Blasting pre-pressure-relief anti-impact method for island working face of high-gas rock burst mine

Abstract

The invention discloses a high gas impact ground pressure mine island working face blasting pre-pressure-relief scour prevention method which comprises the steps that a scour inducing key layer in a top plate above an island working face is determined, a top plate pre-splitting pressure relief roadway with specific construction parameters is arranged in the scour inducing key layer, and by means of the mode, elastic deformation accumulated in the scour inducing key layer can be effectively reduced, and one-time pressure relief can be achieved; then, a plurality of blast holes with specific parameters are constructed from the roof presplitting pressure relief roadway to the inducing key layer, finally, the blast holes are sectioned according to the hole depth and sequentially blasted, energy release of each time of blasting is accurately controlled through sectioned blasting, meanwhile, continuous pressure relief is achieved in time and space through sectioned blasting, and the blasting efficiency is improved. The stress of the inducing key layer is effectively released to realize secondary pressure relief; through mutual cooperation of primary pressure relief of the roof presplitting pressure relief roadway and secondary pressure relief of segmented blasting of the blast hole, the mine roof type impact risk facing high gas, an island working face and mining rock burst is effectively reduced, and subsequent safe mining of the island working face is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of safe mining of coal mines, and in particular relates to a method for blasting pre-pressure relief and anti-bumping of an isolated island working face in a high gassy rock burst pressure mine. Background Art

[0002] During the mining process, the isolated working face of a mine with high gas and rock burst pressure needs to deal with the dual threats of rock burst pressure and high gas. The isolated working face itself is a special type of working face. Since it is surrounded by goafs, tunnels or mined areas, the surrounding rock mass loses support, which makes the stress concentration phenomenon more significant and more prone to rock burst pressure. At the same time, the threat of high gas makes the blasting scheme unsuitable for coal seams. The gas content in the cracks and pores of the coal seams is relatively high, which can easily lead to a large amount of gas being released in a short time, increasing the risk of gas accumulation and even causing a gas explosion. And conventional blasting schemes cannot break the hard rock layers in the middle and high positions of the roof in advance. Therefore, how to provide a new pressure relief and anti-bumping method that can effectively reduce the risk of roof-type impact in mines facing the triple threats of high gas, isolated working faces, and mining rock burst pressure is the research direction required by the present invention. Summary of the invention

[0003] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for blasting pre-pressure relief and anti-impact of isolated working faces in mines with high gas and rock burst pressure, which can effectively reduce the risk of roof-type impact in mines facing the triple threats of high gas, isolated working faces and mining rock burst pressure.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: a method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas rock burst mine, the specific steps are:

[0005] Step 1: First identify the location of each hard rock layer in the roof above the isolated working face, and select the key layer that induces impact in each hard rock layer; the reason for determining the key layer that induces impact is that it is an important rock layer that affects the stability of the coal body during coal mining. Under the combined effect of dynamic and static loads, it can induce hard roof type impact rock pressure. Correctly identifying and determining the key layer that induces impact is crucial to improving the accuracy of early warning and formulating effective crisis resolution measures.

[0006] Step 2. Construct multiple equally spaced roof pre-splitting and pressure-relieving tunnels in the key induced impact layer determined in step 1 along the advancing direction perpendicular to the isolated island working face; the spacing between adjacent roof pre-splitting and pressure-relieving tunnels is determined according to the blasting range of the blasting holes, and the number of roof pre-splitting and pressure-relieving tunnels is determined according to the total advancing length of the isolated island working face and the geological conditions.

[0007] Step three, in each roof pre-splitting and pressure-relieving tunnel in step two, multiple blasting holes are constructed on both sides respectively towards the rock masses on both sides, and each blasting hole is parallel to the advancing direction of the isolated working face; the diameter of the blasting hole is determined according to the rock properties and the blasting charge, and the conventional hole diameter range is 42mm~100mm; the spacing between adjacent blasting holes in the same side is determined according to the crushing zone radius and the fracture zone radius of the blasting hole; and the hole depth and charge of the blasting hole are determined according to the situation of the isolated working face.

