Coal fragment impact kinetic energy index testing device and testing method

Abstract

The invention relates to the technical field of underground engineering simulation tests, and provides a coal fragment impact kinetic energy index testing device and a testing method. The testing device comprises a cushion block, a fragment mass measuring module, a fragment ejection kinetic energy measuring module, a fragment ejection impact force measuring module and a fragment ejection initial velocity Doppler measuring module. Through the fragment ejection kinetic energy measuring module, the fragment ejection impact force measuring module and the fragment ejection initial velocity Doppler measuring module, the data volume such as the initial velocity and the impact force of fragment ejection is obtained, and meanwhile the mass and the landing time of fragments scattered in each sector-ring-shaped partition are obtained in cooperation with the weighing sensor. According to the method, the initial ejection kinetic energy after the test piece is damaged can be obtained, weighted average processing is carried out on the initial ejection kinetic energy obtained through the three methods, and therefore the more accurate initial ejection kinetic energy can be obtained finally, the system measurement error is reduced, and the ejection kinetic energy of the fragments of the test piece can well reflect the impact damage degree of the test piece.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering simulation test, in particular to a coal body fragment impact kinetic energy index test device and a test method. Background Art

[0002] Rock burst is the coal ejection phenomenon that occurs during deep coal mining. The kinetic energy is released with sound, vibration, air wave or shock wave. In severe cases, it may damage the roof and floor or even destroy the tunnel, resulting in casualties. The study of coal rock burst tendency is very important for the mechanism, prediction and prevention of rock burst, and is one of the main bases for evaluating and predicting the danger of rock burst in coal mines. The elastic energy index W is given in the national standard GB / T 2517.2-2010 "Methods for determination, monitoring and prevention of rock burst Part 2: Classification of coal rock burst tendency and determination of index". ET , Impact energy index K E , uniaxial compressive strengthσ c and dynamic failure time D T To comprehensively judge the impact tendency of coal. Most impact tendency indexes are dimensionless ratios and cannot quantitatively describe the impact energy released when the coal sample is destroyed.

[0003] According to the impact failure process and post-failure state of coal under uniaxial compression, it is very necessary to evaluate the impact tendency of coal samples based on experimental phenomena. Similar to the rock burst phenomenon at coal mine sites, the failure of coal samples with impact tendency in indoor tests is also accompanied by the ejection and flying of coal fragments. The impact tendency of coal is closely related to the kinetic energy of the damaged fragments. In indoor tests, high-speed cameras are generally used to capture the motion trajectory of coal sample fragments. The size and speed of coal sample fragments are obtained through image processing, and the kinetic energy of the fragments is approximately calculated. However, in the actual destruction process of coal samples, a large number of fragments and debris fly out in all directions around the coal samples in a very short time. It is difficult to accurately track the motion trajectory of each fragment with the current monitoring method, and it is also difficult to collect and weigh each fragment after the test is completed.

[0004] To this end, the present invention proposes a simple coal fragment impact kinetic energy index testing device and testing method. Summary of the invention

[0005] The purpose of the present invention is to provide a coal fragment impact kinetic energy index testing device and testing method, which can measure the fragment impact kinetic energy index when a coal specimen is destroyed, thereby quantitatively characterizing the impact energy released when the coal sample is destroyed.

[0006] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A coal body fragment impact kinetic energy index testing device comprises a cushion block, a device support structure layer, a fragment mass measurement module, a fragment ejection kinetic energy measurement module, a fragment ejection impact force measurement module and a fragment ejection initial velocity Doppler measurement module;

[0008] The cushion block is arranged on the pressure column platform of the testing machine and is located directly above the top center of the supporting structure layer of the device;

[0009] A fragment mass determination module is arranged on the top of the supporting structure layer of the device, and the fragment mass determination module comprises a plurality of sensor limit plates and a weighing sensor, wherein the plurality of sensor limit plates spread outward with the cushion block as the center to form a multi-layer concentric ring structure, and slots are provided between radially adjacent sensor limit plates and sensor limit plates in the same layer of concentric rings, and each weighing sensor is correspondingly arranged on a sensor limit plate;

[0010] A fragment collection layer is arranged above the sensor limit plate, wherein the fragment collection layer and the sensor limit plate are arranged in one-to-one correspondence;

[0011] The fragment ejection kinetic energy measurement module comprises a plurality of fragment force measuring baffles, wherein the fragment force measuring baffles spread outwards with the cushion block as the center to form a multi-layer concentric ring shape, and the fragment force measuring baffles are vertically arranged in the card slot;

[0012] The fragment ejection initial velocity Doppler measurement module is arranged on the outer side of the outermost fragment force measuring baffle plate, and is used to measure the initial velocity of the fragment ejection;

[0013] The fragment ejection impact force measuring module is arranged on the outer side of the fragment force measuring baffle of each layer, and is used to measure the impact force of the fragment ejection.

