Coal rock impact tendency test evaluation method and system based on dynamic strain gauge

Abstract

The invention provides a coal rock impact tendency testing and evaluating method based on a dynamic strain gauge, which comprises the following steps: pretreating a coal rock structure standard test piece, performing a uniaxial compression test on the coal rock structure standard test piece, and acquiring a preset index test result of the coal rock structure standard test piece; constructing a model for evaluating the impact tendency of the coal rock structure based on a BP neural network algorithm; and taking the preset index test result as input, and obtaining the impact tendency grade of the to-be-tested coal rock structure test piece by using a BP neural network-based coal rock structure test piece impact tendency evaluation model. The invention further provides a coal rock impact tendency testing and evaluating system based on the dynamic strain gauge. According to the method, the accuracy and reliability of the impact tendency of the coal and rock mass are improved, the precision of the evaluation result is ensured, and the evaluation result of the impact tendency of the coal and rock mass is obtained more conveniently and efficiently.

Description

Technical Field

[0001] The invention belongs to the field of mining engineering and mine safety technology, and in particular relates to a method and system for testing and evaluating coal-rock impact tendency based on a dynamic strain gauge. Background Art

[0002] Rock burst is the phenomenon of coal and rock being thrown out during deep coal seam mining. The release of kinetic energy is accompanied by sound, vibration, air waves or shock waves. In severe cases, it may cause damage to the roof and floor or even destroy the tunnel, resulting in casualties. It is one of the typical deep engineering geological disasters. The impact tendency of coal and rock mass is the basis for the generation of rock burst. The impact tendency of coal and rock mass refers to the ability and inherent properties of coal and rock to accumulate energy and produce impact damage, which is a necessary condition for the generation of rock burst. Therefore, the impact tendency of coal and rock mass is an important indicator for identifying rock burst mines and conducting regional predictions of rock burst mines.

[0003] At present, the test method of coal rock impact tendency index is mainly based on the national standard GB / T25217.1-2010 "Methods for determination, monitoring and prevention of rock burst pressure Part 1: Classification and determination method of roof rock impact tendency index" and GB / T25217.2-2010 "Methods for determination, monitoring and prevention of rock burst pressure Part 2: Classification and determination method of coal impact tendency index", and the impact tendency of coal rock mass is determined by measuring the elastic energy index WET, impact energy index KE, uniaxial compressive strength and dynamic failure time DT of coal rock structure standard specimens. However, there are still the following problems in using this method to test the impact tendency of coal rock mass: because the current ordinary rigid testing machine cannot realize high-frequency real-time sampling of stress, strain and displacement data, the results of the coal rock mass impact tendency index determination process are inaccurate, and the evaluation results of the coal rock mass impact tendency cannot be accurately obtained. In addition, during the test process, the computer system is unable to realize the real-time drawing of the coal rock impact tendency characteristic parameter curve, the reporting of various impact tendency indexes and results. Secondly, the current impact tendency evaluation method is mainly based on statistical mathematics evaluation method, which requires weight replication of the above four indicators. The evaluation results are highly subjective and cannot independently analyze the test results to directly output the impact tendency level. Summary of the invention

[0004] An object of the present invention is to provide a testing method and an autonomous evaluation system for testing the impact tendency index of coal and rock mass based on a dynamic strain gauge, and to provide at least the advantages to be described later.

[0005] According to the deficiency that high-frequency real-time sampling of stress, strain and displacement data cannot be achieved in the existing coal rock impact tendency index determination process, and at the same time, the existing coal rock impact tendency evaluation method has a highly subjective evaluation result and cannot directly obtain the impact tendency grade of the coal rock in the test process, the present invention proposes a coal rock impact tendency index determination method with a wider application range and higher accuracy, that is, a high-precision testing method and evaluation system for testing the coal rock impact tendency index based on a dynamic strain gauge, the impact tendency index of the coal rock is tested, and on this basis, a new impact tendency evaluation method is developed based on the BT neural network algorithm, and the impact tendency grade of the coal rock is directly output by a computer data processing system. The ultimate purpose of the present invention can improve the accuracy and reliability of the coal rock impact tendency, ensure the accuracy of the evaluation result, and obtain the coal rock impact tendency evaluation result more conveniently and efficiently.

