City dense area surface wave geological exploration system and method based on scattering type sensor

Abstract

The invention belongs to the field of surface wave geological exploration, and provides an urban dense area surface wave geological exploration system and method based on a scattering type sensor. The urban dense area surface wave geological exploration system comprises a scattering type surface wave sensor and a surface wave data processing system, the scattering type surface wave sensor synchronously collects surface wave signals and sends the surface wave signals and the space positioning information to the surface wave data processing system; the surface wave data processing system is used for positioning the position of a detection area according to the spatial positioning information of the scattering type surface wave sensor; sequentially carrying out preprocessing, spectral analysis and band-pass filtering, body wave removal, time domain normalization and modal separation processing on the received surface wave signal to obtain a seismic record after modal separation; earthquake interference is carried out between any two scattering type surface wave sensors; and extracting a phase velocity frequency dispersion curve and travel time information between the two seismic records, and then performing surface wave tomography inversion to obtain a transverse wave velocity structure of a detection area, so that advanced prediction of the geological anomalous body can be realized.

Description

Technical Field

[0001] The invention belongs to the field of surface wave geological exploration, and in particular relates to a surface wave geological exploration system and method for densely populated urban areas based on scatter-type sensors. 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] Due to the complex geological environment of the shallow surface of the city, urban underground construction faces severe challenges in disaster prevention and control and safe construction. Among them, unfavorable geology such as isolated rocks and karst is the main source of disasters that threaten the safe construction of the tunnel boring machine. If the above unfavorable geology is not detected in advance and dealt with in advance, it is easy to cause abnormal damage to the tunnel boring machine cutter head, jamming, landslides, surface collapse and other disasters, which will lead to serious consequences such as project delays, casualties, and major economic losses. Therefore, the construction of urban underground tunnels requires the early detection of unfavorable geological conditions in front of the tunnel boring machine excavation face to guide the safe construction of the tunnel boring machine.

[0004] In the existing technology, surface wave exploration is a shallow surface seismic exploration method with the advantages of non-intrusion, low shallow surface attenuation, strong site adaptability, and low construction cost. It has been widely used in engineering geological exploration, non-destructive testing and other fields. Surface wave exploration requires the deployment of an observation system on the surface. In order to obtain high-quality surface wave records, a larger observation space is often required. However, urban underground tunnels are generally located under densely built-up areas such as urban traffic arteries and commercial areas. The surface environment is complex and surface wave observation conditions are difficult to meet.

[0005] Therefore, one of the key challenges of surface wave geological exploration in densely populated urban areas is that the conditions for the deployment of surface wave observation systems are difficult to meet. Existing surface wave data processing methods have put forward requirements for the arrangement of sensors. At present, surface wave observation systems mainly have one-dimensional linear arrangement and two-dimensional arrangement such as circular, cross, and T-shaped. These all require a longer measurement line length or a larger two-dimensional observation space, which is difficult to meet in the complex surface environment of densely populated urban areas. Summary of the invention

[0006] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a surface wave geological exploration system and method for densely populated urban areas based on scatter-type sensors. The scatter-type sensors are used to deploy irregular surface wave observation systems, thereby obtaining shallow surface geological conditions in densely populated urban areas, detecting the distribution of unfavorable geological bodies in front of the tunnel excavation face, predicting the quality grade of the rock mass ahead of drilling and timely discovering unfavorable geological bodies in front of the excavation face, thereby optimizing the construction plan and providing reference for ensuring the safety of tunnel construction.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a surface wave geological exploration system for densely populated urban areas based on scatter-type sensors.

[0009] A surface wave geological exploration system for densely populated urban areas based on a scattering type sensor, comprising: a scattering type surface wave sensor and a surface wave data processing system;

[0010] The scatter-type surface wave sensor is used to synchronously collect surface wave signals, and send the surface wave signals together with the spatial positioning information of the scatter-type surface wave sensor itself to the surface wave data processing system; wherein the surface wave signals include seismic waves, surface waves and background noise generated by the cutterhead rock-breaking source collected synchronously;

[0011] The surface wave data processing system is used for:

[0012] Locate the detection area according to the spatial positioning information of the scattered surface wave sensor;

[0013] The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation;

[0014] Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors;

[0015] According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

[0016] As an implementation method, the scatter-type surface wave sensors are randomly arranged according to the urban surface conditions.

