Unsaturated soil permeability coefficient measuring system and method considering soil deformation

Abstract

The invention relates to the technical field of geotechnical tests, and discloses a system and a method for measuring an unsaturated soil permeability coefficient by considering soil deformation. The system for measuring the permeability coefficient of the unsaturated soil comprises a soil column casing, a camera module, a water supply device, a micro soil tensiometer and a water content sensor. The soil column cylinder comprises a transparent cylinder body, a cover plate and a base, the transparent cylinder body is used for placing a soil sample, the cover plate is used for reducing water evaporation, and the base is used for connecting and fixing the transparent cylinder body and ensuring uniform permeation speed. The camera modules and the soil column cylinders are distributed at intervals in the horizontal direction. The water supply device is connected to the bottom end of the transparent barrel. The micro soil tensiometer and the water content sensor are fixedly connected to the same layer of a soil sample and can descend synchronously, so that the soil sample on the same layer can be continuously detected while the permeation-collapse coupling phenomenon is captured, the unsaturated soil permeability coefficient is dynamically monitored, and the error of the calculated permeability coefficient is reduced.

Description

Technical Field

[0001] This invention relates to the field of geotechnical testing technology, specifically to a measurement system and method for the permeability coefficient of unsaturated soil that takes into account soil deformation. Background Technology

[0002] In geotechnical engineering, soil is often in an unsaturated state. Soil permeability varies significantly under different water content conditions. Accurately determining the relationship between the water content and permeability of unsaturated soil helps in understanding soil behavior during water content changes (e.g., a sharp increase in water content during extreme rainfall), which is of great significance for the safety design of slopes, roadbeds, and foundation pits. However, existing methods often result in significant deformation under rainfall infiltration, groundwater level rise, and external traffic loads. To study the deformation of slopes or roadbeds and its impact on their hydraulic properties, a system for measuring the permeability coefficient of unsaturated soil is needed. Existing systems and methods for measuring the permeability coefficient of unsaturated soil cannot move with soil sample deformation, limiting experimental design and preventing the determination of the permeability coefficient of unsaturated soil under seepage-collapse coupling phenomena, thus failing to simulate real overburden loads. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a measurement system for the permeability coefficient of unsaturated soil that takes into account soil deformation, which can capture the permeation-collapse coupling phenomenon during the soil sample permeation process and reduce the measurement error of the permeability coefficient.

[0004] The present invention also proposes a measurement method for the above-mentioned measurement system for the permeability coefficient of unsaturated soil considering soil deformation.

[0005] A measurement system for the permeability coefficient of unsaturated soil considering soil deformation, according to a first aspect embodiment of the present invention, includes a soil column, a camera module, a water supply device, a miniature soil tensiometer, and a moisture content sensor. The soil column includes a transparent cylinder, a cover plate, and a base. The transparent cylinder is used to hold a soil sample, the cover plate is used to reduce water evaporation, and the base is used to connect and fix the transparent cylinder and ensure uniform permeation rate. The camera module is distributed horizontally at intervals with the soil column and is used to acquire images of the transparent cylinder. The water supply device is connected to the bottom end of the transparent cylinder and can inject water into the transparent cylinder from bottom to top through the base. The miniature soil tensiometer is movably disposed within the transparent cylinder and is used to detect the matrix suction of the soil sample. The moisture content sensor is movably disposed within the transparent cylinder and is used to detect the volumetric moisture content of the soil sample. The miniature soil tensiometer and the moisture content sensor are fixedly connected to the same layer of the soil sample. When the soil sample undergoes a seepage-collapse coupling phenomenon, the miniature soil tensiometer and the moisture content sensor descend synchronously with the soil sample as it collapses.

