Device and method for testing influence of moisture seepage on soil structure

Abstract

The invention discloses a device and method for testing the influence of moisture seepage on a soil structure, and the device comprises a sample assembly, a CT radiation imaging module, an axial loading module, a variable head seepage module, and a control module. A soil body sample is rigidly fixed through the sample assembly, and a coaxial coupling test system is established among the CT radiation imaging module, the axial loading module and the variable head seepage module, so that the soil body is kept relatively static when the axial stress and the controllable head gradient are applied; imaging artifacts, mechanical response deviation and boundary condition inconsistency caused by sample displacement or repositioning are fundamentally avoided. Based on symmetrical arrangement and real-time synchronous control of a radioactive source and a detector, high-resolution and dynamic capture and quantitative analysis can be carried out on the pore structure, water content distribution and the microscopic deformation process in the soil body under the condition that a sample is not damaged.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing technology, and in particular to a test apparatus and method for the effect of water seepage on soil structure. Background Technology

[0002] Most commonly used triaxial seepage test devices only set a constant initial head or allow the head to slowly decrease with natural seepage to determine the mechanical and seepage parameters of soil under a single head condition. However, in areas near natural water bodies such as rivers and seas, shallow aquifers are affected by tides, waves, or artificial precipitation, resulting in significant periodic fluctuations in groundwater head. At the same time, the interior of traditional Darcy seepage devices is not visible, making it impossible to directly observe particle loss and transport processes. This greatly limits the study of the mechanism of soil erosion and changes in mechanical properties under tidal action.

[0003] Existing soil seepage shear parameter tests mostly employ Darcy triaxial seepage apparatus with constant initial head or naturally decaying head. Furthermore, the tests often focus only on external mechanical response parameters of the sample, such as stress, strain curves, and permeability coefficients, lacking direct observation of changes in the soil's internal microstructure. Simultaneously, the seepage conditions are limited, making it difficult to simulate the pulsating effects of groundwater levels under actual conditions such as tides, waves, or artificial periodic precipitation. Moreover, the sample must be disassembled or removed multiple times before and after the test for cross-sectional observation, which easily disturbs the soil structure and fails to obtain full-process, in-situ structural evolution information. Therefore, it is impossible to comprehensively observe the mechanisms of soil structural disturbance, particle initiation and migration, and dynamic changes in shear parameters throughout the entire water seepage process. Summary of the Invention

[0004] This invention provides an experimental apparatus and method for the impact of water seepage on soil structure, to simulate the dynamic seepage conditions of shallow aquifers under tidal or periodic water level changes, thereby enabling real-time visual observation of the soil interior.

[0005] To address the aforementioned technical problems, this invention provides a test apparatus for the impact of water seepage on soil structure, comprising: a sample assembly, a CT radiographic imaging module, an axial loading module, a variable head seepage module, and a control module;

[0006] The sample assembly is coaxially arranged with the axial loading module, the top of the sample assembly is connected to the axial loading module, and the bottom of the sample assembly is fixedly arranged above the variable head seepage module.

[0007] The CT radiographic imaging module includes a radiation source and a detector, which are symmetrically arranged on both sides of the sample assembly.

[0008] The control module is electrically connected to the CT radiographic imaging module, the axial loading module, and the variable head seepage module, respectively.

[0009] The sample assembly is used to fix the soil sample and control the soil sample to prevent it from shifting during the test of the effect of water seepage on the soil structure; the axial loading module is used to apply axial stress to the soil sample; the variable head seepage module is used to conduct seepage tests on the soil sample; the radiation source is used to detect the internal structure distribution of the soil sample, and the detector is used to image the internal structure distribution; the control module is used to control the CT radiographic imaging module, the axial loading module, and the variable head seepage module to conduct the test of the effect of water seepage on the soil structure.

[0010] This invention organically integrates a sample assembly, a CT imaging module, an axial loading module, a variable head seepage module, and a control module. It enables simultaneous coupling of axial loading, controlled seepage, and real-time tomographic imaging of soil samples on a single testing platform. The sample assembly rigidly fixes the soil sample and establishes a coaxially coupled testing system between the CT imaging module, the axial loading module, and the variable head seepage module. This keeps the soil relatively stationary under axial stress and a controlled head gradient, fundamentally avoiding imaging artifacts, mechanical response deviations, and boundary condition inconsistencies caused by sample displacement or repositioning. Based on the symmetrical arrangement and real-time synchronous control of the radiation source and detector, high-resolution, dynamic capture and quantitative analysis of the soil's internal pore structure, water content distribution, and micro-deformation processes can be performed without damaging the sample. Simultaneously, the axial loading module and the variable head seepage module ensure the alignment of the load and water flow axes, avoiding errors caused by eccentricity or lateral displacement.

[0011] Furthermore, the sample assembly includes a sample and a sample cap;

[0012] The sample is placed vertically above the variable head seepage module;

[0013] The sample cap is detachably mounted on the top of the sample and is connected to the axial loading module.

[0014] The technical feature of this invention, which places the sample vertically on the variable head seepage module, enables uniform stress transfer and stable drainage at the end of the soil sample. The detachable sample cap facilitates the replacement of sample structures of different sizes or with different drainage characteristics, thereby enhancing the applicability and ease of operation of the device.

[0015] Furthermore, the axial loading module includes a loading rod and an axial loading body;

[0016] The loading rod is a hollow structure, located below the axial loading body, and extends vertically downwards to the top of the sample, and is connected to the sample through a sample cap.

[0017] This invention combines a hollow loading rod with an axial loading body. The loading rod extends vertically through the top of the specimen and is connected via a specimen cap. This ensures precise transmission of the axial load along the specimen's central axis while also providing a channel for internal pore water pressure piping. This structure enables coaxial coupling of loading and pore water pressure measurement or injection, reducing secondary disturbance to the specimen. Simultaneously, high-sensitivity force and displacement sensors on the rod synchronously acquire load and deformation data, improving testing accuracy.

[0018] Furthermore, the variable head seepage module includes a seepage base, a diversion joint, a seepage outlet, a water collection chamber, a particle collection chamber, and a seepage system;

[0019] The seepage base is located below the sample assembly. A diversion connector is installed at the lower part of the seepage base. The first end of the diversion connector is connected to the seepage port and the water collection chamber, and the second end of the diversion connector is connected to the particle collection chamber. The third end of the diversion connector is connected to the seepage system through a pipe.

[0020] This invention combines a seepage base, a diversion connector, a seepage port, a water collection chamber, a particle collection chamber, and a seepage system into a variable head seepage module, achieving precise separation and simultaneous management of drainage, particle erosion, and multi-channel head control. The multi-port design of the diversion connector allows for simultaneous monitoring of water flow, turbidity, and particle quantity, and flexible switching between different head inputs; the seepage system provides a controllable head gradient, thereby comprehensively studying the dynamic characteristics of seepage erosion and permeability coefficient changes with head, greatly improving the adjustability of experimental conditions and the completeness of data.

[0021] Furthermore, the testing apparatus also includes an exhaust structure disposed at the connection between the sample assembly and the axial loading module.

[0022] This invention incorporates an exhaust structure at the connection between the sample assembly and the axial loading module, effectively removing residual gas from the sample and ensuring that the soil sample pores are filled with water throughout the test, maintaining constant pore water pressure boundary conditions. This design not only avoids pressure errors caused by gas compression or degassing but also improves the repeatability and accuracy of consolidation drainage tests and seepage tests.

