Method of determining the barrier properties of a filling

Abstract

The embodiment of the present application relates to the field of testing the permeability of materials, and particularly to a method for determining the sealing performance of a filler. The method simulates the ground stress, temperature, pore water pressure and water chemical environment in the near field of a high-level waste repository, and restores the geological environment of a rock sample in the near field of the high-level waste repository as much as possible, so that the sealing performance of the filler determined in the environment is more accurate; by monitoring parameters such as the normal displacement of the fracture, the pore water pressure and the axial pressure, in combination with the microstructure and porosity data of the filler, different stages of the sealing of the fracture by the filler can be clearly identified, and the parameters can be quantitatively analyzed, so as to obtain data such as the deformation amount of the filler, the variation law of the porosity and the mineral precipitation amount, which reflect the sealing performance, and the data can reveal the physical-chemical mechanism of the mineral reaction of the filler, and thus can assist in the long-term safety prediction of the repository.

Description

Technical Field

[0001] Embodiments of this application relate to the field of testing the permeability of materials, and particularly to a method for determining the sealing performance of fillers. Background Technology

[0002] The statements herein are provided merely as background information in connection with this application and do not necessarily constitute prior art.

[0003] Deep geological repositories for high-level radioactive waste are used for the permanent disposal of such waste. The geological bodies selected for their site must possess low permeability and high stability to effectively prevent groundwater flow and radionuclide diffusion. During the operation of the repository, factors such as heat generated by the high-level radioactive waste, groundwater seepage, changes in geostress, and chemical reactions are highly likely to interact and alter the permeability and connectivity of fissures in the surrounding rock. Sealing these fissures can effectively block radionuclide migration pathways, reduce the risk of radioactive material leakage, and ensure the long-term safety of the repository. Summary of the Invention

[0004] A brief overview of this application is provided below to offer a basic understanding of certain aspects thereof. It should be understood that this overview is not an exhaustive summary of the application. It is not intended to identify key or essential parts of the application, nor is it intended to limit its scope. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0005] This application provides a method for determining the sealing performance of a filler material, wherein the filler material is filled into fissures in natural rock to seal the fissures. The method includes the following steps: S1: preparing a rock sample having fissures; S2: preparing a filler material and filling the entire fissure with the filler material; S3: placing the rock sample filled with the filler material in a sealed environment; S4: simulating the geostress, temperature, pore water pressure, and hydrochemical environment of the near-field of a high-level radioactive waste repository in the sealed environment, wherein the geostress, temperature, pore water pressure, and hydrochemical environment exert their effects on the rock sample; S5: monitoring temperature, axial pressure, pore water pressure, hydrochemical data, and normal displacement data of fissures in the rock sample to make the test conditions of the rock sample closely resemble the geological environment of the near-field of a high-level radioactive waste repository; S6: under the test conditions determined in step S5, determining the microstructure and porosity data of the filler material, and determining the sealing performance of the filler material.

[0006] The method for determining the plugging performance of packing materials provided in the embodiments of this application simulates the geostress, temperature, pore water pressure, and hydrochemical environment in the near field of a high-level radioactive waste repository to recreate the geological environment of the rock sample in the near field of the repository as closely as possible, so that the plugging performance of the packing material determined under this environment is more accurate. By monitoring parameters such as fracture normal displacement, pore water pressure, and axial pressure, combined with the microstructure and porosity data of the packing material, different stages of packing material plugging of fractures can be clearly identified, and these parameters can be quantitatively analyzed to obtain data reflecting the plugging performance, such as the amount of packing material deformation, the pattern of porosity change, and the amount of mineral precipitation. These data can reveal the physicochemical mechanism of the mineral reaction of the packing material, thereby assisting in the prediction of the long-term safety of the repository. Attached Figure Description

[0007] To further illustrate the above and other advantages and features of this application, the specific embodiments of this application will be described in more detail below with reference to the accompanying drawings. The drawings, together with the following detailed description, are included in and form a part of this specification. Elements having the same function and structure are indicated by the same reference numerals. It should be understood that these drawings only depict typical examples of this application and should not be considered as limiting the scope of this application.

[0008] Figure 1 This is a schematic diagram of the structure of a rock sample containing fissures and filling material obtained by the method provided in the embodiments of this application;

[0009] Figure 2 This is a schematic diagram of the experimental apparatus used in the method provided in the embodiments of this application.

