Multi-pulse spark source directional acoustic wave advance detection system and advance geological prediction method

Abstract

The present invention belongs to the field of advanced geological prediction, and discloses a multi-pulse spark source directional acoustic wave advanced detection system and an advanced geological prediction method. The system includes a directional spark excitation source, an acoustic wave receiving sensor, a host computer, and a multi-level energy storage capacitor; there are multiple directional spark excitation sources, and each of them can independently excite a directional high-frequency acoustic wave signal; each directional spark excitation source is equipped with a rotation azimuth controller; there are multiple acoustic wave receiving sensors; the multi-level energy storage capacitor is connected to each directional spark excitation source, and is used to apply multi-pulse spark signal excitation to each directional spark excitation source. The present invention utilizes a directional spark excitation source and multiple pulse excitations to enhance the propagation distance of the acoustic wave signal, and through the directional spark source acoustic wave excitation and multi-band signal superposition, all-round directional focusing is performed in front of the excavation face to enhance the resolution of poor geological bodies, thereby obtaining an accurate description of the location and occurrence state of abnormal geological bodies.

Description

Technical Field

[0001] The invention belongs to the technical field of advanced geological prediction, and in particular relates to a multi-pulse electric spark source directional acoustic wave advanced detection system and an advanced geological prediction method. Background Art

[0002] Shallow surface engineering geophysical detection issues such as urban near-surface tunnel excavation and open-pit mineral mining conditions are mainly soft rock and soil conditions. The main disaster sources they face are isolated rocks, voids, loose contacts, and composite strata, which can easily cause geological disasters such as water gushing, sand bursting, unstable collapse, and landslides, leading to casualties, tunnel boring machines being submerged, design route changes, and construction delays.

[0003] Therefore, if the source of disasters in front of the excavation face can be detected in advance, so as to obtain the scale and occurrence status of the adverse geological body, it will be possible to provide geological information along the line for actual construction and excavation, realize advance disposal of disasters, and at the same time provide scientific guidance for the adjustment of the excavation parameters of the tunnel boring machine and the mine slope support parameters, realize the effective avoidance of geological risks, and thus ensure the safety of personnel and property and efficient construction.

[0004] At present, the commonly used advance detection methods mainly include drilling method and geophysical method. Among them, although the drilling method can accurately and intuitively obtain geological parameters, the information obtained by the drilling method is small, which reduces the construction efficiency and does not meet the needs of high-precision construction. Geophysical methods represented by seismic wave method and electromagnetic method are feasible ideas for solving high-precision tunnel advance detection. However, the tunnel boring machine is a kind of equipment composed of huge electromagnetic components. The mechanical equipment that operates normally in the mining environment is complex, resulting in strong interference background electromagnetic fields in the tunnel and normal construction mining environment. The electromagnetic information of the poor geological body is submerged by the background electromagnetic field, resulting in the high-precision radar detection method. Ineffective in solving the problem of advance detection.

[0005] The main frequency of the signal excited by the seismic wave method is about 200 Hz, and the resolution is within a few meters. Although the acoustic wave detection method using sonar with a main frequency of several thousand Hz as the excitation source can achieve meter-level resolution, it is mainly suitable for hard rock formations with weak energy attenuation. For soft rock and soil conditions near the surface, high-frequency acoustic wave signals have strong attenuation, and effective signals are easily submerged by noise, resulting in insufficient detection distance. Summary of the invention

[0006] The purpose of the present invention is to propose a multi-pulse electric spark source directional acoustic wave advance detection system to achieve long-distance propagation of acoustic wave signals under soft rock and soil conditions and to achieve fine imaging of the unfavorable geological body in front of the excavation face. In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A multi-pulse spark source directional acoustic wave advance detection system, comprising a directional spark excitation source, an acoustic wave receiving sensor, a host computer and a multi-level energy storage capacitor;

[0008] There are multiple directional electric spark excitation sources, and each directional electric spark excitation source can independently excite a directional high-frequency acoustic wave signal;

[0009] Each directional electric spark excitation source is equipped with a rotational position controller, and each rotational position controller is used to drive the corresponding directional electric spark excitation source to rotate;

[0010] There are multiple sound wave receiving sensors, and the sound wave receiving sensors are used to receive echo signals and transmit the received echo signals to the host computer;

[0011] The multi-level energy storage capacitor is connected to each directional electric spark excitation source, and the multi-level energy storage capacitor applies a multi-pulse electric spark signal excitation to each directional electric spark excitation source;

[0012] Wherein, the rotational position controller and the multi-level energy storage capacitor are respectively connected to the host computer.

