Experimental method and device for identifying risk of rock burst induced by dissimilatory overlying strata structure while drilling

Abstract

The invention discloses an experimental method and device for identifying the risk of rock burst induced by dissimilatory overlying strata structure while drilling, and the method comprises the steps: constructing a geologic model of non-uniform-thickness hard overlying strata, combining a drilling device and a coal cutting device which are controlled by a computer, and simulating an underground drilling and logging process and an overlying strata response process under different mining intensities; through stress, acoustic emission, digital speckles and the like, the stope mine ground pressure and the rock burst appearing intensity are judged; through tests of different key layer thicknesses, interlayer spacing and combination forms, while-drilling multi-source information of different overlying strata structures and a large amount of data corresponding to rock burst risk grades are economically, simply and conveniently obtained; the device comprises a model frame, a loading device, a drilling device and a coal cutting device, array small holes are formed in the bottom of the model frame, and a drill rod upwards drills from the bottom of the model through the small holes. According to the method, the field actual measurement cost can be remarkably reduced, and key data are provided for establishing a risk assessment technology for identifying the dissimilatory overburden rock structure induced rock burst while drilling.

Description

Technical Field

[0001] The present invention relates to a mine safety technology, in particular to a safety experiment method, and specifically to an experimental method and device for identifying the risk of rock burst induced by abnormal overlying rock structure during drilling. Background Art

[0002] The overlying rock structure of the roof, especially the hard and thick sandstone roof above the coal seam, is one of the main factors affecting the occurrence of rock burst. The main reason is that the hard and thick sandstone roof is prone to accumulating a large amount of elastic energy. During the breaking or sliding instability process of the hard roof, a large amount of elastic energy is suddenly released, forming a strong vibration, resulting in roof coal seam type (impact pressure type) rock burst or roof type (impact type) rock burst. The thicker the roof rock layer, the larger the weighting interval, and the more elastic energy is accumulated, the more likely it is to occur rock burst. The large-area hanging roof and breaking of the thick and hard old roof above the coal mining face will cause high stress concentration in the coal seam and roof, forming roof-coal impact and dynamic breaking of the roof rock layer, releasing a large amount of energy and causing serious consequences.

[0003] However, the overlying rock structure in coal mines is complex and variable, and is still considered a black box structure. The complexity and variability of the overlying rock structure make the strong mine tremors and rock burst disasters in coal mines extremely sudden, seriously threatening the safety production of coal mines. When drilling through different rock layers and their interfaces, the drilling torque, thrust, and drill pipe vibration are different, and the corresponding gamma, resistivity, and acoustic wave responses are also different. Therefore, the real-time identification of the overlying rock structure during drilling provides a new way to control strong mine tremors and rock burst disasters of hard roof type.

[0004] Revealing the correlation mechanism between the multi-source information during drilling and the characteristics of impact hazards is the key to establishing the technology for identifying the risk of rock burst induced by abnormal overlying rock structure during drilling. The engineering quantity of underground tests in coal mines is large, the cost is high, and the underground rock layer structure is complex, variable, and opaque. Laboratory tests are an important means to reveal this correlation mechanism. At present, there is a lack of relevant experimental methods and devices in the laboratory. The conventional similarity simulation test is for overlying rock with uniform thickness, and the method of building a model for each overlying rock structure is time-consuming and laborious. How to design the test device and method to simply and economically determine the corresponding relationship between the multi-source information during drilling and the risk of rock burst induced by different overlying rock structures is a difficult problem that needs to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to invent an experimental method and device for identifying the risk of rock burst induced by abnormal overlying rock structure during drilling to solve the problem that it is difficult to prevent due to the lack of experimental devices and methods to predict the overlying rock structure and impact risk in coal mines.

