Visualizing device for solute transport in rock single fracture under cyclic temperature variation

Abstract

The application provides a visual device for rock single fracture solute migration under cyclic temperature variation, comprising: a transparent fractured rock mass, comprising upper and lower transparent fractured rock masses each provided with a rough fracture surface, and the upper and lower transparent fractured rock masses are placed in opposition to form a single fracture channel; a cyclic temperature variation assembly for simulating the cyclic temperature variation phenomenon in a natural environment; a solute concentration monitoring assembly for injecting a fluorescent reagent solution into the single fracture channel, visualizing the solute migration in the single fracture channel based on laser-induced fluorescence, and monitoring the solute concentration in the single fracture channel; a fracture temperature monitoring assembly for monitoring the temperature change inside the single fracture channel under the cyclic temperature variation based on a fiber Bragg grating sensor; and a data processing unit connected with the cyclic temperature variation assembly, the solute concentration monitoring assembly and the fracture temperature monitoring assembly. The application can simultaneously visualize and monitor the solute exchange concentration, flow characteristics and thermodynamic characteristics in the fracture.

Description

Technical Field

[0001] This invention relates to the fields of geological engineering and environmental science, and more specifically to a visualization device that considers solute transport in a single fracture of rock under cyclic temperature changes. Background Technology

[0002] In the fields of geological engineering and environmental science, the study of solute transport within rock fractures is of great significance for many engineering projects, such as underground resource extraction, predicting pollutant diffusion, industrial wastewater treatment, and nuclear contamination transport. Fractured rock masses are important channels for groundwater and solute transport, and their flow and transport characteristics are influenced by various factors, such as temperature and pressure variations. Considering the complexity of actual geological conditions and the alternating hot and cold temperatures, the study of solute transport in rock fractures is simplified to the study of solute transport under single fractures. Research on solute transport within single fractures of rocks under cyclic temperature variations is of great significance for a deeper understanding and prediction of solute transport patterns within rock fractures.

[0003] Existing solute transport research facilities are mostly focused on experiments under constant temperature conditions, lacking systematic studies on solute transport behavior under cyclic temperature variations. Under such conditions, processes such as solute diffusion, convection, and adsorption may change significantly, affecting the accuracy and applicability of the research results. Furthermore, while traditional single-rock fracture solute transport devices can measure solute concentration, they cannot directly observe and record the solute transport process within the fracture, limiting a deeper understanding of solute transport mechanisms. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems existing in the prior art.

[0005] Therefore, the purpose of this invention is to provide a visualization device and experimental method for solute transport in a single fracture of rock under cyclic temperature changes. While accurately monitoring the concentration and temperature changes during solute transport, the device allows for intuitive observation and recording of the transport path and distribution of solute in the fracture through visualization.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of this invention provides a visualization device for solute transport in a single fracture of rock under cyclic temperature changes, comprising:

[0008] A transparent fractured rock mass includes an upper transparent fractured rock mass and a lower transparent fractured rock mass, both of which have rough fracture surfaces. The rough fracture surfaces of the upper transparent fractured rock mass and the lower transparent fractured rock mass are placed facing each other to form a single fracture channel along the horizontal direction.

[0009] A circulating temperature control component includes a circulating temperature control chamber and a temperature control panel. The transparent fractured rock mass is placed inside the circulating temperature control chamber. The circulating temperature control component is used to simulate the circulating temperature phenomenon in the natural environment.

[0010] The solute concentration monitoring component visualizes and monitors the solute concentration within the single-slit channel by injecting a fluorescent reagent solution into the single-slit channel based on laser-induced fluorescence.

[0011] A fracture temperature monitoring component, based on a fiber Bragg grating sensor, monitors the temperature change inside the single fracture channel under cyclic temperature variations; and

[0012] The data processing unit is connected to the circulating temperature control component, the solute concentration monitoring component, and the crack temperature monitoring component.

[0013] In some embodiments, the upper transparent fractured rock mass and the lower transparent fractured rock mass are formed by casting a mold of a natural fractured rock mass and pouring it with a transparent material. Holes are drilled in the upper transparent fractured rock mass and the lower transparent fractured rock mass in the vertical direction to install the fiber Bragg grating sensor.

[0014] In some embodiments, the transparent fractured rock mass is fixed by a rock mass clamping assembly, which includes a clamping base, a transparent baffle, and two clamping sliders arranged opposite each other. The two clamping sliders are symmetrically arranged on the left and right sides of the transparent fractured rock mass and are connected to the clamping base by bolts. Water channels connected to the solute concentration monitoring component are respectively provided on the two clamping sliders at the same height as the single fracture channel. The transparent baffle seals the front and rear sides of the single fracture channel by inserting into the slots provided on the two clamping sliders.