[0014] Preferably, the fragment ejection impact force measuring module includes a plurality of limit rods and a beam load sensor;

[0015] The bottom end of the limit rod is threadedly connected to the device support structure layer, the top end of the limit rod is connected to the beam load sensor, and the beam load sensor is closely attached to the outer side of the fragment force measuring baffle.

[0016] Preferably, the fragment ejection initial velocity Doppler measurement module comprises a connecting rod, a multi-degree-of-freedom mobile platform and a Doppler sensor;

[0017] The bottom end of the connecting rod is threadedly connected to the device supporting structure layer, the multi-degree-of-freedom mobile platform is arranged on the top end of the connecting rod, and the Doppler sensor is arranged on the multi-degree-of-freedom mobile platform, wherein the multi-degree-of-freedom mobile platform can adjust the detection angle of the Doppler sensor so that the probe of the Doppler sensor faces the center of the test piece.

[0018] Preferably, the sensor limit plates located on the same layer of concentric rings have slots arranged at intervals of 60°.

[0019] Preferably, the height of the outermost fragment force baffle is higher than the height of the upper plane after the pad is placed on the test piece, and the heights of the remaining fragment force baffles are consistent with the height of the innermost fragment force baffle;

[0020] The inner diameter of the innermost fragment force measuring baffle is larger than the diameter of the circumscribed circle of the upper surface of the cushion block, and the cushion block does not contact the plate wall of the innermost fragment force measuring baffle.

[0021] Preferably, a plurality of grooves are provided on the lower surface of the fragment collection layer, and each weighing sensor is correspondingly arranged in a groove.

[0022] Preferably, a retractable support rod is provided at the bottom of the supporting structure layer of the device, and the retractable support rod can adjust the height of the coal fragment impact kinetic energy index testing device.

[0023] Preferably, a sound emission device hole is provided on the cushion block, and a sound emission device is arranged in the sound emission device hole.

[0024] Preferably, a level is provided on the fragment collection layer.

[0025] A method for testing the impact kinetic energy index of coal body fragments, using the above-mentioned coal body fragments impact kinetic energy index testing device, comprises the following steps:

[0026] Step 1: Place the coal fragment impact kinetic energy index test device on the test machine platform, adjust the length of the retractable support rod so that there is a height difference between the lower surface of the device support structure layer and the plane of the pressure column platform of the test machine, observe the level meter and keep the fragment collection layer level;

[0027] Step 2: Place the cushion block on the plane of the pressure column platform of the testing machine, and make the upper end surface of the cushion block flush with the upper edge of the innermost layer of the fragment force measuring baffle in the horizontal direction;

[0028] Step 3, respectively connect the weighing sensor, beam load sensor and Doppler sensor to their respective data acquisition devices, install the acoustic emission device in the acoustic emission device hole of the pad, adjust the zero and set the sampling frequency in turn, and place the coal body specimen at the top center of the pad;

[0029] Step 4: Start the testing machine to load the coal specimen, and the testing machine and the data acquisition equipment collect data simultaneously;

[0030] Step 5: After the coal specimen is destroyed, stop loading the testing machine, record the data of each group of weighing sensors, beam load sensors, and Doppler sensors, process and analyze the collected data, and obtain the total ejection kinetic energy and impact kinetic energy index.

