CN108343378A - A kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling - Google Patents

A kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling Download PDF

Info

Publication number
CN108343378A
CN108343378A CN201810081618.3A CN201810081618A CN108343378A CN 108343378 A CN108343378 A CN 108343378A CN 201810081618 A CN201810081618 A CN 201810081618A CN 108343378 A CN108343378 A CN 108343378A
Authority
CN
China
Prior art keywords
drilling
needle
coal seam
coal body
coal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
CN201810081618.3A
Other languages
Chinese (zh)
Other versions
CN108343378B (en
Inventor
林柏泉
李彦君
张祥良
李永
孔佳
朱传杰
任洁
王正
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
China University of Mining and Technology CUMT
Original Assignee
China University of Mining and Technology CUMT
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by China University of Mining and Technology CUMT filed Critical China University of Mining and Technology CUMT
Priority to CN201810081618.3A priority Critical patent/CN108343378B/en
Publication of CN108343378A publication Critical patent/CN108343378A/en
Application granted granted Critical
Publication of CN108343378B publication Critical patent/CN108343378B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B7/00Special methods or apparatus for drilling

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Earth Drilling (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
  • Drilling And Exploitation, And Mining Machines And Methods (AREA)

Abstract

A kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling, the coal body in drilling front is impregnated first with the conductive ion solution with certain pressure, coal body electric conductivity is set to enhance, then high electric field pulse generator is utilized, is discharged drilling front coal body, is generated huge energy and act directly on coal body, coal body is set to generate crack, to reduce machinery drilling resistance, finally starts drilling machine, further extend drilling.One aspect of the present invention is remarkably improved the rate of penetration of profound drilling, ensures the construction efficiency of drilling, on the other hand can effectively extend the service life of drilling tool.

