Seismic source-based surface wave and body wave comprehensive exploration system and exploration method

Abstract

The invention belongs to the technical field of rock-soil exploration, and provides a surface wave and body wave comprehensive exploration system and method based on a seismic source. The system comprises a seismic source device, the seismic source device comprises a seismic source and a driving control module, the seismic source is installed on a cutterhead and connected with the driving control module, a main control module is used for adjusting the seismic source to be supported on a tunnel face through the driving control module, and the seismic source is used for receiving an excitation instruction of the main control module and conducting seismic source excitation; the detector is linearly arranged on the earth surface along the tunneling direction of the shield tunneling machine and is used for acquiring a seismic source waveform signal; the main control module is used for preprocessing the seismic source waveform signal and separating a surface wave from a body wave; performing basis-high order joint inversion according to the separated surface wave data; obtaining a reflection imaging profile according to the separated body wave data; and obtaining a shear wave velocity profile and a stratum thickness according to basis-high order joint inversion, obtaining an underground wave velocity image based on a reflection imaging profile, and carrying out comprehensive identification on a target area by combining the two inversion results.

Description

Technical Field

[0001] The present invention belongs to the technical field of rock and soil exploration, and in particular relates to a surface wave and body wave comprehensive exploration system and an exploration method based on a seismic source. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Body waves are divided into longitudinal waves (P) and shear waves (S). The reflection and refraction of seismic waves underground contain rich information. Body waves are seismic waves that are directly generated by the vibration of the earthquake source and propagate inside the earth. At present, body waves are generally used for geological exploration. Surface waves are a type of seismic wave that mainly propagates on the surface. They have the largest energy and a wave speed of about 3.8 km / s, which is lower than body waves and is often recorded last. If the earthquake is very strong, surface waves may orbit the earth for several days after the earthquake. Surface waves are actually secondary waves derived from body waves on the surface. The propagation of surface waves is relatively complex. They can cause ups and downs of the surface and can also cause lateral shearing of the surface. Shearing movement is the most destructive to buildings. Surface waves pose great challenges to the full waveform inversion of land data. Although surface waves will be partially fitted, the surface wave residual is still much larger than the body wave part, so the deep information of the model carried by the surface waves cannot be extracted.

[0004] The inventors found that since the deep information of the model carried by the surface wave cannot be extracted, only using body waves for waveform inversion for geological exploration reduces the accuracy of the exploration results and cannot provide accurate guidance for the actual underground engineering construction. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a surface wave and body wave comprehensive exploration system and exploration method based on a seismic source, which adopts an artificial seismic source to return the seismic source waveform data for subsequent data processing, and then obtains higher quality surface wave and body wave data through data processing and surface and body separation, which is used for subsequent inversion imaging, and can improve the accuracy of the exploration results.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] The first aspect of the present invention provides a surface wave and body wave comprehensive exploration system based on a seismic source, which includes a seismic source device, a geophone and a main control module;

[0008] The seismic source device comprises a seismic source and a drive control module. The seismic source is installed on the cutterhead and connected to the drive control module. The main control module is used to adjust the seismic source support on the tunnel face through the drive control module. The seismic source is used to receive the excitation instruction of the main control module and perform seismic source excitation.

[0009] The geophones are arranged linearly on the surface along the tunneling direction of the shield machine and are used to collect source waveform signals;

[0010] The main control module is used to: pre-process the source waveform signal and separate the surface wave and the body wave; perform base-high order joint inversion based on the separated surface wave data; obtain the reflection imaging profile based on the separated body wave data; then obtain the shear wave velocity profile and the formation thickness based on the base-high order joint inversion, obtain the underground wave velocity imaging based on the reflection imaging profile, and comprehensively identify the target area by combining these two inversion results.

[0011] As an implementation mode, in the main control module, the preprocessed source waveform signal is transformed through FK transformation, and the surface waves and body waves are separated in the fk domain according to the velocity difference characteristics of the surface waves and body waves, and then the separated data are inversely transformed back to the tx domain.

