Method and system for realizing energy calculation in rock mechanics experiment process

Abstract

The invention discloses a method and a system for realizing energy calculation in a rock mechanics experiment process, and the method and the system can accurately calculate the energy in the rock mechanics experiment. The embodiment of the invention provides an energy calculation method for the whole rock deformation-damage-damage process considering the nonlinear rigidity and impact load of a testing machine (loading system), and the method has important practical significance for accurately calculating energy evolution in the testing process and exploring the energy mechanism of rock burst.

Description

Technical Field

[0001] The present application relates to but is not limited to the field of rock mechanics test technology, and specifically to a method and system for realizing energy calculation in a rock mechanics experiment process. Background Art

[0002] Rockburst is one of the most challenging geological hazards in deep tunnels, posing a huge threat to the safety of workers and equipment during tunnel construction. Rockburst is generally defined as the violent rock ejection caused by the sudden release of energy stored in the rock mass during hard rock excavation unloading under high ground stress conditions. Studying the energy evolution law of the whole process of rock mass deformation, damage and destruction after tunnel excavation will help to better understand the mechanism of rockburst, thereby providing a basis for rockburst warning and control.

[0003] Due to the complexity of rockbursts in tunnel sites, indoor tests have been widely used to simulate and reproduce rockbursts in recent years. Based on different indoor test methods and test machines, a large number of studies have been carried out on the characteristics and evolution laws of rockbursts under different conditions. Among them, the energy-based method is an important method to study rockburst destruction, and exploring the energy evolution process in the process of rockburst incubation is crucial for rockburst early warning. A test machine refers to an experimental device used to apply controlled loading and measure parameters such as stress and strain. The test machine is used to simulate the behavior of rocks under various stress conditions to study the mechanical properties, failure characteristics and energy evolution laws of rocks. Test machines can include: uniaxial compression test machine, triaxial test machine, true triaxial test machine, impact test machine, etc.

[0004] Previous studies have mainly focused on microseismic rockbursts in deep tunnels. In terms of indoor experiments, although many studies have discussed the energy evolution of rocks during true triaxial tests (i.e., input energy, elastic strain energy, and dissipated energy), true triaxial rockburst experiments are currently mainly used to compare and analyze macroscopic experimental phenomena and do not involve the analysis of stress-strain data, which is crucial for energy calculation. In addition, according to the stiffness theory of rockbursts, when a fully rigid testing machine is used for uniaxial compression tests, rockburst phenomena will not be observed, indicating that stiffness has a significant effect on the occurrence and intensity level of rockbursts. However, previous studies have rarely considered the effect of testing machine stiffness on the energy evolution process of rockbursts.

[0005] Therefore, how to accurately calculate the energy evolution during the test and explore the energy mechanism of rockburst is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The present application provides a method and system for realizing energy calculation in a rock mechanics experiment process, which can accurately calculate the energy in the rock mechanics experiment.

[0007] An embodiment of the present invention provides a method for realizing energy calculation in a rock mechanics experiment process, comprising:

[0008] In rock mechanics tests, acoustic emission sensors are used to monitor the entire process and obtain mechanical behavior information of the rock samples under loading, transient unloading and failure.

[0009] After the rock mechanics test, a mechanical model of the combined system of the testing machine and rock samples is established based on the nonlinear stiffness of the testing machine loading system in different directions, the full-process acoustic emission monitoring results, and the obtained mechanical behavior information;

[0010] The energy analysis of rock deformation-damage-destruction process is carried out through the established mechanical model, and the energy parameters and dissipation indicators are calculated.

[0011] In an exemplary embodiment, before the rock mechanics test, the method further includes:

[0012] The nonlinear stiffness of the loading system of the testing machine is measured using a rigid calibration block.

[0013] In an exemplary embodiment, the method of using a rigid calibration block to perform nonlinear stiffness measurement of a testing machine loading system includes:

[0014] The rigid calibration block is used to measure the nonlinear stiffness of the loading system of the testing machine in different directions, and loads are applied independently in different loading directions until the load-displacement curve is linearly related;

[0015] According to the slope of the load-displacement curve, the relationship between the stiffness and load in different directions of the testing machine, that is, the stiffness-load change relationship, is obtained.

[0016] In an exemplary embodiment, the acoustic emission sensors include three or more.

