Transparent fractured rock mass stress-seepage-corrosion coupling dynamic visualization test device and method

Abstract

The invention discloses a transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device and method. The device comprises a sample fixing and adjusting platform, a pair of opposite transparent plates are arranged, a transparent soluble fracture sample can be fixed, and an adjustable mechanism is arranged to change and lock the fracture opening degree; the seepage pressure control and measurement device can inject fluid into the fracture, control the flow velocity and monitor the pressure; the confining pressure loading device is provided with a closed pressure gas cavity, an inert gas injection device and a gas pressure sensor and is positioned on the outer side of a transparent plate, and after inert gas is injected into the cavity, uniform confining pressure is applied to a transparent fracture surface through the transparent plate and is monitored; the visual observation device comprises a CCD camera, a light source and a three-dimensional XT-DIC full-field strain measurement system, and the CCD camera and the light source are arranged on the observable side of the sample and can dynamically observe and record the corrosion form, displacement and full-field strain of the fracture wall surface in real time. According to the invention, direct observation of the seepage behavior, the deformation damage change and the corrosion form in the hydraulic coupling process of the soluble rock mass fracture can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of rock mass fracture, and particularly relates to a transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test device and method. BACKGROUND

[0002] The stress-seepage-dissolution coupling effect, as a core mechanism of the interaction of multiple physical fields of rock-soil medium, widely exists in the fields of dam foundation stability control of water conservancy and hydropower projects, seepage water inrush prevention of tunnel surrounding rock, and optimization of fracture network diversion capacity in geothermal resource exploitation. The dissolution process feedbacks and regulates the dynamic cycle process of the permeability characteristics of rock mass, and is directly related to the long-term stability and efficiency of major engineering operation.

[0003] The reservoir constructed in the karst area will be in a superimposed state of high stress and high water head after impoundment. High stress causes deformation and damage of rock mass, and high water head accelerates the migration of dam foundation reservoir water. At this time, the seepage water containing erosive substances reacts with the minerals of the rock mass to cause dissolution effect, changes the spatial structure of the rock mass fracture and the seepage channel, and weakens the mechanical properties of the rock mass, causing the dam foundation to be in a seepage instability state. The stress-dissolution coupling effect affects the rock mass fracture seepage when changing the fracture geometry structure, and the changes of fracture width, roughness and dominant seepage channel are ultimately fed back to the permeability-averaged opening degree relationship. And under the condition of high permeation pressure difference of reservoir water, the non-Darcy seepage phenomenon caused by high seepage velocity and the seepage breakthrough caused by karst will affect the seepage stability of the dam foundation. Therefore, it is very important to explore the mechanism of the stress-seepage-dissolution coupling process of soluble rock mass. The existing technology does not directly observe the action process of the water force coupling on the soluble rock mass. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test device and method. The transparent soluble rock mass fracture sample can directly observe the seepage behavior, deformation damage change and dissolution morphology of the fracture rock mass in the water force coupling process compared with the rock mass sample used in the traditional confining test device.

[0005] To solve the above technical problems, the present application is implemented by the following technical solutions:

[0006] According to a first aspect of the present application, a transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test device is provided, comprising:

[0007] A sample fixing and adjusting platform for fixing a transparent soluble fracture sample, comprising a pair of opposite transparent plates, rough fracture surfaces of the transparent soluble fracture sample being fixed on the pair of transparent plates respectively, the sample fixing and adjusting platform being provided with an adjustable mechanism for adjusting the distance between the two transparent plates to change and lock the fracture opening;

[0008] A permeation pressure control and measurement device for injecting fluid into the fracture and controlling the flow rate while monitoring the fluid pressure.

[0009] A confining pressure loading device, comprising a closed pressure gas cavity, an inert gas injection device and a gas pressure sensor, for applying uniform confining pressure to the fracture surface and monitoring the confining pressure; the pressure gas cavity is located outside one of the transparent plates of the sample fixing and adjusting platform, adjacent to the space between the transparent soluble fracture sample and the other transparent plate, the inert gas injection device injects inert gas into the pressure gas cavity and transmits uniform confining pressure to the fracture surface of the transparent soluble fracture sample through the transparent plate.