[0017] As an implementation mode, the cast-type surface wave sensor is placed on the surface or buried underground.

[0018] As an implementation mode, the scatter-type surface wave sensors are evenly arranged in a set detection area.

[0019] As an implementation mode, the scattering sensor is a three-component detector, which collects multi-component surface wave data simultaneously.

[0020] As an implementation mode, the scattering sensor has an automatic positioning system and a time synchronization system.

[0021] As an implementation mode, in the surface wave data processing system, a phase scanning method is used to extract a phase velocity dispersion curve between two seismic records.

[0022] As an implementation mode, in the surface wave data processing system, the corresponding travel time information is calculated based on the phase velocity dispersion curve between any two seismic records and a pre-constructed target grid.

[0023] As an implementation mode, in the surface wave data processing system, the damped least square method is used to perform surface wave tomography inversion according to the phase velocity dispersion curve and travel time information between any two seismic records.

[0024] The second aspect of the present invention provides a surface wave geological exploration method for densely populated urban areas based on scatter-type sensors.

[0025] A surface wave geological exploration method for densely populated urban areas based on a scattering sensor, comprising:

[0026] Receive the scattering surface wave sensor to synchronously collect the surface wave signal and its spatial positioning information, wherein the surface wave signal includes the seismic wave, surface wave and background noise generated by the cutterhead rock breaking source that are synchronously collected;

[0027] Locate the detection area according to the spatial positioning information of the scattered surface wave sensor;

[0028] The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation;

[0029] Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors;

[0030] According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) In order to solve the problem that the surface environment in urban dense areas is complex and difficult to meet the requirements of surface wave exploration and observation, the present invention provides a system and method for surface wave geological exploration in urban dense areas based on scattered sensors, wherein the observation system does not need to be arranged regularly and can be applied to the complex surface environment in urban dense areas;

[0033] (2) The present invention utilizes multimodal information to perform surface wave tomography, which can effectively improve the accuracy of surface wave tomography results and obtain more realistic and reliable exploration results.

[0034] 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

[0035] 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.

[0036] Figure 1 Schematic diagram of a surface wave geological exploration and observation system for densely populated urban areas based on a scattering sensor according to an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of the working state of surface wave geological exploration and observation in densely populated urban areas based on a scattering sensor according to an embodiment of the present invention;

[0038] Figure 3 It is a data processing flow chart of a surface wave geological exploration method for densely populated urban areas based on a scatter-type sensor according to an embodiment of the present invention.

[0039] Among them, 1. Scattered surface wave sensors, 2. Surface wave data processing instrument system, 3. Surface buildings and structures, 4. Tunneling machine excavation source. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0041] 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.

[0042] 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.

[0043] Embodiment 1

[0044] like Figure 1 As shown, the urban densely populated area surface wave geological exploration and observation system based on the scatter-type sensor mainly includes the scatter-type surface wave sensor 1 and the surface wave data processing system 2.

[0045] The scatter-type surface wave sensor is used to synchronously collect surface wave signals and send the surface wave signals together with the spatial positioning information of the scatter-type surface wave sensor itself to a surface wave data processing system; wherein the surface wave signals include seismic waves, surface waves and background noise generated by the synchronously collected cutterhead rock-breaking source.

[0046] The surface wave data processing system is used for:

[0047] Locate the detection area according to the spatial positioning information of the scattered surface wave sensor;

[0048] The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation;

[0049] Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors;

[0050] According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

[0051] like Figure 1 and Figure 2 As shown, the tunnel boring machine passes through a densely populated urban area, and the geological conditions in front of the tunnel boring machine working face are complex, so it is necessary to explore the unfavorable geological conditions in front of the working face in advance. The surface buildings in the detection area are dense, and the available detection space is small. The scatter sensor observation system randomly deploys scatter sensors 1 according to the distribution of buildings. The scatter sensor 1 is located on the surface in front of the tunnel boring machine's route to collect the tunnel boring machine's excavation noise signal 4. After the data collection is completed, the scatter sensor 1 collects the surface wave data and the position information of each scatter sensor and summarizes it to the surface wave data processing instrument system 2, performs surface wave data processing, and obtains the shear wave velocity structure of the detection area in front of the tunnel.

