Hydrophone-based landslide river blocking monitoring system and method

Abstract

The invention provides a hydrophone-based landslide river blocking monitoring system and method, and the system comprises a hydrophone for underwater signal collection, the hydrophone is connected with a data collection front-end module through a cable, and the data collection front-end module is used for digitalizing the data collected by the hydrophone and transmitting the digitalized data to the hydrophone. The data acquisition front-end module is connected to the integrated platform through a network cable; the integrated platform is used for controlling acoustic data to be collected according to a certain rate and resolution ratio, obtaining downstream water body time-frequency sound pressure fluctuation signals caused by landslide, and storing the signals on an external hard disk. According to the monitoring system, the hydrophone is adopted for monitoring, aiming at the advantage that the sampling frequency of the hydrophone is high, high sensitivity to instantaneous data in the monitoring process is guaranteed, the water inflow of a landslide accumulation body can be rapidly determined to judge whether the river is blocked or not, and real-time early warning is achieved; and the acoustic method is easy to deploy, and comprehensive, continuous and effective monitoring can be provided.

Description

Technical Field

[0001] The invention relates to the technical field of landslide monitoring, and in particular to a landslide and river blocking monitoring system and method based on a hydrophone. Background Art

[0002] The particularity of the geological environment and structure has led to the concentration of landslide disasters in western my country, such as Yunnan, Guizhou, Chongqing, Gansu, and Shaanxi. The economic losses caused by landslides are huge. When there are rivers in the direction of landslide movement, the landslide body is very easy to accumulate in the river to form a barrier dam, which will raise the water level upstream. Once the dam body loses stability and collapses, it will also cause huge flood disasters downstream, amplifying the scope and scale of the disaster. To carry out effective disaster prevention and mitigation work, it is necessary to have an effective understanding of landslide blocking the river. Therefore, it is particularly important to carry out comprehensive monitoring, analysis and research on the landslide blocking river disaster chain, and to prevent disasters such as river blocking caused by landslides in a targeted manner, so as to provide a reliable basis for scientific disaster prevention and mitigation. Establishing an effective monitoring network, timely prediction and protection have become important ways to resist disasters and reduce losses.

[0003] A hydrophone is a transducer that converts acoustic signals into electrical signals. It is used to receive acoustic signals in water and is also called a receiving transducer. Hydrophones are widely used in underwater communications, exploration, target positioning, tracking, etc.

[0004] As people's research on landslides continues to deepen, factors that induce landslide disasters are constantly being discovered by researchers at home and abroad, and various monitoring technologies are being applied in landslide monitoring. At present, the main methods of landslide monitoring include four dimensions: "air, ground, and interior". "Air" refers to the use of space positioning and remote sensing satellite technology to monitor landslides around the clock; "sky" refers to the use of low-altitude aircraft equipped with photography, remote sensing, three-dimensional laser scanning and other technologies to conduct periodic monitoring of landslides; "ground" and "interior" refer to the use of wireless sensor technology to monitor the surface and interior of the landslide in real time. Specifically: Existing technical means for monitoring landslide displacement: (1) “Air and sky” image monitoring methods based on landslides: The monitoring principles of "air" and "sky" are similar, both of which are based on the image information of the landslide body. The more commonly used methods are satellite remote sensing landslide monitoring technology, drone landslide monitoring technology or fixed-point cameras. By analyzing and processing the spatial image information of the landslide body, it is possible to obtain the dynamic deformation information of the landslide.

[0005] (2) Sensor monitoring methods based on landslide bodies such as “ground, inside”, etc.: The monitoring principles of "ground" and "inside" are similar, and are based on sensors. Commonly used sensor types are direct monitoring and indirect monitoring. Direct monitoring includes landslide surface sensors such as displacement meter landslide monitoring technology to obtain the three-dimensional coordinates of the monitoring point, and then use the coordinate difference to calculate the displacement change of the monitoring point; landslide internal sensors such as rock and soil internal landslide monitoring technology can obtain the direction and size of the internal displacement of the landslide body by calculating the angle between the pre-buried inclinometer and the vertical direction.

