Inclined coal seam small coal pillar dilatation behavior test system and method considering goaf gangue accumulation influence

Abstract

The invention relates to an inclined coal seam small coal pillar dilatation behavior test system and method taking goaf gangue accumulation influence into consideration, and the system comprises a fixed frame, a sliding frame, an axial pressure loading oil cylinder, a pressure-bearing column, a trapezoidal pressure head, a displacement limiting device, a controller and a monitoring device, an axial pressure loading oil cylinder is arranged at the top of the sliding frame, a pressure-bearing column is arranged at the bottom of the axial pressure loading oil cylinder, a trapezoidal pressure head is arranged at the bottom of the pressure-bearing column, a displacement limiting device is arranged in the sliding frame on the lower side of the trapezoidal pressure head, a monitoring device is arranged on the peripheral side of the displacement limiting device, and the monitoring device is connected with a controller through a data collector. Different rotation angles of the gob-side entry driving lateral top plate are simulated by replacing different trapezoidal pressure heads, continuous gradient load application can be realized in the axial direction, the gradient load effect of rotation sinking of the gob-side entry driving lateral top plate on the coal pillar is truly simulated, and the test operation is simple.

Description

Technical Field

[0001] The invention relates to a small coal pillar expansion behavior test system and method for an inclined coal seam taking into account the influence of gangue accumulation in a goaf area, belonging to the technical field of small coal pillar expansion deformation test in a goaf-side tunneling of an inclined coal seam in a coal mine. Background Art

[0002] Mining without coal pillars or with small coal pillars has the advantages of reducing resource waste and improving resource recovery rate. With the promotion of green mining theory, it has been widely used in my country. Gob-side roadway driving is a common method in small coal pillar mining technology. It refers to the roadway driven along the edge of the gob of the previous longwall working face to the next working face. A 4-8m small coal pillar is often left between the new roadway and the gob to isolate the gob. For inclined coal seams, affected by the inclination of the coal seam, the small coal pillars in the gob-side roadway driving will be squeezed by the gangue accumulation in the gob, resulting in a significant difference in their deformation and damage compared with horizontal or near-horizontal coal seams. In addition, in the process of gob-side roadway driving, the coal pillars are more severely deformed by the gradient load generated by the rotation and sinking of the lateral roof and the displacement constraint in the length direction of the coal pillars, and often break and expand, and even squeeze into the roadway as a whole. Therefore, accurately grasping the expansion and deformation behavior of small coal pillars in gob-side roadway driving in inclined coal seams under real stress environment is of great significance for guiding the stability control of coal pillars in engineering sites.

[0003] In the prior art, Chinese patent document CN115184584A discloses a two-dimensional physical simulation test device and method with adjustable size and angle, and Chinese patent document CN104237462A discloses a steeply inclined coal seam gangue filling test device and test method, both of which can be used to simulate the goaf-side tunneling of inclined coal seams. However, the above methods do not consider the influence of the gangue accumulation degree after the goaf collapse on the coal pillar of the goaf-side tunneling, nor can they realize the gradient load effect caused by the lateral roof rotation and sinking above the small coal pillar and the displacement constraint in the length direction of the coal pillar, which is of little significance for guiding the stability control of the coal pillar under actual engineering conditions.

[0004] Chinese patent document CN111208010A discloses a method for simulating the rotation and breaking of roof strata. This method uses a roof strata rotation and breaking loading device to load the sample, effectively restoring the effect of lateral roof rotation on small coal pillars along goaf. However, this method does not consider the displacement constraint of the coal pillar in the length direction and the influence of the coal seam inclination and the accumulation of gangue in the goaf area. Moreover, the roof strata rotation and breaking loading device in this method can only simulate the rotation of the lateral roof of goaf, while in actual engineering, the rotation and sinking of the lateral roof exist at the same time, which is inconsistent with the actual engineering and cannot accurately obtain the mechanical characteristics of the small coal pillar. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a test system for the expansion behavior of small coal pillars in inclined coal seams taking into account the influence of gangue accumulation in goaf areas. By replacing different trapezoidal pressure heads, different rotation angles of the lateral roof along the goaf are simulated, and continuous gradient load application can be achieved in the axial direction. The gradient load effect on the coal pillar caused by the rotation and sinking of the lateral roof along the goaf is truly simulated, and the test operation is simple.

[0006] The present invention also provides a test method for the above-mentioned test system for the expansion behavior of small coal pillars in inclined coal seams taking into account the influence of gangue accumulation in the goaf area.