[0012] As an implementation mode, in the main control module, the separated surface roll data is segmented, the dispersion energy spectrum is calculated by the phase shift method, the dispersion spectra of all segments are screened, the dispersion energy spectra that meet the preset conditions are superimposed, the dispersion curve is extracted and the initial model is established, and the basis-higher-order joint inversion is performed.

[0013] As an implementation mode, in the main control module, the separated body wave data are processed according to the active source reflection seismic process to obtain a reflection imaging profile.

[0014] As an implementation mode, in the main control module, the step of preprocessing the source waveform signal includes: removing instrument response, resampling, removing mean, removing linear trend, bandpass filtering, time domain normalization and spectral whitening.

[0015] As an implementation mode, the seismic source is installed at the cutter opening of the cutter disc.

[0016] As an implementation mode, the drive control module includes a hydraulic system and a source controller, the source controller is connected to the main control module, and the source controller is used to receive instructions from the main control module and control the action of the hydraulic system.

[0017] As an implementation method, the excitation intensity and frequency of the seismic source can be adjusted.

[0018] As an implementation mode, the seismic source device further includes a seismic source signal detector, which is fixed on the tunnel face and is used to receive the seismic source signal and transmit the seismic source signal back to the main control module.

[0019] The second aspect of the present invention provides an exploration method of the surface wave and body wave integrated exploration system based on the seismic source as described above, which comprises:

[0020] The seismic source is installed at the cutterhead of the shield machine. When the shield machine is stopped, seismic waves are excited on the tunnel face and the waveform signal of the seismic source is collected at the same time.

[0021] Preprocess the source waveform signal and separate the surface wave and body wave;

[0022] Perform base-high order joint inversion based on the separated surface wave data; obtain reflection imaging profile based on the separated body wave data;

[0023] Then, the shear wave velocity profile and stratum thickness are obtained based on the base-high order joint inversion, and the underground wave velocity imaging is obtained based on the reflection imaging profile. The target area is comprehensively identified by combining these two inversion results.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention installs the seismic source at the cutter head position of the shield machine. When the shield machine is stopped, seismic waves are excited at the tunnel face, and the seismic source waveform signal is collected at the same time, the seismic source waveform signal is preprocessed, and the surface wave and the body wave are separated. By inverting the separated surface wave and body wave data respectively, the underground geological conditions are comprehensively identified, which solves the obvious shortcomings of inversion using only surface wave dispersion or body wave receiver function. The combination of the two data can complement each other's advantages, well compensates for the problems of single data inversion, and improves the reliability of the inversion result.

[0026] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 A flow chart of a surface wave and body wave integrated exploration system based on a seismic source according to an embodiment of the present invention;

[0029] Figure 2 A system diagram of the seismic source device according to an embodiment of the present invention;

[0030] Figure 3 A diagram of the surface observation system according to an embodiment of the present invention;

[0031] Figure 4 This is a preprocessing flow chart of an embodiment of the present invention;

[0032] Figure 5 This is a diagram of the body wave inversion result of an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0034] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] Reference Figure 1 , this embodiment provides a surface wave and body wave comprehensive exploration system based on a seismic source, which includes a seismic source device, a detector and a main control module.

[0037] In the specific implementation process, the seismic source device includes a seismic source and a drive control module. The seismic source is installed on the cutterhead and connected to the drive control module. The main control module is used to adjust the seismic source support on the palm face through the drive control module. The seismic source is used to receive the excitation instruction of the main control module and perform seismic source excitation.

[0038] like Figure 2 As shown, the seismic source device has a fixing system and can be installed at the cutterhead of the shield machine for vibration. It can be removed after the detection is completed without affecting the construction of the shield machine. The seismic source has a wireless control system, which is easy to use and does not require manual hammering, and can meet the use requirements of the cutterhead environment of the shield machine. The vibration intensity and frequency of the seismic source are adjustable to meet the use requirements of various detection conditions, and the consistency of the seismic source is better than that of ordinary artificial seismic sources. The seismic source can return source waveform data, which can be used for later data processing to improve the inversion quality.

[0039] The seismic source of the present embodiment can be used on the surface and in shield tunnels respectively. When used on the surface, the method of use is the same as other artificial seismic sources, that is, the seismic source is fixed on the surface and excitation detection is performed.