[0006] In summary, the existing landslide displacement detection methods pay little attention to the subsequent landslide-blocking river disaster chain, and have weak recognition and monitoring functions for the underwater morphology of landslide-blocking rivers. There is no direct relationship between the occurrence of landslide displacement and the entry of landslide bodies into water. Therefore, the existing landslide displacement monitoring technology cannot effectively complete the monitoring of the landslide-blocking river process.

[0007] In addition, the subsequent river blocking disasters caused by landslides are currently mainly predicted by empirical statistical methods, using empirical evaluation methods such as sedimentation index, dimensionless sedimentation index, and morphological blocking index to predict landslide river blocking. Existing landslide river blocking evaluation methods: (1) Geomorphic index evaluation parameters: Previous researchers proposed a series of indicators to predict the degree of blockage of landslide deposits, such as sedimentation index, dimensionless sedimentation index, and morphological blockage index. However, different evaluation indices have great differences in different study areas and poor real-time predictability.

[0008] (2) Numerical simulation method and experimental simulation method: Numerical simulation methods and experimental simulation methods can take into account the physical mechanism of landslide blocking the river. By describing the dynamic process of landslide blocking the river and forming a dam, key parameter information such as dam shape and range of barrier lake can be obtained. However, key parameters such as geotechnical mechanics parameters are not easy to obtain, and the final experimental results may be different from the actual landslide blocking the river process. In addition, the experimental simulation method has problems such as high experimental cost.

[0009] Potential landslides and landslides blocking the river are characterized by significant concealment and short-term suddenness. Therefore, there is an urgent need for a method to assess the water inflow of landslide accumulation bodies to determine whether the river is blocked and to achieve real-time early warning, which is of great significance for the prevention and emergency management of subsequent chain disasters. Summary of the invention

[0010] In view of the above problems, the present invention provides a landslide and river blocking monitoring system and method based on hydrophones. This monitoring system adopts hydrophones for monitoring. Taking advantage of the high sampling frequency of hydrophones, it ensures high sensitivity to instantaneous data during the monitoring process, and can quickly determine whether the landslide accumulation body has blocked the river and realize real-time early warning. The acoustic method is easy to deploy and can provide comprehensive, continuous and effective monitoring. The present invention has distinct scientificity, can effectively monitor the problem of reservoir bank landslide and river blocking, and is of great value to the smooth scheduling and safe operation of the reservoir.

[0011] In order to realize the above-mentioned technical features, the object of the present invention is realized as follows: a landslide and river blocking monitoring system based on a hydrophone comprises a hydrophone for collecting underwater signals, wherein the hydrophone is connected to a data acquisition front-end module via a cable, wherein the data acquisition front-end module is used to digitize the data collected by the hydrophone, and wherein the data acquisition front-end module is connected to an integrated platform via a network cable; wherein the integrated platform is used to control the collection of acoustic data at a certain rate and resolution, obtain the time-frequency sound pressure fluctuation signal of the downstream water body caused by the landslide, and store it on an external hard disk.

[0012] The hydrophone collects underwater sound signals with a sensitivity of at least 219.7 dB re1 V / μPa, a flat frequency response, and a frequency range of 0.1-100 kHz.

[0013] The data acquisition front-end module uses National Instrument equipment to digitize the data.

[0014] The integrated platform controls the acquisition of acoustic data at a rate of at least 25.6 kHz and 4-bit resolution.

[0015] The data acquisition front-end module and integrated platform can perform multi-channel, real-time, FFT, analysis simultaneously, so as to facilitate the practical application of subsequent short-term response monitoring of landslides.

[0016] The integrated platform adopts a computer.