[0010] A visual observation device, comprising a CCD camera, a light source and a three-dimensional XT-DIC full-field strain measurement system, for real-time dynamic observation and recording of the dissolution morphology, displacement and full-field strain of the fracture wall; the CCD camera and the light source are arranged on the observable side of the transparent soluble fracture sample, and the light source is used to provide illumination for the CCD camera and / or the three-dimensional XT-DIC full-field strain measurement system.

[0011] In a possible implementation manner of the first aspect, the permeation pressure control and measurement device comprises an injection pump, a micro-flow injector, a water pressure sensor, an inlet channel and an outlet channel, the output end of the injection pump is connected to the input end of the micro-flow injector, the output end of the micro-flow injector is connected to one end of the inlet channel, the other end of the inlet channel is connected to the water inlet of the fracture of the transparent soluble fracture sample, one end of the outlet channel is connected to the water outlet of the fracture of the transparent soluble fracture sample, and the water pressure sensor is arranged on the inlet channel.

[0012] In a possible implementation manner of the first aspect, the permeation pressure control and measurement device further comprises an external water tank in communication with the inlet channel and an external waste liquid barrel in communication with the outlet channel.

[0013] In a possible implementation manner of the first aspect, the inert gas injection device is connected to the pressure gas cavity through a pipeline, and the inert gas is nitrogen.

[0014] In a possible implementation manner of the first aspect, the permeation pressure control and measurement device further comprises a computer for controlling the inert gas injection device according to the feedback signal of the gas pressure sensor to maintain a constant confining pressure.

[0015] In a possible implementation manner of the first aspect, the light source is an LED light source or a laser emission light source.

[0016] In a possible implementation manner of the first aspect, the three-dimensional XT-DIC full-field strain measurement system is used to record the three-dimensional coordinates, displacement, strain and damage evolution process of the transparent soluble fractured sample during loading, and can generate a measurement report containing three-dimensional views, curves, charts and videos.

[0017] In a possible implementation manner of the first aspect, the injection pump is a plunger pump.

[0018] In a possible implementation manner of the first aspect, the preparation method of the transparent soluble fractured sample is:

[0019] A target soluble rock sample is collected, and a fractured rock sample is obtained by splitting or cutting;

[0020] A non-contact 3D profile scanner and / or a CT scanner are used to obtain the topographic feature data of the rock sample fractures, including wall roughness and spatial opening, while retaining the intersection points of the fractures and the characteristics of the roughness peak areas of the walls;

[0021] An MRI scan is used to obtain the pore structure and distribution characteristics of the rock mass, and MATLAB is used to reconstruct the three-dimensional image of the rock mass and to statistically analyze the characteristic parameters of the fractures and pores;

[0022] A light-transmitting soluble calcite material is selected as the base material, the surface of the selected calcite block is polished, and HCl solution is used for pre-erosion;

[0023] Based on the obtained fracture topographic feature data, a laser etching technique is used to reproduce the rough surface topography of the fractures on one surface of the calcite base material, forming a light-transmitting rough soluble fracture surface;

[0024] In the local area of the rough fracture surface formed by laser etching, impurities with different solubilities are added to simulate the differential erosion caused by mineral heterogeneity in natural rock mass;

[0025] The calcite block etched by laser and doped with impurities is divided along the reproduced fracture surface to form two parts with complementary rough surfaces;

[0026] The two divided calcite parts are fixed on a transparent plate respectively, and the two transparent plates with fixed calcite parts are placed opposite to each other on an adjustable opening stage;

[0027] A pressure gas cavity is cut in the middle of the top acrylic plate, and transparent gaskets and first and second side water stop strips are installed on both sides of the fracture surface for sealing.

[0028] According to a second aspect of the present application, a transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test method is provided, comprising:

[0029] Fix the light-transmitting soluble fractured sample on the sample fixing and adjusting platform, and adjust the opening of the adjusting platform to an initial setting value;

[0030] Inject saturated clean water into the fracture through the seepage pressure control and measurement device, and stand still after the air bubbles are discharged;

[0031] Start the confining pressure loading device, inject inert gas into the pressure gas cavity through the inert gas injection device, monitor and control the confining pressure to the target value through the air pressure sensor;

[0032] Switch the seepage fluid to the erosive solution, and inject the fracture at a constant flow rate through the seepage pressure control and measurement device;

