A Method and System for Determining Rockburst Tendency Level Based on Relative Post-Peak Energy Release Rate Index

Abstract

This invention provides a method and system for determining rockburst tendency levels based on the relative post-peak energy release rate index. The method involves: first, preparing a cylindrical rock sample; then conducting a uniaxial compression test until complete failure, recording acoustic signals, image information of the failure process, stress-strain curves, and stress-time curves; classifying the sample's energy evolution type based on the acoustic signals and image information of the failure process; then calculating the total input energy characteristic value and the post-peak energy characteristic value according to the energy evolution type; defining parameters for failure duration and total loading duration, thereby deriving the total energy input rate and the post-peak energy release rate; finally, obtaining the relative post-peak energy release rate based on the ratio of the two rates, and evaluating the rockburst level of the rock sample. This invention comprehensively considers the energy and time factors throughout the entire rock sample failure process, while eliminating the influence of loading rate on rockburst tendency, resulting in a more accurate assessment of rockburst tendency.

Description

Technical Field

[0001] This invention relates to the field of rockburst tendency level discrimination technology, and in particular to a method and system for rockburst tendency level discrimination based on the relative post-peak energy release rate index. Background Technology

[0002] With the increasing scarcity of shallow resources and space, mining, tunneling, and other rock engineering projects are continuously extending deeper into the Earth. As the construction depth increases, the frequency and intensity of rockbursts rise dramatically, seriously threatening the safety of construction workers and causing incalculable economic losses. Rockburst tendency, as a crucial indicator for assessing the rockburst potential of rock materials, is fundamental to guiding deep-earth engineering design and rockburst disaster prevention. Therefore, scientifically, accurately, and quantitatively assessing the rockburst tendency of rock materials and rationally classifying rockburst tendency levels is key to preventing rockbursts in deep-earth engineering.

[0003] Rockburst is a typical rock instability phenomenon driven by energy. The violent energy release during rockburst destruction is a typical characteristic of rockburst disasters in deep engineering. Therefore, it is reasonable and necessary to assess the rockburst tendency from the perspective of energy evolution throughout the entire rock destruction process. Currently, scholars at home and abroad have proposed many rockburst tendency criteria based on energy indices, including strain storage index, energy impact index, elastic strain energy index, peak energy impact index, residual elastic energy index, rockburst potential occurrence type assessment energy ratio (CN202210750932.2), and stress energy ratio (CN202010767256.0). These rockburst tendency criteria evaluate the rock material's rockburst tendency from the perspective of pre-peak and post-peak energy, reflecting the high energy storage characteristics of rockburst occurrence. However, rockburst destruction is a dynamic process of rapid energy release. It is necessary to consider not only the energy inside the rock at the time of rockburst occurrence but also the energy release rate at the time of rockburst occurrence, that is, to consider the energy release per unit time in order to comprehensively reflect the true rockburst tendency of the rock material. Currently, existing methods (patents with application numbers CN201910430760.9 and CN201910429937.3) have considered the time characteristics of rockbursts and calculated the lag time ratio through uniaxial compression experiments or uniaxial graded loading and unloading experiments. However, this indicator only considers the time aspect of rockbursts and does not take into account the energy characteristics of the rockburst process, so it cannot scientifically assess the rockburst tendency of rock materials.

[0004] In addition, different types of rocks (soft rock and hard rock) have different energy storage capacities, and their energy evolution during the failure process is also different. However, the same energy calculation model is currently used to calculate the energy parameters of rocks with different properties, which introduces errors into the calculation of rockburst tendency index.

[0005] In view of this, it is necessary to design an improved method and system for judging rockburst tendency level based on the relative post-peak energy release rate index to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for judging rockburst tendency level based on the relative post-peak energy release rate index. The method first uses the dual standard of acoustic signal and image information of the destruction process to accurately classify the energy evolution of rock samples, providing favorable conditions for accurate calculation of rock sample energy. Then, it comprehensively considers the energy and time factors of the entire rock sample destruction process to obtain the post-peak energy release rate and the total energy input rate. The ratio of the post-peak energy release rate and the total energy input rate is used to eliminate the influence of the loading rate on the rockburst tendency, and finally accurately determines the rockburst tendency of the rock.

[0007] To achieve the above-mentioned objectives, this invention provides a method for determining rockburst tendency level based on the relative post-peak energy release rate index, comprising the following steps:

[0008] S1. The obtained rock blocks are processed into standard cylindrical rock samples;

[0009] S2. The cylindrical rock sample is subjected to a uniaxial compression test until it is completely destroyed, and acoustic signals, image information of the failure process, all-axial stress-axial strain curves and all-axial stress-time curves are obtained.

