A method for arranging a continuous mining protected layer working face and an empty roadway

Abstract

A method for arranging roadways in the goaf of a continuously mined protected seam, the method comprising: calculating the range x1 of the ultimate stress equilibrium zone of the lateral coal body in the goaf; and calculating the horizontal distance x from the boundary line of the stress reduction zone to the edge of the protective seam coal pillar. f Compare x1 and x f The invention determines whether the width of the limit equilibrium zone is entirely within the stress reduction zone; it calculates the distance L2 from the peak stress point of the protective layer coal pillar to the edge of the coal pillar; it calculates the periodic caving step distance of the overlying rock of the protective layer; it calculates the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf; it determines the distance x′ from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area; it determines the position of the stress peak point in the coal seam based on the distance L2, and then determines the location of the goaf roadway based on x′, that is, the goaf roadway is placed at the lowest stress point of the coal and rock mass below the protective layer. This invention can determine the reasonable location of the goaf roadway and reduce the impact risk of the goaf roadway.

Description

Technical Field

[0001] This invention relates to a method for arranging working roadways facing the working face of a protected layer in continuous mining, belonging to the field of coal mine safety mining technology. Background Technology

[0002] Rockburst is a typical dynamic phenomenon in mining and is extremely hazardous. This dynamic phenomenon releases a large amount of elastic deformation energy accumulated in the coal and rock mass in a rapid and violent manner, causing the coal and rock mass to break up and generating strong vibrations. The force throws the broken coal and rock into the mining tunnel, producing loud noises, causing equipment damage, tunnel destruction, and casualties.

[0003] Traditional discontinuous single-face protective layer mining methods require the establishment of relatively wide coal pillars between the protected working faces to ensure that the protected working faces are within the effective protection range of the protective layer. However, this arrangement contradicts the principle that narrow coal pillars are preferable for rockburst-prone coal seams. In other words, when narrow coal pillars are left between the protected working faces to form continuous mining, the risk of rockburst disasters is lower.

[0004] For multi-seam mining, mining the upper protective layer first protects the coal seams below within the effective pressure relief range, effectively reducing the impact risk of subsequent coal seams. Currently, extensive research has been conducted on the pressure relief effect after mining the upper protective layer, but research on continuous mining of accessible roadways within the protected layer is relatively limited, failing to meet the needs of safe coal mining. Summary of the Invention

[0005] The purpose of this invention is to provide a method for arranging access roadways in the working face of protected layers during continuous mining. This method can determine the reasonable location of access roadways, reduce the impact risk of access roadways, and ensure safe mining in coal mines.

[0006] To achieve the above objectives, the present invention provides a method for arranging roadways for continuous mining of protected strata facing open space, comprising the following steps:

[0007] S1. Calculate the range of the ultimate stress equilibrium zone of the lateral coal body in the goaf. The calculation formula is as follows:

[0008]

[0009] Where H represents the coal seam thickness in meters (m); x1 represents the width of the limit equilibrium zone in meters (m); and m represents the coal seam mining height. γ is the internal friction angle of the coal seam, reflecting the magnitude of the internal friction force between particles within the coal and rock mass; k is the stress concentration factor of the coal mass; γ is the average density of the rock strata; C0 is the cohesion of the coal mass; P x The lateral constraint force of the goaf of the protected layer on the coal pillar; A represents the proportionality coefficient;

[0010] S2, Calculate the horizontal distance x from the edge of the protective coal pillar to the stress reduction dividing line. f The calculation formula is:

[0011]

[0012] Where, x f The horizontal distance from the stress reduction boundary line to the edge of the coal pillar is expressed in meters (m); h f The depth of the roadway from the coal seam floor is expressed in meters (m); α represents the coal seam dip angle; δ represents the stress transfer angle of the floor; and L0 represents the length of the coal seam working face in meters (m).

