Method and system for evaluating influence of underground water level change on subway station safety based on centrifugal model test and storage medium

Abstract

The invention discloses a centrifugal model test-based method and system for evaluating the influence of underground water level variation on subway station safety, and a storage medium, and relates to the field of research on the influence of underground water level variation on underground space safety. In the centrifugal test model, after the centrifugal machine accelerates and stably operates for a period of time, the stress, strain, deformation and displacement of the subway station structure are recorded as first state data of the subway structure; gradually raising the water level, and recording second state data of the subway station structure; comparing and analyzing the second state data and the first state data, and judging the structural safety, anti-floating stability and influence factors of the subway station caused by the rising of the underground water level; lowering the water level, recording third state data of the subway station structure, comparing and analyzing the third state data with the first state data and the second state data, and analyzing the influence of underground water drop on the safety of the subway station structure. The invention aims to evaluate and analyze the influence of the underground water level change on the anti-floating and structural safety of the subway station.

Description

Technical Field

[0001] The present invention relates to the field of groundwater level fluctuation research, and more specifically to an analysis of the influence of groundwater level fluctuation on the anti-floating stability of subway station structures based on centrifuge model tests, and analyzes the floating deformation and failure mode of structures under different water level conditions. Background Art

[0002] Many cities around the world have experienced significant changes in groundwater levels. For example, Tokyo, Japan, and some cities in my country have experienced a significant drop and then a significant rise in groundwater levels.

[0003] In the late 1970s, the groundwater level in a certain city in my country was generally buried within 10 meters of the surface, showing rich water resources. With the rapid development of the economy and society, and the longest continuous dry year in history in the city in the early 21st century, the amount of groundwater extraction has increased significantly. The average depth of groundwater in the city has dropped to about 25 meters. This long-term decline in groundwater levels has led to a series of ecological and geological disasters such as river drying up, wetland disappearance, groundwater pollution, and increased ground subsidence, paying a heavy price. To solve these problems, the city began to implement a series of groundwater recovery measures, such as groundwater pressure extraction policies and the introduction of water diversion projects. With the gradual implementation of these measures, groundwater has rebounded significantly. At the same time, it is possible that the groundwater level has dropped due to other reasons.

[0004] The rise and fall of groundwater is likely to have an adverse impact on the space of underground structural engineering, especially for subway projects buried deep in the groundwater level fluctuation zone, which are likely to face risks such as floating and structural instability, as well as subsidence and cracking. However, the damage caused by groundwater level changes to subway projects is not clear at present, and large-scale physical experiments and prototype observations are deeply constrained by the site, and the time and economic costs are also huge.

[0005] For most geotechnical structures, their stress state and deformation characteristics are largely determined by the gravity they are subjected to, especially for high earth-rock buildings, where gravity determines their stress-deformation characteristics. Geotechnical centrifuges can provide an artificial high gravity field to reproduce the properties of the prototype in model geotechnical buildings.

[0006] The present invention uses the super gravity field formed by the centrifuge to achieve similar stress between the small-sized model and the prototype structure, and has the advantage of using a small-sized model to simulate the prototype. It has the advantages of accurately simulating the gravity field of the structure and the foundation, ensuring that the model material bears the same stress level as the prototype structure; studying large-sized prototype problems on a small model, saving material space; and having a relatively short test 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 centrifuge model tests, aiming to evaluate and analyze the comprehensive impact of groundwater level changes on the structure of subway stations, and explore the impact of rising groundwater levels on the buoyancy and deformation of subway stations by simulating the dynamic changes of groundwater levels.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model tests comprises the following steps:

[0010] Arrange the subway station model in the foundation model. The thickness of each layer of the foundation model is determined by scaling down according to the actual stratum conditions and the size of the subway station model is also determined according to the scale relationship. At the same time, the subway station takes into account the similarity of weight (the similarity relationship is attached), and steel or aluminum is used to replace the concrete, steel bars and other materials of the subway station. The use of metal materials to make the subway station model can make up for the deficiency that concrete materials are not easy to make small-sized models.

