CN110273684B - Method for reducing composite strong mine pressure of thick hard top plate and left coal pillar in plasma U-type manner - Google Patents
Method for reducing composite strong mine pressure of thick hard top plate and left coal pillar in plasma U-type manner Download PDFInfo
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Abstract
The invention discloses a method for reducing composite strong mine pressure of a thick hard roof and a left coal pillar by a plasma U-type, which fully utilizes the characteristic that strong motion among ions instantly generates high temperature and high pressure to drill a U-type well on the ground, wherein the number of the U-type well is L/d, L is the length of a working surface of an underlying coal seam, d is the well drilling distance, the U-type well is divided into a U-type well drilling left vertical section, a U-type well drilling horizontal section and a U-type well drilling right vertical section, a left vertical section and a right vertical section respectively penetrate through two left coal pillars in a residual mining area to reach the thick hard roof of the underlying coal seam, and the horizontal section is parallel to the pushing direction of the working surface in the thick hard roof of the underlying coal seam. The coal mining device has the advantages that the coal mining device is dual-purpose in one well and operates in two directions, pre-splitting is carried out on a thick hard top plate and a residual mining area left coal pillar of a lower coal seam, shock waves are formed to enable the thick hard top plate and the residual mining area left coal pillar to generate cracks and expand, and the purpose of reducing the composite strong mine pressure of the thick hard top plate and the residual mining area left coal pillar is achieved, so that green mining and safe production of a coal mine are achieved.
Description
Technical Field
The invention relates to a method for reducing composite strong mine pressure of a thick hard top plate and a left coal pillar in a plasma U-type mode, and belongs to the technical field of coal mining.
Background
Most of the coal mines in China use a downward mining method, namely, an overlying coal seam is mined firstly and an underlying coal seam is mined secondly. When the underlying coal seam is mined, the coal mining work is influenced by the composite strong mine pressure through the thick and hard top plates between the layers and the residual coal pillar groups in the overlying mining areas.
The composite strong mine pressure mainly comes from: (a) thick hard roof board: due to natural geological conditions, the underlying coal seams of a plurality of mining areas have thick and hard top plates with large thickness, high strength, no development of joint cracks and good integrity; (b) and (3) remaining coal pillars in the residual mining area: the coal mining process of China is relatively lagged behind in the initial stage of establishment of new China, and partial coal pillars are reserved for supporting overlying strata so as to ensure the stability of surrounding rocks and the safe production of a working face; in the modern highly mechanized mining process, the reservation of part of coal pillars is inevitable due to the limitation of construction and other mining conditions; when the pillar system coal mining method is adopted, part of coal pillars can be left without mining. This results in a large amount of coal pillars left behind in the residual zone after the coal seam has been mined.
When the underlying coal bed influenced by the composite strong mine pressure of the thick hard top plate and the residual coal pillars in the mining area is mined, the mine pressure of a working face is strongly shown, the side of the working face is serious, the roof of a goaf is severely collapsed and is accompanied with loud sound, the pressure of a bracket of the working face is obviously increased, the bracket is pressed, the single prop of a roadway is damaged, the initial period/pressure step distance of the thick hard top plate of the mining area is increased, a large amount of energy is accumulated, and when the thick hard top plate of the mining area suddenly strides, the accumulated energy is released instantly, so that the severe impact dynamic disaster is caused, the equipment is damaged, the personnel are injured and killed, and the safety production of a mine is seriously damaged.
The composite strong mine pressure caused by the thick and hard top plate and the residual mining area left coal pillars is difficult to predict and prevent, and the current control method for the composite strong mine pressure of the working face of the underlying coal seam influenced by the thick and hard top plate and the residual mining area left coal pillars comprises the following steps: a. and (3) a passive control method: (1) the mining direction and the arrangement direction of the working face of the underlying coal seam are adjusted, so that a concentrated stress influence area of a residual coal pillar in a residual mining area is avoided, but the working face is still influenced by the pressure of a thick hard top plate, and the problem is not solved fundamentally; (2) the support of the working face of the underlying coal seam is strengthened, but when the mine pressure of the working face is strong, the safe production is difficult to ensure by the technical measure of simply strengthening the support, and the support cost is high; (3) larger coal pillars are reserved on the working surface of the underlying coal bed influenced by the thick hard top plate and the coal pillars left in the residual mining area, but great waste of coal resources is caused; b. an active control method comprises the following steps: (1) blasting in thick and hard top plates and residual coal pillars in a residual mining area, but the construction work amount is large, the controllability is poor, and especially for high-gas mines, gas explosion is easy to cause, and potential safety hazards exist; (2) the method has the advantages that the thick and hard top plate and the residual coal pillars are fractured by adopting hydraulic pressure, a large amount of water resources are consumed, and chemical reagents in high-pressure fracturing fluid in the fracturing process easily pollute the underground environment. As can be seen from the above control method of composite strong mine pressure, the passive control method has poor effect and does not really solve the problem; the construction sites of the active control method are mostly on the working face or in the roadway, coal mining work is affected, thick and hard top plates and residual mining area remaining coal pillars need to be cracked respectively, and the steps are complex. Therefore, a method for reducing the composite strong mine pressure of thick and hard top plates and residual coal pillars in the mining areas with high efficiency, easy control and good effect is needed to be found to ensure the safe production of the working face.
