Ultra-large vertical compression horizontal seepage erosion experiment box device and experiment method

Abstract

The invention discloses an ultra-large vertical compression horizontal seepage erosion experiment box device and an experiment method, and belongs to the field of civil and hydraulic engineering. The main body of the device is a high-strength test box body, the internal size of a sample bin is 1000mm * 1000mm * 1000mm, and the maximum vertical load reaches 10MPa; the top cover is provided with a peripheral air bag and an anti-seepage strip, so that self-adaptive sealing under ultrahigh pressure is realized; 64 pressure sensors are arranged in the sample in a three-dimensional layered array mode and matched with wired sensors of the side wall and the water inlet and outlet bin to form a wireless-wired cooperative refined monitoring layout. The test method comprises the standard steps of sample loading, sealing, loading, saturation, step-by-step increase of hydraulic gradient, data acquisition and test ending, and is combined with a multi-index system including hydraulic gradient, hydraulic gradient non-uniform coefficient, water head distribution uniformity index and the like, so that the size effect and the side wall effect are eliminated, the actual stress and seepage state of a soil body are accurately simulated, and the test accuracy is improved. Perceiving and visualization of the gradual erosion process in the sample caused by seepage are achieved, and the efficient and scientific device and method are provided for research on the seepage characteristics of the soil body of the deep and thick covering layer.

Description

Technical Field

[0001] This invention belongs to the field of civil engineering and water conservancy technology, specifically relating to an ultra-large vertical compression horizontal seepage erosion test box device and test method, which is suitable for testing the permeability characteristics of deep overburden soil under different stress conditions and exploring the evolution law of soil seepage erosion and particle loss. Background Technology

[0002] As my country's water conservancy and hydropower projects expand westward, many major projects need to be built on deep, complex overburden layers. These deep overburden layers are prone to seepage erosion and particle loss under long-term seepage, directly threatening the safety and stability of the dam foundation and the overall project. Therefore, systematic research on the permeability characteristics of deep overburden layers is a crucial prerequisite for ensuring the safe construction and long-term operation of such projects.

[0003] Currently, scholars both domestically and internationally have designed various seepage and erosion testing devices that can provide high overburden stress conditions to explore the seepage and erosion characteristics of deep overburden soils. However, existing devices still have significant shortcomings and are difficult to meet the actual testing needs of engineering projects: First, the test devices are small in size, requiring samples to be scaled down, and the size effect will seriously affect the accuracy and authenticity of the test results, leading to a large deviation between the test data and the actual engineering conditions; Second, the overburden pressure that existing devices can provide is limited, making it impossible to accurately simulate the actual stress state of deep overburden soils under natural conditions, and difficult to truly reflect the evolution law of seepage and erosion of soils under deep stress conditions; Third, some test devices use traditional rubber strips to seal the sample top cover, and the deformation of the sample box under ultra-high pressure can easily cause the seal to fail, and it is impossible to observe the gradual development process of concentrated dominant seepage channels inside the sample, resulting in poor treatment of sidewall seepage and dominant seepage.

[0004] Chinese patent CN110907329A discloses a large-scale submerged erosion test system and its test method. Although the hydraulic gradient can be adjusted by adjusting the height of the water tank, the aforementioned problems of sealing failure, inability to observe the development of internal seepage, poor treatment of sidewall seepage and dominant seepage still exist.

[0005] Therefore, developing an ultra-large vertical compression horizontal seepage erosion experimental device that can overcome the shortcomings of existing devices has significant engineering practical value and theoretical research significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing seepage erosion test devices and provide an ultra-large vertical compression horizontal seepage erosion test box device and test method. This device achieves adaptive sealing after the sample box deforms under ultra-high pressure, effectively suppressing sidewall seepage and dominant seepage. At the same time, it can more accurately and intuitively perceive and visualize the gradual development process of seepage erosion inside the soil, simulate the actual stress state of deep overburden soil, and avoid the influence of size effect on test results.