[0006] It should be noted that the selection of evaluation indicators is an important part of the impact tendency evaluation. The preset evaluation indicators are the existing national standards for evaluating the impact tendency of coal and rock. The preset indicators include the elastic energy index W ET , Impact energy index K E , uniaxial compressive strengthσ c and dynamic failure time D T The conventional method for measuring the impact tendency of coal rock structure is to sample the coal rock from the working face and transport it back to the laboratory for indoor testing. The impact tendency indicators such as impact energy index, elastic energy index, dynamic failure time and uniaxial compressive strength are obtained by calculating and analyzing the stress-strain relationship. The impact indicators of a large number of coal rock samples are statistically analyzed to determine the strength of the impact tendency of the measured coal rock structure.

[0007] The technical solution of the present invention is as follows:

[0008] The coal-rock impact tendency test and evaluation method based on dynamic strain gauge includes the following steps:

[0009] Pre-processing the coal-rock structure standard specimen and performing a uniaxial compression test on it, and collecting the preset index test results of the coal-rock structure standard specimen;

[0010] Collect coal impact tendency data and use it as sample data, divide the sample data into a training set and a test set in a ratio of 7:3, build a coal rock structure impact tendency evaluation model based on a BP neural network algorithm, and use the training set and the test set to train and optimize it respectively;

[0011] The preset index test results are used as input, and the impact tendency evaluation model of the coal-rock structure specimen based on the BP neural network is used to obtain the impact tendency grade of the coal-rock structure specimen to be tested.

[0012] Preferably, in the coal-rock impact tendency test and evaluation method based on the dynamic strain gauge, pre-processing the coal-rock structure standard specimen includes:

[0013] Group and number standard specimens of coal and rock structures, check processing accuracy and measure dimensions, describe and record joints, cracks, water content and problems encountered during processing of standard specimens;

[0014] The high-precision strain gauge is glued to the side of the coal-rock structure standard specimen with AB glue.

[0015] Preferably, in the coal-rock impact tendency test and evaluation method based on dynamic strain gauge, the preset indicators include elastic energy index WET, impact energy index KE, uniaxial compressive strength and dynamic failure time DT;

[0016] The elastic energy index is the ratio of the elastic deformation energy to the plastic deformation energy of the standard specimen of coal-rock structure under uniaxial compression and when the stress reaches 75%-85% of the strength and is completely unloaded;

[0017] The impact energy index refers to the ratio of the deformation energy accumulated before the peak value to the deformation energy lost after the peak value in the full stress-strain curve of the standard specimen of coal-rock structure under uniaxial compression;

[0018] The uniaxial compressive strength is the peak strength of the stress-strain curve, that is, the ratio of the failure load borne by the standard specimen of coal-rock structure under uniaxial compression to its pressure-bearing surface area during the test;

[0019] Dynamic failure time refers to the time it takes for a standard specimen of coal and rock structure to go from ultimate strength to complete failure.

[0020] The coal-rock impact tendency test and evaluation system based on dynamic strain gauge includes:

[0021] An electro-hydraulic servo testing machine, which performs uniaxial compression tests on standard specimens of coal and rock structures to be tested;

[0022] An external stress sensor is arranged at the central groove of the base of the electro-hydraulic servo testing machine and detects the stress value of the standard specimen of the coal-rock structure to be tested in the uniaxial compression test;

[0023] An external displacement sensor is fixed on the standard specimen of coal-rock structure to be tested and detects the displacement value of the standard specimen of coal-rock structure to be tested in a uniaxial compression test;

[0024] A high-precision welding-free strain gauge, which is pasted on the side of the standard coal-rock structure specimen to be tested, and detects the strain value of the standard coal-rock structure specimen to be tested in a uniaxial compression test;

[0025] A real-time dynamic strain gauge data acquisition system, which is electrically connected to the external stress sensor, the external displacement sensor and the high-precision welding-free strain gauge;

[0026] and a computer data processing system, which is communicatively connected to the real-time dynamic strain gauge data acquisition system;

[0027] in;

[0028] The computer data processing system pre-stores the basic parameters of the standard test piece of coal-rock structure to be tested, and calculates the preset index test results for evaluating the impact tendency of coal-rock according to the basic parameters, the stress value, the displacement value and the strain value;

[0029] The computer data processing system is also used to construct a coal-rock structure specimen impact tendency evaluation model based on a BP neural network, and the preset index test results are used as input to obtain the impact tendency grade of the coal-rock structure standard specimen to be tested.