The plasma state is an aggregation state different from solid, liquid and gas states, when some liquid is excited by external energy to generate liquid-phase plasma, the characteristics of high temperature and high pressure instantly generated by strong motion among ions are utilized to form shock waves to enable a rock body to generate cracks and expand. At present, the method is widely applied to oil and gas drilling and exploitation, metal cutting and directional rock breaking. However, the technology of plasma abatement of composite strong mine pressure has little application in the technical field of coal mining (especially in the aspect of plasma ground 'U' abatement of composite strong mine pressure of thick and hard roof and residual coal pillars in a residual mining area).
Disclosure of Invention
The invention aims to provide a method for reducing the composite strong mine pressure of thick and hard top plates and residual coal pillars in a plasma ground in a U-shaped manner, which has the advantages of high efficiency, easy control, good effect, strong flexibility, no dust and no noise and can avoid the disadvantages and the defects of the method. If the coal seam is mined through the residual coal pillar group and the thick hard top plate between the layers of the upper covering residual mining area, two stable coal pillars exist in the residual coal pillar group in the residual mining area, and when the coal pillars are left at intervals of 40-200 meters, U-shaped drilling can be selected for use, two-way operation is carried out from the ground, and the purpose of reducing the composite strong mine pressure of the thick hard top plate and the residual coal pillars is achieved.
The invention fully utilizes the characteristic that strong motion among ions instantly generates high temperature and high pressure to drill a U-shaped well on the ground, wherein the number of the U-shaped wells is L/d, L is the length of the working surface of the underlying coal seam, d is the well drilling distance, the U-shaped well is divided into a left vertical section of the U-shaped well, a horizontal section of the U-shaped well and a right vertical section of the U-shaped well, the left vertical section and the right vertical section respectively penetrate through two residual mining area residual coal pillars to reach the thick hard top plate of the underlying coal seam, and the horizontal section is parallel to the propelling direction of the working surface in the thick hard top plate of the underlying coal seam. The coal mining device has the advantages that the coal mining device is dual-purpose in one well and operates in two directions, pre-splitting is carried out on a thick hard top plate and a residual mining area left coal pillar of a lower coal seam, shock waves are formed to enable the thick hard top plate and the residual mining area left coal pillar to generate cracks and expand, and the purpose of reducing the composite strong mine pressure of the thick hard top plate and the residual mining area left coal pillar is achieved, so that green mining and safe production of a coal mine are achieved.
The invention provides a method for reducing composite strong mine pressure of a thick hard top plate and a left coal pillar in a plasma U-type manner, which specifically comprises the following steps:
the first step is as follows: the plasma pulse controller, the plasma generator, the electrode stabilizing device and the liquid phase discharge plasma electrode are connected through a high-voltage cable; the plasma pulse controller is connected with the data acquisition instrument through a lead; the data acquisition instrument, the signal amplifier and the detection probe are connected through a signal transmission line; the water storage tank, the high-pressure pump, the cooler and the plasma generator are connected through a dual-purpose water pipe to form a complete loop, and the plasma generator cools a control valve to control a switch; the high-pressure pump, the pressure gauge and the high-pressure water nozzle are connected through a dual-purpose water pipe, and the high-pressure water nozzle controls a valve to control a switch; and is connected with a ground power supply system;
the second step is that: determining the position and distance relationship between the ground and the residual coal pillar in the residual mining area and the thick and hard top plate of the underlying coal seam, drilling a U-shaped well on the ground right above the residual coal pillar in the residual mining area, wherein the number of the U-shaped wells is L/d, L is the length of the working face of the underlying coal seam, d is the well drilling distance, the U-shaped well is divided into a left vertical section of the U-shaped well, a horizontal section of the U-shaped well and a right vertical section of the U-shaped well, the left vertical section and the right vertical section respectively penetrate through the two residual coal pillars in the residual mining area to reach the thick and hard top plate of the underlying coal seam, and the horizontal section is parallel to the advancing direction of the working face in the thick and hard top plate of the, the junction of the left vertical section and the right vertical section and the junction of the left horizontal section and the right horizontal section are both provided with guide wheels, the first U-shaped drilling well is called a U-shaped plasma fracturing drilling well, and the second U-shaped drilling well is called a U-shaped detection drilling well; the plasma ground U-type devices for reducing the composite strong mine pressure of the thick and hard top plate and the residual coal pillar in the residual mining area are respectively arranged on the left and the right of the ground above the left and the right vertical sections of the U-type drilling well, the construction steps of the two sets of devices on the left and the right sides of the U-type drilling well are the same, and therefore, only one side is described;
