A visual test system and method for testing seepage erosion damage of foundation pit soil

Abstract

The present invention discloses a visualization test system for testing seepage erosion damage in foundation pit soil, comprising: a CT scanning system; a supporting system disposed on top of the CT scanning system; a triaxial pressurization system disposed inside the supporting system; a control system disposed on top of the triaxial pressurization system; and a collection system disposed outside the triaxial pressurization system. The CT scanning system comprises a CT gantry, a turntable, a turntable base, an X-ray transmitter, an array detector, and two gantry trays. The CT gantry comprises a base and two support rods, the two support rods being symmetrically and perpendicularly disposed on the upper surface of the base. The turntable base is disposed on top of the base, the turntable is rotatably disposed on the top of the turntable base, and the two gantry trays are respectively disposed on the inner side surfaces of the two support rods. The present invention can not only visually monitor the entire seepage erosion damage process of foundation pit soil samples, but also obtain high-definition CT images of the movement changes of soil particles during seepage damage in real time.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical engineering, and in particular relates to a visual test system and method for testing seepage erosion damage of foundation pit soil. Background Art

[0002] In recent years, with rapid economic development and a continuously increasing urbanization rate, the scale of large and medium-sized cities has continued to increase, and high-rise buildings are becoming ubiquitous. Better utilization of urban underground space has become a major trend, and the number of foundation pit projects for underground structures has increased. Consequently, foundation pit safety has become extremely important. In engineering construction, groundwater is always one of the key factors affecting the entire project. Groundwater is not only an important part of people's lives, but also plays an indispensable role in the construction process. Statistical analysis shows that in domestic cities with rail transit, regardless of their hydrogeological conditions, urban underground engineering accidents are primarily caused by seepage damage.

[0003] Seepage failure refers to the localized movement or loss of soil particles caused by seepage, leading to deformation and instability. In foundation pit projects, this primarily manifests as sand drift, piping, and erosion, impacting the stability of the pit and the safety of the surrounding environment. Loose soil has a high porosity. When seepage flows through its pores, soil particles obstruct the flow. Based on the principle of force interaction, the water flow generates a force (seepage pressure) acting perpendicularly to the surface of the soil particles. In addition to the seepage pressure, soil particles are also subject to tangential seepage friction. The combined effects of the seepage pressure and friction on each soil particle create the net seepage force. When the net seepage force is greater than the weight of the soil particles, the particles roll with the water flow. When the weight of the soil is less than the net seepage force generated by the water flow, the soil mass destabilizes under the influence of the water flow. There are two main forms of seepage damage: 1) Quicksand: During deep foundation pit excavation, after loose soil particles become saturated with groundwater, quicksand damage may occur due to the infiltration gradient reaching a certain value. Quicksand generally occurs when the upward seepage force is greater than the weight of the overlying soil, causing it to lift and break. Alternatively, in the case of a vertical pit wall, the horizontal seepage force only needs to overcome the frictional resistance between soil particles, causing the soil behind the pit to surge out, which can easily cause engineering accidents. 2) Piping: This occurs when water with a certain seepage velocity washes away fine particles of foundation soil, gradually increasing the voids within the soil. Fine particles then flow out through the pores of larger particles with the water flow. This often occurs in poorly graded, cohesionless soils. The continued development of piping will form cavities within the soil, posing a significant threat to the safety of the foundation pit project. The presence of foundation seepage forces affects the stress distribution of the foundation pit soil. The boundary conditions of the foundation pit project determine that the effects of seepage forces will adversely affect the overall stability of the foundation pit project. In foundation pit projects, especially in areas with abundant groundwater, anti-seepage structures play a key role in preventing groundwater seepage damage and ensuring construction safety. Different anti-seepage structures are adapted to different strata. Under the influence of the seepage field, the effective stress drop in the pit soil directly reduces the support provided by the retaining structure, causing deformation. Once seepage damage occurs, the soil in the pit completely loses its support function, seriously threatening the safety of the foundation pit project and the surrounding environment. Therefore, studying seepage erosion damage to soil in foundation pits is of great value and significance.