[0010] Explanation of reference numerals in the attached figures:

[0011] 10. Rock sample; 11. Rock; 12. Filler; 121. Adhesive layer; 122. Transition layer; 123. Intermediate layer; 2. Uniaxial pressure chamber; 21. Piston; 22. Loading head; 23. Sealing ring; 24. Gasket; 25. Thermocouple; 26. Base; 3. Displacement sensor; 4. Osmotic pressure volume control device; 41. Pore solution storage tank; 42. Pore water pressure sensor; 43. Pore solution pipeline; 51. Circulating thermostat; 52. Dimethyl silicone oil circulation pipeline; 53. Insulation jacket. Detailed Implementation

[0012] Exemplary embodiments of this application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the development of any such actual embodiment to achieve the developer's specific goals, such as complying with constraints related to the system and business, and these constraints may vary depending on the implementation. Furthermore, it should be understood that while development work can be very complex and time-consuming, such development work is merely a routine task for those skilled in the art who benefit from the content of this application.

[0013] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the equipment structure and / or processing steps closely related to the solution according to this application are shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0014] The following disclosure provides several different implementations or examples for carrying out this application. To simplify the disclosure of this application, specific examples of components and methods are described below. Of course, these are merely examples and are not intended to limit this application. In the description of the embodiments of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0015] After sealing the cracks with sealing materials, the performance of the sealing materials may change under long-term thermo-hydraulic-mechanical-chemical coupling effects. Therefore, it is necessary to monitor parameters such as temperature, pressure and groundwater quality in the treatment reservoir in real time to ensure the stability of the barrier system after sealing.

[0016] This application provides a method for determining the sealing performance of a filler material, wherein the filler material is filled into fissures in natural rock to seal the fissures. The method includes the following steps: S1: preparing a rock sample having fissures; S2: preparing a filler material and filling the entire fissure with the filler material; S3: placing the rock sample filled with the filler material in a sealed environment; S4: simulating the geostress, temperature, pore water pressure, and hydrochemical environment of the near-field of a high-level radioactive waste repository in the sealed environment, wherein the geostress, temperature, pore water pressure, and hydrochemical environment exert their effects on the rock sample; S5: monitoring temperature, axial pressure, pore water pressure, hydrochemical data, and normal displacement data of fissures in the rock sample to make the test conditions of the rock sample closely resemble the geological environment of the near-field of a high-level radioactive waste repository; S6: under the test conditions determined in step S5, determining the microstructure and porosity data of the filler material, and determining the sealing performance of the filler material.

[0017] The method for determining the plugging performance of packing materials provided in the embodiments of this application simulates the geostress, temperature, pore water pressure, and hydrochemical environment in the near field of a high-level radioactive waste repository to recreate the geological environment of the rock sample in the near field of the repository as closely as possible, so that the plugging performance of the packing material determined under this environment is more accurate. By monitoring parameters such as fracture normal displacement, pore water pressure, and axial pressure, combined with the microstructure and porosity data of the packing material, different stages of packing material plugging of fractures can be clearly identified, and these parameters can be quantitatively analyzed to obtain data reflecting the plugging performance, such as the amount of packing material deformation, the pattern of porosity change, and the amount of mineral precipitation. These data can reveal the physicochemical mechanism of the mineral reaction of the packing material, thereby assisting in the prediction of the long-term safety of the repository.

[0018] In some embodiments, in step S1, the cracks can be biomimetic processed to make the processed cracks match the actual cracks. This can restore the real cracks as much as possible, so that the determined filling effect is more in line with reality.

[0019] In some embodiments, step S1 further includes the following steps: S11: laser processing the crack to make the processed crack conform to a predetermined morphology; S12: acid etching the crack processed in step S11 to eliminate laser processing traces and introduce mineral-scale chemical inhomogeneities. This treatment makes the roughness of the crack consistent with that of a natural, real crack, improving the contact stability between the crack surface and the filling material.

[0020] In some embodiments, in steps S11 and S12, the parameters of the laser treatment and the acid etching treatment are adjusted so that the treated fissures have anisotropic groove textures similar to natural fissures, thus restoring the surface morphology of fissures formed by geological shearing and compression.

[0021] Figure 1 This is a schematic diagram of the structure of a rock sample containing fractures and filling material obtained by the method provided in the embodiments of this application. In some embodiments, such as Figure 1 As shown, step S2 further includes the following steps: S21: Filling the fracture surface of the filler 12 with the bonding layer 121 close to the rock 11; S22: Filling the transition layer 122 in the filler 12, with the transition layer 122 disposed outside the bonding layer 121; S23: Filling the intermediate layer 123 in the filler 12, with the intermediate layer 123 disposed outside the transition layer 122; S24: Steps S22 and S21 can be repeated to fill the transition layer 122 and bonding layer 121 again outside the intermediate layer 123. This layered filling method better reflects the actual structure of mineral filling in real fractures, resulting in more reliable sealing performance.

