Seepage device considering acid, alkali and salt environments based on ultrasonic tomography and test method

Abstract

The invention discloses a seepage device based on ultrasonic tomography and considering acid, alkali and salt environments and a test method, the seepage device comprises a seepage barrel, a sample is placed in the seepage barrel, and a liquid adding device is mounted above the seepage barrel; a water collecting tank is arranged below the seepage barrel; a lower flowmeter is arranged on a liquid seepage pipeline at the bottom of the seepage barrel; a plurality of sound wave transmitting probes and sound wave receiving probes are respectively fixed on two sides of the seepage barrel and are symmetrically distributed on two sides of the seepage barrel; the sound wave transmitting probe and the sound wave receiving probe are connected with a computer through wires, and the computer is used for processing received ultrasonic signals to obtain pore development laws of the sample under different seepage conditions. Real-time inversion imaging of the soft rock seepage process is achieved, the change conditions of the particle outflow volume and the permeability coefficient of the soft rock in different time periods under the influence of different chemical fields and temperature fields are better observed, the test precision is improved, and the labor intensity is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of seepage experiments, and relates to a seepage device and a test method considering acid, alkali, and salt environments based on ultrasonic tomography. Background Art

[0002] Soft rocks are widely distributed in China. Their main components include various mineral components, aqueous phase, and gas phase, and they have complex structures and textures. These components interact with each other and jointly determine the physical and mechanical properties of soft rocks. With the development of industry, acid rain environments occur from time to time in Central China, South China, Southwest China, and East China regions in China. Some mineral components in soft rocks react chemically with acid rain, which will cause changes in the mesoscopic structure inside the rock mass. With the infiltration of acid rain, the initial particle pores, microcracks, joints, and other defects in the rock mass continuously increase, resulting in continuous deterioration of mechanical properties, and further threatening the long-term stability of soft rock slopes or soft rock roadbeds. Therefore, studying the change law of the pore structure of soft rocks in an acidic environment and revealing the deterioration mechanism of acid rain on soft rocks can provide references for the design, construction, and protection measures of soft rock slopes, soft rock roadbeds, etc.

[0003] With the rapid development of China's economy and the acceleration of the industrialization process, industrial sewage and waste generated by industrial activities are wantonly discharged into the natural environment without proper treatment. These substances containing complex chemical components not only directly pollute water sources and soil, but also indirectly cause significant changes in water alkalinity, especially the increase in alkalinity, posing a long-term and profound threat to rock masses. When exposed to an alkaline environment for a long time, the mineral components inside the rock mass gradually undergo chemical reactions, resulting in structural deterioration. In this process, alkaline substances react with minerals such as silicates and carbonates in the rock, causing complex reactions such as dissolution, precipitation, and crystallization, increasing the porosity of the rock, reducing its strength, and even causing physical damage phenomena such as disintegration and exfoliation. The erosion of the alkaline environment will also accelerate the decomposition of organic matter in the rock, further weakening the overall stability of the rock mass. In addition, in coal-accumulating areas (usually referring to areas where rich coal seams and coal-bearing sediments were formed during the geological history period), due to the formation and deposition process of coal, soft rocks such as mudstone, sandy mudstone, carbonaceous mudstone, and shale often appear. As the mining depth of coal resources increases, coal mining faces more and more technical problems and safety challenges, including the alkaline environment in the groundwater environment in coal-accumulating areas, the dissolution and infiltration erosion effects on the mineral components of soft rocks in roadways, resulting in damage to the internal structure of soft rocks, deterioration of macroscopic mechanical properties, and decline in bearing capacity. Therefore, when carrying out coal mining in coal-accumulating areas, it is necessary to fully understand and evaluate the deterioration law of soft rocks in an alkaline environment to formulate reasonable mining and support plans.

[0004] The discharge of industrial sewage and waste often contains various salts. After these substances enter the soil and groundwater, they will affect the seepage characteristics of soft rock. Studying the influence of salt solution on the seepage of soft rock helps to evaluate the potential threat of environmental pollution to the groundwater system and provides technical support for environmental protection and treatment. In the field of resource extraction, understanding the influence of salt solution on the seepage of soft rock also helps to improve the resource recovery rate and extraction efficiency. For the development of mineral resources such as coal and oil, mastering the variation law of the seepage characteristics of soft rock under the action of salt solution can optimize the mining plan and reduce resource waste. Ions in the salt solution may react with the mineral components in the soft rock, resulting in the decomposition of mineral particles and the enlargement of pores, thus increasing the permeability of the soft rock. They may also react chemically with certain components in the soft rock to form new mineral phases. These newly formed mineral phases may block the pores and reduce the permeability of the soft rock; they may also form new seepage channels and increase the permeability. Under the action of flowing salt solution, the soft rock may be scoured, resulting in the shedding of particles and the expansion of pores, thereby affecting its seepage characteristics. At the same time, in the research field of exploring the influence of salt solution on the seepage of soft rock, relevant research results are still scarce, and the research depth and breadth in this field still need to be further expanded and deepened.

[0005] The application of ultrasonic tomography technology in non-destructive detection is very extensive. Based on the propagation characteristics of ultrasonic waves in the medium, by receiving and analyzing the signals of ultrasonic waves after reflection, refraction or scattering inside the medium, the internal structure image of the object is inversely deduced, so as to realize the non-destructive detection of information such as internal defects and properties of the object; When ultrasonic waves propagate in geotechnical media, they carry a lot of information related to the physical and mechanical properties of geotechnical materials. These information can be comprehensively reflected in the changes of acoustic parameters such as ultrasonic wave velocity, attenuation coefficient, waveform, frequency, spectrum and amplitude. According to these parameters, the physical and mechanical indexes and mesoscopic structural characteristics of geotechnical bodies can be inversely deduced, so as to solve a series of geotechnical engineering problems. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a seepage device based on ultrasonic tomography considering acid, alkali and salt environments, which can realize real-time inverse imaging of the seepage process of soft rock, better observe the changes of particle outflow and permeability coefficient of soft rock at different time periods under the influence of different chemical fields and temperature fields, improve the test accuracy and reduce the labor intensity.

[0007] Another object of the present invention is to provide a test method for a seepage device based on ultrasonic tomography considering acid, alkali and salt environments.