[0004] At present, most of the research on the seepage erosion damage of soil in foundation pits still uses self-made foundation pit seepage model boxes and supporting test equipment to simulate, observe soil damage and water head changes, study the relationship between pressure head changes and soil seepage damage, and reveal the seepage damage mechanism of foundation pit soil. The test changes the burial depth of the anti-seepage wall and other factors to observe the critical water head difference for seepage damage of soil. Combined with PLAXIS finite element numerical simulation software, the seepage field of the foundation pit is analyzed. The accuracy of the numerical simulation results mainly depends on the correctness of the established constitutive model, whether it is close to the actual situation, and whether the mechanical parameters and analysis methods used are correct. Therefore, the seepage erosion damage mechanism of foundation pit soil still remains in the qualitative stage and cannot be further quantitatively analyzed. Further research and improvement are needed.

[0005] Patent publication number CN 111337650 A discloses a multifunctional test device for studying the seepage failure mechanism of underground engineering soil. The device comprises a main housing, a loading system, a pipe simulation system, a regulating system, a foundation pit support mechanism, a measurement system, and a testing system. The main housing supports the soil, the loading system applies load to the soil, the pipe simulation system simulates pipe jacking, the regulating system supplies water to the soil and controls water pressure, the foundation pit support mechanism simulates foundation pit support, the measuring system detects pressure within the loading system and observes soil movement and changes, and the measuring system measures the particle size and amount of discharged sand. The main housing can accommodate three seepage modes: piping, sudden surge, and sand leakage caused by localized pipe erosion. The test device enables the main housing to simulate multiple groundwater modes, enabling seepage simulation under different pressure water directions at the bottom and sides. The pressure head regulating system simulates stable groundwater flow pressures of varying magnitudes. This indoor model test device is used to simulate the deformation of soil and the changes in pore water pressure under the action of groundwater, thereby better solving the problem of foundation pit damage caused by groundwater seepage. Although the above multifunctional test device can solve the problem of foundation pit damage caused by groundwater seepage to a certain extent, the above structure still has the following technical defects:

[0006] (1) The above invention patent cannot obtain the soil seepage erosion and destruction process in real time.

[0007] (2) The loading system of the above invention patent is a rigid loading system, which cannot load the force more evenly to the soil sample, and thus cannot obtain better accuracy.

[0008] (3) The above invention patent cannot quantitatively characterize the changing characteristics of internal soil particles and pore structure during the seepage erosion process. Summary of the Invention

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a visual test system and method for testing seepage erosion damage of foundation pit soil.

[0010] The first object of the present invention is to provide a visual test system for testing seepage erosion damage of foundation pit soil, comprising:

[0011] CT scanning system;

[0012] A carrying system, arranged on top of the CT scanning system;

[0013] A triaxial pressurizing system is provided inside the bearing system;

[0014] A control system is provided on top of the triaxial pressurization system;

[0015] The collection system is arranged outside the triaxial pressurizing system.

[0016] Preferably, the CT scanning system includes a CT gantry, a turntable, a turntable base, an X-ray transmitter, an array detector and two gantry trays. The CT gantry includes a base and two support rods. The two support rods are symmetrically and vertically arranged on the upper surface of the base. The turntable base is arranged on the top of the base. The turntable is rotatably arranged on the top of the turntable base. The two gantry trays are respectively arranged on the inner side surfaces of the two support rods. The X-ray transmitter and the array detector are respectively arranged on the top of the two gantry trays.

[0017] Preferably, the bearing system includes an upper beam platform, a lifting platform, a lower platform, a positioning hole and two reaction columns, the lower platform is arranged on the top of the turntable, the lifting platform is arranged above the lower platform, the upper beam platform is arranged above the lifting platform, and the two reaction columns are vertically symmetrically arranged between the lower platform and the upper beam platform, the top of each reaction column is connected to the bottom of the upper beam platform, and the bottom of each reaction column passes through the lifting platform and is connected to the top of the lower platform, and the positioning hole is opened in the middle of the top of the upper beam platform.

[0018] Preferably, the three-axis pressurizing system includes a sensor, an upper pad, a lower pad, a cylinder, a cover, a jack, a pressure gauge, a dial indicator, a supercharger and an airbag, the sensor is arranged at the bottom of the upper beam platform, the sensor is threadedly connected to the positioning hole, the bottom of the jack is connected to the top of the lower platform, the top is connected to the bottom of the lifting platform, the lower pad is placed on the top of the lifting platform, the cylinder is arranged on the top of the lower pad, the cover is arranged at the opening at the top of the cylinder, the upper pad is placed on the top of the cover, the top of the upper pad is in contact with the bottom of the sensor, the pressure gauge is arranged on the top of the lower platform, the airbag is annularly arranged on the inner wall of the cylinder, the dial indicator is arranged on the top of the lifting platform, the dial indicator is connected to the lower platform, the supercharger is arranged on the top of the turntable, and the supercharger and the pressure gauge are respectively connected to the airbag through pipelines.