[0015] In some embodiments, the circulating temperature chamber includes a transparent and sealed chamber body and a heater and a cooler disposed within the chamber body. Holes are drilled on the left and right sides of the chamber body to allow the water pipe connecting the single-slit channel within the solute concentration monitoring component and the optical fiber connecting the fiber Bragg grating sensor within the slit temperature monitoring component to pass through. The heater is mounted on the inner surface of the top of the chamber body via a slide rail equipped with a motor. The heater is connected to the output end of the motor to form a movable heating source, thereby simulating the solar radiation trajectory. The control panel is connected to the data processing unit and is used to set the operating parameters of the motor, the heater, and the cooler according to a preset solar radiation-temperature change curve.

[0016] In some embodiments, the heater is a resistance heater; the cooler is a cooling fan located at the four inner corners of the top of the housing.

[0017] In some embodiments, the solute concentration monitoring component includes a laser, a fluorescence filter, a fluorescence reagent circulation unit, and a camera; the laser and the fluorescence filter are both disposed outside the circulating temperature-controlled component, and the fluorescence filter is at the same height as the single-slit channel; the camera is disposed directly in front of the fluorescence filter to capture the fluorescence signal passing through the fluorescence filter, convert it into an electrical signal to form a fluorescence image, and import it into the data processing unit for fluorescence intensity analysis to determine the solute transport and concentration distribution; the fluorescence reagent circulation unit is connected to the single-slit channel and is used to circulate the fluorescence reagent solution into the single-slit channel.

[0018] In some embodiments, the fluorescent reagent circulation unit includes a storage bottle containing the fluorescent reagent solution, an inlet connector and an outlet connector communicating with the single-slit channel and at the same height, and a water pipe connecting the inlet connector, the storage bottle, and the outlet connector; a circulation pump is provided on the water pipe between the outlet connector and the storage bottle.

[0019] In some embodiments, a mesh screen is provided at the connection between the water pipe and the storage bottle located between the water inlet connector and the storage bottle, for filtering rock particles that may be washed out during solute transport.

[0020] In some embodiments, the fracture temperature monitoring component includes a broadband light source, an optical fiber coupler, an optical fiber amplifier, an optical fiber, an optical fiber demodulator, and a plurality of optical fiber Bragg grating sensors; a portion of the optical fiber Bragg grating sensors extend from top to bottom into the upper transparent fractured rock mass to its rough fracture surface, and another portion of the optical fiber Bragg grating sensors extend from bottom to top into the lower transparent fractured rock mass to its rough fracture surface; the broadband light source is used to send optical signals to the optical fiber Bragg grating sensors; the optical fiber amplifier is connected to the output end of the broadband light source through the optical fiber; the optical fiber coupler is connected to the optical fiber amplifier, the optical fiber Bragg grating sensors, and the optical fiber demodulator; the optical fiber demodulator is connected to the data processing unit, and the data processing unit converts the signal transmitted by the optical fiber demodulator into a corresponding temperature value.

[0021] The second aspect of this invention provides a visualization experimental method for solute transport in a single fracture of rock under cyclic temperature changes, comprising:

[0022] Assemble the visualization device according to any embodiment of the first aspect of the present invention;

[0023] The temperature range and cycle period are set via the temperature control panel to correspond to a preset solar radiation-temperature change curve, simulating the changes in solar radiation throughout the day. The heating source in the circulating temperature chamber is heated, and its position is adjusted. Once the temperature of the heating source reaches the set high temperature threshold, this temperature is maintained for a specified duration. Subsequently, the heating source is stopped, and the cooling source in the circulating temperature chamber is cooled down until its temperature reaches the set low temperature threshold, which is then maintained for a specified duration. The above operation is repeated according to the set cycle period until the end of the experimental period.

[0024] During the simulated cyclic temperature change process, the solute concentration monitoring component is used to acquire fluorescence images in real time, and the data processing unit performs fluorescence intensity analysis on the fluorescence images to determine the solute transport and concentration distribution in the single-crack channel.

[0025] During the simulated cyclic temperature change process, the crack temperature monitoring component is used to acquire the Bragg wavelength change in the spectrum of the fiber Bragg grating sensor inside it in real time, and the data processing unit converts the wavelength change into the corresponding temperature value.

[0026] Features and beneficial effects of the present invention:

[0027] This invention simulates the solute transport process in a single fracture of rock under real-world cyclic temperature variations. It employs visualization methods, fiber grating (FBG) sensors, and laser-induced fluorescence (LIF) technology to simultaneously monitor solute exchange concentration, flow characteristics, and thermodynamic properties within the fracture. This invention accurately monitors concentration and temperature changes during solute transport, while visually observing and recording the transport paths and distribution of solutes within the fracture. This will help improve pollutant diffusion prediction models, optimize resource development strategies, and formulate more effective environmental protection measures. Attached Figure Description

[0028] Figure 1 This invention provides a visualization device that considers solute transport in a single fracture of rock under cyclic temperature changes.

[0029] Figure 2 This shows a two-dimensional structural schematic diagram of the transparent fractured rock mass in an embodiment of the present invention;

[0030] Figure 3 A three-dimensional structural schematic diagram of the rock mass clamping assembly in an embodiment of the present invention is shown;

[0031] Figure label:

[0032] 100. Transparent fractured rock mass; 110. Upper transparent fractured rock mass; 120. Lower transparent fractured rock mass; 130. Single fracture channel;

[0033] 200. Rock mass clamping assembly; 210. Clamping base; 211. First slide rail; 212. Bolt; 220. Clamping slider; 221. Slot; 222. Water channel; 230. Transparent baffle.