[0022] In some embodiments, in steps S21, S22, S23 and S24, different types and sizes of mineral particles or powders are used for layered filling of different layers. By selecting mineral materials with specific types and sizes for layered filling based on the actual fracture filling characteristics, the filling material and its structure in the fracture can be made more realistic.

[0023] Figure 2 This is a schematic diagram of the experimental apparatus used in the method provided in the embodiments of this application. In some embodiments, such as... Figure 2 As shown, step S3 further includes the following steps: S31: Before the test begins, determine the diameter of the circular crack, the total mass of the filler 12, and the average density of the filler 12; S32: Place the rock sample 10 in the uniaxial pressure chamber 2, wherein the crack of the rock sample 10 has been filled with the filler 12, and pre-compact the rock sample 10. Determining the total mass and average density of the filler allows for reasonable planning of the filler material usage and adjustment of the filler composition ratio according to the average density to meet the sealing requirements of the specific rock sample crack morphology; pre-compacting the rock sample 10 enhances the contact interface between the filler 12 and the rock 11 crack prevention.

[0024] In some embodiments, such as Figure 2 As shown, in step S32, the loading head 22 can drive the piston 21 to continuously apply axial pressure to the rock sample 10 in the uniaxial pressure chamber 2 to precompact the rock sample 10.

[0025] In some embodiments, step S4 further includes the following steps: S41: setting the displacement sensor 3, injecting pore solution into the rock sample 10, and maintaining a predetermined pore water pressure; S42: maintaining a predetermined temperature inside the uniaxial pressure chamber 2; S43: continuously applying axial pressure and recording the fracture from... to The normal displacement over time, and the following method is used to determine the filling material in... The thickness of time: , For filler in The thickness of time, For filler in The thickness of time, For the crack from to The normal displacement over time. By measuring and calculating the normal displacement of rock sample 10, the strain of the filler at any time can be obtained accurately and quickly, providing a data basis for quantitatively evaluating the sealing performance of the filler.

[0026] In some embodiments, in step S32, pre-compaction can be performed in a dry environment before injecting the pore solution, and axial pressure is applied to the rock sample 10 for a predetermined time. The pressure value should be greater than the axial pressure in step S43. Through the above operation, the influence of purely mechanical behaviors such as grain rearrangement on the fracture sealing performance can be eliminated, and a microstructure that is easy to observe under a microscope can be obtained. At the same time, the loss of the filler after the solution is injected can be effectively prevented, and the accuracy of quantitative evaluation of sealing performance can be improved.

[0027] In some embodiments, after pre-compaction and stabilization of the uniaxial pressure chamber 2 at a predetermined temperature, the metering pump on the pore solution pipeline 43 can be turned on to inject the pore solution in the pore solution storage tank 41 into the uniaxial pressure chamber 2.

[0028] In some embodiments, the piston 21 and the base 26 restrict the rock sample 10 in the axial direction. The piston 21 and the base 26 are respectively provided with openings for pore liquid to flow in and out. The openings for pore liquid to flow in and out are connected to the pore solution pipeline 43. The pore solution pipeline 43 is provided with pore water pressure sensors 42 near the openings for pore liquid to flow in and out, so as to monitor the changes in pore water pressure at the upper and lower ends of the uniaxial pressure chamber 2.

[0029] In some embodiments, the displacement sensor 3 can be mounted on the piston 21, and the loading head 22 drives the piston 21 to move axially so as to apply axial force to the crack position of the rock sample 10. The displacement sensor 3 can simultaneously detect the axial displacement generated by the axial pressure on the rock sample 10.

[0030] In some embodiments, a thermocouple 25 (e.g., a type K thermocouple) is embedded in the base 26. The temperature measurement range of the thermocouple 25 can be set to 0-150°C to stabilize the temperature inside the uniaxial pressure chamber 2.

[0031] In some embodiments, in step S5, the signals of sensors such as displacement sensor 3, pore water pressure sensor 42 and thermocouple 25 are all connected to a multi-channel data acquisition unit so that the displacement, water pressure and temperature data obtained are displayed and recorded in real time, which facilitates precise control of the test conditions of rock sample 10.