[0007] To achieve the above objectives, one of the technical solutions adopted by the present invention is as follows: An ultra-large vertical compression horizontal seepage erosion experimental chamber device is disclosed. The main body of the device is a high-strength test chamber. The high-strength test chamber is a steel structure with a maximum vertical load of 10 MPa. Inside the high-strength test chamber is a sample chamber for placing test samples. The internal dimensions of the sample chamber are 1000 mm × 1000 mm × 1000 mm. An upstream inlet chamber is located on one side of the sample chamber, and a downstream outlet chamber is located on the other side. The upstream inlet chamber has a water inlet, and the downstream outlet chamber has an outlet funnel for collecting fine-particle soil samples. A top cover is provided on the top of the sample chamber. An adaptive sealing structure for suppressing dominant seepage is provided between the top cover and the chamber body. Multiple wireless micro-pressure sensors are arrayed inside the sample chamber. These multiple wireless micro-pressure sensors are used to monitor the spatiotemporal changes of pore water pressure at different locations within the soil, enabling the perception and visualization of the gradual development process of seepage erosion within the soil. A pore water pressure sensor is installed at the inlet of the upstream inlet chamber, and a pore water pressure sensor is installed at the outlet of the downstream outlet chamber.

[0008] Furthermore, the adaptive sealing structure includes a peripheral airbag disposed around the top cover. The bottom of the top cover is provided with an airbag groove for fixing the peripheral airbag and an air inlet for inflating the peripheral airbag. The peripheral airbag is inflated through the air inlet. After the peripheral airbag inflates, it comes into close contact with the inner wall of the sample chamber, the top cover, and the upper surface of the sample, thereby achieving a seal and suppressing dominant seepage.

[0009] Furthermore, a seepage-suppressing wall is provided between the sample chamber and the upstream and downstream water chambers to suppress dominant seepage. The seepage-suppressing wall is the two side walls through which the influent flows inside the sample chamber, and transparent resin airbags that suppress seepage are fixedly provided on the two side walls.

[0010] Furthermore, a first retaining plate and a second retaining plate are provided between the upstream water tank and the downstream water tank in the sample chamber. The first retaining plate and the second retaining plate are porous mesh plates that are parallel to and perpendicular to the direction of water flow.

[0011] Furthermore, all of the aforementioned wireless micro pressure sensors are wireless micro piezoresistive pore water pressure sensors, encapsulated in a high-strength metal shell with permeable holes, and embedded inside the sample in a three-dimensional layered array of inlet end cross-section, middle cross-section, and outlet end cross-section.

[0012] Furthermore, the wireless miniature piezoresistive pore water pressure sensor is treated as a coarse particle inside the soil sample, embedded inside the sample according to the arrangement of coarse particles in the soil, and directly participates in the formation of the soil skeleton.

[0013] To achieve the above objectives, the second technical solution adopted by the present invention is as follows: A test method for an ultra-large vertical compression horizontal seepage erosion test chamber device includes the following steps: (1) According to the test plan, the soil sample is layered and placed into the sample chamber. The wireless miniature piezoresistive pore water pressure sensor is arranged in the set manner for each layer of sample and is embedded in the soil sample in a coordinated manner to participate in the seepage test as coarse particles. (2) Place the top cover above the sample and inflate the surrounding airbags on the top cover through the air vents so that the airbags are in close contact with the side wall of the sample chamber and the soil sample. (3) Connect the sample box to the water supply system, supply water to the sample chamber through the water supply system, stop the water supply after the sample chamber is full, load the sample through the vertical loading system, stabilize the load after the load reaches the predetermined value, and wait for the soil sample to saturate. (4) After the soil sample is saturated, add a sedimentation flocculant to the sedimentation tank and connect the downstream outlet funnel of the sample box to the sedimentation tank. (5) Turn on the wireless miniature piezoresistive pore water pressure sensor, the sidewall pore water pressure sensor, the inlet pore water pressure sensor and the outlet pore water pressure sensor. After the readings of 100 pore pressure gauges stabilize, start the test. Gradually increase the hydraulic gradient through the water supply system. Record the changes in the pore pressure gauge readings at each stage. Monitor the permeation development of the sample through data inversion. Stop increasing the hydraulic gradient when the hydraulic gradient of the test plan is reached or the soil sample is damaged. (6) After the test, stop the water supply, unload the sample, wait for all the water in the sample chamber to be drained, remove the top cover, take pictures of the sample and record the results, and then remove the sample.

