Filled fracture seepage-erosion visualization test device and test method

Abstract

The invention discloses a test device and a test method for filling fracture seepage-erosion visualization. The test device comprises a fracture overflowing model, a fluid flow control system and an image and pressure data acquisition and analysis system. The fracture overflowing model has the appearance of a real rock fracture surface, and the opening degree can be quantitatively adjusted through a filler gauge gasket; the fluid flow control system uses a peristaltic pump and a stirrer to provide constant-flow fluid and particle input for the fracture overflowing model; according to the test device, the light transmission principle is utilized, quantitative and visual observation and research of the seepage-erosion process of the filled fracture are achieved, and form and permeability evolution data of a particle erosion area in the filled fracture are accurately obtained.

Description

Technical Field

[0001] The invention relates to the technical field of rock fissure seepage and particle transmission testing, and in particular to a test device and method for visualizing seepage and erosion of filled fissures. Background Art

[0002] Natural rock masses contain numerous rock structural surfaces, such as joints, faults, and fissures, which are filled with large quantities of particles. The seepage-erosion process in filled fractures is a major scientific issue of shared concern in fields such as energy, environment, water conservancy, and geology, with significant engineering applications and theoretical research significance. The invisibility of real rock structural surfaces severely restricts the study of particle-filled erosion processes in fractured media. Conventional experimental techniques have various limitations. For example, black-box experiments based on real rock can only capture permeability changes during the seepage-erosion process in filled fractures; using CT scanning to characterize particle distribution in fractures is costly and technically challenging; and destructively separating the upper and lower walls of real rock after the seepage-erosion process in filled fractures allows for observation of the spatial distribution of particles, but this can lead to experimental difficulties in reproducibility. Visualization experimental methods based on optical principles are widely used to study liquid-liquid two-phase seepage processes in fractured media, providing valuable technical support for the study of multiphase flow behavior in fractured media. However, few visualization models exist for studying seepage and particle transport processes in rock fractures. Therefore, researchers are in urgent need of developing a low-cost, easy-to-operate, and repeatable filled fracture seepage-erosion visualization test device and test method. Summary of the Invention

[0003] The purpose of the present invention is to provide a test device and a test method for visualization of seepage and erosion in filled fractures in response to the problems existing in the prior art.

[0004] To achieve the above object, the technical solution adopted by the present invention is: On the one hand, a test device for visualizing seepage and erosion in filled fractures is provided, comprising a device base, on which a transparent fracture flow model is provided, and a fluid control system connected to the fracture flow model, wherein the fracture flow model is also connected to an image and pressure data acquisition and analysis system; the fracture flow model comprises a left model disk, a right model disk, and a feeler gauge gasket located between the left model disk and the right model disk for adjusting the fracture opening, the left model disk and the right model disk being assembled and sealed to form a flow channel in which an inlet end buffer tank, a fracture model flow channel, and an outlet end buffer tank are interconnected, the inlet end buffer tank being provided with a liquid inlet, and the outlet end buffer tank being provided with a liquid outlet; the fluid control system is connected to the liquid inlet to provide a constant flow rate of fluid and particle flow input to the fracture flow model, and is connected to the liquid outlet to recover the output fluid and particles; the image and pressure data acquisition and analysis system is used to collect and analyze images of the particle migration process and the fluid pressures at the liquid inlet and the liquid outlet.

[0005] Furthermore, a model bracket is provided on the base of the device, and a plurality of clamps are provided on the model bracket. The clamps clamp the fracture flow model. The fracture flow model is arranged vertically, with the liquid inlet facing upward and the liquid outlet facing downward.

[0006] Furthermore, the image and pressure data acquisition and analysis system includes a plane light source and a CCD camera arranged on both sides of the fracture flow model, and a hydraulic sensor connected to the fracture flow model, the CCD camera is connected to a computer via a line, and the hydraulic sensor is arranged at the liquid inlet and the liquid outlet, and is connected to the computer via lines respectively; the computer is used to collect the image signal captured by the CCD camera and the pressure signal obtained by the hydraulic sensor, and analyze and process the image signal and pressure signal.

[0007] Furthermore, the planar light source is installed on the device base through a planar light source bracket, and the CCD camera is installed on the device base through a camera bracket. The lens center of the CCD camera is on the same line as the center of the crack flow model and the planar light source.