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

[0008] A small coal pillar expansion behavior test system for an inclined coal seam taking into account the influence of gangue accumulation in goaf areas comprises a fixed frame, a sliding frame, an axial pressure loading cylinder, a pressure column, a trapezoidal pressure head, a displacement limiting device, a controller and a monitoring device, wherein a sliding frame is arranged in the fixed frame, an axial pressure loading cylinder is arranged on the top of the sliding frame, a pressure column is arranged at the bottom of the axial pressure loading cylinder, a trapezoidal pressure head is arranged at the bottom of the pressure column, a displacement limiting device is arranged in the sliding frame on the lower side of the trapezoidal pressure head, a monitoring device is arranged around the displacement limiting device, and the monitoring device is connected to the controller via a data collector.

[0009] Preferably, according to the present invention, the fixed frame includes a base, a lower cross beam, an upper cross beam and a column. An arc-shaped slide groove is fixedly arranged in the middle of the base, lower cross beams are fixedly arranged on both sides of the base, and an upper cross beam is arranged on the upper side of the lower cross beam through the support of the column. The sliding frame is clamped by two pairs of lower cross beams and upper cross beams.

[0010] Preferably, according to the present invention, the sliding frame includes a rigid circular frame, a fixed beam, a fixed column, a rigid rod and a motor. The rigid circular frame is provided with a fixed beam and a fixed column in a rectangular shape. A rigid rod is provided between the fixed column and the rigid circular frame. A displacement limiting device is provided on the fixed beam. The lower beam and the upper beam are provided with arc grooves corresponding to the positions of the rigid circular frame. The two sides of the rigid circular frame are respectively provided in the arc grooves so that the rigid circular frame can slide between two pairs of lower beams and upper beams. The side of the rigid circular frame is provided with meshing teeth, which are connected to the output shaft of the motor through gears. During the test, the inclination angle of the rigid circular frame does not need to be too large. Therefore, only partial meshing teeth are provided on the side of the rigid circular frame to meet the rotation requirements, and will not affect the bottom rotation of the rigid circular frame.

[0011] Preferably according to the present invention, the displacement limiting device includes an acrylic vertical plate and an acrylic cover plate, two acrylic vertical plates are vertically arranged in parallel on the fixed crossbeam at the bottom of the sliding frame by installing bolts, and an acrylic cover plate is horizontally arranged between the two acrylic vertical plates.

[0012] Preferably according to the present invention, the monitoring device includes a stress sensor, a displacement sensor, an angle sensor, a full-section infrared laser scanning device, a wireless signal receiving device and a high-speed camera; a stress sensor and a displacement sensor are arranged on the axial pressure loading cylinder, an angle sensor is arranged in the rigid circular ring frame, a full-section infrared laser scanning device is arranged on the fixed column on one side of the displacement limiting device, the full-section infrared laser scanning device is wirelessly connected to the wireless signal receiving device, a high-speed camera is arranged on the outside of the fixed frame, and the stress sensor, displacement sensor, angle sensor, high-speed camera and wireless signal receiving device are all connected to a data collector.

[0013] Preferably, according to the present invention, at least two trapezoidal pressure heads are provided, and the inclination angle of the bottom of the trapezoidal pressure heads is associated with the rotation angle θ of the top plate rock beam 26, and the number and the inclination angle are set according to demand.

[0014] The test method of the test system for the expansion behavior of small coal pillars in inclined coal seams considering the influence of gangue accumulation in the goaf mentioned above has the following steps:

[0015] (1) Prepare a rectangular coal sample to simulate a small coal pillar in a gob-side tunnel in an inclined coal seam, and spray the coal sample with speckle;

[0016] (2) Place the coal sample in the displacement limiting device, select a trapezoidal pressure head, tighten the top of the trapezoidal pressure head to the pressure column by fixing bolts, and adjust the position of the coal sample so that it is directly below the trapezoidal pressure head;

[0017] (3) Arrange monitoring devices and connect them to data collectors;

[0018] (4) applying initial axial pressure to the coal sample through the axial pressure loading cylinder to fix the position of the coal sample;

[0019] (5) Place simulated gangue fragments on one side of the coal sample to simulate the gangue in the goaf, and insert the acrylic cover between the two acrylic vertical plates. Keep the bottom of the acrylic cover at the same horizontal line as the top of the coal sample;

[0020] (6) adjusting the rotation angle of the rigid circular frame through the controller to simulate the angle of the inclined coal seam;

[0021] (7) applying a gradient load to the coal sample through an axial pressure loading cylinder until the coal sample undergoes expansion failure;

[0022] (8) The angle sensor monitors the rotation angle of the rigid ring frame, the stress sensor and displacement sensor monitor the axial stress and strain during the loading process of the coal sample, the full-section infrared laser scanning device monitors the full-section deformation of the coal sample on the side without gangue accumulation, and the high-speed camera records the changes in the speckle displacement field and the expansion and destruction process of the coal sample.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention simulates different rotation angles of the lateral roof along the goaf by replacing different trapezoidal pressure heads, and can realize continuous gradient load application in the axial direction, truly simulating the gradient load effect on the coal pillar caused by the rotation and sinking of the lateral roof along the goaf, and the test operation is simple.

