Slope surface soil burst process measuring device and method based on rock-soil interface depression

Abstract

The invention provides a rock-soil interface depression-based slope surface soil burst process measuring device and method, and the device comprises a box body which is obliquely arranged, a continuous concave support frame is arranged at the bottom in the box body, one side surface of the box body is a transparent glass plate, and a plurality of water outlet holes are formed in the downward inclined side of the box body; the gradient control mechanism is located at the bottom of the box; the PIV system comprises a speed measuring system and a laser emitting system, and the speed measuring system is located on one side, where the transparent glass plate is located, of the box body; the collecting assembly is located on the side, inclining downwards, of the box body. According to the application, accurate measurement of the internal flow velocity in the process of underflow migration and reliability research on the hydrological mechanism in the process of surge and sudden change of mountain torrent can be carried out, and meanwhile, two components of surface runoff and underflow of a soil-bedrock interface structure are simulated and considered; the experimental method and steps which are economical, feasible, scientific and reasonable in design are provided for depression filling-water overflowing movement of a rock-soil interface containing a depression structure, especially for the hydrological mechanism of formation of extra-large mountain torrent debris flow.

Description

Technical Field

[0001] This application relates to the technical fields of hydrogeology, pedology, and mountain flood disasters, and particularly relates to a device and method for measuring the subsurface stormflow process on a slope based on a depression in the rock-soil interface. Background Art

[0002] Mountain slopes often have the characteristics of being steep, wide-graded, and highly permeable. Under strong rainfall conditions, the subsurface stormflow hydrological process mainly occurs at the soil-bedrock interface and above it, which is a special form of subsurface flow in the vadose zone of steep slopes in mountainous areas and is widespread in different climate zones and geomorphic regions of the world. The contribution ratio to the water source of mountain floods, mudslides, and debris flows can exceed 70%. Moreover, the depression structure and channels at the rock-soil interface profoundly affect the gestation, formation, and development of subsurface stormflow, and also make it difficult to accurately describe the hydrological conditions during the sudden process of the current mountain flood-landslide-debris flow homologous chain disaster, severely restricting the development and popularization of disaster hydrological driving theories and defense technologies. Currently, to understand the influence of the depression structure at the rock-soil interface on the ponding-overflow subsurface stormflow process and the internal seepage field on the runoff mutation effect, the method adopted is the artificial rainfall slope runoff method without considering the rock-soil interface structure. This method mainly relies on indoor conventional runoff plots to carry out control experiments on runoff and sediment production under artificial rainfall conditions, but it fails to fully consider the characteristics of the internal seepage field under wide-graded macropore flow conditions and the hydrological nonlinear mutation process of subsurface stormflow, nor does it fully consider the influence of the actual bedrock depression structure in the field on the initial mutation process and recession process of runoff, thus limiting the accurate measurement and understanding of the subsurface stormflow process. At the same time, the isotope / hydrochemical tracer runoff partitioning method is also often used currently, such as water isotopes (δD, δ18O), hydrochemistry (electrical conductivity EC, Cl-), etc. as tracers to carry out research on the water source path and water source contribution degree at the watershed scale or slope scale, and partition the contribution amounts of different water sources such as precipitation, subsurface flow, and groundwater. However, it cannot quantify the migration flow process within the soil body or at the interface, and fails to well describe the hydro-physical process of the formation of mountain floods, mudslides, and debris flows and landslides, restricting the development of the hydrological driving disaster-causing theory. Summary of the Invention

[0003] In view of this, the purpose of this application is to provide a device and method for measuring the subsurface stormflow process on a slope based on a depression in the rock-soil interface to solve the problem that the prior art cannot quantify the migration flow process within the soil body or at the interface.

[0004] In a first aspect, this application provides a device for measuring the subsurface stormflow process on a slope based on a depression in the rock-soil interface, including: a box body, the box body is inclined, a continuous concave support frame is arranged at the bottom inside the box body, one side surface of the box body is a transparent glass plate, and a plurality of water outlet holes are arranged on the downward-inclined side of the box body; The slope control mechanism is located at the bottom of the box body; The PIV system includes a speed measurement system and a laser emission system. The speed measurement system is located on one side of the box body where the transparent glass plate is located; the laser emission system is located on one side of the box body; The collection assembly is located on the inclined side of the box body.

[0005] In one embodiment, the diameter of the water outlet hole is 0.3 cm to 0.6 cm; and / or The inclination of the box body is 0 degrees to 50 degrees.

[0006] In one embodiment, the continuous concave support frame includes a support frame. The support frame has a first end and a second end. Along the direction from the first end to the second end, a plurality of rectangular depression grooves are provided on the support frame. A U-shaped liner is provided in each rectangular depression groove. The plurality of rectangular depression grooves and the U-shaped liners in each rectangular depression groove form a depression structure. The upper part of the support frame on both sides of the U-shaped liner in each rectangular depression groove is a non-depression structure; and / or The slope control mechanism includes a support box. A first heavy-duty hinge is provided between the support box near the second end and the box body. A hydraulic lift is provided at the bottom of the support box near the first end. The hydraulic lift extends to the outside of the support box. The top pillar of the hydraulic lift is connected to the box body through a second heavy-duty hinge; and / or The speed measurement system includes: a high-speed camera and an image analyzer. The high-speed camera is located on one side of the box body where the transparent glass plate is located; and / or The laser emission system includes: a laser and a light guide arm connected to the laser; and / or The collection assembly includes a bottom subsurface flow collection tank, a middle subsurface flow collection tank, and a surface runoff collection tank that are sequentially arranged from bottom to top on the inclined side of the box body. The bottom subsurface flow collection tank, the middle subsurface flow collection tank, and the surface runoff collection tank are all connected to a collecting bucket through a water guide pipe.