[0017] A landslide and river blocking monitoring method based on hydrophone, wherein the monitoring method is implemented by using any one of the landslide and river blocking monitoring systems, comprising the following steps: Step 1: Determine the specific frequency of landslides through landslide pre-experiments: Conduct landslide pre-experiments and determine the main frequencies of water pressure fluctuations generated by landslides by analyzing the short-term response of hydrophones and sound pressure spectrograms; Step 2: Practical application of short-term response of hydrophone in landslide and river blocking monitoring: The landslide river blocking monitoring system is arranged at the location where landslide monitoring is required, and the short-term response of the hydrophone signal is analyzed to complete the daily landslide monitoring work; wherein, the acoustic data is sampled at a rate of at least 25.6 kHz and a 4-bit resolution, and stored on an external hard disk; the underwater sound pressure fluctuation is subjected to a fast Fourier transform algorithm, and the time domain and exponential averaging are performed, and the exponential averaging time is 1 s, and the sound pressure spectrum is presented in real time. If the amplitude of the main frequency of the water pressure fluctuation caused by the landslide exceeds a certain specified value, a landslide warning signal is issued.

[0018] The step 1 specifically includes: Step 1.1, background noise and landslide pre-experiment recording: Select a pre-experimental site and place the hydrophone on a stable structure in the downstream river channel to avoid vibration affecting the hydrophone. Place the hydrophone at a depth of 10-20 cm underwater, facing downstream, to ensure that the landslide body does not directly impact the surface of the hydrophone, and keep a certain distance between the hydrophone and the reflective surface and obstacles. Complete the connection of the hardware equipment of the landslide river blocking monitoring system, and connect the hydrophone, data acquisition front-end module and integration platform in turn. Conduct audio recording of landslide pre-experiment. The content of landslide pre-experiment includes: making landslide materials slide freely along the chute to the downstream. The number of landslide pre-experiment is not less than 4 times. In each experiment, landslide materials with the same density but different masses are selected to obtain audio data of water pressure fluctuation caused by landslide, that is, time domain sound pressure data, with a total duration of not less than 20s. Step 1.2, process the acoustic data and identify the specific frequencies that the landslide generates: By processing the time-domain acoustic pressure data in step 1.1, the specific frequency of the water pressure fluctuation generated by the landslide can be determined.

[0019] The step 1.2 specifically includes: Step 1.2.1, perform fast Fourier transform: For each set of original audio data, extract effective time domain sound pressure data of no less than 1s. p , the sound pressure data p Convert to sound pressure level data SPL , the formula is as follows: ; In the formula, SPL is the sound pressure level data, p 0 is the reference value of the sound pressure level; Perform fast Fourier transform (FFT) on the sound pressure level time domain data to convert the audio data from the time domain to the frequency domain, and obtain the sound pressure level spectrum of the water pressure fluctuation caused by the landslide; ; In the formula,X ( k ) is the frequency domain signal; x ( n ) is the time domain signal; N is the length of the signal; is the kernel of the Fourier transform, including the complex exponential term; Step 1.2.2, remove the background noise in the original audio data by spectral subtraction to obtain a pure sound pressure level spectrum: In each experiment, the 3s audio data before the landslide occurred was selected as the background noise of each group. The spectral subtraction process was written as follows: Assuming that y(n) is a noise-contaminated signal, y(n) consists of a pure audio signal x(n) and background noise d(n), that is, y(n)=x(n)+d(n). After Fourier transformation, it is expressed as: Y(ω)=X(ω)+D(ω), then: ; Among them, α is the over-reduction factor, which is greater than or equal to 1 and mainly affects the degree of distortion of the speech spectrum; β is the spectrum lower limit parameter, which is greater than 0 and less than 1, and controls the amount of residual noise; Step 1.2.3, compare the sound pressure spectrum to determine the main frequency of water fluctuation caused by landslide: In order to summarize the sound pressure level spectrum data, the pure sound pressure level spectrum was divided into 11 octave frequencies from 16 Hz to 16 kHz, and the average value of the sound pressure level in each frequency band was calculated. The main frequencies of the water pressure fluctuations caused by the landslide were determined by comparing the four groups of sound pressure spectrum in the eleven-frequency form.

[0020] In step 1.2.1, the reference value of the sound pressure level in the liquid p 0 is 1μPa.

