Buried pipeline positioning device and method based on sound wave reflection time delay

Abstract

The invention provides a buried pipeline positioning device and method based on sound wave reflection time delay. The method comprises the following steps: step 1, setting initial parameters: geophone spacing and vibration exciter position; and step 2, detecting field longitudinal wave velocity test: acquiring signals, calculating sound wave propagation distance and time, and performing linear fitting to obtain the longitudinal wave velocity. And step 3, reflection time delay extraction: the upper computer processes the collected signals, and compares signal waveforms in a similar frequency range to obtain a reflection time delay range. And 4, determining a pipeline position trajectory equation according to the reflection time delay range, and drawing a curve to obtain a pipeline positioning result. According to the method, the buried pipeline can be positioned with high precision and low cost, and the actual engineering requirements are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of buried pipeline detection, and in particular relates to a buried pipeline positioning device and method based on sound wave reflection delay. Background Art

[0002] Pipelines are widely used in the transportation of tap water, natural gas, oil and other resources due to their safety and efficiency. Polyethylene (PE) pipes are widely used in the construction of medium and low pressure gas pipeline networks in cities and towns due to their advantages such as easy installation and maintenance, low price, corrosion resistance and long service life. However, due to the lack of pipeline planning change information, the complexity of pipeline management system and affiliated units, and the low accuracy of existing pipeline detection instruments, the location of the pipeline is unclear, making PE pipes very easy to be damaged during construction, thus causing natural gas leakage, explosion and even casualties. Therefore, it is of great significance to accurately locate buried PE pipes.

[0003] At present, the commonly used detection methods mainly include geological radar detection method, electromagnetic-tracer line method and acoustic detection method, but all of them have certain limitations. The geological radar detection method is greatly affected by the soil environment; the electromagnetic-tracer line method requires the laying of tracer lines, which is complicated to operate, and the surrounding cables have a great impact on the positioning accuracy; the acoustic detection method includes the acoustic wave excitation method and the acoustic wave emission method, among which the acoustic wave excitation method can only detect pipelines exposed on the ground, and the acoustic wave reflection method requires the reflected wave signal to be completely separated from the direct wave signal, which has very high requirements for the source equipment.

[0004] Technical solution of prior art 1

[0005] Acoustic detection is a new detection technology. This method uses a seismic source to generate an acoustic excitation signal. The signal propagates to the surface of the pipeline to generate a reflected wave signal. The signal receiving device receives the reflected wave signal and performs translation, superposition and other processing on the received reflected wave signal, thereby realizing the positioning of the buried pipeline.

[0006] Disadvantages of the prior art 1

[0007] The acoustic wave reflection method places very high demands on the source equipment and requires that the reflected wave signal be completely separated from the direct wave signal.

[0008] Technical solution of prior art 2

[0009] At present, geological radar detection is a commonly used method for locating buried pipelines. The radar instrument transmits electromagnetic waves to the detection area through the transmitting antenna. During the propagation process, the electromagnetic waves encounter the dust on the surface of the PE pipe and reflect and generate reflected waves. The receiving antenna receives the reflected waves and transmits them to the ground penetrating radar host for data storage, processing and display.

[0010] Disadvantages of the second prior art

[0011] When the pipeline is buried deep and the pipeline diameter is small, the positioning accuracy of the geological radar detection method is poor and it is greatly affected by the soil environment, such as soil moisture, soil environmental conductivity, etc. In addition, the cost of the geological radar detection method is relatively high. Summary of the invention

[0012] In view of the problems existing in the existing buried pipeline positioning technology, namely, the positioning accuracy is greatly affected by the detection environment, the equipment requirements are too high and the cost is high, the present invention designs a buried pipeline positioning device and method based on sound wave reflection delay.

