A coal body drilling deformation-crack evolution whole process testing device and evaluation method

Abstract

The present invention provides a testing device and evaluation method for the whole process of coal borehole deformation and crack evolution, which relates to the field of coal borehole deformation testing. The testing device mainly includes a loading mechanism and a monitoring mechanism; the loading mechanism includes an outer frame, a pressure plate, a loading cylinder, a pad and a coal specimen; the monitoring mechanism includes an industrial camera, an acoustic emission detector and an information acquisition unit; the information acquisition unit is used to monitor and obtain the internal state information of the borehole, which can use a micro camera or a borehole deformation monitoring sensor. This testing device uses a pressure plate made of high-strength transparent material to achieve visual observation of the pressure surface under three-dimensional stress loading, which is convenient for intuitively or using a monitoring device to monitor the deformation of the borehole and the micro-fracture information of the nearby coal body; for borehole state monitoring, a borehole deformation monitoring sensor or a micro camera can be selected, which provides a diversified method for full-process monitoring, and the monitoring information is more comprehensive, realizing the whole process test of the borehole from deformation to closure.

Description

Technical Field

[0001] The invention relates to the field of coal body borehole deformation testing, and in particular to a coal body borehole deformation-crack evolution whole process testing device and evaluation method. Background Art

[0002] Rock burst is a typical mining dynamic phenomenon, which can release a large amount of elastic deformation energy accumulated in coal and rock mass in a sharp and violent form, causing coal and rock mass destruction and strong vibration. The power throws the broken coal and rock into the mining space of the shaft and tunnel, making a strong noise, causing equipment damage, shaft and tunnel damage, and casualties. In the prevention and control of rock burst, large-diameter drilling pressure relief is one of the main means, with the characteristics of low construction difficulty and obvious pressure relief effect, so this technology is widely used.

[0003] Large-diameter borehole pressure relief is to reduce the stress concentration of the coal body in the nearby area or change the mechanical properties of the coal body in the nearby area by constructing large-diameter boreholes, so as to eliminate or reduce the risk of deformation and damage of the surrounding rock of the tunnel. The pressure relief effect of the borehole is closely related to the deformation of the borehole and the range of coal body rupture around the borehole. With the deformation, shrinkage and collapse of the borehole, the cracks in the coal body around the borehole continue to expand, and the pressure relief effect gradually comes into play. Therefore, monitoring the deformation of the borehole and the surrounding coal body is helpful to study the pressure relief effect of the borehole and effectively guide the design of pressure relief parameters.

[0004] However, at present, the research on the pressure relief effect of coal bodies with boreholes mainly focuses on the overall mechanical properties and impact tendency of the coal bodies, and pays little attention to the deformation process of the boreholes themselves. At present, there is a lack of effective borehole deformation monitoring and quantitative evaluation methods. Therefore, the present invention proposes a coal body borehole deformation-crack evolution whole process testing device and evaluation method. Summary of the invention

[0005] The purpose of the present invention is to provide a coal body borehole deformation-crack evolution whole process testing device and evaluation method, which can monitor the deformation of the borehole and the micro-fracture information of the nearby coal body while loading the coal body specimen containing the borehole.

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

[0007] A coal body drilling deformation-crack evolution whole process testing device, comprising a loading mechanism and a monitoring mechanism; the loading mechanism comprises an outer frame, a pressure plate, a loading cylinder, a cushion block and a coal body specimen; the pressure plate is fixedly arranged at one end of the outer frame, and a through hole is opened at the center of the pressure plate; the coal body specimen is arranged between the outer frame and the pressure plate; a drill hole is opened at the position of the coal body specimen corresponding to the through hole, and the coal body specimen is in contact with the cushion block except for one side connected to the pressure plate and the opposite side, and the loading cylinder is arranged on the cushion block; the cushion block is opened with a hole;

[0008] The monitoring mechanism includes an industrial camera, an acoustic emission detector and an information collection unit; the industrial camera is placed in front of the pressure plate and opposite to the through hole; the acoustic emission detector is placed in the hole opened in the pad and arranged on the surface of the coal specimen; the information collection unit is used to monitor and obtain drilling status information.

[0009] Preferably, the information acquisition unit is configured as a micro camera, and the micro camera is disposed in a through hole formed in the pressure plate.

