CN115653593A - Safe and environment-friendly treatment method for end coal rock suspended ceiling of caving coal working face - Google Patents
Safe and environment-friendly treatment method for end coal rock suspended ceiling of caving coal working face Download PDFInfo
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- CN115653593A CN115653593A CN202210582465.7A CN202210582465A CN115653593A CN 115653593 A CN115653593 A CN 115653593A CN 202210582465 A CN202210582465 A CN 202210582465A CN 115653593 A CN115653593 A CN 115653593A
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Abstract
The invention relates to the field of coal mining by caving coal in a coal mine, in particular to a safe and environment-friendly treatment method for the end head coal rock overhanging roof of a caving coal working face, which adopts a high-voltage pulse device to discharge to generate shock waves to generate a continuous horizontal breaking interface in a coal rock top plate, so that the thickness of the end overhanging roof is reduced, and the length of the end overhanging roof is further reduced to meet the requirements of an engineering site; the invention replaces explosive explosion, and provides a reasonable operation parameter determination method and a process construction method aiming at the top suspension of the end head of the top coal caving working face. The invention has controllable impact rock breaking energy, high safety, uniform impact energy density distribution, no rock over-breaking and flying stone hazard, no need of large-range warning, environmental protection, no generation of toxic and harmful gas, capability of performing other operations after the operation is finished and small production interference.
Description
Technical Field
The invention relates to the field of coal mine caving coal mining, in particular to a safe and environment-friendly processing method for end coal rock suspended ceiling of a caving coal working face.
Background
The roof above the stoping roadway of part of the coal face is hard, and the overhung area at the end of the working face is often too large (as shown in fig. 1). The end top plate is suspended without collapse, the suspended top area is too large, a good space condition is provided for end gas accumulation, the end gas of a working face is accumulated for a long time in a large amount, and gas overrun and gas explosion are possibly induced to become a huge potential safety hazard. The hard roof is weakened in advance by means of hydraulic fracturing or blasting to reduce the length of the end overhang.
For a caving coal face, the end suspended roof is coal rock. Although the strength of the coal rock is lower than that of hard rock, the integrity of the coal rock of a part of the top coal caving working face is better, and the thickness of the top coal is larger, so that the end head of the top coal caving working face has a longer suspended roof, which exceeds the limit requirement of mines, and the phenomenon is more common particularly in super-thick coal seam mines of Shanxi, nemonte and the like in China. For hard and dense rock, the hydraulic fracturing mode can produce good rock breaking effect, but for coal rock with remarkable anisotropy, the hydraulic fracturing effect can be reduced. The top plate is treated in a blasting mode, so that underground gas explosion can be caused, and great potential safety hazards exist; the explosive is too large in explosion energy, the coal rock strength is far lower than that of hard rocks, the explosive is a 'big horse-drawn trolley', flying stones are often generated by shallow hole blasting, long-distance and long-time warning is needed during blasting operation due to safety considerations, and the explosive occupies production time and space to a certain extent; the explosion of the explosive generates a large amount of toxic and harmful gases, which is not in accordance with the concept of green mining. Therefore, it is necessary to invent a safe and environment-friendly treatment method for the end coal rock suspended ceiling of the caving coal working face.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a safe and environment-friendly treatment method for the end coal-rock suspended ceiling of a caving coal working face, which comprises the following steps:
s1, determining a high-voltage pulse discharge operation layer position: determining the maximum end suspended ceiling length l limited by the engineering site, simplifying the end suspended ceiling of the working face into a cantilever beam structure, and measuring the ultimate tensile strength sigma of the coal rock roof according to the actual measurement t Determining a reasonable cantilever beam thickness of
The height or depth of the high-voltage pulse discharge operation layer from the coal rock top plate of the mining roadway is
S2, determining high-voltage pulse discharge excitation energy: adjusting voltage and capacitance by adopting a numerical simulation or field test mode, and determining reasonable single high-voltage pulse discharge excitation energy and corresponding capacitance and voltage operation parameters according to the coal rock roof cracking effect;
s3, determining the row spacing between high-voltage pulse discharge operations: the reasonable high-voltage pulse discharge operation interval is researched and determined by adopting a numerical simulation or field test mode, and after the high-voltage pulse discharge operation is completed based on the determined interval, a continuous horizontal breaking interface can be generated in the coal rock top plate, so that the thickness of a cantilever beam formed by the end suspended ceiling is reduced to
S4, constructing advanced drilling in the stoping roadway: constructing an advanced drilling hole to the coal rock top plate in the advanced support section of the mining roadway according to the spacing determined in the step S3, and constructing the hole bottom of the advanced drilling hole to the pulse discharge operation layer position determined in the step S1;
preferably, the specific advance working face of the advance support section is within 15m, and the advancing depth of the high-voltage pulse discharge operation every day is not less than the advancing speed of the working face.
