Urban karst water guide channel detection system and method based on earthquake Krauklis waves

Abstract

The invention discloses an urban karst water guide channel detection system and method based on earthquake Krauklis waves. The urban karst water guide channel detection system comprises a piezoelectric type vibroseis, an array type earthquake receiving system and a multi-wave seismograph. The piezoelectric vibroseis is used for exciting seismic waves; and the multi-wave seismograph is used for acquiring seismic data acquired by each seismic acceleration sensor in the array type seismic receiving system. The structure can ensure the precision of seismic wave data acquisition each time; separating and extracting Krauklis waves from the acquired seismic wave data by adopting an energy-frequency double-selection method; then, based on the frequency dispersion characteristic of Krauklis waves, a mapping model of crack opening and wave field response is established; and finally, determining the opening degree of the urban karst water guide channel according to the mapping model, and performing inversion to obtain the dynamic flow of the urban karst water guide channel. Through treatment in the mode, the opening degree and the dynamic flow of the urban karst water guiding channel can be monitored, and finally prevention and control over hidden geological disasters are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical fields of geophysical exploration and urban geological disaster prevention and control, and particularly relates to a detection system and method for urban karst water-conducting channels based on seismic Krauklis waves. Background Art

[0002] Traditional karst water-conducting channel detection relies on seismic wave methods (such as P-wave / S-wave reflection signals) and electromagnetic methods. However, these methods have insufficient ability to identify dynamic water flow characteristics and are severely interfered by urban environmental noise, resulting in an error rate of up to 30% in the connectivity assessment of water-conducting channels. For example, the conventional seismic wave method has insufficient resolution for centimeter-scale fractures (>10 meters), and it is difficult for the electromagnetic method to distinguish static water storage structures from dynamic water-conducting channels. In recent years, it has been found that the dispersion characteristics of Krauklis waves (i.e., a slow guided wave in fluid-filled fractures) are directly related to the fracture aperture, fluid filling properties, and flow velocity, and can dynamically invert the size and water conductivity of fractures. However, the signal extraction and fracture inversion technology in urban complex environments are not yet mature.

[0003] Therefore, how to provide a new method to monitor the aperture and dynamic flow rate of urban karst water-conducting channels by exploiting the hydrodynamic response characteristics of Krauklis waves, and ultimately effectively improve the prevention and control of hidden geological disasters, is the research direction required by the present invention. Summary of the Invention

[0004] Aiming at the problems existing in the above-mentioned prior art, the present invention provides a detection system and method for urban karst water-conducting channels based on seismic Krauklis waves, which can monitor the aperture and dynamic flow rate of urban karst water-conducting channels by exploiting the hydrodynamic response characteristics of Krauklis waves, and ultimately effectively improve the prevention and control of hidden geological disasters.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a detection system for urban karst water-conducting channels based on seismic Krauklis waves, comprising a piezoelectric controllable seismic source, an array seismic receiving system, and a multi-wave seismograph;

[0006] The piezoelectric controllable seismic source is used to generate seismic waves;

[0007] The array seismic receiving system includes multiple survey lines arranged in parallel and at equal intervals. Each survey line includes multiple seismic acceleration sensors arranged in a straight line and connected in sequence. The number of seismic acceleration sensors on each survey line is the same, and the seismic acceleration sensors on each survey line are equally spaced;

[0008] The multi-wave seismograph is connected to the array-type seismic receiving system, and is used to acquire seismic data collected by each seismic acceleration sensor in each survey line, and determine the opening degree and dynamic flow rate of the urban karst water-conducting channel after subsequent analysis and processing.

[0009] Further, the frequency of the seismic wave excited by the piezoelectric vibrator is 0.1 - 100 Hz.

[0010] Further, the sampling frequency of the multi-wave seismograph is 1 kHz - 100 kHz.

[0011] Further, the distances between adjacent two seismic acceleration sensors on different survey lines are the same.

[0012] Further, it also includes a vehicle-mounted mobile detection platform, which is used to transport the piezoelectric vibrator, the array-type seismic receiving system and the multi-wave seismograph, and deploy the piezoelectric vibrator and the array-type seismic receiving system to the required positions.