[0006] The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to embodiments of the present invention has at least the following beneficial effects: When determining the unsaturated permeability coefficient of unsaturated soil under rainfall infiltration or groundwater level rise conditions using a one-dimensional soil column test in the laboratory, the soil sample will actually undergo a permeation-collapse coupling phenomenon under the action of external forces. However, the devices used in related technologies for detecting water content and micro soil tensiometers are fixedly set on the soil column containing the soil sample, without considering the change in soil density caused by soil collapse, which affects the accuracy of permeability coefficient measurement. Furthermore, soil collapse will damage the corresponding sensor probe, making it impossible to continue the experiment. In fact, due to the difference in water content at different layers during the infiltration process, soil samples at different layers will collapse sequentially. At the time of collapse, the density of soil samples at different layers differs. Previous related measurement techniques that did not consider the permeation-collapse coupling phenomenon do not measure the water content and matrix suction of the soil layer at the time of soil collapse as the initial water content and matrix suction of the soil layer after collapse, resulting in a large error in the calculated permeability coefficient. The measurement system of this invention incorporates a movable moisture content sensor and a miniature soil tensiometer, both positioned at the same level as the soil sample. These sensors descend synchronously when the soil sample collapses, enabling continuous monitoring of soil samples at the same level and reducing errors in the calculated permeability coefficient.

[0007] According to some embodiments of the present invention, the measurement system for the permeability coefficient of unsaturated soil that takes into account soil deformation further includes a pressurizing device, wherein an opening is provided on the transparent cylinder, a portion of the pressurizing device extends into the transparent cylinder through the opening, and the pressurizing device is used to apply pressure to the soil sample.

[0008] According to some embodiments of the present invention, the measurement system for the permeability coefficient of unsaturated soil considering soil deformation further includes an upper axial force gauge and a reaction frame. The pressurizing device includes a linear actuator and a force transmission rod. The linear actuator is disposed on the reaction frame. The two ends of the upper axial force gauge are respectively connected to the linear actuator and the force transmission rod. The transparent cylinder is spaced below the linear actuator and located inside the reaction frame. The end of the force transmission rod away from the upper axial force gauge extends into the transparent cylinder. The upper axial force gauge is used to detect the pressure applied by the linear actuator to the upper surface of the soil sample.

[0009] According to some embodiments of the present invention, the measurement system for the permeability coefficient of unsaturated soil considering soil deformation further includes a lower axial force gauge, the two ends of which are respectively connected to the lower end face of the transparent cylinder and the reaction frame. The lower axial force gauge is coaxial with the upper axial force gauge. When the pressurizing device applies pressure to the soil sample, the lower axial force gauge is used to detect the pressure on the lower end face of the soil sample.

[0010] According to some embodiments of the present invention, a linear displacement sensor is also included, one end of which is fixedly connected to the reaction frame and the other end is connected to the force transmission rod. When the soil sample undergoes a seepage-collapse coupling phenomenon, the linear displacement sensor is used to detect the amount of displacement of the upper surface of the soil sample in the vertical direction.

[0011] According to some embodiments of the present invention, the transparent cylinder is provided with a moisture content sensor mounting hole and a tensiometer mounting hole. The moisture content sensor can be installed in the transparent cylinder through the moisture content sensor mounting hole, and the micro soil tensiometer can be installed in the transparent cylinder through the tensiometer mounting hole. The axis of the moisture content sensor mounting hole and the axis of the tensiometer mounting hole are located on the same horizontal plane.

[0012] According to some embodiments of the present invention, the measurement system for the permeability coefficient of unsaturated soil considering soil deformation further includes a supplementary light lamp, which is disposed between the camera module and the transparent cylinder. The emission direction of the light source of the supplementary light lamp is perpendicular to the spacing direction between the camera module and the transparent cylinder. The supplementary light lamp is used to ensure the brightness and light intensity stability between the camera module and the transparent cylinder.

[0013] According to some embodiments of the present invention, a lower axial force gauge, a lower perforated plate, and a filter screen are placed inside the base. The lower perforated plate and the lower axial force gauge are threaded together from top to bottom and placed on the base cylinder. The upper surface of the lower perforated plate is flush with the upper surface of the base. A metal filter screen with pores smaller than the minimum particle size of the soil is affixed to the upper surface of the lower perforated plate. The filter screen, the lower perforated plate, and the lower axial force gauge are placed inside the base in a top-to-bottom order and cover the water inlet. The water supply device includes a water inlet. The water supply device enters the base through the water inlet and injects water into the transparent cylinder through the lower perforated plate and the filter screen. The lower perforated plate and the filter screen allow water to pass through while restricting the passage of the soil sample.