Description

A kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling
Technical field
The present invention relates to a kind of boring method suitable for the profound drilling in coal seam, especially a kind of electric pulse assists power auger Into coal seam rapid drilling method.
Background technology
China's geological condition of coal mine is complicated, and with being continuously increased for pit mining depth, Gas Disaster has become restriction coal One big factor of the safe and efficient production of mine, gas pumping are the important means for administering Gas Disaster, are directed to apply to coal seam Work mash gas pumping drilling, boring method efficiently, safe have gas pumping efficiency important influence.
The tradition machinery drilling method that coal mine drilling uses at present, mainly using bore tooth to the impact of coal body, scraping and Shear action is crushed coal body, and to promote drilling, this method is simple in structure, easy to operate, but in deep well drilling, with brill The increase of hole depth, the torque and pulling force that drilling rod is born incrementally increase, and difficulty of construction significantly increases, and construction efficiency is caused to reduce, Drill tool wear is serious.
Invention content
In order to overcome the above-mentioned deficiency of the prior art, it is quick that the present invention provides a kind of coal seam of electric pulse auxiliary machinery drilling Boring method, this method can either significantly improve the rate of penetration of profound drilling, ensure the construction efficiency of drilling, and can effectively prolong The service life of long drilling tool.
The present invention solve its technical problem the technical solution adopted is that:It is molten first with the conductive ion with certain pressure Liquid impregnates the coal body in drilling front, and coal body electric conductivity is made to enhance, and then utilizes high electric field pulse generator, to drilling front coal body It discharges, generates huge energy and act directly on coal body, coal body is made to generate crack, reduce machinery drilling resistance, finally Start drilling machine, further extends drilling.
Compared with prior art, the coal seam rapid drilling method of a kind of electric pulse of the invention auxiliary machinery drilling, first with The electric conductivity of conductive ion solution enhancing coal body with certain pressure, recycles high electric field pulse generator to generate huge energy Amount directly acts on coal body, and advance fracturing is carried out to coal seam, and coal body in front of drilling is made to generate crack, reduces machinery drilling Resistance effectively increases drilling efficiency, extends the service life of drill bit, solves the problems, such as that profound drilling drilling is difficult.
Description of the drawings
Present invention will be further explained below with reference to the attached drawings and examples.
Fig. 1 is the construction schematic diagram of one embodiment of the invention.
Fig. 2 is I-I sectional view in Fig. 1.
In figure:The coal seams 1-, 2- drillings, 3- drill bits, 4- auger stems, 5- drilling machines, 6- hole packers, the needle-shaped positive electrodes of 7-, 8- Needle-shaped negative electrode, 9- insulation pistons, 10- insulated springs, 11- insulated spring holders, 12- cables, 13- crimping noses, 14- high pressures Electric pulse generator, 15- high-pressure pipe connectors, 16- high pressure water injection pipes, 17- pressure gauges, 18- water fillings switch, 19- high pressure water-injection pumps It stands, 20- drainage switches, 21- drainage pumping plants.
Specific implementation mode
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is A part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, ordinary skill people The every other embodiment that member is obtained without making creative work, belongs to protection scope of the present invention.
Figures 1 and 2 show that the structural schematic diagram of a preferred embodiment of the invention, a kind of electric pulse in Fig. 1 is auxiliary The coal seam rapid drilling method for helping machinery to creep into, is as follows:
A, the drilling 2 for a 2m depth of constructing in coal seam 1;
B, installation high electric field pulse generator 14, high-pressure water injecting pump station 19 and drainage pumping plant 21, connection drill bit 3, auger Bar 4 and drilling machine 5 inlay needle-shaped positive electrode 7, needle-shaped negative electrode 8 and high pressure water injection pipe 16,7 He of needle-shaped positive electrode inside drill bit 3 Needle-shaped negative electrode 8 is embedded in one end of 3 tail portion inner cavity of drill bit through cable 12 and crimping nose 13 and high electric field pulse generator 14 Positive and negative anodes connect, and needle-shaped positive electrode 7 and needle-shaped negative electrode 8 stretch out the other end of drill bit 3 next to coal seam 1, high pressure water injection pipe 16 It is connected to high-pressure water injecting pump station 19 and drainage pumping plant 21 through high-pressure pipe connector 15;Wherein, centre bore there are one the tools of the drill bit 3, Four side holes are uniformly distributed around centre bore, centre bore is embedded in needle-shaped positive electrode 7, and four side holes are embedded in needle-shaped negative electrode 8, are boring Any position on first 3 is additionally provided with a side hole for being embedded in high pressure water injection pipe 16, and the setting on the side hole meets high pressure water injection Pipe 16 is stretched by 3 tail portion inner cavity of drill bit and is stretched out by 3 front end of drill bit;Needle-shaped positive electrode 7, needle-shaped negative electrode 8 and high pressure injection Water pipe 16 is fixed on insulation piston 9, and insulation piston 9 is connected with insulated spring 10, and insulated spring 10 is fixed on insulated spring branch On frame 11, needle-shaped positive electrode 7 and needle-shaped negative electrode 8 are connect with cable 12 respectively;The auger stem 4 is hollow drill pipe, center High pressure water injection pipe 16 and cable 12 are installed;
C, drilling 2 is sealed using hole packer 6, opens water filling switch 18, passes through high-pressure water injecting pump station 19 and high pressure The solion that the injection pressure into drilling 2 of water injection pipe 16 is 30MPa, observes pressure gauge 17, keeps 2 internal water pressures of drilling constant Water filling switch 18 is closed after 2h, and passes through the ion in drainage switch 20, drainage pumping plant 21, the extraction of high pressure water injection pipe 16 drilling 2 Solution, to improve the electric conductivity of 2 front coal bodies of drilling;
D, open high electric field pulse generator 14 charged (such as 100kV) pass through needle when voltage reaches setting value Shape positive electrode 7 and needle-shaped negative electrode 8 discharge to 2 front coal bodies of drilling, and huge energy directly acts on coal body, makes coal body A large amount of cracks are generated, to reduce machinery drilling resistance, after multiple discharge, close high electric field pulse generator 14;The electric discharge Number can be 50 times;
E, start drilling machine 5, continue to promote drilling 2 using auger stem 4 and drill bit 3, when drilling resistance increases, bed drain purge subtracts When small, stop drilling;During drilling, stretching structure is used for guard electrode, electrode can be made to retract, i.e., when needle-shaped positive electricity Pole 7 and needle-shaped negative electrode 8 are contracted under the action of insulated spring 10 in hole after encountering coal body, to avoid abrasion;
F, when 4 length of auger stem is inadequate, stop creeping into, continued access auger stem 4, pass through spiral shell between multiple auger stems 4 Line connects, their internal cables 12 and high pressure water injection pipe 16 use crimping nose 13 and high-pressure pipe connector 15 to connect respectively, installation After the completion, continue to creep into;
G, step c, d, e, f are repeated, until drilling 2 reaches predetermined depth.
In the present embodiment, 3 tail portion of the drill bit is set there are one cavity, and cavity is interior to be equipped with stretching structure, stretching structure packet Insulated spring holder 11, insulated spring 10 and insulation piston 9 are included, the installation of insulation piston 9 is in the cavity, needle-shaped positive electrode 7, needle-shaped One end that negative electrode 8 and high pressure water injection pipe 16 stretch into cavity is fixed on insulation piston 9, and insulate piston 9 and 10 phase of insulated spring Even, insulated spring 10 is fixed on insulated spring holder 11, and insulated spring holder 11 is supported on the end face of cavity bottom, it is needle-shaped just Electrode 7 and needle-shaped negative electrode 8 are connect with cable 12 respectively.
Another embodiment can also be done, place unlike the embodiments above is only that, the pressure of the conductive ion solution Power takes 12MPa, i.e., by high-pressure water injecting pump station 19 and high pressure water injection pipe 16, into drilling 2, injection pressure is that the ion of 12MPa is molten Liquid, then pressure gauge 17 is observed, close water filling switch 18 after keeping the constant 1h of 2 internal water pressures of drilling;The high electric field pulse occurs The discharge frequency that device 14 is set is set as 15Hz, and discharge voltage takes 25kV.
Further embodiment is also only with the embodiment difference of front two, the conductive ion solution Pressure takes 45MPa, i.e., the ion that injection pressure is 45MPa into drilling 2 by high-pressure water injecting pump station 19 and high pressure water injection pipe 16 Water, then pressure gauge 17 is observed, close water filling switch 18 after keeping the constant 1.5h of 2 internal water pressures of drilling;The high electric field pulse hair The discharge frequency that raw device 14 is set is set as 50Hz, and discharge voltage takes 180kV.
Three embodiments of the present invention can quickly penetrate into 2 front coal bodies of drilling using high-pressure ion solution, effectively be promoted The conductivity of front coal body utilizes high electric field pulse generator 14 to discharge front coal body, it is direct to generate huge energy later It acts on coal body, so that 2 front coal body of drilling is generated crack, reduce the resistance of machinery drilling, elevating mechanism drilling efficiency is reduced Drill tool wear, the fast and efficient construction for the profound drilling in coal seam provide important technological means.
The above is only presently preferred embodiments of the present invention, not does limitation in any form to the present invention, it is every according to According to the technical spirit of the present invention, any simple modification and same variation are made to above example, each fall within the guarantor of the present invention Within the scope of shield.