[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 one side of the subway station model is close to the transparent window of the model box, with lubricating materials such as silicone oil applied in between to reduce the friction between the station model and the transparent window.

[0012] Obtain relevant data of subway stations under different water levels, and construct centrifugal test models of foundation and subway stations based on the basic principles of centrifugal model according to relevant data of subway stations;

[0013] An initial water level is set in the centrifuge test model, and the centrifuge is started. After reaching a preset centrifuge acceleration value and running stably for a period of time, the stress, strain, deformation, and displacement of the subway station structure are recorded as the first state data of the subway structure.

[0014] gradually raising the water level to a predetermined high test water level, and recording the second state data of the subway station structure;

[0015] Compare and analyze the second state data with the first state data to determine the impact of the rising groundwater level on the structural safety, anti-floating stability and other factors of the subway station;

[0016] 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 safety of the subway station structure;

[0017] The test water level is repeatedly raised and lowered, and the corresponding status data is recorded. The multiple status data are compared and analyzed to analyze the impact of groundwater level changes on the anti-floating and structural safety of subway stations.

[0018] Optional, contact, image, laser multi-method coupling measurement method, this method is used to measure the deformation and displacement of subway station models and soil. The contact measurement method is implemented by linear displacement sensor (LVDT displacement sensor), the image measurement method is implemented by particle image velocimetry (PIV) method, and the laser displacement measurement is implemented by laser displacement sensor.

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

[0020] One end of the linear displacement sensor is fixed on the top of the subway station model. The linear displacement sensor passes through the soil covering the station model, and the other end is fixed to the beam fixed on the top of the model box. The floating and sinking of the station model caused by the change of water level in the model is analyzed through the displacement change value of the linear displacement sensor.

[0021] Use laser displacement sensors to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and use particle image velocimetry equipment to monitor the displacement of the soil and subway station model from the front of the transparent window of the model box, based on the deformation analysis of the station model and foundation soil;

[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 centrifugal test model to monitor the pore water pressure and obtain the water level value in the model through the pore water pressure, and then calculate the buoyancy of the model station; soil pressure gauges are placed in the middle section of the station of the groundwater and subway centrifugal test model to monitor the pressure exerted on the station in all directions; 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.

[0024] Optionally, the control signal and signal acquisition of the centrifuge are transmitted using digital optical fiber.

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

[0026]

[0027] Where: L p is the prototype size; L m is the model size; g is the gravitational acceleration.

[0028] A system for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model tests, including:

[0029] Groundwater and subway centrifuge test model construction module: used to obtain subway station related data under different water levels, and build foundation and subway station centrifuge test models based on the basic principles of centrifuge model and subway station related data;

[0030] The first state data acquisition module is used to set the initial water level in the centrifuge test model, start the centrifuge, and after reaching the preset centrifuge acceleration value and running stably for a period of time, record the stress, strain, deformation, and displacement of the subway station structure as the first state data of the subway structure;

[0031] Second state data acquisition module: used to gradually raise the water level to a predetermined high test water level and record the second state data of the subway station structure;

[0032] 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-floating stability and other influencing factors of subway stations;

[0033] 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 safety of the subway station structure;

[0034] Stability and safety evaluation module: used to repeatedly rise and fall the test water level and record the corresponding status data, compare and analyze multiple status data, and analyze the impact of groundwater level changes on the anti-floating and structural safety of subway stations.

[0035] Optionally, the rise and fall of the groundwater level in the groundwater and subway centrifugal test model is controlled by supplying and discharging water to and from the tank and by air pressure.

[0036] Optionally, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge, connect the steel pipe and the explosion-proof water pipe on the centrifuge to the bottom of the model box, set the flow rate, and control the water level rise in the model box by controlling the valve.

