A method for determining a site-specific optimal p-wave velocity constant

Abstract

A method for determining the optimal P-wave velocity constant in the field, first determine the station and the shooting position coordinates which need to be corrected, select the distance between each source and the farthest station corresponding to it, calculate the reasonable charge of each source according to the distance, after shooting according to the regulations, use the SOS microseismic monitoring system to calculate the theoretical coordinates of each source, calculate the cumulative error between the theoretical coordinates of the source and the actual shooting position coordinates corresponding to it, finally adjust the P-wave velocity constant V continuously, so that the total error reaches the minimum value, at this time V is the optimal wave velocity in the field. This method realizes the optimal wave velocity constant for the field environment, improves the accuracy of the microseismic monitoring system, provides reliable data basis for subsequent impact risk judgment, and reduces the unstable factors of coal production.

Description

Technical Field

[0001] This invention relates to a method for determining the optimal constant value of P-wave velocity in a field, belonging to the field of coal mine safety technology. Background Technology

[0002] Currently, microseismic monitoring systems collect, process, and analyze information such as microseismic signals, locations, and energy released during the fracturing process of coal and rock masses. This allows for the study of stress distribution characteristics within coal mine rock masses and the evolution of coal and rock strata fracturing patterns. The systems monitor and prevent dynamic disasters occurring in coal mines and have been widely used in domestic coal mines, providing a guarantee for safe mining.

[0003] However, in the actual use of microseismic monitoring systems, the P-wave velocity constant, a key parameter used to determine the location and energy of the seismic source, is often manually determined based on long-term experience. In reality, due to various factors such as geographical environment, actual working face structure, and different rock properties, P-wave velocities often differ between mines and working faces. Therefore, the use of empirical values ​​inevitably leads to a decrease in the accuracy of the microseismic monitoring system; if the manually determined P-wave velocity constant deviates significantly from the actual value, subsequent shock hazard assessments are also likely to be significantly inaccurate, adding instability to coal mine production. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method for determining the optimal P-wave velocity constant value in the field. This method can obtain the optimal wave velocity constant value for the field environment, improve the accuracy of the microseismic monitoring system, provide a reliable data basis for subsequent impact hazard assessment, and reduce the instability factors in coal mine production.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a method for determining the optimal P-wave velocity constant value in the field, comprising the following steps:

[0006] (1) Determine the stations that require wave velocity constant correction and their coordinates (X). i ,Y i Z i The coordinates of the location where the blasting operation was carried out, i.e., the coordinates of the seismic source (X). j0 ,Y j0 Z j0 );

[0007] (2) The average value N of the ambient noise energy intensity at the site was obtained using the SOS microseismic monitoring system;

[0008] (3) Select the farthest station ii corresponding to each seismic source j, and calculate the distance r between them. j ii and j are the station and source numbers, respectively;

[0009] (4) Based on the distance r obtained in step (3) j The appropriate charge P for each blasting point was calculated using the formula for vibration wave attenuation with propagation distance and the formula for explosive energy release. e And ensure that the signal-to-noise ratio of the microseismic signal is greater than 3;

[0010] (5) The charge amount P calculated in step (4) e Blasting operations were carried out at each blasting point in accordance with the mine's safe operating procedures.

[0011] (6) Using the SOS microseismic monitoring system to mark the arrival time of P waves, the theoretical coordinates of each seismic source were obtained. The theoretical coordinates of each earthquake source The coordinates of each blasting point, i.e., each seismic source (X) j0 ,Y j0 Z j0 By comparison, the total error Δr is calculated;

[0012] (7) Continuously adjust the constant value V of P-wave velocity and repeat step (6) until the total error Δr reaches the minimum value. At this time, V is the optimal wave velocity on site.

