Centrifuge model test-based method and system for evaluating impact of groundwater level fluctuations on metro station safety, and storage medium

Abstract

Provided is a centrifuge model test-based method for evaluating the impact of groundwater level fluctuations on metro station safety. In a centrifuge test model, after a centrifuge reaches a preset centrifuge acceleration value and operates stably for a period of time, the stress, strain, deformation and displacement of a metro station structure are recorded as first state data of the metro station structure; and a test water level is repeatedly raised and lowered, corresponding state data is recorded, and comparative analysis is performed on multiple sets of state data to analyze the impact of groundwater level fluctuations on the uplift resistance and structural safety of a metro station.

Description

A method, system, and storage medium for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests. Technical Field

[0001] This invention relates to the field of groundwater level fluctuation research, and more specifically to an analysis of the impact of groundwater level fluctuations on the buoyancy stability of subway station structures based on centrifugal model tests. The analysis examines the upward deformation and failure modes of structures under different water level conditions. Background Technology

[0002] Many cities around the world have experienced significant changes in groundwater levels, such as Tokyo, Japan, and some cities in my country, where groundwater levels have dropped sharply and then rebounded sharply.

[0003] In the late 1970s, the groundwater level in a certain city in my country was generally less than 10 meters below the surface, indicating abundant water resources. With rapid economic and social development, coupled with the city experiencing its longest consecutive dry year in history at the beginning of the 21st century, groundwater extraction increased significantly, and the average groundwater depth dropped to approximately 25 meters. This prolonged decline in the groundwater level led to a series of ecological and geological disasters, including river drying up, wetland disappearance, groundwater pollution, and accelerated land subsidence, resulting in heavy costs. To address these problems, the city implemented a series of groundwater restoration measures, such as groundwater extraction reduction policies and the introduction of water diversion projects. With the gradual implementation of these measures, the groundwater level rebounded significantly. However, it is possible that the groundwater level may decline again due to other factors.

[0004] The rise and fall of groundwater can have adverse effects on existing underground structures, especially subway projects located in areas of fluctuating groundwater levels. These projects may face risks such as uplift and structural instability, as well as subsidence and cracking. However, the extent to which groundwater level fluctuations cause damage to subway projects is not yet clear. Conducting large-scale physical experiments and prototype observations is severely constrained by site conditions, and the time and economic costs are enormous.

[0005] For most geotechnical structures, their stress state and deformation characteristics largely depend on the gravity they experience, especially for tall earth and rock structures, where gravity determines their stress-deformation characteristics. A geotechnical centrifuge can provide an artificial high-gravity field, reproducing the properties of the prototype in a model geotechnical structure.

[0006] This invention utilizes the hypergravity field created by a centrifuge to achieve stress similarity between a small-scale model and the prototype structure, offering the advantage of simulating the prototype using a small model. It provides advantages such as accurately simulating the gravity field of the structure and foundation, ensuring that the model materials bear the same stress level as the prototype structure; saving material space by studying large-scale prototype problems on a small model; and a relatively short experimental cycle. Summary of the Invention

[0007] In view of this, the present invention provides a method, system and storage medium for evaluating the impact of groundwater level changes on the safety of subway stations based on centrifugal model tests. The aim is to assess and analyze the comprehensive impact of groundwater level changes on the structure of subway stations, and to explore the impact of groundwater level rise on the buoyancy and deformation of subway stations by simulating the dynamic changes of groundwater level.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests includes the following steps:

[0010] The subway station model is placed within the foundation model. The thickness of each stratum in the foundation model is determined by scaling down according to the actual stratum conditions, and the dimensions of the subway station model are also determined accordingly based on the scale. Simultaneously, considering the similarity in weight (similarity relationships are attached), steel or aluminum is used instead of concrete, steel bars, etc., to replace the concrete and steel reinforcement materials used in the subway station. Using metal materials to make the subway station model can compensate for the difficulty of making small-sized models from concrete.

[0011] The subway station model is buried at a certain depth, with the foundation soil at the bottom and the overlying soil at the top. One side of the subway station model is close to the transparent window of the model box, and the other side of the subway station model is in close contact with the transparent window of the model box. Lubricating materials such as silicone oil are applied between them to reduce the friction between the station model and the transparent window.

[0012] Acquire relevant data of subway stations at different water levels, and construct a centrifugal test model of the foundation and subway station based on the basic principle of the centrifugal model and the relevant data of the subway station.