the third step: the dual-purpose water pipe, the high-pressure water spray head, the high-voltage cable, the electrode stabilizing device and the liquid-phase discharge plasma electrode penetrate through the U-shaped plasma cracking drilling vertical section and are arranged in front of a drilling packer at the initial position of the U-shaped plasma cracking drilling horizontal section drilled in the second step through a guide wheel, the drilling packer at the U-shaped plasma cracking drilling horizontal section is expanded to seal a well, and meanwhile, a signal transmission line and a detection probe penetrate through the U-shaped detection drilling vertical section and are arranged at the initial position of the U-shaped detection drilling horizontal section drilled in the second step through the guide wheel;
the fourth step: opening a high-pressure water spray head control valve, enabling water in a water storage tank to pass through a high-pressure pump through a dual-purpose water pipe, enabling the high-pressure water spray head to jet into the U-shaped plasma fracturing well drilling horizontal section, observing through a pressure gauge, and closing the high-pressure water spray head control valve when the water is filled in the U-shaped plasma fracturing well drilling horizontal section;
the fifth step: starting a plasma generator, after the alternating current passes through the plasma generator, a high-voltage cable and an electrode stabilizing device, namely a liquid-phase discharge plasma electrode, discharging, rapidly converting electric energy into impact energy, rapidly increasing the pressure in a horizontal section of a water-filled U-shaped plasma fracturing well, and starting to expand the original fracture of the underlying coal seam thick hard roof and generate a new fracture; meanwhile, the detection probe receives a signal sent by the liquid phase discharge plasma electrode, the signal is transmitted to the data acquisition instrument through the signal transmission line and the signal amplifier, the received reflected waveform delay time frequency spectrum condition is analyzed, the crack development condition of the underlying coal seam thick and hard roof is analyzed, and the plasma pulse controller is operated so as to adjust the discharge frequency until the U-shaped plasma cracks the thick and hard roof around the horizontal section of the drilling well to realize cracking; turning off the plasma generator;
and a sixth step: moving a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a dual-purpose water pipe, a high-pressure water spray head and a detection probe to be close to a residual mining area residual coal pillar at a vertical section of the 'U-shaped' plasma fracturing drilling, wherein drilling packers are arranged on top and bottom plates of the residual mining area residual coal pillar in the vertical section of the 'U-shaped' plasma fracturing drilling, a signal transmission line and the detection probe are synchronously moved, and the fourth step and the fifth step are repeated until the residual mining area residual coal pillar near the vertical section of the 'U-shaped' plasma fracturing drilling is fractured; turning off the plasma generator;
the seventh step: recovering a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a dual-purpose water pipe, a high-pressure water spray head and a detection probe, then opening a cooling control valve of a plasma generator, returning water in a water storage tank to the water storage tank through the dual-purpose water pipe via a high-pressure pump, a cooler and the plasma generator, closing the cooling control valve of the plasma generator after cooling the plasma generator, and finally plugging the U-shaped plasma fracturing drilling well;
eighth step: and (3) taking the 'U-shaped' detection drilling well as the next 'U-shaped' plasma cracking drilling well, taking the adjacent non-presplitting 'U-shaped' drilling well as the next 'U-shaped' detection drilling well, and repeating the third step to the seventh step until all the thick and hard top plates and residual coal pillars near the 'U-shaped' drilling well drilled in the second step are cracked completely.
In the scheme, in the second step, the distance d between the U-shaped drilling wells is 6-10 meters; the diameter of the U-shaped well is do which is 155 mm-335 mm.
In the scheme, in the second step, the included angle a between the left and right vertical sections of the U-shaped drilling well and the ground is 75-90 degrees.
In the scheme, in the second step, the U-shaped drilling horizontal section is positioned at the junction of the thick hard top plate and the overburden.
In the scheme, in the third step, the drilling packer is positioned in the plasma fracturing drilling horizontal section 5-10 meters in front of the guide wheel.
In the scheme, in the third step, the working pressure of the drilling packer is 30 MPa-55 MPa.
In the above scheme, in the third step, the drilling packer can be a self-sealing type, a compression type or a combined type drilling packer.
In the scheme, in the fourth step, a proper amount of electrolyte solution can be added into the horizontal section of the water-filled U-shaped plasma fracturing drilling well, wherein the electrolyte solution is NaOH solution).
In the scheme, in the fifth step, the discharge voltage of the liquid phase discharge plasma electrode is 100kV to 220kV, and the discharge frequency is 100Hz to 600 Hz.