[0013] Furthermore, in step (3), the farthest station ii corresponding to each seismic source j and the distance r between them are... j The steps to obtain are as follows:

[0014] a. The distance between each seismic source and each station is calculated using the following distance formula:

[0015]

[0016] b. For each seismic source, select the largest distance from the distances calculated in step a as r. j That is, r j =max{r j-i}

[0017] Furthermore, in step (4), the appropriate charge amount P e The solution steps are as follows:

[0018] a. Based on the distance r corresponding to each seismic source j obtained in step (3). j In addition, the formula for seismic wave attenuation with distance is used to calculate the minimum energy threshold required to be received by the farthest station ii corresponding to each seismic source j, while ensuring that the signal-to-noise ratio of the microseismic signal is greater than 3. The calculation formula is as follows:

[0019]

[0020] In the formula, E j distance r from the epicenterj The energy received by the station at that location;

[0021] E j0 The initial energy of earthquake source j;

[0022] α is the vibration wave propagation attenuation factor;

[0023] b. Based on the minimum energy threshold required to be received by each farthest station obtained in step a, calculate the minimum charge required for each corresponding blasting point, and take the maximum value as the actual charge for each blasting point in this blasting operation, so that each station can receive a complete and clear signal. The specific formula is as follows:

[0024]

[0025] P e =MAX{P ej};

[0026] In the formula, E p Theoretical energy released per unit of explosive;

[0027] P ej The amount of explosives fired at blasting point J;

[0028] K S : The ratio of induced energy to total energy of explosives.

[0029] Furthermore, in step (6), the theoretical coordinates of the earthquake source... The steps for solving the total error Δr are as follows:

[0030] a. By accurately acquiring microseismic signals from microseismic signal monitoring stations, and then implementing P-wave arrival time marking on these signals, the specific time of the seismic wave arrival at station ii can be obtained, denoted as t. i Based on the characteristics of vibration wave propagation, the following equations are derived:

[0031]

[0032] The equation has four unknowns: t0, X, ... j0 Y j0 Z j0 The system of simultaneous equations can be solved when there are four equations. In practice, there are usually more than four equations, in which case the least squares estimate is used to obtain the theoretical coordinates of the earthquake source.

[0033] b. Based on the theoretical coordinates of each seismic source obtained in step a. The actual coordinates (X, Y) of the epicenter can be obtained using the Euclidean distance formula. j0 ,Y j0 Z j0The distance difference between the values ​​is summed to obtain the total error under the constant wave velocity, denoted as Δr. The calculation formula is as follows:

[0034]

[0035] Furthermore, in step (7), the adjustment of the P-wave velocity constant V adopts a bisection method, and the specific steps are as follows:

[0036] a. Define Vmax, Vmin, and n, where Vmax and Vmin are the maximum and minimum propagation velocities of seismic waves under various lithological conditions in the field environment, respectively; n is the number of iterations for this calculation, initially n = 0;

[0037] b. Among them, V n V′ n V″ n These represent the wave velocity magnitudes at 1 / 4, 1 / 2, and 3 / 4 of the range [Vmin, Vmax], respectively; V n V′ n V″ n The values ​​are all taken from the nearest multiple of 50.

[0038] c. V n V′ n V″ n The error is calculated according to step (6), and the corresponding error is denoted as Δr. n , Δr′ n ,Δr″ n ;

[0039] d. If Δr′ n If the minimum value is Vmax, then Vmax = V n V n+1 =V′ n If Δr n If the minimum value is reached, then Vmax = V″ n V min =V′ n If V″ n If the minimum value is reached, then Vmin = V n V n+1 =V″ n ;

[0040] en = n + 1;

[0041] f. Repeat steps b through e until V. n =V n-1 .

