Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a method for predicting the gas emission quantity of a mine working face, which can monitor the stress condition of an anchor rod in real time, improve safety support monitoring and remind workers of discharging potential safety hazards in time.
In order to solve the technical problems, the invention adopts the following technical scheme: a method for predicting gas emission quantity of a mine working face comprises the following steps,
(1) according to the action effect of mine pressure on the working surface, the coal body in front of the working surface is divided into a first initial compression and plastic deformation area A, a strong compression and damage area B of the first coal body and a first top plate rotation action area C from back to front in sequence;
(2) the regional transportation lane under the mine is parallel to the regional return airway, the regional transportation lane is positioned on the left side of the regional return airway, the right side of the regional transportation lane is sequentially divided into a second initial compression and plastic deformation area A1, a strong compression and destruction area B1 of a second coal body and a second roof rotation action area C1 from left to right, and the left side of the regional return airway is sequentially divided into a third initial compression and plastic deformation area A2, a strong compression and destruction area B2 of a third coal body and a third roof rotation action area C2 from right to left;
(3) and (3) carrying out absolute emission Q of coal gas in front of the working surface in the step (1)A;
(4) And (3) carrying out absolute gas emission quantity Q on the coal body on the right side wall of the regional transportation roadway and the left side wall of the regional return airway in the step (2)1+2;
(5) Finally obtaining the gas emission quantity Q = Q at the mine working faceA+ Q1+2。
Q in step (3)AThe determination process of (2) is:
the first initial compression and plastic deformation area A is adjacent to the strong compression and damage area B of the first coal body, the boundary line is formed by the support pressure points for the damage of each layer of the coal body, the intercept and the horizontal distance x from the coal wall to the intersection point of the boundary line and the coal bed bottom plate interface0Can be represented by the following formula:
wherein x0-horizontal distance, m, from the coal wall to the intersection of the curve and the seam floor interface;
m-coal seam thickness, M;
lambda-the lateral pressure coefficient,
mu is the Poisson's ratio of the coal body;
phi is the internal friction angle of the coal body, °;
k is the stress concentration coefficient of the peak bearing pressure;
h-coal seam mining depth, m;
gamma-the average volume weight of the overburden,
;
c is the cohesion of the coal body, MPa;
px is the supporting strength formed by the supporting counter force of the working face support to the coal wall, and is MPa;
;
Ft-the scaffold working resistance, MN;
alpha-the angle of inclination, degree, of the stand column;
b-width of the stent, m.
The curve equation of the boundary between the first initial compression and plastic deformation region a and the strong compression and destruction region B of the first coal body may be expressed as:
x= 0.0784H2+0.376 H + x0
the width Lp of the fragmentation zone can then be calculated as:
Lp= 0.0784M2+0.376M+ x0
1) determination of coal volume in first initial compression and plastic deformation zone A
The strong compression and damage area B of the first coal body is a part enclosed by x0 to Lp below a boundary line; assuming that the length of the working face is D meters and the thickness of the coal seam, i.e. the mining height, is M meters, the volume V of the coal body in the first initial compression and plastic deformation area AAComprises the following steps:
2) gas emission amount of coal in first initial compression and plastic deformation zone A
Setting the depth of a working face to be E meters, and the coal cutting speed of a coal mining machine to be V meters/minute, wherein according to field statistics, the L/V of the time for cutting the coal on the working face is generally not less than 15 minutes, and when the L/V is not less than 15 and not more than 30, the gas emission quantity of the crushed coal body is 60 percent of the total gas content; when L/V is more than or equal to 31 and less than or equal to 60, the gas emission amount of the crushed coal body is 85 percent of the total gas content; when the L/V is not more than 61, the gas emission quantity of the crushed coal body is 95 percent of the total gas content;
therefore, when the depth of a working face is E meters, the coal cutting speed of a coal mining machine is V meters/minute, and the original relative gas content is q cubic meters/ton, the absolute gas emission amount in the area A after coal cutting can be calculated:
in the formula:
k is the uniform coefficient of gas release, and the uniform degree can be 1.0-1.5 according to the occurrence of gas;
the gas release degree coefficient is 0.6 when L/V is more than or equal to 15 and less than or equal to 30; when L/V is more than or equal to 31 and less than or equal to 60, taking 0.85; when L/V is not more than 61, 0.95 is selected.