[0031] The beneficial technical effects of the present invention are:

[0032] The present invention provides a coal body fragment impact kinetic energy index testing device and testing method, which can measure the fragment impact kinetic energy index when a coal body specimen is destroyed, thereby quantitatively describing the impact energy released when the coal sample is destroyed, and evaluating the impact tendency of the coal body based on the destruction characteristics; the present invention divides the sensor limit plate and the fragment collection layer into a plurality of fan-shaped areas, each fan-shaped area is individually configured with a weighing sensor, and can independently measure the mass of the fragments scattered in each partition and the landing time, thereby ultimately improving the accuracy of the test results;

[0033] The present invention obtains data such as the initial velocity and impact force of fragment ejection through a fragment ejection kinetic energy measuring module, a fragment ejection impact force measuring module and a fragment ejection initial velocity Doppler measuring module, and simultaneously cooperates with a weighing sensor of a fragment mass measuring module to obtain the mass and landing time of fragments scattered in each fan-shaped annular partition, so as to obtain the initial ejection kinetic energy of the specimen after destruction, and then performs weighted average processing on the initial ejection kinetic energies obtained by the three methods, so as to finally obtain a more accurate initial ejection kinetic energy, reduce the system measurement error, and the specimen fragment ejection kinetic energy can well reflect the impact damage degree of the specimen, and can be used to evaluate the impact hazard of the specimen. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a cross-sectional view of a testing device in an embodiment of the present invention;

[0035] Figure 2 is a three-dimensional diagram of a testing device in an embodiment of the present invention;

[0036] Figure 3 is a top view of a testing device in an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the structure of the fragment mass determination module in an embodiment of the present invention;

[0038] Figure 5 Schematic diagram of the impact trajectory of the coal specimen under load and broken fragments in the embodiment of the present invention;

[0039] Figure 6 is the impact load curve of the coal specimen in the embodiment of the present invention;

[0040] Figure 7 The partition quality and time curve in the embodiment of the present invention;

[0041] Figure 8 The speed-time curve measured by the Doppler sensor in the embodiment of the present invention;

[0042] Fig. 9 is the Doppler sensor data after processing in the embodiment of the present invention. 2 -t curve;

[0043] Fig.10 It is an operation flow chart of the testing method in an embodiment of the present invention;

[0044] Among them, A1-pad, A2-hole for acoustic emission device, A3-retractable support rod;

[0045] A4-fragment collection layer, A5-device support structure layer; A6-level meter;

[0046] 1-fragment ejection kinetic energy measurement module: 11-fragment force measurement baffle;

[0047] 2-fragment ejection impact force measurement module: 21-beam load sensor, 22-limit rod;

[0048] 3- Doppler measurement module for initial velocity of fragment ejection: 31- Doppler sensor, 32- multi-degree-of-freedom mobile platform, 33- connecting rod;

[0049] 4-fragment mass measurement module: 41-weighing sensor, 42-sensor limit plate, 43-card slot;

[0050] 51-testing machine pressure head, 52-coal specimen, 54-fragmentation trajectory, 55-scattering plane. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Certain embodiments of the present invention will be described more comprehensively with reference to the accompanying drawings, in which some but not all embodiments will be shown. In fact, the various embodiments of the present invention can be implemented in many different forms and should not be construed as being limited to the embodiments described herein; rather, these embodiments are provided so that the present invention meets applicable legal requirements.

[0052] In the description of the present invention, it should be noted that the terms "inside", "outside", "upper", "lower", "front", "back" and the like indicate directions or positional relationships based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0053] In an embodiment of the present invention, a coal fragment impact kinetic energy index testing device is provided. Figures 1 to 10As shown, the coal fragment impact kinetic energy index testing device can measure the fragment ejection kinetic energy of the coal specimen and the fragment impact kinetic energy index of the coal specimen, thereby quantitatively characterizing the impact energy released when the coal sample is destroyed.

[0054] Combination Figures 1 to 4 As shown, the coal fragment impact kinetic energy index testing device mainly includes a cushion block A1, a device supporting structure layer A5, a fragment ejection kinetic energy measuring module 1, a fragment ejection impact force measuring module 2, a fragment ejection initial velocity Doppler measuring module 3, a fragment mass measuring module 4 and other related structural components.

[0055] Combination Figure 1 As shown, the pad A1 is set on the pressure column platform of the test machine and is located directly above the top center of the device support structure layer A5. The coal body specimen can be placed on the pad A1. The pad A1 is provided with an acoustic emission device A2, and an acoustic emission device is set in the acoustic emission device hole A2 to cooperate with the collection of later experimental data.