[0014] Furthermore, the hydraulic gradient is calculated by inverting the seepage development within the soil mass through changes in the pore water pressure sensor readings. Where: i—hydraulic gradient; ΔH—difference in readings between two coaxial manometers; L—distance between two coaxial manometers.

[0015] Furthermore, through the hydraulic gradient non-uniformity coefficient and the uniformity index of water head distribution To determine the uniformity of seepage, the following criteria are used: The maximum hydraulic gradient within the cross section. The average hydraulic gradient of the cross section is determined by the following criteria: ≤1.2, uniform seepage, no dominant seepage; 1.2 < <1.5, seepage is basically uniform, with localized dominant seepage; ≥1.5 indicates significantly uneven seepage, with dominant seepage flow developing; The measured head of the j-th orifice pressure gauge within the cross-section is... denoted as the cross-sectional average head, and n as the number of orifice pressure gauges within the cross-section. The criteria for judgment are: <3%, uniform head distribution, stable seepage; 3%≤ ≤8%, the head distribution is relatively uniform, and the seepage stability is generally average; >8%, indicating a severely uneven distribution of hydraulic head and a clear dominant seepage flow; Furthermore, the development intensity of dominant seepage channels is quantified by the dominant seepage channel development degree D: The average hydraulic gradient of the corresponding cross section. The hydraulic gradient at the measuring point is determined by the following criteria: D≤10% indicates no dominant seepage channels; 10%<D≤30% indicates the initial development of dominant seepage channels; D>30% indicates the complete connection of dominant seepage channels. Through mutation function Analyze the spatial correlation of hydraulic gradients to determine the spatial distribution characteristics of dominant seepage. For spatial distance, Let xi be the hydraulic gradient. Let h be the number of sample logs at a distance of h. If the variogram stabilizes rapidly with increasing distance, it indicates that the spatial correlation of the seepage field is strong and the seepage is uniform. If the fluctuations are violent and irregular, it proves that the dominant seepage is randomly developed and the spatial distribution is uneven.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The internal dimensions of the test chamber are 1000mm×1000mm×1000mm, which is the largest horizontal seepage test instrument available today. It can accommodate large-sized undisturbed or remolded soil samples, avoiding the size effect caused by scaled-down sample loading, and making the test results more consistent with engineering practice.

[0017] 2. The device can withstand a maximum vertical load of 10MPa, accurately simulating the deep stress state of thick overburden soil under natural conditions, and truly reflecting the evolution law of soil permeation and erosion under actual stress conditions.

[0018] 3. The top cover adopts a sealing structure of peripheral airbags combined with anti-seepage strips. After the airbags are inflated, they can achieve self-adaptive sealing by deforming with the sample box, which solves the problem of traditional rubber strip sealing failure under ultra-high pressure. The airbags are embedded in the pores of the soil sample surface, and the anti-seepage strips are attached to the side wall and the soil sample surface, which effectively inhibits the occurrence of side wall seepage and dominant seepage, and improves the accuracy of the test.

[0019] 4. A three-dimensional layered array sensor layout with wireless-wired collaboration is adopted. Wireless micro sensors are embedded in the soil as coarse particles to achieve in-situ non-disruptive monitoring and avoid the disturbance to the soil caused by traditional monitoring. 64 wireless sensors are combined with multiple sets of wired sensors to achieve full-area coverage monitoring of pore water pressure inside the soil. Through data calculation and inversion of seepage characteristics, seepage fronts and dominant seepage channels are accurately identified, and the gradual development process of seepage erosion inside the soil can be intuitively perceived.

[0020] 5. A multi-index judgment system was constructed, including hydraulic gradient non-uniformity coefficient, head distribution uniformity index, dominant seepage channel development degree, and variogram. This system can comprehensively and accurately determine seepage uniformity, quantify the development degree of dominant seepage channels, and analyze the spatial distribution characteristics of dominant seepage, providing a scientific and systematic evaluation basis for seepage erosion research.

