Artificial rock core as well as preparation method and application thereof

Abstract

The invention discloses an artificial core as well as a preparation method and application thereof. The method comprises the following steps: determining ingredient components and ingredient specifications of the artificial core according to a rock type in a high-level radioactive repository site selection area; the preparation method comprises the following steps: pre-drying ingredients meeting the specification, weighing the ingredients according to a predetermined component proportion, adding at least one of a water reducing agent, a retarder and an early strength agent, uniformly mixing to obtain a solid material, and synchronously and uniformly mixing the solid material and water in batches to obtain mortar; the mortar is added into the mold in batches, and compaction treatment is carried out after each time of addition; and after the mortar is solidified, demolding and maintaining to obtain the artificial rock core. The method effectively solves the technical problems that in the prior art, original core materials are difficult to obtain and large in demand quantity.

Description

Technical Field

[0001] This invention belongs to the field of nuclear waste geological disposal technology, and relates to an artificial rock core, its preparation method and application. Background Technology

[0002] In recent years, the nuclear power industry has experienced rapid development. However, the disposal of radioactive waste generated during the operation of nuclear power facilities has also become a prominent issue that urgently needs to be addressed. High-level radioactive waste (HLD) has become a key focus due to its high toxicity, high heat release rate, and long half-life of radioactive toxins. The safe and effective disposal of HLD is not only crucial for environmental protection and human health, but has also become a significant factor restricting the sustainable development of the nuclear industry. Currently, HLD is typically processed by relevant departments and then placed in storage facilities hundreds of meters underground for long-term geological disposal. Before constructing these storage facilities, laboratory studies on the properties of the local claystone are essential. Research on the properties of the claystone helps to gain a deeper understanding of the geological environment of the storage facility, providing crucial information for the safe disposal of HLD.

[0003] In this research process, obtaining core materials is crucial, serving as the foundation and core of laboratory research. However, obtaining raw core materials faces significant challenges. Typically, core material acquisition relies on large-scale mining projects. These projects have their own plans, schedules, and objectives; their mining activities are not specifically designed for core material acquisition. This severely restricts the core material acquisition cycle to the overall arrangements of the large-scale mining project, making it impossible to flexibly adjust the acquisition time according to research needs. Furthermore, from a convenience perspective, the procedures and numerous steps involved in obtaining core materials, due to the need to coordinate with the processes and pace of large-scale mining projects, further increase the difficulty and inconvenience.

[0004] Furthermore, laboratory research requires a large quantity of core samples. On the one hand, to ensure the accuracy and reliability of research results, multiple repeated experiments are necessary, requiring a large number of core samples as support. On the other hand, different experimental projects and research directions have different requirements for the specifications and properties of core samples, further expanding the overall demand for core samples. Simultaneously, the experimental process can damage core samples, making them difficult to reuse once consumed in the experiment. This further exacerbates the urgency and importance of obtaining core samples.

[0005] In summary, obtaining original core materials is difficult and constrained by many factors, posing a significant challenge to the study of clay rock properties before the disposal of high-level radioactive waste, and an effective solution is urgently needed. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides an artificial rock core, its preparation method and application, thereby solving the technical problems of difficulty in obtaining raw rock core materials and large demand in the prior art.

[0007] This invention is achieved through the following technical solution: A method for preparing an artificial rock core includes the following steps: S1: Determine the composition and specifications of the artificial core based on the rock type of the site selection area for the high-level radioactive waste disposal facility; S2: Pre-dry the ingredients that meet the specifications, weigh the ingredients according to the predetermined composition ratio, add at least one of water-reducing agent, retarder and early strength agent, mix evenly to obtain solid material, and then mix the solid material with water in batches to obtain mortar. S3: Add the mortar into the mold in batches, and compact it after each addition; S4: After the mortar has solidified, demolding and curing are carried out to obtain the artificial rock core.

[0008] Preferably, when the rock type is clay rock, the ingredients consist of a binder, aggregate, and weighting agent; the binder includes cement and gypsum, the aggregate is quartz sand, and the weighting agent includes barite powder and iron powder.

