A dynamic impact test device and method under a loaded combined coal-rock state

Abstract

The present invention belongs to the field of research on the dynamic effect of coal-rock working face under external disturbance in coal mine excavation, mechanical properties of coal-rock strata in goaf and coal-rock tunnel roof, and coal-rock dynamic disasters, and particularly relates to a dynamic impact test device and method under a loaded combined coal-rock state, the device comprises a gantry frame, a base arranged at the center of the gantry frame, a rectangular frame hydraulic cylinder mounting seat surrounded by four supporting side plates is arranged on the base, a side hydraulic cylinder is arranged at the center of each supporting side plate of the rectangular frame, two top hydraulic cylinders are also arranged at the top of the rectangular frame, and a test piece is arranged at the center of the rectangular frame. The present invention is simple in design, scientific, and reasonable, easy to operate, and convenient for data monitoring. By constructing a multi-layer thin plate combined coal-rock model, the dynamic damage mechanism of the coal-rock mass and the disaster-causing mechanism of the dynamic load are studied and revealed, which can effectively solve the key problems in the field of coal-rock dynamic disasters in my country.

Description

Technical Field

[0001] The present invention belongs to the field of research on dynamic effects of coal-rock working faces in coal mine excavation under external disturbances, mechanical properties of coal-rock strata in goafs and coal-rock tunnel roofs, and coal-rock dynamic disasters, and in particular to a dynamic effect test device and method for triaxially loaded multi-layer combined thin plate coal-rock bodies under dynamic loads. Background Art

[0002] With the increasing demand for mineral resources and the continuous consumption of shallow resources, the mining of coal and metal mines at home and abroad has gradually shifted to deep areas. Under high stress conditions, the occurrence of dynamic disasters such as coal and gas outbursts has become more serious. At present, the research on the occurrence mechanism and disaster-causing mechanism of coal-rock dynamic disasters by domestic and foreign scholars is mostly based on static theoretical experimental research and analysis of preliminary dynamic exploration results. For coal-rock mass, especially multi-layer combined coal-rock mass, the research on dynamic mechanical response characteristics, the interaction mechanism of contact surfaces between layers, and vibration characteristics is still in the experimental exploration stage, resulting in the fact that the dynamic damage, destruction mechanism and disaster-causing mechanism of external dynamic loads of coal-rock mass are still unclear, which fails to provide strong support for fundamentally revealing the occurrence of coal-rock dynamic disasters.