[0008] Furthermore, the fluid control system includes a circulating liquid tank and a peristaltic pump arranged on the base of the device, the circulating liquid tank is adjacent to the inlet of the peristaltic pump through a flow pipe, the outlet of the peristaltic pump is connected to the liquid inlet through an inlet pipe, and the liquid outlet is connected to the bottom of the circulating liquid tank through an outlet pipe; the flow pipe connected to the upper part of the circulating liquid tank has an inlet located below the fluid liquid level and extends to the middle height of the circulating liquid tank.

[0009] Furthermore, an agitator is provided in the circulating liquid tank, liquid and particles are added into the circulating liquid tank, and blades of the agitator are placed inside the circulating liquid tank to achieve stirring and suspension of the particles.

[0010] Furthermore, the left plate of the model and the right plate of the model both include a transparent replica of a rock fracture and a rigid transparent channel auxiliary structure that seals and fixes the transparent replica of the rock fracture, the channel auxiliary structure includes a pair of fracture side fixing plates, the transparent replica of the rock fracture is arranged between the pair of fracture side fixing plates, and an inlet buffer groove structure and an outlet buffer groove structure are located above and below the transparent replica of the rock fracture; the feeler gauge gasket is arranged between the left and right fracture side fixing plates, and the left and right fracture side fixing plates are connected by a peelable sealant.

[0011] Furthermore, the rock fracture transparent replica includes a matching left-disc rock fracture transparent replica and a right-disc rock fracture transparent replica, and the fracture model flow channel is formed between the left-disc rock fracture transparent replica and the right-disc rock fracture transparent replica; the inlet buffer tank structure includes a matching left-disc inlet buffer tank part and a right-disc inlet buffer tank part, and the inlet end buffer tank is formed between the left-disc inlet buffer tank part and the right-disc inlet buffer tank part; the outlet buffer tank structure includes a matching left-disc outlet buffer tank part and a right-disc outlet buffer tank part, and the outlet end buffer tank is formed between the left-disc outlet buffer tank part and the right-disc outlet buffer tank part; the inlet end buffer tank and the outlet end buffer tank are respectively wedge-shaped structures, and the cross-sectional dimensions are gradually reduced toward the direction of the fracture model flow channel.

[0012] In another aspect, a test method for visualizing seepage and erosion in filled fractures is provided, the test method comprising the following steps: Making the fracture flow model, installing the fracture flow model on the device base, and connecting the circulating liquid tank and peristaltic pump installed on the fluid control system, as well as the plane light source, CCD camera, hydraulic sensor and computer in the image and pressure data acquisition and analysis system; Adjust the relative positions of the plane light source, the crack flow model, and the CCD camera, and adjust the focal length, exposure intensity, and image acquisition frame rate of the CCD camera, and check to ensure that the hydraulic pressure sensor is working properly; The fluid control system for sampling: calculating and weighing the test liquid and particles required for the test; pouring the test liquid into the circulating liquid tank, turning on the peristaltic pump to saturate the flow pipe and the fracture flow model with the test liquid; turning off the peristaltic pump, operating the computer to control the CCD camera to capture and record an initial saturation image of the fracture flow model, pouring the weighed particles into the circulating liquid tank, and turning on the agitator in the circulating liquid tank to form a uniform suspension (fluid); Preparing to fill the fracture flow model: turning on the peristaltic pump to allow particles to be injected into the fracture model flow channel under the action of the suspension and gradually block the fracture model flow channel. When the particle blockage area of ​​the fracture model flow channel observed in real time in the image acquisition software no longer increases significantly, turning off the peristaltic pump and the stirrer; After the particles in the circulating liquid tank are completely deposited, the filling fracture seepage-erosion test is started: the flow conditions of the peristaltic pump are set, the computer is operated to start recording the image data of the CCD camera and the pressure data of the hydraulic sensor, the peristaltic pump is turned on to allow the suspension to be injected into the fracture flow model at the set flow rate, and the filling fracture seepage-erosion process is started; After the filling fracture seepage-erosion process is completed, stop recording the image data of the CCD camera and the pressure data of the hydraulic sensor, turn off the peristaltic pump, remove the fracture flow model, clean it with detergent and dry it, and centrally recycle the waste liquid for treatment. The test operation is completed.