[0030] Preferably, in the coal-rock impact tendency test and evaluation system based on the dynamic strain gauge,

[0031] The electro-hydraulic servo testing machine has an accuracy of not less than 0.5 grade;

[0032] The external stress sensor is a load sensor with a measuring range of less than or equal to 150 kN and a collection frequency of more than 10 kHz;

[0033] The external displacement sensor is a push rod displacement sensor with a measuring range of less than or equal to 5 mm, an accuracy of 0.001 mm, and a collection frequency of more than 10 kHz.

[0034] The present invention has the following beneficial effects:

[0035] (1) It overcomes the deficiency of the existing coal rock impact tendency index determination process that cannot realize high-frequency real-time sampling of stress, strain and displacement data;

[0036] (2) The accuracy and reliability of the impact tendency of coal and rock masses are improved, the accuracy of the evaluation results is ensured, and the evaluation results of the impact tendency of coal and rock masses are obtained more conveniently and efficiently.

[0037] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the structure of a coal-rock impact tendency testing and evaluation system based on a dynamic strain gauge provided by the present invention;

[0039] Figure 2 A computer data processing system startup interface in one embodiment of a coal-rock impact tendency testing and evaluation system based on a dynamic strain gauge provided by the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0041] It should be understood that terms such as “having”, “including” and “comprising” used herein do not specify the existence or addition of one or more other elements or combinations thereof.

[0042] The present invention provides a method for testing and evaluating the impact tendency of coal and rock based on a dynamic strain gauge, which comprises the following steps:

[0043] Pre-processing the coal-rock structure standard specimen and performing a uniaxial compression test on it, and collecting the preset index test results of the coal-rock structure standard specimen;

[0044] Collect coal impact tendency data and use it as sample data, divide the sample data into a training set and a test set in a ratio of 7:3, build a coal rock structure impact tendency evaluation model based on a BP neural network algorithm, and use the training set and the test set to train and optimize it respectively;

[0045] The preset index test results are used as input, and the impact tendency evaluation model of the coal-rock structure specimen based on the BP neural network is used to obtain the impact tendency grade of the coal-rock structure specimen to be tested.

[0046] In one embodiment of the coal-rock impact tendency test and evaluation method based on the dynamic strain gauge provided by the present invention, pre-processing the coal-rock structure standard specimen includes:

[0047] Group and number standard specimens of coal and rock structures, check processing accuracy and measure dimensions, describe and record joints, cracks, water content and problems encountered during processing of standard specimens;

[0048] The high-precision strain gauge is glued to the side of the coal-rock structure standard specimen with AB glue.

[0049] Use a digital multimeter to measure the resistance of the strain gauge.

[0050] The resistance error of strain gauges pasted on the same specimen shall not exceed 0.3~0.5Ω.

[0051] In one embodiment of the coal-rock impact tendency test and evaluation method based on the dynamic strain gauge provided by the present invention, the preset indicators include elastic energy index WET, impact energy index KE, uniaxial compressive strength and dynamic failure time DT;

[0052] The elastic energy index is the ratio of the elastic deformation energy to the plastic deformation energy of the standard specimen of coal-rock structure under uniaxial compression and when the stress reaches 75%-85% of the strength and is completely unloaded;

[0053] The impact energy index refers to the ratio of the deformation energy accumulated before the peak value to the deformation energy lost after the peak value in the full stress-strain curve of the standard specimen of coal-rock structure under uniaxial compression;

[0054] The uniaxial compressive strength is the peak strength of the stress-strain curve, that is, the ratio of the failure load borne by the standard specimen of coal-rock structure under uniaxial compression to its pressure-bearing surface area during the test;

[0055] Dynamic failure time refers to the time it takes for a standard specimen of coal and rock structure to go from ultimate strength to complete failure.