[0013] S3. Compare x1 and x f The magnitude of x1 is used to determine whether the width of the limit equilibrium region is entirely within the stress reduction region: x1≤x f When x1 > x, it means the entire roadway is located in a stress-reduced zone, and there is no risk of impact. f When this occurs, it means that the roadways are not all located within the stress reduction zone, and roadways should be avoided being located outside the stress reduction zone.

[0014] S4. Calculate the distance from the peak stress point of the protective coal pillar to the edge of the coal pillar. The calculation formula is as follows:

[0015]

[0016] Where m′ represents the mining height of the protective layer; L2 represents the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar; L1 is the width of the protective layer coal pillar area, in meters;

[0017] S5. Calculate the periodic caving step distance of the overlying surrounding rock of the protective layer. The calculation formula is as follows:

[0018]

[0019] Among them, L w The unit is the periodic collapse step distance of the overlying rock layer, in meters; σ is the tensile strength of the top rock layer, in Pa; H′ is the height of the top rock layer, in meters; q is the pressure exerted by the overlying rock layer on the top rock, in Pa.

[0020] S6. Calculate the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf. The calculation formula is:

[0021] L3 = 2.5L w ;

[0022] Where L3 represents the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf, in meters;

[0023] S7. Determine the distance from the lowest stress point in the coal and rock mass below the protective layer to the peak stress point in the coal pillar area. The calculation formula is as follows:

[0024]

[0025] Where x′ represents the distance from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area, in meters;

[0026] S8. First, based on L2 obtained from S4, which is the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar, since the position of the coal pillar is determined, the position of the peak stress point in the coal seam is obtained; then, based on x′ obtained from S7, the distance x′ from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area is the location of the access roadway. This location is the location of the lowest stress point in the access roadway, which is the optimal location.

[0027] Furthermore, in S1, P x The formulas for calculating A and B are as follows:

[0028] P x =KHC;

[0029] Where K represents the ratio of the elastic modulus of the coal seam to the elastic modulus of the rock strata; H represents the thickness of the coal seam, in meters; and C represents the lateral constraint coefficient, reflecting the degree of constraint between the coal seam and the surrounding rock.

[0030] A = (μ / (1-μ));

[0031] Where μ represents Poisson's ratio.

[0032] This invention calculates the pressure relief range and angle after mining the upper protective layer to determine the optimal location for the exposed roadways. The rationality of the roadway layout is then verified by calculating the vertical stress at the location of these exposed roadways. This provides theoretical guidance for determining whether adjustments to the exposed roadway layout are necessary for subsequent continuous mining operations. This invention ensures safe coal mining and has significant practical implications and substantial social benefits for continuous safe production in protective layer mining operations, with broad application prospects. Attached Figure Description

[0033] Figure 1 This is a flowchart of the method of the present invention;

[0034] Figure 2 This is a schematic diagram of continuous mining of the protective layer according to the present invention;

[0035] Figure 3 This is a schematic diagram of the stress distribution around the air-supported tunnel of the present invention. Detailed Implementation

[0036] The invention will now be further described with reference to the accompanying drawings.

[0037] like Figure 1 As shown, a method for arranging roadways for continuous mining of protected layers facing open areas includes the following steps:

[0038] S1. Calculate the range of the ultimate stress equilibrium zone of the lateral coal body in the goaf. The calculation formula is as follows:

[0039]

[0040] Where H represents the coal seam thickness in meters (m); x1 represents the width of the limit equilibrium zone in meters (m); and m represents the coal seam mining height. γ is the internal friction angle of the coal seam, reflecting the magnitude of the internal friction force between particles within the coal and rock mass; k is the stress concentration factor of the coal mass; γ is the average density of the rock strata; C0 is the cohesion of the coal mass; P x The lateral constraint force of the goaf of the protected layer on the coal pillar; A represents the proportionality coefficient;

[0041] S2, Calculate the horizontal distance x from the edge of the protective coal pillar to the stress reduction dividing line. f The calculation formula is:

[0042]

[0043] Where, x f The horizontal distance from the stress reduction boundary line to the edge of the coal pillar is expressed in meters (m); h f The depth of the roadway from the coal seam floor is expressed in meters (m); α represents the coal seam dip angle; δ represents the stress transfer angle of the floor; and L0 represents the length of the coal seam working face in meters (m).