[0009] Preferably, the pre-drying process is carried out at a temperature of 90°C for 12 hours.

[0010] Preferably, the process of determining the component ratio is as follows: several influencing factors are set through the orthogonal experimental principle, and several levels are set for each factor to obtain the orthogonal experimental ratio. The batching experiment is carried out according to the orthogonal experimental ratio, and the mechanical properties, permeability and radionuclide diffusion properties of the obtained experimental artificial rock core are tested. The ratio of the sample with the best performance is selected as the final component ratio.

[0011] Preferably, when the solid material is mixed with water in batches simultaneously, the raw material added in each batch is 1 / 3 to 1 / 5 of the total raw material mass.

[0012] Preferably, when mixing the solid material with water in batches simultaneously, after each batch of solid material and water is mixed, it is stirred for 15 to 20 minutes before adding the next batch of solid material and water.

[0013] Preferably, during the compaction process, the pressure is 10~20MPa and the compaction time is 30~60s.

[0014] Preferably, the process of waiting for the mortar to solidify before demolding and curing specifically involves placing the mold and sample together in a constant temperature and humidity curing chamber and curing at 25°C and 80% humidity for 18 hours. After curing, the mold is removed, and the sample is placed in the curing chamber and cured for another 14 days at 25°C and 80% humidity.

[0015] An artificial rock core is prepared by the method described above.

[0016] The above-mentioned application of artificial rock cores in the study of surrounding rock of the treatment reservoir.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: This invention discloses a method for preparing artificial rock cores. The method first determines the composition and specifications of the artificial rock core based on the rock type of the selected high-level radioactive waste disposal site. This targeted design avoids the limitations of relying on original rock core materials from specific regions, making the material sources more widely available. Secondly, the ingredients meeting the specifications are pre-dried, weighed, and at least one of a water-reducing agent, a retarder, and an early-strength agent is added. These are then mixed with water in batches to obtain a uniform mortar. These additives optimize the mortar's properties; for example, the water-reducing agent improves fluidity, and the early-strength agent accelerates hardening, making the preparation process more efficient and controllable, reducing material waste due to experimental failures, and indirectly meeting the requirements of large-scale production. Next, the mortar is added to a mold in batches and compacted to ensure a uniform and dense structure of the artificial rock core, improving material utilization. Finally, after the mortar has solidified, it is demolded and cured to obtain the artificial rock core. This method eliminates the dependence on original core materials by independently preparing artificial cores, solving the problem of difficult acquisition. At the same time, by optimizing the preparation process and material properties, it improves the preparation efficiency and success rate, and can stably produce artificial cores that meet research needs, effectively addressing the challenge of large demand.

[0018] Furthermore, when the rock type is claystone, the ingredients consist of a binder, aggregate, and weighting agent; the binder includes cement and gypsum, the aggregate is quartz sand, and the weighting agent includes barite powder and iron powder. When the rock type is claystone, the ingredients are clearly defined as a binder (cement and gypsum), aggregate (quartz sand), and weighting agent (barite powder and iron powder), which can accurately simulate the characteristics and structure of claystone, making the prepared artificial rock core closer to the physicochemical properties of real claystone. This provides a more reliable material basis for research on high-level radioactive waste disposal based on claystone, and improves the accuracy and effectiveness of research results.

[0019] Furthermore, during the pre-drying process, the temperature is 90℃ and the time is 12 hours. These suitable temperature and time conditions can effectively remove moisture from the ingredients, avoid the adverse effects of moisture on the subsequent preparation process and the performance of the artificial core, ensure the stability of the ingredient quality, and thus improve the overall quality and performance consistency of the artificial core.

[0020] Furthermore, the process of determining the component ratio is as follows: several influencing factors are set through the orthogonal experimental principle, and several levels are set for each factor to obtain the orthogonal experimental ratio. The batching experiment is carried out according to the orthogonal experimental ratio, and the mechanical properties, permeability, and radionuclide diffusion properties of the obtained experimental artificial rock core are tested. The ratio of the sample with the best performance is selected as the final component ratio. This method can scientifically and systematically screen out the optimal component ratio, so that the prepared artificial rock core achieves the best performance in terms of mechanics, permeability, and radionuclide diffusion, and better meets the strict requirements of high-level radioactive waste disposal research for core performance.

