Evaluation method, device, equipment and medium for coal rock true triaxial fracturing sample containing cleat structure

Abstract

The present application provides a kind of coal rock true triaxial fracturing sample evaluation method, device, equipment and medium containing cleavage structure, the evaluation method first prepares multiple groups of gradient artificial coal rock sample, then selects the optimal proportion of artificial coal rock sample, subsequently inorganic salt and inorganic salt flake are filled in cleavage structure, and the inorganic salt and inorganic salt flake reserved are removed by cleavage network activation, and the coal rock true triaxial fracturing sample is prepared, finally CRITIC-TOPSIS evaluation model is used to carry out comprehensive evaluation, and then the optimal formula of coal rock true triaxial fracturing sample is determined.

Description

Technical Field

[0001] This invention belongs to the technical field of indoor physical simulation experiments for coalbed methane development, and relates to an evaluation method, device, equipment and medium for true triaxial fracturing samples of coal and rock with cleavage structure. Background Technology

[0002] Coalbed methane (CBM), as an important unconventional natural gas resource, occupies a crucial strategic position in the energy structure. With the gradual development of shallow CBM resources, deep CBM reservoirs (burial depths greater than 1500m) have become an important replacement area for increasing CBM reserves and production. Compared with shallow CBM, deep coal reservoirs are characterized by high geostress, strong heterogeneity, well-developed primary cleavage, and significant mechanical anisotropy. Their fracturing initiation and propagation mechanisms differ from those of conventional sandstone reservoirs, making traditional fracturing theories difficult to adapt to the refined design requirements of deep CBM fracturing.

[0003] Indoor true triaxial hydraulic fracturing physical simulation experiments are a core method for studying the propagation law of fracturing fractures in deep coal reservoirs. This technology can recreate the true triaxial stress state of underground coal reservoirs, simulate the propagation of fracturing fractures, and study the fracture propagation law in conjunction with different monitoring methods. The preparation of true triaxial fracturing samples is a crucial factor in the authenticity and accuracy of true triaxial fracturing experimental results. The structural fidelity and mechanical similarity of the coal and rock samples determine the uniformity of experimental stress loading, the authenticity of fracture propagation law, and the reliability of test data, making it a fundamental step in fracturing simulation experiments.

[0004] However, existing sample preparation technologies suffer from core bottlenecks such as poor structural fidelity, insufficient processing precision, weak batch consistency, low matching degree with real formations, low yield, and insufficient reliability of experimental data. Furthermore, multi-index evaluation of formulations is a critical and complex challenge for researchers, hindering in-depth research on coal fracturing mechanisms and failing to provide reliable experimental support for optimizing fracturing designs for the efficient development of deep, low-permeability coalbed methane.

[0005] Therefore, developing a high-fidelity, high-precision, and highly adaptable evaluation method for true triaxial fracturing samples of coal and rock has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide an evaluation method, apparatus, equipment, and medium for true triaxial fracturing samples of coal and rock containing cleavage structures, which is suitable for in-depth research on the fracturing mechanism of coal and rock and provides reliable experimental support for the optimization of fracturing design for the efficient development of deep, low-permeability coalbed methane.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides an evaluation method for true triaxial fracturing specimens of coal and rock containing cleavage structures, the evaluation method comprising: The target stratum coal and rock are obtained and crushed to obtain coal and rock powder of different grades; the coal and rock powder of different grades, cementitious materials and aggregate materials are mixed to prepare multiple sets of gradient artificial coal and rock samples; Based on the mechanical parameters of the coal and rock in the target strata, the optimal ratio of artificial coal and rock samples was selected. The selected artificial coal and rock samples are loaded into a mold and subjected to the first pressure molding to prefabricate surface cleavage and end cleavage that perfectly match the natural cleavage occurrence of the target stratum. Inorganic salts and inorganic salt sheets are used to fill the mold and construct the first layer of cleavage network of coal and rock. The above operation is repeated to construct cleavage networks of other layers. Then, the first static curing, the first standard curing and cleavage network activation are performed in sequence to obtain a true triaxial fracturing sample of coal and rock. Evaluation index data of the true triaxial fracturing samples of coal and rock were collected and preprocessed, and then the CRITIC-TOPSIS evaluation model was used for comprehensive evaluation.

[0008] In this invention, the formulation of multiple sets of gradient artificial coal and rock samples is mainly achieved by adjusting the ratio between coal and rock powders of different particle sizes.

[0009] The evaluation method provided by this invention first prepares multiple sets of gradient artificial coal and rock samples, then selects the artificial coal and rock sample with the optimal ratio, subsequently fills the cleavage structure with inorganic salts and inorganic salt flakes, and removes the reserved inorganic salts and inorganic salt flakes through cleavage network activation to obtain a true triaxial fracturing sample of coal and rock. Finally, a comprehensive evaluation is performed using the CRITIC-TOPSIS evaluation model to determine the optimal formulation of the true triaxial fracturing sample of coal and rock. The method is more standardized and considers more comprehensive factors, ensuring the authenticity and accuracy of the physical simulation experimental results of true triaxial fracturing, and providing technical support for the efficient development of deep, low-permeability coalbed methane.

[0010] It should be noted that the natural coal and rock in the target stratum is not homogeneous, but rather a multi-scale aggregate composed of particles of different sizes. Therefore, this invention uses coal and rock powders with different gradations. The functional roles of various coal and rock powders in the gradation scheme are as follows: large-particle-size skeleton coal and rock powders provide particle support and maintain the stress transmission path near cleavages; medium-particle-size filling coal and rock powders fill the skeleton pores, enhance the interlocking density between skeleton particles, and suppress local segregation; small-particle-size interstitial coal and rock powders fill the residual pores, improve cementation continuity, and achieve fine control over porosity and permeability.

[0011] By using the synergistic gradation of coal and rock powders of different particle sizes, problems such as excessive homogenization of samples, distortion of pore connectivity, and deviation of fracture propagation paths from reality caused by single fine powder preparation are overcome. This also avoids the defects of poor forming stability, excessively large pores, and high dispersion of mechanical parameters caused by single coarse particle preparation. Thus, accurate simulation of the multi-scale particle composition, pore structure, and mechanical heterogeneity of natural coal and rock is achieved, making the samples more closely resemble actual formation conditions.