[0044] S3. Compare x1 and x f The magnitude of x1 is used to determine whether the width of the limit equilibrium region is entirely within the stress reduction region: x1≤x f When x1 > x, it means the entire roadway is located in a stress-reduced zone, and there is no risk of impact. f When this occurs, it means that the roadways are not all located within the stress reduction zone, and roadways should be avoided being located outside the stress reduction zone.

[0045] S4, such as Figure 2 and Figure 3 As shown, the distance from the peak stress point of the protective coal pillar to the edge of the coal pillar is calculated using the following formula:

[0046]

[0047] Where m′ represents the mining height of the protective layer; L2 represents the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar; L1 is the width of the protective layer coal pillar area, in meters;

[0048] S5. Calculate the periodic caving step distance of the overlying surrounding rock of the protective layer. The calculation formula is as follows:

[0049]

[0050] Among them, L w The unit is the periodic collapse step distance of the overlying rock layer, in meters; σ is the tensile strength of the top rock layer, in Pa; H′ is the height of the top rock layer, in meters; q is the pressure exerted by the overlying rock layer on the top rock, in Pa.

[0051] S6. Calculate the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf. The calculation formula is:

[0052] L3 = 2.5L w ;

[0053] Where L3 represents the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf, in meters;

[0054] S7. Determine the distance from the lowest stress point in the coal and rock mass below the protective layer to the peak stress point in the coal pillar area. The calculation formula is as follows:

[0055]

[0056] Where x′ represents the distance from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area, in meters;

[0057] S8. First, based on L2 obtained from S4, which is the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar, since the position of the coal pillar is determined, the position of the peak stress point in the coal seam is obtained; then, based on x′ obtained from S7, the distance x′ from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area is the location of the access roadway. This location is the location of the lowest stress point in the access roadway, which is the optimal location.

[0058] Furthermore, P x The formulas for calculating A and B are as follows:

[0059] P x =KHC;

[0060] Where K represents the ratio of the elastic modulus of the coal seam to the elastic modulus of the rock strata; H represents the thickness of the coal seam, in meters; and C represents the lateral constraint coefficient, reflecting the degree of constraint between the coal seam and the surrounding rock.

[0061] A = μ / (1-μ);

[0062] Where μ represents Poisson's ratio.

[0063] A rockburst manifestation has occurred in the accessible roadway of a protected layer mine. The location of the accessible roadway in this mine has a potential rockburst hazard. The steps for determining the location of the accessible roadway are as follows:

[0064] (1) The coal seam mining height is 10m, Poisson's ratio is 0.5, internal friction angle is 20°, stress concentration factor is 2, and average rock density is 2.5t / m³. 3 With a burial depth of 1200m, a cohesion of 2MPa, and a lateral constraint force of 0, the width of the limit equilibrium zone can be calculated.

[0065] (2) The depth of the goaf from the coal seam floor is 10m, the dip angle of the coal seam is 15°, the vertical stress transfer angle of the coal seam floor is 20°, and the minimum distance from the stress reduction zone to the edge of the coal pillar is:

[0066] (3) Since x1 is calculated to be less than x f0 The ultimate equilibrium zone of the mine is not entirely within the stress reduction zone. It is necessary to find the point of lowest stress to arrange the roadways and avoid arranging the roadways outside the stress reduction zone.

[0067] (4) With a working height of 4m, a Poisson's ratio of 0.5, an internal friction angle of 20°, and a rock pillar width of 5m, determine the location of the peak stress point under the coal-rock pillar of the protective layer:

[0068] (5) The tensile strength of the top stratum is 8.1 MPa, the height of the top stratum is 20 m, and the pressure of the overlying stratum on the top stratum is 10 MPa. Therefore, the periodic collapse step distance is...

