Method and system for predicting tensile strength of stratified rock mass based on Brazilian splitting experiment

Abstract

The invention discloses a stratified rock tensile strength prediction method and system based on a Brazilian splitting experiment, and relates to the technical field of rock mechanics and geotechnical engineering.The method comprises the steps that the Brazilian splitting experiment is conducted on multiple sets of shale disc samples with different bedding dip angles, and initial experiment data is obtained; calculating theoretical tensile strength based on a Brazilian splitting experiment principle; performing normalization processing on the initial experimental data and the theoretical tensile strength to obtain preprocessed experimental data; based on the preprocessed experimental data, constructing a target relational expression between the dynamic increase factor and the relative strain rate; and based on the target relational expression and a preset static stratified strength criterion, constructing a dynamic fracture pressure model based on the stratified rock mass dynamic strength criterion, and predicting the tensile strength of the stratified rock mass. The method not only can perfectly fit the strength characteristic that the strength of the stratified rock is firstly reduced and then increased along with the increase of the bedding dip angle, but also can predict the dynamic tensile strength of the stratified rock mass within a certain strain rate range.

Description

Technical Field

[0001] The invention relates to the technical field of rock mechanics and geotechnical engineering, and in particular to a method and system for predicting the tensile strength of layered rock mass based on a Brazilian splitting experiment. Background Art

[0002] Layered rock mass is a composite medium formed by alternating rocks or rock layers of different properties. Its failure mechanism is complex and is affected by many factors such as the direction of the bedding plane, the anisotropy of the rock mass, and the bonding strength between the layers. Understanding the failure mechanism of layered rock mass and predicting its strength are important topics in rock mechanics research, especially in mining, tunneling, slope engineering and other projects.

[0003] The technology of predicting the failure mechanism and strength of layered rock mass has important value in engineering applications and has become a hot spot for invention protection in the field of rock mechanics and engineering. The invention technology involved covers multiple levels from experimental devices, numerical simulation to engineering application methods, aiming to improve the prediction accuracy of the failure behavior of layered rock mass and its application effect in engineering.

[0004] Due to the preferential orientation of mineral particles in the formation process of sedimentary rocks, shale has obvious bedding structural characteristics, which makes the tensile strength of shale greatly affected by the bedding plane. At present, there are two commonly used methods to measure the tensile strength of rocks, namely direct tensile method and indirect tensile method. Since it is difficult to control the tensile stress through the central axis in the direct tensile method, eccentricity occurs. The operation process and accuracy of the direct tensile physical experiment are difficult to control, but the Brazilian splitting test can effectively solve the above problems due to its simple operation. Therefore, many experts and scholars at home and abroad use the indirect tensile method, namely the Brazilian disc splitting test, to measure the tensile strength of rock materials.

[0005] The study of rate effect of materials is mainly based on uniaxial tests. Under semi-logarithmic coordinates, the dynamic strength of rock has obvious rate effect. When the strain rate is small, the strength remains constant, which is called quasi-static. When the strain rate exceeds a certain range, the dynamic strength of the material increases with the increase of the strain rate. However, due to the high loading difficulty, unstable operation and less reliable data at extremely high strain rates, it is still difficult to determine or predict the ultimate peak strength. When the stress and strain generated by the deformation of the rock specimen under the action of external loads reach a certain value, the rock will fail unstable. The relationship equation that characterizes the rock failure conditions is called the strength criterion, also known as the failure criterion. The purpose of establishing the rock strength criterion is mainly to reflect the failure mechanism of the rock through the relationship equation between related parameters. Through the investigation of domestic and foreign literature, it is found that the research on the tensile strength of rock is mostly focused on experimental methods and theoretical derivation, and there is little research on the relationship between strain rate and fracture mode.

[0006] In order to more accurately predict the strength of layered rock mass, researchers have proposed strength models based on anisotropy theory in the prior art. These models usually take into account the differences in different material parameters of the rock mass (such as elastic modulus, Poisson's ratio, etc.) in different directions, and can better describe the complex mechanical behavior of layered rock mass.