[0013] The present invention adopts the following technical solution:

[0014] A buried pipeline positioning device based on acoustic wave reflection delay includes a power supply, a signal generator, a power amplifier, an exciter, a longitudinal wave detector array, an acoustic detection signal detection and acquisition system, and a host computer. The host computer controls the signal generator to generate a sound source excitation signal of a specific frequency. The signal generator sends this signal to the power amplifier, and the amplified signal is sent to the exciter to drive the exciter to generate the sound wave required for detection. The host computer is connected to the signal generator and the acoustic detection signal detection and acquisition system in the vehicle body, processes the signal collected by the acoustic detection signal detection and acquisition system, determines the acoustic reflection delay, draws a pipeline positioning result diagram, and calculates the positioning coordinates.

[0015] The exciter includes an exciter housing, a movable mechanism, a permanent magnet and a constraint guide mechanism. The permanent magnet is installed at the bottom of the exciter housing, the constraint guide mechanism is two columns, both of which are installed on the permanent magnet, the movable mechanism includes a movable rod between the two columns and a coil wound on the movable rod, the energized coil acts on the magnetic field to generate a force, driving the movable rod to reciprocate along the axial direction of the constraint guide mechanism, vibration generates sound waves, and an air gap is formed between the movable mechanism and the exciter housing.

[0016] Furthermore, the host computer is connected to the signal generator and the acoustic detection signal detection and collection system in the vehicle body through the outlet holes on the side of the vehicle body.

[0017] Furthermore, the power supply, signal generator, power amplifier, vibration exciter, longitudinal wave detector array, acoustic detection signal detection and collection system are all integrated in the vehicle body. The power supply is connected to the signal generator, power amplifier, vibration exciter, longitudinal wave detector array, acoustic detection signal detection and collection system to supply power to the above components. The power supply, signal generator, power amplifier, vibration exciter, longitudinal wave detector array, acoustic detection signal detection and collection system are all installed on the internal cross beam of the vehicle body.

[0018] Furthermore, two longitudinal wave geophones are used for pipeline location detection.

[0019] Furthermore, the acoustic detection signal detection and acquisition system includes an acoustic detection signal detection circuit, a low-pass filter circuit, an automatic gain adjustment amplifier circuit, and a signal acquisition card. The acoustic detection signal detection circuit collects the signal received by the longitudinal wave detector array, and the acoustic detection signal detection circuit sends the signal to the low-pass filter circuit, and the low-pass filter circuit filters the high-frequency noise in the detection signal to obtain a clean low-frequency acoustic detection signal; the low-pass filter circuit sends the low-frequency acoustic detection signal to the automatic gain adjustment amplifier circuit, and the automatic gain adjustment amplifier circuit sends the signal to the signal acquisition card, and the acoustic detection signal of the signal acquisition card is uploaded to the host computer for processing.

[0020] A buried pipeline positioning method based on acoustic wave reflection delay, the steps are as follows:

[0021] Step 1. Set the initial parameters: detector spacing, exciter position;

[0022] Adjust the position of the exciter and the distance between the detectors according to the actual situation at the detection site.

[0023] Step 2. Wave velocity test in the non-pipeline area;

[0024] Based on the collected signals, the time when each detector receives the signal is calculated, and the time when each detector receives the signal and the distance between the detector and the earthquake source are fitted with a first-order linear fit. The slope of the curve obtained is the longitudinal wave velocity of the soil on site, and the average value is taken after multiple measurements.

[0025] Step 3. Extract reflection delay;

[0026] S301. The host computer controls and sends control instructions. The signal generator generates an excitation signal, which is amplified by the power amplifier and drives the exciter to emit sound waves to the detection area. The longitudinal wave detector array receives the acoustic detection signal, and then the signal is uploaded to the host computer through the acoustic detection signal detection and acquisition system.

[0027] S302. Filter the detection signal through a digital bandpass filter on the host computer, retain the signal waveforms of different frequency ranges in the range of 0 Hz-600 Hz, take the absolute value, and perform normalization processing.

[0028] Step 4. Draw the pipeline position trajectory curve determined by the two detectors according to the determined reflection delay range. The area surrounded by the intersection of the curves is the located pipeline position. The midpoint of the area is taken as the positioning coordinate to obtain the position of the pipeline. Connect the pipeline positions on different survey lines to obtain the direction of the pipeline in the detection area.