[0007] In one embodiment, the second end is greater than the first end; and / or Both ends of each U-shaped liner are provided with flanges extending outward; and / or Along the direction from the first end to the second end, the continuous concave support frame is provided with a plurality of vertical support plates; and / or A detachable cover plate is provided on the upper part of each rectangular depression groove; and / or The U-shaped liner includes an arc portion at the bottom and vertical portions on both sides of the arc portion. The radius of the arc portion is R, the slope of the soil body of the continuous concave support frame is θ, and b is the width of the box body. Then the volume V of the arc portion 圆弧 ​ V 圆弧 =R²×b[π / 2-θ-(sin2θ) / 2] Based on the slope of the soil body of the continuous concave support frame being θ and the depth ℎ of the U-shaped liner, the volume V of the diamond part of the U-shaped liner is obtained 菱形 : V 菱形 =2R×h×b×cos²θ Based on the slope of the soil body of the continuous concave support frame being θ, the radius of the arc part being R, and the depth ℎ of the U-shaped liner, the volume of the depression formed by the U-shaped liner and the inside of the box is obtained: V = 2R×h×b×cos²θ + R²×b[π / 2 - θ - (sin2θ) / 2]; and / or The bottom of the support box is provided with universal wheels, and the setting of the universal wheels facilitates the movement of the box; and / or The bottom subsurface flow collection tank, the middle subsurface flow collection tank, and the surface runoff collection tank all include triangular plates located on the downward-sloping side of the box. One side of the triangular plate is fixed to the downward-sloping side of the box, baffles are provided on the other two sides of the triangular plate, a water guide pipe is connected to the end of the triangular plate far from the downward-sloping side of the box, and a flow meter is connected inside the flow collection bucket.

[0008] In a second aspect, the present application provides an experimental method for a device for measuring the process of subsurface storm flow on a slope based on a depression at the rock-soil interface, including the following steps: Provide transparent test soil T1, transparent test soil T2, and transparent test soil T3; Fill the inside of the box with transparent test soil T1, transparent test soil T2, and transparent test soil T3 in sequence from bottom to top; Adjust the box to an inclined angle; Set the rainfall intensity, start the rainfall, then turn on the speed measurement system and the laser emission system, and at the same time collect runoff samples through the collection component.

[0009] In an embodiment, the first type of transparent soil and the fourth type of transparent soil are respectively mixed at mass ratios of 1:4, 1:2, and 1:1 to obtain transparent test soil T1, transparent test soil T2, and transparent test soil T3; and / or The thickness of transparent test soil T1 is 10 cm, the thickness of transparent test soil T2 is 10 cm, and the thickness of transparent test soil T3 is 20 cm; and / or ​The rainfall intensity is set at 7 gradients of rainfall, namely 5 mm / h, 10 mm / h, 30 mm / h, 60 mm / h, 90 mm / h, 120 mm / h, and 150 mm / h. The duration of each gradient of rainfall is 45 minutes. The flow meters connected to the subsurface flow collection tank at the bottom of the box, the subsurface flow collection tank in the middle, and the surface runoff collection tank automatically collect the flow rate every 1 minute. After each rainfall, a pause of 30 minutes is taken or the next rainfall is carried out after leaving it for 3 - 5 days.

[0010] In one embodiment, the method for obtaining the first type of transparent soil includes: Sieve the fused quartz sand into 0 - 1 mm, 1 - 2 mm, 2 - 3 mm, 3 - 5 mm, 5 - 8 mm, 8 - 10 mm, 10 - 20 mm, and 20 - 40 mm; Mix the 0 - 1 mm and 1 - 2 mm fused quartz sand in a mass ratio of 1:1 to obtain 0 - 2 mm fused quartz sand; Add the pore fluid to the 0 - 2 mm fused quartz sand to uniformly wet the surface of the 0 - 2 mm fused quartz sand, forming specimen a; Place specimen a in a vacuum environment for 6 h - 10 h to exhaust air, obtaining specimen b; In a vacuum environment, continue to add the pore fluid to specimen b while continuously evacuating until the liquid level of the pore fluid covers the upper surface of specimen b, forming specimen c; Take specimen c out of the vacuum environment and let it stand at room temperature for 12 h - 16 h to form specimen d, which is the first type of transparent soil; and / or The method for obtaining the second type of transparent soil includes: Mix the 2 - 3 mm, 3 - 5 mm, 5 - 8 mm, and 8 - 10 mm fused quartz sand in a mass ratio of 1:1:1:1 to obtain 2 - 10 mm fused quartz sand; the remaining steps are the same as the method for preparing the first type of transparent soil; and / or The method for obtaining the third type of transparent soil includes: Mix the 10 - 20 mm and 20 - 40 mm fused quartz sand in a mass ratio of 1:1 to obtain 10 - 40 mm fused quartz sand; the remaining steps are the same as the method for preparing the first type of transparent soil.

[0011] In one embodiment, the pore fluid includes n - dodecane and No. 15 white oil, and the mass ratio of n - dodecane to No. 15 white oil is 1:4. After configuration, add Nile red dye until the pore fluid is completely colored; and / or Mix the second type of transparent soil and the third type of transparent soil in a mass ratio of 1:1 to obtain the fourth type of transparent soil.

[0012] In one embodiment, the top, middle, and bottom of the transparent test soils T1, T2, and T3 are backfilled in the box body, and a plurality of soil moisture monitoring probes and matrix suction probes are provided at the edges and the center of the U-shaped lining plate.

[0013] In one embodiment, before the rainfall starts, the laser emission system and the velocity measurement system are turned on. The planar laser emitted by the laser and the light guide arm performs layer cutting on the transparent soil sample T1 and / or transparent soil sample T2 and / or transparent soil sample T3 in the box body to form laser speckles, ensuring that the laser beam can evenly illuminate the cross-section of the seepage field of the transparent soil sample T1 and / or transparent soil sample T2 and / or transparent soil sample T3 in the depression structure area and the non-depression structure area; the high-speed camera is used to record the laser speckles, and the image analyzer is used to analyze the laser speckles. The high-speed camera and the image analyzer cooperate with each other to capture the detailed velocity distribution density, magnitude, and direction of the subsurface flow around the U-shaped lining plate at the bottom of the box body during the entire rainfall process.