[0034] 310. Circulating temperature chamber; 311. Cooler; 312. Heater; 313. Second slide rail; 314. Linear motor; 315. Chamber; 320. Temperature control panel.

[0035] 410. Green laser; 420. Fluorescent filter; 431. Fluorescent reagent solution; 432. Storage bottle; 433. Circulation pump; 434. Water pipe; 435. Gauze screen; 436. Water outlet connector; 437. Water inlet connector; 440. Camera.

[0036] 510. Broadband light source; 520. Fiber optic coupler; 530. Fiber optic amplifier; 540. FBG sensor; 550. Fiber optic cable; 560. Fiber optic demodulator.

[0037] 610. Communication cable; 620. Computer. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this application clearer, the application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0039] Conversely, this application covers any alternatives, modifications, equivalent methods, and schemes made within the spirit and scope of this application as defined by the claims. Furthermore, to provide the public with a better understanding of this application, certain specific details are described in detail below. However, this application can be fully understood by those skilled in the art even without these detailed descriptions.

[0040] The structures, proportions, and sizes illustrated in the accompanying drawings are solely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of this application and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this application, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of this application. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of this application's implementation.

[0041] like Figures 1-3 As shown, a visualization device considering solute transport in a single fracture of rock under cyclic temperature changes includes:

[0042] Transparent fractured rock mass 100 includes an upper transparent fractured rock mass 110 and a lower transparent fractured rock mass 120, both of which are provided with rough fracture surfaces. The rough fracture surfaces of the upper transparent fractured rock mass 110 and the lower transparent fractured rock mass 120 are placed facing each other to form a single fracture channel 130 along the horizontal direction.

[0043] The circulating temperature component includes a sealed and transparent circulating temperature chamber 310 and a temperature control panel 320. The transparent fractured rock mass 100 is placed inside the circulating temperature chamber 310. The circulating temperature component is used to simulate the circulating temperature phenomenon in the natural environment.

[0044] The solute concentration monitoring component visualizes and monitors the solute concentration within the single-slit channel 130 by injecting a fluorescent reagent solution into the single-slit channel 130 based on laser-induced fluorescence (LIF).

[0045] The fracture temperature monitoring component uses a fiber Bragg grating (FBG) sensor to monitor temperature changes inside a single fracture channel 130 under cyclic temperature variations; and

[0046] The data processing unit is connected to the circulating temperature control component, the solute concentration monitoring component, and the crack temperature monitoring component.

[0047] In some embodiments, see Figure 2The upper transparent fractured rock mass 110 and the lower transparent fractured rock mass 120 within the transparent fractured rock mass 100 are formed by casting a mold of natural fractured rock mass and pouring transparent resin. Furthermore, the material for the upper transparent fractured rock mass 110 and the lower transparent fractured rock mass 120 is preferably epoxy resin. The upper transparent fractured rock mass 110 and the lower transparent fractured rock mass 120 are respectively drilled to form a first hole for installing the FBG sensor in the fracture temperature monitoring component.

[0048] In one specific embodiment of this application, it is preferred to use an ultrasonic drill to drill several first holes vertically and symmetrically on the upper transparent fractured rock mass 110 and the lower transparent fractured rock mass 120. The hole diameter is 3mm, and the hole spacing is equidistant from the length of the transparent fractured rock mass 100.

[0049] In some embodiments, a rock mass clamping assembly 200 is used to clamp and fix the transparent fractured rock mass 100 to form an integral structure, and the integral structure is placed in the circulating temperature chamber 310.

[0050] Further, see Figure 3The rock mass clamping assembly 200 includes a clamping base 210, a transparent baffle 230, and two clamping sliders 220 arranged opposite each other. The clamping base 210 has parallel first slide rails 211 on its front and rear sides, the length direction of which is consistent with the length direction of the single fracture channel 130. The clamping base 210 also has several bolt mounting slots on its front and rear sides. The two clamping sliders 220 have identical structures, each with an L-shaped cross-section, and are positioned at both ends of the transparent fractured rock mass 100, placed on the first slide rails 211 to clamp the transparent fractured rock mass 100. The position of the clamping sliders 220 is fixed by bolts 212 tightened on the clamping base 210, thus forming a single integrated structure with the clamping base 210 and the clamping sliders 220. A second hole is formed by drilling along the length of the single fracture channel 130 on each of the two clamping sliders 220. A water channel 222 is installed along the length of each second hole. The water channel 222 on one of the clamping sliders 220 connects the outlet of the single fracture channel 130 to the inlet connector 437 of the solute concentration monitoring component, and the water channel 222 on the other clamping slider connects the inlet of the single fracture channel 130 to the outlet connector 436 of the solute concentration monitoring component. The transparent baffle 230 is made of a transparent and light-transmitting material, preferably polymethyl methacrylate (PMMA). The transparent baffle 230 is set on the front and rear sides of the transparent fracture rock mass 100. A slot 221 is provided on the opposite side of the two clamping sliders 220. By inserting the transparent baffle 230 into the slot 221, the front and rear sides of the single fracture channel 130 are sealed. Polymethyl methacrylate (PMMA) has good optical transparency and chemical resistance, making it suitable for use in lenses for optical components and laser devices. This invention mainly utilizes the high transparency and ultra-high definition of polymethyl methacrylate (PMMA) to facilitate the capture of fluorescent particles in the visualization of solute concentration monitoring.