[0021] The present invention has the following beneficial effects: The present invention considers the use of hydrophones for monitoring. Taking advantage of the high sampling frequency of hydrophones, the high sensitivity of instantaneous data during the monitoring process is ensured, and the amount of water entering the landslide accumulation body can be quickly determined to determine whether the river is blocked and to achieve real-time early warning. In addition, the acoustic method is easy to deploy and can provide comprehensive, continuous and effective monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0023] Figure 1 This is a system framework diagram of the present invention.

[0024] In the figure: hydrophone 1, cable 2, data acquisition front-end module 3, network cable 4, integration platform 5. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by technical personnel in the field based on the above invention content still fall within the scope of protection of the present invention.

[0026] Embodiment 1: See also Figure 1 The landslide and river blocking monitoring system based on hydrophone includes a hydrophone 1 for underwater signal collection, wherein the hydrophone 1 is connected to a data collection front-end module 3 via a cable 2, wherein the data collection front-end module 3 is used to digitize the data collected by the hydrophone 1, and the data collection front-end module 3 is connected to an integrated platform 5 via a network cable 4; the integrated platform 5 is used to control the collection of acoustic data at a certain rate and resolution, obtain the time-frequency sound pressure fluctuation signal of the downstream water body caused by the landslide, and store it on an external hard disk.

[0027] Furthermore, the hydrophone collects underwater sound signals with a sensitivity of at least 219.7 dB re1 V / μPa, a flat frequency response, and a frequency range of 0.1-100 kHz.

[0028] Furthermore, the data acquisition front-end module uses National Instrument equipment to digitally process the data.

[0029] Furthermore, the integrated platform controls the acquisition of acoustic data at a rate of at least 25.6 kHz and a 4-bit resolution.

[0030] Furthermore, the data acquisition front-end module and integrated platform can simultaneously perform multi-channel, real-time, FFT, analysis, so as to facilitate practical application of subsequent short-term response monitoring of landslides.

[0031] Furthermore, the integrated platform adopts a computer.

[0032] Embodiment 2: A landslide and river blocking monitoring method based on hydrophone, wherein the monitoring method is implemented by using any one of the landslide and river blocking monitoring systems, comprising the following steps: Step 1: Determine the specific frequency of landslides through landslide pre-experiments: A landslide pre-experiment was conducted to determine the main frequencies of water pressure fluctuations generated by the landslide by analyzing the short-term response of the hydrophone and the acoustic pressure spectrum, and an algorithm for processing the acoustic data set was proposed; Step 1.1, background noise and landslide pre-experiment recording: Select a pre-experimental site and place the hydrophone on a stable structure in the downstream river channel to avoid vibration affecting the hydrophone. Place the hydrophone at a depth of 10-20 cm underwater, facing downstream, to ensure that the landslide body does not directly impact the surface of the hydrophone, and keep a certain distance between the hydrophone and the reflective surface and obstacles. Complete the connection of the hardware equipment of the landslide river blocking monitoring system, and connect the hydrophone, data acquisition front-end module and integration platform in turn. Conduct audio recording of landslide pre-experiment. The content of landslide pre-experiment includes: making landslide materials slide freely along the chute to the downstream. The number of landslide pre-experiment is not less than 4 times. In each experiment, landslide materials with the same density but different masses are selected to obtain audio data of water pressure fluctuation caused by landslide, that is, time domain sound pressure data, with a total duration of not less than 20s. Step 1.2, process the acoustic data and identify the specific frequencies that the landslide generates: By processing the time-domain acoustic pressure data in step 1.1, the specific frequency of the water pressure fluctuation generated by the landslide can be determined.

[0033] The step 1.2 specifically includes: Step 1.2.1, perform fast Fourier transform: For each set of original audio data, extract effective time domain sound pressure data of no less than 1s. p , the sound pressure data p Convert to sound pressure level data SPL , the formula is as follows: ; In the formula, SPL is the sound pressure level data, p 0 is the reference value of the sound pressure level; p 0 is 1μPa.

