Non-contact vehicle-mounted pull-type seismic data acquisition system and method

Abstract

The invention provides a non-contact vehicle-mounted pull-type seismic data acquisition system and method. The system comprises a plurality of pull-type movable moving vehicles, a controller installed on the large pull-type moving vehicles and a movable vibration isolation table used for bearing a laser Doppler vibration meter. According to the invention, non-contact seismic trace gathers are realized through array networking of the laser Doppler vibrometers; seismic signals of different measuring points of the same measuring line are synchronously measured through seismic gathers, preliminary seismic data are obtained through signal processing, further data processing is carried out on the preliminary seismic data, underground structure and stratum characteristics can be explained, and the method is an effective means for mineral resource exploration and urban underground space detection; the non-contact earthquake detection method is adopted, mobile measurement can be achieved, efficiency is high, implementation is easy, applicability is wide, the method can be flexibly suitable for complex geological conditions, and the method is applied to various underground detection scenes such as exploration of mineral resources of various earth surfaces and urban underground space detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of geophysical earthquake detection, and in particular relates to a non-contact vehicle-mounted towed earthquake data acquisition system and method under complex terrain conditions. Background Art

[0002] At present, seismic exploration is generally carried out using cabled or cableless seismometers. As an absolute shallow surface vibration measurement instrument, it is necessary to consider the coupling between the seismometer and the ground, which brings inconvenience to the large-scale deployment of the instrument. At the same time, the development of new technologies has also led to the emergence of new seismic measurement technologies such as electrochemical detectors and DAS systems. However, these new technologies still have their own limitations, and have not broken through the traditional seismic signal measurement method, and have not deviated from the scope of traditional direct contact measurement of seismic signals.

[0003] In order to realize non-contact mobile measurement of seismic signals, it is necessary to introduce a vibration measurement technology based on a new technology. At present, laser Doppler vibrometer technology has developed to a relatively mature stage. With the reduction of the cost of this technology, its large bandwidth and high precision make it possible for non-contact mobile applications in the field of seismic exploration. Based on this, it is very necessary to develop a non-contact vehicle-mounted towed seismic data acquisition system and method, which has a wide range of application value. Summary of the invention

[0004] The purpose of the present invention is to provide a non-contact, mobile seismic data acquisition system and method based on laser Doppler vibrometer technology, which directly collects vibration signals of measuring points on the ground through a laser Doppler vibrometer array, and obtains reliable seismic data through a signal processing algorithm, so as to solve the problem that existing seismic exploration instruments need to consider coupling with the ground during deployment, which brings a lot of manpower costs and limited application scenarios.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A non-contact vehicle-mounted towed seismic data acquisition system, comprising a plurality of towed movable vehicles 1, a controller 2 mounted on the large towed movable vehicles 1, and a movable vibration isolation table 3 mounted on the plurality of small towed movable vehicles 1 for carrying a laser Doppler vibrometer 4;

[0007] Wherein, a movable vibration isolation platform 3 is arranged on each small towed mobile vehicle 1, and a laser Doppler vibrometer 4 is arranged on each movable vibration isolation platform 3 to form an array laser Doppler seismic measurement node. Each laser Doppler vibrometer 4 emits laser vertically to the surface and forms a linear array laser Doppler seismic measurement node network. The array laser Doppler seismic measurement node network is connected to a computer.

[0008] The controller 2 is connected to each laser Doppler vibrometer 4, controls each node of the array laser Doppler seismic node network to synchronously collect data, the laser Doppler vibrometer 4 collects surface vibration signals and synchronously outputs them to the controller 2, the controller 2 processes the collected signals in real time, extracts effective seismic signals from the collected data, and the upper computer connected to it displays and stores the data of the single node or line array laser Doppler seismic node network in real time.

[0009] Furthermore, the towed mobile vehicles 1 are rigidly connected via a rigid connection structure 6 .

[0010] Furthermore, the controller 2 includes a non-contact node networking connection control and triggering unit, a seismic data extraction unit, a vibration signal display unit and a track integration imaging unit;

[0011] The contactless node networking connection control and triggering unit controls the networking and synchronous triggering start of multiple contactless nodes, and the sampling rate can be set according to engineering requirements;

[0012] The seismic data extraction unit extracts effective seismic signals to improve the data signal-to-noise ratio;

[0013] The vibration signal display unit displays real-time single-point or multi-point ground vibration data, and can set digital filters according to user needs;

[0014] After the measurement is completed, the gather imaging unit integrates the data collected by each non-contact node to generate a seismic gather image.