[0008] The technical solution adopted by the present invention is a seepage device based on ultrasonic tomography considering acid, alkali, and salt environments, including a seepage barrel. A sample is placed inside the seepage barrel. A liquid adding device is installed above the seepage barrel for adding different acidic solutions, alkaline solutions, or salt solutions into the seepage barrel; A water collecting tank is provided below the seepage barrel. A turbidimeter is installed inside the water collecting tank. The water collecting tank successively guides the seepage liquid to a first measuring cylinder and a second measuring cylinder through a hard water guiding pipe. A hydrometer is arranged inside the first measuring cylinder; An upper flowmeter is provided on the pipe for adding liquid at the top of the seepage barrel, and a lower flowmeter is provided on the pipeline for seeping out liquid at the bottom of the seepage barrel; A plurality of acoustic wave transmitting probes and acoustic wave receiving probes are respectively fixed on both sides of the seepage barrel. The acoustic wave transmitting probes and the acoustic wave receiving probes are in one-to-one correspondence and symmetrically distributed on both sides of the seepage barrel; The acoustic wave transmitting probes and the acoustic wave receiving probes are connected to a computer through wires. The computer is used to process the received ultrasonic signals to obtain the pore development law of the sample under different seepage conditions.

[0009] Further, the liquid adding device includes a lifting platform. An acidic liquid tank, an alkaline liquid tank, a salt solution tank, and a water storage tank are arranged on the lifting platform. The acidic liquid tank, the alkaline liquid tank, the salt solution tank, and the water storage tank are respectively communicated with a mixing tank through corresponding water guiding hoses provided with valves. A pH value measuring instrument is arranged on the side wall of the mixing tank. A temperature control tank is arranged below the mixing tank. The mixing tank is communicated with the temperature control tank through a water guiding hose. The bottom of the temperature control tank is connected to a water inlet pipe.

[0010] Further, an upper permeable stone is arranged at the top of the sample, and a lower permeable stone is arranged at the bottom of the sample. The top end of the seepage barrel is hermetically connected to a top cover, and the bottom end of the seepage barrel is hermetically connected to a bottom cover. A seepage storage area is formed between the top cover and the upper permeable stone. An upper water outlet pipe is arranged on the side of the seepage storage area to ensure the same water head difference between the upstream and downstream of the seepage when measuring the permeability coefficient of soft rock; A water inlet pipe is arranged at the center of the top cover, and a lower water outlet pipe is arranged at the center of the bottom cover.

[0011] Further, there are three acoustic wave transmitting probes and three acoustic wave receiving probes respectively, which are arranged in fixed grooves with springs. The fixed grooves are symmetrically fixed on both sides of the seepage barrel through rubber strips.

[0012] Further, a valve is provided on the hard water guiding pipe to control whether the liquid in the water collecting tank flows into the first measuring cylinder or the second measuring cylinder.

[0013] Further, both the upper flowmeter and the lower flowmeter are acid and alkali resistant intelligent electromagnetic flowmeters.

[0014] A test method for a seepage device based on ultrasonic tomography considering acid, alkali, and salt environments includes the following steps: Step 1: Fabricate a sample from soft rock; Step 2: Place the specimen into the seepage bucket and install the seepage device; Step 3: According to the test plan, change the type of infiltrating liquid and adjust the temperature to simulate different seepage environments of the specimen; Step 4: Conduct a seepage test. Process the ultrasonic signals received by a computer, and then inversely reconstruct the internal structure image of the specimen through image reconstruction to perform real-time imaging of the internal structure of the specimen, and obtain the pore development law of the specimen under different seepage conditions; Step 5: A funnel support is arranged in the water collecting tank, a funnel is arranged on the funnel support, filter paper is placed in the funnel, the water collecting tank is placed on the first electronic balance, and the second measuring cylinder is placed on the second electronic balance; close the valve at the outlet of the water collecting tank, open the upper flowmeter and the lower flowmeter, separate the seeping liquid from the soil particles through the filter paper, the seeping liquid enters the water collecting tank, and accurately measure the mass of the outflowing soil particles and the seeping liquid respectively through the first electronic balance and the second electronic balance; record the difference between the upper flowmeter and the lower flowmeter and the mass of the outflowing soil particles within a fixed period, and quantitatively characterize the mass of the outflowing soil particles with the difference in flow rate; Step 6: Remove the funnel support and the funnel, and open the valve at the outlet of the water collecting tank; open the valve on the first measuring cylinder and close the valve on the second measuring cylinder, the seeping liquid flows into the first measuring cylinder, and when it contains a fixed volume, close the valve of the water collecting tank, and conduct particle analysis on the seeping liquid by the density meter method; Step 7: Close the valve on the first measuring cylinder, open the valve on the second measuring cylinder, the seeping liquid flows into the second measuring cylinder, open the upper water outlet pipe to ensure that the head difference is consistent, and measure the permeability coefficient of the soft rock under different seepage conditions; Step 8: When the seepage environment is acid, alkali, or salt, use an energy spectrum detector to scan and analyze the surface of the specimen and the seeping liquid to obtain the change law of chemical element content.

[0015] Furthermore, in Step 4, before the seepage starts, add a contrast agent to the seepage liquid. The contrast agent is sulfur hexafluoride microbubbles in sulfuric acid. The treatment method of the contrast agent includes the following steps: S1, Prepare a 2-ethyl-4-methylimidazole aqueous solution with a mass concentration of 2-ethyl-4-methylimidazole of 18% - 22%; S2, Wash the protein shell of the contrast agent with Tris buffer solution, where the mass ratio of Tris buffer solution to the contrast agent is 1:1.2 - 1.4; S3, Adjust the pH values of both the contrast agent and the 2-ethyl-4-methylimidazole aqueous solution to 7.0 - 7.3; S4. Slowly add the 2-ethyl-4-methylimidazole aqueous solution to the contrast agent, with the mass ratio of the contrast agent to the 2-ethyl-4-methylimidazole aqueous solution being 1:1.0 - 1.4; stir evenly at 19.5°C - 20.5°C and react for 50 - 60 minutes. S5. Centrifuge the reaction product to separate the contrast agent.

[0016] The beneficial effects of the present invention are as follows: (1) The present invention combines the seepage test with ultrasonic tomography to achieve real-time all-round imaging of the seepage process of the specimen through computer inversion of the received signals, reconstruct the pore distribution image inside the soil sample, and measure the porosity by calculating the proportion of the pore area to the total area; obtain the pore development law of soft rock under different seepage conditions and the physical and mechanical indexes of the specimen, which helps to more accurately obtain the pore development law and the change law of the mechanical properties of the specimen.

