Device and method for real-time monitoring of pebble bed load sediment transport rate based on vibration signal processing

Abstract

The present invention discloses a real-time monitoring device and method for the pebble bedload sediment transport rate based on vibration signal processing. The device includes a vibration impact plate, an acceleration vibration sensor, a mounting base, a data collector, and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is provided in the middle of the mounting base, the vibration impact plate covers and is fixed on the mounting base, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting base. The mounting base is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed. The present invention installs the vibration sensor at the bottom center of the vibration impact plate flush with the riverbed surface, and infers the real-time bedload sediment transport rate by analyzing the vibration signal characteristics generated by the pebble bedload impacting the vibration impact plate. The present invention realizes accurate, effective, continuous, and real-time measurement of the pebble bedload sediment transport rate in a convenient and simple way.

Description

Technical Field

[0001] The present invention belongs to the field of pebble bed load measurement, and in particular relates to a novel device and method for real-time monitoring of pebble bed load sediment transport rate based on vibration signal processing. Background Art

[0002] The transport of pebble bedload is a crucial and complex scientific issue in river dynamics. It plays a crucial role in mountain disaster prevention and early warning, the transport and deposition of sediment in mountain rivers, and ecosystem restoration. As early as the late 19th century, P. Duboys of France first proposed the drag force theory of bedload motion. Since then, numerous researchers have engaged in this area of research, and a vast number of formulas have been proposed for calculating bedload transport rates. These theories differ widely in their foundations, their hydraulic element notations, and their use of drag force, velocity, and power. The formula structures and formalisms vary widely. From the perspective of research methods, the most important ones are: (1) bed load formulas based on a large number of flume experiments, represented by the Meyer-Peter-Müller bed load sediment transport rate formula; (2) theories based on the basic concepts of general physics and through certain mechanical analysis, represented by the Bagnold bed load formula; (3) bed load theories based on a combination of probability theory and mechanics, represented by the Einstein bed load formula; (4) formulas based on certain concepts of Einstein or Bagnold, supplemented by dimensional analysis, line fitting of measured data, or certain reasoning, represented by the Engelund, Yalin, and Ackers-White bed load formulas. In addition, with the development of computer technology, data mining algorithms have also been used to analyze bed load sediment transport calculations. Comparisons have shown that the calculation accuracy of bagging, M5P, and random tree mining methods is relatively high, and they have great potential in predicting pebble bed load sediment transport in mountainous areas.

[0003] Currently, there are numerous methods for measuring pebble bedload both domestically and internationally, using a wide variety of direct-measurement samplers. These can be broadly categorized as instrument-based and pit-based methods. The instrument-based method involves placing a specially designed mechanical device or sampler directly into the riverbed to measure bedload sand samples. These include basket-type, differential pressure-type, and anchor-based methods. Basket-type samplers are typically used for measuring coarse-grained bedload, such as pebbles and gravel. They typically consist of an inlet frame, covered with a metal or nylon mesh with a defined aperture, and a stainless steel hard or soft bottom. Representative international samplers include the BLH-84 designed by the United States Geological Survey. Representative domestic samplers include the M1 and M2 samplers developed by the Sichuan Hydrological Station, the Y64 sampler developed by the Chongqing Hydrological Station, and the Y802 sampler developed by the Yangtze River Commission. Differential pressure samplers operate on the principle of negative pressure, with the outlet area of the sampler designed to be larger than the inlet area, creating negative pressure. Representative samplers abroad include the Helley-Smith sampler designed by the United States Geological Survey, and representative samplers in China include the Y781 sampler developed by the Yangtze River Commission. Anchored samplers are used to fix some troughs on the riverbed along the cross section, and sand samples are taken out at regular intervals for analysis. The pit measurement method is a method of setting up several fixed test pits or test troughs along the cross section of the riverbed to measure the bed load. However, these conventional direct measurement samplers currently face the following difficulties: (1) The instrument is usually manually operated, so it may be difficult and very dangerous to operate at high flow or when coarse bed load particles are transported; (2) The sampler easily interferes with the local flow field and affects the measurement accuracy, and the sampling time depends on the volume of the sampler, resulting in low sampling efficiency; (3) The bed load movement is highly spatiotemporal and pulsating, and non-continuous sampling cannot effectively reflect the movement law of the bed load. Summary of the Invention

[0004] The purpose of the present invention is to address the current situation in which it is difficult to measure the bed load sediment transport rate in pebble and gravel rivers or streams in mountainous areas in real time over a long period of time in the existing technology. A real-time monitoring device and method for the bed load sediment transport rate of pebble bed load based on vibration signal processing are provided to achieve accurate, effective, continuous and real-time measurement of the pebble bed load sediment transport rate in a convenient and simple way.