[0021] Furthermore, when mixing the solid material with water in batches, each batch of raw material is 1 / 3 to 1 / 5 of the total raw material mass. This batch addition method allows the solid material and water to be mixed more fully and evenly, avoiding the problem of uneven mixing caused by adding all at once, improving the quality and uniformity of the mortar, and thus ensuring the uniformity of the internal structure of the artificial rock core.

[0022] Furthermore, when mixing solid materials and water in batches simultaneously, after each batch of solid materials and water is mixed, it is stirred for 15-20 minutes before adding the next batch of solid materials and water. The reasonable stirring time can ensure that each batch of solid materials and water reacts and mixes fully, further enhancing the mixing effect, making the mortar performance more stable, and helping to improve the quality of artificial rock cores.

[0023] Furthermore, during the compaction process, the pressure is 10-20 MPa, and the compaction time is 30-60 seconds each time. Appropriate pressure and time parameters can ensure that the mortar is fully compacted in the mold, expel internal air bubbles and excess water, improve the density of the artificial rock core, enhance its mechanical properties, and make it more in line with research requirements.

[0024] Furthermore, the process of waiting for the mortar to solidify before demolding and curing is as follows: the mold and the sample are placed together in a constant temperature and humidity curing chamber and cured at 25°C and 80% humidity for 18 hours. After curing, the mold is removed, and the sample is placed in the curing chamber and cured for another 14 days at 25°C and 80% humidity. Precise curing conditions can provide a stable solidification environment for the artificial rock core, allowing its strength and other properties to be fully developed and stabilized, thus ensuring the quality and performance of the artificial rock core. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the process flow for a method of preparing artificial clay rock cores according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the mold device in this invention; wherein, 1, shell; 2, sample groove; 3, clamping cover; Figure 3 The mechanical test stress-strain curve of an artificial clay rock core provided in Embodiment 1 of the present invention; Figure 4 The permeability test results of an artificial clay rock core provided in Embodiment 1 of the present invention; Figure 5 The results of the nuclide diffusion performance test of an artificial clay rock core provided in Embodiment 1 of the present invention are shown, wherein (a) is the Cs ion diffusion curve and (b) is the Sr ion diffusion curve. Detailed Implementation

[0027] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0029] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0030] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0031] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0032] This invention provides a method for preparing artificial rock cores, comprising the following steps: S1: Determine the composition and specifications of the artificial core based on the rock type of the site selection area for the high-level radioactive waste disposal facility; Here, a high-level radioactive waste repository refers to an underground facility used to store high-level radioactive waste (high-level radioactive waste) that has been processed by relevant departments and to carry out long-term geological disposal of nuclear waste. It is usually located hundreds of meters underground.

[0033] The rock type includes one of granite and claystone. When determining the ingredients and specifications of the artificial rock core according to the rock type, existing technologies such as sandstone artificial rock core technology, carbonate artificial rock core technology, and claystone artificial rock core technology are referenced.

[0034] When the rock type is clay rock, the ingredients consist of cementitious agents, aggregates, and weighting agents; The binder includes cement and gypsum, the aggregate is quartz sand, and the weighting agent includes barite powder and iron powder.

[0035] Specifically, the cement is 425-mesh cement with a silica content greater than 90%; the gypsum is high-quality gypsum with a calcium sulfate content greater than 95%; the quartz sand is quartz sand with a silica content greater than 90% and a particle size of 0.3~0.5mm; the barite powder is 800-mesh barium sulfate powder with a barium sulfate content greater than 95%; and the iron powder is 100-mesh refined iron powder with an iron content of 99%.