[0017] (2) The seepage collection device of the present invention can quantitatively analyze the difference between the inflow and outflow rates and the particle loss amount. By recording the difference between the inflow and outflow rates, the particle loss amount can be quantitatively analyzed, which is more accurate than the traditional qualitative description and helps to deeply understand the particle erosion mechanism caused by seepage.

[0018] (3) The seepage collection device of the present invention can perform particle analysis on the exuded liquid in real time to obtain the particle size and the content of particle groups in the exuded liquid at different time periods under different seepage conditions.

[0019] (4) The present invention can adjust the temperature of the infiltrating liquid to simulate the rainfall infiltration conditions at different temperatures in different regions, making the experimental data more accurate; at the same time, it can also measure the permeability coefficient in real time. On the one hand, it can measure the change of the permeability coefficient with the increase of seepage time; on the other hand, it can measure the change of the permeability coefficient under different temperature conditions.

[0020] (5) The present invention adjusts the infiltrating liquid to form acidic or alkaline solutions with different pH values or different salt solutions to explore the effects of different solutions on the specimen, such as porosity, fracture development, mechanical properties (elastic modulus), etc.; it can adjust the pH value of the infiltrating liquid at any time to better conduct the experiment. Description of the Drawings

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1Schematic structural diagram of an embodiment of the present invention.

[0023] Figure 2 Schematic diagram of the seepage device of an embodiment of the present invention.

[0024] Figure 3 Schematic diagram of the seepage collection device in an embodiment of the present invention.

[0025] Figure 4 Schematic diagram of the mixing tank in an embodiment of the present invention.

[0026] Figure 5 Schematic diagram of the symmetrical probe arrangement in an embodiment of the present invention.

[0027] Wherein: 1 - wire; 2 - upper flowmeter; 3 - valve; 4 - water inlet pipe; 5 - top cover; 6 - soft pad; 7 - bolt; 8 - nut; 9 - seepage water storage area; 10 - upper water outlet pipe; 11 - seepage barrel; 12 - upper permeable stone; 13 - specimen; 14 - lower permeable stone; 15 - bottom cover; 16 - rubber strip; 17 - lower flowmeter; 18 - lower water outlet pipe; 19 - object stage; 20 - water collection tank; 21 - funnel; 22 - filter paper; 23 - funnel support; 24 - turbidimeter; 25 - water guide hose; 26 - first electronic balance; 27 - first measuring cylinder; 28 - hydrometer; 29 - second measuring cylinder; 30 - second electronic balance; 31 - fixed groove; 32 - spring; 33 - computer; 34 - temperature control box; 35 - water storage tank; 36 - mixing tank; 37 - lifting platform; 38 - acoustic wave transmitting probe; 39 - acoustic wave receiving probe; 40 - pH value measuring instrument; 41 - acidic liquid tank; 42 - alkaline liquid tank; 43 - salt solution tank; 44 - water collection cup; 45 - water guide hard pipe. Specific embodiments

[0028] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0029] Embodiment 1 As Figure 1 shown, a seepage device considering acid, alkali, and salt environments based on ultrasonic tomography includes a liquid adding device, a seepage device, a non-destructive detection system, an object stage 19, and a seepage collection device.

[0030] The liquid adding device includes a lifting platform 37, an acidic liquid tank 41, an alkaline liquid tank 42, a salt solution tank 43, a water storage tank 35, a pH meter 40, a mixing tank 36 and a temperature control tank 34; the lifting platform 37 is fixedly arranged on the ground; the acidic liquid tank 41, the alkaline liquid tank 42, the salt solution tank 43 and the water storage tank 35 are arranged on the lifting platform 37 and are respectively communicated with the mixing tank 36 by water guiding hoses 25; the pH meter 40 is arranged on the side wall of the mixing tank 36; the mixing tank 36 is communicated with the temperature control tank 34 by a water guiding hose 25.

[0031] The temperature control tank 34 detects the ambient temperature based on a sensor and compares it with a set target temperature through a controller. When the ambient temperature is higher than the target temperature, the temperature control tank will start the refrigeration system; conversely, when the ambient temperature is lower than the target temperature, the temperature control tank will start the heating system. The refrigeration system includes components such as a compressor, a condenser, an evaporator and a throttling device. Through the circulation of the refrigerant, the refrigeration system can absorb and take away the heat in the tank, thereby reducing the temperature. The heating system includes heating elements such as heating wires and heaters. Through the heating elements providing heat, the heating system can increase the temperature in the tank. The model of the controller: REXC100.

[0032] The seepage device is arranged on the top of the object bearing platform 19 and includes a seepage bucket 11. A specimen 13 is placed inside the seepage bucket 11. An upper permeable stone 12 is arranged at the top of the specimen 13, and a lower permeable stone 14 is arranged at the bottom of the specimen 13. The top end of the seepage bucket 11 is hermetically connected to the top cover 5, and the bottom end of the seepage bucket 11 is hermetically connected to the bottom cover 15; between the top cover 5 and the upper permeable stone 12 is a seepage water storage area 9. An upper water outlet pipe 10 is arranged on the side of the seepage water storage area 9, and the upper water outlet pipe 10 is connected to a water collecting cup 44 to ensure the same water head difference between the upstream and downstream of the seepage when measuring the permeability coefficient of soft rock; a water inlet pipe 4 is arranged at the center of the top cover 5, and an upper flowmeter 2 and a valve 3 are arranged on the water inlet pipe 4 from top to bottom in sequence; a lower water outlet pipe 18 is arranged at the center of the bottom cover 15, and a lower flowmeter 17 and a valve 3 are arranged on the lower water outlet pipe 18 from top to bottom in sequence.

[0033] As Figure 2 、 5 shown, the non-destructive detection system includes acoustic emission probes 38 and acoustic receiving probes 39. There are three acoustic emission probes 38 and three acoustic receiving probes 39 respectively, and they are respectively arranged in fixed slots 31 with springs 32 and are connected to a computer 33 through wires 1; the fixed slots 31 are symmetrically fixed on both sides of the seepage bucket 11 through rubber strips 16. The overall shape of the fixed slots 31 is square, and the acoustic emission probes 38 and acoustic receiving probes 39 are fixed through the fixed slots 31. One side is the fixed slot 31 with the acoustic emission probe 38, and the other side is the fixed slot 31 with the acoustic receiving probe 39; fixing through the rubber strip 16 has the characteristics of being easy to obtain, low cost, reusable, easy to adjust, and not causing damage to the object surface.

