Mine vector excitation and slot wave receiving system and exploration method thereof

Abstract

The invention discloses a mine vector excitation and slot wave receiving system and an exploration method thereof. The mine vector excitation and slot wave receiving system comprises a slot wave excitation device and a slot wave receiving device, the slot wave excitation device comprises a plurality of phase control array excitation units, and each phase control array excitation unit is composed of a plurality of controllable CO2 seismic sources which are linearly arranged at equal intervals; the slot wave receiving device comprises a plurality of detectors, when slot wave detection is carried out, slot waves are excited through the controllable CO2 seismic sources in the phase control array excitation units, the slot waves pass through a coal seam from a roadway on one side to reach a roadway on the other side to be received by the detectors, and coal seam exploration data are obtained. According to the invention, by arranging the plurality of phase control array excitation units and delaying phase control vector excitation, accurate detection and positioning of the concealed structure in the coal seam can be realized on the premise of ensuring safe construction and a relatively large detection range.

Description

Technical Field

[0001] The present invention relates to a system for vector excitation and reception of trough waves in a mine and an exploration method thereof, belonging to the field of coal mine seismic exploration. Background Art

[0002] There is a large dip undulating coal seam in the coal mine, that is, the coal seam presents a syncline or anticline shape, the drop between the return airway and the machine roadway is large, and the cutting eye part shows a 30° trend. Under the influence of this structure, the coal seam mining is difficult, and effective exploration means are urgently needed to expose hidden structures such as faults that may be encountered during the coal seam mining process.

[0003] The mine trough wave seismic exploration technology is often used for detecting coal seam geological structures. However, due to the influence of adverse factors such as complex geological structures, too large coal seam dip angles, and inconvenient roadway construction, the exploration accuracy of trough waves is limited. As a result, the exploration results can delineate the geological structure area, but it is difficult to accurately detect. In addition, trough wave exploration requires a seismic source to generate seismic waves. The traditional method mostly uses an explosive seismic source to generate seismic waves. Although this method can generate strong seismic waves, it has many drawbacks. First, the explosive seismic source has great destructiveness to the environment and is prone to secondary disasters such as gas explosion and roof collapse, seriously threatening the safety of the mine. Second, the excitation efficiency and accuracy of the explosive seismic source are relatively low, and it is difficult to meet the requirements for fine control of seismic waves under complex geological conditions. In addition, the use of the explosive seismic source is also restricted by strict laws and regulations, increasing the exploration cost and operation difficulty.

[0004] The phase change CO2 seismic source excitation technology can use the energy generated by phase change CO2 to replace the traditional seismic source. The CO2 seismic source has the characteristics of higher frequency and stronger energy, which not only reduces the possibility of inducing secondary disasters but also improves the construction efficiency, meeting the first priority of safe construction. Combining with the vector excitation technology can improve the exploration effect in a certain direction by directionally exciting the CO2 seismic source, thereby improving the excitation efficiency and accuracy of seismic waves. However, in the actual mine trough wave exploration, the application of the CO2 seismic source vector excitation technology still faces many challenges. Especially in coal seams with large dip angles, the complex geological conditions and high construction requirements result in more leakage of the seismic source excitation energy, making it difficult to meet the requirements of high-precision trough wave exploration.

[0005] Aiming at the problems existing in the above-mentioned prior art, how to provide a new system for excitation and reception of trough waves and an exploration method thereof, so that it can achieve accurate detection and positioning of hidden structures in the coal seam on the premise of ensuring safe construction and a large detection range, is the research direction required by the present invention. Summary of the Invention

[0006] In view of the problems existing in the above-mentioned prior art, the present invention provides a system and exploration method for vector excitation and reception of slot waves in a mine. By arranging a plurality of phased array excitation units and the method of delayed phased vector excitation, it is possible to accurately detect and locate hidden structures in the coal seam on the premise of ensuring safe construction and a large detection range.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A system for vector excitation and reception of slot waves in a mine, including a slot wave excitation device and a slot wave reception device;

[0008] The slot wave excitation device includes a plurality of phased array excitation units, and the plurality of phased array excitation units are arranged at equal intervals in a roadway on one side of the coal seam; each phased array excitation unit is composed of a plurality of controllable CO2 sources arranged at equal intervals and in a straight line;

[0009] The slot wave reception device includes a plurality of geophones, and the plurality of geophones are arranged at equal intervals and in a straight line in a roadway on the other side of the coal seam; when conducting slot wave detection, the slot wave is excited by each controllable CO2 source in each phased array excitation unit, and the slot wave passes through the coal seam from one roadway to the other roadway and is received by each geophone to obtain coal seam exploration data.

