A method for evaluating the tendency of rock burst types

Abstract

The present invention relates to a method for evaluating the tendency of rock burst types, including: S1. For a pre-prepared rock specimen, the residual elastic energy U of the rock specimen is obtained through a true triaxial cyclic loading and unloading test r ; the critical energy U for rock burst ejection of the rock specimen is obtained through a true triaxial rock burst test c ; S2. Based on the residual elastic energy U r and the critical energy U for rock burst ejection c , calculate the evaluation energy ratio ω for the potential occurrence type of rock burst, ω = U r / U c ; S3. Judge the tendency of the rock burst occurrence type according to the value of ω. This evaluation method can predict the potential occurrence type of rock burst, so as to evaluate the possible rock burst types in underground engineering, provide a more comprehensive reference for the construction work of underground engineering, facilitate the precise implementation of prevention and control measures for different types of rock burst disasters, and improve the safety of underground engineering.

Description

Technical Field

[0001] The invention relates to the technical field of rock burst prediction, and in particular to a method for evaluating the tendency of rock burst types. Background Art

[0002] Rockburst is a dynamic disaster caused by the sudden release of the accumulated elastic deformation potential of the rock mass in underground engineering under engineering excavation or other external disturbances in high-stress areas, resulting in the bursting and ejection of surrounding rocks, which brings huge engineering challenges to the design, construction and production of deep underground engineering. Due to the uncertainty of the occurrence process and the severity of the consequences, the study of rockburst tendency has become an important topic in evaluating the performance of rock mass in underground engineering.

[0003] The incubation and occurrence of rockbursts are affected by multiple factors such as ground stress, geological conditions, and excavation methods. In addition to the different intensity levels of rockbursts that need to be quantitatively distinguished, their characteristics and types are diverse. Specifically, according to the time of occurrence, rockbursts can be divided into immediate rockbursts and time-delay rockbursts. Immediate rockbursts refer to rockbursts that occur during the excavation unloading effect; time-delay rockbursts refer to rockbursts that occur under the continued action of external disturbances after the stress is adjusted and balanced after excavation unloading. Different types of rockbursts have different incubation processes, and the degree and form of their impact on the project are also different, and the measures and methods required for rockburst prevention and control are also different. However, existing studies on rockburst tendency are mostly based on empirical criteria to evaluate the intensity level of rockbursts, ignoring the impact of different types of rockbursts on underground projects. Construction personnel are unable to take preventive measures for the potential occurrence of rockbursts, resulting in safety hazards in the excavation process or even in underground projects that have been excavated. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present invention provides a method for evaluating rock burst type tendency, which solves the technical problem that in the existing rock burst tendency research, the rock burst tendency assessment is incomplete, resulting in safety hazards in underground projects.

[0006] (II) Technical solution

[0007] In order to achieve the above object, the main technical solutions adopted by the present invention include:

[0008] An embodiment of the present invention provides a method for evaluating rock burst type tendency, comprising:

[0009] S1. For the pre-prepared rock samples, the residual elastic energy U of the rock samples is obtained through true triaxial cyclic loading and unloading tests. r ; Obtain the rockburst ejection critical energy U of the rock sample through true triaxial rockburst test c ;

[0010] S2, based on residual elastic energy U r and rockburst ejection critical energy U c , calculate the potential type of rockburst assessment energy ratio ω=U r / U c ;

[0011] S3. Determine the tendency of rock burst occurrence type based on the value of ω.

[0012] The evaluation method proposed in the embodiment of the present invention is based on the residual elastic energy U of the rock from the perspective of energy. r and rockburst ejection critical energy U c , calculate the energy ratio ω for assessing the potential occurrence type of rockburst, and judge the tendency of the rockburst occurrence type according to the value of the energy ratio ω for assessing the potential occurrence type of rockburst, so as to evaluate the possible rockburst types in underground projects and provide a more comprehensive reference for the construction of underground projects, so as to accurately implement prevention and control measures for different types of rockburst disasters and improve the safety of underground projects.

[0013] Optionally, the S3 includes:

[0014] Based on the value of ω, the tendency of rock burst occurrence type is judged:

[0015] When ω≥1, it is determined that there is a tendency for immediate rockburst to occur;

[0016] When ω<1, it is determined that there is a tendency for a time-delay rockburst to occur or there is no tendency for a rockburst to occur.