[0012] It should be noted that by using inorganic salts and inorganic salt flakes to construct cleavage structures, the degree of crack penetration, aperture, and location can be precisely controlled. The inorganic salts and inorganic salt flakes pre-existing in the coal and rock can be removed by water activation, leaving no residue and causing no new pollution. The method is simple to implement.

[0013] It should be noted that the CRITIS-TOPSIS evaluation model is used to objectively score each influencing indicator, avoiding the subjectivity and uncertainty in indicator selection. This allows for a comprehensive evaluation of the formulation of true triaxial fracturing samples of coal and rock, and ultimately determines the optimal formulation composition.

[0014] Preferably, the coal and rock powders with different gradations include: skeletal coal and rock powder with an average particle size > 5 mm and ≤ 20 mm, filled coal and rock powder with an average particle size > 1 mm and ≤ 5 mm, and interstitial coal and rock powder with an average particle size > 0.075 mm and ≤ 1 mm.

[0015] Preferably, the mass percentage of the skeleton coal powder in the different gradations of coal powder is 60% to 80%, for example, it can be 62%, 64%, 65%, 66%, 68%, 70%, 72%, 74%, 75%, 76% or 78%, etc.

[0016] Preferably, the mass percentage of coal and rock powder filling in the different gradations is 15% to 30%, for example, it can be 17%, 18%, 20%, 22%, 24%, 25%, 26% or 28%, etc.

[0017] Preferably, the mass percentage of interstitial coal and rock powder in the different gradations is 5% to 25%, for example, it can be 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, or 24%, etc.

[0018] Preferably, the cementitious material includes cement.

[0019] Preferably, the aggregate material includes quartz sand.

[0020] Preferably, the aggregate material has a mesh size of 40 to 70 mesh, such as 42 mesh, 45 mesh, 48 mesh, 50 mesh, 52 mesh, 55 mesh, 58 mesh, 60 mesh, 62 mesh, 65 mesh, 66 mesh, or 68 mesh.

[0021] Preferably, the mass ratio of the coal and rock powder, cementitious materials and aggregate materials of different grades is (25~35):(30~40):(25~35), for example, it can be 25:30:25, 30:35:30 or 35:40:35, etc.

[0022] Preferably, the method for preparing the artificial coal and rock sample includes sequentially performing a first stirring, a second stirring, a second pressure molding, a second settling, and a second standard curing.

[0023] Preferably, the solvent is added during the second stirring.

[0024] Preferably, the mass ratio of the gelling material to the solvent is 1:(0.4~0.6), for example, it can be 1:0.42, 1:0.45, 1:0.46, 1:0.48, 1:0.5, 1:0.52, 1:0.55, 1:0.56 or 1:0.58, etc.

[0025] Preferably, the screening conditions are that the relative deviation of the mechanical properties of the artificial coal and rock sample from those of the target stratum is ≤5%, and there are no original microcracks inside.

[0026] Preferably, before the artificial coal and rock sample is loaded into the mold, the inner wall of the mold is wiped and coated with a release agent in sequence.

[0027] Preferably, the pressure of the first pressurization molding is 1 kPa to 2 kPa, for example, it can be 1.1 kPa, 1.2 kPa, 1.3 kPa, 1.4 kPa, 1.5 kPa, 1.6 kPa, 1.7 kPa, 1.8 kPa or 1.9 kPa.

[0028] Preferably, the first pressure molding time is 6h to 12h, for example, it can be 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h or 11.5h.

[0029] Preferably, the inorganic salt includes sodium chloride.

[0030] Preferably, the thickness of the inorganic salt sheet is 1mm to 3mm, for example, it can be 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.6mm or 2.8mm, etc.

[0031] Preferably, the inorganic salt flakes include sodium chloride flakes.

[0032] Preferably, the cutting height of the cutting network is the thickness of the first layer, and the width is 1mm to 3mm, for example, it can be 1.2mm, 1.5mm, 1.6mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.6mm or 2.8mm, etc.; the opening is 0.1mm to 1.2mm, for example, it can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, etc. Preferably, the method for activating the cleavage network includes immersing the sample in water for at least 48 hours.

[0033] Preferably, the evaluation index data includes mechanical indices, reservoir physical property indices, and cleavage characteristic indices; Preferably, the mechanical evaluation indicators include uniaxial compressive strength (UCS), elastic modulus (E), Poisson's ratio (μ), and Brazilian splitting tensile strength (σ). t ), internal friction angle (φ), and cohesion (c).

[0034] Preferably, the reservoir properties include effective porosity (Φ) and permeability (K).

[0035] Preferably, the cleavage characteristic indicators include the average cleavage aperture (D), cleavage surface density (ρ), and cleavage connectivity (η).

[0036] Preferably, the preprocessing includes removing outliers and using the arithmetic mean as the measured value of the corresponding index of the formula.

