CN114002330A - System for monitoring slope soil moisture content based on piezoelectric intelligent aggregate - Google Patents
System for monitoring slope soil moisture content based on piezoelectric intelligent aggregate Download PDFInfo
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Abstract
The invention discloses a system for monitoring the water content of a side slope soil body based on piezoelectric intelligent aggregate, which comprises a computer, an NI data acquisition and analysis system, a power amplifier, a piezoelectric intelligent aggregate sensor, a sliding slope surface, a sliding bed, a side slope body, a piezoelectric ceramic piece and an electric lead. The invention relates to the technical field of long-term online monitoring methods for soil moisture content of soil slopes, and provides a system for monitoring the moisture content of soil bodies of the soil slopes based on piezoelectric intelligent aggregates, which is simple, convenient, economical and efficient to use, and combines Labview, Matlab and other related processing software to perform long-term real-time online monitoring on the moisture content of the soil slopes, so that long-term, online, remote and rapid monitoring of the moisture content inside the soil slopes is realized, the moisture content conditions of all key positions inside the soil slopes can be accurately evaluated, the response speed is high, and the whole system has good stability and durability.
Description
Technical Field
The invention relates to the technical field of long-term online monitoring methods for soil slope water content, in particular to a system for monitoring the slope soil water content based on piezoelectric intelligent aggregates.
Background
The deep water content of the side slope is one of basic parameters for evaluating the stability of the soil quality side slope and is also a basic physical quantity for evaluating the engineering properties of the soil body of the side slope. A plurality of researches show that the moisture content of the soil body has very important influence on geological disasters such as unstable sliding of the side slope, large-scale collapse and landslide and the like. At present, a plurality of methods are used for measuring the water content of soil. According to its different characteristics and application range, it can be divided into local method and regional method. The local method mainly comprises an indoor test and measurement methods of some field original sites, such as a drying method, a resistivity method, a time domain reflection method, a ground penetrating radar method, a frequency domain reflection method and the like. The area rule is that the moisture content of the whole slope soil body is integrally grasped and determined by some macroscopic methods, such as an infrared sensing method, a remote sensing image method, a spectrum analysis method and the like. Due to the sensor technology and other reasons, the monitoring of the water content of the side slope is always a recognized problem at home and abroad, and the difference of the measurement results of different methods for the water content of the interior of the side slope is large.
Most of the above mentioned local measurement methods are suitable for being used in laboratories, and all the methods are point measurement methods, and the moisture content of the soil body at the deep part of the side slope cannot be continuously obtained, so that the application of the method in the analysis of the side slope stability and the monitoring and early warning of the landslide is limited. The regional method can only roughly and roughly estimate the overall water-containing condition of the soil body on the surface of the side slope, and cannot realize accurate measurement. The Nanjing university old android couples the hydrophilic rubber and the optical fiber, and the FBG optical fiber sensing technology is utilized to obtain the water content of the soil body by measuring the deformation of the optical fiber. The method has reliable precision when the water content is lower, but the testing precision is difficult to ensure under the condition of higher water content. In addition, the optical fiber sensor is placed in the deep part of the soil slope for a long time, and under the influence of severe environment conditions, the measurement characteristic value of the optical fiber sensor can drift, so that the measurement precision of the optical fiber sensor is influenced.
Disclosure of Invention
Technical problem to be solved
Aiming at the defects of the prior art, the invention provides a system for monitoring the water content of a side slope soil body based on a piezoelectric intelligent aggregate, which solves the problem of low monitoring precision of the water content of the side slope soil body in the prior art.
(II) technical scheme
In order to achieve the purpose, the invention provides the following technical scheme: a system for monitoring the water content of a side slope soil body based on piezoelectric intelligent aggregate comprises a computer, an NI data acquisition and analysis system, a power amplifier, a piezoelectric intelligent aggregate sensor, a sliding slope surface, a sliding bed, a side slope body, a piezoelectric ceramic piece and an electric lead.
The NI data acquisition and analysis system is externally connected with a computer, and the NI data acquisition and analysis system is electrically connected with the power amplifier.
A slope body is arranged on a sliding slope surface on the sliding bed, a plurality of piezoelectric intelligent aggregate sensors are arranged in the slope body, and the piezoelectric intelligent aggregate sensors are respectively and electrically connected with the NI data acquisition and analysis system and the power amplifier.