[0010] Preferably, the information collection unit is configured as a borehole deformation monitoring sensor; the borehole deformation monitoring sensor comprises a water bag, a catheter and a flow monitor; the water bag is placed inside the borehole of the coal specimen, and the flow monitor is connected to the water bag via a catheter.

[0011] Preferably, the outer frame includes a first support plate, a second support plate and multiple groups of support rods; the first support plate and the second support plate are arranged in parallel, and the four corner positions of the first support plate are correspondingly connected to the four corner positions of the second support plate through support rods; the first support plate is arranged at one end of the support rod, and the second support plate is arranged at the middle position of the support rod; the pressure plate is fixedly arranged at the other end of the support rod, and the coal body specimen is arranged between the pressure plate and the second support plate.

[0012] Preferably, the holes are arranged along the diagonal lines of the pad.

[0013] Preferably, the pressure plate is made of high-strength transparent material.

[0014] An evaluation method for a coal body borehole deformation-crack evolution whole process testing device, using the above-mentioned coal body borehole deformation-crack evolution whole process testing device, comprises the following steps:

[0015] Step 1: Select coals of various strengths as test samples, make a plurality of cubic coal specimens, drill holes in the middle of the coal specimens in advance to obtain coal specimens with holes, and make artificial speckle fields on the surfaces of the coal specimens where the holes are located;

[0016] Step 2: Install the coal specimen, place a cushion block between the coal specimen and the loading cylinder, place the acoustic emission detector in the hole opened in the cushion block, and arrange the acoustic emission detector on the surface of the coal specimen;

[0017] Step 3: Arrange an industrial camera in front of the transparent pressure plate and facing the through hole of the pressure plate;

[0018] Step 4: For drilling status monitoring, use method 1 or method 2 for comprehensive analysis:

[0019] Method 1: a micro camera is arranged in the through hole opened in the front end pressure plate of the drilling hole to photograph the shape of the inner hole wall of the drilling hole;

[0020] Method 2: Place the water bag of the borehole deformation monitoring sensor in the borehole, connect the flow monitor to the water bag through a catheter, and monitor and obtain the overall deformation-closing process information of the borehole;

[0021] Step 5, for the coal body loading scheme: the horizontal stress σ2 of the coal body specimen is equal to σ3, which remains unchanged during the loading process, and multiple groups of stress values ​​are designed in sequence. The vertical stress σ1 of the specimen is loaded by displacement control, and the loading speed is set. During the test, σ1, σ2, and σ3 are loaded synchronously to the horizontal stress design value, σ2 and σ3 remain unchanged, and σ1 is continuously loaded;

[0022] Step 6: Turn on the micro camera or the borehole deformation monitoring sensor to collect data, load through the loading cylinder, and continue to load 2mm after the borehole is closed, then stop the test;

[0023] Step 7: Based on the monitoring data, conduct quantitative analysis on the cracking and deformation of the coal body around the borehole:

[0024] Overall rupture degree:

[0025]

[0026] in, is the cumulative number of rings at a certain time i, n AE It is the cumulative number of ringings of acoustic emission after the test;

[0027] Crack Extension Index:

[0028]

[0029] Among them, a, b, c, d are weight coefficients, is the number of acoustic emission events within different radii from the center of the borehole;

[0030] Drilling closure:

[0031]

[0032] Among them, A i is the drilling area at a certain time i, A 初 is the drilling area at the initial moment;

[0033] or

[0034]

[0035] Among them, V i is the cumulative water discharge at a certain time i, V 总 is the total amount of water in the water bag.

[0036] The beneficial technical effects of the present invention are:

[0037] The present invention relates to a testing device and an evaluation method for the whole process of coal borehole deformation-crack evolution. By adopting a pressure plate made of high-strength transparent material, visual observation of a pressure surface containing a hole under three-dimensional stress loading is achieved, which is convenient for intuitively monitoring the deformation of the borehole and micro-fracture information of the nearby coal body or using a monitoring device; by monitoring the borehole state, a borehole deformation monitoring sensor or a micro camera can be selected to provide a diversified method for whole-process monitoring, the monitoring information is more comprehensive, and the whole process test from deformation to closure of the borehole is achieved; by quantitatively characterizing the borehole deformation, quantitative evaluation of the borehole deformation is achieved from multiple angles such as overall rupture, expansion of cracks around the hole, and shrinkage deformation of the borehole itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a three-dimensional schematic diagram of a testing device in an embodiment of the present invention;