[0013] Furthermore, the test method further includes image data processing after the test, the steps are as follows: Step a: using the initial saturation image of the crack flow model as the initial image P1; Step b: sequentially subtracting the collected images of the filling fracture seepage-erosion test process from the initial image P1 to obtain a grayscale image P2 with the background removed; Step c: taking a time window average of the value of each cell of the grayscale image P2 at each moment, to obtain an image P3 with enhanced grayscale contrast between the blocked area and the unblocked area. Step d: binarizing the image P3 to obtain an image P4 in which the particle-blocked area is white and the particle-eroded area is black; Step e: Add the image P4 to the initial crack morphology spatial distribution to obtain the particle erosion distribution data of the crack filling seepage-erosion process.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. The test device can realize the visual observation of the seepage-erosion process of filling the fissures and the analysis of the whole process. The test device is simple and convenient to use and can accurately identify the particle blockage area in the fissure. The displayed results are intuitive and clear. Moreover, the test device is easy to make, low in cost and highly repeatable. 2. The test device can shoot the movement process of the particles in the fissure flow model and analyze the shot images through the setting of the image and pressure data acquisition and analysis system. It can also monitor the fluid pressure at the inlet and outlet of the fissure flow model, obtain the fluid pressure and perform data analysis. 3. The fluid control system can not only The flow model provides liquid and can also provide particles that enter with the liquid. At the same time, it can also recover waste liquid flowing out of the fracture flow model, forming a fluid cycle; 4. The fracture flow model is not only a fully transparent structure, but also a structure that can be split in half. After splicing, it is convenient for seepage and erosion tests to be carried out. After the test, it can also be split for cleaning; at the same time, this structure can cooperate with the setting of the feeler gauge gasket to control the fracture opening and improve the applicability of the test; 5. The setting of the buffer groove at the inlet end can make the fluid more evenly fill the flow channel of the fracture model, and can also play a buffering role to avoid large fluctuations in fluid flow, and can avoid the accumulation of particles at the inlet and outlet to cause blockage of the inlet and outlet. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the overall structure of a test device for visualizing seepage and erosion in filled fractures according to the present invention; Figure 2 Schematic diagram of the front view of the crack flow model of the present invention; Figure 3 for Figure 2 Schematic diagram of the A-A' section of the medium crack flow model; Figure 4 This is a schematic diagram of the splitting of the fracture flow model; Figure 5 To obtain the schematic diagram of the eroded area of ​​the filled cracks by using the image time window averaging and binarization method; Figure: 1, plane light source bracket; 2, plane light source; 3, crack flow model; 4, model bracket; 5, fixture; 6, CCD camera; 7, computer; 8, stirrer; 9, circulating liquid tank; 10, flow pipe; 11, peristaltic pump; 12, hydraulic sensor; 13, device base; 14, liquid inlet; 15, inlet end buffer tank; 1501, left plate inlet buffer tank section; 1502, right plate inlet buffer tank section; 16, crack side fixing plate; 160 1. Fracture side fixing plate of the left plate of the model; 1602. Fracture side fixing plate of the right plate of the model; 17. Feeler gauge; 18. Transparent replica of rock fracture; 1801. Transparent replica of rock fracture in the left plate; 1802. Transparent replica of rock fracture in the right plate; 19. Outlet buffer tank; 1901. Outlet buffer tank section of the left plate; 1902. Outlet buffer tank section of the right plate; 20. Liquid outlet; 21. Peelable seal; 22. Flow channel of the fracture model; Figure 5 The numbers in the cells represent the light intensity. DETAILED DESCRIPTION

[0016] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0017] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," etc., etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] Example 1

[0019] This embodiment provides a test device for visualizing seepage and erosion in filled fractures. Figures 1 to 4As shown, it includes a device base 13, on which a transparent fracture flow model 3 is provided, and a fluid control system connected to the fracture flow model 3, and the fracture flow model is also connected to an image and pressure data acquisition and analysis system; the fracture flow model 3 includes a model left disk, a model right disk and a feeler gauge gasket 17 located between the model left disk and the model right disk for adjusting the fracture opening, the model left disk and the model right disk are assembled and sealed to form an inlet end buffer groove 15, a fracture model flow channel 22 and an outlet end buffer groove 19 that are interconnected. The inlet end buffer groove 15 is provided with a liquid inlet 14, and the outlet end buffer groove 19 is provided with a liquid outlet 20; the fluid control system is connected to the liquid inlet 14 to provide a constant flow rate of fluid and particle flow input to the fracture flow model 3, and is connected to the liquid outlet 20 to recover the output fluid and particles; the image and pressure data acquisition and analysis system is used to collect and analyze the image of the particle migration process and the fluid pressure of the liquid inlet and outlet.

