Roadway advanced detection migration imaging method based on Love-type slot waves

Abstract

The invention discloses a roadway advanced detection migration imaging method based on Love-type slot waves, and relates to the technical field of slot wave seismic exploration, and the method comprises the steps: collecting and preprocessing slot wave data; carrying out single shot record analysis, obtaining a dispersion curve of the Love type slot wave based on a Love type slot wave dispersion equation, and designing a filter; obtaining corresponding Love-type slot wave data through band-pass filtering, and carrying out speed analysis, thereby obtaining an angstrom phase speed; and carrying out dynamic correction processing on the CDP gathers of the same reflection point based on the obtained angel phase velocity, carrying out superposition imaging by using a signal envelope method, and then carrying out offset correction to obtain an offset event angle, namely the abnormal geological trend. Therefore, by the adoption of the roadway advanced detection migration imaging method based on the Love type groove waves, advanced detection of the abnormal geology in front of the roadway is achieved, the type and the trend of the abnormal geology are judged, and a reliable basis is provided for guaranteeing construction safety.

Description

Technical Field

[0001] The invention relates to the technical field of slot wave seismic exploration, and in particular to a tunnel advance detection offset imaging method based on Love type slot waves. Background Art

[0002] Slot wave seismic exploration is a geophysical method that uses guided waves excited and propagated in coal seams to detect coal seam discontinuities. It is a branch of seismic exploration. Slot wave seismic exploration can detect geological anomalies such as small faults, collapse columns, coal seam bifurcations and thinning zones, water-filled goafs and abandoned tunnels. It has the advantages of large detection distance, high accuracy, strong anti-interference ability, easy-to-identify waveform characteristics, and intuitive final results. It is superior to other underground coal mine exploration methods in terms of detection accuracy and distance, and is currently one of the most effective detection methods.

[0003] According to the different characteristics of slot waves formed by the interference of different body waves, they are usually divided into two types: one is the Rayleigh slot wave, which is formed by the mutual interference of P wave and SV wave, and its particles are elliptically retrograde polarized in the plane perpendicular to the coal seam and containing the rays; the other is the Love slot wave, which is formed by the interference of SH wave and SH wave, and its particles are linearly polarized in the plane parallel to the coal seam and perpendicular to the propagation direction. It is a pure SH wave.

[0004] At present, the slot wave seismic exploration methods are mainly divided into two categories: transmission exploration and reflection exploration. Transmission exploration is applicable to the excitation in one tunnel and reception in another tunnel, so as to find out the geological structure in the coal seam area where the rays of the excitation point and the receiving point pass through; reflection exploration is applicable to the excitation in the same tunnel and reception in the same tunnel, so as to detect the structural conditions in the coal seams in front, behind and on both sides of the tunnel.

[0005] Slot wave tunnel advance detection is a special case of slot wave reflection method exploration. Its main purpose is to detect the fault in front of the tunnel, and it can also detect faults on both sides of the tunnel. However, in the process of reflection method exploration, the effective reflection section will become smaller as the angle between the fault and the tunnel increases, and the difficulty of exploration is gradually increasing. When the fault is perpendicular to the tunnel, the effective reflection section is only one point. Slot wave advance detection mainly detects faults in front of the tunnel, which means that it is more difficult than conventional slot wave reflection method exploration.

[0006] In addition, the reflected slot wave signal is generally weak, and the recorded signal-to-noise ratio is low, which seriously affects the successful application of reflected wave measurement. Moreover, slot waves are dispersive waves, and there is a significant difference between the phase velocity and the group velocity and they are dependent on the frequency, which increases the difficulty and complexity of imaging. Therefore, it is necessary to provide a multiple stacking imaging technology to improve the signal-to-noise ratio, suppress multiple waves and highlight the reflected waves, so as to provide a reliable basis for advanced detection of tunnels. Summary of the invention

[0007] The purpose of the present invention is to provide a tunnel advance detection migration imaging method based on Love-type slot waves, which can effectively identify faults with large drop heights, boundaries of collapse columns and hidden coal seam pinch-out locations, realize all-round migration imaging technology, and quantitatively interpret abnormal geology.

[0008] To achieve the above object, the present invention provides a lane advance detection migration imaging method based on Love type slot wave, comprising the following steps:

[0009] S1. Determine the combination of the observation system, use porous explosion to excite the slot wave, collect the slot wave data of the seismic trace through the detector, and pre-process the collected slot wave data to improve the slot wave signal-to-noise ratio;

[0010] S2, performing data analysis on the pre-processed single-shot slot wave record to obtain corresponding parameters, and then using the Love-type slot wave dispersion equation to obtain the Love-type slot wave dispersion curve through numerical calculation, and designing a filter based on the Love-type slot wave dispersion curve;

[0011] S3, using the designed filter to perform bandpass filtering on the acquired slot wave data to obtain the corresponding Love type slot wave data, and then perform velocity analysis on the Love type transmission slot wave to obtain the Airy phase velocity of the Love type slot wave;

[0012] S4. Based on the obtained Airy phase velocity, the CDP gathers at the same reflection point are subjected to dynamic correction, and stack imaging is performed using the signal envelope method. Then, offset correction is performed to obtain the event axis angle after offset, that is, the abnormal geological trend.

[0013] Preferably, the observation system includes reflection survey and transmission survey, and the corresponding combination is determined according to actual conditions.

[0014] Preferably, data analysis of the preprocessed single-shot slot wave record includes wave field type analysis, reflection slot wave analysis, and transmission slot wave analysis to preliminarily determine the slot wave data of abnormal geology.

[0015] Preferably, the Love-type slot wave dispersion equation is obtained according to the coal seam structure through the Love-type slot wave displacement equation and the stress-displacement boundary condition in seismic wave dynamics.

[0016] Preferably, the Love type transmission slot wave is subjected to velocity analysis as follows:

[0017] In the transmission detection method, there are N detectors at the shot point, and their distance is R i (i=1,2,3,...,N), given speed v j(j=1,2,3,…), then the travel time of the i-th detector in the shot channel is:

[0018]

[0019] Using the time window method, calculate the envelope amplitude superposition value M(v j ):

[0020]

[0021] Among them, E i (t) is the signal envelope of the i-th detector, Δt is the time window length, when M(v j ) reaches its maximum value, at this time v j is the Airy phase velocity.

[0022] Preferably, the offset correction satisfies the formula:

[0023] sinα=tanβ;

[0024] In the formula, α is the angle between the superimposed event and the roadway, and β is the angle between the event and the roadway after the offset.

[0025] Therefore, the present invention adopts the above-mentioned lane advance detection migration imaging method based on Love type slot wave, which has the following technical effects:

[0026] (1) Coal trough quality factor Q of Love type trough wave L There is a minimum point at the Airy phase point. Based on this, the Love-type slot wave can more accurately extract the Airy phase velocity and then obtain the phase axis of the corresponding reflected slot wave.

[0027] (2) Combining the reflection method and the transmission method for advanced detection can improve the detection accuracy of abnormal geology and realize preliminary detection of unknown abnormal areas, providing a reference for further accurate detection;

[0028] (3) By using the offset imaging method, filtering, direct wave removal, interpolation between traces and envelope superposition processing methods, effective detection of abnormal geology ahead of the tunnel can be achieved, and its actual direction can be obtained, providing a basis for subsequent mining work.

[0029] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flow chart of a tunnel advance detection migration imaging method based on Love type slot waves;

[0031] Figure 2is a curve diagram of the amplitude distribution characteristics of the Love type slot wave in an embodiment of a lane advance detection migration imaging method based on the Love type slot wave;

[0032] Figure 3 A method for lane advance detection migration imaging based on Love type slot wave is provided. In the embodiment, the Q of the Love type slot wave is L Value curve. DETAILED DESCRIPTION

[0033] The present invention can be explained in more detail by the following examples. The purpose of disclosing the present invention is to protect all changes and improvements within the scope of the present invention. The present invention is not limited to the following examples.

[0034] Embodiment 1

[0035] Usually, when constructing a stacking observation system, the consistency of the source is very important. If the consistency between shots is poor, it will cause unstable spectral characteristics and poor signal waveform repeatability, which will cause problems in data processing and interpretation. Therefore, it is required that the excitation conditions should be as consistent as possible.

[0036] The channel wave images recorded underground are often complicated by the influence of interference waves. The main interference waves are: surface waves and conversion waves related to the low-speed zone on the surface of the roadway coal wall; conversion waves related to the reflection and refraction of the surrounding rock-coal interface; direct and diffracted channel waves; sound waves and roadway reverberation waves; working vibrations of mining machinery and transportation machinery; walking of people and other micro-seismic events, etc. Since the spectrum of various interference waves is similar to the spectrum of effective waves, it is very difficult and sometimes even impossible to distinguish effective waves against the interference background. Therefore, it is very important to properly select the parameters of the excitation and receiving observation system and the instrument recording factors.

[0037] According to the geological task of slot wave detection, the layout of the tunnels in the detection area, the placement of mining equipment, the source of noise interference, etc. are carefully studied to determine the best combination of observation system methods, that is, the combined application of slot wave transmission method and reflection method. In addition, the best arrangement parameters should be selected for each observation method, such as track spacing, shot offset distance, offset distance, and farthest shot offset distance. The selection of these parameters is very important for the detection of geological tasks, and the following characteristics need to be met: first, the required structural size of the detection is to be achieved; second, the workload is reasonable, the detection efficiency is met, and the structure will not be missed. When encountering areas with large changes in signal waveform and amplitude, the method of encrypting observation points should be adopted, that is, reducing the shot point spacing and track spacing. In this embodiment, multi-hole explosion (some holes do not contain explosives) is used for slot wave excitation, which is conducive to the generation of Love waves and can significantly improve the radiation characteristics and frequency components. In order to ensure safety and loosening of anchor bolts during blasting, shallow holes and small amounts of excitation parameters are selected. The hole depth is 1.5m, the single hole charge is 100-200g, the shot point spacing should be 10m-20m, and the detection point spacing should be 10m.

[0038] After selecting the best observation system and combination of observation methods, the transmission method should be used for detection first. In the non-structural area, it can determine the wave velocity of the coal seam and the wave velocity of the surrounding rock, laying the foundation for the reflection method data processing and interpretation. When there is an unknown structure, it can also detect the structural belt in the coal seam, laying a good foundation for further detailed detection.

[0039] In this embodiment, a certain working face of Jingfang Coal Mine in Changzhi, Shanxi Province is selected as the research object to explore the scheme of tunnel advance detection. The coal seam of this coal mine is mainly a single layer of coal containing two layers of interlayered gangue. In order to explore the characteristics of Love-type slot waves, it is necessary to perform dispersion analysis on them. First, according to the coal seam structure, combined with the displacement equation of Love-type slot waves and the stress-displacement boundary conditions in seismic wave dynamics, the Love-type slot wave dispersion equation applicable to the coal seam structure is obtained. Then, the formation parameters are substituted into the Love-type slot wave dispersion equation, and the Love-type slot wave dispersion curve can be obtained by solving it.

[0040] In this embodiment, the Love-type channel wave dispersion curve of a single coal seam structure is analyzed, as shown in FIG. Figure 2 By analyzing the Love-type slot wave dispersion curve, the following characteristics are obtained:

[0041] (1) The phase velocity of the Love-type slot wave is between the shear wave velocity of the roof and floor plates and the coal seam, and gradually decreases and approaches the shear wave velocity of the coal seam with the increase of frequency;

[0042] (2) The group velocity of the Love-type slot wave is smaller than the phase velocity. With the increase of frequency, the group velocity gradually decreases and then gradually increases. When the frequency is high, the group velocity is close to the shear wave velocity of the coal seam. Therefore, there is a minimum point in the Love-type slot wave group velocity curve, which we call the Airy phase point.

[0043] (3) Each vibration mode of the Love-type slot wave has a starting frequency. Different vibration modes have different starting frequencies. The higher the order, the higher the starting frequency.

[0044] Since the energy frequency of the fundamental-order Love wave is lower than that of the higher-order Love-type slot wave, and its energy is equivalent to that of the higher-order Love-type slot wave, the fundamental-order Love-type slot wave is used as the standard in this embodiment.

[0045] In addition, this embodiment analyzes the variation of the energy distribution of the slot wave with the frequency, which is as follows:

[0046] Among them, the slot wave energy distribution ratio E is defined r :

[0047]

[0048] In the application process, the maximum amplitude in the coal seam is selected as the energy in the coal seam, and the maximum amplitude of the surrounding rock is selected as the energy of the surrounding rock, and the Love type slot wave amplitude distribution characteristic curve is obtained, such as Figure 2 As the frequency increases, E r The gradual increase means that the energy of the trough wave is more concentrated in the coal seam.

[0049] In addition, this embodiment also analyzes the coal trough quality factor Q of the Love type trough wave L curve, and explore the Erythrocyte phase point Q L The characteristics of the value can reduce the influence of the weakening of the energy of the Airy phase due to the absorption of the coal seam on the Airy phase on the geological exploration results. Figure 3 As shown, coal chute Q L The value is not only determined by the Q value of the coal seam, but also related to the Q value of the surrounding rock. L The value is related to the frequency. When the frequency is low, Q L The value tends to the Q value of the surrounding rock. At this time, the attenuation of the slot wave mainly depends on the Q value of the surrounding rock. When the frequency is high, Q L The value tends to the Q value of the coal seam because when the frequency is high, the energy of the slot wave is mainly concentrated in the coal seam. In addition, the Q value of the Love type slot wave L The value curve is similar to the group velocity curve, with a steep left branch and a gentle right branch, and has a minimum point near the Airy phase point.

[0050] Embodiment 2

[0051] like Figure 1 As shown, the present invention provides a tunnel advance detection offset imaging method based on Love type slot wave, and performs tunnel advance detection imaging on a collapse column in a certain working face of Jingfang Coal Mine in Changzhi, Shanxi Province, as follows:

[0052] First, based on the selected observation system, the collapse column in front of the working face is detected to obtain the corresponding seismic trace data. Through data preprocessing (such as first arrival correction, bad track removal, broadband bandpass filtering, etc.), the longitudinal and transverse waves can be significantly suppressed, the signal-to-noise ratio of the slot wave can be improved, and the slot waves of different modes can also be separated. The preprocessed data is analyzed. First, a single shot record analysis (including wave field type analysis, reflection slot wave analysis, transmission slot wave analysis, etc.) is performed to distinguish different types of wave fields and preliminary detection of collapse columns; secondly, a Love-type slot wave dispersion analysis is performed to provide a basis for the design of the filter; then, a velocity analysis is performed to obtain the Airy phase velocity corresponding to the Love-type slot wave.

[0053] Since the group velocity and phase velocity can be converted to each other, once one of them is calculated, the other can be derived from the formula. In this embodiment, the group velocity of the collected seismic trace data is obtained through multiple filtering and numerical calculation methods. The key to group velocity calculation is to measure the dominant frequency f of the slot wave train at any time t from the transmission slot wave record. P , thus obtaining the group velocity U(f P )=x / t, where x is the distance from the earthquake source to the receiving point, which is a known value.

[0054] In practical applications, let the trough wave record observed at the receiving point with the source x be x(t), and let X(f) be the Fourier transform or spectrum of x(t), with different center frequencies f i (i=1,2,3,…) a narrowband filter H(f,f i ) performs multiple filtering on X(f) to obtain a series of output spectra Y i (f) = F(f i )H(f,f i ), generally H(f,f i ) using a Gaussian filter. i (f) After inverse Fourier transform, we get the corresponding series of time signals y i (t), calculate each signal y i (t) is the instantaneous amplitude or envelope where z i (t) is y i (t) is the orthogonal seismic trace, i.e., the virtual seismic trace. Envelope A i (t) The time corresponding to the maximum value t i is the narrowband filter center frequency f i The travel time of the components near the source to the receiving point is then calculated as U(f i )=x / t iVelocity analysis is performed based on the measured channel wave data to obtain velocity spectra and stacking velocities, which can be used for dynamic correction to achieve common center point stacking, and can also be used for other processing and lithology interpretation.

[0055] In this embodiment, Love-type transmission slot wave data without structure is used to extract the Airy phase through rotation and narrow-band filtering to provide parameters for subsequent stacking and migration processing. The Airy phase velocity is relatively low, and it is the main energy part of the slot wave, which can be used as a sign to identify the slot wave, as follows:

[0056] If there is a transmission measurement detector array, the distance between the shot point and N detectors is R i (i=1,2,3,…,N), given speed v j (j=1,2,3,…), then the travel time of the shot channel detector is:

[0057]

[0058] So, at t i,j Open a time window t with a length of Δt forward i,j →t i,j +Δt, calculate a function value M(v j ):

[0059]

[0060] Among them, E i (t) is the signal envelope of the ith detector. Only when v is given j It is maximum when it is equal to the Airy phase velocity, that is, when M(v j ) reaches its maximum value, at which time v j is the Airy phase velocity.

[0061] Based on the extracted Airy phase velocity, the Love-type reflection slot wave detected in advance is migrated and imaged using the signal envelope method, thereby obtaining possible abnormal geology such as faults and collapse columns. Since the slot wave signal generally has a relatively high frequency, especially near the Airy phase, and the slot wave has a strong dispersion effect during propagation and the wave train of the slot wave is very wide, the phases of the slot waves between adjacent traces cannot be compared, which will cause reverse cancellation of the phases when performing related superposition and other processing. To this end, in this embodiment, the same reflection point is repeatedly observed multiple times through different shot offsets, and the reflection slot wave data obtained by the advance detection system are processed. Based on the extracted Airy phase, the corresponding velocity is obtained, and the CDP gathers of the same reflection point are subjected to normal time difference correction or dynamic correction processing, and the signal envelope method is used for superposition imaging to improve the signal-to-noise ratio, suppress multiple waves, and highlight the reflection waves.