[0023] Furthermore, a porous plate is provided on the top of the sample assembly.

[0024] The present invention adds a porous plate to the top of the sample assembly, which can further optimize the uniformity of the upper drainage channel, control the drainage rate and pore pressure distribution during the test, and reduce the influence of end friction constraint on the deformation results.

[0025] Secondly, the present invention provides a test method for the effect of water seepage on soil structure, comprising: using the aforementioned test apparatus for the effect of water seepage on soil structure to conduct tests on the effect of water seepage on soil structure, including:

[0026] The CT imaging module acquires CT scan image data of the site soil sample and performs three-dimensional reconstruction processing on the CT scan image data to obtain the initial internal structure distribution information of the site soil sample.

[0027] The physical parameters of the site soil sample are obtained, and the axial loading module is controlled to conduct a triaxial compression test on the site soil sample based on the preset axial speed and preset axial pressure. In the triaxial compression test, the strength parameters and deformation parameters of the site soil sample are obtained based on the physical parameters.

[0028] Based on a preset cycle and hydraulic gradient control, the variable head seepage module conducts a stepped variable head seepage test on the site soil sample. In the variable head seepage test, the seepage erosion characteristics and permeability coefficient variation curves of the site soil sample under various hydraulic gradients are obtained based on the strength parameters and deformation parameters.

[0029] Based on the seepage erosion characteristics, the permeability coefficient variation curve, and the initial internal structure distribution information, the critical hydraulic gradient and soil deformation parameters of the site soil sample are determined, and the soil change observation of the site soil sample is completed.

[0030] This invention utilizes this device to conduct CT three-dimensional reconstruction, physical parameter testing, axial compression, and stepped variable head seepage tests, enabling comprehensive characterization of soil from three dimensions: microstructure, mechanical properties, and seepage characteristics. For the first time, it obtains initial structural distribution information under dynamic loading and seepage coupling conditions, and, combined with strength deformation and seepage erosion parameters, fully reveals the influence mechanism of water seepage on soil structural disturbance and shear parameters. This provides highly reliable experimental evidence for subsequent theoretical modeling and engineering design, while also making soil structural changes visible and facilitating experimental observation.

[0031] Furthermore, before conducting a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure, the triaxial compression test, prior to obtaining the strength and deformation parameters of the site soil sample based on the physical parameters, further includes:

[0032] Consolidation and drainage tests were conducted on soil samples from the site based on a preset confining pressure. The drainage volume and drainage rate of the soil samples were monitored until the drainage rate reached a preset drainage threshold, thus completing the consolidation and drainage test.

[0033] This invention adds a consolidation-drainage test before the compression test and monitors the drainage rate to a threshold, ensuring that the specimen reaches a fully consolidated state before loading and eliminating the interference of pre-consolidation effect differences on subsequent mechanical parameter measurements. The standardized consolidation-drainage procedure enhances the comparability of strength-deformation parameters and provides stable initial conditions for penetration erosion tests.

[0034] Furthermore, the process of obtaining the physical parameters of the site soil sample involves controlling the axial loading module to conduct a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure. During the triaxial compression test, the strength and deformation parameters of the site soil sample are obtained based on the physical parameters, including:

[0035] Physical property tests were performed on the soil samples from the site to obtain the physical parameters of the soil samples, including moisture content and dry density.

[0036] A triaxial compression test was conducted on the soil sample of the site based on a preset axial velocity and a preset axial pressure to obtain the axial load, axial displacement and drainage of the soil sample.

[0037] In the triaxial compression test, the consolidation height is calculated based on the dry density, and the axial strain is calculated based on the consolidation height and the axial displacement.

[0038] The strength parameters are determined based on the axial strain force, and the strength parameters include the effective internal friction angle and the effective cohesion.

[0039] The deformation parameters are determined based on the dry density, water content, and axial strain, and the deformation parameters include the compressive modulus, volumetric compressibility coefficient, and Poisson's ratio.

[0040] This invention obtains moisture content and dry density through physical property testing, and simultaneously collects axial load, displacement, and displacement during triaxial compression tests. By combining this with the consolidation height, axial strain force is calculated, and effective internal friction angle, cohesion, and various deformation parameters are accurately derived. This achieves multi-source verification of test data and automated calculation. This method improves the accuracy and efficiency of strength and deformation parameters, providing a systematic data processing workflow for soil mechanical property research.

[0041] Furthermore, the variable head seepage module, based on a preset period and hydraulic gradient control, conducts a stepped variable head seepage test on the site soil sample. In the variable head seepage test, based on the strength parameters and deformation parameters, the seepage erosion characteristics and permeability coefficient variation curves of the site soil sample under various hydraulic gradients are obtained, including:

[0042] During the steady flow cycle, the soil sample of the site is subjected to steady flow infiltration based on a preset initial head difference to obtain the basic seepage flow rate;

[0043] In the stepped cycle, the water head difference is increased based on the preset water head difference increment and the corresponding increment time to conduct a variable head seepage test on the soil sample of the site. In the variable head seepage test, the real-time seepage flow rate, effluent turbidity and particle collection amount are obtained.

[0044] The permeability coefficient variation curve is determined based on the strength parameters, deformation parameters, and particle capture amount in each step cycle.

[0045] The characteristics of seepage erosion are obtained based on the real-time seepage flow rate and effluent turbidity in each step cycle.

[0046] This invention combines steady flow with stepped variable head seepage, and obtains real-time seepage flow, turbidity and particle collection in each cycle to plot the permeability coefficient change curve and erosion characteristics. It can meticulously depict the seepage erosion dynamics under different hydraulic gradients. This segmented measurement method can obtain basic seepage parameters and capture particle migration and media damage evolution in real time, providing rich experimental data support for predicting critical hydraulic gradients and soil stability. Attached Figure Description

[0047] Figure 1 A schematic diagram of a test apparatus for the effect of water seepage on soil structure provided in an embodiment of the present invention;

[0048] Figure 2 Another structural schematic diagram of an experimental device for testing the effect of water seepage on soil structure, provided in an embodiment of the present invention;

[0049] Figure 3 A schematic flowchart of an experimental method for the effect of water seepage on soil structure provided in an embodiment of the present invention;

[0050] The reference numerals for the accompanying drawings in the specification are as follows:

[0051] 1. Axial loading module; 2. Sample assembly; 3. CT radiographic imaging module; 4. Variable head seepage module; 5. Loading rod; 6. Sample cap; 7. Sample; 8. Seepage system; 9. Seepage base; 10. Diverter; 11. Seepage port; 12. Particle collection chamber; 13. Water collection chamber; 14. Exhaust structure; 15. Porous plate; 16. CT radiographic source; 17. Flat panel detector; 18. Axial loading body. Detailed Implementation

[0052] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0053] The terms "first" and "second," etc., in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0054] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0055] Example 1

[0056] See Figure 1 , Figure 1 This is a schematic diagram of a test apparatus for investigating the effect of water seepage on soil structure, provided in an embodiment of the present invention. The apparatus includes: a sample assembly, a CT imaging module, an axial loading module, a variable head seepage module, and a control module.

[0057] The sample assembly is coaxially arranged with the axial loading module, the top of the sample assembly is connected to the axial loading module, and the bottom of the sample assembly is fixedly arranged above the variable head seepage module.

[0058] The CT radiographic imaging module includes a radiation source and a detector, which are symmetrically arranged on both sides of the sample assembly.

[0059] The control module is electrically connected to the CT imaging module, the axial loading module, and the variable head seepage module, respectively.