[0014] According to a second aspect embodiment of the present invention, a method for measuring the permeability coefficient of unsaturated soil is applied to a system for measuring the permeability coefficient of unsaturated soil considering soil deformation, as described in any one of the first aspect embodiments. The method includes: placing soil into a transparent cylinder and compacting it to a target density; setting the moisture content sensor and the micro soil tensiometer on the same experimental level of the soil sample; injecting water into the transparent cylinder using a water supply device, and recording the total height change of the soil sample, the height change of the experimental level, and the height change of the water-soil mixture portion during the experimental time period using a camera module; recording the data from the moisture content sensor and the micro soil tensiometer during the experimental time period; and calculating the permeability coefficient of the soil sample based on the parameters recorded during the experimental time period.

[0015] The method for measuring the permeability coefficient of unsaturated soil according to a second aspect of the present invention has at least the following beneficial effects: During the infiltration process of unsaturated soil, a permeability-collapse coupling phenomenon occurs, and the permeability coefficient changes dynamically under this phenomenon. However, in related technologies, the devices used for detecting moisture content and micro soil tensiometers are fixedly installed on the container holding the soil sample, failing to consider the change in soil density caused by soil collapse, which affects the accuracy of the permeability coefficient measurement. Furthermore, soil collapse can damage the corresponding sensor probe, making it impossible to continue the experiment. In reality, due to the differences in water content at different layers during the infiltration process, soil samples at different layers will collapse sequentially. During collapse, the density of soil samples at different layers differs. Previous related measurement techniques that did not consider the permeability-collapse coupling phenomenon do not measure the moisture content and matrix suction of the soil layer after collapse as the initial soil layer, resulting in a large error in the calculated permeability coefficient. The measurement system of this invention achieves continuous detection of soil samples at the same level by setting a moisture content sensor that can move synchronously with the soil and a miniature soil tensiometer. On the one hand, it takes into account the influence of the seepage-collapse coupling phenomenon on the permeability of unsaturated soil, and on the other hand, it reduces the error in calculating the permeability coefficient.

[0016] According to some embodiments of the present invention, before the water supply device injects water into the transparent cylinder, the measurement method further includes applying pressure to the soil sample to bring the soil sample to a target stress level.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the structure of a system for measuring the permeability coefficient of unsaturated soil according to one embodiment of the present invention; Figure 2 This is a schematic diagram of the soil column structure of the measurement system in one embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the height changes of a soil sample during water infiltration in one embodiment of the present invention. Figure 4 This is a curve showing the relationship between water content and soil height at different times during the water infiltration process of a soil sample in one embodiment of the present invention. Figure 5 This is a curve showing the relationship between matrix suction and soil sample height at different times during the water infiltration process of a soil sample in one embodiment of the present invention. Figure 6 This is a curve showing the relationship between the permeability coefficient and the void ratio of a soil sample in a permeability-collapse coupling phenomenon according to one embodiment of the present invention.

[0019] Reference numerals in the attached figures: 100, soil column 101, transparent cylinder 102, cover plate 103, base 104, camera module 105, water supply device 106, reaction frame 107, supplementary light 108, miniature soil tensiometer 201, soil moisture sensor 202, pressurization device 203, linear actuator 204, force transmission rod 205, upper axial force gauge 206, lower axial force gauge 207, linear displacement sensor 208, moisture sensor mounting hole 209, tensiometer mounting hole 210, upper perforated plate 211, lower perforated plate 212, water inlet 213. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They 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. Therefore, they should not be construed as limiting this invention.

