CN109538209B - Method for weakening hard roof of coal seam based on electric pulse technology - Google Patents
Method for weakening hard roof of coal seam based on electric pulse technology Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 25
- 230000003313 weakening effect Effects 0.000 title claims abstract description 20
- 238000000034 method Methods 0.000 title claims abstract description 19
- 238000005516 engineering process Methods 0.000 title claims abstract description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 44
- 238000007599 discharging Methods 0.000 claims abstract description 20
- 238000005336 cracking Methods 0.000 claims abstract description 3
- 239000003990 capacitor Substances 0.000 claims description 29
- 238000004146 energy storage Methods 0.000 claims description 29
- 230000001681 protective effect Effects 0.000 claims description 17
- 238000002347 injection Methods 0.000 claims description 9
- 239000007924 injection Substances 0.000 claims description 9
- 238000007789 sealing Methods 0.000 claims description 5
- 239000011435 rock Substances 0.000 abstract description 7
- 230000035939 shock Effects 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 6
- 239000000243 solution Substances 0.000 description 4
- 238000010276 construction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000005553 drilling Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21C—MINING OR QUARRYING
- E21C41/00—Methods of underground or surface mining; Layouts therefor
- E21C41/16—Methods of underground mining; Layouts therefor
- E21C41/18—Methods of underground mining; Layouts therefor for brown or hard coal
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Abstract
A method for weakening a hard roof of a coal seam based on an electric pulse technology is characterized in that a discharge electrode instantaneously discharges in water in a cracking drill hole to form a rapid and strong shock wave, so that water around the discharge electrode generates a 'water hammer' effect and a 'water wedge' effect to impact roof rocks, and the roof is repeatedly impacted by discharging for multiple times to generate accumulated damage, so that the roof of the coal seam is weakened, the effective collapse of the roof is realized, and the problem of increase of a coming pressure step distance caused by large area of the roof left in a goaf can be effectively solved; the method for weakening the hard roof of the coal bed based on the electric pulse technology converts the electric energy of the high-voltage electric pulse into the shock wave to break the rock stratum, and has the advantages of simple operation, high efficiency, cleanness, low cost and wide application range.
Description
Technical Field
The invention relates to a roof weakening method in coal mining, in particular to a method for weakening a hard roof of a coal bed based on an electric pulse technology.
Background
With the continuous forward propulsion of the working face, the area of the top plate in the goaf is increased, and the energy accumulated by the working face is increased under the action of the gravity of the overlying strata, so that the difficulty of supporting the working face is inevitably increased if the overlying strata of the goaf cannot be effectively collapsed. In addition, if the top plate of the goaf does not collapse in any sign, strong shock waves are certainly caused in the roadway, equipment in the roadway is damaged, and even the safety of workers in the roadway is threatened. In addition, the purposeful collapse can also reduce the sudden settlement of the earth surface and avoid causing unnecessary damage. High-pressure hydraulic fracturing is the most common artificial caving method at present, but the method has certain limitation, most of rocks in a goaf have cracks, so that the sealing requirement in a high-pressure state is difficult to meet; in addition, high-pressure hydraulic fracturing needs to consume a large amount of water resources, so that resource waste is easily caused; because the hardness of the rock is high, the hydraulic fracturing effect is not ideal, and the rock stratum is difficult to achieve the expected weakening effect. Therefore, aiming at the problems of large reserved area of the top plate of the goaf and difficult roof caving, a method for weakening the hard top plate of the coal bed, which is simple to operate, efficient to clean and low in cost, is urgently needed to be developed.
Disclosure of Invention
The invention aims to provide a method for weakening a hard roof of a coal seam, which is simple to operate, efficient to clean and low in cost, so as to overcome the defect of the existing high-pressure hydraulic fracturing in roof weakening.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for weakening a hard roof of a coal seam based on an electric pulse technology comprises the following steps:
s1: when the coal seam is mined, constructing fracturing drill holes from the gaps of the hydraulic support to the top plate;
s2: fixing a discharge electrode at the front end of a high-voltage cable protective tube, wherein one end of a high-voltage cable is connected with the discharge electrode, the other end of the high-voltage cable penetrates through the high-voltage cable protective tube and then is connected with a high-voltage energy storage capacitor, the high-voltage energy storage capacitor is connected with a high-voltage charging power supply, and the discharge electrode is sent into the deep part of a fracturing drill hole through the high-voltage cable protective tube; sending the water injection pipe into a cracking drill hole, then sealing the hole of a hole packer, and then installing a high-voltage discharge switch on a high-voltage cable between the hole packer and a high-voltage energy storage capacitor;
s3: injecting water into the fracturing drill hole through a water injection pipe until the fracturing drill hole is filled with water;
s4: and charging the energy storage capacitor through the high-voltage charging power supply, closing the high-voltage discharging switch to discharge the discharging electrode when the voltage of the energy storage capacitor reaches a preset value, and then disconnecting the high-voltage discharging switch.
