A fine imaging method and system for time-reversal tunnel boring machines

Abstract

This invention provides a method and system for fine imaging of time-reversal tunnel boring machines. Based on observation data, a pseudo-spectral energy function is constructed to obtain the azimuth information of echoes from anomalous geological bodies. Using the azimuth scanning information of the reflected signals as prior information, the weights of the Green's function for different imaging azimuths are corrected to enhance the resolution of anomalous bodies that are close to each other in azimuth, thus obtaining fine imaging results. This invention can provide a more accurate velocity distribution for fine imaging of array acoustic wave advanced geological exploration, achieving relatively accurate imaging of anomalous bodies at the meter to sub-meter level.

Description

Technical Field

[0001] This invention belongs to the field of tunnel imaging technology, specifically relating to a fine imaging method and system for time-reversal tunnel boring machines. Background Technology

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

[0003] During tunnel boring machine construction, the coexistence of multiple meter- to sub-meter-level unfavorable geological bodies results in small differences in travel time between adjacent and closely spaced abnormal geological bodies, which can easily cause crosstalk and superposition of reflected signals, leading to insufficient imaging accuracy of the detection results. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a fine imaging method and system for time-reversal tunnel boring machines. This invention can provide a more accurate velocity distribution for fine imaging of array acoustic wave advanced geological exploration, achieving more accurate imaging of anomalies at the meter to sub-meter level.

[0005] According to some embodiments, the present invention adopts the following technical solution:

[0006] A method for fine imaging of a time-reversal tunnel boring machine includes the following steps:

[0007] Based on observational data, a pseudo-spectral energy function is constructed to obtain the echo azimuth information of adverse geological bodies.

[0008] Using the azimuth scanning information of the reflected signal as prior information, the weight of the Green's function for different imaging azimuths is corrected to enhance the ability to distinguish between anomalous objects that are close to each other, thus obtaining fine imaging results.

[0009] As an alternative implementation method, the specific process of constructing the pseudospectral energy function includes: constructing the pseudospectral function:

[0010]

[0011] in The phase delay is measured under different azimuth scans. The vector corresponding to the signal subspace is used to estimate the pseudospectral energy intensity by delaying the signal at different angles. The location with high pseudospectral energy intensity indicates the presence of an anomalous geological body in that direction.

[0012] As an alternative implementation method, the specific process for obtaining the azimuth information of adverse geological bodies includes: incorporating the azimuth estimate of the target location into the improved Green's function, and estimating the direction of the target reflector using a constructed pseudospectral function.

[0013]

[0014] KR is the covariance matrix of the frequency domain data. Eigenvalue decomposition is performed on the covariance matrix to obtain the signal subspace corresponding to the vector with larger eigenvalues ​​and the noise subspace corresponding to the vector with smaller eigenvalues.

[0015] As an alternative implementation method, the specific process of modifying the weight of the Green function for different imaging orientations includes representing the Green function in terms of orientation, and the greater the energy intensity of the pseudospectral function, the greater its weight in the orientation.

[0016] Furthermore, the weights for different imaging orientations are the energy normalization values ​​of the corresponding pseudospectral functions.

[0017] As an alternative implementation, the process of obtaining fine imaging results includes a distortion-corrected reflection matrix and a time-reversal operator, which expresses the imaging function.

[0018] Furthermore, the imaging function is:

[0019]

[0020] The matrix after distortion correction is represented as a variable containing the azimuth angle.

[0021] Furthermore, by selecting a certain time width for the data, depth-by-depth scanning imaging results can be achieved within the maximum detection depth range.

[0022] A high-precision imaging system for a time-reversal tunnel boring machine includes:

[0023] The echo azimuth information representation module is configured to construct a pseudo-spectral energy function based on observation data to obtain the echo azimuth information of adverse geological bodies;

[0024] The fine imaging module is configured to use the azimuth scanning information of the reflected signal as prior information, correct the weight of the Green's function for different imaging azimuths, enhance the ability to distinguish between anomalous objects that are close to each other in azimuth, and obtain fine imaging results.

[0025] A tunnel boring machine includes a processor that loads and executes the steps of the method.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] This invention proposes a fine imaging method using azimuth scanning information of reflected signals as prior information and by modifying the weights of the Green's function for different imaging azimuths, an azimuth-weighted time-reversal operator is implemented. First, the echo azimuth is extracted based on the received data, and azimuth constraint information is added to the Green's function to enhance the resolution of anomalous bodies that are close to each other in the azimuth direction. This achieves fine imaging of meter-level to sub-meter-level anomalous geological bodies, providing a theoretical basis and guarantee for the interpretation of anomalous geological bodies in tunnel array acoustic advanced geological detection.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 These are geological anomalous body models in different orientations according to the present invention;

[0031] Figure 2 This is a target body scanning orientation diagram of the present invention;

[0032] Figure 3 This is the distribution of scanning weight factors in different orientations according to the present invention;

[0033] Figure 4 This is the sub-meter level fine imaging result of the karst cave of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0037] For complex rock media, the reflected echo signals from laterally adjacent anomalous geological bodies arrive at similar times. That is, signals from the same reflecting target may have traveled through different propagation paths. According to Huygens' principle, the travel times of different signals are significantly different.