[0015] Furthermore, the outgoing light beam of each laser Doppler vibrometer 4 is arranged perpendicular to the measured surface, and the laser Doppler effect is used to measure the vibration velocity of the surface measuring point 5. When the laser is incident on the vibrating surface, a Doppler frequency shift is generated, which can be obtained by the following formula:

[0016]

[0017] Among them, Δf is the laser Doppler frequency shift, v is the velocity information, and λ is the laser wavelength.

[0018] In order to convert the high-frequency optical signal into an obtainable signal, the optical signal is converted into an electrical signal by using the balanced photodetector 8 with the help of optical beat technology, and the photocurrent is demodulated by the following formula, and then the measured vibration signal can be further obtained;

[0019]

[0020] Wherein, K is the photoelectric conversion parameter of the photodetector 8, I s To measure the DC component generated by light, I r is the DC component generated by the reference light, fb is the frequency difference introduced by heterodyne interference, is the phase difference between the two light beams.

[0021] Furthermore, the surface to be measured includes but is not limited to soil, gravel, vegetation, concrete, asphalt and other natural or artificial surfaces that can be used in mineral resource exploration and urban underground space detection.

[0022] Furthermore, when the surface to be measured is a soil surface, at the measuring point, artificial external force is used to compact the surface and the loose surface is compacted and leveled to enhance the conduction of vibrations and enhance the reflection and reception of laser signals; 3M reflective film is attached to the hard surface to enhance the conduction of vibrations and enhance the reflection and reception of laser signals.

[0023] Furthermore, the array-type laser Doppler seismic measurement nodes are all connected to a computer via wired means for node connection control and data transmission and storage.

[0024] A non-contact vehicle-mounted towed seismic data acquisition method based on the above system comprises the following steps:

[0025] A. Arrange the spacing and number of array laser Doppler seismic measurement nodes reasonably according to the detection requirements, connect the towed mobile vehicle 1 through a rigid medium, and connect them together through a movable vibration isolation platform 3; wherein the outgoing light beam of the array laser Doppler seismic measurement node is perpendicular to the measured surface;

[0026] B. Configuring an array laser Doppler seismic node network, the host computer triggers and controls the laser Doppler vibrometer 4 of each array laser Doppler seismic node to collect surface vibration signals and synchronously output them to the controller 2, and then transmits them to the host computer to synchronously record and store high-speed images and vibration velocity signals;

[0027] C. The host computer extracts effective signals from the collected surface vibration signals and performs time-frequency domain analysis. Based on the array arrangement of non-contact nodes, high-precision seismic data is obtained to synthesize seismic records.

[0028] Furthermore, the signal sampling rate of the laser Doppler vibrometer 4 is adjustable from 1k to 10kHz.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention realizes non-contact seismic gather through the networking of laser Doppler vibrometer arrays; the seismic gather is used to obtain the same synchronous measurement of seismic signals at different measuring points on the same measuring line, and after signal processing, preliminary seismic data can be obtained, and further data processing of the seismic data can be performed to interpret underground structures and stratum characteristics, which is an effective means for mineral resource exploration and urban underground space detection; compared with traditional seismic exploration equipment, the non-contact movable seismic measurement method of the present invention adopts a non-contact seismic measurement method, which can realize mobile measurement, has high efficiency, is easy to implement, has wide applicability, can be flexibly applied to complex geological conditions, and can be applied to various underground detection scenarios such as mineral resource exploration on various surfaces and urban underground space detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 It is a structural schematic diagram of the non-contact vehicle-mounted towed seismic data acquisition system of the present invention;

[0033] Figure 2 Schematic diagram of the optical path for contactless node measurement;

[0034] Figure 3 It is a schematic diagram of the effect of the embodiment.