[0037] Optionally, use a laboratory water pump injection system to pump water from underground to the centrifuge, use an explosion-proof hose to connect to the explosion-proof water pipe on the centrifuge, the explosion-proof hose is connected to the bottom of the model box through the side wall of the model box, connected to the three-way adapter 40mm from the bottom, the two sides of the three-way adapter are connected to the plastic hose and then connected to the three-way adapter in parallel to form multiple channels, connect a plastic hose to the vertical outlet of each tee, arrange it along the vertical direction of the model box, the water pipe is 650mm long, and the plastic water pipe outlet is stopped by a water stop valve. The vertically arranged water pipes are punched at intervals of 50mm, for a total of 13 holes, and the hole diameter is 3mm. The hole diameter is kept consistent so that water flows out evenly from the small holes. The flow rate is set to control the uniform rise of the water level in the model box by controlling the valve. The hose arrangement position, the number of holes, and the hole diameter are adjusted according to the simulated groundwater level position and change speed. The hose arrangement position is raised or lowered, and at the same time, the number of holes is increased or decreased, and the hole diameter is adjusted.

[0038] A computer storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of any one of the methods for evaluating the impact of groundwater level changes on subway station safety based on a centrifuge model test are implemented.

[0039] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a method, system and storage medium for evaluating the impact of groundwater level changes on subway station safety based on a centrifuge model test, which has the following beneficial effects:

[0040] 1. By constructing a groundwater and subway centrifuge test model, the impact of groundwater level changes on subway stations and their tunnel structures can be accurately simulated. This method can take into account the actual changes in groundwater levels and the stress characteristics of subway structures under complex geological conditions, thereby providing more accurate prediction results.

[0041] 2. By gradually raising the water level to different predetermined test heights and recording the stress data of 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 of subway station structures during water level changes, which helps to promptly discover potential safety hazards.

[0042] 3. Starting the centrifuge to simulate actual gravity conditions can further verify the stability and safety of the subway station structure under gravity. This helps to more accurately evaluate the stress conditions and safety performance of the subway station structure during actual operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0044] Figure 1 It is a schematic diagram of the process of the present invention;

[0045] Figure 2 It is a structural schematic diagram of the present invention;

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

[0047] Figure 3b It is a schematic diagram of the tunnel centrifugal model test of the present invention;

[0048] Figure 4 This is a schematic diagram of a subway station test of the present invention;

[0049] Figure 5a It is a schematic diagram of a groundwater level simulation hydraulic chamber of the present invention;

[0050] Figure 5b It is a schematic diagram of the pipeline of the hydraulic chamber for simulating the groundwater level of the present invention; DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Example 1

[0053] The embodiment of the present invention discloses a method for evaluating the impact of groundwater level changes on subway station safety based on a centrifuge model test, comprising the following steps:

[0054] Arrange the subway station model in the foundation model. The thickness of each layer of the foundation model is determined by scaling down according to the actual stratum conditions and the size of the subway station model is also determined according to the scale relationship. At the same time, the subway station takes into account the similarity of weight (the similarity relationship is attached), and steel or aluminum is used instead of concrete, steel bars and other materials of the subway station. The use of metal materials to make the subway station model can make up for the deficiency that concrete materials are not easy to make small-sized models.

[0055] 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 one side of the subway station model is close to the transparent window of the model box, with lubricating materials such as silicone oil applied in between to reduce the friction between the station model and the transparent window.

[0056] Step 1: Obtain relevant data of the subway station under different water levels, and construct a centrifugal test model of the foundation and the subway station based on the relevant data of the subway station based on the basic principle of the centrifugal model;

[0057] Step 2: Set the initial water level in the centrifuge test model, start the centrifuge, and after reaching the preset centrifuge acceleration value and running stably for a period of time, record the stress, strain, deformation, and displacement of the subway station structure as the first state data of the subway structure;

[0058] Step 3: gradually raise the water level to a predetermined high test water level, and record the second state data of the subway station structure;

[0059] Step 4: Compare and analyze the second state data with the first state data to determine the impact of the rising groundwater level on the structural safety, anti-floating stability and other influencing factors of the subway station;

[0060] Step 5: 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 safety of the subway station structure;

[0061] Step 6: Repeatedly rise and fall the test water level and record the corresponding status data. Compare and analyze the multiple status data to analyze the impact of groundwater level changes on the anti-floating and structural safety of the subway station.

