Roof presplitting drilling parameter determining method for preventing rock burst of working face

Abstract

A roof presplitting drilling parameter determination method for preventing rock burst of a working face comprises the steps of determining an impact danger area of the working face according to a working face impact danger evaluation report, drilling a roadway roof in the impact danger area to take a rock core, and determining the lithology and thickness of a roof rock stratum and the distance to a coal seam. Determining a key layer position according to a key layer theory; carrying out strike presplitting blasting on a top plate with an impact dangerous area on the working surface along the strike of the roadway, wherein strike presplitting drill holes are arranged every 10-15m along the strike of the roadway; tilt presplitting blasting is carried out on a top plate with an impact dangerous area on a working face along the tendency of a roadway, a group of inclined presplitting drill holes are arranged every 10-15 m along the trend of the roadway, each group comprises n inclined presplitting drill holes, and n is larger than or equal to 2. According to the method, the pre-splitting drilling parameters are accurately determined, the coal seam roof is accurately broken, a better pressure relief effect is achieved, rock burst is prevented in advance, and safe production of a mine is guaranteed.

Description

Technical Field

[0001] The invention relates to a method for determining parameters of a roof pre-splitting drilling hole for preventing and controlling rock burst on a working face, and belongs to the technical field of safe mining of coal mines. Background Art

[0002] Rock burst is a typical mining dynamic phenomenon, which is extremely harmful to the normal production of coal mines. The hard roof above the coal mining face is one of the main factors affecting rock burst disasters. The thicker the hard rock layer, the less likely it is to fall off, the longer the suspended roof is, and the larger the exposed area is, thus accumulating more elastic energy. When the working face is in the stage of breaking the square, sub-critical layer or main critical layer, the impact risk is relatively high, and preventive measures need to be taken to break the hard roof in advance to avoid rock burst on the working face.

[0003] Due to the complex geological conditions of the mine, the thickness of the roof rock layer of the coal mining working face in different areas varies greatly. In order to prevent and control rock burst, the hard roof rock layer above the working face needs to be broken in advance. At present, the hard roof rock layer above the working face is mostly broken based on the pre-splitting drilling parameters determined by experience or drilling column chart. Due to the strong subjectivity, the accuracy of the parameters is difficult to guarantee, and it is impossible to meet the requirements of pre-splitting drilling to reasonably break the hard roof, and ultimately it is difficult to achieve the purpose of preventing the sudden collapse of the long-hanging roof from inducing rock burst. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining roof pre-splitting drilling parameters for preventing and controlling rock burst on a working face. The method can improve the accuracy of roof pre-splitting drilling parameters, reasonably break the hard roof, achieve early prevention of rock burst, and ensure the safety of mine production.

[0005] In order to achieve the above object, the present invention provides a method for determining parameters of roof pre-cracking drilling for preventing and controlling rock burst on a working face, comprising the following steps:

[0006] S1. Determine the area with impact hazard in the working face according to the impact hazard assessment report, drill holes in the tunnel roof in the impact hazard area to take cores, determine the lithology, thickness and distance of the roof rock layer from the coal seam, and determine the key layer position according to the key layer theory;

[0007] S2. Carry out strike pre-splitting blasting along the direction of the tunnel for the roof in the impact danger area of ​​the working face. The strike pre-splitting drill holes used for strike pre-splitting blasting are arranged every 10 to 15 meters along the direction of the tunnel;

[0008] S3. Pre-splitting blasting is carried out along the inclination of the tunnel for the roof in the impact hazard area of ​​the working face. The pre-splitting drill holes used for pre-splitting blasting are arranged in a group every 10 to 15 meters along the tunnel direction. Each group contains n pre-splitting drill holes, where n ≥ 2.

[0009] Furthermore, the angle between the strike pre-splitting borehole and the mining direction of the working face is not less than 70°, the hole depth is 15 to 20 m, the borehole diameter is 42 to 100 mm, the length of the charging section is not less than 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth.

[0010] Furthermore, in S3, each group of inclined pre-splitting boreholes includes inclined pre-splitting borehole A and inclined pre-splitting borehole B; the angle between the inclined pre-splitting borehole A and the horizontal plane is tan -1 (H / L), and the value is an integer multiple of 5. The drilling length of the pre-splitting borehole A is And take an integer value that is a multiple of 5, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; where L is the horizontal projection of the top plate of the key layer, and H is the vertical height of the top plate;

[0011] The inclined pre-splitting borehole B is used to blast the topmost key layer of rock within the vertical height H′, with an angle of 70° with the horizontal plane. The depth of the inclined pre-splitting borehole B is H / sin70°, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; wherein H′ is the theoretical pre-splitting height, in m.