[0040] During the shutdown of the shield machine, the seismic source is placed at the cutterhead position, and the seismic source is installed at the cutterhead hob opening by fixing bolts 1, and then the support column 5 is adjusted to support the seismic source at the tunnel face. Among them, the support column 5 is connected to the drive control module. Among them, the drive control module includes a hydraulic system and a seismic source controller, and the seismic source controller is connected to the main control module. The seismic source controller is used to receive instructions from the main control module and control the action of the hydraulic system.

[0041] After the installation is completed, the source excitation is controlled by the main control module (for example, a wireless controller). The main control module (for example, a wireless controller) issues instructions during the excitation process, and the source controller 2 receives the instructions and controls the excitation hammer 4 to work through the hydraulic system 3.

[0042] A sensor is also provided on the connecting pipeline between the oil pump of the hydraulic system 3 and the shock hammer 4. The sensor is connected to the source controller 2 and can transmit the real-time data of the shock source back to the main control module to monitor the working state of the source. The shock intensity and frequency of the source can be adjusted to meet the use requirements of different burial depths.

[0043] When the seismic source is working, the seismic source signal detector 6 is fixed on the tunnel face to receive the seismic source signal and transmit the signal back to the main control module for subsequent data processing.

[0044] In some embodiments, the seismic source has a satellite positioning and time system, the satellite positioning system is used to calculate the burial depth and the shot offset, and the time system is used to control and record the excitation time. In this way, the seismic source can be located and the burial depth of the seismic source can be measured when the seismic source is turned on, providing guidance for the layout of the observation system.

[0045] After the detection is completed, the support column 5 and the exciting hammer 4 are retracted and the seismic source is removed from the cutter head.

[0046] The seismic source device of this embodiment has a high degree of automation and high efficiency, does not interfere with the construction of the shield machine, and meets the requirements for safe and efficient detection of shallow buried tunnels in cities.

[0047] In this embodiment, the detectors are arranged linearly on the surface along the tunneling direction of the shield machine to collect the source waveform signal. The detectors arranged linearly on the surface along the tunneling direction of the shield machine constitute a surface observation system, such as Figure 3 As shown, the survey line layout length and the horizontal distance between the first detector and the shield machine cutterhead should be long enough, the number of detectors should be no less than 12, and the sampling rate should be no less than 2kHz. In order to ensure data quality and inversion accuracy, the data acquisition time should be long enough.

[0048] During the specific implementation process, the main control module is used to preprocess the source waveform signal and separate the surface wave and body wave; perform base-high order joint inversion based on the separated surface wave data; obtain the reflection imaging profile based on the separated body wave data; then obtain the shear wave velocity profile and formation thickness based on the base-high order joint inversion, obtain the underground wave velocity imaging based on the reflection imaging profile, and combine these two inversion results to make a comprehensive judgment on the target area.

[0049] Specifically, the collected data is preprocessed, such as Figure 4As shown in the figure, the specific steps include removing instrument response, resampling, removing mean, removing linear trend, bandpass filtering, time domain normalization, spectral whitening and surface body wave separation. Through data preprocessing, higher quality virtual source shot gather records and body wave data are obtained to reduce the errors in subsequent dispersion curve extraction and inversion.

[0050] The fk filter is used to separate the surface waves of the data. The fk filter method is based on the two-dimensional Fourier transform, which converts the time-space domain data f(t,x) into frequency wavenumbers and F(f,k) through Fourier transform, that is:

[0051]

[0052] F(f,k) is the frequency wavenumber spectrum

[0053] Where f is the frequency, k is the wave number, t is the time, and x is the distance.

[0054] Since there is a large difference in wave velocity between surface waves and body waves, this property can be used to design filters in the fk domain:

[0055]

[0056] D is a certain area on the frequency wavenumber spectrum. The shape of area D is determined according to the distribution of body waves and surface waves in the fk domain, and then the body waves and surface waves are separated by filters, and finally the body waves and surface waves are transformed back to the tx domain by inverse transformation.