[0013] In addition, based on the multi-pulse spark source directional acoustic wave advance detection system, the present invention also proposes a multi-pulse spark source directional advanced geological prediction method, which utilizes a directional spark excitation source and multiple pulse excitations to enhance the propagation distance of the acoustic wave signal, and uses directional spark source acoustic wave excitation and multi-frequency band signal superposition to achieve all-round directional focusing in front of the excavation face to enhance the resolution of adverse geological bodies, thereby obtaining a more accurate characterization of the location and occurrence state of abnormal geological bodies.

[0014] In order to achieve the above object, the present invention adopts the following technical scheme:

[0015] A multi-pulse spark source directional advance geological prediction method, based on the multi-pulse spark source directional acoustic wave advance detection system mentioned above, comprises the following steps:

[0016] Step 1. First, place the directional electric spark excitation source on the excavation surface and make it in close contact with the surrounding rock; use the multi-level energy storage capacitor for the first excitation to generate a multi-pulse electric spark excitation signal, each directional electric spark excitation source performs the first excitation zero time delay signal, all the sound wave receiving sensors receive and save the echo signals excited at different positions; use each rotation azimuth controller to control the rotation of the corresponding directional electric spark excitation source, so that the excitation direction of each directional electric spark excitation source traverses and excites at various radial angles of the excavation surface, and records the echo signals excited at different positions;

[0017] Step 2. Calculate the background wave velocity using the distance between the directional electric spark excitation source and the acoustic wave receiving sensor and the arrival time of the first arrival wave signal between the two, and obtain the possible occurrence positions of multiple target unfavorable geological conditions using the signal waveform azimuth correlation scanning method;

[0018] Step 3. Use the multi-level energy storage capacitor to generate a multi-pulse electric spark excitation signal for the second time. Based on the fact that the travel time from different electric spark excitation positions to a certain focus point is the same, design delayed excitation of different directional electric spark excitation sources, perform acoustic wave energy focusing detection on the possible locations of multiple target unfavorable geological conditions obtained in step 2, and record the echo signals at all excitation locations again;

[0019] Step 4. Divide all positions in front of the excavation face into grid areas, encrypt the grids for possible locations of target unfavorable geology, and calculate the Green's function of the directional electric spark excitation source position and the acoustic wave receiving sensor position according to the ray paths at different positions under background wave velocity conditions;

[0020] Step 5. Correlate and superimpose the multi-pulse signals received by the acoustic wave receiving sensor, transform the correlated superimposed signals into the frequency domain and perform frequency band processing, wherein the low-frequency band signals restore the global information and the high-frequency band signals restore the local details; traverse all grids, and use the Green's function to re-project the correlated superimposed data into frequency bands to obtain the frequency domain imaging results;

[0021] Step 6. Select the effective signal frequency band in the superimposed data that is consistent with the frequency band width of the reflected signal for traversal, use the Green function to obtain the virtual focus of the reflected signal at different frequencies, combine the imaging results of the low-frequency band and high-frequency band data, and finally realize the imaging of multi-pulse acoustic wave signals, obtain the location information of the unfavorable geological body in front of the excavation face, and thus realize advanced geological prediction.

[0022] The present invention has the following advantages:

[0023] As described above, the present invention relates to a multi-pulse spark source directional acoustic wave advance detection system. The method proposes to use multi-pulse spark signal excitation, and integrates the directional multi-pulse spark source excitation of strong energy, which has the dual advantages of enhancing the detection distance and improving the accuracy of low-high frequency multi-band signal superposition imaging, so that it can achieve the strong attenuation of the acoustic signal in the soft rock medium, and enhance the illumination ability of the distant target. In addition, the present invention also proposes a multi-pulse spark source directional advance geological prediction method. The method extracts information from the data by exciting the acoustic wave signal in two steps. The first step is to excite the plane wave acoustic wave signal to predict the possible orientation of the bad geological body, and the second step is to excite the directional focusing signal to enhance the echo information of the bad geological body and improve the imaging accuracy of the detection. In addition, the present invention introduces the Green's function projection in the optical field into the field of advance detection, and obtains the imaging characteristics of the target geological body in the form of multi-band signal superposition and local grid encryption, thereby providing a scientific basis for the adjustment of the tunneling parameters of the tunnel boring machine, the slope support parameters of the mine, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural diagram of the directional acoustic wave advance detection system of a multi-pulse electric spark source in an embodiment of the present invention.

[0025] Figure 2 This is a diagram showing the use status of the multi-pulse spark source directional acoustic wave advance detection system mounted on a shield machine in an embodiment of the present invention;

[0026] Figure 3 is a cross-sectional view of a directional electric spark excitation source in an embodiment of the present invention;

[0027] Figure 4 is an orientation distribution diagram of the target body scanned in an embodiment of the present invention;

[0028] Figure 5 The present invention is a flowchart of a method for directional advanced geological prediction using a multi-pulse electric spark source in an embodiment of the present invention.