[0036] S2: Pre-dry the ingredients that meet the specifications, weigh the ingredients according to the predetermined composition ratio, add at least one of water-reducing agent, retarder and early strength agent, mix evenly to obtain solid material, and then mix the solid material with water in batches to obtain mortar. During the pre-drying process here, the temperature is 90℃ and the heating time is 12 hours. After this pre-drying process, the moisture in the ingredients is effectively removed, so that the moisture content of the raw materials meets the experimental requirements. That is, the pre-drying process here is a heating dehydration process. In a further preferred embodiment, the determination process of the component ratio is as follows: several influencing factors are set through the orthogonal experimental principle, and several levels are set for each factor to obtain the orthogonal experimental ratio. The batching experiment is carried out according to the orthogonal experimental ratio, and the mechanical properties, permeability and radionuclide diffusion properties of the obtained experimental artificial rock core are tested. The ratio of the sample with the best performance is selected as the final component ratio.

[0037] When the rock type is clay rock, the influencing factors set in the orthogonal experiment are the bone glue ratio, the mass of the weight gain agent and the ratio of the weight gain agent and the total mass of the aggregate, the proportion of iron powder in the weight gain agent, and the ratio of cement to gypsum, and each influencing factor is set with three levels. The bone-bond ratio here refers to the mass ratio of aggregate to binder.

[0038] The water-reducing agent is a polycarboxylate water-reducing agent, preferably in powder form. Its dosage is 0.6% of the mass of the binder. It is added to the raw materials before adding water and mixed evenly to ensure that the mortar can still maintain good fluidity even with a small amount of water added, thus providing an experimental basis for the mixing of raw materials and the contact reaction between cement and water.

[0039] The retarder is a silicate cement-compatible retarder, and its dosage is 0.8% of the cement mass. It is added at the same time as the water-reducing agent. When the mortar prepared by the batching solidifies in a relatively short time, it is not conducive to subsequent filling and molding. Therefore, a retarder needs to be added to ensure the smooth progress of the filling and molding process.

[0040] The amount of the early strength agent is 1.2% of the mass of the binder, and it is added simultaneously with the water-reducing agent. If the binder content is low in certain proportions, the mortar will remain in a soil-like state for a long time without the action of the early strength agent, and will not be able to be molded and demolded. Therefore, the early strength agent is added to the raw materials in this proportion to ensure the smooth progress of the molding and demolding process.

[0041] During the batch mixing process, each batch of raw materials added is 1 / 3 to 1 / 5 of the total raw material mass. Preferably, after the solid materials are mixed evenly, water and solid materials are usually added in five batches, that is, each batch is one-fifth of the total amount. After adding, the mixture is thoroughly stirred with a mixer for 15 to 20 minutes. That is, after each batch of solid materials and water is mixed, the next batch of solid materials and water is added after stirring for 15 to 20 minutes. The purpose is to ensure that the water and raw materials are fully mixed with a small amount of water, so as to facilitate the formation of fluid mortar.

[0042] Here, the ingredients that meet the specifications are pre-dried, and weighed according to a predetermined component ratio. At least one of a water-reducing agent, retarder, and accelerator is added and mixed evenly to obtain a solid material. Then, the solid material is mixed with water in batches simultaneously to obtain mortar. Specifically: all ingredients are placed on an iron tray, ensuring uniform heating, and then placed in a drying oven for dehydration. The dried ingredients are then weighed according to the ratio, and one of a water-reducing agent, retarder, or accelerator is added. This mixture is then placed in a mixing drum and stirred evenly to obtain a solid material. This stirring can be manual or automatic. Water and solid material are then added in batches simultaneously in the mixing drum, and the mixture is stirred evenly before adding the next batch of water and raw materials. This process, by mixing water and solid material in small batches, effectively avoids the situation where the solid material clumps and cannot be stirred or evenly mixed due to a single mixing. During the mixing process of water and solid material, a mixer ensures that the mortar is fully mixed.

[0043] In addition, ten samples are usually prepared under one ratio for parallel observation; S3: Add the mortar into the mold in batches, and compact it after each addition; Specifically, the raw materials are mixed evenly and then filled into a special stainless steel mold. This mold can ensure that the diameter of similar samples is within 50 mm and the error is less than 0.1 mm, so that the geometric dimensions of the formed samples strictly meet the standards and satisfy the requirements of subsequent experiments.