[0013] In the centrifuge test model, the initial water level is set, the centrifuge is started, and after the preset centrifuge acceleration value is reached and the centrifuge runs stably for a period of time, the force, strain, deformation and displacement of the subway station structure are recorded as the first state data of the subway structure.

[0014] Gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure;

[0015] By comparing and analyzing the data from the second state with the data from the first state, we can determine the impact of rising groundwater levels on the structural safety, buoyancy stability, and other influencing factors of subway stations.

[0016] The water level was gradually lowered to the predetermined low test water level, and the third state data of the subway station structure was recorded. The third state data was compared and analyzed with the first and second state data to analyze the impact of groundwater drop on the structural safety of the subway station.

[0017] The water level was repeatedly raised and lowered to test the water level, and the corresponding status data was recorded. The data from multiple tests were compared and analyzed to determine the impact of groundwater level fluctuations on the buoyancy resistance and structural safety of subway stations.

[0018] Optionally, a multi-method coupled measurement method combining contact, image, and laser techniques can be used to measure the deformation and displacement of a subway station model and soil. The contact measurement method employs a linear displacement sensor (LVDT displacement sensor), the image measurement method uses particle image velocimetry (PIV), and the laser displacement measurement uses a laser displacement sensor.

[0019] During the raising and lowering of the water level, and after reaching the preset water level, the following displacements were measured:

[0020] One end of a linear displacement sensor is fixed to the top of the subway station model, passing through the overlying soil of the station model, and the other end is fixed to a crossbeam fixed to the top of the model box. The displacement change value of the linear displacement sensor is used to analyze the rise and fall of the station model caused by the change of water level inside the model.

[0021] A laser displacement sensor was used to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and a particle image velocimetry device was used to monitor the displacement of the soil and the subway station model from the front of the transparent window of the model box. The deformation of the station model and the foundation soil was analyzed based on the analysis.

[0022] Laser displacement sensors are used to measure the deformation of the soil on the upper surface of the model, which indirectly reflects the displacement and deformation of the subway station model.

[0023] Optionally, pore water pressure gauges are placed in the soil in all directions of the groundwater and subway centrifuge test model to monitor pore water pressure and obtain the water level value in the model through pore water pressure, and then calculate the buoyancy of the model station; earth pressure gauges are placed in the middle section of the station of the groundwater and subway centrifuge test model to monitor the pressure of the station in all directions; strain gauges are placed on the four walls of the station of the groundwater and subway centrifuge test model to monitor the stress change of the station during the centrifuge test.

[0024] Optionally, the control signals and signal acquisition of the centrifuge are transmitted via digital fiber optics.

[0025] Optionally, when the ratio of the size of the subway prototype to the size of the groundwater and the subway centrifuge test model is n, the centrifuge acceleration a m for:

[0026] In the formula: L p For prototype dimensions; L m denoted as the model size; g represents the acceleration due to gravity.

[0027] An impact assessment system for groundwater level fluctuations on subway station safety based on centrifugal model tests includes:

[0028] Groundwater and subway centrifuge test model construction module: used to obtain relevant data of subway stations at different water levels, and construct a centrifuge test model of the foundation and subway station based on the basic principle of the centrifuge model and the relevant data of the subway station.

[0029] First-state data acquisition module: used to set the initial water level in the centrifuge test model, start the centrifuge, reach the preset centrifuge acceleration value and run stably for a period of time, and record the force, strain, deformation and displacement of the subway station structure, which are recorded as the first-state data of the subway structure.

[0030] Second state data acquisition module: used to gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure;

[0031] Groundwater level rise evaluation module: used to compare and analyze the second state data with the first state data to determine the impact of groundwater level rise on the structural safety, anti-buoyancy stability and other influencing factors of subway station structure;

[0032] The third-state data acquisition module is used to gradually lower the water level to a predetermined low test water level, record the third-state data of the subway station structure, compare and analyze the third-state data with the first and second-state data, and analyze the impact of groundwater drop on the structural safety of the subway station.

[0033] Stability and safety evaluation module: used for repeated rising and falling test water levels, recording corresponding status data, comparing and analyzing multiple status data to analyze the impact of groundwater level changes on the buoyancy resistance and structural safety of subway stations.