[0062] 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 the station structure from above, and a particle image velocimetry device is used to monitor the soil displacement from the transparent front side of the model box to determine the soil displacement.

[0063] The contact, image, and laser multi-method coupling measurement method is used to measure the deformation and displacement of subway station models and soil. The contact measurement method is implemented using a linear displacement sensor (LVDT displacement sensor), the image measurement method is implemented using a particle image velocimetry (PIV) method, and the laser displacement measurement is implemented using a laser displacement sensor.

[0064] During the process of raising and lowering the water level and after reaching the preset water level, the following displacements are measured:

[0065] One end of the linear displacement sensor is fixed on the top of the subway station model. The linear displacement sensor passes through the soil covering the station model, and the other end is fixed to the beam fixed on the top of the model box. The floating and sinking of the station model caused by the change of water level in the model is analyzed through the displacement change value of the linear displacement sensor.

[0066] Use laser displacement sensors to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and use particle image velocimetry equipment to monitor the displacement of the soil and subway station model from the front of the transparent window of the model box, based on the deformation analysis of the station model and foundation soil;

[0067] 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.

[0068] Furthermore, in steps three to four, pore water pressure gauges are placed in the soil in all directions of the groundwater and subway centrifugal test model to monitor the pore water pressure and obtain the water level value in the model through the pore water pressure, and then calculate the buoyancy of the model station; soil pressure gauges are placed in the middle section of the station of the groundwater and subway centrifugal 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 centrifugal test model to monitor the stress changes of the station during the centrifugal test.

[0069] In step 4, the control signal and signal acquisition of the centrifuge are transmitted using digital optical fiber.

[0070] Furthermore, when the ratio of the size of the subway prototype to the size of the groundwater and subway centrifuge test model is n, the centrifuge acceleration a m for:

[0071]

[0072] Where: L p is the prototype size; L m is the model size; g is the gravitational acceleration.

[0073] When a 1 / n prototype test model is placed in a ng centrifugal gravity field, the weight of the test model increases by n times, and the stress on each point in the model is the same as the stress on the corresponding point in the prototype. This is the similarity law of centrifuge model test. Table 1 lists the similarity law of the main parameters of the centrifuge model test.

[0074] Table 1 Similarity laws of centrifugal model test

[0075]

[0076]

[0077] The centrifuge in this embodiment adopts LXJ-4-450 450g-ton geotechnical centrifuge. The maximum rotation radius of LXJ-4-450 450g-ton geotechnical centrifuge is 5.03m, the maximum acceleration is 300g, the effective load is 1.5ton, the effective load capacity is 450g-ton, it is driven by a DC motor, and the motor power is 700kW. The size of the test hanging basket is 1.5m×1.0m×1.5m. At the beginning of its construction, its equipment scale was the first in Asia and the fourth in the world. To this day, it is still one of the largest capacity centrifuges in China, with the ability to simulate geotechnical engineering such as 150-meter-high earth-rock dams, 150-meter-high slopes, and 150-meter-level underground caverns. The LXJ-4-450 large geotechnical centrifuge adopts symmetrical rotating arms, double hanging baskets, and double swinging methods. The main machine has a reasonable structure, stable operation, a speed regulation accuracy of 0.1%, and is equipped with a safety monitoring system. All control and signal acquisition of the centrifuge are realized by digital fiber optic transmission. It is equipped with advanced data acquisition system and high-precision sensors, including high-precision low-speed acquisition instrument (24-bit high-precision AD), high-density high-speed acquisition instrument (maximum sampling rate 250MHz), fiber optic signal acquisition instrument, high-definition (4800 pixels × 3400 pixels), high-speed (4000 frames / second) image acquisition system and PIV analysis system. It can collect and process soil pressure, pore water pressure, temperature, acceleration, displacement and other information in real time, and can meet the signal acquisition needs of various static and dynamic processes such as vibration, impact, explosion, etc.