[0014] For the slope subsurface stormflow process measurement device of the present application that considers the depression structure of the geotechnical interface, the continuously concave support frame at the bottom can adjust the volume size, depth, and position, maximizing the restoration of the real depression structure of the geotechnical interface. Moreover, the PIV system on the side assists in the real-time observation of the migration and diffusion process of the depression-filling - overflow seepage field (flow velocity and flow direction) of the geotechnical interface depression structure, which can accurately characterize the near-saturated dynamic process of the hydrological mechanism of depression-filling - overflow at the moment of sediment yield mutation at the geotechnical interface, and depict the sediment yield process of the wide-graded highly permeable slope in mountainous areas more realistically and reasonably.

[0015] The present application mainly uses transparent test soils to carry out the migration and change process of the flow velocity magnitude, direction, and density in the subsurface stormflow process in the depression structure area of the internal geotechnical interface, and compares the runoff yield at the moment of runoff yield mutation in the catchment trough, which helps to more accurately decompose the dynamic contributions of surface runoff and subsurface stormflow in the sudden change process of mountain flood formation, and can improve the accuracy and reliability of watershed mountain flood hydrological simulation from the mechanism.

[0016] The subsurface stormflow method and experimental results of the present application can provide key hydrological parameters for the simulation of mountain hydrological processes, shallow landslides, and debris flow formation processes, and can form key hydrological theories for the study of the formation of compound chain disasters of mountain floods, landslides, and debris flows in the wide-graded highly permeable soil body watershed in hilly mountainous areas, promoting the development of the mountain flood and debris flow disaster theory system and the deepening of disaster reduction principles. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present application and do not limit the present application, where: Figure 1 It is a schematic structural diagram of the slope subsurface stormflow process measurement device based on the geotechnical interface depression of the embodiment of the present application; Figure 2 It is a structural schematic diagram of the continuous concave support frame in the embodiment of the present application; Figure 3 It is a non-linear behavior diagram of flood formation mutation caused by subsurface stormflow process at a certain slope in the embodiment of the present application.

[0018] Explanation of reference numerals: 1 - box body, 2 - continuous concave support frame, 21 - U-shaped lining plate, 22 - rectangular depression groove, 23 - support plate, 24 - cover plate, 3 - transparent glass plate, 41 - high-speed camera, 42 - image analyzer, 51 - bottom subsurface flow collection tank, 52 - middle subsurface flow collection tank, 53 - surface runoff collection tank, 54 - triangular plate, 55 - water conduit, 56 - flow collection bucket, 61 - support box, 62 - hydraulic lift, 63 - universal wheel, 71 - laser, 72 - light guide arm. Specific implementation manners

[0019] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0020] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "thickness", "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a unique orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "a plurality" means two or more, unless otherwise specifically defined.

[0021] In the application, the term "exemplary" is used to mean "serving as an example, illustration, or instance". Any embodiment described as "exemplary" in this application is not necessarily to be construed as more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. In the following description, details are set forth for purposes of explanation. It should be understood that those of ordinary skill in the art can recognize that this application can be implemented without these specific details. In other instances, well-known structures and processes are not elaborated in detail to avoid obscuring the description of this application with unnecessary details. Accordingly, this application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles disclosed herein.

[0022] In a first aspect, please refer to Figure 1 and Figure 2 , an embodiment of the present application provides a device for measuring the process of subsurface stormflow on a slope based on a depression in a geotechnical interface, including: A box body 1, the box body 1 is inclined, a continuous concave support frame 2 is arranged at the bottom inside the box body 1, one side surface of the box body 1 is a transparent glass plate 3, and a plurality of water outlet holes are arranged on the side of the box body 1 that slopes downward; A slope control mechanism, located at the bottom of the box body 1; A PIV system, including a velocity measurement system and a laser emission system. The velocity measurement system is located on one side of the box body 1 where the transparent glass plate 3 is located; the laser emission system is located on one side of the box body 1; A collection component, located on the side of the box body 1 that slopes downward.

[0023] The present application provides a device for measuring the process of subsurface stormflow on a slope considering the structure of a depression in a geotechnical interface. The continuous concave support frame 2 at the bottom can adjust the volume size, depth, and position, maximizing the restoration of the true structure of the depression in the geotechnical interface. Moreover, the PIV system on the side assists in real-time observing the migration and diffusion process of the filling - overflow seepage field (flow velocity and flow direction) of the depression structure in the geotechnical interface, and can accurately characterize the near - saturated dynamic process of the filling - overflow hydrological mechanism at the moment of sudden change in sediment production, depicting the sediment production process on wide - graded and highly permeable slopes in mountainous areas more realistically and reasonably.

[0024] This application mainly uses transparent test soil to carry out the migration and change process of the flow velocity magnitude, direction, and density in the subsurface stormflow process in the internal geotechnical interface depression structure area, and compares the runoff volume at the moment of sudden change in runoff in the catchment trough, which helps to more accurately decompose the dynamic contributions of surface runoff and subsurface stormflow in the sudden change process of mountain flood formation, and can improve the accuracy and reliability of watershed mountain flood hydrological simulation from the mechanism.

[0025] The subsurface stormflow method and experimental results of this application can provide key hydrological parameters for the simulation of mountain hydrological processes, shallow landslides, and debris flow formation processes, and can form key hydrological theories for the study of the formation of compound chain disasters of flash floods, landslides, and debris flows in wide-graded and highly permeable soil basins in hilly and mountainous areas, promoting the development of the flash flood and debris flow disaster theory system and the deepening of disaster reduction principles.

[0026] This application uses a device for measuring the subsurface stormflow process based on depressions at the rock-soil interface, which can accurately measure the internal flow velocity during the subsurface stormflow migration process and conduct reliable research on the hydrological mechanism of the sudden increase in flash floods. At the same time, it simulates and considers two components of surface runoff and subsurface flow considering the structure of the soil-bedrock interface, providing an economically feasible and scientifically reasonable experimental method and procedure for the water movement of ponding-overflow at the rock-soil interface with depression structure, especially for the hydrological mechanism of the formation of extremely large flash floods and debris flows.

[0027] This application realizes the quantitative characterization of the migration and extension seepage field of ponding-overflow subsurface stormflow at the wide-graded and highly permeable slope rock-soil interface, reveals the internal hydrological mechanism at the moment of rainfall runoff mutation, and can improve the simulation of the nonlinear process of flood formation mutation from the runoff mechanism, making it more scientific and realistic.