[0008] Step 4: Divide each blasting hole into multiple sections according to the hole depth, and divide the charge of each blasting hole into multiple parts according to the number of sections. Charge and blast each blasting hole in sequence from the deepest section to the hole mouth. The energy release of each blasting is accurately controlled through segmented blasting. At the same time, segmented blasting realizes continuous pressure relief in time and space, effectively releasing the stress of the key layer that induces impact, thereby reducing the risk of roof-type impact.

[0009] Step 5. Monitor the stress changes of the isolated working face during the construction of steps 2 to 4 through online stress monitoring technology, and use microseismic monitoring to evaluate the pressure relief effect of the roof pre-crack pressure relief tunnel. If the pressure relief requirements are met, complete the pre-pressure relief construction of the isolated working face to reduce the risk of roof impact; if not, repeat step 4 to perform segmented blasting on each blasting hole again until the pre-pressure relief effect of the isolated working face meets the pressure relief requirements and the pre-pressure relief construction is completed.

[0010] Furthermore, the determination of the hard rock layer in step 1 is specifically as follows:

[0011] q (n+1)m <q (n)m (1)

[0012] Where: q (n+1)m is the load of the n+1th rock layer on the mth rock layer, in kilopascals (kPa); q (n)m is the load of the nth rock layer on the mth rock layer, in kilopascals (kPa);

[0013] When the load of the n+1th rock layer on the mth rock layer is less than the load of the nth rock layer on the mth rock layer, the nth rock layer is determined to be a hard rock layer;

[0014] The key layers that induce impact are screened out from each hard rock layer as follows:

[0015]

[0016] Where: c is the impact energy ratio, which is the ratio of the total energy released by the coal body after the hard rock layer breaks to the minimum impact energy of the coal body; R Tis the ultimate tensile strength of the hard rock layer, in megapascals (MPa); h is the thickness of the hard rock layer, in meters (m); e is the elastic modulus of the hard rock layer, in megapascals (MPa); Q is the overburden load of the hard rock layer, in kilopascals (kPa); H is the distance between the earthquake source and the coal seam, in meters (m); η is the attenuation index; E c is the accumulated elastic energy of coal deformation, in kilojoules (kJ); E0 is the minimum energy of coal impact failure, in kilojoules (kJ);

[0017] The impact energy ratio c of each hard rock layer is calculated according to the above formula, and the hard rock layer with impact energy ratio c ≥ 1 is regarded as the key impact inducing layer.

[0018] Furthermore, the spacing between adjacent roof pre-splitting and pressure relief tunnels in step 2 should not be less than the radius of the blasting hole fissure zone to avoid overlapping blasting ranges between roof pre-splitting and pressure relief tunnels; the length of each roof pre-splitting and pressure relief tunnel is determined according to the width of the isolated island working face.

[0019] Furthermore, the specific formula for determining the number of roof pre-splitting and pressure relief tunnels in step 2 is as follows:

[0020]

[0021] Where: N is the number of roof pre-cracking pressure relief tunnels, in units; L g is the length of the isolated working face, in meters (m); L is the spacing between the roof pre-cracking and pressure relief tunnels, in meters (m).

[0022] Furthermore, the spacing X between adjacent blast holes in the same gang in step 3 is specifically determined as follows:

[0023] The spacing X is affected by the blasting range, so it is necessary to calculate the radius of the crushing zone and the radius of the fissure zone after the blasting hole is charged. Using the coupled charging method, the crushing zone radius is calculated as follows:

[0024]

[0025] The radius of the fracture zone is calculated as follows:

[0026]

[0027] Where: R c is the radius of the crushing zone, in millimeters (mm); R p is the radius of the crack zone, in millimeters (mm); b is the ratio of radial stress to tangential stress; S T is the uniaxial tensile strength of the key rock layer, in megapascals (MPa); ρ m is the density of the key rock layer, in kg / m 3 (kg / m3 );D m is the velocity of the longitudinal wave, in meters per second (m / s); ρ0 is the density of the explosive, in kilograms per meter 3 (kg / m 3 ) ; D is the detonation velocity of the explosive, in meters per second (m / s); r b is the blast hole radius, in millimeters (mm); α is the stress wave attenuation index; r c is the charge diameter, in millimeters (mm); σ c is the uniaxial compressive strength of coal rock mass, in megapascals (MPa); B is the empirical coefficient; μ is Poisson’s ratio;