[0057] Surface wave inversion:

[0058] The separated surface wave data are segmented, the dispersion energy spectrum is calculated by the phase shift method, the dispersion spectra of all segments are screened, the dispersion energy spectra that meet the conditions are superimposed, the dispersion curve is extracted, the initial model is established according to the geological data, and the base-high order joint inversion is performed. The joint inversion objective function can be expressed as:

[0059]

[0060] Where: V R基阶反演 represents the fundamental order dispersion curve obtained by inversion, V R高阶反演 represents the high-order dispersion curve obtained by inversion. V R基阶实测 and V R高阶实测 is the target dispersion curve to be fitted. α1 and α2 represent the weight coefficients of the fundamental and higher-order dispersion curves, respectively, and α1+α2=1; m and n are the number of frequency points. The weight coefficient represents the sensitivity of different modal dispersion curves to the velocity of medium-deep formations. The dispersion curve of the higher-order mode is more sensitive to the velocity of medium-deep formations than the fundamental dispersion curve.

[0061] Body wave inversion:

[0062] Frequency domain acoustic wave equation under point source excitation:

[0063]

[0064] Among them, G(x,x A ,ω) means the earthquake source is at x and the detector point is at x A The frequency domain representation of the wave propagation Green's function at is: ρ(x) and υ(x) are the density and velocity of the propagation medium, ω is the angular frequency, δ(x A ) is the pulse source.

[0065] Green's function G(x A ,x B ,ω) is:

[0066]

[0067] in, is any closed interval, n i =(n1,n2,n3) represents the normal vector of the interval, and R{} is calculated by taking the real part. In practical applications, assuming that the medium is homogeneous, the density and velocity are constants, etc., formula (2) is simplified to:

[0068]

[0069] Using the source function N(x,ω) returned by the source, the seismic records of points A and B are:

[0070]

[0071] Substituting formula (4) into formula (3) yields:

[0072]

[0073] Where S(ω) is the random noise power spectrum; <> represents the spatial weighted average.

[0074] The pseudo-shot gather record is obtained by formula (5). The shot gather record is processed according to the active source reflection seismic process to obtain the reflection imaging profile, as shown in Figure 5 shown.

[0075] Comprehensive interpretation:

[0076] Seismic surface waves have the characteristics of dispersion, that is, the propagation velocity of surface waves changes with the frequency, and its sampling depth generally increases with the period. Therefore, the underground velocity structure can be effectively constrained by the surface wave dispersion information. Extracting medium and short period surface wave signals from background noise effectively improves the resolution of surface wave imaging. The surface wave dispersion inversion obtains the average structure on the path, which is sensitive to the absolute velocity of S waves, often restores the smooth shear wave velocity structure, and is difficult to constrain the fine discontinuous surface structure. The body wave receiver function eliminates the influence of the source and propagation path by deconvolving the teleseismic body wave records of radial and vertical components, and then obtains information about the structure below the detector. The receiver function is sensitive to the cross-sectional structure below the station and is widely used to obtain the average wave velocity ratio or invert the fine shear wave velocity structure, but the receiver function inversion is often highly dependent on the initial model and has strong non-uniqueness. There are obvious shortcomings in the inversion using only surface wave dispersion or body wave receiver function, and the combination of the two data can complement each other. It can well make up for the problems of single data inversion and improve the reliability of the inversion results.

[0077] The exploration method of the surface wave and body wave integrated exploration system based on the earthquake source as described above comprises:

[0078] The seismic source is installed at the cutterhead of the shield machine. When the shield machine is stopped, seismic waves are excited on the tunnel face and the waveform signal of the seismic source is collected at the same time.

[0079] Preprocess the source waveform signal and separate the surface wave and body wave;

[0080] Perform base-high order joint inversion based on the separated surface wave data; obtain reflection imaging profile based on the separated body wave data;

[0081] Then, the shear wave velocity profile and stratum thickness are obtained based on the base-high order joint inversion, and the underground wave velocity imaging is obtained based on the reflection imaging profile. The target area is comprehensively identified by combining these two inversion results.