[0017] In an exemplary embodiment, the mechanical behavior information includes one or any combination of the following: the moment when transient unloading occurs, load-displacement data in different loading directions, and final load and displacement data in different loading directions when the rock sample is destroyed.

[0018] In an exemplary embodiment, the step of establishing a mechanical model for a combined system of a testing machine and a rock sample includes:

[0019] The loading rod of the testing machine is regarded as a nonlinear elastic material, the rock sample is regarded as an orthotropic elastic damaged material, and the cumulative ringing count of acoustic emission in the data collected by the acoustic emission sensor is used as a damage variable. The load-displacement curve in the mechanical behavior information obtained during the test is fitted to obtain the parameters of the mechanical model, so as to establish the mechanical model that takes into account the nonlinear stiffness and impact load of the testing machine.

[0020] In an exemplary embodiment, the parameters of the mechanical model include one or any combination of the following: elastic modulus of rock, final damage variable, impact coefficient, initial stiffness, final stiffness, and material constant.

[0021] In an exemplary embodiment, the energy parameters and dissipation indicators include one or any combination of the following: total input energy, elastic strain energy, dissipated energy, total input energy density, elastic strain energy density, dissipated energy density and other energy indicators.

[0022] In an exemplary embodiment, the energy parameters and dissipation indicators also include: calculating indicators such as energy dissipation rate and / or energy release rate.

[0023] The present application also provides a system for realizing energy calculation in a rock mechanics experiment process, comprising:

[0024] A testing machine capable of applying loads in different directions, used to: measure the ability of nonlinear stiffness, and control and record the load-displacement relationship; load the rock sample in multiple directions to obtain its stiffness-load variation relationship in different directions;

[0025] Rigidity calibration block, used to measure the nonlinear stiffness of the testing machine loading system before the test;

[0026] Acoustic emission sensor device, used to monitor the acoustic emission signal generated by the rock sample during loading, record the transient signal of the acoustic emission, and obtain the mechanical behavior information of the rock sample to be tested during loading, transient unloading and failure;

[0027] Data acquisition system, used to record load and displacement data during the test;

[0028] The data processing unit is used to establish a mechanical model of the combined system of the testing machine and the rock sample after the test according to the nonlinear stiffness of the testing machine loading system in different directions, the full-process acoustic emission monitoring results and the obtained mechanical behavior information; and to perform energy analysis of the rock deformation-damage-destruction process through the established mechanical model, and calculate energy parameters and dissipation indicators.

[0029] By implementing the method for energy calculation during rock mechanics testing provided in the embodiment of the present application, the energy in the rock mechanics test is accurately calculated. The embodiment of the present application is a method for calculating the energy of the entire process of rock deformation-damage-destruction taking into account the nonlinear stiffness of the testing machine (loading system) and the impact load, which has important practical significance for accurately calculating the energy evolution during the test and exploring the energy mechanism of rock burst.

[0030] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide further understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0032] Figure 1 A schematic flow chart of a method for realizing energy calculation during a rock mechanics experiment in an embodiment of the present application;

[0033] Figure 2 This is a schematic diagram of the nonlinear stiffness changes of the testing machine in different directions in the embodiment of the present application;

[0034] Figure 3 A schematic diagram of establishing a staged mechanical model of a system composed of a testing machine and a rock in the entire loading process in an embodiment of the present application;

[0035] FIG4( a ) is a schematic diagram showing the trend of energy density of the whole process of rock damage and destruction calculated in an embodiment of the present application over time;

[0036] FIG4( b ) is a schematic diagram showing the trend of energy variation over time during the entire rock damage and destruction process calculated in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present application more clear, the embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other arbitrarily without conflict.

[0038] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0040] It is understood that the terms "first" and "second" used in this application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0041] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0042] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0043] Figure 1 FIG. 1 is a flow chart of a method for realizing energy calculation in a rock mechanics test process in an embodiment of the present application. Figure 1 As shown, it may include:

[0044] Step 101: In the rock mechanics test, an acoustic emission sensor is used to perform full-process acoustic emission monitoring and obtain mechanical behavior information of the rock sample to be tested during loading, transient unloading and destruction.