[0034] Optionally, the rise and fall of the groundwater level in the metro centrifugal test model can be controlled by supplying and discharging water into and from the water tank, and by air pressure.

[0035] Optionally, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge. The connecting steel pipe and the explosion-proof water pipe on the centrifuge are connected to the bottom of the model box. The flow rate is set, and the water level in the model box is controlled by a control valve.

[0036] Optionally, a laboratory water pump injection system is used to pump water from underground to the centrifuge. Explosion-proof hoses are connected to the explosion-proof water pipes on the centrifuge. The explosion-proof hoses are connected to the bottom of the model box through the side wall, and then connected to a T-connector 40mm from the bottom. Plastic hoses are connected to both sides of the T-connector and then connected in parallel to the T-connector to form multiple channels. Plastic hoses are connected to the vertical outlets of each T-connector, arranged along the vertical direction of the model box. The water pipes are 650mm long, and the outlets of the plastic water pipes are sealed with stop valves. Holes are drilled at 50mm intervals in the vertically arranged water pipes, for a total of 13 holes with a hole diameter of 3mm. The hole diameter is kept consistent to ensure that the water seeps out evenly from the small holes. The flow rate is set by controlling the valve to control the uniform rise of the water level in the model box. The hose arrangement position, number of holes, and hole diameter are adjusted according to the simulated groundwater level position and change rate. The hose arrangement position is raised or lowered, and the number of holes and hole diameter are increased or decreased.

[0037] A computer storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of any one of the methods described above for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests are implemented.

[0038] As can be seen from the above technical solution, compared with the prior art, the present invention provides a method, system, and storage medium for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests, which has the following beneficial effects:

[0039] 1. By constructing a centrifugal test model of groundwater and subway systems, the impact of groundwater level fluctuations on subway stations and their tunnel structures can be accurately simulated. This method takes into account the actual changes in groundwater levels and the stress characteristics of subway structures under complex geological conditions, thus providing more accurate prediction results.

[0040] 2. By gradually raising the water level to different predetermined test heights and recording the stress data of the subway and tunnel structures, the impact of groundwater level changes on subway station safety can be dynamically analyzed. This method can capture subtle changes in the stress on the subway station structure during water level changes, helping to promptly identify potential safety hazards.

[0041] 3. Simulating actual gravity conditions using a centrifuge can further verify the stability and safety of the subway station structure under gravity. This helps to more accurately assess the stress and safety performance of the subway station structure during actual operation. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0043] Figure 1 is a schematic diagram of the process of the present invention;

[0044] Figure 2 is a schematic diagram of the structure of the present invention;

[0045] Figure 3a is a schematic diagram of the tunnel centrifugal model test of the present invention;

[0046] Figure 3b is a schematic diagram of the tunnel centrifugal model test of the present invention;

[0047] Figure 4 is a schematic diagram of the subway station test of the present invention;

[0048] Figure 5a is a schematic diagram of the groundwater level simulation hydraulic chamber of the present invention;

[0049] Figure 5b is a schematic diagram of the hydraulic chamber pipeline for simulating groundwater level according to the present invention; Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] This invention discloses a method for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests, comprising the following steps:

[0053] The subway station model is placed within the foundation model. The thickness of each stratum in the foundation model is determined by scaling down according to the actual geological conditions, and the dimensions of the subway station model are also determined accordingly. Furthermore, considering the similarity in weight (similarity relationships are attached), steel or aluminum is used instead of concrete and reinforcing steel in the subway station model. Using metal materials to construct the subway station model can compensate for the difficulty of using concrete to create small-sized models.

[0054] The subway station model is buried at a certain depth, with the foundation soil at the bottom and the overlying soil at the top. One side of the subway station model is close to the transparent window of the model box, and the other side of the subway station model is in close contact with the transparent window of the model box. Lubricating materials such as silicone oil are applied between them to reduce the friction between the station model and the transparent window.

[0055] Step 1: Obtain relevant data of subway stations at different water levels, and construct a centrifugal test model of the foundation and subway station based on the basic principle of the centrifugal model and the relevant data of the subway stations.

[0056] Step 2: Set the initial water level in the centrifuge test model, start the centrifuge, and after the preset centrifuge acceleration value is reached and the centrifuge runs stably for a period of time, record the force, strain, deformation, and displacement of the subway station structure, which are recorded as the first state data of the subway structure.

