CN111140283A - Device and method for measuring initial gas emission speed with fixed hole sealing length - Google Patents
Device and method for measuring initial gas emission speed with fixed hole sealing length Download PDFInfo
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Abstract
The device comprises a measuring pipe, a vortex street flowmeter, a hole sealing air bag, an explosion-proof display and an inflator pump, wherein the front end and the rear end of the measuring pipe are permeable, the hole sealing air bag is fixedly arranged on the outer circumference of the front end part of the measuring pipe, the vortex street flowmeter is arranged at the rear part of the measuring pipe, the inflator pump is arranged inside the explosion-proof display, the explosion-proof display is provided with a gas emission flow display screen and an air bag pressure display screen, the vortex street flowmeter is connected with the explosion-proof display through a data line, the rear side of the hole sealing air bag is connected with the inflator pump through a high-pressure hose, the high-pressure hose is provided with a valve close to the front end of the measuring pipe, and the monitoring end of the air pump pressure display screen is connected to the high. The invention has scientific principle, simple structure, convenient operation and more rotational measured data, can provide reference for observing the gas emission rule, has certain significance and practical value for preventing and controlling gas outburst in a coal mine and guaranteeing safe production of a mine.
Description
Technical Field
The invention belongs to the technical field of coal mine gas control, and particularly relates to a device and a method for measuring the initial gas emission speed of a fixed hole sealing length.
Background
The initial velocity q of gas emission from the drilled hole refers to the initial velocity of gas emission flowing out through the gas guide pipe, which is measured 2min after hole sealing, in a coal seam, wherein phi is 42mm, the length of the drilled hole of 3.5m is used as the initial length, the air chamber is sealed by an air bag hole sealing device, the length of the air chamber is ensured to be 1m, the length of the hole of 1m is increased every time, the hole is increased to about 10m according to needs, and the initial velocity of gas. The principle is based on the difference between the gas desorption amount and the desorption speed of the outburst coal and the non-outburst coal, the gas desorption amount of the outburst coal is large, the initial gas desorption speed is high, and the initial measured gas emission speed (q value) of the drill hole is high. The initial value of the gas burst of the drill hole depends on factors such as the gas content of the coal bed, the gas pressure of the coal bed, the damage type of the coal, the physical and mechanical properties of the coal, the ground stress of the coal bed and the like, is an important local index widely applied to prediction of coal and gas outburst danger of a coal mining working face at home and abroad and inspection of the effect of outburst prevention measures, and is a reliable prediction index obtained by long-term theoretical research and engineering practice of vast coal technologists at home and abroad.
At present, the method for measuring the initial gas emission speed of a drilled hole adopted on site is to drill a hole in a coal seam, withdraw a drill rod when drilling for 1m or drilling to a preset depth, ensure the length of an air chamber for 1m, install and send the hole sealing device according to the required hole sealing length, inflate the hole sealing device by an inflator, and measure the initial gas emission speed of the specified drilled hole length by a flowmeter. The whole process needs to be completed within 2min after drilling is finished. In the field implementation process, a plurality of sections of observation pipes are required to be manually carried to a working face, an inflator is required to be carried, the orifice plate or the flowmeter with other measuring ranges is required to be replaced according to the gas emission size, the carrying and the operation are not convenient enough, and the measurement efficiency is influenced.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides the device and the method for measuring the initial gas emission speed with the fixed hole sealing length; the intelligent gas emission initial speed measuring device is matched, and the vortex street flowmeter is used for replacing the orifice plate flowmeter, so that the steps of replacing the orifice plate are reduced, the intelligent degree is higher, and the reading is accurate; the electric inflator pump is used for replacing manual inflation, the inflation time is short, the air pressure is stable, and the gas emission initial speed measurement is guaranteed within 2 min.
In order to solve the technical problems, the invention adopts the following technical scheme: the device for measuring the initial gas emission speed with the fixed hole sealing length comprises a measuring pipe, a vortex street flow meter, a hole sealing air bag, an explosion-proof display instrument and an inflator pump, wherein the front end and the rear end of the measuring pipe are permeable, the hole sealing air bag is fixedly arranged on the outer circumference of the front end part of the measuring pipe, the vortex street flow meter is arranged at the rear part of the measuring pipe, the inflator pump is arranged inside the explosion-proof display instrument, a gas emission flow display screen and an air bag pressure display screen are arranged on the explosion-proof display instrument, the vortex street flow meter is connected with the explosion-proof display instrument through a data line, the rear side of the hole sealing air bag is connected with the inflator pump through a high-pressure hose, a valve close to the front end of the measuring pipe is arranged on.