The piezoelectric intelligent aggregate sensor comprises a piezoelectric ceramic piece and an electric lead used for being connected with an external electric appliance element.
Preferably, the method for monitoring the water content comprises the following steps: the method comprises the following steps that (1) the piezoelectric intelligent aggregate sensor is buried in a position, where the water content of a soil body needs to be monitored, of the deep part of a side slope body, and the directionality and the position accuracy of the piezoelectric intelligent aggregate sensor need to be maintained during burying.
Connecting relevant equipment in a monitoring system, switching on a power supply and turning on an instrument switch, and exciting a high-frequency excitation signal to the piezoelectric intelligent aggregate sensor through an NI data acquisition and analysis system, wherein the frequency of a frequency sweep signal is 100-150 KHz, the amplitude is 3V, and the period is 1 s;
step (3) converting the electric signal into a stress wave signal by the piezoelectric intelligent aggregate sensor according to the inverse piezoelectric effect of the piezoelectric intelligent material, and after the piezoelectric intelligent aggregate sensor arranged at different positions in the side slope receives the stress wave signal, converting the signal into the electric signal again according to the positive piezoelectric effect of the piezoelectric intelligent material and acquiring and storing the electric signal by an NI data acquisition and analysis system;
and (4) establishing a functional relation between the stress wave signal and the water content of the side slope soil body according to the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor in the side slope body, and further determining the water content of the side slope body at different positions.
Preferably, in the step (2), the excitation signal is amplified by using a high-frequency high-voltage signal amplifier.
Preferably, before performing step (4), filtering and denoising processing is performed on the received stress wave signal.
Preferably, in the step (2), the high-frequency signal excited by the piezoelectric intelligent aggregate sensor through the NI data acquisition and analysis system is a sine sweep wave.
Preferably, in the step (4), the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the sensor propagated inside the soil slope body are compared with a system test calibration to determine the water content of different positions inside the soil slope.
Preferably, the system test calibration comprises the following steps:
step (I): collecting a representative soil sample in the soil slope to be monitored, and putting the soil sample into a drying box for full drying until the soil sample is in a completely dry state, wherein the soil sample quality is not reduced any more;
step (II): taking out the soil sample, weighing to obtain a soil sample mass m1 in a completely dry state, wherein the water content of the soil body is 0%;
step (III): and fully stirring and mixing the completely dried soil sample with water with the same mass, and preparing a soil slope test piece by using a mould, wherein the initial water content of the slope test piece is 100%. Before a side slope test piece is manufactured, a piezoelectric intelligent aggregate sensor is embedded in a specific position in the soil side slope test piece in advance, a certain distance is reserved between the two sensors, and the distance is consistent with the distance between the sensors in the soil side slope to be monitored. In order to ensure the stability and reliability of test results, three groups of test pieces are selected;
step (IV): by utilizing the monitoring system and the fluctuation method in the active sensing method, the stress wave signals of the three groups of soil slope test pieces are detected, and the waveform information of the received stress wave under the condition that the initial water content is 100 percent is obtained;
and (V) calibrating the relative water content: and (3) placing the soil slope test piece on a digital balance, and placing the soil slope test piece and the digital balance in a thermostat at 40 ℃ to dry and dehydrate the soil slope test piece. And obtaining the evaporation capacity of the water of the soil slope test piece according to the reading of the balance, weighing and recording as mi, and further calculating the water content of the test piece. Detecting stress wave signals under the water content to obtain stress wave information under different relative water content conditions; for each working condition, testing is carried out according to a single pulse wave of sine sweep frequency of 100-150 KHz; the sweep frequency wave is used for comparing the difference of received stress wave signals under different water content conditions, and relevant water content evaluation indexes are calculated through later-stage data analysis and processing. Meanwhile, the sweep frequency wave detects the loss condition of waves with different frequency components under the condition of different water content, the influence of the water content on signals with different excitation frequencies is determined through time domain analysis and frequency domain analysis of the sweep frequency signal, and the excitation frequency suitable for monitoring the water content is selected. In the sweep frequency wave detection stage, firstly, a sine sweep frequency wave is transmitted by an NI data acquisition and analysis system, a signal is amplified by a power amplifier and then input into a piezoelectric intelligent aggregate sensor positioned on one side of a test piece, an electric signal is converted into a stress wave vibration signal due to the inverse piezoelectric effect and is transmitted in a side slope test piece in a wave form, and the piezoelectric intelligent aggregate sensor positioned on the other side of the test piece converts the stress wave signal into an electric signal after receiving the stress wave signal and transmits the electric signal back to the NI data acquisition and analysis system;