[0057] Step 3: Gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure;

[0058] Step 4: Compare and analyze the data from the second state with the data from the first state to determine the impact of rising groundwater levels on the structural safety, buoyancy stability, and other influencing factors of the subway station.

[0059] Step 5: Gradually lower the water level to the predetermined low test water level, record the third state data of the subway station structure, compare and analyze the third state data with the first and second state data, and analyze the impact of groundwater drop on the structural safety of the subway station.

[0060] Step 6: Repeatedly raise and lower the water level test and record the corresponding status data. Compare and analyze the multiple status data to analyze the impact of groundwater level changes on the buoyancy resistance and structural safety of the subway station.

[0061] Furthermore, in step three, during the process of raising the water level, a laser displacement sensor is used to monitor the vertical displacement of the soil and station structure from above, and a particle image velocimetry device is used to monitor the soil displacement from the transparent front of the model box to determine the soil displacement situation.

[0062] A multi-method coupled measurement approach, incorporating contact, image, and laser techniques, is used to measure the deformation and displacement of a subway station model and its soil. The contact measurement method utilizes a linear low-light displacement sensor (LVDT), the image measurement method employs particle image velocimetry (PIV), and the laser displacement measurement utilizes a laser displacement sensor.

[0063] During the raising and lowering of the water level, and after reaching the preset water level, the following displacements were measured:

[0064] One end of a linear displacement sensor is fixed to the top of the subway station model, passing through the overlying soil of the station model, and the other end is fixed to a crossbeam fixed to the top of the model box. The displacement change value of the linear displacement sensor is used to analyze the rise and fall of the station model caused by the change of water level inside the model.

[0065] A laser displacement sensor was used to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and a particle image velocimetry device was used to monitor the displacement of the soil and the subway station model from the front of the transparent window of the model box. The deformation of the station model and the foundation soil was analyzed based on the analysis.

[0066] Laser displacement sensors are used to measure the deformation of the soil on the upper surface of the model, which indirectly reflects the displacement and deformation of the subway station model.

[0067] Furthermore, in steps three and four, pore water pressure gauges are placed in the soil in each direction of the groundwater and subway centrifugal test model to monitor pore water pressure and obtain the water level value in the model, thereby calculating the buoyancy force on the model station; earth pressure gauges are placed in the middle section of the station of the groundwater and subway centrifugal test model to monitor the pressure on the station in each direction; strain gauges are placed on the four walls of the station of the groundwater and subway centrifugal test model to monitor the stress changes of the station during the centrifugal test.

[0068] In step four, the control signals and signal acquisition of the centrifuge are transmitted via digital optical fiber.

[0069] Furthermore, when the ratio of the size of the subway prototype to the size of the groundwater and the subway centrifuge test model is n, the centrifuge acceleration a m for:

[0070] In the formula: L p For prototype dimensions; L m denoted as the model size; g represents the acceleration due to gravity.

[0071] When a prototype model of size 1 / n is placed in a centrifugal gravitational field of size ng, and the self-weight of the prototype model is increased by a factor of n, the stress at each point in the prototype model is the same as the stress at the corresponding point in the prototype model. This is the similarity law of centrifuge model testing. Table 1 lists the similarity laws of the main parameters of centrifuge model testing.

[0072] Table 1 Similarity Laws of Centrifugation Model Tests

[0073] The centrifuge used in this embodiment is the LXJ-4-450 450g-ton geotextile centrifuge. The LXJ-4-450 450g-ton geotextile centrifuge from the China Institute of Water Resources and Hydropower Research has a maximum rotation radius of 5.03m, a maximum acceleration of 300g, an effective load of 1.5ton, and an effective load capacity of 450g-ton. It is driven by a DC motor with a power of 700kW. The test basket dimensions are 1.5m × 1.0m × 1.5m. At its inception, its equipment scale was the largest in Asia and the fourth largest in the world. Even today, it remains one of the largest centrifuges in China, capable of simulating geotechnical engineering projects such as 150-meter-class high earth-rock dams, 150-meter-class high slopes, and 150-meter-class underground caverns. The LXJ-4-450 large geotextile centrifuge adopts a symmetrical rotating arm, double baskets, and double swing mechanism. The main unit has a reasonable structure, runs smoothly, has a speed regulation accuracy of 0.1%, and is equipped with a safety monitoring system. All control and signal acquisition of the centrifuge are achieved through digital fiber optic transmission. It is equipped with an advanced data acquisition system and high-precision sensors, including a high-precision low-speed acquisition instrument (24-bit high-precision AD), a high-density high-speed acquisition instrument (maximum sampling rate 250MHz), a fiber optic signal acquisition instrument, a high-definition (4800 pixels × 3400 pixels) and high-speed (4000 frames / second) image acquisition system, and a PIV analysis system. It can collect and process information such as soil pressure, pore water pressure, temperature, acceleration, and displacement in real time, and can meet the signal acquisition needs of various static and dynamic processes such as vibration, impact, and explosion.