[0007] Traditional strength criteria, such as the Mohr-Coulomb criterion and the Hoek-Brown criterion, are mostly designed for isotropic rock masses, and the anisotropy of layered rock masses is not sufficiently considered. Although some studies in recent years have modified these criteria to adapt to layered rock masses, the existing models are still insufficient for the combined influence of multiple factors in complex rock masses. The mechanical parameters of layered rock masses (such as elastic modulus, Poisson's ratio, shear strength, etc.) are often difficult to obtain accurately due to the heterogeneity and anisotropy of rock samples. The determination of these parameters is not only time-consuming and costly, but also difficult to measure accurately under some special conditions. The mechanical behavior of layered rock masses is not only manifested in the reduction or increase of strength, but also includes its complex behaviors such as progressive failure, slip, and interlacing of bedding planes. The existing theoretical models are still not sufficient in describing these aspects, especially in capturing nonlinear failure behaviors. The theoretical models are often oversimplified and cannot accurately reflect the mechanical properties of actual rock masses.

[0008] The current research on the strength prediction of layered rock has made important progress in many aspects, but it still faces many limitations and shortcomings. Experimental research is difficult to fully simulate actual engineering conditions, theoretical models are insufficiently simplified when capturing complex mechanical behaviors, and numerical simulations face problems such as computational resource limitations and model parameter sensitivity. Uncertainties in engineering applications and inadequate model verification also have a significant impact on the accuracy of prediction results. Summary of the invention

[0009] For mining and tunnel engineering in layered rock mass, the embodiment of the present invention provides a method and system for predicting the tensile strength of layered rock mass based on the Brazilian splitting test, which accurately predicts the failure position and failure mode of the layered rock mass, designs a reasonable support scheme, and reduces engineering risks and costs. The technical scheme is as follows:

[0010] On the one hand, a method for predicting the tensile strength of layered rock mass based on a Brazilian splitting experiment is provided, the method comprising: performing Brazilian splitting experiments on multiple groups of shale disc specimens with different bedding inclinations to obtain initial experimental data; calculating the theoretical tensile strength corresponding to each group of shale disc specimens based on the Brazilian splitting experiment principle and the initial experimental data; normalizing the initial experimental data and the theoretical tensile strength to obtain pre-processed experimental data; constructing a target relationship between a dynamic increase factor and a relative strain rate based on the pre-processed experimental data; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale specimen; constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock mass based on the target relationship and a preset static layered strength criterion; and predicting the tensile strength of layered rock mass based on the dynamic fracture pressure model.

[0011] Furthermore, before conducting Brazilian splitting experiments on multiple groups of shale samples with different bedding inclinations, the method also includes: preparing multiple groups of shale samples with different bedding inclinations; the bedding inclination is the angle between the bedding direction and the first principal stress baseline direction; based on preset experimental standards, making the multiple groups of shale samples into disc-shaped samples respectively, to obtain the multiple groups of shale disc samples; wherein each group of shale disc samples includes multiple parallel samples.

[0012] Furthermore, the theoretical tensile strength includes:

[0013]

[0014] Wherein, p is the maximum axial pressure when the shale disc sample is destroyed, D is the diameter of the shale disc sample, and t is the thickness of the shale disc sample.

[0015] Furthermore, before constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock mass based on the target relationship and the preset static layered strength criterion, the method also includes: predicting the tensile strength of the multiple groups of shale disc specimens based on multiple different static layered strength criteria to obtain multiple predicted tensile strengths; comparing the theoretical tensile strength with the multiple predicted tensile strengths respectively, and using the static layered strength criterion corresponding to the predicted tensile strength with the smallest difference with the theoretical tensile strength as the preset static layered strength criterion.

[0016] Furthermore, the multiple different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, and Hobbs-Barron tensile strength criterion.