Claims (7)

1. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling, first with the conductive ion with certain pressure Solution impregnates the coal body in drilling front, and coal body electric conductivity is made to enhance, and then utilizes high electric field pulse generator, to drilling front coal Body discharges, and generates huge energy and acts directly on coal body, and coal body is made to generate crack, reduces machinery drilling resistance, most After start drilling machine, further extend drilling.
2. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 1, it is characterized in that:Tool Steps are as follows for gymnastics work:
A, the drilling (2) for a 2m depth of constructing in coal seam (1);
B, installation high electric field pulse generator (14), high-pressure water injecting pump station (19) and drainage pumping plant (21), connection drill bit (3), spiral shell Rotary drill bar (4) and drilling machine (5) inlay needle-shaped positive electrode (7), needle-shaped negative electrode (8) and high pressure water injection pipe inside drill bit (3) (16), one end of needle-shaped positive electrode (7) and embedded drill bit (3) the tail portion inner cavity of needle-shaped negative electrode (8) is through cable (12) and crimping nose Sub (13) are connect with the positive and negative anodes of high electric field pulse generator (14), and needle-shaped positive electrode (7) and needle-shaped negative electrode (8) stretch out drill bit (3) the other end is located next to coal seam (1), and high pressure water injection pipe (16) is connected to high-pressure water injecting pump station (19) through high-pressure pipe connector (15) With drainage pumping plant (21);
C, drilling (2) is sealed using hole packer (6), by high-pressure water injecting pump station (19) and high pressure water injection pipe (16) to brill The solion of injection certain pressure in hole (2), keeps the drilling constant 1-2h of (2) internal water pressure, then passes through drainage pumping plant (21) the residual ion solution in extraction drilling (2), to make coal body in front of drilling (2) immerse conductive ion solution;
D, high electric field pulse generator (14) is opened to charge, when voltage reaches setting value, by needle-shaped positive electrode (7) and Needle-shaped negative electrode (8) discharges to coal body in front of drilling (2), after multiple discharge, closes high electric field pulse generator (14);
E, drilling machine (5) is opened, continues to promote drilling (2) using auger stem (4) and drill bit (3), when drilling resistance increases, deslagging When amount reduces, stop drilling;
F, when auger stem (4) length is inadequate, stop drilling, continued access auger stem (4), when installation, by cable (12) and height Pressure injection water pipe (16) uses crimping nose (13) and high-pressure pipe connector (15) to connect respectively, after installation is complete, continues to creep into;
G, c-d-e-f is repeated, until drilling (2) reaches predetermined depth.
3. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 1 or 2, feature It is:The pressure limit of the conductive ion solution is 10-50MPa.
4. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 1 or 2, feature It is:The discharge frequency that the high electric field pulse generator (14) sets is 10-50Hz, voltage range 20-200kV.
5. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 2, it is characterized in that:Institute Drill bit (3) tool to be stated there are one centre bore, is uniformly distributed four side holes around centre bore, centre bore is embedded in needle-shaped positive electrode (7), and four A side hole is embedded in needle-shaped negative electrode (8), and a side hole for being embedded in high pressure water injection pipe (16) is additionally provided on drill bit (3).
6. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 2, it is characterized in that:Institute It states drill bit (3) tail portion to set there are one cavity, is equipped with stretching structure in cavity, stretching structure includes insulated spring holder (11), absolutely Edge spring (10) and insulation piston (9), insulation piston (9) install in the cavity, needle-shaped positive electrode (7), needle-shaped negative electrode (8) and One end that high pressure water injection pipe (16) stretches into cavity is fixed on insulation piston (9), insulation piston (9) and insulated spring (10) phase Even, insulated spring (10) is fixed on insulated spring holder (11), and insulated spring holder (11) is supported on the end face of cavity bottom, Needle-shaped positive electrode (7) and needle-shaped negative electrode (8) are connect with cable (12) respectively.
7. a kind of coal seam rapid drilling method of electric pulse auxiliary machinery drilling according to claim 5 or 6, feature It is:The auger stem (4) is hollow drill pipe, and middle part is equipped with high pressure water injection pipe (16) and cable (12), multiple spirals Drilling rod is connected through a screw thread between (4).
CN201810081618.3A 2018-01-29 2018-01-29 A kind of coal seam rapid drilling method of the mechanical drilling of electric pulse auxiliary Active CN108343378B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201810081618.3A CN108343378B (en) 2018-01-29 2018-01-29 A kind of coal seam rapid drilling method of the mechanical drilling of electric pulse auxiliary