The outer circumference of the measuring tube is respectively provided with a front guide sleeve and a rear guide sleeve at the front side and the rear side of the hole sealing air bag; the outer diameter of the hole sealing air bag is smaller than the outer diameters of the front guide sleeve and the rear guide sleeve when the hole sealing air bag is not inflated, the front end of the front guide sleeve is flush with the front end of the measuring tube, a conical guide structure with a thin front part and a thick rear part is arranged at the front end of the front guide sleeve and the excircle of the front end of the measuring tube, and expansion reserved gaps are arranged between the rear side of the front guide sleeve and the front side of the hole sealing air bag and between the front side of the rear guide sleeve and the rear.
The upper part of the outer wall of the measuring tube is provided with a protective tube along the length direction, the rear guide sleeve is provided with a through hole for penetrating through the protective tube along the length direction, and the high-pressure hose penetrates through the protective tube.
The length of the measuring tube is 3.5-4m, the outer diameter of the measuring tube is 22mm, the inner diameter of the measuring tube is 15mm, the outer diameters of the front guide sleeve and the rear guide sleeve are 40mm, and the length of the hole sealing air bag is 50 cm.
The measuring method of the gas emission initial velocity measuring device with fixed hole sealing length comprises the following steps,
(1) drilling a drill hole which is parallel to the tunneling direction, has the diameter of 42mm and the hole depth of 4m at a position 0.5m away from the roadway wall on the tunneling working surface along the direction of the coal bed;
(2) after drilling is finished, immediately extending a hole sealing air bag at the front end of the measuring pipe into a drill hole, enabling a front guide sleeve and a rear guide sleeve to move forwards along the inner wall of the drill hole, stopping after a drill rod extends into the drill hole for 3m, turning on a switch of an inflator pump, setting inflation pressure to be 0.2MPa, inflating the hole sealing air bag by using the inflator pump, enabling the outer wall of the cylindrical hole sealing air bag to be in jacking contact with the inner wall of the drill hole after the cylindrical hole sealing air bag expands, closing a valve, and sealing the drill hole, wherein an air chamber with the length of 1m is formed at the front end of the hole;
(3) the vortex flow meter is positioned outside the orifice of the drill hole, the switch of the vortex flow meter is opened, the reading displayed by the gas emission flow display screen on the explosion-proof display instrument is observed, and the initial gas emission speed q is measured within 2min0；
(4) Opening the valve, drawing out the measuring pipe and the hole sealing air bag backwards immediately after the hole sealing air bag is deflated, continuously drilling the drill hole forwards for 1m, repeating the step (2), forming an air chamber with the length of 2m between the front end of the hole sealing air bag and the bottom of the drill hole, repeating the step (3), and measuring the initial gas emission value q of the air chamber with the length of 2mbComparing the measured data with a numerical simulation gas emission critical value to see whether the region has the outburst danger or not;
(5) repeating the operation mode of the step (4)Successively drilling the drill holes to increase the length of the air chamber, wherein the length of the air chamber is sequentially increased from 2m to 3m, 4m, 5m, 6m, 7m and 8 m; measuring initial gas emission values q in gas chambers one by onebThe initial value q of gas emission measured each timebRespectively comparing the gas emission critical values with the numerical simulation gas emission critical values corresponding to the lengths of the gas chambers; if the gas emission initial speed exceeds the corresponding gas emission critical value, the area is indicated to have the outburst danger.