[0042] This invention, based on the existing microseismic monitoring system and network layout, first identifies the stations requiring wave velocity constant correction and the coordinates of blasting locations. It then selects the distance between each seismic source (blasting location) and its corresponding farthest station, calculates the appropriate charge amount for each source based on this distance, and performs blasting operations according to procedures. The SOS microseismic monitoring system is then used to calculate the theoretical coordinates of each source. By calculating the cumulative error between the theoretical coordinates and the corresponding actual blasting location coordinates, the P-wave velocity constant V is continuously adjusted until the total error reaches its minimum. This V represents the optimal wave velocity on-site. This method achieves the optimal wave velocity constant for the specific on-site environment, improves the accuracy of the microseismic monitoring system, provides a reliable data foundation for subsequent impact hazard assessment, and reduces instability factors in coal mine production. Furthermore, this method requires minimal space, is quick to implement, does not affect working face production, offers high operational safety, and is highly feasible. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the workflow of the present invention;

[0044] Figure 2 In this invention, r is the distance between each seismic source and its corresponding farthest station. j A schematic diagram;

[0045] Figure 3 This is a schematic diagram illustrating the relationship between error and wave speed with the number of iterations in an embodiment of the present invention. Detailed Implementation

[0046] The invention will now be further described with reference to the accompanying drawings.

[0047] like Figure 1 and Figure 2 As shown, a method for determining the optimal P-wave velocity constant in the field includes the following steps:

[0048] (1) Determine the stations that require wave velocity constant correction and their coordinates (X). i ,Y i Z i The coordinates of the location where the blasting operation was carried out, i.e., the coordinates of the seismic source (X). j0 ,Y j0 Z j0 );

[0049] (2) The average value N of the ambient noise energy intensity at the site was obtained using the SOS microseismic monitoring system;

[0050] (3) Select the farthest station i corresponding to each seismic source j, and calculate the distance r between them. j i and j are the station and source numbers, respectively;

[0051] (4) Based on the distance r obtained in step (3) j The appropriate charge P for each blasting point was calculated using the formula for vibration wave attenuation with propagation distance and the formula for explosive energy release. e And ensure that the signal-to-noise ratio of the microseismic signal is greater than 3;

[0052] (5) The charge amount P calculated in step (4) e Blasting operations were carried out at each blasting point in accordance with the mine's safe operating procedures.

[0053] (6) Using the SOS microseismic monitoring system to mark the arrival time of P waves, the theoretical coordinates of each seismic source were obtained. The theoretical coordinates of each earthquake source The coordinates of each blasting point, i.e., each seismic source (X) j0 ,Y j0 Z j0 By comparison, the total error Δr is calculated;

[0054] (7) Continuously adjust the constant value V of P-wave velocity and repeat step (6) until the total error Δr reaches the minimum value. At this time, V is the optimal wave velocity on site.

[0055] Furthermore, in step (3), the farthest station i corresponding to each seismic source j and the distance r between them are... j The steps to obtain are as follows:

[0056] a. The distance between each seismic source and each station is calculated using the following distance formula:

[0057]

[0058] b. For each seismic source, select the largest distance from the distances calculated in step a as r. j That is, r j =max{r j-i}

[0059] Furthermore, in step (4), the appropriate charge amount P e The solution steps are as follows:

[0060] a. Based on the distance r corresponding to each seismic source j obtained in step (3). j In addition, the formula for seismic wave attenuation with distance is used to calculate the minimum energy threshold required to be received by the farthest station ii corresponding to each seismic source j, while ensuring that the signal-to-noise ratio of the microseismic signal is greater than 3. The calculation formula is as follows:

[0061]

[0062] In the formula, W j distance r from the epicenter jThe energy received by the station at that location;

[0063] E j0 The initial energy of earthquake source j;

[0064] α is the vibration wave propagation attenuation factor;

[0065] b. Based on the minimum energy threshold required to be received by each farthest station obtained in step a, calculate the minimum charge required for each corresponding blasting point, and take the maximum value as the actual charge for each blasting point in this blasting operation, so that each station can receive a complete and clear signal. The specific formula is as follows:

[0066]

[0067] P e =MAX{P ej};

[0068] In the formula, E p Theoretical energy released per unit of explosive;

[0069] P ej The amount of explosives fired at blasting point J;

[0070] K S : The ratio of induced energy to total energy of explosives.