[0033] Synchronously start the visualization observation device, turn on the light source and adjust the angle, make the light penetrate the transparent soluble fractured sample, start the CCD camera to record the dissolution morphology and displacement change of the fracture wall surface at a set frame rate, and start the three-dimensional XT-DIC full-field strain measurement system to collect the full-field strain and damage evolution data of the sample in real time;

[0034] Monitor the inlet and outlet pressure-flow rate change through the water pressure sensor;

[0035] Transmit the data of the CCD camera, the XT-DIC system, the water pressure sensor and the air pressure sensor to the data acquisition and analysis system, and generate the fracture opening evolution cloud chart, the strain field distribution and the dissolution rate quantitative analysis result in real time.

[0036] In a possible implementation manner of the second aspect, the erosive solution is a dyed HCl solution, and the dyeing agent is a bright blue dye;

[0037] The image acquisition rate of the CCD camera ranges from 0.2 fps to 200 fps, and the acquisition pixel accuracy is 0.03 mm / pixel;

[0038] Control the CCD camera to capture the fracture light intensity change through the MATLAB program, and reconstruct the fracture opening evolution process.

[0039] Compared with the prior art, the present application has at least the following beneficial effects:

[0040] The application provides a transparent fissure rock mass stress-seepage-dissolution coupling dynamic visualization test device, through the visualization observation device, the CCD camera, the light source and the three-dimensional XT-DIC full-field strain measurement system, the dissolution form, the displacement and the full-field strain of the fissure wall surface can be dynamically observed and recorded in real time, so that researchers can directly observe the change of the soluble rock mass in the stress-seepage-dissolution coupling process. The sample fixing and adjusting platform can accurately adjust the distance between the two transparent plates through the adjustable mechanism, so as to change and lock the fissure opening, and meet the requirements of different tests on the fissure opening; the seepage pressure control and measurement device can not only inject fluid into the fissure and accurately control the flow rate, but also can monitor the fluid pressure in real time; the confining pressure loading device can apply uniform confining pressure to the fissure surface by using the closed pressure gas cavity, the inert gas injection device and the air pressure sensor, and accurately monitor the confining pressure, so that the test conditions can highly simulate the complex environment in the actual engineering, and the accuracy of the test results is improved. In the test process, the application realizes the synchronous monitoring of multiple parameters. Through the water pressure sensor, the inlet and outlet pressure-flow rate changes are monitored, the dissolution form and displacement change of the fissure wall surface are recorded by the visualization observation device, and the full-field strain and damage evolution data of the sample are collected by the three-dimensional XT-DIC full-field strain measurement system, so that various key information of the rock mass fissure in the stress-seepage-dissolution coupling process can be comprehensively obtained.

[0041] The data of the CCD camera, the XT-DIC system, the water pressure sensor and the air pressure sensor are transmitted to the data acquisition and analysis system, the fissure opening evolution cloud chart, the strain field distribution and the dissolution rate quantitative analysis results can be generated in real time, so that researchers can obtain the dynamic information of the test in time, and the problems of complicated data post-processing and long analysis period in the traditional test method are avoided.

[0042] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the specific embodiments of the application, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creating laborious work.

[0044] Figure 1 A structure schematic diagram of a transparent fissure rock mass stress-seepage-dissolution coupling dynamic visualization test device of the embodiments of the present disclosure;

[0045] Figure 2A transparent soluble fracture sample combination schematic diagram of a stress-seepage-dissolution coupling dynamic visualization test device for an embodiment of the present disclosure;

[0046] Figure 3 An image post-processing flow for rock mass fracture aperture evolution reconstruction of an embodiment of the present disclosure.

[0047] In the figure: 1, injection pump; 2, micro-flow injector; 3, water pressure sensor; 4, inert gas injection device; 5, air pressure sensor; 6, LVDT micro-strain measuring instrument; 7, CCD camera; 8, three-dimensional XT-DIC full-field strain measurement system; 9, light source; 10, data acquisition and analysis system; 11, pressure gas cavity; 12, water inlet channel; 13, water outlet channel; 14, water inlet; 15, water outlet; 16, gasket; 17, first side water stop; 18, laser-engraved light-transmitting rough fracture; 19, second side water stop. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are some 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 labor fall within the scope of protection of the present application.