[0029] Figure 6 It is a schematic diagram of a three-dimensional spatial orientation local encrypted imaging grid according to an embodiment of the present invention.

[0030] In the figure: 1-directional electric spark excitation source, 2-multi-link telescopic device, 3-rotational azimuth controller, 4-multi-level energy storage capacitor, 5-host computer, 6-receiving data preprocessing unit, 7-acoustic wave receiving sensor, 8-signal transmission cable, 9-conical drill bit, 10-pressure sensor; 11-excitation source electrode, 12-telescopic link protective shell, 13-first-stage telescopic link, 14-second-stage telescopic link, 15-cutter head main beam, 16-cutter head panel hollow area, 17-tool, 18-shield, 19-segment splicing system, 20-main control room; 21-acoustic wave signal reflection plate, 22-acoustic wave signal absorption backing, 23-directional acoustic wave beam. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0032] Example 1

[0033] like Figure 1 As shown, this embodiment describes a multi-pulse electric spark source directional acoustic wave advance detection system, which includes a directional electric spark excitation source 1, a multi-level energy storage capacitor 4, a host computer 5 and an acoustic wave receiving sensor 7.

[0034] There are multiple directional spark excitation sources 1 (for example, 3-8 in practical applications), and each directional spark excitation source 1 can independently excite a directional high-frequency sound wave signal with strong energy.

[0035] like Figure 3 As shown, this embodiment provides a preferred structure of a directional electric spark excitation source.

[0036] The directional electric spark excitation source comprises an excitation source electrode 11, an acoustic wave signal reflection plate 21 and an acoustic wave signal absorption backing 22 which are arranged in sequence from the center to the outside. The acoustic wave signal reflection plate 21 adopts a curved surface structure.

[0037] The excitation source electrode 11 is located at the focus of the curved surface of the acoustic wave signal reflecting plate 21. The excitation source electrode 11 generates an acoustic wave source and forms a directional acoustic wave beam 23, i.e., a directional high-frequency acoustic wave signal, after being reflected by the acoustic wave signal reflecting plate 21. The acoustic wave signal absorbing backing 22 is used to absorb the residual acoustic waves propagating through the reflecting plate.

[0038] The present invention realizes the ability to stimulate a directional acoustic wave signal with an optimal radiation angle of 3° through the acoustic wave signal reflecting plate 21 and the acoustic wave signal absorbing backing 22, so as to predict the possible orientation of a poor geological body.

[0039] The front end of each directional electric spark excitation source 1 is equipped with a conical drill bit 9. The conical structure is conducive to the insertion of the directional electric spark excitation source 1 into soft rock and soil geological conditions such as water-rich sand layers and water-rich pebbles.

[0040] The rear end of each directional electric spark excitation source 1 is equipped with a multi-link retractor 2, such as Figure 1 As shown, the multi-link telescopic device 2 is connected to the directional electric spark excitation source 1.

[0041] The multi-link telescopic device 2 is used to realize the telescopic control of the directional electric spark excitation source 1 .

[0042] In this embodiment, the multi-link telescopic device 2 can be, for example, a mature telescopic device in the prior art.

[0043] like Figure 1A preferred structure of a multi-link telescopic device 2 is shown. The multi-link telescopic device 2 includes a telescopic link protection shell 12 , a primary telescopic link 13 and a secondary telescopic link 14 .

[0044] The telescopic link protection shell 12 is arranged at the outermost side of the multi-link telescoping device 2 .

[0045] The outermost side of the multi-link telescopic device 2 is wrapped by a telescopic link protective shell 12, and it can withstand a maximum pressure of 5 MPa and still remain sealed to meet the pressure balance problem under special conditions.

[0046] In addition, a pressure sensor 10 is provided at the front end of the conical drill bit 9. Figure 1 shown.

[0047] The directional spark excitation source 1 is driven by oil pressure / air pressure to drill into the formation, and the coupling degree between the directional spark excitation source 1 and the formation is determined by the pressure sensor 10 at the front end.

[0048] After the conical drill bit 9 is inserted into the formation, the pressure sensor 10 is subjected to a pressure reaching a preset resistance value, and the directional electric spark excitation source 1 stops drilling. At this time, the acoustic impedance matching capability is better, and the conversion efficiency of electrical signals to acoustic signals is high, so acoustic detection can be carried out.

[0049] Each directional electric spark excitation source 1 is equipped with a rotational position controller 3, and each rotational position controller 3 is used to drive the corresponding directional electric spark excitation source 1 to rotate.

[0050] Each rotation position controller 3 is connected to the host computer 5 via a signal transmission cable 8 , for example.