[0020] This test device can realize the visual observation of the seepage-erosion process of filling cracks and its full process analysis. The test device is simple and convenient to use and can accurately identify the particle blockage area in the cracks, and the display results are intuitive and clear. In addition, the test device is easy to make, low in cost, and highly repeatable.

[0021] Through the setting of the image and pressure data acquisition and analysis system, this experimental device can capture the movement process of particles in the fracture flow model 3 and analyze the captured images. It can also monitor the fluid pressure at the inlet and outlet of the fracture flow model 3, obtain the fluid pressure and perform data analysis.

[0022] The fluid control system not only provides liquid to the fracture flow model 3, but also provides particles entering with the liquid, and can also recover waste liquid flowing out of the fracture flow model 3, thereby forming a circulating use of the fluid.

[0023] The fracture flow model 3 is not only a fully transparent structure, but also a structure that can be split in half. When assembled, it can form a flow channel containing a liquid inlet 14, an inlet end buffer tank 15, a fracture model flow channel 22, an outlet end buffer tank 19 and a liquid outlet 20, so as to facilitate the conduct of seepage and erosion tests. After the test, it can also be disassembled for cleaning. At the same time, this structure can cooperate with the setting of the feeler gauge gasket 17 to control the fracture opening and improve the applicability of the test. The feeler gauge gasket 17 is available in a variety of sizes.

[0024] The setting of the inlet end buffer groove 15 can, on the one hand, accommodate a certain amount of fluid, allowing the fluid to be more evenly filled into the flow channel of the fracture model, and can also play a buffering role to avoid large fluctuations in the fluid flow. On the other hand, the buffer groove is conducive to the entry and flow of particles, reducing the adhesion of particles to the inner wall and entrance of the channel to cause blockage.

[0025] Furthermore, a model support 4 is provided on the device base 13, and a plurality of clamps 5 are provided on the model support 4. The clamps 5 clamp the fracture flow model. The fracture flow model is arranged vertically, with the liquid inlet facing upward and the liquid outlet facing downward.

[0026] The clamps 5 clamp the crack flow model 3 from both sides of its edge. The clamps 5 are symmetrically arranged on a pair of model supports 4, and the crack flow model 3 is suspended and clamped between the pair of model supports 4. This arrangement can reduce the obstruction of the crack flow model 3 by foreign objects, and can place the entire crack within the lens of the light source and CCD camera to accurately capture the image. The vertical arrangement of the crack flow model 3 can further save space in the device base and facilitate the arrangement of the plane light source and CCD camera.

[0027] In some embodiments, the model bracket 4 is a vertical pole, one end of the clamp 5 is mounted on the vertical pole and can be raised and lowered and adjusted, and can be fastened by a locking screw, and the other end of the clamp is a claw or a clamp that can clamp and fix the fracture flow model.

[0028] Furthermore, the image and pressure data acquisition and analysis system includes a plane light source 2 and a CCD camera 6 arranged on both sides of the fracture flow model 3, and a hydraulic sensor 12 connected to the fracture flow model 3, the CCD camera 6 is connected to the computer 7 through a line, and the hydraulic sensor 12 is arranged at the liquid inlet 14 and the liquid outlet 20, and is respectively connected to the computer 7 through lines; the computer 7 is used to collect the image signal captured by the CCD camera 6 and the pressure signal obtained by the hydraulic sensor 12, and analyze and process the image signal and pressure signal.

[0029] Furthermore, the plane light source 2 is installed on the device base 13 through a plane light source bracket 1, and the CCD camera 6 is installed on the device base 13 through a camera bracket. The lens center of the CCD camera 6 is on the same line as the crack flow model 3 and the center of the plane light source 2. The plane light source 2 is arranged parallel to the crack flow model 3, and its area is not less than the area of ​​the crack flow model 3, so as to ensure that each position in the crack can be equally illuminated by the light source.