[0006] One of the technical solutions of the present invention is as follows:

[0007] An experimental method for identifying the risk of rock burst induced by abnormal overlying strata structure during drilling, characterized by the following steps:

[0008] 1) Refer to the coal mine borehole columnar diagram and the model similarity simulation theory to build a geological model of the overlying strata structure. The model is placed in the model frame 3. The model includes a floor 51, a coal seam 50, and multiple layers of roof overlying strata, where the thickness of the thick and hard key stratum 52 gradually increases. Use the top hydraulic actuator 1 and the lateral hydraulic actuator 4 to apply loads to the top and side of the model to simulate the application of in-situ stress. Transparent baffles are provided at the front and back of the model. A stress box 9 is installed at the bottom of the coal seam, and acoustic emission sensors 10 are installed at the four corners of the front and back of the model.

[0009] 2) The model floor is drilled upward from the bottom of the model using a horizontally movable drilling device. The drilling device is driven by a rotary motor 82 and a drilling rig guide rail 80 to move horizontally from one side of the model to the other side. After the first hole is constructed, the drilling device is moved, and after a certain distance, multiple holes are constructed in sequence. The position, drilling speed, rotation speed, and displacement are controlled by a computer program.

[0010] 3) Use sensors to monitor data such as drilling torque, thrust, and drill pipe vibration when drilling through different rock strata and their interfaces. After the hole is formed, gamma, resistivity, and acoustic wave sensor probes are inserted into the hole from shallow to deep to detect curve data such as gamma, resistivity, and acoustic wave velocity at the entire drilling depth.

[0011] 4) A coal cutting device that can move horizontally along the coal seam is installed on the side of the model. The coal cutting device is driven by a rotary motor 62 and a coal cutting guide rail 60 to move horizontally from one side of the model to the other side. Use the coal cutting device to start cutting coal from one side of the model to simulate underground coal seam mining. The coal cutting device includes a coal cutting guide rail 60, a horizontal movement driving member 62, and a rotary coal cutting member 61. The rotary coal cutting member 61 drives the cutter to complete coal cutting, and the horizontal movement and coal cutting are controlled by a computer.

[0012] 5) During the coal cutting process, record the overlying strata caving process through a camera, and obtain the displacement field of the digital speckle measurement of the obtained pictures. Record the sound through the acoustic emission probe 10, and measure the stress distribution in the stope by the pressure box 9. Judge the mine pressure and the intensity of rock burst manifestation in the stope through the suspended roof length, sound size, peak stope stress, and influence distance, etc. The intensity level is divided into three levels: no danger, yellow warning, and red warning.

[0013] 6) Build models with gradually decreasing thickness of the thick and hard key stratum 52, models with an increasing distance between the thick and hard key stratum 52 and the coal seam, and models with multiple thick and hard key strata 52 and 53. Build a non-uniform model according to the borehole columnar diagrams of multiple underground holes; repeat steps 1 to 5.

[0014] 7) In Step 5, when abnormal occurrences of mine pressure and intensity of rock burst appear at different drilling positions, analyze the changes in data curves such as drilling torque, thrust, and drill pipe vibration, as well as the spectral characteristics such as gamma, resistivity, and acoustic wave at this position, and study and establish the relationship between the characteristics of multi-parameter data curves of the borehole and the mine pressure and the intensity of rock burst:

[0015] R p = f(T, n, F, v, S v , Y1, Y2, Y3)

[0016] Where: R p is the intensity level, T is the drilling torque, n is the rotational speed, F is the thrust, v is the drilling speed, S v is the vibration velocity, Y1 is the natural gamma, Y2 is the resistivity, and Y3 is the acoustic wave velocity.

[0017] The second technical solution of the present invention is:

[0018] An experimental device for identifying the risk of rock burst induced by abnormal overlying rock structure during drilling, characterized in that: it includes a model frame, a loading device, a drilling device, and a coal cutting device; the top plate and the side surface of the model frame are respectively arranged with top hydraulic actuators (1) and lateral hydraulic actuators (4) in an array; the drilling device includes a drill rig guide rail 80, a rotary drive drilling member 81, a horizontal movement drive member 82, and a drill pipe 83, which are installed at the bottom of the model. There are fine grooves with arrayed small holes or openings at the bottom of the model frame, and the drill pipe drills upward from the bottom of the model through the small holes; the coal cutting device includes a coal cutting guide rail 60, a horizontal movement drive member 62, and a rotary coal cutting member 61; the drilling device is equipped with torque, thrust, vibration sensors, displacement, drilling speed, and rotational speed sensors.