[0051] On the premise that the directional electric spark excitation source 1 can excite a directional acoustic wave beam, the directional electric spark excitation source 1 is rotationally controlled by the rotation azimuth controller 3 to obtain the radial orientation of the excavation surface.

[0052] In this embodiment, the rotational orientation controller 3 is, for example, connected to the rear side of the multi-link telescopic device 2 and is used to drive the multi-link telescopic device 2 and the directional electric spark excitation source 1 to rotate simultaneously.

[0053] In this embodiment, the rotational position controller 3 adopts a turntable structure, for example.

[0054] In this embodiment, there are multiple sound wave receiving sensors 7 , wherein the sound wave receiving sensors 7 are used to receive broadband echo signals and transmit the received echo signals to the host computer 5 .

[0055] In addition, the multi-pulse spark source directional acoustic wave advance detection system also includes a receiving data preprocessing unit 6; the receiving data preprocessing unit 6 is connected to the host computer 5 (for example, through a signal transmission cable 8).

[0056] Each sound wave receiving sensor 7 is connected to the receiving data preprocessing unit 6 .

[0057] After receiving the broadband echo signals sent by each acoustic wave receiving sensor 7, the receiving data preprocessing unit 6 first amplifies the echo signals and removes noise interference such as industrial interference and instrument crosstalk to improve the data quality of the received signals, and then sends the processed signals to the host computer 5.

[0058] In this embodiment, the received data preprocessing unit 6 may adopt an existing sound wave preprocessing unit.

[0059] The multi-level energy storage capacitor 4 is connected to each directional electric spark excitation source 1 , wherein the multi-level energy storage capacitor 4 is used to apply multi-pulse electric spark signal excitation to each directional electric spark excitation source 1 .

[0060] The multi-level energy storage capacitor 4 is connected to the host computer 5. The host computer controls the multi-level energy storage capacitor to excite each of the directional electric spark excitation sources with zero time delay or delayed excitation to generate a directional high-frequency sound wave signal.

[0061] The multi-pulse acoustic wave source excitation requires that the multi-level energy storage capacitor 4 be able to release electrical signals multiple times in a short period of time. Therefore, the traditional method of using a single energy storage device cannot meet the multiple release requirements.

[0062] Based on this, the present embodiment designs a multi-level energy storage capacitor, which includes a plurality of energy storage capacitors and an activation circuit for switching between the energy storage capacitors.

[0063] When the multi-level energy storage capacitor 4 is working, one of the multiple energy storage capacitors is always in a working state (referred to as the working capacitor), and the remaining energy storage capacitors are in a standby state (referred to as the standby capacitor).

[0064] The activation circuit switches between the working capacitor and the standby capacitor, establishing a cyclic excitation mode in which the working capacitor is excited and the standby capacitor is excited in sequence and charged alternately, thereby realizing multi-pulse electric spark signal excitation.

[0065] The working process of the multi-level energy storage capacitor 4 in this embodiment is as follows:

[0066] First, the activation circuit switches to the working capacitor part, and the backup capacitor is charged at the same time, releasing the working capacitor to stimulate the first pulse; then, the excitation circuit switches to the fully charged backup capacitor, and the fully charged backup capacitor serves as the new working capacitor to stimulate the second pulse; and so on. After each excitation, the working capacitor is converted to the backup capacitor for charging, and the activation circuit switches to another fully charged backup capacitor.

[0067] Therefore, in this embodiment, the multi-level energy storage capacitor realizes multi-pulse, high-capacity electric spark signal source excitation through a cyclic excitation mode in which the working capacitor is excited and the standby capacitor is excited in sequence and charged alternately.

[0068] In this embodiment, an enhanced acoustic signal excitation mode is adopted to improve the utilization efficiency of the capacitor.

[0069] The host computer 5 can control pulse parameter control, record rotation azimuth control parameters, sensor position and imaging algorithm calculation, etc. The host computer 5 can realize multi-pulse excitation with arbitrary time delay, record the position of directional electric spark excitation source 1 and acoustic wave receiving sensor 7, and real-time imaging display of bad geological bodies.

[0070] In order to better illustrate the present invention, this embodiment also provides a specific application example, that is, the multi-pulse electric spark source directional acoustic wave advance detection system in this embodiment is mounted on a shield machine for use.

[0071] How to install the multi-pulse spark source directional acoustic wave advance detection system on the shield machine Figure 2 shown.

[0072] Among them, each directional electric spark excitation source 1 is installed at a fixed position inside the shield 18 behind the hollow area 16 of the shield machine cutter head panel. When the tunnel boring machine is working, the cutter head rotates, and the position of the cutter head panel hollow area 16 rotates like a fan blade. When the cutter head panel hollow area 16 corresponds to the directional electric spark excitation source 1, the excitation source extends to work.

