A prestressed pipeline grouting compactness floating-point acquisition system and method

Abstract

The application discloses a prestressed pipeline grouting compactness floating point acquisition system and method, effectively solves the problem of huge elastic wave vibration signal quantity caused by the prestressed pipeline grouting compactness detection by using the variable frequency elastic wave excitation detection method. The prestressed pipeline grouting compactness floating point acquisition system is provided with a floating point collector, a single component acceleration sensor, a sweep frequency exciter and a power supply, and the prestressed pipeline grouting compactness floating point acquisition method is adopted. The sweep frequency exciter is arranged to generate uniform linearly changed elastic wave vibration signals, and the frequency change interval of the sweep frequency exciter is arranged, so that the elastic wave signal data is generated, the quality of the prestressed pipeline grouting is judged by using the elastic wave signal data, and according to the frequency of the elastic wave vibration signal of the sweep frequency exciter, the sampling interval of the floating point acquisition circuit is set as a variable interval mode, and the data quantity of the elastic wave vibration signal is reduced.

Description

Technical Field

[0001] This invention relates to the field of building quality inspection, and in particular to a floating-point acquisition system and method for the density of grouting in prestressed ducts. Background Technology

[0002] Currently, there is an increasing number of cases of incomplete grouting in prestressed structures and pipelines in my country's transportation construction. This phenomenon poses a safety hazard to numerous transportation roads and bridges.

[0003] Grouting density testing of prestressed concrete ducts in beams and slabs is a key aspect of evaluating construction quality, and its development has evolved from destructive testing to non-destructive testing. Destructive testing provides direct and accurate results, but is costly, inefficient, prone to damaging steel strands, and unable to determine the overall grouting density of the duct. While several non-destructive testing methods exist, each has drawbacks. For example, radiographic testing is costly, inefficient, difficult to perform large-scale testing, and involves radiation exposure. Ultrasonic testing requires stringent conditions; insufficient coupling can generate chaotic reflected waves, making defects difficult to detect or even identify. Electromagnetic wave testing is unsuitable due to the shielding of reinforcing steel. Elastic wave testing can only determine the presence of defects, not their location, and has low resolution.

[0004] To address the shortcomings of the aforementioned detection methods, existing technologies also provide a method for detecting elastic waves excited by a frequency sweep exciter. The frequency sweep exciter can be found in the variable frequency vibration source device described in patent application number 202010603089.6, which can improve the accuracy of detecting the grouting density of prestressed ducts in beams and slabs and has shown good results in actual testing. However, the frequency of elastic waves varies significantly when changing from low to high frequency or vice versa. According to the signal sampling theorem, the elastic waves received by the accelerometer must be sampled at fixed intervals to generate vibration signals. To ensure the sampling accuracy of the high-frequency elastic wave vibration signal, the sampling frequency of the sampling instrument needs to be at least twice the frequency of the high-frequency component. Therefore, if conventional elastic wave vibration signal acquisition methods are used, the amount of data obtained after sampling the elastic waves received by the accelerometer is enormous, directly affecting the wireless transmission efficiency and speed of the elastic wave vibration signal.

[0005] Therefore, the present invention provides a new solution to this problem. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a floating-point acquisition system and method for prestressed pipe grouting density, which effectively solves the problem of the huge amount of elastic wave vibration signal data caused by using frequency conversion excited elastic wave detection method to detect the density of pipe grouting.

[0007] The technical solution is a floating-point acquisition system for the density of grouting in prestressed pipes, the acquisition system including a floating-point acquisition unit, a single-component acceleration sensor, a frequency sweep exciter, and a power supply.

[0008] The floating-point acquisition unit is connected to the single-component accelerometer via a four-core cable, and the floating-point acquisition unit is connected to the sweep frequency exciter via a two-core cable. The power supply provides power to the floating-point acquisition unit, the single-component accelerometer, and the sweep frequency exciter respectively.

[0009] The floating-point acquisition unit includes a floating-point acquisition control circuit, four floating-point acquisition circuits, and an acquisition power supply circuit. The four floating-point acquisition circuits include floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four. The floating-point acquisition control circuit is connected to floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four respectively. The power supply provides power to the floating-point acquisition control circuit, floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four respectively through the acquisition power supply circuit.