and (VI) analyzing and processing data: under the conditions of different water contents, analyzing the average value of the amplitude of the received stress wave signal to obtain the variation trend of the amplitude of the stress wave along with the water contents; meanwhile, calculating an energy index based on the wavelet packet according to the collected stress wave information to obtain the variation trend of waveform energy along with the water content under different frequencies; making preliminary judgment on the water containing condition in the soil slope test piece according to the relative sizes of the stress wave amplitude value, the energy index and the like; by the formula
MCIi＝d·ω·s·(Ii-I0)/I0·100％
Calculating the water content index, wherein: MIi is a water content index, Ii is an amplitude and an energy index of a received stress wave signal under the ith working condition, I0 is the amplitude and the energy index of the received stress wave under the initial state, omega is a frequency influence coefficient of an excitation signal, d is an influence coefficient of a distance between sensors on the stress wave signal, and s is a soil property parameter influence coefficient. And calibrating monitoring systems of different excitation sweep frequency waves, different sensor intervals and different types of soil bodies, determining numerical values of parameters omega, d and s, and obtaining the water content index of the soil slope under the condition of different water contents.
Preferably, in the step (V), 100 to 150KHz is optimally used as an excitation frequency range of sine frequency sweep, the amplitude of the frequency sweep signal is 3V, and the period is 1 s.
(III) advantageous effects
The invention provides a system for monitoring the water content of a side slope soil body based on piezoelectric intelligent aggregate. The method has the following beneficial effects:
the system for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate is a novel Nondestructive testing (NDT) method, a piezoelectric intelligent aggregate sensor array (Smart aggregate transducer) is arranged inside the soil side slope, related functional devices are integrated together to form a set of water content data acquisition, analysis and processing system which is simple and convenient to use, economical and efficient, and long-term real-time online monitoring is carried out on the water content of the soil side slope by combining related processing software such as Labview and Matlab. Test results show that the sensor and the integrated system have good adaptability, stability and high measurement precision, and can be widely applied to various soil slope engineering structures.
Drawings
FIG. 1 is a schematic diagram of a concrete device of the soil moisture content monitoring method of the invention;
FIG. 2 is a schematic view of the internal structure of the piezoelectric ceramic piece implanted intelligent aggregate of the present invention;
FIG. 3 is a time domain signal diagram of stress wave received by the piezoelectric intelligent aggregate when the moisture content is 20% according to the invention;
FIG. 4 is a time domain signal diagram of stress wave received by the piezoelectric intelligent aggregate when the moisture content is 40% according to the invention;
FIG. 5 is a time domain signal diagram of stress wave received by the piezoelectric intelligent aggregate when the moisture content is 60% according to the invention;
FIG. 6 is a time domain signal diagram of stress wave received by the piezoelectric intelligent aggregate when the moisture content is 80% according to the invention;
FIG. 7 is a time domain signal diagram of stress wave received by the piezoelectric intelligent aggregate when the moisture content is 100% according to the invention;
FIG. 8 is a graph showing the relationship between the index of the water content of the soil body and the water content of the soil body.
In the figure: 1. a computer; 2. an NI data acquisition and analysis system; 3. a power amplifier; 4. a piezoelectric intelligent aggregate sensor; 5. sliding the slope surface; 6. sliding the bed; 7. a side slope body; 8. piezoelectric ceramic plates; 9. an electrical lead.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 to 8, the present invention provides a technical solution: a system for monitoring water content of a slope soil body based on piezoelectric intelligent aggregate comprises a computer 1, an NI data acquisition and analysis system 2, a power amplifier 3, a piezoelectric intelligent aggregate sensor 4, a sliding slope surface 5, a sliding bed 6, a slope body 7, a piezoelectric ceramic piece 8 and an electric lead 9.
The NI data acquisition and analysis system 2 is externally connected with the computer 1, and the NI data acquisition and analysis system 2 is electrically connected with the power amplifier (4).