[0073] The acoustic wave receiving sensor 7 is installed on the cutter head panel of the shield machine. Since the acoustic wave receiving sensor 7 is relatively small in size, 8 to 15 of them are installed on a conventional size cutter head (8m diameter).

[0074] The host computer 5 and the multi-level energy storage capacitor 4 are both located in the main control room 20 .

[0075] In addition, Figure 2 The components shown in the figure also include the cutter head main beam 15, the cutter 17, the shield 18 and the segment splicing system 19, etc. These are all structural components of the shield machine itself and will not be described in detail here.

[0076] During detection, the multi-link retractor 2 drives each corresponding directional electric spark excitation source 1 to extend from the hollow area 16 of the cutter head panel and insert into adverse geological conditions such as water-rich sand layers and water-rich pebbles. After the detection is completed, the multi-link retractor 2 drives each directional electric spark excitation source 1 to retract into the shield 18.

[0077] The above design is conducive to solving the limitation of the size and number of holes in the cutter disc panel on the stability of the cutter disc structure, eliminating the transmission path of the high-voltage acoustic wave excitation signal from the main control room 20 to the cutter disc through the rotary joint, avoiding signal distortion caused by wear of the rotary joint and the size limitation of the large rotary joint required for high-voltage signals; at the same time, it avoids the risk of operating with pressure on the cutter chamber, and facilitates the later maintenance and repair of the equipment.

[0078] In addition, compared with the traditional sonar probe with a combined transmitter and receiver, the use of a separate sound wave receiving sensor 7 can reduce the opening area of ​​the cutter head as much as possible, increase the number of sensors and the structural stability of the cutter head.

[0079] When the multi-link telescopic device 2 is at the hollow position of the cutter head, the multi-link telescopic device 2 extends and drives the directional electric spark excitation source 1 to be inserted into the formation. The secondary telescopic link 14 is extended first, and when it reaches the maximum telescopic capacity, the primary telescopic link 13 is extended. When the multi-stage telescopic link reaches a certain preset resistance threshold, the extension action is stopped to protect the directional electric spark excitation source 1 at the front end.

[0080] The directional electric spark excitation source 1 excites the acoustic wave signal with strong directionality and can excite the function of high-energy signal. The upper computer 5 adjusts the excitation direction of the directional electric spark excitation source 1 by rotating the azimuth controller 3 to realize the orientation and focusing of the acoustic wave signal in the radial direction of the excavated rock mass. In addition, the upper computer 5 realizes the orientation and focusing of the acoustic wave signal in the axial direction of the excavated rock mass by adjusting the excitation time between adjacent directional electric spark excitation sources 1.

[0081] Of course, the multi-pulse spark source directional acoustic wave advance detection system in this embodiment is not limited to the application in the environment of shield machine tunnel excavation. For example, it can also be applied to technical fields such as open-pit mine landslides, goaf detection and shallow surface urban geophysical exploration. It should be noted that the application environment or technical field mentioned above is only exemplary. As long as it is an environment that requires acoustic wave advance detection, the multi-pulse spark source directional acoustic wave advance detection system described in the present invention can be used, which will not be repeated here.

[0082] Example 2

[0083] This embodiment 2 describes a multi-pulse electric spark source directional advance geological prediction method, which is based on the multi-pulse electric spark source directional acoustic wave advance detection system in the above embodiment 1.

[0084] In the present embodiment, the advanced geological prediction method obtains radial and axial directional acoustic wave signals of the excavated rock mass by a double excitation method, thereby realizing the orientation identification of the unfavorable geological body and enhancing the echo signal respectively.

[0085] In addition, by rotating the electric spark excitation direction and adjusting the excitation time of the adjacent directional electric spark excitation source 1, the ability of the acoustic wave signal to focus in three-dimensional space is achieved, thereby improving the detection imaging accuracy.

[0086] In addition, this embodiment also introduces the Green's function projection in the optical field into the field of advanced detection, and obtains the imaging characteristics of the target geological body in the form of multi-band signal superposition and local grid encryption, and finally realizes the more accurate positioning of the three-dimensional unfavorable geological body under the conditions of soft rock and soil media with strong sound wave attenuation.

[0087] In a specific implementation, for the first step of excitation, a directional electric spark excitation source 1 is used to excite a zero-delay plane waveform signal, and the orientation information of the geological body can be obtained by scanning the signals in different orientations.

[0088] Then, the focused excitation of the multi-pulse acoustic wave signal in the second step is used to accurately locate the unfavorable geological body.