[0028] This application can carry out indoor artificial rainfall slope runoff model experiments, process static pictures and dynamic videos with the help of high-definition image analysis technology, obtain data such as seepage paths, seepage velocities, and near-saturated horizontal transport fluxes in the depression structure area of the bedrock interface, reproduce the whole process of rainfall infiltration, subsurface runoff generation, and landslide deformation initiation, realize the visual observation of seepage and deformation inside the transparent soil body, and analyze the hysteretic effects of the ponding-overflow process in the depression on the small amount of runoff at the initial stage of rainfall and the flood recession process after rainfall stops.

[0029] This application adopts the transparent soil technology to allow direct observation of processes such as seepage, erosion, and deformation inside the soil body, enabling researchers to intuitively understand the physical processes inside the soil body. At the same time, experiments can also be carried out on real soil in the field according to needs.

[0030] It can be understood that the bottom of the continuous concave support frame 2 coincides with the bottom of the box body 1, and vaseline is applied at the connection gap between the box body 11 and the continuous concave support frame 2 for sealing treatment to reduce the boundary effect.

[0031] It can be understood that the box body 1 is rectangular, and the slope control structure at the bottom of the box body 1 is used to control the inclination of the box body 1.

[0032] In some embodiments, the diameter of the water outlet hole is 0.3 cm to 0.6 cm, and can be, for example, 0.3 cm, 0.4 cm, 0.5 cm, 0.6 cm, etc.

[0033] Exemplarily, on the side of the box body 1 that slopes downward, there are 12 drain holes, with 20 drain holes in each row, for a total of 240 drain holes. The diameter of each drain hole is 0.5 cm, and the area of the box body 1 on the side where the drain holes are located is 0.3 m².

[0034] In some embodiments, the inclination of the box body 1 is from 0° to 50°, for example, it can be 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, 40°, 45°, 50°, etc.

[0035] Exemplarily, the inclination of the box body 1 is 35°.

[0036] Exemplarily, the shape of the box body 1 is square, for example, it can be a cuboid shape or a cube shape.

[0037] In some embodiments, the continuous concave support frame 2 includes a support frame, the support frame has a first end and a second end, along the direction from the first end to the second end, a plurality of rectangular depression grooves 22 are provided on the support frame, and a U-shaped lining plate 21 is provided in each rectangular depression groove 22. The plurality of rectangular depression grooves 22 and the U-shaped lining plates 21 in each rectangular depression groove 22 form a depression structure, and the upper part of the support frame on both sides of the U-shaped lining plate 21 in each rectangular depression groove 22 is a non-depression structure.

[0038] It can be understood that the plurality of rectangular depression grooves 22 on the support frame and the U-shaped lining plates 21 provided in each rectangular depression groove 22 are imitation depression structures.

[0039] Further, the second end is larger than the first end.

[0040] Further, both ends of each U-shaped lining plate 21 are provided with flanges extending outwards.

[0041] Further, along the direction from the first end to the second end, the continuous concave support frame 2 is provided with a plurality of vertical support plates 23.

[0042] It can be understood that the vertical support plates 23 are located between adjacent rectangular depression grooves 22.

[0043] It can be understood that the continuous concave support frame 2 is equivalent to the bedrock layer.

[0044] Further, a detachable cover plate 24 is provided on the upper part of each rectangular depression groove 22. It can be understood that the cover plate 24 is a rectangular acrylic plate. When the depression structure of the bedrock layer in nature is relatively simple and only located at the bottom of the slope, the cover plate 24 can be used to close the rectangular depression grooves 22 in the upper and middle parts of the continuous concave support frame 2. Similarly, when located in the middle or at the top of the slope, the other two rectangular depression grooves 22 are closed with the cover plate 24.

[0045] Exemplarily, the length × width × height of the rectangular acrylic plate is 500 mm × 140 mm × 2 mm, and the overlapping part of the cover plate 24 and the continuous concave support frame 2 is sealed with glass glue.

[0046] When a certain rectangular depression groove 22 is not needed, the corresponding unnecessary rectangular depression groove 22 is covered with the cover plate 24, and the periphery of the cover plate 24 is sealed with glass glue.

[0047] Exemplarily, the continuous concave support frame 2 is made of six acrylic plates. The acrylic plates on both sides are right trapezoids with one end small and the other end large. The upper base of the right trapezoid is 65 mm, the lower base is 130 mm, the bottom acrylic plate is rectangular, the length of the rectangle is 980 mm, and the width of the rectangle is 500 mm. Then the upper part and both ends are closed to form the continuous concave support frame 2; three rectangular depression grooves 22 are opened on the support frame, and each rectangular depression groove 22 is provided with a U-shaped lining plate 21, which is adhered to both sides of the upper part of the continuous concave support frame 2 by lapping and glass glue.

[0048] It can be understood that the rectangular depression groove 22 can also be reserved in advance when making the continuous concave support frame 2.

[0049] Exemplarily, the width of the U-shaped lining plate 21 can be 15 cm, 20 cm or 30 cm. It can be understood that the number of U-shaped lining plates 21 corresponding to the rectangular depression groove 22 can be adjusted and reduced according to the situation.

[0050] Furthermore, the U-shaped lining plate 21 includes an arc part at the bottom and vertical parts on both sides of the arc part. The radius of the arc part is R, and the soil slope of the continuous concave support frame 2 is θ. Then the volume V of the arc part 圆弧 is: V 圆弧 =R²×b[π / 2-θ-(sin2θ) / 2] According to the soil slope θ of the continuous concave support frame 2 and the depth ℎ of the U-shaped lining plate 21, the volume V of the rhombus part of the U-shaped lining plate 21 is obtained 菱形 : V 菱形 =2R×h×b×cos²θ According to the soil slope θ of the continuous concave support frame 2, the radius R of the arc part and the depth ℎ of the U-shaped lining plate 21, the volume of the depression formed by the U-shaped lining plate 21 and the inside of the box body 1 is obtained: V = 2R×h×b×cos²θ + R²×b[π / 2 - θ - (sin2θ) / 2].