As a further improved technical solution of the present invention, step S5 is further included after step S4: and repeating the step S4 to discharge the high-voltage electrode for 20-150 times.
As a further improved technical solution of the present invention, step S6 is further included after step S5: and moving the discharge electrode to the fracturing drill hole for 1-2m through the high-voltage cable protective pipe, and repeating the steps S4 and S5.
As a further improved technical solution of the present invention, step S7 is further included after step S6: and repeating the step S6 until the discharge electrode is 1-2m away from the hole packer.
As a further improved technical solution of the present invention, step S8 is further included after step S7: and selecting a new fracturing drill hole, and repeating the steps S2-S7.
As a further improved technical scheme of the invention, the rated output voltage of the high-voltage charging power supply is 50-600kV, the frequency is 2-15Hz, and the number of pulses is 150-700.
As a further improved technical scheme of the invention, the capacitance of the high-voltage energy storage capacitor is 5-30 muF.
As a further improved technical scheme of the invention, the fracturing drill holes are arranged in two rows, and the distance between two adjacent fracturing drill holes in the same row is 3-10 m; the first row of fracturing drill holes are perpendicular to the top plate, the second row of fracturing drill holes and the first row of fracturing drill holes form an included angle of 45 degrees, and the second row of fracturing drill holes are inclined to the goaf.
Compared with the prior art, the invention has the beneficial effects that: according to the method for weakening the hard roof of the coal bed based on the electric pulse technology, the discharge electrode is instantaneously discharged in water in a fracturing drill hole to form rapid and strong shock waves, so that water around the discharge electrode generates 'water hammer' and 'water wedge' effects to impact roof rocks, and the roof is repeatedly impacted through multiple discharges to generate accumulated damage, so that the roof of the coal bed is weakened, the roof is effectively collapsed, and the problem of increase of periodic pressure step distance caused by large area of the roof left in a goaf can be effectively solved; the method for weakening the hard roof of the coal bed based on the electric pulse technology converts the electric energy of the high-voltage electric pulse into the shock wave to break the rock stratum, and has the advantages of simple operation, high efficiency, cleanness, low cost and wide application range.
Drawings
Fig. 1 is a schematic installation diagram of a discharging device in a method for weakening a hard roof of a coal seam based on an electric pulse technology in embodiments 1 and 2 of the invention;
FIG. 2 is a plan view of the fracturing bore hole layout in examples 1 and 2 of the present invention;
FIG. 3 is a schematic diagram of the fracturing borehole placement in examples 1 and 2 of the present invention;
in FIGS. 1-3 above: the method comprises the following steps of 1-a high-voltage charging power supply, 2-a high-voltage energy storage capacitor, 3-a high-voltage discharge switch, 4-a discharge electrode, 5-a water tank, 6-a water pump, 7-a stop valve, 8-a hole packer, 9-a water injection pipe, 10-a fracturing drill hole, 11-a top plate, 12-a hydraulic support, 13-a first fracturing drill hole, 14-a second fracturing drill hole, 15-a high-voltage cable protective pipe, A-an air inlet tunnel, B-an air return tunnel, C-a goaf, D-a working face and E-a coal bed.
The specific implementation mode is as follows:
the invention is further described below with reference to the accompanying drawings.