[0010] S3. Based on the acoustic signals and image information of the destruction process obtained in step S2, classify the cylindrical rock sample into either the first type of energy evolution or the second type of energy evolution to determine the energy calculation model;

[0011] S4. Calculate the total input energy characteristic value U based on the all-axial stress-axial strain curve obtained in step S2 and the energy evolution type obtained in step S3. total and post-peak energy characteristic value U post-peak ;

[0012] S5. Define the time interval between the peak stress and the termination stress of the cylindrical rock specimen as the failure time T1, and the time interval between the initial loading stress and the termination stress as the total loading time T2;

[0013] Based on the post-peak energy characteristic value U obtained in step S4 post-peak The peak energy release rate VE is derived from the destruction duration T1. post-peak VE post-peak =U post-peak / T1;

[0014] Based on the total input energy characteristic value U obtained in step S4 totalThe total energy input rate VE is derived from the total loading time T2. total VE total =U total / T2;

[0015] S6. Based on the post-peak energy release rate VE obtained in step S5 post-peak and the total energy input rate VE total The relative peak energy release rate (RVE) was obtained. post-peak RVE post-peak =VE post-peak / VE total ;

[0016] S7. The relative post-peak energy release rate (RVE) obtained in step S6 post-peak The value is used to determine the rockburst tendency level of the cylindrical rock sample:

[0017] When RVE post-peak When the rock strength is ≤5, the rock material has no tendency to rockburst; when the rock strength is ≤5, the rock <RVE post-peak When the rock temperature is ≤8, the rock material has a slight tendency to rockburst; when the temperature is ≤8, the rock material has a slight tendency to rockburst. <RVE post-peak When ≤12, the rock material has a moderate tendency to rockburst; when RVE post-peak When the value is ≥12, the rock material has a strong tendency to rockburst.

[0018] As a further improvement of the present invention, in step S3, the first type of energy evolution includes one of the following two situations: after noise reduction, there is no acoustic signal and no rock fragments are splashed during the destruction process of the cylindrical rock sample; or after noise reduction, there is a weak acoustic signal and a very small amount of rock fragments loosen and slide off the cylindrical rock sample during the destruction process. The termination stress of the first type of energy evolution is the residual stress.

[0019] The second type of energy evolution is characterized by a large acoustic signal after noise reduction and a large number of rock fragments being ejected during the destruction process of the cylindrical rock sample; the termination stress of the second type of energy evolution is the rockburst stress.

[0020] As a further improvement of the present invention, the total input energy characteristic value U in step S4 total and the post-peak energy characteristic value U post-peak The calculation formula is:

[0021]

[0022]

[0023]

[0024] in, The first type of total input energy eigenvalue;

[0025] U o The total input energy before the peak is obtained by the area integral under the curve before the peak of the all-axial stress-axial strain curve.

[0026] The total input energy after the first type of peak is obtained by the area integral under the curve of the post-peak stage of the all-axial stress-axial strain curve, and the termination stress is the residual stress.

[0027] These are the energy characteristic values ​​after the first type of peak;

[0028] This represents the post-peak fracture energy of the first type.

[0029] U e Pre-peak elasticity;

[0030] U er This refers to the residual elastic energy after the peak.

[0031]

[0032]

[0033]

[0034] in, This represents the second type of total input energy characteristic value;

[0035] U o The total input energy before the peak is obtained by the area integral under the curve before the peak of the all-axial stress-axial strain curve.

[0036] The total input energy after the second type of peak is obtained by the area integral under the curve of the post-peak stage of the all-axial stress-axial strain curve, and the termination stress is the rockburst failure stress.

[0037] This refers to the energy characteristic value after the second type of peak;

[0038] This represents the fracture energy following the second type of peak.

[0039] As a further improvement of the present invention, the peak-precession total input energy U o Total input energy after the first type of peak Pre-peak elastic energy U e Post-peak residual elastic energy U er and the total input energy after the second type of peak The calculation formula is:

[0040]

[0041]

[0042]

[0043]

[0044]

[0045] Where σ is the applied stress, which is a known value;

[0046] σ c The peak stress is known from the all-axial stress-axial strain curve.

[0047] σ r The stress is residual stress, as can be seen from the all-axial stress-axial strain curve.

[0048] E0 is Young's modulus, which can be determined from the slope of the elastic deformation stage of the all-axial stress-axial strain curve.

[0049] ε c The strain corresponding to the peak stress can be determined from the all-axial stress-axial strain curve.

[0050] ε r The strain corresponding to the residual stress can be seen from the all-axial stress-axial strain curve.

[0051] ε bf The strain is the stress corresponding to the rockburst failure stress, which can be seen from the all-axial stress-axial strain curve.

[0052] As a further improvement of the present invention, the uniaxial compression test in step S2 is performed on an electro-hydraulic servo material testing machine; the loading rate of the electro-hydraulic servo material testing machine is 0.04-0.07 mm / min or 110-130 KN / min.

[0053] As a further improvement of the present invention, the acoustic signal in step S2 is measured and stored by a sound decibel meter; the image information of the rock failure process is stored and recorded by a camera.

[0054] As a further improvement of the present invention, the cylindrical rock sample in step S1 has a diameter of 48-52 mm and a height that is 1.8-2.2 times the diameter.

[0055] As a further improvement of the present invention, a uniaxial graded cyclic loading test is performed on the cylindrical rock sample, with loading and unloading at the same rate, cyclically repeated at least three times until complete failure, to obtain the cyclic loading and unloading stress-strain curves of the cyclic loading and unloading process; when unloading at the peak stress point, the unloading stress-strain curve at the peak stress point is obtained; when unloading at the residual stress point, the unloading stress-strain curve at the residual stress point is obtained; the pre-peak elastic energy U e Residual elastic energy U after peak er The calculation formula is:

[0056]

[0057]

[0058] Where, σ u The unloading stress is known.

[0059] E u This is the unloading modulus at the peak stress, which can be determined from the slope of the unloading stress-strain curve at the peak stress.