[0017] Further, the dynamic increase factor is the ratio of dynamic tensile strength to quasi-static tensile strength; the target relationship includes:

[0018]

[0019] Where DIF is the dynamic increase factor, σ0 is the average value of the static Brazilian splitting tensile strength of the shale disc sample corresponding to the bedding angle of 0° and the shale disc sample corresponding to the bedding angle of 90°, σ d is the dynamic strength of shale disc specimens at different strain rates; is the strain rate (s -1 );K a , m and b are fitting coefficients.

[0020] Furthermore, the dynamic rupture pressure model comprises:

[0021]

[0022] Among them, T m is the tensile strength of rock matrix, θ is the bedding inclination angle, T(θ) is the tensile strength of rock when the bedding inclination angle is θ, T b It is the tensile strength of rock when the loading direction is consistent with the bedding dip.

[0023] On the other hand, a layered rock tensile strength prediction system based on the Brazilian splitting experiment is also provided, comprising: an experimental module, a calculation module, a preprocessing module, a first construction module, a second construction module and a prediction module; wherein the experimental module is used to perform Brazilian splitting experiments on multiple groups of shale disc specimens with different bedding inclinations to obtain initial experimental data; the calculation module is used to calculate the theoretical tensile strength corresponding to each group of shale disc specimens based on the Brazilian splitting experiment principle and the initial experimental data; the preprocessing module is used to normalize the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing; the first construction module is used to construct a target relationship between a dynamic increase factor and a relative strain rate based on the experimental data after preprocessing; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale specimen; the second construction module is used to construct a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock based on the target relationship and a preset static layered strength criterion; the prediction module is used to predict the tensile strength of the layered rock based on the dynamic fracture pressure model.

[0024] On the other hand, an electronic device is provided, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method provided by the present invention when executing the computer program.

[0025] On the other hand, a computer-readable storage medium is provided, in which a program code is stored. The program code can be called by a processor to execute the method provided by the present invention.

[0026] The embodiment of the present invention provides a method and system for predicting the tensile strength of layered rock mass based on the Brazilian splitting experiment, which can perfectly fit the strength characteristics of layered rock that first decreases and then increases with the increase of bedding inclination, and can predict the dynamic tensile strength of layered rock mass within a certain strain rate range, thereby alleviating the technical problem that it is difficult to determine or predict the ultimate peak strength of layered rock mass in the prior art. Layered rock mass destruction may cause serious engineering accidents, such as tunnel collapse, mine collapse, etc. Such accidents often lead to huge economic losses, including compensation for casualties, equipment damage, and construction delays. In mining and tunnel engineering, accurate prediction of rock mass strength can effectively prevent the occurrence of engineering accidents, such as landslides, instability, and rock bursts. By predicting the strength of layered rock mass, engineers can better design and plan construction plans to ensure the safety of the construction process. For projects such as tunnels and mines, excessive reinforcement or support not only increases construction costs, but may also cause extended construction periods, while insufficient support will lead to increased costs for later remedial work. Therefore, by accurately predicting rock mass strength, the occurrence of such accidents can be prevented and reduced, reducing the potential risk of economic compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is a flow chart of a method for predicting the tensile strength of layered rock mass based on the Brazilian splitting experiment provided by an embodiment of the present invention;

[0029] Figure 2 It is a schematic diagram of a bedding failure surface of a transversely isotropic rock provided by an embodiment of the present invention;

[0030] Figure 3 It is a structural schematic diagram of comparing a theoretical tensile strength with a plurality of predicted tensile strengths provided by an embodiment of the present invention;

[0031] Figure 4 is a curve diagram showing the relationship between the dynamic tensile strength and the strain rate of a shale disc specimen provided by an embodiment of the present invention;

[0032] Figure 5is a curve diagram showing the variation of the dynamic tensile strength of a shale disc sample with the strain rate provided by an embodiment of the present invention;

[0033] Figure 6 It is a schematic diagram of a layered rock mass tensile strength prediction system based on the Brazilian splitting experiment provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0035] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0036] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0037] Embodiment 1

[0038] Figure 1 FIG. 1 is a flow chart of a method for predicting the tensile strength of layered rock mass based on the Brazilian splitting experiment according to an embodiment of the present invention. Figure 1 As shown, the method specifically comprises the following steps:

[0039] Step S102, Brazilian splitting experiments are performed on multiple groups of shale disc samples with different bedding inclination angles to obtain initial experimental data.