[0049] In combination with Figure 1 and Figure 2 It is shown that the embodiments of the present application provide a transparent fracture rock stress-seepage-dissolution coupling dynamic visualization test device, which mainly consists of a sample fixing and adjusting platform, a seepage pressure control and measurement device, a confining pressure loading device, a visualization observation device and a data acquisition and analysis system 10. The parts work cooperatively to realize the control and real-time observation of various parameters of rock fractures in the stress-seepage-dissolution coupling process.

[0050] The sample fixing and adjusting platform is used to fix the transparent soluble fracture sample 18. The sample fixing and adjusting platform comprises a pair of opposite transparent plates, and the rough fracture surfaces of the transparent soluble fracture sample 18 are fixed on the pair of transparent plates, respectively. The sample fixing and adjusting platform is provided with an adjustable mechanism. By operating the mechanism, the distance between the two transparent plates can be adjusted, and the fracture aperture can be changed and locked to meet the requirements of the fracture aperture under different test conditions.

[0051] The osmotic pressure control and measurement device comprises an injection pump 1, a micro-flow injector 2, a water pressure sensor 3, an inlet channel 12, an outlet channel 13, an external water tank connected to the inlet channel 12, and an external waste tank connected to the outlet channel 13. The injection pump 1 is a plunger pump with excellent sealing performance between the plunger and the pump body, which can ensure stable flow output at a very low flow rate. The output end of the injection pump 1 is connected to the input end of the micro-flow injector 2, the output end of the micro-flow injector 2 is connected to one end of the inlet channel 12, the other end of the inlet channel 12 is connected to the water inlet 14 of the fracture of the transparent soluble fracture sample 18, one end of the outlet channel 13 is connected to the water outlet 15 of the fracture of the transparent soluble fracture sample 18, and the water pressure sensor 3 is arranged on the inlet channel 12 for monitoring the fluid pressure.

[0052] During the test, the injection pump 1 draws liquid medium from the external water tank, accurately controls the flow rate through the micro-flow injector 2, and then injects it into the fracture of the transparent soluble fracture sample 18 through the inlet channel 12. The liquid medium flows in the fracture and is discharged into the external waste tank through the outlet channel 13 from the water outlet 15. The water pressure sensor 3 monitors the fluid pressure in the inlet channel 12 in real time and transmits the data to the data acquisition and analysis system 10 for control and measurement of the osmotic pressure.

[0053] The confining pressure loading device comprises a closed pressure gas cavity 11, an inert gas injection device 4, and a gas pressure sensor 5. The pressure gas cavity 11 is located outside a transparent plate of the sample fixing and adjusting platform, adjacent to the space between the transparent soluble fracture sample 18 and another transparent plate. The inert gas injection device 4 is connected to the pressure gas cavity 11 through a pipeline and an inert gas bottle, and in this embodiment, the inert gas is nitrogen. The gas pressure sensor 5 is used to monitor the gas pressure in the pressure gas cavity 11.

[0054] During the test, the inert gas injection device 4 injects nitrogen into the pressure gas cavity 11, and the nitrogen transmits uniform confining pressure to the fracture surface of the transparent soluble fracture sample 18 through the transparent plate, thereby simulating the confining pressure environment of the rock mass in actual engineering. The gas pressure sensor 5 monitors the gas pressure in the pressure gas cavity 11 in real time and feeds back the data to the data acquisition and analysis system 10, and the data acquisition and analysis system 10 controls the inert gas injection device 4 according to the feedback signal to maintain a constant confining pressure.

[0055] The visual observation device includes a CCD camera 7, a light source 9, and a three-dimensional XT-DIC full-field strain measurement system 8. The CCD camera 7 and the light source 9 are arranged on the observable side of the transparent soluble fissure sample 18, respectively. The light source 9 can be an LED light source or a laser emitting light source. In this embodiment, an LED light source is taken as an example for illustration. The three-dimensional XT-DIC full-field strain measurement system 8 is used to record the three-dimensional coordinates, displacement, strain, and damage evolution process of the transparent soluble fissure sample 18 during the loading process, and can generate a measurement report containing three-dimensional views, curves, charts, and videos.