[0010] Further, the distance between each controllable CO2 source in the phased array excitation unit is d, and it satisfies the following formula:

[0011]

[0012] In the formula, λ is the excitation wavelength of the controllable CO2 source.

[0013] Further, when the phased array excitation unit excites the slot wave, the amplitudes of the slot waves excited by each controllable CO2 source inside it are distributed symmetrically and gradually decreasing from the center position of the phased array excitation unit to both sides. This can further reduce the influence of the sidelobes in the excited slot waves on the exploration effect.

[0014] Further, the frequency range excited by each controllable CO2 source is 200 - 350 Hz, and the corresponding wavelength of the mine slot wave is 3 - 6 m; the number and spacing of the controllable CO2 sources in each phased array excitation unit are the same, and the number is in the range of 4 - 10; the spacing is selected in the range of 1.5 m - 3 m. The selection of the number and spacing of the sources directly affects the appearance of grating lobes and sidelobes (as shown in the presence of the first sidelobe). In order to meet the requirements of high-resolution seismic exploration, the high-frequency signal components should be strengthened as much as possible; therefore, in the exploration of mine slot waves, in order to meet the signal-to-noise ratio requirements, the optimal exploration effect can be achieved according to the above parameters. Figure 2 shown).

[0015] The exploration method of the above-mentioned system for vector excitation and reception of slot waves in a mine specifically includes the following steps:

[0016] Step 1: Collect and analyze the mine geological data in detail to understand information such as the dip angle of the coal seam, thickness variation, elevation difference of the roadway, and potential hidden structures, and determine the target area for coal seam exploration.

[0017] Step 2: Arrange the shear wave excitation device and the shear wave receiving device in the roadways on both sides of the target area determined in Step 1 respectively; and determine the spacing between the controllable CO2 seismic sources in each phased array excitation unit.

[0018] Step 3: Based on the spacing determined in Step 2, the number of controllable CO2 seismic sources, and the excitation wavelength of the controllable CO2 seismic sources, further determine the main beam direction θ max and the main beam width (main lobe width).

[0019] Step 4: Select the delay phase control method to determine the delay time for each controllable CO2 seismic source to be excited in sequence within each phased array excitation unit, so that the elastic wave signals excited by each controllable CO2 seismic source have a constant phase difference, thereby exciting the required directional seismic wave.

[0020] Step 5: According to the delay phase control method determined in Step 4, control each phased array excitation unit to perform delay phase control vector excitation. The excited shear wave is transmitted through the target area to the shear wave receiving device, and each detector continuously receives the shear waves excited by all phased array excitation units. After all phased array excitation units complete the excitation work, obtain the exploration data of the target area.

[0021] Furthermore, in Step 2, the shear wave excitation device consists of m phased array excitation units, and each phased array excitation unit consists of n controllable CO2 seismic sources. Then the length L of each phased array excitation unit is L=(n - 1)d, where d is the spacing between the controllable CO2 seismic sources.

[0022] Furthermore, in Step 2, according to the coal seam dip angle α, horizontal exploration distance x, and elevation difference h between the machine roadway and the ventilation roadway, reasonably set the number of detectors and the trace interval of the shear wave receiving device. The coverage distance px of the main beam direction of each phased array excitation unit is:

[0023]

[0024] If there is no overlapping exploration area for the main beams of each phased array excitation unit, then x = px×m, and the number of detectors r is the trace interval; m is the number of phased array excitation units;

[0025] If there is an overlapping exploration distance c for the main beams of each phased array excitation unit, then x = px×m−(m−1)c, and the number of detectors

[0026] Furthermore, in Step 3, the main beam direction θ max and the main beam width 2θ 0.5 are determined. The specific formula is as follows:

[0027]

[0028] 2θ 0.5 = |θ1 - θ2|

[0029]

[0030] where θ max is the main beam direction, 2θ 0.5 is the main beam width, n is the number of controllable CO2 sources, d is the spacing between controllable CO2 sources, and λ is the excitation wavelength of the controllable CO2 sources;

[0031] If the main beam direction is near θ max = 90°, then

[0032]

[0033] Furthermore, the specific calculation formula for the delay time in Step 4 is as follows:

[0034]

[0035] where τ is the delay time.