[0003] In view of the layered structure and plate cracking and layer cracking in the formation process of coal-bearing rock mass, the mechanical behavior of plate cracking and spalling damage of coal-rock mass has been extensively studied using thin plate theory. The research results show that the thin plate model has significant advantages in studying the propagation and action of stress waves, vibration morphology and characteristics, and dynamic damage occurrence process in coal-rock mass under dynamic load, and can achieve quantitative description. Based on the actual needs of the development of monitoring, early warning and prevention technology of coal-rock dynamic disasters in deep mine mining, a multi-layer thin plate combined coal-rock mass calculation model is constructed. Through theoretical and experimental research, the dynamic damage mechanism of coal-rock mass and the disaster-causing mechanism of dynamic load are revealed, which can effectively solve the key problems in the field of coal-rock dynamic disasters in my country. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a dynamic effect test device and method for coal rock mass under dynamic load with multi-layer combined thin plate under triaxial loading. Through the triaxial confining pressure test and drop hammer data of the simulated coal seam plate conducted by the device, the relationship between the layered structure in the formation process of coal-bearing rock mass and the destruction phenomena such as plate cracking and layer cracking in dynamic disasters can be analyzed; and the roof pressure of goafs and tunnels with different widths under different confining pressures, different roof heights, different disturbances, different top pressures, and the mechanical properties of the top rock mass under the influence of mining of different lithology roofs can be studied. The multi-layer thin plate specimen is located in the middle of the instrument, and pressure plates are distributed around the specimen to pressurize it. When the size of the specimen changes, the pressure plates are also replaced accordingly; the loading pressure comes from six hydraulic cylinders; the upper pressure plate is connected to the drop hammer connecting rod so that the drop hammer can impact the upper pressure plate to generate a uniform load on the specimen; the bottom of the specimen is a rigid structure, which is designed to be freely disassembled, so as to facilitate the simulation of the changes of goafs and tunnel roofs under different external boundaries. The present invention is simple, scientific, and reasonable in design, easy to operate, and convenient for data monitoring. By constructing a multi-layer thin plate combined coal-rock model, the dynamic damage mechanism of coal-rock mass and the disaster-causing mechanism of dynamic loads are revealed, which can effectively solve the key problems in the field of coal-rock dynamic disasters in my country.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A dynamic effect test device for a triaxially loaded multi-layer composite thin-plate coal rock mass under dynamic loads comprises a gantry frame, a base arranged at the center of the gantry frame, a rectangular frame hydraulic cylinder mounting seat surrounded by four supporting side plates is arranged on the base, a side hydraulic cylinder is arranged in the center of each supporting side plate of the rectangular frame, a top hydraulic cylinder is also arranged on the top of the rectangular frame, and a test piece is arranged in the center of the rectangular frame. The power of the present invention adopts a hydraulic pump station for continuous pressurization, and a pressure sensor is installed at the connection of the pressure cylinder to monitor the loading pressure; the pressure cylinder is uniformly loaded by the displacement loading of the plunger; the top drop hammer directly acts on the top pressure plate, and impacts under the loading environment, and the impact load is uniformly transmitted from the top pressure plate to the test piece, and at the same time, strain bricks and pressure sensors are buried in a layered and stepped manner in the single-layer thick test piece, and strain bricks and pressure sensors are buried at intervals in the multi-layer thin test piece under the test state, such as one layer, three layers, and five layers. The test plates are buried at intervals and connected to the signal receiver to collect data. The acoustic emission devices are arranged on the upper and lower pressure plates according to the different test function requirements. The present invention determines the ratio of similar materials and then produces the required single-layer, double-layer and multi-layer test plates so as to produce the dynamic effect of uniformly distributed load by the drop hammer impact under the triaxial pressurization state. The loading system adopts the hydraulic cylinder inner diameter stroke displacement control. The power source is provided by the hydraulic pump station. The positive and negative loading support points of the X and Y axes are the side plates, which act on the boundary pressure plates of the test pieces around to form a confining pressure environment. The numbers are displayed synchronously during the loading process. The top is pressurized by two pressure cylinders to act on the top pressure plate to simulate the vertical pressure and determine to maintain the triaxial pressurization environment. Impacts are carried out under different weights, different shapes, different heights and different boundary conditions to explore the fracture mechanism of coal rock mass. The data is collected by connecting the strain brick and the pressure sensor to the ultra-dynamic strain collector for collection.

[0007] Furthermore, the gantry frame includes side frames on both sides and a bottom frame at the bottom, the bottom frame is connected to the base by bolts, and also includes a top side frame and a fixed plate located at the bottom thereof and parallel to the top side frame, and the top hydraulic cylinder is fixed on the fixed plate.

[0008] Furthermore, a drop hammer system is provided at the center top of the specimen, and the drop hammer system includes a sleeve arranged at the center top of the specimen, and a drop hammer located at the top of the sleeve. The sleeve can be slidably fixed on a sleeve support frame, and the sleeve support frame is fixed on the top frame. The sleeve is connected to the sleeve support frame through a clamping ring.

[0009] Furthermore, a hollow side hydraulic cylinder mounting hole is provided in the center of each supporting side plate, and the side hydraulic cylinder is fixedly connected to the supporting side plate by bolts, and the plunger of the hydraulic cylinder can contact the side of the test piece when extended.