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201810081618.3A CN108343378B (en) 2018-01-29 2018-01-29 A kind of coal seam rapid drilling method of the mechanical drilling of electric pulse auxiliary

Publications (2)

Publication Number Publication Date
CN108343378A true CN108343378A (en) 2018-07-31
CN108343378B CN108343378B (en) 2019-09-03

Family

ID=62960694

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201810081618.3A Active CN108343378B (en) 2018-01-29 2018-01-29 A kind of coal seam rapid drilling method of the mechanical drilling of electric pulse auxiliary

Country Status (1)

Country Link
CN (1) CN108343378B (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109372514A (en) * 2018-11-12 2019-02-22 中铁工程装备集团有限公司 Based on high pressure pulse discharge-mechanically combining broken rock novel silo drilling machine
CN110485940A (en) * 2019-09-30 2019-11-22 中国铁建重工集团股份有限公司 A kind of drill jumbo
CN110630173A (en) * 2019-09-30 2019-12-31 中国铁建重工集团股份有限公司 Core drilling machine
CN110656879A (en) * 2019-09-30 2020-01-07 中国铁建重工集团股份有限公司 Electric pulse drill bit
CN111042732A (en) * 2020-01-15 2020-04-21 中国矿业大学 High-voltage electric pulse drilling device and using method thereof
CN111101868A (en) * 2019-11-14 2020-05-05 中国石油大学(北京) Jet flow PDC drill bit
CN113216853A (en) * 2020-01-21 2021-08-06 新奥科技发展有限公司 Composite drill bit and rock drilling device

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202023547U (en) * 2011-04-29 2011-11-02 中国矿业大学 Coal mine underground pulsed hydraulic fracturing equipment
CN105275443A (en) * 2015-11-06 2016-01-27 中国矿业大学 Coal mine underground high-power electric knock assisted hydraulic fracturing permeability enhancement method
CN105298462A (en) * 2015-11-06 2016-02-03 中国矿业大学 High-power electric knocking assisted hydrofracture coal seam permeability increase method for end-located drainage roadway
CN106988680A (en) * 2017-05-27 2017-07-28 湖南科技大学 Ice pellets abradant jet Aided Machine drills and coal seam cutting method
CN107630717A (en) * 2017-09-18 2018-01-26 中国矿业大学 The coal seam anti-reflection method that a kind of electric pulse mutually cooperates with coal-bed flooding