[0017] Optionally, in S1, the residual elastic energy U of the rock sample is obtained by a true triaxial cyclic loading and unloading test. r include:

[0018] A true triaxial cyclic loading and unloading test corresponding to the ground stress level of the sampling area of ​​the rock sample is carried out on the rock sample to obtain the total stress-strain curve of the rock sample; based on the unloading curve of the rock sample under the residual strength condition in the total stress-strain curve, the residual elastic energy U of the rock sample is calculated. r ;

[0019] Wherein, the residual elastic energy U of the rock sample is calculated r include:

[0020] The area integral method is used to calculate the area integral value of the unloading curve with respect to stress, and the area integral value is used as the residual elastic energy U of the rock sample. r .

[0021] Optionally, the true triaxial cyclic loading and unloading test includes:

[0022] According to the preset stress path, the rock sample is subjected to cyclic loading and unloading operations, and the strain data of the rock sample under the cyclic loading and unloading operations is recorded to form a full stress-strain curve;

[0023] The preset stress path includes:

[0024] A constant minimum principal stress is applied in the direction of the minimum principal stress, a constant intermediate principal stress is applied in the direction of the intermediate principal stress, and a cyclic loading and unloading operation of the maximum principal stress is performed in the direction of the maximum principal stress.

[0025] Optionally, the cyclic loading and unloading operation of the maximum principal stress in the direction of the maximum principal stress includes:

[0026] Cyclic loading and unloading of the maximum principal stress is performed in a strain-controlled manner in the direction of the maximum principal stress until the rock sample reaches residual strength;

[0027] or,

[0028] First, the maximum principal stress is cyclically loaded and unloaded in a stress control mode. When the maximum principal stress is loaded to a preset value, the maximum principal stress is cyclically loaded and unloaded in a strain control mode in the direction of the minimum principal stress until the rock sample reaches the residual strength.

[0029] The preset value is 60% to 80% of the maximum principal stress value corresponding to when the rock sample reaches the peak strength.

[0030] Optionally, the number of loading and unloading cycles of the maximum principal stress is 10 to 15 times.

[0031] Optionally, in S1, the rock burst ejection critical energy U of the rock sample is obtained by a true triaxial rock burst test. c include:

[0032] A true triaxial rockburst test is performed on the rock sample to obtain the rockburst data of the ejected debris when the rock sample undergoes rockburst. Based on the rockburst data, the total ejection kinetic energy U of the rock sample is calculated. v , the total ejection kinetic energy U v As the rockburst ejection critical energy U c ;

[0033] Among them, the total ejection kinetic energy of the rock sample U v It is the sum of the kinetic energy of all ejected debris when a rock burst occurs in a rock sample.

[0034] Optionally, the rockburst data includes:

[0035] The weight of each ejected fragment when a rock sample experiences a rockburst is m i , ejection distance s i and ejection flight time t i, where i is a positive integer, indicating the number of the ejected debris;

[0036] The total ejection kinetic energy U of the rock sample is calculated based on the rock burst data v include:

[0037] Based on rock burst data, according to the formula The total ejection kinetic energy U of the rock sample is calculated v , where v i =s i / t i .

[0038] Optionally, the true triaxial rockburst test includes:

[0039] Stress is applied to the rock sample in a way that five sides are loaded and one side is empty until rock burst occurs. The ejection distance s of each ejected fragment is measured based on the pre-set scale. i , based on the pre-set high-speed camera, the ejection flight time t of each ejected debris is obtained i , use a balance to weigh each ejected debris to get the weight m i ;

[0040] Among them, any side corresponding to the minimum principal stress direction of the rock sample is the free side.

[0041] Optionally, the rock sample is prepared by sampling from an underground engineering site to be evaluated, and the specification of the rock sample is any one of the first sample or the second sample;

[0042] The first sample is a rectangular rock sample with a length of 50 mm, a width of 50 mm and a height of 100 mm; the second sample is a rectangular rock sample with a length of 25 mm, a width of 25 mm and a height of 50 mm.