[0005] The basic idea of the present invention is to install a vibration sensor at the bottom center of a vibration impact plate flush with the riverbed surface, and to infer the real-time bed load sediment transport rate by analyzing the vibration signal characteristics generated by the pebble bed load impacting the vibration impact plate.

[0006] Based on the above ideas, the present invention provides a real-time monitoring device for the sediment transport rate of pebble bed load based on vibration signal processing, including a vibration impact plate, an acceleration vibration sensor, a mounting seat, a data collector and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is opened in the middle of the mounting seat, the vibration impact plate covers and is fixed on the mounting seat, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting seat. The mounting seat is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed; the acceleration vibration sensor is signal-connected to the data collector, and the data collector is connected to the computer.

[0007] The present invention provides a real-time monitoring method for pebble bed load sediment transport rate based on vibration signal processing, comprising the following steps:

[0008] (1) Determination of vibration impact plate size

[0009] The river section to be measured was selected, and the sediment on the riverbed surface was sampled in the floodplain of the unflooded area. The sediment gradation of the samples was measured separately to obtain three representative particle sizes of the bed surface, and then the average median particle size D of the three sampling frames was obtained. 50 (mm). Due to the high pulsation of bed load movement, the maximum intermittent movement length of the bed load must be considered in the design of the vibrating impact plate's downstream length to ensure that all bed load movement can vibrate on the vibrating impact plate to generate a corresponding signal. The vibrating impact plate is a standard rectangular shape, and the main consideration in the size design is the length of the vibrating impact plate in the downstream direction, which is calculated as follows:

[0010] L p >L=u * w (1)

[0011]

[0012]

[0013] Where, L p is the length of the vibrating impact plate in the direction of water flow (m); L is the moving length of the bed load (m); u * is the friction velocity (m / s); w is the sedimentation velocity (m / s); g is the acceleration due to gravity (m / s 2 ); h is the average water depth of the section (m), J is the river gradient; ρ s is the density of the pebble bed load (kg / m 3 ); ρ is the density of water (kg / m 3 );C d is the drag coefficient.

[0014] (2) Install a real-time monitoring device for the sediment transport rate of pebble bed load

[0015] Fix the acceleration vibration sensor at the center of the vibration impact plate, then fix the vibration impact plate on the mounting base, and place the acceleration vibration sensor in the groove opened in the middle of the mounting base, connect the acceleration vibration sensor to the data collector signal, and connect the data collector to the computer; fix the mounting base in the riverbed to ensure that it does not move relative to the riverbed.

[0016] (3) Signal acquisition and processing

[0017] The collector is used to record the original vibration signal data generated by the transport of bed load on the vibrating impact plate, and the corresponding vibration TDMS original file is obtained on the host computer. The absolute value of the original data in the TDMS file is taken; then the original data is divided according to the number of sampling data points in 1 minute (number = sampling frequency × 60) to obtain 1-minute signal packages, and then the data in each signal package is segmented and statistically analyzed to obtain the statistical parameters of the 1-minute signal package, including mean, standard deviation, maximum value, kurtosis, and skewness.

[0018] (4) Calculation of pebble bed load transport rate

[0019] The signal parameters obtained in step (3) are substituted into the following formula to obtain the signal characteristic value. The calculation expression is as follows:

[0020]

[0021] Where, δ * is the characteristic value of the vibration signal; is the mean value of the vibration signal within 1 minute; δ max is the maximum value of the vibration signal within 1 minute; then, gravity acceleration and density are introduced, and the characteristic value of the vibration signal is substituted into the calculation to obtain the bed load transport rate per width. The calculation expression is as follows:

[0022]

[0023] Where G b is the single-width non-uniform bed load transport rate (kg / m / min); ρ s is the density of the pebble bed load (kg / m 3 ); ρ is the density of water (kg / m 3 );δ * is the characteristic value of the vibration signal; g is the acceleration of gravity (m / s 2 ).