[0045] In an exemplary embodiment, when conducting rock mechanics tests, a preset number of acoustic emission sensors, such as more than 3, are arranged on the surface of the rock sample; full-process acoustic emission monitoring is performed, and the mechanical behavior information obtained at the same time may include one or any combination of the following: the moment when transient unloading occurs, load-displacement data in different loading directions, and final load and displacement data in different loading directions when the rock sample is destroyed.

[0046] In the embodiments of the present application, during the rock mechanics test, especially in the loading and unloading test and other scenarios, the rock sample sometimes experiences sudden unloading (i.e., transient unloading). This transient unloading may be caused by human operation or local instability of the rock sample, crack extension, etc. Transient unloading refers to the phenomenon that the applied load is suddenly reduced or removed in a short period of time. At this time, the stress and strain of the rock sample will change greatly in an instant. Recording the moment when transient unloading occurs, that is, recording the time point when sudden unloading or instability occurs, to observe the stress response of the rock, can provide technical support for further analysis of the mechanical response of the rock under different load conditions, especially at the moment of unloading, to observe the stress relaxation, crack development or other stress recovery behaviors of the rock.

[0047] In the embodiments of the present application, during the rock mechanics test, the applied load is usually distributed in multiple directions, such as the three mutually perpendicular directions in the true triaxial test. Therefore, it is necessary to record the load-displacement relationship of each loading direction throughout the entire process. The load-displacement data is the relationship between the external load (load) applied to the rock sample and its corresponding displacement (deformation), reflecting the stress and deformation of the rock sample in different directions during the loading process. The purpose of recording the entire data is to capture the various stages of the rock during the loading process, including the elastic stage, the plastic stage, and the crack propagation and failure stage, so as to more accurately analyze the deformation and failure characteristics of the rock.

[0048] In the embodiments of the present application, when the rock sample reaches the ultimate strength and fails during the loading process, the final load and displacement at this time are recorded, which are the key data points when the rock sample fails. The final load at failure refers to the maximum load value reached by the rock sample in a certain direction, which usually corresponds to the ultimate strength of the rock; the displacement at failure is the deformation of the rock sample when failure occurs. The key data points when the rock sample fails can reflect the deformation characteristics and failure mode of the rock at the ultimate strength.

[0049] In one embodiment, through step 101, a rock sample is placed on a loading table of a testing machine, and rock mechanics tests are carried out, including but not limited to uniaxial tests, triaxial tests, loading and unloading tests, creep tests, Brazilian splitting tests, rock burst tests, etc. More than three acoustic emission sensors are arranged on the surface of the rock sample, and acoustic emission monitoring is carried out simultaneously during the loading process by connecting an acoustic emission amplifier and a host; during the test, the moment of transient unloading is recorded, and the load-displacement data of different loading directions, as well as the final load and displacement data of different loading directions when the rock sample is destroyed are recorded throughout the test, until the test is terminated after the rock sample is destroyed. The data collected in step 101 (such as load-displacement curves, acoustic emission cumulative ring counts) will serve as the basis for subsequent mechanical model fitting and parameter calculation, especially the acoustic emission signal as a damage variable, which will be directly used for damage analysis of the model.

[0050] Step 102: After the rock mechanics test, a mechanical model of the combined system of the testing machine and the rock sample is established based on the nonlinear stiffness of the testing machine loading system in different directions, the full-process acoustic emission monitoring results and the obtained mechanical behavior information.

[0051] In an exemplary embodiment, before the rock mechanics test, the method further includes:

[0052] Step 100: Use a rigid calibration block to measure the nonlinear stiffness of the testing machine loading system.

[0053] In one exemplary embodiment, step 100 may include:

[0054] Before the test, the nonlinear stiffness of the loading system of the testing machine in different directions can be measured using a rigid calibration block, and loads can be applied independently in different loading directions until the load-displacement curve is linear.

[0055] According to the slope of the load-displacement curve, the relationship between the stiffness and load in different directions of the testing machine, that is, the stiffness-load change relationship, is obtained.

[0056] A rigid calibration block is a device used to calibrate and verify the loading accuracy of test equipment (such as rock mechanics testing machines). The rigid calibration block has high rigidity, that is, it will not deform significantly when a load is applied, which can ensure that the loading performance of the test equipment will not be affected by the deformation of the tested object.