[0069] (6) With a periodic collapse step distance of 6m, calculate the distance from the peak stress point of the protective layer goaf to the edge of the goaf: L3 = 2.5L w =15m;

[0070] (7) Formula for calculating the location of the lowest stress point in the coal and rock mass below the protective layer:

[0071] (8) The location of the continuous mining protected layer roadway in the mine is 8.25m away from the edge of the coal pillar. The calculated stress is the lowest and the possibility of rockburst event is the lowest. The optimized layout of the roadway is reasonable.

Claims

1. A method for arranging roadways in the working face of a protected layer during continuous mining, characterized in that, Includes the following steps: S1. Calculate the range of the ultimate stress equilibrium zone of the lateral coal body in the goaf. The calculation formula is as follows: Where H represents the coal seam thickness in meters (m); x1 represents the width of the limit equilibrium zone in meters (m); and m represents the coal seam mining height. γ is the internal friction angle of the coal seam, reflecting the magnitude of the internal friction force between particles within the coal and rock mass; k is the stress concentration factor of the coal mass; γ is the average density of the rock strata; C0 is the cohesion of the coal mass; P x The lateral constraint force of the goaf of the protected layer on the coal pillar; A represents the proportionality coefficient; S2, Calculate the horizontal distance x from the edge of the protective coal pillar to the stress reduction dividing line. f The calculation formula is: Where, x f The horizontal distance from the stress reduction boundary line to the edge of the coal pillar is expressed in meters (m); h f The depth of the roadway from the coal seam floor is expressed in meters (m); α represents the coal seam dip angle; δ represents the stress transfer angle of the floor; and L0 represents the length of the coal seam working face in meters (m). S3. Compare x1 and x f The magnitude of x1 is used to determine whether the width of the limit equilibrium region is entirely within the stress reduction region: when x1 ≤ x f When x1 > x, it means the entire roadway is located in a stress-reduced zone, and there is no risk of impact. f When this occurs, it means that the roadways are not all located within the stress reduction zone, and roadways should be avoided being located outside the stress reduction zone. S4. Calculate the distance from the peak stress point of the protective coal pillar to the edge of the coal pillar. The calculation formula is as follows: Where m' represents the mining height of the protective layer; L2 represents the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar; L1 is the width of the protective layer coal pillar area, in meters. S5. Calculate the periodic caving step distance of the overlying surrounding rock of the protective layer. The calculation formula is as follows: Among them, L w The periodic collapse step distance of the overlying rock layer is given in meters; σ is the tensile strength of the top rock layer in Pa; H' is the height of the top rock layer in meters; and q is the pressure exerted by the overlying rock layer on the top rock layer in Pa. S6. Calculate the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf. The calculation formula is: L3=2.5L w ; Where L3 represents the distance from the peak stress point of the compacted zone of the protective layer goaf to the edge of the goaf, in meters; S7. Determine the distance from the lowest stress point in the coal and rock mass below the protective layer to the peak stress point in the coal pillar area. The calculation formula is as follows: Where x' represents the distance from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area, in meters; S8. First, based on L2 obtained from S4, which is the distance from the peak stress point of the protective layer coal pillar to the edge of the coal pillar, since the position of the coal pillar is determined, the position of the peak stress point in the coal seam is obtained; then, based on x' obtained from S7, the distance x' from the lowest stress point of the coal and rock mass below the protective layer to the peak stress point of the coal pillar area is the location of the access roadway. This location is the location of the lowest stress point in the access roadway, which is the optimal location.

2. The method for arranging roadways for continuous mining of protected layers facing open space according to claim 1, characterized in that, P in S1 x The formulas for calculating A and B are as follows: P x =KHC; Where K represents the ratio of the elastic modulus of the coal seam to the elastic modulus of the rock strata; H represents the thickness of the coal seam, in meters; and C represents the lateral constraint coefficient, reflecting the degree of constraint between the coal seam and the surrounding rock. A = μ / (1-μ); Where μ represents Poisson's ratio.

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