[0028] The determination of the spacing X needs to ensure that the destruction zones (crushed zones and fissure zones) formed after the blasting of the blasting holes are interconnected so that adjacent blasting holes can be connected to form a complete pressure relief zone; therefore, the spacing X value needs to be greater than the crushed zone radius R c and the radius of the crack zone R p However, if the spacing between blasting holes is too large, the crack zone cannot be penetrated and the ideal pressure relief effect cannot be achieved; if the spacing between blasting holes is too small, excessive pressure relief will occur, resulting in a waste of construction costs. c Usually smaller than the radius R of the fracture zone p , so the spacing X is taken as twice the radius of the crack area R p The effect is best.

[0029] Furthermore, the blasting holes arranged on both sides of the roof pre-splitting and pressure relief tunnel in step three are symmetrically distributed around the center of the roof pre-splitting and pressure relief tunnel.

[0030] Furthermore, the depth of the blasting hole in the step three is determined comprehensively based on the thickness of the key layer for inducing impact, rock properties, range of stress concentration zone and field test results; the charge of the blasting hole is determined comprehensively based on the rock layer position, thickness, strength and height of the key layer for inducing impact, to ensure that the energy of each blasting can form a sufficient pressure relief range.

[0031] Compared with the prior art, the present invention first screens and determines the key layer of inducing impact in the roof of the isolated working face, arranges the roof pre-splitting pressure relief tunnel in the key layer of inducing impact, and determines the layout parameters of the roof pre-splitting pressure relief tunnel in a specific way according to the geological conditions. This method can effectively reduce the elastic deformation energy accumulated in the key layer of inducing impact and realize one-time pressure relief; then, multiple blasting holes are constructed from the roof pre-splitting pressure relief tunnel into the key layer of inducing impact, and the layout spacing, hole depth and charge of the blasting holes are calculated and determined in a specific way according to the geological conditions; finally, each blasting hole is segmented according to the hole depth, and each blasting hole is segmented according to the hole depth. The blasting holes are charged and blasted in sequence from the deepest to the hole mouth. The energy release of each blasting is accurately controlled by segmented blasting. At the same time, segmented blasting realizes continuous pressure relief in time and space, effectively releasing the stress of the key layer that induces impact to realize secondary pressure relief. The present invention coordinates the primary pressure relief of the roof pre-cracking pressure relief tunnel and the secondary pressure relief of the segmented blasting of the blasting holes, thereby effectively reducing the roof-type impact hazard of the mine facing the triple threats of high gas, isolated working face and mining impact pressure, and ensures the subsequent safe mining of the isolated working face of the mine with high gas and impact pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a construction flow chart of the present invention.

[0033] Figure 2 It is a schematic diagram of the overall layout of the present invention;

[0034] Figure 3 yes Figure 2 Cross-section view along the AA direction.

[0035] In the figure: 1. blasting hole; 2. roof pre-cracking and pressure relief tunnel; 3. upper section return air tunnel; 4. goaf; 5. upper section transport tunnel; 6. island working face return air tunnel; 7. island working face transport tunnel; 8. lower section return air tunnel; 9. lower section transport tunnel; 10. fine-grained sandstone layer; 11. key induced impact layer; 12. direct roof; 13. direct bottom. DETAILED DESCRIPTION

[0036] The present invention will be further described below.

