A method for directional seismic detection of tunnel rock surface

Abstract

The present invention discloses a method for directional seismic detection of a tunnel rock surface, comprising the following steps: determining a target seismic source excitation point; determining two acquisition areas based on the target seismic source excitation point, each acquisition area including one of two centrally symmetrical sensor placement points, each of the two sensor placement points being centrally symmetrical about the target seismic source excitation point; initiating excitation of the target seismic source excitation point, and sequentially placing two sensors connected to a data acquisition instrument at the two centrally symmetrical sensor placement points, respectively, to sequentially acquire two sets of mixed seismic recording signals through the data acquisition instrument, each set of mixed seismic recording signals including multiple seismic recording signals, each seismic recording signal corresponding to a signal received by each sensor at each sensor placement point within the corresponding acquisition area; and determining the fault structure of the tunnel based on each seismic recording signal. The present invention aims to improve the reliability of detection results and thereby enhance the efficiency of subsequent construction operations.

Description

Technical Field

[0001] The present invention relates to the field of geophysical exploration technology, and in particular to a method for directional seismic detection of tunnel rock surfaces. Background Art

[0002] Currently, efficient detection operations within confined underground tunnels are hampered by the complex internal environment. Because tunnel operations inevitably use metal materials or equipment for support, transportation, plumbing, and ventilation, electromagnetic detection methods are impractical. Seismic detection, on the other hand, is generally immune to interference from metal components and can be applied in engineering practice. Therefore, obtaining as many standardized data records as possible, while ensuring safety, is crucial for seismic data interpretation. Among them, not using drilling assistance is a convenient method for seismic data acquisition in a confined tunnel environment. This convenient seismic data acquisition method mainly involves moving the source excitation point, but it is greatly affected by the unevenness of the tunnel rock surface, the force conditions at the source point are not consistent, and there is a risk of collapse when the rock surface at the excitation point is excited. At the same time, the existing publication number CN107643542A discloses a three-dimensional elastic wave tomography detection method for coal mine goafs based on well-ground integration. By exciting seismic waves in the tunnel in the lower coal group below the detected coal seam, receiving seismic waves on the ground, and performing single-difference tomography on the acquired direct waves, the three-dimensional velocity spatial distribution between the lower coal group and the ground is obtained. Although this method effectively expands the perspective angle of direct wave CT detection and improves the ray coverage of direct waves, due to the use of multiple source points, the force conditions at each source point are inconsistent when the seismic waves are actually excited by the source, which makes it difficult to compare the seismic records generated by the seismic waves at different source excitation points.

[0003] Furthermore, there is an urgent need to propose an operating method and a corresponding convenient data solution method that can realize convenient data collection in the confined space of the tunnel and efficiently process the collected data. Summary of the Invention

[0004] The main purpose of the present invention is to provide a method for directional seismic detection of rock surfaces in tunnels, aiming to solve the technical problem of limited existing tunnel operations.

[0005] To achieve the above object, the present invention provides a method for directional seismic detection of a tunnel rock surface, the method comprising the following steps:

[0006] Determine the target earthquake source excitation point;

[0007] Two acquisition areas are determined according to the target source excitation point, each acquisition area includes one of two centrally symmetrical sensor placement points, and each of the two sensor placement points is a centrally symmetrical point with the target source excitation point;

[0008] The target source excitation point is activated, and two sensors connected to a data acquisition instrument are sequentially placed at two centrally symmetrical sensor placement points, so as to sequentially obtain two sets of mixed seismic recording signals through the data acquisition instrument. Each set of mixed seismic recording signals includes multiple channels of seismic recording signals, and each channel of seismic recording signals corresponds to a signal received by each sensor at each sensor placement point within the corresponding acquisition area;

[0009] The fault structure of the tunnel is determined based on the seismic recording signals of each channel.

