Tensile Strength Prediction Method and System for Layered Rock Masses Based on Brazilian Splitting Test

Abstract

The present invention discloses a method and system for predicting the tensile strength of layered rock masses based on the Brazilian splitting test, which relates to the technical fields of rock mechanics and geotechnical engineering, and includes: performing Brazilian splitting tests on multiple groups of shale disc specimens with different bedding dip angles respectively to obtain initial experimental data; calculating the theoretical tensile strength based on the principle of the Brazilian splitting test; performing normalization processing on the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing; constructing a target relationship between the dynamic increase factor and the relative strain rate based on the experimental data after preprocessing; constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock masses based on the target relationship and a preset static layered strength criterion to predict the tensile strength of layered rock masses. The present invention can not only perfectly fit the strength characteristic that the strength of layered rocks first decreases and then increases with the increase of the bedding dip angle, but also predict the dynamic tensile strength of layered rock masses within a certain strain rate range.

Description

Technical Field

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

[0002] Layered rock mass is a composite medium formed by the alternating arrangement of rocks with different properties or rock bedding planes. Its failure mechanism is complex and is affected by various factors such as the direction of bedding planes, the anisotropy of rock masses, and the bonding strength between bedding planes. Understanding the failure mechanism of layered rock masses and predicting their strength is an important topic in rock mechanics research, especially crucial in engineering such as mining, tunneling, and slopes.

[0003] The technologies for the failure mechanism and strength prediction of layered rock masses have important value in engineering applications and have become a hot spot for invention protection in the fields of rock mechanics and engineering. The invention technologies involved cover multiple levels from experimental devices, numerical simulations to engineering application methods, aiming to improve the prediction accuracy of the failure behavior of layered rock masses and their application effects in engineering.

[0004] Due to the preferred orientation of mineral grains during the formation of sedimentary rocks, shale has obvious bedding structure characteristics, resulting in a greater influence of the bedding plane on the tensile strength of shale. Currently, there are two commonly used methods for measuring the tensile strength of rocks, namely the direct tensile method and the indirect tensile method. In the direct tensile method, it is difficult to control the tensile stress to pass through the central axis, resulting in eccentricity. The operation process and accuracy of direct tensile physical experiments are difficult to control. However, since the Brazilian splitting test is easy to operate and can effectively solve the above problems. Therefore, many experts and scholars at home and abroad use the indirect tensile method, that is, the Brazilian disk splitting test, to measure the tensile strength of rock materials.

[0005] The research on the rate effect of materials mainly focuses on uniaxial tests. In the semi-logarithmic coordinate system, the dynamic strength of rocks has an obvious rate effect. When the strain rate is small, the strength remains constant, which is called quasi-static at this time. When the strain rate exceeds a certain range, with the increase of the strain rate, the dynamic strength of the material increases. However, due to the high loading difficulty, unstable operation, and less reliable data in extremely high strain rate tests, it is currently difficult to determine or predict the ultimate peak strength. When the stress and strain generated by the deformation of a rock specimen under an external load reach a certain value, the rock will undergo unstable failure. The relationship equation characterizing the rock failure condition is called the strength criterion, also known as the failure criterion. The purpose of establishing the rock strength criterion is mainly to reflect the rock failure mechanism through the relationship equation between relevant parameters. Through research on domestic and foreign literature, it is found that the research on the tensile strength of rocks mainly focuses on experimental methods and theoretical derivations, and there is less research on the relationship between strain rate and fracture mode.

[0006] To more accurately predict the strength of layered rock masses, in the existing technology, researchers have proposed strength models based on anisotropy theory. These models generally consider the differences in different material parameters (such as elastic modulus, Poisson's ratio, etc.) of the rock mass in different directions and can better describe the complex mechanical behavior of layered rock masses.