[0037] Preferably, the comprehensive evaluation method of the CRITIC-TOPSIS evaluation model includes: (1) Data normalization processing: The normalization process maps all evaluation index data to the interval [0,1] through linear transformation, where all evaluation index data are moderate indicators, as shown in the following formula (I): (I) In equation (I), x' ij Let x be the normalized value of the j-th index of the i-th formulation. ij T represents the measured average value of the j-th index of the i-th formulation. j The unique objective value for the j-th indicator is max|x ij -T j | represents the maximum absolute deviation between the j-th indicator and the target value in all formulations; (2) CRITIC weight calculation: First, calculate the variability of the j-th indicator, i.e., the standard deviation. The formula is shown in equation (II) below: (II) In formula (II), The arithmetic mean of the normalized values ​​of all formulas for the j-th index; Then, the correlation coefficients between the indicators are calculated, and the Pearson correlation coefficient matrix R = (r jk ) n×n , where r jk Let be the correlation coefficient between the j-th indicator and the k-th indicator; Next, calculate the information carrying capacity C of the indicator. j The formula is shown in equation (III) below: (III) Finally, the weight w of each indicator is calculated. j The formula is shown in equation (IV) below: (IV) (3) Construct a weighted decision matrix: The weights calculated by the CRITIC method are combined with the normalized matrix to construct the weighted normalized matrix Z=(z ij ) m×n , z ij The formula is shown in equation (V) below: (V) (4) Determine the positive ideal solution Z for each index. + and negative ideal solution Z - The formulas are shown in equations (VI) and (VII) below, respectively: (VI) (VII) (5) Calculate the Euclidean distance and the overall score Calculate the Euclidean distance D from the i-th formula to the positive ideal solution. i + The Euclidean distance D to the negative ideal solution i - The formulas are shown in equations (VIII) and (IX) below, respectively: (VIII) (IX) Calculate the overall score S (out of 100) for the i-th recipe. i The formula is shown in equation (X) below: (X) (6) Classification of formulation performance levels and determination of optimal formulation Formulas are graded based on a comprehensive score, with higher scores indicating higher performance levels, specifically S. i ≥90 points is excellent, 80 points ≤S i <90 points is Good, 70 points ≤S i A score below 80 indicates a passing grade, S i A score of 70 or below is considered unqualified. The formula with the highest overall score is the optimal formula.

[0038] The evaluation method provided by this invention is also applicable to true triaxial fracturing specimens of coal and rock without cleavage. The preparation method of true triaxial fracturing specimens of coal and rock without cleavage is not specifically limited here. It can be prepared by referring to the prior art or by the following method.

[0039] In this invention, the method for preparing the true triaxial fracturing specimen of coal and rock without cleavage structure includes: Obtain coal and rock from the target stratum, crush them to obtain ultrafine coal and rock powder; mix the ultrafine coal and rock powder, cementitious materials and aggregate materials to prepare multiple sets of gradient artificial coal and rock samples; The ultrafine coal and rock powder is obtained by passing it through a 200-mesh sieve. Based on the mechanical parameters of the coal and rock in the target strata, the optimal ratio of artificial coal and rock samples was selected. All the selected artificial coal and rock samples were loaded into the mold, and then subjected to vibration, static treatment and standard curing in sequence to obtain true triaxial fracturing samples of coal and rock without cleavage structure.

[0040] Secondly, the present invention provides a sample preparation and evaluation device for true triaxial fracturing samples of coal and rock, the sample preparation and evaluation device comprising: The artificial coal and rock sample preparation module is used to obtain coal and rock from the target stratum, crush it to obtain coal and rock powder of different grades, and mix the coal and rock powder of different grades, cementitious materials and aggregate materials to prepare multiple sets of gradient artificial coal and rock samples. The screening module is used to select the optimal ratio of artificial coal and rock samples based on the mechanical parameters of coal and rock in the target stratum. The coal and rock true triaxial fracturing sample preparation module is used to load the selected artificial coal and rock samples into a mold and perform the first pressure molding, prefabricate the face cleavage and end cleavage that are completely matched with the natural cleavage occurrence of the target stratum, and fill them with inorganic salts and inorganic salt sheets to construct the first layer of cleavage network of coal and rock. Then, the above operation is repeated to construct the cleavage network of other layers. Subsequently, the first static setting, the first standard curing and the cleavage network activation are performed in sequence to obtain the coal and rock true triaxial fracturing sample. The comprehensive evaluation module is used to collect and preprocess the evaluation index data of the true triaxial fracturing samples of coal and rock, and then use the CRITIC-TOPSIS evaluation model for comprehensive evaluation.

[0041] Thirdly, the present invention provides an electronic device, the electronic device comprising: At least one processor; and A memory communicatively connected to the at least one processor; wherein, The memory stores a computer program that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the evaluation method for true triaxial fracturing samples of coal and rock as described in the first aspect.

[0042] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a processor to execute and implement the evaluation method for true triaxial fracturing samples of coal and rock as described in the first aspect.

[0043] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0044] Compared with the prior art, the present invention has the following beneficial effects: The evaluation method provided by this invention first prepares multiple sets of gradient artificial coal and rock samples, then selects the artificial coal and rock sample with the optimal ratio, subsequently fills the cleavage structure with inorganic salts and inorganic salt flakes, and removes the reserved inorganic salts and inorganic salt flakes through cleavage network activation to obtain a true triaxial fracturing sample of coal and rock. Finally, a comprehensive evaluation is performed using the CRITIC-TOPSIS evaluation model to determine the optimal formulation of the true triaxial fracturing sample of coal and rock. The method is more standardized and considers more comprehensive factors, ensuring the authenticity and accuracy of the physical simulation experimental results of true triaxial fracturing, and providing technical support for the efficient development of deep, low-permeability coalbed methane. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the evaluation method for true triaxial fracturing samples of coal and rock with cleavage structures provided in Example 1; Figure 2 This is a schematic diagram of the sample preparation and evaluation device for true triaxial fracturing samples of coal and rock provided in the specific implementation method; Figure 3This is a schematic diagram of the electronic equipment structure provided in the specific implementation method for preparing and evaluating true triaxial fracturing samples of coal and rock. Detailed Implementation

[0047] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0048] It should be noted that the terms "first," "second," "candidate," "target," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0049] Example 1 This embodiment provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. This method is applicable to determining the optimal formulation of true triaxial fracturing samples of coal and rock based on the CRITIC-TOPSIS evaluation model. This method can be executed by a well type selection device for deep, thin, and tight sandstone gas reservoirs. The sample preparation and evaluation device for true triaxial fracturing samples of coal and rock can be implemented in hardware and / or software. The sample preparation and evaluation device for true triaxial fracturing samples of coal and rock can be configured in electronic equipment with the ability to prepare and evaluate true triaxial fracturing samples of coal and rock.

[0050] like Figure 1 As shown, the method provided in this embodiment includes: S101. Obtain coal and rock from the target stratum, crush them to obtain coal and rock powder of different grades; mix the coal and rock powder of different grades, cementitious materials and aggregate materials to prepare multiple sets of gradient artificial coal and rock samples.