[0010] Optionally, the step of determining the fault structure of the tunnel according to each seismic recording signal includes:

[0011] The seismic recording signals in each group of seismic recording signals are horizontally superimposed to obtain the corresponding average superimposed signal;

[0012] Determining whether each averaged superimposed signal includes valid time window feature information;

[0013] When each average superimposed signal includes at least one valid time window characteristic information, correlation analysis is performed on each valid time window characteristic information and the corresponding seismic recording signals in the same time period to obtain the correlation coefficient corresponding to each seismic recording signal in the same time period;

[0014] Determine whether the correlation coefficient corresponding to each seismic recording signal meets the preset standard. If so, determine the reflected wave signal of the fault structure of the tunnel in the corresponding acquisition area;

[0015] The fault structure of the tunnel is determined according to the reflected wave signal.

[0016] Optionally, the step of determining whether the average superimposed signal includes valid time window feature information includes:

[0017] Determine whether the maximum amplitude of each average superposition signal within the preset wavelength time window is greater than 5% of the maximum amplitude of the entire record after superposition;

[0018] If the maximum amplitude of each average superposition signal in the window within the preset wavelength time is greater than 5% of the maximum amplitude after superposition of the entire record, the maximum amplitude in the window within the wavelength time is regarded as valid time window feature information.

[0019] Optionally, the step of determining whether the correlation coefficient corresponding to each seismic recording signal meets a preset standard includes:

[0020] Determine the magnitude of the correlation coefficient corresponding to each seismic recording signal in the same time period and the first threshold, as well as the proportion of the correlation coefficient corresponding to each seismic recording signal that is greater than the first threshold and the magnitude of the second threshold;

[0021] If the correlation coefficients of the seismic recording signals in the same time period are greater than a first threshold and the proportion of the correlation coefficients greater than the first threshold is greater than a second threshold, it is considered that the preset standard is met.

[0022] Optionally, the step of performing correlation analysis on the corresponding seismic recording signals in the same time period according to the characteristic information of each effective time window includes:

[0023] The characteristic information of each effective time window is correlated and analyzed with the corresponding seismic recording signals in the same period according to the time sequence.

[0024] Optionally, the step of performing correlation analysis on the characteristic information of each effective time window and the corresponding seismic recording signals in the same time period according to the time sequence includes:

[0025] The average superposition signals are correlated and analyzed from the first time period with the corresponding seismic recording signals according to the effective time window characteristic information to obtain the correlation coefficient corresponding to each seismic recording signal, and it is judged whether the correlation coefficient meets the preset standard. If not, the correlation analysis of the next time period is carried out.

[0026] Optionally, the step of determining the fault structure of the tunnel according to the reflected wave signal includes:

[0027] Acquire, according to the time period corresponding to the reflected wave signal, a first reflected wave transmission time of a corresponding time period of any sensor placement point in the acquisition area and a second reflected wave transmission time of a sensor placement point symmetrical thereto in another acquisition area;

[0028] If the transmission time of the first reflected wave is the same as the transmission time of the second reflected wave, then the reflection surface of the fault structure of the tunnel is perpendicular to the directional detection direction;

[0029] If the transmission time of the first reflected wave is different from the transmission time of the second reflected wave, the oblique angle e between the fault structural surface of the tunnel and the directional detection direction is determined according to the approximate formula.

[0030] Optionally, the approximate formula is:

[0031] e≈arcsin{(t1-t2)*V / (r1+r2)};

[0032] V is the average wave velocity of the rock mass, r1 and r2 are the distances from the two symmetrical sensor placement points to the source excitation point, and t1 and t2 are the arrival times of the reflected waves from the same fault structure surface obtained by the two sensors at the two symmetrical sensor placement points.

[0033] Optionally, the step of sequentially placing two sensors connected to the data acquisition device at two centrally symmetrical sensor placement points includes:

[0034] With the target source excitation point as the center, gradually move the two sensors from near to far to two centrally symmetrical sensor placement points.