[0052] There is no fixed arrangement of scatter-type sensors. The receiving point of each sensor is selected according to the on-site conditions. The number of sensors, sensor spacing and coverage are all controlled by the surface environment.

[0053] Among them, the scattered surface wave sensors are randomly arranged according to the surface conditions of the city. The scattered sensors can be placed on the surface or buried underground. When there is a lack of detector arrangement environment on the surface, the sensors can be buried underground.

[0054] In different embodiments, the scattering sensor observation system is located on the surface in front of the tunnel boring machine working face, including multiple sensors, and the number of sensors and the arrangement of the observation system are adjusted according to the actual situation of the detection area. Each receiver is a three-component receiver and has an automatic positioning system. Before transmitting the data to the surface wave data processing instrument system, it is necessary to first perform spatial positioning to record the spatial position of each sensor. The scattering sensor has a time synchronization system, and time synchronization is first required before data collection. Surface wave data collection should meet the collection time requirements. In order to obtain high-quality geological detection results, it is necessary to perform time domain superposition on the surface wave data to enhance the signal-to-noise ratio of the surface wave data.

[0055] When the tunnel boring machine is excavating, the cutter head cuts the rock to generate a vibration signal, which contains the geological information of the propagation medium as it propagates forward. The longitudinal wave and the transverse wave interfere on the surface to generate surface waves, which are received by the scattered sensor.

[0056] The data collected by each sensor is finally transmitted to the surface wave data processing instrument system, and the surface wave data processing instrument system quickly processes the surface wave data to obtain the shear wave velocity structure in front of the working face of the tunnel boring machine.

[0057] The data processing process of surface wave exploration in densely populated urban areas based on scatter-type sensors includes the restoration of the scatter-type sensor observation system, surface wave data preprocessing, surface wave data processing, extraction of phase velocity dispersion curves and surface wave travel times, and surface wave tomography to obtain the shear wave velocity structure of the detection area.

[0058] First, before detection, the scattering detector observation system is deployed. In this embodiment, 32 scattering sensors 1 are deployed between buildings in the densely populated urban area on the surface ahead of the tunnel boring machine's route. Each scattering sensor is set to automatically perform spatial positioning and store position information. Before starting to collect surface wave data, time synchronization is performed to ensure the time consistency of surface wave recording.

[0059] When the accompanying tunnel boring machine starts to dig, the tunnel boring machine generates tunneling noise 4, which acts as a seismic source to generate seismic waves for forward sensing. When passing through the wave impedance interface, refraction and reflection occur. After the seismic waves carrying the propagation medium information reach the surface, the longitudinal and transverse waves interfere to generate surface waves, which are received by the scattering sensor 1. After the data collection is completed, the data collected by each sensor and the spatial position information of each sensor are transmitted to the surface wave data processing instrument system 2 for rapid processing.

[0060] like Figure 3 As shown in Figure 2, the surface wave data processing flow includes:

[0061] (1) Observation system recovery:

[0062] According to the spatial position information of each scattering sensor, the position of each sensor is first restored in the processing instrument system to accurately locate the position of the detection area.

[0063] (2) Surface wave data preprocessing:

[0064] The components of directly collected surface wave data are relatively complex and contain multiple noise components, so they need to be preprocessed. The preprocessing steps mainly include: resampling, removing instrument response, removing mean, baseline correction and quality control. After surface wave data preprocessing, the noise signal is suppressed to obtain surface wave records with a high signal-to-noise ratio.

[0065] (3) Spectrum analysis and bandpass filtering:

[0066] The surface wave records after preprocessing are subjected to spectrum analysis. The spectrum analysis mainly checks the frequency band distribution of various noises in the collected seismic records, selects the main frequency bands that are beneficial to detection, and provides a frequency band distribution reference for bandpass filtering. Specifically, the time domain surface wave records are transformed into the frequency domain through Fourier transform, and the noise signals of different frequency bands are removed through bandpass filtering, and the frequency bands of effective surface waves are retained. Finally, the seismic records in the frequency domain are transformed back to the time domain through inverse Fourier transform.

[0067] (4) Body wave removal:

[0068] The data collected by the surface receiving station array contains seismic waves, surface waves and background noise generated by the cutterhead rock breaking source, and body waves need to be removed. When body waves exist, the surface wave energy at the same frequency will be suppressed. Removing body waves helps to obtain higher quality dispersion energy maps.