[0019] The beneficial effects of the present invention are:

[0020] By constructing a geological model of non-uniform thick hard overburden, the present invention can highly reproduce the characteristics of complex overburden structures underground in coal mines and can adapt to the geological occurrence conditions of different mining areas; and by combining a drilling device and a coal cutting device controlled by a computer, it can accurately simulate the downhole borehole logging process and the overburden response process under different mining intensities; through stress, acoustic emission, digital speckle, etc., it can judge the abutment pressure in the stope and the intensity of rock burst manifestation. Through the drilling, mining simulation of a dissimilar overburden model and the observation of abutment pressure and impact intensity at different stages, a large amount of data on multi-source information while drilling and the corresponding rock burst risk levels of different overburden structures can be obtained economically and simply. Through experiments on different key layer thicknesses, layer spacings and combination forms, the multi-source information while drilling and the rock burst risk levels corresponding to complex overburden structures can be further obtained. The present invention can reproduce the evolution process of multi-source information while drilling and impact hazard characteristics at the laboratory scale, providing key data for establishing a risk assessment technology for identifying the risk of rock burst induced by dissimilar overburden structures while drilling. Thus, the on-site measurement cost can be significantly reduced, providing a low-cost and high-precision risk assessment solution for deep mines and high-risk rock burst mines. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of a model with the thickness of the thick hard key layer gradually increasing according to the present invention.

[0022] Figure 2 It is a schematic diagram of constructing boreholes at a certain distance.

[0023] Figure 3 It is a schematic diagram of a model with the thickness of the thick hard key layer gradually decreasing.

[0024] Figure 4 It is a schematic diagram of a model with the distance between the thick hard key layer and the coal seam increasing.

[0025] Figure 5 It is a schematic diagram of a model with multiple thick hard key layers.

[0026] Figure 6 It is a schematic diagram of a non-uniform model built according to the borehole histograms of multiple boreholes underground.

[0027] In the figure: 1 is the top hydraulic actuator, 2 is the vertical pressure plate, 3 is the model frame, 4 is the lateral hydraulic actuator, 51 is the bottom plate, 50 is the coal seam, 52 and 53 are the thick hard key layers, 60 is the coal cutting guide rail, 62 is the horizontal movement driving member, 61 is the rotary coal cutting member, 7 is the horizontal pressure plate, 80 is the drill guide rail, 81 is the rotary driving drilling member, 82 is the horizontal movement driving member 83 is the drill pipe, 9 is the stress box, and 10 is the acoustic emission sensor. Detailed Embodiment

[0028] The present invention will be further described below with reference to the drawings and embodiments.

[0029] As Figure 1-2 shown

[0030] An experimental method for identifying the risk of rock burst induced by abnormal overlying strata structure during drilling includes the following steps:

[0031] First, build an experimental device as Figure 1 shown. The entire experimental device consists of a model frame, a loading device, a drilling device, and a coal cutting device; the roof and sides of the model frame are loaded with an array of devices; the drilling device includes a drill rig guide rail 80, a rotary drive drilling component 81, a horizontal movement drive component 82, and a drill pipe 83, which are installed at the bottom of the model. There are small holes or fine grooves with openings arranged in an array at the bottom of the model frame. The drill pipe drills upward from the bottom of the model through the small holes; torque, thrust, vibration sensors, displacement, drilling speed, and rotation speed sensors are installed on the drilling device; the coal cutting device includes a coal cutting guide rail 60, a horizontal movement drive component 62, and a rotary coal cutting component 61.