[0051] In some embodiments, the slope control mechanism includes a support box 61. A first heavy-duty hinge is provided between the support box 61 near the second end and the box body 1. A hydraulic lift 62 is provided at the bottom of the support box 61 near the first end. The hydraulic lift 62 extends to the outside of the support box 61. The top pillar of the hydraulic lift 62 is connected to the box body 1 through a second heavy-duty hinge.

[0052] Further, universal wheels 63 are provided at the bottom of the support box 61. The provision of the universal wheels 63 facilitates the movement of the box body 1.

[0053] It can be understood that the box body 1 can rotate around the first heavy-duty hinge; adjusting the lifting of the pillar of the hydraulic lift 62 can change the slope of the box body 1.

[0054] In some embodiments, the velocity measurement system includes: a high-speed camera 41 and an image analyzer 42. The high-speed camera 41 is located on one side of the box body 1 where the transparent glass plate 3 is located.

[0055] In some embodiments, the laser emission system includes: a laser 71 and a light guide arm 72 connected to the laser 71.

[0056] It can be understood that the laser source emits a sheet-shaped laser beam to illuminate a cross-section of the flow field in the box body 1. The tracer particles added to the flow field scatter the laser, causing the laser to be scattered to the side of the flow field. A high-speed camera 41 is provided in the direction perpendicular to the illuminated cross-section. The behavior of the illuminated flow field is continuously photographed at set time intervals, and then the data is transmitted to a computer. The computer then processes the data according to set programs and algorithms to obtain the velocity and density information of the flow field.

[0057] It can be understood that the high-speed camera 41 is used to record laser speckles, and the image analyzer is used to analyze laser speckles. PIV technology can capture the detailed flow velocity distribution, flow characteristics, and average flow velocity of the flow in the soil, including the magnitude and direction of the flow velocity. This is crucial for understanding the dynamic mutation behavior of overland flow under different hydraulic gradients and its contribution to the peak flow of mountain floods, as well as for studying the landslide initiation mechanism.

[0058] It can be understood that under rainfall conditions, by arranging the laser emission system on the side of the box body 1, it is ensured that the laser beam can evenly illuminate the cross-section of the transparent soil seepage field in the U-shaped liner 21 area (i.e., the depression structure area) and the smooth areas of the support plates 23 on both sides of the U-shaped liner 21 area (i.e., the non-depression structure areas).

[0059] It can be understood that the laser 71 and the light guide arm 72 are used to emit a planar laser to perform layer cutting on the transparent soil in the box body 1 to form laser speckles.

[0060] Exemplarily, the light guide arm 72 uses a Powell prism, model KS-PB10A30-D6. The Powell prism is an optical scribing prism that can optimize the laser beam into a straight line with uniform light density, good stability, and good linearity after passing through. The scribing of the Powell prism is superior to that of the cylindrical lens, and can eliminate the central hot spot and fading edge distribution of the Gaussian beam. The incident diameter is 5 mm, and the fan angle is 30°. The laser 71, model MW-GL-532 / 1~500 mW, is a solid-state laser 71 that can emit green light, with a wavelength of 532 nm.

[0061] In some embodiments, the collection assembly includes a bottom subsurface flow collection tank 51, a middle subsurface flow collection tank 52, and a surface runoff collection tank 53 that are sequentially arranged from bottom to top on the downwardly inclined side of the box body 1. The bottom subsurface flow collection tank 51, the middle subsurface flow collection tank 52, and the surface runoff collection tank 53 are all connected to a flow collection bucket 56 through a water guide pipe 55.

[0062] Further, the bottom subsurface flow collection tank 51, the middle subsurface flow collection tank 52, and the surface runoff collection tank 53 all include a triangular plate 54 on the downwardly inclined side of the box body 1. One side of the triangular plate 54 is fixed to the downwardly inclined side of the box body 1, and baffles are provided on the other two sides of the triangular plate 54. The end of the triangular plate 54 away from the downwardly inclined side of the box body 1 is connected to the water guide pipe 55, and a flow meter is connected inside the flow collection bucket 56.

[0063] It can be understood that the flow meter can monitor the yield of subsurface stormflow inside the soil mass in real time.

[0064] Exemplarily, the height of the baffle is 2 cm, which can prevent overflow. The distances from the bottom subsurface flow collection tank 51, the middle subsurface flow collection tank 52, and the surface runoff collection tank 53 to the bottom of the box body 1 are 10 cm, 25 cm, and 40 cm respectively. The bottom of the surface runoff collection tank 53 is flush with the surface of the transparent test soil T3 filled in the box body 1. The bottom of the middle subsurface flow collection tank 52 is 15 cm away from the surface of the transparent test soil T1, and the bottom of the bottom subsurface flow collection tank 51 is 10 cm away from the bottom of the box body 1.

[0065] In a second aspect, an experimental method for a device for measuring the process of subsurface stormflow on a slope based on a depression at the geotechnical interface provided by an embodiment of the present application includes the following steps: S01. Provide transparent test soil T1, transparent test soil T2, and transparent test soil T3; S02. Fill the box body 1 with transparent test soil T1, transparent test soil T2, and transparent test soil T3 in sequence from bottom to top; S03. Adjust the box body 1 to an inclined angle; S04. Set the rainfall intensity. After starting the rainfall, turn on the speed measurement system and the laser emission system, and at the same time collect the runoff samples through the collection component.

[0066] In the above S01: In some embodiments, the first type of transparent soil and the fourth type of transparent soil are respectively mixed in a mass ratio of 1:4, 1:2, and 1:1 to obtain transparent specimen soils T1, T2, and T3.

[0067] Furthermore, the method for obtaining the first type of transparent soil includes: S011. Screen the fused quartz sand into 0 - 1mm, 1 - 2mm, 2 - 3mm, 3 - 5mm, 5 - 8mm, 8 - 10mm, 10 - 20mm, and 20 - 40mm; S012. Mix the 0 - 1mm and 1 - 2mm in a mass ratio of 1:1 to obtain 0 - 2mm fused quartz sand; S013. Add the pore fluid to the 0 - 2mm fused quartz sand to uniformly wet the surface of the 0 - 2mm fused quartz sand, forming specimen a; It can be understood that at this time, specimen a is in a certain state. The amount of pore fluid added should be sufficient to wet all the transparent soil raw materials, and not too much to avoid affecting the subsequent air exhaust effect.