[0056] Combination Figure 1 As shown, a retractable support rod A3 is provided at the bottom of the device support structure layer A5. The retractable support rod A3 can be extended or contracted to adjust the overall height of the coal fragment impact kinetic energy index test device. When conducting coal specimen experiments, the vibration of the testing machine and the specimen pad A1 will have a significant impact on the accuracy of the test measurement. In order to reduce the error, it is necessary to adjust the length of the retractable support rod A3 before the test so that there is a certain height difference between the lower plane of the device structure support layer A5 and the plane of the pressure column platform of the testing machine, reduce vibration interference to reduce measurement errors, and ultimately ensure the accuracy of data and measurement results. After adjusting the height, ensure that the plane of the fragment collection layer A4 is level by observing the level gauge A6.

[0057] Combination Figure 1 and Figure 4As shown, a fragment mass determination module 4 is arranged on the top of the device support structure layer A5, and the fragment mass determination module 4 includes a plurality of sensor limit plates 42 and a weighing sensor 41, etc. Among them, the plurality of sensor limit plates 42 spread outward with the pad A1 as the center to form a multi-layer concentric ring shape, and slots 43 are provided between radially adjacent sensor limit plates 42 and sensor limit plates 42 in the same layer of concentric rings, and the sensor limit plates 42 in the same layer of concentric rings have slots 43 every 60 degrees, that is, the sensor limit plates 42 in the same layer of concentric rings are divided into six fan-shaped areas of equal area by the slots 43, and the area of ​​the fan-shaped areas away from the center of the circle in the radial direction increases layer by layer. Each weighing sensor 41 is correspondingly arranged on a sensor limit plate 42, and the weighing sensor 41 is used to obtain data such as the mass of the fragments. The fragment mass determination module 4 can obtain the mass of the fragments falling on each sector annular partition and the time when the fragments fall to the ground, and can provide corresponding parameters for other kinetic energy determination modules.

[0058] Combination Figure 1 and Figure 3 As shown, a debris collection layer A4 is provided above the sensor limit plate 42, wherein the structure and arrangement of the debris collection layer A4 are the same as those of the sensor limit plate 42, and are arranged one-to-one with the sensor limit plate 42. It should be noted that a plurality of grooves are provided on the lower surface of the debris collection layer A4, and each weighing sensor 41 is correspondingly arranged in a groove. Since the weighing sensor 41 is located above the top of the sensor limit plate 42, and the protruding position of the upper end of the weighing sensor 41 corresponds to the position of the groove on the lower plane of the debris collection layer A4, the weighing sensor 41 can be limited.

[0059] Combination Figure 1 and Figure 2 As shown, the fragment ejection kinetic energy measurement module 1 includes a plurality of fragment force measuring baffles 11, wherein the fragment force measuring baffles 11 spread outward with the pad A1 as the center to form a multi-layer concentric ring structure, and the fragment force measuring baffles 11 are all vertically arranged in the slots 43, and the slots 43 can limit the fragment force measuring baffles 11.

[0060] The height of the outermost broken force measuring baffle 11 is higher than the height of the upper plane of the pad A1 after the coal body specimen 52 is placed, and the heights of the remaining broken force measuring baffles 11 are consistent with the height of the innermost broken force measuring baffle 11. The inner diameter of the innermost broken force measuring baffle 11 is larger than the diameter of the circumscribed circle of the upper surface of the pad A1, and the pad A1 does not contact the plate wall of the innermost broken force measuring baffle 11.

[0061] The principle of testing the kinetic energy of coal fragments ejection by the fragment ejection kinetic energy determination module 1 is as follows:

[0062] When the coal body specimen 52 is squeezed and impacted, it will be ejected in all directions. The greater the ejection speed of the coal body fragments, the farther the ejection distance. According to the magnitude of the ejection kinetic energy, the coal body fragments will be scattered on the fragment collection layer A4. The falling time of the coal body fragments can be calculated according to the vertical distance between the coal body specimen 52 and the scattering plane 55. Then, according to the horizontal distance between the fragment force measuring baffle 11 and the center of the coal body specimen 52, the initial ejection speed of the coal body fragments can be obtained by the horizontal projection motion. Then, the mass of the coal body fragments in each area measured by the weighing sensor 41 can be used to obtain the ejection kinetic energy of the coal body fragments.