The specific determination process of the absolute gas emission quantity Q of the coal bodies on the right side wall of the regional transportation roadway and the left side wall of the regional return airway in the step (4) is as follows:
a boundary between the second initial compression and plastic deformation region a1 and the strong compression and destruction region B1 of the second coal body and a boundary between the third initial compression and plastic deformation region a2 and the strong compression and destruction region B2 of the third coal body are symmetrically arranged at left and right sides,
its intercept and the horizontal distance x from the coal wall to the intersection point of the boundary line and the coal seam floor interface1Can be represented by the following formula
Px 1-pressure ahead of coal wall
Curve equation according to the boundary:
x= 0.0784H2+0.376H+X1
the width L of the crushing zone can be calculated therefromp1Comprises the following steps:
Lp1= 0.0784M2+0.376M+ X1
the crushing conditions of the second initial compression and plastic deformation zone a1 and the third initial compression and plastic deformation zone a2 under the influence of the advance pressure are similar to those along the working face direction, because the influence of the advance pressure has a certain range, and the crushing range is approximately 20 m;
the volume of the crushing zone of the two sides under the influence of the advancing pressure
When the original relative gas content is Q cubic meters per ton, under the influence of the advanced pressure, the gas emission quantity of the coal walls at the two sides is calculated according to 50%, and the gas emission quantity Q1+2 of the coal walls at the two sides is as follows:
。
by adopting the technical scheme, according to the action effect of mine pressure on the working face, the right side wall of the regional transportation roadway and the left side wall of the regional return airway are divided into an initial compression and plastic deformation area, a strong compression and damage area of coal and a top plate rotation action area. The strong compression and damage area of the coal body and the top plate rotation action area are positioned in the stress increasing area, and the pressure in the coal body is increased due to the increase of the stress, so that part of free gas in the part of the coal body can be changed into adsorbed gas, and the release of the gas is not facilitated. Due to the influence of the advance pressure, the coal walls of the initial compression and plastic deformation area and the two sides in front of the working face are more broken, and therefore a certain amount of gas is released. Therefore, the gas release of the working face can be regarded as the gas release of the two parts, and therefore the gas content of the working face can be approximately expressed by calculating the gas amount of the initial compression and plastic deformation area and the release amount of the right side wall of the regional transportation roadway and the left side wall of the regional return airway.
In conclusion, the coal seam in front of the working face is divided into different regions, and the gas emission amount of the working face is obtained by calculating the gas emission content of the broken region. The data obtained by calculation is used for guiding the mine to take more economic and appropriate measures to prevent gas, so that the safe production level of the mine is improved.
Detailed Description
The invention relates to a method for predicting gas emission quantity of a mine working face, which comprises the following steps,
(1) as shown in fig. 1, according to the action effect of mine pressure on the working surface, the coal body in front of the working surface is divided into a first initial compression and plastic deformation area A, a strong compression and destruction area B of the first coal body and a first top plate rotation action area C from back to front in sequence;
(2) as shown in fig. 2, the regional transportation lane 1 under the mine is parallel to the regional return airway 2, the regional transportation lane 1 is located on the left side of the regional return airway 2, the right side of the regional transportation lane 1 is sequentially divided into a second initial compression and plastic deformation region a1, a second coal body strong compression and damage region B1 and a second roof rotation action region C1 from left to right, and the left side of the regional return airway 2 is sequentially divided into a third initial compression and plastic deformation region a2, a third coal body strong compression and damage region B2 and a third roof rotation action region C2 from right to left;
(3) and (3) carrying out absolute emission Q of coal gas in front of the working surface in the step (1)A;
(4) And (3) carrying out absolute gas emission quantity Q on the coal body on the right side of the regional transportation roadway 1 and the left side of the regional return airway 2 in the step (2)1+2;
(5) Finally obtaining the gas emission quantity Q = Q at the mine working faceA+ Q1+2。
Q in step (3)AThe determination process of (2) is:
as shown in FIG. 1, a first initial compression and plastic deformation zone A is adjacent to a first coal body intense compression and destruction zone B, the boundary line of which is formed by the points of destructive support pressure at each level of the coal body, the intercept and the horizontal distance x from the intersection of the coal wall to the boundary line and the coal seam floor interface0Can be represented by the following formula:
wherein x0-horizontal distance, m, from the coal wall to the intersection of the curve and the seam floor interface;
m-coal seam thickness, M;
lambda-the lateral pressure coefficient,
mu is the Poisson's ratio of the coal body;
phi is the internal friction angle of the coal body, °;
k is the stress concentration coefficient of the peak bearing pressure;
h-coal seam mining depth, m;
gamma-the average volume weight of the overburden,
;
c is the cohesion of the coal body, MPa;
px is the supporting strength formed by the supporting counter force of the working face support to the coal wall, and is MPa;
;
Ft-the scaffold working resistance, MN;
alpha-the angle of inclination, degree, of the stand column;
b-width of the stent, m.