[0089] Based on the above invention concept, the detailed steps of the multi-pulse electric spark source directional advanced geological prediction method in this embodiment are as follows: Figure 5 As shown in the figure, the advanced geological prediction method realizes advanced detection by stimulating acoustic wave signals twice, first estimating the azimuth and then locally focusing on fine imaging. The specific steps are as follows:

[0090] Step 1. First, place the directional electric spark excitation source on the excavation face and make close contact with the surrounding rock.

[0091] In the tunnel excavation example scenario of the shield machine mentioned in the above embodiment 1, first, for example, each directional electric spark excitation source 1 is pushed into the water-rich surrounding rock layer through a multi-link telescopic device 2, and then the first step of excitation is performed when a good coupling between the directional electric spark excitation source 1 and the surrounding rock is achieved.

[0092] Then, a multi-pulse spark excitation signal is generated by the first excitation of the multi-level energy storage capacitor. Each directional spark excitation source points to 0°, and the first excitation zero time delay signal is performed. The receiving signal Dt of all the sound wave receiving sensors 7 is recorded. The corresponding directional spark excitation source is controlled to rotate by the rotation azimuth controller, so that the excitation direction of each directional spark excitation source is traversed from 0° to 360° in the radial direction of the tunnel (with Figure 6 For example, the tunnel excavation direction is taken as the forward direction, the top of the tunnel is 0°, and the azimuth increases in clockwise direction. Therefore, the right side of the tunnel forward direction is 90°; the vertical downward direction of the tunnel is 180 degrees; the left side of the tunnel forward direction is 270°), and the echo signals excited at different positions are recorded.

[0093] Step 2. Analyze the preliminary received signal, calculate the background wave velocity using the distance between the directional electric spark excitation source and the acoustic wave receiving sensor and the arrival time of the first wave signal between the two, and use the signal waveform azimuth correlation scanning method to obtain the possible locations of multiple target adverse geological conditions.

[0094] Among them, the location information of the adverse geological body is obtained as follows:

[0095] The rotational azimuth controller of the directional EDM array group is kept unchanged, and the zero-delay signal is stimulated to obtain the directional acoustic wave signal in the forward direction of the tunnel face (i.e., the excavation face). The data obtained by the high-sensitivity receiving sensor is interpreted, and the orientation-related curve is drawn to realize the identification of the target body's orientation.

[0096] Define the observation data obtained by the first step of excitation as Dt, then the azimuth correlation curve Ps(θ) is expressed as:

[0097]

[0098] Among them, a(θ) represents different scanning angles, which is expressed as the angle between the scanning direction and the tunnel excavation direction. The forward direction is 0°, and the azimuth angle decreases on the left side of the excavation direction. Similarly, the azimuth angle increases on the right side. Represents the frequency domain information of the observed data Dt after Fourier transformation, and T represents the transpose of the matrix. The resolution of the angle direction can be adjusted by modifying the scanning angle. Too large a scanning angle interval may lead to a large error in the azimuth identification of bad geological bodies, while too small a scanning interval improves the azimuth identification accuracy, but reduces the calculation efficiency. After determining the scanning angle by combining the regional geological conditions and the resolution requirements of engineering detection, the azimuth-related curves obtained by scanning the observed data from 0° to 360° are as follows: Figure 4 As shown in the figure, when the value of a certain direction in the azimuth correlation curve is large, it indicates that there is a bad geological body in this direction, and then the second step of exciting the focused acoustic wave signal is carried out. The angle interval is selected as 5°, and there is a maximum value in the direction of 48° in front of the tunnel face. Therefore, it can be preliminarily determined that there is a bad geological body in this direction.

[0099] Step 3. Use the multi-level energy storage capacitor 4 to generate a multi-pulse spark excitation signal for the second time. The principle is that the sound wave front arrives at a certain point at the same time and the sound wave energy is enhanced. According to the same travel time from the excitation position of different spark sources to a certain focusing point, different directional spark excitation sources are designed for delayed excitation. The multiple target locations of possible bad geological conditions obtained in step 2 are detected by focusing sound wave energy, and the echo signal Dt1 of the multi-pulse spark excitation is recorded again.

[0100] In a specific example, for example, the focused acoustic wave signal is first excited in the 48° azimuth, and all acoustic wave receiving sensors 7 receive the echo signal Dt1 and save the data. Then, the following is established: Figure 6 The coordinate system and the schematic diagram of the local encrypted imaging grid in the three-dimensional space orientation are shown, where the excavation direction is defined as the Y direction, the radial and horizontal excavation is defined as the X direction, and the radial and vertical excavation is defined as the Z direction. The imaging area (imaging area size X×Y×Z, for example, 25m×50m×25m) is gridded, and the grid is encrypted in the estimated target orientation. In this embodiment, the imaging grid is 0.1m, and the local encrypted grid interval is 0.05m, which is 400*500, with a total of 200,000.