[0056] During the test, the light source 9 provides illumination for the CCD camera 7 and the three-dimensional XT-DIC full-field strain measurement system 8, ensuring that the internal conditions of the transparent soluble fissure sample 18 can be clearly observed. The CCD camera 7 records the fissure wall dissolution morphology and displacement changes at a set frame rate. The image acquisition rate ranges from 0.2 fps to 200 fps, and the pixel accuracy of the acquired image is 0.03 mm / pixel. The three-dimensional XT-DIC full-field strain measurement system 8 collects real-time sample full-field strain and damage evolution data. The MATLAB program is used to control the CCD camera 7 to capture the fissure light intensity changes and reconstruct the fissure opening evolution process.

[0057] The data acquisition and analysis system 10 is connected with the water pressure sensor 3, the air pressure sensor 5, the three-dimensional XT-DIC full-field strain measurement system 8, and the CCD camera 7, and is used to collect, process, and analyze the test data. The data acquisition and analysis system 10 receives data signals from various sensors, performs real-time processing and analysis, and generates fissure opening evolution cloud maps, strain field distributions, and dissolution rate quantitative analysis results.

[0058] In this embodiment, the preparation method of the transparent soluble fissure sample is as follows:

[0059] A natural soluble rock cube (a square of 75 mm x 75 mm x 75 mm) sample is subjected to a Brazilian split (MTS815) to obtain a rock sample containing original fissures. A non-contact 3D profile scanner (OKIO 5M Plus) and / or a CT scanner are used to obtain the morphological feature data of the fissures of the rock sample, including wall roughness and spatial opening, while retaining the characteristics of the intersection points and the wall roughness peak areas, which are the subsequent preferential dissolution areas. An MRI scan is used to obtain the pore structure and distribution characteristics of the rock body, and MATLAB is used to reconstruct the three-dimensional image of the rock body and count the characteristic parameters of the fissures and pores.

[0060] A piece of transparent and soluble calcite block is selected as the base material. The surface of the selected calcite block is polished (a piece of transparent and soluble calcite sample with appropriate length, width and thickness is selected, and a polisher is used to polish the four surfaces uniformly), and a low-concentration HCl solution is used for short-time pre-erosion to avoid the formation of irregular erosion pits. Based on the obtained fracture morphology characteristic data, a laser etching technology is used to re-etch a fracture surface with specific roughness parameters and spatial opening characteristics on one surface of the calcite block, and the precision of laser etching is 10 μm. In the local area of the rough fracture surface etched by laser, such as the intersection of the fractures, the peak area of the roughness, and the subsequent erosion preferential area, impurities with different solubilities are added to simulate the differential erosion caused by the mineral heterogeneity in the natural rock mass. The calcite block etched by laser and mixed with impurities is divided along the re-etched fracture surface to form two parts with complementary rough surfaces. The two calcite parts after division are fixed on a transparent acrylic plate respectively using transparent NPA81 glue. The two transparent acrylic plates fixed with the calcite parts are placed opposite to each other on an adjustable opening loading table (the two transparent acrylic plates are fixed on the loading table by threads, and the distance between the two can be adjusted), and the distance between the two is controlled by the adjusting mechanism to set the initial fracture opening, and the distance can be locked or fine-tuned in real time during the test according to the opening change caused by erosion.

[0061] The transparent calcite sample is reconstructed by 3D printing to form a transparent and soluble fracture sample. The differential erosion caused by mineral heterogeneity in natural soluble rocks is simulated by adding impurities with different solubilities to the local part of the transparent calcite fracture surface. The control parameters of the transparent and soluble fracture sample are the roughness of the fracture, the degree of fluctuation of the fracture surface, and the distribution follows the statistical analysis proposed in the study of natural fracture characterization.

[0062] Specifically, a cavity is cut in the middle of the upper cover plate acrylic as a pressure gas cavity, and the gap space between the fracture surface and the pressure gas cavity is provided with stable gas pressure by a N2 inert gas cylinder. The two sides of the fracture surface are sealed boundaries, and a transparent polyvinyl chloride (PVC) gasket and a water stop glue are used for sealing.