[0043] (III) Beneficial effects

[0044] The method of the embodiment of the present invention calculates the energy ratio for assessing the potential occurrence type of rockburst based on the residual elastic energy of the rock sample and the critical energy of rockburst ejection obtained from the experiment, and judges the tendency of the rockburst type according to the numerical value of the energy ratio for assessing the potential occurrence type of rockburst, thereby assessing the type of rockburst that may occur in the underground project, providing a more comprehensive reference for the construction work of the underground project, facilitating the precise prevention and control of different types of rockburst disasters, and improving the safety of the underground project. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of a flow chart of a method for evaluating rock burst type tendency provided in an embodiment;

[0046] Figure 2is the stress path applied to the rock sample in the true triaxial cyclic loading and unloading test in the embodiment;

[0047] Figure 3 The rock sample in the embodiment Figure 2 Full stress-strain curve for the stress path shown. DETAILED DESCRIPTION

[0048] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0049] The principle of the present invention for evaluating the tendency of rockburst types is as follows: the rock mass is subjected to a three-dimensional unequal stress state under the action of the original ground stress. Engineering excavation will change the stress state of the rock mass and provide it with additional energy input, which is converted into elastic energy and stored inside the rock mass. The excavation process induces stress redistribution and continuously provides additional energy input to the rock mass. When the accumulated elastic energy is greater than the energy storage limit of the rock mass, the rock mass breaks, and part of the elastic energy stored inside is converted into dissipated energy consumption used for breaking, and the other part is converted into residual elastic energy. When the residual elastic energy inside the rock mass is greater than the critical energy for debris ejection, the residual elastic energy of the rock mass after rupture can provide kinetic energy for the rock debris ejection, and instability failure may occur at any time, resulting in an immediate ejection failure phenomenon, which can be determined as an immediate rockburst; when the residual elastic energy inside the rock mass after rupture is not enough to provide enough kinetic energy for the rock debris ejection, the rock mass still maintains a relatively stable state. The rock mass that maintains a relatively stable state after rupture continues to absorb external energy input. After a period of time, when the cumulative energy of the residual elastic energy and the input energy is greater than the critical energy for rock debris ejection, the rock mass will experience instability ejection after a period of relative rupture, which is determined as a time-delay rockburst; or when the accumulated energy has not reached the critical energy for rock debris ejection before the end of the external elastic energy input, the rock mass will not eject debris, which can be determined as no rockburst.

[0050] Generally, immediate rockbursts occur within a few hours or 1 to 3 days after excavation, and the location of occurrence is mostly within 3 times the tunnel diameter from the working face; time-delay rockbursts occur several days, 1 month or several months after excavation, and the location of occurrence can be hundreds of meters away from the working face. In actual engineering, different prevention and control measures need to be taken according to the characteristics of different potential rockburst types, so it is very necessary to evaluate the tendency of rockburst types.

[0051] The method for evaluating the tendency of rock burst types proposed in the embodiment of the present invention, from the energy perspective, obtains the residual elastic energy and the rock burst ejection critical energy of the rock sample at the excavation site through experiments, calculates the energy ratio for evaluating the potential occurrence type of rock burst, and predicts the potential occurrence type of rock burst according to the value of the energy ratio for evaluating the potential occurrence type of rock burst, thereby providing a more comprehensive reference for underground engineering construction work, facilitating construction personnel to accurately formulate policies and measures for different types of potential rock burst disasters, and improving the safety of underground engineering.

[0052] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0053] Embodiment 1

[0054] like Figure 1 As shown, an embodiment of the present invention provides a method for evaluating rock burst type tendency, comprising:

[0055] S1. For the pre-prepared rock samples, the residual elastic energy U of the rock samples is obtained through true triaxial cyclic loading and unloading tests. r ; Obtain the rockburst ejection critical energy U of the rock sample through true triaxial rockburst test c ;

[0056] S2, based on residual elastic energy U r and rockburst ejection critical energy U c , calculate the potential type of rockburst assessment energy ratio ω=U r / U c ;

[0057] S3. Determine the tendency of rock burst occurrence type based on the value of ω.

[0058] It should be noted that the rockburst ejection critical energy U c It refers to the maximum internal energy stored in the rock at the moment when rock fragments are about to be ejected; the residual elastic energy U r It refers to the elastic energy stored in rock when it regains its residual strength after being deformed and fractured under compressive load.