[0051] Optionally, on one side of the two clamping sliders 220 that are positioned opposite each other ( Figure 3 The two clamping sliders shown in the figure are respectively provided with a side plate 240 that spans the clamping base 210. The two clamping sliders 220 are fixedly connected to the corresponding side plate 240 by bolts to further enhance the fixing effect of the clamping sliders 220 on the transparent fractured rock mass 100.

[0052] In some embodiments, the circulating temperature control assembly includes a circulating temperature control chamber 310 and a temperature control panel 320 connected to the chamber 310. The temperature range and cycle time within the chamber 310 are set via the temperature control panel 320 to simulate the changes in sunlight throughout the day. The temperature control panel 320 is also connected to a computer 620 in a data processing unit, and the settings parameters of the temperature control panel 320 are adjusted via the computer 620.

[0053] Furthermore, the circulating temperature chamber 310 includes a transparent and sealed chamber 315 and a heater 312 and a cooler 311 disposed within the chamber 315. The chamber 315 is made of a transparent and light-transmitting material, preferably plexiglass. The circulating temperature chamber is preferably perforated. On the left and right sides of the chamber 315, at the same height as the single-slit channel 130, a third circular hole with a radius of 20 mm is ultrasonically drilled for inserting the water pipe 434 of the solute concentration monitoring component into the chamber 315 to connect the single-slit channel 130 to the solute concentration monitoring component. On the right side of the chamber 315, a fourth circular hole with a radius of 15 mm is symmetrically drilled along the center, for inserting the parallel optical fiber 560 of the slit temperature monitoring component into the chamber 315 to connect the FBG sensor 540 to the optical fiber coupler 520. The housing 315 has an openable top cover. A second slide rail 313, housing a linear motor 314, is positioned in the center of the top cover. The second slide rail 313 is integrally formed with the top cover of the housing 315 by set bolts. A heater 312 is mounted on the second slide rail 313 and driven by the linear motor 314, forming a movable heating source. The parameters of the linear motor 314 are set according to the solar radiation-temperature change curve, allowing the heater 312 to adjust its position on the second slide rail 313 according to the solar radiation trajectory. Simultaneously, the parameters of the heater 312 and the cooler 311 are set to cyclically simulate solar radiation temperature within the experimental cycle. The linear motor is used to precisely control the speed and position of the heater 312 on the second slide rail 313.

[0054] In one specific embodiment of this application, a heater 312 and four coolers 311 are installed inside the housing 315. The heater 312 is preferably a resistance heater, fixed to the mover of a linear motor 314, allowing it to move along a second slide rail 313 to adjust the heating position and form a heating circulation system. The coolers 311 are preferably cooling fans, installed at the four corners of the top of the housing 315 to form a cooling circulation system.

[0055] When using a cyclic temperature control component to simulate cyclic temperature changes in the natural environment, the temperature range and cycle period corresponding to the designed solar radiation-temperature change curve are first set via the temperature control panel 320. Next, the heater 312 is used to raise the temperature, and its position is adjusted using a linear motor 314 and a second slide rail 313. Once the temperature reaches the set high-temperature threshold, it is maintained at that temperature for a specified duration. Subsequently, the heater 312 stops working, and the cooler 311 is activated to lower the temperature to the set low-temperature threshold and maintain this low-temperature state. This process is repeated according to the set cycle until the end of the experimental period.

[0056] In some embodiments, the solute concentration monitoring component includes a laser 410, a fluorescence filter 420, a fluorescence reagent circulation unit, and a camera 440. The laser 410 is positioned on the left side outside the circulating temperature chamber 310 and is used to excite the fluorescence energy of the fluorescent particles provided by the fluorescence reagent circulation unit. The fluorescence filter 420 is installed outside the circulating temperature chamber 310, directly in front of the transparent fractured rock mass 100 and at the same height as the single fracture channel 130. It effectively blocks the excitation wavelength, matches and retains the fluorescence emission wavelength, and the light corresponding to this emission wavelength is captured by the camera 440 installed directly in front of the fluorescence filter 420, converted into an electrical signal to form a fluorescence image, and imported into the data processing unit for fluorescence intensity analysis to determine the solute transport and concentration distribution. The fluorescence reagent circulation unit is connected to the single fracture channel 130 of the transparent fractured rock mass 100 and is used to circulate a fluorescent reagent solution 431 containing fluorescent particles into the single fracture channel 130.