[0010] Furthermore, the specimen is provided with lateral pressure plates on all sides, a top pressure plate is provided on the top of the specimen, and a plurality of detachable pads are provided at the bottom of the specimen. The plurality of detachable pads are horizontally arranged and located at the bottom of the specimen as support. An elastic base is provided on each side of the pad. The lateral pressure plates and the top pressure plates are consistent with the size of the specimen. A groove is provided in the center of the lateral pressure plates and the top pressure plates. The size of the groove matches the end of the plunger. The pressure plates on each side of the specimen are adjusted accordingly according to the size of the specimen. The cylinder plunger acts on the pressure plate groove. The cylinder telescopic rod is consistent with the groove to prevent slippage. The bottom of the specimen has detachable pads When the base is completely flat, it is used to simulate the dynamic damage of soft coal seams under triaxial loading. When half or more of the pads are removed, the rupture of the roof under the conditions of stratification of the goaf roof, changes in loading intensity, and changes in goaf width can be simulated. In this process, pre-cracks can be made in the roof rock layer to analyze the impact of the goaf breakage under different loading methods; when one or two pads are removed, the mechanical properties of the rock at the top of the tunnel are simulated under different loading pressures at the top of the tunnel; at the same time, the top pressure plate continues to be impacted in this process, and the boundary conditions are changed for experimental analysis.

[0011] Furthermore, strain bricks and pressure sensors are embedded inside the test piece to measure the internal stress, strain and pressure at different positions of the coal and rock mass; an acoustic emission device is placed at a suitable position; the above elements are connected to an ultra-dynamic strain collector to collect signals. Coupling agent is applied between the test pieces for connection.

[0012] Furthermore, the test piece is in a state of a combination of thin or thick plates, and the test piece is at least one layer.

[0013] Furthermore, the top hydraulic cylinder is a double hydraulic cylinder, and the drop hammer system is located at the center of the double hydraulic cylinder.

[0014] A testing method of a dynamic effect testing device for a triaxially loaded multi-layered composite thin plate coal rock mass under dynamic load comprises the following steps:

[0015] (1) Prepare the required pressing plate and test piece, ensure that the six surfaces of the test piece are smooth and flat, and let them stand to dry for later use;

[0016] (2) In single-layer thick specimens, strain bricks and pressure sensors are buried in a stepped manner. In multi-layer thin specimens, strain bricks and pressure sensors are buried at intervals in the test state, such as one, three, or five layers, and connected to signal receivers;

[0017] (3) Coupling agent is applied to the contact surface between the multi-layer specimen thin plates, and the manufactured multi-layer composite thin plate coal rock mass is placed in the experimental device. The back of the bottom thin plate is supported by a steel plate, which can be regarded as a rigid foundation. Then the top is fixed and the pressure plate is lowered. The top fixed pressure plate is the loading area;

[0018] (4) Wrap the artificial leather on both sides of the left and right front and back pressure plates, and wrap the artificial leather on the upper surface of the upper pressure plate, load the confining pressure and axial pressure, and pressurize according to the required pressurization strength. The reading is displayed on the parameter table. Stop pressurization after the requirement is met, wait for two minutes, and observe whether the test piece has any abnormality under the pressurized environment;

[0019] (5) According to the test requirements, drop the hammer to impact and test the parameters, and finally perform the calculation.

[0020] The present invention has the following beneficial effects:

[0021] 1. The present invention aims at the dynamic effect caused by the breaking of the roof of the goaf during the forward advancement of the coal mining face, the prone occurrence of outburst accidents when encountering faults and stone gates during the advancement of the excavation face, the stress concentration of the top plate of the excavation head, the occurrence of coal cannon, excessive pressure, abnormal gas outburst and other phenomena during the process, and provides a strong basis for the analysis and research of the stress concentration and fracturing of the rock strata on the top plate of the mining face through the simulation test data under different working conditions of the device of the present invention; in this process, the top impact is carried out, and the propagation law of the stress wave, dynamic damage, and energy transfer after the bottom pads are taken out one by one are observed, and the corresponding data support is provided for the dynamic effects such as the fracture of the mining roof and the propagation of stress waves, and also provides an experimental basis for providing a normal mining environment for the mining process, which is of great significance for preventing accidents on the top plate of the mining face and conducting timely research and judgment, and applying the theoretical model to the mining process;