[0012] Furthermore, the roof vertical height H is determined by the theoretical pre-splitting height H′. If H′≥50, then H is the vertical height of the upper interface of the uppermost key layer in H′ from the tunnel roof; if H′<50, then H=50; wherein the calculation formula of H′ is:

[0013]

[0014] Where, ∑M is the cumulative mining thickness, in m; R c It is the uniaxial compressive strength, in MPa.

[0015] Furthermore, the horizontal projection L of the top plate of the key layer satisfies:

[0016]

[0017] In the formula, σ ti is the tensile strength of the i-th key layer of rock within the vertical height H′, in MPa;

[0018] k i is the cracking coefficient of the i-th key rock layer within the vertical height H′, k = 0.25 ~ 0.75;

[0019] m i is the thickness of the i-th key layer within the vertical height H′, in m;

[0020] b is the inclined length of the working surface, in m;

[0021] γ i is the density of the key layer i within the vertical height H′, in N / m 3 ;

[0022] α is the inclination angle of the working surface.

[0023] Furthermore, the opening position of the inclined pre-splitting drilling hole is located at the top plate of the tunnel near the working face, and the spacing between adjacent inclined pre-splitting drilling holes is D, and the calculation formula of D is:

[0024]

[0025] Where S is the adjustment coefficient; r b is the radius of the blasthole, in m; f is the rock strength coefficient.

[0026] Further, in the case of (H / tan70°-L) / 10>1, the calculation formula for the number n of each group of inclined pre-splitting drill holes is:

[0027]

[0028] When n>2, the rock layer between the intersection of the inclined pre-splitting borehole A and the inclined pre-splitting borehole B at the uppermost key layer is divided equally according to the value of (H / tan70°-L) / 10+1, the end hole position of the added inclined pre-splitting borehole is located at the equal division position, the added borehole diameter is 42~100mm, the charging section length needs to be 1 / 2 of the borehole depth, and the sealing section length is not less than 1 / 3 of the borehole depth.

[0029] Furthermore, the length of the core drilled on the tunnel roof in the impact danger zone is at least 100m; the strike pre-splitting drill hole and the dip pre-splitting drill hole are both at least 200m ahead of the working face and mining surface.

[0030] The present invention determines the area with impact hazard of the working face according to the impact hazard assessment report, drills holes in the tunnel roof in the impact hazard area to take cores, determines the lithology, thickness and distance from the coal seam of the roof rock layer, and determines the key layer position according to the key layer theory; performs strike pre-splitting blasting on the roof of the working face with impact hazard area along the strike of the tunnel, and arranges one strike pre-splitting drill hole for strike pre-splitting blasting every 10 to 15 meters along the strike of the tunnel; performs inclination pre-splitting blasting on the roof of the working face with impact hazard area along the inclination of the tunnel, and arranges one group of inclination pre-splitting drill holes for inclination pre-splitting blasting every 10 to 15 meters along the strike of the tunnel, each group includes n inclination pre-splitting drill holes, n≥2, and the parameters of the inclination pre-splitting drill holes are determined according to the theoretical pre-splitting height and the maximum length of the roof cantilever. The present invention realizes accurate determination of pre-splitting drilling parameters, avoids the occurrence of the phenomenon that the main key layer is cut off due to too long drilling length and the key layer cannot be effectively cut off due to too short drilling length, and accurately breaks the coal seam roof in a targeted manner, achieves better pressure relief effect and early prevention of impact ground pressure, ensures the safety of mine production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the planar arrangement of the top plate strike pre-splitting drill holes and the inclination pre-splitting drill holes of the present invention;

[0032] Figure 2 It is a schematic diagram of the arrangement of the pre-splitting drilling holes in the top plate direction of the present invention;

[0033] Figure 3 1 is a schematic diagram of the arrangement of the roof inclination pre-splitting drill holes of the present invention when the number n=2;

[0034] Figure 4 It is a schematic diagram of the arrangement of the roof inclination pre-splitting drill holes when the number n>2 of the top plate in the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with the accompanying drawings.