[0007] Traditional strength criteria, such as the Mohr-Coulomb criterion and the Hoek-Brown criterion, are mostly designed for isotropic rock masses and insufficiently consider the anisotropy of layered rock masses. Although in recent years some studies have modified these criteria to adapt to layered rock masses, for the comprehensive influence of multiple factors in complex rock masses, the existing models are still insufficient. The mechanical parameters (such as elastic modulus, Poisson's ratio, shear strength, etc.) of layered rock masses are often difficult to accurately obtain due to the inhomogeneity and anisotropy of rock samples. The determination of these parameters is not only time-consuming and costly but also difficult to accurately measure in some special environments. The mechanical behavior of layered rock masses not only shows a decrease or increase in strength but also includes complex behaviors such as progressive failure, slip, and bedding plane intersection. The existing theoretical models are still not sufficient in describing these aspects. Especially in capturing the nonlinear failure behavior, the theoretical models are often too simplified to accurately reflect the mechanical properties of actual rock masses.

[0008] Current research on the prediction of layered rock mass strength has made important progress in many aspects but still faces many limitations and deficiencies. Experimental research is difficult to fully simulate actual engineering conditions. Theoretical models have deficiencies in simplification when capturing complex mechanical behaviors. Numerical simulations face computational resource limitations and model parameter sensitivity problems. The uncertainties in engineering applications and the lack of model verification also have a greater impact on the accuracy of prediction results. Summary of the Invention

[0009] For mining and tunneling projects in layered rock masses, the embodiments of the present invention provide a method and system for predicting the tensile strength of layered rock masses based on the Brazilian splitting test. By accurately predicting the failure position and failure mode of layered rock masses, a reasonable support plan is designed to reduce engineering risks and costs. The technical solution is as follows:

[0010] On the one hand, a method for predicting the tensile strength of layered rock masses based on the Brazilian splitting test is provided. The method includes: conducting Brazilian splitting tests on multiple groups of shale disc specimens with different bedding dip angles respectively to obtain initial experimental data; calculating the theoretical tensile strength corresponding to each group of shale disc specimens based on the principle of the Brazilian splitting test and the initial experimental data; normalizing the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing; constructing a target relationship between the dynamic increase factor and the relative strain rate based on the experimental data after preprocessing, where the dynamic increase factor is a characteristic quantity of the dynamic tensile strength of the shale specimens; constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock masses based on the target relationship and a preset static layered strength criterion; and predicting the tensile strength of the layered rock masses based on the dynamic fracture pressure model.

[0011] Further, before conducting Brazilian splitting tests on multiple groups of shale specimens with different bedding dip angles respectively, the method further includes: preparing multiple groups of shale specimens with different bedding dip angles, where the bedding dip angle is the angle between the bedding direction and the direction of the first principal stress baseline; making the multiple groups of shale specimens into disc-shaped specimens respectively based on a preset experimental standard to obtain the multiple groups of shale disc specimens, where each group of shale disc specimens includes multiple parallel specimens.

[0012] Further, the theoretical tensile strength includes:

[0013]

[0014] where p is the maximum axial pressure when the shale disc specimen fails, D is the diameter of the shale disc specimen, and t is the thickness of the shale disc specimen.

[0015] Further, before constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock masses based on the target relationship and a preset static layered strength criterion, the method further 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 taking the static layered strength criterion corresponding to the predicted tensile strength with the smallest difference from the theoretical tensile strength as the preset static layered strength criterion.

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

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

[0018]

[0019] Among them, 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 dip angle of 0° and the shale disc specimen corresponding to the bedding dip angle of 90°, and σ d is the dynamic strength of the shale disc specimen at different strain rates; is the strain rate (s -1 ); K a , m and b are fitting coefficients.

[0020] Furthermore, the dynamic fracture pressure model includes:

[0021]

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

[0023] On the other hand, a layered rock mass tensile strength prediction system based on the Brazilian splitting experiment is also provided, including: an experimental module, a calculation module, a preprocessing module, a first construction module, a second construction module and a prediction module; among them, the experimental module is used to perform Brazilian splitting experiments on multiple groups of shale disc specimens with different bedding dip angles respectively 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 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 specimen; the second construction module is used to construct a dynamic fracture pressure model based on the layered rock mass dynamic strength criterion 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.