[0022] 2. The present invention disassembles the bottom pad of the specimen accordingly to achieve different functions, adjusts the bottom disassembly range, triaxial loading pressure and other external conditions accordingly, and loads vertically on the top to simulate the influence of ground stress on the breaking of the goaf and the tunnel roof, and stress concentration. At the same time, corresponding cracks are arranged inside the prefabricated specimen to simulate the pressure of the goaf and the tunnel roof, and then the test is carried out to determine the appropriate fracture parameters, the breaking and pressure relief methods, and the pressure control of the top plate of the mining working face, as well as the stress concentration of the tunneling head, the difficulty of tunneling, the sound of coal cannon, and the easy occurrence of coal and gas outbursts. When the test simulates the above process, the upper pressure plate is continuously impacted to obtain the propagation characteristics, dynamic effects, energy diffusion, loss, vibration form and characteristics of stress waves at different empty top distances;

[0023] 3. Based on the data of the simulation test of the device of the present invention, according to the Mohr-Coulomb criterion and the third strength theory, and according to the dynamic change law of the maximum shear stress of each layer of thin plate coal rock mass with time during the vibration of each effective vibration mode, the dynamic distribution characteristics and the characteristics of the convergence and concentration area of ​​the maximum shear stress are obtained, the starting position and main development trend of the dynamic damage of the multi-layer thin plate combined coal rock mass during the vibration process are analyzed, and the dynamic damage characteristics of the multi-layer thin plate combined coal rock mass are found; the dynamic change law of energy storage, release and concentration during the vibration of the coal rock mass is analyzed, and the effect of dynamic load in the multi-layer thin plate combined coal rock mass is revealed;

[0024] 4. Based on the data from the simulation test of the device of the present invention, according to the existing fast Fourier transform theory (FFT), combined with the MATLAB platform, the interaction mechanism between the LS-DYNA∕MatDEM simulation software and the combined rock mass, the vibration effect of the thin plate under different dynamic loads (shock wave, simple harmonic wave, triangular wave, etc.) is analyzed, and the dynamic distribution law of the "three fields" of stress field, strain field and energy field in the coal-rock state of multi-layer thin plate combination under different boundary conditions (CCCC, CSCS, SFSF) is obtained. The fracture of the top plate of the mining working face under different boundary conditions and the prefabricated crack simulation of the top plate decompression have practical significance for guiding engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a front view of the device of the present invention;

[0026] Figure 2 is a side view of the device of the present invention;

[0027] Figure 3 It is a top view of the device of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to the embodiments shown in the accompanying drawings. Example

[0029] A dynamic effect test device for a triaxially loaded multi-layer composite thin-plate coal rock mass under dynamic load, comprising a gantry frame, the gantry frame comprising side frames 6 on both sides and a bottom frame 11 at the bottom, the bottom frame 11 being connected to a base 10 by bolts 12, and also comprising a top side frame and a fixing plate 16 located at the bottom thereof in parallel with the top side frame, the top hydraulic cylinder being fixed to the fixing plate; a base 10 arranged at the center of the gantry frame, the base 10 being provided with a rectangular frame hydraulic cylinder mounting seat formed by being surrounded by four supporting side plates 15, each supporting side plate 15 being provided with a hollow side hydraulic cylinder 14 mounting hole at its center, the side hydraulic cylinder 14 being fixedly connected to the supporting side plate 15 by bolts 12, the column of the side hydraulic cylinder 14 The plug 18 can contact the side of the test piece 5 when it is extended; a side hydraulic cylinder 14 is provided in the center of each supporting side plate of the rectangular frame, a top hydraulic cylinder 4 is also provided on the top of the rectangular frame, a test piece 5 is provided in the center of the rectangular frame, and a drop hammer system is also provided on the top of the center of the test piece 5, the drop hammer system includes a sleeve 2 arranged at the top of the center of the test piece, a drop hammer 1 located at the top of the sleeve, the sleeve 2 can be slidably fixed on the sleeve support frame 3, the sleeve support frame 3 is fixed on the top frame, and the sleeve is connected to the sleeve support frame 3 by a clamping ring; side pressure plates 8 are provided around the test piece 5, a top pressure plate 7 is provided on the top of the test piece, and a plurality of detachable pads 9 are provided at the bottom of the test piece, and the plurality of detachable pads 9 are arranged horizontally and laterally at the bottom of the test piece as Support, when used specifically, the pad can be pulled out to simulate the bottom goaf, and a cavity 17 is formed after the pad is pulled out. An elastic base 13 is provided on each side of the pad, and the lateral pressure plate 8 is located on the elastic base 13. The lateral pressure plate 8 and the top pressure plate 7 are consistent with the size of the specimen 5. The centers of the lateral pressure plate 8 and the top pressure plate 7 are each provided with a groove, and the size of the groove matches the end of the plunger 18. The pressure plates on each side of the specimen are adjusted accordingly according to the size of the specimen, and the cylinder plunger 18 acts on the pressure plate groove, and the cylinder telescopic rod is consistent with the groove to prevent slippage. The bottom of the specimen has a detachable pad. When the base is completely flat, it is a study on the dynamic damage of the simulated specimen in soft coal seams under triaxial loading. When half or more of the pads are removed , it can simulate the roof rupture under the conditions of goaf roof stratification, loading intensity change, and goaf width change. In this process, the roof rock layer can be prefabricated to analyze the impact of goaf breakage under different loading methods; when one or two pads are removed, the mechanical properties of the rock at the top of the tunnel under different loading pressures are simulated; at the same time, the top pressure plate is continuously impacted in this process to change the boundary conditions for experimental analysis; during the test, strain bricks and pressure sensors are buried inside the test piece to measure the internal stress, strain and pressure at different positions of the coal rock mass; an acoustic emission device is placed at a suitable position; the above components are connected to the ultra-dynamic strain collector to collect signals. Coupling agent is applied between the test pieces for connection.The test piece is in a thin and thick combination state, the test piece has at least one layer, the top hydraulic cylinder is a double hydraulic cylinder, and the drop hammer system is located at the center of the double hydraulic cylinder.