A slope body 7 is arranged on a sliding slope surface 5 on the sliding bed 6, a plurality of piezoelectric intelligent aggregate sensors 4 are arranged in the slope body 7, and the piezoelectric intelligent aggregate sensors 4 are electrically connected with the NI data acquisition and analysis system 2 and the power amplifier 3 respectively.
The piezoelectric intelligent aggregate sensor 4 comprises a piezoelectric ceramic piece 8 and an electric lead 9 for connecting with an external electric appliance element.
A system for monitoring the water content of a slope soil body based on a piezoelectric intelligent aggregate comprises the following steps: step (1), embedding the piezoelectric intelligent aggregate sensor 4 into a position, needing to monitor the water content of a soil body, of the deep part of a side slope body 7, and keeping the directionality and the position accuracy of the piezoelectric intelligent aggregate sensor 4 during embedding.
Connecting relevant equipment in the monitoring system, switching on a power supply and turning on an instrument switch, and exciting a high-frequency excitation signal to the piezoelectric intelligent aggregate sensor 4 through the NI data acquisition and analysis system 2, wherein the frequency of the frequency sweep signal is 100-150 KHz, the amplitude is 3V, and the period is 1 s;
in the step (2), a high-frequency high-voltage signal amplifier is used for amplifying the excitation signal, and in the step (2), the high-frequency signal excited by the NI data acquisition and analysis system 2 to the piezoelectric intelligent aggregate sensor 4 is a sine sweep wave.
Step (3) converting the electric signal into a stress wave signal by the piezoelectric intelligent aggregate sensor 4 according to the inverse piezoelectric effect of the piezoelectric intelligent material, and after receiving the stress wave signal, converting the signal into the electric signal again according to the positive piezoelectric effect of the piezoelectric intelligent material and acquiring and storing the electric signal by the NI data acquisition and analysis system 2;
and (4) filtering and denoising the received stress wave signal before the step (4).
In the step (4), the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor 4 propagated inside the side slope body 7 are compared with system test calibration to determine the water content of different positions inside the soil slope.
And (4) establishing a functional relation between the stress wave signal and the water content of the side slope soil body according to the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor 4 propagated in the side slope soil body 7, and further determining the water content of different positions of the side slope soil body 7.
The system test calibration comprises the following steps:
step (I): collecting a representative soil sample in the soil slope to be monitored, and putting the soil sample into a drying box for full drying until the soil sample is in a completely dry state, wherein the soil sample quality is not reduced any more;
step (II): taking out the soil sample, weighing to obtain a soil sample mass m1 in a completely dry state, wherein the water content of the soil body is 0%;
step (III): and fully stirring and mixing the completely dried soil sample with water with the same mass, and preparing a soil slope test piece by using a mould, wherein the initial water content of the slope test piece is 100%. Before a side slope test piece is manufactured, a piezoelectric intelligent aggregate sensor 4 is embedded in a specific position in the soil side slope test piece in advance, a certain distance is reserved between the two sensors, and the distance is consistent with the distance between the sensors in the soil side slope to be monitored. In order to ensure the stability and reliability of test results, three groups of test pieces are selected;
step (IV): by utilizing the monitoring system and the fluctuation method in the active sensing method, the stress wave signals of the three groups of soil slope test pieces are detected, and the waveform information of the received stress wave under the condition that the initial water content is 100 percent is obtained;
and (V) calibrating the relative water content: and (3) placing the soil slope test piece on a digital balance, and placing the soil slope test piece and the digital balance in a thermostat at 40 ℃ to dry and dehydrate the soil slope test piece. And obtaining the evaporation capacity of the water of the soil slope test piece according to the reading of the balance, weighing and recording as mi, and further calculating the water content of the test piece. Detecting stress wave signals under the water content to obtain stress wave information under different relative water content conditions; for each working condition, testing is carried out according to a single pulse wave of sine sweep frequency of 100-150 KHz; the sweep frequency wave is used for comparing the difference of received stress wave signals under different water content conditions, and relevant water content evaluation indexes are calculated through later-stage data analysis and processing. Meanwhile, the sweep frequency wave detects the loss condition of waves with different frequency components under the condition of different water content, the influence of the water content on signals with different excitation frequencies is determined through time domain analysis and frequency domain analysis of the sweep frequency signal, and the excitation frequency suitable for monitoring the water content is selected. In the detection stage of the frequency sweep wave, firstly, a sine frequency sweep wave is emitted by an NI data acquisition and analysis system, a signal is amplified by a power amplifier 3 and then input into a piezoelectric intelligent aggregate sensor 4 positioned on one side of a test piece, an electric signal is converted into a stress wave vibration signal due to the inverse piezoelectric effect and is transmitted in the slope test piece in the form of a wave, and the piezoelectric intelligent aggregate sensor 4 positioned on the other side of the test piece receives the stress wave signal, converts the stress wave signal into an electric signal and transmits the electric signal back to the NI data acquisition and analysis system 2;
in the step (V), 100-150 KHz is optimally used as an excitation frequency range of sine frequency sweep, the amplitude of a frequency sweep signal is 3V, and the period is 1 s.