[0034] As Figure 3 shown, the seepage collection device is arranged under the object stage 19 and includes a first electronic balance 26, on which a water collection tank 20 is arranged; a funnel support 23 is arranged in the water collection tank 20, a turbidimeter 24 is arranged on the inner side, and a water guide hard pipe 45 is communicated with the bottom of the side surface; a funnel 21 is arranged on the funnel support 23; the water guide hard pipe 45 can successively guide the seepage liquid to a first measuring cylinder 27 and a second measuring cylinder 29 respectively; a hydrometer 28 is arranged in the first measuring cylinder 27; the second measuring cylinder 29 is arranged on a second electronic balance 30.

[0035] The first electronic balance 26 is used to weigh the mass of the seepage liquid and seepage particles; the second electronic balance 30 is used to separately weigh the mass of the seepage liquid. By controlling the switch, the mass of the seepage liquid and seepage particles can be weighed separately. Before seepage, the mass of the filter paper is weighed. During seepage, the seepage liquid flows through the filter paper in the funnel, and the seepage particles will remain on the filter paper. After seepage, the filter paper is taken off and dried, and then the total mass of the filter paper and seepage particles can be weighed, and subtracting the mass of the filter paper can obtain the mass of the seepage particles.

[0036] Function of the first measuring cylinder 27: Remove the funnel, open the valve at the water collection tank, and close the valve above the second measuring cylinder. The particle size analysis of the seepage liquid can be carried out by the hydrometer method.

[0037] Function of the second measuring cylinder 29: ① Remove the funnel, open the valve at the water collection tank, and close the valve above the first measuring cylinder to measure the volume of the seepage liquid for measuring the permeability coefficient of soft rock. ② Open the valve at the water collection tank and close the valve above the first measuring cylinder to measure the volume of the seepage liquid after seepage.

[0038] The height of the acidic liquid tank 41, alkaline liquid tank 42, salt solution tank 43 and water storage tank 35 is adjusted by the lifting platform 37, thereby controlling the seepage rate.

[0039] As Figure 4 shown, the acidic liquid tank 41, alkaline liquid tank 42 and mixing tank 36 are all customized from PP materials. The valve 3 is a flange ball valve made of PP materials. The water guide hose 25 connecting the mixing tank 36 and the temperature control box 34 and the water guide hose 25 connecting the acidic liquid tank 41 and the alkaline liquid tank 42 are transparent FEP hoses. The water inlet pipe 4, upper water outlet pipe 10 and lower water outlet pipe 18 are metal pipes. The water guide hard pipe 45 outside the water collection tank 20 is a transparent FEP hard pipe. The above materials all have strong acid and alkali resistance and can be used normally in the acid-base-salt environment.

[0040] The water inlet pipe 4 and the top cover 5, the upper water outlet pipe 10 and the seepage water storage area 9, and the lower water outlet pipe 18 and the bottom cover 15 are all connected by threads.

[0041] Both the upper flowmeter 2 and the lower flowmeter 17 are acid- and alkali-resistant intelligent electromagnetic flowmeters (UHLDG type strong acid and strong alkali anti-corrosion electromagnetic flowmeters); when the infiltrating liquid is acid or alkali, the acid- and alkali-resistant property can ensure the effectiveness of the experiment and save costs. The intelligent flowmeter has a variety of intelligent functions, such as intelligent filtering processing, intelligent zeroing, and fast response. These functions improve the measurement accuracy and response speed, and at the same time can reduce the errors caused by manual operation. It has a relatively wide nominal diameter range, as well as a variety of lining materials and electrode material selections, which can meet the requirements of a variety of conductive fluids. The measurement process is not affected by changes in the physical parameters of the fluid.

[0042] Both between the seepage bucket 11 and the seepage storage area 9, and between the top cover 5 and the seepage storage area 9 are fixedly connected by bolts 7 and nuts 8; the funnel support 23 is fixed to the wall of the water collection tank 20 by bolts 7 and nuts 8 and can be installed and disassembled according to the progress of the experiment; the production materials of the bolts 7 and nuts 8 are C276 Hastelloy.

[0043] The seepage bucket 11, the seepage storage area 9, the top cover 5, and the bottom cover 15 are all made of PVC material.

[0044] Soft pads 6 are provided between the connections of the seepage bucket 11, the seepage storage area 9, the top cover 5, and the bottom cover 15, which are made of FKM.

[0045] Example 2, A method for using a seepage device based on ultrasonic tomography considering acid, alkali, and salt environments, including the following steps: Step 1, press the soft rock into a cylindrical specimen; process circular grooves at the top and bottom of the cylindrical specimen respectively for placing circular permeable stones, and clean the cylindrical specimen to obtain specimen 13.

[0046] Step 2, apply vaseline to the side wall of the seepage bucket 11, place the specimen 13 into the seepage bucket 11, and install the seepage device; place the upper permeable stone 12 and the lower permeable stone 14 at the upper and lower parts of the specimen 13 respectively. The upper end of the seepage bucket 11 is connected to the seepage storage area 9 by bolts 7 and nuts 8, and the lower end is connected to the bottom cover 15; then connect the seepage storage area 9 to the top cover 5 and place it on the carrier 19; place the acoustic emission probe 38, the acoustic receiving probe 39, and the spring 32 into the fixing groove 31, apply gel coupling agent at the corresponding positions of the probes on the seepage bucket 11, symmetrically fix the fixing groove 31 on both sides of the seepage bucket 11 through the rubber strip 16, and turn on the computer 33.

[0047] Step 3, according to the test plan, the infiltrating liquid can be changed, the seepage environment of the specimen 13 can be set, and the temperature of the infiltrating liquid can be adjusted through the temperature control box 34.