[0040] Step S104, based on the Brazilian splitting test principle and the initial experimental data, the theoretical tensile strength corresponding to each group of shale disc specimens is calculated.

[0041] Step S106, normalizing the initial experimental data and the theoretical tensile strength to obtain pre-processed experimental data.

[0042] Step S108, based on the experimental data after preprocessing, construct a target relationship between the dynamic increase factor and the relative strain rate; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale sample.

[0043] Step S110, based on the target relationship and the preset static layered strength criterion, a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock mass is constructed.

[0044] Step S112, predicting the tensile strength of the layered rock mass based on the dynamic fracture pressure model.

[0045] In the method provided in the embodiment of the present invention, before step S102, the method further includes: preparing multiple groups of shale disc samples. Specifically, the method includes the following steps:

[0046] Prepare multiple groups of shale samples with different bedding dip angles; the bedding dip angle is the angle between the bedding direction and the first principal stress baseline direction;

[0047] Based on the preset experimental standards, multiple groups of shale samples are made into disc-shaped samples to obtain multiple groups of shale disc samples; wherein each group of shale disc samples includes multiple parallel samples.

[0048] Specifically, because layered rock has obvious transverse isotropy, its strength is not only related to the rock matrix itself, but also has a great correlation with the inclination of the structural plane and joint plane.

[0049] In some optional implementations provided in the embodiments of the present invention, in order to obtain samples with different bedding inclination angles, the bedding inclination angle θ of the rock block is defined as the angle between the bedding direction and the first principal stress baseline direction, and a drill bit with a diameter of 50 mm is used to perform core sampling along the directions of 0°, 15°, 30°, 45°, 60°, 75°, and 90°, respectively, to prepare seven shale samples with different bedding inclination angles.

[0050] Furthermore, in order to test the uniaxial tensile strength of shale samples, the shale was made into The disc-shaped specimens were divided into seven groups according to the bedding angle, and three parallel specimens were prepared in each group. Seven groups of shale disc specimens were obtained, and Brazilian splitting tensile tests were carried out in turn.

[0051] According to the Brazilian splitting test principle, the theoretical tensile strength of isotropic rock materials can be expressed as:

[0052]

[0053] Among them, p is the maximum axial pressure when the shale disc specimen is destroyed, D is the diameter of the shale disc specimen, and t is the thickness of the shale disc specimen.

[0054] Specifically, the method provided in the embodiment of the present invention further includes selecting a preset static layered strength criterion. The preset static layered strength criterion is to predict transverse isotropy, and specifically includes the following steps:

[0055] Based on multiple different static layered strength criteria, the tensile strength of multiple groups of shale disc specimens is predicted to obtain multiple predicted tensile strengths;

[0056] The theoretical tensile strength is compared with a plurality of predicted tensile strengths respectively, and the static layered strength criterion corresponding to the predicted tensile strength having the smallest difference with the theoretical tensile strength is used as the preset static layered strength criterion.

[0057] In some optional implementations provided in the embodiments of the present invention, a plurality of different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, and Hobbs-Barron tensile strength criterion.

[0058] (1) Nova-Zaninetti criterion:

[0059] Nova and Zaninetti proposed a new failure criterion for orthotropic materials. This criterion is similar in concept to the Mohr-Coulomb criterion in that both assume failure occurs when the shear strength is reached. Considering the rock isotropic in transverse direction, one of them is assumed to be orthotropic with a maximum strength T m The characteristic axis x2 is the principal stress axis, and for convenience the principal stress axis is selected as the reference frame. Figure 2 FIG. 1 is a schematic diagram of a bedding failure surface of a transversely isotropic rock provided according to an embodiment of the present invention. Figure 2 As shown, according to T(m)=T mm =T ij m i m j (m represents the normal stress vector on the bedding plane, m i represents the cosine of m), therefore, T ij The non-zero vectors of are:

[0060]

[0061] Therefore, the determinant (2) can be written as:

[0062]

[0063] Therefore, the failure criterion can be expressed as:

[0064]

[0065] (2) SPW criteria:

[0066] The single weak plane criterion for equivalent tension assumes that each bedding plane has the same tensile strength except for the weak bedding plane. Since the tensile strength of the weak plane is usually lower than that of the intact rock, the probability of tensile failure occurring along this plane is the lowest, provided that its inclination exceeds a critical value.