[0030] Furthermore, the fluid control system includes a circulating liquid tank 9 and a peristaltic pump 11 arranged on the base 13 of the device, the circulating liquid tank 9 is adjacent to the inlet of the peristaltic pump 11 through a flow pipe 10, the outlet of the peristaltic pump 11 is connected to the liquid inlet 14 through a liquid inlet pipe, and the liquid outlet 20 is connected to the bottom of the circulating liquid tank 9 through a liquid outlet pipe.

[0031] The peristaltic pump 11 can pump the liquid or the mixture of liquid and particles in the circulating liquid tank 9 from the liquid inlet into the fracture flow model 3. The liquid or the mixture of liquid and particles flowing out from the bottom of the fracture flow model 3 can be discharged into the circulating liquid tank 9 again, and they can be used again after being evenly mixed in the circulating liquid tank.

[0032] Furthermore, a stirrer 8 is provided above the circulating liquid tank 9 , liquid and particles are added into the circulating liquid tank 9 , and blades of the stirrer 8 are placed inside the circulating liquid tank to achieve stirring and suspension of the particles.

[0033] The stirrer 8 can stir and mix the liquid and particles in the circulating liquid tank to form a uniformly mixed suspension. Through the setting of this system, particle-liquid mixed supply can be achieved, and crack filling in the early stage of the erosion test can be realized.

[0034] The flow pipe connected to the upper part of the circulating liquid tank 9 has an inlet located below the fluid liquid level and extends to the middle height of the circulating liquid tank 9. When the agitator 8 is not turned on, the particles deposited at the bottom of the circulating liquid tank 9 will not enter the flow channel. The purpose of this setting is to be able to pump pure liquid into the fracture flow model 3 when the agitator is not turned on, so as to obtain the first fracture flow image, and to pump in mixed suspensions after the agitator is turned on. The pumping of two different fluids only requires starting and closing the peristaltic pump, without the need for additional operation or liquid supply, making its operation simpler.

[0035] Furthermore, the left plate of the model and the right plate of the model both include a transparent replica of a rock fracture 18 and a rigid transparent channel auxiliary structure that is sealed and fixedly connected to the transparent replica of the rock fracture 18. The channel auxiliary structure includes a pair of fracture side fixing plates 16, the transparent replica of the rock fracture 18 is arranged between the pair of fracture side fixing plates 16, and an inlet buffer groove structure and an outlet buffer groove structure are located above and below the transparent replica of the rock fracture 18; the feeler gauge gasket 17 is arranged between the left and right fracture side fixing plates 16, and the left and right fracture side fixing plates 16 are connected by a peelable sealant, and the clamp can also clamp it, which not only clamps the entire fracture flow model, but also further clamps the left and right fracture side fixing plates.

[0036] The number of parts of the left and right discs of the model is basically the same, but the shapes of the transparent replicas 18 of the rock cracks on the left and right discs are different. Although the left and right discs of the model are detachable in half, they are not symmetrically identical. There are differences in thickness and shape between the two. This setting can make the surface where the crack is located and the parting surface where the left and right discs are spliced ​​(the docking surface of the side fixing plates of the crack) not on the same plane, so that the integrity of the flow channel of the crack model is better and the sealing is better, reducing the influence of the model itself on the crack. At the same time, it can also make the liquid inlet and outlet in the complete buffer tank structure, rather than a separate spliced ​​structure.

[0037] Furthermore, the rock fracture transparent replica 18 includes a matching left plate rock fracture transparent replica 1801 and a right plate rock fracture transparent replica 1802, and the fracture model flow channel 22 is formed between the left plate rock fracture transparent replica 1801 and the right plate rock fracture transparent replica 1802; the inlet buffer tank structure includes a matching left plate inlet buffer tank part 1501 and a right plate inlet buffer tank part 1502, and the left plate inlet buffer tank part 1501 and the right plate inlet buffer tank part 1502 are connected. The inlet end buffer groove 15 is formed between the inlet buffer groove parts 1502; the outlet buffer groove structure includes a corresponding left disk outlet buffer groove part 1901 and a right disk outlet buffer groove part 1902, and the outlet end buffer groove 19 is formed between the left disk outlet buffer groove part 1901 and the right disk outlet buffer groove part 1902; the inlet end buffer groove 15 and the outlet end buffer groove 19 are respectively wedge-shaped structures, and the cross-sectional dimensions are gradually reduced toward the direction of the fracture model flow channel 22.