[0056] like Figure 1 As shown, the present invention provides a coal-rock impact tendency testing and evaluation system based on a dynamic strain gauge, which includes:

[0057] An electro-hydraulic servo testing machine, which performs a uniaxial compression test on a standard specimen of a coal-rock structure to be tested, comprises a rigid column 1 and a rigid frame 2, and is provided with a rigid cushion block 7 and a pressure plate 8;

[0058] An external stress sensor 3, which is arranged at the central groove of the base of the electro-hydraulic servo testing machine and detects the stress value of the standard specimen of the coal-rock structure to be tested in the uniaxial compression test;

[0059] An external displacement sensor 4, which is fixed on the standard specimen of coal-rock structure to be tested and detects the displacement value of the standard specimen of coal-rock structure to be tested in a uniaxial compression test;

[0060] A high-precision welding-free strain gauge 5, which is pasted on the side of the standard coal-rock structure specimen to be tested, and detects the strain value of the standard coal-rock structure specimen to be tested in a uniaxial compression test;

[0061] A real-time dynamic strain gauge data acquisition system 9, which is electrically connected to the external stress sensor, the external displacement sensor and the high-precision welding-free strain gauge;

[0062] and a computer data processing system 10, which is communicatively connected to the real-time dynamic strain gauge data acquisition system 9;

[0063] in;

[0064] The computer data processing system 10 pre-stores the basic parameters of the standard test piece of coal-rock structure to be tested, and calculates the preset index test results for evaluating the impact tendency of coal-rock according to the basic parameters, the stress value, the displacement value and the strain value;

[0065] The computer data processing system 10 is also used to construct a coal-rock structure specimen impact tendency evaluation model based on a BP neural network, and use the preset index test results as input to obtain the impact tendency grade of the coal-rock structure standard specimen to be tested.

[0066] The working process of the coal-rock impact tendency test and evaluation system based on dynamic strain gauge provided by the present invention is as follows:

[0067] Step 1: Preparation of standard specimens of coal and rock structures

[0068] Before the test, the standard specimens of coal-rock structure were grouped and numbered, the processing accuracy was checked and the dimensions were measured, and the joints, cracks, water content and problems encountered during the processing of the standard specimens were described and recorded. The high-precision strain gauges were glued to the side surface of the standard specimens of coal-rock structure with AB glue.

[0069] Use a digital multimeter to measure the resistance of the strain gauge.

[0070] The resistance error of strain gauges pasted on the same specimen shall not exceed 0.3~0.5Ω.

[0071] Step 2: Turn on the machine and connect the sensor, dynamic strain gauge and computer

[0072] Start the electro-hydraulic servo test machine and make it available. Place the external stress sensor (load sensor) in the center groove of the base of the electro-hydraulic servo test machine, so that the sensor and the base of the test machine are perfectly fitted, and place the rigid pad on the load sensor. Place the rigid pad between the upper end of the specimen and the pressure plate of the test machine. At the same time, place the coal-rock structure standard specimen with the strain gauge attached to it at the center of the rigid pad, and make the axes of the pressure plate, coal-rock structure specimen, and rigid pad coincide. Furthermore, fix the displacement sensor on the coal-rock structure standard specimen to ensure that it will not move relative to the specimen, and prevent the influence of external factors such as temperature and magnetic field on the sensor.

[0073] Step 3: Connect each sensor to the real-time dynamic strain gauge data acquisition system and computer data processing system

[0074] Connect all devices in this system and plug the connection interface tightly to prevent loosening during operation. This includes: connecting the external stress sensor, displacement sensor and high-precision strain gauge to the real-time dynamic strain gauge in sequence (pay attention to the wiring method at this stage), and communicating the real-time dynamic strain gauge with the computer USB, connecting the instrument power, preheating, debugging, and inspection, so that the device is in standby working state.

[0075] Step 4: Determination of impact tendency index of coal-rock structure specimens

[0076] Start the testing machine, open the computer application and dynamic strain gauge, and the computer data processing system startup interface is as follows: Figure 2 As shown, the basic parameters of the coal rock structure specimen to be tested (specimen type, specimen diameter, height, etc.) are input into the program. A uniaxial compression test is performed on the target coal rock, so that the upper pressure plate contacts the coal rock structure specimen (but the specimen should not be under stress at this time), and the data acquisition button and the test machine loading button are turned on at the same time. The preset indicators of the target coal rock structure are measured and stored in the computer system. Among them, the preset indicators as mentioned above are the existing national standards for evaluating the impact tendency of coal rock, and the preset indicators include (elastic energy index W ET , Impact energy index K E , uniaxial compressive strengthσ c and dynamic failure time D T ). During the measurement of each index, the number of test pieces should be no less than 5.