[0030] The power of the present invention is to use a hydraulic pump station to continuously pressurize, and a pressure sensor is installed at the connection of the pressure cylinder to monitor the loading pressure; the pressure cylinder is uniformly loaded by the plunger displacement loading; the top drop hammer directly acts on the top pressure plate, and impacts under the loading environment, and the impact load is evenly transmitted from the top pressure plate to the test piece, and at the same time, strain bricks and pressure sensors are buried inside the test piece to measure the internal stress, strain and pressure at different positions of the coal rock mass; the above-mentioned elements are connected to the ultra-dynamic strain collector to collect data, and the acoustic emission device is arranged on the upper and lower pressure plates according to the different test function requirements; the present invention determines the ratio of similar materials, and then produces the required single-layer, double-layer, and multi-layer test pieces. In order to carry out the dynamic effect of uniformly distributed load produced by the drop hammer impact under the triaxial pressurization state, the loading system adopts hydraulic cylinder inner diameter stroke displacement control, and the power source is provided by the hydraulic pump station. The positive and negative loading support points of the X and Y axes are side plates, which act on the boundary pressure plates of the specimens around to form a confining pressure environment. During the loading process, the indications are displayed synchronously. The top is pressurized by two pressure cylinders to act on the top pressure plate to simulate vertical pressure and maintain the triaxial pressurization environment. Impacts are carried out under different weights, shapes, heights and boundary conditions to explore the dynamic fracturing mechanism of soft coal seams. Data collection is carried out using strain bricks and pressure sensors connected to ultra-dynamic strain acquisition instruments.

[0031] A test method for a dynamic effect test device of a triaxially loaded multi-layer composite thin-plate coal-rock mass under dynamic loads comprises the following steps: ① preparing a certain number of required pressing plates, a certain number of medium-thickness test pieces, and a certain number of integral raw coal and structural coal test pieces, ensuring that the six surfaces of the test pieces are smooth and flat, and standing them to dry for use; ② burying strain bricks and pressure sensors inside the thin-plate coal-rock mass of the test piece to measure the internal stress, strain and pressure at different positions of the coal-rock mass; placing an acoustic emission device at a suitable position; connecting the above-mentioned components to an ultra-dynamic strain collector to collect signals; ③ after the test piece meets the experimental conditions, applying a coupling agent to the contact surfaces between the multi-layer thin plates, placing the manufactured multi-layer composite thin-plate coal-rock mass in the experimental device, and supporting the back of the bottom thin plate with a steel plate, which can be regarded as a rigid ④ Wrap the artificial leather or rubber pads on both sides of the left, right, front and back directions of the pressing plate to protect the contact damage between the specimen and the pressure cylinder and the contact between the pressing plate and the edge of the specimen to produce fracturing and damage the integrity of the specimen. The upper pressing plate only needs to be wrapped with artificial leather on the upper surface, because the lower surface needs to be impacted and the area is larger; ⑤ Load the confining pressure and axial pressure, pressurize according to the required pressurization intensity, display the number on the parameter table, stop pressurizing after meeting the requirements, wait for two minutes, and observe whether the specimen has any abnormalities under the pressurized environment; ⑥ Drop the hammer to impact (adjust the height, change the weight, change the confining pressure and axial pressure, and impact the thin and thick plates in different combinations) and test the parameters.