[0021] 6. The test methods and procedures are clear and standardized. From sample loading, sealing, loading, saturation to seepage test, data recording, and test termination, each step has been optimized to ensure the controllability of the test process and the reliability and repeatability of the test results. Attached Figure Description

[0022] Figure 1 This is a system diagram of the present invention; Figure 2 This is a schematic diagram of the first direction of the present invention; Figure 3 This is a schematic diagram of the second direction of the present invention; Figure 4 This is a cross-sectional view of the present invention in the first direction; Figure 5 This is a schematic diagram of the top cover of the present invention; Figure 6 This is a cross-sectional view of the top cover of the present invention; Figure 7 This is a cross-sectional view of the invention in a second direction; Figure 8 This is a schematic diagram of the wireless miniature pressure sensor array of the present invention.

[0023] Explanation of reference numerals in the attached figures: 1-High-strength test chamber; 2-Inlet; 3-Side viewing window; 4-Downstream viewing window; 5-Outlet funnel; 6-Downstream outlet chamber; 7-Upstream inlet chamber; 8-First retaining plate; 9-Second retaining plate; 10-Side wall airbag; 11-Transition water chamber; 12-Air inlet; 13-Surrounding airbag; 14-Pressure bearing platform; 15-Axial force transmission platform; 16-Impering strip; 17-Top cover; 18-Light source; 19-Inlet pore water pressure sensor; 20-Outlet pore water pressure sensor; 21-Wireless miniature pressure sensor; 22-Pressure transmission hole; 23-Side wall pore water pressure sensor. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship as a relative relationship of orientation or position, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0026] Please see Figures 1-8 This invention provides an embodiment of an ultra-large vertical compression horizontal seepage erosion test chamber device, comprising a high-strength test chamber body 1, which is a steel structure with a maximum vertical load of 10 MPa. The high-strength test chamber body contains a sample chamber for placing test samples, with internal dimensions of 1000 mm × 1000 mm × 1000 mm. An upstream water inlet chamber 7 is located on one side of the sample chamber, and a downstream water outlet chamber 6 is located on the other side. The upstream water inlet chamber has a water inlet 2, and the downstream water inlet chamber has a water outlet funnel 5 for collecting fine-particle soil samples. It can concentrate the fine particles flowing out of the soil sample, which is convenient for subsequent collection and measurement. The top of the sample chamber is equipped with a top cover 17. An adaptive sealing structure is set between the top cover and the box body to suppress the occurrence of dominant seepage. Multiple wireless micro pressure sensors 21 are arrayed inside the sample. Multiple wireless micro pressure sensors are used to monitor the spatiotemporal changes of pore water pressure at different locations inside the soil, and to perceive and visualize the gradual development process of seepage erosion inside the soil. The upstream inlet chamber is equipped with an inlet pore water pressure sensor 19, and the downstream outlet chamber is equipped with an outlet pore water pressure sensor 20.

[0027] In this embodiment, a downstream viewing window 4 is provided in the downstream area and a side viewing window 3 is provided on the side wall of the sample box to achieve test visualization.

[0028] In this embodiment, the top cover 17 can be made of steel. The device includes an air inlet 12, peripheral airbags 13, a pressure plate 14, and a seepage-proof strip 16. The pressure plate 14 is positioned at the center of the upper surface of the pressure plate, directly contacting the axial reaction rod, and uniformly transferring the overburden pressure to the test soil sample. An air inlet 12 is located above the top cover, communicating with a groove on the lower surface of the pressure plate. The adaptive sealing structure includes peripheral airbags 13 surrounding the top cover. A groove is formed on the small surface of the pressure plate, within which the peripheral airbags 13 can be placed. The airbags are connected to the air inlet; inflation of the airbags through the air inlet causes them to inflate and seal against the inner wall of the sample chamber, providing waterproofing. It also ensures close contact with the upper surface of the test soil sample, suppressing dominant seepage. A seepage-proof strip 16 is applied to the bottom of the top cover, ensuring full contact with the upper surface of the soil sample and further suppressing dominant seepage. The axial loading device, through the axial force transmission platform 15, can apply axial stress to the test soil sample, effectively simulating the stress state of a deep overburden layer.