[0068] S014. Place specimen a in a vacuum environment for 6h - 10h to exhaust air, obtaining specimen b; It can be understood that placing specimen a in a vacuum environment for 6h - 10h can be, for example, 6h, 7h, 8h, 9h, 10h, etc.

[0069] Exemplarily, specimen a is put into a vacuum bucket, the vacuum pump is turned on, and it is exhausted in a vacuum environment for 8h. It can be understood that in this way, the purpose is to discharge the air adsorbed inside and on the surface of specimen a (transparent soil), reduce the generation of air bubbles, and enable specimen a (transparent soil) to better combine with the pore fluid, obtaining specimen b. During the air exhaust process, specimen a will gradually become transparent, and specimen b is light white.

[0070] S015. In a vacuum environment, continue to add pore fluid to specimen b while continuously pumping vacuum until the liquid level of the pore fluid covers the upper surface of specimen b, forming specimen c; It can be understood that at this time, specimen c is semi - transparent and has a large number of air bubbles. The pore fluid has completely immersed the fused quartz sand, and the pores inside the transparent soil raw materials are filled with the pore fluid.

[0071] S016. Take specimen c out of the vacuum environment and let it stand at room temperature for 12h - 16h to form specimen d, which is the first type of transparent soil.

[0072] It can be understood that it is left standing at room temperature indoors for 12 h to 16 h, for example, it can be 12 h, 13 h, 14 h, 15 h, 16 h, etc.

[0073] It can be understood that at this time, the bubbles in the pore fluid will gradually escape, and the transparent soil raw material will further combine with the pore fluid to finally form transparent soil, that is, the specimen d is in a transparent state. The transparent soil raw material and the pore fluid are evenly mixed, without obvious bubbles, and have good light transmittance and uniformity. The prepared specimen d is placed in a constant temperature environment and sealed for storage.

[0074] In the S013: In some embodiments, the pore fluid includes dodecane and No. 15 white oil, and the mass ratio of dodecane to No. 15 white oil is 1:4. After the preparation is completed, Nile red dye is added until the pore fluid is completely colored.

[0075] In some embodiments, the method for obtaining the second type of transparent soil includes: mixing fused quartz sands of 2 - 3 mm, 3 - 5 mm, 5 - 8 mm, and 8 - 10 mm according to a mass ratio of 1:1:1:1 to obtain fused quartz sand of 2 - 10 mm; the remaining steps are the same as the method for preparing the first type of transparent soil.

[0076] In some embodiments, the method for obtaining the third type of transparent soil includes: mixing fused quartz sands of 10 - 20 mm and 20 - 40 mm according to a mass ratio of 1:1 to obtain fused quartz sand of 10 - 40 mm; the remaining steps are the same as the method for preparing the first type of transparent soil.

[0077] Furthermore, the second type of transparent soil and the third type of transparent soil are mixed according to a mass ratio of 1:1 to obtain the fourth type of transparent soil.

[0078] It can be understood that the first type of transparent soil is the soil part in the simulated slope soil mass; the second type of transparent soil is the small gravel part in the simulated slope soil mass; the third type of transparent soil is the medium gravel part in the simulated slope mass; the fourth type of transparent soil is the rock part in the simulated slope soil mass.

[0079] Exemplarily, first, the transparent soil sample T1 is filled into the box body 1 as the bottom layer with a thickness of 10 cm. The transparent soil sample T1 is shoveled into the U-shaped liner 21 on the rectangular depression groove 22 using a small shovel. First, fill the bottom of the U-shaped liner 21, and gently scrape the surface of the transparent soil sample T1 on the U-shaped liner 21 with a scraper to remove the excess transparent soil sample T1, making the surface of the transparent soil sample T1 flush with the upper edge of the U-shaped liner 21, and then gradually fill it up by 10 cm. During the filling process, it is necessary to ensure that the transparent soil is evenly distributed to avoid local accumulation or voids. Every time the soil filling thickness reaches 5 cm, gently tap it with a wooden hammer to make the soil layer dense, but do not over-compact it to avoid damaging the transparent soil structure, and continue to fill the transparent soil sample T1 to 10 cm. Then, on the basis of the bottom transparent soil sample T1, fill the transparent soil sample T2 as the second layer with a thickness of 15 cm. Finally, on the basis of the surface of the second transparent soil sample T2, fill the transparent soil sample T3 with a thickness of 15 cm. After filling each layer of transparent soil sample, gently tap it with a wooden hammer to ensure that the soil layer is dense.

[0080] It can be understood that after making the surface of the transparent soil sample T1 flush with the upper edge of the U-shaped liner 21 and then filling it up by 10 cm, it is the thickness of the transparent soil sample T1, which is 10 cm.

[0081] In some embodiments, multiple soil moisture monitoring probes and matrix suction probes are provided at the top, middle, and bottom of the slopes of the transparent soil samples T1, T2, and T3 backfilled in the box body 1, as well as at the edges and center of the U-shaped liner 21.

[0082] It can be understood that in this way, the purpose is to continuously record the continuous change and mutation information of the soil moisture content at each monitoring position during the migration and diffusion process of subsurface stormflow inside the soil mass. The longitudinal distance between any two probes is 10 cm, and the transverse distance is greater than 10 cm to reduce the mutual influence between sensors when collecting data.

[0083] In S04: In some embodiments, the rainfall intensities are set to 7 gradient rainfalls of 5 mm / h, 10 mm / h, 30 mm / h, 60 mm / h, 90 mm / h, 120 mm / h, and 150 mm / h. The time for each gradient rainfall is 45 min. The flowmeters connected to the subsurface flow collection tank 51 at the bottom of the box body 1, the subsurface flow collection tank 52 in the middle, and the surface runoff collection tank 53 automatically collect the flow rate every 1 min. After each rainfall ends, pause for 30 min or leave it for 3 - 5 days before conducting the next rainfall.