[0038] A pair of crack side fixing plates, the left plate rock crack transparent replica, the left plate inlet buffer tank part and the left plate outlet buffer tank part are fixedly connected together by AB adhesive to form a complete model left plate, the top center position of the left plate inlet buffer tank part 1501 is provided with the liquid inlet 14, and the bottom center position of the left plate outlet buffer tank part 1901 is provided with the liquid outlet 20; similarly, a pair of crack side fixing plates, the right plate rock crack transparent replica, the right plate inlet buffer tank part and the right plate outlet buffer tank part are fixedly connected together by AB adhesive to form a complete model right plate; the model left plate and the model right plate are connected to the crack side fixing plates by the peelable sealant (such as glass glue) to form the entire model structure, so that they can be separated after the test for internal cleaning, and it is also convenient to set feeler gauge gaskets of different thicknesses for the test and adjust the crack opening.

[0039] Example 2

[0040] This embodiment provides a test method for the test device for visualizing seepage and erosion in filled fractures in Example 1, the test method comprising the following steps: Step 1: Prepare the fracture flow model 3, install the fracture flow model 3 on the device base 13, and connect the circulating liquid tank 9 and peristaltic pump 11 installed on the fluid control system, as well as the plane light source 2, CCD camera 6, hydraulic pressure sensor 12 and computer 7 in the image and pressure data acquisition and analysis system; Specifically, the transparent replicas 18 of rock fractures and the auxiliary structure of the fracture model channel are made by silicone molding and epoxy resin pouring on the surfaces of two real rock fractures obtained by rock splitting; the transparent replicas of rock fractures on the left and right plates of the fracture model are 10 cm long, 5 cm wide and about 2 cm thick.

[0041] Step 2: Adjust the relative positions of the plane light source 2, the crack flow model 3 and the CCD camera 6, and adjust the focal length, exposure intensity and image acquisition frame rate of the CCD camera 6 to achieve good imaging effect, and check to ensure that the hydraulic sensor 12 is working properly.

[0042] Step 3: The fluid control system injects samples: calculate and weigh the test liquid and particles required for the test; pour the test liquid into the circulating liquid tank 9, turn on the peristaltic pump 11, and saturate the flow pipe and the fracture flow model 3 with the test liquid; turn off the peristaltic pump 11, operate the computer to control the CCD camera 6 to capture and record an initial saturation image of the fracture flow model, pour the weighed particles into the circulating liquid tank 9, and turn on the agitator 8 in the circulating liquid tank to form a uniform suspension (fluid).

[0043] Step 4: Prepare to fill the fracture flow model: Turn on the peristaltic pump 11, so that the particles are injected into the fracture model flow channel 22 under the action of the suspension, and gradually fill the fracture model flow channel 22. When the particle filling (blocking) area of ​​the fracture model flow channel observed in real time in the image acquisition software no longer increases significantly, turn off the peristaltic pump 11 and the agitator 8.

[0044] Step 5: After the particles in the circulating liquid tank 9 are completely deposited, the filling crack seepage-erosion test is started: the flow conditions of the peristaltic pump 11 are set, and the computer is operated to start recording the image data of the CCD camera 6 and the pressure data of the hydraulic sensor 12. The peristaltic pump is turned on to allow the suspension to be injected into the crack flow model 3 at the set flow rate, and the filling crack seepage-erosion process is started.

[0045] Step 6: After the filling fracture seepage-erosion process is completed, stop recording the image data of the CCD camera 6 and the pressure data of the hydraulic sensor 12, turn off the peristaltic pump 11, remove the fracture flow model 3, clean it with detergent and dry it, and centrally recycle the waste liquid for treatment. The test operation is completed.

[0046] The above method can conveniently study the seepage and particle transport processes in rock fractures. The transparent fracture replica specimen, combined with the channel auxiliary structure, has wedge-shaped inlet and outlet buffer grooves arranged at the liquid inlet and outlet positions to achieve visualization of the particle transport process and the smooth transmission of liquid and particles in the fracture. It can also accurately identify the particle blockage area in the fracture flow channel and display the test results intuitively and clearly.