[0060] E ur The unloading modulus at the residual stress point can be determined from the slope of the unloading stress-strain curve at the residual stress point.

[0061] ε u The permanent strain after unloading at the peak stress point can be determined from the unloading stress-strain curve at the peak stress point.

[0062] ε ur The permanent strain after unloading at the residual stress point can be seen from the unloading stress-strain curve at the residual stress point.

[0063] Or the pre-peak elastic energy U e It was calculated using linear energy storage laws.

[0064] To achieve the above-mentioned objectives, the present invention also provides a system for implementing the rockburst tendency level discrimination method based on the relative post-peak energy release rate index as described in any of the above claims, comprising an electro-hydraulic servo material testing machine, a sound decibel meter, and a camera; the cylindrical rock sample is placed on the loading platform of the electro-hydraulic servo material testing machine, which is used to perform a uniaxial compression test on the cylindrical rock sample; the distance between the sound decibel meter and the cylindrical rock sample does not exceed 0.3m; the camera is located on the same horizontal plane as the cylindrical rock sample and is used to store and record image information of the rockburst process of the cylindrical rock sample.

[0065] As a further improvement of the present invention, the number of frames of the camera is not less than 125.

[0066] The beneficial effects of this invention are:

[0067] (1) The rockburst tendency level discrimination method based on the relative peak energy release rate index provided by the present invention first prepares the rock sample into a shape that meets the requirements, loads it through a uniaxial compression test, and records the acoustic signal of the loading process and the image information of the destruction process. The rock sample is accurately classified by the dual standard of acoustic signal and image information of the destruction process, which provides favorable conditions for the accurate calculation of energy in the rock sample crushing process.

[0068] Based on this, and considering the energy changes throughout the entire rock sample failure process, the total input energy characteristic value and post-peak energy characteristic value are accurately calculated according to the energy evolution model. Since rockburst is a dynamic failure process, the temporal characteristics of the rockburst occurrence process have a significant impact on rockburst tendency. This invention calculates the post-peak energy release rate (i.e., the energy release rate per unit time) and the total energy input rate based on the temporal characteristics of the rock sample failure process, thereby obtaining the relative post-peak energy release rate. Finally, considering both energy and time factors, the rockburst tendency level of the cylindrical rock sample is determined by the value of the relative post-peak energy release rate.

[0069] Meanwhile, the rockburst tendency level discrimination method based on the relative post-peak energy release rate is obtained based on experimental phenomena. The rockburst tendency level discrimination results are consistent with the experimental phenomena, which can more accurately assess the rockburst tendency of rocks.

[0070] (2) The rockburst tendency classification method based on the relative post-peak energy release rate index provided by the present invention, compared with the rockburst tendency criteria based on mechanical parameters, considers the energy evolution of the entire rock failure process; compared with the existing rockburst tendency criteria based on energy parameters, the relative post-peak energy release rate index considers the time effect of the energy evolution of the entire process and quantitatively calculates the rock energy release rate; and compared with other rockburst tendency criteria, the relative post-peak energy release rate eliminates the influence of the loading rate on the rockburst tendency. Attached Figure Description

[0071] Figure 1 This is a flowchart of the rockburst tendency level discrimination method based on the relative post-peak energy release rate index of the present invention.

[0072] Figure 2 This is a schematic diagram of the energy of rock materials in the first type of energy calculation model.

[0073] Figure 3A schematic diagram illustrating the method for determining the failure time and total loading time of rock materials in the first type of energy calculation model.

[0074] Figure 4 This is a schematic diagram of the energy of rock materials in the second type of energy calculation model.

[0075] Figure 5 A schematic diagram illustrating the method for determining the failure time and total loading time of rock materials in the second type of energy calculation model.

[0076] Figure 6 This is a schematic diagram of the system structure of the rockburst tendency level discrimination method based on the relative peak energy release rate index of the present invention.

[0077] Figure 7 This is the all-axial stress-axial strain curve of the rock sample in Example 1 of the present invention during the uniaxial compression test (belonging to the second type of energy calculation model).

[0078] Figure Labels

[0079] 1-Electro-hydraulic servo material testing machine; 2-Cylindrical rock sample; 3-Sound decibel meter; 4-Camera. Detailed Implementation

[0080] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0081] It should also be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and / or processing steps closely related to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0082] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0083] Please see Figures 1 to 5 As shown, this invention provides a method for determining rockburst tendency level based on the relative post-peak energy release rate index, comprising the following steps:

[0084] S1. Sample Preparation:

[0085] On-site sampling was conducted, and the obtained rock blocks were processed into cylindrical rock specimens according to the rock mechanics testing procedures. The diameter of these cylindrical rock specimens was 48-52 mm, and the height was 1.8-2.2 times the diameter. According to the standards of the International Society for Rock Mechanics, processing the test rock samples into cylindrical rock specimens of the above dimensions improves the accuracy of the test and ensures the repeatability of the test results by standardizing the shape and size of the specimens.

[0086] S2. Experiment:

[0087] Using an electro-hydraulic servo material testing machine, a uniaxial compression test was performed on the cylindrical rock sample from step S1 until it was completely destroyed. The acoustic signal of the process was measured and stored using a sound decibel meter, and the image information of the destruction process was stored using a camera. At the same time, the axial stress-axial strain curve and the axial stress-time curve of the process were plotted (these two curves were obtained by importing axial stress, axial strain and time into the computer).