[0063] The embodiment provides another structure and working process of a visualization test device, which includes four parts of a permeation pressure control and measurement device, a confining pressure loading device, a creep measurement device and a visualization observation device. The permeation pressure control and measurement device is composed of three parts of a syringe pump 1, a micro-flow injector 2 and a water pressure sensor 3; the confining pressure loading device is composed of three parts of a closed gas cavity 11, an inert gas injection device 4 and a gas pressure sensor 5; the creep measurement device is composed of an LVDT micro-strain measurement instrument 6; and the visualization observation device applies a PIV particle image measurement instrument (including a CCD camera 7 and a light source 9) and a three-dimensional XT-DIC full-range strain measurement system 8.

[0064] The sealing performance between the plunger of the injection pump and the pump body is excellent, which can ensure stable flow output at extremely low flow rate. The water pressure sensor is responsible for monitoring the solution inflow flow rate. The inlet and outlet water pipeline system includes an inlet-outlet seepage channel and an external water tank connected thereto, which introduces and discharges the liquid medium into the fracture surface, and an external waste liquid barrel connected thereto, which is responsible for introducing and discharging the liquid medium into the waste liquid barrel.

[0065] The pipeline of the confining pressure loading device is connected with the inert gas bottle and the pressure gas cavity. The injection of inert gas is controlled by the calculator to make the confining pressure applied by the confining pressure supply source uniformly act on the surrounding of the fracture surface. The gas pressure sensor detects the pressure in the gas cavity.

[0066] The top of the sample is connected with the pressure sensor and the displacement sensor. The creep and opening change during the pressure solution process are measured by the LVDT micro-strain measuring instrument 6.

[0067] The particle image velocimetry (PIV) system is used, and fluorescent particles with a diameter of about 5-10 μm are added to the seepage liquid as tracers (it has been proved in the previous experiment that the seepage liquid does not react with the fluorescent particles).

[0068] During the sample loading process, the three-dimensional XT-DIC full-field strain measurement system synchronously collects images and synchronously records the analog signals transmitted by the testing machine to obtain the full-field strain and damage and failure process.

[0069] The three-dimensional XT-DIC full-field strain measurement system automatically calculates the three-dimensional coordinates of the sample in all loading stages, obtains the geometric surface, displacement and strain results, calculates the material performance parameters, imports the CAD and comparative analysis, calculates the geometric elements, calculates the external analog signals, imports the finite element theoretical calculation values, compares and analyzes with the measured results, and outputs the results on the computer.

[0070] The test process is dynamically observed in real time by the CCD camera, and the preferential dissolution rate in the high solubility region is recorded. The image acquisition rate is as high as 27 frames / second, and the acquisition pixel is 0.03 mm / pixel. The acquired fracture images are connected to the computer through the data line and transmitted to the computer.

[0071] The three-dimensional XT-DIC full-field strain measurement system records the displacement change of the transparent sample and generates a measurement report, including three-dimensional view, curve, chart, video, etc., and exports the test data in a standard format. Due to the insufficient contrast caused by the transmission of light by the transparent sample, the images obtained by the CCD camera need to be processed to reconstruct the evolution of the rock fracture opening.

[0072] The embodiment provides a transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test method, in particular to:

[0073] The deionized water and completely dry HCl powder of a certain mass are weighed to prepare a fixed concentration HCl solution, the HCl solution is dyed with bright blue dye, and the dyed solution needs to be placed in a vacuum box to extract vacuum for five minutes to remove bubbles in the solution to avoid interference of bubbles on the test results.

[0074] Before the test starts, the prepared transparent soluble fracture sample 18 is fixed on the acrylic flat plate, and after being fixed on the sample stage, the opening is adjusted, and the prepared pore fluid is injected into the water supply device;

[0075] After the soluble fracture model is assembled, the saturated clean water is injected into the fracture at a very low flow rate through the injection pump 1, and after the solution fills the fracture, the whole device is placed at normal pressure for 1 h to make the air in the fracture fully discharged to ensure that the fracture is filled with clean water.

[0076] The inert gas bottle is opened to inject inert gas into the gas cavity 11, the pressure in the gas cavity is detected by the pressure sensor 5, and the injection of the gas is controlled by the calculator to make the pressure of the fracture medium stable at a fixed pressure to simulate the confining pressure environment in the actual project.