[0048] Step 4: Conduct a seepage test. The computer 33 processes the received ultrasonic signals, and then inversely reconstructs the structural image inside the object through image reconstruction to obtain a real-time image of the internal structure of the specimen 13 by means of a non-destructive detection system, so as to acquire the law of pore development of the specimen 13 under different seepage conditions. When ultrasonic waves propagate in a porous medium, they will encounter pore structures of different sizes and shapes. These pore structures will cause the scattering and reflection of ultrasonic waves, forming a complex scattered wave field. An ultrasonic pulse is emitted into the porous medium through an ultrasonic probe, and the ultrasonic signals scattered and reflected by the pore structures are received. These signals contain information about the internal pore structure of the porous medium. The received ultrasonic signals are preprocessed, such as filtering and amplifying, to improve the signal-to-noise ratio and resolution of the signals. Then, signal processing techniques are used to extract the characteristic information related to the pore structure, such as wave velocity, attenuation coefficient, etc. Based on the collected ultrasonic signals and the extracted characteristic information, an image reconstruction algorithm is used to generate an image of the internal structure of the porous medium. These images can visually display the characteristics of the pore size, shape, connectivity, etc.

[0049] Before the seepage starts, an ultrasonic contrast agent is added to the seepage liquid, which is a liquid containing bubbles with a diameter of several micrometers. The contrast agent microbubbles will vibrate under the action of ultrasonic waves and scatter strong ultrasonic signals. By using the characteristic that the liquid containing bubbles has strong scattering for ultrasonic waves, the ultrasonic Doppler signal is enhanced, and the clarity and resolution of the ultrasonic image are improved. In the embodiment, the second-generation ultrasonic contrast agent (model: Sonovue) is used, which is a bubble with a thin and soft outer membrane mainly composed of a high-density inert gas (not easily soluble in water), generally with a diameter of about 2 - 5 μm, having a long stable time, good vibration and echo characteristics, and containing a high-density inert gas sulfur hexafluoride, with advantages such as good stability and long contrast duration. Its thin and soft outer membrane enables the microbubbles to have good resonance characteristics under the action of low sound pressure, and can generate strong harmonic signals, thereby obtaining a real-time harmonic image with lower noise.

[0050] The processing method of the contrast agent includes the following steps: S1: Prepare a 2 - ethyl - 4 - methylimidazole aqueous solution with a mass concentration of 20% of 2 - ethyl - 4 - methylimidazole: Add 20 g of 2 - ethyl - 4 - methylimidazole (density: 0.975 g / ml) to 79.48 ml of deionized water, and stir with a glass rod until completely dissolved (since 2 - ethyl - 4 - methylimidazole has good solubility and can usually be quickly dissolved at room temperature and can also be completely dissolved at PH = 7, so there is no need to control the temperature and PH value); transfer the solution to a 100 mL volumetric flask, rinse the beaker with a small amount of deionized water, and add the rinsing liquid to the volumetric flask. Finally, make up the volume to 100 mL with deionized water and shake well.

[0051] S2. Wash the protein shell of the contrast agent with Tris (tris-(hydroxymethyl)aminomethane) buffer, where the mass ratio of the buffer to the contrast agent is 1:1.3; whether the common name of the contrast agent is sulfur hexafluoride microbubble; S3. Adjust the pH values of both the contrast agent and the 2-ethyl-4-methylimidazole aqueous solution within the range of 7.2. S4. Slowly add the 2-ethyl-4-methylimidazole aqueous solution to the contrast agent, and the mass ratio of the contrast agent to the 2-ethyl-4-methylimidazole aqueous solution is 1:1.1; stir evenly at 20 °C, stir one circle every five seconds for one minute, and stop the reaction after reacting for 55 minutes by reducing the temperature to 10 °C. S5. Centrifuge the reaction product to separate the contrast agent.

[0052] After testing, the contrast agent obtained in this example remained stable after being stored at 4 °C for 6 months without precipitation.

[0053] Specimen 13 is a cylindrical specimen of carbonaceous mudstone. The dosage of the contrast agent added to the seepage fluid is 0.2 mL of the contrast agent per kg of the cylindrical carbonaceous mudstone specimen, and then the seepage test is started. Stop the seepage test until a clear image appears in the ultrasonic wave. Close all the inlet pipes and outlet pipes and record the clear imaging time. The imaging clarity score and the contrast score are 9.2 points and 8.5 points respectively; the imaging time is 45 minutes. It shows excellent imaging effects and helps the operator to observe and analyze the situation for a longer time.

[0054] Step 5: Close the valve 3 of the water collection tank 20, open the upper flowmeter 2 and the lower flowmeter 17, separate the exudate from the soil particles through the filter paper 22, the exudate enters the water collection tank 20, and the weighing device (two electronic balances) can be used to accurately measure the mass of the outflowing soil particles and the exudate respectively; there are other technical effects: the disintegration rate I of the soft rock specimen in n hours can be calculated. Method: Record the initial specimen weight m1; record the weight m2 of the specimen when it exits the water outlet pipe; record the specimen mass m3 after n hours; calculate the volume v of the lost particles after n hours, and the specimen disintegration rate I = m3 - [(m2 - m1) + v×ρwater] / m1 can be calculated. The calculation method for calculating the volume v of the lost particles after n hours: Collect the exuded particles, dry them, and then put them into a graduated cylinder with a certain volume of water, and the volume of the exuded particles can be measured. Record the difference between the upper flowmeter 2 and the lower flowmeter 17 and the mass of the outflowing soil particles within a fixed period, and the difference in flow rate can be used to quantitatively characterize the mass of the outflowing soil particles. The upper flowmeter 2 is at the water inlet, and the lower flowmeter 17 is at the water outlet. Because the exudate will carry the lost particles, the flow rate will change. By recording the amount of particle loss within a certain period of time, the corresponding flow rate difference can quantitatively characterize the amount of particle loss. For example: In the first five minutes of seepage of a specimen, measure the amount of particle loss, and then correspond to the difference in the flowmeter. Then, in subsequent experiments, the difference in the flowmeter can be used to indirectly represent the amount of particle loss. Example calculation of the operation steps: Within the first 5 minutes of the start of seepage, synchronously record the flow rate difference ΔQ and the time Δt, and collect the suspended particles at the water outlet, dry and weigh them to get Δm 实测 ; Calculate the actual calibration coefficient k = Δm 实测 / ΔQ×Δt; For example, ΔQ = 2×10 −6  m³ / s, Δt = 300 s, Δm 实测 = 0.9 kg, then k = 0.9 / 2×10 −6 ×300 = 1500 ; Calculate the amount of particle loss Δm through the formula Δm = k×ΔQ×Δt