The method for determining the numerical simulation gas emission critical value comprises the following steps:
the length from the orifice of the drill hole to the rear end of the air chamber is fixed by 3m, the length of the air chamber changes along with the depth of the drill hole, and the length of the air chamber increases by 1m each time; the initial gas emission speed of the drilled hole is measured, wherein the initial gas emission speed comprises the initial gas emission speed of a newly drilled hole with the length of 1m and the initial gas emission speed of the previous gas chamber, and the initial gas emission speed of the previous gas chamber is gradually attenuated by a negative power exponent along with the time; gas emission initial velocity q of measured gas chamber lengthbThe superposition value of the new drilling length and the original drilling length is obtained;
the attenuation coefficient of the initial gas emission speed of the drilled hole is a variation coefficient which shows that the gas emission speed of the drilled hole is attenuated along with the time extension, a representative tunneling working face is selected, the drilled hole with the diameter of 42mm is drilled according to the specification, and the initial gas emission speed q is measured0Measuring the flow q after a time ttThen, it is calculated as follows:
in the formula:
β -attenuation coefficient of gas emission velocity in borehole, min-1；
q0-initial gas emission initial velocity at hole drilling, L/min;
qt-the gas emission rate per borehole at time t, L/min;
t-time, min;
according to a calculation formula of the attenuation coefficient of the gas emission speed of the drilling hole, measuring the initial gas emission speed of the drilling hole and the gas emission speed at a certain time later to calculate β value, drilling 4m in the coal seam of the driving face, sealing holes at a position 3m away from the hole opening of the drilling hole, keeping the length of an air chamber of 1m, measuring q immediately after drilling, and calculating1Taking the measured drilling gas emission speed as a reference, measuring the drilling gas emission speed at a fixed time delta t and recording data, wherein the delta t is the time for drilling a drilling hole and measuring the initial gas emission speed, obtaining the change data of the gas emission speed of a unit drilling hole along with the time, determining an array according to the natural gas emission speed of the drilling hole, and calculating the attenuation coefficient of the drilling gas emission speed of the gas chamber with the length of 1m by regression analysis;
by adopting a regression analysis method, the attenuation coefficients β and q of the gas emission speed of the drill hole can be obtainedtDrawing a gas emission speed attenuation curve of unit air chamber length along with the change rule of t, wherein the unit air chamber length is 1 m;
the hole sealing length is fixed, and the initial velocity q of gas emission in the gas chamber with variable lengthbThe sum is the accumulation of each unit length gas cell, namely:
in the formula: q. q.si-gas emission speed of unit gas chamber;
l-the measured length of the gas cell, m;
the 3m hole sealing length is kept fixed, measurement data are obtained every delta t time, and the data of the gas emission speed along with the change of the drilling length in the fixed air chamber length can be calculated through the formula, as shown in table 1.
TABLE 1 calculation formula of initial velocity of gas emission for fixed chamber length
In conclusion, the initial gas emission speed q of the fixed air chamber lengthbCan be expressed as:
lwhen =1, q1= q0
lWhen the ratio is not less than 2,
fitting the data to obtain the initial gas emission speed q with fixed gas chamber lengthbTrend with chamber length.
By adopting the technical scheme, according to 'fine rules for preventing and treating coal and gas outburst', the gas chamber for measuring the q value is a space which is 1m long at the front end of the drill hole, the space is taken as a research object, the length of the drill hole is gradually increased on the basis of the length of the 1m gas chamber by taking the fixed length of 1m as a reference, and the length of the gas chamber is synchronously increased, so that the influence of the length change of the gas chamber on the initial velocity emission rule of the gas in the drill hole is analyzed and researched. In actual measurement, the length of a planned drilling hole is increased from 4m to 11m, the hole sealing length is 3m (the length of a measuring pipe extending into the drilling hole), the length of a gas chamber is increased from 1m to 8m, and the linear relation between the length of a changed gas chamber and the length of a fixed 1m gas chamber can be calculated by taking unit gas chamber length measurement data as a reference through numerical analysis.
In order to ensure that the measurement result of the variable gas chamber length can accurately reflect the outburst danger of the driving working face, the measurement result is required to be compared and contrasted with the measurement value of the length of the 1m fixed gas chamber, a gas emission calculation model is established by analyzing the coal bed gas migration rule, the influence of the change of the length of the gas chamber on the initial velocity of gas emitted from a drill hole is analyzed, and the initial velocity q of the initial gas emitted from the drill hole is determinedbInitial gas emission speed q corresponding to unit gas chamber length 1m1The length of the gas chamber is increased in steps of each meter, and the initial velocity q of gas emission in the gas chamber with the variable length is analyzedbAnd q is1The measured value is compared with q, and the comparison result with q is determined1Q corresponding to critical valuebThe critical value can provide a certain reference method for researching the gas emission rule, has certain significance and actual price for preventing and controlling coal and gas outburst and guaranteeing mine safety productionThe value is obtained.
Practice shows that when the length of the air chamber is 1m, the critical value of the initial velocity of gas emission is generally 4.5L/min to 5.0L/min, and the critical value can be increased along with the increase of the length of the air chamber, so that the change characteristics of the critical values of different air chamber lengths are determined.
The protection tube plays the effect of protection high pressure hose not destroyed, and in the in-process along with survey the pipe and stretch into the drilling or take out the drilling, the protection tube best position surveys the top of pipe, can avoid the protection tube to receive great friction like this. The front guide sleeve and the rear guide sleeve are respectively positioned on the front side and the rear side of the hole sealing air bag, the outer diameter of the air bag after air release of the hole sealing air bag is smaller than the outer diameters of the front guide sleeve and the rear guide sleeve, so that the hole wall of a drilled hole is prevented from being damaged due to friction with the hole sealing air bag, the front guide sleeve and the conical guide structure which is arranged at the front end of the measuring tube and is thin in the front and thick in the rear can prevent the hole wall of the drilled hole from being blocked, and the.