The invention provides a device for reducing the composite strong mine pressure of a thick hard top plate and a left coal pillar in a plasma U-type manner for implementing the method, which comprises a plasma generator, a plasma pulse controller, a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a data acquisition instrument, a signal amplifier, a signal transmission line, a detection probe, a water storage tank, a high-pressure pump, a cooler, a pressure gauge, a dual-purpose water pipe, a high-pressure water spray head, a plasma generator cooling control valve and a high-pressure water spray head control valve;
the plasma pulse controller, the plasma generator, the electrode stabilizing device and the liquid phase discharge plasma electrode are connected through a high-voltage cable; the plasma generator releases electric energy through a high-voltage cable, an electrode stabilizing device and a liquid-phase discharge plasma electrode, wherein the high-voltage cable is responsible for transmitting the electric energy, and the electrode stabilizing device ensures the normal work of the liquid-phase discharge plasma electrode;
the plasma pulse controller, the data acquisition instrument, the signal amplifier and the detection probe are sequentially connected through a signal transmission line; the wave detection probe is used for receiving a wave signal penetrating through the coal/rock mass and transmitting wave data to the signal amplifier through the signal transmission line, the signal amplifier amplifies the wave data and finally transmits the amplified wave data to the data acquisition instrument, and the data acquisition instrument analyzes the obtained wave data and judges the cracking effect of the coal/rock mass;
the water storage tank, the high-pressure pump, the cooler and the plasma generator are connected through a dual-purpose water pipe to form a complete loop, and the control valve T is cooled through the plasma generator1A control switch; the high-pressure pump cools the water in the water storage tank through the dual-purpose water pipe and the cooler, and then conveys the water to the plasma generator to cool the plasma generator, so that the plasma generator is prevented from being overheated and cannot be used; the high-pressure pump, the pressure gauge and the high-pressure water nozzle are connected through a dual-purpose water pipe and a control valve T of the high-pressure water nozzle2A control switch; the high-pressure pump conveys water in the water storage tank to the high-pressure water spray head through the dual-purpose water pipe, and finally the water is sprayed out through the high-pressure water spray head.
The invention has the beneficial effects that:
the invention fully utilizes the characteristics of high temperature and high pressure instantly generated by strong motion among ions to form shock waves to enable the rock mass to generate cracks and expand, drill a U-shaped well on the ground, realize double purposes of one well and two-way operation, pre-crack the thick and hard top plate of the underlying coal bed and the residual coal pillar in the residual mining area, is not limited by space, does not influence the coal mining work of the underlying coal bed, and has convenient operation, simple method, no dust and no noise. And the method for reducing the composite strong mine pressure of the thick hard roof and the residual coal pillars in the residual mining area by the plasma ground in the U-shaped mode has high efficiency, easy control, good effect and strong flexibility, reduces the integrity of the thick hard roof and the residual coal pillars, achieves the purpose of reducing the composite strong mine pressure of the thick hard roof and the residual coal pillars in the residual mining area, and is a conversion from a 'rough type' to a 'fine type' compared with the existing method for reducing the composite strong mine pressure of the thick hard roof and the residual coal pillars in the residual mining area, thereby realizing green mining and safe production of a coal mine.
Drawings
FIG. 1 is a schematic diagram of a plasma ground U-type device for reducing composite strong mine pressure of thick and hard top plates and residual coal pillars in a residual mining area;
FIG. 2 is a schematic view of a U-shaped plasma fracturing drilling working state section of a plasma ground U-shaped device for reducing composite strong mine pressure of a thick hard top plate and a residual coal pillar in a residual mining area;
FIG. 3 is a schematic cross-sectional view of a working state of a U-shaped detection drilling well for reducing composite strong mine pressure of a thick hard top plate and a residual coal pillar on the plasma ground in a U-shaped manner;
FIG. 4 is a schematic diagram of a plasma ground U-type drilling layout for reducing composite strong mine pressure of thick and hard top plates and residual coal pillars in a mining area.
In the figure: 1-a plasma generator; 2-plasma pulse controller; 3-high voltage cable; 4-electrode stabilizing device; 5-liquid phase discharge plasma electrode; 6, a data acquisition instrument; 7-a signal amplifier; 8-signal transmission line; 9-a detection probe; 10-a water storage tank; 11-a high pressure pump; 12-a cooler; 13-pressure gauge; 14-a dual-purpose water pipe; 15-high pressure water jet; 16-a wire; 17-a drilling packer; 18-a guide wheel; 19- (U type) plasma fracturing drilling; 191-U type plasma fracturing the vertical section of the well; 192- "U-shaped" plasma fracturing the horizontal section of the well; 20-U-shaped detection drilling; 201-a "U-mode" demodulation drilling vertical section; 202- "U-mode" demodulation drilling horizontal section; 21-an underlying coal seam; 22-residual coal pillars in the residual mining area; 23-thick hard top plate of the underlying coal bed; 24-ground; 25- "U-shaped" well drilling; 25 a-a "U-drilling left vertical section; 25 b-a "U-shaped" drilling right vertical section; 25 c-a "U-shaped" drilling horizontal section; d, drilling distance; do-the borehole diameter; l is the length of the working face of the underlying coal bed; t1 — plasma generator cooling control valve; t2 — high pressure water jet control valve.