[0029] In this embodiment, a seepage-suppressing wall is provided between the sample chamber and the upstream and downstream water chambers to suppress dominant seepage. The seepage-suppressing wall is the two side walls through which the influent flows into the sample chamber. Side wall airbags 10 that suppress seepage are fixedly provided on the two side walls. The side wall airbags are made of transparent resin material.

[0030] Meanwhile, four side pressure transmission holes 22 are provided on each of the two side walls, which can be used to install side wall pore water pressure sensors 23.

[0031] In this embodiment, a first retaining plate 8 and a second retaining plate 9 are provided between the upstream water tank and the downstream water tank in the sample chamber. The first retaining plate and the second retaining plate are porous mesh plates that are parallel and perpendicular to the direction of water flow, which can further buffer the water flow. The two are arranged at intervals, and the area between the two forms a transition water tank 11.

[0032] As a preferred option, multiple wireless miniature pressure sensors are all wireless miniature piezoresistive pore water pressure sensors. These sensors are encapsulated within a high-strength metal housing, with perforations on the housing surface. They are arranged in a three-dimensional layered array: 16 sensors are arranged in a 4×4 grid at the inlet, middle, and outlet sections, with 32 sensors arranged internally, for a total of 64 sensors. Figure 8 As shown.

[0033] Meanwhile, the sensors are set at a distance of 30cm between each other to monitor the spatiotemporal changes of pore water pressure inside the soil from different spatial locations, record the gradual development process of seepage erosion inside the soil, and visualize it so that researchers can intuitively feel this change.

[0034] As a preferred option, the side wireless sensor is 5cm away from the side wall; 16 wired side wall pore water pressure sensors are installed on each side wall of the sample box. At the same time, 4 wired pore pressure sensors are installed in the front and rear water inlet chambers to measure the water pressure difference between the inlet and outlet chambers, and to further investigate the inlet and outlet water.

[0035] As a preferred option, the wireless miniature piezoresistive pore water pressure sensor is integrated into the soil sample as if it were coarse particles, embedded within the sample in the same manner as the coarse particles in the soil mass, directly participating in the formation of the soil skeleton. The sensor as a whole becomes part of the soil skeleton, and seepage can flow into the interior through the fine pores on the surface of the metal shell, where it is measured by a pore pressure gauge. This allows the device to perform its observation function without affecting the research results, thus ensuring the accuracy of the results.

[0036] As an improvement to this embodiment, a light source 18 is installed in the downstream outlet chamber. When the light source is turned on during the test, the seepage development of the soil sample in the downstream outlet chamber can be clearly observed.

[0037] Based on the above-mentioned device, a seepage erosion test was conducted on a deep overburden soil. The specific steps are as follows: 1. Sample loading and sensor arrangement: Clean the sample chamber, attach sidewall airbags 10 to both sides, and load the thick overburden remolded soil into the sample chamber in layers according to the test plan. After loading each layer, arrange the wireless micro pore water pressure sensor 21 according to the three-dimensional array requirements to ensure that the sensor is tightly integrated with the soil sample and embedded in the soil as coarse particles.

[0038] 2. Top cover sealing installation: Apply anti-seepage strip 16 to the lower surface of top cover 17, place the top cover on top of the soil sample, and inflate the surrounding air bladders 13 through air inlet 12 until the air bladders are in close contact with the inner wall of the sample chamber and the upper surface of the soil sample, thus completing the sealing and suppressing of dominant seepage.

[0039] 3. Water supply and vertical loading: Connect the upstream water inlet 2 of the sample box to the water supply system and slowly supply water into the sample chamber until it is full. Then stop. Start the vertical loading system and apply vertical load to the soil sample through the axial force transmission platform 15 and the pressure bearing platform 14. Gradually load the sample to the predetermined value of 8 MPa (simulating the deep stress of the thick overburden layer). Stabilize the load and let it stand until the soil sample is completely saturated. The saturation time is about 48 hours.

[0040] 4. Sedimentation tank connection: Add polyacrylamide flocculant to the sedimentation tank, and connect the sample box outlet funnel 5 to the sedimentation tank through a pipe to collect the fine soil particles lost during the seepage process.