[0060] The sample assembly is used to fix the soil sample and control the soil sample to prevent it from shifting during the test of the effect of water seepage on the soil structure; the axial loading module is used to apply axial stress to the soil sample; the variable head seepage module is used to conduct seepage tests on the soil sample; the radiation source is used to detect the internal structure distribution of the soil sample, and the detector is used to image the internal structure distribution; the control module is used to control the CT radiographic imaging module, the axial loading module, and the variable head seepage module to conduct the test of the effect of water seepage on the soil structure.

[0061] See Figure 2 , Figure 2 This is another schematic diagram of a test device for the effect of water seepage on soil structure provided in an embodiment of the present invention.

[0062] In this embodiment, the sample assembly, CT imaging module, axial loading module, variable head seepage module, and control module are organically integrated. This enables simultaneous coupling of axial loading, controlled seepage, and real-time tomographic imaging of soil samples on the same test platform. On one hand, the axial loading module and variable head seepage module ensure the alignment of the load and water flow axes, avoiding errors caused by eccentricity or lateral displacement. On the other hand, the CT imaging module symmetrically surrounds the sample assembly, allowing real-time acquisition of information on the evolution of the internal structure of the sample during loading and seepage. Therefore, this device can achieve multi-physics field linkage testing of force, deformation, flow, and structural evolution, thereby simulating the dynamic seepage conditions of shallow aquifers under tidal or periodic water level changes, and thus enabling real-time visual observation of the soil interior.

[0063] In this embodiment, the sample assembly includes a sample and a sample cap;

[0064] The sample is placed vertically above the variable head seepage module;

[0065] The sample cap is detachably mounted on the top of the sample and is connected to the axial loading module.

[0066] In this embodiment, the sample assembly consists of a sample and a detachable sample cap. Specifically, the sample is a soil sample, which is pre-saturated and shaped to the designed dimensions, and then placed vertically on the seepage base of the variable head seepage module. Its upper and lower ends are connected to the seepage channel and the axial loading channel through perforated plates, respectively, to ensure the uniformity of pore water discharge and axial load transfer under steady flow conditions. The sample cap is made of rigid metal and is detachably fitted onto the top of the sample, securely engaging with the sample body via threads or a quick-release mechanism. Its upper end is coaxially connected to the loading rod of the axial loading module through a connector, enabling accurate load transfer along the central axis of the sample during loading. It can also be easily disassembled after the test for sample replacement or subsequent maintenance.

[0067] In this embodiment, the technical feature of placing the sample vertically on the variable head seepage module can achieve uniform stress transfer and stable drainage at the end of the soil sample. The detachable sample cap facilitates the replacement of sample structures of different sizes or with different drainage characteristics, thereby enhancing the applicability and ease of operation of the device.

[0068] In this embodiment, the axial loading module includes a loading rod and an axial loading body;

[0069] The loading rod is a hollow structure, located below the axial loading body, and extends vertically downwards to the top of the sample, and is connected to the sample through a sample cap.

[0070] In this embodiment, the axial loading module consists of an axial loading body and a hollow loading rod. The axial loading body is located at the top of the device and contains an electric or servo drive mechanism that can apply force downwards according to a preset rate and path. The loading rod is made of high-strength alloy material and has a hollow structure. Its upper end is connected to the axial loading body via a pin or flange, and its lower end extends vertically downwards to the top of the sample assembly, and is coaxially fastened to the sample body through the central through-hole of the sample cap. The hollow loading rod has a pore water pressure pipeline or a sensor cable channel inside, which ensures accurate force transmission and facilitates online monitoring of the pore water pressure or deformation signal inside the sample during loading. This does not affect the loading stiffness and coaxiality, thus ensuring that the axial load is applied uniformly along the central axis of the sample.

[0071] In this embodiment, a hollow loading rod is combined with the axial loading body, with the loading rod vertically penetrating to the top of the specimen and connected via a specimen cap. This ensures accurate transmission of the axial load along the central axis of the specimen while also providing a channel for the internal pore water pressure pipeline. This structure enables coaxial coupling of loading and pore water pressure measurement or injection, reducing secondary disturbance to the specimen. Simultaneously, high-sensitivity force and displacement sensors on the rod synchronously acquire load and deformation data, improving testing accuracy.

[0072] In this embodiment, the variable head seepage module includes a seepage base, a diversion joint, a seepage port, a water collection chamber, a particle collection chamber, and a seepage system;

[0073] The seepage base is located below the sample assembly. A diversion connector is installed at the lower part of the seepage base. The first end of the diversion connector is connected to the seepage port and the water collection chamber, and the second end of the diversion connector is connected to the particle collection chamber. The third end of the diversion connector is connected to the seepage system through a pipe.

[0074] In this embodiment, the variable head seepage module comprises a seepage base, a diversion connector, a seepage outlet, a water collection chamber, a particle collection chamber, and an external seepage system. Specifically, the seepage base is located below the sample assembly and fits tightly with the porous plate at the bottom of the sample to ensure uniform water flow into the sample. A multi-channel diversion connector is fixedly installed at the bottom of the base. Its first end is connected to the seepage outlet and the water collection chamber via short pipes to guide and collect the clean water discharged from the sample. Its second end is connected to the particle collection chamber to capture and isolate fine particles lost with the drainage. The third end of the diversion connector is connected to the external seepage system via a flexible pipe. This system can provide adjustable stepped or steady-flow head to precisely control the seepage pressure and flow rate at different stages of the test. Through the above combined structure, the drainage volume, water turbidity, and particle erosion volume can be obtained simultaneously in a single test, achieving comprehensive and dynamic monitoring of soil permeability and erosion characteristics.

[0075] In this embodiment, the seepage base, diversion connector, seepage port, water collection chamber, particle collection chamber, and seepage system are combined into a variable head seepage module, achieving precise separation and synchronous management of drainage, particle erosion, and multi-channel head control. The multi-port design of the diversion connector can simultaneously monitor the outflow rate, turbidity, and particle quantity, and flexibly switch between different head inputs; the seepage system can provide a controllable head gradient, thereby comprehensively studying the dynamic characteristics of seepage erosion and permeability coefficient changes with head, greatly improving the adjustability of experimental conditions and the completeness of data.

[0076] In this embodiment, the testing apparatus further includes an exhaust structure, which is disposed at the connection between the sample assembly and the axial loading module.

[0077] In this embodiment, the venting structure is located on the side or in the center channel of the sample cap at the connection between the sample assembly and the axial loading module. Specifically, an airtight interface is reserved between the sample cap and the flange connection surface of the loading rod, and an openable venting valve or one-way venting valve core is installed. This venting structure communicates with the internal pores of the sample through a small through hole on the valve or valve core, so that residual air between the top of the sample and the loading system can be removed by opening the venting valve before the saturated soil sample is installed and loading begins. During loading or seepage, if overpressure is generated due to gas accumulation, it can also be released in time to ensure accurate pore water pressure and full saturation of the soil sample, thereby eliminating the interference of gas on load transfer and pore pressure measurement, and improving the repeatability and measurement accuracy of the test.

[0078] In this embodiment, an exhaust structure is added at the connection between the sample assembly and the axial loading module. This effectively removes residual gas from the sample, ensuring that the soil sample pores are filled with water throughout the test, maintaining constant pore water pressure boundary conditions. This design not only avoids pressure errors caused by gas compression or degassing but also improves the repeatability and accuracy of consolidation drainage tests and seepage tests.

[0079] In this embodiment, a porous plate is provided on the top of the sample assembly.