[0055] Although the electronic balance can accurately weigh the mass of soil particles, in a long-term seepage experiment, it is necessary to continuously collect and weigh the outflowing soil particles, which is not only cumbersome to operate but also prone to introducing human errors. In addition, if the seepage rate is fast or the soil particle flow rate is large, it may be impractical to use an electronic balance for real-time weighing. In the embodiment of the present invention, the difference in flow rate is used to quantitatively characterize the mass of the outflowing soil particles, which not only simplifies the operation steps but also enables real-time monitoring without interrupting the seepage process, achieving more convenient and continuous monitoring, improving the monitoring efficiency and accuracy, and reducing the labor cost

[0056] Step 6: Open the valve 3 of the water collecting tank 20, remove the funnel support 23 and the funnel 21, open the valve 3 on the first measuring cylinder 27, close the valve 3 on the second measuring cylinder 29. The seeping liquid flows into the first measuring cylinder. When it contains 1000 ml, close the valve 3 of the water collecting tank 20, and perform particle analysis on the seeping liquid by the hydrometer method to obtain the percentage of particles with different particle sizes in the seeping liquid, that is, the percentage of the mass of soil particles in the seeping liquid.

[0057] Step 7: Close the valve 3 on the first measuring cylinder 27, open the valve 3 on the second measuring cylinder 29. The seeping liquid flows into the second measuring cylinder 29. Open the upper outlet pipe 10. When measuring the permeability coefficient of soft rock, ensure that the water head difference is consistent, and measure the permeability coefficient of soft rock under different seepage conditions. Measurement method: During the seepage process, open the valve at the upper outlet pipe 10, remove the funnel, open the valve at the water collecting tank, close the valve above the first measuring cylinder, and open the valve above the second measuring cylinder. Measure the relative height Δh between the upper outlet pipe 10 and the bottom of the water collecting tank 20, measure the area A of the filling cross-section of the seepage bucket, measure the height L of the specimen, and measure the flow rate Q of the seeping liquid.

[0058] Use the formula: Permeability coefficient k = Q×L / A×Δh, and it can be calculated with this formula.

[0059] During the seepage process, the constant head method needs to be adopted to measure the permeability coefficient of the specimen. In the embodiment of the present invention, a seepage water storage area is added above the seepage bucket, a water outlet pipe with a fixed height is set in this area, and a water pipe is set at a fixed height of the water collecting tank, so as to ensure the consistency of the upstream and downstream water head differences.

[0060] Step 8: When the seepage environment is an acid, alkali, or salt environment, use an energy spectrum detector to scan and analyze the surface of the specimen 13 and the seeping liquid, and the change law of chemical element content can be obtained (known in the art). Replace the specimen 13, and repeat Steps 1 - 8 for the test.

[0061] Summarize the results of multiple tests to obtain conclusions such as the law of crack development and the influence law on the permeability coefficient of soft rock under different seepage conditions of soft rock.

[0062] The specific seepage conditions include: different temperature conditions, different infiltrating liquids (acids, alkalis, salts), and different pH value environments; the test results include: ① Under different seepage conditions, the evolution of internal cracks in the specimen, changes in microstructure, the process of water-rock interaction sites, damage, and softening processes can be detected through ultrasonic tomography. ② The amount of particles lost by the specimen at different times can be obtained through the upper and lower flow meters. ③ Under different seepage conditions, the permeability coefficient of the specimen can be found, and the change law of the test permeability coefficient under different seepage conditions can be obtained. ④ When the seepage environment is an acid, alkali, or salt environment, after the seepage test, the change law of the surface elements of the specimen after seepage can be obtained using an energy spectrum detector.

[0063] Example 3 The treatment method of the contrast agent includes the following steps: S1, Prepare an aqueous solution of 2-ethyl-4-methylimidazole with a mass concentration of 18% of 2-ethyl-4-methylimidazole: Add 18 g of 2-ethyl-4-methylimidazole (density 0.975 g / ml) to 81.54 ml of deionized water, stir with a glass rod until completely dissolved; transfer the solution to a 100 mL volumetric flask, rinse the beaker with a small amount of deionized water, and add the rinsing solution to the volumetric flask. Finally, make up to 100 mL with deionized water and shake well.

[0064] S2, Wash the protein shell of the contrast agent with Tris (tris-(hydroxymethyl)aminomethane) buffer, where the mass ratio of the buffer to the contrast agent is 1:1.2; whether the common name of the contrast agent is sulfur hexafluoride microbubbles; S3, Adjust the pH values of both the contrast agent and the aqueous solution of 2-ethyl-4-methylimidazole within the range of 7.0; S4, Slowly add the aqueous solution of 2-ethyl-4-methylimidazole to the contrast agent, and the mass ratio of the contrast agent to the aqueous solution of 2-ethyl-4-methylimidazole is 1:1.0; stir evenly at 19.5 °C, stir one circle every five seconds for one minute, and stop the reaction after reacting for 50 minutes by reducing the temperature to 10 °C; S5, Centrifuge the reaction product to separate out the contrast agent.

[0065] After testing, the contrast agent obtained in this example can remain stable for 3 - 5 days at 4 °C without precipitation.

[0066] The dosage of the contrast agent added to the seepage fluid is 0.1 mL of the contrast agent per kg of the cylindrical specimen of carbonaceous mudstone; the image clarity score and the contrast score are at a medium level, and the imaging time is 40 minutes, which can meet the imaging requirements.

[0067] Example 4 The treatment method of the contrast agent includes the following steps: S1, Prepare an aqueous solution of 2-ethyl-4-methylimidazole with a mass concentration of 22%: Add 18 g of 2-ethyl-4-methylimidazole (density 0.975 g / ml) to 77.44 ml of deionized water, stir with a glass rod until completely dissolved; transfer the solution to a 100 mL volumetric flask, rinse the beaker with a small amount of deionized water and add the rinsing solution to the volumetric flask, and finally make up to 100 mL with deionized water and shake well.