[0024] The purpose of step S4 is to establish a relationship between the vibration signal and the bed load transport rate, and to directly use the characteristic value of the vibration signal to deduce the real-time bed load transport rate.

[0025] Furthermore, the material of the vibration impact plate in step (1) can be selected as a steel plate with relatively high rigidity, and its width (along the riverbed horizontally) can be calculated according to the actual budgeted section width, which can generally be set to 50 cm and the thickness to 0.5 cm.

[0026] Furthermore, depending on the width of the river section being measured, multiple devices are fixed transversely along the riverbed, perpendicular to the direction of water flow. Because the bedload sediment transport rate is inconsistent across the river width, the devices described in the present invention can be treated as a single unit and evenly arranged on the riverbed. All data are then averaged to obtain the average signal characteristic value for the river section.

[0027] Furthermore, in step (2), the mounting base is cast together with the concrete, or multiple sleeves are symmetrically arranged on the outer edge of the mounting base, stainless steel bars are connected to the sleeves by threading, and nuts are tightened on the steel bars at the positions corresponding to the ends of the sleeves to limit the mounting base, ensuring that the top of the vibration plate on the mounting base is flush with the riverbed surface. At the same time, the steel bars are inserted into the riverbed at a depth of less than 1 meter, thereby ensuring that the mounting base is rigidly connected to the riverbed and will not be displaced due to the impact and movement of the bedload.

[0028] Furthermore, the acceleration vibration sensor in step (3) uses an IEPE acceleration vibration sensor, which has an amplifier and a constant current source. The constant current source introduces current into the acceleration sensor. The internal circuit of the acceleration sensor behaves like a resistor, and the acceleration of the sensor is proportional to the resistance it shows to the outside. Therefore, the signal voltage returned by the sensor is also proportional to the acceleration. When there is no vibration on the bed surface, a signal voltage of about 0V is output. When there is vibration, a signal voltage that fluctuates up and down with the 0V level as the reference is output. The greater the vibration amplitude, the greater the voltage value. The acquisition frequency can be set to 1000Hz~10000Hz.

[0029] The present invention also provides a real-time measurement simulation experimental device for pebble bed load sediment transport rate based on vibration signal processing, comprising a real-time monitoring device for pebble bed load sediment transport rate based on vibration signal processing, a water reservoir, a water trough, a honeycomb pipe, and a flat-top weir;

[0030] The device for real-time monitoring of pebble bed load sediment transport rate based on vibration signal processing is composed of a vibration impact plate, an acceleration vibration sensor, a mounting base, a data collector and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is provided in the middle of the mounting base, the vibration impact plate covers and is fixed on the mounting base, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting base. The mounting base is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed. The acceleration vibration sensor is connected to the data collector signal, and the data collector is connected to the computer terminal.

[0031] The inlet end of the water trough is located downstream of the water reservoir, a honeycomb pipe is provided at the inlet of the water trough, a flat-top weir for measuring flow is provided in the water reservoir, the slope of the water trough is set according to the needs of the simulation experiment, the inlet section of the water trough bottom plate is paved with immovable large particles as a transition zone, and non-uniform gravel bed sand is laid downstream of the transition zone. A fixed plate is fixed at the tail of the water trough to fix the riverbed and prevent the overall layer shift of the bed sand. The pebble bed load sediment transport rate real-time monitoring device is installed on the water trough bottom plate on the downstream side of the fixed plate.

[0032] Furthermore, the simulation experimental device also includes a pebble bed load weighing mechanism, including a gantry, a tension sensor, a sand receiving pool, and a sand receiving basket. The sand receiving pool is connected to the downstream of the pebble bed load sand transport rate real-time monitoring device, and the sand receiving pool entrance is flush with the vibration impact plate; the sand receiving basket is located in the sand receiving pool, so that the bed load enters the sand receiving basket after passing through the vibration impact plate, and the sand receiving basket is connected to the tension sensor through a steel rope; the gantry is an open rectangle, and the left and right vertical bars are symmetrically located on both sides of the water tank and fixed, so that the gantry is upright and the cross bar of the gantry is kept horizontal; the tension sensor is fixed at the midpoint of the cross bar of the gantry and should also be located at the center of the sand receiving basket.