[0080] In this embodiment, a porous plate is installed on the top of the sample assembly. The porous plate is made of corrosion-resistant metal or high-strength ceramic, and its pore size is much smaller than the particle size of the finest particles in the soil sample. It is also vacuum saturated to eliminate air bubbles. The porous plate is tightly fitted to the sample cap by a sealing ring, which can withstand axial loads during the test and achieve uniform drainage. Under loading or seepage, pore water is uniformly discharged upward through the porous plate, avoiding the influence of uneven flow velocity at the end or sudden changes in pore pressure gradient on soil sample deformation. At the same time, it effectively prevents the loss of fine soil particles, thereby ensuring the accuracy and repeatability of the test results.

[0081] In this embodiment, a porous plate is added to the top of the sample assembly, which can further optimize the uniformity of the upper drainage channel, control the drainage rate and pore pressure distribution during the test, and reduce the influence of end friction constraints on the deformation results.

[0082] Please refer to Figure 3 , Figure 3 A schematic flowchart of an experimental method for assessing the impact of water seepage on soil structure, provided by an embodiment of the present invention, includes steps 301 to 304, as detailed below:

[0083] In this embodiment, an experiment on the effect of water seepage on soil structure is conducted using the aforementioned experimental apparatus, including:

[0084] Step 301: Obtain CT scan image data of the site soil sample through the CT radiographic imaging module, and perform three-dimensional reconstruction processing on the CT scan image data to obtain the initial internal structure distribution information of the site soil sample.

[0085] Step 302: Obtain the physical parameters of the soil sample, and control the axial loading module to conduct a triaxial compression test on the site soil sample based on the preset axial speed and preset axial pressure. In the triaxial compression test, obtain the strength parameters and deformation parameters of the site soil sample based on the physical parameters.

[0086] Step 303: Based on the preset period and hydraulic gradient, the variable head seepage module is used to conduct a stepped variable head seepage test on the site soil sample. In the variable head seepage test, the seepage erosion characteristics and permeability coefficient change curves of the site soil sample under various hydraulic gradients are obtained based on the strength parameters and deformation parameters.

[0087] Step 304: Based on the seepage erosion characteristics, the permeability coefficient variation curve and the initial internal structure distribution information, determine the critical hydraulic gradient and soil deformation parameters of the site soil sample, and complete the soil change observation of the site soil sample.

[0088] In this embodiment, a saturated soil sample is first loaded into the sample assembly of the test apparatus. The CT imaging module is then activated via the control module to perform multi-angle CT scans on the sample to obtain continuous tomographic images. Subsequently, an image reconstruction algorithm is used to perform three-dimensional reconstruction of the CT scan data to obtain the initial pore structure and density distribution information of the soil. Next, according to the experimental design, the axial loading module is controlled to apply triaxial compression loading to the soil sample based on the set axial velocity and axial pressure. Simultaneously, built-in sensors record the axial load, displacement, and drainage volume in real time, and calculate the sample's effective internal friction angle, effective cohesion, compression modulus, volumetric compressibility coefficient, and Poisson's ratio, among other strength-deformation parameters. Following this, based on a preset steady-flow and stepped hydraulic gradient scheme, the variable head seepage module is activated in stages, maintaining a constant seepage cycle at each hydraulic gradient level. Drainage volume, turbidity, and particle erosion are collected through the water collection chamber and particle collection chamber, respectively, and the permeability coefficient variation curve and erosion characteristics are derived accordingly. Finally, by combining the initial three-dimensional structural distribution, the obtained strength-deformation parameters and seepage erosion data, the critical hydraulic gradient and corresponding deformation response of the soil were determined through comprehensive analysis, so as to realize the observation and evaluation of the entire process of soil structural disturbance and shear parameter changes under the action of water seepage.

[0089] In this embodiment, based on this device, CT three-dimensional reconstruction, physical parameter testing, axial compression, and stepped variable head seepage tests are conducted, enabling comprehensive characterization of the soil from three dimensions: microstructure, mechanical properties, and seepage characteristics. For the first time, initial structural distribution information is obtained under dynamic loading and seepage coupling conditions. Combined with strength deformation and seepage erosion parameters, the influence mechanism of water seepage on soil structural disturbance and shear parameters is fully revealed, providing highly reliable experimental evidence for subsequent theoretical modeling and engineering design. Simultaneously, it visualizes soil structural changes, facilitating experimental observation.

[0090] In this embodiment, representative saturated water-bearing soil samples are collected from sites experiencing actual foundation settlement due to tidal influences. The soil samples can be retained undisturbed or reshaped in the laboratory. For undisturbed samples, careful handling is required during preparation. For reshaped samples, the samples are compacted or pressed in a sample preparation tube according to the designed dry density and moisture content to form cylindrical specimens that meet the requirements of triaxial testing. The specimen dimensions should match the specifications of the triaxial testing apparatus, with a commonly used diameter of 39.1 mm (approximately 12 cm² cross-sectional area). 2 ), height 80mm (height-to-diameter ratio approximately 2:1), or diameter 50mm and height 100mm.

[0091] In this embodiment, the initial physical properties of the soil sample are first determined, including moisture content, dry density, and particle size distribution. When the prepared soil sample is installed in the triaxial testing apparatus, its original structure, density, and moisture content should be maintained to the greatest extent possible, while ensuring close contact, accurate alignment, and reliable sealing between the sample and components such as the seepage base, sample cap, and rubber diaphragm. Specific operations include:

[0092] Place permeable stones on the seepage base;

[0093] Place the sample into the rubber membrane and use O-rings to secure the upper and lower edges of the membrane to the seepage base and the sample cap respectively, ensuring that there are no wrinkles or damage.

[0094] Install the sample cap onto the top of the sample;

[0095] Place the entire seepage base along with the sample into the pressure chamber, cover it with the top cover and tighten the bolts to ensure a tight seal.

[0096] Slowly fill the pressure chamber with water while opening the vent to purge the air from the chamber until water overflows from the vent, then close the vent.

[0097] Connect the confining pressure (σ3) supply pipeline, the axial loading system, and the drainage measurement device (i.e., the water collection tank).

[0098] In this embodiment, an observation window should be reserved on the side wall of the sample to facilitate visual monitoring of the initiation and migration process of soil particles using CT scanning equipment. Finally, the seepage observation system and data acquisition system should be connected, and the parameters of each sensor and instrument should be checked and calibrated to ensure that the equipment is in normal working order and the data is accurate and reliable.

[0099] In this embodiment, before conducting a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure, the triaxial compression test further includes the following step:

[0100] Consolidation and drainage tests were conducted on soil samples from the site based on a preset confining pressure. The drainage volume and drainage rate of the soil samples were monitored until the drainage rate reached a preset drainage threshold, thus completing the consolidation and drainage test.

[0101] In this embodiment, before conducting the triaxial compression test and obtaining the sample strength and deformation parameters based on the preset axial velocity and axial pressure, a lateral omnidirectional confining pressure is first applied to the site soil sample according to the set confining pressure value, and kept constant. At the same time, the sample is consolidated and drained through the top and bottom perforated plates and drainage channels, and the cumulative volume and drainage rate of the drained water are monitored and recorded in real time. When the continuously monitored drainage rate gradually decreases to below the preset drainage rate threshold, the consolidation and drainage process is considered to be basically completed, thereby eliminating the influence of pore water pressure on subsequent loading and ensuring that the soil sample reaches a fully consolidated state before conducting the triaxial compression test.