[0084] Further, before the rainfall begins, turn on the laser emission system and the velocity measurement system. The planar laser emitted by the laser 71 and the light guide arm 72 performs layer cutting on the transparent soil specimen T1 and / or the transparent soil specimen T2 and / or the transparent soil specimen T3 in the box body 1 to form laser speckles, ensuring that the laser beam can evenly illuminate the cross-section of the seepage field of the transparent soil specimen T1 and / or the transparent soil specimen T2 and / or the transparent soil specimen T3 in the depression structure area and the non-depression structure area; the high-speed camera 41 is used to record the laser speckles, and the image analyzer is used to analyze the laser speckles. The high-speed camera 41 and the image analyzer cooperate with each other to capture the detailed velocity distribution density, magnitude, and direction of the subsurface flow around the U-shaped liner 21 at the bottom of the box body 1 during the entire rainfall process.

[0085] Exemplarily, please refer to Figure 3 , this application mainly provides the non-linear behavior of flood formation mutation caused by the subsurface storm flow process under a certain slope, including: The top, middle, and bottom of the box body 1 are backfilled with the transparent specimen soil T1, the transparent specimen soil T2, and the transparent specimen soil T3, and a plurality of soil moisture monitoring probes and matrix suction probes are provided at the edges and the center of the U-shaped liner 21.

[0086] It can be understood that in this way, the purpose is to continuously record the continuous change and mutation information of the soil moisture content at each monitoring position during the migration and diffusion process of the subsurface storm flow inside the soil mass. The longitudinal distance between any two probes is 10 cm, the vertical distance is 10 cm, and the lateral distance is greater than 10 cm to reduce the mutual influence between the sensors when collecting data. The pre-rainfall soil storage capacity (DASI) is the weighted average of the pre-rainfall volumetric water content monitored by the soil moisture monitoring probes of different stratifications: ;

[0087] where DASI is the pre-rainfall soil storage capacity before the runoff event occurs, i is the different vertical layers of the transparent soil, n is the total number of transparent soil layers during the observation of the transparent soil, θ i is the average volumetric water content between the i-th layer and the (i - 1)-th layer of the transparent soil, D i is the depth of the i-th layer of the soil profile, and D i-1 is the depth of the (i - 1)-th layer of the soil profile.

[0088] Further, superimpose the experimental rainfall amount per event and the pre-rainfall soil storage capacity before the runoff event occurs; It can be understood that by entering the superimposed value of the rainfall amount per event + the pre-rainfall soil storage capacity before the runoff event occurs and the runoff data of the collection tank into the computer to make a scatter plot, the runoff and runoff surge processes of the bottom subsurface flow collection tank 51, the middle subsurface flow collection tank 52, and the surface runoff collection tank 53 during the entire rainfall process can be intuitively understood.

[0089] Furthermore, by combining the Levenberg-Marquardt method and the global optimization method, a non-linear response relationship function of the sum of the experimental rainfall per event and the pre-runoff soil water storage capacity to the runoff yield is obtained, and the non-linear behavior of the flood-forming abrupt change caused by the subsurface stormflow process at a certain slope is quantitatively understood.

[0090] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only an example and does not constitute a limitation to this application. Although not explicitly stated here, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are proposed in this application, so such modifications, improvements, and corrections still fall within the spirit and scope of the exemplary embodiments of this application.

[0091] Meanwhile, specific terms are used in this application to describe the embodiments of this application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification is not necessarily the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application can be appropriately combined.

Claims

1. A device for measuring the process of subsurface stormflow on a slope based on a depression in the rock-soil interface, characterized in that, Including: A box body, the box body is inclined, a continuous concave support frame is arranged at the bottom inside the box body, one side of the box body is a transparent glass plate, and a plurality of water outlet holes are arranged on the side of the box body that slopes downward; A slope control mechanism, located at the bottom of the box body; A PIV system, including a velocity measurement system and a laser emission system, the velocity measurement system is located on one side of the box body where the transparent glass plate is located; the laser emission system is located on one side of the box body; A collection assembly, located on the side of the box body that slopes downward.

2. The device for measuring the hillslope subsurface stormflow process based on the depression in the rock-soil interface according to claim 1, wherein The diameter of the water outlet hole is 0.3 cm to 0.6 cm; and / or The inclination of the box body is 0 degrees to 50 degrees.

3. The device for measuring the hillslope subsurface stormflow process based on the depression in the rock-soil interface according to claim 1, characterized in that, The continuous concave support frame includes a support frame, the support frame has a first end and a second end, along the direction from the first end to the second end, a plurality of rectangular depression grooves are arranged on the support frame, and a U-shaped lining plate is arranged in each rectangular depression groove. The plurality of rectangular depression grooves and the U-shaped lining plates in each rectangular depression groove form a depression structure, and the upper part of the support frame on both sides of the U-shaped lining plate in each rectangular depression groove is a non-depression structure; and / or The slope control mechanism includes a support box, a first heavy hinge is arranged between the support box near the second end and the box body, a hydraulic lift is arranged at the bottom inside the support box near the first end, the hydraulic lift extends to the outside of the support box, and the top support column of the hydraulic lift is connected to the box body through a second heavy hinge; and / or The velocity measurement system includes: a high-speed camera and an image analyzer, the high-speed camera is located on one side of the box body where the transparent glass plate is located; and / or The laser emission system includes: a laser and a light guide arm connected to the laser; and / or The collection assembly includes a bottom subsurface flow collection tank, a middle subsurface flow collection tank and a surface runoff collection tank which are arranged in sequence from bottom to top on the side of the box body that slopes downward, and the bottom subsurface flow collection tank, the middle subsurface flow collection tank and the surface runoff collection tank are all connected to a flow collection barrel through a water guide pipe.