[0047] Furthermore, the test method also includes post-test image data processing, using Matlab self-written code to remove background, time-homogenize, and binarize the image, and statistically analyze the morphological characteristics of the eroded area during the seepage-erosion process of filling cracks. The steps are as follows: Step a: using the initial saturation image of the crack flow model as the initial image P1; Step b: sequentially subtracting the collected images of the filling fracture seepage-erosion test process from the initial image P1 to obtain a grayscale image P2 with the background removed; Step c: taking a time window average of the value of each cell of the grayscale image P2 at each moment, to obtain an image P3 with enhanced grayscale contrast between the blocked area and the unblocked area. Step d: binarizing the image P3 to obtain an image P4 in which the particle-blocked area is white and the particle-eroded area is black; Step e: Add the image P4 to the initial crack morphology spatial distribution to obtain the particle erosion distribution data of the crack filling seepage-erosion process, such as Figure 5 shown.

[0048] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A test device for visualizing seepage and erosion in filled fractures, characterized in that: The invention comprises a device base, on which a transparent fracture flow model is provided, and a fluid control system connected to the fracture flow model, wherein the fracture flow model is also connected to an image and pressure data acquisition and analysis system; the fracture flow model comprises a left model disk, a right model disk and a feeler gauge gasket located between the left model disk and the right model disk for adjusting the fracture opening, the left model disk and the right model disk are assembled and sealed to form a flow channel in which an inlet end buffer tank, a fracture model flow channel and an outlet end buffer tank are interconnected, the inlet end buffer tank is provided with a liquid inlet, and the outlet end buffer tank is provided with a liquid outlet; the fluid control system is connected to the liquid inlet to provide the fracture flow model with a constant flow rate of fluid and particle flow input, and is connected to the liquid outlet to recover the output fluid and particles; the image and pressure data acquisition and analysis system is used to collect and analyze images of the particle migration process and the fluid pressures of the liquid inlet and the liquid outlet.

2. The test device for visualizing seepage and erosion in filled fractures according to claim 1, characterized in that: A model support is provided on the device base, and a plurality of clamps are provided on the model support. The clamps clamp the fracture flow model. The fracture flow model is arranged vertically, with the liquid inlet facing upward and the liquid outlet facing downward.

3. The test device for visualizing seepage and erosion in filled fractures according to claim 1, characterized in that: The image and pressure data acquisition and analysis system includes a plane light source and a CCD camera arranged on both sides of the fracture flow model, and a hydraulic sensor connected to the fracture flow model. The CCD camera is connected to a computer via a line. The hydraulic sensor is arranged at the liquid inlet and the liquid outlet and is connected to the computer via lines respectively. The computer is used to collect the image signal captured by the CCD camera and the pressure signal obtained by the hydraulic sensor, and analyze and process the image signal and pressure signal.

4. The test device for visualizing seepage and erosion in filled fractures according to claim 3, characterized in that: The plane light source is installed on the device base through a plane light source bracket, and the CCD camera is installed on the device base through a camera bracket. The lens center of the CCD camera is in the same straight line as the center of the crack flow model and the plane light source.

5. The test device for visualizing seepage and erosion in filled fractures according to claim 1, characterized in that: The fluid control system includes a circulating liquid tank and a peristaltic pump arranged on the base of the device. The circulating liquid tank is adjacent to the inlet of the peristaltic pump through a flow pipe, the outlet of the peristaltic pump is connected to the liquid inlet through an inlet pipe, and the liquid outlet is connected to the bottom of the circulating liquid tank through an outlet pipe; the flow pipe connected to the upper part of the circulating liquid tank has an inlet located below the fluid liquid level and extends to the middle height of the circulating liquid tank.

6. The test device for visualizing seepage and erosion in filled fractures according to claim 5, characterized in that: The circulating liquid tank is provided with an agitator, liquid and particles are added into the circulating liquid tank, and the blades of the agitator are placed inside the circulating liquid tank to achieve stirring and suspension of the particles.