[0010] The single-component acceleration sensor includes four single-component acceleration sensors and a sensor power supply circuit. The four single-component acceleration sensors include single-component acceleration sensor one, single-component acceleration sensor two, single-component acceleration sensor three, and single-component acceleration sensor four. The power supply circuit provides power to single-component acceleration sensor one, single-component acceleration sensor two, single-component acceleration sensor three, and single-component acceleration sensor four respectively.

[0011] The floating-point acquisition circuit is connected to the single-component accelerometer sensor via core 1 of the four-core cable.

[0012] The second floating-point acquisition circuit is connected to the second single-component accelerometer via core 2 of the four-core cable;

[0013] The floating-point acquisition circuit 3 is connected to the single-component accelerometer 3 via core 3 of the four-core cable;

[0014] The floating-point acquisition circuit is connected to the single-component acceleration sensor via core 4 of a four-core cable. A floating-point acquisition method for the density of grouting in prestressed pipes includes the following steps:

[0015] S1. The frequency sweep exciter is controlled using a floating-point acquisition control circuit, causing it to generate a uniformly linearly varying elastic wave vibration signal, where the sweep frequency range is f. min ~f max And set the minimum frequency f on the frequency sweep exciter. min Maximum frequency fmax Frequency change Δf;

[0016] S2. When the four-channel floating-point acquisition circuit acquires the elastic wave vibration signal, it simultaneously calculates the sampling interval of the elastic wave vibration signal and sets the number of sampling points in the next cycle of a certain frequency of the frequency sweep exciter to M and the total number of sampling points to N during the frequency sweep process. The total number of sampling points N is an integer multiple of the number of periodic sampling points M.

[0017] S3. After the sweep frequency exciter is set according to steps S1 and S2, it starts to generate impact elastic wave vibration signal. At the same time, the single-component acceleration sensor performs variable sampling interval to collect elastic wave vibration signal data.

[0018] S4. Calculate the correlation coefficient from the elastic wave vibration signal data obtained in step S3 to determine the grouting quality.

[0019] Furthermore, the specific process of calculating the sampling interval in step S2 is as follows:

[0020] A1. As the sweep frequency increases, it can be seen from step S1 that the sweep frequency at point i is f. i =f min +Δf×i, the frequency sweep period at point i is Therefore, the sampling interval at point i

[0021] A2. As the sweep frequency decreases, it can be seen from step S1 that the sweep frequency at point i is f. i =f max -Δf×i, the sweep period at point i is Therefore, the sampling interval at point i

[0022] Furthermore, the specific steps in step S4 of calculating the correlation coefficient from the elastic wave vibration signal data are as follows:

[0023] B1. Use rectangularly arranged single-component accelerometers R1, R2, R3, and R4 to move along the direction of the prestressed duct on the surface of the bridge deck to collect elastic wave vibration signals.

[0024] B2. Calculate the correlation coefficient r of the elastic wave vibration signals received by single-component accelerometers R1, R2, R3, and R4 using the following formula. ij :

[0025]

[0026] Where z it z jtIt is the sequence of measured signals received by any two single-component accelerometers (i, j) out of the four single-component accelerometers, with N sample points in the signal sequence. It is the average value of the measured signal sequence, r ij It is the correlation coefficient between two measured signal sequences;

[0027] B3. Calculate the correlation coefficient r using step B2. 12 and r 34 And using r2 = (r 12 +r 34 ) / 2 calculates the average of the two correlation coefficients;

[0028] B4. Calculate the correlation coefficient r using step B2. 13 r 14 r 23 r 24 And the average value of the four correlation coefficients, r4 = (r 13 +r 14 +r 23 +r 24 ) / 4;

[0029] B5. When both r2 and r4 are greater than 0.7, the grouting of the prestressed duct is considered uniform.

[0030] The present invention achieves the following beneficial effects:

[0031] By incorporating a floating-point acquisition unit, a single-component accelerometer, a frequency sweep exciter, and a power supply into the prestressed pipe grouting density floating-point acquisition system, and employing a prestressed pipe grouting density floating-point acquisition method, the system utilizes a floating-point acquisition control circuit to control the frequency sweep exciter. The exciter is configured to generate a uniformly linearly varying elastic wave vibration signal, and the frequency variation interval (step size) of the exciter is set to generate elastic wave signal data. This data is then used to determine the quality of the prestressed pipe grouting. Furthermore, based on the frequency of the elastic wave vibration signal from the frequency sweep exciter, the floating-point acquisition circuit is set to a variable-interval sampling mode. This ensures the sampling accuracy of elastic wave vibration signals at different frequencies, overcomes the significant difference in the number of acquisition points (i.e., data volume) between low-frequency and high-frequency bands, and reduces the amount of elastic wave vibration signal data. This effectively solves the problem of the enormous elastic wave vibration signal data volume caused by using variable-frequency excited elastic wave detection methods for pipe grouting density detection, and avoids affecting the wireless transmission efficiency and speed of the elastic wave vibration signal. Attached Figure Description