[0041] 5. Seepage Test and Data Acquisition: Turn on all pore water pressure sensors and wait for the readings of 100 pore pressure gauges to stabilize. Then, gradually increase the hydraulic gradient through the water supply system, increasing it by 0.2 each time. Stabilize for 3 hours at each hydraulic gradient stage and record the pore water pressure readings of all sensors. Calculate the hydraulic gradient, hydraulic gradient non-uniformity coefficient CU, and hydraulic head distribution uniformity index IH based on the readings to invert the seepage development process. When the hydraulic gradient increases to 2.0, significant particle loss occurs in the soil sample, and the increase in hydraulic gradient is stopped.

[0042] 6. Test completion: Turn off the water supply system, unload the vertical loading system step by step, open the drain of the sample chamber, and after all the water has been drained, remove the top cover 17, take pictures and record the seepage erosion pattern and the location of the dominant seepage channels of the soil sample, then decompose the sample in layers, collect the lost fine particles and perform particle size analysis.

[0043] Data calculation and analysis includes the following steps: Based on the collected pore water pressure data, relevant indicators are calculated using the following formulas to analyze the seepage state: 1) The hydraulic gradient is calculated by inverting the seepage development inside the soil through the changes in the readings of the pore water pressure sensor: Where: i—hydraulic gradient; ΔH—difference in readings between two coaxial manometers; L—distance between two coaxial manometers.

[0044] 2) Through the hydraulic gradient non-uniformity coefficient and uniformity of head distribution index To determine the uniformity of seepage, the following criteria are used: The maximum hydraulic gradient within the cross section. The average hydraulic gradient of the cross section is determined by the following criteria: ≤1.2, uniform seepage, no dominant seepage; 1.2 < <1.5, seepage is basically uniform, with localized dominant seepage; ≥1.5 indicates significantly uneven seepage, with dominant seepage flow developing; The measured head of the j-th orifice pressure gauge within the cross-section is... denoted as the cross-sectional average head, and n as the number of orifice pressure gauges within the cross-section. The criteria for judgment are: <3%, uniform head distribution, stable seepage; 3%≤ ≤8%, the head distribution is relatively uniform, and the seepage stability is generally average; >8%, the head distribution is severely uneven, and the dominant seepage is obvious.

[0045] 3) Quantify the development intensity of dominant seepage channels by the development degree D: The average hydraulic gradient of the corresponding cross section. The hydraulic gradient at the measuring point is determined by the following criteria: D≤10% indicates no dominant seepage channels, 10%<D≤30% indicates the initial development of dominant seepage channels, and D>30% indicates the complete connection of dominant seepage channels.

[0046] 4) Through the variogram function Analyze the spatial correlation of hydraulic gradients to determine the spatial distribution characteristics of dominant seepage. For spatial distance, Let xi be the hydraulic gradient. Let h be the number of sample logs at a distance of h. If the variogram stabilizes rapidly with increasing distance, it indicates that the spatial correlation of the seepage field is strong and the seepage is uniform. If the fluctuations are violent and irregular, it proves that the dominant seepage is randomly developed and the spatial distribution is uneven.

[0047] This method monitors the spatiotemporal variations of pore water pressure at different locations within soil using a wireless micro-pressure sensor array, calculates the hydraulic gradient distribution, and indirectly inverts the seepage characteristics within the soil. The essence of non-uniform seepage is the difference in hydraulic gradients across different regions. Within dominant seepage channels, the head loss for the same seepage path length is small, resulting in a lower hydraulic gradient; while in low-velocity regions, seepage resistance is high, head loss is large, and the hydraulic gradient is high. By collecting pore water pressure at different locations using a sensor array and calculating the changes in the hydraulic gradient in each region, the seepage variations within the soil can be inverted.