[0059] Based on the above principle of evaluating the tendency of rockburst type, the method provided by the embodiment of the present invention is essentially to compare the residual elastic energy U r and rockburst ejection critical energy U cThe size of the residual elastic energy U r Greater than or equal to the critical energy of rock burst ejection U c , the rock has a tendency to undergo instant rockburst; when the residual elastic energy U r Less than the critical energy of rock burst ejection U c , the rock has a tendency to time-delay rockburst or no tendency to rockburst.

[0060] In practical applications, the S3 can be reasonably set according to actual needs. As a preferred implementation of this embodiment, the S3 includes:

[0061] Based on the value of ω, the tendency of rock burst occurrence type is judged:

[0062] When ω≥1, it is determined that there is a tendency for immediate rockburst to occur;

[0063] When ω<1, it is determined that there is a tendency for a time-delay rockburst to occur or there is no tendency for a rockburst to occur.

[0064] It should be noted that the sampling time of the rock sample can be in the survey and design stage or the underground engineering excavation stage, and the sampling area of ​​the rock sample can be set according to actual needs. In this embodiment, the rock sample is sampled and prepared from the underground engineering site to be evaluated, and the specifications of the rock sample are any one of the first sample or the second sample; the first sample is a rectangular rock sample with a length of 50 mm, a width of 50 mm, and a height of 100 mm; the second sample is a rectangular rock sample with a length of 25 mm, a width of 25 mm, and a height of 50 mm. In addition, in order to further improve the accuracy of the test data, the parallelism error, size error, and cross-section verticality of the rock sample section can be processed according to the ISRM rock true triaxial test procedure. The public website of the ISRM rock true triaxial test procedure is https: / / isrm.net / isrm / page / show / 177.

[0065] In addition, it should be noted that the residual elastic energy U of the rock sample is obtained through the experiment. r And obtain the rock burst ejection critical energy U of the rock sample through the test c The process is usually accompanied by the destruction of the rock sample; therefore, only one test can be carried out on one rock sample.

[0066] Specifically, in practical applications, the rock samples can be divided into group A and group B, each group includes multiple rock samples. A true triaxial cyclic loading and unloading test is performed on each rock sample in group A to obtain the residual elastic energy of each rock sample. The weighted average of the residual elastic energy of all rock samples is taken as the residual elastic energy U of the rock sample. rSimilarly, a true triaxial rockburst test was performed on each rock sample in group B to obtain the rockburst ejection critical energy of each rock sample. The weighted average of the rockburst ejection critical energy of all rock samples was taken as the rockburst ejection critical energy U of the rock sample. c .

[0067] Embodiment 2

[0068] In order to better understand the first embodiment, this embodiment is described in detail with reference to specific sub-steps.

[0069] An embodiment of the present invention provides a method for evaluating rock burst type tendency, comprising:

[0070] S1. For the pre-prepared rock samples, the residual elastic energy U of the rock samples is obtained through true triaxial cyclic loading and unloading tests. r ; Obtain the rockburst ejection critical energy U of the rock sample through true triaxial rockburst test c .

[0071] Specifically, S1 includes the following sub-steps:

[0072] S101, performing a true triaxial cyclic loading and unloading test corresponding to the ground stress level of the sampling area of ​​the rock sample on the rock sample to obtain a full stress-strain curve of the rock sample;

[0073] The true triaxial cyclic loading and unloading test includes:

[0074] According to the preset stress path, the rock sample is subjected to cyclic loading and unloading operations, and the strain data of the rock sample under the cyclic loading and unloading operations is recorded to form a full stress-strain curve.

[0075] The preset stress path includes:

[0076] A constant minimum principal stress is applied in the direction of the minimum principal stress, a constant intermediate principal stress is applied in the direction of the intermediate principal stress, and a cyclic loading and unloading operation of the maximum principal stress is performed in the direction of the maximum principal stress. The number of cycles of the loading and unloading operation of the maximum principal stress is 10 to 15 times. Specifically, the number of cycles of the loading and unloading operation of the maximum principal stress can be 10, 11, 12, 13, 14 or 15 times.