[0069] (5) Time domain normalization:

[0070] Time domain normalization can be used to suppress the noise sources near the sensor and the influence of sensor instruments, and reduce the interference of strong noise. Currently, commonly used time domain normalization methods include the one-bit method and the sliding absolute average.

[0071] (6) Mode separation of surface wave shot gather records:

[0072] The noise source of the tunnel boring machine can easily excite the high-order modal dispersion information of the surface wave. There are often multiple dispersion energies in the dispersion energy diagram, which is not conducive to the extraction of the surface wave travel time. Modal separation helps to pick up the travel time of each mode of the surface wave separately, and the multi-modal surface wave travel time information can be used together to improve the imaging accuracy.

[0073] (7) Seismic interference between scattered sensors:

[0074] After mode separation, the surface wave records are subjected to seismic interference respectively. At present, the commonly used seismic interference methods mainly include cross-correlation method, mutual interference method and convolution method. Taking the cross-correlation method as an example, when the cross-correlation method is used, the cross-correlation function between two seismic records is:

[0075]

[0076] Among them, R2(f) and R1(f) are the frequency domain representations of the two surface wave records, represents the complex conjugate function of R1(f), is the phase difference between the two surface wave records corresponding to the frequency f.

[0077] (8) Extract phase velocity dispersion curve:

[0078] When extracting the dispersion curve, the phase scanning method is used. First, the phase velocity scanning range V R ∈(v min ,v max ), and the frequency scanning range f∈(f min ,f max ), the energy V in the frequency-phase velocity domain can be expressed as:

[0079]

[0080] After obtaining the dispersion energy diagram in the frequency-phase velocity domain, the energy maximum point at each frequency is picked up to obtain the dispersion curve of each mode.

[0081] (9) Extract the surface wave travel time of each mode dispersion curve:

[0082] Before calculating the travel time of surface waves, the target grid is first established, and the total travel time of each ray in the study area is calculated according to the phase velocity dispersion curve. Among them, the phase velocity refers to the propagation speed of the seismic wave crest; the phase velocity dispersion curve is the corresponding relationship between frequency and phase velocity; there are countless dispersion curves; and the ray refers to the geometric path of the seismic wave propagation in the model.

[0083] The total wave travel time under each mode dispersion curve is calculated as follows:

[0084]

[0085] in, is the travel time of the jth ray passing through the study area in mode p, is the phase velocity of mode p when the ray passes through the i-th grid, d ij is the ray path length of the j-th ray in the i-th grid.

[0086] The target grid is constructed as follows:

[0087] Based on the modified shortest path search method, the velocity model is divided into squares, nodes are added on the grid lines by setting secondary nodes, and the nodes are connected with straight lines to form a network diagram on the velocity model. There are many possible paths between any two points in this network diagram to connect them. The shortest path method is to select the path with the shortest travel time from the receiving point to the source point as the true ray path of the receiving point according to the Fermat principle. The construction of the grid needs to consider the calculation efficiency and calculation accuracy, and the relationship between the two is weighed to determine the grid size.

[0088] (10) Surface wave tomography:

[0089] When inverting, the multi-modal surface wave information is jointly inverted, and the damped least squares method is used for surface wave tomography inversion. The objective function used is:

[0090]

[0091] Where d is the ray path matrix, Δs is the modification vector about the initial model, and Δt is the observed value of the surface wave travel time t obs The error vector between the travel time t0 calculated by the initial model, || ||2 represents the second norm of the vector, w is the weighting matrix, α is the damping coefficient, which controls the change direction and convergence speed of Δs, ||dΔs-Δt||2W||DΔs-Δt||2 represents the fitting error of the data, Represents the model length.

[0092] It should be noted here that those skilled in the art may also use Newton's method, quasi-Newton's method, steepest descent method, genetic algorithm or particle swarm algorithm to perform joint inversion.