[0037] like Figure 1 As shown, the specific steps of the present invention are:

[0038] Step 1: First identify the location of each hard rock layer in the roof above the isolated working face, and select the key layer 11 that induces impact in each hard rock layer; the reason for determining the key layer 11 is that it is an important rock layer that affects the stability of the coal body during coal mining. Under the combined effect of dynamic and static loads, it can induce hard roof type impact ground pressure. Correctly identifying and determining the key layer that induces impact is crucial to improving the accuracy of early warning and formulating effective emergency measures. The specific process is as follows:

[0039] The identification of hard rock formations is as follows:

[0040] q (n+1)m <q (n)m (1)

[0041] Where: q (n+1)m is the load of the n+1th rock layer on the mth rock layer, in kilopascals (kPa); q (n)m is the load of the nth rock layer on the mth rock layer, in kilopascals (kPa);

[0042] When the load of the n+1th rock layer on the mth rock layer is less than the load of the nth rock layer on the mth rock layer, the nth rock layer is determined to be a hard rock layer;

[0043] The key impact-inducing layers 11 are screened out from each hard rock layer as follows:

[0044]

[0045] Where: c is the impact energy ratio, which is the ratio of the total energy released by the coal body after the hard rock layer breaks to the minimum impact energy of the coal body; R T is the ultimate tensile strength of the hard rock layer, in megapascals (MPa); h is the thickness of the hard rock layer, in meters (m); e is the elastic modulus of the hard rock layer, in megapascals (MPa); Q is the overburden load of the hard rock layer, in kilopascals (kPa); H is the distance between the earthquake source and the coal seam, in meters (m); η is the attenuation index; E c is the accumulated elastic energy of coal deformation, in kilojoules (kJ); E0 is the minimum energy of coal impact failure, in kilojoules (kJ);

[0046] The impact energy ratio c of each hard rock layer is calculated according to the above formula, and the hard rock layer with an impact energy ratio c≥1 is taken as the key impact inducing layer 11.

[0047] Step 2: construct multiple equally spaced roof pre-splitting and pressure relief tunnels 2 in the key induced impact layer 11 determined in step 1 along the advancing direction perpendicular to the isolated island working face. Figure 2 and 3 As shown; the spacing between adjacent roof pre-splitting and pressure relief tunnels 2 should not be less than the radius of the fissure zone of the blast hole 1 to avoid overlapping blasting ranges between roof pre-splitting and pressure relief tunnels 2; the length of each roof pre-splitting and pressure relief tunnel 2 is determined according to the width of the isolated island working face. The number of roof pre-splitting and pressure relief tunnels 2 is determined according to the total advancement length of the isolated island working face and geological conditions. The specific determination formula is as follows:

[0048]

[0049] Where: N is the number of roof pre-cracking pressure relief tunnels 2, in units; L gis the length of the isolated working face, in meters (m); L is the spacing between the roof pre-cracking and pressure relief tunnels 2, in meters (m).

[0050] Step 3: In each roof pre-splitting and pressure relief tunnel 2 in step 2, multiple blasting holes 1 are constructed on both sides toward the rock masses on both sides, and each blasting hole 1 is parallel to the advancing direction of the isolated island working face. The blasting holes 1 arranged on both sides of the roof pre-splitting and pressure relief tunnel 2 are symmetrically distributed around the center of the roof pre-splitting and pressure relief tunnel 2 as shown in FIG. Figure 2 and 3 As shown; the diameter of the blasting hole 1 is determined according to the rock properties and the blasting charge, and the conventional aperture range is 42mm to 100mm; the spacing between adjacent blasting holes 1 in the same gang is determined according to the radius of the crushing zone and the radius of the fissure zone of the blasting hole 1, and is specifically determined as follows:

[0051] The spacing X is affected by the blasting range, so it is necessary to calculate the radius of the crushing zone and the radius of the fissure zone after the blasting of blast hole 1. Using the coupled charging method, the crushing zone radius is calculated as follows:

[0052]

[0053] The radius of the fracture zone is calculated as follows:

[0054]

[0055] Where: R c is the radius of the crushing zone, in millimeters (mm); R p is the radius of the crack zone, in millimeters (mm); b is the ratio of radial stress to tangential stress; S T is the uniaxial tensile strength of the key rock layer, in megapascals (MPa); ρ m is the density of the key rock layer, in kg / m 3 (kg / m 3 );D m is the velocity of the longitudinal wave, in meters per second (m / s); ρ0 is the density of the explosive, in kilograms per meter 3 (kg / m 3 ) ; D is the detonation velocity of the explosive, in meters per second (m / s); r b is the blast hole radius, in millimeters (mm); α is the stress wave attenuation index; r c is the charge diameter, in millimeters (mm); σ c is the uniaxial compressive strength of coal rock mass, in megapascals (MPa); B is the empirical coefficient; μ is Poisson's ratio.