[0022] In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0023] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0024] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0025] refer to Figure 1 and Figure 2According to a first aspect embodiment of the present invention, a measurement system 100 for the permeability coefficient of unsaturated soil considering soil deformation includes a soil column 101, a camera module 105, a water supply device 106, a miniature soil tensiometer 201, a moisture content sensor 202, and a pressurization device 203. The soil column 101 includes a transparent cylinder 102, a cover plate 103, and a base 104, which are connected by a flange structure and waterproofed with a rubber ring; the transparent cylinder 102 is used to fill soil samples. The camera module 105 is distributed horizontally at intervals with the soil column 101, and the camera module 105 is used to acquire images of the soil inside the transparent cylinder 102. The water supply device 106 is connected to the bottom end of the base 104, and a ball valve is installed in the pipeline. The water supply device 106 can inject water into the transparent cylinder 102 and the base 104 from bottom to top. A high-air-intake clay probe of a miniature soil tensiometer 201 is installed inside a transparent cylinder 102 through a tensiometer mounting hole 210 to detect the matrix suction of the soil sample. A wire or conduit connected to the probe of the miniature soil tensiometer 201 is fixed to the tensiometer mounting hole 210 via a waterproof connector. A moisture content sensor 202 is integrally installed inside the transparent cylinder 102 through a moisture content sensor mounting hole 209 to detect the volumetric moisture content of the soil sample. The wire of the moisture content sensor 202 is fixed to the moisture content sensor mounting hole 209 via a waterproof connector. The miniature soil tensiometer 201 and the moisture content sensor 202 are installed in pairs in the soil sample, with their axes on the same horizontal plane. The number of pairs is generally no less than three. The measurement system of this embodiment uses only the wire or conduit of the flexible miniature soil tensiometer 201 and the wire of the moisture content sensor 202 for fixed installation. This allows the miniature soil tensiometer 201 and the moisture content sensor 202 to move synchronously with the soil sample deformation during the infiltration process, reducing the measurement error of the unsaturated soil permeability coefficient and sensor damage caused by soil deformation.

[0026] It should be noted that, in some embodiments of the present invention, the transparent cylinder 102 is preferably made of acrylic material.

[0027] It should be noted that the camera module 105 can monitor and acquire images of the soil sample inside the transparent cylinder 102 facing the camera in real time, and analyze the displacement field of the soil using Digital Image Correlation (DIC), a technique commonly used in geotechnical testing. In some embodiments of the present invention, the measurement system 100 for the unsaturated soil permeability coefficient considering soil deformation also includes a supplementary light 108 and a light-shielding cloth. The supplementary light 108 is positioned between the camera module 105 and the transparent cylinder 102, and the emission direction of the light source of the supplementary light 108 is perpendicular to the spacing direction between the camera module 105 and the transparent cylinder 102. The light-shielding cloth is arranged around the outer periphery of the transparent cylinder 102, leaving only the optical path channel for the transparent cylinder 102, the supplementary light 108, and the camera module 105. The supplementary light 108 and the light-shielding cloth are used to fully illuminate the soil and ensure the stability of the light intensity, thereby improving the quality of the analysis results of the digital image correlation technique.

[0028] It should be noted that the probe of the miniature soil tensiometer 201 and the moisture content sensor 202 must be able to be fitted inside the transparent cylinder 102. In some embodiments of the present invention, the miniature soil tensiometer 201 is recommended to be a TS10 2100F mechanical soil tensiometer, and the moisture content sensor 202 is recommended to be an EC-5 moisture content sensor.

[0029] It should be noted that the pressurization device 203 includes a reaction frame 107, a linear actuator 204, a force transmission rod 205, an upper perforated plate 211, and an upper axial force gauge 206. The linear actuator 204 is fixed to the reaction frame 107. The extension rod of the linear actuator 204 extends vertically downward and is connected to the upper axial force gauge 206, the force transmission rod 205, and the upper perforated plate 211 in sequence via threads. The transparent cylinder 102 is spaced below the linear actuator 204 and located inside the reaction frame 107. The outer diameter of the upper perforated plate 211 is slightly smaller than the inner diameter of the transparent cylinder 102 to facilitate force transmission. The upper perforated plate 211 has multiple through holes in the vertical direction for discharging gas and air from the soil during the test. The cover plate 103 has an opening through which the force transmission rod 205 extends into the transparent cylinder 102. Driven vertically downward by the linear actuator 204, the pressurizing device 203 can apply pressure to the soil sample to achieve different overburden load conditions, improving the applicability of the measuring device. The upper axial force gauge 206 can detect the actual pressure applied above the soil. In some embodiments of the present invention, the pressurizing device 203 also includes a linear displacement sensor 208 mounted on the reaction frame 107 for measuring the overall deformation of the soil. One end of the linear displacement sensor 208 is fixedly connected to the reaction frame 107, and the other end is connected to the force transmission rod 205. When the soil sample undergoes a seepage-collapse coupling phenomenon, the linear displacement sensor 208 detects the amount of vertical displacement of the upper surface of the soil sample. In some embodiments of the present invention, the linear actuator 204 can be selected from electric cylinders, pneumatic cylinders, hydraulic cylinders, etc.