[0077] It should be noted that the uniaxial compressive strength of the coal-rock structure standard specimen in step 4 is the peak strength of the stress-strain curve, that is, the ratio of the failure load borne by the coal-rock structure standard specimen under uniaxial compression to its pressure-bearing surface area during the test. During the test, the uniaxial compressive strength of the specimen can be directly obtained by the computer data processing system according to the loading process curve, and the average compressive strength of the group of specimens can be obtained synchronously.

[0078] It should be noted that the impact energy index of the coal-rock structure standard specimen in step 4 refers to the ratio of the deformation energy accumulated before the peak to the deformation energy lost after the peak in the full stress-strain curve of the coal-rock structure standard specimen under uniaxial compression. During the test, the impact energy index of the specimen can be divided by the computer data processing system through the stress-strain curve of the whole process. The built-in algorithm in the software automatically calculates it according to the impact energy index calculation formula, and can simultaneously obtain the average impact energy index of the group of specimens. The specific calculation formula of the impact energy index is as follows:

[0079]

[0080] Where K E is the impact energy index; A Sis the deformation energy accumulated before the peak value; A x K is the post-peak loss deformation energy; ES is the average value of impact energy index; K Ei is the impact energy index of the i-th specimen; n is the number of specimens.

[0081] It should be noted that in step 4, the elastic energy index of the coal-rock structure standard specimen is the ratio of its elastic deformation energy to its plastic deformation energy when the coal-rock structure standard specimen is completely unloaded under uniaxial compression when the stress reaches 75%-85% of the strength. During the test, the elastic energy index of the specimen can be divided by the computer data processing system through the stress-strain curve of the whole process, and the computer draws the elastic energy index curve, and then the computer directly integrates the elastic strain energy value and the total strain energy value, and the average elastic energy index of the group of specimens can be obtained simultaneously. The specific calculation formula of the elastic energy index is as follows:

[0082] Φ SP =Φ C -Φ SE ,

[0083] Where W ET is the elastic energy index; Φ SE is the elastic strain energy, which is the area under the unloading curve; Φ C is the total strain energy; Φ SP is the plastic strain energy, which is the area enclosed by the loading curve and the unloading curve; W ETS is the average value of elastic energy index; W ETi is the elastic energy index of the i-th specimen; n is the number of specimens.

[0084] It should be noted that the dynamic failure time of the coal-rock structure standard specimen in step 4 refers to the time it takes for the coal-rock structure standard specimen to go from ultimate strength to complete failure. During the test, the dynamic failure time of the specimen can be displayed by the computer data processing system based on the measured data, and the dynamic failure time curve of each specimen can be displayed. The dynamic failure time of each specimen can be manually determined using the data curve interception and automatic point selection functions provided by the software. The system calculates the average dynamic failure time value of the group of specimens through a built-in algorithm formula, and prints out the dynamic failure time curve, dynamic failure time and average dynamic failure time value of each coal sample in a graphical form. The specific calculation formula for the average dynamic failure time of the specimen is as follows:

[0085]

[0086] Where DT S DT is the average dynamic failure time in milliseconds.i is the dynamic failure time of the ith specimen, in milliseconds; n is the number of specimens.

[0087] In this embodiment, the construction of the impact tendency evaluation model of coal-rock structure specimens based on BP neural network in step five specifically includes: collecting and collating coal impact tendency data (according to national standards, coal impact tendency data are the average values ​​of data measured by multiple coal samples in this group) by consulting a large number of literature and related materials, and constructing a database containing multiple groups of impact tendency samples. At the same time, the sample indicators are analyzed using the Person correlation coefficient to determine whether the indicator data is scientific and reasonable, which provides a data basis for the subsequent construction and analysis of the coal-rock structure impact tendency evaluation model.