Detailed Description
The present invention is further illustrated by, but is not limited to, the following examples.
Example 1:
as shown in fig. 1, a plasma U-type device for reducing the composite strong mine pressure of a thick hard roof and a left coal pillar specifically comprises:
the plasma generator comprises a plasma generator 1, a plasma pulse controller 2, a high-voltage cable 3, an electrode stabilizing device 4, a liquid phase discharge plasma electrode 5, a data acquisition instrument 6, a signal amplifier 7, a signal transmission line 8, a detection probe 9, a water storage tank 10, a high-pressure pump 11, a cooler 12, a pressure gauge 13, a dual-purpose water pipe 14, a high-pressure water spray head 15, a plasma generator cooling control valve T1 and a high-pressure water spray head control valve T2.
The plasma pulse controller, the plasma generator, the electrode stabilizing device and the liquid phase discharge plasma electrode are connected through a high-voltage cable; the plasma generator releases electric energy through a high-voltage cable, an electrode stabilizing device and a liquid-phase discharge plasma electrode, wherein the high-voltage cable is responsible for transmitting the electric energy, and the electrode stabilizing device ensures the normal work of the liquid-phase discharge plasma electrode;
the plasma pulse controller, the data acquisition instrument, the signal amplifier and the detection probe are sequentially connected through a signal transmission line; the wave detection probe is used for receiving a wave signal penetrating through the coal/rock mass and transmitting wave data to the signal amplifier through the signal transmission line, the signal amplifier amplifies the wave data and finally transmits the amplified wave data to the data acquisition instrument, and the data acquisition instrument analyzes the obtained wave data and judges the cracking effect of the coal/rock mass;
the water storage tank, the high-pressure pump, the cooler and the plasma generator are connected through a dual-purpose water pipe to form a complete loop, and the control valve T is cooled through the plasma generator1A control switch; the high-pressure pump cools the water in the water storage tank through the dual-purpose water pipe and the cooler, and then conveys the water to the plasma generator to cool the plasma generator, so that the plasma generator is prevented from being overheated and cannot be used; the high-pressure pump, the pressure gauge and the high-pressure water nozzle are connected through a dual-purpose water pipe and a control valve T of the high-pressure water nozzle2A control switch; the high-pressure pump conveys water in the water storage tank to the high-pressure water spray head through the dual-purpose water pipe, and finally the water is sprayed out through the high-pressure water spray head. The dual-purpose water pipe can play a role in cooling the plasma generator; and the function of injecting water into the plasma cracking drill hole can be achieved.
In the invention, the device is respectively arranged on the left and the right of the ground above the left and the right vertical sections of the U-shaped drilling well.
As shown in fig. 2 to 4, the mining of the underlying coal seam 21 is affected by the composite strong mine pressure of the remaining coal pillars 22 in the residual mining area and the thick hard roof 23 of the underlying coal seam, and the following describes in detail an embodiment of the present invention with reference to the drawings.
A method for reducing composite strong mine pressure of thick and hard top plates and residual coal pillars in a residual mining area in a plasma ground U-shaped mode specifically comprises the following steps:
the first step is as follows: the plasma pulse controller 2, the plasma generator 1, the electrode stabilizing device 4 and the liquid phase discharge plasma electrode 5 are connected through a high-voltage cable 3; the plasma pulse controller 2 is connected with the data acquisition instrument 6 through a lead 16; the data acquisition instrument 6, the signal amplifier 7 and the detection probe 9 are connected through a signal transmission line 8; the water storage tank 10, the high-pressure pump 11, the cooler 12 and the plasma generator 1 are connected through a dual-purpose water pipe 14 to form a complete loop, and a cooling control valve of the plasma generator controls a switch; the high-pressure pump 11, the pressure gauge 13 and the high-pressure water nozzle 15 are connected through a dual-purpose water pipe 14, and the high-pressure water nozzle control valve controls a switch; and is connected with a ground power supply system;
the second step is that: determining the position and distance relationship between the ground 24 and the residual mining area residual coal pillar 22 and the thick and hard top plate 23 of the underlying coal bed, drilling a 'U-shaped' well 25 on the ground 24 right above the residual mining area residual coal pillar 22, wherein the number of the 'U-shaped' well 25 is L/d (L is the length of the working surface of the underlying coal bed, and d is the well drilling distance), and the distance d between the 'U-shaped' well 25 is 8 meters; the diameter of the U-shaped drilling well 25 is 275mm, the U-shaped drilling well 25 is divided into a U-shaped drilling left vertical section 25a, a U-shaped drilling horizontal section 25c and a U-shaped drilling right vertical section 25b, the included angle a between the U-shaped drilling left vertical section 25a and the U-shaped drilling right vertical section 25b and the ground is 90 degrees, the U-shaped drilling left vertical section 25a and the U-shaped drilling right vertical section 25b penetrate through two residual mining area remaining coal columns 22 to reach