[0044] In addition, before filling the mold, a soft brush is used to apply lubricating oil evenly to the inside of the mold. This step is intended to reduce the adhesion between the mortar and the inner wall of the mold, making it easier to demold the raw material after it has solidified, and also to produce a smooth, bubble-free surface for the sample.

[0045] Meanwhile, the mortar is placed into the stainless steel mold in batches. After each batch of mortar is added, it is pressurized up and down through the plug. The pressure is 10-20 MPa, and the compaction time is maintained at 30-60 seconds each time. The pressurization is carried out about five times. The mortar is added to the mold in three batches and pressurized three times in total.

[0046] S4: After the mortar has solidified, demold and cure it to obtain the artificial rock core. That is, after the mortar has solidified, demold the core sample and place it in a constant temperature and humidity curing chamber for curing to finally obtain a stable core sample.

[0047] The specific steps are as follows: After the mortar has solidified, place the mold and sample together in a constant temperature and humidity curing chamber and cure for 18 hours at 25℃ and 80% humidity. Then, remove the mold and place the sample in the curing chamber again for 14 days at 25℃ and 80% humidity to complete the sample preparation. After demolding, the sample is placed in a constant temperature curing chamber for further curing to maintain the exothermic hydration reaction in the sample, enabling the sample to have strength similar to claystone.

[0048] The method for preparing artificial rock cores proposed in this invention provides a sample foundation and experimental conditions for laboratory research in specific regional repositories, filling a gap in this field. The raw materials used in this invention can reasonably simulate the properties of claystone in specific regions. Through the addition of water-reducing agents, early-strength agents, and retarders, and improvements in the preparation process, this invention enables the preparation of claystone-like artificial rock cores with low porosity, low water content, and high density. The unique process of this experiment, the pre-drying and thorough mixing of raw materials, and subsequent curing ensure excellent consistency, homogeneity, and strength close to that of mined rock cores in the artificial samples. By screening different proportions, claystone-like samples simulating different bottom depths and core structures in terms of porosity, mechanical strength, and water content can be obtained under different conditions.

[0049] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0050] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0051] Example 1 Taking a claystone from a certain region as an example, the technical solution of this invention will be explained. The claystone has a water content of 5.8% and a density of 2.43 g / m³. 3 The core sample was prepared as a cylindrical sample with a diameter of 50 mm and a height of 100 mm. Therefore, the theoretical mass of a single sample is 481.05 g, the solid material is 453 g, and the water content is 18% of the solid phase.

[0052] The preparation method is as follows: Figure 1 As shown, the specific steps include: S1: Determine the composition and raw material specifications of the artificial rock core based on the rock type of a certain location; In this embodiment, the rock type is clay rock, so its components, i.e., the ingredients, include cementitious materials, aggregates, and weighting agents. The cementitious material is composed of cement and gypsum, the aggregate is quartz sand, and the weighting agent is barite powder and refined iron powder. The raw material specifications are as follows: the cement is 425-mesh cement with a silica content greater than 90%, the gypsum is high-quality gypsum with a calcium sulfate content greater than 95%, the barite powder is 800-mesh barium sulfate powder with a barium sulfate content greater than 95%, the quartz sand is high-quality quartz sand with a silica content greater than 90% and a particle size of 0.3~0.5mm, and the iron powder is 100-mesh refined iron powder with an iron content of 99%.

[0053] S2: Design orthogonal experiments based on the principle of similarity to determine the proportion and amount of each component sample in each experimental group: Table 1. Influencing factors and their levels in the orthogonal experiment of this embodiment.