[0019] Preferably, the control system includes a servo water pump and a controller, both of which are located on the top of the upper beam platform. The controller is connected to the sensor and the servo water pump through pipelines, and the servo water pump is connected to the upper pad through pipelines.

[0020] Preferably, the collection system includes an electronic balance and a measuring cylinder, the electronic balance is arranged on the top of the lower platform, the measuring cylinder is placed on the top of the electronic balance, the servo water pump is connected to the measuring cylinder through a pipeline, and the measuring cylinder is connected to the lower pad through a pipeline.

[0021] Preferably, a control valve is provided on the pipeline between the booster and the airbag.

[0022] A second object of the present invention is to provide a visual test method for testing seepage erosion damage of foundation pit soil, comprising the following steps:

[0023] S1. Place the sample inside the cylinder. After placing it, tighten the lid to the top of the cylinder. Then place the lower pad on the top of the lifting platform, place the cylinder on the lower pad, and place the upper pad on the top of the lid. At this time, the top of the upper pad is in contact with the bottom of the sensor.

[0024] S2. Open the booster and control valve to increase the pressure in the cylinder, so that the specimen is subjected to a certain confining pressure stress. At the same time, start the jack to apply pressure in the axial direction to reach an axial pressure equal to the confining pressure, so that the specimen reaches a hydrostatic stress state.

[0025] S3: Using the controller, the servo water pump is used to saturate the sample with a certain initial pressure difference to ensure that the pressure difference p is constant. The sample gradually tends to saturation over time. When water flows into the measuring cylinder, the servo water pump is turned off, indicating that the saturation state has been reached.

[0026] S4: Start the X-ray transmitter, select the preheating mode according to the length of time since the last shutdown, and preheat. After the preheating is completed, the X-ray transmitter emits a beam and the array detector receives the signal;

[0027] S5: Stepwise pressurization. For each step, the corresponding permeability coefficient is calculated. The mass of water flowing into the graduated cylinder over a certain period of time is recorded to obtain the permeability coefficient. For each step of water pressure increase, when the water flowing into the graduated cylinder just begins to become turbid, the X-ray transmitter scan is started. The turntable drives the cylinder to rotate and perform CT scanning. CT images of the soil interior during the seepage damage process are obtained in real time and three-dimensionally reconstructed.

[0028] S6: Apply loads step by step to make the sample penetrate and damage more seriously. The water flowing into the measuring cylinder becomes increasingly turbid until it is completely destroyed. Then the X-ray transmitter stops emitting beams, all systems stop working, the CT machine radiation source is turned off, the cylinder is removed, and the test ends.

[0029] S7: After all detection tasks are completed, wait for the X-ray transmitter to cool down, turn off the power of the X-ray transmitter, and disconnect all subsystems except the computer.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The visualization test system for seepage erosion damage testing of foundation pit soil provided by the present invention, combined with industrial CT scanning, can not only visually monitor the entire process of seepage erosion damage of foundation pit soil samples, but also obtain high-definition CT images of soil particle movement changes during seepage damage in real time, thereby realizing visualization and digital representation of the entire process of seepage damage of foundation pit soil samples;

[0032] (2) The airbag in the triaxial pressurization system of the present invention provides confining pressure stress to the sample, and the jack provides axial pressure to the sample, so that the sample is in a hydrostatic stress state, thereby not only simulating the formation conditions, but also simulating the fluid-solid coupling effect, and also performing consolidation to realize the triaxial test;

[0033] (3) After scanning, the present invention extracts, identifies and analyzes the CT number, crack distribution, porosity evolution, rock movement, CT damage and strain localization characteristics of the region of interest (ROI) of the two-dimensional CT slice and the three-dimensional reconstructed image, and quantitatively describes the microscopic physical quantities in the destruction process, revealing the mechanism of penetration erosion destruction;