[0063] Combination Figures 1 to 3 As shown, the fragment ejection impact force measuring module 2 is arranged outside the fragment force measuring baffle 11 of each layer, and is used to measure the impact force of the fragment ejection. The fragment ejection impact force measuring module 2 includes a plurality of limit rods 22 and a beam load sensor 21 and other structural components.

[0064] Combination Figure 1 and Figure 2 As shown, the bottom end of the limit rod 22 is threadedly connected to the support structure layer A5. The threaded connection method can facilitate the disassembly and installation of the test device, effectively improving the efficiency of the experimental test. The top end of the limit rod 22 is connected and fixed to the beam load sensor 21 by threaded connection, and the beam load sensor 21 is close to the outer side of the fragment force measuring baffle 11. At the same time, there is no connection and fixation between the beam load sensor 21 and the fragment force measuring baffle 11.

[0065] The principle of testing the kinetic energy of coal fragment ejection by the fragment ejection impact force measurement module 2 is as follows:

[0066] When the coal specimen is squeezed to form fragments and hits the fragment force measuring baffle 11, the fragment force measuring baffle 11 will be deformed, causing the geometric shape and resistivity of the beam load sensor 21 close to the fragment force measuring baffle 11 to change, and the resistance value will also change accordingly, and finally the force signal is obtained through resistance measurement, and the fragment ejection impact force is obtained. The ejection kinetic energy of the coal fragment is obtained by analyzing the impulse theorem and the mass of the coal fragment measured by the weighing sensor 41.

[0067] Combination Figures 1 to 3 As shown, the fragment ejection initial velocity Doppler measurement module 3 is arranged outside the outermost fragment force measuring baffle 11, and is used to measure the initial velocity of the fragment ejection. The fragment ejection initial velocity Doppler measurement module 3 mainly includes structural components such as a connecting rod 33, a multi-degree-of-freedom mobile platform 32 and a Doppler sensor 31.

[0068] The threaded connection device at the bottom end of the connecting rod 33 supports the structural layer A5. The threaded connection method can facilitate the disassembly and installation of the test device, effectively improving the efficiency of the experimental test. The top of the connecting rod 33 is provided with a multi-degree-of-freedom mobile platform 32 by threaded connection. The Doppler sensor 31 is installed on the multi-degree-of-freedom mobile platform 32. The multi-degree-of-freedom mobile platform 32 can flexibly adjust the detection angle of the Doppler sensor 31 so that the probe of the Doppler sensor 31 is facing the center of the coal body specimen 52, so as to accurately obtain the initial velocity of the fragment ejection.

[0069] The principle of the Doppler determination module 3 for testing the kinetic energy of coal fragment ejection is as follows:

[0070] Based on the principle of the Doppler effect, that is, when the wave source and the observed object move relative to each other, the frequency of the wave will be observed to change, so the moving speed of the object can be determined by measuring the frequency change of the reflected wave. In this embodiment, when the coal body specimen 52 is destroyed during the test, the Doppler sensor 31 will monitor the initial velocity of the fragments ejected when the coal body specimen is destroyed, and analyze the coal body fragment mass data to obtain the ejection kinetic energy of the coal body.

[0071] Combination Figure 3 As shown, a level meter A6 is provided on the fragment collection layer A4, and the level meter A6 is used to judge whether the fragment collection layer A4 is kept horizontal, thereby ensuring the accuracy of the test data. The fragment collection layer A4, the sensor limit plate 42 and the device support structure layer A5 are fixedly connected accordingly by embedded bolts, wherein the device support structure layer A5 adopts an integrated structure to ensure stability, and at the same time, the position of each partition must correspond when each layer is fixed. The device support structure layer A5 establishes limit buckles at the left and right boundaries of each fan-shaped area formed by the sensor limit plate 42 and the fragment collection layer A4, which are used to limit the sensor limit plate 42 and the fragment collection layer A4, prevent the sensor limit plate 42 and the fragment collection layer A4 from moving and misaligning, and can ensure the smooth progress of the test and the accuracy of the test results.