[0068] S2, Wash the protein shell of the contrast agent with Tris (tris-(hydroxymethyl)aminomethane) buffer, where the mass ratio of the buffer to the contrast agent is 1:1.4; whether the common name of the contrast agent is sulfur hexafluoride microbubbles; S3, Adjust the pH values of both the contrast agent and the aqueous solution of 2-ethyl-4-methylimidazole within the range of 7.3; S4, Slowly add the aqueous solution of 2-ethyl-4-methylimidazole to the contrast agent, and the mass ratio of the contrast agent to the aqueous solution of 2-ethyl-4-methylimidazole is 1:1.2; stir evenly at 20.5 °C, stir one circle every five seconds for one minute, and stop the reaction after reacting for 60 minutes by reducing the temperature to 10 °C; S5, Centrifuge the reaction product to separate the contrast agent.

[0069] After testing, the contrast agent obtained in this example can remain stable for 3 - 5 days at 4 °C without precipitation.

[0070] The dosage of the contrast agent added to the seepage fluid is 0.2 mL of the contrast agent per kg of the carbonaceous mudstone cylindrical sample; the imaging effect also shows a relatively high level, with an imaging time of 42 minutes, which can meet the imaging requirements.

[0071] Comparative example: Treatment method of the contrast agent: Replace 2-ethyl-4-methylimidazole with sodium tripolyphosphate, and the remaining steps are the same as the treatment method of the contrast agent in Example 2. The obtained contrast agent has poor stability and precipitation occurs after being stored at 4 °C for 1 month. The dosage of the contrast agent added to the seepage fluid is 0.2 mL of the contrast agent per kg of the carbonaceous mudstone cylindrical sample; the imaging clarity score and contrast score are 7.5 points and 6.8 points respectively; the imaging time is 25 minutes.

[0072] The microbubble shell of SonoVue is a phospholipid monolayer (such as dipalmitoylphosphatidylcholine, DPPC), with its polar head groups (phosphate groups) facing outward and hydrophobic tails wrapping the gas (SF6) inward; the hydrophobic alkyl chains (ethyl, methyl) of 2-ethyl-4-methylimidazole are adsorbed on the phospholipid hydrophobic tails through hydrophobic interaction, while the hydrophilic imidazole ring binds to the phospholipid polar head groups through hydrogen bonds or electrostatic interaction, forming a "double-layer stable structure". 2-ethyl-4-methylimidazole forms a dense interfacial layer by adsorbing on the microbubble surface, reducing gas diffusion (such as nitrogen or perfluorocarbon) and microbubble rupture, and prolonging its lifespan in a complex fluid environment (such as seepage in porous media). In seepage experiments, the persistence of microbubbles directly determines the ultrasonic signal intensity and imaging resolution, especially in long-term dynamic monitoring.

[0073] The surface of SonoVue microbubbles carries a weak negative charge (Zeta potential about -10 mV) due to phospholipid head groups (such as DPPC). After adding 2-ethyl-4-methylimidazole, there is cation adsorption and charge reversal. The imidazolium cation (protonated form) of 2-ethyl-4-methylimidazole is adsorbed on the microbubble surface to neutralize the negative charge; 2-ethyl-4-methylimidazole can impart a positive charge to the microbubbles (the Zeta potential changes from negative to positive), reducing electrostatic adsorption to negatively charged porous media (such as clay, silicate).

[0074] The lone pair electrons of the imidazole ring form coordination complexes with metal ions such as Fe³⁺ and Cu²⁺, inhibiting their oxidative damage to phospholipids (such as lipid peroxidation), and broadening the application scope of microbubbles in a complex chemical environment (such as acidic groundwater or seepage systems containing metal ions).

[0075] In the embodiment of the present invention, the mass concentration of 2-ethyl-4-methylimidazole is 18% - 22%. If the imidazole group concentration is too low, it is difficult to form sufficient covalent bonds to stabilize the protein shell of the contrast agent; if the concentration is too high, it will increase unnecessary costs and may affect the performance of the contrast agent.

[0076] Tris buffer is used to wash the protein shell of the contrast agent to remove impurities and unbound components. The mass ratio of Tris buffer to the contrast agent is 1:1.2 - 1.4, based on the cleaning effect and the stability of the contrast agent; if the ratio is too low, the contrast agent may not be fully cleaned; if the ratio is too high, the contrast agent may be diluted, affecting its performance. By adjusting the ratio of the contrast agent to the aqueous solution of 2-ethyl-4-methylimidazole, the contrast agent can rapidly form microbubbles after injection and reflect more ultrasonic signals, thus enhancing the imaging effect; the microbubbles in the contrast agent are more stable, thus prolonging the imaging time; the optimized contrast agent has better adaptability, enabling the contrast agent to exist for a longer time and further prolonging the imaging time. In addition, the optimized contrast agent has better dispersibility and uniformity, making the imaging clearer.

[0077] The embodiment of the present invention can obtain the pore development law of soft rock under different seepage conditions and the change law of physical and mechanical indicators of the sample through ultrasonic tomography technology, quantitatively analyze the particle loss through the difference between the infiltration and seepage flow rates, perform particle analysis on the seepage liquid in real time, and measure the permeability coefficient of soft rock under different seepage conditions. The embodiment of the present invention directly associates the difference in flow rate with the particle loss. Compared with measuring the mass difference before and after particle loss, the embodiment of the present invention saves a lot of cumbersome steps and reduces errors; the particle loss can be obtained at any time during the seepage, and the particle loss within a certain period of time can also be obtained.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A seepage device based on ultrasonic tomography taking into account acid, alkali and salt environments, comprising a seepage bucket (11), wherein a sample (13) is placed inside the seepage bucket (11), characterized in that: A liquid adding device is installed above the seepage barrel (11) for adding different acidic solutions, alkaline solutions or salt solutions into the seepage barrel (11); A water collecting box (20) is provided below the seepage bucket (11), a turbidity meter (24) is installed in the water collecting box (20), the water collecting box (20) guides the seepage liquid to the first measuring cylinder (27) and the second measuring cylinder (29) respectively through the water guiding hard pipe (45), and a hydrometer (28) is provided in the first measuring cylinder (27); An upper flow meter (2) is provided on the pipeline for adding liquid at the top of the seepage barrel (11), and a lower flow meter (17) is provided on the pipeline for letting liquid seep out at the bottom of the seepage barrel (11); A plurality of acoustic wave transmitting probes (38) and acoustic wave receiving probes (39) are fixed on both sides of the seepage barrel (11), respectively. The acoustic wave transmitting probes (38) and the acoustic wave receiving probes (39) correspond to each other one by one and are symmetrically distributed on both sides of the seepage barrel (11). The acoustic wave transmitting probes (38) and the acoustic wave receiving probes (39) are connected to a computer (33) via a wire (1), and the computer (33) is used to process received ultrasonic signals to obtain the pore development law of the sample (13) under different seepage conditions.