[0057] Furthermore, the fluorescent reagent circulation unit includes a storage bottle 432 containing the fluorescent reagent solution 431, an inlet connector 437 and an outlet connector 436 respectively mounted on two clamping sliders 220 at the same height as the single fracture channel 130, and a water pipe 434 connecting the inlet connector 437, the storage bottle 432, and the outlet connector 436. The outlet connector 436 is connected to the inlet of the single fracture channel 130 through a water channel 222 in the clamping slider 220 on the left side of the transparent fracture rock mass 100, and the inlet connector 437 is connected to the outlet of the single fracture channel 130 through a water channel 222 in the clamping slider 220 on the right side of the transparent fracture rock mass 100. A circulation pump 433 is installed on the water pipe 434 between the outlet connector 436 and the storage bottle 432, and by setting the appropriate opening and flow rate, the fluorescent reagent solution 431 is ensured to circulate in the single fracture channel 130. A mesh screen 435 is provided at the connection between the water pipe and the storage bottle 432, located between the water inlet connector 437 and the storage bottle 432, to filter epoxy resin particles that may be washed out by solute transport.

[0058] In one specific embodiment of this application, the fluorescent reagent solution 431 is an inorganic salt solution with added fluorescent particles. Rhodamine green is preferably used as the fluorescent particle, considering its high fluorescence quantum yield and spectral adaptability, effectively absorbing light energy and converting it into fluorescence emission for easy concentration visualization. It also exhibits good chemical stability, showing high tolerance to cyclic high and low temperature changes, ensuring that the monitored concentration results are minimally affected by temperature variations. Since Rhodamine green is used as the fluorescent particle, a 532nm wavelength laser is preferred for the laser 410 to most effectively excite the Rhodamine green particles in the solution to a higher excited state during the experiment. The fluorescence emission wavelength after excitation is generally 550nm; therefore, a 550nm fluorescence filter 420 is selected in this embodiment to meet the experimental requirements. The water pipe 434 is preferably a soft water pipe with a radius of 15mm. The circulation pump 433 is preferably connected to the water pipe 434 by a threaded connection. A threaded connector is used at a position 5cm from the storage bottle, with PTFE tape wrapped around the threads and the connector tightened. The gauze 435 is preferably made of 80-mesh gauze, and the cut gauze is preferably secured to the water pipe 434 with cable ties. The camera 440 is preferably a CCD high-speed camera to detect fluorescence signals.

[0059] Understandably, this embodiment employs LIF technology to monitor solute transport concentration in rock fractures under cyclic temperature variations. On one hand, LIF technology has high sensitivity, enabling the detection of very low concentration samples and yielding high signal-to-noise ratio concentration detection results. On the other hand, since liquid, gas, and solid samples may contain internal rock fractures, LIF technology can monitor the concentration of various types of solutes within fractured rock masses.

[0060] In some embodiments, the fracture temperature monitoring assembly includes a broadband light source 510, an optical fiber coupler 520, an optical fiber amplifier 530, an FBG sensor 540, an optical fiber 550, and an optical fiber demodulator 560. The FBG sensor 540 measures the temperature within a single fracture channel 130 under cyclic temperature variations. The FBG sensor 540 extends from top to bottom into the upper rough fracture surface through a first hole drilled along the upper transparent fracture rock mass 110, and from bottom to top into the lower rough fracture surface through a first hole drilled along the lower transparent fracture rock mass 120. An optical fiber protective sleeve (not shown in the figure) is fitted onto the surface of the FBG sensor 540 and fixed to the fracture surface, protecting the FBG sensor 540 and the optical fiber 550 from damage. The broadband light source 510 effectively transmits optical signals to the FBG sensor 540. The optical fiber amplifier 530 is connected to the output end of the broadband light source 510 via the optical fiber 550, amplifying the optical signal in the optical fiber 550 and reducing loss during long-distance transmission. Fiber optic coupler 520 is connected to fiber optic amplifier 530, FBG sensor 540, and fiber optic demodulator 560 for optical signal distribution and combining. Specifically, fiber optic coupler 520 distributes the optical signal to FBG sensor 540 and combines the signals returned by FBG sensor 540 for transmission to fiber optic demodulator 560. Fiber optic demodulator 560 is connected to data processing unit for wavelength extraction and demodulation of the optical signal returned by FBG sensor 540, and sends the resulting demodulated signal to data processing unit. Data processing unit uses the FBG method to convert spectral changes into corresponding temperature values.