[0102] In this embodiment, the acquisition of physical parameters of the soil sample involves controlling the axial loading module to perform a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure. During the triaxial compression test, the strength and deformation parameters of the site soil sample are acquired based on the physical parameters, including:

[0103] Physical property tests were performed on the soil samples from the site to obtain the physical parameters of the soil samples, including moisture content and dry density.

[0104] A triaxial compression test was conducted on the soil sample of the site based on a preset axial velocity and a preset axial pressure to obtain the axial load, axial displacement and drainage of the soil sample.

[0105] In the triaxial compression test, the consolidation height is calculated based on the dry density, and the axial strain is calculated based on the consolidation height and the axial displacement.

[0106] The strength parameters are determined based on the axial strain force, and the strength parameters include the effective internal friction angle and the effective cohesion.

[0107] The deformation parameters are determined based on the dry density, water content, and axial strain, and the deformation parameters include the compressive modulus, volumetric compressibility coefficient, and Poisson's ratio.

[0108] In this embodiment, before the experiment begins, the soil samples collected from the site are first subjected to physical property tests to determine their basic physical parameters such as moisture content and dry density. Then, the samples are loaded into the specimen assembly and a preset axial loading speed and axial pressure are applied to initiate the triaxial compression test. Simultaneously, the axial load, axial displacement, and drainage volume of the samples are recorded in real time using force sensors, displacement sensors, and a bottom plate drainage measurement device on the loading rod. During the experiment, the consolidation height of the samples is calculated based on their dry density, and the axial strain force of the samples is obtained by combining this with the axial displacement measured during loading. Furthermore, based on the obtained axial strain force, the effective internal friction angle φ′ and effective cohesion c′ of the samples are derived using the Mohr-Coulomb failure criterion. Based on the dry density, moisture content, and axial strain force, the compressibility modulus Es, volumetric compressibility coefficient mv, and Poisson's ratio ν of the samples are calculated using the relationship between the slope of the stress-strain curve and the volumetric strain rate, thereby obtaining complete strength and deformation parameters, providing a basis for data analysis in subsequent seepage erosion tests.

[0109] In this embodiment, before compression loading is applied using the triaxial testing equipment, the specimen is first scanned using a CT radiation source to obtain an initial image of the soil structure under no-load conditions. After the initial state acquisition is completed, a conventional triaxial consolidated drained (CD) compression test is conducted under no seepage head. The test employs axial strain control, with the loading rod driven at a constant, slow rate of 0.5%–2% / min to gradually apply the axial load. Simultaneously, a pressure control system maintains a constant lateral confining pressure σ3, which can be estimated based on field surveys or experience to simulate the initial stress state in the field and eliminate installation disturbances. During the shearing process, the drain valve is opened to allow pore water to drain freely, and the drainage volume is measured in real time through a water collection chamber to calculate the specimen volume change.

[0110] In this embodiment, the axial load P and axial displacement ΔL (and the axial strain ε) should be recorded continuously or at fixed intervals throughout the test. a=ΔL / H0, where H0 is the height of the consolidated sample), confining pressure σ3, and drainage ΔVd; and under the combined action of tidal forces and axial load, radial strain, pore water pressure, and seepage flow rate are monitored simultaneously. The test ends when any of the following conditions are met: ① axial strain reaches the predetermined upper limit (15%–20%); ② axial stress reaches a peak and decreases significantly; ③ axial stress enters the ideal plastic stage and remains stable. After the compression stage, the axial load and confining pressure are slowly removed, and the water in the pressure chamber is drained through the drain valve; subsequently, without removing the sample, in-situ scanning is performed using a CT radiation source to obtain the structural changes of the soil after loading. By analyzing the stress-strain curves and failure envelope, strength parameters such as the effective internal friction angle φ′ and effective cohesion c′ can be calculated; and deformation parameters such as the compression modulus Es, volumetric compressibility coefficient mv, and Poisson's ratio ν are simultaneously measured from the stress-strain relationship, volume change rate, and transverse strain, providing complete experimental evidence for evaluating the impact of water seepage on soil structural disturbance and shear characteristics.

[0111] In this embodiment, moisture content and dry density are obtained through physical property testing, and axial load, displacement, and displacement are simultaneously collected during triaxial compression tests. This allows for the calculation of axial strain force and the accurate derivation of effective internal friction angle, cohesion, and various deformation parameters by combining the consolidation height. This achieves multi-source verification and automated calculation of test data. This method improves the accuracy and efficiency of strength and deformation parameters, providing a systematic data processing workflow for soil mechanical property research.

[0112] In this embodiment, the variable head seepage module, based on a preset period and hydraulic gradient control, conducts a stepped variable head seepage test on the site soil sample. During the variable head seepage test, the seepage erosion characteristics and permeability coefficient variation curves of the site soil sample under various hydraulic gradients are obtained based on the strength parameters and deformation parameters, including:

[0113] During the steady flow cycle, the soil sample of the site is subjected to steady flow infiltration based on a preset initial head difference to obtain the basic seepage flow rate;

[0114] In the stepped cycle, the water head difference is increased based on the preset water head difference increment and the corresponding increment time to conduct a variable head seepage test on the soil sample of the site. In the variable head seepage test, the real-time seepage flow rate, effluent turbidity and particle collection amount are obtained.

[0115] The permeability coefficient variation curve is determined based on the strength parameters, deformation parameters, and particle capture amount in each step cycle.

[0116] The characteristics of seepage erosion are obtained based on the real-time seepage flow rate and effluent turbidity in each step cycle.

[0117] In this embodiment, firstly, during the steady flow cycle, the seepage system is controlled to provide a preset initial head difference to the sample and keep it constant. The basic seepage flow rate is accurately measured using a water collection chamber as a benchmark for subsequent permeability coefficient calculation. Subsequently, a stepped cycle is entered, and the head difference is gradually increased by the control module according to preset head difference increments and increment times. Seepage continues at each head level, while the seepage flow rate obtained from the water collection chamber, the particle amount collected by the particle collection chamber, and the effluent turbidity are recorded in real time. Combining the previously obtained soil strength parameters (effective internal friction angle, effective cohesion) and deformation parameters (compression modulus, volume compressibility coefficient, Poisson's ratio), according to Darcy's law and the principle of particle mass conservation, the permeability coefficient variation curve with head difference is calculated based on the particle collection amount and flow rate data of each stepped cycle. The hydraulic erosion characteristics are analyzed based on the relationship between flow rate and turbidity, thereby systematically characterizing the seepage erosion behavior and permeability performance evolution law of soil samples under different hydraulic gradients.

[0118] In this embodiment, changes in groundwater level generate varying degrees of water erosion, causing soil particles to migrate and altering the soil structure. A specific water head is applied to the sample through a seepage system, and a booster pump is used to periodically change the water pressure to induce seepage. To ensure the uniformity of fluid flow at the top of the sample, a perforated plate is installed at the top, while no filter is installed at the bottom to prevent fine particles from clogging the filter layer in the seepage base during downward flow. The mixture of seepage water and particles flows from the bottom of the sample into the inlet section of the diversion connector. The diversion connector employs a spiral channel design, generating centrifugal force during fluid rotation, which throws particles against the cavity wall and causes them to settle into the particle collection chamber, while the clean water flows along the outlet section into the water collection chamber, achieving water-solid separation and subsequent treatment.