[0088] Specifically, a cylindrical rock sample is placed on the loading platform of an electro-hydraulic servo material testing machine. The indenter of the electro-hydraulic servo material testing machine is adjusted to make slight contact with the end face of the cylindrical rock sample. A sound decibel meter is placed within 0.3m of the cylindrical rock sample, and a camera is set up to record the entire failure process. Based on the loading rate of conventional static load tests, the electro-hydraulic servo material testing machine controls the loading rate with a displacement of 0.04-0.07mm / min or a force of 110-130KN / min until the cylindrical rock sample fails, obtaining the full axial stress-axial strain curve.

[0089] Preferably, the electro-hydraulic servo material testing machine controls the loading rate with a displacement of 0.06 mm / min or a force of 120 KN / min, which ensures the acquisition of stress and strain data during loading and improves the accuracy of the test results. Excessive or insufficient loading displacement will affect the acquisition of stress and strain data, and will also affect the peak strength of the rock sample.

[0090] The sound decibel meter is started before the electro-hydraulic servo material testing machine to maintain a quiet testing environment. The noise level of the testing environment is recorded first (for noise reduction) to obtain the acoustic signal during the test. The camera is started simultaneously with the electro-hydraulic servo material testing machine to ensure that the sound decibel meter and camera work throughout the entire process.

[0091] S3. Classification:

[0092] The acoustic signals and image information of the destruction process obtained in step S2 are imported into the computer. After identification, the cylindrical rock samples are classified into either the first type of energy evolution or the second type of energy evolution to determine the energy calculation model.

[0093] If there is no acoustic signal (after noise reduction) and no rock fragments are ejected during the destruction of the cylindrical rock sample; or if there is a weak acoustic signal (after noise reduction) and a very small amount of rock fragments loosen and slide off the cylindrical rock sample during the destruction process (i.e., the fragments slide off the sidewall of the sample), then it is classified as the first type of energy evolution; the termination stress of the first type of energy evolution is the residual stress.

[0094] If there is a large acoustic signal (after noise reduction) and a large number of rock fragments are ejected during the destruction process of the cylindrical rock sample, it is classified as the second type of energy evolution; the termination stress of the second type of energy evolution is the rockburst failure stress.

[0095] During the above classification process, a fragment distribution collection plate can be placed between the rock sample and the loading platform to observe the fragment distribution after the rock sample is destroyed. The fragment distribution collection plate is a series of concentric rings extending outwards from the rock sample, with each ring extending 2.5 cm in length (i.e., the radius continuously expands outwards by 2.5 cm); the material is one that is not easily deformed under pressure. Rock samples from the first type of energy evolution model loosen and slide into the first concentric ring of the fragment distribution collection plate; fragments from rock samples from the second type of energy evolution model land outside the first concentric ring. This method further confirms the accuracy of the classification of cylindrical rock samples.

[0096] In some embodiments, an acoustic emission instrument is used in the uniaxial compression test to monitor the acoustic emission signal of the rock, obtain the acoustic emission energy parameters of the entire rock failure process, and calculate the average acoustic emission energy or the maximum acoustic emission energy to quantitatively determine the energy evolution type of the cylindrical rock sample. Specifically, an average acoustic emission energy value of 950 mV·mS is set; values ​​below this energy value are classified as the first type of energy evolution, and values ​​above this energy value are classified as the second type of energy evolution. Alternatively, a maximum acoustic emission energy value of 14000 mV·mS is set; values ​​below this energy value are classified as the first type of energy evolution, and values ​​above this energy value are classified as the second type of energy evolution.

[0097] S4. Calculate the total input energy eigenvalue U total and post-peak energy characteristic value U post-peak :

[0098] Calculate the total input energy characteristic value U based on the all-axial stress-axial strain curve obtained in step S2 and the energy evolution type obtained in step S3. total and post-peak energy characteristic value U post-peak .

[0099] Due to differences in rock properties, the failure characteristics and post-peak stress-strain curves of different rock types differ in uniaxial compression tests. For soft rocks, the rock strength is low, plastic deformation is significant, the rock's energy storage capacity is poor, energy release during rock failure is slow, and the rock still retains some load-bearing capacity after failure; the post-peak stress-strain curve shows a residual stress stage. For hard and brittle rocks, the rock strength is high, brittle characteristics are obvious, the rock's pre-peak energy storage capacity is good, energy release during rock failure is rapid, and the rock completely loses its load-bearing capacity after failure; the post-peak stress-strain curve shows no residual stress stage. Post-peak fracture energy reflects the energy released through microcrack penetration and compressive plastic deformation within the rock during the post-peak stage, as well as a small amount of energy radiated as heat, kinetic energy, and sound radiation. For soft rocks, the post-peak released energy is the first type of post-peak fracture energy, while for hard rocks, the post-peak released energy is the second type of post-peak fracture energy. Because hard and brittle rocks completely lose their load-bearing capacity after failure, no elastic energy remains within the rock; some of the remaining elastic energy after the peak is released in the form of kinetic energy from splashed rock fragments. Therefore, the post-peak energy release rate considers both the rock's energy storage capacity and the rate of post-peak energy release. Rockburst tendency, on the other hand, is a comprehensive indicator characterizing the rock material's potential for rockburst; it should be an objective property of the rock, related to the microstructure of the rock crystals, but independent of loading conditions. The relative post-peak energy release rate takes this into account.