[0036] Furthermore, in Step 5, each phased array excitation unit is sequentially numbered from P1 to Pm, and then each phased array excitation unit is controlled to perform delayed phased vector excitation in the order of the numbers.

[0037] Compared with the prior art, the present invention first determines that the phased array excitation unit is composed of multiple controllable CO2 sources. To ensure the accuracy and efficiency of the trough wave transmission exploration, the number and spacing of the controllable CO2 sources are set, and then the main beam direction and main beam width of the phased array excitation unit are determined; then the delay time is set so that each controllable CO2 source in the phased array excitation unit is excited in sequence according to the delay time, making the elastic wave signals emitted by each source have a constant phase difference, thereby exciting the required directional seismic wave; to ensure the accuracy of data acquisition, on the basis of specific settings for the excitation device, the trough wave receiving device is composed of multiple geophones, and according to the coverage distance of the main beam direction of the phased array excitation unit, the number of geophones and the trace interval are determined, and finally this system is used to perform trough wave transmission exploration on the target area; the present invention can effectively achieve precise illumination and detailed detection of hidden structures in the coal seam under complex geological conditions such as large dip roadways, improve the accuracy and efficiency of mine trough wave transmission exploration, and provide a reliable technical guarantee for the safe mining and rational utilization of coal resources. Brief Description of the Drawings

[0038] Figure 1 is a schematic diagram of the beamforming principle of the phased array excitation unit of the present invention;

[0039] Figure 2 is a schematic diagram of the beam detection direction of the phased array excitation unit;

[0040] where (a) θ max = 30°, (b) θ max = 45°, (c) θ max = 60°, (d) θ max = 90° wave fields and directional characteristics generated by the phased array excitation unit;

[0041] Figure 3 is a schematic diagram of the trough wave transmission exploration of the present invention.

[0042] where (a) three-dimensional diagram of a large dip angle coal seam, (b) side view sectional drawing of the model, (c) enlarged schematic diagram of the phased array excitation unit, (d) plan view of the trough wave transmission exploration. Detailed Embodiment

[0043] The present invention will be further described below.

[0044] As Figure 3 shown, a system for vector excitation and reception of trough waves in a mine includes a trough wave excitation device and a trough wave reception device;

[0045] The trough wave excitation device includes a plurality of phased array excitation units, and the plurality of phased array excitation units are arranged at equal intervals in a roadway on one side of the coal seam; each phased array excitation unit is composed of a plurality of controllable CO2 sources arranged at equal intervals and in a straight line;

[0046] The trough wave reception device includes a plurality of geophones, and the plurality of geophones are arranged at equal intervals and in a straight line in a roadway on the other side of the coal seam; when performing trough wave detection, the trough wave is excited by each controllable CO2 source in each phased array excitation unit, and the trough wave passes through the coal seam from one roadway to the other roadway and is received by each geophone to obtain coal seam exploration data; when the phased array excitation unit excites the trough wave, the amplitudes of the trough waves excited by each controllable CO2 source inside it are the largest at the center position of the phased array excitation unit and gradually decrease symmetrically towards both sides. This can further reduce the influence of the sidelobes in the excited trough waves on the exploration effect. The distance between each controllable CO2 source in the phased array excitation unit is d, and it satisfies the following formula:

[0047]

[0048] In the formula, λ is the excitation wavelength of the controllable CO2 source.

[0049] As an improvement of the present invention, the frequency range excited by each controllable CO2 seismic source is 200 - 350 Hz, corresponding to a wavelength of 3 - 6 m for the mine trough wave; the number and spacing of the controllable CO2 seismic sources in each phased array excitation unit are the same, and the number is in the range of 4 - 10; the spacing is selected to be 1.5 m - 3 m. The selection of the number and spacing of the seismic sources directly affects the appearance of grating lobes and side lobes (as shown in Figure 2 there is a first side lobe). To meet the requirements of high-resolution seismic exploration, the high-frequency signal components should be strengthened as much as possible; therefore, in the mine trough wave exploration, to meet the signal-to-noise ratio requirements, the optimal exploration effect can be achieved according to the above parameters.