[0034] (4) The present invention can conduct penetration damage test research on various soils by taking soil samples from different strata in the foundation pit;

[0035] (5) The tube in the present invention is made of a glass non-metallic material with high strength and low density, which not only has good optical properties, thermoplasticity and processing properties, but also has the characteristics of low specific gravity, high mechanical strength, outstanding compressive and tensile properties, etc., and also improves the attenuation of X-ray energy when passing through. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the structure of a visual test system for testing seepage erosion and damage of foundation pit soil provided by an embodiment of the present invention;

[0037] Figure 2 A front view of a visualization test system for testing seepage erosion and damage of foundation pit soil provided by an embodiment of the present invention;

[0038] Figure 3 A side view of a visualization test system for testing seepage erosion and damage of foundation pit soil provided by an embodiment of the present invention;

[0039] Figure 4Schematic diagram of the structure of a CT scanning system in an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the structure of the bearing system, triaxial pressurizing system and control system in an embodiment of the present invention;

[0041] Figure 6 It is a front view of the bearing system, triaxial pressurizing system and control system in an embodiment of the present invention;

[0042] In the figure: 1-CT rack; 2-X-ray transmitter; 3-rack tray; 4-turntable base; 5-turntable; 6-area array detector; 7-servo water pump; 8-controller; 9-upper beam platform; 10-pipeline; 11-sensor; 12-upper pad; 13-lid; 14-cylinder; 15-airbag; 16-lower pad; 17-lifting platform; 18-boost; 19-pressure gauge; 20-lower platform; 21-reaction column; 22-dial indicator; 23-jack; 24-electronic balance; 25-gradual cylinder; 26-control valve; 27-positioning hole. DETAILED DESCRIPTION

[0043] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0044] The visualization test system for foundation pit soil seepage erosion damage testing provided by the embodiment of the present invention can simulate the entire process of soil in the foundation pit being damaged by water seepage erosion under stress, and realizes digital and visualization representation of the entire process through CT scanning and image acquisition, providing a certain theoretical basis for ensuring foundation pit safety.

[0045] like Figures 1 to 6 As shown, the visualization test system for foundation pit soil seepage erosion damage testing provided by the embodiment of the present invention includes:

[0046] CT scanning system;

[0047] A carrying system, arranged on top of the CT scanning system;

[0048] A triaxial pressurizing system is provided inside the bearing system;

[0049] A control system is provided on top of the triaxial pressurization system;

[0050] The collection system is arranged outside the triaxial pressurizing system.

[0051] The CT scanning system includes a CT gantry 1, a turntable 5, a turntable base 4, an X-ray transmitter 2, an array detector 6 and two gantry trays 3. The CT gantry 1 includes a base and two support rods. The two support rods are symmetrically and vertically arranged on the upper surface of the base. The turntable base 4 is arranged on the top of the base. The turntable 5 is rotatably arranged on the top of the turntable base 4. A drive motor is arranged inside the turntable base 4. The output end of the drive motor is fixedly connected to a rotating shaft. The top of the rotating shaft is fixedly connected to the bottom of the turntable 5. This design enables the turntable 5 to rotate 360 ​​degrees. The two gantry trays 3 are respectively arranged on the inner sides of the two support rods. The X-ray transmitter 2 and the array detector 6 are respectively arranged on the top of the two gantry trays 3. The X-ray transmitter 2 adopts a 450kV high-energy industrial CT.

[0052] The bearing system includes an upper beam platform 9, a lifting platform 17, a lower platform 20, a positioning hole 27 and two reaction columns 21. The lower platform 20 is arranged on the top of the turntable 5, the lifting platform 17 is arranged above the lower platform 20, and the upper beam platform 9 is arranged above the lifting platform 17. The two reaction columns 21 are vertically symmetrically arranged between the lower platform 20 and the upper beam platform 9. The top of each reaction column 21 is connected to the bottom of the upper beam platform 9, and the bottom of each reaction column 21 passes through the lifting platform 17 and is connected to the top of the lower platform 20. The positioning hole 27 is opened in the middle of the top of the upper beam platform 9.