S5, performing high-voltage pulse discharge operation
S51, preparing a high-voltage pulse discharge system: specifically, the high-voltage pulse discharge system comprises a high-voltage rectification circuit, a capacitor and an electrode, wherein the high-voltage rectification circuit is connected with the capacitor through a first switch, the capacitor is connected with one end of the electrode through a discharge cable and a second switch on the discharge cable, and the electrode comprises a positive stage and a negative stage.
S52, installing a pulse discharge operation device in the pilot hole; specifically, a gun head at the other end of the electrode is inserted into the sealed water bag, so that the gun head and the sealed water bag are connected together; and then the gun head and the sealing water bag are sent to the hole bottom of the advance drill hole together, and a detachable sealing device is adopted to seal the advance drill hole.
S53, adopting the operation parameters determined in the step S2 to enable water between the electrodes to generate shock waves and destroy the coal rock roof; specifically, the first switch is turned on, the capacitor is charged by the high-voltage rectification circuit, then the first switch is turned off, the second switch is turned on, and the electrodes suddenly obtain several kilovolts of high voltage from the capacitor, so that shock waves are generated by water between the electrodes, and a coal rock top plate is effectively damaged; and (4) disconnecting the second switch, removing the detachable sealing device, and taking out the electrode and the gun head.
S6, establishing an end suspended ceiling treatment effect inspection and feedback mechanism: inspecting whether the suspended top length of the end is up to the expected target or not by observing the suspended top length of the end on site, and entering the next working cycle if the target is up to the expected target; and if the target is not reached, correcting the operation parameters in the steps S1-S3, carrying out engineering practice again, and verifying the engineering effect until the engineering operation parameters reaching the expected end head suspension top length are obtained.
Has the beneficial effects that: 1. the invention adopts a high-voltage pulse device to discharge to generate shock waves to generate a continuous horizontal fracture interface in the coal rock top plate, so that the thickness of the end head overhang is reduced, and the length of the end head overhang is further reduced to meet the requirements of engineering sites; the invention replaces explosive explosion, and provides a reasonable operation parameter determination method and a process construction method aiming at the top suspension of the end head of the top coal caving working face.
2. The invention has controllable impact rock breaking energy, high safety, uniform impact energy density distribution, no rock over-breaking and flying stone hazard, no need of large-range warning, environmental protection, no generation of toxic and harmful gas, capability of performing other operations after the operation is finished and small production interference.
Drawings
FIG. 1 is a schematic end-suspended roof of a caving coal face;
FIG. 2 is a force diagram of the end suspension of the caving coal face simplified into a cantilever beam;
FIG. 3 is a layout diagram of a high voltage pulse discharge operation bay;
FIG. 4 is a schematic view of construction of a pilot borehole in a recovery roadway;
FIG. 5 is a schematic diagram of a pulsed discharge operation device arrangement in a lead borehole;
in the figure: the device comprises a working surface 1, an end suspension roof 2, a cantilever beam 3, a forepoling section 4, a coal rock roof 5, a horizontal fracture interface 6, a gob 7, a stoping roadway 8, a high-voltage pulse discharge working layer 9, a forepoling hole 10, an electrode 11, a positive stage 111, a negative stage 112, a gun head 12, a sealed water bag 13 and a detachable sealing device 14.