[0088] Secondly, based on the BP neural network algorithm, the collected four evaluation indexes (elastic energy index WET, impact energy index KE, uniaxial compressive strength and dynamic failure time DT) database is autonomously trained and learned to construct a coal rock structure impact tendency evaluation model based on the BP neural network. Preferably, the ratio of the training set to the test set of the model is 7:3. In order to solve the imbalance of the samples, the present invention adopts cross-validation for training. After debugging, 10-fold cross-validation is selected for training.

[0089] The coal-rock structure impact tendency evaluation model based on BP neural network is introduced into the computer data processing system. According to the test results of various evaluation indicators of coal-rock structure impact tendency, the computer data processing system automatically outputs the impact tendency level: strong, weak or no (level 1, 2 or 3).

[0090] In one embodiment of the coal-rock impact tendency testing and evaluation system based on dynamic strain gauge provided by the present invention,

[0091] The electro-hydraulic servo testing machine (rigidity testing machine) has an accuracy of not less than 0.5 grade;

[0092] The external stress sensor is a load sensor with a range of less than or equal to 150kN and a collection frequency of more than 10kHz. It should be noted that compared with the built-in load sensor in the test machine, it can achieve high-frequency real-time collection, which can improve the accuracy of measuring the impact tendency index of coal and rock structures. It is placed in the groove of the test machine base to achieve a perfect fit with the base, and the terminal is connected to the real-time dynamic strain gauge data acquisition system.

[0093] The external displacement sensor is a top rod displacement sensor with a range of less than or equal to 5mm, an accuracy of 0.001mm, and an acquisition frequency of more than 10kHz. It should be noted that compared with the built-in displacement sensor in the test machine (accuracy 0.1mm), it has higher accuracy and can achieve high-frequency real-time acquisition, which can improve the accuracy of measuring the impact tendency index of coal and rock structures. Its internal structure is: a built-in cantilever beam structure with an elastically recoverable metal rod for measuring the displacement change of the structure.

[0094] The cantilever beam is made of highly elastic material, with a high-precision resistance strain gauge inside. It adopts a strain full bridge bridge assembly method, which can self-compensate for temperature, has stable signal output, and strong anti-interference ability. The external displacement sensor is fixed on the coal rock structure standard specimen to ensure that it will not move relative to the specimen. At the same time, the terminal is connected to the real-time dynamic strain gauge data acquisition system.

[0095] The high-precision welding-free strain gauge is mainly used for measuring the strain generated during the uniaxial compression of the specimen. It should be noted that its working principle is to use a special adhesive to stick the strain gauge to the measuring part of the coal rock specimen. The measuring part is under the action of external force (tension or pressure) and stretching (or compression). Since the strain gauge itself has an inherent resistance value, it reflects the mechanical strain to be measured by the change of its own resistance. The strain gauge is composed of a measuring bridge. When the resistance of the bridge arm changes, the bridge outputs a voltage that is linearly related to its change. By amplifying the voltage and normalizing the sensitivity coefficient K of the resistance strain gauge, the output voltage can correspond to the actual strain. The high-precision strain gauge is respectively pasted on the side surface of the coal rock specimen in the horizontal and vertical directions, and is used to measure the lateral strain and longitudinal strain generated by the specimen during the uniaxial compression process.

[0096] The real-time dynamic strain gauge data acquisition system can simultaneously acquire multi-channel, high-precision digital bus data signals, and can realize the acquisition, storage and transmission of stress, strain and displacement data. Preferably, the acquisition frequency is not less than 10kHz.

[0097] The computer data processing system is a self-developed computer application with functions such as data collection, display, storage, calculation and processing, and data evaluation. The system software based on the Windows operating platform can control all functions of the dynamic strain gauge. The sampling control and analysis software compiled in C++ has strong real-time performance and good portability, expandability and upgradeability. The computer application interface can display the specimen serial number and parameters, sensor parameters and result data (impact tendency index of coal-rock structure specimens), and can simultaneously display the graphics (stress distribution curve) during the loading process, and can realize the screenshot function of any point of the curve, providing the most intuitive measurement results. More importantly, the system collects elastic energy index WET , Impact energy index K E , uniaxial compressive strengthσ c and dynamic failure time D T A database of multiple groups of impact tendency samples for evaluation indicators is established. Based on the autonomous training and learning of the BP neural network algorithm, a computer data processing system has built a coal rock structure impact tendency evaluation model based on the BP neural network. It can autonomously analyze and process the test indicators and finally output the results of the coal rock impact tendency grade.