[0013] The detection method of the above urban karst water-conducting channel detection system based on seismic Krauklis waves is specifically as follows:

[0014] Step 1. Deploy the detection system: First, determine the detection area, then lay out multiple survey lines along the direction of the vehicle-mounted mobile detection platform in the detection area to form an array-type seismic receiving system, then deploy the piezoelectric vibrator on one side of the array-type seismic receiving system, and connect the array-type seismic receiving system to the multi-wave seismograph;

[0015] Step 2. Collect data: Turn on the multi-wave seismograph and the piezoelectric vibrator. The piezoelectric vibrator excites seismic waves for a certain duration once. The array-type seismic receiving system continuously feeds back the seismic wave data received during this excitation time to the multi-wave seismograph, and performs cross-correlation processing on the seismic wave data to remove noise, and obtains the seismic wave data of this excitation; Repeat this step to continue exciting seismic waves multiple times at this position, and correspondingly obtain multiple sets of seismic data of multiple excitations. Vertically stack the multiple sets of seismic data to finally obtain the effective seismic data at this position;

[0016] Step 3. Extract Krauklis waves: Cut off the direct waves in the effective seismic data obtained in Step 2, and use the energy-frequency double-selection method to separate and extract Krauklis waves from the remaining signals;

[0017] Step 4. Establish a model: Based on the dispersion characteristics of Krauklis waves (i.e., the relationship between phase velocity and frequency), establish a mapping model between the crack opening degree and the wave field response;

[0018] Step 5. Determine the opening degree and dynamic flow rate of the urban karst water-conducting channel: According to the mapping model in Step 4, determine the opening degree of the urban karst water-conducting channel, and inversely obtain the dynamic flow rate of the urban karst water-conducting channel.

[0019] Further, in the third step, the energy-frequency dual-selection method is adopted to separate and extract Krauklis waves, specifically as follows:

[0020] ① Short-time energy detection:

[0021] Define the signal energy within the time window: where N is the number of sampling points, t is the point number at the end of the time window, and n is the point number within the time window. When E(t) > γ·E avg it is determined as the effective segment of Krauklis waves, where γ is the threshold factor, usually taken as 0.5; E avg is the average energy of background noise, thus initially separating the effective segment of Krauklis waves;

[0022] ② Frequency feature screening:

[0023] Calculate the power spectral density (PSD) of the effective segment of Krauklis waves obtained in step ①. The specific formula is: where N is the number of sampling points, f s is the sampling rate, and f n is the target frequency; then extract the main frequency band between 10 and 200 Hz in the power spectral density, and finally separate and extract Krauklis waves.

[0024] Further, the fourth step is specifically as follows:

[0025] Use the high-precision linear Radon transform to calculate the dispersion curve of the u(t) signal of Krauklis waves, obtain the relationship between wave velocity and frequency, and establish a mapping model between crack opening and wave field response. The specific steps are as follows:

[0026] 1. Fracture parameterized integration path

[0027] Assume that the main direction of the fracture is θ. At this time, the coordinates (x, y) of the seismic acceleration sensor satisfy:

[0028] x = dcosθ - ssinθ, y = dsinθ + scosθ

[0029] where d is the projection distance and s is the parameter along the fracture extension;

[0030] Integrate the amplitude of Krauklis waves along the main direction θ of the fracture:

[0031]

[0032] where u(x, y) is the displacement field of Krauklis waves, and the integration path corresponds to the normal projection of the fracture surface;

[0033] 2. Dispersion feature extraction

[0034] Dispersion relation of the phase velocity and frequency of Krauklis waves:

[0035] In the formula, v p is the phase velocity, h is the crack aperture, υ is the Poisson's ratio, and v s is the shear wave velocity; thus, a mapping model between the crack aperture and the wave field response is established.

[0036] Furthermore, the dynamic flow rate of the urban karst water conduction channel obtained by inversion in step five is specifically as follows: First, the Krauklis group velocity v g (f, t) is extracted by time-frequency analysis, and then the dynamic flow rate of the urban karst water conduction channel is obtained by inversion calculation based on the group velocity information. The specific formula is:

[0037] Transient flow rate In the formula, f is the frequency variable, used to characterize the Krauklis waves in different frequency bands, v g (f, t) is the group velocity, K(f) is the dimensionless frequency-dependent weight coefficient, and C(t) is the correction term, used to compensate for the background flow rate or the steady-state / low-frequency components not covered by the model.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1. The detection system of the present invention adopts an array-type seismic receiving system with a specific layout method, and a piezoelectric controllable seismic source is used to excite multiple seismic wave data at the same position. Each excited seismic wave is propagated through the formation and the fracture water conduction channel and is received by the array-type seismic receiving system. This structure can ensure the accuracy of the acquisition of each seismic wave data, and by superimposing the seismic wave data excited multiple times at the same position, the accuracy of the seismic wave data collected at the same position is further improved, facilitating the subsequent extraction of the seismic wave data.