[0056] The determination of the spacing X needs to ensure that the destruction zones (crushing zones and fissure zones) formed after the blasting of the blasting holes 1 are interconnected, so that the adjacent blasting holes 1 are connected to form a complete pressure relief zone; therefore, the spacing X value needs to be greater than the crushing zone radius R c and the radius of the crack zone R p However, if the spacing between blasting holes 1 is too large, the fracture zone cannot be penetrated, and the ideal pressure relief effect cannot be achieved; if the spacing between blasting holes is small, excessive pressure relief will occur, resulting in a waste of construction costs. c Usually smaller than the radius R of the fracture zone p , so the spacing X is taken as twice the radius of the crack area R p The effect is best.

[0057] The depth of each blast hole 1 is determined comprehensively based on the thickness of the key induced impact layer, rock properties, stress concentration area range and field test results, and it is necessary to ensure that the blasting range covers all stress concentration areas of the top plate of the working face. The charge amount of each blast hole 1 is determined comprehensively based on the rock layer position, thickness, strength and height of the key induced impact layer 11, ensuring that the energy of each blasting can form a sufficient pressure relief range.

[0058] Step 4: Divide each blasting hole 1 into multiple sections according to the hole depth, and divide the charge of each blasting hole 1 into multiple parts according to the number of sections. Charge and blast each blasting hole 1 in sequence from the deepest section to the hole mouth. The energy release of each blasting is accurately controlled by segmented blasting. At the same time, segmented blasting realizes continuous pressure relief in time and space, effectively releasing the stress of the key layer 11 that induces impact, thereby reducing the risk of roof-type impact.

[0059] Step 5: Monitor the stress changes of the isolated working face during the construction of steps 2 to 4 through online stress monitoring technology, and use microseismic monitoring to evaluate the pressure relief effect of the roof pre-crack pressure relief tunnel 2. If the pressure relief requirements are met, the pre-pressure relief construction of the isolated working face is completed, thereby reducing the risk of roof-type impact; if not, repeat step 4 and perform segmented blasting on each blasting hole 1 again until the pre-pressure relief effect of the isolated working face meets the pressure relief requirements and the pre-pressure relief construction is completed.

[0060] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact ground pressure mine, characterized in that: The specific steps are: Step 1: First identify the locations of the hard rock layers in the roof above the isolated island working face, and select the key layers that induce impact in each hard rock layer; Step 2: construct multiple equally spaced roof pre-splitting and pressure relief tunnels in the key induced impact layer determined in step 1 along the advancing direction perpendicular to the isolated island working face; the spacing between adjacent roof pre-splitting and pressure relief tunnels is determined according to the blasting range of the blasting hole, and the number of roof pre-splitting and pressure relief tunnels is determined according to the total advancing length of the isolated island working face and the geological conditions; Step 3: In each roof pre-splitting and pressure-relieving tunnel of step 2, multiple blasting holes are constructed on both sides toward the rock masses on both sides, and each blasting hole is parallel to the advancing direction of the isolated island working face; the diameter of the blasting hole is determined according to the rock properties and the blasting charge; the spacing between adjacent blasting holes in the same gang is determined according to the crushing zone radius and the fracture zone radius of the blasting hole; and the hole depth and charge of the blasting hole are determined according to the situation of the isolated island working face; Step 4: Divide each blast hole into multiple sections according to the hole depth, and divide the charge of each blast hole into multiple parts according to the number of sections. Charge and blast each blast hole in sequence from the deepest section to the hole mouth. The energy release of each blast is accurately controlled by segmented blasting. At the same time, segmented blasting realizes continuous pressure relief in time and space, effectively releasing the stress of the key layer of impact inducing, thereby reducing the risk of roof impact. Step 5. Monitor the stress changes of the isolated working face during the construction of steps 2 to 4 through online stress monitoring technology, and use microseismic monitoring to evaluate the pressure relief effect of the roof pre-crack pressure relief tunnel. If the pressure relief requirements are met, complete the pre-pressure relief construction of the isolated working face to reduce the risk of roof impact; if not, repeat step 4 to perform segmented blasting on each blasting hole again until the pre-pressure relief effect of the isolated working face meets the pressure relief requirements and the pre-pressure relief construction is completed.

2. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 1, characterized in that: The determination of the hard rock layer in step 1 is as follows: q (n+1)m <q (n)m (1) Where: q (n+1)m is the load of the n+1th rock layer on the mth rock layer; q (n)m is the load of the nth rock layer on the mth rock layer; When the load of the n+1th rock layer on the mth rock layer is less than the load of the nth rock layer on the mth rock layer, the nth rock layer is determined to be a hard rock layer; The key layers that induce impact are screened out from each hard rock layer as follows: Where: c is the impact energy ratio, which is the ratio of the total energy released by the coal body after the hard rock layer breaks to the minimum impact energy of the coal body; R T is the ultimate tensile strength of the hard rock layer; h is the thickness of the hard rock layer; e is the elastic modulus of the hard rock layer; Q is the overburden load of the hard rock layer; H is the distance between the earthquake source and the coal seam; η is the attenuation index; E c is the accumulated elastic energy of coal deformation; E0 is the minimum energy of coal impact failure; The impact energy ratio c of each hard rock layer is calculated according to the above formula, and the hard rock layer with impact energy ratio c ≥ 1 is regarded as the key impact inducing layer.

3. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 1, characterized in that: In the step 2, the spacing between adjacent roof pre-splitting and pressure relief tunnels should not be less than the radius of the blasting hole fissure zone to avoid overlapping blasting ranges between roof pre-splitting and pressure relief tunnels; the length of each roof pre-splitting and pressure relief tunnel is determined according to the width of the island working face.

4. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 3 is characterized in that: The specific formula for determining the number of roof pre-splitting and pressure relief tunnels in step 2 is as follows: Where: N is the number of roof pre-cracking pressure relief tunnels; L g is the length of the isolated working face; L is the spacing between the roof pre-cracking and pressure relief tunnels.

5. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 1, characterized in that: The spacing X between adjacent blast holes in the same gang in step 3 is specifically determined as follows: The spacing X is affected by the blasting range, so it is necessary to calculate the radius of the crushing zone and the radius of the fissure zone after the blasting hole is charged. Using the coupled charging method, the crushing zone radius is calculated as follows: The radius of the fracture zone is calculated as follows: Where: R c R is the radius of the crushing area; p is the radius of the crack area; b is the ratio of radial stress to tangential stress; S T is the uniaxial tensile strength of the rock in the key induced impact layer; m is the density of the key rock layer that induces impact; D m is the velocity of longitudinal wave; ρ0 is the density of explosive; D is the detonation velocity of explosive; r b is the blast hole radius; α is the stress wave attenuation index; r c is the charge diameter; σ c is the uniaxial compressive strength of coal rock mass; B is the empirical coefficient; μ is Poisson's ratio; The spacing X must be larger than the radius R of the crushing area c and the radius of the crack zone R p sum.

6. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 1, characterized in that: In the step 3, the blasting holes arranged on both sides of the roof pre-splitting and pressure relief tunnel are symmetrically distributed around the center of the roof pre-splitting and pressure relief tunnel.

7. The method for blasting pre-pressure relief and anti-bumping of isolated island working face in high gas impact rock pressure mine according to claim 1, characterized in that: The depth of the blasting hole in the step three is determined comprehensively based on the thickness of the key layer for inducing impact, the rock properties, the range of the stress concentration zone and the results of field tests; the charge of the blasting hole is determined comprehensively based on the rock layer position, thickness, strength and height of the key layer for inducing impact, to ensure that the energy of each blasting can form a sufficient pressure relief range.

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