CN115748837A - Method for testing foundation pit anchor cable prestress based on millimeter wave radar - Google Patents
Method for testing foundation pit anchor cable prestress based on millimeter wave radar Download PDFInfo
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- CN115748837A CN115748837A CN202211374221.6A CN202211374221A CN115748837A CN 115748837 A CN115748837 A CN 115748837A CN 202211374221 A CN202211374221 A CN 202211374221A CN 115748837 A CN115748837 A CN 115748837A
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Abstract
The invention discloses a method for testing the prestress of a foundation pit anchor cable based on a millimeter wave radar, which comprises the steps of continuously transmitting electromagnetic waves to the anchor cable based on a radar detector to obtain corresponding phase change, and further calculating the vibration change displacement of the anchor cable; and then analyzing by software to obtain an anchor cable vibration frequency time-course curve, performing discrete Fourier transform on the anchor cable vibration frequency time-course curve, converting a time-domain signal into a frequency-domain signal, and calculating the prestress of the anchor cable. The scheme adopts non-contact measurement, can simultaneously realize the measurement of the prestress of a plurality of anchor cables, and has reliable principle and high working efficiency; the millimeter wave radar can penetrate through the sheath to directly test stronger anchor cable reflection signals, the reliability of a test result is improved, and the radar can measure the middle position of the anchor cable, which is less affected by boundary conditions, by adjusting the angle; the method has the advantages of non-contact measurement, all weather, small interference by external environment, capability of penetrating through the anchor cable sheath and the like.
Description
Technical Field
The invention relates to the technical field of building construction, in particular to a method for testing foundation pit anchor cable prestress based on a millimeter wave radar.
Background
Effective prestress is very important for a prestressed concrete structure, and the construction quality of the effective prestress is directly related to the safety state of the engineering. In the process of prestress construction, the influence of factors such as material elastic modulus, system error and human factors can influence the prestress effect, and the construction quality is difficult to control.
In the current engineering, a reverse pulling method and an anchor cable dynamometer are common methods for testing the effective prestress under the anchor in the construction process, the reverse pulling method is mainly a process of tensioning again, namely, a load is applied to the tensioned prestressed tendons so as to determine the effective prestress under the anchor, and the method is easy to damage the stability of the anchor cable and generate errors on the measurement result; the anchor cable dynamometer method is to stick a sensor on an anchor cable and feed back prestress through sensor data, the monitoring method is heavy, the detection methods are low in efficiency, insufficient in detection proportion, incapable of performing large-scale detection and incapable of finding out the anchor cable with problems in time, and at present, a reliable and effective detection method for the prestress loss of the foundation pit anchor cable still does not exist, so that effective supervision on hidden engineering is difficult.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for testing the prestress of the anchor cable of the foundation pit based on a millimeter wave radar, the test of the anchor cable force is realized based on an interference measurement technology, the non-contact measurement is realized, the measurement is accurate, and the efficiency is high.
The invention is realized by adopting the following technical scheme: a method for testing foundation pit anchor cable prestress based on a millimeter wave radar comprises the following steps:
a, continuously transmitting electromagnetic waves based on a millimeter wave radar, and reflecting the electromagnetic waves after encountering an anchor cable to obtain corresponding phase change;
b, calculating the vibration change displacement of the anchor cable according to the phase change of the anchor cable, and analyzing by software to obtain an anchor cable vibration frequency time-course curve;
and C, performing discrete Fourier transform on the anchor cable vibration frequency time-course curve, converting the time-domain signal into a frequency-domain signal, and calculating the prestress of the anchor cable.
Further, in the step a, firstly, a corresponding relation between the detection anchor cable and the detection signal is determined, and specifically, a divergence-convergence device is arranged between the millimeter radar wave and the anchor cable;
the divergence-convergence device comprises a signal receiving module, a signal divergence module and a signal processing module, wherein the signal receiving module is designed to be in a convex surface shape and is made of nickel-plated carbon fiber materials, the signal divergence module is designed to be in a concave surface shape and is made of polytetrafluoroethylene materials, the signal receiving module is aligned to the millimeter wave radar to receive electromagnetic wave signals transmitted by the millimeter wave radar, the signal divergence module is aligned to the anchor cable area of the foundation pit, and the signal processing module is used for diverging the received electromagnetic wave signals; the signal processing module realizes the one-to-one correspondence between the detection anchor cables and the emitted detection signals.