[0029] S401. The distance that the sound wave propagates from the earthquake source to the reflection point and then is reflected back to the ground detector I: τ is the reflection delay; υ pis the longitudinal wave velocity; d is the detector spacing.

[0030] l=l1+l2=τ×υ p +d (1)

[0031] S402. From formula (1), after determining the reflection delay and longitudinal wave velocity, l is a constant, then the pipeline is located on an elliptical trajectory with the source coordinates and the geophone I coordinates as the focus, and the center of the trajectory is the midpoint of the source and the geophone, so the trajectory equation is:

[0032]

[0033] Where: b is the length of the minor semi-axis of the trajectory equation; a is the length of the major semi-axis of the trajectory equation.

[0034] From the definition of ellipse:

[0035]

[0036] Substituting equations (1), (3) and (4) into equation (2), we get the pipeline position trajectory equation determined by detector I:

[0037]

[0038] According to step 3, the reflection delay range determined by detector I is τ 1l <τ1<τ 1h , then the pipeline position range determined by the detector is the area between the elliptical trajectories y1 and y2.

[0039]

[0040] S403. Similarly, the reflection delay range determined by detector II is τ 2l <τ2<τ 2h , then the pipeline position range determined by detector II is the area between the elliptical trajectories y3 and y4.

[0041]

[0042] S404. Draw the curves shown in equations (6) and (7). The area enclosed by the intersection of the curves is the position of the buried pipeline located by extracting the reflection delay. Select the midpoint of the area as the pipeline positioning coordinate, connect the pipeline positions on each survey line, and obtain the pipeline direction of this detection area.

[0043] Furthermore, step 302 includes comparing signal waveforms in similar frequency ranges. If there is no obvious difference in the signal waveforms of all similar frequency ranges, there is no pipeline in the detection area; if there is no obvious difference in the signal waveforms of similar frequency ranges at lower frequencies and higher frequencies, but there is an obvious difference in the intermediate frequencies, there is a pipeline in the detection area. If there is an obvious difference in the signal waveforms of similar frequency ranges, the range of the reflection delay is determined by determining the time when the difference begins to appear and the initial time of the signal.

[0044] Beneficial effects of the present invention:

[0045] 1. The method proposed in the present invention can detect buried pipelines in various environments with high positioning accuracy.

[0046] 2. The method proposed in the present invention processes the superposition signal of the direct wave and the reflected wave, thereby solving the problem that the traditional acoustic positioning method cannot locate non-metallic pipes when the reflected wave and the direct wave overlap.

[0047] 3. The method proposed by the present invention can detect buried pipelines at a very low cost.

[0048] 4. The present invention is a non-destructive detection, does not need to be connected to a tracer line, and will not cause damage to the pipeline during the detection and positioning process.

[0049] 5. The method proposed in the present invention can detect buried pipelines of various diameters and burial depths by adjusting the frequency of sound waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the buried pipeline detection principle of the present invention;

[0051] Figure 2 It is a schematic diagram of the overall structure of the integrated vehicle body of the present invention;

[0052] Figure 3 A top view of the internal structure of the integrated vehicle body of the present invention;

[0053] Figure 4 It is a schematic diagram of the structure of the vibration exciter of the present invention;

[0054] Figure 5 A flow chart for locating buried pipelines according to the present invention;

[0055] Figure 6 Extract the reflection delay graph;

[0056] Figure 7 This is the buried pipeline positioning result diagram.