[0100] Specifically, such as Figure 2 The diagram shows the energy characteristics of the rock material (soft rock) in the first type of energy calculation model. The first type of total input energy characteristic value for this type of rock is also shown. The total input energy U before the peak o (Area under the curve before the peak of the all-axial stress-axial strain curve) and total input energy after the first type of peak The sum of the areas under the peak of the axial stress-axial strain curve (excluding the area under the horizontal straight line, which is denoted as the residual stress stage). The total input energy before the peak, U... o Part of the energy is used for the generation and propagation of microcracks inside the rock sample during the pre-peak stage (denoted as dissipated energy), and the other part is stored in the rock sample (denoted as pre-peak elastic energy U). e This type of rock sample has a low tendency to burst; after the rock sample fractures, energy is still stored within the rock sample (denoted as post-peak residual elastic energy U). er Therefore, the energy used for post-peak destruction of rock samples (denoted as the first type of post-peak energy characteristic value) Or the post-peak fracture energy of the first type () represents the pre-peak elastic energy U e Total input energy after the first type peak The remaining elastic energy U after subtracting the peak er .

[0101] Therefore, the first type of total input energy eigenvalue and the energy characteristic value after the first type of peak The calculation formula is:

[0102]

[0103]

[0104]

[0105] in, The first type of total input energy eigenvalue;

[0106] U o The total input energy before the peak is obtained by the area integral under the curve before the peak of the all-axial stress-axial strain curve.

[0107] The total input energy after the first type of peak is obtained by the area integral under the curve of the post-peak stage of the all-axial stress-axial strain curve, and the termination stress is the residual stress.

[0108] These are the energy characteristic values ​​after the first type of peak;

[0109] This represents the post-peak fracture energy of the first type.

[0110] U e Pre-peak elasticity;

[0111] U er This represents the remaining elastic energy after the peak.

[0112] like Figure 4 The diagram shows the energy characteristics of rock material (hard rock) in the second type of energy calculation model, and the total input energy characteristic of this type of rock. The total input energy U before the peak o (Area under the curve before the peak of the all-axial stress-axial strain curve) and total input energy after the second type of peak (The area under the peak of the all-axial stress-axial strain curve; this type of curve does not exist as...) Figure 2 The horizontal straight line shown represents the residual stress stage. Since the rock sample underwent rockburst failure before reaching the residual stress stage, the termination stress is the sum of the rockburst failure stresses. The total input energy before the peak, U... o Part of the energy is used for the generation and propagation of microcracks inside the rock sample during the pre-peak stage (denoted as dissipated energy), and the other part is stored in the rock sample (denoted as pre-peak elastic energy U). eThis type of rock sample has a high tendency to explode. After the rock sample is destroyed, the rock sample becomes completely unstable and there is no energy storage within the rock sample. Therefore, the energy used for post-peak destruction of the rock sample (denoted as the second type of post-peak energy characteristic value) is limited. Or the post-peak fracture energy of the second type. () represents the pre-peak elastic energy U e Total input energy after the second type peak The sum of.

[0113] Therefore, the second type of total input energy eigenvalue Energy characteristic values ​​after the second type peak The calculation formula is:

[0114]

[0115]

[0116]

[0117] in, This represents the second type of total input energy characteristic value;

[0118] U o The total input energy before the peak is obtained by the area integral under the curve before the peak of the all-axial stress-axial strain curve.

[0119] The total input energy after the second type of peak is obtained by the area integral under the curve of the post-peak stage of the all-axial stress-axial strain curve, and the termination stress is the rockburst failure stress.

[0120] This refers to the energy characteristic value after the second type of peak;

[0121] This represents the fracture energy following the second type of peak.

[0122] Next, we will analyze the total input energy U before the peak. o Total input energy after the first type of peak Pre-peak elastic energy U e Post-peak residual elastic energy U er and the total input energy after the second type of peak The calculation is performed using the following formula:

[0123]

[0124]

[0125]

[0126]

[0127]

[0128] Where σ is the applied stress, which is a known value;

[0129] σ c The peak stress is known from the maximum stress on the all-axial stress-axial strain curve.

[0130] σ r The residual stress can be determined from the stress corresponding to the residual stress stage of the all-axial stress-axial strain curve.

[0131] E0 is Young's modulus, which can be determined from the slope of the elastic deformation stage of the all-axial stress-axial strain curve.

[0132] ε c The strain corresponding to the peak stress can be determined from the strain corresponding to the maximum stress on the all-axial stress-axial strain curve.

[0133] ε r The strain corresponding to the residual stress can be determined from the strain at the starting point of the residual stress stage of the all-axial stress-axial strain curve.

[0134] ε bf The strain corresponding to the rockburst failure stress can be determined from the strain corresponding to the rockburst failure stress in the latter part of the upper peak of the all-axial stress-axial strain curve.

[0135] In some embodiments, a uniaxial graded cyclic loading test is performed on a cylindrical rock specimen, with loading and unloading at the same rate, cyclically repeated at least three times until complete failure, to obtain the cyclic loading and unloading stress-strain curves for the cyclic loading and unloading process; when unloading at the peak stress, the unloading stress-strain curve at the peak stress is obtained; when unloading at the residual stress, the unloading stress-strain curve at the residual stress is obtained; the pre-peak elastic energy U e Residual elastic energy U after peak er The calculation formula is:

[0136]

[0137]

[0138] Where, σ y The unloading stress is known.