[0098] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A method for testing and evaluating coal-rock impact tendency based on a dynamic strain gauge, characterized in that: The following steps are involved: Pre-processing the coal-rock structure standard specimen and performing a uniaxial compression test on it, and collecting the preset index test results of the coal-rock structure standard specimen; Collect coal impact tendency data and use it as sample data, divide the sample data into a training set and a test set in a ratio of 7:3, build a coal rock structure impact tendency evaluation model based on a BP neural network algorithm, and use the training set and the test set to train and optimize it respectively; The preset index test results are used as input, and the impact tendency evaluation model of the coal-rock structure specimen based on the BP neural network is used to obtain the impact tendency grade of the coal-rock structure specimen to be tested.

2. The method for testing and evaluating coal-rock impact tendency based on dynamic strain gauge according to claim 1, characterized in that: Pretreatment of standard specimens of coal and rock structures includes: Group and number standard specimens of coal and rock structures, check processing accuracy and measure dimensions, describe and record joints, cracks, water content and problems encountered during processing of standard specimens; The high-precision strain gauge is glued to the side of the coal-rock structure standard specimen with AB glue.

3. The coal-rock impact tendency test and evaluation method based on dynamic strain gauge according to claim 2, characterized in that: The preset index includes the elastic energy index W ET , Impact energy index K E , uniaxial compressive strengthσ c and dynamic failure time D T ; The elastic energy index is the ratio of the elastic deformation energy to the plastic deformation energy of the standard specimen of coal-rock structure under uniaxial compression and when the stress reaches 75%-85% of the strength and is completely unloaded; The impact energy index refers to the ratio of the deformation energy accumulated before the peak value to the deformation energy lost after the peak value in the full stress-strain curve of the standard specimen of coal-rock structure under uniaxial compression; The uniaxial compressive strength is the peak strength of the stress-strain curve, that is, the ratio of the failure load borne by the standard specimen of coal-rock structure under uniaxial compression to its pressure-bearing surface area during the test; Dynamic failure time refers to the time it takes for a standard specimen of coal and rock structure to go from ultimate strength to complete failure.

4. A coal-rock impact tendency test and evaluation system based on a dynamic strain gauge is characterized by: include: An electro-hydraulic servo testing machine, which performs uniaxial compression tests on standard specimens of coal and rock structures to be tested; An external stress sensor is arranged at the central groove of the base of the electro-hydraulic servo testing machine and detects the stress value of the standard specimen of the coal-rock structure to be tested in the uniaxial compression test; An external displacement sensor is fixed on the standard specimen of coal-rock structure to be tested and detects the displacement value of the standard specimen of coal-rock structure to be tested in a uniaxial compression test; A high-precision welding-free strain gauge, which is pasted on the side of the standard coal-rock structure specimen to be tested, and detects the strain value of the standard coal-rock structure specimen to be tested in a uniaxial compression test; A real-time dynamic strain gauge data acquisition system, which is electrically connected to the external stress sensor, the external displacement sensor and the high-precision welding-free strain gauge; and a computer data processing system, which is communicatively connected to the real-time dynamic strain gauge data acquisition system; in; The computer data processing system pre-stores the basic parameters of the standard test piece of coal-rock structure to be tested, and calculates the preset index test results for evaluating the impact tendency of coal-rock according to the basic parameters, the stress value, the displacement value and the strain value; The computer data processing system is also used to construct a coal-rock structure specimen impact tendency evaluation model based on a BP neural network, and the preset index test results are used as input to obtain the impact tendency grade of the coal-rock structure standard specimen to be tested.

5. The coal-rock impact tendency testing and evaluation system based on dynamic strain gauge according to claim 4 is characterized in that: The electro-hydraulic servo testing machine has an accuracy of not less than 0.5 grade; The external stress sensor is a load sensor with a measuring range of less than or equal to 150 kN and a collection frequency of more than 10 kHz; The external displacement sensor is a push rod displacement sensor with a measuring range of less than or equal to 5 mm, an accuracy of 0.001 mm, and a collection frequency of more than 10 kHz.

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