[0051] In step S101, the coal and rock powders of different gradations include: skeleton coal and rock powder with an average particle size > 5 mm and ≤ 20 mm, filled coal and rock powder with an average particle size > 1 mm and ≤ 5 mm, and interstitial coal and rock powder with an average particle size > 0.075 mm and ≤ 1 mm. The mass percentage of skeleton coal and rock powder in the different gradations is 60%~80%, the mass percentage of filled coal and rock powder is 15%~30%, and the mass percentage of interstitial coal and rock powder is 5%~25%.

[0052] In order to ensure the uniformity of coal and rock powder of different grades in the sample, the cone-shaped quartering method was used to reduce the coal fragments of each grade separately.

[0053] In step S101, the cementitious material is C425 cement conforming to GB 10238 standard; the aggregate material is quartz sand of 40-70 mesh; and the solvent is water.

[0054] In step S101, multiple gradient formulations are set according to mass ratio. The total mass ratio of the formulation is (25~35):(30~40):(25~35) for coal and rock powder, cementitious materials and aggregates of different grades; the mass ratio of cementitious materials to solvent is 1:(0.4~0.6).

[0055] In step S101, the preparation process of artificial coal and rock samples is as follows: weigh the raw materials according to the formula of each group, put them in a mixer and stir for 5 min to 10 min, then add solvent and stir for 6 min to 12 min until the mixture is uniform and free of lumps, put it into a true triaxial sample standard steel mold and perform a second pressing and molding, a second standing for at least 24 h, and then perform a second standard curing after demolding.

[0056] In this embodiment, the temperature of the second standard curing is 20℃±2℃, the relative humidity is ≥95%, and the time is at least 14 days; S102. Based on the mechanical parameters of the coal and rock in the target stratum, select the artificial coal and rock samples with the optimal ratio.

[0057] In step S102, based on the benchmark values ​​of the target stratum coal and rock, a formula with a relative deviation of ≤5% from the mechanical property parameters of the target stratum coal and rock and no original micro-cracks is selected as the optimal formula for this implementation.

[0058] S103. The selected artificial coal and rock samples are loaded into a mold and subjected to the first pressure molding to prefabricate surface cleavage and end cleavage that perfectly match the natural cleavage occurrence of the target stratum. Inorganic salts and inorganic salt sheets are used to fill the mold to construct the first layer of cleavage network of the coal and rock. The above operation is repeated to construct cleavage networks of other layers. Then, the first static curing, the first standard curing and the cleavage network activation are performed in sequence to obtain a true triaxial fracturing sample of coal and rock.

[0059] In step S103, before molding, the mold is pretreated by wiping the inner wall of the 300mm×300mm×300mm true triaxial fracturing test standard steel mold with acetone, and after drying, a release agent (oil-based concrete release agent) is evenly applied to the inner wall of the mold and the surface of the pressure head.

[0060] In step S103, the preparation process of the true triaxial fracturing sample for coal and rock specifically includes: (A) Divide the optimally proportioned artificial coal and rock sample into 4 equal parts; (B) First, the first mixture is loaded into the mold and spread horizontally by scraper. Then, the first pressure molding is carried out. A high-precision scraper is used to pre-form the surface cleavage and end cleavage on the surface of the first pressing layer, which are completely matched with the natural cleavage occurrence of the target layer. Then, inorganic salt powder is uniformly filled into the cleavage groove, and inorganic salt flakes matching the cleavage size are embedded in the cleavage direction to construct the cleavage network of the first layer of coal and rock. Wherein, the pressure of the first pressure molding is 1kPa~2kPa, and the time is 6h~12h; the inorganic salt includes sodium chloride; the inorganic salt sheet includes sodium chloride sheet with a thickness of 1mm~3mm; The cutting height of the cutting network is equal to the thickness of the first layer, the width is 1mm to 3mm, and the opening is 0.1m to 1.2mm. (C) Repeat step (B) to construct the other three layers of the cutting network; (D) After depressurization, the mold is placed at room temperature for a first static period of at least 24 hours, and then demolding, first standard curing, cleavage network activation and finishing are performed in sequence to obtain a true triaxial fracturing sample of coal and rock. The first standard curing temperature is 20℃±2℃, relative humidity is ≥95%, and the time is at least 14 days; The method for activating the cleavage network includes immersing the sample in water for at least 48 hours; The finishing method includes grinding both ends of the sample to ensure that the non-parallelism and non-perpendicularity of the end faces are ≤0.02mm.

[0061] In the above preparation process, a scraper is used to spread the first batch of mixture back and forth in the horizontal direction to ensure that the large-diameter coal fragments are evenly distributed to form a stable skeleton.

[0062] S104. Collect and preprocess the evaluation index data of the true triaxial fracturing samples of coal and rock, and then use the CRITIC-TOPSIS evaluation model for comprehensive evaluation.

[0063] In step S104, the evaluation index data includes mechanical indices, reservoir physical property indices, and cleavage characteristic indices; the mechanical evaluation indices include uniaxial compressive strength, elastic modulus, Poisson's ratio, Brazilian splitting tensile strength, internal friction angle, and cohesion; the reservoir physical property indices include effective porosity and permeability; the cleavage characteristic indices include average cleavage aperture, cleavage surface density, and cleavage connectivity.

[0064] In step S104, the preprocessing includes removing outliers and using the arithmetic mean as the measured value of the corresponding index of the formula.

[0065] In this embodiment, all evaluation index tests conform to "GB / T 23561 Methods for Determination of Physical and Mechanical Properties of Coal and Rock" and "SY / T 5368 Methods for Testing Rock Mechanical Parameters". For each formulation, at least three standard parallel samples must be prepared. After removing outliers, the arithmetic mean is taken as the measured value of the index for that formulation, ensuring the statistical reliability of the data.