[0025] 2. The present invention realizes the displacement constraint of coal samples in the front-to-back direction by means of high-strength transparent acrylic plates, truly restores the displacement constraint of small coal pillars in the length direction along the goaf, and can observe the expansion and destruction process of coal pillars in real time, with strong engineering applicability.

[0026] 3. The present invention truly restores the coal seam inclination through a rotatable rigid circular frame, and takes into account the influence of gangue accumulation in the goaf area on the deformation and destruction of small coal pillars along the goaf, truly restores the gangue distribution pattern in the goaf area of ​​the inclined coal seam, and the test process is clear.

[0027] 4. The present invention can restore the real stress environment of small coal pillars in inclined coal seams along goafs to a certain extent, and truly reproduce the expansion and deformation process of small coal pillars in inclined coal seams along goafs in the laboratory. It can also accurately monitor the stress, deformation and destruction process in the expansion process, and can provide more accurate experimental data support for guiding the stability control of small coal pillars in inclined coal seams. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 For the structural intention of the present invention;

[0029] Figure 2 It is a schematic diagram of the rigid circular frame structure of the present invention;

[0030] Figure 3 It is a schematic diagram of the structure of the trapezoidal pressure head of the present invention;

[0031] Figure 4 It is a structural diagram of the displacement limiting device of the present invention;

[0032] Figure 5 This is a diagram of the simulated gangue fragment filling structure of the present invention;

[0033] Figure 6 It is a principle diagram of the test method for the expansion behavior of small coal pillars in inclined coal seams of the present invention;

[0034] Figure 7 It is a schematic diagram of the base structure of the present invention;

[0035] Figure 8 This is the axial stress-volume strain curve of the coal sample obtained in the embodiment of the present invention.

[0036] In the figure:

[0037] 1—upper beam, 2—upright column, 3—base, 4—motor, 5—rigid circular frame, 6—lower beam, 7—slide, 8—axial pressure loading cylinder, 9—pressure-bearing column, 10—trapezoidal pressure head, 11—coal sample, 12—acrylic vertical plate, 13—mounting bolts, 14—acrylic cover plate, 15—controller, 16—full-section infrared laser scanning device, 17—wireless signal receiving device, 18—high-speed camera, 19—data collector, 20—fixed beam, 21—fixed column, 22—rigid rod, 23—fixing bolts, 24—simulated gangue fragments, 25—small coal pillar, 26—roof rock beam, 27—goaf gangue. DETAILED DESCRIPTION

[0038] The present invention will be further described below by way of embodiments in conjunction with the accompanying drawings, but is not limited thereto.

[0039] Embodiment 1:

[0040] like Figure 1-7 As shown, this embodiment provides a small coal pillar expansion behavior test system for inclined coal seams taking into account the influence of gangue accumulation in goaf areas, including a fixed frame, a sliding frame, an axial pressure loading cylinder 8, a pressure column 9, a trapezoidal pressure head 10, a displacement limiting device, a controller 15 and a monitoring device, wherein a sliding frame is arranged in the fixed frame, an axial pressure loading cylinder 8 is arranged on the top of the sliding frame, a pressure column 9 is arranged at the bottom of the axial pressure loading cylinder 8, a trapezoidal pressure head 10 is arranged at the bottom of the pressure column 9, a displacement limiting device is arranged in the sliding frame on the lower side of the trapezoidal pressure head 10, a monitoring device is arranged around the displacement limiting device, and the monitoring device is connected to the controller 15 through a data acquisition device 19.

[0041] The fixed frame includes a base 3, a lower crossbeam 6, an upper crossbeam 1 and a column 2. An arc-shaped slide groove 7 is fixedly arranged in the middle of the base 3, and lower crossbeams 6 are fixedly arranged on both sides of the base 3. An upper crossbeam 1 is arranged on the upper side of the lower crossbeam 6 through the support of the column 2, and the sliding frame is clamped by two pairs of lower crossbeams and upper crossbeams.