In conclusion, the invention has scientific principle, simple structure, convenient operation and more rotational measured data, can provide reference for observing the gas emission rule, has certain significance and practical value for preventing and treating gas outburst in a coal mine and ensuring the safe production of a mine.
Drawings
FIG. 1 is a schematic view of the overall structure of the invention during measurement on a heading face;
FIG. 2 is an enlarged view of the measuring apparatus of FIG. 1;
FIG. 3 is a gas emission velocity decay curve per unit length of the chamber;
FIG. 4 shows the initial velocity threshold of gas gush for different chamber lengths.
Detailed Description
As shown in fig. 1-2, the device for measuring initial gas emission speed with fixed hole sealing length of the invention comprises a measuring tube 1, a vortex street flow meter 2, a hole sealing air bag 3, an explosion-proof display instrument 4 and an inflator pump, wherein the front end and the rear end of the measuring tube 1 are both transparent, the hole sealing air bag 3 is fixedly arranged on the outer circumference of the front end part of the measuring tube 1, the vortex street flow meter 2 is arranged on the measuring tube 1, the inflator pump is arranged in the explosion-proof display instrument 4, the explosion-proof display instrument 4 is provided with a gas emission flow display screen and an air bag pressure display screen, the vortex street flow meter 2 is connected with the explosion-proof display instrument 4 through a data line 5, the rear side of the hole sealing air bag 3 is connected with the inflator pump through a high-pressure hose 6, the high-pressure hose 6 is provided with a valve 7 adjacent to the front end of the measuring tube 1.
The outer circumference of the measuring tube 1 is respectively provided with a front guide sleeve 8 and a rear guide sleeve 9 at the front side and the rear side of the hole sealing air bag 3; the outer diameter of the hole sealing air bag 3 when the hole sealing air bag is not inflated is smaller than the outer diameters of the front guide sleeve 8 and the rear guide sleeve 9 (fig. 2 is a schematic diagram of the hole sealing air bag 3 after being inflated and expanded), the front end of the front guide sleeve 8 is flush with the front end of the measuring tube 1, a conical guide structure 10 which is thin in the front and thick in the rear is arranged at the front end of the front guide sleeve 8 and the outer circle of the front end of the measuring tube 1, and expansion reserved gaps 12 are arranged between the rear side of the front guide sleeve 8 and the front side of the hole sealing air bag 3 and between the front.
The upper part of the outer wall of the measuring tube 1 is provided with a protective tube 11 along the length direction, the rear guide sleeve 9 is provided with a through hole for penetrating through the protective tube 11 along the length direction, and the high-pressure hose is arranged in the protective tube 11 in a penetrating way.
The length of the measuring tube 1 is 3.5-4m, the outer diameter of the measuring tube 1 is 22mm, the inner diameter of the measuring tube 1 is 15mm, the outer diameters of the front guide sleeve 8 and the rear guide sleeve 9 are 40mm, and the length of the hole sealing air bag 3 is 50 cm.
The measuring method of the gas emission initial velocity measuring device with fixed hole sealing length comprises the following steps,
(1) drilling a drill hole 14 which is parallel to the tunneling direction, has the diameter of 42mm and the hole depth of 4m at a position 0.5m away from a roadway side on a tunneling working surface 15 along the direction of a coal seam 16; the arrow in fig. 1 indicates the heading direction of the heading face 15;
(2) after drilling is finished, immediately extending the hole sealing air bag 3 at the front end of the measuring pipe 1 into the drill hole 14, enabling the front guide sleeve 8 and the rear guide sleeve 9 to move forwards along the inner wall of the drill hole 14, stopping after a drill rod extends into the drill hole 14 for 3m, turning on a switch of an inflator pump, setting inflation pressure to be 0.2MPa, inflating the hole sealing air bag 3 by using the inflator pump, enabling the outer wall of the cylindrical hole sealing air bag 3 to be in abutting contact with the inner wall of the drill hole 14 after expansion, and closing a valve 7, so that hole sealing is carried out on the drill hole 14, and an air chamber 17 with the length of 1m is formed at the front end of the hole sealing air;
(3) the vortex street flow meter 2 is positioned outside the orifice of the drill hole 14, the switch of the vortex street flow meter 2 is opened, the reading displayed by the gas emission flow display screen on the anti-explosion display instrument 4 is observed, and the initial gas emission speed q is measured within 2min0；
(4) Opening the valve 7, drawing out the measuring pipe 1 and the hole sealing air bag 3 backwards immediately after the hole sealing air bag 3 is deflated, continuing to drill 1m forwards in the drill hole 14, repeating the step (2), forming an air chamber 17 with the length of 2m by the front end of the hole sealing air bag 3 and the bottom of the drill hole 14, repeating the step (3), and measuring the initial gas emission value q of the air chamber 17 with the length of 2mbComparing the measured data with a numerical simulation gas emission critical value to see whether the region has the outburst danger or not;
(5) repeating the operation mode of the step (4), and gradually drilling the drill hole 14 to increase the length of the air chamber 17, wherein the length of the air chamber 17 is sequentially increased from 2m to 3m, 4m, 5m, 6m, 7m and 8 m; measuring the initial value q of gas emission in the air chamber 17 one by onebThe initial value q of gas emission measured each timebRespectively comparing the gas emission critical values with the numerical simulation gas emission critical values corresponding to the lengths of the gas chambers 17; if the gas emission initial speed exceeds the corresponding gas emission critical value, the area is indicated to have the outburst danger.