[0074] As shown in Figures 5a and 5b, the laboratory is specially designed and manufactured to simulate groundwater fluctuations in soil samples. A water tank is installed at the bottom of the laboratory, below the soil sample. A perforated flow channel is provided between the water tank and the soil sample to allow water to flow in and out during groundwater level fluctuations. A metal mesh and geotextile are placed below the soil sample to prevent particle movement and maintain a uniform water flow. The rise and fall of the groundwater level are controlled by supplying and discharging water into the tank, and by air pressure.

[0075] Particle image velocimetry (PIV) is a non-contact optical flow measurement technique used to measure the distribution and changes in velocity in fluids such as air and water. PIV technology provides instantaneous velocity and turbulence characteristics of the flow field by tracking the movement of tiny suspended particles in the fluid. PIV analysis systems are widely used in fluid mechanics, environmental science, engineering experiments, and biomedical engineering. Specifically, the camera should be 20cm horizontally from the model box and 15cm high from the bottom of the model box. The camera should be calibrated on-site depending on the lighting conditions and the camera's focusing distance. The camera should be able to clearly and completely capture the model, including the soil, strip foundation, and some hydraulic rods. Colored lines are used as markers. The color lines are layered. The color of the lines is initially bright red, but other colors can be selected based on the sensitive hue of the PIV camera, ensuring accurate identification. The color line paint should be a low-water-soluble paint to prevent diffusion during soil drainage.

[0076] During groundwater level fluctuations, displacement tracking image analysis technology is used to monitor the movement of particles inside the sample.

[0077] Corresponding to the method shown in Figure 1, this invention also discloses an impact assessment system for groundwater level fluctuations on subway station safety based on centrifugal model tests, used to implement the method in Figure 1. The specific structure is shown in Figure 2, including:

[0078] Groundwater and subway centrifuge test model construction module: used to obtain relevant data of subway stations at different water levels, and construct a centrifuge test model of the foundation and subway station based on the basic principle of the centrifuge model and the relevant data of the subway station.

[0079] First-state data acquisition module: used to set the initial water level in the centrifuge test model, start the centrifuge, reach the preset centrifuge acceleration value and run stably for a period of time, and record the force, strain, deformation and displacement of the subway station structure, which are recorded as the first-state data of the subway structure.

[0080] Second state data acquisition module: used to gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure;

[0081] Groundwater level rise evaluation module: used to compare and analyze the second state data with the first state data to determine the impact of groundwater level rise on the structural safety, anti-buoyancy stability and other influencing factors of subway station structure;

[0082] The third-state data acquisition module is used to gradually lower the water level to a predetermined low test water level, record the third-state data of the subway station structure, compare and analyze the third-state data with the first and second-state data, and analyze the impact of groundwater drop on the structural safety of the subway station.

[0083] Stability and safety evaluation module: used for repeated rising and falling test water levels, recording corresponding status data, comparing and analyzing multiple status data to analyze the impact of groundwater level changes on the buoyancy resistance and structural safety of subway stations.

[0084] Furthermore, the rise and fall of the groundwater level in the groundwater centrifugal test model of the subway is controlled by supplying and discharging water into and out of the water tank, and by air pressure.

[0085] Furthermore, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge. The connecting steel pipe and the explosion-proof water pipe on the centrifuge are connected to the bottom of the model box. The flow rate is set, and the water level in the model box is controlled by a control valve.