Detailed Description
As shown in fig. 2-5, the invention provides a safe and environment-friendly treatment method for end coal-rock suspended ceiling of a caving coal working face, which comprises the following steps:
s1, determining a high-voltage pulse discharge operation layer position
Simplifying the end suspended ceiling 2 of the working surface 1 into a cantilever beam 3 structure, wherein the stress of the cantilever beam 3 structure is shown in figure 2, q is the uniform load given by the overlying strata to which the end suspended ceiling 2, namely the cantilever beam 3, is subjected, h is the thickness of the end suspended ceiling 2, namely the cantilever beam 3, and l is the engineering field limitThe maximum end head overhang length is manufactured, M is the bending moment of the section of the investigation point in the cantilever beam, and M is o The bending moment of the section at the fixed branch end is used, and y is the section distance between the investigation point and the neutral axis of the section;
the normal stress sigma of any point in the cantilever beam is obtained by calculation as follows:
j in formula (1) z Is the section distance of the cantilever beam,
according to the theory of material mechanics, the maximum bending moment occurs at the section of the cantilever beam fixed end, and the maximum bending moment M is obtained through calculation o Is composed of
Obtaining the ultimate tensile strength of the coal rock roof as sigma through mechanical test t Then, the following equation can be satisfied under the cantilever beam limit state:
it can be seen from the formula (2) that h ℃ ∈ l, that is, the cantilever beam thickness is proportional to the cantilever beam length, and to reduce the cantilever beam length, the cantilever beam thickness can be reduced, that is, the smaller the cantilever beam thickness is, the easier the collapse is, and the shorter the overhang length at the end is;
in engineering practice, if l is the maximum cantilever beam length limited in the engineering field, the cantilever beam thickness must be reduced at least to
The end suspended ceiling can collapse before reaching the limited maximum suspended ceiling length so as to meet the requirements of engineering sites; the smaller the cantilever beam thickness, the more easily collapsed, the smaller the tip overhang length, but if the taste is reducedThe thickness of the cantilever beam is low, so that the thickness of the collapsed cantilever beam is small, and the mining space cannot be filled, so that the thickness of the cantilever beam cannot be reduced excessively; in order to meet the requirement that the end suspension top collapses before reaching the limited maximum suspension top length and simultaneously enable the thickness of the collapsed cantilever beam to be as large as possible so as to fill the goaf as much as possible, and determining the reasonable cantilever beam thickness as
Correspondingly, the height or the depth of the high-voltage pulse discharge operation layer 9 from the coal rock top plate of the mining roadway 8 is required to be
S2, determining high-voltage pulse discharge excitation energy
The high-voltage pulse discharge excitation energy is calculated according to the stored energy, and under the rated discharge voltage, the single discharge excitation energy is proportional to the capacitance of the energy storage device, and the excitation energy is proportional to the square of the discharge voltage, as shown in the following formula:
in the formula, Q E Excitation energy, in units of J; c is capacitance with the unit of F; u is voltage, and the unit is V;
adjusting voltage and capacitance by adopting a numerical simulation or field test mode, and determining reasonable single high-voltage pulse discharge excitation energy and corresponding capacitance and voltage operation parameters according to the coal rock roof fracture effect;
s3, determining the row spacing between high-voltage pulse discharge operations
Performing high-voltage pulse discharge operation in the coal-rock top plate 5 above the forepoling section 4 of the caving coal working face 1, wherein the shock wave generated by the high-voltage pulse discharge operation destroys the coal-rock top plate 5 to generate an obvious horizontal fracture interface 6 in the coal-rock top plate, so that the length of the end suspended ceiling 2 of the coal-rock top plate 5 entering the goaf 7 is limited, and the coal-rock thickness below the horizontal fracture interface 6 can be known from the step S1Is composed of