When the measuring pipe 1 is used for measuring the initial gas gushing speed, the gas in the gas chamber 17 flows out of the measuring pipe 1, and the flow rate is measured when the gas flows through the vortex flowmeter 2; the data line 5 guides the flow data measured by the vortex shedding flowmeter 2 into the explosion-proof display instrument 4;
the surface of the anti-explosion display instrument 4 is provided with a gas emission flow display screen and an air bag pressure display screen, a miniature electric inflator pump is further arranged in a shell of the anti-explosion display instrument 4, the inflator pump is modified by an AKS-5501 vehicle-mounted inflator pump, is provided with a 12V battery and is provided with an electric control inflation system and used for inflating the hole sealing air bag 3, and when the anti-explosion display instrument is used, the hole sealing air bag 3 can be fully filled within 1min by pressing an inflation button, so that the pressure of the hole sealing air bag 3 reaches 0.2 MPa;
the valve 7 is arranged on the high-pressure hose 6, and after the measurement is finished, the valve 7 is opened to release the pressure, so that the gas in the hole sealing air bag 3 is discharged;
the vortex flowmeter 2 adopts an explosion-proof vortex flowmeter 2, can measure the flow of methane gas, adopts split display, leads a display instrument out of an explosion-proof display instrument 4, ensures that the display instrument does not influence the extension of the measuring tube 1 into the drill hole 14, adopts a 15mm caliber to match with the measuring tube 1, and has a measuring range of 0-20m3Compared with a hole plate type flowmeter, the hole plate type flowmeter has the advantages that the steps of replacing the hole plate are reduced, recalibration is not needed, measurement is more convenient, errors caused by reading of human eyes can be reduced by using an electronic display, accuracy is high, the advantages of no rotating part and pulse digital output are realized, and installation and maintenance are simpler; the vortex flowmeter 2 is internally provided with an electronic power supply battery with voltage of 3.6V, does not need an external power supply, can continuously work for more than two years, and has small energy loss, wide measuring range and convenient use. When the length of the air chamber 17 is 1m, the maximum range of a common drilling gas emission initial speed measuring device is 0-100L/min, the length of the maximum air chamber 17 of the invention is 8m, the maximum value of the gas emission initial speed is increased along with the maximum value, and considering that the same drilling hole 14 is drilled for multiple times and a part of gas is released, the gas emission initial speed cannot be increased along with the length of the air chamber 17 in a linear function relationship, and the vortex street flowmeter 2 is selected to have the range of 0-20m3And h, namely the maximum measurement flow can reach 333L/min, and the measurement requirement can be met through estimation.
The high-pressure hose 6 is connected with the explosion-proof display instrument 43, the tester is sent into the drill hole 14 after drilling is finished, and the hole sealing purpose is achieved by inflating the hole sealing air bag 37;
the front end of the measuring tube 1 is wrapped with a hole sealing air bag 3, the length of the hole sealing air bag is 0.5m, the hole sealing air bag 3 is filled with air pumped by an inflator pump through a valve 7 and a high-pressure hose 6 during measurement, and the purpose of sealing a drilled hole 14 is achieved.
This intelligent gas gushes out initial velocity survey device has improved original orifice plate flowmeter measuring device, through electron vortex flowmeter 2, can realize the digital accurate measurement in the pit, is furnished with electronic pump, can realize quick automatic charging in the pit, aerifys fast, labour saving and time saving has improved measurement of efficiency.