[0119] In this embodiment, during the first stage (steady flow period): an initial head difference of 0.5m (corresponding to a hydraulic gradient i≈0.1) is applied by a booster pump to establish stable seepage. After the flow rate stabilizes (change <5% / 10min), the basic seepage flow rate Q0 is recorded.

[0120] In this embodiment, the second stage (stepped cycle): stepped voltage boost:

[0121]

[0122] In this embodiment, as the seepage erosion process progresses, movable soil particles are gradually lost from the soil, and k gradually increases and eventually tends towards k0. This indicates that seepage erosion will increase the local permeability coefficient of the soil. Furthermore, seepage erosion causes fine particles to migrate with the water flow, forming localized siltation structures that block the pore channels of the soil, resulting in a decrease in the local soil permeability coefficient. The permeability coefficient k0 after all movable particles in the soil have been lost and the permeability coefficient k in the soil at any time during seepage erosion are specifically as follows:

[0123]

[0124] Where d1 is the minimum diameter of the skeletal pores; μ is the apparent viscosity coefficient of the particle-fluid system; n a n is the porosity of a hypothetical soil mass composed of skeleton particles; n′ is the porosity of the soil mass at a certain moment of infiltration; α is the shape factor of the soil particles; D h The effective particle size of the skeletal particles; s k This represents the volumetric content of the k-th particle group within the skeletal pores.

[0125] In this embodiment, pressurization is stopped immediately when any of the following phenomena occur: (1) after excluding instrument error, the flow rate increases by more than 15%; (2) visible particles are observed peeling off the sample surface through the transparent confining pressure chamber; (3) a large number of soil particles appear in the particle collection chamber.

[0126] In this embodiment, under the action of groundwater seepage, the pore water pressure increases, and the effective stress of the soil decreases. If fine particles cannot fill the pores between coarse particles, the fine particles bear relatively low stress and may move under seepage, resulting in internally unstable soil. Under seepage, fine particles within the soil gradually detach from the interparticle forces, migrating into the pores of the coarse particle skeleton, potentially causing stress redistribution and deformation of the soil skeleton, leading to an erosion process. The type of erosion damage is determined by the following formula:

[0127]

[0128] Among them, P Z Let P' be the critical fine particle content, n be the soil porosity, and β be a correction factor, typically taken as 0.95–1.0. If the fine particle content P′... z ≤P z If it is not piping, then it is considered piping failure; otherwise, it is considered soil erosion failure.

[0129] In this embodiment, under the condition that Darcy's law is satisfied, the arrangement of particles inside the soil remains basically unchanged, and the effective porosity remains unchanged.

[0130] In this embodiment, the critical hydraulic gradient is a crucial criterion for determining the occurrence of seepage erosion and is the initiating condition for large-scale particle movement. Under vertical upward seepage, based on the balance between the buoyant weight of a unit soil volume and water pressure, the Terzaghi critical hydraulic gradient calculation formula is derived:

[0131]

[0132] Among them, I cr γ is the critical hydraulic gradient; s γ represents the relative mass density of the particles; w ρ is the relative mass density of water; n is the porosity.

[0133] However, as seepage progresses, the particle composition in the soil also changes, and calculating the critical hydraulic gradient based on the initial porosity of the sample will result in an overestimation of the calculated value.

[0134] The lower water collection chamber was removed and replaced at constant time intervals, and the water volume was measured. This allowed for the assessment of changes in soil permeability during the testing process. The weight of eroded particles was also measured after sedimentation and drying. Multiple tests were conducted under different hydraulic gradients, and the percentage of fine-particle erosion increasing with time was observed and recorded under varying hydraulic gradients and under constant seepage time.

[0135] If the movable fine particles and the particles that form the initial structure of the soil sample have the same unit weight value (i.e., the same density), then the volume percentage of the eroded particles is equal to the weight percentage.

[0136] Under the above assumptions, the porosity and the resulting changes in volumetric strain can be calculated. These changes can be expressed as the percentage of eroded particles, μ. e The function has the following three possible cases:

[0137] (1) Soil erosion and loss increase the pore volume without changing the main structure of the soil. Under the condition of constant total volume, the void ratio e is related to the volumetric strain ε. v The relationship is as follows:

[0138]

[0139] ε v =0 (5)

[0140] (2) The volume of voids remains constant, and the decrease in total volume is solely due to the loss of soil particles. According to the relationship, this results in a finite increase in volumetric strain and a finite increase in void ratio.

[0141]

[0142] (3) The reduction in total volume is caused by the loss of solid material and the compaction of voids, resulting in the largest volumetric strain and a smaller change in void ratio.

[0143] ΔV V =e0ΔV S (7)

[0144] e = e0

[0145] ε V (μ e )=μ e (8)

[0146] In this embodiment, the compaction of pores caused by the erosion process may further reduce the void ratio relative to the initial value e0. The minimum limit of the void ratio is determined by the maximum allowable compaction amount of the sample. The calculation formula for the critical hydraulic gradient for fine particle initiation in sandy soil, based on the ultimate stress equilibrium state, is as follows:

[0147]

[0148] Where: α is the stress reduction factor; γ′ is the buoyancy unit of the soil; d is the particle size; e is the void ratio; H is the burial depth of fine particles; γ w The specific weight of water; d θk θ represents the equivalent particle size of the soil particles; θ represents the permeation direction; β represents the angle between the pore channel and the horizontal direction; and φ′ represents the effective internal friction angle.

[0149] In this embodiment, the seepage path length within the soil sample is very long compared to the average particle size. In this case, erosion is considered as an effective separation and transport of soil particles. The following relationship represents the percentage of eroded fine particles by weight with respect to the hydraulic gradient (i) and time (t, in hours):

[0150]

[0151] Where μ0 is the initial fine particle content (by weight), t0 = 1 hour, and a, b, c are dimensionless parameters. These parameters are calculated by minimizing the following function E(a, b, c), which represents the numerical result μ. e Compared with experimental results μ′ e The difference between them, the numerical results are given by the equation:

[0152]

[0153] In this embodiment, erosion occurs for any non-zero hydraulic gradient. In well-graded soils with fine-grained components in the silt range, even very low hydraulic gradients can lead to the erosion of the finest particles. The situation may differ for relatively homogeneous coarse-grained soils. Given sufficient time, complete erosion will occur, meaning the erosion process will eventually remove all fine particles (e approaches e0 as t approaches infinity).

[0154] In this embodiment, after particle migration is detected, the current water head is maintained for continuous flushing for 10 minutes, after which the dynamic water head input is stopped. Lost particles are collected and particle size analysis is performed by comparing them with the original gradation.

[0155] In this embodiment, within the continuous domain of the porous soil subjected to seepage, let ρ and ρ fLet represent the mass density of fine particles and the mass density of stationary fine particles per unit volume of soil, respectively. These quantities are functions of position x and time t in a Cartesian three-dimensional coordinate system. Let vector ... v ( x , t () indicates the speed of water flow.

[0156] In this embodiment, the mass conservation relationship of fine particles per unit volume of soil is as follows:

[0157]

[0158] The left-hand side represents the cumulative mass rate change of fine particles, while the right-hand side represents the balance between the inflow and outflow of moving particles.

[0159] In this embodiment, the percentage μ of non-moving fine particles f It can be defined as the initial value μ0 and the value μ of the eroded particles. e Difference:

[0160] μ f ( x ,t)=μ0( x )-μ e ( x ,t) (13)

[0161] Based on the erosion pattern, μ is obtained. f The expression is as follows:

[0162]

[0163] The parameters a, b, and c should be known through inverse analysis of the experimental data. The scalar variable i represents the appropriate mean of the hydraulic gradient at position x at time t, which is equal to the norm of the vector i(x, t).