4. The device for measuring the hillslope subsurface stormflow process based on the depression on the geotechnical interface according to claim 3, wherein The second end is larger than the first end; and / or Both ends of each U-shaped lining plate are provided with flanges outward; and / or Along the direction from the first end to the second end, the continuous concave support frame is provided with a plurality of vertical support plates; and / or A detachable cover plate is arranged on the upper part of each rectangular depression groove; and / or The U-shaped liner includes an arc portion at the bottom and vertical portions on both sides of the arc portion. The radius of the arc portion is R, the slope of the continuously concave support frame soil body is θ (θ is in radians), b is the width of the box body, and the volume V of the arc portion 圆弧 is as follows: V 圆弧 =R²×b[π / 2-θ-(sin2θ) / 2] According to the slope θ of the continuous concave support frame soil body and the depth ℎ of the U-shaped lining plate, the volume V of the diamond part of the U-shaped lining plate is obtained 菱形 : V 菱形 = 2R × h × b × cos²θ According to the slope of the soil body of the continuous concave support frame is θ, the radius of the arc part is R and the depth of the U-shaped lining plate is ℎ, the volume of the depression formed by the U-shaped lining plate and the inside of the box body is obtained: V = 2R×h×b×cos²θ + R²×b[π / 2 - θ - (sin2θ) / 2]; and / or Universal wheels are arranged at the bottom of the support box, and the arrangement of the universal wheels facilitates the movement of the box body; and / or The bottom subsurface flow collection tank, the middle subsurface flow collection tank, and the surface runoff collection tank all include a triangular plate located on the downwardly inclined side of the box body. One side of the triangular plate is fixed to the downwardly inclined side of the box body, and baffles are provided on the other two sides of the triangular plate. The end of the triangular plate away from the downwardly inclined side of the box body is connected to the water conduit, and a flowmeter is connected inside the flow collection bucket.

5. Experimental method for measuring the process of subsurface stormflow on the slope based on the depression of the geotechnical interface, characterized in that It includes the following steps: Provide transparent specimen soil T1, transparent specimen soil T2, and transparent specimen soil T3; Fill the box body with transparent specimen soil T1, transparent specimen soil T2, and transparent specimen soil T3 in sequence from bottom to top; Adjust the box body to an inclined angle; Set the rainfall intensity. After starting the rainfall, turn on the speed measurement system and the laser emission system, and at the same time collect the runoff samples through the collection component.

6. The experimental method of the hillslope subsurface stormflow process measurement device based on the depression in the rock-soil interface according to claim 5, characterized in that, Mix the first type of transparent soil and the fourth type of transparent soil according to mass ratios of 1:4, 1:2, and 1:1 respectively to obtain transparent specimen soil T1, transparent specimen soil T2, and transparent specimen soil T3; and / or The thickness of transparent specimen soil T1 is 10 cm, the thickness of transparent specimen soil T2 is 10 cm, and the thickness of transparent specimen soil T3 is 20 cm; and / or Set the rainfall intensity to 7 gradient rainfalls of 5 mm / h, 10 mm / h, 30 mm / h, 60 mm / h, 90 mm / h, 120 mm / h, and 150 mm / h. The time for each gradient rainfall is 45 min. The flowmeters connected to the bottom subsurface flow collection tank, the middle subsurface flow collection tank, and the surface runoff collection tank of the box body automatically collect the runoff every 1 min. After each rainfall ends, pause for 30 min or leave it for 3 - 5 days before conducting the next rainfall.

7. The experimental method of the hillslope subsurface stormflow process measurement device based on the depression in the rock-soil interface according to claim 6, characterized in that, The method for obtaining the first type of transparent soil includes: Sieve the fused quartz sand into 0 - 1 mm, 1 - 2 mm, 2 - 3 mm, 3 - 5 mm, 5 - 8 mm, 8 - 10 mm, 10 - 20 mm, and 20 - 40 mm; Mix 0 - 1 mm and 1 - 2 mm according to a mass ratio of 1:1 to obtain 0 - 2 mm fused quartz sand; Add the pore fluid to the 0 - 2 mm fused quartz sand to uniformly wet the surface of the 0 - 2 mm fused quartz sand to form specimen a; Place specimen a in a vacuum environment for 6 h - 10 h to exhaust air to obtain specimen b; In the vacuum environment, continue to add the pore fluid to specimen b while continuously evacuating until the liquid level of the pore fluid covers the upper surface of specimen b to form specimen c; Take specimen c out of the vacuum environment and let it stand at room temperature for 12 h - 16 h to form specimen d, which is the first type of transparent soil; and / or The method for obtaining the second type of transparent soil includes: Mix the 2 - 3 mm, 3 - 5 mm, 5 - 8 mm, and 8 - 10 mm fused quartz sand according to a mass ratio of 1:1:1:1 to obtain 2 - 10 mm fused quartz sand; the remaining steps are the same as the method for preparing the first type of transparent soil; and / or The method for obtaining the third type of transparent soil includes: Mix the 10 - 20 mm and 20 - 40 mm fused quartz sand according to a mass ratio of 1:1 to obtain 10 - 40 mm fused quartz sand; the remaining steps are the same as the method for preparing the first type of transparent soil.

8. The experimental method of the slope subsurface stormflow process measuring device based on the depression in the rock-soil interface according to claim 7, characterized in that, The pore fluid includes n-dodecane and No. 15 white oil, and the mass ratio of n-dodecane to No. 15 white oil is 1:

4. After the configuration is completed, add Nile red dye until the pore fluid is completely colored; and / or Mix the second type of transparent soil and the third type of transparent soil in a mass ratio of 1:1 to obtain the fourth type of transparent soil.

9. The experimental method of the slope subsurface stormflow process measurement device based on the depression in the rock-soil interface according to claim 5, characterized in that, Backfill the top, middle, and bottom of the transparent test soil T1, transparent test soil T2, and transparent test soil T3 in the box, and a plurality of soil moisture monitoring probes and matrix suction probes are provided at the edges and center of the U-shaped liner.

10. The experimental method of the slope subsurface stormflow process measurement device based on the depression in the rock-soil interface according to claim 6, characterized in that, Before the start of rainfall, turn on the laser emission system and the velocity measurement system. The planar laser emitted by the laser and the light guide arm performs layer cutting on the transparent soil sample T1 and / or transparent soil sample T2 and / or transparent soil sample T3 in the box to form laser speckles, ensuring that the laser beam can evenly illuminate the cross-section of the seepage field of the transparent soil sample T1 and / or transparent soil sample T2 and / or transparent soil sample T3 in the depression structure area and non-depression structure area; the high-speed camera is used to record the laser speckles, and the image analyzer is used to analyze the laser speckles. The high-speed camera and the image analyzer cooperate with each other to capture the detailed velocity distribution density, magnitude, and direction of the subsurface flow around the U-shaped liner at the bottom of the box during the entire rainfall process.

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