[0072] A method for testing the impact kinetic energy index of coal body fragments, using the above-mentioned coal body fragments impact kinetic energy index testing device, specifically comprises the following steps:

[0073] Step 1: Place the coal fragment impact kinetic energy index test device on the test machine platform, adjust the length of the retractable support rod A3 so that there is a certain height difference between the lower surface of the device support structure layer A5 and the plane of the pressure column platform of the test machine, observe the level meter A6 and keep the fragment collection layer A4 in a horizontal state;

[0074] Step 2: Place the pad A1 on the plane of the pressure column platform of the testing machine, and make the upper end surface of the pad A1 flush with the upper edge of the innermost fragment force measuring baffle 11 in the horizontal direction;

[0075] Step 3, connect the weighing sensor 41, the beam load sensor 21 and the Doppler sensor 31 to their respective data acquisition devices, install the acoustic emission device in the acoustic emission device hole A2 of the pad A1, adjust the zero and set the sampling frequency in sequence, and place the coal body specimen 52 at the top center of the pad A1;

[0076] Step 4: Start the testing machine to load the coal specimen 52, and the testing machine and the data acquisition device collect data simultaneously;

[0077] Step 5: After the coal specimen is destroyed, the testing machine is stopped from loading, and the data of each group of weighing sensors 41, beam load sensors 21, and Doppler sensors 31 are recorded. The collected data are processed and analyzed to obtain the total ejection kinetic energy and impact kinetic energy index.

[0078] Combination Fig.10 As shown, the specific data processing and calculation process is as follows:

[0079] First, the fragment scattering area needs to be divided. In this embodiment, the fragment collection layer A4 is expanded outward layer by layer into five concentric rings with the coal body specimen 52 as the center, that is, i = 1, ..., 5. At the same time, each concentric ring is divided into six sector rings of equal area, that is, j = 1, ..., 6. Therefore, the mass can be expressed as m i,j For example, the mass of the fragments scattered in the third partition of the second concentric ring can be recorded as m 2,3 .

[0080] Specifically, the weighing sensor 41 is connected to the data acquisition device to obtain the mass of the broken pieces and the landing time;

[0081] like Figure 5 As shown in the figure, when the coal specimen 52 is impacted, the fragments all fly out horizontally, and the horizontal distance between the falling point of the fragments and the edge of the specimen is positively correlated with the initial velocity of the fragments. The average distance between each layer of concentric rings and the edge of the specimen is L i , assuming that the fragments are thrown at the same height, this position is taken as the mean value of the fragment throwing position, that is, the height center of the specimen (h / 2) is taken as the impact fragment throwing point. Then:

[0082] The initial velocity of the fragment ejection kinetic energy determination module 1 is calculated as:

[0083]

[0084] Where: L iis the average distance between each layer of concentric rings and the edge of the specimen, g is the gravitational acceleration, and h is the height of the coal specimen;

[0085] The initial kinetic energy of coal specimen destruction obtained by the fragment ejection kinetic energy measurement module 1 is:

[0086]

[0087] Where: E 1 is the initial kinetic energy of the specimen destroyed by the ejection of fragments, m i,j is the mass of the fragments in each sector ring partition.

[0088] In the calculation of the initial kinetic energy in formula (2), the initial velocity corresponds to the mass of the corresponding concentric rings, and the initial velocity of the falling fragments in the corresponding area of ​​each concentric ring is basically the same.

[0089] Specifically, the beam load sensor 21 is connected to the data acquisition device to obtain the impact force of the fragment ejection;

[0090] Combination Figure 6 As shown, the corresponding curve of impact force and time can be obtained by the beam load sensor 21, and the impulse can be obtained from the impulse formula:

[0091] I i,j =∫F i,j (t)dt (3)

[0092] Where: F i,j is the impact force of the fragment ejection corresponding to each partition, I i,j is the impulse of each partition.

[0093] The initial velocity of the coal block is deduced from the impulse theorem:

[0094]

[0095] The initial kinetic energy of coal specimen destruction obtained by the fragment ejection impact force measurement module 2 is:

[0096]

[0097] Where: E 2 Invert the initial kinetic energy of specimen destruction for the impact force of fragment ejection;

[0098] Specifically, the Doppler sensor 31 is connected to the data acquisition device to obtain the initial ejection velocity of the fragments;

[0099] The Doppler sensor 31 can measure the initial velocity of the coal block thrown out when the specimen is destroyed. There are six Doppler sensors 31 in total, corresponding to the corresponding concentric circle partitions (each Doppler sensor is numbered k=1,...,6). The mass obtained by the weighing sensor 41 of the corresponding partition (that is, all the concentric ring areas within the 60° sector corresponding to the Doppler sensor) is added up to obtain the mass time curve (m k -t), such as Figure 7 shown.