The protective tube 11 serves to protect the high-pressure hose from damage, and during the process of inserting or extracting the measuring tube 1 into or out of the borehole, the protective tube 11 is preferably located at the top of the measuring tube 1, so that the protective tube 11 is prevented from being subjected to large friction. The front guide sleeve 8 and the rear guide sleeve 9 are respectively positioned on the front side and the rear side of the hole sealing air bag 3, the outer diameter of the air bag 3 after air release is smaller than the outer diameters of the front guide sleeve 8 and the rear guide sleeve 9, so that the hole wall of a drilled hole is prevented from being damaged due to friction with the hole sealing air bag 3, the front guide sleeve 8 and the conical guide structure 10 arranged at the front end of the measuring tube 1 and provided with a thin front part and a thick rear part can prevent the hole wall of the drilled hole from blocking, and the thrust force for pushing the measuring tube 1 forward.
The vortex shedding flowmeter 2, the hole sealing air bag 3, the explosion-proof display instrument 4 and the inflator pump are all the existing mature technologies and can be purchased in the market, and the specific structure is not described any more.
The method for determining the numerical simulation gas emission critical value comprises the following steps:
the length from the orifice of the drill hole 14 to the rear end of the air chamber 17 is fixed at 3m, the length of the air chamber 17 changes along with the depth of the drill hole 14, and the length of the air chamber 17 increases by 1m each time; the measured initial gas emission speed of the drill hole 14 comprises the initial gas emission speed of a newly drilled hole with the length of 1m and the initial gas emission speed of the previous gas chamber 17, and the initial gas emission speed of the previous gas chamber 17 shows negative power exponent attenuation gradually along with time; initial gas emission speed q of measured gas chamber 17 lengthbThe superposition value of the new drilling length and the original drilling length is obtained;
the attenuation coefficient of the initial gas emission velocity of the borehole 14 is a variation coefficient showing the attenuation tendency of the gas emission velocity of the borehole with the time, a representative excavation face 15 is selected, a borehole with a diameter of 42mm is drilled according to the specification, and the initial gas emission velocity q is measured0Measuring the flow q after a time ttThen, it is calculated as follows:
in the formula:
β -attenuation coefficient of gas emission velocity in borehole, min-1；
q0-initial gas emission initial velocity at hole drilling, L/min;
qt-the gas emission rate per borehole at time t, L/min;
t-time, min;
according to a calculation formula of the attenuation coefficient of the gas emission speed of the drilling hole, measuring the initial gas emission speed of the drilling hole and the gas emission speed at a certain time later to calculate β value, drilling 4m in the coal seam 16 of the driving face 15, sealing holes at a position 3m away from the hole opening of the drilling hole, keeping the length of an air chamber 17 of 1m, firstly, immediately measuring q after drilling1Taking the measured drilling gas emission speed as a reference, measuring the drilling gas emission speed at a fixed time delta t and recording data, wherein the delta t is the time for drilling a drilling hole and measuring the initial gas emission speed, obtaining the change data of the gas emission speed of a unit drilling hole along with the time, determining an array according to the natural gas emission speed of the drilling hole, and calculating the attenuation coefficient of the drilling gas emission speed of the air chamber 17 with the length of 1m by regression analysis;
by adopting a regression analysis method, the attenuation coefficients β and q of the gas emission speed of the drill hole can be obtainedtDrawing a gas emission speed attenuation curve of the unit air chamber 17 length along with the change rule of t, wherein the unit air chamber length is 1 m; as shown in fig. 3;
the hole sealing length is fixed, and the initial velocity q of gas emission in the gas chamber with variable lengthbThe sum is the accumulation of each unit length gas cell, namely:
in the formula: q. q.si-gas emission speed of unit gas chamber;
l-the measured length of the gas cell, m;
the 3m hole sealing length is kept fixed, measurement data are obtained every delta t time, and the data of the gas emission speed along with the change of the drilling length in the fixed air chamber length can be calculated through the formula, as shown in table 1.
TABLE 1 calculation formula of initial velocity of gas emission for fixed chamber length
In conclusion, the initial gas emission speed q of the fixed air chamber lengthbCan be expressed as:
lwhen =1, q1= q0
lWhen the ratio is not less than 2,
fitting the data to obtain the initial gas emission speed q with fixed gas chamber lengthbTrend with chamber length.