[0032] Figure 1 This is a block diagram of the data acquisition system proposed in this invention;

[0033] Figure 2This is a connection diagram of the acquisition system proposed in this invention. Detailed Implementation

[0034] For the purposes of this invention, the foregoing and other technical contents, features and effects are described in conjunction with the appendix below. Figure 1-2 The detailed description of the embodiments will make this clear. All structural details mentioned in the following embodiments are based on the accompanying drawings.

[0035] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0036] A floating-point acquisition system for the density of grouting in prestressed ducts, the acquisition system comprising a floating-point acquisition unit, a single-component accelerometer, a frequency sweep exciter, and a power supply;

[0037] The floating-point acquisition unit is connected to the single-component accelerometer via a four-core cable, and the floating-point acquisition unit is connected to the sweep frequency exciter via a two-core cable. The power supply provides power to the floating-point acquisition unit, the single-component accelerometer, and the sweep frequency exciter respectively.

[0038] The floating-point acquisition unit includes a floating-point acquisition control circuit, four floating-point acquisition circuits, and an acquisition power supply circuit. The four floating-point acquisition circuits include floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four. The floating-point acquisition control circuit is connected to floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four respectively. The power supply provides power to the floating-point acquisition control circuit, floating-point acquisition circuit one, floating-point acquisition circuit two, floating-point acquisition circuit three, and floating-point acquisition circuit four respectively through the acquisition power supply circuit. The acquisition power supply circuit filters and regulates the power supplied by the power supply, so that the power received by the floating-point acquisition control circuit and the four floating-point acquisition circuits is low-noise and stable.

[0039] The single-component acceleration sensor includes four single-component acceleration sensors and a sensor power supply circuit. The four single-component acceleration sensors include single-component acceleration sensor one, single-component acceleration sensor two, single-component acceleration sensor three, and single-component acceleration sensor four. The power supply circuit provides power to single-component acceleration sensor one, single-component acceleration sensor two, single-component acceleration sensor three, and single-component acceleration sensor four respectively. The sensor power supply circuit processes the power supplied by the power supply in the same way as the power acquisition circuit.

[0040] The floating-point acquisition circuit is connected to the single-component accelerometer sensor via core 1 of the four-core cable.

[0041] The second floating-point acquisition circuit is connected to the second single-component accelerometer via core 2 of the four-core cable;

[0042] The floating-point acquisition circuit 3 is connected to the single-component accelerometer 3 via core 3 of the four-core cable;

[0043] The floating-point acquisition circuit four is connected to the single-component acceleration sensor four through core 4 of the four-core cable;

[0044] exist Figure 1 In this process, the floating-point acquisition unit simultaneously controls the frequency sweep exciter and the single-component accelerometer. The floating-point acquisition unit provides the frequency sweep signal to the frequency sweep exciter, which generates the minimum frequency f of the shock elastic wave sweep range. min Maximum frequency f max The frequency change Δf is controlled by the floating-point acquisition unit. The sweep frequency exciter amplifies the sweep frequency signal provided by the floating-point acquisition unit and drives the excitation head to generate an impact elastic wave with sufficient energy. This wave is then supplied to the single-component accelerometer for sensing and conversion into an electrical signal. The floating-point acquisition unit then converts the signal into a digital signal for storage. The power supply consists of a battery pack, a protection board, and a mechanical power switch, which provide reliable power to the floating-point acquisition unit, the single-component accelerometer, and the sweep frequency exciter, respectively.

[0045] exist Figure 2 In this system, the acquisition and control circuit is a high-speed, highly integrated, high-performance microcontroller unit with an FPGA as its core. It controls the variable sampling interval acquisition of data from four floating-point acquisition circuits while simultaneously controlling a sweep frequency exciter to generate uniformly frequency-converted impact elastic waves. The four floating-point acquisition circuits each contain four independent, identical floating-point acquisition circuits, each with programmable gain preamplifier amplification, eighth-order analog filtering, and high-speed, high-precision analog-to-digital conversion functions. All logic control and coordination are executed by the FPGA. The single-component accelerometer consists of four independent, low-noise, high-performance MEMS accelerometers, each with high sensitivity, wide bandwidth, and second-order analog filtering. Furthermore, each of the four floating-point acquisition circuits is independently connected to each of the four single-component accelerometers (i.e., four independent channels), significantly reducing crosstalk between channels and improving the acquisition speed of the system.

[0046] This invention also provides a method for collecting floating-point data on the grouting density of prestressed ducts, the method specifically including the following steps:

[0047] S1. The frequency sweep exciter is controlled using a floating-point acquisition control circuit, causing it to generate a uniformly linearly varying elastic wave vibration signal, where the sweep frequency range is f. min ~f max And set the minimum frequency f on the frequency sweep exciter. minMaximum frequency f max Frequency change Δf;

[0048] S2. When the four-channel floating-point acquisition circuit acquires the elastic wave vibration signal, it simultaneously calculates the sampling interval of the elastic wave vibration signal and sets the number of sampling points in the next cycle of a certain frequency of the frequency sweep exciter to M and the total number of sampling points to N during the frequency sweep process. The total number of sampling points N is an integer multiple of the number of periodic sampling points M, and the number of periodic sampling points M is a constant during one frequency sweep process.

[0049] S3. After being set according to steps S1 and S2, the frequency sweep exciter begins to generate impact elastic wave vibration signals. Simultaneously, the single-component accelerometer performs variable sampling interval acquisition of elastic wave vibration signal data. That is, before the first sampling point, the sampling interval s is automatically set by the floating-point acquisition unit control circuit. jg1 It continuously collects M points, and immediately sets the sampling interval s upon completion. jg2 Collect M points, and immediately set the sampling interval s upon completion. jg3 And collect M points, and so on until the total number of sampling points N is completed, that is, complete a fixed sampling frequency of N / M sampling times and M sampling points, and store the collected data;

[0050] S4. Calculate the correlation coefficient from the elastic wave vibration signal data obtained in step S3 to determine the grouting quality.

[0051] In step S1, the minimum frequency f is set. min =20Hz, maximum frequency f max =10KHz, select incremental mode, frequency increment Δf = 1Hz, determine the sweep frequency range as 1Hz~10KHz, frequency step as 1Hz, set these three parameters as initial values, under the control of the floating point acquisition unit, the sweep frequency exciter can generate shock elastic waves with a frequency range of 1Hz~10KHz and an increment of 1Hz.

[0052] In step S2, the number of periodic sampling points M = 10, and the total number of sampling points N = 100000. From step S1, we know f min =20Hz, frequency increment Δf = 1Hz, then the frequency points are 20Hz, 21Hz, 22Hz, ..., 10KHz, that is, 10 points are continuously collected at 20Hz, 10 points are continuously collected at 21Hz, ..., 10 points are continuously collected at 10KHz. It must be pointed out here that the total number of sampling points is only a constraint condition within the frequency sweep range, and its value setting cannot exceed the frequency sweep range.

[0053] The specific process for calculating the sampling interval in step S2 is as follows:

[0054] A1. As the sweep frequency increases, it can be seen from step S1 that the sweep frequency at point i is f. i =f min +Δf×i, the frequency sweep period at point i is Therefore, the sampling interval at point i

[0055] A2. As the sweep frequency decreases, it can be seen from step S1 that the sweep frequency at point i is f. i =f max -Δf×i, the sweep period at point i is Therefore, the sampling interval at point i

[0056] In frequency sweeping, the sampling interval corresponding to each frequency point that is increased or decreased is s. jg0 s jg1 s jg2 …s jg(i-1) The frequency changes by (N / M)-1 times, so the value of i should be 0, 1, 2...(N / M)-1;

[0057] From step S1, we know that: f min =20Hz, frequency increment Δf=1Hz; From step S2, we know that: M=10. Since the incremental method is selected, according to the calculation in step A1, the sampling intervals corresponding to the frequency points i=0, 1, 2, 3, 4, 5 are 5.0mS, 4.8mS, 4.5mS, 4.3mS, 4.0mS, ..., and so on, the remaining sampling intervals can be calculated.