[0053] The triaxial pressurization system includes a sensor 11, an upper pad 12, a lower pad 16, a cylinder 14, a cover 13, a jack 23, a pressure gauge 19, a dial indicator 22, a supercharger 18 and an airbag 15. The sensor 11 is arranged at the bottom of the upper beam platform 9, and the sensor 11 is threadedly connected to the positioning hole 27. The interior of the positioning hole 27 is provided with an internal thread, and the exterior of the sensor 11 is provided with an external thread. The sensor 11 is connected to the positioning hole 27 through the external thread and the internal thread. The bottom of the jack 23 is connected to the top of the lower platform 20, and the top is connected to the bottom of the lifting platform 17. The lower pad 1 6 is placed on the top of the lifting platform 17, the cylinder 14 is set on the top of the lower pad 16, the cover 13 is set at the opening at the top of the cylinder 14, the upper pad 12 is placed on the top of the cover 13, the top of the upper pad 12 is in contact with the bottom of the sensor 11, the pressure gauge 19 is set on the top of the lower platform 20, the airbag 15 is annularly arranged on the inner wall of the cylinder 14, the dial indicator 22 is set on the top of the lifting platform 17, the dial indicator 22 is connected to the lower platform 20, the supercharger 18 is set on the top of the turntable 5, and the supercharger 18 and the pressure gauge 19 are respectively connected to the airbag 15 through the pipeline 10.

[0054] In the specific design, the cylinder 14, pipeline 10, reaction column 21, upper pad 12, lower pad 16, supercharger 18, cover 13, sensor 11, upper beam platform 9, lifting platform 17, and lower platform 20 are all made of high-strength, low-density glass non-metallic materials. This not only has good optical properties, thermoplasticity and processing properties, but also has the characteristics of low specific gravity, high mechanical strength, outstanding compressive and tensile properties, etc., and also improves the attenuation of X-ray energy when passing through.

[0055] The airbag 15 is made of flexible material, which can make the sample evenly stressed and the confining pressure constant. The vertical stress applied to the sample by the jack 23 is measured by the sensor 11 above the cylinder 14. The pressure gauge displays the size of the confining pressure applied by the airbag, and the dial indicator located on the lifting platform measures the vertical displacement of the lifting platform when the jack applies pressure.

[0056] The control system includes a servo water pump 7 and a controller 8, both of which are located on the top of the upper beam platform 9. The controller 8 is connected to the sensor 11 and the servo water pump 7 through a pipeline 10 respectively. The servo water pump 7 is connected to the upper pad 12 through the pipeline 10. The upper pad 12 and the cover 13 are respectively provided with small water injection holes that are interconnected in the middle. The servo water pump 7 is connected to the water injection hole on the upper pad 12 through the pipeline 10.

[0057] The collection system includes an electronic balance 24 and a measuring cylinder 25. The electronic balance 24 is arranged on the top of the lower platform 20, and the measuring cylinder 25 is placed on the top of the electronic balance 24. The servo water pump 7 is connected to the measuring cylinder 25 through a pipeline 10, and the measuring cylinder 25 is connected to the lower pad 16 through a pipeline 10. The middle part of the bottom of the cylinder 14 and the middle part of the lower pad 16 are respectively provided with water injection holes that are interconnected. The measuring cylinder 25 is connected to the water injection hole on the lower pad 16 through a wire.

[0058] A control valve 26 is provided on the pipeline between the supercharger 18 and the airbag 15 .

[0059] The working method of the visualization test system for foundation pit soil seepage erosion damage testing provided by the embodiment of the present invention specifically includes the following steps:

[0060] S1. Place the sample inside the cylinder 14. After placing it, tightly cover the lid 13 and the top of the cylinder 14. Then place the lower pad 16 on the top of the lifting platform 17, place the cylinder 14 on the lower pad 16, and place the upper pad 12 on the top of the lid 13. At this time, the top of the upper pad 12 is in contact with the bottom of the sensor 11.

[0061] S2. Open the booster 18 and the control valve 26 to increase the pressure in the cylinder 14, so that the sample is subjected to a certain confining pressure stress. Start the jack 23 to apply pressure in the axial direction to reach an axial pressure equal to the confining pressure, so that the sample reaches a hydrostatic stress state.

[0062] S3: Utilize the controller 8 to saturate the sample with a certain initial pressure difference through the servo water pump 7 to ensure that the pressure difference p is constant. The sample gradually tends to saturation over time. When water flows into the measuring cylinder 25, the servo water pump 7 is turned off, indicating that the sample has reached the saturation state.