[0066] In step S104, the comprehensive evaluation method of the CRITIC-TOPSIS evaluation model includes: (1) Data normalization processing: The normalization process maps all evaluation index data to the interval [0,1] through linear transformation, where all evaluation index data are moderate indicators, as shown in the following formula (I): (I) In equation (I), x' ij Let x be the normalized value of the j-th index of the i-th formulation. ij T represents the measured average value of the j-th index of the i-th formulation. j The unique objective value for the j-th indicator is max|x ij -T j | represents the maximum absolute deviation between the j-th indicator and the target value in all formulations; Where, x' ij The closer the value is to 1, the smaller the numerical deviation from the target coal and rock layer.

[0067] (2) CRITIC weight calculation: First, calculate the variability of the j-th indicator, i.e., the standard deviation. The formula is shown in equation (II) below: (II) In formula (II), The arithmetic mean of the normalized values ​​of all formulas for the j-th index; in, The higher the value, the stronger the ability of the indicator to distinguish between different formulations, and the higher the information value.

[0068] Then, the correlation coefficients between the indicators are calculated, and the Pearson correlation coefficient matrix R = (r jk ) n×n , where r jk Let r be the correlation coefficient between the j-th indicator and the k-th indicator; jk The closer to 1, the higher the information overlap between the two indicators and the lower the conflict, so the weight should be reduced accordingly.

[0069] Next, calculate the information carrying capacity C of the indicator. j The formula is shown in equation (III) below: (III) Among them, C j The larger the value, the higher the evaluation weight of that indicator.

[0070] Finally, the weight w of each indicator is calculated. j The formula is shown in equation (IV) below: (IV) (3) Construct a weighted decision matrix: The weights calculated by the CRITIC method are combined with the normalized matrix to construct the weighted normalized matrix Z=(z ij ) m×n , z ij The formula is shown in equation (V) below: (V) (4) Determine the positive ideal solution Z for each index. + and negative ideal solution Z - The formulas are shown in equations (VI) and (VII) below, respectively: (VI) (VII) (5) Calculate the Euclidean distance and the overall score Calculate the Euclidean distance D from the i-th formula to the positive ideal solution. i + The Euclidean distance D to the negative ideal solution i - The formulas are shown in equations (VIII) and (IX) below, respectively: (VIII) (IX) Calculate the overall score S (out of 100) for the i-th recipe. i The formula is shown in equation (X) below: (X) (6) Classification of formulation performance levels and determination of optimal formulation Formulas are graded based on a comprehensive score, with higher scores indicating higher performance levels, specifically S. i ≥90 points is excellent, 80 points ≤S i <90 points is Good, 70 points ≤S i A score below 80 indicates a passing grade, S i A score of 70 or below is considered unqualified. The formula with the highest overall score is the optimal formula.

[0071] In this embodiment, the engineering suitability of the formulation can also be determined based on the comprehensive score, as shown in Table 1.

[0072] Table 1 The evaluation method provided by this invention first prepares multiple sets of gradient artificial coal and rock samples, then selects the artificial coal and rock sample with the optimal ratio, subsequently fills the cleavage structure with inorganic salts and inorganic salt flakes, and removes the reserved inorganic salts and inorganic salt flakes through cleavage network activation to obtain a true triaxial fracturing sample of coal and rock. Finally, a comprehensive evaluation is performed using the CRITIC-TOPSIS evaluation model to determine the optimal formulation of the true triaxial fracturing sample of coal and rock. The method is more standardized and considers more comprehensive factors, ensuring the authenticity and accuracy of the physical simulation experimental results of true triaxial fracturing, and providing technical support for the efficient development of deep, low-permeability coalbed methane.

[0073] Example 2 This embodiment takes the No. 8 coal seam in the Linxing Block of Shenfu, Ordos as an example to further explain the composition of the specific technical solution.

[0074] First, based on step S101, coal and rock powder, cementitious materials and aggregates of different grades are mixed in a mass ratio of 30:35:30, and the mass ratio of cementitious materials to solvent is 1:0.5. Multiple groups of gradient artificial coal and rock samples are prepared according to the preparation method provided in Example 1. The specific composition of coal and rock powder of different grades is shown in Table 2.

[0075] Table 2 Secondly, based on step S102, the optimal artificial coal and rock sample was selected by comparing the core mechanical parameters of the target stratum coal and rock with the five formulations (as shown in Table 3).

[0076] Table 3 Then, based on step S103, the selected formulation 3 was used to prepare a true triaxial fracturing sample of coal and rock according to the preparation method provided in Example 1.

[0077] Finally, based on step S104, the weights of each evaluation index are calculated according to formulas (I) to (IV). Then, after determining the index weights using the CRITIC method, the weights are imported into formula (V) to construct a weighted normalization matrix. The positive and negative ideal solutions for each evaluation index are calculated according to formulas (VI) and (VII). Subsequently, the Euclidean distances between the formula and the positive and negative ideal solutions are calculated according to formulas (VIII) and (IX). Finally, the percentage-based comprehensive score of the formula is calculated according to formula (X). The specific data results are shown in Table 4 below.

[0078] Table 4 In this embodiment, S in formulation 3 i It scored 92.6 points, with an excellent performance level, and can be directly used in the core experiments of true triaxial hydraulic fracturing physical simulation.

[0079] The evaluation method provided by this invention first prepares multiple sets of gradient artificial coal and rock samples, then selects the artificial coal and rock sample with the optimal ratio, then fills the cleavage structure with inorganic salts and inorganic salt flakes, and removes the reserved inorganic salts and inorganic salt flakes by cleavage network activation to obtain a true triaxial fracturing sample of coal and rock. Finally, the CRITIC-TOPSIS evaluation model is used for comprehensive evaluation to determine the optimal formulation of the true triaxial fracturing sample of coal and rock.

[0080] Example 3 This embodiment provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. Except for adjusting the mass ratio of skeleton coal and rock powder, filling coal and rock powder and interstitial coal and rock powder in formula 3 to 50:25:25, all other conditions are the same as in Example 3.