[0035] In the figure: 1. Mobile vehicle 2. Controller 3. Movable vibration isolation table 4. Laser Doppler vibrometer 5. Surface measuring point 6. Rigid connection structure 7. Laser 8. Photodetector 9. Internal optical path 10. Lens 11. Single node data collection 12. Synthetic seismic record. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with embodiments:

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0038] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0039] The present invention is based on laser Doppler vibrometer technology and uses laser Doppler vibrometer sensors for synchronous measurement. It realizes the seismic signal measurement of a single channel set and provides primary seismic data for mineral resource exploration and urban underground space detection. The system is easy to operate, has high measurement accuracy, and can be flexibly applied to the detection needs of different surface conditions.

[0040] like Figure 1 As shown, the non-contact vehicle-mounted towed seismic data acquisition system of the present invention includes a plurality of towed movable vehicles 1, a controller 2 installed on the large towed movable vehicles 1, and a movable vibration isolation platform 3 installed on a plurality of small towed movable vehicles 1 for carrying a laser Doppler vibrometer 4.

[0041] There are multiple movable vibration isolation platforms 3, one of which is arranged on each small towed mobile vehicle 1, and one laser Doppler vibrometer 4 is arranged on each movable vibration isolation platform 3. Each laser Doppler vibrometer 4 emits laser vertically to the surface and forms a linear array laser Doppler seismic node network, and the array laser Doppler seismic node network is connected to a computer.

[0042] The plurality of movable vibration isolation platforms 3 are used to carry the laser Doppler vibrometer 4. Since the towed mobile vehicles 1 are rigidly connected by a rigid connection structure 6 such as a chain, the stability of the system during the seismic data acquisition process is guaranteed. The movable vibration isolation platform 3 has the characteristics of stability, low resonance frequency and low-frequency vibration isolation, has a high static-low dynamic stiffness characteristic, has an extremely low natural frequency, and has a good effect on isolating other vibrations, especially low-frequency vibrations transmitted by the ground.

[0043] The controller 2 is connected to each laser Doppler vibrometer 4, synchronously controls the array laser Doppler seismic node network to synchronously collect data, the laser Doppler vibrometer 4 collects surface vibration signals and synchronously outputs them to the controller 2, the controller 2 processes the collected signals in real time, extracts effective seismic signals from the collected data, and the host computer connected to it displays and stores the data of the single node or line array laser Doppler seismic node network in real time. After the measurement is completed, primary seismic data is obtained.

[0044] Specifically, the controller 2 includes a non-contact node networking connection control and triggering unit, a seismic data extraction unit, a vibration signal display unit and a track integration imaging unit.

[0045] The contactless node networking connection control and triggering unit controls the networking and synchronous triggering start of multiple contactless nodes, and the sampling rate can be set according to engineering requirements.

[0046] The seismic data extraction unit extracts effective seismic signals and improves the data signal-to-noise ratio.

[0047] The vibration signal display unit displays real-time single-point or multi-point surface vibration data, and can set digital filters etc. according to user needs.

[0048] After the measurement is completed, the gather imaging unit integrates the data collected by each non-contact node to generate a seismic gather image.

[0049] In the present invention, the outgoing light beam of each laser Doppler vibrometer 4 is arranged perpendicular to the measured surface, and the laser Doppler effect is used to measure the vibration velocity of the surface measuring point 5. When the laser is incident on the vibrating surface, a Doppler frequency shift is generated, which can be obtained by the following formula:

[0050]

[0051] Among them, Δf is the laser Doppler frequency shift, v is the velocity information, and λ is the laser wavelength.

[0052] In order to convert the high-frequency optical signal into an achievable signal, the optical beat technology is used to convert the optical signal into an electrical signal using a balanced photodetector 8, and then the photocurrent is demodulated using the following formula, and then the measured vibration signal can be further obtained.

[0053]

[0054] Wherein, K is the photoelectric conversion parameter of the photodetector 8, I s To measure the DC component generated by light, I r is the DC component generated by the reference light, f b is the frequency difference introduced by heterodyne interference, is the phase difference between the two light beams.

[0055] The single-point laser Doppler vibrometer 4 is based on the Doppler frequency shift principle. It measures single-point array seismic signals on the earth's surface through networking. It has the characteristics of high synchronization, high precision, high sensitivity, and adjustable sampling frequency.