[0032] Application Examples

[0033] When it comes to breaking the roof rock layers in front and behind the mining working face under different boundary conditions in a loading environment, and reserving cracks for experimental simulation of roof fracturing tests, the specific steps are: ① Prepare a certain number of required thin plates, a certain number of thin plate (layer), medium thickness, and thick plate (layer) thickness specimens, and a certain number of integral raw coal and structural coal specimens, ensure that the six surfaces of the specimen plate are smooth and flat, let them stand and dry for use, and during the specimen preparation process, pre-set cracks inside the specimen; ② Bury strain bricks and pressure sensors along the thin plate coal rock mass to measure the internal stress, strain and pressure at different positions of the coal rock mass; place the acoustic emission device at a suitable position; connect the above components to the ultra-dynamic strain collector to collect signals; ③ Take out the detachable pads in different widths to simulate goafs of different widths. When the width is the smallest, it simulates the excavation tunnel. Roof fracture model; ④ After the specimen meets the experimental conditions, the contact surface between the multi-layer thin plates is coated with coupling agent, and the multi-layer combined thin plate coal rock mass is placed in the experimental device. The back of the bottom thin plate is supported by a steel plate, which can be regarded as a rigid foundation. Then the top is fixed and the pressure plate is lowered. The middle part of the top fixed pressure plate is the loading area; ⑤ Wrap the two sides of the pressure plate in the left and right directions to protect the contact damage between the specimen and the pressure cylinder and the contact between the pressure plate and the edge of the specimen to produce fracturing and damage the integrity of the specimen. The upper pressure plate is wrapped with artificial leather on the upper and lower surfaces; ⑥ Load the confining pressure, pressurize according to the required pressure strength, display the number on the parameter table, stop pressurizing after reaching the requirements, wait for two minutes, and observe whether the specimen is abnormal under the pressure environment; ⑦ Slowly load the axial pressure, test the corresponding parameters, and observe the fracture. ⑧ Load from step ⑦ to a fixed value, release the drop hammer for impact, and record the corresponding parameters.

[0034] Impact test was carried out on the side pressure plate and top pressure plate loading specimen 5, and the roof fracture simulation test of the mining working face roof (single layer and multi-layer combination) during the pressurization process was carried out. The external boundary conditions (different thickness, different length and width, different loading strength, pad removal width, reserved cracks) were adjusted to simulate the dynamic damage mechanism and dynamic load disaster mechanism of the multi-layer thin plate combination coal rock mass under different states, as well as the roof fracture and destruction characteristics during mining.

[0035] The top pressure plate 7 and the side pressure plate 8 are both detachable and replaceable pressure plates. The size and thickness of the pressure plates can be changed according to the size of the test piece 5. The contact surface with the hydraulic cylinder 4 has corresponding grooves to fix the telescopic rod of the pressure cylinder. During the impact process, the top pressure plate 7 is replaced according to the weight of the drop hammer 1 and the falling height of the drop hammer. The impact load acts on the top pressure plate and then continues to propagate to the test piece to achieve the purpose of uniform loading.