[0071] Furthermore, in step (6), the theoretical coordinates of the earthquake source... The steps for solving the total error Δr are as follows:

[0072] a. By accurately acquiring microseismic signals from microseismic signal monitoring stations, and then implementing P-wave arrival time marking on these signals, the specific time of the seismic wave arrival at station i can be obtained, denoted as t. i Based on the characteristics of vibration wave propagation, the following equations are derived:

[0073]

[0074] The equation has four unknowns: t0, X, ... j0 Y j0 Z j0 The system of simultaneous equations can be solved when there are four equations. In practice, there are usually more than four equations, in which case the least squares estimate is used to obtain the theoretical coordinates of the earthquake source.

[0075] b. Based on the theoretical coordinates of each seismic source obtained in step a. The actual coordinates (X, Y) of the epicenter can be obtained using the Euclidean distance formula. j0 ,Y j0 Z j0The distance difference between the values ​​is summed to obtain the total error under the constant wave velocity, denoted as Δr. The calculation formula is as follows:

[0076]

[0077] Furthermore, in step (7), the adjustment of the P-wave velocity constant V adopts a bisection method, and the specific steps are as follows:

[0078] a. Define Vmax, Vmin, and n, where Vmax and Vmin are the maximum and minimum propagation velocities of seismic waves under various lithological conditions in the field environment, respectively; n is the number of iterations for this calculation, initially n = 0;

[0079] b. Among them, V n V′ n V″ n These represent the wave velocity magnitudes at 1 / 4, 1 / 2, and 3 / 4 of the range [Vmin, Vmax], respectively; V n V′ n V″ n The values ​​are all taken from the nearest multiple of 50.

[0080] c. V n V′ n 、V″ n The error is calculated according to step (6), and the corresponding error is denoted as Δr. n , Δr′ n ,Δr″ n ;

[0081] d. If Δr′ n If the minimum value is Vmax, then Vmax = V n V n+1 =V′ n If Δr n If the minimum value is reached, then Vmax = V″ n V min =V′ n If V″ n If the minimum value is reached, then Vmin = V n V n+1 =V″ n ;

[0082] en = n - n + 1;

[0083] f. Repeat steps b through e until V. n =V n-1 .

[0084] Example:

[0085] For a specific coal mine, the steps for determining the constant value of the P-wave velocity at the site are as follows:

[0086] (1) Determine the stations 1, 4, 5, 7, 14, 17, and 20 that require P-wave velocity constant V correction, and their coordinates (X). i ,Y i Z i The coordinates of the location where the blasting operation was carried out, i.e., the coordinates of the seismic source (X). j0 ,Y j0 Z j0 The results are shown in Table 1 and Table 2, respectively:

[0087] Table 1. Station coordinates for the proposed corrected wave velocity constant.

[0088]

[0089] Table 2. Coordinates of the locations where blasting operations are planned.

[0090]

[0091] (2) The average environmental noise energy intensity at the site was obtained using the SOS microseismic monitoring system, N = 1.0E-37;

[0092] (3) Calculate the distance between each seismic source and its corresponding farthest station:

[0093] 301) The distance to each seismic source was calculated using the Euclidean distance formula, and the results are shown in Table 3:

[0094] Table 3 Distance between earthquake source and station

[0095]

[0096] 302) From the distances listed in Table 3, the distance to the farthest station corresponding to each seismic source is obtained, and the results are shown in Table 4:

[0097] Table 4. Distances between each earthquake source and its corresponding farthest station.