[0057] In one embodiment, before conducting a rock mechanics test, a rigid calibration block is placed on the loading table of the testing machine, and then a load control mode is used to independently apply loads in different loading directions, and the load-displacement curves of the loading rods in different loading directions are recorded throughout the process until the load-displacement curves are linear. At this time, loading is stopped, the rigid calibration block is withdrawn, and the load-displacement data is derived. Taking a true triaxial testing machine as an example, it has the function of independent loading in three directions. The testing machine itself is regarded as a nonlinear elastic material. The testing machine only has elastic deformation during the loading process, without damage and energy dissipation. The load-displacement relationship of the testing machine in the i direction can be expressed as shown in formula (1):

[0058]

[0059] In formula (1), F i represents the load in the i direction, k i represents the stiffness of the testing machine in the i direction, represents the displacement of the testing machine in the i direction.

[0060] In a certain loading direction, the loading platform, loading rod, pressure plate and other components of the testing machine have a certain stiffness, and there is a certain gap between these components, which leads to nonlinear deformation of the testing machine. In other words, the stiffness of the testing machine is relatively small at the beginning of loading, and gradually becomes normal stiffness as the load increases. The nonlinear stiffness of the testing machine can be described by an exponential function as shown in formula (2):

[0061]

[0062] In formula (2), is the final stiffness in the i direction, is the initial stiffness in the i direction, It is the material constant that controls how fast the stiffness changes in the i direction.

[0063] The schematic diagram of the nonlinear stiffness change of the testing machine in different directions is shown in Figure 2 As shown, Figure 2 Taking the true triaxial testing machine as an example, the nonlinear stiffness change relationship of the true triaxial testing machine in different directions is demonstrated. Figure 2 The solid and dashed curves in the figure represent the stiffness k in two directions respectively. h and stiffness k H With load F h and load F H According to formula (2), the stiffness gradually changes from the initial stiffness to Increase to final stiffness The rate of change of stiffness is determined by the material constant It can be seen that the initial stiffness and Relatively small, with the increase of load, the stiffness gradually increases and tends to the respective final stiffness and

[0064] Through step 100, before the test, the nonlinear stiffness of the loading system of the testing machine in different directions is measured using a calibration block to determine the deformation characteristics of the testing machine itself. The measurement result is the nonlinear stiffness characteristic of the testing machine, which will affect the mechanical behavior analysis of the entire system when the mechanical model is subsequently established.

[0065] In an exemplary embodiment, after the rock mechanics test, a mechanical model is established for the system consisting of a testing machine and a rock sample (hereinafter referred to as the rock system), the loading rod of the testing machine is regarded as a nonlinear elastic material, the rock sample is regarded as an orthotropic elastic damage material, and the cumulative ringing count of acoustic emission in the data collected by the acoustic emission sensor is used as the damage variable. The load-displacement curve in the mechanical behavior information obtained during the test is fitted to obtain the parameters of the mechanical model, so as to establish a mechanical model that takes into account the nonlinear stiffness and impact load of the testing machine.

[0066] In an exemplary embodiment, the parameters of the mechanical model may include, but are not limited to, one or any combination of the following: elastic modulus of rock, final damage variable, impact coefficient, initial stiffness, final stiffness, and material constant.

[0067] The energy stored in the rock system is an important source of energy for rock bursts. Taking the true triaxial test as an example, since there is no absolutely rigid testing machine, during the loading process, energy is stored both in the rock itself and in the testing machine. In addition, rock mechanics tests often involve changes in boundary conditions and loading control methods. For this reason, a simplified model of the rock system consisting of a testing machine and a rock sample can be established, such as Figure 3 As shown, it can include the initial loading stage, transient unloading stage, stress concentration stage, and rock failure stage.

[0068] During the initial loading phase, the system responds in an elastic manner, with the stiffness of the testing machine and the rock playing a major role. During the initial loading phase, the testing machine applies a load to the rock, and the testing machine and the rock interact as an elastic system. Figure 3 The spring (representing stiffness) shown in reflects the stiffness of the testing machine and the rock. At this time, the deformation of the rock is mainly in the elastic range and no damage occurs.

[0069] During the transient unloading stage, a short unloading phenomenon may occur during the loading process, resulting in local stress relaxation. During the transient unloading stage, as the loading progresses, transient unloading may occur at a certain moment. The occurrence of transient unloading may be due to the sudden instability of a local part of the rock or the sudden generation of cracks. During this stage, the stress state of the testing machine-rock system changes suddenly, which may lead to sudden changes in the acoustic emission signal or other mechanical responses.