an underlying coal seam thick hard top plate 23, the U-shaped drilling horizontal section 25c is positioned at the intersection of the underlying coal seam thick hard top plate 23 and an overlying rock layer and is parallel to the advancing direction of the working surface of the underlying coal seam 22, guide wheels 18 are arranged at the intersection of the U-shaped drilling left vertical section 25a and the U-shaped drilling right vertical section 25b and the U-shaped drilling horizontal section 25c, the first U-shaped drilling well 25 is called a U-shaped plasma fracturing 19, the second "U" well 25 is referred to as the "U" demodulation well 20; two sets of devices for reducing the plasma ground U-shaped composite strong mine pressure of a thick hard top plate and a residual coal pillar in a residual mining area, which are connected in a first step, are respectively prepared on the ground 24 above the left vertical section 25a and the right vertical section 25b of the U-shaped drilling well 25, and the construction steps of the two sets of devices on the left side and the right side of the U-shaped drilling well are the same, so that only one side is described;
the third step: the dual-purpose water pipe 14, the high-pressure water spray head 15, the high-voltage cable 3, the electrode stabilizing device 4 and the liquid-phase discharge plasma electrode 5 penetrate through the U-shaped plasma cracking drilling vertical section 191 and are arranged 5 meters in front of a drilling packer at the initial position of the U-shaped plasma cracking drilling horizontal section 192 drilled in the second step through a guide wheel 18, the drilling packer 17 of the U-shaped plasma cracking drilling horizontal section 192 is expanded and sealed (the working pressure is 40 MPa-50 MPa), and meanwhile, the signal transmission line 8 and the detection probe 9 penetrate through the U-shaped detection drilling vertical section 201 and are arranged at the initial position of the U-shaped detection drilling horizontal section 202 drilled in the second step through the guide wheel 18;
the fourth step: opening a high-pressure water spray head control valve, injecting water in the water storage tank 10 into the U-shaped plasma fracturing drilling horizontal section 192 through a dual-purpose water pipe 14 via a high-pressure pump 11 and a high-pressure water spray head 15, observing by a pressure gauge 13, and closing the high-pressure water spray head control valve when the water is filled in the U-shaped plasma fracturing drilling horizontal section 192;
the fifth step: after the plasma generator 1 is started and 180KV/320Hz passes through the plasma generator 1, the high-voltage cable 3 and the electrode stabilizing device 4, and the liquid-phase discharge plasma electrode 5 discharges, electric energy is quickly converted into impact energy, and the pressure in the horizontal section 192 of the U-shaped plasma fracturing well filled with water is quickly increased, so that the original fracture of the underlying coal seam thick and hard top plate 23 begins to expand and a new fracture is generated; meanwhile, the wave detection probe 9 receives a signal sent by the liquid phase discharge plasma electrode 5, the signal is transmitted to the data acquisition instrument 6 through the signal transmission line 8 and the signal amplifier 7, the received reflected waveform delay time frequency spectrum condition is analyzed, the crack development condition of the underlying coal seam thick and hard top plate 23 is analyzed, and the plasma pulse controller 2 is operated so as to adjust the discharge frequency (100 Hz-600 Hz) until the thick and hard top plate 23 around the U-shaped plasma cracking drilling horizontal section 192 realizes cracking;
and a sixth step: closing the plasma generator 1, moving the high-voltage cable 3, the electrode stabilizing device 4, the liquid-phase discharge plasma electrode 5, the dual-purpose water pipe 14, the high-pressure water spray head 15 and the detection probe 9 to be close to the residual mining area residual coal pillar 22 of the U-shaped plasma cracking drilling vertical section 191, installing a drilling packer 17 on the top and bottom plates of the residual mining area residual coal pillar 22 in the U-shaped plasma cracking drilling vertical section 191, synchronously moving the signal transmission line 8 and the detection probe 9, and repeating the fourth step and the fifth step until the residual mining area residual coal pillar 22 close to the U-shaped plasma cracking drilling vertical section 191 is cracked;
the seventh step: closing the plasma generator 1, recovering the high-voltage cable 3, the electrode stabilizing device 4, the liquid-phase discharge plasma electrode 5, the dual-purpose water pipe 14, the high-pressure water spray head 15 and the detection probe 9, then opening a cooling control valve of the plasma generator, enabling water in the water storage tank 10 to pass through the dual-purpose water pipe 14, the high-pressure pump 11, the cooler 12 and the plasma generator 1 to return to the water storage tank 10, cooling the plasma generator 1, closing the cooling control valve of the plasma generator, and finally plugging the U-shaped plasma fracturing well 19;
eighth step: and (3) taking the 'U-shaped' detection well 20 as the next 'U-shaped' plasma cracking well 19, taking the adjacent non-presplitting 'U-shaped' well as the next 'U-shaped' detection well 20, and repeating the third step to the seventh step until all thick and hard top plates 23 and residual coal pillars 22 near all 'U-shaped' wells drilled in the second step are cracked completely.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the technical spirit and principle of the present invention should be included in the scope of the present invention.