And (VI) analyzing and processing data: under the conditions of different water contents, analyzing the average value of the amplitude of the received stress wave signal to obtain the variation trend of the amplitude of the stress wave along with the water contents; meanwhile, calculating an energy index based on the wavelet packet according to the collected stress wave information to obtain the variation trend of waveform energy along with the water content under different frequencies; making preliminary judgment on the water containing condition in the soil slope test piece according to the relative sizes of the stress wave amplitude value, the energy index and the like; by the formula
MCIi＝d·ω·s·(Ii-I0)/I0·100％
Calculating the water content index, wherein: MIi is a water content index, Ii is an amplitude and an energy index of a received stress wave signal under the ith working condition, I0 is the amplitude and the energy index of the received stress wave under the initial state, omega is a frequency influence coefficient of an excitation signal, d is an influence coefficient of a distance between sensors on the stress wave signal, and s is a soil property parameter influence coefficient. And calibrating monitoring systems of different excitation sweep frequency waves, different sensor intervals and different types of soil bodies, determining numerical values of parameters omega, d and s, and obtaining the water content index of the soil slope under the condition of different water contents.
When in use, the method comprises the following steps of 1: calibrating the system before use according to different excitation frequencies, sensor intervals and soil slopes of different soil types; and after the calibration is finished, the corresponding relation between the water content index and the water content of the soil slope under the conditions of the excitation frequency and the sensor spacing can be obtained.
Step 2: the piezoelectric intelligent aggregate sensor 4 is buried in a region where the water content of a soil body needs to be monitored at the deep part of a side slope body 7 (soil slope), and the directionality and the position accuracy of the piezoelectric intelligent aggregate sensor 4 need to be maintained during burying.
Step 3: connecting related equipment in a monitoring system, switching on a power supply and turning on an instrument switch, and sending a high-frequency excitation signal to the piezoelectric intelligent aggregate sensor 4 through the NI data acquisition and analysis system 2, wherein the frequency of the frequency sweep signal is 100-150 KHz, the amplitude is 3V, and the period is 1 s;
the time of the whole stress wave data acquisition process is very short, and is only 1 second, so that the volatilization of the water in the soil slope in the process can be completely ignored, and the water content in the slope is considered to be kept unchanged in each data acquisition process.
And 4, step 4: according to the inverse piezoelectric effect of the piezoelectric intelligent material, the piezoelectric intelligent aggregate sensor 4 converts the electric signal into a stress wave signal, and after the piezoelectric intelligent aggregate sensor 4 arranged at different positions in the side slope body 7 receives the stress wave signal, the piezoelectric intelligent aggregate sensor converts the signal into the electric signal again according to the positive piezoelectric effect of the piezoelectric intelligent material and acquires and stores the electric signal by an oscilloscope;
and 5: and determining the water content of different positions of the slope body according to the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor 4 in the slope body 7. And (3) calculating the water content index of the soil slope between the sensors according to the formula (1).
Step 6: and according to a system calibration result, determining the moisture content information of the monitored soil slope by detecting the stress wave waveform information to obtain the moisture content index of the soil slope.
To sum up, according to the system for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate, the piezoelectric intelligent aggregate sensor array (Smart aggregate transducer) is arranged in the soil side slope, related functional devices are integrated together, a set of water content data acquisition, analysis and processing system which is simple, convenient, economical and efficient to use is formed, relevant processing software such as Labview and Matlab is combined, long-term real-time online monitoring is carried out on the water content of the soil side slope, long-term, online, remote and rapid monitoring of the water content in the soil side slope is achieved, the water content condition of each key position in the soil side slope can be accurately evaluated, the response speed is high, and the whole system has good stability and durability.