[0032] Second, referring to the coal mine borehole columnar diagram and the model similarity simulation theory, build a geological model of the overlying strata structure with the gradually increasing thickness of the thick and hard key strata. The model is placed in the model frame 3. The model includes a floor 51, a coal seam 50, and multiple layers of roof overlying strata, among which the thickness of the thick and hard key strata 52 gradually increases; use the top hydraulic actuator 1 and the lateral hydraulic actuator 4 to apply loads to the top and sides of the model to simulate the application of in-situ stress. Transparent baffles are provided in the front and back of the model; a stress box 9 is installed at the bottom of the coal seam, and acoustic emission sensors 10 are installed at the four corners of the front and back of the model.

[0033] Third, use the horizontally movable drilling device at the bottom of the model to drill upward from the bottom of the model. Drive the drilling device to move horizontally from one side of the model to the other side through the rotary motor drive 82 and the drill rig guide rail 80. After the first hole is constructed, move the drilling device, leave a certain distance, and construct multiple holes in sequence; control the position, drilling speed, rotation speed, and displacement by a computer program, as Figure 2 shown

[0034] Fourth, use sensors to monitor data such as drilling torque, thrust, and drill pipe vibration when drilling through different rock layers and their interfaces; after the hole is formed, insert gamma, resistivity, and acoustic wave sensor probes into the hole from shallow to deep to detect curve data such as gamma, resistivity, and acoustic wave velocity at the entire drilling depth.

[0035] Fifth, a coal cutting device that can move horizontally along the coal seam is installed on the side of the model. Drive the coal cutting device to move horizontally from one side of the model to the other side through the rotary motor 62 and the coal cutting guide rail 60; use the coal cutting device to start cutting coal from one side of the model to simulate underground coal seam mining; the coal cutting device includes a coal cutting guide rail 60, a horizontal movement drive component 62, and a rotary coal cutting component 61. The rotary coal cutting component 61 drives the cutter to complete coal cutting, and the horizontal movement and coal cutting are controlled by a computer.

[0036] Sixth, during the coal cutting process, the caving process of overlying strata is recorded by a camera, and the obtained images are used to measure the displacement field through digital speckle; the sound is recorded by the acoustic emission probe 10, and the stress distribution in the stope is measured by the pressure cell 9; the abutment pressure in the stope and the intensity of rock burst manifestation are judged by the suspended roof length, sound volume, peak stope stress, and influence distance, etc.

[0037] 6) In step 5, when the abutment pressure and the intensity of rock burst manifestation are abnormal at different borehole positions, analyze the changes in the data curves of drilling torque, thrust, drill pipe vibration, etc. and the spectral characteristics of gamma, resistivity, acoustic wave, etc. at this position, and study and establish the relationship between the multi-parameter data curve characteristics of the borehole and the abutment pressure and the intensity of rock burst manifestation:

[0038] R p = f(T, n, F, v, S v , Y1, Y2, Y3)

[0039] Where: R p is the intensity level, T is the drilling torque, n is the rotational speed, F is the thrust, v is the drilling speed, S v is the vibration velocity, Y1 is the natural gamma, Y2 is the resistivity, and Y3 is the acoustic wave velocity.

[0040] Example two.

[0041] As Figure 2-3 shown.

[0042] The difference between this example and Example one is to build a model in which the thickness of the thick and hard key stratum 52 gradually decreases as Figure 3 shown. The rest is the same as Example one.

[0043] Example three.

[0044] As Figure 2 , 4 shown.

[0045] The difference between this example and Example one is to build a model in which the distance between the thick and hard key stratum 52 and the coal seam increases as Figure 4 shown.

[0046] Example four.

[0047] As Figure 5-6 shown.

[0048] The difference between this example and Example one is to build a model with multiple thick and hard key strata 52 and 53 as Figure 5 shown, and build a non-uniform model as Figure 6 shown according to the borehole histograms of multiple boreholes underground.

[0049] The parts not involved in the present invention are the same as or can be implemented by the prior art.