[0054] S3: Pre-treatment of raw materials by heating. All raw materials are placed in an iron tray and then heated in a heating chamber at 90℃ for 12 hours to remove moisture. The raw materials are mixed, and 0.6% of FK-A type polycarboxylate superplasticizer (powder) by weight of the binder is added. When preparing samples with a bone-bond ratio of 2:1, an additional 0.8% of silicate cement-compatible retarder by weight of cement is added to slow down the setting time. When preparing samples with a bone-bond ratio of 3:1 and 4:1, an additional 1.2% of a setting accelerator by weight of the binder is added to accelerate the solidification of the raw materials. The samples are mixed evenly in a bucket before adding water. Water and raw materials are usually added to the mixing tank in five batches, each batch being one-fifth of the total volume. After addition, the mixture is thoroughly stirred with a mixer for 15 minutes to ensure even mixing of the raw materials and water.

[0055] In this embodiment, taking the proportion of No. 2 in the orthogonal experiment as an example, the solid materials are weighed as follows: 755g cement, 755g gypsum, 834g barite powder, 2114g quartz sand, 72g iron powder, 9.06g water-reducing agent, and 815.4g water.

[0056] In the orthogonal experiment, 10 portions of each ratio were weighed, that is, 10 parallel experiments were conducted under each ratio, resulting in a total of nine groups of samples; S4: Using a soft brush, apply lubricating oil evenly to the inner wall of a special stainless steel mold (this mold ensures that the diameter of similar samples is within 50mm and the error is less than 0.1mm). Add the mortar to the stainless steel mold in three batches. After each addition, pressurize the mold by moving it up and down through the plug at a pressure of 10-20MPa for 30-60 seconds, repeating five times. A schematic diagram of the mold device used in this compaction process is shown below. Figure 2 As shown, the mold device includes a housing 1, a sample groove 2 inside the housing 1, and a clamping cover 3 on the sample groove 2. The clamping cover 3 can move along the vertical direction of the sample groove 2 under the action of a pressure device; the sample groove 2 is a cylindrical structure.

[0057] S5: After 18 hours, the sample can be demolded. After demolding, the sample is placed in a constant temperature curing chamber with a humidity of 80% and a temperature of 25℃ for further curing. After 14 days, the sample properties are considered to be stable and the preparation is complete.

[0058] The density and porosity of the nine groups of samples were measured, and the test results are shown in Table 2. The data in the table are the average values ​​of the test results of 10 samples in each group. As can be seen from Table 2, the density of the artificial clay rock core prepared in this embodiment can be consistent with that of the original rock in a certain region. The porosity is generally larger due to the exothermic reaction of cement hydration, but the error with the original rock is within 5%, which meets the requirements for use.

[0059] Table 2. Density and porosity test results of the nine sets of artificial clay rock cores prepared in this embodiment.

[0060] Simultaneously, uniaxial compressive mechanical tests were conducted on the nine groups of samples obtained, yielding uniaxial compressive stress-strain curves. Figure 3 ,Depend on Figure 3 The compressive strength, Poisson's ratio, and elastic modulus of each group of samples were calculated using the curves. Specific test results are shown in Table 3, where the data represent the average of the test results for each group of 10 samples. Table 3 shows that although the artificial rock core prepared using the concrete method is rock-like, the stress-strain curves can effectively observe the distribution of rock mass fracture closure, elastic deformation, yielding, deformation failure, and complete failure stages. Furthermore, based on the selection of various parameters, it can be seen that the mix proportion numbered 2 in the orthogonal experiment closely approximates the uniaxial strength, Poisson's ratio, and elastic modulus of the rock core from a depth of 400 meters in a certain area, and closely reflects the properties of the actual rock core. Therefore, this method can effectively select the raw material mix proportion closest to the actual site selection, effectively meeting the usage requirements.

[0061] Table 3. Mechanical property test results of the nine sets of artificial clay rock cores prepared in this embodiment.

[0062] in addition Figure 4 The permeability test results for three parallel samples (i.e., the three parallel samples numbered 2 in Table 1) from the optimal ratio group 2 selected through mechanical testing out of the nine groups of samples prepared in this embodiment are shown in the figure. As can be seen from the figure, the permeability distribution range of this sample is 0.785~2.221×10⁻⁶. -19 m 2 The permeability of the surrounding rock in a typical claystone-type treatment reservoir is generally 1×10⁻⁶. -19 ~1×10 -20 m 2 The average permeability of the samples obtained by this invention is on the order of magnitude, ranging from 0.785 to 2.221 × 10⁻⁶. -19 m 2 Within a certain range, its permeability coefficient can effectively reach 1×10⁻⁶. -20 m 2 The quantity is sufficient to meet usage requirements.