[0078] like Figure 5a and Figure 5b As shown in the figure, the test chamber is specially designed and manufactured to simulate groundwater fluctuations in soil samples. A water tank is installed at the bottom of the test chamber, below the soil sample. A flow channel with holes is provided between the water tank and the soil sample for the in and out flow of water when the groundwater level fluctuates. A metal mesh and geotextile are placed under the soil sample to prevent particle movement and maintain uniform water flow. The rise and fall of the groundwater level is controlled by supplying and discharging water to the water tank and by air pressure.

[0079] Particle image velocimetry (PIV) is a non-contact optical flow measurement technology used to measure the distribution and changes of flow 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 particles suspended in the fluid. PIV analysis systems are widely used in fields such as fluid mechanics, environmental science, engineering experiments, and biomedical engineering. Specifically, the camera is 20 cm horizontally away from the model box and the height rises 15 cm from the level surface of the bottom of the model box. The camera should be debugged on site according to the light environment and the focusing distance of the camera. The camera screen can clearly and completely shoot the model, including the soil, strip foundation, and part of the hydraulic rod. Use color lines to assume the function of markers. The color line position is completed in layers. The color line color is selected as bright red, but other colors can also be selected according to the sensitive hue of the particle image velocimetry (PIV) camera to accurately identify it. The color line paint should be a low water-soluble paint to prevent it from spreading with the water flow during soil drainage.

[0080] During groundwater level fluctuations, the movement of particles inside the specimen is monitored using displacement tracking image analysis technology.

[0081] and Figure 1 Corresponding to the method shown, the present invention also discloses an evaluation system for the impact of groundwater level changes on subway station safety based on centrifuge model test for evaluating Figure 1 The implementation of the method, the specific structure is as follows Figure 2 As shown, including:

[0082] Groundwater and subway centrifuge test model construction module: used to obtain subway station related data under different water levels, and build foundation and subway station centrifuge test models based on the basic principles of centrifuge model and subway station related data;

[0083] The first state data acquisition module is used to set the initial water level in the centrifuge test model, start the centrifuge, and after reaching the preset centrifuge acceleration value and running stably for a period of time, record the stress, strain, deformation, and displacement of the subway station structure as the first state data of the subway structure;

[0084] Second state data acquisition module: used to gradually raise the water level to a predetermined high test water level and record the second state data of the subway station structure;

[0085] 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-floating stability and other influencing factors of subway stations;

[0086] 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 safety of the subway station structure;

[0087] Stability and safety evaluation module: used to repeatedly rise and fall the test water level and record the corresponding status data, compare and analyze multiple status data, and analyze the impact of groundwater level changes on the anti-floating and structural safety of subway stations.

[0088] Further, the rise and fall of the groundwater level in the groundwater and subway centrifugal test model is controlled by supplying and discharging water to and from the tank and by air pressure.

[0089] Furthermore, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge, connects the steel pipe and the explosion-proof water pipe on the centrifuge to the bottom of the model box, sets the flow rate, and controls the water level rise in the model box by controlling the valve.

[0090] Furthermore, a laboratory water pump injection system is used to pump water from underground to the centrifuge, and an explosion-proof hose is used to connect to the explosion-proof water pipe on the centrifuge. The explosion-proof hose is connected to the bottom of the model box through the side wall of the model box, and is connected to the three-way adapter 40mm from the bottom. The two sides of the three-way adapter are connected to the plastic hose and then connected in parallel with the three-way adapter to form multiple channels. The plastic hose is connected to the vertical outlet of each three-way, and arranged along the vertical direction of the model box. The water pipe is 650mm long, and the plastic water pipe outlet is stopped by a water stop valve. The vertically arranged water pipe is punched at intervals of 50mm, with a total of 13 holes, and the hole diameter is 3mm. The hole diameter is kept consistent so that the water flows out evenly from the small hole, and the flow rate is set to control the uniform rise of the water level in the model box by controlling the valve. The hose arrangement position, the number of holes, and the hole diameter are adjusted according to the simulated groundwater level position and change speed, and the hose arrangement position is raised or lowered. At the same time, the number of holes is increased or decreased, and the hole diameter is adjusted.