[0070] In the stress concentration stage, as cracks appear and expand, local stress concentrates, the system stiffness gradually decreases, and damage begins to accumulate. When loading continues, cracks may gradually expand inside the rock, leading to local stress concentration. The stress concentration area is the key part where the rock is about to fail. At this time, the stiffness in the model will decrease as the crack expands, reflecting the evolution of damage inside the rock.

[0071] When the bearing capacity of the rock reaches its limit, the rock failure stage will occur ( Figure 3 (not explicitly shown in the figure), crack expansion leads to overall destruction, damage reaches the maximum, and energy is released through acoustic emission and other forms. In the final stage of loading, the cracks in the stress concentration area expand to a certain extent, resulting in overall destruction of the rock. The crack mark (red part) shown in the figure indicates that the rock has reached the critical point of destruction, and the acoustic emission signal may show strong energy release. At this time, the testing machine is still applying load, but the bearing capacity of the rock decreases and the overall stiffness of the system also decreases.

[0072] In an exemplary embodiment, the rock is regarded as an orthotropic elastic damaged material. Based on the basic principles of elasticity and damage mechanics (generalized Hooke's law), the rock constitutive equation represented by three principal stresses is shown in formula (3):

[0073]

[0074] In formula (3), ε i represents the principal strain in the i direction, σ i represents the principal stress in the i direction, E i represents the elastic modulus in the i direction, μ i Expressed as Poisson's ratio in the i direction, D i represents the damage variable in the i direction, and i, j, and k are Einstein summation symbols.

[0075] The acoustic emission cumulative ring counts in the data collected by the acoustic emission sensor reflect the accumulated microscopic damage inside the rock. In the embodiment of the present application, the acoustic emission cumulative ring counts can be used to describe the degree of damage inside the rock. Considering that the rock sample is not completely damaged when the rock burst occurs, the damage variable in the i direction can be defined as: Among them, D i represents the final damage variable, C i Indicates the cumulative ring count at a certain moment. Indicates the final accumulated ring count.

[0076] Changes in boundary conditions such as single-sided unloading of rocks may lead to transient impact loads. At this time, the strain increment of the rock sample can include two parts: the strain increment caused by the impact load and the strain increment caused by the Poisson effect. In one embodiment, the impact load coefficient K can be introduced d To describe the impact dynamic amplification effect, the strain of rock under transient unloading can be calculated according to formula (4):

[0077]

[0078] In this way, the load-displacement relationship of the entire testing machine-rock sample system in the i direction is shown in formula (5):

[0079]

[0080] In formula (5), x i represents the total displacement in the i direction, represents the displacement of the rock in the i direction, l i represents the length of the rock sample in the i direction.

[0081] In one embodiment, by performing parameter fitting on the load-displacement curve recorded during the test in step 102, the three-dimensional damage model parameters considering the nonlinear stiffness of the testing machine and the impact load are obtained, as shown in Table 1:

[0082]

[0083] Table 1

[0084] Step 103: Perform energy analysis of the rock deformation-damage-destruction process through the established mechanical model, and calculate energy parameters and dissipation indicators.

[0085] In an exemplary embodiment, the model parameters obtained in step 102 are substituted into the energy calculation formula to calculate the basic energy indicators of the rock during the entire loading process, which may include one or any combination of the following energy indicators: total input energy, elastic strain energy, dissipated energy, total input energy density, elastic strain energy density, dissipated energy density, etc.

[0086] Furthermore, based on the basic energy index, indicators such as energy dissipation rate and / or energy release rate can also be calculated. Furthermore, curves showing changes of these indicators over time can also be plotted.

[0087] Through step 103, energy calculation is performed based on the parameters of the established mechanical model, thereby analyzing the energy dissipation and release of the rock during deformation, damage and destruction.