It should be noted that the electrical components shown in this document are all electrically connected to an external master controller and 220V mains, and the master controller may be a conventional known device such as a computer for controlling, and the control principle, internal structure, and control switching manner of the device are conventional means in the prior art, and are directly referred to herein without further description. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. The utility model provides a system based on piezoelectric intelligent aggregate monitoring side slope soil body moisture content which characterized in that: the system comprises a computer (1), an NI data acquisition and analysis system (2), a power amplifier (3), a piezoelectric intelligent aggregate sensor (4), a sliding slope surface (5), a sliding bed (6), a side slope body (7), a piezoelectric ceramic piece (8) and an electric lead (9);
the NI data acquisition and analysis system (2) is externally connected with a computer (1), and the NI data acquisition and analysis system (2) is electrically connected with the power amplifier (4);
a slope body (7) is arranged on a sliding slope surface (5) on the sliding bed (6), a plurality of piezoelectric intelligent aggregate sensors (4) are arranged in the slope body (7), and the piezoelectric intelligent aggregate sensors (4) are respectively and electrically connected with the NI data acquisition and analysis system (2) and the power amplifier (3);
the piezoelectric intelligent aggregate sensor (4) comprises a piezoelectric ceramic piece (8) and an electric lead (9) connected with an external electric appliance element.
2. The system for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate according to claim 1, wherein the method for monitoring the water content comprises the following steps: the method comprises the following steps that (1) the piezoelectric intelligent aggregate sensor (4) is buried in a position where the water content of a soil body needs to be monitored at the deep part of a side slope body (7), and the directionality and the position accuracy of the piezoelectric intelligent aggregate sensor (4) need to be kept during burying.
Connecting relevant equipment in a monitoring system, switching on a power supply and turning on an instrument switch, and exciting a high-frequency excitation signal to the piezoelectric intelligent aggregate sensor (4) through the NI data acquisition and analysis system (2), wherein the frequency of the frequency sweep signal is 100-150 KHz, the amplitude is 3V, and the period is 1 s;
step (3) converting the electric signal into a stress wave signal by the piezoelectric intelligent aggregate sensor (4) according to the inverse piezoelectric effect of the piezoelectric intelligent material, and after the piezoelectric intelligent aggregate sensors (4) arranged at different positions in the side slope body (7) receive the stress wave signal, converting the signal into the electric signal again according to the positive piezoelectric effect of the piezoelectric intelligent material and acquiring and storing the electric signal by the NI data acquisition and analysis system (2);
and (4) establishing a function relation between the stress wave signal and the water content of the slope soil body according to the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor (4) propagated in the slope soil body (7), and further determining the water content of the slope soil body (7) at different positions.
3. The monitoring method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate as claimed in claim 2, is characterized in that: in the step (2), the excitation signal is amplified by using a high-frequency high-voltage signal amplifier.
4. The monitoring method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate as claimed in claim 2, is characterized in that: filtering and denoising the received stress wave signal before the step (4).
5. The monitoring method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate as claimed in claim 2, is characterized in that: in the step (2), the high-frequency signal excited by the piezoelectric intelligent aggregate sensor (4) is a sine sweep wave through the NI data acquisition and analysis system (2).
6. The monitoring method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate as claimed in claim 2, is characterized in that: in the step (4), the amplitude, energy, mode, wave speed, propagation path, propagation time and the like of the stress wave signal received by the piezoelectric intelligent aggregate sensor (4) propagating inside the slope body (7) are compared with system test calibration to determine the water content of different positions inside the soil slope.