[0042] The sliding frame includes a rigid circular frame 5, a fixed beam 20, a fixed column 21, a rigid rod 22 and a motor 4. The rigid circular frame 5 is provided with a fixed beam 20 and a fixed column 21 in a rectangular shape. A rigid rod 22 is provided between the fixed column 21 and the rigid circular frame 5. A displacement limiting device is provided on the fixed beam 20. The lower beam 6 and the upper beam 1 are provided with arc grooves corresponding to the positions of the rigid circular frame 5. The two sides of the rigid circular frame 5 are respectively provided in the arc grooves so that the rigid circular frame can slide between two pairs of lower beams and upper beams. The side of the rigid circular frame 5 is provided with meshing teeth, which are connected to the motor output shaft through gears. During the test, the inclination angle of the rigid circular frame does not need to be too large. Therefore, only part of the meshing teeth are provided on the side of the rigid circular frame to meet the rotation requirements, and will not affect the bottom rotation of the rigid circular frame.

[0043] The displacement limiting device includes an acrylic vertical plate 12 and an acrylic cover plate 14 . Two acrylic vertical plates 12 are vertically arranged in parallel on the fixed crossbeam 20 at the bottom of the sliding frame through mounting bolts 13 , and an acrylic cover plate 14 is horizontally arranged between the two acrylic vertical plates 12 .

[0044] The monitoring device includes a stress sensor, a displacement sensor, an angle sensor, a full-section infrared laser scanning device 16, a wireless signal receiving device 17 and a high-speed camera 18. The axial pressure loading cylinder 8 is provided with a stress sensor and a displacement sensor, the rigid circular frame 5 is provided with an angle sensor, the fixed column on one side of the displacement limiting device is provided with a full-section infrared laser scanning device 16, the full-section infrared laser scanning device 16 is wirelessly connected to the wireless signal receiving device 17, a high-speed camera 18 is provided on the outside of the fixed frame, and the stress sensor, displacement sensor, angle sensor, high-speed camera and wireless signal receiving device are all connected with a data collector.

[0045] The test method of the test system for the expansion behavior of small coal pillars in inclined coal seams considering the influence of gangue accumulation in the goaf is as follows:

[0046] (1) A rectangular coal sample 11 with a length × width × height = 50 mm × 50 mm × 100 mm is prepared to simulate a small coal pillar 25 in a gob-side tunnel of an inclined coal seam, and a speckle pattern is sprayed on the coal sample 11;

[0047] (2) Place the coal sample 11 in the displacement limiting device, select the trapezoidal pressure head 10, and tighten the top of the trapezoidal pressure head to the pressure column 9 by means of the fixing bolts 23. The selection of the trapezoidal pressure head 10 is related to the rotation angle θ of the roof rock beam 26 above the small coal pillar 25 in the inclined coal seam. At the same time, adjust the position of the coal sample 11 so that it is located directly below the trapezoidal pressure head 10;

[0048] (3) Arrange monitoring devices and connect them to data collector 19;

[0049] (4) applying initial axial pressure to the coal sample 11 through the axial pressure loading cylinder to fix the position of the coal sample 11;

[0050] (5) Place simulated gangue fragments 24 on one side of the coal sample 11 to simulate goaf gangue 27, and insert the acrylic cover plate 14 between two transparent acrylic vertical plates 12. The bottom of the acrylic cover plate 14 is kept at the same horizontal line as the top of the coal sample 11 or slightly lower than the top of the coal sample 11 to prevent the simulated gangue fragments 24 from falling from the top during the rotation of the rigid ring frame 5;

[0051] (6) adjusting the rotation angle of the rigid circular frame 5 through the controller 15 to simulate the inclined coal seam angle α;

[0052] (7) applying a gradient load to the coal sample 11 through an axial pressure loading cylinder until the coal sample 11 undergoes expansion failure;

[0053] (8) The angle sensor monitors the rotation angle of the rigid ring frame 5, the stress sensor and the displacement sensor monitor the axial stress and strain of the coal sample 11 during the loading process, the full-section infrared laser scanning device 16 monitors the full-section deformation of the coal sample 11 on the side without gangue accumulation, and the high-speed camera 18 records the changes in the speckle displacement field and the expansion and destruction process of the coal sample 11.