[0067] Critical angle β b *The expression is as follows:

[0068]

[0069] The SPW criterion is:

[0070]

[0071] (3) Hobbs-Barron tensile strength criterion:

[0072] According to Griffith crack theory, the isotropic plane is the main fracture surface, and the cracks are distributed along the bedding plane. b *The expression is as follows:

[0073]

[0074] When the critical angle β b *≤β b , this failure criterion holds. b *≤β b ≤90°, tensile strength equal to rock matrix tensile strength T m . Therefore, the failure criterion is:

[0075]

[0076] Figure 3 1 is a schematic diagram of a structure for comparing a theoretical tensile strength with a plurality of predicted tensile strengths according to an embodiment of the present invention. Figure 3 As shown in the figure, the prediction results of the Nova-Zaninetti criterion are closest to the calculation results based on the Brazilian splitting experiment. Therefore, the Nova-Zaninetti criterion is selected as the preset static layered strength criterion.

[0077] Specifically, the tensile strength and fracture toughness of rock increase with the increase of loading rate, and the static fracture strength of rock is close to a constant. In particular, when the strain rate exceeds a certain critical value, the dynamic response changes significantly. The present invention organizes the Brazilian splitting test data and establishes a dynamic coordinate system such as Figure 4 As shown, a strength criterion considering the strain rate effect is proposed.

[0078] In the embodiment of the present invention, in order to describe the change of dynamic strength with strain rate, the dynamic increase factor (DIF) is expressed as a characteristic quantity of strength. It is defined as the ratio of dynamic strength to quasi-static strength. For strain rate, a dimensionless method is constructed to characterize the relative strain rate. By using dimensionless method to organize the test data, it is found that the dynamic increase factor DIF and the relative strain rate are linearly related in the semi-logarithmic coordinate system as follows: Figure 5 shown.

[0079] Expressing DIF as a function of the logarithm of strain rate, the target relationship includes:

[0080]

[0081] Where DIF is the dynamic increase factor, σ0 is the average value of the static Brazilian splitting tensile strength of the shale disc specimen corresponding to the bedding angle of 0° and the shale disc specimen corresponding to the bedding angle of 90°, σ d is the dynamic strength of shale disc specimens at different strain rates; is the strain rate (s -1 );K a , m and b are fitting coefficients.

[0082] When the strain rate is high, Very close, K is obtained by fitting the experimental data a The relationship with the inclination angle is as follows:

[0083]

[0084] Where θ0 is a critical angle constant.

[0085] Then, a unified equation is used to describe the dynamic strength characteristics of rock within a given strain rate range:

[0086]

[0087] By substituting equation (9) into equation (4) using the previously selected Nova-Zaninetti criterion for the anisotropic tensile strength of static layered rocks, the dynamic fracture pressure model can be obtained, including:

[0088]

[0089] Among them, T m is the tensile strength of rock matrix, θ is the bedding inclination angle, T(θ) is the tensile strength of rock when the bedding inclination angle is θ, T b It is the tensile strength of rock when the loading direction is consistent with the bedding dip.

[0090] From the above description, it can be seen that the embodiment of the present invention provides a method for predicting the tensile strength of layered rock mass based on the Brazilian splitting test, which has the following advantages compared with the prior art:

[0091] (1) The parameters used in this method to determine the strength of layered rocks have clear physical meanings, are simple and easy to use, and are more reasonable. The dynamic tensile strength of layered rock is directly related to the bedding inclination of the layered rock mass, and is based on the original classical layered rock mass tensile strength criterion. This method is simple and reasonable to characterize the strength characteristics of layered rocks.