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN202023547U (en) * 2011-04-29 2011-11-02 中国矿业大学 Coal mine underground pulsed hydraulic fracturing equipment
CN105275443A (en) * 2015-11-06 2016-01-27 中国矿业大学 Coal mine underground high-power electric knock assisted hydraulic fracturing permeability enhancement method
CN105298462A (en) * 2015-11-06 2016-02-03 中国矿业大学 High-power electric knocking assisted hydrofracture coal seam permeability increase method for end-located drainage roadway
CN106988680A (en) * 2017-05-27 2017-07-28 湖南科技大学 Ice pellets abradant jet Aided Machine drills and coal seam cutting method
CN107630717A (en) * 2017-09-18 2018-01-26 中国矿业大学 The coal seam anti-reflection method that a kind of electric pulse mutually cooperates with coal-bed flooding

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109372514A (en) * 2018-11-12 2019-02-22 中铁工程装备集团有限公司 Based on high pressure pulse discharge-mechanically combining broken rock novel silo drilling machine
CN110485940A (en) * 2019-09-30 2019-11-22 中国铁建重工集团股份有限公司 A kind of drill jumbo
CN110630173A (en) * 2019-09-30 2019-12-31 中国铁建重工集团股份有限公司 Core drilling machine
CN110656879A (en) * 2019-09-30 2020-01-07 中国铁建重工集团股份有限公司 Electric pulse drill bit
CN110656879B (en) * 2019-09-30 2021-07-30 中国铁建重工集团股份有限公司 Electric pulse drill bit
CN111101868A (en) * 2019-11-14 2020-05-05 中国石油大学(北京) Jet flow PDC drill bit
CN111101868B (en) * 2019-11-14 2021-04-06 中国石油大学(北京) Jet flow PDC drill bit
CN111042732A (en) * 2020-01-15 2020-04-21 中国矿业大学 High-voltage electric pulse drilling device and using method thereof
CN111042732B (en) * 2020-01-15 2020-10-30 中国矿业大学 High-voltage electric pulse drilling device and using method thereof
CN113216853A (en) * 2020-01-21 2021-08-06 新奥科技发展有限公司 Composite drill bit and rock drilling device

Also Published As

Publication number Publication date
CN108343378B (en) 2019-09-03

Similar Documents

Publication Publication Date Title
CN108343378B (en) A kind of coal seam rapid drilling method of the mechanical drilling of electric pulse auxiliary
CN108222838B (en) Rock breaking experimental device of electric pulse rock breaking drill bit
CN107816317B (en) A kind of fast drilling device and method that high electric field pulse is mutually cooperateed with power auger
CN104863561B (en) A kind of down-hole coal bed pulse detonation wave orientation fracturing anti-reflection method
CN112922575B (en) Electric pulse directional slotting-hydraulic blasting integrated coal seam permeability increasing method
CN109162755B (en) Rock cross-cut coal uncovering method combining electric pulse and grouting reinforcement
CN108267053B (en) Mechanical device for producing plasma to blast rock by utilizing hydro-electric effect
CN106593388A (en) Coal-bed gas well electric pulse blockage releasing and permeation enhancing method
CN105370257A (en) High-power electric-knocking auxiliary hydraulic fracturing production increase method for coal-bed gas well
CN108397182A (en) Electric pulse cooperates with the device and method in the anti-reflection coal seam of frozen-thawed
CN109578059B (en) Underground coal bed gas extraction method and liquid nitrogen flowing frost cracking device used by same
CN109252861A (en) A kind of electric pulse auxiliary liquid nitrogen freezing formula coal uncovering method
CN106703685B (en) A kind of high-voltage pulse power hammer drilling tool
CN104389574A (en) Gaseous phase fracturing device
CN111042732B (en) High-voltage electric pulse drilling device and using method thereof
CN206545484U (en) A kind of high-voltage pulse power hammer drilling tool
CN112412425A (en) Electric pulse prefabricated crack directional hydraulic fracturing integrated method
CN114483177A (en) Electric pulse and water pulse co-frequency injection increasing collapse column filling device and method
CN208168859U (en) The device in the electric pulse collaboration anti-reflection coal seam of frozen-thawed
CN108533172B (en) A kind of well system and method
CN102817632B (en) Method for draining gas of mining layer of mine
CN214464159U (en) Coal mine wall protection type drilling and phase change cracking device
CN205387926U (en) Fracturing safety backwash well valve
CN219012638U (en) Underground collapse column electric pulse directional presplitting grouting reinforcement device
CN111472779B (en) Pre-splitting method for hard roof of coal seam

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant