Top and bottom coal rock identification method based on high-frequency pulse mechanical vibration slippage time window method

Abstract

The invention discloses a top and bottom coal rock identification method based on a high-frequency pulse mechanical vibration slippage time window method. The method comprises the steps of coal seam thickness measurement attribute data calibration, high-frequency pulse mechanical vibration signal excitation and receiving, top coal or bottom coal thickness calculation and top coal or bottom coal rock identification completion. Mechanical vibration signals are adopted, and interference of metal and electromagnetic wave signals on the method is small; a large amount of drilling operation is not involved, and the advantages of low cost and high efficiency are achieved; and the universal advantage is achieved in the aspect of popularization.

Description

Technical Field

[0001] The invention belongs to the technical field of mine geology and relates to a method for identifying top and bottom coal rocks based on a high-frequency pulse mechanical vibration sliding time window method. Background Art

[0002] There are generally three major methods for coal rock identification in top coal and bottom coal caving. The first is the drilling method, which arranges multiple drilling operations in the working face, uses drill cuttings or other parameters to determine the coal seam thickness and identify the coal-rock interface, and performs spatial interpolation to predict the coal-rock interface of the entire mining area. However, this method has the problems of high construction cost and low efficiency; the second is the ground penetrating radar method, which is currently in the experimental stage and has good adaptability in certain environments. However, in locations close to hydraulic supports, the presence of metal interference inhibits its detection effect; the third is the manual experience method, which does not meet the conditions for application and promotion in intelligent coal mines. Summary of the Invention

[0003] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a method for top and bottom coal rock identification based on the high-frequency pulse mechanical vibration sliding time window method, to solve the technical problem that the existing technology is difficult to accurately realize the coal rock identification of top coal and bottom coal, and to improve the accuracy and efficiency of top coal thickness detection.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The top and bottom coal rock identification method based on the high-frequency pulse mechanical vibration sliding time window method includes the following steps:

[0006] Step 1: Calibration of coal seam thickness measurement attribute data: Place a transmitting probe and a receiving probe in the coal seam. Calibrate the propagation speed of high-frequency mechanical waves in the coal seam based on the distance between the receiving probe and the transmitting probe and the time it takes for the transmitted signal to reach the receiving probe.

[0007] Step 2: Excitation and reception of high-frequency pulse mechanical vibration signals: a transmitting probe and a receiving probe are arranged in the detection area of the top coal or bottom coal to be tested. The transmitting probe triggers the high-frequency pulse mechanical vibration signal, while the receiving probe receives and records the signal.

[0008] Step 3, calculate the top coal or bottom coal thickness:

[0009] s3.1, filter the signal recorded in step 2 through Fourier transform to retain the signal s within the effective frequency range;

[0010] S3.2, use the sliding time window method to calculate the time it takes for the signal to pass through the top coal or bottom coal, reach the surrounding rock interface, and return to the receiving probe: From the signal s obtained in S3.1, select the signal s1 that covers the time window of the transmitted signal; combine the signal s and the signal s1 to calculate the vector Tc(τ): Where τ is the slip variable, m is the moving range, and n is the time variable; thus, the interval length t between the first and second extreme values in Tc(τ) is obtained;

[0011] S3.3. Calculate the thickness of the top or bottom coal: Using the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated in step 1 and the interval duration t calculated in S3.2, calculate the thickness of the top or bottom coal: hc = (v × t) / 2, where hc is the thickness of the top or bottom coal, v is the propagation velocity of the high-frequency mechanical wave in the coal seam, and t is the interval duration.

[0012] Step 4, top coal or bottom coal rock identification: The position of the top and bottom coal rock interfaces is calculated by receiving the elevation coordinate z of the probe location and the thickness obtained in step 3 to complete the top and bottom coal rock identification.

[0013] The present invention also includes the following technical features:

[0014] Specifically, the step 1 includes:

[0015] s1.1, placing the transmitting probe in the coal seam;

[0016] s1.2, place multiple receiving probes in the coal seam at the same level as the transmitting probes, and calculate the distance between the receiving probes and the transmitting probes: d x =Randint(d a ,d b ), where d a and d b The upper and lower limits of the distance range are determined by the on-site working conditions;

[0017] s1.3, stimulate the signal of the transmitting probe, and at the same time, the receiving probe starts the signal receiving mode synchronously, and records the time when the transmitting signal reaches different receiving probes;

[0018] s1.4, using the distance calculated by s1.2 and the time recorded by s1.3, calculate the different propagation speeds of the high-frequency mechanical wave in the coal seam, calculate the average value, and finally obtain the propagation speed of the high-frequency mechanical wave in the coal seam.

[0019] Specifically, the step 2 includes:

[0020] S2.1, high-frequency pulse mechanical vibration signal excitation: For top coal, a transmitting probe is placed on the top of the hydraulic support top beam, or at the coal seam outcrop between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal; for bottom coal, a transmitting probe is placed on the bottom of the hydraulic support base, or at the coal seam outcrop between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal;

[0021] s2.2, high-frequency pulse mechanical vibration signal reception: Place a receiving probe 5-10 cm away from the transmitting probe in step s2.1. When the signal is triggered, start the receiving probe to receive and record the signal. Stop recording after recording for Δt.

[0022] Specifically, the Δt is: Δt=2h×(3 / 2) / v=3h / v; wherein h is the coal seam thickness determined by exploration drilling logging; and v is the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated by step 1.

[0023] Specifically, the s3.1 includes:

[0024] s3.1.1, convert the transmission signal of the transmitting probe in s2.1 from the time domain to the frequency domain through Fourier transform;

[0025] s3.1.2, converting the received signal of the receiving probe in s2.2 from the time domain to the frequency domain through Fourier transform;

[0026] s3.1.3, the highest frequency in the frequency domain of the received signal shall not exceed the highest frequency in the effective spectrum of the transmitted signal;

[0027] s3.1.4, convert the new frequency components of the received signal retained in s3.1.3 from the frequency domain to the time domain through inverse Fourier transform to obtain signal s within the effective frequency range.

[0028] Specifically, in step 4, the coal-rock interface position of the top coal and the coal-rock interface position of the bottom coal are calculated by the following formula:

[0029] Coal-rock interface position X of top coal u :X u =z+hc; Coal-rock interface position of bottom coal X d :X d =z-hc; where z is the elevation coordinate of the receiving probe, and hc is the thickness of the top coal or bottom coal.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] The present invention has low interference and low cost; the present invention adopts mechanical vibration, and compared with ground penetrating radar methods, the metal and electromagnetic wave signals have less interference on the present method; and the present invention does not involve a large amount of drilling operations, and compared with drilling methods, it has the advantages of low cost and high efficiency; compared with traditional manual experience, the present invention has more universal advantages in terms of promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Flow chart of the method of the present invention.

[0033] Figure 2 Schematic diagram of the detection scene.

[0034] Figure 3 Schematic diagram for frequency range calculation.

[0035] Figure 4 Calculate time curves for coal thickness measurements. DETAILED DESCRIPTION

[0036] The present invention provides a method for identifying top and bottom coal rocks based on a high-frequency pulse mechanical vibration sliding time window method, comprising the following steps:

[0037] Step 1: Calibration of coal seam thickness measurement attribute data: Deploy a transmitting probe and a receiving probe in the coal seam. Calibrate the propagation speed of the high-frequency mechanical wave in the coal seam based on the distance between the receiving probe and the transmitting probe and the time it takes for the transmitted signal to reach the receiving probe. This includes:

[0038] s1.1, place the transmitting probe at a depth of not less than 1.5m in the coal seam;

[0039] S1.2. Place multiple (not less than three) receiving probes in the coal seam at the same level as the transmitting probe, with no more than two of these probes being in the same straight line. Calculate the distance between the receiving and transmitting probes using the following formula (1):

[0040] d x = Randint (d a , d b ) Formula 1

[0041] In the above formula, Randint is the random number generation function, d a and d b The upper and lower limits of the distance range are determined by the on-site working conditions, d a and d b The distance between them is generally no more than 2m;

[0042] s1.3, stimulate the signal of the transmitting probe, and at the same time, the receiving probe starts the signal receiving mode synchronously, and records the time when the transmitting signal reaches different receiving probes;

[0043] s1.4. Calculate the different propagation speeds of the high-frequency mechanical wave in the coal seam using the distance calculated in step s1.2 and the time recorded in step 1.3, calculate the average value, and finally obtain the propagation speed of the high-frequency mechanical wave in the coal seam.

[0044] If the receiving probe and the transmitting probe are not arranged on the same horizontal plane in the actual project, directly measure the actual distance between the receiving probe and the transmitting probe, and then calculate the propagation speed of the high-frequency mechanical wave in the coal seam according to steps s1.3 and s1.4.

[0045] Step 2, excitation and reception of high-frequency pulse mechanical vibration signals: a transmitting probe and a receiving probe are arranged in the detection area of the top coal or bottom coal to be tested. The transmitting probe triggers the high-frequency pulse mechanical vibration signal, while the receiving probe receives and records the signal. Specifically, the steps include:

[0046] s2.1, high-frequency pulse mechanical vibration signal excitation:

[0047] For top coal, a transmitting probe is placed on the top of the hydraulic support top beam, or at the coal seam exposed position between two hydraulic supports, or in the coal seam drill hole to trigger a high-frequency pulse mechanical vibration signal; for bottom coal, a transmitting probe is placed on the bottom of the hydraulic support base, or at the coal seam exposed position between two hydraulic supports, or in the coal seam drill hole to trigger a high-frequency pulse mechanical vibration signal;

[0048] s2.2, high-frequency pulse mechanical vibration signal reception:

[0049] Place a receiving probe 5-10 cm away from the transmitting probe in step s2.1. When the signal is triggered, start the receiving probe to receive and record the signal. After recording the time Δt, stop recording. Δt is calculated using the following formula 2:

[0050] Δt = 2h × (3 / 2) / v = 3h / v; Formula 2

[0051] Wherein, h is the thickness of the coal seam determined by exploration borehole logging; v is the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated by step 1.

[0052] Step 3, calculate the top coal or bottom coal thickness:

[0053] s3.1, filtering the signal recorded within Δt in step 2 by Fourier transform or other methods to retain the signal s within the effective frequency range; specifically, the following steps are performed:

[0054] s3.1.1, convert the transmission signal of the transmitting probe in s2.1 from the time domain to the frequency domain through Fourier transform;

[0055] s3.1.2, converting the received signal of the receiving probe in s2.2 from the time domain to the frequency domain through Fourier transform;

[0056] s3.1.3, the highest frequency in the frequency domain of the received signal shall not exceed the highest frequency in the effective spectrum of the transmitted signal;

[0057] S3.1.4, convert the new frequency components of the received signal retained in S3.1.3 from the frequency domain to the time domain through inverse Fourier transform to obtain signal s within the effective frequency range;

[0058] S3.2, using the sliding time window method to calculate the time it takes for the signal to pass through the top coal or bottom coal, reach the surrounding rock interface, and return to the receiving probe:

[0059] s3.2.1, from the signal s obtained in s3.1, select the signal s1 that covers the time window of the transmitted signal;

[0060] s3.2.2, combining signals s and s1, calculate the vector Tc(τ) according to the following equation 3:

[0061]

[0062] Among them, τ is the slip variable, m is the moving range, and n is the time variable;

[0063] s3.2.3, find the duration t of the interval covered by the first and second extreme values in Tc(τ).

[0064] S3.3, calculate the thickness of top coal or bottom coal:

[0065] Substitute the propagation velocity v of the high-frequency mechanical wave in the coal seam calibrated in step 1 and the interval duration t obtained in step 3.2 into the following equation 4 to obtain the thickness of the top coal or bottom coal:

[0066] hc=(v×t) / 2 Equation 4

[0067] Among them, hc is the thickness of the top coal or bottom coal, v is the propagation speed of high-frequency mechanical waves in the coal seam, and t is the duration.

[0068] Step 4: Complete the coal rock identification of top coal or bottom coal:

[0069] The positions of the top and bottom coal-rock interfaces are calculated by receiving the elevation coordinate z of the probe location and the thickness obtained in step 3:

[0070] Coal-rock interface position X of top coal u :

[0071] X u =z+hc; Formula 5

[0072] Coal-rock interface position X of bottom coal d :

[0073] X d =z-hc; Formula 6.

[0074] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0075] Example:

[0076] This embodiment provides a method for identifying top and bottom coal rocks based on a high-frequency pulse mechanical vibration sliding time window method. The flow chart is as follows: Figure 1 As shown, it mainly includes coal seam thickness measurement attribute data calibration, high-frequency pulse mechanical vibration signal excitation and reception, calculation of top coal or bottom coal thickness, and completion of top coal or bottom coal coal rock identification; specifically:

[0077] Step 1: Calibration of coal seam thickness measurement attribute data:

[0078] (1) The transmitting probe is placed at a depth of 1.5 m in the coal seam;

[0079] (2) Calculate the plane position of the four receiving probes relative to the transmitting probe using formula 1:

[0080] d x = Randint (d a , d b ) Formula 1

[0081] In formula 1, d a and d b The position is determined by the on-site working conditions, d a and d b The distance between them is generally no more than 2m. The positions of the four receiving probes, d1, d2, d3, and d4, can be calculated using formula 1.

[0082] (3) The distances between the transmitting probe and the receiving probes are combined with the depth to calculate the distances w1, w2, w3, and w4:

[0083] w1=sqrt(d1 2 +dg 2 ), sqrt represents the non-negative square root, dg represents the height difference between the transmitting and receiving probes; w2, w3, and w4 can be calculated accordingly.

[0084] (4) Stimulate the signal of the transmitting probe, and at the same time, the receiving probe starts the signal receiving mode synchronously, and record the time t1, t2, t3, and t4 when the transmitting signal arrives at different receiving probes;

[0085] (5) Different speeds are obtained by calculating the distance between the transmitting probe and different receiving probes and the time it takes for the transmitted signal to reach different receiving probes, v1 = w1 / t1; v2, v3, and v4 are calculated accordingly; and the propagation speed of the high-frequency mechanical wave in the coal seam is finally obtained based on the average value: the calibrated speed v can be obtained as v = (v1+v2+v3+v4) / 4.

[0086] Step 2: Excitation and reception of high-frequency pulse mechanical vibration signals:

[0087] (1) Excitation of high-frequency pulse mechanical vibration signal: For top coal, a transmitting probe is placed on the top of the hydraulic support top beam, or at the coal seam exposed position between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal; for bottom coal, a transmitting probe is placed on the bottom of the hydraulic support base, or at the coal seam exposed position between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal;

[0088] When the signal is excited above the top beam of the hydraulic support, such as Figure 2 As shown, the hollow box in the figure represents the transmitting probe;

[0089] (2) Receiving high-frequency pulse mechanical vibration signals: When the signal is excited, the receiving probe is started to receive the signal, and the signal can be received on the top beam of the hydraulic support at the same time, such as Figure 2 As shown in the figure, the solid box represents the receiving probe; after recording the time Δt, the recording stops; Δt is calculated by formula 2:

[0090] Δt = 2h × (3 / 2) / v = 3h / v; Equation 2

[0091] Wherein, h is the thickness of the coal seam determined by exploration borehole logging; v is the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated by step 1.

[0092] Step 3, calculate the top coal or bottom coal thickness:

[0093] (1) The signal recorded within Δt in step 2 is filtered by Fourier transform and other methods to retain the signal s within the effective frequency range, such as Figure 3 As shown;

[0094] ① Convert the transmitted signal from the time domain to the frequency domain, as shown by the dotted line in the figure;

[0095] ② Convert the received signal from the time domain to the frequency domain, as shown by the solid line in the figure;

[0096] ③ The frequency domain of the received signal is kept smaller than the highest frequency of the effective spectrum of the transmitted signal, such as Figure 3 The range indicated by the arrow in the middle;

[0097] ④Transfer the new frequency component of the received signal from the frequency domain to the time domain to obtain signal s.

[0098] (2) The sliding time window method is used to calculate the time it takes for the excitation signal to pass through the top coal or bottom coal, reach the surrounding rock interface, and return to the receiving probe:

[0099] ① From the signal s, select the signal s1 that covers the time window of the transmitted signal;

[0100] ② Combine the signal s and the signal s1, and use the formula 3 to obtain the vector Tc(τ). The result is as follows: Figure 4 signal;

[0101]

[0102] In Equation 3, τ is the slip variable, m is the moving range, and n is the time variable;

[0103] ③ Obtain the length t of the time interval covered by the first and second extreme values in Tc(τ), such as Figure 4 The arrow indicates the direction.

[0104] (3) Calculation of top coal or bottom coal thickness:

[0105] Substitute the propagation velocity v of the high-frequency mechanical wave in the coal seam calibrated in step 1 and the interval duration t obtained in step 3 into equation 4 to obtain the thickness of the top coal or bottom coal:

[0106] hc=(v×t) / 2 Equation 4

[0107] Among them, hc is the thickness of the top coal or bottom coal, v is the propagation speed of high-frequency mechanical waves in the coal seam, and t is the duration.

[0108] Step 4: Complete the coal rock identification of top coal or bottom coal:

[0109] The positions of the top and bottom coal-rock interfaces are calculated by receiving the elevation coordinate z of the probe location and the thickness obtained in step 3:

[0110] The coal-rock interface position X of the top coal u Calculated by formula 5:

[0111] X u =z+hc; Formula 5

[0112] The coal-rock interface position X of the bottom coal d Calculated by formula 6:

[0113] X d =z-hc; Formula 6.

[0114] The method of the present invention has low interference and low cost. It uses mechanical vibration. Compared with ground penetrating radar methods, metal and electromagnetic wave signals have less interference with the method of the present invention. Moreover, the method of the present invention does not involve a large amount of drilling operations. Compared with drilling methods, it has the advantages of low cost and high efficiency. At the same time, if there is a drill hole on site, the method of the present invention can also be used in the drill hole. Compared with traditional manual experience, the method of the present invention has more universal advantages in promotion.

[0115] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0116] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0117] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for identifying top and bottom coal rocks based on a high-frequency pulse mechanical vibration sliding time window method, characterized in that: The following steps are involved: Step 1: Calibration of coal seam thickness measurement attribute data: Place a transmitting probe and a receiving probe in the coal seam. Calibrate the propagation speed of high-frequency mechanical waves in the coal seam based on the distance between the receiving probe and the transmitting probe and the time it takes for the transmitted signal to reach the receiving probe. Step 2: Excitation and reception of high-frequency pulse mechanical vibration signals: a transmitting probe and a receiving probe are arranged in the detection area of the top coal or bottom coal to be tested. The transmitting probe triggers the high-frequency pulse mechanical vibration signal, while the receiving probe receives and records the signal. Step 3, calculate the top coal or bottom coal thickness: s3.1, filter the signal recorded in step 2 through Fourier transform to retain the signal s within the effective frequency range; S3.2, use the sliding time window method to calculate the time it takes for the signal to pass through the top coal or bottom coal, reach the surrounding rock interface, and return to the receiving probe: From the signal s obtained in S3.1, select the signal s1 that covers the time window of the transmitted signal; combine the signal s and the signal s1 to calculate the vector Tc(τ): Where τ is the slip variable, m is the moving range, and n is the time variable; thus, the interval length t between the first and second extreme values in Tc(τ) is obtained; S3.