[0088] In one embodiment, in the energy calculation of the whole process of rock deformation, damage and destruction, the unit volume of rock is regarded as a closed system without heat exchange with the outside world, and the total input energy density generated by external work is u. According to the first law of thermodynamics and the principle of elastic mechanics, the total input energy density u and elastic strain energy density u of rock at a certain stress level are e and dissipated energy density u d The calculation is shown in formula (6):

[0089]

[0090] In particular, when the rock is regarded as an isotropic elastic material, in one embodiment, the elastic strain energy density u e It can be calculated according to formula (7):

[0091]

[0092] Thus, in one embodiment, the total input energy U, elastic strain energy U of the entire testing machine-rock sample system e , dissipated energy U d As shown in formula (8):

[0093]

[0094] In formula (8), U r and U m denote the total input energy of rock and testing machine respectively, and represent the elastic strain energy of rock and testing machine respectively, and V represents the volume of rock sample.

[0095] In one embodiment, the energy dissipation rate Φ is defined as the dissipated energy U d The time derivative of is shown in formula (9):

[0096]

[0097] Formula (9) greater than or equal to 0 indicates the irreversibility of energy dissipation.

[0098] In one embodiment, the energy release rate ERR can be defined as the elastic strain energy U e The time derivative of is shown in formula (10):

[0099]

[0100] The energy calculation results of the whole process of rock damage and destruction obtained by the final calculation are shown in Figure 4(a) and Figure 4(b). Figure 4(a) shows the trend of energy density changing with time (seconds). In Figure 4(a), the vertical axis represents energy density in mJ / mm3, and the horizontal axis represents time in seconds (s). Curve 41 is the trend of input energy density changing with time (seconds), curve 42 is the trend of elastic strain energy density changing with time (seconds), and curve 43 is the trend of dissipated energy density changing with time (seconds). The locally enlarged area in Figure 4(a) shows the details of the energy density change between about 1000 and 1500 seconds. Figure 4(b) shows the trend of energy changing with time. In Figure 4(b), the vertical axis represents energy, with the unit being kilojoule (KJ), and the horizontal axis represents time, with the unit being second (s). Curve 51 represents the trend of input energy changing with time, curve 52 represents the trend of elastic strain energy of rock changing with time, curve 53 represents the trend of elastic strain energy of the testing machine changing with time, and curve 54 represents the trend of dissipated energy changing with time.

[0101] By implementing the method for energy calculation during rock mechanics testing provided in the embodiment of the present application, the energy in the rock mechanics test is accurately calculated. The embodiment of the present application is a method for calculating the energy of the entire process of rock deformation-damage-destruction taking into account the nonlinear stiffness of the testing machine (loading system) and the impact load, which has important practical significance for accurately calculating the energy evolution during the test and exploring the energy mechanism of rock burst.

[0102] The present application also provides a system for realizing energy calculation in a rock mechanics test process, comprising at least:

[0103] The testing machine (loading system) is a device that can apply loads in different directions. The testing machine is used to: measure the ability of nonlinear stiffness, and control and record the load-displacement relationship; load the rock sample in multiple directions in order to obtain its stiffness-load change relationship in different directions.

[0104] The rigid calibration block is used to measure the nonlinear stiffness of the loading system of the test machine before the test, that is, to calibrate the nonlinear stiffness of the test machine. In one embodiment, the rigid calibration block can be used to apply loads in different directions and measure the response of the test machine to ensure that the nonlinear stiffness characteristics of the system are correctly recorded.

[0105] The acoustic emission sensor device is used to monitor the acoustic emission signals generated by the rock sample during loading, record the transient signals of the acoustic emission, and obtain the mechanical behavior information of the rock sample to be tested during loading, transient unloading and failure, such as the transient unloading moment and the accumulated ringing count, etc. At least three or more acoustic emission sensors need to be deployed on the rock surface.

[0106] The data acquisition system is used to record the load and displacement data during the test, especially the final load and displacement data when the rock fails. The data acquisition system needs to work synchronously with the testing machine so that the load-displacement curve can be accurately obtained during the entire loading process.

[0107] The data processing unit is used to establish a mechanical model of the combined system of the testing machine and the rock sample after the test according to the nonlinear stiffness of the testing machine loading system in different directions, the full-process acoustic emission monitoring results and the obtained mechanical behavior information; and to perform energy analysis of the rock deformation-damage-destruction process through the established mechanical model, and calculate energy parameters and dissipation indicators.