[0077] Generally, in order to make the test data more consistent with the actual situation at the excavation site, the values ​​of the minimum principal stress, the intermediate principal stress and the maximum principal stress can be set according to the ground stress level at the excavation site. For example, the vertical ground stress and the horizontal ground stress are determined according to the measured ground stress level at the excavation site or the geological survey data corresponding to the excavation site, and the minimum value of the vertical ground stress and the horizontal ground stress is used as the minimum principal stress, and the other value is used as the intermediate principal stress.

[0078] Specifically, the vertical geostress σ z =γH, where H is the burial depth, γ is the bulk density corresponding to the rock sample sampling area, the bulk density can be obtained by actual measurement at the excavation site or by referring to geological survey data, and the horizontal ground stress can be determined based on the lateral pressure coefficient measured at the excavation site.

[0079] In a preferred embodiment, the cyclic loading and unloading operation of the maximum principal stress in the direction of the maximum principal stress includes:

[0080] The maximum principal stress cyclic loading and unloading operation is performed in the maximum principal stress direction strain control mode, and the loading and unloading rate of the maximum principal stress direction strain control is 0.01mm / min until the rock sample reaches the residual strength. The loading and unloading rate is determined according to the lithology of the rock.

[0081] In another preferred embodiment, the cyclic loading and unloading operation of the maximum principal stress in the direction of the maximum principal stress includes:

[0082] First, cyclic loading and unloading operations of the maximum principal stress are performed in a stress-controlled manner, and the loading and unloading rate of stress control is 0.5 MPa / s. When the maximum principal stress is loaded to the preset value, cyclic loading and unloading operations of the maximum principal stress are performed in the strain control mode in the direction of the minimum principal stress, that is, the strain rate in the direction of the minimum principal strain of the rock sample is used to control the loading and unloading rate of the maximum principal stress in the direction of the maximum principal stress, and the loading and unloading rate of the strain control in the direction of the minimum principal stress is 0.008 mm / min, until the rock sample reaches the residual strength.

[0083] The preset value is 60% to 80% of the maximum principal stress value corresponding to when the rock sample reaches the peak strength, and the loading and unloading rate is determined according to the lithology of the rock.

[0084] It should be noted that the peak strength refers to the maximum axial stress that the rock bears when the sample is destroyed under the action of compression load; the residual strength refers to the final strength that is roughly stable after the peak value on the stress-strain curve of the rock sample, also known as residual strength or final strength. The peak strength can be obtained based on the preliminary test of the rock sample, or by searching geological survey data.

[0085] In addition, in order to ensure that the number of cycles of loading and unloading operations of the maximum principal stress is between 10 and 15 times, the loading and unloading load gradient of the maximum principal stress can be set according to the difference between the peak strength and the load value of the first loading and unloading. For example, for a rock sample, according to the aforementioned method, the peak strength of the rock sample is determined to be 370 MPa. In order to ensure that the number of cycles of loading and unloading operations of the maximum principal stress is 15 times, 9 cyclic loading and unloading operations can be set before the load of the cyclic loading and unloading reaches the peak strength. The load of the first loading and unloading is 130 MPa, and the load gradient of the 2nd to 9th cycles is 30 MPa, so that the load of the 9th loading and unloading reaches the peak strength of 370 MPa; for the subsequent 6 loading and unloading operations, the cyclic loading and unloading operations of the maximum principal stress are performed in the strain control mode in the direction of the minimum principal stress. The loading and unloading gradient of the strain control in the direction of the minimum principal stress can be set according to the rock lithology related data of geological exploration, and is set to 0.5 mm in this embodiment.

[0086] The stress paths of the minimum principal stress σ3, the intermediate principal stress σ2 and the maximum principal stress σ1 applied to the rock specimen are as follows: Figure 2 shown.

[0087] The rock samples Figure 2 The total stress-strain curve under the stress path shown is as follows Figure 3 shown.

[0088] S102. Based on the unloading curve of the rock sample under the residual strength condition in the full stress-strain curve obtained in S101, calculate the residual elastic energy U of the rock sample r .