[0063] S4: Start the X-ray transmitter 2, select a preheating mode based on the length of time since the last shutdown, and preheat. After the preheating is completed, the X-ray transmitter 2 emits a beam, and the array detector 6 receives the signal;

[0064] S5: Stepwise pressurization. For each step, the corresponding permeability coefficient is calculated according to Darcy's law. The mass of water flowing into the graduated cylinder 25 over a certain period of time is recorded to obtain the permeability coefficient. Each time the water pressure is increased by one level, when the water flowing into the graduated cylinder 25 just begins to become turbid, it indicates that the water is on the verge of seepage failure at this pressure. The X-ray transmitter 2 is activated for scanning. The turntable 5 drives the cylinder 14 to rotate and perform CT scanning. CT images of the soil interior during the seepage failure process are obtained in real time and three-dimensionally reconstructed.

[0065] S6: Apply loads step by step to make the sample more severely damaged by penetration. The water flowing into the measuring cylinder 25 becomes increasingly turbid until it is completely destroyed. Then the X-ray transmitter 2 stops emitting beams, all systems stop working, the CT machine radiation source is turned off, the cylinder 14 is removed, and the test ends.

[0066] S7: After all detection tasks are completed, wait for the X-ray transmitter 2 to dissipate heat, turn off the power of the X-ray transmitter 2, disconnect the switches of all subsystems except the computer, and use industrial computed tomography data processing software to perform three-dimensional reconstruction, damage evolution description and damage variable analysis on the soil sample, obtain the penetration erosion and damage process of the soil sample under different stress waves, reveal the penetration erosion and damage mechanism of the soil, and realize visualization and digital representation of the whole process.

[0067] In summary, the lifting platform in the visualization test system for seepage erosion damage testing of foundation pit soil provided by the embodiment of the present invention has a lifting and moving function, which facilitates loading. The axial load of the jack and the confining pressure of the airbag can simulate the stress state of the specimen in the foundation pit. If the pressurized axial load and the confining pressure are consistent, the specimen is in a hydrostatic pressure state. If they are inconsistent, the triaxial stress state can be explored, and the mechanism of seepage damage of different soil specimens can also be explored, enriching the experimental plan. This system uses high-energy X-ray industrial CT technology based on area array detectors to obtain real-time high-definition CT images of the entire soil specimen after seepage erosion damage, realizing visualization and digital representation of the entire process of soil seepage erosion damage.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A visualization test system for foundation pit soil seepage erosion damage test, characterized in that: include: CT scanning system; A carrying system, arranged on top of the CT scanning system; The bearing system comprises an upper beam platform (9), a lifting platform (17), a lower platform (20), a positioning hole (27) and two reaction columns (21), wherein the lower platform (20) is arranged on the top of the turntable (5), the lifting platform (17) is arranged above the lower platform (20), the upper beam platform (9) is arranged above the lifting platform (17), and the two reaction columns (21) are respectively arranged vertically and symmetrically between the lower platform (20) and the upper beam platform (9), the top of each reaction column (21) is connected to the bottom of the upper beam platform (9), and the bottom of each reaction column (21) passes through the lifting platform (17) and is connected to the top of the lower platform (20), and the positioning hole (27) is opened in the middle of the top of the upper beam platform (9); A triaxial pressurizing system is provided inside the bearing system; The triaxial pressurizing system comprises a sensor (11), an upper pad (12), a lower pad (16), a cylinder (14), a cover (13), a jack (23), a pressure gauge (19), a dial indicator (22), a supercharger (18) and an airbag (15), wherein the sensor (11) is arranged at the bottom of the upper beam platform (9), the sensor (11) is threadedly connected to the positioning hole (27), the bottom of the jack (23) is connected to the top of the lower platform (20), and the top is connected to the bottom of the lifting platform (17), the lower pad (16) is placed on the top of the lifting platform (17), the cylinder (14) is arranged on the top of the lower pad (16), the cover (13) is arranged on the cylinder (14), and the pressure gauge (19) is provided on the upper beam platform (9). ) at the top opening, an upper pad (12) is placed on the top of the cover (13), the top of the upper pad (12) contacts the bottom of the sensor (11), a pressure gauge (19) is arranged on the top of the lower platform (20), an air bag (15) is arranged in an annular shape on the inner wall of the cylinder (14), a dial indicator (22) is arranged on the top of the lifting platform (17), the dial indicator (22) is connected to the lower platform (20) through a pipeline, a booster (18) is arranged on the top of the turntable (5), the booster (18) and the pressure gauge (19) are respectively connected to the air bag (15) through a pipeline (10); a control valve (26) is provided on the pipeline between the booster (18) and the air bag (15); A control system is provided on top of the triaxial pressurization system; The control system comprises a servo water pump (7) and a controller (8), both of which are located on the top of the upper beam platform (9), the controller (8) being connected to the sensor (11) and the servo water pump (7) via pipelines (10), respectively, and the servo water pump (7) being connected to the upper pad (12) via pipelines (10); The collection system is arranged outside the triaxial pressurizing system.