[0101] On this basis, the background wave velocity of the medium is calculated using the arrival time of the first wave of the data; the Green's functions of the excitation source, receiving sensor and imaging point in this embodiment are further solved, which are expressed as Gs and Gr respectively. For four directional electric spark excitation sources 1 and 20 acoustic wave receiving sensors 7, the size of Gs is 4*200000, and the size of Gr is 20*200000. The present invention designs multi-pulse delayed excitation of different directional electric spark excitation sources to obtain the azimuth focusing of the acoustic wave signal in the tunnel axis, and finally obtains the information of the bad geological body in the whole space, thereby improving the detection range capability.

[0102] Step 4. Divide all positions in front of the excavation face into grid areas, encrypt the grids for possible locations of target adverse geology, and calculate the Green's function of the directional electric spark excitation source position and the acoustic wave receiving sensor position based on the ray paths at different positions under background wave velocity conditions.

[0103] In a specific example, the received multi-pulse source data Dt1 is correlated and superimposed with the excitation signal (cross-correlation or mutual interference and other correlation algorithms), and the causal part after correlation is selected as the extracted effective wave field information, which is equivalent to the wave field response Dt2 under single pulse excitation. Compared with single pulse excitation, the present invention uses multi-pulse excitation to detect acoustic waves at a longer distance and uses correlation algorithms to extract data with higher quality.

[0104] So far, the two-step method of multi-pulse signal source excitation and effective wave field information extraction have been realized. After the two-step excitation is completed, the multi-pulse spark source directional advance detection system is retrieved to complete the data acquisition.

[0105] Step 5. Correlate and superimpose the multi-pulse signals received by the acoustic wave receiving sensor, transform the correlated and superimposed signals into the frequency domain and perform frequency band processing, wherein the low-frequency band signals restore the global information and the high-frequency band signals restore the local details; traverse all grids, and use the Green's function to re-project the correlated and superimposed data into frequency bands to obtain the frequency domain imaging results.

[0106] In the specific example, Dt2, which extracts the effective information of the wave field, is transformed into the frequency domain to obtain Df2. The low-frequency (80Hz-200Hz) and high-frequency (200Hz-1000Hz) segments of the reflected wave are processed, and the noise frequency band is not imaged. The low-frequency data is projected using Gs and Gr using Green's function. The elements on the main diagonal in the projection result represent the imaging result of virtual focus. The imaging result of the low-frequency data reflects the global information of the target body, and the high-frequency signal restores the local details.

[0107] Step 6. Select the effective signal frequency band in the superimposed data that is consistent with the frequency band width of the reflected signal for traversal, use the Green function to obtain the virtual focus of the reflected signal at different frequencies, combine the imaging results of the low-frequency band and high-frequency band data, and finally realize the imaging of multi-pulse acoustic wave signals, obtain the location information of the unfavorable geological body in front of the excavation face, and thus realize advanced geological prediction.

[0108] Repeat step 5 to further image the high-frequency band, so that the high-frequency imaging results can reflect the imaging characteristics of the details. Finally, the imaging results of the low-frequency band and the high-frequency band are directly added to complete the multi-band superposition and local encrypted imaging, and finally the location information of the unfavorable geological body in front of the excavation face is obtained.

[0109] Of course, the above description is only a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It should be noted that all equivalent substitutions and obvious deformation forms made by any technician familiar with the field under the guidance of this specification fall within the essential scope of this specification and should be protected by the present invention.

Claims

1. A multi-pulse spark source directional acoustic wave advance detection system, characterized in that: It includes a directional electric spark excitation source, an acoustic wave receiving sensor, a host computer and a multi-level energy storage capacitor; There are multiple directional electric spark excitation sources, and each directional electric spark excitation source can independently excite a directional high-frequency acoustic wave signal; Each directional electric spark excitation source is equipped with a rotational position controller, and each rotational position controller is used to drive the corresponding directional electric spark excitation source to rotate; There are multiple sound wave receiving sensors, and the sound wave receiving sensors are used to receive echo signals and transmit the received echo signals to the host computer; The multi-level energy storage capacitor is connected to each directional electric spark excitation source, wherein the multi-level energy storage capacitor applies a multi-pulse electric spark signal excitation to each directional electric spark excitation source; The rotational position controller and the multi-level energy storage capacitor are respectively connected to the host computer; The directional electric spark excitation source includes an excitation source electrode and an acoustic wave signal reflection plate; The sound wave signal reflection plate adopts a curved surface structure; The excitation source electrode is located at the focus of the curved surface of the acoustic wave signal reflection plate, and the excitation source electrode generates an acoustic wave source and forms a directional high-frequency acoustic wave signal after being reflected by the acoustic wave signal reflection plate; The multi-level energy storage capacitor includes a plurality of energy storage capacitors and an activation circuit; The energy storage capacitor in the discharge state is defined as the working capacitor, and the energy storage capacitor in the charge state is defined as the standby capacitor; the activation circuit switches between the energy storage capacitors, and a cyclic excitation mode is established in which the working capacitor is excited and the standby capacitor is excited in sequence and charged alternately, so as to realize multi-pulse electric spark signal excitation; When the multi-level energy storage capacitor is working, one of the multiple energy storage capacitors is always in a working state, namely, a working capacitor, and the remaining energy storage capacitors are in a standby state, namely, a standby capacitor.

