the simulated stratum (101) above the pipe segment identification port (103); the drainage recovery system includes a water storage tank (7), the water storage tank (7) is connected to the test box (1) through a water outlet pipe (4), and the water inlet end of the water outlet pipe (4) is located in the simulated stratum (101) below the pipe segment identification port (103); The water outlet of the water inlet pipe (3) is divided into a plurality of first branch pipes (301), each of which is connected to an independent first valve (302), and the water inlet pipe (3) is sequentially connected to a first flow meter (303) and a first water pump (304) along the water flow direction; the water outlet of each of the first branch pipes (301) is connected to a plurality of first seepage branch pipes (305) along different heights and directions of the test box (1), and the water outlets of the plurality of first seepage branch pipes (305) are connected to the inside of the test box (1) and are located in the simulated stratum (101) above the segment identification port (103); The water inlet end of the water outlet pipe (4) is divided into a plurality of second branch pipes (401), each of which is connected to an independent second valve (402), and the water outlet pipe (4) is connected to a second flow meter (403); the water inlet end of each of the second branch pipes (401) is connected to a plurality of second seepage branch pipes (404) along different heights and directions of the test box (1), and the water inlet ends of the plurality of second seepage branch pipes (404) are connected to the inside of the test box (1) and are located in the simulated stratum (101) below the segment identification port (103).

2. The model test device for simulating the floating of a subway tunnel segment during operation according to claim 1, characterized in that: The rainfall water distribution mechanism comprises a continuous U-shaped rainfall pipe (6), the U-shaped rainfall pipe (6) is connected to the lower part of the water inlet tank (5) through a rainfall pipeline (2), a plurality of nozzles are evenly distributed at the bottom of the U-shaped rainfall pipe (6), the rainfall pipeline (2) is connected to the test box (1) through a hose (201), and a rainfall valve (202), a rainfall flow meter (203), and a rainfall water pump (204) are sequentially connected to the rainfall pipeline (2) along the water flow direction.

3. The model test device for simulating the floating of a subway tunnel segment during operation according to claim 1, characterized in that: The number and position of the first seepage branch pipe (305) and the second seepage branch pipe (404) correspond to each other, and the pipe sections of the first seepage branch pipe (305) and the second seepage branch pipe (404) located in the test box (1) are evenly distributed with seepage holes (8).

4. The model test device for simulating the floating of a subway tunnel segment during operation according to claim 1, characterized in that: The test box (1) is a transparent box body, wherein a water level rising space (9) is provided in the transparent box body above the simulated stratum (101), and an openable sealing cover (10) is provided on the top of the water inlet tank (5) and the water storage tank (7).

5. A model test method for simulating the floating of subway tunnel segments during operation, characterized in that: A model test device for simulating the floating of a subway tunnel segment during operation according to any one of claims 1 to 4 is used, wherein the method comprises the following steps: Step 1: Lay the simulated stratum (101) in layers in the test box (1) to the height of the segment identification port (103), install the simulated segment structure (102) and arrange the displacement and pressure monitoring device, continue to fill the simulated stratum (101) to a preset height, and compact it to the designed density; Step 2: After the simulated formation (101) is allowed to stand for at least 24 hours and stabilize, the first valve (302) on each first branch pipe (301) is opened, and a target flow rate is set for the first water pump (304). At the same time, the second valve (402) on each second branch pipe (401) is opened until the readings of the first flow meter and the second flow meter are stable. Step 3, performing at least one seepage simulation, collecting the displacement and pore pressure of the simulated segment structure (102) in real time through a displacement and pressure monitoring device, so as to study the effects of different seepage paths and rainfall on the seepage field; Step 4, close the first valve (302) on the first branch pipe (301), and drain the water in the test box (1) into the water storage tank (7) until the second flow meter (403) reads zero, thus ending the test.

6. The model test method for simulating the floating of a subway tunnel segment during operation according to claim 5, characterized in that: In step 3, the seepage simulation includes unilateral seepage simulation, vertical seepage dominant simulation, reverse coupling simulation of rainstorm period and underground seepage, and spatial non-uniform seepage simulation, wherein, When performing a unilateral seepage simulation, the first valve (302) and the second valve (402) in the non-target area are closed, and only the first valve (302) and the second valve (402) corresponding to both sides of the test box (1) are opened to form a directional horizontal seepage field; When performing vertical seepage-dominated simulation, the flow rate of the first water pump (304) is adjusted so that the reading of the first flow meter (303) is greater than the reading of the second flow meter (403), thereby forming a vertical seepage field from shallow to deep; When conducting reverse coupling simulation of rainstorm period and underground seepage, based on the vertical seepage field, the rainfall distribution mechanism is activated to the rainstorm intensity, so that the surface infiltration flow and the underground vertical seepage flow act in the opposite direction; When performing spatial non-uniform seepage simulation, the first valve (302) and the second valve (402) are differentially adjusted to control the flow of the first seepage branch (305) and the second seepage branch (404) at different positions, thereby constructing a non-uniform seepage field with a sudden change in spatial water head gradient.

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