[0139] E u This is the unloading modulus at the peak stress, which can be determined from the slope of the unloading stress-strain curve at the peak stress.

[0140] E ur The unloading modulus at the residual stress point can be determined from the slope of the unloading stress-strain curve at the residual stress point.

[0141] ε u The permanent strain after unloading at the peak stress point can be determined from the unloading stress-strain curve at the peak stress point.

[0142] ε ur The permanent strain after unloading at the residual stress point can be seen from the unloading stress-strain curve at the residual stress point.

[0143] Or the pre-peak elastic energy U e It was calculated using linear energy storage laws.

[0144] In summary, the pre-peak elastic energy U e It can be obtained from (1) the area under the unloading curve after unloading at the peak stress, and (2) from Calculations show that (3) is approximately derived from... The calculation yields the following result; alternatively, it can be calculated using linear energy storage laws. The post-peak residual elastic energy U... er It can be obtained from (1) the area under the unloading curve after unloading at the residual stress, and (2) from Calculations show that (3) is approximately derived from... The calculation yielded the result. Those skilled in the art should understand that, if an unloading process is involved and an unloading curve is plotted, the area under the unloading curve should be used preferentially to calculate the pre-peak elastic energy U. e Residual elastic energy U after peak er .

[0145] S5. Calculate the post-peak energy release rate VE post-peak and total energy input rate VE total :

[0146] like Figure 3 and Figure 5 As shown, the time interval between the peak stress and the termination stress of the cylindrical rock specimen is defined as the failure time T1, and the time interval between the initial loading stress and the termination stress is defined as the total loading time T2.

[0147] Based on the post-peak energy characteristic value U obtained in step S4 post-peak The peak energy release rate VE was derived from the destruction duration T1. post-peak VE post-peak =U post-peak / T1;

[0148] Based on the total input energy characteristic value U obtained in step S4 total The total energy input rate VE is derived from the total loading time T2. total VE total =U total / T2.

[0149] Upost-peak and U total The value corresponds to different types of energy evolution.

[0150] S6. Calculate the relative post-peak energy release rate (RVE). post-peak :

[0151] Based on the post-peak energy release rate VE obtained in step S5 post-peak and the total energy input rate VE total The relative peak energy release rate (RVE) was obtained. post-peak RVE post-peak =VE post-peak / VE total .

[0152] Due to the post-peak energy release rate VE post-peak The value will vary with the loading speed, by measuring the post-peak energy release rate VE. post-peak and total energy input rate VE total Performing ratio calculations can reduce the impact of loading speed on the results and further improve the accuracy of the judgment.

[0153] S7. Rockburst tendency level determination:

[0154] Based on the relative post-peak energy release rate (RVE) obtained in step S6 post-peak The value is used to determine the rockburst tendency level of a cylindrical rock sample:

[0155] When RVE post-peak When the rock strength is ≤5, the rock material has no tendency to rockburst; when the rock strength is ≤5, the rock <RVE post-peak When the rock temperature is ≤8, the rock material has a slight tendency to rockburst; when the temperature is ≤8, the rock material has a slight tendency to rockburst. <RVE post-peak When ≤12, the rock material has a moderate tendency to rockburst; when RVE post-peak When the value is ≥12, the rock material has a strong tendency to rockburst.

[0156] The entire calculation process and rockburst tendency level determination can be obtained from the corresponding computer program's data import module (step S2), energy calculation model identification module (step S3), energy characteristic value calculation module (step S4), relative post-peak energy release rate calculation module (steps S5-S6), and evaluation module (step S7).

[0157] like Figure 6As shown, the present invention also provides a system for the above-mentioned method for judging rockburst tendency level based on the relative post-peak energy release rate index, including an electro-hydraulic servo material testing machine 1, a sound decibel meter 3, and a camera 4. A cylindrical rock sample 2 is placed on the loading platform of the electro-hydraulic servo material testing machine 1, which is used to perform a uniaxial compression test on the cylindrical rock sample 2; the distance between the sound decibel meter 3 and the cylindrical rock sample 2 does not exceed 0.3m; the camera 4 is located on the same horizontal plane as the cylindrical rock sample 2 and is used to store and record image information of the rockburst process of the cylindrical rock sample 2.

[0158] Among them, the frame rate of camera 4 is no less than 125 frames.

[0159] The present invention will now be described in detail through several embodiments.

[0160] Example 1

[0161] A method for determining the rockburst tendency of fine granite based on the relative post-peak energy release rate includes the following steps:

[0162] S1. Sample Preparation:

[0163] The fine granite blocks retrieved from the engineering site were processed into cylindrical rock samples with a diameter of 50 mm and a length of 100 mm.

[0164] S2. Experiment:

[0165] The obtained cylindrical rock specimens were subjected to uniaxial compression tests on an INSTRON 1346 electro-hydraulic servo material testing machine. Force-controlled loading was applied at a loading rate of 120 kN / min. Acoustic signals during the process were measured and recorded using a sound decibel meter, and image information of the failure process was recorded using a camera. Simultaneously, the all-axial stress-axial strain curves of the process were plotted (e.g., ...). Figure 7 (as shown) and the all-axial stress-time curve.