[0086] Furthermore, a laboratory water pump injection system was used to pump water from underground to the centrifuge. Explosion-proof hoses were connected to the explosion-proof water pipes on the centrifuge. These hoses connected to the bottom of the model box via the side wall, and then to a T-connector 40mm from the bottom. Plastic hoses were connected to both sides of the T-connector and then linked in parallel to form multiple channels. Plastic hoses were connected to the vertical outlets of each T-connector, arranged vertically along the model box. The water pipes were 650mm long, and stop valves were used to stop the water flow at the outlets. Holes were drilled at 50mm intervals along the vertically arranged water pipes, totaling 13 holes with a diameter of 3mm. Maintaining a consistent hole diameter ensured uniform water seepage from the small holes. The flow rate was controlled by a valve to regulate the uniform rise of the water level inside the model box. The hose placement, number of holes, and hole diameters were adjusted based on the simulated groundwater level and its rate of change. The hose placement was adjusted by raising or lowering the hoses, and the number and diameter of holes were adjusted accordingly.

[0087] Furthermore, the rise and fall of the groundwater level in the groundwater centrifugal test model of the subway is controlled by supplying and discharging water into and out of the water tank, and by air pressure.

[0088] Furthermore, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge. The connecting steel pipe and the explosion-proof water pipe on the centrifuge are connected to the bottom of the model box. The flow rate is set, and the water level in the model box is controlled by a control valve.

[0089] This embodiment uses a laboratory water pump injection system to pump water from underground to the centrifuge. Explosion-proof hoses are connected to the explosion-proof water pipes on the centrifuge. The explosion-proof hoses are connected to the bottom of the model box through the side wall, and 40mm from the bottom, they are connected to a T-connector. Both sides of the T-connector are connected to plastic hoses, which are then connected in parallel to the T-connector to form multiple channels. Plastic hoses are connected to the vertical outlets of each T-connector, arranged along the vertical direction of the model box. The water pipes are 650mm long, and the outlets of the plastic water pipes are sealed with stop valves. Holes are drilled at 50mm intervals in the vertically arranged water pipes, for a total of 13 holes with a hole diameter of 3mm. The consistent hole diameter ensures that the water flows out evenly from the small holes. The flow rate is set by controlling the valve to control the uniform rise of the water level in the model box.

[0090] Data from sensors were collected comprehensively under each water level condition to analyze and evaluate the stress state and stability of the structure under different water levels. Eight laser displacement sensors were used to monitor soil displacement from above. A rigid rod was connected above the station structure, extending beyond the soil surface. A contact platform was constructed at the top of the rod, and six LVDT displacement gauges (maximum stroke 30mm) were placed there to monitor the displacement of the station structure. The distribution of the probe positions is shown in Figure 3a. Particle image velocimetry (PIV) instruments were used to monitor soil displacement from the transparent front of the model box. Seven pore water pressure gauges (range 0-800kPa) were placed in the soil near the model station in various directions to monitor pore water pressure and calculate the buoyancy force on the model station.

[0091] In this embodiment, geotextile is wrapped around the flexible hose to prevent excessive water pressure at the orifice from impacting the foundation soil and causing damage. Simultaneously, the geotextile also prevents foundation soil from clogging the orifice and entering the hose. The pipe diameter and the size and number of orifices can be adjusted according to the required water flow rate. Gravel is used to fill the area around the flexible hose, providing support and reducing the deformation caused by the pressure from the overlying foundation model. This reduces the impact of hose deformation and changes in pipe diameter on water flow.

[0092] Finally, this embodiment discloses a computer storage medium storing a computer program, which, when executed by a processor, implements the steps of any one of the methods for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests.

[0093] Example 2

[0094] The only difference between this embodiment and Embodiment 1 is that:

[0095] As shown in Figures 3a, 3b, and 4, the total mass of the test model = mass of the model box (607 kg) + mass of the soil (1094.86 kg) + weight of the reaction frame and crossbeam (500.33 kg) + weight of the subway tunnel (7.57 kg) = 2209.76 kg

[0096] Assuming the centrifugal field is N times the gravitational acceleration g, i.e., N = prototype size / model size, then the scaling relationship is as follows:

[0097] L p L m These represent the base width of the prototype and the base width of the model, respectively, in meters.

[0098] H p H m These represent the depth of the prototype foundation and the depth of the model foundation, respectively, in meters (m).

[0099] σ p σ m L represents the earth pressure on the prototype foundation and the earth pressure on the model foundation, respectively, in kPa; p =150L mmax =1.2;

[0100] Based on the principle of similarity and considering the length of the prototype and the inner length of the model box, let L be... m =1 The scaling ratio (N) is calculated as:

[0101] The other length dimensions of the station model are reduced synchronously according to the calculated scaling factor.