Combining the actual measurement of a certain coal mine site, q0Taking 3.5L/min, delta t 3.5min, β 0.0787 as an example, calculate q1Numerical value, and length q of each variable air chamberbQ with a fixed chamber length of 1m1(the detailed rules for preventing coal and gas outburst) is called q0) As shown in table 2:
TABLE 2 initial velocity of gas emission for fixed length of gas chamber
Fitting the data into a scatter plot, as shown in FIG. 4, q per cell length1Gradually becomes smaller with time and shows negative exponential change; along with the gradual increase of the length of the measuring air chamber (the measuring air chamber is the accumulated value of the previous air chambers), the initial gas emission speed q measured by fixing the sealing hole lengthbWith a concomitant increase in qbThe increasing amplitude of the gas is gradually reduced, which shows that the initial velocity of the gas emission is gradually reduced along with the time.
By analogy, the length measurement value q of each variable air chamber of the coal mine can be calculatedbMeasured value q of corresponding fixed air chamber length 1m1Can be used for the mining of the coal mineAnd predicting the local outburst risk of the working surface. Similarly, the initial velocity attenuation coefficient, min, of gas emission in any coal mine drilling hole is determined through research-1The method can also be applied to predicting the local outburst risk of the mining working face of the coal mine.
The present embodiment is not intended to limit the shape, material, structure, etc. of the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (6)
1. The gas emission initial velocity measuring device with fixed hole sealing length is characterized in that: including survey the pipe, the vortex flowmeter, the hole sealing gasbag, explosion-proof display instrument and pump, both ends are all penetrating around the survey pipe, the hole sealing gasbag is fixed to be established on survey pipe front end portion outer circumference, the rear portion on survey pipe is installed to the vortex flowmeter, the pump setting is inside explosion-proof display instrument, be equipped with gas emission flow display screen and gasbag pressure display screen on the explosion-proof display instrument, the vortex flowmeter passes through the data line and is connected with explosion-proof display instrument, the rear side of hole sealing gasbag is passed through high-pressure hose and is connected with the pump, be equipped with the valve of neighbouring survey pipe front end on the high-pressure hose, the monitoring end of air pump pressure display screen is connected on high-pressure hose.
2. The device and the method for measuring the initial velocity of gas emission with a fixed hole sealing length according to claim 1, wherein: the outer circumference of the measuring tube is respectively provided with a front guide sleeve and a rear guide sleeve at the front side and the rear side of the hole sealing air bag; the outer diameter of the hole sealing air bag is smaller than the outer diameters of the front guide sleeve and the rear guide sleeve when the hole sealing air bag is not inflated, the front end of the front guide sleeve is flush with the front end of the measuring tube, a conical guide structure with a thin front part and a thick rear part is arranged at the front end of the front guide sleeve and the excircle of the front end of the measuring tube, and expansion reserved gaps are arranged between the rear side of the front guide sleeve and the front side of the hole sealing air bag and between the front side of the rear guide sleeve and the rear.
3. The device and the method for measuring the initial velocity of gas emission with a fixed hole sealing length according to claim 2, wherein: the upper part of the outer wall of the measuring tube is provided with a protective tube along the length direction, the rear guide sleeve is provided with a through hole for penetrating through the protective tube along the length direction, and the high-pressure hose penetrates through the protective tube.
4. The apparatus and method for measuring the initial velocity of gas emission with a fixed hole sealing length according to claim 1, 2 or 3, wherein: the length of the measuring tube is 3.5-4m, the outer diameter of the measuring tube is 22mm, the inner diameter of the measuring tube is 15mm, the outer diameters of the front guide sleeve and the rear guide sleeve are 40mm, and the length of the hole sealing air bag is 50 cm.