[0100]

[0101] The Doppler sensor 31 can collect speed-time data, and its corresponding curve is as follows: Figure 8 As shown. By squaring the speed, we can get v 2 -t data, its corresponding curve is as follows Fig. 9 Through the time correspondence, the velocity data collected by the Doppler sensor 31 can be matched with the mass data obtained by the fragment mass determination module 4 to obtain v 2 -m k Corresponding data. Data acquisition equipment integrates v 2 -m k The data is integrated (the data acquisition equipment integrates the data in real time at a time scale, i.e. every 20 milliseconds, and automatically sums the integral), and the initial kinetic energy can be obtained by taking 1 / 2 of the integral. That is, the initial kinetic energy of the coal specimen destruction obtained by the Doppler measurement module 3 of the initial velocity of the fragment ejection is:

[0102]

[0103] Where: E 3 Doppler inversion of the initial kinetic energy of specimen destruction for fragment ejection;

[0104] The initial ejection kinetic energy after the specimen is destroyed is obtained through the above calculations. Since it cannot reach the assumed ideal state, there are certain calculation errors. In order to obtain accurate initial ejection kinetic energy, the results obtained by the three methods are weighted averaged, namely:

[0105]

[0106] Where: W k is the kinetic energy of ejection of specimen fragments.

[0107] Indoor tests show that the ejection kinetic energy of specimen fragments can well reflect the degree of impact damage of the specimen and can be used to evaluate the impact hazard of the specimen. The unit of the ejection kinetic energy of fragments calculated in the test is J, which is related to the specimen size. In practical applications, in order to avoid the calculation error of the ejection kinetic energy of fragments and the difference in impact hazard evaluation caused by the specimen size effect, a dimensionless variable α is introduced to offset the specimen size effect, and then the impact kinetic energy index I is proposed. k , defined as the ejection kinetic energy W of the specimen fragments k The product of the variable α is:

[0108] I k =αW k (9)

[0109] Definition of variable α: First, the basic size of the coal specimen is determined to be a standard cylindrical specimen of 50×100, and its volume is V 0 The variable α is:

[0110]

[0111] Where: V 0 is the volume corresponding to the basic size; V i is the corresponding volume of the specimen.

[0112] The present invention provides a coal body fragment impact kinetic energy index testing device and testing method, which can measure the fragment impact kinetic energy index when the coal body specimen is destroyed, so as to quantitatively characterize the impact energy released when the coal sample is destroyed, and evaluate the impact tendency of the coal body based on the destruction characteristics; the present invention divides the sensor limit plate 42 and the fragment collection layer A4 into a plurality of fan-shaped areas, each fan-shaped area is individually configured with a weighing sensor 41, which can independently measure the mass of the fragments scattered in each partition and the landing time, and finally improve the accuracy of the test results;

[0113] The present invention obtains data such as the initial velocity and impact force of fragment ejection through a fragment ejection kinetic energy measuring module 1, a fragment ejection impact force measuring module 2 and a fragment ejection initial velocity Doppler measuring module 3, and simultaneously cooperates with a fragment mass measuring module 4 to obtain the mass of fragments scattered in each fan-shaped partition and the landing time, so as to obtain the initial ejection kinetic energy of the specimen after destruction, and then performs weighted average processing on the initial ejection kinetic energy obtained by the three methods, so as to finally obtain a more accurate initial ejection kinetic energy, reduce the system measurement error, and the specimen fragment ejection kinetic energy can well reflect the impact damage degree of the specimen, and can be used to evaluate the impact hazard of the specimen.