[0035] The present invention provides a method for directional seismic detection of a tunnel rock surface, which comprises determining a target seismic source excitation point; determining two acquisition areas according to the target seismic source excitation point, each acquisition area including one of two centrally symmetrical sensor placement points, each of the two sensor placement points being centrally symmetrical with the target seismic source excitation point; starting the excitation of the target seismic source excitation point, and sequentially placing two sensors connected to a data acquisition instrument on the two centrally symmetrical sensor placement points, so as to sequentially obtain two groups of mixed seismic recording signals through the data acquisition instrument, each group of mixed seismic recording signals including multiple seismic recording signals, each seismic recording signal corresponding to a signal received by each sensor at each sensor placement point when the sensor moves within the corresponding acquisition area; and determining the fault structure of the tunnel according to each seismic recording signal.

[0036] Among them, each seismic recording signal is horizontally stacked in advance to obtain an average superposition signal, and then the processed average superposition signal is subjected to correlation analysis with the original collected signal, and the reflected wave signal of the fault structure of the tunnel in the corresponding collection area is determined according to the correlation situation, and then the fault structure of the tunnel is determined according to the reflected wave signal. The present invention keeps the source excitation point fixed and symmetrically transforms the position of the signal collection point, thereby realizing the phase shift of the received signal and confirming it through horizontal stacking and re-correlation, so as to realize reliable extraction of the reflected wave signal of the target structural surface, calculate the distance of the relevant hidden structural surface in the directional detection direction according to the arrival time of the qualified reflected wave signal and the average wave velocity of the rock mass, and calculate the difference in distance between the same hidden structural surface on the left and right sides. The oblique angle of the hidden structure relative to the directional detection direction is used to determine the fault structure of the tunnel. This is because the present invention uses a "fixed source-moving sensor" operating mode, which takes into account the complexity of the construction conditions in the confined tunnel space and ensures high consistency of the multi-channel seismic data acquisition signals. By superimposing signals at different source-offset distances (the distance between the fixed source excitation point and the receiving sensor) within a single acquisition area, the half-wave loss method is used to suppress the interference of surface waves and direct waves. Effective reflection waves are then extracted through correlation analysis of effective reflection signals, improving the recognition of effective reflection waves from within the tunnel rock mass. By comparing the arrival times of reflection wave signals in two symmetrical acquisition areas about the source excitation point, the inclination characteristics of the fault plane within the tunnel rock mass are confirmed. The algorithm is simple, fast, and easy to master. As can be seen, the entire construction operation is simple, effectively improving the reliability and efficiency of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of an embodiment of a method for directional seismic detection of a tunnel rock surface according to the present invention;

[0038] Figure 2 This is a schematic diagram of the data collection operation for directional seismic detection on the rock face of a roadway using the Nebula laser positioning assistance;

[0039] Figure 3 for Figure 2 A schematic diagram of a hybrid seismic record obtained in one acquisition area at a source excitation point in the illustrated embodiment;

[0040] Figure 4 for Figure 3 A comparison diagram of the seismic record after horizontal stacking and averaging of the mixed seismic record in the embodiment and the record before stacking;

[0041] Figure 5 Schematic diagram of the data acquisition operation for directional seismic detection on the rock surface of a roadway using multi-layer ring laser positioning assistance;

[0042] Figure 6 This is a schematic diagram of the principle of channel half-wave superposition suppressing direct waves in the second embodiment of a method for directional seismic detection of a tunnel rock surface according to the present invention;

[0043] Figure 7 This is a schematic diagram of the geometric principle of seismic wave ray propagation for determining the fault structure of a tunnel based on reflected wave signals in the present invention.

[0044] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0045] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] like Figure 1 FIG. 1 is a flow chart of an embodiment of a method for directional seismic detection of a tunnel rock surface according to the present invention, wherein the method comprises:

[0047] Step S100: determining the target source excitation point.

[0048] Step S200: determining two acquisition areas according to the target source excitation point, each acquisition area including one of two centrally symmetrical sensor placement points, each of the two sensor placement points being centrally symmetrical with the target source excitation point.