[0102] Therefore, the centrifuge acceleration (a) is calculated as: a = N·g = 150g;

[0103] During soil preparation, firstly, apply an even layer of oil-based lubricant to the four walls of the model box, then prepare the sample using the sand rain method, in several layers. More specific steps are as follows:

[0104] S1. Soil Sample Arrangement and Compaction: Arrange and compact soil samples in model containers to ensure they are stable and accurately aligned. Place necessary monitoring equipment in the structure and soil layers.

[0105] S2. Set the initial water level and simulate normal groundwater conditions: record the buoyancy and stability of the structure under the initial state.

[0106] S3. Centrifugal Loading and Data Recording: Start the centrifuge to simulate actual gravity conditions. Gradually increase the water level to different predetermined test heights to simulate the rising groundwater level. After each water level adjustment, record the buoyancy changes and responses of the station and tunnel structures.

[0107] S4. Use the laboratory water pump injection system to pump water from underground to the centrifuge, connect the steel pipe to the explosion-proof water pipe on the centrifuge to the bottom of the model box, set the flow rate, and control the rise of the water level in the model box by controlling the valve.

[0108] S5, Water Level Rise: Set the initial water level height to [value], inject water in several stages to reach the desired height, and let it stand for [time] minutes.

[0109] The specific experimental steps are as follows: After hoisting and fixing the prepared test model onto the centrifuge, install and test each monitoring device. At the start of the experiment, the initial water level is [mm]. The centrifugal acceleration is increased stepwise in increments of 25g, in six stages. After each acceleration reaches the set value, the process continues for 10 minutes before moving to the next stage. Once the centrifugal acceleration reaches 150g, the initially set groundwater level is raised. The rate of rise of the groundwater level should meet the actual environmental conditions, i.e., avoid generating excess pore water pressure.

[0110] Under each water level condition, comprehensive sensor data, including buoyancy, pressure, stress, and displacement, were collected to analyze and evaluate the stress state and stability of the structure under different water levels. Two laser displacement sensors were used to monitor the vertical displacement of the soil and station structure from above, and a particle image velocimetry (PIV) instrument was used to monitor soil displacement from the transparent front of the model box. Eleven pore water pressure gauges were placed in the soil near the model station in various directions to monitor pore water pressure and calculate the buoyancy of the model station. Four soil pressure gauges were placed in the middle section of the model station to monitor the pressure on the model station in various directions. Strain gauges were placed on the four walls of the model station to monitor stress changes during centrifugation tests.

[0111] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0112] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the influence of groundwater level fluctuation on the safety of a subway station based on a centrifugal model test, characterized by, Includes the following steps: Acquire relevant data of subway stations at different water levels, and construct a centrifugal test model of the foundation and subway station based on the basic principle of the centrifugal model and the relevant data of the subway station. In the centrifuge test model, the initial water level is set, the centrifuge is started, and after the preset centrifuge acceleration value is reached and the centrifuge runs stably for a period of time, the force, strain, deformation and displacement of the subway station structure are recorded as the first state data of the subway structure. Gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure; By comparing and analyzing the data from the second state with the data from the first state, we can determine the impact of rising groundwater levels on the structural safety, buoyancy stability, and other influencing factors of subway stations. The water level was gradually lowered to the predetermined low test water level, and the third state data of the subway station structure was recorded. The third state data was compared and analyzed with the first and second state data to analyze the impact of groundwater drop on the structural safety of the subway station. The water level was repeatedly raised and lowered to test the water level, and the corresponding status data was recorded. The data from multiple tests were compared and analyzed to determine the impact of groundwater level fluctuations on the buoyancy resistance and structural safety of subway stations.

2. The method for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests according to claim 1, characterized in that, During the raising and lowering of the water level, and after reaching the preset water level, the following displacements were measured: One end of a linear displacement sensor is fixed to the top of the subway station model, passing through the overlying soil of the station model, and the other end is fixed to a crossbeam fixed to the top of the model box; the displacement change value of the linear displacement sensor is used to analyze the rise and fall of the station model caused by the change of water level inside the model; A laser displacement sensor was used to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and a particle image velocimetry device was used to monitor the displacement of the soil and the subway station model from the front of the transparent window of the model box. The deformation of the station model and the foundation soil was analyzed based on the analysis. Laser displacement sensors are used to measure the deformation of the soil on the upper surface of the model, which indirectly reflects the displacement and deformation of the subway station model.