[0166] S3. Classification:

[0167] The acoustic signals and image information of the destruction process obtained in step S2 are imported into the computer, and after identification, the cylindrical rock sample is classified into the second type of energy evolution to determine the energy calculation model.

[0168] S4. Calculate the eigenvalues ​​of the second type of total input energy. Energy characteristic values ​​after the second type peak

[0169]

[0170] S5. Calculate the post-peak energy release rate VE post-peak and total energy input rate VE total :

[0171] In the uniaxial compression test of fine granite, the fine granite reached its peak stress at 256 s and completely failed at 268 s. Therefore, the total loading time of the fine granite is T2 = 268 s, and the failure time is T1 = 268 - 256 = 12 s.

[0172] VE post-peak =U post-peak / T1=0.5832 / 12=0.0486mJ·mm -3 ·s -1 ;

[0173] VE total =U total / T2=0.7025 / 268=0.00262mJ·mm -3 ·s -1 .

[0174] S6. Calculate the relative post-peak energy release rate (RVE). post-peak :

[0175] RVE post-peak =VE post-peak / VE total =0.0486 / 0.00262=18.55.

[0176] S7. Rockburst tendency level determination:

[0177] Based on the relative post-peak energy release rate (RVE) obtained in step S6 post-peak The value used to determine the rockburst tendency level of a cylindrical rock sample: RVE post-peak =18.55, located in RVE post-peak The value is within the range of ≥12, therefore it belongs to the category of strong rockburst tendency.

[0178] Example 2-10

[0179] Using the discrimination method of the present invention, the rockburst tendency of different types of rocks such as shale, yellow granite, and limestone was determined, and the results are shown in Table 1.

[0180] Table 1. Rockburst tendency determination for different types of rocks in Examples 1-10

[0181]

[0182]

[0183] Table 1 shows that the relative post-peak energy release rate of shale is 15.25, indicating a strong rockburst tendency; the relative post-peak energy release rate of yellow granite is 14.03, also indicating a strong rockburst tendency; the relative post-peak energy release rate of limestone is 13.25, indicating a strong rockburst tendency; the relative post-peak energy release rate of marble 1 is 10.32, indicating a moderate rockburst tendency; and the relative post-peak energy release rate of red sandstone is... 9.07, rockburst tendency assessment result is moderate rockburst; Yellow rust stone has a relative post-peak energy release rate of 7.62, rockburst tendency assessment result is slight rockburst; Marble 2 has a relative post-peak energy release rate of 5.45, rockburst tendency assessment result is slight rockburst; Biotite chlorite schist has a relative post-peak energy release rate of 4.91, rockburst tendency assessment result is no rockburst; White marble has a relative post-peak energy release rate of 4.45, rockburst tendency assessment result is no rockburst.

[0184] The rockburst tendency classification method proposed in this patent, based on the relative post-peak energy release rate index, yielded results consistent with indoor experimental phenomena, demonstrating the effectiveness and accuracy of the method. Furthermore, the fine granite, yellow granite, limestone, red sandstone, and white marble in Table 1 are from the same origin as the rocks described in the article "Gong Fengqiang, Yan Jingyi, Li Xibing, Rockburst Tendency Criterion Based on Linear Energy Storage Law and Residual Elastic Energy Index, Chinese Journal of Rock Mechanics and Engineering, 2018, 37(09):1993-2014." Using the residual elastic energy rockburst tendency criterion, the rockburst tendency of these rocks was classified, and the results were identical to those of this patent. Moreover, the residual elastic energy index has been incorporated into national energy standards, further validating the accuracy of the rockburst tendency classification method proposed in this patent.

[0185] In summary, this invention provides a method and system for determining rockburst tendency based on the relative post-peak energy release rate index. This method first uses a dual standard of acoustic signals and image information of the failure process to accurately classify the energy evolution of rock samples, providing favorable conditions for precise energy calculation during the rock sample fracturing process. Then, it comprehensively considers the energy and time factors throughout the entire rock sample failure process to obtain the post-peak energy release rate and the total energy input rate. The ratio of the post-peak energy release rate to the total energy input rate is used to eliminate the influence of the loading rate on rockburst tendency, ultimately accurately determining the rockburst tendency of the rock.