[0032] In some embodiments, step S6 further includes the following step: S61: determining in the following manner to Change in porosity of the filler over time: ; express to The change in porosity of the filling material over a period of time. For filler in The thickness of time, For filler in The thickness of time; The total mass of the filler; The average density of the filler; S62: After the test, the rock sample is unloaded, the pore solution is drained, and the compacted sample is removed for microscopic observation. By measuring and calculating temperature, axial pressure, pore water pressure, hydrochemical data, and normal displacement data, the porosity of the filling material at any time and its changes can be obtained, thereby quantitatively evaluating the sealing performance of the filling material.

[0033] In some embodiments, step S62 further includes the following steps: S621: After removing the rock sample 10, polishing and coating the filler 12 on the fracture surface; S622: Determining the morphology and structure of the filler 12 using a scanning electron microscope to obtain a microscopic image; S623: Identifying the particles of the filler 12 and their contact relationships in the microscopic image to determine the porosity of the filler 12, and determining the sealing performance of the filler 12 based on the porosity. The morphology and structure of the filler 12 after the experiment can be directly observed through the microscopic image, providing an intuitive basis for evaluating the sealing performance of the filler 12; the porosity determined by step S623 can verify the accuracy of the porosity determined in step S61, determining the sealing performance of the filler from multiple dimensions and ensuring the reliability of the evaluation results.

[0034] In some embodiments, after the prepared rock sample 10 is placed into the uniaxial pressure chamber 2, gaskets 24 (e.g., metal cross groove gaskets) and sealing rings 23 (e.g., high-temperature resistant fluororubber sealing rings) can be provided at both ends of the rock sample 10 to allow the pore solution to flow uniformly through both ends of the rock sample 10 to avoid leakage and to ensure that the rock sample 10 can withstand high temperature, high pressure and continuous seepage conditions in subsequent tests.

[0035] In some embodiments, after the rock sample 10 is sealed in the uniaxial pressure chamber 2 and sealed, the piston 21 is driven to move axially by the loading head 22 to gradually apply axial pressure to the rock sample 10, thereby simulating the geostress conditions in the near field of the treatment reservoir.

[0036] In some embodiments, the rock sample 10 can be cylindrical and can be provided with a heat insulation jacket 53 to circumferentially surround and confine the rock sample 10. The dimethyl silicone oil in the circulating thermostat 51 enters the heat insulation jacket 53 through the dimethyl silicone oil circulation pipeline 52 for heat exchange, so that the temperature in the uniaxial pressure chamber 2 is stably controlled within the range of 20-150°C. Insulation cotton can also be wrapped around the outer layer of the heat insulation jacket 53 to reduce heat loss and ensure uniform thermal field, so that the rock sample is under stress and simultaneously under thermal field loading.

[0037] In some embodiments, the pore water pressure can be controlled by the osmotic pressure volume control device 4 so that the pore solution is injected into the fissures of the rock sample 10. The pore solution stays in the fissures for 30-120 minutes, and the liquid flowing into the uniaxial pressure chamber 2 can be switched by the three-way valve to flush the fissures with the clear liquid until the chemical parameters are restored to the reference value.

[0038] In some embodiments, the filler 12 may use calcite powder as the main mineral, with a particle size controlled to ≤75μm, and add 10–20wt% montmorillonite or a predetermined amount of quartz powder to simulate the real mixed composition of fracture particles in the treatment chamber. The filler 12 must be fully dried before filling the fractures of the rock 11 and uniformly filled into the fracture space.

[0039] In some embodiments, the pore solution can be set as a saturated calcium carbonate solution, and the ion concentration and pH can be adjusted according to the hydrochemical environment near the treatment reservoir. After the pore solution flows out of the uniaxial pressure chamber 2, it can be connected to an online detection instrument to detect chemical parameters such as pH, conductivity, calcium ion concentration, and saturation index, so as to reflect the mineral dissolution-precipitation process in the fracture in real time.

[0040] The method provided by the embodiments of this application can clearly identify three typical stages of fracture sealing: In the initial stage of loading, mechanical compaction of mineral particles and free surface precipitation are the main processes, during which the normal strain of the fracture increases rapidly and the porosity decreases rapidly; In the middle stage of loading, the controllable axial force and the local supersaturation of the pore solution jointly drive the calcite particles to undergo pressure dissolution, and calcium ions migrate along the local stress gradient and reprecipitate in the low stress zone, forming a directional secondary precipitation structure; In the later stage of loading, continuous intergranular bridges appear in the fracture, the degree of fracture healing is enhanced, and the permeability gradually decreases to a stable low value, thereby achieving long-term sealing of the fracture.