Further, the principle of the signal processing module is as follows:
the method comprises the steps that a foundation pit anchor cable to be detected is preset as an anchor cable 1, an anchor cable 2, an anchor cable 3 and an anchor cable 4. The amplitude of a signal sent by n anchor cables is known and different, when a signal processing module receives an electromagnetic wave signal transmitted by a signal receiving module, the signal processing module encodes a wave 1, a wave 2, a wave 3, a wave 4. And a wave n which are sent by a millimeter wave radar on the basis of the preset anchor cable 1, the anchor cable 2, the anchor cable 3, the anchor cable 4. And the different amplitude of the anchor cable n, so that the amplitude of the wave 1, the wave 2, the wave 3, the wave 4. And the wave n at the moment has a one-to-one correspondence with the amplitude of the anchor cable 1, the anchor cable 2, the anchor cable 3, the anchor cable 4. And the anchor cable n, and the wave 1, the wave 2, the wave 3, the wave 4. And the wave n are diffused to the anchor cable so as to progress the one-to-one correspondence of the anchor cables.
Compared with the prior art, the invention has the advantages and positive effects that:
the method for predicting the prestress of the anchor cable based on the millimeter radar waves adopts non-contact measurement, a reflecting device does not need to be installed on the anchor cable during testing, and the method belongs to the 'non-contact' measurement in the true sense; the testing principle is reliable, the prestress of a plurality of anchor cables can be measured at the same time, and the working efficiency is greatly improved; the millimeter wave radar can penetrate through the sheath to directly test stronger anchor cable reflection signals, the reliability of a test result is improved, and meanwhile, the radar can measure the middle position of the anchor cable, which is less affected by boundary conditions, by adjusting the angle; the millimeter wave radar has high test precision and can test the tiny vibration of the anchor cable; the method has the characteristics of non-contact measurement, all weather, small interference from external environment, capability of penetrating through the anchor cable sheath and the like.
Drawings
FIG. 1 is a schematic diagram of a radar testing principle according to an embodiment of the present invention;
FIG. 2 is a flowchart of an embodiment of the invention for detecting anchor cable force by using a millimeter wave radar;
FIG. 3 is a schematic diagram of detecting prestress of an anchor cable of a foundation pit by electromagnetic waves according to an embodiment of the invention;
fig. 4 is a schematic diagram of a spectrum analysis result of an anchor cable according to an embodiment of the present invention.
Detailed Description
In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be further described with reference to the accompanying drawings and examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced otherwise than as described herein, and thus, the present invention is not limited to the specific embodiments disclosed below.
Introduction of the principle:
the millimeter wave radar is equipment based on an electromagnetic wave principle, adopts non-contact measurement, and tests the prestress of the anchor cable based on a frequency method. And when the anchor cable force is detected, measuring the vibration displacement of the anchor cable according to the phase difference between the target echo signal and the transmitting signal. The radar feeds microwave signals through the transmitting antenna, the signals are reflected back after encountering the anchor cable and finally received by the receiving antenna, and 1 sampling complex signal of the measurement can be obtained through related signal and data processing, wherein the sampling complex signal comprises signal intensity and an observation phase value. The radar system continuously samples the anchor cable body target in the radiation field area, and if the target is deformed by deltar at the beginning of the 2 nd sampling, the 2 nd sampling complex signal obtained by the radar contains corresponding signal strength and an observation phase value, and the test principle is as shown in fig. 1:
the deformation phase is a difference value of 2 observation phases, and the calculation formula is as follows:
when the prestress of the anchor cable is detected, the radar detector emits electromagnetic waves, and the electromagnetic waves are reflected back after encountering the anchor cable to obtain phase change; a series of variable phases are obtained through continuous emission and reflection, so that the vibration variation displacement of the anchor cable is calculated, an anchor cable vibration frequency time-course curve is obtained through software such as Matlab and the like, then DFT (discrete Fourier transform) transformation is carried out, and the formula is as follows:
wherein x is a signal, x a (jf) is anchor cable frequency domain data, f is anchor cable amplitude, t is time, x a (t) anchor cable time domain data, e -j2πft Is a complex function, e is the base of the natural logarithm, j is the unit of an imaginary number;
converting the time domain signal into a frequency domain signal through DFT (discrete Fourier transform), and finally obtaining the anchor cable prestress value, wherein the formula is as follows:
specifically, the embodiment provides a method for testing the prestress of the anchor cable of the foundation pit based on the millimeter radar wave based on the above principle, as shown in fig. 2, the method includes the following steps:
1. installation of instrumentation
And during testing, selecting a proper instrument and equipment mounting position on the foundation pit surface according to the position detected by the anchor cable. And after the position is determined, a radar testing tripod is installed, a testing radar is arranged on the tripod, and a radar host is adjusted by an adjusting device to enable the fan-shaped beam range of the radar host to cover as many anchor cables as possible.