[0186] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A rockburst proneness grade discrimination method based on a relative post-peak energy release rate indicator, characterized by, The method comprises the following steps: S1. Process the obtained rock mass into a standard cylindrical rock sample; S2. Perform a uniaxial compression test on the cylindrical rock sample until complete failure, obtaining an acoustic signal, image information of the failure process, a full axial stress-axial strain curve, and a full axial stress-time curve; S3. According to the acoustic signal and the image information of the failure process obtained in step S2, classify the cylindrical rock sample into a first type of energy evolution type or a second type of energy evolution type to determine an energy calculation model; S4. Calculate the total input energy characteristic value U from the full axial stress-axial strain curve obtained in step S2 and the energy evolution type obtained in step S3 total and the post-peak energy characteristic value U post-peak ; S5. Define the interval time between the peak stress and the termination stress of the cylindrical rock sample as a failure duration T1, and the interval time between the initial loading stress and the termination stress as a total loading duration T2; The post-peak energy characteristic value U obtained according to step S4 post-peak The post-peak energy release rate VE derived from the post-peak energy characteristic value U and the damage duration T1 post-peak , VE post-peak = U post-peak / T1; The total input energy characteristic value U obtained according to step S4 total and the total loading duration T2 to derive a total energy input rate VE total , VE total = U total / T2; S6. The post-peak energy release rate VE obtained from step S5 post-peak and the total energy input rate VE total The relative post-peak energy release rate RVE is derived post-peak RVE post-peak = VE post-peak / VE total ; S7. The relative post-peak energy release rate (RVE) obtained in step S6 post-peak The value is used to determine the rockburst tendency level of the cylindrical rock sample: When RVE post-peak ≤5, the rock material has no rockburst tendency; when 5 < RVE post-peak ≤8, the rock material has a slight rockburst tendency; when 8 < RVE post-peak ≤12, the rock material has a medium rockburst tendency; and when RVE post-peak ≥12, the rock material has a strong rockburst tendency.

2. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 1, characterized in that, In step S3, the first type of energy evolution type includes one of the following two situations: no acoustic signal after denoising, and no rock debris splashing during the failure process of the cylindrical rock sample, or weak acoustic signal after denoising, and a small amount of rock debris tightly adhering to the cylindrical rock sample falling off during the failure process of the cylindrical rock sample; the termination stress of the first type of energy evolution type is the residual stress; The second type of energy evolution type is the situation that there is a larger acoustic signal after denoising, and a large amount of rock debris splashes during the failure process of the cylindrical rock sample; the termination stress of the second type of energy evolution type is the rock burst failure stress.

3. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 2, characterized in that, The total input energy characteristic value U in step S4 total and the post-peak energy characteristic value U post-peak The calculation formula is: ； ； ； wherein, is the first type of total input energy eigenvalue; Total pre-peak input energy, obtained by integrating the area under the curve of the full axial stress-axial strain curve up to the peak; The first type of total post-peak input energy is obtained by integrating the area under the post-peak stage curve of the full axial stress-axial strain curve, with the final stress being the residual stress. is a first type of post-peak energy eigenvalue; is the first type of peak post- fragmentation energy; Pre-peak resilience; Residual elastic energy remaining after peak; ； ； ； wherein, is the second type of total input energy eigenvalue; Total pre-peak input energy, obtained by integrating the area under the curve of the full axial stress-axial strain curve up to the peak; The second type of total post-peak input energy is obtained by integrating the area under the post-peak stage curve of the full axial stress-axial strain curve, and the terminal stress is the rockburst failure stress; is a second type of post-peak energy eigenvalue; The second type of peak is post-peak fracture energy.

4. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 3, characterized in that, the total pre-peak input energy the first type of total post-peak input energy the pre-peak elastic energy the post-peak residual elastic energy and the second type of total post-peak input energy is calculated as ； ； ； ； ； wherein, is the loading stress, a known value; The peak stress is obtained from the full axial stress-axial strain curve. For the residual stress, it can be obtained from the full axial stress-axial strain curve. The Young's modulus is known from the slope of the elastic deformation phase of the full axial stress-axial strain curve. The strain corresponding to the peak stress can be obtained from the full axial stress-axial strain curve. The strain corresponding to the residual stress can be obtained from the full axial stress-axial strain curve. The strain corresponding to the rockburst failure stress can be obtained from the full axial stress-axial strain curve.

5. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 1, characterized in that, In step S2, the uniaxial compression test is performed on an electro-hydraulic servo material testing machine; the loading rate of the electro-hydraulic servo material testing machine is 0.04-0.07 mm / min or 110-130 KN / min.

6. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 1, characterized by, In step S2, the acoustic signal is measured and recorded by a sound decibel tester; and the image information of the failure process is recorded by a video camera.

7. The rockburst proneness grade discrimination method based on the relative post-peak energy release rate indicator according to claim 1, characterized by, In step S1, the diameter of the cylindrical rock sample is 48-52 mm, and the height is 1.8-2.2 times the diameter.

8. The method according to claim 4, wherein the rockburst proneness classification method based on the relative post-peak energy release rate index is characterized by, Perform a uniaxial graded cyclic loading test on the cylindrical rock sample, load and unload at the same rate, cycle at least three times until complete failure, and obtain a cyclic loading and unloading stress-strain curve of the cyclic loading and unloading process; When unloading at the peak stress, an unloading stress-strain curve of unloading at the peak stress is obtained; Upon unloading at the residual stress, an unloading stress-strain curve of the unloading at the residual stress is obtained; the pre-peak elastic energy and the post-peak residual elastic energy The calculation formula is: ； ； wherein known value for unloading stress The peak stress is the stress at the peak of the stress-strain curve. The peak strain is the strain at the peak of the stress-strain curve. The peak modulus is the slope of the stress-strain curve at the peak stress. The peak stress is the stress at the peak of the stress-strain curve. The peak strain is the strain at the peak of the stress-strain curve. The peak modulus is The unloading modulus at the residual stress is known from the slope of the unloading stress-strain curve at the residual stress. Permanent strain after unloading at peak stress is known from the unloading stress-strain curve at peak stress. The permanent strain after unloading at the residual stress is known from the unloading stress-strain curve at the residual stress. or the peak pre-elastic energy Calculated by linear energy storage law.

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