[0048] Meanwhile, a wireless miniature piezoresistive pore water pressure sensor was selected as the internal sensor for the sample. The sensor was placed inside a specially designed metal casing with high strength and permeable pores on its surface. The sensor as a whole was incorporated into the soil sample as if it were coarse particles arranged in a specific pattern, possessing equivalent coarse particle morphology, size, and mechanical properties. It directly participated in the formation of the soil skeleton, and seepage flowed into the sample through the fine pores on the metal casing for measurement. Figure 8As shown, the wireless sensors are arranged in a three-dimensional layered array. Sixteen sensors are arranged in a 4×4 grid at the inlet section, and 16 sensors are also arranged in a 4×4 grid at the middle and outlet sections, with an additional 32 sensors arranged in a 4×4 grid inside. A total of 64 wireless miniature piezoresistive pore water pressure sensors are arranged, with each sensor spaced 30cm apart. This layered array layout allows for real-time capture of the spatiotemporal evolution of pore water pressure during seepage propagation, accurately identifying high pore pressure zones, areas of sudden pore pressure changes, and the location and migration path of the seepage front. To prevent potential sidewall-dominant seepage influence, the side wireless sensors are positioned 5cm away from the sidewalls. Furthermore, to monitor seepage development on both the instrument and sample sidewalls, 16 wired pore water pressure sensors are installed on both sides of the sample chamber, and four wired pore pressure sensors are installed in the front and rear inlet chambers. This method focuses on the three-dimensional spatial evolution characteristics of coarse-grained soil seepage, burrowing, and seepage erosion. It addresses the core problems of traditional pore water pressure monitoring, such as "large soil disturbance, single measurement point dimension, difficulty in quantifying sidewall effects, and limited data acquisition." It constructs a refined monitoring layout that features in-situ non-disturbing embedding, three-dimensional full-domain coverage, sidewall targeted prevention and control, and wireless-wired collaborative complementarity.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A super-large vertical compression horizontal seepage erosion experimental chamber device, the main body of which is a high-strength experimental chamber body, characterized in that: The high-strength test chamber is a steel structure with a maximum vertical load of 10 MPa. Inside the chamber is a sample chamber for holding the test specimen, with internal dimensions of 1000 mm × 1000 mm × 1000 mm. An upstream water inlet chamber is located on one side of the sample chamber, and a downstream water outlet chamber is located on the other side. The upstream water inlet chamber has a water inlet, and the downstream water outlet chamber has a funnel for collecting fine-particle soil samples. A top cover is provided on the top of the sample chamber, and an adaptive sealing structure is installed between the top cover and the chamber to suppress leakage after high-pressure deformation. Multiple wireless micro-pressure sensors are arrayed inside the sample chamber to monitor the spatiotemporal changes in pore water pressure at different locations within the soil, enabling the perception and visualization of the gradual development process of seepage erosion within the soil. A pore water pressure sensor is installed at the inlet of the upstream water inlet chamber, and a pore water pressure sensor is installed at the outlet of the downstream water outlet chamber.

2. The ultra-large vertical compression horizontal seepage erosion experimental chamber device according to claim 1, characterized in that: The adaptive sealing structure includes a peripheral airbag disposed around the top cover. The bottom of the top cover is provided with an airbag groove for fixing the peripheral airbag and an air inlet for inflating the peripheral airbag. The peripheral airbag is inflated through the air inlet. After the peripheral airbag inflates, it comes into close contact with the inner wall of the sample chamber, the top cover and the upper surface of the sample, thereby achieving a seal and suppressing leakage of the sample box after high pressure deformation.

3. The ultra-large vertical compression horizontal seepage erosion experimental chamber device according to claim 1, characterized in that: The sample chamber is provided with a seepage-suppressing wall between the upstream water chamber and the downstream water chamber to suppress dominant seepage. The seepage-suppressing wall is the two side walls through which the influent flows into the sample chamber, and transparent resin airbags that suppress seepage are fixedly installed on the two side walls.

4. The ultra-large vertical compression horizontal seepage erosion experimental chamber device according to claim 1, characterized in that: The sample chamber contains a first retaining plate and a second retaining plate between the upstream and downstream water tanks. The first and second retaining plates are porous mesh plates that are parallel to and perpendicular to the direction of water flow.

5. The high-strength test chamber configuration of the ultra-large vertical compression horizontal seepage erosion test chamber device according to claim 1, characterized in that, The aforementioned wireless miniature pressure sensors are all wireless miniature piezoresistive pore water pressure sensors, encapsulated in a high-strength metal shell with water-permeable holes, and embedded inside the sample in a three-dimensional layered array of inlet end cross-section, middle cross-section, and outlet end cross-section.