[0038] To further improve the azimuth resolution of the imaging results, this invention introduces an improved Green's function for the azimuth scanning method. The Green's function is:

[0039]

[0040] in, Let z be the virtual source location and z be the depth of a certain imaging point. For the focal point, the spatial Green's function Virtual source location To any focal point on the z-plane of a certain imaging point Virtual focus, V0 is the wave velocity of the rock mass medium, where V is the selected data imaging frequency.

[0041] The azimuth estimate of the target position is incorporated into the improved Green's function, and the direction of the target reflector is estimated using equation (2).

[0042] (1)

[0043] KR is the covariance matrix of the frequency domain data. Then, eigenvalue decomposition is performed on the covariance matrix to obtain the signal subspace corresponding to vectors with larger eigenvalues ​​and the noise subspace corresponding to vectors with smaller eigenvalues. Based on this, a pseudospectral function is constructed. Ps for:

[0044] (2)

[0045] in The phase delay is measured under different azimuth scans. Let be the vector corresponding to the signal subspace. By estimating the pseudospectral energy intensity from signals delayed at different angles, locations with high pseudospectral energy intensity indicate the presence of anomalous geological bodies in that direction.

[0046] The time-reversal operator has a multipath compensator effect; for example, for an excitation pulse signal, the sound field intensity at a point in space can be expressed as:

[0047] (3)

[0048] Where S(w) represents the frequency domain expression of the excitation signal, the excitation point is zi, the receiving point is zj, r is the horizontal distance between the excitation and receiving points, and t is the signal propagation time. The time reversal of the signal at the receiving point can then be expressed as: Substituting it into equation (3), we get:

[0049] (4)

[0050] in Represented as the conjugate in the complex domain, by the properties of the Fourier transform, the conjugate in the complex domain is represented by time reversal in the time domain. Using the time-reversed signal as the new excitation source, the sound field intensity at the reversed excitation signal S can be obtained as:

[0051] (5)

[0052] in This represents the process of receiving a signal at position z after the excitation signal at position zi has undergone time flipping. When the receiving position z coincides with zi, it can be seen from the above equation that the time flipping operator implements the matched filtering function, where the transfer function is... Therefore, the signal time can achieve an enhanced focusing effect after being processed by the inversion operator.

[0053] To verify the effectiveness of the azimuth estimation, this invention designs a model as follows: Figure 1 As shown, at a distance of 10m from the face of the tunnel face, there are two karst caves with a diameter of 0.8m at 20° and -20° azimuths. The background rock wave velocity is 3000m / s, and the wave velocity of the karst caves and tunnel cavities is 340m / s. The tunnel cavity is 10m high and 5m long.

[0054] Based on this, a delayed scan is performed on the processed data to obtain the echo azimuth of the target geological body, such as... Figure 2 As shown in the figure, for the acoustic data excited at the middle position, its pseudospectral function exhibits two peaks at -20° and 20°, while the pseudospectral energy of the signal is lower at other positions. This is consistent with the designed model azimuth angle, indicating that the azimuth estimation based on delayed scanning can determine the reflected echo position of small targets. Therefore, it can be demonstrated that the azimuth scanning method of this invention is effective. Furthermore, this invention normalizes the azimuth scanning results, adding different weighting factors to different positions in the radial direction of the tunnel.

[0055] By using the azimuth information of anomalous geological bodies as constraints, the lateral resolution of meter- to sub-meter-level anomalous geological bodies can be improved, thereby enhancing the imaging accuracy of these anomalous bodies. For ease of derivation, this invention represents the Green's function in terms of azimuth:

[0056] (6)

[0057] in The pseudospectral function represents the normalized value for a given imaging depth. z For directions with higher pseudospectral function energy intensity, the weight is larger; for directions with lower pseudospectral function weight, the weight is smaller. Since equation (6) only performs a linear transformation on the Green's function, it is multiplied by only a constant factor in different directions. Therefore, the distortion correction of the reflection matrix does not change fundamentally, and the derivation of this part of the formula is omitted. For ease of description, this invention uses the distortion-corrected matrix... Represented as a variable containing azimuth angle Based on this, by fusing the distortion-corrected reflection matrix and the time-reversal operator, its imaging function can be expressed as:

[0058] (7)

[0059] The reflection matrix after distortion correction is:

[0060]

[0061] in, J(k) x ，k x ） It is the original reflection matrix. k x It is the wave number in the x-direction, and the transfer matrix. .