Claims (9)
1. A method for reducing the composite strong mine pressure of a thick hard top plate and a left coal pillar in a plasma U-type manner is characterized by comprising the following steps: the method is used for: the mined coal seam passes through an overlying residual mining area left coal pillar group and an interlayer thick hard roof, and two stable residual coal pillars with the interval of 40-200 meters exist in the residual mining area left coal pillar group; the method specifically comprises the following steps:
the first step is as follows: the plasma pulse controller, the plasma generator, the electrode stabilizing device and the liquid phase discharge plasma electrode are connected through a high-voltage cable; the plasma pulse controller is connected with the data acquisition instrument through a lead; the data acquisition instrument, the signal amplifier and the detection probe are connected through a signal transmission line; the water storage tank, the high-pressure pump, the cooler and the plasma generator are connected through a dual-purpose water pipe to form a complete loop, and the plasma generator cools a control valve to control a switch; the high-pressure pump, the pressure gauge and the high-pressure water nozzle are connected through a dual-purpose water pipe, and the high-pressure water nozzle controls a valve to control a switch; and is connected with a ground power supply system;
the second step is that: determining the position and distance relationship between the ground and the residual coal pillar in the residual mining area and the thick and hard top plate of the underlying coal seam, drilling a U-shaped well on the ground right above the residual coal pillar in the residual mining area, wherein the number of the U-shaped wells is L/d, L is the length of the working face of the underlying coal seam, d is the well drilling distance, the U-shaped well is divided into a left vertical section of the U-shaped well, a horizontal section of the U-shaped well and a right vertical section of the U-shaped well, the left vertical section and the right vertical section respectively penetrate through the two residual coal pillars in the residual mining area to reach the thick and hard top plate of the underlying coal seam, and the horizontal section is parallel to the advancing direction of the working face in the thick and hard top plate of the, the junction of the left vertical section and the right vertical section and the junction of the left horizontal section and the right horizontal section are both provided with guide wheels, the first U-shaped drilling well is called a U-shaped plasma fracturing drilling well, and the second U-shaped drilling well is called a U-shaped detection drilling well; the plasma ground U-shaped devices for reducing the composite strong mine pressure of the thick hard top plate and the residual coal pillar in the residual mining area are respectively arranged on the left and the right of the ground above the left and the right vertical sections of the U-shaped drilling well, and the construction steps of the two sets of devices on the left and the right sides of the U-shaped drilling well are the same; the included angle a between the left and right vertical sections of the U-shaped drilling well and the ground is 75-90 degrees;
the third step: the dual-purpose water pipe, the high-pressure water spray head, the high-voltage cable, the electrode stabilizing device and the liquid-phase discharge plasma electrode penetrate through the U-shaped plasma cracking drilling vertical section and are arranged in front of a drilling packer at the initial position of the U-shaped plasma cracking drilling horizontal section drilled in the second step through a guide wheel, the drilling packer at the U-shaped plasma cracking drilling horizontal section is expanded to seal a well, and meanwhile, a signal transmission line and a detection probe penetrate through the U-shaped detection drilling vertical section and are arranged at the initial position of the U-shaped detection drilling horizontal section drilled in the second step through the guide wheel;
the fourth step: opening a high-pressure water spray head control valve, enabling water in a water storage tank to pass through a high-pressure pump through a dual-purpose water pipe, enabling the high-pressure water spray head to jet into the U-shaped plasma fracturing well drilling horizontal section, observing through a pressure gauge, and closing the high-pressure water spray head control valve when the water is filled in the U-shaped plasma fracturing well drilling horizontal section;
the fifth step: starting a plasma generator, after the alternating current passes through the plasma generator, a high-voltage cable and an electrode stabilizing device, namely a liquid-phase discharge plasma electrode, discharging, rapidly converting electric energy into impact energy, rapidly increasing the pressure in a horizontal section of a water-filled U-shaped plasma fracturing well, and starting to expand the original fracture of the underlying coal seam thick hard roof and generate a new fracture; meanwhile, the detection probe receives a signal sent by the liquid phase discharge plasma electrode, the signal is transmitted to the data acquisition instrument through the signal transmission line and the signal amplifier, the received reflected waveform delay time frequency spectrum condition is analyzed, the crack development condition of the underlying coal seam thick and hard roof is analyzed, and the plasma pulse controller is operated so as to adjust the discharge frequency until the U-shaped plasma cracks the thick and hard roof around the horizontal section of the drilling well to realize cracking; turning off the plasma generator;