[0098]

[0099] (4) Calculate the reasonable charge amount P using the formula for vibration wave attenuation with propagation distance and the formula for explosive energy release. e And ensure that the signal-to-noise ratio is greater than 3 so that P-wave arrival time marking can be performed subsequently. The specific steps are as follows:

[0100] 401) Based on the distance r between the farthest station and the seismic source obtained in step (3), jAnd the seismic wave attenuation formula, ensuring the microseismic signal-to-noise ratio is greater than 3, based on long-term monitoring of the working face, the attenuation factor α = 0.1 can be taken, and the average ambient noise energy intensity N = 1.0E-37, to obtain the minimum energy threshold required for the farthest station to receive, the calculation formula is as follows:

[0101]

[0102] In this calculation, based on Table 4, the distance between the farthest epicenter and the station is rounded up to 900m. Therefore, the minimum epicenter vibration energy E required for this correction can be obtained. j0 Approximately 3000J;

[0103] 402) Based on the minimum energy threshold required to be received by the farthest station obtained in step 401), calculate the minimum charge required for each blasting point, and take the maximum value as the actual charge for each blasting point in this blasting operation, so that each station can receive a complete and clear signal as much as possible, thereby improving the reliability of the experiment. Depending on the actual situation, E p That is, the theoretical energy released per unit of explosive is 4100 kJ / kg, K S That is, the ratio of the induced energy of the explosive to the total energy is 0.025%, and the specific formula and results are as follows:

[0104]

[0105] P e =MAX{P ej};

[0106] Adjustments were made based on actual construction requirements; the actual explosive charge for this blasting operation should be 3 kg.

[0107] (5) Obtain the theoretical coordinates of the earthquake source The total error Δr is calculated, and the wave velocity constant V is continuously adjusted to minimize the error. The corresponding wave velocity constant V at this point is the optimal wave velocity constant for this site. The specific steps are as follows:

[0108] 501) Adjust the calculation mode of the SOS microseismic system to station mode, selecting only the station signals for which wave velocity constant correction is to be performed to participate in the source coordinate inverse calculation, thereby reducing systematic errors. Continuously perform the following steps: perform coordinate calculation—obtain the theoretical source coordinates—calculate the total error—adjust the wave velocity constant until the error is minimized. The wave velocity constant adjustment strategy is as follows:

[0109] i. Let Vmax=6000m / s, Vmin=2500m / s, n=0;

[0110] ii. And all are approximately multiples of 50;

[0111] iii. Solve for the error, and denote the corresponding error as Δr. n ,Δr′ n ,Δr″ n ;

[0112] iv. If Δr′ n If the minimum value is Vmax, then Vmax = V n V n+1 =V′ n If Δr n If the minimum value is reached, then Vmax = V″ n V min =V′ n If V″ n If the minimum value is reached, then Vmin = V n V n+1 =V″ n ;

[0113] vn = n + 1;

[0114] vi. Repeat steps ii to v until V. n =V n-1 .

[0115] from Figure 3 As can be seen, after the 5th iteration, the optimal wave velocity was 5000 m / s, and the error was reduced to 3.19 m. Compared with the commonly used 4200 m / s in the mine, the error was reduced by about 120 m, and the accuracy of microseismic monitoring was significantly improved. The wave velocity optimization iteration process in this example is shown in Table 5:

[0116] Table 5 Results of Wave Speed ​​Optimization Iteration

[0117]