[0061] In one specific embodiment of this application, the fissure temperature monitoring component includes a broadband light source 510, two fiber optic couplers 520, two fiber optic amplifiers 530, multiple FBG sensors 540 and optical fibers 550, and a fiber optic demodulator 560. The broadband light source 510 is preferably a 1550nm wavelength broadband light source, located on the left side outside the cyclic temperature chamber 310, and connected to the two fiber optic amplifiers via optical fibers 550. The fiber optic amplifiers 530 are preferably erbium-doped fiber amplifiers. In this embodiment, the complex environment of cyclic temperature changes and the significant loss of optical signals during long-distance transmission of solute transport are considered important factors. Using erbium-doped fiber amplifiers can reduce cyclic temperature interference and provide high gain and high output power, significantly amplifying weak signals and effectively extending the transmission distance of optical signals. The two fiber optic amplifiers 530 are first connected to the output end of the broadband light source 510 via optical fibers 550, and then connected to the corresponding fiber optic couplers 520 for signal amplification. The fiber optic coupler 520 preferably uses a 2x2 fiber optic coupler to distribute the optical signal to the FBG sensor 540 via fiber optic cable 550, and combines the signals returned by the FBG sensor 540 for transmission to the fiber optic demodulator 560. After the two fiber optic couplers 520 are connected to the corresponding fiber optic amplifiers 530, they pass through the housing 315 of the circulating temperature chamber 310 via fiber optic cable 550, and are respectively connected to multiple FBG sensors 540 within the upper and lower roughened fracture surfaces. Preferably, the FBG sensors 540 within the upper and lower roughened fracture surfaces are connected in parallel on a single fiber optic cable. A different initial Bragg wavelength is set for each FBG sensor 540, selectively reflecting light of the corresponding wavelength and projecting light of other wavelengths. The reflected light is transmitted to the fiber optic demodulator 560 via fiber optic cable 550. The fiber optic protective sleeve is preferably made of a waterproof material, and more preferably silicone. The fiber optic protective sleeve is fixed to each FBG sensor 540 using epoxy resin. By drilling 3mm holes in the upper and lower rough fractured rock mass using an ultrasonic drill, the FBG sensor 540 was inserted into the upper and lower rough fracture surfaces and then fixed to the fracture sidewalls using epoxy resin.

[0062] Understandably, in this embodiment, FBG technology is preferentially used to monitor the temperature of rock fractures under cyclic temperature variations. On one hand, FBG sensors are highly sensitive to temperature changes, enabling precise monitoring of temperature variations. Furthermore, since this embodiment is set under cyclic temperature variations, long-term temperature monitoring is required, and FBG sensors offer long-term stability and durability. On the other hand, multiple FBG sensors can be cascaded along optical fibers to achieve distributed temperature measurement, efficiently acquiring the temperature distribution at different locations within the rock fractures.

[0063] In some embodiments, the data processing unit includes a cable 610 and a computer 620. The computer 620 and the fiber optic demodulator 560 are located on the same side. FBG sensors 540 within the upper and lower rough fracture surfaces selectively reflect light of corresponding wavelengths and project light of other wavelengths. The reflected light is transmitted to the fiber optic demodulator 560 via optical fibers 550. The computer 620 receives signals from the fiber optic demodulator 560 using FBG technology, analyzes the changes in the reflected wavelength of each FBG sensor 540, and calculates the temperature changes at different locations within the single fracture channel 130. Furthermore, the computer 620 is connected to the output of a camera 440 via cable 610. The computer 620 processes the fluorescence signal intensity in the image and calculates the concentration value using LIF technology and fluorescence imaging technology.

[0064] A second aspect of the present invention provides a method for visualizing solute transport in a single fracture of rock under cyclic temperature changes, comprising the following steps:

[0065] Step 1: Create upper and lower transparent fractured rock masses, which specifically includes the following steps:

[0066] Step 1A: Making a silicone model: Prepare a container, place the natural fractured rock mass inside, pour in silicone, put the container into a vacuum chamber after the silicone is poured in, vacuum for 1 hour, let it stand, and after the silicone solidifies, take out the natural fractured rock mass to form a silicone mold.

[0067] Step 1B: Creating the upper and lower transparent fractured rock masses: Using the silicone mold created in Step 1A, pour a 4cm thick layer of epoxy resin into it. After the epoxy resin has solidified, remove it to obtain the upper transparent fractured rock mass. Create the lower transparent fractured rock mass in the same way.

[0068] Step 1C: Drilling the transparent fractured rock mass: Using an ultrasonic drill, drill several holes symmetrically vertically into the upper and lower transparent fractured rock masses prepared in Step 1B until the holes penetrate to the upper and lower rough fracture surfaces. Each of the upper and lower transparent fractured rock masses will have a row of symmetrical holes with a diameter of 3 mm. The hole spacing will be equidistant according to the length of the transparent fractured rock mass.

[0069] Step 2: Clamping the transparent fractured rock mass

[0070] Step 2A: Install and fix the clamping slider: Place the transparent fractured rock mass into the clamping slider, connect the clamping slider through the first slide rail of the clamping base, so that the clamping base, clamping slider and transparent fractured rock mass become a whole, and fix the clamping slider by tightening the bolts on the side of the first slide rail.

[0071] Step 2B: Sealing the transparent fractured rock mass: After the clamping slider and clamping base are fixed, the transparent baffle is installed on the front and rear sides of the transparent fractured rock mass using the slot to seal the single fracture channel.

[0072] Step 3: Install the circulating temperature control unit

[0073] Step 3A, Drilling holes in the circulating temperature chamber: Use an ultrasonic drill to drill one round hole on each of the left and right sides of the circulating temperature chamber at the same height as the single-slit channel; drill one round hole on each of the right side of the chamber at symmetrical positions above and below the center.