[0040] 2. For the acquired seismic wave data, the present invention first uses the energy-frequency dual-selection method to separate and extract the Krauklis waves; then, based on the dispersion characteristics of the Krauklis waves (i.e., the relationship between the phase velocity and frequency), a mapping model between the crack aperture and the wave field response is established; finally, according to the mapping model, the aperture of the urban karst water conduction channel is determined, and a formula is established to invert and obtain the dynamic flow rate of the urban karst water conduction channel. Through this processing method, the monitoring of the aperture and dynamic flow rate of the urban karst water conduction channel can be realized, and ultimately the prevention and control of hidden geological disasters can be effectively improved. Description of the Drawings

[0041] Figure 1 is the layout schematic diagram of the detection system of the present invention;

[0042] Figure 2The relationships between the Krauklis wave parameters after being processed by the present invention and the crack opening and dynamic flow rate respectively;

[0043] Among them, (a) is the relationship between the Krauklis wave parameters and the crack opening; (b) is the relationship between the Krauklis wave parameters and the dynamic flow rate. Specific implementation mode

[0044] The present invention will be further described below.

[0045] As Figure 1 shown, an urban karst water-conducting channel detection system based on seismic Krauklis waves includes a piezoelectric controllable seismic source, an array seismic receiving system, and a multi-wave seismograph;

[0046] The piezoelectric controllable seismic source is used to generate seismic waves; the frequency of the seismic waves generated by the piezoelectric controllable seismic source is 0.1 - 100 Hz.

[0047] The array seismic receiving system includes multiple survey lines arranged in parallel and at equal intervals. Each survey line consists of multiple seismic acceleration sensors arranged in a straight line and connected in sequence. The number of seismic acceleration sensors on each survey line is the same, and the seismic acceleration sensors on each survey line are evenly distributed; the distance between adjacent two seismic acceleration sensors on different survey lines is the same, which is 1 m.

[0048] The multi-wave seismograph is connected to the array seismic receiving system. The sampling frequency of the multi-wave seismograph is 1 kHz - 100 kHz; it is used to obtain the seismic data collected by each seismic acceleration sensor in each survey line, and determine the opening and dynamic flow rate of the urban karst water-conducting channel after subsequent analysis and processing.

[0049] As an improvement of the present invention, it further includes a vehicle-mounted mobile detection platform, which is used to transport the piezoelectric controllable seismic source, the array seismic receiving system, and the multi-wave seismograph, and deploy the piezoelectric controllable seismic source and the array seismic receiving system to the required positions.

[0050] The detection method of the above-mentioned urban karst water-conducting channel detection system based on seismic Krauklis waves specifically includes the following steps:

[0051] Step 1. Deploy the detection system: First, determine the detection area, then establish a two-dimensional coordinate system within the detection area, define the x-direction as the direction of the vehicle-mounted mobile detection platform, the y-direction is perpendicular to the x-direction in the horizontal plane, lay out survey lines along the x-direction. The survey line is composed of 5 seismic acceleration sensors arranged at equal intervals, forming a strike survey line with a total length of 4m. Parallelly arrange 3 survey lines in the y-direction, with a line spacing of 1m between the survey lines, finally forming a 5×3 array seismic receiving system; then deploy a piezoelectric controllable seismic source on one side of the array seismic receiving system, and connect the array seismic receiving system to a multi-wave seismograph;

[0052] Step 2. Collect data: Turn on the multi-wave seismograph and the piezoelectric controllable seismic source. The piezoelectric controllable seismic source emits seismic waves for 10 seconds in a single excitation. The array seismic receiving system continuously feeds back the seismic wave data received during this excitation time to the multi-wave seismograph, and performs cross-correlation processing on the seismic wave data to remove noise, obtaining the seismic wave data of this excitation; Repeat this step to continue exciting seismic waves 3 times at this position, and obtain seismic data of a total of 4 excitations. Vertically stack the 4 seismic data to finally obtain the effective seismic data at this position;