[0091] Further, the rise and fall of the groundwater level in the groundwater and subway centrifugal test model is controlled by supplying and discharging water to and from the tank and by air pressure.

[0092] Furthermore, the groundwater and subway centrifuge test model uses a laboratory water pump injection system to pump water from underground to the centrifuge, connects the steel pipe and the explosion-proof water pipe on the centrifuge to the bottom of the model box, sets the flow rate, and controls the water level rise in the model box by controlling the valve.

[0093] This embodiment uses a laboratory water pump water injection system to pump water from underground to the centrifuge. An explosion-proof hose is used to connect to the explosion-proof water pipe on the centrifuge. The explosion-proof hose is connected to the bottom of the model box through the side wall of the model box and connected to the three-way adapter 40 mm from the bottom. The two sides of the three-way adapter are connected to plastic hoses and then connected in parallel with the three-way adapter to form multiple channels. A plastic hose is connected to the vertical outlet of each three-way and arranged in the vertical direction of the model box. The water pipe is 650 mm long. The water outlet of the plastic water pipe is stopped by a water stop valve. The vertically arranged water pipes are punched at intervals of 50 mm, with a total of 13 holes. The hole diameter is 3 mm. The hole diameter is kept consistent so that water flows out evenly from the small holes. The flow rate is set to control the uniform rise of the water level in the model box by controlling the valve.

[0094] Under each water level condition, the sensor data is fully collected to analyze and evaluate the stress state and stability of the structure under different water level conditions. A laser displacement sensor is used to monitor the soil displacement from the top (8). A rigid rod is connected above the station structure, and the rigid rod protrudes from the soil surface. A contact platform is made at the upper end of the rod and an LVDT displacement meter (maximum stroke 30mm, 6 pieces) is arranged to monitor the displacement of the station structure. The probe rod position distribution diagram is shown in Figure 3a The soil displacement was monitored from the transparent front of the model box using a particle image velocimetry (PIV) instrument. Pore water pressure gauges (range 0-800 kPa, 7 gauges) were placed in the soil near the model station in each direction to monitor the pore water pressure and calculate the buoyancy of the model station through the pore water pressure.

[0095] In this embodiment, geotextile is wrapped around the outer periphery of the hose to prevent the excessive pressure of the water flow from the orifice from impacting the foundation soil and causing soil damage; at the same time, wrapping the geotextile also prevents the foundation soil from blocking the pipe hole and entering the pipe body. The pipe diameter and the size and number of holes can be adjusted according to the water supply speed requirements. Gravel is used to fill the periphery of the hose. The gravel supports the hose, reduces the deformation of the hose caused by the pressure generated by the overlying foundation model, and reduces the impact of the change in pipe diameter caused by the deformation of the hose on the water flow.

[0096] Finally, this embodiment discloses a computer storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of any one of the methods for evaluating the impact of groundwater level changes on subway station safety based on a centrifuge model test are implemented.

[0097] Example 2

[0098] The difference between this embodiment and embodiment 1 is only that:

[0099] like Figure 3a , Figure 3b , Figure 4As shown, the total mass of the test model = the mass of the model box (607kg) + the mass of the soil (1094.86kg) + the weight of the reaction frame and beam (500.33kg) + the weight of the subway tunnel (7.57kg) = 2209.76kg

[0100] Assume that the centrifugal field is N times the gravitational acceleration g, that is, N = prototype size / model size, then the scaling relationship is as follows:

[0101]

[0102] L p , L m Respectively represent the prototype foundation width and model foundation width, m;

[0103] H p , H m Respectively represent the prototype foundation depth and model foundation depth, m;

[0104] σ p , σ m They represent the prototype foundation soil pressure and model foundation soil pressure, kPa respectively;

[0105] L p =150L mmax =1.2;

[0106] According to the similarity principle and considering the prototype length and the inner length of the model box, take L m =1The scale factor (N) is calculated as:

[0107]

[0108] The other length dimensions of the station model are reduced synchronously according to the calculated scale ratio.