[0050] The exploration method of the above mine vector excitation and receiving trough wave system specifically comprises the following steps:

[0051] Step 1: Collect and analyze the mine geological data in detail to understand information such as the inclination angle of the coal seam, thickness variation, elevation difference of the roadway, and possible hidden structures, and determine the target area for coal seam exploration;

[0052] Step 2: Arrange the trough wave excitation device and the trough wave receiving device in the roadways on both sides of the target area determined in Step 1 respectively; and determine the spacing of the controllable CO2 seismic sources in each phased array excitation unit; since the phased seismic source beam has a direction scanning property, as shown in Figure 2 the excitation parameters are as follows: the number of controllable CO2 seismic sources n = 4, the spacing d of the controllable CO2 seismic sources = 2 m, the sampling frequency f of the geophones = 200 Hz, and the trough wave velocity v = 800 m / s; the direction with relatively concentrated main beam energy is 60° - 120°, that is, within the range of ±30° of the main exploration direction, it should be ensured that the signals received by each geophone of the trough wave receiving device are all in the main beam direction and can cover the detection area. The trough wave excitation device is composed of m phased array excitation units, and each phased array excitation unit is composed of n controllable CO2 seismic sources, then the length L of each phased array excitation unit = (n - 1)d, where d is the spacing of the controllable CO2 seismic sources; according to the coal seam dip angle α, the horizontal exploration distance x, and the elevation difference h between the machine roadway and the air roadway, reasonably set the number of geophones and the trace interval of the trough wave receiving device. The coverage distance px of the main beam direction of each phased array excitation unit is:

[0053]

[0054] If there is no overlapping exploration area for the main beams of each phased array excitation unit, then x = px × m, and the number of geophones r is the trace interval; m is the number of phased array excitation units;

[0055] If there is a coincidence exploration distance c for the main beams of each phased array excitation unit, then x = px × m - (m - 1)c, and the number of detectors

[0056] Step 3: Determine the main beam direction θ based on the spacing determined in Step 2, the number of controllable CO2 sources, and the excitation wavelength of the controllable CO2 sources max and the main beam width (main lobe width). The specific formula is as follows:

[0057]

[0058] 2θ 0.5 = |θ1 - θ2|

[0059]

[0060] where θ max is the main beam direction, 2θ 0.5 is the main beam width, n is the number of controllable CO2 sources, d is the spacing of the controllable CO2 sources, and λ is the excitation wavelength of the controllable CO2 sources;

[0061] If the main beam direction is near θ max = 90°, then

[0062]

[0063] The principle of phased array beamforming is as Figure 1 shown. When sources 1 and 2 start vibrating with the same frequency and phase, the seismic wave field generated by source 2 at point p has a shorter wave path than that generated by source 1, that is, there is a wave path difference Δr = dsinθ. The spatial phase difference of the field caused by the wave path difference is That is to say, at point P, the seismic wave caused by source 2 leads that caused by source 1 by a phase difference. It can be seen that if the phase of source 1 is always ahead of that of source 2 by then at any time at the observation point p, the waveforms generated by each source are always in-phase and added, and the signal is strengthened. OP is the main beam direction of the array, denoted as θ. The main beam has a certain width, called the main beam width (main lobe width);

[0064] Step 4: Select the delay phased method to determine the delay time for each controllable CO2 source to be excited in sequence within each phased array excitation unit, so that the elastic wave signals excited by each controllable CO2 source have a constant phase difference, thereby exciting the required directional seismic wave; the specific formula for the delay time is:

[0065]

[0066] where τ is the delay time.

[0067] Step Five: According to the delay phased control method determined in Step Four, first sequentially number each phased array excitation unit from P1 to Pm, and then sequentially control each phased array excitation unit to perform delay phased vector excitation in the order of the numbers. The slot wave excited is transmitted through the target area to the slot wave receiving device, and each detector continuously receives the slot waves excited by all phased array excitation units until after the excitation work of all phased array excitation units is completed, the exploration data of the target area is obtained.