[0041] Regarding the embodiments of this application, it should also be noted that, without conflict, the embodiments of this application and the features in the embodiments can be combined with each other to obtain new embodiments.

[0042] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. The scope of protection of this application shall be determined by the scope of the claims.

Claims

1. A method for determining the sealing performance of a filler, wherein the filler is inserted into fissures in natural rock to seal the fissures, characterized in that, It includes the following steps: S1: Prepare a rock sample, wherein the rock sample has fissures; S2: Prepare the filler and fill the entire fissure with the filler; S3: The rock sample filled with the filler is placed in a sealed environment; S4: Simulate the geostress, temperature, pore water pressure, and hydrochemical environment in the near field of the high-level radioactive waste disposal repository in the sealed environment, wherein the geostress, temperature, pore water pressure, and hydrochemical environment exert their effects on the rock sample; S5: Monitor the temperature, axial pressure, pore water pressure, hydrochemical data, and normal displacement data of the fractures in the rock sample, so that the test conditions of the rock sample are close to the geological environment near the high-level radioactive waste disposal site. S6: Under the test conditions determined in step S5, determine the microstructure and porosity data of the filler, and determine the sealing performance of the filler; In step S3, the rock sample is placed in a uniaxial pressure chamber, wherein the fissures of the rock sample have been filled with the filler. In step S4, axial pressure is continuously applied to the rock sample, and the fracture is recorded from... to The normal displacement over time, and the filling material is determined in the following manner. The thickness of time: , For the filler in The thickness of time, For the filler in The thickness of time, For the crack from to The normal displacement over time; Step S6 also includes the following steps: S61: Determined in the following manner to Change in porosity of the filler over time: ; express to The change in porosity of the filler over a time period. For the filler in The thickness of time, For the filler in The thickness of time; The total mass of the filler; The average density of the filler; The diameter of the circular crack; S62: After the test, unload the rock sample, drain the pore solution, take out the compacted sample and carry out microscopic observation; S63: Identify the filler particles and their contact relationships in the microscopic image of the filler, determine the porosity of the filler, and determine the sealing performance of the filler based on the porosity.

2. The method according to claim 1, characterized in that, In step S1, the crack is subjected to biomimetic processing so that the processed crack matches the actual crack.

3. The method according to claim 2, characterized in that, Step S1 also includes the following steps: S11: The crack is laser-treated to make the treated crack conform to a predetermined morphology; S12: Acid etching is performed on the cracks treated in step S11 to eliminate laser processing traces and introduce mineral-scale chemical inhomogeneities.

4. The method according to claim 3, characterized in that, In steps S11 and S12, the parameters of the laser treatment and the acid etching treatment are adjusted so that the treated cracks have anisotropic groove textures similar to those of natural cracks.

5. The method according to claim 1, characterized in that, Step S2 also includes the following steps: S21: Close to the crack surface, fill the adhesive layer in the filler; S22: Fill the transition layer in the filler, the transition layer being disposed outside the adhesive layer; S23: Fill the intermediate layer in the filler, the intermediate layer being disposed outside the transition layer; S24: Repeat steps S22 and S21 to fill the transition layer and adhesive layer again outside the intermediate layer.

6. The method according to claim 5, characterized in that, In steps S21, S22, S23 and S24, different types and sizes of mineral particles or powders are filled for different layers.

7. The method according to claim 1, characterized in that, Step S3 also includes the following steps: S31: Before the test begins, determine the diameter of the circular crack, the total mass of the filler, and the average density of the filler; S32: Pre-compacted rock sample.

8. The method according to claim 7, characterized in that, Step S4 also includes the following steps: S41: Set up a displacement sensor, inject pore solution into the rock sample, and maintain a predetermined pore water pressure; S42: Maintain a predetermined temperature inside the uniaxial pressure chamber.

9. The method according to claim 8, characterized in that, In step S32, pre-compaction is performed in a dry environment before the pore solution is injected, and axial pressure is applied to the rock sample for a predetermined time. The pressure value should be greater than the axial pressure in step S4.

10. The method according to claim 1, characterized in that, Step S63 also includes the following steps: S631: After the rock sample is removed, the filler on the fracture surface is polished and coated. S632: Use a scanning electron microscope to determine the morphology and structure of the filler and obtain a microscopic image.

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