The reasonable high-voltage pulse discharge operation interval is researched and determined by adopting a numerical simulation or field test mode, and after the high-voltage pulse discharge operation is finished based on the determined interval, a continuous horizontal breaking interface 6 is generated in the coal rock top plate 5, so that the thickness of a cantilever beam formed by the end suspended ceiling is reduced to
As shown in fig. 3, a is the interval of the high-voltage pulse discharge operation, b is the row interval of the high-voltage pulse discharge operation, and h is the height of the coal roof after the high-voltage pulse discharge operation
Is also the high-voltage pulse discharge operation layer position, and H is the height of the stoping roadway 8;
s4, constructing advanced drilling in a stoping roadway
As shown in fig. 4, constructing an advanced drilling hole 10 to the coal rock top plate 5 in the advance support section 4 of the mining roadway 8 according to the spacing determined in the step S3, and constructing the hole bottom of the advanced drilling hole to the pulse discharge operation layer position 9 determined in the step S1; the advance support section is specifically within the range of 15m of an advance working surface, and the advancing depth of high-voltage pulse discharge operation every day is not less than the advancing speed of the working surface;
s5, performing high-voltage pulse discharge operation
S51, preparing a high-voltage pulse discharge system, wherein the high-voltage pulse discharge system comprises a high-voltage rectifying circuit, a capacitor and an electrode 11, the high-voltage rectifying circuit is connected with the capacitor through a first switch, the capacitor is connected with one end of the electrode 11 through a discharge cable and a second switch on the discharge cable, and the electrode comprises a positive stage 111 and a negative stage 112;
s52, as shown in figure 5, inserting the gun head 12 at the other end of the electrode 11 into the sealed water bag 13, and effectively sealing to connect the gun head 12 and the sealed water bag 13 together; then the gun head 12 and the sealing water bag 13 are sent to the bottom of the advance borehole 10, the detachable sealing device 14 is adopted to seal the advance borehole 10, and the hole sealing function is to improve the utilization rate of high-voltage pulse discharge energy, so that most of the energy is used for breaking rocks instead of being dissipated into the air;
s53, setting a warning distance and a warning process; the operation parameters determined in the step S2 are adopted, the first switch is opened, the capacitor is charged to kilovolt by the high-voltage rectifying circuit, then the first switch is disconnected, the second switch is opened, the electrode suddenly obtains the high voltage of kilovolt from the capacitor, tens of thousands of amperes of discharge current are formed in the water medium between the electrodes, tens of thousands or even hundreds of thousands of joules of heat energy are generated instantaneously, water is vaporized, huge impact force is generated on water, and shock waves are generated, and the coal rock top plate can be effectively damaged by the shock waves; the second switch is switched off, the detachable sealing device 14 is removed, and the electrode 11 and the gun head 12 are taken out;
the invention adopts high-voltage pulse discharge to replace explosive explosion as rock breaking power, and the high-voltage pulse discharge process means that a strong electric field (103-104V) is suddenly applied between a positive electrode and a negative electrode, so that water between the electrodes is ionized and vaporized within a very short time (mu s level) to generate shock waves with high temperature, high pressure and high speed expansion so as to effectively break rocks, thereby being safe and effective and being green and environment-friendly;
s6, establishing an end suspended ceiling treatment effect inspection and feedback mechanism
Inspecting whether the length of the suspended top of the end is up to the expected target or not by observing the length of the suspended top of the end on site, and entering the next working cycle if the length of the suspended top of the end is up to the expected target; and if the target is not reached, correcting the operation parameters in the steps S1-S3, carrying out engineering practice again, and verifying the engineering effect until the engineering operation parameters reaching the expected end head suspended ceiling length are obtained.