[0039] Figure 2 It is a three-dimensional schematic diagram of the inner and outer frames in an embodiment of the present invention;

[0040] Figure 3 It is a schematic diagram of the assembly of a coal specimen, a cushion block, an acoustic emission detector, and a loading cylinder in an embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of the structure of a coal body specimen and an acoustic emission detector in an embodiment of the present invention;

[0042] Figure 5 Schematic diagram of the structure of a drilling deformation monitoring sensor in an embodiment of the present invention;

[0043] Figure 6 It is a schematic diagram of the assembly of a coal specimen and a borehole deformation monitoring sensor in an embodiment of the present invention;

[0044] Figure 7 It is a cross-sectional view of a coal body specimen, a micro camera, and a pressure plate in an embodiment of the present invention;

[0045] Figure 8 This is the stress loading path of the coal body with a borehole in the embodiment of the present invention;

[0046] Among them, 1-loading mechanism: 11-outer frame, 111-first support plate, 112-second support plate, 113-support rod;

[0047] 12-loading cylinder; 13-pressure plate, 131-through hole; 14-pad; 15-coal specimen, 151-drilling hole;

[0048] 2- Monitoring mechanism: 21- Industrial camera, 22- Acoustic emission detector, 23- Mini camera;

[0049] 24-borehole deformation monitoring sensor, 241-water bag, 242-catheter, 243-flow monitor. DETAILED DESCRIPTION

[0050] 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.

[0051] 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.

[0052] The present invention relates to a coal body drilling deformation-crack evolution whole process testing device, comprising a loading mechanism 1 and a monitoring mechanism 2. Figures 1 to 4 As shown, the loading mechanism 1 includes structural components such as an outer frame 11, a loading cylinder 12, a pressure plate 13, a cushion block 14 and a coal specimen 15.

[0053] like Figure 2As shown, the outer frame 11 includes a first support plate 111, a second support plate 112, and a plurality of support rods 113. The first support plate 111 and the second support plate 112 are arranged in parallel, and the four corners of the first support plate 111 are connected to the four corners of the second support plate 112 through the support rods 113. The first support plate 111 is arranged at one end of the support rod 113, and the second support plate 112 is arranged at the middle position of the support rod 113. Figure 1 As shown, a pressure plate 13 is fixedly arranged at the other end of the support rod 113, a through hole 131 is opened at the center of the pressure plate 13, and the pressure plate 13 is made of a high-strength transparent material. The pressure plate 13 is used to limit the displacement of the coal specimen 15 and facilitate the use of an industrial camera 21 to take a speckle picture. The coal specimen 15 is arranged between the pressure plate 13 and the second support plate 112. By adopting the pressure plate 13 made of a high-strength transparent material, the visual observation of the pressure surface containing the hole under the three-dimensional stress loading is realized, which is convenient for intuitively or using a monitoring device to monitor the deformation of the borehole and the micro-fracture information of the nearby coal body.

[0054] like Figure 3 As shown, a bore hole 151 is provided at the position of the coal specimen 15 corresponding to the through hole 131. Except for one side connected to the pressure plate 13 and the opposite side, the coal specimen 15 is in contact with the connecting pad 14. The pad 14 is provided with a loading cylinder 12. The position of the loading cylinder 12 is adjusted to adapt to the loading test of coal specimens 15 of different sizes, and the coal specimen 15 is loaded by controlling the loading cylinder 12. Figure 4 As shown, holes for installing the acoustic emission detector 22 are provided on the cushion block 14 , and the holes are arranged along the diagonal lines of the cushion block 14 .

[0055] like Figure 4 As shown, the monitoring mechanism 2 includes structural components such as an industrial camera 21, an acoustic emission detector 22, and an information collection unit. The industrial camera 21 is placed in front of the pressure plate 13, opposite to the through hole 131 opened at the center of the pressure plate 13. An artificial speckle field is made on the side of the coal specimen 15 connected to the pressure plate 13, and the industrial camera 21 is used to take speckle pictures of the entire test process. The deformation field of the surface of the coal specimen 15 is obtained by using the digital speckle correlation method (DIC), and the data such as the shape and surface area of ​​the borehole 151 are obtained by using the digital image processing technology (DIP). The acoustic emission detector 22 is placed in the hole opened in the pad 14 and arranged on the surface of the coal specimen 15. The micro-fracture information of the coal body near the borehole 151 is monitored by using the acoustic emission detector 22.

[0056] The information acquisition unit can be used to monitor and obtain status information of the borehole 151 .

[0057] like Figure 7As shown, the information collection unit is configured as a micro camera 23 , which is disposed in a through hole 131 formed in the pressure plate 13 , and the micro camera 23 can capture the shape of the inner wall of the drill hole 151 .

[0058] like Figure 5 and Figure 6 As shown, the information collection unit can also use a borehole deformation monitoring sensor 24. The borehole deformation monitoring sensor 24 includes a water bag 241, a catheter 242, and a flow monitor 243. The water bag 241 is placed inside the borehole 151 opened by the coal body specimen 15, and the flow monitor 243 is connected to the water bag 241 through the catheter 242. The borehole deformation monitoring sensor 24 is used to monitor and obtain the overall deformation-closing process information of the borehole 151.

[0059] By monitoring the state of the borehole 151, the device can choose to use the borehole deformation monitoring sensor 24 or the micro camera 23, providing a diversified method for full-process monitoring, with more comprehensive monitoring information, and realizing the full-process test of the borehole 151 from deformation to closure.

[0060] refer to Figures 1 to 8 As shown, an evaluation method for a coal body drilling deformation-crack evolution whole process testing device, using the above-mentioned coal body drilling deformation-crack evolution whole process testing device, includes the following steps:

[0061] Step 1, select 3-4 kinds of coal strength as test samples, make a plurality of cubic coal specimens 15 with a size of 100×100×100 mm, drill holes 151 with apertures of 8, 10, 12, 14, and 16 mm in the middle of the coal specimen 15 in advance, obtain the coal specimen 15 containing the drill holes 151, and make an artificial speckle field on one side of the coal specimen 15 connected to the pressure plate 13;

[0062] Step 2, installing the coal sample 15, placing a cushion block 14 between the coal sample 15 and the loading cylinder 12, placing the acoustic emission detector 22 in the hole opened in the cushion block 14, and arranging the acoustic emission detector 22 on the surface of the coal sample 15;

[0063] Step 3, arranging an industrial camera 21 in front of the transparent pressure plate 13 and facing the through hole 131 of the pressure plate 13;

[0064] Step 4: For drilling status monitoring, use method 1 or method 2 for comprehensive analysis:

[0065] Method 1: a micro camera 23 is arranged in the through hole 131 opened by the pressure plate 13 at the front end of the bore hole 151 to photograph the shape of the inner hole wall of the bore hole 151;

[0066] Method 2: The water bag 241 of the borehole deformation monitoring sensor 24 is placed in the borehole, and the flow monitor 243 is connected to the water bag 241 through the catheter 242 to monitor and obtain the deformation-closing process information of the entire borehole 151;

[0067] Step 5: For the coal body loading scheme: the horizontal stress of the specimen σ2 = σ3, which remains unchanged during the loading process, and the stress values ​​are designed to be 50%, 80%, 100%, 120% and 150%σ c , the vertical stress σ1 of the specimen was loaded by displacement control, and the loading speed was set to 0.01, 0.02, 0.04, 0.06, 0.08 and 0.1 mm / min. During the test, after σ1, σ2, and σ3 were loaded synchronously to the horizontal stress design value, σ2 and σ3 remained unchanged, and σ1 continued to be loaded;

[0068] Step 6: Turn on the micro camera 23 or the borehole deformation monitoring sensor 24 to collect data, and load through the loading cylinder 12 until the borehole 151 is closed and continue to load 2 mm, then stop the test;

[0069] Step 7: Based on the monitoring data, conduct a quantitative analysis of the cracking and deformation of the coal body around borehole 151:

[0070] Overall rupture degree:

[0071]

[0072] in, is the cumulative number of rings at a certain time i, n AE It is the cumulative number of ringings of acoustic emission after the test;

[0073] Crack Extension Index:

[0074]

[0075] Among them, a, b, c, d are weight coefficients, is the number of acoustic emission events within different radii from the center of the borehole 151;

[0076] Drilling closure:

[0077]

[0078] Among them, A i is the drilling area at a certain time i, A 初 is the drilling area at the initial moment;

[0079] or

[0080]

[0081] Among them, V iis the cumulative water discharge at a certain time i, V 总 is the total amount of water in the water bag 241.