[0054] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A test system for the expansion behavior of small coal pillars in inclined coal seams considering the influence of gangue accumulation in goaf areas, characterized in that: It includes a fixed frame, a sliding frame, an axial pressure loading cylinder, a pressure column, a trapezoidal pressure head, a displacement limiting device, a controller and a monitoring device, wherein a sliding frame is arranged in the fixed frame, an axial pressure loading cylinder is arranged on the top of the sliding frame, a pressure column is arranged at the bottom of the axial pressure loading cylinder, a trapezoidal pressure head is arranged at the bottom of the pressure column, a displacement limiting device is arranged in the sliding frame on the lower side of the trapezoidal pressure head, a monitoring device is arranged around the displacement limiting device, and the monitoring device is connected to the controller through a data acquisition device.

2. The small coal pillar expansion behavior test system for inclined coal seams considering the influence of goaf gangue accumulation as claimed in claim 1, characterized in that: The fixed frame includes a base, a lower crossbeam, an upper crossbeam and a column. An arc-shaped slide groove is fixedly arranged in the middle of the base, lower crossbeams are fixedly arranged on both sides of the base, and an upper crossbeam is arranged on the upper side of the lower crossbeam through the support of the column.

3. The small coal pillar expansion behavior test system for inclined coal seams considering the influence of goaf gangue accumulation as claimed in claim 2, characterized in that: The sliding frame includes a rigid circular frame, a fixed beam, a fixed column, a rigid rod and a motor. The rigid circular frame is provided with a fixed beam and a fixed column in a rectangular shape. A rigid rod is provided between the fixed column and the rigid circular frame. A displacement limiting device is provided on the fixed beam. The lower beam and the upper beam are provided with arc grooves at positions corresponding to the rigid circular frame. Both sides of the rigid circular frame are respectively provided in the arc grooves. Gears are provided on the sides of the rigid circular frame, and the gears are connected to the motor output shaft through gears.

4. The small coal pillar expansion behavior test system for inclined coal seams considering the influence of gangue accumulation in goaf as claimed in claim 3, characterized in that: The displacement limiting device comprises an acrylic vertical plate and an acrylic cover plate. Two acrylic vertical plates are vertically arranged in parallel on the fixed crossbeam at the bottom of the sliding frame, and an acrylic cover plate is horizontally arranged between the two acrylic vertical plates.

5. The small coal pillar expansion behavior test system for inclined coal seams considering the influence of gangue accumulation in goaf as claimed in claim 4, characterized in that: The monitoring device includes stress sensors, displacement sensors, angle sensors, full-section infrared laser scanning devices, wireless signal receiving devices and high-speed cameras. Stress sensors and displacement sensors are arranged on the axial pressure loading cylinder, an angle sensor is arranged in the rigid circular ring frame, a full-section infrared laser scanning device is arranged on the fixed column on one side of the displacement limiting device, the full-section infrared laser scanning device is wirelessly connected to the wireless signal receiving device, a high-speed camera is arranged on the outside of the fixed frame, and the stress sensor, displacement sensor, angle sensor, high-speed camera and wireless signal receiving device are all connected to a data collector.

6. The small coal pillar expansion behavior test system for inclined coal seams considering the influence of gangue accumulation in goaf as claimed in claim 5, characterized in that: At least two trapezoidal pressure heads are provided.

7. The test method of the test system for the expansion behavior of small coal pillars in inclined coal seams considering the influence of gangue accumulation in goaf as claimed in claim 6, characterized in that: Here are the steps: (1) Prepare a rectangular coal sample to simulate a small coal pillar in a gob-side tunnel in an inclined coal seam, and spray the coal sample with speckle; (2) Place the coal sample in the displacement limiting device, select a trapezoidal pressure head, tighten the top of the trapezoidal pressure head to the pressure column by fixing bolts, and adjust the position of the coal sample so that it is directly below the trapezoidal pressure head; (3) Arrange monitoring devices and connect them to data collectors; (4) applying initial axial pressure to the coal sample through the axial pressure loading cylinder to fix the position of the coal sample; (5) Place simulated gangue fragments on one side of the coal sample to simulate the gangue in the goaf, and insert the acrylic cover between the two acrylic vertical plates. Keep the bottom of the acrylic cover at the same horizontal line as the top of the coal sample; (6) adjusting the rotation angle of the rigid circular frame through the controller to simulate the angle of the inclined coal seam; (7) applying a gradient load to the coal sample through an axial pressure loading cylinder until the coal sample undergoes expansion failure; (8) The angle sensor monitors the rotation angle of the rigid ring frame, the stress sensor and displacement sensor monitor the axial stress and strain during the loading process of the coal sample, the full-section infrared laser scanning device monitors the full-section deformation of the coal sample on the side without gangue accumulation, and the high-speed camera records the changes in the speckle displacement field and the expansion and destruction process of the coal sample.

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