[0109] Therefore, the centrifuge acceleration (a) is calculated as:

[0110] a=N·g=150g;

[0111] In the soil preparation process, firstly, evenly apply oil lubricant on the four walls of the model box, and prepare the sample by sand rain method in several layers. The more specific steps are as follows:

[0112] S1. Soil sample arrangement and compaction: Arrange and compact the soil sample in the model container to ensure that it is stable and accurately aligned. Arrange necessary monitoring equipment in the structure and soil layer.

[0113] S2. Set the initial water level to simulate normal groundwater level conditions: record the buoyancy and stability of the structure in the initial state.

[0114] S3, Centrifugal loading and data recording: Start the centrifuge to simulate actual gravity conditions. Gradually raise the water level to different predetermined test heights to simulate the process of groundwater level rise. After each water level adjustment, record the buoyancy changes and responses of the station and tunnel structures.

[0115] S4. Use the laboratory water pump injection system to pump water from underground to the centrifuge, connect the steel pipe and the explosion-proof water pipe on the centrifuge to the bottom of the model box, set the flow rate, and control the water level in the model box by controlling the valve.

[0116] S5, water level rise: Set the initial water level to , fill with water several times, reach the required heights in sequence, and let stand for min.

[0117] The specific test steps are as follows: After the prepared test model is hoisted and fixed on the centrifuge, each monitoring device is installed and tested. At the beginning of the test, the initial water level is mm, and the centrifugal acceleration is increased step by step by 25g, and loaded in 6 times. When each level of acceleration is loaded to the set value, it will continue to run for 10 minutes before entering the next level of loading process. After the centrifugal acceleration reaches 150g, the initially set groundwater level will be raised. The rising speed of the groundwater level should meet the actual environment, that is, to avoid the generation of excess pore water pressure.

[0118] Under each water level condition, the sensor data, including buoyancy, pressure, stress and displacement, are fully collected to analyze and evaluate the stress state and stability of the structure under different water level conditions. Two laser displacement sensors are used to monitor the vertical displacement of the soil and station structure from the top, and a particle image velocimetry (PIV) instrument is used to monitor the soil displacement from the transparent front of the model box. Eleven pore water pressure gauges are placed in the soil near the model station in all directions to monitor the pore water pressure and calculate the buoyancy of the model station through the pore water pressure. Four soil pressure gauges are placed in the middle of the model station to monitor the pressure of the model station in all directions. Strain gauges are placed on the four walls of the model station to monitor the stress changes of the model station during the centrifugal test.

[0119] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0120] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one 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 present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model tests, characterized in that: The following steps are involved: Obtain relevant data of subway stations under different water levels, and construct centrifugal test models of foundation and subway stations based on the basic principles of centrifugal model according to relevant data of subway stations; An initial water level is set in the centrifuge test model, and the centrifuge is started. After reaching a preset centrifuge acceleration value and running stably for a period of time, the stress, strain, deformation, and displacement of the subway station structure are recorded as the first state data of the subway structure. gradually raising the water level to a predetermined high test water level, and recording the second state data of the subway station structure; Compare and analyze the second state data with the first state data to determine the impact of the rising groundwater level on the structural safety, anti-floating stability and other factors of the subway station; 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 safety of the subway station structure; The test water level is repeatedly raised and lowered, and the corresponding status data is recorded. The multiple status data are compared and analyzed to analyze the impact of groundwater level changes on the anti-floating and structural safety of subway stations.