Example 1
As shown in fig. 1, 2 and 3, a method for weakening a hard roof of a coal seam based on an electric pulse technology comprises the following steps:
a. when a coal seam E is mined, two rows of fracturing drill holes 10 with the diameter of 10cm are constructed towards a top plate 11 in a conventional drilling mode at the gap between two hydraulic supports 12, and the distance between two adjacent fracturing drill holes in the same row is 3 m; the first row of fracturing drill holes 13 are perpendicular to the top plate, the included angle between the second row of fracturing drill holes 14 and the first row of fracturing drill holes 13 is 45 degrees, and the second row of fracturing drill holes 14 are inclined to the goaf C.
b. After the construction of the fracturing drill hole 10 is completed, a discharging device is installed,
fixing a discharge electrode 4 at the front end of a high-voltage cable protective tube 15, wherein one end of a high-voltage cable is connected with the discharge electrode 4, the other end of the high-voltage cable penetrates through the high-voltage cable protective tube 15 and then is connected with a high-voltage energy storage capacitor 2, and the high-voltage energy storage capacitor 2 is connected with a high-voltage charging power supply 1, wherein the rated output voltage of the high-voltage charging power supply 1 is 50kV, and the frequency is 2 Hz; the capacitance of the high-voltage energy storage capacitor 2 is 5 muF, and the number of pulses is 150;
the discharge electrode 4 is sent to the deep part of the fracturing drill hole 10 through a high-voltage cable protective pipe 15 at the hydraulic support 12; then the water injection pipe 9 is sent into a fracturing drill hole 10, then a hole packer 8 is used for sealing the hole, and then a high-voltage discharge switch is arranged on a high-voltage cable between the hole packer and the high-voltage energy storage capacitor;
c. opening a stop valve 7, injecting water in a water tank 5 into a fracturing drill hole 10 by using a water pump 6, wherein the water injection pressure is 0.2MPa, and closing the stop valve 7 after the water is filled;
d. the high-voltage charging power supply 1 is started to charge the high-voltage energy storage capacitor 2, when the voltage reaches 40Kv, the high-voltage discharging switch 3 is closed to discharge the electric energy stored in the high-voltage energy storage capacitor 2 in water through the discharging electrode 4, and the discharging electrode 4 generates strong shock waves in the water at the moment of discharging, so that water around the discharging electrode generates 'water hammer' and 'water wedge' effects to impact the top plate 11, the top plate 11 generates cracks, and the strength is weakened; the high-voltage charging power supply 1 is started again to charge the high-voltage energy storage capacitor 2, when the voltage reaches 80kV, the high-voltage discharge switch 3 is closed again to discharge the electric energy stored in the high-voltage energy storage capacitor 2 in the water through the discharge electrode 4, and the discharge is stopped after the discharge is repeated for 20 times;
e. disconnecting the high-voltage discharge switch 3, and retreating the discharge electrode 4 by 2m from the inside of the drill hole 10 through the high-voltage cable protective tube 15;
f. repeating the steps d and e until the distance between the discharge electrode 4 and the hole packer 8 is 2m, and stopping the operation;
g. and (e) selecting a new fracturing drill hole 10, and repeating the steps b-f until the roof weakening operation is completed in all fracturing drill holes 10.
Repeating steps a-g for each 5m advance of the coal seam E along the working surface D.
Example 2
1, 2 and 3, a method for weakening the hard roof of a coal seam based on an electric pulse technology comprises the following steps:
a. when a coal seam E is mined, two rows of fracturing drill holes 10 with the diameter of 10cm are constructed towards a top plate 11 in a conventional drilling mode at the gap between two hydraulic supports 12, and the distance between two adjacent fracturing drill holes in the same row is 10 m; the first row of fracturing drill holes 13 are perpendicular to the top plate, the included angle between the second row of fracturing drill holes 14 and the first row of fracturing drill holes 13 is 45 degrees, and the second row of fracturing drill holes 14 are inclined to the goaf C.