[0024] On the other hand, an electronic device is also provided, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, the method provided by the present invention is implemented.

[0025] On the other hand, a computer-readable storage medium is also provided. Program codes are stored in the computer-readable storage medium and can be called by a processor to execute the method provided by the present invention.

[0026] The embodiments of the present invention provide a method and a system for predicting the tensile strength of layered rock masses based on the Brazilian splitting test. It can not only perfectly fit the strength characteristic that the strength of layered rocks first decreases and then increases with the increase of bedding dip angle, but also predict the dynamic tensile strength of layered rock masses within a certain strain rate range, alleviating the technical problem in the prior art that it is difficult to determine or predict the ultimate peak strength for layered rock masses. The failure of layered rock masses may trigger serious engineering accidents, such as tunnel collapses, mine collapses, etc. Such accidents often result in huge economic losses, including compensation for casualties, equipment damage, project delays, etc. In mining and tunnel engineering, accurately predicting the strength of rock masses can effectively prevent the occurrence of engineering accidents, such as collapses, instability, and rock bursts. By predicting the strength of layered rock masses, engineers can better design and plan construction schemes to ensure the safety of the construction process. For projects such as tunnels and mines, excessive reinforcement or support not only increases the construction cost but also may cause a prolongation of the construction period, while insufficient support will lead to an increase in the cost of later remedial work. Therefore, by accurately predicting the strength of rock masses, the occurrence of such accidents can be prevented and reduced, and the potential economic compensation risk can be lowered. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0028] Figure 1 is a flowchart of a method for predicting the tensile strength of layered rock masses based on the Brazilian splitting test provided by the embodiments of the present invention;

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

[0030] Figure 3 is a schematic diagram of a structure for comparing the theoretical tensile strength with multiple predicted tensile strengths provided by the embodiments of the present invention;

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

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

[0033] Figure 6 It is a schematic diagram of a tensile strength prediction system for layered rock masses based on the Brazilian splitting test provided by an embodiment of the present invention. Detailed implementation manners

[0034] The technical solutions in the present invention will be described below with reference to the accompanying drawings.

[0035] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to represent examples, illustrations or explanations. Any embodiment or design solution described as an "example" in the present invention should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of the word "example" is intended to present concepts in a specific manner. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one of the two.

[0036] To make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] Embodiment 1

[0038] Figure 1 It is a flowchart of a method for predicting the tensile strength of layered rock masses based on the Brazilian splitting test provided by an embodiment of the present invention. As Figure 1 shown, the method specifically includes the following steps:

[0039] Step S102, perform Brazilian splitting tests on multiple groups of shale disc specimens with different bedding dip angles respectively to obtain initial experimental data.

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

[0041] Step S106, perform normalization processing on the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing.

[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 specimen.

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

[0044] Step S112, predict the tensile strength of layered rock masses 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 preset experimental standards, multiple groups of shale samples are made into disc-shaped samples to obtain multiple groups of shale disc samples; each group of shale disc samples includes multiple parallel samples.

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

[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° 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, with three parallel specimens prepared in each group. Seven groups of shale disc specimens were obtained and Brazilian splitting tensile tests were carried out in sequence.

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

[0052]

[0053] Where p is the maximum axial pressure when the shale disc specimen fails, 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 was predicted to obtain multiple predicted tensile strengths;

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

[0057] In some alternative embodiments provided by the embodiments of the present invention, multiple different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, 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 conceptually similar to the Mohr-Coulomb criterion, both assuming that failure occurs when the shear strength is reached. Considering the transverse isotropy of rocks, assuming one of them is orthotropic with the maximum strength T m The axis x2 with the characteristic is taken as the stress principal axis, and it is convenient to select the principal stress axis as the reference frame. Figure 2 It is a schematic diagram of the bedding failure surface of a transversely isotropic rock provided by the embodiments of the present invention. As Figure 2 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, the non-zero vector of T ij is:

[0060]

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

[0062]

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

[0064]

[0065] (2) SPW criterion:

[0066] The single weak plane criterion of 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 least, provided that its dip angle exceeds the critical value.