2. The visualization test system for foundation pit soil seepage erosion damage test according to claim 1, characterized in that: The CT scanning system comprises a CT rack (1), a turntable (5), a turntable base (4), an X-ray transmitter (2), an array detector (6) and two rack trays (3), wherein the CT rack (1) comprises a base and two support rods, wherein the two support rods are symmetrically and vertically arranged on the upper surface of the base, the turntable base (4) is arranged on the top of the base, the turntable (5) is rotatably arranged on the top of the turntable base (4), the two rack trays (3) are respectively arranged on the inner side surfaces of the two support rods, and the X-ray transmitter (2) and the array detector (6) are respectively arranged on the top of the two rack trays (3).

3. The visualization test system for foundation pit soil seepage erosion damage test according to claim 1, characterized in that: The collection system comprises an electronic balance (24) and a measuring cylinder (25), wherein the electronic balance (24) is arranged on the top of the lower platform (20), the measuring cylinder (25) is placed on the top of the electronic balance (24), the servo water pump (7) is connected to the measuring cylinder (25) through a pipeline (10), and the measuring cylinder (25) is connected to the lower pad (16) through a pipeline (10).

4. A visual test method for testing seepage erosion damage of foundation pit soil, characterized in that: The method is realized by the visualization test system for foundation pit soil seepage erosion damage test according to claim 3, comprising the following steps: S1. Place the sample inside the cylinder (14). After placing it, tightly cover the lid (13) and the top of the cylinder (14). Then place the lower pad (16) on the top of the lifting platform (17). Place the cylinder (14) on the lower pad (16), and place the upper pad (12) on the top of the lid (13). At this time, the top of the upper pad (12) is in contact with the bottom of the sensor (11); S2, opening the booster (18) and the control valve (26) to pressurize the cylinder (14) so ​​that the sample is subjected to a certain confining pressure stress, and at the same time starting the jack (23) to apply pressure in its axial direction to reach an axial pressure equal to the confining pressure, so that the sample reaches a hydrostatic stress state; S3: Using the controller (8), the servo water pump (7) is used to saturate the sample with a certain initial pressure difference, ensuring that the pressure difference p is constant. The sample gradually tends to be saturated over time. When water flows into the measuring cylinder (25), the servo water pump (7) is turned off, indicating that the saturation state has been reached. S4: Start the X-ray transmitter (2), select a preheating mode according to the length of time since the last shutdown, and preheat. After the preheating is completed, the X-ray transmitter (2) emits a beam, and the array detector (6) receives the signal; S5: Pressurize in stages. For each stage, calculate the corresponding permeability coefficient. Record the mass of water flowing into the measuring cylinder (25) within a certain period of time to obtain the permeability coefficient. For each stage of water pressure increase, when it is found that the water flowing into the measuring cylinder (25) has just become turbid, start the X-ray transmitter (2) to scan, start the motor to drive the turntable (5) to rotate, and the turntable (5) drives the cylinder (14) to rotate to perform CT scanning, obtain the CT image of the soil inside during the seepage damage process in real time, and perform three-dimensional reconstruction of the soil. S6: Apply loads step by step to make the sample more severely damaged by penetration, and the water flowing into the measuring cylinder (25) becomes increasingly turbid until it is completely destroyed. Then the X-ray transmitter (2) stops emitting beams, all systems stop working, the CT machine radiation source is turned off, the cylinder (14) is removed, and the test ends; S7: After all detection tasks are completed, wait for the X-ray transmitter (2) to cool down, turn off the power of the X-ray transmitter (2), and disconnect all subsystems except the computer.

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