[0049] Specifically, if Figure 2As shown in the figure, a relatively complete and stable rock surface point is found near the middle of the tunnel rock surface 1 for directional seismic detection as the source excitation point 5, and a star point laser is used to arrange sensor placement points symmetrically left and right or up and down with the source excitation point 5 as the center. Figure 2 In the illustrated embodiment, sensor placement points are bilaterally symmetrical, with left and right sensor points 3 and 4 positioned symmetrically around the source excitation point 5. Laser nebula point 2 is a pre-determined sensor placement point for the star point laser. The star point laser is positioned perpendicular to the rock face, with adjacent nebula points positioned at consistent horizontal and vertical distances, all located on laser nebula point 2. Furthermore, multi-layer circular lasers or infrared projection devices can be used as auxiliary devices to quickly and conveniently improve sensor positioning accuracy and enhance the comparability of symmetrical hybrid seismic recordings. Furthermore, the rock surface for tunnel directional seismic exploration can also include the tunnel face, side walls, and top and bottom surfaces of the tunnel.

[0050] Step S300, start the excitation of the target source excitation point, and place two sensors connected to the data acquisition instrument on two centrally symmetrical sensor placement points respectively, so as to obtain two groups of mixed seismic recording signals in sequence through the data acquisition instrument. Each group of mixed seismic recording signals includes multiple seismic recording signals, and each seismic recording signal corresponds to the signal received by each sensor at each sensor placement point in the corresponding acquisition area.

[0051] Specifically, two sensors are placed symmetrically around the source excitation point, and the signals from the two sensors are connected to a data acquisition instrument. Typically, the data acquisition instrument uses a dual-channel seismometer, which excites seismic waves at the source excitation point and simultaneously records the seismic wave signals from the two sensors. Preferably, the two sensors are moved symmetrically from near to far, repeating the source excitation to obtain a mixed seismic recording signal from all sensor placement points. Generally, the distance between two sensor movements can be set to half the wavelength of the surface wave, facilitating the subsequent use of the half-wave loss method to suppress surface waves using the horizontal stacking of shot gather records collected by an even number of geophones.

[0052] Step S400: determining the fault structure of the tunnel based on each seismic recording signal. The step of determining the fault structure of the tunnel based on each seismic recording signal specifically includes:

[0053] Step S410 : horizontally superimpose each seismic recording signal in each group of seismic recording signals to obtain a corresponding average superimposed signal.

[0054] Specifically, horizontal stacking means that the time coordinates of all recorded signals participating in the stack remain unchanged. The amplitude values ​​at each identical time point on each record are summed and then divided by the number of records participating in the stacking to form a new record. Furthermore, before horizontal stacking, each set of mixed seismic records is filtered using an analog or numerical high-pass filter to obtain a high-frequency signal that initially suppresses direct shear waves and surface waves, thereby enhancing the effectiveness of horizontal stacking in suppressing interference and extracting reflected waves. Furthermore, amplitude compensation can be performed on the amplitude of the effective signal before stacking to ensure energy balance between the individual traces in the mixed seismic record.

[0055] Step S420: Determine whether each averaged superimposed signal includes valid time window feature information.

[0056] Specifically, a determination is made as to whether the maximum amplitude of each averaged superimposed signal within a preset wavelength period is greater than or equal to 5% of the maximum amplitude of the entire superimposed record. If the maximum amplitude of each averaged superimposed signal within the preset wavelength period is greater than 5% of the maximum amplitude of the entire superimposed record, the maximum amplitude within that wavelength period is considered valid time window characteristic information. Furthermore, the length of the valid correlation time window characteristic information is greater than or equal to one period of the valid reflected wave signal. Generally, one to three wavelength periods are used to determine valid time window characteristic information, and in actual applications, multiple preset wavelength periods can be selected to determine whether the information is valid.