5. The method of claim 4, wherein the method comprises the steps of: comprises the following steps of (a) carrying out,
(1) drilling a drill hole which is parallel to the tunneling direction, has the diameter of 42mm and the hole depth of 4m at a position 0.5m away from the roadway wall on the tunneling working surface along the direction of the coal bed;
(2) after drilling is finished, immediately extending a hole sealing air bag at the front end of the measuring pipe into a drill hole, enabling a front guide sleeve and a rear guide sleeve to move forwards along the inner wall of the drill hole, stopping after a drill rod extends into the drill hole for 3m, turning on a switch of an inflator pump, setting inflation pressure to be 0.2MPa, inflating the hole sealing air bag by using the inflator pump, enabling the outer wall of the cylindrical hole sealing air bag to be in jacking contact with the inner wall of the drill hole after the cylindrical hole sealing air bag expands, closing a valve, and sealing the drill hole, wherein an air chamber with the length of 1m is formed at the front end of the hole;
(3) the vortex flow meter is positioned outside the orifice of the drill hole, the switch of the vortex flow meter is opened, the reading displayed by the gas emission flow display screen on the explosion-proof display instrument is observed, and the initial gas emission speed q is measured within 2min0；
(4) Opening the valve, drawing out the measuring pipe and the hole sealing air bag backwards immediately after the hole sealing air bag is deflated, continuously drilling the drill hole forwards for 1m, repeating the step (2), forming an air chamber with the length of 2m between the front end of the hole sealing air bag and the bottom of the drill hole, repeating the step (3), and measuring the initial gas emission value q of the air chamber with the length of 2mbComparing the measured data with the numerical simulation gas emission critical value to see the areaWhether there is a risk of outbreak;
(5) repeating the operation mode of the step (4), and gradually drilling the drill holes to increase the length of the air chamber, wherein the length of the air chamber is sequentially increased from 2m to 3m, 4m, 5m, 6m, 7m and 8 m; measuring initial gas emission values q in gas chambers one by onebThe initial value q of gas emission measured each timebRespectively comparing the gas emission critical values with the numerical simulation gas emission critical values corresponding to the lengths of the gas chambers; if the gas emission initial speed exceeds the corresponding gas emission critical value, the area is indicated to have the outburst danger.
6. The method of claim 5, wherein the method comprises the steps of: the method for determining the numerical simulation gas emission critical value comprises the following steps:
the length from the orifice of the drill hole to the rear end of the air chamber is fixed by 3m, the length of the air chamber changes along with the depth of the drill hole, and the length of the air chamber increases by 1m each time; the initial gas emission speed of the drilled hole is measured, wherein the initial gas emission speed comprises the initial gas emission speed of a newly drilled hole with the length of 1m and the initial gas emission speed of the previous gas chamber, and the initial gas emission speed of the previous gas chamber is gradually attenuated by a negative power exponent along with the time; gas emission initial velocity q of measured gas chamber lengthbThe superposition value of the new drilling length and the original drilling length is obtained;
the attenuation coefficient of the initial gas emission speed of the drilled hole is a variation coefficient which shows that the gas emission speed of the drilled hole is attenuated along with the time extension, a representative tunneling working face is selected, the drilled hole with the diameter of 42mm is drilled according to the specification, and the initial gas emission speed q is measured0Measuring the flow q after a time ttThen, it is calculated as follows:
in the formula:
β -attenuation coefficient of gas emission velocity in borehole, min-1；
q0-initial gas emission initial velocity at hole drilling, L/min;
qt-the gas emission rate per borehole at time t, L/min;
t-time, min;
according to a calculation formula of the attenuation coefficient of the gas emission speed of the drilling hole, measuring the initial gas emission speed of the drilling hole and the gas emission speed at a certain time later to calculate β value, drilling 4m in the coal seam of the driving face, sealing holes at a position 3m away from the hole opening of the drilling hole, keeping the length of an air chamber of 1m, measuring q immediately after drilling, and calculating1Taking the measured drilling gas emission speed as a reference, measuring the drilling gas emission speed at a fixed time delta t and recording data, wherein the delta t is the time for drilling a drilling hole and measuring the initial gas emission speed, obtaining the change data of the gas emission speed of a unit drilling hole along with the time, determining an array according to the natural gas emission speed of the drilling hole, and calculating the attenuation coefficient of the drilling gas emission speed of the gas chamber with the length of 1m by regression analysis;
by adopting a regression analysis method, the attenuation coefficients β and q of the gas emission speed of the drill hole can be obtainedtDrawing a gas emission speed attenuation curve of unit air chamber length along with the change rule of t, wherein the unit air chamber length is 1 m;
the hole sealing length is fixed, and the initial velocity q of gas emission in the gas chamber with variable lengthbThe sum is the accumulation of each unit length gas cell, namely:
in the formula: q. q.si-gas emission speed of unit gas chamber;
l-the measured length of the gas cell, m;
keeping the 3m hole sealing length fixed, obtaining measurement data every delta t time, and calculating the change data of the gas emission speed along with the drilling length in the fixed air chamber length by the formula, wherein the change data are shown in table 1;
TABLE 1 calculation formula of initial velocity of gas emission for fixed chamber length
In conclusion, the initial gas emission speed q is fixed at the length of the gas chamberbCan be expressed as:
lwhen =1, q1= q0
lWhen the ratio is not less than 2,
；
fitting the data to obtain the initial gas emission speed q with fixed gas chamber lengthbTrend with chamber length.
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