3. Calculate the thickness of the top or bottom coal: Using the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated in step 1 and the interval duration t calculated in S3.2, calculate the thickness of the top or bottom coal: hc = (v × t) / 2, where hc is the thickness of the top or bottom coal, v is the propagation velocity of the high-frequency mechanical wave in the coal seam, and t is the interval duration. Step 4, top coal or bottom coal rock identification: The position of the top and bottom coal rock interfaces is calculated by receiving the elevation coordinate z of the probe location and the thickness obtained in step 3 to complete the top and bottom coal rock identification.

2. The top and bottom coal rock identification method based on high-frequency pulse mechanical vibration sliding time window method according to claim 1 is characterized in that: The step 1 comprises: s1.1, placing the transmitting probe in the coal seam; s1.2, place multiple receiving probes in the coal seam at the same level as the transmitting probes, and calculate the distance between the receiving probes and the transmitting probes: d x =Randint(d a ,d b ), where d a and d b The upper and lower limits of the distance range are determined by the on-site working conditions; s1.3, stimulate the signal of the transmitting probe, and at the same time, the receiving probe starts the signal receiving mode synchronously, and records the time when the transmitting signal reaches different receiving probes; s1.4, using the distance calculated by s1.2 and the time recorded by s1.3, calculate the different propagation speeds of the high-frequency mechanical wave in the coal seam, calculate the average value, and finally obtain the propagation speed of the high-frequency mechanical wave in the coal seam.

3. The top and bottom coal rock identification method based on high-frequency pulse mechanical vibration sliding time window method according to claim 1 is characterized in that: The step 2 includes: S2.1, high-frequency pulse mechanical vibration signal excitation: For top coal, a transmitting probe is placed on the top of the hydraulic support top beam, or at the coal seam outcrop between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal; for bottom coal, a transmitting probe is placed on the bottom of the hydraulic support base, or at the coal seam outcrop between two hydraulic supports, or in the coal seam drill hole to trigger the high-frequency pulse mechanical vibration signal; s2.2, high-frequency pulse mechanical vibration signal reception: Place a receiving probe 5-10 cm away from the transmitting probe in step s2.

1. When the signal is triggered, start the receiving probe to receive and record the signal. Stop recording after recording for Δt.

4. The top and bottom coal rock identification method based on high-frequency pulse mechanical vibration sliding time window method according to claim 3 is characterized in that: The Δt is: Δt=2h×(3 / 2) / v=3h / v; wherein h is the thickness of the coal seam determined by exploration drilling and logging; and v is the propagation velocity of the high-frequency mechanical wave in the coal seam calibrated by step 1.

5. The top and bottom coal rock identification method based on high-frequency pulse mechanical vibration sliding time window method according to claim 3 is characterized in that: The s3.1 includes: s3.1.1, convert the transmission signal of the transmitting probe in s2.1 from the time domain to the frequency domain through Fourier transform; s3.1.2, converting the received signal of the receiving probe in s2.2 from the time domain to the frequency domain through Fourier transform; s3.1.3, the highest frequency in the frequency domain of the received signal shall not exceed the highest frequency in the effective spectrum of the transmitted signal; s3.1.4, convert the new frequency components of the received signal retained in s3.1.3 from the frequency domain to the time domain through inverse Fourier transform to obtain signal s within the effective frequency range.

6. The top and bottom coal rock identification method based on high-frequency pulse mechanical vibration sliding time window method according to claim 1 is characterized in that: In step 4, the coal-rock interface position of the top coal and the coal-rock interface position of the bottom coal are calculated by the following formula: Coal-rock interface position X of top coal u :X u =z+hc; Coal-rock interface position of bottom coal X d :X d =z-hc; where z is the elevation coordinate of the receiving probe, and hc is the thickness of the top coal or bottom coal.

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