[0058] Step S2 reveals the sampling interval for each frequency point. For each frequency point, 10 points are collected according to their corresponding sampling interval. For example, at a frequency of 20Hz, 10 points are collected continuously after a sampling interval of 5.0ms; at 21Hz, 10 points are collected continuously after a sampling interval of 4.8ms; at 22Hz, 10 points are collected continuously after a sampling interval of 4.5ms; at 23Hz, 10 points are collected continuously after a sampling interval of 4.3ms; at 24Hz, 10 points are collected continuously after a sampling interval of 4.3ms; and at 25Hz, 10 points are collected continuously after a sampling interval of 4.0ms, until sampling is completed as required.

[0059] The specific steps for calculating the correlation coefficient from the elastic wave vibration signal data in step S4 are as follows:

[0060] B1. Using rectangularly arranged single-component accelerometers R1, R2, R3, and R4, the bridge deck surface is moved along the direction of the prestressed duct to collect elastic wave vibration signals. These single-component accelerometers R1, R2, R3, and R4 correspond one-to-one with single-component accelerometers one, two, three, and four of the four single-component accelerometers.

[0061] B2. Calculate the correlation coefficient r of the elastic wave vibration signals received by single-component accelerometers R1, R2, R3, and R4 using the following formula. ij :

[0062]

[0063] Among them, z it z jt It is the sequence of measured signals received by any two single-component accelerometers (i, j) out of the four single-component accelerometers, with N sample points in the signal sequence. It is the average value of the measured signal sequence, r ij It is the correlation coefficient between two measured signal sequences;

[0064] B3. Calculate the correlation coefficient r using step B2. 12 and r 34 And using r2 = (r 12 +r 34 ) / 2 calculates the average of the two correlation coefficients;

[0065] B4. Calculate the correlation coefficient r using step B2. 13 r 14 r 23 r 24 And the average value of the four correlation coefficients, r4 = (r 13 +r 14 +r 23 +r 24 ) / 4;

[0066] B5. When both r2 and r4 are greater than 0.7, it indicates that the elastic wave vibration signals between the two ends of the rectangle have a good correlation, that is, the grouting of the prestressed duct is uniform; when r2>0.7 and r4<0.4, it indicates that the elastic wave vibration signals between the two ends of the rectangle have a very poor correlation, indicating that the grouting quality of the prestressed duct has uneven variation.

[0067] In practical application, this invention provides a floating-point acquisition system for the grouting density of prestressed ducts. The system includes a floating-point acquisition unit, single-component accelerometers, a frequency sweep exciter, and a power supply. The floating-point acquisition unit comprises a floating-point acquisition control circuit, four-channel floating-point acquisition circuits, and an acquisition power supply circuit. The single-component accelerometers include four single-component accelerometers and a sensor power supply circuit. The four single-component accelerometers are single-component accelerometer 1, 2, 3, and 4. A floating-point acquisition method for the grouting density of prestressed ducts is also provided. The floating-point acquisition control circuit controls the frequency sweep exciter, which generates a uniformly linearly varying elastic wave vibration signal. Based on the frequency of the elastic wave vibration signal generated by the frequency sweep exciter, the sampling interval of the floating-point acquisition circuit is set to a variable interval mode. Finally, the grouting quality of the prestressed duct is determined from the obtained elastic wave vibration signal.

[0068] The present invention achieves the following beneficial effects:

[0069] By incorporating a floating-point acquisition unit, a single-component accelerometer, a frequency sweep exciter, and a power supply into the prestressed pipe grouting density floating-point acquisition system, and employing a prestressed pipe grouting density floating-point acquisition method, the system utilizes a floating-point acquisition control circuit to control the frequency sweep exciter. The exciter is configured to generate a uniformly linearly varying elastic wave vibration signal, and the frequency variation interval (step size) of the exciter is set to generate elastic wave signal data. This data is then used to determine the quality of the prestressed pipe grouting. Furthermore, based on the frequency of the elastic wave vibration signal from the frequency sweep exciter, the floating-point acquisition circuit is set to a variable-interval sampling mode. This ensures the sampling accuracy of elastic wave vibration signals at different frequencies, overcomes the significant difference in the number of acquisition points (i.e., data volume) between low-frequency and high-frequency bands, and reduces the amount of elastic wave vibration signal data. This effectively solves the problem of the enormous elastic wave vibration signal data volume caused by using variable-frequency excited elastic wave detection methods for pipe grouting density detection, and avoids affecting the wireless transmission efficiency and speed of the elastic wave vibration signal.