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

[0068]

[0069] The SPW criterion is as follows:

[0070]

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

[0072] According to Griffith crack theory, the isotropic plane is the main location where the rupture surface occurs, and the cracks are distributed along the bedding plane direction. The critical angle β b *The expression is as follows:

[0073]

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

[0075]

[0076] Figure 3 is a schematic structural diagram for comparing the theoretical tensile strength with multiple predicted tensile strengths provided by an embodiment of the present invention. As Figure 3 shown, the prediction result of the Nova-Zaninetti criterion is closest to the calculation result based on the Brazilian splitting test. Therefore, the Nova-Zaninetti criterion is selected as the preset static layered strength criterion.

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

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

[0079] ​

[0080]

[0081] Among them, DIF is the dynamic increase factor, σ0 is the average value of the static Brazilian splitting tensile strength of the shale disk specimens corresponding to the bedding dip angle of 0° and the shale disk specimens corresponding to the bedding dip angle of 90°, and σ d is the dynamic strength of the shale disk specimen 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, is very close. By fitting the experimental data, the relationship between K a and the dip angle change is as follows:

[0083]

[0084] In the formula, θ0 is a critical angle constant.

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

[0086]

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

[0088]

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

[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 masses based on the Brazilian splitting experiment. Compared with the prior art, it has the following advantages:

[0091] (1) The physical meaning of the parameters for determining the strength of layered rocks by this method is clear, simple and easy to implement, and more reasonable. The dynamic tensile strength of layered rock masses is directly related to the bedding dip angle of layered rock masses, and is based on the original classical tensile strength criterion of layered rock masses. It is simple and reasonable to characterize the strength characteristics of layered rocks by this method.

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

[0093] Example Two

[0094] Figure 6 is a schematic diagram of a layered rock mass tensile strength prediction system based on the Brazilian splitting test provided by an embodiment of the present invention. As Figure 6 shown, the system includes: an experimental 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 tests on multiple groups of shale disc specimens with different bedding dip angles respectively 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 principle of the Brazilian splitting test and the initial experimental data.

[0097] Specifically, the theoretical tensile strength includes:

[0098]

[0099] where p is the maximum axial pressure when the shale disc specimen fails, 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 specimen.

[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 specimens corresponding to 0° bedding dip angle and 90° bedding dip angle, σ dis the dynamic strength of the shale disk specimen 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 layered rock mass dynamic strength criterion based on the target relational expression and the preset static layered strength criterion.

[0106] The dynamic fracture pressure model includes:

[0107]

[0108] where T m is the tensile strength of the rock matrix, and θ is the bedding dip angle.

[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, as Figure 6 shown, the system further includes a preparation module 70 and a comparison module 80. Among them,

[0111] The preparation module 70 is used for:

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

[0113] Based on the preset experimental standard, making the multiple groups of shale specimens into disk-shaped specimens respectively to obtain multiple groups of shale disk specimens; among them, each group of shale disk specimens includes multiple parallel specimens.

[0114] The comparison module 80 is used for:

[0115] Predicting the tensile strength of multiple groups of shale disk specimens based on multiple different static layered strength criteria to obtain multiple predicted tensile strengths; preferably, the multiple different static layered strength criteria include: Nova-Zaninetti criterion, SPW criterion, Hobbs-Barron tensile strength criterion;

[0116] Comparing the theoretical tensile strength with the multiple predicted tensile strengths respectively, and taking the static layered strength criterion corresponding to the predicted tensile strength with the smallest difference from the theoretical tensile strength as the preset static layered strength criterion.

[0117] An embodiment of the present invention also provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the method in the first embodiment above is implemented.