[0082] Seismic surface waves have the characteristic of dispersion, that is, the propagation velocity of surface waves changes with the change of frequency, and its sampling depth generally increases with the period. Therefore, the present invention can effectively constrain the underground velocity structure through the surface wave dispersion information. The surface wave dispersion inversion obtains the average structure on the path, which is sensitive to the absolute velocity of S waves, often restores the smooth shear wave velocity structure, and is difficult to constrain the fine discontinuous surface structure. The body wave receiver function eliminates the influence of the source and the propagation path by deconvolution of the teleseismic body wave records of radial components and vertical components, and then obtains information related to the structure below the detector. The receiver function is sensitive to the cross-sectional structure below the station, and is widely used to obtain the average wave velocity ratio or invert the fine shear wave velocity structure, but the receiver function inversion is often highly dependent on the initial model and has strong non-uniqueness. There are obvious deficiencies in the inversion of only using surface wave dispersion or body wave receiver function, and the combination of the two data can complement each other. It can well make up for the problems of single data inversion and improve the reliability of the inversion results.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A surface wave and body wave integrated exploration system based on earthquake source, characterized in that: It includes a source device, a detector and a main control module; The seismic source device comprises a seismic source and a drive control module. The seismic source is installed on the cutterhead and connected to the drive control module. The main control module is used to adjust the seismic source support on the tunnel face through the drive control module. The seismic source is used to receive the excitation instruction of the main control module and perform seismic source excitation. The geophones are arranged linearly on the ground surface along the tunneling direction of the shield machine and are used to collect source waveform signals; The main control module is used to: pre-process the source waveform signal and separate the surface wave and the body wave; perform base-high order joint inversion based on the separated surface wave data; obtain the reflection imaging profile based on the separated body wave data; then obtain the shear wave velocity profile and the formation thickness based on the base-high order joint inversion, obtain the underground wave velocity imaging based on the reflection imaging profile, and comprehensively identify the target area by combining these two inversion results.

2. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: In the main control module, the pre-processed source waveform signal is transformed through FK transformation, and the surface wave and body wave are separated in the fk domain according to the velocity difference characteristics of the surface wave and body wave, and then the separated data are inversely transformed back to the tx domain.

3. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: In the main control module, the separated surface wave data are segmented, the dispersion energy spectrum is calculated by the phase shift method, the dispersion spectra of all segments are screened, the dispersion energy spectra that meet the preset conditions are superimposed, the dispersion curve is extracted and the initial model is established, and the basis-higher order joint inversion is performed.

4. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: In the main control module, the separated body wave data are processed according to the active source reflection seismic process to obtain the reflection imaging profile.

5. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: In the main control module, the steps of preprocessing the source waveform signal include: removing instrument response, resampling, removing mean, removing linear trend, bandpass filtering, time domain normalization and spectral whitening.

6. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: The vibration source is installed at the opening of the cutter head.

7. The surface wave and body wave integrated exploration system based on earthquake source according to claim 1, characterized in that: The drive control module includes a hydraulic system and a source controller. The source controller is connected to the main control module. The source controller is used to receive instructions from the main control module and control the action of the hydraulic system.

8. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: The excitation intensity and frequency of the earthquake source can be adjusted.

9. The surface wave and body wave comprehensive exploration system based on earthquake source according to claim 1, characterized in that: The seismic source device also includes a seismic source signal detector, which is fixed on the tunnel face and is used to receive the seismic source signal and transmit the seismic source signal back to the main control module.

10. A prospecting method of a surface wave and body wave integrated prospecting system based on a seismic source as claimed in any one of claims 1 to 9, characterized in that: include: The seismic source is installed at the cutterhead of the shield machine. When the shield machine is stopped, seismic waves are excited on the tunnel face and the waveform signal of the seismic source is collected at the same time. Preprocess the source waveform signal and separate the surface wave and body wave; Perform base-high order joint inversion based on the separated surface wave data; obtain reflection imaging profile based on the separated body wave data; Then, the shear wave velocity profile and stratum thickness are obtained based on the base-high order joint inversion, and the underground wave velocity imaging is obtained based on the reflection imaging profile. The target area is comprehensively identified by combining these two inversion results.

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