[0062] By selecting a certain time width for the data, depth-by-depth scanning imaging results were achieved within the maximum detection depth Dep range. IM :

[0063] (8)

[0064] To illustrate the effectiveness of the azimuth scanning time-reversal imaging method proposed in this invention, Figure 1 To further illustrate, let's take an example. Data is extracted from the central location as the seismic source, with all other locations as signal receiving points for analysis. Based on this, the present invention uses different weighting factors for different azimuths. The Green's function is used to weight the data with the scanning echo azimuth as the scanning center and ±0.5° as the scanning weight interval. For example, if the maximum peak values ​​obtained during the scan are -20° and 20°, then -20.5° to -19.5° is used as the filter parameter selection range at -20°, and 20.5° to 19.5° is used as the filter parameter selection range at 20°. For the weight values ​​at -20° and 20°, the pseudospectral function energy normalization value is used as the parameter magnitude. Figure 1 The model shown has different orientation scan weights. The distribution is shown in Figure 3 .

[0065] Based on this, sub-meter-level fine imaging of the cave was obtained by modifying the Green's function, and the imaging results are as follows: Figure 4 As shown in the figure, the imaging results show that the artifact interference is small, the location of the cave is relatively accurate, and the boundary is clearly delineated. Therefore, it can be shown that azimuth scanning can be used as prior information to enhance the resolution of targets in the lateral direction.

[0066] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., that can be made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A time reversal tunneling boring machine fine imaging method, characterized by, The method comprises the following steps: Based on the observation data, a pseudo-spectrum energy function is constructed to obtain echo azimuth information of the adverse geological body; The weight of the Green function for different imaging azimuths is corrected based on the prior information of the reflection signal azimuth scanning information, the resolution capability of the abnormal body with azimuths close to each other is enhanced, and a fine imaging result is obtained; The specific process of constructing the pseudo-spectrum energy function comprises: constructing a pseudo-spectrum function: wherein is the phase delay size under different azimuth scanning, is the vector corresponding to the signal subspace, by estimating the pseudo-spectrum energy intensity of different angle delay signals, the position with high pseudo-spectrum energy intensity indicates that there is an abnormal geological body in this direction; The specific process of obtaining echo azimuth information of the adverse geological body comprises: adding the azimuth estimation of the target position to the improved Green function, and estimating the direction of the target reflector through the constructed pseudo-spectrum function: （1） KR is a covariance matrix of frequency domain data, the covariance matrix is subjected to eigenvalue decomposition, a signal subspace corresponding to a larger eigenvalue and a noise subspace corresponding to a smaller eigenvalue are obtained; The specific process of correcting the weight of the Green function for different imaging azimuths comprises: representing the Green function in azimuth, and the greater the energy intensity of the pseudo-spectrum function, the greater the weight of the azimuth; The process of obtaining the fine imaging result comprises a reflection matrix after distortion correction and a time reversal operator, and an imaging function is expressed; For an excited pulse signal, the sound field intensity at a point in space is represented as: （3） where S(w) represents the frequency domain representation of the excitation signal, the excitation point is z ii , the receiving point is z jj , r is the horizontal distance between the excitation point and the receiving point, and t is the signal propagation time. The time reversal representation of the signal at the receiving point is then , into equation (3): （4） wherein The sound field intensity at the position S after the time reversal is obtained by taking the time reversed signal as a new excitation source, and is represented as a complex conjugate of the sound field intensity at the position S before the time reversal. （5） wherein is represented as z ii The position excitation signal after time reversal at z position receiving signal process, transfer function is .

2. A time reversal tunneling machine fine imaging method as claimed in claim 1, characterized by, The weight of different imaging azimuths is a normalized value of the energy of the corresponding pseudo-spectrum function.

3. A time reversal tunneling machine fine imaging method as claimed in claim 1, characterized by, The imaging function is: The matrix for distortion correction is represented as a variable with azimuth angle.

4. A time reversal tunneling machine fine imaging method as claimed in claim 1, characterized by, For a certain time width selected by data, a depth scanning imaging result in the maximum detection depth range is realized.

5. A time reversal tunnel boring machine fine imaging system employing a time reversal tunnel boring machine fine imaging method according to any one of claims 1-4, characterized by, It comprises: An echo azimuth information representation module configured to construct a pseudo-spectrum energy function based on observation data to obtain echo azimuth information of an adverse geological body; A fine imaging module configured to correct the weight of the Green function for different imaging azimuths based on the prior information of the reflection signal azimuth scanning information, enhance the resolution capability of abnormal bodies with azimuths close to each other, and obtain a fine imaging result; The process of obtaining the fine imaging result comprises a reflection matrix after distortion correction and a time reversal operator, and an imaging function is expressed; The time reversal operator has a multipath compensator effect, and for an excited pulse signal, the sound field intensity at a point in space is represented as: （3） where S(w) represents the frequency domain representation of the excitation signal, the excitation point is z ii , the receiving point is z jj , r is the horizontal distance between the excitation point and the receiving point, and t is the signal propagation time. The time reversal representation of the signal at the receiving point is then , into equation (3): （4） wherein The sound field intensity at the position S after the time reversal is obtained by taking the time reversed signal as a new excitation source, which is expressed as a complex conjugate of the original signal, and is given by （5） wherein represents z ii The position excitation signal after time reversal of the received signal at z position, the transfer function is .

6. A tunnel boring machine characterized by, It comprises a processor, and the processor loads and executes the steps in the method of any one of claims 1-4.

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