[0057] In the figure: 1-vehicle body, 2-host computer, 3-wire outlet, 4-universal wheel, 5-hand push handle, 6-power supply, 7-signal generator, 8-power amplifier, 9-exciter, 901-exciter housing, 902-constraint guide mechanism, 903-movable mechanism, 904-air gap, 905-permanent magnet, 10-longitudinal wave detector array, 11-acoustic detection signal detection and acquisition system, 12-internal beam. DETAILED DESCRIPTION

[0058] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0059] like Figure 2 As shown, a buried pipeline positioning device based on acoustic wave reflection delay of the present invention comprises a power supply 6, a signal generator 7, a power amplifier 8, a vibrator 9, a longitudinal wave geophone array 10, an acoustic detection signal detection and collection system 11, and a host computer 2, wherein the power supply 6, the signal generator 7, the power amplifier 8, the vibrator 9, the longitudinal wave geophone array 10, and the acoustic detection signal detection and collection system 11 are all integrated in the vehicle body 1. The power supply 6 is connected to the signal generator 7, the power amplifier 8, the vibrator 9, the longitudinal wave geophone array 10, and the acoustic detection signal detection and collection system 11 to supply power to the above components.

[0060] The host computer 2 controls the signal generator 7 to generate a sound source excitation signal of a specific frequency. The signal generator 7 sends this signal to the power amplifier 8, and the power amplifier 8 amplifies the excitation signal. The power amplifier 8 is connected to the exciter 9, and the amplified signal is sent to the exciter 9 to drive the exciter 9 to generate the sound waves required for detection.

[0061] like Figure 3 As shown, the power supply 6 , the signal generator 7 , the power amplifier 8 , the exciter 9 , the longitudinal wave geophone array 10 , and the acoustic detection signal detection and collection system 11 are all installed on the internal cross beam 12 of the vehicle body 1 .

[0062] like Figure 4As shown, the exciter 9 includes an exciter housing 901, a movable mechanism 903, a permanent magnet 905 and a constraint guide mechanism 902. The permanent magnet 905 is installed at the bottom of the exciter housing 901. The function of the permanent magnet 905 is to provide a stable magnetic field for the exciter 9. The exciter housing 901 mainly protects the normal operation of the exciter 9. The constraint guide mechanism 902 is two columns, both of which are installed on the permanent magnet 905. The movable mechanism 903 includes a movable rod between the two columns and a coil wound on the movable rod. The energized coil acts on the magnetic field to generate a force, driving the movable rod to reciprocate along the axial direction of the constraint guide mechanism 902, vibrating to generate sound waves, and forming an air gap 904 between the movable mechanism 903 and the exciter housing 901. When the exciter 9 is working, the permanent magnet 905 forms a constant magnetic field in the annular air gap 904 of the magnetic circuit. The signal generator 7 generates an excitation signal, which is amplified by the power amplifier 8 and then input into the movable mechanism 903 of the exciter 9, driving the movable mechanism 903 to move, generate vibration, and send sound waves to the detection area.

[0063] The longitudinal wave geophone array 10 is used to collect acoustic detection signals. The specific number is determined according to the actual situation on site. Generally, 4-6 longitudinal wave geophones are used at the test site, and 2 longitudinal wave geophones 10 are used for pipeline positioning detection.

[0064] The acoustic detection signal detection and acquisition system 11 includes an acoustic detection signal detection circuit, a low-pass filter circuit, an automatic gain adjustment amplifier circuit, and a signal acquisition card. The acoustic detection signal detection circuit collects the signal received by the longitudinal wave detector array 10, and the acoustic detection signal detection circuit sends the signal to the low-pass filter circuit, which filters the high-frequency noise in the detection signal to obtain a clean low-frequency acoustic detection signal; the low-pass filter circuit sends the low-frequency acoustic detection signal to the automatic gain adjustment amplifier circuit, which automatically adjusts the amplification factor according to the actual detection situation, and amplifies the weak acoustic detection signal under the strong noise background to meet the detection signal detection requirements in the actual buried pipeline detection process, and the automatic gain adjustment amplifier circuit sends the signal to the signal acquisition card, which uploads the acoustic detection signal after amplification, filtering, etc. to the host computer for processing.

[0065] The host computer 2 is connected to the signal generator 7 and the acoustic detection signal detection and acquisition system 11 in the vehicle body 1 through the wire outlet 3 on the side of the vehicle body 1, and is used to control the frequency of the output signal of the signal generator 7, and process the signal collected by the acoustic detection signal detection and acquisition system 11, determine the acoustic reflection delay, draw the pipeline positioning result diagram, and calculate the positioning coordinates.