2. The method for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 1 is characterized in that: During the process of raising and lowering the water level and after reaching the preset water level, the following displacements are measured: One end of the linear displacement sensor is fixed on the top of the subway station model. The linear displacement sensor passes through the soil covering the station model, and the other end is fixed to the beam fixed on the top of the model box. The displacement change value of the linear displacement sensor is used to analyze the floating and sinking of the station model caused by the change of the water level in the model. Use laser displacement sensors to monitor the vertical displacement of the soil on the upper surface of the model from the top of the model box, and use particle image velocimetry equipment to monitor the displacement of the soil and subway station model from the front of the transparent window of the model box, based on the deformation analysis of the station model and foundation soil; 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 for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 1 is characterized in that: Pore ​​water pressure gauges are placed in the soil in all directions of the groundwater and subway centrifuge test model to monitor the pore water pressure and obtain the water level value in the model through the pore water pressure, and then calculate the buoyancy of the model station; soil pressure gauges are placed in the middle section of the station of the groundwater and subway centrifuge test model to monitor the pressure exerted on 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 changes of the station during the centrifuge test.

4. The method for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 1 is characterized in that: The control signal and signal acquisition of the centrifuge are transmitted by digital optical fiber.

5. The method for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 1 is characterized in that: When the ratio of the size of the subway prototype to the size of the groundwater and subway centrifuge test model is n, the centrifuge acceleration a m for: Where: L p is the prototype size; L m is the model size; g is the gravitational acceleration.

6. A system for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model tests, characterized in that: include: Groundwater and subway centrifuge test model construction module: used to obtain subway station related data under different water levels, and build foundation and subway station centrifuge test models based on the basic principles of centrifuge model and subway station related data; The first state data acquisition module is used to set the initial water level in the centrifuge test model, start the centrifuge, and after reaching the preset centrifuge acceleration value and running stably for a period of time, record the stress, strain, deformation, and displacement of the subway station structure as the first state data of the subway structure; Second state data acquisition module: used to gradually raise the water level to a 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-floating stability and other influencing factors of subway stations; 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 safety of the subway station structure; Stability and safety evaluation module: used to repeatedly rise and fall the test water level and record the corresponding status data, compare and analyze multiple status data, and analyze the impact of groundwater level changes on the anti-floating and structural safety of subway stations.

7. The system for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 6 is characterized in that: Groundwater and Subway Centrifuge Test ModelThe rise and fall of the groundwater level in the model is controlled by supplying and discharging water to and from the tank and by air pressure.

8. The system for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 6 is 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, connect the steel pipe and the explosion-proof water pipe on the centrifuge to the bottom of the model box, set the flow rate, and control the water level in the model box by controlling the valve.

9. The system for evaluating the impact of groundwater level changes on subway station safety based on centrifuge model test according to claim 6, characterized in that: Use the laboratory water pump water injection system to pump water from underground to the centrifuge, use an explosion-proof hose to connect to the explosion-proof water pipe on the centrifuge, connect the explosion-proof hose to the bottom of the model box through the side wall of the model box, and connect to the three-way adapter 40mm from the bottom. The two sides of the three-way adapter are connected to plastic hoses and then connected to the three-way adapter in parallel to form multiple channels. Connect a plastic hose to the vertical outlet of each three-way and arrange it in the vertical direction of the model box. The water pipe is 650mm long. The water outlet of the plastic water pipe is stopped by a water stop valve. The vertically arranged water pipes are punched at intervals of 50mm, for a total of 13 holes with a hole diameter of 3mm. The hole diameter is kept consistent so that water flows out evenly from the small holes. Set the flow rate to control the uniform rise of the water level in the model box by controlling the valve. The hose arrangement position, the number of holes, and the hole diameter are adjusted according to the simulated groundwater level position and change speed. The hose arrangement position is raised or lowered, and at the same time, the number of holes is increased or decreased, and the hole diameter is adjusted.

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 a method for evaluating the impact of groundwater level changes on subway station safety based on a centrifuge model test as described in any one of claims 1 to 5.

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