[0114] Of course, the specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A coal fragment impact kinetic energy index testing device, characterized in that: It includes a cushion block, a device supporting structure layer, a fragment mass measuring module, a fragment ejection kinetic energy measuring module, a fragment ejection impact force measuring module and a fragment ejection initial velocity Doppler measuring module; Wherein, the cushion block is arranged on the pressure column platform of the testing machine and is located directly above the top center of the device support structure layer; A fragment mass determination module is arranged on the top of the supporting structure layer of the device, and the fragment mass determination module includes a sensor limit plate and a weighing sensor, wherein a plurality of sensor limit plates spread outwards with the cushion block as the center to form a multi-layer concentric ring shape, and slots are provided between radially adjacent sensor limit plates and sensor limit plates in the same layer of concentric rings, and each weighing sensor is correspondingly arranged on each sensor limit plate; A fragment collection layer is arranged above the sensor limit plate, wherein the fragment collection layer and the sensor limit plate are arranged in one-to-one correspondence; The fragment ejection kinetic energy measurement module comprises a plurality of fragment force measuring baffles, wherein the fragment force measuring baffles spread outwards with the cushion block as the center to form a multi-layer concentric ring shape, and the fragment force measuring baffles are vertically arranged in the card slot; The fragment ejection initial velocity Doppler measurement module is arranged on the outer side of the outermost fragment force measuring baffle plate, and is used to measure the initial velocity of the fragment ejection; The fragment ejection impact force measuring module is arranged on the outside of each fragment force measuring baffle plate, and is used to measure the impact force of the fragment ejection.

2. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: The fragment ejection impact force measurement module includes a limit rod and a beam load sensor; The bottom end of the limit rod is threadedly connected to the device support structure layer, the top end of the limit rod is connected to the beam load sensor, and the beam load sensor is closely attached to the outer side of the fragment force measuring baffle.

3. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: The fragment ejection initial velocity Doppler measurement module comprises a connecting rod, a multi-degree-of-freedom mobile platform and a Doppler sensor; The bottom end of the connecting rod is threadedly connected to the device supporting structure layer, the multi-degree-of-freedom mobile platform is arranged on the top end of the connecting rod, and the Doppler sensor is arranged on the multi-degree-of-freedom mobile platform, wherein the multi-degree-of-freedom mobile platform can adjust the detection angle of the Doppler sensor so that the probe of the Doppler sensor faces the center of the test piece.

4. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: The sensor limit plates located on the same concentric ring layer have slots arranged at intervals of 60 degrees.

5. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: The height of the outermost fragment force baffle is higher than the height of the upper plane after the pad is placed on the test piece, and the heights of the remaining fragment force baffles are consistent with the height of the innermost fragment force baffle; Among them, the inner diameter of the innermost fragment force measuring baffle is larger than the diameter of the circumscribed circle of the upper surface of the cushion block, and the cushion block does not contact the plate wall of the innermost fragment force measuring baffle.

6. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: A plurality of grooves are provided on the lower surface of the fragment collection layer, and each weighing sensor is correspondingly arranged in a groove.

7. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: A retractable support rod is arranged at the bottom of the supporting structure layer of the device, and the retractable support rod can adjust the height of the coal body fragment impact kinetic energy index testing device.

8. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: The cushion block is provided with a sound emission device hole, and a sound emission device is arranged in the sound emission device hole.

9. The device for testing the impact kinetic energy index of coal fragments according to claim 1, characterized in that: A level is provided on the fragment collecting layer.

10. A method for testing the impact kinetic energy index of coal fragments, using the coal fragment impact kinetic energy index testing device according to any one of claims 1 to 9, characterized in that: The steps include: Step 1: Place the coal fragment impact kinetic energy index test device on the test machine platform, adjust the length of the retractable support rod so that there is a height difference between the lower surface of the device support structure layer and the plane of the pressure column platform of the test machine, observe the level meter and keep the fragment collection layer level; Step 2: Place the cushion block on the plane of the pressure column platform of the testing machine, and make the upper end surface of the cushion block flush with the upper edge of the innermost layer of the fragment force measuring baffle in the horizontal direction; Step 3, respectively connect the weighing sensor, beam load sensor and Doppler sensor to their respective data acquisition devices, install the acoustic emission device in the acoustic emission device hole of the pad, adjust the zero and set the sampling frequency in turn, and place the coal body specimen at the top center of the pad; Step 4: Start the testing machine to load the coal specimen, and the data acquisition equipment synchronously collects data; Step 5: After the coal specimen is destroyed, stop loading the testing machine, record the data of each group of weighing sensors, beam load sensors, and Doppler sensors, process and analyze the collected data, and obtain the total ejection kinetic energy and impact kinetic energy index.

Images