3. The method according to claim 1, characterized in that, Pore ​​water pressure gauges were placed in the soil in all directions of the groundwater and subway centrifuge test model to monitor pore water pressure and obtain the water level value in the model, and then calculate the buoyancy of the model station; earth pressure gauges were placed in the middle section of the station of the groundwater and subway centrifuge test model to monitor the pressure on the station in all directions; strain gauges were placed on the four walls of the station of the groundwater and subway centrifuge test model to monitor the stress change of the station during the centrifuge test.

4. The method according to claim 1, wherein The centrifuge's control signals and signal acquisition are transmitted via digital fiber optics.

5. The method according to claim 1, wherein When the ratio of the prototype size of the subway to the size of the centrifuge test model of the subway and the groundwater is n, the acceleration a of the centrifuge is: m : where: L p is the prototype size; L m is the model size; g is the acceleration of gravity.

6. A system for evaluating the influence of groundwater level fluctuation on the safety of a subway station based on centrifugal model tests, characterized by include: Groundwater and subway centrifuge test model construction module: used to obtain relevant data of subway stations at different water levels, and construct a centrifuge test model of the foundation and subway station based on the basic principle of the centrifuge model and the relevant data of the subway station. First-state data acquisition module: used to set the initial water level in the centrifuge test model, start the centrifuge, reach the preset centrifuge acceleration value and run stably for a period of time, and record the force, strain, deformation and displacement of the subway station structure, which are recorded as the first-state data of the subway structure. Second state data acquisition module: used to gradually raise the water level to the predetermined high test water level and record the second state data of the subway station structure; Groundwater level rise evaluation module: used to compare and analyze the second state data with the first state data to determine the impact of groundwater level rise on the structural safety, anti-buoyancy stability and other influencing factors of subway station structure; The third-state data acquisition module is used to gradually lower the water level to a predetermined low test water level, record the third-state data of the subway station structure, compare and analyze the third-state data with the first and second-state data, and analyze the impact of groundwater drop on the structural safety of the subway station. Stability and safety evaluation module: used for repeated rising and falling test water levels, recording corresponding status data, comparing and analyzing multiple status data to analyze the impact of groundwater level changes on the buoyancy resistance and structural safety of subway stations.

7. The system for evaluating the influence of groundwater level fluctuation on the safety of a subway station based on centrifugal model test according to claim 6, characterized in that, The rise and fall of the groundwater level in the groundwater centrifuge test model of the subway is controlled by supplying and discharging water into the water tank and by air pressure.

8. The system for evaluating influence of groundwater level fluctuation on safety of a subway station based on centrifugal model test according to claim 6, characterized in that, The groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge. The connecting steel pipe and the explosion-proof water pipe on the centrifuge are connected to the bottom of the model box. The flow rate is set, and the water level in the model box is controlled by a control valve.

9. The system for evaluating influence of groundwater level fluctuation on safety of a subway station based on centrifugal model test according to claim 6, characterized in that, A laboratory water pump system was used to pump water from underground to the centrifuge. Explosion-proof hoses were connected to the explosion-proof water pipes on the centrifuge. The explosion-proof hoses were connected to the bottom of the model box through the side wall, and then connected to a T-connector 40mm from the bottom. Plastic hoses were connected to both sides of the T-connector and then connected in parallel to the T-connector to form multiple channels. Plastic hoses were connected to the vertical outlets of each T-connector, arranged along the vertical direction of the model box. The water pipes were 650mm long, and the outlets of the plastic water pipes were sealed with stop valves. Holes were drilled at 50mm intervals in the vertical arrangement of the water pipes, for a total of 13 holes with a diameter of 3mm. The hole diameter was kept consistent to ensure that the water flowed out evenly from the small holes. The flow rate was set and the water level in the model box was controlled by a control valve to rise evenly. The hose arrangement, number of holes, and hole diameter were adjusted according to the simulated groundwater level and its rate of change. The hose arrangement was raised or lowered, and the number of holes and hole diameters were adjusted accordingly.

10. A computer storage medium, characterized in that, The computer storage medium stores a computer program, which, when executed by a processor, implements the steps of the method for evaluating the impact of groundwater level fluctuations on subway station safety based on centrifugal model tests as described in any one of claims 1-5.

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