[0030] It should be noted that the lower axial force gauge 207, the lower perforated plate 212, and the filter screen are housed inside the base 104. The lower surface of the base cylinder is sealed, with only a water inlet 213 provided for the water inlet channel, and it is placed on the base plate of the reaction frame 107. The lower perforated plate 212 and the lower axial force gauge 207 are threaded onto the base cylinder from top to bottom. The outer diameter of the lower perforated plate 212 is slightly smaller than the inner diameter of the transparent cylinder 102 to facilitate force transmission. The lower perforated plate 212 has multiple through holes in the vertical direction to allow gas and air to escape from the soil during the test. The upper surface of the lower perforated plate 212 is flush with the upper surface of the base cylinder. A metal filter screen with pores smaller than the minimum particle size of the soil is affixed to the upper surface of the lower perforated plate 212 to prevent soil loss. A filter screen, a lower perforated plate 212, and a lower axial force gauge 207 are placed in the base 104 from top to bottom, covering the water inlet 213. A water supply device 106 enters the base 104 through the water inlet 213 and injects water into the transparent cylinder 102 through the lower perforated plate 212 and the filter screen. The lower perforated plate 212 allows water to pass through while restricting the passage of the soil sample. When the soil sample deforms, friction occurs between the soil sample and the inner wall of the transparent cylinder 102. The lower axial force gauge 207 enables the measurement of the true average vertical pressure on the lower surface of the soil. The two ends of the lower axial force gauge 207 are connected to the lower surface of the transparent cylinder 102 and the base 104, respectively, and the lower axial force gauge 207 is coaxial with the upper axial force gauge 206.

[0031] It should be noted that in some embodiments of the present invention, the water supply device 106 uses a constant pressure Marvi bottle, which can achieve a constant water head pressure at the bottom of the soil and reduce the influence of boundary condition changes on soil sample permeability tests.

[0032] According to a second aspect embodiment of the present invention, a method for measuring the permeability coefficient of unsaturated soil is applied to a system 100 for measuring the permeability coefficient of unsaturated soil considering soil deformation, as described in any of the first aspect embodiments. The method includes: placing soil into a transparent cylinder 102 and compacting it to a target density; setting a moisture content sensor 202 and a miniature soil tensiometer 201 on the same experimental level of the soil sample; injecting water into the transparent cylinder 102 via a base 104 through a water supply device 106 connected to a water inlet 213, and recording the total height change of the soil sample, the height change of the experimental level, and the height change of the water-soil mixture during the experimental time period using a camera module 105; recording the data from the moisture content sensor 202 and the miniature soil tensiometer 201 during the experimental time period; and calculating the permeability coefficient of the soil sample based on the parameters recorded during the experimental time period.

[0033] The method for measuring the permeability coefficient of unsaturated soil that takes into account soil deformation proposed in this invention is as follows: refer to Figure 3 , tIn state 1, the internal wetting front (the highest point of water wetting) of the soil sample reaches... F Position 1, height is h F At this point, the height of section B (i.e., the test surface detected by the moisture content sensor 202 and the miniature soil tensiometer 201) is recorded. h B Soil sample height h A The above height can be used to analyze camera module 105. t The image was acquired at time t1. Simultaneously, the moisture content sensor 202 and the miniature soil tensiometer 201 installed at section B can obtain the moisture content and matrix suction at time t1, respectively. θ ( h B , t 1) ψ ( h B , t 1). Similarly, t When the soil sample reaches state 2, the internal wetting peak is reached. F Position 2, the height of the rising moist front is denoted as Δ. h At this point, the soil sample deforms, and the overall displacement of the soil sample is denoted as Δ. D t The displacement of section B is denoted as Δ. D B The displacement magnitudes described above can be analyzed using camera module 105. t 1. t Images were acquired at section B. Simultaneously, the moisture content sensor 202 and the miniature soil tensiometer 201, installed at section B, could obtain... t Moisture content and suction strength at time 1 θ ( h B ', t 2) ψ ( h B ', t 2).