[0089] Wherein, the residual elastic energy U of the rock sample is calculated r Including, using the area integration method, calculating the area integral value of stress to strain under the unloading curve, that is, the area of ​​the closed area surrounded by the unloading curve, the ε axis and the vertical line from the end point of the unloading curve to the ε axis. The area integral value is used as the residual elastic energy U of the rock sample r .

[0090] Specifically, according to Figure 3 The full stress-strain curve shown in the figure uses the area integration method to calculate the area integral value U of stress to strain under the unloading curve at the residual strength of the rock sample according to the following formula:

[0091]

[0092] Among them, σ1, σ2, σ3 are the maximum principal stress, intermediate principal stress and minimum principal stress, respectively, and ε1, ε2, ε3 correspond to the strains of the rock specimen in the direction of maximum principal stress, intermediate principal stress and minimum principal stress, respectively.

[0093] S103. Perform a true triaxial rockburst test on the rock sample to obtain the weight m of each ejected fragment when the rock sample undergoes a rockburst. i , ejection distance s i and ejection flight time t i , where i is a positive integer representing the number of the ejected debris.

[0094] Specifically, the true triaxial rockburst test includes:

[0095] Stress is applied to the rock sample in a way that five sides are loaded and one side is empty until rock burst occurs. The ejection distance s of each ejected fragment is measured based on the pre-set scale. i , based on the pre-set high-speed camera, the ejection flight time t of each ejected debris is obtained i , use a high-precision balance to weigh each ejected debris to get the weight m i ;

[0096] Among them, any side of the rock specimen corresponding to the direction of the minimum principal stress is the free side.

[0097] S104, based on the weight of each ejected fragment m i , ejection distance s i and ejection flight time t i , calculate the total ejection kinetic energy U of the rock sample v , the total ejection kinetic energy U v As the rockburst ejection critical energy U c ;

[0098] Among them, U v The calculation formula is In the formula, v i =s i / t i .

[0099] Here, the critical energy of rock burst ejection U c It refers to the maximum internal energy that can be stored in the rock before the rock burst occurs when the external energy is continuously input. In this step, based on the understanding that the rock ejection process is actually the process of converting internal energy into the ejection kinetic energy of rock burst debris, the total ejection kinetic energy U v Approximately equivalent to the rock burst ejection critical energy U c , and thus the critical energy of rock burst ejection U is obtained c The value of .

[0100] In addition, affected by air resistance and friction, the kinetic energy of each ejected fragment is gradually lost during the ejection flight. Therefore, measuring the kinetic energy of each ejected fragment at the moment when the rock burst occurs in the rock sample will make the total ejection kinetic energy U vThe value of is more accurate, but in this step, for the sake of simplifying the calculation, the average speed of each ejected debris during the entire flight process is calculated.

[0101] S2, based on the residual elastic energy U obtained in S1 r and rockburst ejection critical energy U c , calculate the potential type of rockburst assessment energy ratio ω=U r / U c .

[0102] S3. Determine the tendency of rock burst occurrence type according to the value of ω:

[0103] Based on the value of ω, the tendency of rock burst generation type can be judged by comparing the size of ω with 1:

[0104] When ω≥1, it is determined that there is a tendency for immediate rockburst to occur;

[0105] When ω<1, it is determined that there is a tendency for a time-delay rockburst to occur or there is no tendency for a rockburst to occur.

[0106] It should be noted that in the claims, any reference numerals placed between brackets shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention may be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In the claims enumerating several means, several of these means may be embodied by the same hardware. The use of the words first, second, third, etc., is for convenience of expression only and does not indicate any order. These words may be understood as part of the component name.

[0107] In addition, it should be noted that, in the description of this specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0108] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments after knowing the basic creative concept. Therefore, the claims should be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present invention.

[0109] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include these modifications and variations.