[0081] In this embodiment, when the amount of skeleton coal rock powder is too low, it is difficult to form a continuous and stable particle-bearing skeleton inside the sample. The proportion of medium and fine coal rock powder is relatively high, which makes the overall structure of the sample tend to be homogeneous and dense, weakening the original particle support, weak surface distribution and fracture extension characteristics of the target layer coal rock. This leads to an increase in the deviation between the mechanical response and fracture extension law of the true triaxial fracturing sample of coal rock and the natural coal rock.

[0082] Example 4 This embodiment provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. Except for adjusting the mass ratio of skeleton coal and rock powder, filling coal and rock powder and interstitial coal and rock powder in formula 3 to 90:5:5, all other conditions are the same as in Example 3.

[0083] In this embodiment, when the amount of skeleton coal rock powder is too large, the medium and fine-grained coal rock powder is insufficient to fully fill the pores between the skeleton particles. The sample is prone to problems such as local voids, segregation and discontinuous cementation, resulting in excessive internal pores, increased strength dispersion and decreased sidewall stability during the cleavage prefabrication process, which leads to a reduction in the molding quality and test repeatability of the true triaxial fracturing sample of coal rock.

[0084] Example 5 This embodiment provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. Except for adjusting the mass ratio of skeleton coal and rock powder with an average particle size >5mm and ≤20mm in formula 3 to 60% and the mass ratio of filler coal and rock powder with an average particle size >1mm and ≤5mm to 40%, all other conditions are the same as in Example 3.

[0085] In this embodiment, when no interstitial coal rock powder is added, the residual fine pores between the skeleton coal rock powder and the filling coal rock powder are difficult to be fully filled. Cementitious materials are prone to enrichment or absence in local areas, making it difficult to stably control the pore structure and cementation continuity of the sample. Consequently, the porosity, permeability and strength parameters of the true triaxial fracturing coal rock sample fluctuate more.

[0086] Example 6 This embodiment provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. Except for adjusting the mass ratio of skeleton coal and rock powder with an average particle size >5mm and ≤20mm in formula 3 to 60% and interstitial coal and rock powder with an average particle size >0.075mm and ≤1mm to 40%, all other conditions are the same as in Example 3.

[0087] In this embodiment, when no filler coal rock powder is added, there are no transitional particles between the skeleton coal rock powder and the interstitial coal rock powder, the gradation continuity is destroyed, and the interstitial coal rock powder is difficult to uniformly enter the large pores between the skeleton coal rock powder, which easily leads to particle stratification and local density differences, resulting in enhanced non-uniformity of the internal structure of the true triaxial fracturing coal rock sample and increased dispersion of mechanical parameters.

[0088] Comparative Example 1 This comparative example provides an evaluation method for true triaxial fracturing samples of coal and rock containing cleavage structures. Except for replacing the coal and rock powder in Formula 3 with ultrafine coal and rock powder passing through 200 mesh, all other conditions are the same as in Example 3.

[0089] In this comparative example, because coal and rock powders of different grades were not used, the particle size of the sample formed by mixing single ultrafine coal and rock powder with cementitious materials was too uniform. It lacked the skeletal support and multi-level pore structure formed by the combined action of coarse, medium and fine particles in natural coal and rock. The sample was overly homogeneous, with low pore connectivity and the fracture propagation path was too strongly controlled by the cementing matrix. This resulted in a reduction in the realism of the simulation of the heterogeneous structure of the target coal and rock and the fracturing response of the true triaxial fracturing sample.

[0090] The present invention also provides a sample preparation and evaluation device for true triaxial fracturing specimens in coal and rock, such as... Figure 2 As shown, the device includes: an artificial coal and rock sample preparation module 201, a screening module 202, a coal and rock true triaxial fracturing sample preparation module 203, and a comprehensive evaluation module 204. Among them: The artificial coal and rock sample preparation module 201 is used to obtain coal and rock from the target stratum, crush it to obtain coal and rock powder of different grades, and mix the coal and rock powder of different grades, cementitious materials and aggregate materials to prepare multiple sets of gradient artificial coal and rock samples. The screening module 202 is used to screen artificial coal and rock samples with the optimal ratio based on the mechanical parameters of coal and rock in the target stratum. The coal and rock true triaxial fracturing sample preparation module 203 is used to load the selected artificial coal and rock sample into a mold and perform the first pressure molding. Inorganic salt and inorganic salt sheet are used to generate face cleavage and end cleavage in sequence to construct the first layer of cleavage network of coal and rock. Then, the above operation is repeated to construct other layers of cleavage network. Subsequently, the first static setting, the first standard curing and cleavage network activation are performed in sequence to obtain the coal and rock true triaxial fracturing sample. The comprehensive evaluation module 204 is used to collect and preprocess the evaluation index data of the true triaxial fracturing sample of coal and rock, and to conduct a comprehensive evaluation using the CRITIC-TOPSIS evaluation model.

[0091] The device provided in the specific embodiments of the present invention can perform the evaluation method for true triaxial fracturing samples of coal and rock provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects for performing the method.

[0092] The present invention also provides an electronic device for implementing a true triaxial fracturing test sample evaluation method for coal and rock, such as... Figure 3As shown, this electronic device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. This electronic device can also represent various forms of mobile devices, such as personal digital processors, cellular phones, smartphones, wearable devices (such as helmets, glasses, watches, etc.), and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely illustrative and are not intended to limit the implementation of the present application described and / or claimed herein.

[0093] like Figure 3 As shown, the electronic device 10 includes at least one processor 11 and a memory, such as a read-only memory (ROM) 12 or a random access memory (RAM) 13, communicatively connected to the at least one processor 11. The memory stores computer programs executable by the at least one processor. The processor 11 can perform various appropriate actions and processes based on the computer program stored in the ROM 12 or loaded from storage unit 18 into the RAM 13. The RAM 13 can also store various programs and data required for the operation of the electronic device 10. The processor 11, ROM 12, and RAM 13 are interconnected via a bus 14. An input / output (I / O) interface 15 is also connected to the bus 14.