[0034] like Figure 4 As shown, it is assumed that the water content distribution along the soil sample height satisfies: (1)

[0035] like Figure 5 As shown, assume that the suction force distribution along the height of the soil sample satisfies: (2)

[0036] like Figure 4 and Figure 5 As shown, in the time interval ( t2- t 1) The water flow rate through section B can be expressed as: (3)

[0037] like Figure 4 and Figure 5 As shown, in the time interval ( t 2- t 1) Within the section, the hydraulic gradient at section B can be expressed as: (4)

[0038] like Figure 4 and Figure 5 As shown, after introducing the moisture content distribution curve and the suction distribution curve, section B at the time interval ( t 2- t 1) The permeability coefficient within can be expressed as: (5)

[0039] The complete expression is as follows: (6)

[0040] (7)

[0041] (8)

[0042] in, k The permeability coefficient of unsaturated soil θ i The initial volumetric water content of the unsaturated soil sample. θ i 'This represents the initial volumetric water content of the soil sample after displacement.' A c Δ is the cross-sectional area of ​​the unsaturated soil sample. t For time intervals. Preferably, the moisture content sensor 202 is used to measure the volumetric flow rate at section B. Q B Volumetric water content at time t1 θ ( h B , t 1) and t Volumetric water content at time 2 θ ( h B ', t 2) The miniature soil tensiometer 201 is used to measure the hydraulic gradient at section B. i middle t 1 moment of suction ψ ( h B, t 1) and t 2-hour suction ψ ( h B ', t 2) The images acquired by camera module 105 are used to obtain the soil sample height in the calculation model through Digital Image Correlation (DIC), a technique commonly used in geotechnical testing. h A Measure the height of section B h B , humid peak t 1 moment altitude h F , t Displacement Δ at section B at time 2 D B , t Total displacement Δ of soil sample at time 2 D t as well as t 2. Moist front opposite t The distance traveled at time 1 is Δ h .

[0043] In some embodiments of the present invention, before the water supply device 106 injects water into the transparent cylinder 102 and the base 104, the measurement method further includes applying pressure to the soil sample to bring it to a target stress level. Based on the above formula, a permeability coefficient variation diagram of the soil sample under a certain stress level is obtained using the current measurement system. This allows for a better understanding of more influencing factors on the measurement system 100 for the unsaturated soil permeability coefficient considering soil deformation in embodiments of the present invention. Furthermore, it ensures that each experiment is conducted under the target pressure, and more controllable factors in the testing system reduce experimental errors.

[0044] Figure 6 This is a curve showing the relationship between permeability coefficient and void ratio during water infiltration and collapse of a soil sample in one embodiment of the present invention. The soil sample used in this embodiment is completely weathered granite. In this embodiment, the volume deformation of the soil sample was monitored. The greater the volume deformation, the greater the decrease in void ratio, and the corresponding decrease in permeability coefficient. When the void ratio decreases by 10%, the unsaturated permeability coefficient corresponding to the completely weathered granite decreases by approximately two orders of magnitude. By detecting the changes in the relationship between void ratio and permeability coefficient, the permeability of soil under different void ratios can be predicted, thereby optimizing the design of foundations, dams, or tailings ponds. Alternatively, in roadbed or embankment projects, the curve can be used to determine the target void ratio range to ensure that the permeability coefficient meets requirements after compaction.

[0045] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A measurement system for the permeability coefficient of unsaturated soil considering soil deformation, characterized in that, include: A soil column includes a transparent cylinder, a cover plate, and a base. The transparent cylinder is used to place soil samples, the cover plate is used to reduce water evaporation, and the base is used to connect and fix the transparent cylinder and ensure uniform infiltration rate. A camera module is provided, which is distributed horizontally at intervals with the soil column. The camera module is used to acquire images of the transparent cylinder. A water supply device is connected to the base of the soil column, and the water supply device can inject water into the soil column from bottom to top; A miniature soil tensiometer is movably disposed within the transparent cylinder and is used to detect the matrix suction of the soil sample. A moisture content sensor is movably disposed within the transparent cylinder and is used to detect the volumetric moisture content of the soil sample. The miniature soil tensiometer and the moisture content sensor are fixedly connected to the same layer of the soil sample. When the soil sample undergoes a seepage-collapse coupling phenomenon, the miniature soil tensiometer and the moisture content sensor descend synchronously.

2. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 1, characterized in that, The measurement system for the permeability coefficient of unsaturated soil that takes into account soil deformation also includes a pressurizing device. An opening is provided on the cover plate of the soil column, and part of the pressurizing device extends into the soil column through the opening. The pressurizing device is used to apply pressure to the soil sample.

3. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 2, characterized in that, The measurement system for the permeability coefficient of unsaturated soil considering soil deformation also includes an upper axial force gauge and a reaction frame. The pressurization device includes a linear actuator and a force transmission rod. The linear actuator is disposed on the reaction frame. The two ends of the upper axial force gauge are respectively connected to the linear actuator and the force transmission rod. The transparent cylinder is spaced below the linear actuator and located inside the reaction frame. The end of the force transmission rod away from the upper axial force gauge extends into the transparent cylinder. The upper axial force gauge is used to detect the pressure applied by the linear actuator to the upper surface of the soil sample.

4. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 3, characterized in that, The measurement system for the permeability coefficient of unsaturated soil that takes into account soil deformation also includes a lower axial force gauge. The two ends of the lower axial force gauge are respectively connected to the lower end face of the transparent cylinder and the base. The base is connected to the reaction frame. The lower axial force gauge is coaxial with the upper axial force gauge. When the pressurizing device applies pressure to the soil sample, the lower axial force gauge is used to detect the pressure on the lower end face of the soil sample.

5. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 3, characterized in that, It also includes a linear displacement sensor, one end of which is fixedly connected to the reaction frame and the other end is connected to the force transmission rod. When the soil sample undergoes a seepage-collapse coupling phenomenon, the linear displacement sensor is used to detect the amount of vertical displacement of the upper surface of the soil sample.

6. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 1, characterized in that, The transparent cylinder has a moisture content sensor mounting hole and a tensiometer mounting hole. The moisture content sensor can be installed in the transparent cylinder through the moisture content sensor mounting hole, and the micro soil tensiometer can be installed in the transparent cylinder through the tensiometer mounting hole. The axis of the moisture content sensor mounting hole and the axis of the tensiometer mounting hole are located on the same horizontal plane.

7. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 1, characterized in that, The measurement system for the permeability coefficient of unsaturated soil that takes into account soil deformation also includes a supplementary light lamp. The supplementary light lamp is positioned between the camera module and the transparent cylinder. The emission direction of the light source of the supplementary light lamp is perpendicular to the spacing direction between the camera module and the transparent cylinder. The supplementary light lamp is used to ensure the brightness and light intensity stability between the camera module and the transparent cylinder.

8. The measurement system for the permeability coefficient of unsaturated soil considering soil deformation according to claim 1, characterized in that, The base houses a lower axial force gauge, a lower perforated plate, and a filter screen. The lower perforated plate and the lower axial force gauge are threaded together from top to bottom and placed on the base cylinder. The upper surface of the lower perforated plate is flush with the upper surface of the base. A layer of metal filter screen with pores smaller than the minimum particle size of the soil is affixed to the upper surface of the lower perforated plate. The filter screen, the lower perforated plate, and the lower axial force gauge are placed in the base in a top-to-bottom order and cover the water inlet. The water supply device includes the water inlet. The water supply device enters the base through the water inlet and injects water into the transparent cylinder through the lower perforated plate and the filter screen. The lower perforated plate and the filter screen allow water to pass through while restricting the passage of the soil sample.

9. A method for measuring the permeability coefficient of unsaturated soil, applied to the measurement system for the permeability coefficient of unsaturated soil considering soil deformation as described in any one of claims 1 to 8, characterized in that, The measurement method includes: Soil was placed into the transparent cylinder and compacted to the target density to form a sample. The moisture content sensor and the miniature soil tensiometer are installed at the same experimental level as the soil sample; The water supply device injects water into the transparent cylinder, and the camera module records the total height change of the soil sample, the height change of the experimental layer, and the height change of the water-soil mixture during the experimental period. Record the data from the moisture content sensor and the miniature soil tensiometer during the experimental period; The permeability coefficient of the soil sample was calculated based on the parameters recorded during the experimental period.

10. The measurement method according to claim 9, characterized in that, Before the water supply device injects water into the transparent cylinder, the measurement method further includes applying pressure to the soil sample to bring the soil sample to a target stress level.

Images