b. After the construction of the fracturing drill hole 10 is completed, a discharging device is installed,
fixing a discharge electrode 4 at the front end of a high-voltage cable protective tube 15, wherein one end of a high-voltage cable is connected with the discharge electrode 4, the other end of the high-voltage cable penetrates through the high-voltage cable protective tube 15 and then is connected with a high-voltage energy storage capacitor 2, and the high-voltage energy storage capacitor 2 is connected with a high-voltage charging power supply 1, wherein the rated output voltage of the high-voltage charging power supply 1 is 600kV, and the frequency is 15 Hz; the capacitance of the high-voltage energy storage capacitor 2 is 30 muF, and the number of pulses is 700;
the discharge electrode 4 is sent to the deep part of the fracturing drill hole 10 through a high-voltage cable protective pipe 15 at the hydraulic support 12; then the water injection pipe 9 is sent into a fracturing drill hole 10, then a hole packer 8 is used for sealing the hole, and then a high-voltage discharge switch is arranged on a high-voltage cable between the sealer and the high-voltage energy storage capacitor;
c. opening a stop valve 7, injecting water in a water tank 5 into a fracturing drill hole 10 by using a water pump 6, wherein the water injection pressure is 0.2MPa, and closing the stop valve 7 after the water is filled;
d. the high-voltage charging power supply 1 is started to charge the high-voltage energy storage capacitor 2, when the voltage reaches 80kV, the high-voltage discharging switch 3 is closed to discharge the electric energy stored in the high-voltage energy storage capacitor 2 in water through the discharging electrode 4, and the discharging electrode 4 generates strong shock waves in the water at the moment of discharging, so that water around the discharging electrode generates 'water hammer' and 'water wedge' effects to impact the top plate 11, the top plate 11 generates cracks, and the strength is weakened; the high-voltage charging power supply 1 is started again to charge the high-voltage energy storage capacitor 2, when the voltage reaches 80kV, the high-voltage discharge switch 3 is closed again to discharge the electric energy stored in the high-voltage energy storage capacitor 2 in the water through the discharge electrode 4, and the discharge is stopped after the discharge is repeated for 150 times;
e. disconnecting the high-voltage discharge switch 3, and retreating the discharge electrode 4 by 2m from the inside of the drill hole 10 through the high-voltage cable protective tube 15;
f. repeating the steps d and e until the distance between the discharge electrode 4 and the hole packer 8 is 2m, and stopping the operation;
g. and (e) selecting a new fracturing drill hole 10, and repeating the steps b-f until the roof weakening operation is completed in all fracturing drill holes 10.
Repeating steps a-g for each 8m advance of the coal seam E along the working surface D.
Claims (2)
1. A method for weakening a hard roof of a coal seam based on an electric pulse technology is characterized by comprising the following steps:
s1: when the coal seam is mined, constructing fracturing drill holes from the gaps of the hydraulic support to the top plate; the fracturing drill holes are arranged in two rows, the distance between every two adjacent fracturing drill holes in the same row is 3-10m, the first row of fracturing drill holes are perpendicular to the top plate, the included angle between the second row of fracturing drill holes and the first row of fracturing drill holes is 45 degrees, and the second row of fracturing drill holes are inclined to a goaf;
s2: fixing a discharge electrode at the front end of a high-voltage cable protective tube, wherein one end of a high-voltage cable is connected with the discharge electrode, the other end of the high-voltage cable penetrates through the high-voltage cable protective tube and then is connected with a high-voltage energy storage capacitor, the high-voltage energy storage capacitor is connected with a high-voltage charging power supply, and the discharge electrode is sent into the deep part of a fracturing drill hole through the high-voltage cable protective tube; sending the water injection pipe into a cracking drill hole, then sealing the hole of a hole packer, and then installing a high-voltage discharge switch on a high-voltage cable between the hole packer and a high-voltage energy storage capacitor;
s3: injecting water into the fracturing drill hole through a water injection pipe until the fracturing drill hole is filled with water;
s4: charging the energy storage capacitor through the high-voltage charging power supply, closing the high-voltage discharging switch to discharge the discharging electrode when the voltage of the energy storage capacitor reaches a preset value, and then disconnecting the high-voltage discharging switch; the rated output voltage of the high-voltage charging power supply is 50-600kV, the frequency is 2-15Hz, and the number of pulses is 150-700;
s5: repeating the step S4 to discharge the high voltage electrode for 20-150 times;
s6: moving the discharge electrode to the fracturing drill hole for 1-2m through the high-voltage cable protective pipe, and repeating the steps S4 and S5;
s7: repeating the step S6 until the distance between the discharge electrode and the hole packer is 1-2 m;
s8: and selecting a new fracturing drill hole, and repeating the steps S2-S7.
2. The method for weakening the hard roof of the coal seam based on the electric pulse technology is characterized in that the capacitance of the high-voltage energy storage capacitor is 5-30 mu F.
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| CN108397182B (en) * | 2018-04-27 | 2024-03-01 | 河南理工大学 | Device and method for enhancing permeability of coal seam through electric pulse and liquid nitrogen freeze thawing |
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