[0063] Figure 5 The diffusion curves of Sr(II) and Cs(I) for sample 2, the optimal mix ratio selected from the nine samples prepared in this embodiment through mechanical testing, are shown in the figure (i.e., the diffusion curves of Sr(II) and Cs(I) for sample number 2 in Table 1). As can be seen from the figure, the diffusion coefficient of Sr(II) in clayey rocks, measured by the penetration diffusion method, is (0.648±0.093)×10⁻⁶. -12 m 2 ·s -1 The diffusion coefficient of Cs(Ⅰ) in clayey rocks is (1.408±0.095)×10 -12 m 2 ·s -1 Relevant test data of Sr(II) and Cs(I) in claystone and clay minerals indicate that the diffusion coefficient is within 1×10⁻⁶. -10 ~×10 -12 m 2 ·s -1 All of them are distributed, therefore, the diffusion performance of the similar sample prepared by this invention is on the same order of magnitude as that of the original rock, and it can effectively replace the original rock.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing an artificial rock core, characterized in that, Includes the following steps: S1: Determine the composition and specifications of the artificial core based on the rock type of the site selection area for the high-level radioactive waste disposal facility; S2: Pre-dry the ingredients that meet the specifications, weigh the ingredients according to the predetermined composition ratio, add at least one of water-reducing agent, retarder and early strength agent, mix evenly to obtain solid material, and then mix the solid material with water in batches to obtain mortar. S3: Add the mortar into the mold in batches, and compact it after each addition; S4: After the mortar has solidified, demolding and curing are carried out to obtain the artificial rock core.

2. The method for preparing an artificial rock core according to claim 1, characterized in that, When the rock type is clay rock, the ingredients consist of a binder, aggregate, and weighting agent; the binder includes cement and gypsum, the aggregate is quartz sand, and the weighting agent includes barite powder and iron powder.

3. The method for preparing an artificial rock core according to claim 1, characterized in that, The pre-drying process is carried out at a temperature of 90°C for 12 hours.

4. The method for preparing an artificial rock core according to claim 1, characterized in that, The process of determining the component ratio is as follows: several influencing factors are set through the orthogonal experimental principle, and several levels are set for each factor to obtain the orthogonal experimental ratio. The batching experiment is carried out according to the orthogonal experimental ratio, and the mechanical properties, permeability and radionuclide diffusion properties of the obtained artificial rock core are tested. The ratio of the sample with the best performance is selected as the final component ratio.

5. The method for preparing an artificial rock core according to claim 1, characterized in that, When mixing solid materials with water in batches, each batch of raw materials added is 1 / 3 to 1 / 5 of the total raw material mass.

6. The method for preparing an artificial rock core according to claim 1, characterized in that, When mixing solid materials and water in batches simultaneously, after each batch of solid materials and water is mixed, it is stirred for 15 to 20 minutes before adding the next batch of solid materials and water.

7. The method for preparing an artificial rock core according to claim 1, characterized in that, During the compaction process, the pressure is 10-20 MPa, and the compaction time is 30-60 seconds each time.

8. The method for preparing an artificial rock core according to claim 1, characterized in that, The process of waiting for the mortar to solidify, followed by demolding and curing, involves placing the mold and sample together in a constant temperature and humidity curing chamber and curing at 25°C and 80% humidity for 18 hours. After curing, the mold is removed, and the sample is placed back in the curing chamber and cured for another 14 days at 25°C and 80% humidity.

9. An artificial rock core, characterized in that, It is prepared by the method described in any one of claims 1 to 8.

10. The application of the artificial rock core as described in claim 9 in the study of the surrounding rock of the treatment reservoir.

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