The curve equation of the boundary between the first initial compression and plastic deformation region a and the strong compression and destruction region B of the first coal body may be expressed as:
x= 0.0784H2+0.376 H + x0
the width Lp of the fragmentation zone can then be calculated as:
Lp= 0.0784M2+0.376M+ x0
1) determination of coal volume in first initial compression and plastic deformation zone A
The strong compression and damage area B of the first coal body is a part enclosed by x0 to Lp below a boundary line; assuming that the length of the working face is D meters and the thickness of the coal seam, i.e. the mining height, is M meters, the volume V of the coal body in the first initial compression and plastic deformation area AAComprises the following steps:
2) gas emission amount of coal in first initial compression and plastic deformation zone A
Setting the depth of a working face to be E meters, and the coal cutting speed of a coal mining machine to be V meters/minute, wherein according to field statistics, the L/V of the time for cutting the coal on the working face is generally not less than 15 minutes, and when the L/V is not less than 15 and not more than 30, the gas emission quantity of the crushed coal body is 60 percent of the total gas content; when L/V is more than or equal to 31 and less than or equal to 60, the gas emission amount of the crushed coal body is 85 percent of the total gas content; when the L/V is not more than 61, the gas emission quantity of the crushed coal body is 95 percent of the total gas content;
therefore, when the depth of a working face is E meters, the coal cutting speed of a coal mining machine is V meters/minute, and the original relative gas content is q cubic meters/ton, the absolute gas emission amount in the area A after coal cutting can be calculated:
in the formula:
k is the uniform coefficient of gas release, and the uniform degree can be 1.0-1.5 according to the occurrence of gas;
the gas release degree coefficient is 0.6 when L/V is more than or equal to 15 and less than or equal to 30; when L/V is more than or equal to 31 and less than or equal to 60, taking 0.85; when L/V is not more than 61, 0.95 is selected.
As shown in fig. 2, the specific determination process of the absolute gas emission Q of the coal on the right side of the regional transportation roadway 1 and the left side of the regional return airway 2 in step (4) is as follows:
a boundary between the second initial compression and plastic deformation region a1 and the strong compression and destruction region B1 of the second coal body and a boundary between the third initial compression and plastic deformation region a2 and the strong compression and destruction region B2 of the third coal body are symmetrically arranged at left and right sides,
its intercept and the horizontal distance x from the coal wall to the intersection point of the boundary line and the coal seam floor interface1Can be represented by the following formula
Px 1-pressure ahead of coal wall
Curve equation according to the boundary:
x= 0.0784H2+0.376H+X1
the width L of the crushing zone can be calculated therefromp1Comprises the following steps:
Lp1= 0.0784M2+0.376M+ X1
the crushing conditions of the second initial compression and plastic deformation zone a1 and the third initial compression and plastic deformation zone a2 under the influence of the advance pressure are similar to those along the working face direction, because the influence of the advance pressure has a certain range, and the crushing range is approximately 20 m;
the volume of the crushing zone of the two sides under the influence of the advancing pressure
When the original relative gas content is Q cubic meters per ton, under the influence of the advanced pressure, the gas emission quantity of the coal walls at the two sides is calculated according to 50%, and the gas emission quantity Q1+2 of the coal walls at the two sides is as follows:
。
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.