Claims

1. An experimental method for identifying the risk of rock burst induced by alienated overlying strata structure while drilling, characterized in that: Including the following steps: 1) Referring to the coal mine borehole columnar diagram and the model similarity simulation theory, a geological model of overlying strata structure is built. The model is placed in the model frame (3). The model includes a floor (51), a coal seam (50), and multiple layers of roof overlying strata, where the thickness of the thick and hard key stratum (52) gradually increases. The top hydraulic actuator (1) and the lateral hydraulic actuator (4) are used to apply loads to the top and side of the model to simulate the application of in-situ stress. Transparent baffles are provided at the front and back of the model. A stress box (9) is installed at the bottom of the coal seam, and acoustic emission sensors (10) are installed at the four corners of the front and back of the model. 2) The floor of the model is drilled upward from the bottom of the model by a horizontally movable drilling device. The drilling device is driven to move horizontally from one side of the model to the other side through the rotation motor drive (82) and the drill guide (80). After the first hole is constructed, the drilling device is moved, and after a certain distance, multiple holes are constructed in sequence. The position, drilling speed, rotation speed, and displacement are controlled by a computer program. 3) Sensors are used to monitor data such as drilling torque, thrust, and drill pipe vibration when drilling through different rock strata and their interfaces. After the hole is formed, gamma, resistivity, and acoustic wave sensor probes are inserted into the hole from shallow to deep to detect curve data such as gamma, resistivity, and acoustic wave velocity at the entire drilling depth. 4) A coal cutting device that can move horizontally along the coal seam is installed on the side of the model. The coal cutting device is driven to move horizontally from one side of the model to the other side through the rotation motor (62) and the coal cutting guide (60). The coal cutting device is used to cut coal starting from one side of the model to simulate underground coal seam mining. The coal cutting device includes a coal cutting guide (60), a horizontal movement drive member (62), and a rotary coal cutting member (61). The rotary coal cutting member (61) drives the cutter to complete coal cutting, and the horizontal movement and coal cutting are controlled by a computer. 5) During the coal cutting process, the caving process of the overlying strata is recorded by a camera, and the obtained pictures are used to measure the displacement field by digital speckle. The sound is recorded by the acoustic emission probe (10), and the stress distribution in the stope is measured by the pressure box (9). The in-situ pressure and the intensity of rock burst in the stope are judged by the suspended roof length, the sound volume, the peak in-situ stress, and the influence distance, etc. The intensity levels are divided into three levels: no danger, yellow warning, and red warning. 6) Models with gradually decreasing thickness of the thick and hard key stratum (52), models with an increasing distance between the thick and hard key stratum (52) and the coal seam, and models with multiple thick and hard key strata (52, 53) are built respectively. A non-uniform model is built according to the borehole columnar diagrams of multiple underground boreholes. Steps 1 to 5 are repeated. 7) In step 5, when the in-situ pressure and the intensity of rock burst in different borehole positions show anomalies, analyze the changes in the data curve characteristics such as drilling torque, thrust, and drill pipe vibration and the spectral characteristics of gamma, resistivity, and acoustic wave at this position, and establish the relationship between the multi-parameter data curve characteristics of the borehole and the in-situ pressure and the intensity level of rock burst. R p = f(T, n, F, v, S v , Y1, Y2, Y3) Where: R p is the intensity level, T is the drilling torque, n is the rotational speed, F is the thrust, v is the drilling speed, S v is the vibration velocity, Y1 is the natural gamma, Y2 is the resistivity, Y3 is the acoustic velocity.

2. An experimental device for identifying the risk of rock burst induced by abnormal overlying strata structure while drilling, characterized in that: It includes a model frame, a loading device, a drilling device, and a coal cutting device; the top hydraulic actuators (1) and lateral hydraulic actuators (4) are respectively arranged in an array on the top plate and the side surface of the model frame; the drilling device includes a drill rig guide rail (80), a rotary drive drilling member (81), a horizontal movement drive member (82), and a drill pipe (83), which are installed at the bottom of the model; at the bottom of the model frame, there are fine grooves with arrayed small holes or openings, and the drill pipe drills upward from the bottom of the model through the small holes; the coal cutting device includes a coal cutting guide rail (60), a horizontal movement drive member (62), and a rotary coal cutting member (61); the drilling device is equipped with torque, thrust, vibration sensors, displacement, drilling speed, and rotational speed sensors.

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