[0056] In the present invention, the surface to be measured includes but is not limited to soil, gravel, vegetation, concrete, asphalt and other natural or artificial surfaces that can be used in mineral resource exploration and urban underground space detection. If necessary, the loose surface is compacted and leveled to enhance the conduction of vibration and enhance the reflection and reception of laser signals; 3M reflective film is attached to the hard surface to enhance the conduction of vibration and enhance the reflection and reception of laser signals. Specifically, the surface to be measured is a soil surface. At the measuring point, the surface is compacted by artificial external force to ensure the relative flatness of the surface to reduce speckle noise. The outgoing laser of the non-contact node is focused on the plane where the surface to be measured is located to enhance the reflection and reception of the laser. The non-contact nodes are all connected to the computer by wire for node connection control and data transmission and storage.

[0057] A non-contact vehicle-mounted towed seismic data acquisition method based on the above system comprises the following steps:

[0058] A. Arrange the spacing and number of array laser Doppler seismic nodes, i.e., non-contact seismic nodes, in a reasonable manner according to detection requirements, and connect the towed mobile vehicle 1 through a rigid medium, and connect them together through a movable vibration isolation platform 3;

[0059] Among them, the outgoing light beam of the non-contact seismic node is perpendicular to the measured surface, which reduces pseudo vibration and collects the best quality seismic data as much as possible;

[0060] The measured surface area is as flat as possible to reduce the speckle noise caused by the roughness of the measured surface at the experimental layout level.

[0061] B. Configure non-contact node networking, the host computer triggers the array laser Doppler vibrometer 4 of each seismic node to collect the surface vibration signal and synchronously output it to the controller 2, and then transmit it to the host computer for storage;

[0062] The signal sampling rate of the laser Doppler vibrometer 4 is adjustable from 1k to 10kHz.

[0063] The host computer has the ability to display, process and store data of a single node or multiple nodes in real time.

[0064] C. The host computer performs effective signal extraction and analysis on the collected surface vibration signals, and obtains high-precision seismic data based on the array arrangement of non-contact nodes.

[0065] In the present invention, the laser Doppler vibrometer array starts recording and storing data after receiving the trigger signal of the synchronization trigger. The host computer displays the collected seismic data of the single-point or array laser Doppler vibrometer in real time, and synchronously records and stores high-speed images and vibration velocity signals and performs time-frequency domain analysis, and finally synthesizes the seismic record.

[0066] like Figure 2 As shown, the laser 7 emits infrared single-frequency narrow-linewidth laser, which is divided into two beams through the internal optical path 9, one as reference light and the other as measurement light. The measurement light is vertically emitted to the surface measurement point 5 through the lens 10, wherein the focal length of the lens 10 is adjusted to the surface measurement point 5 at the waist position of the measurement beam, and then the lens 10 receives the beam carrying Doppler information modulated by the surface vibration, interferes with the reference beam, and is received by the photoelectric detector 8. The demodulation and related processing of the signal are completed by the controller 2.

[0067] like Figure 3 As shown in the figure, the measurement results of a single node and the generated gather imaging diagram are shown. When an impact signal is applied by a seismic source near the system, each node records the waveform of the measuring point, which is manifested in the gather diagram as the time delay and amplitude attenuation of the vibration impact at each node.

[0068] Compared with the existing technology, the present invention realizes non-contact and movable measurement of seismic data, bringing more possible means of realization for seismic detection; at the same time, by improving the laser Doppler vibration measurement node carrier, remote seismic detection can be realized.

[0069] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A non-contact vehicle-mounted towed seismic data acquisition system, characterized in that: It comprises a plurality of towed movable vehicles (1), a controller (2) installed on the large towed movable vehicles (1), and a movable vibration isolation platform (3) installed on the plurality of small towed movable vehicles (1) and used to carry a laser Doppler vibrometer (4); Wherein, a movable vibration isolation platform (3) is arranged on each small towed mobile vehicle (1), and a laser Doppler vibrometer (4) is arranged on each movable vibration isolation platform (3) to form an array laser Doppler seismic measurement node, each laser Doppler vibrometer (4) emits laser vertically to the surface, and forms a linear array laser Doppler seismic measurement node network, and the array laser Doppler seismic measurement node network is connected to a computer; The controller (2) is connected to each laser Doppler vibrometer (4) to control each node of the array laser Doppler seismic node network to synchronously collect data. The laser Doppler vibrometer (4) collects surface vibration signals and synchronously outputs them to the controller (2). The controller (2) processes the collected signals in real time, extracts effective seismic signals from the collected data, and a host computer connected to the controller displays and stores the data of a single node or a linear array laser Doppler seismic node network in real time.