[0074] Step 3B: Install the second slide rail: Install the stator of the linear motor on the second slide rail, ensuring that the stator is arranged along the second slide rail. Open the top cover of the housing, install the second slide rail in the middle of the top cover, and anchor both sides of the second slide rail to the top cover using bolts.

[0075] Step 3C: Install the heater: Fix the heater to the mover of the linear motor so that it can move along the second slide rail.

[0076] Step 3D: Install the cooler: Use bolts to fix the cooler to the four corners of the top of the box.

[0077] Step 4: Place the rock mass and clamping components into the circulating temperature box: Place the clamped transparent fractured rock mass and clamping components into the circulating temperature box, adjust and fix the position so that the water passage of the clamping components is aligned with the holes on the left and right sides of the circulating temperature box.

[0078] Step 5: Install the FBG sensor: The FBG sensor is fixed inside the fiber optic protective sleeve with epoxy resin. The FBG sensor is connected to the fiber optic cable, extending into the hole drilled in step 1C, and fixed to the upper and lower rough fracture surfaces with epoxy resin. Since multiple FBG sensors are needed to measure the temperature inside multiple fractures, it is preferable to connect the FBG sensors and fibers in parallel. The FBG sensors inside the upper and lower rough fracture surfaces are each connected in parallel to a single fiber optic cable. The fiber optic cable passes through the symmetrical holes on the right side of the circulating temperature chamber and connects to a 2x2 fiber optic coupler.

[0079] Step 6, Preparation and loading of fluorescent reagent: Use a concentration of 10 -5 Rhodamine green (mol / L) was used to stain inorganic salt solutions as tracer particles. The prepared rhodamine green solution was poured into a storage bottle.

[0080] Step 7: Connecting the storage bottle, circulating temperature chamber, and clamping assembly: Pass the water pipe through the holes on the left side of the storage bottle and the left side of the circulating temperature chamber, in that order, followed by the water outlet connector; similarly, pass the water pipe through the holes on the right side of the storage bottle and the right side of the circulating temperature chamber, in that order, followed by the water inlet connector. Turn on the circulating pump to check for any leakage at the connection points during the flow of the fluorescent solute.

[0081] Step 8: Perform cyclic temperature control: After completing steps 3-7, close the top cover of the cyclic temperature control chamber. Simulate daily solar radiation changes using the solar radiation-temperature variation curve set on the temperature control panel, and set the temperature range and cycle period. Use the heater to raise the temperature, and adjust the heater's position relative to the transparent fractured rock mass using a linear motor and a second slide rail. Once the heater temperature reaches the set high-temperature threshold, maintain that temperature for a specified duration. Then, stop the heater and simultaneously start the cooler. When the cooler temperature drops to the set low-temperature threshold, maintain that temperature for a specified duration. Repeat the above heating and cooling process according to the set cycle until the experiment ends.

[0082] Step 9, Concentration Monitoring: During the cyclic temperature change experiment in Step 8, the circulation pump was turned on, and the flow rate was adjusted to fill the single-slit channel with an inorganic salt solution containing the fluorescent reagent Rhodamine Green. After the solution transport stabilized, the 532nm green laser was turned on, allowing the laser to strike the fluorescent reagent solution in the single-slit channel and excite the fluorescent particles in the solution. The fluorescence was filtered by a 550nm fluorescence filter, and the corresponding wavelength of fluorescence was captured by a CCD high-speed camera, converted into an electrical signal to form a fluorescence image, and imported into a computer for fluorescence intensity analysis using LIF technology to determine the solute transport and concentration distribution.

[0083] Step 10, Temperature Monitoring: In the cyclic temperature change experiment in Step 8, turn on the 1550nm broadband light source, start the fiber optic demodulator, detect the reflection spectrum of the FBG sensor, monitor and record the Bragg wavelength change in the FBG sensor spectrum in real time through the fiber optic demodulator, and use a computer to convert the wavelength change into the corresponding temperature value.