[0108] The system for realizing energy calculation during rock mechanics test provided by the embodiment of the present application accurately calculates the energy in the rock mechanics test. The embodiment of the present application is an energy calculation system for the whole process of rock deformation-damage-destruction taking into account the nonlinear stiffness of the testing machine (loading system) and the impact load, which has important practical significance for accurately calculating the energy evolution during the test and exploring the energy mechanism of rock burst.

[0109] Although the embodiments disclosed in this application are as above, the contents described are only embodiments adopted to facilitate understanding of this application and are not intended to limit this application. Any technician in the field to which this application belongs can make any modifications and changes in the form and details of implementation without departing from the spirit and scope disclosed in this application, but the scope of patent protection of this application shall still be based on the scope defined in the attached claims.

Claims

1. A method for realizing energy calculation in a rock mechanics experiment, characterized in that: include: In rock mechanics tests, acoustic emission sensors are used to monitor the entire process and obtain mechanical behavior information of the rock samples under loading, transient unloading and failure. After the rock mechanics test, a mechanical model of the combined system of the testing machine and rock samples is established based on the nonlinear stiffness of the testing machine loading system in different directions, the full-process acoustic emission monitoring results, and the obtained mechanical behavior information; The energy analysis of rock deformation-damage-destruction process is carried out through the established mechanical model, and the energy parameters and dissipation indicators are calculated.

2. The method according to claim 1, before the rock mechanics test, further comprises: The nonlinear stiffness of the loading system of the testing machine is measured using a rigid calibration block.

3. The method according to claim 2, wherein: The nonlinear stiffness measurement of the testing machine loading system using the rigid calibration block includes: The rigid calibration block is used to measure the nonlinear stiffness of the loading system of the testing machine in different directions, and loads are applied independently in different loading directions until the load-displacement curve is linearly related; According to the slope of the load-displacement curve, the relationship between the stiffness and load in different directions of the testing machine, that is, the stiffness-load change relationship, is obtained.

4. The method according to claim 1 or 2, wherein: The acoustic emission sensors include three or more.

5. The method according to claim 1 or 2, wherein: The mechanical behavior information includes one or any combination of the following: the instantaneous unloading occurrence time, the load-displacement data in different loading directions, and the final load and displacement data in different loading directions when the rock sample is destroyed.

6. The method according to claim 1 or 2, wherein: The mechanical model of the combined system of the testing machine and the rock sample is established, including: The loading rod of the testing machine is regarded as a nonlinear elastic material, the rock sample is regarded as an orthotropic elastic damaged material, and the cumulative ringing count of acoustic emission in the data collected by the acoustic emission sensor is used as a damage variable. The load-displacement curve in the mechanical behavior information obtained during the test is fitted to obtain the parameters of the mechanical model, so as to establish the mechanical model that takes into account the nonlinear stiffness and impact load of the testing machine.

7. The method according to claim 6, wherein: The parameters of the mechanical model include one of the following or any combination thereof: elastic modulus of rock, final damage variable, impact coefficient, initial stiffness, final stiffness, and material constant.

8. The method according to claim 1 or 2, wherein: The energy parameters and dissipation indexes include one of the following or any combination thereof: total input energy, elastic strain energy, dissipated energy, total input energy density, elastic strain energy density, dissipated energy density and other energy indexes.

9. The method according to claim 8, wherein the energy parameter and dissipation index further comprises: Calculate indicators such as energy dissipation rate and / or energy release rate.

10. A system for realizing energy calculation in a rock mechanics experiment, characterized in that: include: Testing machines capable of applying loads in different directions for: measuring the ability of nonlinear stiffness and controlling and recording load-displacement relationships; The rock samples are loaded in multiple directions to obtain the stiffness-load variation relationship in different directions; Rigidity calibration block, used to measure the nonlinear stiffness of the testing machine loading system before the test; Acoustic emission sensor device, used to monitor the acoustic emission signal generated by the rock sample during loading, record the transient signal of the acoustic emission, and obtain the mechanical behavior information of the rock sample to be tested during loading, transient unloading and failure; Data acquisition system, used to record load and displacement data during the test; A data processing unit is used to establish a mechanical model of the combined system of the testing machine and the rock sample after the test according to the nonlinear stiffness of the loading system of the testing machine in different directions, the full-course acoustic emission monitoring results and the obtained mechanical behavior information; And through the established mechanical model, the energy analysis of the rock deformation-damage-destruction process is carried out to calculate the energy parameters and dissipation indicators.

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