[0057] Step S430, when each average superposition signal includes at least one valid time window characteristic information, correlation analysis processing is performed on each valid time window characteristic information and the corresponding each seismic recording signal in the same time period to obtain the correlation coefficient corresponding to each seismic recording signal in the same time period. Specifically, correlation analysis is performed on the seismic records in the valid time window characteristic information and the seismic records in the same time period of the records participating in the superposition. Preferably, each valid time window characteristic information is correlated with each corresponding seismic recording signal in the same time period according to the time period sequence, that is, each average superposition signal is correlated with each corresponding seismic recording signal in the same time period from the first time period of the valid time window characteristic information to obtain the correlation coefficient corresponding to each seismic recording signal. Wherein, the correlation analysis is obtained by using the following correlation coefficient calculation formula, the specific correlation coefficient calculation formula is:

[0058]

[0059] Where Cov(X, Y) is the covariance of vectors X and Y, Var[X] is the variance of X, Var[Y] is the variance of Y, and r(X, Y) is the correlation coefficient. In this embodiment, the two sampled signals are pre-formed into signal vectors X and Y of the same length. The correlation coefficient is then calculated according to the above-mentioned correlation coefficient calculation formula. The correlation or similarity between the two signals is determined based on whether the correlation coefficient is 1 or close to 1. Generally, the absolute value of the calculated correlation coefficient between two vectors is between 0 and 1. When the absolute value of the correlation coefficient is close to or equal to 1, it indicates that the two signals are close to the same and are very likely to be of the same type. If it moves away from 1 and approaches 0, it indicates that the two signals are very different and are not of the same type.

[0060] Step S440 determines whether the correlation coefficients corresponding to the seismic recording signals meet a preset standard. Specifically, the correlation coefficients corresponding to the seismic recording signals in the same time period are compared to a first threshold, and the percentage of the seismic recording signals with correlation coefficients greater than the first threshold is compared to a second threshold. If the correlation coefficients of the seismic recording signals in the same time period are greater than the first threshold, and the percentage of the correlation coefficients greater than the first threshold is greater than the second threshold, the preset standard is considered to be met. Specifically, correlation analysis is performed on each averaged superimposed signal with the original mixed seismic recording for the same time period according to the effective time window characteristic information. A qualified reflection wave signal is determined based on the comprehensive evaluation criteria of a correlation coefficient greater than a first threshold Q and a percentage of the number of channels with correlation coefficients greater than Q greater than a second threshold A. The Q value is generally greater than 0.75, and can be appropriately increased for relatively intact roadway rock surfaces. Furthermore, the percentage A of the channels with correlation coefficients greater than the first threshold Q corresponding to the seismic recording signals is generally greater than 90.

[0061] Step S441 : If the correlation coefficients corresponding to the seismic recording signals of each channel meet the preset standard, the reflected wave signals of the fault structure of the tunnel in the corresponding acquisition area are determined.

[0062] Specifically, according to the time period corresponding to the reflected wave signal, a first reflected wave transmission time of a corresponding time period at any sensor placement point in the acquisition area and a second reflected wave transmission time of a sensor placement point symmetrical thereto in another acquisition area are obtained;

[0063] If the transmission time of the first reflected wave is the same as the transmission time of the second reflected wave, then the reflection surface of the fault structure of the tunnel is perpendicular to the directional detection direction;

[0064] If the transmission time of the first reflected wave is different from the transmission time of the second reflected wave, the oblique angle e between the fault structure surface of the tunnel and the directional detection direction is determined according to an approximate formula. The approximate formula is:

[0065] e≈arcsin{(t1-t2)*V / (r1+r2)};

[0066] V is the average wave velocity of the rock mass, r1 and r2 are the distances from two symmetrical sensor locations to the source excitation point, and t1 and t2 are the arrival times of reflected waves from the same fault surface at two sensors at the two symmetrical sensor locations. In this embodiment, effective reflected waves are extracted through correlation analysis of effective reflected signals, improving the recognition of effective reflected waves from within the roadway rock mass. Furthermore, by comparing the arrival times of reflected wave signals from two symmetrically collected areas about the source excitation point, the inclination characteristics of the fault surface within the roadway rock mass are confirmed. The algorithm is simple, fast, and easy to master.