[0092] (2) The strength criterion in the present invention has a solid foundation and clear logic, and can fully evaluate the strength characteristics of layered rocks. The criterion of the present invention not only takes into account the advantages of the Nove-Zaninetti strength criterion, but can also perfectly fit the strength characteristics of layered rocks that first decrease and then increase with the increase of the bedding inclination angle, and can also predict the dynamic tensile strength of layered rock within a certain strain rate range. Therefore, this method has the advantage of fully evaluating the strength characteristics of layered rocks.

[0093] Embodiment 2

[0094] Figure 6 Schematic diagram of a layered rock mass tensile strength prediction system based on the Brazilian splitting experiment provided according to an embodiment of the present invention. Figure 6 As shown, the system includes: an experiment module 10, a calculation module 20, a preprocessing module 30, a first construction module 40, a second construction module 50 and a prediction module 60.

[0095] Specifically, the experimental module 10 is used to perform Brazilian splitting experiments on multiple groups of shale disc samples with different bedding inclination angles to obtain initial experimental data.

[0096] The calculation module 20 is used to calculate the theoretical tensile strength corresponding to each group of shale disc specimens based on the Brazilian splitting experiment principle and initial experimental data.

[0097] Specifically, the theoretical tensile strength includes:

[0098]

[0099] Among them, p is the maximum axial pressure when the shale disc specimen is destroyed, D is the diameter of the shale disc specimen, and t is the thickness of the shale disc specimen.

[0100] The preprocessing module 30 is used to perform normalization processing on the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing.

[0101] The first construction module 40 is used to construct a target relationship between the dynamic increase factor and the relative strain rate based on the experimental data after preprocessing; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale sample.

[0102] Specifically, the dynamic increase factor is the ratio of the dynamic tensile strength to the quasi-static tensile strength; the target relationship includes:

[0103]

[0104] Where DIF is the dynamic increase factor, σ0 is the average value of the static Brazilian splitting tensile strength of the shale disc specimen corresponding to the bedding angle of 0° and the shale disc specimen corresponding to the bedding angle of 90°, σ dis the dynamic strength of shale disc specimens at different strain rates; is the strain rate (s -1 );K a , m and b are fitting coefficients.

[0105] The second construction module 50 is used to construct a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock mass based on the target relationship and the preset static layered strength criterion.

[0106] Dynamic burst pressure model, including:

[0107]

[0108] Among them, T m is the tensile strength of rock matrix and θ is the bedding inclination.

[0109] The prediction module 60 is used to predict the tensile strength of the layered rock mass based on the dynamic fracture pressure model.

[0110] Specifically, Figure 6 As shown, the system further includes a preparation module 70 and a comparison module 80.

[0111] The preparation module 70 is used for:

[0112] Prepare multiple groups of shale samples with different bedding dip angles; the bedding dip angle is the angle between the bedding direction and the first principal stress baseline direction;

[0113] Based on the preset experimental standards, multiple groups of shale samples are made into disc-shaped samples to obtain multiple groups of shale disc samples; wherein each group of shale disc samples includes multiple parallel samples.

[0114] The comparison module 80 is used to:

[0115] Based on a plurality of different static layered strength criteria, the tensile strength of a plurality of groups of shale disc specimens is predicted to obtain a plurality of predicted tensile strengths; preferably, the plurality of different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, and Hobbs-Barron tensile strength criterion;

[0116] The theoretical tensile strength is compared with a plurality of predicted tensile strengths respectively, and the static layered strength criterion corresponding to the predicted tensile strength having the smallest difference with the theoretical tensile strength is used as the preset static layered strength criterion.

[0117] An embodiment of the present invention further provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method in the above-mentioned embodiment 1 when executing the computer program.

[0118] An embodiment of the present invention further provides a computer-readable storage medium, in which a program code is stored. The program code can be called by a processor to execute the method in the above-mentioned embodiment 1.

[0119] It should be understood that the memory in the embodiments of the present invention may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0120] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware or any other combination. When implemented by software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center by wired (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state hard disk.