[0036] like Figure 1 As shown, a method for determining parameters of roof pre-cracking drilling for preventing rock burst at a working face comprises the following steps:

[0037] S1. Determine the area with impact hazard in the working face according to the impact hazard assessment report, drill holes in the tunnel roof in the impact hazard area to take cores, determine the lithology, thickness and distance of the roof rock layer from the coal seam, and determine the key layer position according to the key layer theory;

[0038] S2, such as Figure 2 As shown, the top plate of the working face with impact danger area is subjected to strike pre-splitting blasting along the direction of the tunnel, and the strike pre-splitting drill holes used for strike pre-splitting blasting are arranged every 10 to 15 meters along the direction of the tunnel;

[0039] S3, such as Figure 3 As shown, the roof of the working face with impact danger area is subjected to pre-splitting blasting along the inclination of the tunnel. The pre-splitting drill holes used for pre-splitting blasting are arranged in a group every 10 to 15 m along the direction of the tunnel, and each group contains n pre-splitting drill holes, where n≥2.

[0040] As a preferred embodiment, Figure 2 As shown, the angle between the strike pre-splitting borehole and the mining direction of the working face is not less than 70°, the hole depth is 15 to 20 m, the borehole diameter is 42 to 100 mm, the length of the charging section is not less than 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth.

[0041] As a preferred embodiment, Figure 3 As shown, in S3, each group of inclined pre-splitting boreholes includes inclined pre-splitting borehole A and inclined pre-splitting borehole B; the angle between the inclined pre-splitting borehole A and the horizontal plane is tan -1 (H / L), and the value is an integer multiple of 5. The drilling length of the pre-splitting borehole A is And take an integer value that is a multiple of 5, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; where L is the horizontal projection of the top plate of the key layer, and H is the vertical height of the top plate;

[0042] The inclined pre-splitting borehole B is used to blast the topmost key layer of rock within the vertical height H′, with an angle of 70° with the horizontal plane. The depth of the inclined pre-splitting borehole B is H / sin70°, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; wherein H′ is the theoretical pre-splitting height, in m.

[0043] As a preferred embodiment, the vertical height H of the roof is determined by the theoretical pre-splitting height H′. If H′≥50, H is the vertical height of the upper interface of the uppermost key layer in H′ from the roof of the tunnel; if H′<50, H=50; wherein the calculation formula of H′ is:

[0044]

[0045] Where, ∑M is the cumulative mining thickness, in m; R c It is the uniaxial compressive strength, in MPa.

[0046] As a preferred embodiment, the horizontal projection L of the top plate of the key layer satisfies:

[0047]

[0048] In the formula, σ ti is the tensile strength of the i-th key layer of rock within the vertical height H′, in MPa;

[0049] k i is the cracking coefficient of the i-th key rock layer within the vertical height H′, k = 0.25 ~ 0.75;

[0050] m i is the thickness of the i-th key layer within the vertical height H′, in m;

[0051] b is the inclined length of the working surface, in m;

[0052] γ i is the density of the key layer i within the vertical height H′, in N / m 3 ;

[0053] α is the inclination angle of the working surface.

[0054] As a preferred embodiment, the inclined pre-splitting drilling hole opening position is located at the top plate of the tunnel near the working face side, and the spacing between adjacent inclined pre-splitting drilling hole groups is D, and the calculation formula of D is:

[0055]

[0056] Where S is the adjustment coefficient; r b is the radius of the blasthole, in m; f is the rock strength coefficient.

[0057] In order to improve the effect of decompression of the roof in the impact danger area of ​​the working face, when (H / tan70°-L) / 10>1, the calculation formula of the number n of each group of inclined pre-splitting drill holes is:

[0058]

[0059] like Figure 4 As shown, when n>2, the rock layer between the intersection of the inclined pre-splitting borehole A and the inclined pre-splitting borehole B at the topmost key layer is equally divided according to the value of (H / tan70°-L) / 10+1, the end hole position of the added inclined pre-splitting borehole is located at the equally divided position, the added borehole diameter is 42~100mm, the charging section length needs to be 1 / 2 of the borehole depth, and the sealing section length is not less than 1 / 3 of the borehole depth.

[0060] In order to improve the accuracy of judging the lithology, the length of the core drilled in the tunnel roof in the impact danger zone is at least 100m; in order to prevent the impact on the working face, the strike pre-splitting drill hole and the dip pre-splitting drill hole are both at least 200m ahead of the working face and the mining face.