[0036] A fixed specimen width is reserved at the contact edge position between the positive and negative pressure plates of the X and Y axes and the top pressure plate 7, with a length and width of 3 cm and 2 cm respectively. The dynamic strain gauge is extended and connected to the piezoelectric crystal wire, and the specimen is fixed. The specimen 5 can be impacted in a complete state, impacted with prefabricated cracks, and impacted with a combination of multi-layer medium and thick plates. The detachable pads 9 are removed in different numbers to simulate the fracture of the top plate during the mining process. After the detachable pads 9 at the bottom of the specimen are removed, the top hydraulic cylinder 4 is loaded under different pressures and then impacted to observe the propagation law of stress waves after the bottom pads are removed one by one, dynamic damage, energy transfer, etc. to provide corresponding data support, and also provide an experimental basis for providing a normal mining environment for the mining process.

[0037] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A dynamic impact test device under a loaded combined coal-rock state, characterized in that: It includes a gantry frame, a base arranged in the center of the gantry frame, a rectangular frame hydraulic cylinder mounting seat surrounded by four supporting side panels is provided on the base, a side hydraulic cylinder is provided in the center of each supporting side panel of the rectangular frame, a top hydraulic cylinder is also provided on the top of the rectangular frame, and a test piece is provided in the center of the rectangular frame; the gantry frame includes side frames located on both sides and a bottom frame located at the bottom, the bottom frame is connected to the base by bolts, and also includes a top frame and a fixing plate located at the lower part of the top frame and parallel to the top frame, the top hydraulic cylinder is fixed on the fixing plate; a drop hammer system is also provided on the top of the center of the test piece, the drop hammer system includes a sleeve arranged at the top of the center of the test piece, a drop hammer located at the top of the sleeve, the sleeve can be slidably fixed on the sleeve support frame, The casing support frame is fixed on the top frame, and the casing is connected to the casing support frame through a clamp ring; lateral pressure plates are respectively provided around the specimen, a top pressure plate is provided on the top of the specimen, and a plurality of detachable pads are provided at the bottom of the specimen, and an elastic base is respectively provided on both sides of the pad, and the lateral pressure plates are both located on the elastic base, and the lateral pressure plates and the top pressure plates are consistent in size with the specimen, and the centers of the lateral pressure plates and the top pressure plates are both provided with grooves, and the size of the grooves matches the end of the plunger; strain bricks and pressure sensors are buried inside the specimen, and also include an acoustic emission device; the strain bricks, the acoustic emission device and the pressure sensor are connected to the ultra-dynamic strain collector to collect signals, and the specimens are connected by applying coupling agent; the specimen is plate-shaped, and the specimen is at least one layer.

2. The dynamic impact test device under the loaded combined coal-rock state according to claim 1, characterized in that: A hollow side hydraulic cylinder mounting hole is provided in the center of each supporting side plate. The side hydraulic cylinder is fixedly connected to the supporting side plate by bolts. When the plunger of the hydraulic cylinder is extended, it can contact the side pressure plate of the test piece.

3. The dynamic impact test device under the loaded combined coal-rock state according to claim 2, characterized in that: The top hydraulic cylinder is a double hydraulic cylinder, and the drop hammer system is located at the center of the double hydraulic cylinder.

4. The testing method of the dynamic impact testing device under the loaded combined coal-rock state according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Prepare the required pressing plate and test piece, ensure that the six surfaces of the test piece are smooth and flat, and let them stand to dry for later use; (2) In single-layer thick specimens, strain bricks and pressure sensors are buried in a layered step-like manner. In multi-layer thin specimens, strain bricks and pressure sensors are buried at intervals under the test state and connected to signal receivers; (3) Coupling agent is applied to the contact surface between the multi-layer specimen thin plates, and the manufactured multi-layer composite thin plate coal rock mass is placed in the experimental device. The back of the bottom thin plate is supported by a steel plate, which can be regarded as a rigid foundation. Then the top is fixed and the pressure plate is lowered. The top fixed pressure plate part is the loading area; (4) Wrap the artificial leather or rubber pads on both sides of the upper left, right, front and back pressing plates, and wrap the artificial leather on the upper surface of the upper pressing plate. Load the confining pressure and axial pressure. Pressurize according to the required pressurization strength. Display the reading on the parameter table. Stop pressurization after the requirements are met. Wait for two minutes and observe whether the test piece has any abnormality under the pressurized environment. (5) According to the test requirements, drop the hammer to impact and test the parameters, and finally perform the calculation.

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