2. According to claim 1, a seepage device based on ultrasonic tomography considering acid, alkali and salt environments, characterized in that: The liquid adding device comprises a lifting platform (37), on which an acidic liquid tank (41), an alkaline liquid tank (42), a salt solution tank (43) and a water storage tank (35) are arranged. The acidic liquid tank (41), the alkaline liquid tank (42), the salt solution tank (43) and the water storage tank (35) are respectively connected to a mixing box (36) via corresponding water-conducting hoses (25) provided with valves (3). A pH value measuring instrument (40) is provided on a side wall of the mixing box (36). A temperature control box (34) is provided below the mixing box (36). The mixing box (36) and the temperature control box (34) are connected via the water-conducting hose (25), and the bottom of the temperature control box (34) is connected to a water inlet pipe (4).

3. According to claim 1, a seepage device based on ultrasonic tomography considering acid, alkali and salt environments, characterized in that: An upper permeable stone (12) is provided on the top of the sample (13), and a lower permeable stone (14) is provided on the bottom of the sample (13). The top end of the seepage bucket (11) is sealedly connected to the top cover (5), and the bottom end of the seepage bucket (11) is sealedly connected to the bottom cover (15). A seepage water storage area (9) is provided between the top cover (5) and the upper permeable stone (12). An upper water outlet pipe (10) is provided on the side of the seepage water storage area (9) to ensure that the head difference between the upstream and downstream of the seepage is consistent when measuring the permeability coefficient of soft rock. A water inlet pipe (4) is provided at the center of the top cover (5), and a lower water outlet pipe (18) is provided at the center of the bottom cover (15).

4. According to claim 1, a seepage device based on ultrasonic tomography considering acid, alkali and salt environments is characterized in that: There are three acoustic wave transmitting probes (38) and three acoustic wave receiving probes (39), which are respectively arranged in fixed grooves (31) with springs (32). The fixed grooves (31) are symmetrically fixed to two sides of the seepage barrel (11) through rubber strips (16).

5. According to claim 1, a seepage device based on ultrasonic tomography considering acid, alkali and salt environments, characterized in that: The water-conducting hard pipe (45) is provided with a valve (3) for controlling whether the liquid in the water collecting tank (20) flows into the first measuring cylinder (27) or the second measuring cylinder (29).

6. The seepage device based on ultrasonic tomography considering acid, alkali and salt environments according to claim 1, characterized in that: The upper flow meter (2) and the lower flow meter (17) are both acid- and alkali-resistant intelligent electromagnetic flow meters.

7. A test method for a seepage device in acid, alkali and salt environments based on ultrasonic tomography as claimed in claim 1, characterized in that: The following steps are involved: Step 1: Prepare a sample from soft rock (13); Step 2: placing the sample (13) into the seepage bucket (11) and installing the seepage device; Step 3: According to the test plan, the type of infiltrating liquid is changed, the temperature is adjusted, and different seepage environments of the sample (13) are simulated; Step 4: Conduct a seepage test, process the received ultrasonic signal by a computer (33), and then invert the internal structure image of the sample (13) by image reconstruction, perform real-time imaging of the internal structure of the sample (13), and obtain the pore development law of the sample (13) under different seepage conditions; Step 5: a funnel support (23) is provided in the water collecting box (20), a funnel (21) is provided on the funnel support (23), a filter paper (22) is placed in the funnel (21), the water collecting box (20) is placed on a first electronic balance (26), and the second measuring cylinder (29) is placed on a second electronic balance (30); the valve (3) at the outlet of the water collecting box (20) is closed, the upper flow meter (2) and the lower flow meter (17) are opened, the seepage liquid and the soil particles are separated by the filter paper (22), the seepage liquid enters the water collecting box (20), and the masses of the outflowing soil particles and the seepage liquid are accurately measured by the first electronic balance (26) and the second electronic balance (30), respectively; the difference between the upper flow meter (2) and the lower flow meter (17) and the mass of the outflowing soil particles within a fixed period of time are recorded, and the mass of the outflowing soil particles is quantitatively characterized by the difference in flow rate; Step 6: Remove the funnel support (23) and the funnel (21), open the valve (3) at the outlet of the water collecting box (20); open the valve (3) on the first measuring cylinder (27), close the valve (3) on the second measuring cylinder (29), and allow the exudate to flow into the first measuring cylinder (27). When a fixed volume is contained, close the valve (3) of the water collecting box (20), and perform particle analysis on the exudate by using a density meter method; Step 7: Close the valve (3) on the first measuring cylinder (27), open the valve (3) on the second measuring cylinder (29), allow the seepage liquid to flow into the second measuring cylinder (29), open the upper outlet pipe (10), ensure that the water head difference is consistent, and measure the permeability coefficient of the soft rock under different seepage conditions; Step 8: When the seepage environment is acid, alkali or salt, use an energy spectrum detector to scan and analyze the surface of the sample (13) and the seepage liquid to obtain the change pattern of the chemical element content.

8. The test method of a seepage device based on ultrasonic tomography considering acid, alkali and salt environments according to claim 7, characterized in that: In the step 4, before the infiltration begins, a contrast agent is added to the exudate, and the contrast agent is sulfur hexafluoride microbubbles. The method for processing the contrast agent includes the following steps: S1, preparing a 2-ethyl-4-methylimidazole aqueous solution with a mass concentration of 18% to 22%; S2, washing the protein shell of the contrast agent with Tris buffer, wherein the mass ratio of Tris buffer to contrast agent is 1:1.2-1.4; S3, adjusting the pH values ​​of the contrast agent and the 2-ethyl-4-methylimidazole aqueous solution to 7.0-7.3; S4, slowly adding the 2-ethyl-4-methylimidazole aqueous solution to the contrast agent, the mass ratio of the contrast agent to the 2-ethyl-4-methylimidazole aqueous solution is 1:1.0-1.4; stirring evenly at 19.5°C-20.5°C, and reacting for 50-60 minutes; S5, centrifuging the reaction product to separate the contrast agent.

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