[0033] During each test, at the moment the water was turned on, a data collector simultaneously recorded the raw vibration signal data generated by the bedload transport on the vibrating impact plate and the minute-by-minute bedload weight data transmitted by the tension sensor. The measured bedload mass change was compared with the bedload rate measured by the pebble bedload rate real-time monitoring device to verify the device's measurement accuracy.

[0034] Furthermore, a water trough extension section is provided downstream of the sand receiving pool to form a flow-free area in the sand receiving pool, thereby preventing the sand receiving basket from shaking and affecting the accuracy of the tension sensor.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The method of the present invention can monitor the bed load sediment transport rate data for a long time and at the minute level. It has very high measurement efficiency and does not require manual operation. It realizes accurate, effective, continuous and real-time measurement of the pebble bed load sediment transport rate in a convenient and simple way without interfering with the river flow field.

[0037] 2. The device of the present invention is flexible in layout and can be deployed on a large scale at any position on the riverbed according to actual needs and river sections.

[0038] 3. Simple installation, low cost, unattended, and remote viewing is possible if combined with 5G technology;

[0039] 4. The present invention is particularly suitable for measuring bedload sediment transport rate in shallow sections such as pebble and gravel river channels or streams in mountainous areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of the pebble bedload detector.

[0041] Figure 2 Schematic diagram of the pebble bedload detector installation.

[0042] Figure 3 Data acquisition and processing flow chart of the pebble bed load detector.

[0043] Figure 4 Overall schematic diagram of the water tank for measuring the pebble bed load transport rate in mountainous areas.

[0044] Figure 5 Partial schematic diagram of the water trough for measuring the pebble bed load transport rate in mountainous areas.

[0045] Figure 6 Comparison of the bed load transport rate measured in the flume test and the bed load transport rate detected (signal) by the vibration impact plate for pebble bed load.

[0046] Figure 7 Comparison of bed load transport measured in flume tests and bed load transport detected (signal) by a vibration impact plate for pebble bed load.

[0047] Figure: 1. M6 screw; 2. Vibration impact plate; 3. Waterproof IEPE vibration acceleration sensor; 4. Data and power transmission line; 5. Mounting bracket; 6. 1cm diameter connecting pipe; 7. Water tank; 8. Honeycomb tube; 9. Reservoir; 10. Flat-top weir; 11. Gantry; 12. 3mm steel rope; 13. Sand basket; 14. Computer; 15. Tension sensor. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0049] The following is attached with the instruction manual Figures 1 to 7 The device and method for real-time monitoring of pebble bed load sediment transport rate based on vibration signal processing of this embodiment are described in detail.

[0050] Example 1

[0051] This embodiment provides a real-time monitoring device and method for the sediment transport rate of pebble bed load based on vibration signal processing. The device is composed of a vibration impact plate, an acceleration vibration sensor, a mounting base, a data collector, and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is provided in the middle of the mounting base, the vibration impact plate covers and is fixed to the mounting base, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting base. The mounting base is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed; the acceleration vibration sensor is connected to the data collector signal, and the data collector is connected to the computer terminal.

[0052] The following steps are involved:

[0053] (1) Determination of vibration impact plate size

[0054] Determine the measurement section, set up three 1m×1m sampling frames on the floodplain in the unflooded area, and use the sieving method to measure the sediment gradation on the riverbed surface. The three representative particle sizes of the bed surface are obtained, and then the average median particle size D of the three sampling frames is obtained. 50 (mm). Due to the high pulsation of bed load movement, the maximum intermittent movement length of the bed load must be considered in the design of the vibrating impact plate's downstream length to ensure that all bed load movement can vibrate on the vibrating impact plate to generate a corresponding signal. The vibrating impact plate is a standard rectangular shape, and the main consideration in the size design is the length of the vibrating impact plate in the downstream direction, which is calculated as follows:

[0055] L p >L=u * w (1)

[0056]

[0057]

[0058] Where, L p is the length of the vibrating impact plate in the direction of water flow (m); L is the moving length of the bed load (m); u* is the friction flow velocity (m / s); w is the sedimentation velocity (m / s); g is the acceleration of gravity (m / s 2 ); h is the average water depth of the section (m), J is the river gradient; ρ s is the density of the pebble bed load (kg / m 3 ); ρ is the density of water (kg / m 3 The vibration impact plate can be made of a relatively rigid steel plate, with a width of 50 cm and a thickness of 0.5 cm. Multiple vibration impact plates can be mounted perpendicular to the flow direction, depending on the width of the river section being measured.

[0059] (2) Install a real-time monitoring device for pebble bed load sediment transport rate

[0060] The center of the vibration impact plate is equipped with an M6 threaded hole, which is used to mount a waterproof IEPE vibration acceleration sensor. Two to three M6 threaded holes are arranged around the perimeter of the vibration impact plate along the direction of water flow, and four to five M6 threaded holes are arranged perpendicular to the flow. The vibration impact plate is connected to the mounting base using threads, with the sensor-mounted side of the plate facing downward, so that the sensor is located in a groove in the center of the mounting base that accommodates the sensor and associated wiring. The basic requirement for mounting the base is to ensure that it remains stationary under the influence of water flow and bedload. Therefore, the mounting method can be designed based on the specific conditions of the river section. The mounting base can be directly cast into the concrete, or multiple sleeves can be fixed to the outside of the mounting base. Stainless steel rebar with threads and nuts is then welded to the sleeves. The nuts lock the ends of the sleeves relative to the rebar, limiting the mounting base. The rebar is then directly inserted into the riverbed at least 1 meter below the surface, ensuring a rigid connection between the mounting base and the riverbed and preventing displacement due to bedload impact. The top height of the vibration impact plate on the mounting base should be flush with the upper layer of the riverbed surface. The structure of the real-time monitoring device for pebble bed load sediment transport rate is shown in the attached Figure 1 As shown, the installation diagram is attached Figure 2 shown.

[0061] (3) Signal acquisition and processing

[0062] The IEPE accelerometer includes an amplifier and a constant current source. The current source introduces current into the accelerometer. The accelerometer's internal circuit behaves like a resistor, and the sensor's acceleration is proportional to its apparent resistance. Therefore, the signal voltage returned by the sensor is also proportional to the acceleration. When the bed surface is vibration-free, it outputs a signal voltage of approximately 0V. When vibration is present, it outputs a signal voltage that fluctuates around 0V. The greater the vibration amplitude, the greater the voltage. The acquisition frequency can be set between 1000Hz and 10000Hz. Using a data collector, a TDMS file of the corresponding vibration can be obtained on a computer. The raw data in the TDMS file is then taken to its absolute value. The raw data is then divided into 1-minute signal packets according to the number of sampling data points per minute (number = sampling frequency × 60). Finally, the data within each packet is segmented and statistically analyzed to obtain the statistical parameters of the 1-minute signal packet, including mean, standard deviation, maximum value, kurtosis, and skewness. The data acquisition and processing flow for the real-time monitoring device for pebble bedload transport rate is attached. Figure 3 shown.

[0063] (4) Calculation of pebble bed load transport rate:

[0064] The signal parameters of the 1-minute signal packet statistics obtained in step S3 are substituted into the following formula to obtain the signal characteristic value. The calculation expression is as follows:

[0065]

[0066] Where, δ * is the characteristic value of the vibration signal; is the mean value of the vibration signal within 1 minute; δ max is the maximum value of the vibration signal within 1 minute. Then, gravity acceleration and density are introduced and the characteristic value of the vibration signal is substituted into the calculation to obtain the bed load transport rate per width. The calculation expression is as follows:

[0067]

[0068] Where G b is the single-width non-uniform bed load transport rate (kg / m / min).

[0069] The purpose of step S4 is to establish a relationship between the vibration signal and the bed load transport rate, and to directly use the characteristic value of the vibration signal to deduce the real-time bed load transport rate.

[0070] 1. Purpose of the test

[0071] The results of the water flume test were used to verify whether the real-time monitoring device and method for pebble bed load sediment transport rate based on vibration signal processing was reasonable and effective in measuring bed load.