7. The method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate according to claim 5, wherein the method comprises the following steps: the system test calibration comprises the following steps:
step (I): collecting a representative soil sample in the soil slope to be monitored, and putting the soil sample into a drying box for full drying until the soil sample is in a completely dry state, wherein the soil sample quality is not reduced any more;
step (II): taking out the soil sample, weighing to obtain a soil sample mass m1 in a completely dry state, wherein the water content of the soil body is 0%;
step (III): and fully stirring and mixing the completely dried soil sample with water with the same mass, and preparing a soil slope test piece by using a mould, wherein the initial water content of the slope test piece is 100%. Before a side slope test piece is manufactured, a piezoelectric intelligent aggregate sensor (4) is embedded in a specific position in the soil side slope test piece in advance, a certain distance is reserved between the two sensors, and the distance is consistent with the distance between the sensors in the soil side slope to be monitored. In order to ensure the stability and reliability of test results, three groups of test pieces are selected;
step (IV): by utilizing the monitoring system and the fluctuation method in the active sensing method, the stress wave signals of the three groups of soil slope test pieces are detected, and the waveform information of the received stress wave under the condition that the initial water content is 100 percent is obtained;
and (V) calibrating the relative water content: and (3) placing the soil slope test piece on a digital balance, and placing the soil slope test piece and the digital balance in a thermostat at 40 ℃ to dry and dehydrate the soil slope test piece. And obtaining the evaporation capacity of the water of the soil slope test piece according to the reading of the balance, weighing and recording as mi, and further calculating the water content of the test piece. Detecting stress wave signals under the water content to obtain stress wave information under different relative water content conditions; for each working condition, testing is carried out according to a single pulse wave of sine sweep frequency of 100-150 KHz; the sweep frequency wave is used for comparing the difference of received stress wave signals under different water content conditions, and relevant water content evaluation indexes are calculated through later-stage data analysis and processing. Meanwhile, the sweep frequency wave detects the loss condition of waves with different frequency components under the condition of different water content, the influence of the water content on signals with different excitation frequencies is determined through time domain analysis and frequency domain analysis of the sweep frequency signal, and the excitation frequency suitable for monitoring the water content is selected. In the detection stage of the frequency sweep wave, firstly, a sine frequency sweep wave is transmitted by an NI data acquisition and analysis system, a signal is amplified by a power amplifier (3) and then input into a piezoelectric intelligent aggregate sensor (4) positioned on one side of a test piece, an electric signal is converted into a stress wave vibration signal due to the inverse piezoelectric effect and is transmitted in the slope test piece in the form of wave, and the piezoelectric intelligent aggregate sensor (4) positioned on the other side of the test piece receives the stress wave signal, converts the stress wave signal into an electric signal and transmits the electric signal back to the NI data acquisition and analysis system (2);
and (VI) analyzing and processing data: under the conditions of different water contents, analyzing the average value of the amplitude of the received stress wave signal to obtain the variation trend of the amplitude of the stress wave along with the water contents; meanwhile, calculating an energy index based on the wavelet packet according to the collected stress wave information to obtain the variation trend of waveform energy along with the water content under different frequencies; making preliminary judgment on the water containing condition in the soil slope test piece according to the relative sizes of the stress wave amplitude value, the energy index and the like; by the formula
MCIi＝d·ω·s·(Ii-I0)/I0·100％
Calculating the water content index, wherein: MIi is a water content index, Ii is an amplitude and an energy index of a received stress wave signal under the ith working condition, I0 is the amplitude and the energy index of the received stress wave under the initial state, omega is a frequency influence coefficient of an excitation signal, d is an influence coefficient of a distance between sensors on the stress wave signal, and s is a soil property parameter influence coefficient. And calibrating monitoring systems of different excitation sweep frequency waves, different sensor intervals and different types of soil bodies, determining numerical values of parameters omega, d and s, and obtaining the water content index of the soil slope under the condition of different water contents.
8. The monitoring method for monitoring the water content of the soil body of the side slope based on the piezoelectric intelligent aggregate as claimed in claim 7, is characterized in that: in the step (V), 100-150 KHz is optimally used as an excitation frequency range of sine frequency sweep, the amplitude of a frequency sweep signal is 3V, and the period is 1 s.
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| CN115574702A (en) * | 2022-09-27 | 2023-01-06 | 武汉地震工程研究院有限公司 | Slope slippage monitoring device based on piezoelectric membrane and electromechanical impedance method |
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| CN115574702A (en) * | 2022-09-27 | 2023-01-06 | 武汉地震工程研究院有限公司 | Slope slippage monitoring device based on piezoelectric membrane and electromechanical impedance method |
| CN115574702B (en) * | 2022-09-27 | 2023-09-08 | 武汉地震工程研究院有限公司 | Slope slip monitoring method based on piezoelectric diaphragm and electromechanical impedance method |
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