[0062] Among them, the envelope E(t) of the seismic trace can be calculated as follows:

[0063]

[0064] In the formula, x i (t) is a virtual seismic trace, which can be directly obtained from the real seismic trace according to the Hilbert transform.

[0065] Through the above method, the superposition event axis of the Love type slot wave is obtained. When the angle between the Love type slot wave event axis and the roadway is not large, no offset processing is required. For example, when the angle is less than 25°, no offset is usually performed. When the angle is relatively large, generally exceeding 30°, offset correction is required, and the offset correction satisfies the following formula:

[0066] sinα=tanβ;

[0067] Where α is the superimposed event angle, and β is the event angle after migration.

[0068] Based on the above method, in the forward simulation analysis of fault detection, when the angle between the fault direction and the roadway is large, the conventional reflection slot wave processing process can still be used to process it, and it is only necessary to offset the superimposed phase axis. In the forward simulation analysis of the coal seam thinning area, the transmission method slot wave exploration, the slot wave energy CT effect is not good, and the direction of the scour zone cannot be located. However, the detection method of this embodiment is used, and the reflection interface obtained is consistent with the actual model, which fully proves the effectiveness of the detection method. In addition, the method of this embodiment can also identify faults with a drop greater than 1 / 2 times the thickness of the coal seam within 100m in front of the tunneling head of the excavation working face.

[0069] In another embodiment, possible collapse columns are detected in the working face area of ​​actual excavation. This embodiment combines transmission detection and reflection detection to detect the collapse columns in front of the tunnel. It is capable of finding the boundary positions of concealed collapse columns with a diameter greater than 20 m within 100 m in front of the tunnel excavation head of the excavation working face.

[0070] Therefore, the present invention adopts the above-mentioned tunnel advance detection offset imaging method based on Love-type slot waves, which can detect abnormal geology in front of the tunnel and accurately obtain the direction of the abnormal geology, providing a reliable basis for ensuring the safety of construction.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A tunnel advance detection migration imaging method based on Love-type slot waves, characterized in that: The following steps are involved: S1. Determine the combination of the observation system, use porous explosion to excite the slot wave, collect the slot wave data of the seismic trace through the detector, and pre-process the collected slot wave data to improve the slot wave signal-to-noise ratio; S2, performing data analysis on the pre-processed single-shot slot wave record to obtain corresponding parameters, and then using the Love-type slot wave dispersion equation to obtain the Love-type slot wave dispersion curve through numerical calculation, and designing a filter based on the Love-type slot wave dispersion curve; S3, using the designed filter to perform bandpass filtering on the acquired slot wave data to obtain the corresponding Love type slot wave data, and then perform velocity analysis on the Love type transmission slot wave to obtain the Airy phase velocity of the Love type slot wave; S4. Based on the obtained Airy phase velocity, the CDP gathers at the same reflection point are subjected to dynamic correction, and stack imaging is performed using the signal envelope method. Then, offset correction is performed to obtain the event axis angle after offset, that is, the abnormal geological trend.

2. The method for lane advance detection migration imaging based on Love-type slot waves according to claim 1, characterized in that: The observation system includes reflection survey and transmission survey, and the corresponding combination is determined according to actual conditions.

3. The method for tunnel advance detection migration imaging based on Love-type slot waves according to claim 1, characterized in that: Data analysis of the pre-processed single-shot slot wave records includes wave field type analysis, reflection slot wave analysis, and transmission slot wave analysis to preliminarily determine the slot wave data of abnormal geology.

4. The method for tunnel advance detection migration imaging based on Love type slot wave according to claim 1, characterized in that: The Love-type slot wave dispersion equation is obtained according to the coal seam structure through the Love-type slot wave displacement equation and the stress-displacement boundary conditions in seismic wave dynamics.

5. The method for tunnel advance detection migration imaging based on Love-type slot waves according to claim 1, characterized in that: The velocity analysis of Love-type transmission slot waves is as follows: In the transmission detection method, there are N detectors at the shot point, and their distance is R i (i=1,2,3, … ,N), given speed v j (j=1,2,3, ... ), then the travel time of the i-th detector of the shot point is: Using the time window method, calculate the envelope amplitude superposition value M(v j ): Among them, E i (t) is the signal envelope of the i-th detector, Δt is the time window length, when M(v j ) reaches its maximum value, at this time v j is the Airy phase velocity.

6. The method for tunnel advance detection migration imaging based on Love type slot wave according to claim 1, characterized in that: The offset correction satisfies the formula: sinα=tanβ; Where α is the angle between the superimposed event and the roadway, and β is the angle between the event and the roadway after migration.

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