[0077] The multi-way valve is adjusted to the channel of the unsaturated solution, and the HCl is injected into the fracture at a constant flow rate. The creep and opening change during the pressure solution process are measured by the LVDT micro-strain measuring instrument 6, and the inlet and outlet pressure-flow change curve during the dissolution process is excited by the pressure sensor; the LED light source is turned on and the angle of the light source is adjusted to make it perpendicular to the transparent soluble fracture sample 18 to form a speckle field, and the self-programming of MATLAB controls the CCD camera 7 to record the change of light intensity of the fracture during the dissolution process.

[0078] The data of the LVDT micro-strain measuring instrument 6 and the pressure sensor are transmitted to the data acquisition and analysis system 10 for data processing. At the same time, the CCD camera 7 takes pictures of the surface of the fracture sample at a set frequency to record the retreat and displacement change of the fracture wall surface during the dissolution process, and the three-dimensional XT-DIC full-field strain measurement system 8 detects the three-dimensional coordinates, displacement and strain of the surface of the rock mass fracture to obtain the local damage and deformation of the wall surface. The images taken by the CCD camera 7 are post-processed, the excess part is cut out using Photoshop, and the 8-bit grayscale matrix of the picture light intensity information is converted into a double-precision matrix in Matlab, which is compared with the image recorded at the initial moment and the color tool of Matlab is used to obtain the opening change cloud chart.

[0079] In the description of the application, it should be understood that the terms "upper", "lower", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0080] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0081] In the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected" and the like should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected or in communication with each other; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication or interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0082] In the present application, unless otherwise explicitly specified and limited, the first feature "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "above" and "above" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0083] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification and the features of different embodiments or examples without contradiction.

[0084] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present application, and are used to illustrate the technical solutions of the present application, but are not intended to limit the present application. The protection scope of the present application is not limited thereto. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily think of changes to the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some of the technical features, within the technical scope disclosed by the present application. Such modifications, changes or replacements do not cause the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application.

Claims

1. A transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test device, characterized in that, The application relates to a device for observing the dissolution of a transparent soluble fracture sample (18) under the action of water, comprising the following parts: a sample fixing and adjusting platform for fixing the transparent soluble fracture sample (18), comprising a pair of opposite transparent plates, the rough fracture surfaces of the transparent soluble fracture sample (18) being fixed on the transparent plates respectively, the sample fixing and adjusting platform being provided with an adjustable mechanism for adjusting the distance between the two transparent plates to change and lock the fracture opening; a permeation pressure control and measurement device for injecting fluid into the fracture and controlling the flow rate while monitoring the fluid pressure; a confining pressure loading device, comprising a closed pressure gas cavity (11), an inert gas injection device (4) and a gas pressure sensor (5), for applying uniform confining pressure to the fracture surface and monitoring the confining pressure; the pressure gas cavity (11) is located outside one of the transparent plates of the sample fixing and adjusting platform, adjacent to the space between the transparent soluble fracture sample (18) and the other transparent plate, the inert gas injection device (4) injects inert gas into the pressure gas cavity (11) and transmits uniform confining pressure to the fracture surface of the transparent soluble fracture sample (18) through the transparent plate; a visual observation device, comprising a CCD camera (7), a light source (9) and a three-dimensional XT-DIC full-field strain measurement system (8), for real-time dynamic observation and recording of the dissolution morphology, displacement and full-field strain of the fracture wall; the CCD camera (7) and the light source (9) are arranged on the observable side of the transparent soluble fracture sample (18) respectively, and the light source (9) is used for providing illumination for the CCD camera (7) and / or the three-dimensional XT-DIC full-field strain measurement system (8). 2.The transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 1, characterized in that, The permeation pressure control and measurement device comprises an injection pump (1), a micro-flow injector (2), a water pressure sensor (3), an inlet channel (12) and an outlet channel (13), the output end of the injection pump (1) is connected with the input end of the micro-flow injector (2), the output end of the micro-flow injector (2) is connected with one end of the inlet channel (12), the other end of the inlet channel (12) is connected to the water inlet (14) of the fracture of the transparent soluble fracture sample (18), one end of the outlet channel (13) is connected to the water outlet (15) of the fracture of the transparent soluble fracture sample (18), and the water pressure sensor (3) is arranged on the inlet channel (12). 3.The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 2, characterized in that, The permeation pressure control and measurement device further comprises an external water tank in communication with the inlet channel (12) and an external waste liquid barrel in communication with the outlet channel (13). 4.The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 1, characterized in that, The inert gas injection device (4) is connected with an inert gas bottle and the pressure gas cavity (11) through a pipeline, and the inert gas is nitrogen.