[0053] Step 3. Extract Krauklis waves: Cut off the direct waves in the effective seismic data of Step 2, and use the energy-frequency dual-selection method to separate and extract Krauklis waves from the remaining signals. Specifically:

[0054] ① Short-time energy detection:

[0055] Define the signal energy within the time window: where N is the number of sampling points, t is the point number at the end of the time window, n is the point number within the time window. When E(t) > γ·E avg it is determined as the effective segment of Krauklis waves, where γ is the threshold factor, usually taken as 0.5; E avg is the average energy of background noise, thus initially separating the effective segment of Krauklis waves;

[0056] ② Frequency characteristic screening:

[0057] Calculate the power spectral density (PSD) of the effective segment of Krauklis waves obtained in Step ①. The specific formula is: where N is the number of sampling points, f s is the sampling rate, f n is the target frequency; then extract the main frequency band between 10 and 200Hz in the power spectral density, and finally separate and extract Krauklis waves.

[0058] Step 4. Establish a model: Based on the dispersion characteristics of Krauklis waves (i.e., the relationship between phase velocity and frequency), establish a mapping model between crack opening and wave field response. Specifically:

[0059] The high-precision linear Radon transform is used to calculate the dispersion curve of the u(t) signal of the Krauklis wave, obtain the relationship between the wave velocity and the frequency, and establish a mapping model between the fracture aperture and the wave field response. The specific steps are as follows:

[0060] 1. Fracture parameterized integration path

[0061] Let the main direction of the fracture be θ. At this time, the coordinates (x, y) of the seismic acceleration sensor satisfy:

[0062] x = dcosθ - ssinθ, y = dsinθ + scosθ

[0063] where d is the projection distance and s is the parameter along the fracture extension;

[0064] Along the main direction θ of the fracture, perform Radon integration on the amplitude of the Krauklis wave:

[0065]

[0066] where u(x, y) is the displacement field of the Krauklis wave, and the integration path corresponds to the normal projection of the fracture surface;

[0067] 2. Dispersion feature extraction

[0068] The dispersion relation of the relationship between the phase velocity and the frequency of the Krauklis wave:

[0069] In the formula, v p is the phase velocity, h is the fracture aperture, υ is the Poisson's ratio, and v s is the shear wave velocity; thus, a mapping model between the fracture aperture and the wave field response is established.

[0070] Step 5. Determine the aperture and dynamic flow rate of the urban karst water-conducting channel: According to the mapping model in Step 4, determine the aperture of the urban karst water-conducting channel, and invert to obtain the dynamic flow rate of the urban karst water-conducting channel as Figure 2 shown. Specifically: First, use time-frequency analysis to extract the Krauklis group velocity v g (f, t), and then perform inversion calculation based on the group velocity information to obtain the dynamic flow rate of the urban karst water-conducting channel. The specific formula is:

[0071] Transient flow rate In the formula, f is the frequency variable, which is used to characterize the Krauklis waves in different frequency bands, v g (f, t) is the group velocity, K(f) is the dimensionless frequency-dependent weight coefficient, and C(t) is the correction term, which is used to compensate for the background flow or the steady-state / low-frequency components not covered by the model.

[0072] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. An urban karst water channel detection system based on seismic Krauklis waves, characterized in that: Including piezoelectric controllable vibrator, array seismic receiving system and multi-wave seismograph; The piezoelectric controllable vibrator is used to excite seismic waves; The array-type seismic receiving system comprises a plurality of parallel and equally spaced survey lines, each survey line comprises a plurality of seismic acceleration sensors arranged in a straight line and connected in sequence, the number of seismic acceleration sensors on each survey line is the same, and the seismic acceleration sensors on each survey line are equally spaced; The multi-wave seismograph is connected to an array seismic receiving system to obtain seismic data collected by each seismic acceleration sensor in each survey line, and determine the opening and dynamic flow of the urban karst water channel after subsequent analysis and processing.

2. The urban karst water channel detection system based on seismic Krauklis waves according to claim 1 is characterized in that: The frequency of the seismic waves excited by the piezoelectric controllable vibrator is 0.1-100 Hz.

3. The urban karst water channel detection system based on seismic Krauklis waves according to claim 1 is characterized in that: The sampling frequency of the multi-wave seismograph is 1 kHz to 100 kHz.