[0121] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0122] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0123] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described equipment, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0124] In the several embodiments provided by the present invention, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0125] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0126] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0127] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0128] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for predicting the tensile strength of layered rock mass based on the Brazilian splitting test, characterized in that: The method comprises: Brazilian splitting experiments were conducted on multiple groups of shale disc specimens with different bedding dips to obtain initial experimental data. Based on the Brazilian splitting test principle and the initial experimental data, the theoretical tensile strength corresponding to each group of shale disc specimens is calculated; Normalizing the initial experimental data and the theoretical tensile strength to obtain pre-processed experimental data; Based on the experimental data after the pretreatment, a target relationship between a dynamic increase factor and a relative strain rate is constructed; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale sample; Based on the target relationship and the preset static layered strength criterion, a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock mass is constructed; Based on the dynamic fracture pressure model, the tensile strength of layered rock mass is predicted.

2. The method according to claim 1, characterized in that: Before respectively performing Brazilian splitting experiments on a plurality of shale samples with different bedding inclination angles, the method further comprises: Preparing multiple groups of shale samples with different bedding dip angles; the bedding dip angle is the angle between the bedding direction and the first principal stress baseline direction; Based on the preset experimental standard, the multiple groups of shale samples are respectively made into disc-shaped samples to obtain the multiple groups of shale disc samples; wherein each group of shale disc samples includes multiple parallel samples.

3. The method according to claim 1, characterized in that: The theoretical tensile strength includes: Wherein, p is the maximum axial pressure when the shale disc sample is destroyed, D is the diameter of the shale disc sample, and t is the thickness of the shale disc sample.

4. The method according to claim 1, characterized in that: Before constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock mass based on the target relationship and the preset static layered strength criterion, the method further includes: Based on a plurality of different static layered strength criteria, predicting the tensile strength of the plurality of groups of shale disc specimens to obtain a plurality of predicted tensile strengths; The theoretical tensile strength is compared with the multiple predicted tensile strengths respectively, and the static layered strength criterion corresponding to the predicted tensile strength having the smallest difference with the theoretical tensile strength is used as the preset static layered strength criterion.

5. The method according to claim 4, characterized in that: The multiple different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, and Hobbs-Barron tensile strength criterion.

6. The method according to claim 1, characterized in that: The dynamic increase factor is the ratio of dynamic tensile strength to quasi-static tensile strength; the target relationship includes: Where DIF is the dynamic increase factor, σ0 is the average value of the static Brazilian splitting tensile strength of the shale disc sample corresponding to the bedding angle of 0° and the shale disc sample corresponding to the bedding angle of 90°, σ d is the dynamic strength of shale disc specimens at different strain rates; is the strain rate (s -1 );K a , m and b are fitting coefficients.

7. The method according to claim 6, characterized in that: The dynamic rupture pressure model comprises: Among them, T m is the tensile strength of rock matrix, θ is the bedding inclination angle, T(θ) is the tensile strength of rock when the bedding inclination angle is θ, T b It is the tensile strength of rock when the loading direction is consistent with the bedding dip.

8. A layered rock mass tensile strength prediction system based on the Brazilian splitting experiment, characterized in that: include: Experimental module, calculation module, preprocessing module, first construction module, second construction module and prediction module; wherein, The experimental module is used to perform Brazilian splitting experiments on multiple groups of shale disc samples with different bedding inclination angles to obtain initial experimental data; The calculation module is used to calculate the theoretical tensile strength corresponding to each group of shale disc specimens based on the Brazilian splitting experiment principle and the initial experimental data; The preprocessing module is used to perform normalization processing on the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing; The first construction module is used to construct a target relationship between a dynamic increase factor and a relative strain rate based on the experimental data after the preprocessing; the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale sample; The second construction module is used to construct a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock mass based on the target relationship and the preset static layered strength criterion; The prediction module is used to predict the tensile strength of the layered rock mass based on the dynamic fracture pressure model.

9. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program codes, which can be called by a processor to execute the method according to any one of claims 1 to 7.

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