and a sixth step: moving a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a dual-purpose water pipe, a high-pressure water spray head and a detection probe to be close to a residual mining area residual coal pillar at a vertical section of the 'U-shaped' plasma fracturing drilling, wherein drilling packers are arranged on top and bottom plates of the residual mining area residual coal pillar in the vertical section of the 'U-shaped' plasma fracturing drilling, a signal transmission line and the detection probe are synchronously moved, and the fourth step and the fifth step are repeated until the residual mining area residual coal pillar near the vertical section of the 'U-shaped' plasma fracturing drilling is fractured; turning off the plasma generator;
the seventh step: recovering a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a dual-purpose water pipe, a high-pressure water spray head and a detection probe, then opening a cooling control valve of a plasma generator, returning water in a water storage tank to the water storage tank through the dual-purpose water pipe via a high-pressure pump, a cooler and the plasma generator, closing the cooling control valve of the plasma generator after cooling the plasma generator, and finally plugging the U-shaped plasma fracturing drilling well;
eighth step: and (3) taking the 'U-shaped' detection drilling well as the next 'U-shaped' plasma cracking drilling well, taking the adjacent non-presplitting 'U-shaped' drilling well as the next 'U-shaped' detection drilling well, and repeating the third step to the seventh step until all the thick and hard top plates and residual coal pillars near the 'U-shaped' drilling well drilled in the second step are cracked completely.
2. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: in the second step, the distance d between the U-shaped drilling wells is 6-10 meters; the diameter do of the U-shaped well is 155 mm-335 mm.
3. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: in the second step, the horizontal section of the U-shaped drilling well is positioned at the junction of the thick hard top plate and the overlying rock stratum.
4. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: and in the third step, the drilling packer is positioned in the plasma fracturing drilling horizontal section 5-10 meters in front of the guide wheel.
5. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: in the third step, the working pressure of the well packer is 30 MPa-55 MPa.
6. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: in the third step, the drilling packer can be a self-sealing type, a compression type or a combined type drilling packer.
7. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: and in the fourth step, adding an electrolyte solution into the horizontal section of the water-filled U-shaped plasma fracturing drilling well, wherein the electrolyte solution is a NaOH solution.
8. The method for U-type reduction of composite strong mine pressure of the thick hard roof plate and the left coal pillar by the plasma according to claim 1, wherein the method comprises the following steps: in the fifth step, the discharge voltage of the liquid phase discharge plasma electrode is 100kV to 220kV, and the discharge frequency is 100Hz to 600 Hz.
9. A device for carrying out the method of any one of claims 1 to 8 and reducing the composite strong mine pressure of a thick hard roof and a left coal pillar in a plasma U-type mode is characterized in that: the device comprises a plasma generator, a plasma pulse controller, a high-voltage cable, an electrode stabilizing device, a liquid-phase discharge plasma electrode, a data acquisition instrument, a signal amplifier, a signal transmission line, a detection probe, a water storage tank, a high-voltage pump, a cooler, a pressure gauge, a dual-purpose water pipe, a high-pressure water spray head, a plasma generator cooling control valve and a high-pressure water spray head control valve;
the plasma pulse controller, the plasma generator, the electrode stabilizing device and the liquid phase discharge plasma electrode are connected through a high-voltage cable; the plasma generator releases electric energy through a high-voltage cable, an electrode stabilizing device and a liquid-phase discharge plasma electrode, wherein the high-voltage cable is responsible for transmitting the electric energy, and the electrode stabilizing device ensures the normal work of the liquid-phase discharge plasma electrode;
the plasma pulse controller, the data acquisition instrument, the signal amplifier and the detection probe are sequentially connected through a signal transmission line; the wave detection probe is used for receiving a wave signal penetrating through the coal/rock mass and transmitting wave data to the signal amplifier through the signal transmission line, the signal amplifier amplifies the wave data and finally transmits the amplified wave data to the data acquisition instrument, and the data acquisition instrument analyzes the obtained wave data and judges the cracking effect of the coal/rock mass;
the water storage tank, the high-pressure pump, the cooler and the plasma generator are connected through a dual-purpose water pipe to form a complete loop, and the control valve is controlled to be switched through the cooling control valve of the plasma generator; the high-pressure pump cools the water in the water storage tank through the dual-purpose water pipe and the cooler, and then conveys the water to the plasma generator to cool the plasma generator, so that the plasma generator is prevented from being overheated and cannot be used; the high-pressure pump, the pressure gauge and the high-pressure water nozzle are connected through a dual-purpose water pipe, and a switch is controlled by the high-pressure water nozzle control valve; the high-pressure pump conveys water in the water storage tank to the high-pressure water spray head through the dual-purpose water pipe, and finally the water is sprayed out through the high-pressure water spray head.
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