Claims

1. A method for evaluating the tendency of rock burst type, characterized in that: include: S1. For the pre-prepared rock samples, the residual elastic energy U of the rock samples is obtained through true triaxial cyclic loading and unloading tests. r ; Obtain the rockburst ejection critical energy U of the rock sample through true triaxial rockburst test c ; The rock sample is prepared by sampling from the underground engineering site to be evaluated; S2, based on residual elastic energy U r and rockburst ejection critical energy U c , calculate the potential type of rock burst assessment energy ratio ω=U r / U c ; S3. Determine the tendency of rock burst occurrence type according to the value of ω; The S3 includes: Based on the value of ω, the tendency of rock burst occurrence type is judged: When ω≥1, it is determined that there is a tendency for immediate rockburst to occur; When ω<1, it is determined that there is a tendency for a time-delayed rockburst to occur or there is no tendency for a rockburst to occur; In S1, the residual elastic energy U of the rock sample is obtained by a true triaxial cyclic loading and unloading test. r include: A true triaxial cyclic loading and unloading test corresponding to the ground stress level of the sampling area of ​​the rock sample is carried out on the rock sample to obtain the total stress-strain curve of the rock sample; based on the unloading curve of the rock sample under the residual strength condition in the total stress-strain curve, the residual elastic energy U of the rock sample is calculated. r ; The residual elastic energy U of the rock sample is calculated as r include: The area integral method is used to calculate the area integral value of the unloading curve with respect to stress, and the area integral value is used as the residual elastic energy U of the rock sample. r .

2. The evaluation method according to claim 1, characterized in that: The true triaxial cyclic loading and unloading test includes: According to the preset stress path, the rock sample is subjected to cyclic loading and unloading operations, and the strain data of the rock sample under the cyclic loading and unloading operations is recorded to form a full stress-strain curve; The preset stress path includes: A constant minimum principal stress is applied in the direction of the minimum principal stress, a constant intermediate principal stress is applied in the direction of the intermediate principal stress, and a cyclic loading and unloading operation of the maximum principal stress is performed in the direction of the maximum principal stress.

3. The evaluation method according to claim 2, characterized in that: The cyclic loading and unloading operation of the maximum principal stress in the direction of the maximum principal stress comprises: Cyclic loading and unloading of the maximum principal stress is performed in a strain-controlled manner in the direction of the maximum principal stress until the rock sample reaches residual strength; or, First, the maximum principal stress is cyclically loaded and unloaded in a stress control mode. When the maximum principal stress is loaded to a preset value, the maximum principal stress is cyclically loaded and unloaded in a strain control mode in the direction of the minimum principal stress until the rock sample reaches the residual strength. The preset value is 60% to 80% of the maximum principal stress value corresponding to when the rock sample reaches the peak strength.

4. The evaluation method according to claim 2, characterized in that: The number of loading and unloading cycles of the maximum principal stress is 10 to 15 times.

5. The evaluation method according to claim 1, characterized in that: In S1, the rock burst ejection critical energy U of the rock sample is obtained by a true triaxial rock burst test. c include: A true triaxial rockburst test is performed on the rock sample to obtain the rockburst data of the ejected debris when the rock sample undergoes rockburst. Based on the rockburst data, the total ejection kinetic energy U of the rock sample is calculated. v , the total ejection kinetic energy U v As the rockburst ejection critical energy U c ; Among them, the total ejection kinetic energy of the rock sample U v It is the sum of the kinetic energy of all ejected debris when a rock burst occurs in a rock sample.

6. The evaluation method according to claim 5, characterized in that: The rockburst data include: The weight of each ejected fragment when a rock sample experiences a rockburst is m i , ejection distance s i and ejection flight time t i , where i is a positive integer, indicating the number of the ejected debris; The total ejection kinetic energy U of the rock sample is calculated based on the rock burst data v include: Based on rock burst data, according to the formula The total ejection kinetic energy U of the rock sample is calculated v , where v i =s i / t i .

7. The evaluation method according to claim 6, characterized in that: The true triaxial rockburst test includes: Stress is applied to the rock sample in a way that five sides are loaded and one side is empty until rock burst occurs. The ejection distance s of each ejected fragment is measured based on the pre-set scale. i , based on the pre-set high-speed camera, the ejection flight time t of each ejected debris is obtained i , use a balance to weigh each ejected debris to get the weight m i ; Among them, any side corresponding to the minimum principal stress direction of the rock sample is the free side.

8. The evaluation method according to claim 1, characterized in that: The specification of the rock sample is either the first sample or the second sample; The first sample is a rectangular rock sample with a length of 50 mm, a width of 50 mm and a height of 100 mm; the second sample is a rectangular rock sample with a length of 25 mm, a width of 25 mm and a height of 50 mm.

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