[0066] like Figure 5 As shown, a buried pipeline positioning method based on acoustic wave reflection delay, the steps are as follows:

[0067] Step 1. Set the initial parameters: detector spacing, exciter position;

[0068] According to the actual situation at the detection site, adjust the position of the exciter 9 and the distance between the detectors.

[0069] Step 2. Wave velocity test in the non-pipeline area;

[0070] Based on the collected signals, the time when each detector receives the signal is calculated, and the time when each detector receives the signal and the distance between the detector and the earthquake source are fitted with a first-order linear fit. The slope of the curve obtained is the longitudinal wave velocity of the soil on site, and the average value is taken after multiple measurements.

[0071] Step 3. Extract reflection delay;

[0072] S301. The host computer 2 controls the sending of control instructions, the signal generator 7 generates an excitation signal, which is amplified by the power amplifier 8 and drives the exciter 9 to emit sound waves to the detection area. The longitudinal wave detector array 10 receives the acoustic detection signal, and then the signal is uploaded to the host computer 2 through the acoustic detection signal detection and acquisition system 11.

[0073] S302. Filter the detection signal through a digital bandpass filter on the host computer 2, retain the signal waveforms of different frequency ranges in the range of 0Hz-600Hz, take the absolute value, and normalize. Compare the signal waveforms of similar frequency ranges. If there is no obvious difference in the signal waveforms of all similar frequency ranges, there is no pipeline in the detection area; if there is no obvious difference in the signal waveforms of similar frequency ranges at lower frequencies and higher frequencies, but there is an obvious difference in the intermediate frequency, there is a pipeline in the detection area. If there is an obvious difference in the signal waveforms of similar frequency ranges, the range of the reflection delay is determined by determining the time when the difference begins to appear and the initial time of the signal.

[0074] Step 4. Draw the pipeline position trajectory curve determined by the two detectors according to the determined reflection delay range. The area surrounded by the intersection of the curves is the located pipeline position. The midpoint of the area is taken as the positioning coordinate to obtain the position of the pipeline. Connect the pipeline positions on different survey lines to obtain the direction of the pipeline in the detection area.

[0075] S401. Figure 1 As shown in the figure, the distance that the sound wave propagates from the earthquake source to the reflection point and then is reflected back to the ground detector I: τ is the reflection delay; υ p is the longitudinal wave velocity; d is the detector spacing.

[0076] l=l1+l2=τ×υ p +d (1)

[0077] S402. From formula (1), after determining the reflection delay and longitudinal wave velocity, l is a constant, then the pipeline is located on an elliptical trajectory with the source coordinates and the geophone I coordinates as the focus, and the center of the trajectory is the midpoint of the source and the geophone, so the trajectory equation is:

[0078]

[0079] Where: b is the length of the minor semi-axis of the trajectory equation; a is the length of the major semi-axis of the trajectory equation.

[0080] From the definition of ellipse:

[0081]

[0082] Substituting equations (1), (3) and (4) into equation (2), we get the pipeline position trajectory equation determined by detector I:

[0083]

[0084] According to step 3, the reflection delay range determined by detector I is τ 1l <τ1<τ 1h , then the pipeline position range determined by the detector is the area between the elliptical trajectories y1 and y2.

[0085]

[0086] S403. Similarly, the reflection delay range determined by detector II is τ 2l <τ2<τ 2h , then the pipeline position range determined by detector II is the area between the elliptical trajectories y3 and y4.

[0087]

[0088] S404. Draw the curves shown in equations (6) and (7). The area enclosed by the intersection of the curves is the position of the buried pipeline located by extracting the reflection delay. Select the midpoint of the area as the pipeline positioning coordinate, connect the pipeline positions on each survey line, and obtain the pipeline direction of this detection area.

[0089] Example

[0090] like Figure 1 As shown, based on the above-mentioned buried pipeline positioning device based on sound wave reflection delay, the specific buried pipeline positioning method process is as follows Figure 5 shown.