[0082] So far, the present embodiment has been described in detail with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the coal body borehole deformation-crack evolution whole process testing device and evaluation method of the present invention. By quantitatively characterizing the borehole deformation, quantitative evaluation of the borehole deformation is achieved from multiple angles such as overall rupture, expansion of cracks around the hole, and shrinkage deformation of the borehole itself.

[0083] 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 body drilling deformation-crack evolution whole process testing device, characterized in that: It includes loading mechanism and monitoring mechanism; The loading mechanism comprises an outer frame, a pressure plate, a loading cylinder, a cushion block and a coal specimen; The outer frame includes a first support plate, a second support plate and a plurality of support rods; The first support plate and the second support plate are arranged in parallel, and the four corners of the first support plate are correspondingly connected to the four corners of the second support plate through support rods; the first support plate is arranged at one end of the support rod, and the second support plate is arranged at the middle position of the support rod; the pressure plate is fixedly arranged at the other end of the support rod, and the coal specimen is arranged between the pressure plate and the second support plate; A through hole is provided at the center of the pressure plate, a drill hole is provided at the position of the coal specimen corresponding to the through hole, and the coal specimen is in contact with the cushion block except for one side connected to the pressure plate and the opposite side, and the loading cylinder is provided on the cushion block; holes are provided on the cushion block, and the holes are arranged along the diagonal of the cushion block; The monitoring mechanism includes an industrial camera, an acoustic emission detector and an information collection unit; The industrial camera is placed in front of the pressure plate and opposite to the through hole; the acoustic emission detector is placed in the hole opened by the cushion block and arranged on the surface of the coal specimen; the information acquisition unit is used to monitor and obtain drilling status information, and the information acquisition unit is set as a drilling deformation monitoring sensor; The borehole deformation monitoring sensor comprises a water bag, a catheter and a flow monitor; the water bag is placed inside the borehole of the coal body specimen, and the flow monitor is connected to the water bag through the catheter.

2. A coal body drilling deformation-crack evolution whole process testing device according to claim 1, characterized in that: The pressure bearing plate is made of high-strength transparent material.

3. An evaluation method for a coal body drilling deformation-crack evolution whole process testing device, using the coal body drilling deformation-crack evolution whole process testing device as claimed in any one of claims 1 to 2, characterized in that: The steps include: Step 1: Select coals of various strengths as test samples, make a plurality of cubic coal specimens, drill holes in the middle of the coal specimens in advance to obtain coal specimens with holes, and make artificial speckle fields on the surfaces of the coal specimens where the holes are located; Step 2: Install the coal specimen, place a cushion block between the coal specimen and the loading cylinder, place the acoustic emission detector in the hole opened in the cushion block, and arrange the acoustic emission detector on the surface of the coal specimen; Step 3: Arrange an industrial camera in front of the transparent pressure plate and facing the through hole of the pressure plate; Step 4: For drilling status monitoring, a comprehensive analysis is performed in the following manner: The water bag of the borehole deformation monitoring sensor is placed in the borehole, and the flow monitor is connected to the water bag through a catheter to monitor and obtain the overall deformation-closing process information of the borehole; Step 5, for the coal body loading scheme: the horizontal stress σ2 of the coal body specimen is equal to σ3, which remains unchanged during the loading process, and multiple groups of stress values ​​are designed in sequence. The vertical stress σ1 of the specimen is loaded by displacement control, and the loading speed is set. During the test, σ1, σ2, and σ3 are loaded synchronously to the horizontal stress design value, σ2 and σ3 remain unchanged, and σ1 is continuously loaded; Step 6: Turn on the borehole deformation monitoring sensor to collect data, load through the loading cylinder, and continue to load 2mm after the borehole is closed, then stop the test; Step 7: Based on the monitoring data, conduct quantitative analysis on the cracking and deformation of the coal body around the borehole: Overall rupture degree: in, is the cumulative number of rings at a certain time i, n AE It is the cumulative number of ringings of acoustic emission after the test; Crack Extension Index: Among them, a, b, c, d are weight coefficients, is the number of acoustic emission events within different radii from the center of the borehole; Drilling closure: Among them, A i is the drilling area at a certain time i, A 初 is the drilling area at the initial moment; or Among them, V i is the cumulative water discharge at a certain time i, V 总 is the total amount of water in the water bag.

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