[0164]

[0165] Since weight percentage equals mass percentage, therefore, for density ρ f This relationship also applies to the initial value ρ0 of the fine particle density:

[0166]

[0167] Introducing Darcy's Law, namely:

[0168] v (x, t) = -k( x ,t)· i (x, t) (17)

[0169] In this embodiment, the erosion rate can be calculated as a function G of water velocity and soil hydraulic conductivity:

[0170]

[0171] By combining the equations, we finally obtained the governing equations:

[0172]

[0173] The equations are obtained by analyzing the boundary value problem where both the flow velocity and the density of the moving fine particles are unknown, and by coupling the equations with the equations controlling the seepage.

[0174] In this embodiment, the governing equation establishes a dynamic equilibrium relationship between seepage shear force, particle drag force, gravity, and cohesion by coupling pore water dynamics with fine particle transport processes. This accurately describes the disintegration and migration behavior of fine particles under different hydraulic gradients and time conditions. Simultaneously, the equation combines particle mass conservation with the seepage flux characterized by Darcy's law, achieving a closed-loop feedback between erosion rate and pore structure changes. This provides a mathematical basis for the numerical simulation of boundary value problems and allows experimental data to be extrapolated to engineering sites. It supports the quantitative prediction of seepage erosion and settlement evolution of foundation soil under tidal or variable head environments, providing a reliable theoretical basis for engineering design and risk prevention.

[0175] In this embodiment, this method can achieve a precise pressure increase of 0.5 kPa / min, accurately capturing the particle initiation critical point. Combined with lateral profile images of the sample acquired by a CT radioactive source, the flow field changes inside the sample are analyzed to study the internal erosion mechanism: the radioactive source emits X-rays to locally irradiate the sample column. As the rays pass through the sample column, due to the non-uniform distribution of soil particles, the rays leave a signal with distinct brightness and darkness on a flat panel detector. This signal is input into an electronic analysis device. Without moving the sample and ensuring the overall sample does not collapse, the initiation and migration phenomena of soil particles are observed and recorded, including the time, location, migration speed, and migration range of particle initiation.

[0176] The seepage test ends when the soil sample deformation and particle loss reach a certain level (such as when the settlement stabilizes or the particle loss is too great to continue).

[0177] After the seepage test, a conventional triaxial compression test was conducted to determine the soil sample's shear strength, elastic modulus, and other mechanical parameters, which were then compared with the parameters under the initial state. A certain confining pressure was applied, determined based on the lateral pressure on the actual foundation soil. This pressure could be estimated through field investigation or experience, allowing the soil sample to stabilize under initial stress for a period of time to eliminate stress disturbances during installation and commissioning. During the experiment, axial pressure (calculated based on the expected superstructure load on the foundation soil at the actual site) was simultaneously applied for compression testing to study the soil's mechanical properties under the combined action of groundwater hydrodynamic head pressure and surface load. Throughout the experiment, data such as axial strain, radial strain, and seepage flow rate of the soil sample were monitored and recorded in real time.

[0178] In this embodiment, during the shearing phase, a consolidated drainage (CD) test is performed. The drain valve is opened to allow drainage, the axial load is measured, and the volume change of the sample is obtained by measuring the amount of drainage collected in the water collection chamber.

[0179] The two-dimensional Biot consolidation equation for porous media simplifies to:

[0180]

[0181] Where K is the soil bulk modulus; σ is the average total stress variation; k x k y β represents the horizontal and vertical permeability coefficients of the soil, respectively; n represents the porosity; β represents the horizontal and vertical permeability coefficients of the soil. f is the compressibility coefficient of the pore fluid.

[0182]

[0183] Record the following data continuously or at fixed intervals: (1) Test parameters: axial load (P), axial displacement (ΔL), calculated axial strain (εa=ΔL / H0, H0 is the height of the specimen after consolidation), confining pressure (σ3), and displacement (ΔV). d (2) Permeability and consolidation parameters: Permeability coefficient k: The impact of groundwater seepage is assessed by back-calculating the drainage rate and Terzaghi consolidation theory. Consolidation coefficient c v It reflects the speed of soil consolidation and predicts settlement time in actual engineering projects.

[0184] The test is terminated when one of the following conditions is met: (1) the axial strain reaches a predetermined value (usually 15% to 20%). (2) the axial stress decreases significantly after reaching its peak (the specimen softens). (3) the axial stress remains relatively stable under ideal plastic conditions.

[0185] In this embodiment, after the current compression test is completed, the axial load is slowly removed. The confining pressure is then slowly removed, and the pressure chamber drain valve is opened to drain the water from the pressure chamber. Without removing the specimen, an in-situ scan of the specimen is performed using a CT radiation source. Using the lateral profile image of the specimen acquired by the CT radiation source, the radiation source emits X-rays to locally irradiate the specimen column. As the rays pass through the specimen column, due to the uneven distribution of soil particles, the rays leave a signal with distinct brightness and darkness on the flat panel detector. This signal is input into electronic analysis equipment. Without moving the specimen and ensuring that the specimen does not collapse, the internal structural changes of the specimen are analyzed to study the internal erosion mechanism.

[0186] In this embodiment, during the critical point determination process in the third stage, the seepage flow rate, sample surface condition, and particle concentration in the particle collection chamber should be closely monitored. Pressurization should be stopped immediately if any of the following phenomena are observed: First, after eliminating instrument error interference, a sudden increase of more than 15% in the drainage flow rate compared to the stable baseline indicates that seepage erosion has entered an unstable stage; second, visible soil particles begin to peel off from the sample sidewalls or top surface through visual observation in the transparent confining chamber, indicating that the hydraulic shear force on the internal fine particles has exceeded the cohesion; third, when a significant increase in soil particles appears in the particle collection chamber, large-scale loss can be confirmed. Once any of the above criteria are met, the critical hydraulic gradient can be considered reached, and pressurization should be stopped immediately to avoid excessive erosion or sample damage. Afterward, the current loading and seepage state should be retained for data recording and subsequent imaging analysis to accurately capture the evolution characteristics of the soil structure before and after the critical point.

[0187] In this embodiment, a combination of steady flow and stepped variable head seepage is used, and real-time seepage flow, turbidity and particle collection are obtained in each cycle to plot the permeability coefficient change curve and erosion characteristics. This can meticulously depict the seepage erosion dynamics under different hydraulic gradients. This segmented measurement method can obtain basic seepage parameters and capture particle migration and media damage evolution in real time, providing rich experimental data support for predicting critical hydraulic gradients and soil stability.

[0188] In this embodiment of the invention, a test device for the effect of water seepage on soil structure is also provided, including a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the above-mentioned test method for the effect of water seepage on soil structure.

[0189] In this embodiment of the invention, a computer-readable storage medium is also provided, which includes a stored computer program, wherein the computer program controls the device where the computer-readable storage medium is located to execute the above-described test method for the effect of water seepage on soil structure when it is running.

[0190] For example, a computer program can be divided into one or more modules, one or more of which are stored in memory and executed by a processor to carry out the present invention. One or more modules can be a series of computer program instruction segments capable of performing a specific function, which describes the execution process of the computer program in a test apparatus for the effect of water seepage on soil structure.