[0094] Multiple components in electronic device 10 are connected to I / O interface 15, including: input unit 16, such as keyboard, mouse, etc.; output unit 17, such as various types of displays, speakers, etc.; storage unit 18, such as secondary storage area, optical disc, etc.; and communication unit 19, such as network card, modem, wireless transceiver, etc. Communication unit 19 allows electronic device 10 to exchange information / data with other devices through computer networks such as the Internet and / or various telecommunications networks.

[0095] Processor 11 can be a variety of general-purpose and / or special-purpose processing components with processing and computing capabilities. Some examples of processor 11 include, but are not limited to, central processing unit (CPU), graphics processing unit (GPU), various special-purpose artificial intelligence (AI) computing chips, various processors running machine learning model algorithms, digital signal processors (DSPs), and any suitable processor, controller, microcontroller, etc. Processor 11 performs the various methods and processes described above, such as the evaluation method for true triaxial fracturing samples in coal and rock.

[0096] In some embodiments, the coal and rock true triaxial fracturing specimen evaluation method can be implemented as a computer program tangibly contained in a computer-readable storage medium, such as storage unit 18. In some embodiments, part or all of the computer program can be loaded and / or installed on electronic device 10 via ROM 12 and / or communication unit 19. When the computer program is loaded into RAM 13 and executed by processor 11, one or more steps of the coal and rock true triaxial fracturing specimen evaluation method described above can be performed. Alternatively, in other embodiments, processor 11 can be configured to perform the coal and rock true triaxial fracturing specimen evaluation method by any other suitable means (e.g., by means of firmware).

[0097] Various embodiments of the systems and techniques described above herein can be implemented in digital electronic circuit systems, integrated circuit systems, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), systems-on-a-chip (SoCs), payload-programmable logic devices (CPLDs), computer hardware, firmware, software, and / or combinations thereof. These various embodiments may include implementations in one or more computer programs that can be executed and / or interpreted on a programmable system including at least one programmable processor, which may be a dedicated or general-purpose programmable processor, capable of receiving data and instructions from a storage system, at least one input device, and at least one output device, and transmitting data and instructions to the storage system, the at least one input device, and the at least one output device.

[0098] Computer programs used to implement the methods of this application may be written in any combination of one or more programming languages. These computer programs may be provided to the processor of a general-purpose computer, a special-purpose computer, or other programmable target-determining device, such that when executed by the processor, the computer programs cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The computer programs may be executed entirely on a machine, partially on a machine, or as a standalone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0099] In the context of this application, a computer-readable storage medium can be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, apparatus, or device. A computer-readable storage medium can be, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium can be a machine-readable signal medium. More specific examples of machine-readable storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0100] To provide interaction with a user, the systems and techniques described herein can be implemented on an electronic device having: a display device (e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor) for displaying information to the user; and a keyboard and pointing device (e.g., a mouse or trackball) through which the user provides input to the electronic device. Other types of devices can also be used to provide interaction with the user; for example, feedback provided to the user can be any form of sensory feedback (e.g., visual feedback, auditory feedback, or tactile feedback); and input from the user can be received in any form (including sound input, voice input, or tactile input).

[0101] The systems and technologies described herein can be implemented in computing systems that include backend components (e.g., as data servers), or middleware components (e.g., application servers), or frontend components (e.g., user computers with graphical user interfaces or web browsers through which users can interact with implementations of the systems and technologies described herein), or any combination of such backend, middleware, or frontend components. The components of the system can be interconnected via digital data communication of any form or medium (e.g., communication networks). Examples of communication networks include local area networks (LANs), wide area networks (WANs), blockchain networks, and the Internet.

[0102] A computing system can include clients and servers. Clients and servers are generally located far apart and typically interact through communication networks. The client-server relationship is created by computer programs running on the respective computers and having a client-server relationship with each other. The server can be a cloud server, also known as a cloud computing server or cloud host, which is a hosting product within the cloud computing service system to address the shortcomings of traditional physical hosts and VPS services, such as high management difficulty and weak business scalability.

[0103] It should be understood that the various forms of processes shown above can be used to rearrange, add, or delete steps. For example, the steps described in this application can be executed in parallel, sequentially, or in different orders, as long as the desired information of the technical solution of this application can be achieved, and this is not limited herein.

[0104] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating true triaxial fracturing specimens of coal and rock containing cleavage structures, characterized in that, The evaluation methods include: The target stratum coal and rock are obtained and crushed to obtain coal and rock powder of different grades; the coal and rock powder of different grades, cementitious materials and aggregate materials are mixed to prepare multiple sets of gradient artificial coal and rock samples; Based on the mechanical parameters of the coal and rock in the target stratum, the optimal ratio of artificial coal and rock samples was selected. The selected artificial coal and rock samples are loaded into a mold and subjected to the first pressure molding to prefabricate surface cleavage and end cleavage that perfectly match the natural cleavage occurrence of the target stratum. Inorganic salts and inorganic salt sheets are used to fill the mold and construct the first layer of cleavage network of coal and rock. The above operation is repeated to construct cleavage networks of other layers. Then, the first static curing, the first standard curing and cleavage network activation are performed in sequence to obtain a true triaxial fracturing sample of coal and rock. Evaluation index data of the true triaxial fracturing samples of coal and rock were collected and preprocessed, and then the CRITIC-TOPSIS evaluation model was used for comprehensive evaluation.

2. The evaluation method according to claim 1, characterized in that, The coal and rock powders with different gradations include: skeletal coal and rock powder with an average particle size > 5 mm and ≤ 20 mm, filled coal and rock powder with an average particle size > 1 mm and ≤ 5 mm, and interstitial coal and rock powder with an average particle size > 0.075 mm and ≤ 1 mm. Preferably, the mass percentage of the skeleton coal powder in the coal powder with different gradations is 60% to 80%; Preferably, the mass percentage of the coal and rock powder filling in the different gradations is 15% to 30%. Preferably, the mass percentage of interstitial coal and rock powder in the different gradations is 5% to 25%.