Claims

1. A method for determining the optimal P-wave velocity constant in a field, characterized in that, Includes the following steps: (1) Determine the stations that require wave velocity constant correction and their coordinates (X). i ,Y i Z i The coordinates of the location where the blasting operation was carried out, i.e., the coordinates of the seismic source (X). j0 ,Y j0 Z j0 ); (2) The average value N of the ambient noise energy intensity at the site was obtained using the SOS microseismic monitoring system; (3) Select the farthest station i corresponding to each seismic source j, and calculate the distance r between them. j ; (4) Based on the distance r obtained in step (3) j The appropriate charge P for each blasting point was calculated using the formula for vibration wave attenuation with propagation distance and the formula for explosive energy release. e And ensure that the signal-to-noise ratio of the microseismic signal is greater than 3; (5) The charge amount P calculated in step (4) e Blasting operations were carried out at each blasting point in accordance with the mine's safe operating procedures. (6) Using the SOS microseismic monitoring system to mark the arrival time of P waves, the theoretical coordinates of each seismic source were obtained. The theoretical coordinates of each earthquake source The coordinates of each blasting point, i.e., each seismic source (X) j0 ,Y j0 Z j0 By comparison, the total error Δr is calculated; (7) Continuously adjust the constant value V of P-wave velocity and repeat step (6) until the total error Δr reaches the minimum value. At this time, V is the optimal wave velocity on site. In step (4), the appropriate charge amount P e The solution steps are as follows: a. Based on the distance r corresponding to each seismic source j obtained in step (3). j In addition, the formula for seismic wave attenuation with distance is used to calculate the minimum energy threshold required to be received by the farthest station i corresponding to each seismic source j, while ensuring that the signal-to-noise ratio of the microseismic signal is greater than 3. The calculation formula is as follows: In the formula, E j distance r from the epicenter j The energy received by the station at that location; E j0 The initial energy of earthquake source j; α is the vibration wave propagation attenuation factor; b. Based on the minimum energy threshold required to be received by each farthest station obtained in step a, calculate the minimum charge required for each corresponding blasting point, and take the maximum value as the actual charge for each blasting point in this blasting operation, so that each station can receive a complete and clear signal. The specific formula is as follows: P e =MAX{P ej }; In the formula, E p Theoretical energy released per unit of explosive; P ej The amount of explosives fired at blasting point J; K S : The ratio of induced energy to total energy of explosives.

2. The method for determining the optimal P-wave velocity constant in the field according to claim 1, characterized in that, In step (3), the farthest station i corresponding to each seismic source j and the distance r between them are... j The steps to obtain are as follows: a. The distance between each seismic source and each station is calculated using the following distance formula: b. For each seismic source, select the largest distance from the distances calculated in step a as r. j That is, r j =max{r j-i } 3. The method for determining the optimal P-wave velocity constant in the field according to claim 1, characterized in that, In step (6), the theoretical coordinates of the earthquake source The steps for solving the total error Δr are as follows: a. By accurately acquiring microseismic signals from microseismic signal monitoring stations, and then implementing P-wave arrival time marking on these signals, the specific time of the seismic wave arrival at station i can be obtained, denoted as t. i Based on the characteristics of vibration wave propagation, the following equations are derived: The equation has four unknowns: t0, X, ... j0 Y j0 Z j0 The system of simultaneous equations can be solved when there are four equations; at this point, the theoretical coordinates of the earthquake source are obtained by taking the least squares estimate. b. Based on the theoretical coordinates of each seismic source obtained in step a. The actual coordinates (X, Y) of the epicenter can be obtained using the Euclidean distance formula. j0 ,Y j0 Z j0 The distance difference between the values ​​is summed to obtain the total error under the constant wave velocity, denoted as Δr. The calculation formula is as follows:

4. The method for determining the optimal P-wave velocity constant in the field according to claim 1, characterized in that, In step (7), the adjustment of the P-wave velocity constant V adopts the bisection method, and the specific steps are as follows: a. Define Vmax, Vmin, and n, where Vmax and Vmin are the maximum and minimum propagation velocities of seismic waves under various lithological conditions in the field environment, respectively; n is the number of iterations for this calculation, initially n = 0; b. Among them, V n V′ n V″ n These represent the wave velocity magnitudes at 1 / 4, 1 / 2, and 3 / 4 of the range [Vmin, Vmax], respectively; V n V′ n C″ n The values ​​are all taken from the nearest multiple of 50. c. V n V′ n V″ n The error is calculated according to step (6), and the corresponding error is denoted as Δr. n , Δr′ n ,Δr″ n ; d. If Δr′ n If the minimum value is Vmax, then Vmax = V n V n+1 =V′ n If Δr n If the minimum value is reached, then Vmax = V″ n V min =V′ n If V″ n If the minimum value is reached, then Vmin = V n V n+1 =V″ n ; en = n + 1; f. Repeat steps b through e until V. n =V n-1 .

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