5. The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 4, characterized in that, The permeation pressure control and measurement device further comprises a computer for controlling the inert gas injection device (4) according to the feedback signal of the gas pressure sensor (5) to maintain constant confining pressure. 6.The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 1, characterized in that, The light source (9) is an LED light source or a laser emitting light source. 7.The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 1, characterized in that, The three-dimensional XT-DIC full-field strain measurement system (8) is used for recording the three-dimensional coordinates, displacement, strain and damage evolution process of the transparent soluble fracture sample (18) during loading, and can generate a measurement report containing three-dimensional views, curves, charts and videos. 8.The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test device according to claim 1, characterized in that, The preparation method of the transparent soluble fracture sample is: Collecting a target soluble rock sample, and obtaining a rock sample containing fractures by splitting or cutting; Using a non-contact 3D profile scanner and / or a CT scanner to obtain the fracture morphology data of the rock sample, including wall roughness and spatial opening, while retaining the characteristics of the intersection points and the roughness peak area of the wall; Using MRI scanning to obtain the pore structure and distribution characteristics of the rock mass, and using MATLAB to reconstruct the three-dimensional image of the rock mass and count the characteristic parameters of the fractures and pores; Selecting a light-transmitting soluble calcite material as a substrate, polishing the surface of the selected calcite block, and using an HCl solution for pre-erosion; Based on the obtained fracture morphology data, laser etching technology is used to reproduce the rough surface morphology of the fracture on one surface of the calcite substrate, forming a light-transmitting rough soluble fracture surface; In the local area of the rough fracture surface formed by laser etching, impurities with different solubilities are added to simulate the differential erosion caused by mineral heterogeneity in natural rock mass; The calcite block subjected to laser etching and impurity addition is divided along the reproduced fracture surface to form two parts with complementary rough surfaces; The two divided calcite parts are fixed on a transparent plate respectively, and the two transparent plates with fixed calcite parts are placed opposite each other on an adjustable opening loading platform; A pressure gas cavity (11) is cut in the middle of the top acrylic plate, and transparent gaskets (16) and first and second side water stop strips (17 and 19) are installed on both sides of the fracture surface for sealing.

9. A transparent fracture rock mass stress-seepage-dissolution coupling dynamic visualization test method, characterized in that, It comprises: Fixing the light-transmitting soluble fracture sample (18) on the sample fixing and adjusting platform, and adjusting the opening of the platform to the initial setting value; Injecting saturated clean water into the fracture through the permeation pressure control and measurement device, and standing after the bubbles are discharged; Starting the confining pressure loading device, injecting inert gas into the pressure gas cavity (11) through the inert gas injection device (4), and monitoring and controlling the confining pressure to the target value through the gas pressure sensor (5); Switching the permeation fluid to an erosive solution, and injecting it into the fracture at a constant flow rate through the permeation pressure control and measurement device; Synchronously starting the visualization observation device, turning on the light source (9) and adjusting the angle, making the light penetrate the transparent soluble fracture sample (18), starting the CCD camera (7) to record the fracture wall erosion morphology and displacement change at a set frame rate, and starting the three-dimensional XT-DIC full-field strain measurement system (8) to collect the full-field strain and damage evolution data of the sample in real time; Monitoring the inlet and outlet pressure-flow rate changes through the water pressure sensor (3); Transmitting the data of the CCD camera (7), the XT-DIC system (8), the water pressure sensor (3) and the gas pressure sensor (5) to the data acquisition and analysis system (10), and generating the fracture opening evolution cloud chart, strain field distribution and erosion rate quantitative analysis results in real time.

10. The transparent fractured rock mass stress-seepage-dissolution coupling dynamic visualization test method according to claim 9, characterized in that, The erosive solution is a dyed HCl solution, and the dyeing agent is a bright blue dye; The image acquisition rate of the CCD camera (7) ranges from 0.2 fps to 200 fps, and the acquisition pixel accuracy is 0.03 mm / pixel; The MATLAB program controls the CCD camera (7) to capture the crack light intensity change and reconstruct the crack opening evolution process.

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