[0067] Step S442: If the correlation coefficients corresponding to the seismic recording signals do not meet the preset standard, the correlation analysis process for the next time period is continued until the preset standard is met.

[0068] In this embodiment, the target seismic source excitation point is determined; two acquisition areas are determined according to the target seismic source excitation point, each acquisition area includes one of two centrally symmetrical sensor placement points, and each of the two sensor placement points is centrally symmetrical with the target seismic source excitation point; the target seismic source excitation point is activated, and two sensors connected to a data acquisition instrument are placed on the two centrally symmetrical sensor placement points in turn, so as to obtain two groups of mixed seismic recording signals in turn through the data acquisition instrument, each group of mixed seismic recording signals includes multiple channels of seismic recording signals, and each channel of seismic recording signals corresponds to the signal received by each sensor at each sensor placement point when it moves in the corresponding acquisition area; and the channel seismic recording signals are horizontally superimposed in advance to obtain an average superimposed signal, and then the average superimposed signal is obtained by The processed average superposition signal is subjected to correlation analysis with the originally collected signal, and the reflected wave signal of the fault structure of the tunnel in the corresponding collection area is determined according to the correlation situation, and then the fault structure of the tunnel is determined according to the reflected wave signal. The present invention achieves phase shift of the received signal by keeping the source excitation point fixed and symmetrically transforming the position of the signal collection point, thereby realizing reliable extraction of the reflected wave signal of the target structural surface, and calculating the distance of the relevant hidden structural surface in the directional detection direction according to the arrival time of the qualified reflected wave signal and the average wave velocity of the rock mass, and calculating the oblique angle of the hidden structure relative to the directional detection direction based on the difference in distance between the same hidden structural surface on the left and right sides, thereby determining the fault structure of the tunnel. It can be seen that the entire construction operation is simple at the same time.

[0069] Furthermore, in order to better illustrate the collection steps in the present invention, the following is described through specific examples.

[0070] Example 1

[0071] Find a relatively complete and stable rock surface point near the middle of the tunnel rock surface for directional seismic detection as the source excitation point, and use the star point laser to arrange the sensor placement points symmetrically around the source point. Figure 2 As shown, the vertical distance between the laser and the rock surface is 5 meters, and the horizontal and vertical distances between adjacent nebula points are 0.5 meters. A total of 40 sensor placement points are arranged symmetrically on the left and right, all located on nebula points. A pair of sensors are arranged symmetrically around the source point. The sensor signals are connected to a dual-channel seismometer. Seismic waves are excited at the source excitation point 5, and the seismometer synchronously records the seismic wave signals from both sensors. The left and right sensors are moved symmetrically from near to far, and the source excitation is repeated to obtain mixed seismic records at multiple offsets.

[0072] Then, two groups of 40 symmetrical mixed seismic records are horizontally stacked and averaged to obtain superimposed signals. Take the mixed seismic record of one acquisition area as an example, as shown in Figure 3-4 As shown in the figure, a cross-correlation analysis is performed on the signals in the same time period of the superimposed signal time window and the original mixed seismic records, i.e., the correlation time window. The qualified reflection wave signals are judged by taking the correlation coefficient greater than the threshold value Q=0.85 and the proportion of the number of traces with the correlation coefficient Q greater than or equal to 0.85 greater than the percentage A=90% as the comprehensive evaluation criteria.

[0073] Under the conditions that meet the evaluation criteria, including the qualified reflected wave signal arrival time T = 32ms and the average rock mass wave velocity V = 4500m / s, the distance to the relevant hidden structure surface in the directional detection direction is calculated as S = T × V / 2 = 74m. If the arrival times of the left and right sets of reflected waves are the same, it is confirmed that the reflection interface is perpendicular to the directional detection direction. If there is a difference in the arrival times of the left and right reflected waves, the difference in the distances to the same hidden structure surface on the left and right sides and the intersection angle calculation approximate formula are used to calculate the oblique angle of the hidden structure with respect to the directional detection direction.

[0074] Example 2

[0075] A relatively intact and stable rock surface point is found near the middle of the tunnel rock surface for directional seismic detection as the source excitation point, and a five-layer ring laser is used to arrange left-right symmetrical sensor placement points around the source point. Figure 5The vertical distance between the laser and the rock surface was 8 meters, and the difference in radius between adjacent laser rings was 0.6 meters, which is half the 1.2-meter wavelength of the rock surface wave. A total of 40 sensor placement points were symmetrically arranged, located on the second to fifth laser rings of different radii from the source. A pair of sensors were also symmetrically arranged around the source, with the sensor signals connected to a dual-channel seismometer. Seismic waves were excited at the source excitation point, and the seismometer simultaneously recorded the seismic wave signals from both sensors. The left and right sensors were symmetrically moved point by point from near to far, and repeated source excitation was used to obtain mixed seismic records at multiple offsets. By the end of data acquisition, 20 channels each were recorded, totaling 40 channels.

[0076] Each set of mixed records can be divided into five parts along the radial direction centered on the earthquake source. When the four records in each part are horizontally stacked, the phases of the surface waves of two adjacent records are exactly opposite, and they cancel each other out to a certain extent after horizontal stacking (see Figure 6 ), the five records are superimposed and then horizontally superimposed, which can greatly suppress the surface wave. The reflected wave signal from the front of the working rock face is similar to that in Example 1 (as shown in Figure 3-4 ), the phase shift at different sensor placement points is small and is enhanced to a certain extent after horizontal superposition.

[0077] Similarly, similar to Example 1, the reflected wave signal of the fault structure surface is obtained through correlation analysis, and the fault structure of the tunnel is determined based on the reflected wave signal, such as Figure 7 As shown, according to the actual R 左 、R 右 The travel time of the reflected waves from the same reflection interface on both sides is 41.43ms and 41.90ms. The measured longitudinal wave velocity on site is 4200m / s. It can be calculated that the vertical distances H1 and H2 from the working surface to the reflection surface are 87m and 88m respectively. 左 、R 右 The distance △r between the left and right sides of the same hidden structure is 4.8 meters. The oblique angle of the hidden structure relative to the directional detection direction is calculated using the difference in distance between the left and right sides of the same hidden structure. In the approximate formula [e = arcsin((H1-H2) / △r)], △r = 4.8 meters, H1 = 87 meters, and H2 = 88 meters are the calculated distances between the reflecting surfaces on both sides of the symmetry. The intersection angle e = 12 degrees, obliquely crossing from the direction of H1 to the direction of H2.

[0078] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or system comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or system. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or system comprising the element.

[0079] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for directional seismic detection of a tunnel rock surface, characterized in that: The method comprises the following steps: Determine the target earthquake source excitation point; Two acquisition areas are determined based on the target seismic source excitation point, each of which includes multiple sensor placement points. The sensor placement points in the two acquisition areas form multiple symmetrical point pairs with the target seismic source excitation point as the center. The two sensor placement points included in each symmetrical point pair are located in the two acquisition areas and are symmetrical about the center of the target seismic source excitation point. The target source excitation point is activated, and two sensors connected to a data acquisition instrument are sequentially placed at the two sensor placement points of each symmetrical point pair, so as to sequentially obtain two sets of mixed seismic recording signals through the data acquisition instrument. Each set of mixed seismic recording signals includes multiple channels of seismic recording signals, and each channel of seismic recording signals corresponds to the signal received by each sensor at each sensor placement point within the corresponding acquisition area; The fault structure of the tunnel is determined based on the seismic recording signals of each channel.

2. The method for directional seismic detection of a tunnel rock surface according to claim 1, characterized in that: The step of determining the fault structure of the tunnel according to each seismic recording signal includes: The seismic recording signals in each group of seismic recording signals are horizontally superimposed to obtain the corresponding average superimposed signal; Determining whether each averaged superimposed signal includes valid time window feature information; When each average superimposed signal includes at least one valid time window characteristic information, correlation analysis is performed on each valid time window characteristic information and the corresponding seismic recording signals in the same time period to obtain the correlation coefficient corresponding to each seismic recording signal in the same time period; Determine whether the correlation coefficient corresponding to each seismic recording signal meets the preset standard. If so, determine the reflected wave signal of the fault structure of the tunnel in the corresponding acquisition area; The fault structure of the tunnel is determined according to the reflected wave signal.

3. The method for directional seismic detection of a tunnel rock surface according to claim 2, characterized in that: The step of determining whether the average superimposed signal includes valid time window feature information comprises: Determine whether the maximum amplitude in the window within the preset wavelength time is greater than 5% of the maximum amplitude after the entire record is superimposed; If the maximum amplitude in the window within the preset wavelength time is greater than 5% of the maximum amplitude after superposition of the entire record, the maximum amplitude in the window within the wavelength time is regarded as valid time window feature information.

4. The method for directional seismic detection of a tunnel rock surface according to claim 2, characterized in that: The step of determining whether the correlation coefficient corresponding to each seismic recording signal meets a preset standard includes: Determine the magnitude of the correlation coefficient corresponding to each seismic recording signal in the same time period and the first threshold, as well as the proportion of the correlation coefficient corresponding to each seismic recording signal that is greater than the first threshold and the magnitude of the second threshold; If the correlation coefficient of each seismic recording signal in the same time period is greater than a first threshold and the proportion of the number of channels with correlation coefficients greater than the first threshold is greater than a second threshold, it is considered to meet the preset standard.

5. The method for directional seismic detection of tunnel rock surface according to claim 2, characterized in that: The step of performing correlation analysis and processing on the basis of the characteristic information of each effective time window and the corresponding seismic recording signals in the same time period includes: The characteristic information of each effective time window is correlated and analyzed with the corresponding seismic recording signals in the same time period according to the time period sequence.

6. The method for directional seismic detection of a tunnel rock surface according to claim 5, characterized in that: The step of performing correlation analysis on the characteristic information of each effective time window and the corresponding seismic recording signals in the same time period according to the time sequence includes: The average superposition signals are correlated and analyzed from the first time period with the corresponding seismic recording signals according to the effective time window characteristic information to obtain the correlation coefficient corresponding to each seismic recording signal, and it is judged whether the correlation coefficient meets the preset standard. If not, the correlation analysis of the next time period is carried out.

7. The method for directional seismic detection of a tunnel rock surface according to any one of claims 2 to 6, characterized in that: The step of determining the fault structure of the tunnel according to the reflected wave signal includes: Acquire, according to the time period corresponding to the reflected wave signal, a first reflected wave transmission time of a corresponding time period at any sensor placement point within the acquisition area and a second reflected wave transmission time of a sensor placement point symmetrical thereto in another acquisition area; If the transmission time of the first reflected wave is the same as the transmission time of the second reflected wave, then the reflection surface of the fault structure of the tunnel is perpendicular to the directional detection direction; If the transmission time of the first reflected wave is different from the transmission time of the second reflected wave, the oblique angle e between the fault structural surface of the tunnel and the directional detection direction is determined according to the approximate formula.

8. The method for directional seismic detection of a tunnel rock surface according to claim 7, characterized in that: The approximate formula is: e≈arcsin{(t1-t2)*V / (r1+r2)}; V is the average wave velocity of the rock mass, r1 and r2 are the distances from the two symmetrical sensor placement points to the source excitation point, and t1 and t2 are the arrival times of the reflected waves from the same fault structure surface obtained by the two sensors at the two symmetrical sensor placement points.

9. The method for directional seismic detection of a tunnel rock surface according to claim 8, characterized in that: The step of sequentially placing two sensors connected to a data acquisition instrument at two sensor placement points of each symmetrical point pair comprises: With the target source excitation point as the center, gradually move the two sensors from near to far to the two sensor placement points of each symmetrical point pair.

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