Claims

1. A method for determining parameters of roof pre-splitting drilling for preventing rock burst at a working face, characterized in that: The steps include: S1. Determine the area with impact hazard in the working face according to the impact hazard assessment report, drill holes in the tunnel roof in the impact hazard area to take cores, determine the lithology, thickness and distance of the roof rock layer from the coal seam, and determine the key layer position according to the key layer theory; S2. Carry out strike pre-splitting blasting along the direction of the tunnel for the roof in the impact danger area of ​​the working face. The strike pre-splitting drill holes used for strike pre-splitting blasting are arranged every 10 to 15 meters along the direction of the tunnel; S3. Pre-splitting blasting is carried out along the inclination of the tunnel for the roof in the impact hazard area of ​​the working face. The pre-splitting drill holes used for pre-splitting blasting are arranged in a group every 10 to 15 meters along the tunnel direction. Each group contains n pre-splitting drill holes, where n ≥ 2.

2. The method for determining parameters of roof pre-splitting drilling for preventing and controlling rock burst in a working face according to claim 1 is characterized in that: In S2, the angle between the strike pre-splitting borehole and the mining direction of the working face is not less than 70°, the hole depth is 15 to 20 m, the borehole diameter is 42 to 100 mm, the length of the charging section is not less than 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth.

3. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 1 is characterized in that: In S3, each group of inclined pre-splitting boreholes includes inclined pre-splitting borehole A and inclined pre-splitting borehole B; the angle between the inclined pre-splitting borehole A and the horizontal plane is tan -1 (H / L), and the value is an integer multiple of 5. The drilling length of the pre-splitting borehole A is And take an integer value that is a multiple of 5, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; where L is the horizontal projection of the top plate of the key layer, and H is the vertical height of the top plate; The inclined pre-splitting borehole B is used to blast the topmost key layer of rock within the vertical height H′, with an angle of 70° with the horizontal plane. The depth of the inclined pre-splitting borehole B is H / sin70°, the borehole diameter is 42 to 100 mm, the length of the charging section is 1 / 2 of the borehole depth, and the length of the sealing section is not less than 1 / 3 of the borehole depth; wherein H′ is the theoretical pre-splitting height, in m.

4. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 3 is characterized in that: The roof vertical height H is determined by the theoretical pre-splitting height H′. If H′≥50, then H is the vertical height of the upper interface of the topmost key layer in H′ from the tunnel roof; if H′<50, then H=50; the calculation formula of H′ is: Where, ∑M is the cumulative mining thickness, in m; R c It is the uniaxial compressive strength, in MPa.

5. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 3 is characterized in that: The horizontal projection L of the top plate of the key layer satisfies: In the formula, σ ti is the tensile strength of the i-th key layer of rock within the vertical height H′, in MPa; k i is the cracking coefficient of the i-th key rock layer within the vertical height H′, k = 0.25 ~ 0.75; m i is the thickness of the i-th key layer within the vertical height H′, in m; b is the oblique length of the working surface, in m; γ i is the density of the key layer i within the vertical height H′, in N / m 3 ; α is the inclination angle of the working surface.

6. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 3 is characterized in that: The opening position of the inclined pre-splitting drilling hole is located at the top plate of the tunnel near the working face side, and the spacing between adjacent inclined pre-splitting drilling holes is D, and the calculation formula of D is: Where S is the adjustment coefficient; r b is the radius of the blasthole, in m; f is the rock strength coefficient.

7. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 3 is characterized in that: When (H / tan70°-L) / 10>1, the calculation formula for the number n of each group of inclined pre-splitting boreholes is: When n>2, the rock layer between the intersection of the inclined pre-splitting borehole A and the inclined pre-splitting borehole B at the uppermost key layer is divided equally according to the value of (H / tan70°-L) / 10+1, the end hole position of the added inclined pre-splitting borehole is located at the equal division position, the added borehole diameter is 42~100mm, the charging section length needs to be 1 / 2 of the borehole depth, and the sealing section length is not less than 1 / 3 of the borehole depth.

8. The method for determining parameters of roof pre-splitting drilling for preventing rock burst in a working face according to claim 1, characterized in that: The length of the core drilled on the tunnel roof in the impact danger zone is at least 100m; the strike pre-splitting drill hole and the dip pre-splitting drill hole are both at least 200m ahead of the working face and mining surface.

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