2. The multi-pulse electric spark source directional acoustic wave advance detection system according to claim 1 is characterized in that: The front end of the directional electric spark excitation source is provided with a conical drill bit.

3. The multi-pulse electric spark source directional acoustic wave advance detection system according to claim 1 is characterized in that: Each directional electric spark excitation source is equipped with a multi-link telescope, wherein the multi-link telescope is connected to the directional electric spark excitation source and is used to realize the telescopic control of the directional electric spark excitation source.

4. The multi-pulse electric spark source directional acoustic wave advance detection system according to claim 2 is characterized in that: A pressure sensor is arranged at the front end of the conical drill bit.

5. The multi-pulse electric spark source directional acoustic wave advance detection system according to claim 1 is characterized in that: The host computer controls the multi-level energy storage capacitor to excite each of the directional electric spark excitation sources with zero time delay or delayed excitation to generate a directional high-frequency sound wave signal.

6. The multi-pulse electric spark source directional acoustic wave advance detection system according to claim 1 is characterized in that: The multi-pulse electric spark source directional acoustic wave advance detection system also includes a receiving data preprocessing unit; The received data preprocessing unit is connected to the host computer; Each of the sound wave receiving sensors is connected to the receiving data preprocessing unit; After receiving the echo signals sent by each of the acoustic wave receiving sensors, the receiving data preprocessing unit amplifies the echo signals and removes noise interference, and then sends them to the host computer.

7. A multi-pulse spark source directional advance geological prediction method, using the multi-pulse spark source directional acoustic wave advance detection system as described in any one of claims 1 to 6, characterized in that: The multi-pulse electric spark source directional advanced geological prediction method comprises the following steps: Step 1. First, place the directional electric spark excitation source on the excavation surface and make it in close contact with the surrounding rock; use the multi-level energy storage capacitor for the first excitation to generate a multi-pulse electric spark excitation signal, each directional electric spark excitation source performs the first excitation zero time delay signal, all the sound wave receiving sensors receive and save the echo signals excited at different positions; use each rotation azimuth controller to control the rotation of the corresponding directional electric spark excitation source, so that the excitation direction of each directional electric spark excitation source traverses and excites at various radial angles of the excavation surface, and records the echo signals excited at different positions; Step 2. Calculate the background wave velocity using the distance between the directional electric spark excitation source and the acoustic wave receiving sensor and the arrival time of the first arrival wave signal between the two, and obtain the possible occurrence positions of multiple target unfavorable geological conditions using the signal waveform azimuth correlation scanning method; Step 3. Use the multi-level energy storage capacitor to generate a multi-pulse electric spark excitation signal for the second time. Based on the fact that the travel time from different electric spark excitation positions to a certain focus point is the same, design delayed excitation of different directional electric spark excitation sources, perform acoustic wave energy focusing detection on the possible locations of multiple target unfavorable geological conditions obtained in step 2, and record the echo signals at all excitation locations again; Step 4. Divide all positions in front of the excavation face into grid areas, encrypt the grids for possible locations of target unfavorable geology, and calculate the Green's function of the directional electric spark excitation source position and the acoustic wave receiving sensor position according to the ray paths at different positions under background wave velocity conditions; Step 5. Correlate and superimpose the multi-pulse signals received by the acoustic wave receiving sensor, transform the correlated superimposed signals into the frequency domain and perform frequency band processing, wherein the low-frequency band signals restore the global information and the high-frequency band signals restore the local details; traverse all grids, and use the Green's function to re-project the correlated superimposed data into frequency bands to obtain the frequency domain imaging results; Step 6. Select the effective signal frequency band in the superimposed data that is consistent with the frequency band width of the reflected signal for traversal, use the Green function to obtain the virtual focus of the reflected signal at different frequencies, combine the imaging results of the low-frequency band and high-frequency band data, and finally realize the imaging of multi-pulse acoustic wave signals, obtain the location information of the unfavorable geological body in front of the excavation face, and thus realize advanced geological prediction.

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