[0191] The testing equipment for the impact of water seepage on soil structure can be a desktop computer, laptop, handheld computer, or cloud server, etc. The testing equipment may include, but is not limited to, processors, memory, and displays. Those skilled in the art will understand that the above-mentioned components are merely examples of testing equipment for the impact of water seepage on soil structure and do not constitute a limitation on the testing equipment for the impact of water seepage on soil structure. It may include more or fewer components, or a combination of certain components, or different components. For example, the testing equipment for the impact of water seepage on soil structure may also include input / output devices, network access devices, buses, etc.

[0192] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the testing equipment for the impact of water seepage on soil structure, connecting all parts of the equipment via various interfaces and lines.

[0193] The memory can be used to store computer programs and / or modules. The processor, by running or executing the computer programs and / or modules stored in the memory, and by calling the data stored in the memory, realizes various functions of the test equipment for measuring the impact of water seepage on soil structure. The memory can mainly include a program storage area and a data storage area. The program storage area can store the operating system, at least one application program required for a function (such as sound playback function, text conversion function, etc.), etc.; the data storage area can store data created according to the use of the mobile phone (such as audio data, text message data, etc.). In addition, the memory can include high-speed random access memory, and can also include non-volatile memory, such as hard disk, RAM, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one disk storage device, flash memory device, or other volatile solid-state storage device.

[0194] The module based on the experiment on the impact of water seepage on soil structure, if implemented as a software functional unit and sold or used as an independent product, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc. Those skilled in the art can understand and implement this without any inventive effort.

[0195] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A test apparatus for the effect of water seepage on soil structure, characterized in that, include: Sample assembly, CT radiographic imaging module, axial loading module, variable head seepage module, and control module; The sample assembly is coaxially arranged with the axial loading module, the top of the sample assembly is connected to the axial loading module, and the bottom of the sample assembly is fixedly arranged above the variable head seepage module. The CT radiographic imaging module includes a radiation source and a detector, which are symmetrically arranged on both sides of the sample assembly. The control module is electrically connected to the CT radiographic imaging module, the axial loading module, and the variable head seepage module, respectively. The sample assembly is used to fix the soil sample and control the soil sample from shifting during the test of the effect of water seepage on the soil structure; the axial loading module is used to apply axial stress to the soil sample. The variable head seepage module is used to conduct seepage tests on the soil sample; the radiation source is used to detect the internal structure distribution of the soil sample, and the detector is used to perform imaging processing on the internal structure distribution; the control module is used to control the CT radiation imaging module, the axial loading module and the variable head seepage module to conduct tests on the impact of water seepage on the soil structure.

2. The experimental apparatus for the effect of water seepage on soil structure as described in claim 1, characterized in that, The sample assembly includes a sample and a sample cap; The sample is placed vertically above the variable head seepage module; The sample cap is detachably mounted on the top of the sample and is connected to the axial loading module.

3. The experimental apparatus for the effect of water seepage on soil structure as described in claim 2, characterized in that, The axial loading module includes a loading rod and an axial loading body; The loading rod is a hollow structure, located below the axial loading body, and extends vertically downwards to the top of the sample, and is connected to the sample through a sample cap.

4. The experimental apparatus for the effect of water seepage on soil structure as described in claim 3, characterized in that, The variable head seepage module includes a seepage base, a diversion joint, a seepage port, a water collection chamber, a particle collection chamber, and a seepage system; The seepage base is located below the sample assembly. A diversion connector is installed at the lower part of the seepage base. The first end of the diversion connector is connected to the seepage port and the water collection chamber, and the second end of the diversion connector is connected to the particle collection chamber. The third end of the diversion connector is connected to the seepage system through a pipe.

5. The experimental apparatus for the effect of water seepage on soil structure as described in claim 4, characterized in that, The test apparatus also includes an exhaust structure, which is disposed at the connection between the sample assembly and the axial loading module.

6. A test apparatus for the effect of water seepage on soil structure as described in any one of claims 1 to 5, characterized in that, The top of the sample assembly is provided with a porous plate.

7. A test method for the effect of water seepage on soil structure, characterized in that, The experiment on the effect of water seepage on soil structure is conducted using the experimental apparatus for the effect of water seepage on soil structure as described in any one of claims 1 to 6, comprising: The CT imaging module acquires CT scan image data of the site soil sample and performs three-dimensional reconstruction processing on the CT scan image data to obtain the initial internal structure distribution information of the site soil sample. The physical parameters of the site soil sample are obtained, and the axial loading module is controlled to conduct a triaxial compression test on the site soil sample based on the preset axial speed and preset axial pressure. In the triaxial compression test, the strength parameters and deformation parameters of the site soil sample are obtained based on the physical parameters. Based on a preset cycle and hydraulic gradient control, the variable head seepage module conducts a stepped variable head seepage test on the site soil sample. In the variable head seepage test, the seepage erosion characteristics and permeability coefficient variation curves of the site soil sample under various hydraulic gradients are obtained based on the strength parameters and deformation parameters. Based on the seepage erosion characteristics, the permeability coefficient variation curve, and the initial internal structure distribution information, the critical hydraulic gradient and soil deformation parameters of the site soil sample are determined, and the soil change observation of the site soil sample is completed.

8. The test method for the effect of water seepage on soil structure as described in claim 7, characterized in that, Before conducting a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure, the triaxial compression test further includes, prior to obtaining the strength and deformation parameters of the site soil sample based on the physical parameters: Consolidation and drainage tests were conducted on soil samples from the site based on a preset confining pressure. The drainage volume and drainage rate of the soil samples were monitored until the drainage rate reached a preset drainage threshold, thus completing the consolidation and drainage test.

9. The test method for the effect of water seepage on soil structure as described in claim 8, characterized in that, The process involves acquiring the physical parameters of the site soil sample, controlling the axial loading module to perform a triaxial compression test on the site soil sample based on a preset axial velocity and a preset axial pressure, and acquiring the strength and deformation parameters of the site soil sample based on the physical parameters during the triaxial compression test, including: Physical property tests were performed on the soil samples from the site to obtain the physical parameters of the soil samples, including moisture content and dry density. A triaxial compression test was conducted on the soil sample of the site based on a preset axial velocity and a preset axial pressure to obtain the axial load, axial displacement and drainage of the soil sample. In the triaxial compression test, the consolidation height is calculated based on the dry density, and the axial strain is calculated based on the consolidation height and the axial displacement. The strength parameters are determined based on the axial strain force, and the strength parameters include the effective internal friction angle and the effective cohesion. The deformation parameters are determined based on the dry density, water content, and axial strain, and the deformation parameters include the compressive modulus, volumetric compressibility coefficient, and Poisson's ratio.

10. The test method for the effect of water seepage on soil structure as described in claim 9, characterized in that, The variable head seepage module, based on a preset period and hydraulic gradient control, conducts a stepped variable head seepage test on the site soil samples. During the variable head seepage test, based on the strength and deformation parameters, the seepage erosion characteristics and permeability coefficient variation curves of the site soil samples under various hydraulic gradients are obtained, including: During the steady flow cycle, the soil sample of the site is subjected to steady flow infiltration based on a preset initial head difference to obtain the basic seepage flow rate; In the stepped cycle, the water head difference is increased based on the preset water head difference increment and the corresponding increment time to conduct a variable head seepage test on the soil sample of the site. In the variable head seepage test, the real-time seepage flow rate, effluent turbidity and particle collection amount are obtained. The permeability coefficient variation curve is determined based on the strength parameters, deformation parameters, and particle capture amount in each step cycle. The characteristics of seepage erosion are obtained based on the real-time seepage flow rate and effluent turbidity in each step cycle.

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