4. The urban karst water channel detection system based on seismic Krauklis waves according to claim 1 is characterized in that: The distances between two adjacent seismic acceleration sensors on different survey lines are the same.

5. The urban karst water channel detection system based on seismic Krauklis waves according to claim 1 is characterized in that: It also includes a vehicle-mounted mobile detection platform for transporting piezoelectric controllable vibrators, array seismic receiving systems and multi-wave seismographs, and deploying the piezoelectric controllable vibrators and array seismic receiving systems to desired locations.

6. A detection method for the urban karst water channel detection system based on seismic Krauklis waves according to claims 1 to 5, characterized in that: The specific steps are: Step 1: Deploy the detection system: first determine the detection area, then lay out multiple survey lines along the direction of the vehicle-mounted mobile detection platform in the detection area to form an array seismic receiving system, then lay out a piezoelectric controllable source on one side of the array seismic receiving system, and connect the array seismic receiving system to the multi-wave seismograph; Step 2: Data collection: Turn on the multi-wave seismograph and the piezoelectric controllable vibrator. The piezoelectric controllable vibrator excites seismic waves of a certain duration at a time. The array seismic receiving system continuously feeds back the seismic wave data received during this excitation time to the multi-wave seismograph, and performs cross-correlation processing and denoising on the seismic wave data to obtain the seismic wave data excited this time. Repeat this step to continue to excite multiple seismic waves at the location, and obtain corresponding seismic data of multiple excitations, and vertically stack the multiple seismic data to finally obtain effective seismic data at the location; Step 3: Extract Krauklis waves: remove the direct waves in the effective seismic data in step 2, and use the energy-frequency double selection method to separate and extract Krauklis waves from the remaining signals; Step 4: Establish a model: Based on the dispersion characteristics of Krauklis waves, establish a mapping model between crack aperture and wave field response; Step 5: Determine the opening and dynamic flow of the urban karst water channel: According to the mapping model in step 4, determine the opening of the urban karst water channel, and invert to obtain the dynamic flow of the urban karst water channel.

7. The detection method according to claim 6, characterized in that: The step 3 uses the energy-frequency dual selection method to separate and extract the Krauklis wave, specifically: ①Short-time energy detection: Define the signal energy within the time window: Where N is the number of sampling points, t is the point number at the end of the time window, and n is the point number within the time window. avg When , it is determined as the effective segment of Krauklis wave, where γ is the threshold factor; E avg is the average energy of background noise, thus preliminarily separating the effective segment of Krauklis wave; ② Frequency feature screening: Calculation steps ① Obtain the power spectrum density of the effective band of the Krauklis wave. The specific formula is: Where N is the number of sampling points, f s is the sampling rate, f n is the target frequency; then the main frequency band between 10 and 200 Hz in the power spectrum density is extracted, and finally the Krauklis wave is separated and extracted.

8. The detection method according to claim 6, characterized in that: The step 4 is specifically as follows: The high-precision linear Radon transform is used to calculate the u(t) signal dispersion curve of the Krauklis wave, obtain the relationship between wave velocity and frequency, and establish a mapping model between crack aperture and wave field response. The specific steps are as follows:

1. Fracture parameterization integration path Assume that the main direction of the crack is θ, then the coordinates (x, y) of the seismic acceleration sensor satisfy: x=dcosθ-ssinθ, y=dsinθ+scosθ Where d is the projection distance, and s is the extension parameter along the crack; The Radon integration of the Krauklis wave amplitude along the main crack direction θ is: Where u(x,y) is the Krauklis wave displacement field, and the integral path corresponds to the normal projection of the crack surface; 2. Dispersion feature extraction The relationship between Krauklis wave phase velocity and frequency dispersion relation: Where v p is the phase velocity, h is the crack opening, υ is the Poisson's ratio, v s is the shear wave velocity; based on this, a mapping model between crack aperture and wave field response is established.

9. The detection method according to claim 6, characterized in that: The dynamic flow of the urban karst water channel is obtained by inversion in step 5, specifically: firstly, the Krauklis group velocity v is extracted by time-frequency analysis g (f, t), and then the dynamic flow of the urban karst water channel is obtained by inversion calculation based on the group velocity information. The specific formula is: Transient flow Where f is the frequency variable, v g (f, t) is the group velocity, K(f) is the dimensionless frequency-dependent weight coefficient, and C(t) is the correction term.

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