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

[0119] It should be understood that the memory in the embodiment 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 but not limitation, many forms of random access memory (RAM) are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM).

[0120] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware, or any combination thereof. When implemented using 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 processes or functions described in the embodiments of the present invention are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (such as infrared, wireless, microwave, etc.) means. 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 a collection of one or more available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, or magnetic tape), an optical medium (such as a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0121] It should be understood that in various embodiments of the present invention, the magnitudes of the sequence numbers of the above processes do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0122] Those of ordinary skill in the art can realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed 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 devices, apparatuses, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0124] In 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 merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, 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 displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces. The indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

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

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

[0127] If the functions are implemented in the form of software function 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, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical discs that can store program codes.

[0128] As described above, the above are only the specific implementation manners of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for predicting the tensile strength of layered rock masses based on the Brazilian splitting test, characterized in that The method includes: Conducting Brazilian splitting tests on multiple groups of shale disk specimens with different bedding dip angles respectively to obtain initial experimental data; Calculating the theoretical tensile strength corresponding to each group of shale disk specimens based on the Brazilian splitting test principle and the initial experimental data; Normalizing the initial experimental data and the theoretical tensile strength to obtain the experimental data after preprocessing; Based on the experimental data after preprocessing, constructing 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 specimen; Based on the target relationship and the preset static layered strength criterion, constructing a dynamic fracture pressure model based on the dynamic strength criterion of layered rock masses; Predicting the tensile strength of layered rock masses based on the dynamic fracture pressure model.

2. The method according to claim 1, wherein: Before conducting Brazilian splitting tests on multiple groups of shale specimens with different bedding dip angles respectively, the method further includes: Preparing multiple groups of shale specimens with different bedding dip angles; the bedding dip angle is the angle between the bedding direction and the direction of the first principal stress baseline; Based on the preset experimental standard, making the multiple groups of shale specimens into disk-shaped specimens respectively to obtain the multiple groups of shale disk specimens; where each group of shale disk specimens includes multiple parallel specimens.

3. The method according to claim 1, wherein: The theoretical tensile strength includes: Where p is the maximum axial pressure when the shale disk specimen fails, D is the diameter of the shale disk specimen, and t is the thickness of the shale disk specimen.

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 masses based on the target relationship and the preset static layered strength criterion, the method further includes: Predicting the tensile strength of the multiple groups of shale disk 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 taking the static layered strength criterion corresponding to the predicted tensile strength with the smallest difference from the theoretical tensile strength as the preset static layered strength criterion.

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

6. The method according to claim 1, characterized in that: The dynamic increase factor is the ratio of the dynamic tensile strength to the 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 disk specimens corresponding to the bedding dip angles of 0° and 90°, and σ d is the dynamic strength of the shale disk 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, wherein: The dynamic fracture pressure model includes: Among them, T m is the tensile strength of the rock matrix, θ is the bedding dip angle, T(θ) is the tensile strength of the rock when the bedding dip angle is θ, and T b is the tensile strength of the rock when the loading direction is consistent with the bedding dip angle.

8. A tensile strength prediction system for layered rock masses based on the Brazilian splitting test, characterized in that, Includes: An experimental module, a calculation module, a preprocessing module, a first construction module, a second construction module and a prediction module; where The experimental module is used to conduct Brazilian splitting tests on multiple groups of shale disk specimens with different bedding dip angles respectively to obtain initial experimental data; The calculation module is used to calculate the theoretical tensile strength corresponding to each group of shale disk specimens based on the Brazilian splitting test 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 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 specimen; The second construction module is configured to construct a dynamic fracture pressure model based on the dynamic strength criterion of the layered rock mass based on the target relational expression and the preset static layered strength criterion; The prediction module is configured to predict the tensile strength of the layered rock mass based on the dynamic fracture pressure model.

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

10. A computer-readable storage medium, characterized in that, Program code is stored in the computer-readable storage medium, and the program code can be called by the processor to execute the method according to any one of claims 1 to 7.

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