[0068] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A system for vector excitation and receiving slot waves in a mine, characterized in that: It includes a slot wave exciting device and a slot wave receiving device; The slot wave excitation device comprises a plurality of phased array excitation units, which are arranged at equal intervals in a tunnel on one side of the coal seam; each phased array excitation unit is composed of a plurality of controllable CO2 seismic sources arranged at equal intervals and in a straight line; The slot wave receiving device includes a plurality of detectors, which are arranged in a straight line at equal intervals in the tunnel on the other side of the coal seam. When slot wave detection is performed, the slot wave is excited by each controllable CO2 source in each phased array excitation unit. The slot wave passes through the coal seam from the tunnel on one side to the tunnel on the other side and is received by each detector to obtain coal seam exploration data.

2. The system for vector excitation and receiving slot waves in a mine according to claim 1, characterized in that: The spacing between the controllable CO2 sources in the phased array excitation unit is d, and it satisfies the following formula: Where λ is the excitation wavelength of the controllable CO2 source.

3. The system for vector excitation and receiving slot waves in a mine according to claim 1, characterized in that: When the phased array excitation unit excites the slot wave, the amplitude of the slot wave excited by each controllable CO2 source inside the phased array excitation unit is the largest at the center of the phased array excitation unit and decreases symmetrically on both sides.

4. The system for vector excitation and receiving slot waves in a mine according to claim 1, characterized in that: The frequency range of each controllable CO2 source excitation is 200-350Hz, corresponding to the wavelength of the mine slot wave of 3-6m; the number and spacing of controllable CO2 sources in each phased array excitation unit are the same, with the number ranging from 4 to 10; the spacing is selected from 1.5m to 3m.

5. A method for prospecting a mine vector excitation and receiving slot wave system according to any one of claims 1 to 4, characterized in that: The specific steps are: Step 1: Collect and analyze the mine geological data in detail to determine the target area for coal seam exploration; Step 2: Arrange the slot wave excitation device and the slot wave receiving device in the lanes on both sides of the target area determined in step 1; and determine the spacing of the controllable CO2 seismic sources in each phased array excitation unit; Step 3: According to the spacing determined in step 2, the number of controllable CO2 seismic sources and the excitation wavelength of the controllable CO2 seismic sources, the main beam direction θ is determined. max and main beamwidth; Step 4: Select the time-delay phase control method to determine the delay time for sequentially exciting each controllable CO2 source in each phased array excitation unit, so that the elastic wave signals excited by each controllable CO2 source have a constant phase difference, thereby exciting the required directional seismic waves; Step 5: According to the delayed phase control method determined in step 4, each phased array excitation unit is controlled to perform delayed phased vector excitation. The excited slot wave is transmitted through the target area to the slot wave receiving device. Each detector continues to receive the slot waves excited by all phased array excitation units until the excitation work of all phased array excitation units is completed, and the exploration data of the target area is obtained.

6. The exploration method according to claim 5, characterized in that: In step 2, the slot wave excitation device is composed of m phased array excitation units, each phased array excitation unit is composed of n controllable CO2 seismic sources, and the length of each phased array excitation unit L=(n-1)d, where d is the spacing between the controllable CO2 seismic sources.

7. The exploration method according to claim 5, characterized in that: In the step 2, the number of detectors and the track spacing of the slot wave receiving device are reasonably set according to the coal seam inclination α, the horizontal exploration distance x, and the elevation difference h of the machine and ventilation lanes. The main beam direction coverage distance px of each phased array excitation unit is: If the main beams of the phased array excitation units do not overlap the exploration area, then x = px × m, and the number of detectors is r is the track spacing; m is the number of phased array excitation units; If the main beams of each phased array excitation unit overlap in the exploration distance c, then x = px × m-(m-1)c, and the number of detectors is 8. The exploration method according to claim 5, characterized in that: In step 3, the main beam direction θ is determined max and the main beam width 2θ 0.5 , the specific formula is: 2θ 0.5 =|θ1―θ2| Among them, θ max is the main beam direction, 2θ 0.5 is the main beam width, n is the number of controllable CO2 seismic sources, d is the spacing between controllable CO2 seismic sources, and λ is the excitation wavelength of the controllable CO2 seismic sources; If the main beam direction is θ max = Near 90°, then 9. The exploration method according to claim 5, characterized in that: The specific calculation formula for the delay time in step 4 is: Among them, τ is the delay time.

10. The exploration method according to claim 5, characterized in that: In the step 5, each phased array excitation unit is first numbered from P1 to Pm in sequence, and then each phased array excitation unit is controlled in sequence according to the numbering sequence to perform delayed phased vector excitation.

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