[0091] (1) The device is placed above the pipeline, with the longitudinal wave detector array 10 roughly perpendicular to the pipeline direction. The initial parameters are set according to the site conditions: the spacing of the longitudinal wave detector array 10 and the position of the exciter 9.

[0092] (2) Based on the signals collected by the longitudinal wave geophone array 10, the time when each geophone receives the signal is calculated, and the time when each geophone receives the signal and the distance between the geophone and the earthquake source are fitted by a first-order linear fit. The slope of the obtained curve is the longitudinal wave velocity of the soil on site, and the average value is obtained after multiple measurements.

[0093] (3) The exciter 9 generates a sound wave signal and simultaneously triggers the acoustic detection signal detection and acquisition system to collect the signal and upload the data to the host computer 2.

[0094] (4) Filter the detection signal through a digital bandpass filter on the upper computer 2, retain the signal waveforms of different frequency ranges in the interval of 0Hz-600Hz, take the absolute value, and normalize them. Compare the signal waveforms in similar frequency ranges. If there is no obvious difference in the signal waveforms of all similar frequency ranges, there is no pipeline in the detection area; if there is no obvious difference in the signal waveforms of similar frequency ranges at lower frequencies and higher frequencies, but there is an obvious difference in the intermediate frequency, there is a pipeline in the detection area. If there is an obvious difference in the signal waveforms of similar frequency ranges, the range of the reflection delay is determined by determining the time when the difference begins to appear and the initial time of the signal. The result is as follows: Figure 6 shown.

[0095] (5) Based on the determined reflection delay range, the pipeline position trajectory curve determined by the two detectors is drawn. The area surrounded by the intersection of the curves is the located pipeline position. The midpoint of the area is taken as the positioning coordinate to obtain the position of the pipeline. The imaging result is as follows: Figure 7 Connect the pipeline positions on different survey lines to obtain the direction of the pipeline in the detection area.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A buried pipeline positioning device based on acoustic wave reflection delay, characterized in that , including a power supply, a signal generator, a power amplifier, an exciter, a longitudinal wave detector array, an acoustic detection signal detection and acquisition system, and a host computer. The host computer controls the signal generator to generate a sound source excitation signal of a specific frequency. The signal generator sends the signal to the power amplifier, and the amplified signal is sent to the exciter to drive the exciter to generate the sound wave required for detection. The host computer is connected to the signal generator and the acoustic detection signal detection and acquisition system in the vehicle body, processes the signal collected by the acoustic detection signal detection and acquisition system, determines the acoustic reflection delay, draws a pipeline positioning result diagram, and calculates the positioning coordinates; Among them, the exciter includes an exciter housing, a movable mechanism, a permanent magnet and a constraint guide mechanism. The permanent magnet is installed at the bottom of the exciter housing. The constraint guide mechanism is two columns, both of which are installed on the permanent magnet. The movable mechanism includes a movable rod between the two columns and a coil wound on the movable rod. The energized coil acts on the magnetic field to generate a force, driving the movable rod to reciprocate along the axial direction of the constraint guide mechanism, and the vibration generates sound waves, forming an air gap between the movable mechanism and the exciter housing.

2. The device according to claim 1, characterized in that The host computer is connected to the signal generator and the acoustic detection signal detection and collection system in the vehicle body through the outlet holes on the side of the vehicle body.

3. The device according to claim 1, characterized in that The power supply, signal generator, power amplifier, vibrator, longitudinal wave geophone array, acoustic detection signal detection and collection system are all integrated in the vehicle body, and the power supply, signal generator, power amplifier, vibrator, longitudinal wave geophone array, acoustic detection signal detection and collection system are all installed on the internal cross beam of the vehicle body.

4. The device according to claim 1, characterized in that Two longitudinal wave detectors are used for pipeline location detection.