[0072] 2. Test equipment

[0073] The main equipment is shown in Table 1

[0074] Table 1 Instruments and equipment for the pebble bed load detector bed load measurement test

[0075]

[0076] 3. Test methods

[0077] The test was carried out in a straight glass flume 7 that was 7.5 meters long, 0.4 meters wide, and 0.4 meters high. The flow came from the water reservoir 9 at the top. The flow rate was determined by the height between the water level and the flat-top weir 10. The flume slope was 0.5%. In order to ensure that the water flowed smoothly into the flume, a honeycomb tube 8 was used at the flume inlet to stabilize the flow. The honeycomb tube was made of a number of straight tubes with a normal diameter of 5 cm and a length of 20 cm glued together. A transition zone was set up with large, immobile particles 1 meter away from the flume inlet. These particles would not start or coarsen even at the maximum flow rate. Immediately after the flume, a non-uniform gravel bed was laid with a thickness of 0.1 meters in the 6.5-meter flume. A 0.1-meter PVC board was used to fix the riverbed at the tail of the flume to prevent the overall layering of the bed sand. See the attached diagram for the overall flume for measuring the sediment transport rate of pebble bedload in mountainous areas. Figure 4 As shown, a partial schematic diagram is attached Figure 5 shown.

[0078] Based on the gradation of the bedload in this experiment, if the median particle size is 1.4 mm, the calculated result of step S1 shows that the bedload travel length is 6.8 cm; if the minimum particle size is 0.2 mm, the calculated result of step S1 shows that the bedload travel length is 18.0 cm. Therefore, the length of the vibration plate can be set to 20 cm, and the width can be set to the width of the water tank, which is 40 cm. The waterproof IEPE vibration acceleration sensor 3 is rigidly connected to the bottom of the vibration impact plate 2 using screws and nuts, and the sampling frequency is set to 1000 Hz. The front end of the mounting base 5 of the real-time monitoring device for the sediment transport rate of pebble bedload is then fixed to the PVC board using glass glue, and the vibration impact plate 2 is fixed to the mounting base 5 using M6 screws 1. On the side of the mounting base 5 is a connecting pipe 6, through which the data and power transmission line 4 of the sensor is connected to the collector. The connecting pipe can be a hose for easy laying below the bed surface.

[0079] Build a hole with an inner diameter of 40×70×70cm at the rear end of the mounting seat 5 3 A rectangular pool is used as a sand collection pool. In the direction of water flow, the opening is 40×40cm 2 Make the outlet of the water tank flush with the vibration impact plate 2 and the entrance of the sand pool. The rear end of the mounting base 5 is fixed to the wall of the pool entrance with glass glue, and the downstream of the pool in the direction of water flow is 40×40cm. 2 The cross section extends outwards about 1.0m. The purpose of this design is to form a zero velocity area in the sand receiving pool, so as to avoid the shaking of the sand receiving basket inside and thus affect the accuracy of the tension sensor. A 35×60×50cm 3 The sand receiving basket (13) is directly connected to the lower end of the tension sensor (15) by a steel rope (12) through a snap or welding method. The upper end of the tension sensor is fixed to the crossbar of the gantry (11) by a snap or welding method. The bottom of the gantry (11) is directly embedded in the ground using concrete. The tension sensor is installed at the center of the crossbar of the gantry and should also be located at the center of the sand receiving basket. The tension sensor uses the DYLY-103 tension sensor of Bengbu Dayang Sensing Company to obtain the change of the bed load weight in the frame and obtain the measured bed load sediment transport rate. The sampling frequency can be set to one sediment transport rate per minute, and the sampling range is 0-100 kg.

[0080] Eight test conditions were set based on flow rates. The bed sand in each test was uniformly mixed. However, due to variations in manual laying and bed compaction, bed surface consistency was difficult to achieve. However, bed sand gradation remained constant. The final test parameters and duration are summarized in Table 2. The final stable bed surface for each test should be approximately zero sediment transport. The manually laid bed surface gradually coarsens under the action of the water flow, ultimately forming a coarsened bed surface. The sediment transport rate should initially increase sharply and then gradually decrease to near zero. At the moment of water heating during each test, a data collector was used to record the raw vibration signal data generated by the bed load transport on the vibrating impact plate, as well as minute-by-minute bed load weight data transmitted by the tension sensor. On computer 14, the raw vibration data was stored as a tdms file containing the sampling frequency, start time, and vibration acceleration (voltage value). The minute-by-minute measured bed load rate data was stored as an xlsx file, which included the measured bed load rate per minute and the current time (accurate to the second).

[0081] Table 2 Summary of test parameters and duration

[0082]

[0083]

[0084] 4. Vibration signal processing

[0085] Step S3 is used to obtain an xlsx file of real-time statistical parameter changes of the 1-minute signal package, which includes the mean, standard deviation, maximum value, kurtosis, and skewness.

[0086] 5. Calculation of sediment transport rate of pebble bed load

[0087] By using the real-time vibration signal characteristic value and the bed load sediment transport rate inferred from the vibration signal, the bed load sediment transport rate measured by the flume test is compared with the bed load sediment transport rate detected by the pebble bed load vibration impact plate (signal). Figure 6 As shown in the figure, the comparison between the measured bed load sediment load in the flume test and the bed load sediment load detected by the vibration impact plate (signal) is shown in the figure. Figure 7 As shown in the figure, it can be seen that the sediment transport rate process inferred from the signal is basically consistent with the measured sediment transport rate process. At the same time, the scatter points of bed load sediment transport are also distributed near the 1:1 line, and the errors of most data points are within one order of magnitude. The accuracy is better under medium and high-intensity sediment transport than under low-intensity sediment transport. In actual rivers, the sediment transport intensity is significantly greater than the flume test scale. Therefore, it is shown that the real-time monitoring device and method of pebble bed load sediment transport rate based on vibration signal processing meet actual needs, have high feasibility, and can provide a new idea for existing bed load measurement.

Claims

1. A real-time monitoring method for pebble bed load sediment transport rate based on vibration signal processing, characterized in that: The following steps are involved: A real-time monitoring device for the sediment transport rate of pebble bed load based on vibration signal processing is used, comprising a vibration impact plate, an acceleration vibration sensor, a mounting base, a data collector, and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is provided in the middle of the mounting base, the vibration impact plate covers and is fixed on the mounting base, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting base. The mounting base is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed. The acceleration vibration sensor is signal-connected to the data collector, and the data collector is connected to the computer. (1) Determination of vibration impact plate size The river section to be measured was selected, and the sediment on the riverbed surface was sampled in the floodplain of the unflooded area. The sediment gradation of the samples was measured separately to obtain three representative particle sizes of the bed surface, and then the average median particle size of the three sampling frames was obtained. D 50 (mm); the length of the vibration impact plate in the direction of water flow is: L p >L=u * w (1) Where, L p is the length of the vibration impact plate in the direction of water flow (m); L is the bed load moving length (m); u * is the friction flow velocity (m / s); w is the sedimentation velocity (m / s); g is the acceleration due to gravity (m / s 2 ); h is the average water depth of the section (m), J is the river gradient; ρ s is the density of the pebble bed load (kg / m 3 ); ρ is the density of water (kg / m 3 ); C d is the drag coefficient; (2) Install a real-time monitoring device for pebble bed load sediment transport rate The acceleration vibration sensor is fixedly mounted at the center of the vibration impact plate, and the vibration impact plate is then fixedly mounted on the mounting base. The acceleration vibration sensor is placed in the groove in the middle of the mounting base. The acceleration vibration sensor is connected to the data collector signal, and the data collector is connected to the computer. The mounting base is fixedly mounted in the riverbed to ensure that it does not move relative to the riverbed. (3) Signal acquisition and processing The original vibration signal data generated by the bedload transport on the vibrating impact plate is recorded using a collector. The corresponding vibration TDMS original file is obtained on the host computer. The absolute value of the original data in the TDMS file is taken. The original data is then divided according to the number of sampling data points per minute to obtain a 1-minute signal package. The data in each signal package is then segmented and statistically analyzed to obtain the statistical parameters of the 1-minute signal package, including mean, standard deviation, maximum value, kurtosis, and skewness. (4) Calculation of sediment transport rate of pebble bed load A relationship is established between the vibration signal and the bed load transport rate, and the real-time bed load transport rate is directly inferred using the vibration signal characteristic value. The signal characteristic value is obtained by substituting the signal parameters obtained in step (3) into the following formula: (4) Where, δ * is the characteristic value of the vibration signal; is the average value of the vibration signal within 1 minute; δ max is the maximum value of the vibration signal within 1 minute; then, gravity acceleration and density are introduced, and the characteristic value of the vibration signal is substituted into the calculation to obtain the bed load transport rate per width. The calculation expression is as follows: Where, G b is the single-width non-uniform bed load transport rate (kg / m / min); ρ s is the density of the pebble bed load (kg / m 3 ); ρ is the density of water (kg / m 3 ); δ * is the characteristic value of the vibration signal; g is the acceleration due to gravity (m / s 2 ).