Claims

1. A prestressed pipeline grouting density floating-point acquisition system, characterized in that, The acquisition system comprises a floating point collector, a single-component acceleration sensor, a sweep exciter and a power supply; The floating point collector is connected with the single-component acceleration sensor through a four-core cable, the floating point collector is connected with the sweep exciter through a two-core cable, and the power supply provides power supply for the floating point collector, the single-component acceleration sensor and the sweep exciter respectively; The floating point collector comprises a floating point collection control circuit, four floating point collection circuits and an acquisition power supply circuit, the four floating point collection circuits comprise floating point collection circuit one, floating point collection circuit two, floating point collection circuit three and floating point collection circuit four, the floating point collection control circuit is connected with the floating point collection circuit one, the floating point collection circuit two, the floating point collection circuit three and the floating point collection circuit four respectively, and the power supply provides power supply for the floating point collection control circuit, the floating point collection circuit one, the floating point collection circuit two, the floating point collection circuit three and the floating point collection circuit four through the acquisition power supply circuit; The single-component acceleration sensor comprises four single-component acceleration sensors and a sensor power supply circuit, the four single-component acceleration sensors comprise single-component acceleration sensor one, single-component acceleration sensor two, single-component acceleration sensor three and single-component acceleration sensor four, and the power supply provides power supply for the single-component acceleration sensor one, the single-component acceleration sensor two, the single-component acceleration sensor three and the single-component acceleration sensor four through the sensor power supply circuit; The floating point collection circuit one is connected with the single-component acceleration sensor one through core 1 in the four-core cable; The floating point collection circuit two is connected with the single-component acceleration sensor two through core 2 in the four-core cable; The floating point collection circuit three is connected with the single-component acceleration sensor three through core 3 in the four-core cable; The floating point collection circuit four is connected with the single-component acceleration sensor four through core 4 in the four-core cable; The acquisition method used by the acquisition system comprises the following steps: S1, using the floating-point acquisition control circuit to control the sweep exciter, so that the sweep exciter generates uniform linearly changing elastic wave vibration signals, wherein the sweep frequency ranges from f min ~ f max , and the minimum frequency f min , the maximum frequency f max , and the frequency change amount △f are set on the sweep exciter; S2, the four-way floating-point acquisition circuit acquires the elastic wave vibration signal, calculates the sampling interval of the elastic wave vibration signal at the same time, and sets the next cycle sampling point number of a frequency in the frequency sweeping process of the frequency sweeping exciter as M , and the total sampling point number as N , the total sampling point number N is an integer multiple of the cycle sampling point number M . S3, the sweep exciter starts to generate the impact elastic wave vibration signal according to the settings in steps S1 and S2, and the single-component acceleration sensor executes variable sampling interval acquisition of the elastic wave vibration signal data; S4, the elastic wave vibration signal data obtained in step S3 is calculated to obtain a correlation coefficient, so as to judge the grouting quality; The specific process of calculating the sampling interval in step S2 is: A1, the sampling interval of the point i is f i =f min +△f×i , the sweep period of the point i is , so the sampling interval of the point i is ; A2, the sampling interval of the point i f i = f max -△f×i , the sampling interval of the point i i .​​​​ 2. The pre-stressed pipeline grouting density floating point acquisition system of claim 1, wherein, In the acquisition method used by the system, the specific steps of calculating the correlation coefficient from the elastic wave vibration signal data in step S4 are: B1, the single-component acceleration sensor one, the single-component acceleration sensor two, the single-component acceleration sensor three and the single-component acceleration sensor four arranged in a rectangle are moved along the prestressed pipe direction on the bridge plate surface to collect signals; B2. Calculate the correlation coefficient of the signals received by the detectors R1, R2 and R3, R4 using the following formula r ij : ； wherein z it , z jt is the measured signal sequence received by any two single-component acceleration sensors (A1, A2, A3, A4) of the four single-component acceleration sensors, i , j ) with a number of signal sequence samples of N, 、 is the average of the measured signal sequence, r ij is the correlation coefficient of the two measured signal sequences. B3. Calculate the correlation coefficient r using step B2 12 and r 34 and calculate the average of the two correlation coefficients using r2= (r 12 + r 34 ) / 2. B4. Calculate the correlation coefficient r using the results of step B2 13 14 23 24 13 14 23 24 r4 = (r1 + r2 + r3 + r4) / 4​​​​​​​ B5, when r2 and r4 are both greater than 0.7, it is determined that the prestressed pipe grouting is uniform.

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