5. The device according to claim 1, characterized in that The acoustic detection signal detection and acquisition system includes an acoustic detection signal detection circuit, a low-pass filter circuit, an automatic gain adjustment amplifier circuit, and a signal acquisition card. The acoustic detection signal detection circuit collects the signal received by the longitudinal wave detector array, and the acoustic detection signal detection circuit sends the signal to the low-pass filter circuit. The low-pass filter circuit filters the high-frequency noise in the detection signal to obtain a clean low-frequency acoustic detection signal. The low-pass filter circuit sends the low-frequency acoustic detection signal to the automatic gain adjustment amplifier circuit, and the automatic gain adjustment amplifier circuit sends the signal to the signal acquisition card. The acoustic detection signal of the signal acquisition card is uploaded to the host computer for processing.

6. A buried pipeline positioning method based on acoustic wave reflection delay, characterized in that: The steps are as follows: Step 1. Set the initial parameters: detector spacing, exciter position; Adjust the position of the vibrator and the distance between the detectors according to the actual situation at the detection site; Step 2. Wave velocity test in non-pipeline area; According to the collected signals, the time when each geophone receives the signal is calculated, and the time when each geophone receives the signal and the distance between the geophone and the earthquake source are fitted by a first-order linear fit. The slope of the curve is the longitudinal wave velocity of the soil on site, and the average value is taken after multiple measurements. Step 3. Extract reflection delay; S301. The host computer controls and sends control instructions, the signal generator generates an excitation signal, which is amplified by the power amplifier and drives the exciter to emit sound waves to the detection area, the longitudinal wave detector array receives the acoustic detection signal, and then uploads the signal to the host computer through the acoustic detection signal detection and acquisition system; S302. Filter the detection signal through a digital bandpass filter on the host computer, retain the signal waveforms of different frequency ranges in the range of 0Hz-600Hz, take the absolute value, and normalize; Step 4. Draw the pipeline position trajectory curve determined by the two geophones according to the determined reflection delay range. The area enclosed by the intersection of the curves is the located pipeline position. The midpoint of the area is taken as the positioning coordinate to obtain the pipeline position. The pipeline positions on different survey lines are connected to obtain the direction of the pipeline in the detection area. S401. The distance that the sound wave propagates from the earthquake source to the reflection point and then is reflected back to the ground detector I: τ is the reflection delay; υ p is the longitudinal wave velocity; d is the detector spacing; l=l1+l2=τ×υ p +d (1) S402. From formula (1), after determining the reflection delay and longitudinal wave velocity, l is a constant, then the pipeline is located on an elliptical trajectory with the source coordinates and the geophone I coordinates as the focus, and the center of the trajectory is the midpoint of the source and the geophone, so the trajectory equation is: Where: b is the length of the minor semi-axis of the trajectory equation; a is the length of the major semi-axis of the trajectory equation; From the definition of ellipse: Substituting equations (1), (3) and (4) into equation (2), we get the pipeline position trajectory equation determined by detector I: According to step 3, the reflection delay range determined by detector I is τ 1l <τ1<τ 1h , then the pipeline position range determined by the detector is the area between the elliptical trajectories y1 and y2; S403. Similarly, the reflection delay range determined by detector II is τ 2l <τ2<τ 2h , then the pipeline position range determined by detector II is the area between the elliptical trajectories y3 and y4; S404. Draw the curves shown in equations (6) and (7). The area enclosed by the intersection of the curves is the position of the buried pipeline located by extracting the reflection delay. Select the midpoint of the area as the pipeline positioning coordinate, connect the pipeline positions on each survey line, and obtain the pipeline direction of this detection area.

7. The method according to claim 6, characterized in that Step 302 includes comparing the waveforms of signals in similar frequency ranges. If there is no obvious difference between the waveforms of signals in all similar frequency ranges, there is no pipeline in the detection area. If there is no obvious difference between the waveforms of signals in similar frequency ranges at lower frequencies and higher frequencies, but there is an obvious difference at intermediate frequencies, there is a pipeline in the detection area. If there is an obvious difference between the waveforms of signals in similar frequency ranges, the range of the reflection delay is determined by determining the time when the difference begins to appear and the initial time of the signal.

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