[0034] Perform fast Fourier transform (FFT) on the sound pressure level time domain data to convert the audio data from the time domain to the frequency domain, and obtain the sound pressure level spectrum of the water pressure fluctuation caused by the landslide; ; In the formula, X ( k ) is the frequency domain signal; x ( n ) is the time domain signal; N is the length of the signal; is the kernel of the Fourier transform, including the complex exponential term; Step 1.2.2, remove the background noise in the original audio data by spectral subtraction to obtain a pure sound pressure level spectrum: In each experiment, the 3s audio data before the landslide occurred was selected as the background noise of each group. The spectral subtraction process was written as follows: Assuming that y(n) is a noise-contaminated signal, y(n) consists of a pure audio signal x(n) and background noise d(n), that is, y(n)=x(n)+d(n). After Fourier transformation, it is expressed as: Y(ω)=X(ω)+D(ω), then: ; Among them, α is the over-reduction factor, which is greater than or equal to 1 and mainly affects the degree of distortion of the speech spectrum; β is the spectrum lower limit parameter, which is greater than 0 and less than 1, and controls the amount of residual noise; Step 1.2.3, compare the sound pressure spectrum to determine the main frequency of water fluctuation caused by landslide: In order to summarize the sound pressure level spectrum data, the pure sound pressure level spectrum was divided into 11 octave frequencies from 16 Hz to 16 kHz, and the average value of the sound pressure level in each frequency band was calculated. The main frequencies of the water pressure fluctuations caused by the landslide were determined by comparing the four groups of sound pressure spectrum in the eleven-frequency form.

[0035] Step 2: Practical application of short-term response of hydrophone in landslide and river blocking monitoring: The landslide river blocking monitoring system is arranged at the location where landslide monitoring is required, and the short-term response of the hydrophone signal is analyzed to complete the daily landslide monitoring work; wherein, the acoustic data is sampled at a rate of at least 25.6 kHz and a 4-bit resolution, and stored on an external hard disk; the underwater sound pressure fluctuation is subjected to a fast Fourier transform algorithm, and the time domain and exponential averaging are performed, and the exponential averaging time is 1 s, and the sound pressure spectrum is presented in real time. If the amplitude of the main frequency of the water pressure fluctuation caused by the landslide exceeds a certain specified value, a landslide warning signal is issued.

Claims

1. The landslide and river blocking monitoring system based on hydrophone is characterized by: It includes a hydrophone for underwater signal collection, the hydrophone is connected to a data collection front-end module via a cable, the data collection front-end module is used to digitize the data collected by the hydrophone, and the data collection front-end module is connected to an integrated platform via a network cable; the integrated platform is used to control the collection of acoustic data at a certain rate and resolution, obtain the time-frequency sound pressure fluctuation signal of the downstream water body caused by the landslide, and store it on an external hard disk.

2. The landslide and river blocking monitoring system based on hydrophone according to claim 1 is characterized in that: The hydrophone collects underwater sound signals with a sensitivity of at least 219.7 dB re1 V / μPa, a flat frequency response, and a frequency range of 0.1-100 kHz.

3. The landslide and river blocking monitoring system based on hydrophone according to claim 1 is characterized in that: The data acquisition front-end module uses National Instrument equipment to digitize the data.

4. The landslide and river blocking monitoring system based on hydrophone according to claim 1 is characterized in that: The integrated platform controls the acquisition of acoustic data at a rate of at least 25.6 kHz and 4-bit resolution.

5. The landslide and river blocking monitoring system based on hydrophone according to claim 1 is characterized in that: The data acquisition front-end module and integrated platform can perform multi-channel, real-time, FFT, analysis simultaneously, so as to facilitate the practical application of subsequent short-term response monitoring of landslides.

6. The landslide and river blocking monitoring system based on hydrophone according to claim 1 is characterized in that: The integrated platform adopts a computer.

7. A landslide and river blocking monitoring method based on hydrophone, characterized in that: The monitoring method is implemented by using the landslide and river blocking monitoring system according to any one of claims 1 to 6, and comprises the following steps: Step 1: Determine the specific frequency of landslides through landslide pre-experiments: Conduct landslide pre-experiments and determine the main frequencies of water pressure fluctuations generated by landslides by analyzing the short-term response of hydrophones and sound pressure spectrograms; Step 2: Practical application of short-term response of hydrophone in landslide and river blocking monitoring: The landslide river blocking monitoring system is arranged at the location where landslide monitoring is required, and the short-term response of the hydrophone signal is analyzed to complete the daily landslide monitoring work; wherein, the acoustic data is sampled at a rate of at least 25.6 kHz and a 4-bit resolution, and stored on an external hard disk; the underwater sound pressure fluctuation is subjected to a fast Fourier transform algorithm, and the time domain and exponential averaging are performed, and the exponential averaging time is 1 s, and the sound pressure spectrum is presented in real time. If the amplitude of the main frequency of the water pressure fluctuation caused by the landslide exceeds a certain specified value, a landslide warning signal is issued.

8. The landslide and river blocking monitoring method based on hydrophone according to claim 7 is characterized in that: The step 1 specifically includes: Step 1.1, background noise and landslide pre-experiment recording: Select a pre-experimental site and place the hydrophone on a stable structure in the downstream river channel to avoid vibration affecting the hydrophone. Place the hydrophone at a depth of 10-20 cm underwater, facing downstream, to ensure that the landslide body does not directly impact the surface of the hydrophone, and keep a certain distance between the hydrophone and the reflective surface and obstacles. Complete the connection of the hardware equipment of the landslide river blocking monitoring system, and connect the hydrophone, data acquisition front-end module and integration platform in turn. Conduct audio recording of landslide pre-experiment. The content of landslide pre-experiment includes: making landslide materials slide freely along the chute to the downstream. The number of landslide pre-experiment is not less than 4 times. In each experiment, landslide materials with the same density but different masses are selected to obtain audio data of water pressure fluctuation caused by landslide, that is, time domain sound pressure data, with a total duration of not less than 20s. Step 1.2, process the acoustic data and identify the specific frequencies that the landslide generates: By processing the time-domain acoustic pressure data in step 1.1, the specific frequency of the water pressure fluctuation generated by the landslide can be determined.

9. The landslide and river blocking monitoring method based on hydrophone according to claim 8 is characterized in that: The step 1.2 specifically includes: Step 1.2.1, perform fast Fourier transform: For each set of original audio data, extract effective time domain sound pressure data of no less than 1s. p , the sound pressure data p Convert to sound pressure level data SPL , the formula is as follows: ； In the formula, SPL is the sound pressure level data, p 0 is the reference value of the sound pressure level; Perform fast Fourier transform (FFT) on the sound pressure level time domain data to convert the audio data from the time domain to the frequency domain, and obtain the sound pressure level spectrum of the water pressure fluctuation caused by the landslide; ； In the formula, X ( k ) is the frequency domain signal; x ( n ) is the time domain signal; N is the length of the signal; is the kernel of the Fourier transform, including the complex exponential term; Step 1.2.2, remove the background noise in the original audio data by spectral subtraction to obtain a pure sound pressure level spectrum: In each experiment, the 3s audio data before the landslide occurred was selected as the background noise of each group. The spectral subtraction process was written as follows: Assuming that y(n) is a noise-contaminated signal, y(n) consists of a pure audio signal x(n) and background noise d(n), that is, y(n)=x(n)+d(n). After Fourier transformation, it is expressed as: Y(ω)=X(ω)+D(ω), then: ； Among them, α is the over-reduction factor, which is greater than or equal to 1 and mainly affects the distortion degree of the speech spectrum; β is the spectrum lower limit parameter, which is greater than 0 and less than 1, and controls the amount of residual noise; Step 1.2.3, compare the sound pressure spectrum to determine the main frequency of water fluctuation caused by landslide: In order to summarize the sound pressure level spectrum data, the pure sound pressure level spectrum was divided into 11 octave frequencies from 16 Hz to 16 kHz, and the average value of the sound pressure level in each frequency band was calculated. The main frequencies of the water pressure fluctuations caused by the landslide were determined by comparing the four groups of sound pressure spectrum in the eleven-frequency form.

10. The landslide and river blocking monitoring method based on hydrophone according to claim 8, characterized in that: In step 1.2.1, the reference value of the sound pressure level in the liquid p 0 is 1μPa.

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