6. The ultra-large vertical compression horizontal seepage erosion experimental chamber device according to claim 1, characterized in that: The wireless miniature piezoresistive pore water pressure sensor is treated as a coarse particle inside the soil sample, embedded inside the sample according to the arrangement of coarse particles in the soil, and directly participates in the formation of the soil skeleton.

7. A test method based on the ultra-large vertical compression horizontal seepage erosion test chamber device according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Before the test begins, the soil sample is layered and placed into the sample chamber according to the test plan. The wireless miniature piezoresistive pore water pressure sensor is arranged in the set manner for each layer of sample and is embedded into the soil sample in a coordinated manner to participate in the seepage test as coarse particles. (2) Place the top cover above the sample and inflate the surrounding airbags on the top cover through the air vents so that the airbags are in close contact with the side wall of the sample chamber and the soil sample. (3) Connect the sample box to the water supply system, supply water to the sample chamber through the water supply system, stop the water supply after the sample chamber is full, load the sample through the vertical loading system, stabilize the load after the load reaches the predetermined value, and wait for the soil sample to saturate. (4) After the soil sample is saturated, add a sedimentation flocculant to the sedimentation tank and connect the downstream outlet funnel of the sample box to the sedimentation tank. (5) Turn on the wireless miniature piezoresistive pore water pressure sensor, the sidewall pore water pressure sensor, the inlet pore water pressure sensor and the outlet pore water pressure sensor. After the readings of 100 pore pressure gauges stabilize, start the test. Gradually increase the hydraulic gradient through the water supply system. Record the changes in the pore pressure gauge readings at each stage. Monitor the permeation development of the sample through data inversion. Stop increasing the hydraulic gradient when the hydraulic gradient of the test plan is reached or the soil sample is damaged. (6) After the test, stop the water supply, unload the sample, wait for all the water in the sample chamber to be drained, remove the top cover, take pictures of the sample and record the results, and then remove the sample.

8. The test method according to claim 7, characterized in that: The hydraulic gradient is calculated by inverting the seepage development inside the soil through the changes in the readings of the pore water pressure sensor. Where: i—hydraulic gradient; ΔH—difference in readings between two coaxial manometers; L—distance between two coaxial manometers.

9. The test method according to claim 7, characterized in that: Through the hydraulic gradient non-uniformity coefficient and the uniformity index of water head distribution To determine the uniformity of seepage, the following criteria are used: The maximum hydraulic gradient within the cross section. The average hydraulic gradient of the cross section is determined by the following criteria: ≤1.2, uniform seepage, no dominant seepage; 1.2 < <1.5, seepage is basically uniform, with localized dominant seepage; ≥1.5 indicates significantly uneven seepage, with dominant seepage flow developing; The measured head of the j-th orifice pressure gauge within the cross-section is... denoted as the cross-sectional average head, and n as the number of orifice pressure gauges within the cross-section. The criteria for judgment are: <3%, uniform head distribution, stable seepage; 3%≤ ≤8%, the head distribution is relatively uniform, and the seepage stability is generally average; >8%, the head distribution is severely uneven, and the dominant seepage is obvious.

10. The test method according to claim 7, characterized in that: The development intensity of dominant seepage channels is quantified by the development degree D of dominant seepage channels: The average hydraulic gradient of the corresponding cross section, The hydraulic gradient at the measuring point is determined by the following criteria: D≤10% indicates no dominant seepage channels; 10%<D≤30% indicates the initial development of dominant seepage channels; D>30% indicates the complete connection of dominant seepage channels. Through mutation function Analyze the spatial correlation of hydraulic gradients to determine the spatial distribution characteristics of dominant seepage. For spatial distance, Let xi be the hydraulic gradient. Let h be the number of sample logs at a distance of h. If the variogram stabilizes rapidly with increasing distance, it indicates that the spatial correlation of the seepage field is strong and the seepage is uniform. If the fluctuations are violent and irregular, it proves that the dominant seepage is randomly developed and the spatial distribution is uneven.

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