7. The test device for visualizing seepage and erosion in filled fractures according to claim 1, characterized in that: The left and right model disks both include a transparent replica of a rock fracture and a rigid, transparent channel auxiliary structure that is sealed and fixedly connected to the transparent replica of the rock fracture. The channel auxiliary structure includes a pair of fracture side fixing plates, the transparent replica of the rock fracture is arranged between the pair of fracture side fixing plates, and an inlet buffer groove structure and an outlet buffer groove structure located above and below the transparent replica of the rock fracture. The feeler gauge gasket is arranged between the left and right fracture side fixing plates, and the left and right fracture side fixing plates are connected by a peelable sealant.

8. The test device for visualizing seepage and erosion in filled fractures according to claim 7, characterized in that: The rock fracture transparent replica includes a matching left plate rock fracture transparent replica and a right plate rock fracture transparent replica, and the fracture model flow channel is formed between the left plate rock fracture transparent replica and the right plate rock fracture transparent replica; the inlet buffer tank structure includes a matching left plate inlet buffer tank portion and a right plate inlet buffer tank portion, and the inlet end buffer tank is formed between the left plate inlet buffer tank portion and the right plate inlet buffer tank portion; The outlet buffer tank structure includes a left tray outlet buffer tank portion and a right tray outlet buffer tank portion adapted to each other, and the outlet end buffer tank is formed between the left tray outlet buffer tank portion and the right tray outlet buffer tank portion; The inlet end buffer groove and the outlet end buffer groove are respectively wedge-shaped structures, and the cross-sectional dimensions are gradually reduced toward the flow channel of the fracture model.

9. A test method for visualizing seepage and erosion in filled fractures, applied to the test device for visualizing seepage and erosion in filled fractures according to any one of claims 1 to 8, characterized in that: The test method comprises the following steps: Making the fracture flow model, installing the fracture flow model on the device base, and connecting the circulating liquid tank and peristaltic pump installed on the fluid control system, as well as the plane light source, CCD camera, hydraulic sensor and computer in the image and pressure data acquisition and analysis system; Adjust the relative positions of the plane light source, the crack flow model, and the CCD camera, and adjust the focal length, exposure intensity, and image acquisition frame rate of the CCD camera, and check to ensure that the hydraulic pressure sensor is working properly; The fluid control system performs sampling by calculating and weighing the test liquid and particles required for the test; pouring the test liquid into the circulating liquid tank, turning on the peristaltic pump, and saturating the flow pipe and the fracture flow model with the test liquid; turning off the peristaltic pump, operating the computer to control the CCD camera to capture and record an initial saturation image of the fracture flow model, pouring the weighed particles into the circulating liquid tank, and turning on the agitator in the circulating liquid tank to form a uniform suspension; Preparing to fill the fracture flow model: turning on the peristaltic pump to allow particles to be injected into the fracture model flow channel under the action of the suspension and gradually block the fracture model flow channel. When the particle blockage area of ​​the fracture model flow channel observed in real time in the image acquisition software no longer increases significantly, turning off the peristaltic pump and the stirrer; After the particles in the circulating liquid tank are completely deposited, the filling fracture seepage-erosion test is started: the flow conditions of the peristaltic pump are set, the computer is operated to start recording the image data of the CCD camera and the pressure data of the hydraulic sensor, the peristaltic pump is turned on to allow the suspension to be injected into the fracture flow model at the set flow rate, and the filling fracture seepage-erosion process is started; After the filling fracture seepage-erosion process is completed, stop recording the image data of the CCD camera and the pressure data of the hydraulic sensor, turn off the peristaltic pump, remove the fracture flow model, clean it with detergent and dry it, and centrally recycle the waste liquid for treatment. The test operation is completed.

10. The test method for visualizing seepage and erosion in filled fractures according to claim 9, characterized in that: The test method further includes post-test image data processing, which comprises the following steps: Step a: using the initial saturation image of the crack flow model as the initial image P1; Step b: sequentially subtracting the collected images of the filling fracture seepage-erosion test process from the initial image P1 to obtain a grayscale image P2 with the background removed; Step c: taking a time window average of the value of each cell of the grayscale image P2 at each moment, to obtain an image P3 with enhanced grayscale contrast between the blocked area and the unblocked area. Step d: binarizing the image P3 to obtain an image P4 in which the particle-blocked area is white and the particle-eroded area is black; Step e: Add the image P4 to the initial crack morphology spatial distribution to obtain the particle erosion distribution data of the crack filling seepage-erosion process.

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