3. The evaluation method according to claim 1 or 2, characterized in that, The cementitious materials include cement; Preferably, the aggregate material includes quartz sand; Preferably, the aggregate material has a mesh size of 40 to 70 mesh; Preferably, the mass ratio of the coal and rock powder, cementitious materials and aggregate materials with different gradations is (25~35):(30~40):(25~35); Preferably, the method for preparing the artificial coal and rock sample includes sequentially performing a first stirring, a second stirring, a second pressure molding, a second settling, and a second standard curing. Preferably, a solvent is added during the second stirring process; Preferably, the mass ratio of the gelling material to the solvent is 1:(0.4~0.6).

4. The evaluation method according to any one of claims 1-3, characterized in that, The screening criteria are that the relative deviation of the mechanical properties of the artificial coal and rock sample from those of the target stratum is ≤5%, and there are no primary microcracks inside.

5. The evaluation method according to any one of claims 1-4, characterized in that, Before the artificial coal and rock sample is loaded into the mold, the inner wall of the mold is wiped and coated with a release agent in sequence. Preferably, the pressure of the first pressurization molding is 1 kPa to 2 kPa; Preferably, the first pressure molding time is 6h~12h; Preferably, the inorganic salt includes sodium chloride; Preferably, the thickness of the inorganic salt sheet is 1 mm to 3 mm; Preferably, the inorganic salt sheet includes sodium chloride sheet; Preferably, the cutting height of the cutting network is the thickness of the first layer, the width is 1mm~3mm, and the opening is 0.1m~1.2mm; Preferably, the method for activating the cleavage network includes immersing the sample in water for at least 48 hours.

6. The evaluation method according to any one of claims 1-5, characterized in that, The evaluation index data includes mechanical indices, reservoir physical property indices, and cleavage characteristic indices; Preferably, the mechanical evaluation indicators include uniaxial compressive strength, elastic modulus, Poisson's ratio, Brazilian splitting tensile strength, internal friction angle, and cohesion. Preferably, the reservoir properties include effective porosity and permeability; Preferably, the cleavage characteristic indicators include average cleavage aperture, cleavage surface density, and cleavage connectivity. Preferably, the preprocessing includes removing outliers and using the arithmetic mean as the measured value of the corresponding index of the formula.

7. The evaluation method according to any one of claims 1-6, characterized in that, The comprehensive evaluation method of the CRITIC-TOPSIS evaluation model includes: (1) Data normalization processing: The normalization process maps all evaluation index data to the interval [0,1] through linear transformation, where all evaluation index data are moderate indicators, as shown in the following formula (I): （I） In equation (I), x' ij Let x be the normalized value of the j-th index of the i-th formulation. ij T represents the measured average value of the j-th index of the i-th formulation. j The unique objective value for the j-th indicator is max|x ij -T j | represents the maximum absolute deviation between the j-th indicator and the target value in all formulations; (2) CRITIC weight calculation: First, calculate the variability of the j-th indicator, i.e., the standard deviation. The formula is shown in equation (II) below: (II) In formula (II), The arithmetic mean of the normalized values ​​of all formulas for the j-th index; Then, the correlation coefficients between the indicators are calculated, and the Pearson correlation coefficient matrix R = (r jk ) n×n , where r jk Let be the correlation coefficient between the j-th indicator and the k-th indicator; Next, calculate the information carrying capacity C of the indicator. j The formula is shown in equation (III) below: (III) Finally, the weight w of each indicator is calculated. j The formula is shown in equation (IV) below: (IV) (3) Construct a weighted decision matrix: The weights calculated by the CRITIC method are combined with the normalized matrix to construct the weighted normalized matrix Z=(z ij ) m×n , z ij The formula is shown in equation (V) below: （V） (4) Determine the positive ideal solution Z for each index. + and negative ideal solution Z - The formulas are shown in equations (VI) and (VII) below, respectively: (WE) (VII) (5) Calculate the Euclidean distance and the overall score Calculate the Euclidean distance D from the i-th formula to the positive ideal solution. i + The Euclidean distance D to the negative ideal solution i - The formulas are shown in equations (VIII) and (IX) below, respectively: (VIII) (IX) Calculate the overall score S (out of 100) for the i-th recipe. i The formula is shown in equation (X) below: （X） (6) Classification of formulation performance levels and determination of optimal formulation Formulas are graded based on a comprehensive score, with higher scores indicating higher performance levels, specifically S. i ≥90 points is excellent, 80 points ≤S i <90 points is Good, 70 points ≤S i A score below 80 indicates a passing grade, S i A score of 70 or below is considered unqualified. The formula with the highest overall score is the optimal formula.

8. A sample preparation and evaluation device for true triaxial fracturing specimens in coal and rock, characterized in that, The sample preparation and evaluation device includes: The artificial coal and rock sample preparation module is used to obtain coal and rock from the target stratum, crush it to obtain coal and rock powder of different grades, and mix the coal and rock powder of different grades, cementitious materials and aggregate materials to prepare multiple sets of gradient artificial coal and rock samples. The screening module is used to select the optimal ratio of artificial coal and rock samples based on the mechanical parameters of coal and rock in the target stratum. The coal and rock true triaxial fracturing sample preparation module is used to load the selected artificial coal and rock sample into a mold and perform the first pressure molding. Inorganic salt and inorganic salt flakes are used to generate face cleavage and end cleavage in sequence to construct the first layer of cleavage network of coal and rock. Then, the above operation is repeated to construct other layers of cleavage network. Subsequently, the first static setting, the first standard curing and cleavage network activation are performed in sequence to obtain the coal and rock true triaxial fracturing sample. The comprehensive evaluation module is used to collect and preprocess the evaluation index data of the true triaxial fracturing samples of coal and rock, and then use the CRITIC-TOPSIS evaluation model for comprehensive evaluation.

9. An electronic device, characterized in that, The electronic device includes: At least one processor; and A memory communicatively connected to the at least one processor; wherein, The memory stores a computer program that can be executed by the at least one processor, the computer program being executed by the at least one processor to enable the at least one processor to perform the evaluation method for true triaxial fracturing samples of coal and rock as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that cause a processor to execute the evaluation method for true triaxial fracturing samples of coal and rock as described in any one of claims 1-7.

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