[0093] In one or more embodiments, a method for surface wave geological exploration in densely populated urban areas based on a scattering sensor is provided, comprising:

[0094] Receive the scattering surface wave sensor to synchronously collect the surface wave signal and its spatial positioning information, wherein the surface wave signal includes the seismic wave, surface wave and background noise generated by the cutterhead rock breaking source that are synchronously collected;

[0095] Locate the detection area according to the spatial positioning information of the scattered surface wave sensor;

[0096] The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation;

[0097] Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors;

[0098] According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

[0099] Aiming at the problem that the surface environment in densely populated urban areas is complex and traditional surface wave observation systems are difficult to adapt to, the present invention proposes a randomly arranged scattered sensor observation system. When detecting unfavorable geology in front of the working face of a tunnel boring machine, sensors are arranged on the surface in front of the tunnel boring machine to collect the tunnel boring noise source or the surface environmental noise.

[0100] After the above data collection is completed, the data will be aggregated to the surface wave data processing instrument system and processed. The random scattered sensor observation system needs to aggregate the position information of each sensor and restore it in the surface wave data processing instrument system to restore the observation system. Then the collected surface wave data will be preprocessed, spectrum analyzed and bandpass filtered, body wave removed, time domain normalized and modal separated. Seismic interference will be performed between the sensors in pairs to extract the surface wave dispersion curve and travel time information between the two seismic records. Finally, surface wave tomography will be performed to obtain the shear wave velocity structure of the detection area, and a more accurate assessment of the rock mass quality in front of the working face of the tunnel boring machine will be made.

[0101] 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 geological exploration system for densely populated urban areas based on a scattering sensor, characterized in that: include: Scattered surface wave sensor and surface wave data processing system; The scatter-type surface wave sensor is used to synchronously collect surface wave signals, and send the surface wave signals together with the spatial positioning information of the scatter-type surface wave sensor itself to the surface wave data processing system; wherein the surface wave signals include seismic waves, surface waves and background noise generated by the cutterhead rock breaking source collected synchronously; The surface wave data processing system is used for: Locate the detection area according to the spatial positioning information of the scattered surface wave sensor; The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation; Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors; According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

2. The urban dense area surface wave geological exploration system based on the scattering sensor according to claim 1 is characterized in that: The scatter-type surface wave sensors are randomly arranged according to the urban surface conditions.

3. The urban dense area surface wave geological exploration system based on the scattering sensor as claimed in claim 1 is characterized in that: The scatter-type surface wave sensor is placed on the ground surface or buried underground.

4. The urban dense area surface wave geological exploration system based on the scattering sensor according to claim 1 is characterized in that: The scatter-type surface wave sensors are evenly arranged in a set detection area.

5. The urban dense area surface wave geological exploration system based on the scattering sensor as claimed in claim 1 is characterized in that: The scattering sensor is a three-component detector that collects multi-component surface wave data simultaneously.

6. The urban dense area surface wave geological exploration system based on the scattering sensor as claimed in claim 1 is characterized in that: The scattering sensor has an automatic positioning system and a time synchronization system.

7. The urban dense area surface wave geological exploration system based on the scattering sensor according to claim 1 is characterized in that: In the surface wave data processing system, a phase scanning method is used to extract a phase velocity dispersion curve between two seismic records.

8. The urban dense area surface wave geological exploration system based on the scattering sensor as claimed in claim 1 is characterized in that: In the surface wave data processing system, the corresponding travel time information is calculated based on the phase velocity dispersion curve between any two seismic records and the pre-constructed target grid.

9. The urban dense area surface wave geological exploration system based on the scattering sensor as claimed in claim 1 is characterized in that: In the surface wave data processing system, the damped least square method is used to perform surface wave tomography inversion according to the phase velocity dispersion curve and travel time information between any two seismic records.

10. A method for surface wave geological exploration in densely populated urban areas based on a scattering sensor, characterized in that: include: Receive the scattering surface wave sensor to synchronously collect the surface wave signal and its spatial positioning information, wherein the surface wave signal includes the seismic wave, surface wave and background noise generated by the cutterhead rock breaking source that are synchronously collected; Locate the detection area according to the spatial positioning information of the scattered surface wave sensor; The received surface wave signals are sequentially subjected to preprocessing, spectrum analysis and bandpass filtering, body wave removal, time domain normalization and mode separation to obtain seismic records after mode separation; Based on the seismic records after mode separation, seismic interference is performed between any two scatter-type surface wave sensors; According to the results of seismic interferometry, the phase velocity dispersion curve and travel time information between any two seismic records are extracted, and then surface wave tomography inversion is performed to obtain the shear wave velocity structure of the detection area.

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