[0084] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0085] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A visualization device considering solute transport in a single fracture of rock under cyclic temperature changes, characterized in that, include: A transparent fractured rock mass includes an upper transparent fractured rock mass and a lower transparent fractured rock mass, both of which have rough fracture surfaces. The rough fracture surfaces of the upper transparent fractured rock mass and the lower transparent fractured rock mass are placed facing each other to form a single fracture channel along the horizontal direction. A circulating temperature control component includes a circulating temperature control chamber and a temperature control panel. The transparent fractured rock mass is placed inside the circulating temperature control chamber. The circulating temperature control component is used to simulate the circulating temperature phenomenon in the natural environment. The solute concentration monitoring component visualizes and monitors the solute concentration within the single-slit channel by injecting a fluorescent reagent solution into the single-slit channel based on laser-induced fluorescence. A fracture temperature monitoring component, based on a fiber Bragg grating sensor, monitors the temperature change inside the single fracture channel under cyclic temperature changes; and The data processing unit is connected to the circulating temperature control component, the solute concentration monitoring component, and the crack temperature monitoring component; The circulating temperature chamber includes a transparent and sealed chamber and a heater and a cooler disposed within the chamber. Holes are drilled on both the left and right sides of the chamber to allow the water pipe connecting the single-slit channel within the solute concentration monitoring component and the optical fiber connecting the fiber Bragg grating sensor within the slit temperature monitoring component to pass through. The heater is mounted on the inner surface of the top of the chamber via a slide rail equipped with a motor. The heater is connected to the output end of the motor, forming a movable heating source to simulate the solar radiation trajectory. The control panel is connected to the data processing unit and is used to set the operating parameters of the motor, the heater, and the cooler according to a preset solar radiation-temperature change curve. The solute concentration monitoring component includes a laser, a fluorescence filter, a fluorescence reagent circulation unit, and a camera. The laser and the fluorescence filter are both located outside the circulating temperature-controlled component, with the fluorescence filter at the same height as the single-slit channel. The camera is positioned directly in front of the fluorescence filter to capture the fluorescence signal passing through it, converting it into an electrical signal to form a fluorescence image. This image is then imported into the data processing unit for fluorescence intensity analysis to determine solute transport and concentration distribution. The fluorescence reagent circulation unit is connected to the single-slit channel and is used to circulate the fluorescence reagent solution into the single-slit channel. The fracture temperature monitoring component includes a broadband light source, an optical fiber coupler, an optical fiber amplifier, an optical fiber, an optical fiber demodulator, and multiple optical fiber Bragg grating sensors. A portion of the optical fiber Bragg grating sensors extend from top to bottom into the upper transparent fractured rock mass to its rough fracture surface, while another portion extends from bottom to top into the lower transparent fractured rock mass to its rough fracture surface. The broadband light source transmits optical signals to the optical fiber Bragg grating sensors. The optical fiber amplifier is connected to the output end of the broadband light source via the optical fiber. The optical fiber coupler is connected to the optical fiber amplifier, the optical fiber Bragg grating sensors, and the optical fiber demodulator. The optical fiber demodulator is connected to the data processing unit, which converts the signals transmitted by the optical fiber demodulator into corresponding temperature values.

2. The visualization device according to claim 1, characterized in that, The upper transparent fractured rock mass and the lower transparent fractured rock mass are formed by casting a mold of natural fractured rock mass and pouring it with transparent material. Holes are drilled in the upper transparent fractured rock mass and the lower transparent fractured rock mass in the vertical direction to install the fiber Bragg grating sensor.

3. The visualization device according to claim 1, characterized in that, The transparent fractured rock mass is fixed by a rock mass clamping assembly, which includes a clamping base, a transparent baffle, and two clamping sliders arranged opposite each other. The two clamping sliders are symmetrically arranged on the left and right sides of the transparent fractured rock mass and are connected to the clamping base by bolts. Water channels connected to the solute concentration monitoring component are respectively provided on the two clamping sliders at the same height as the single fracture channel. The transparent baffle seals the front and rear sides of the single fracture channel by inserting into the slots provided on the two clamping sliders.

4. The visualization device according to claim 1, characterized in that, The heater is a resistance heater; the cooler is a cooling fan located at the four inner corners of the top of the housing.

5. The visualization device according to claim 1, characterized in that, The fluorescent reagent circulation unit includes a storage bottle containing the fluorescent reagent solution, an inlet connector and an outlet connector that are connected to the single-slit channel and at the same height, and a water pipe connecting the inlet connector, the storage bottle and the outlet connector; a circulation pump is provided on the water pipe between the outlet connector and the storage bottle.

6. The visualization device according to claim 5, characterized in that, A mesh screen is provided at the connection between the water pipe and the storage bottle, located between the water inlet and the storage bottle, to filter rock particles that may be washed out during solute transport.

7. A visual experimental method for solute transport in a single fracture of rock under cyclic temperature changes, characterized in that, include: Assemble the visualization device according to any one of claims 1 to 6; The temperature range and cycle period are set via the temperature control panel to correspond to a preset solar radiation-temperature change curve, simulating the changes in solar radiation throughout the day. The heating source in the circulating temperature chamber is heated, and its position is adjusted. Once the temperature of the heating source reaches the set high temperature threshold, this temperature is maintained for a specified duration. Subsequently, the heating source is stopped, and the cooling source in the circulating temperature chamber is cooled down until its temperature reaches the set low temperature threshold, which is then maintained for a specified duration. The above operation is repeated according to the set cycle period until the end of the experimental period. During the simulated cyclic temperature change process, the solute concentration monitoring component is used to acquire fluorescence images in real time, and the data processing unit performs fluorescence intensity analysis on the fluorescence images to determine the solute transport and concentration distribution in the single-crack channel. During the simulated cyclic temperature change process, the crack temperature monitoring component is used to acquire the Bragg wavelength change in the spectrum of the fiber Bragg grating sensor inside it in real time, and the data processing unit converts the wavelength change into the corresponding temperature value.

Images