2. A non-contact vehicle-mounted towed seismic data acquisition system according to claim 1, characterized in that: The towed mobile vehicles (1) are rigidly connected to each other via a rigid connection structure (6).

3. The non-contact vehicle-mounted towed seismic data acquisition system according to claim 1, characterized in that: The controller (2) comprises a non-contact node networking connection control and triggering unit, a seismic data extraction unit, a vibration signal display unit and a track integration imaging unit; The contactless node networking connection control and triggering unit controls the networking and synchronous triggering start of multiple contactless nodes, and the sampling rate can be set according to engineering requirements; The seismic data extraction unit extracts effective seismic signals to improve the data signal-to-noise ratio; The vibration signal display unit displays real-time single-point or multi-point ground vibration data, and can set digital filters according to user needs; After the measurement is completed, the gather imaging unit integrates the data collected by each non-contact node to generate a seismic gather image.

4. The non-contact vehicle-mounted towed seismic data acquisition system according to claim 1, characterized in that: The outgoing light beam of each laser Doppler vibrometer (4) is arranged perpendicular to the measured surface, and the laser Doppler effect is used to measure the vibration velocity of the surface measuring point (5). When the laser is incident on the vibrating surface, a Doppler frequency shift is generated, which can be obtained by the following formula: Among them, Δf is the laser Doppler frequency shift, v is the velocity information, and λ is the laser wavelength. In order to convert the high-frequency optical signal into an obtainable signal, the optical signal is converted into an electrical signal by using the balanced photodetector 8 with the help of optical beat technology, and the photocurrent is demodulated by the following formula, and then the measured vibration signal can be further obtained; Wherein, K is the photoelectric conversion parameter of the photodetector (8), I s To measure the DC component generated by light, I r is the DC component generated by the reference light, f b is the frequency difference introduced by heterodyne interference, is the phase difference between the two light beams.

5. The non-contact vehicle-mounted towed seismic data acquisition system according to claim 1, characterized in that: The surface to be measured includes but is not limited to soil, gravel, vegetation, concrete, asphalt and other natural or artificial surfaces that can be used in mineral resource exploration and urban underground space detection.

6. The non-contact vehicle-mounted towed seismic data acquisition system according to claim 5, characterized in that: When the surface to be measured is a soil surface, at the measuring point, the surface is compacted by artificial external force, and the loose surface is compacted and leveled to enhance the conduction of vibrations and the reflection and reception of laser signals; 3M reflective film is attached to the hard surface to enhance the conduction of vibrations and the reflection and reception of laser signals.

7. The non-contact vehicle-mounted towed seismic data acquisition system according to claim 1, characterized in that: The array-type laser Doppler seismic measurement nodes are all connected to a computer in a wired manner, which is used for node connection control and data transmission and storage.

8. A non-contact vehicle-mounted towed seismic data acquisition method based on the above system, characterized in that: The following steps are involved: A. Arrange the spacing and number of array laser Doppler seismic measurement nodes reasonably according to detection requirements, connect the towed mobile vehicle (1) through a rigid medium, and connect them together through a movable vibration isolation platform (3); wherein the outgoing light beams of the array laser Doppler seismic measurement nodes are perpendicular to the measured surface; B. Configuring an array laser Doppler seismic node network, the host computer triggers and controls the laser Doppler vibrometer (4) of each array laser Doppler seismic node to collect surface vibration signals and synchronously output them to the controller (2), and then transmits them to the host computer to synchronously record and store high-speed images and vibration velocity signals; C. The host computer extracts effective signals from the collected surface vibration signals and performs time-frequency domain analysis. Based on the array arrangement of non-contact nodes, high-precision seismic data is obtained to synthesize seismic records.

9. A non-contact vehicle-mounted towed seismic data acquisition method based on the above system according to claim 8, characterized in that: The signal sampling rate of the laser Doppler vibrometer (4) is adjustable from 1k to 10kHz.

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