Claims (6)
1. A safe and environment-friendly treatment method for the end coal-rock suspended ceiling of a caving coal working face is characterized by comprising the following steps:
s1, determining the maximum end suspended ceiling length l limited by an engineering site, simplifying the end suspended ceiling of a working face into a cantilever beam structure, and actually measuring the ultimate tensile strength sigma of the coal rock roof t Determining a reasonable cantilever beam thickness of
The height or depth of the high-voltage pulse discharge operation layer from the coal rock top plate of the mining roadway is
S2, determining reasonable single high-voltage pulse discharge excitation energy and corresponding capacitance and voltage operation parameters;
s3, determining a reasonable row spacing between high-voltage pulse discharge operations, so that the reasonable row spacing can generate a continuous horizontal fracture interface in the coal rock top plate, and the thickness of a cantilever beam formed by the end suspended ceiling is reduced to
S4, constructing advanced drilling holes to the coal rock top plate in the advanced support section of the mining roadway according to the spacing determined in the step S3, and constructing the hole bottoms of the advanced drilling holes to the pulse discharge operation layer position determined in the step S1;
s5, performing high-voltage pulse discharge operation
S51, preparing a high-voltage pulse discharge system; s52, installing a pulse discharge operation device in the pilot hole; s53, adopting the operation parameters determined in the step S2 to enable water between the electrodes to generate shock waves to damage the coal rock top plate;
and S6, establishing an end suspended ceiling treatment effect inspection and feedback mechanism.
2. The safe and environment-friendly treatment method for the coal-rock hanging roof at the end of the caving coal face as claimed in claim 1, characterized in that in step S4, the specific advance support section is advanced by 15m from the working face, and the advancing range of the high-voltage pulse discharge operation every day is not less than the advancing range of the working face.
3. The safe and environment-friendly treatment method for the coal-top suspended ceiling at the end of the caving coal face as claimed in claim 1, wherein in step S51, the high-voltage pulse discharge system comprises a high-voltage rectification circuit, a capacitor and an electrode, the high-voltage rectification circuit is connected with the capacitor through a first switch, the capacitor is connected with one end of the electrode through a discharge cable and a second switch on the discharge cable, and the electrode comprises a positive stage and a negative stage.
4. The safe and environment-friendly processing method for the end coal-rock hanging roof of the caving coal face as claimed in claim 3, wherein in the step S52, the gun head at the other end of the electrode is inserted into the sealed water bag, so that the gun head and the sealed water bag are connected together; and then the gun head and the sealing water bag are sent to the hole bottom of the advance drill hole together, and a detachable sealing device is adopted to seal the advance drill hole.
5. The safe and environment-friendly treatment method for the end coal-rock hanging roof of the caving coal face as claimed in claim 4, wherein in the step S53, the first switch is turned on, the capacitor is charged by the high-voltage rectification circuit, then the first switch is turned off, the second switch is turned on, and the electrodes suddenly obtain the high voltage of several kilovolts from the capacitor, so that the water between the electrodes generates shock waves to damage the coal-rock roof; and (4) disconnecting the second switch, removing the detachable sealing device, and taking out the electrode and the gun head.
6. The safe and environment-friendly treatment method for the end coal-rock hanging roof of the caving coal face as claimed in claim 1 or 5, characterized in that the length of the end hanging roof is observed on site to check whether the expected target is reached, if so, the next working cycle is started; and if the target is not reached, correcting the operation parameters in the steps S1-S3, carrying out engineering practice again, and verifying the engineering effect until the engineering operation parameters reaching the expected end head suspension top length are obtained.
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| CN202210582465.7A CN115653593A (en) | 2022-05-26 | 2022-05-26 | Safe and environment-friendly treatment method for end coal rock suspended ceiling of caving coal working face |
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| CN202210582465.7A CN115653593A (en) | 2022-05-26 | 2022-05-26 | Safe and environment-friendly treatment method for end coal rock suspended ceiling of caving coal working face |
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