2. The method according to claim 1, characterized in that According to the width of the river section to be measured, a plurality of the devices are fixed transversely along the riverbed perpendicular to the direction of water flow.

3. The method according to claim 1, characterized in that In step (2), the mounting base is poured together with the concrete.

4. The method according to claim 1, characterized in that In step (2), multiple sleeves fixedly connected to the mounting base are symmetrically arranged on the outer edge of the mounting base, the stainless steel bars are connected to the sleeves through threads, and the nuts are tightened at the positions corresponding to the two ends of the sleeves on the steel bars to limit the mounting base. Then, the steel bars are inserted to less than 1m below the riverbed, and it is ensured that the top of the vibration plate on the mounting base is flush with the riverbed surface elevation.

5. The method according to claim 1, characterized in that: The acceleration vibration sensor described in step (3) is an IEPE acceleration vibration sensor; the acquisition frequency is set to 1000Hz~10000Hz.

6. A real-time measurement simulation experimental device for pebble bedload transport rate based on vibration signal processing, characterized in that: It includes a real-time monitoring device for pebble bed load sediment transport rate based on vibration signal processing, a water reservoir, a water flume, a honeycomb pipe, and a flat-top weir; The device for real-time monitoring of pebble bed load sediment transport rate based on vibration signal processing is composed of a vibration impact plate, an acceleration vibration sensor, a mounting base, a data collector and a computer. The acceleration vibration sensor is fixedly mounted on the vibration impact plate, a groove is provided in the middle of the mounting base, the vibration impact plate covers and is fixed on the mounting base, and the side on which the acceleration vibration sensor is mounted faces downward so that the acceleration vibration sensor is placed in the groove space of the mounting base. The mounting base is fixed in the riverbed, and the installation elevation satisfies the requirement that the vibration impact plate is flush with the riverbed. The acceleration vibration sensor is connected to the data collector signal, and the data collector is connected to the computer terminal. The inlet end of the water flume is located downstream of the water reservoir. A honeycomb pipe is provided at the inlet of the water flume. A flat-top weir for measuring flow is provided in the water reservoir. The water flume is sloped according to the needs of the simulation experiment. The inlet section of the water flume bottom plate is paved with immovable large particles as a transition zone. A non-uniform gravel bed sand is laid downstream of the transition zone. A fixed plate is fixed at the tail of the water flume to fix the riverbed and prevent the overall layer shift of the bed sand. The pebble bed load sediment transport rate real-time monitoring device is installed on the water flume bottom plate downstream of the fixed plate. The simulation experimental device also includes a pebble bed load weighing mechanism, including a gantry, a tension sensor, a sand receiving pool, and a sand receiving frame. The sand receiving pool is connected to the downstream of the pebble bed load sediment transport rate real-time monitoring device, and the sand receiving pool entrance is flush with the vibration impact plate; the sand receiving frame is located in the sand receiving pool, so that the bed load enters the sand receiving frame after passing through the vibration impact plate, and the sand receiving frame is connected to the tension sensor through a steel rope; the gantry is an open rectangle, and the left and right vertical bars are symmetrically located on both sides of the water tank and fixed, so that the gantry is upright and the cross bar of the gantry is kept horizontal; the tension sensor is fixed at the midpoint of the cross bar of the gantry and should also be located at the center of the sand receiving frame.

7. The experimental device according to claim 6, characterized in that: A water trough extension section is provided downstream of the sand receiving pool to form a flow-free area in the sand receiving pool, thereby preventing the sand receiving frame from shaking and affecting the accuracy of the tension sensor.

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