2. Instrumentation commissioning
After the instrument equipment is installed, the radar host is connected with the acquisition control computer through a data line, and because the power of the radar host is small, a mobile power supply is adopted for power supply in field detection, a detection control interface is opened, the whole detection system is debugged, and the measurement can be started only after a test signal is normal.
3. Anchor cable prestress test
The anchor cable prestress test can be carried out after the millimeter wave radar equipment is debugged, and due to non-contact measurement, the corresponding relation between the detection anchor cable and a detection signal is firstly determined in the test process.
(1) The principle of detecting the prestress of the anchor cable of the foundation pit by using the electromagnetic waves is shown in fig. 3, when the radar detector emits the electromagnetic waves, due to the non-correspondence between the electromagnetic waves and the anchor cable (the electromagnetic waves cannot feel the specific position of the anchor cable), the embodiment adopts a divergence-convergence device of the electromagnetic waves to scatter and converge signals of the electromagnetic waves emitted by the millimeter wave radar.
The divergence-convergence device comprises a signal receiving module, a signal divergence module and a signal processing module, wherein the signal receiving module is mainly aligned to the millimeter wave radar detection device and is called an A surface, the main material of the A surface is designed into nickel-plated carbon fiber, the A surface is designed into a convex surface, and the A surface is determined by the material and the shape to receive a wave signal transmitted by the radar detection device.
The signal divergence module is mainly aligned to an anchor cable area of the foundation pit and is called as a surface B, the surface B is designed to be made of polytetrafluoroethylene, the surface B is designed to be concave, and the surface B determines a wave signal transmitted by the surface A to be diverged according to the material and the shape.
The signal processing module is installed in the divergence-convergence body and has the following principle: a set of calculation program is input in advance into the wave detection program device. The method comprises the steps that a foundation pit anchor cable to be detected is preset as an anchor cable 1, an anchor cable 2, an anchor cable 4. And an anchor cable n (the amplitude of a signal sent by each anchor cable is known and different), when a signal processing module receives an electromagnetic wave signal transmitted from a surface A, the signal processing module encodes the wave 1, the wave 2, the wave 3, the wave 4. And the wave n based on different preset amplitudes of the anchor cable 1, the anchor cable 2, the anchor cable 3 and the anchor cable 4. So that the amplitudes of the wave 1, the wave 2, the wave 3, the wave 4. And the wave n have one-to-one correspondence with the amplitudes of the anchor cable 1, the anchor cable 2, the anchor cable 3, the anchor cable 4. And the anchor cable n (the amplitudes are equal and correspond to each other), and the wave 1, the wave 2, the wave 3, the wave 4. And the wave n are diffused out through the surface B to correspond to the foundation pit anchor cable one to one; after the electromagnetic waves reach the anchor cable, electromagnetic wave signals of the electromagnetic waves with the force signals in the anchor cable 1, the anchor cable 2, the anchor cable 3 and the anchor cable 4 are brought back to a divergence-collector by electromagnetic echo waves, the force signals can be directly transmitted to the surface A through the surface B at the moment, then the force signals are returned to a millimeter wave radar detection device to be transmitted to a computer end, and a frequency-time curve shown in the graph 4 is formed through software processing.
By carrying out fast Fourier transform on the anchor cable vibration frequency time-course curve, the method can pass through a formula
And calculating the prestress of the anchor cable, and realizing the detection of the prestress of the anchor cable of the foundation pit based on millimeter radar waves.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above modifications or changes to the equivalent embodiments with equivalent changes, without departing from the technical spirit of the present invention, and any simple modification, equivalent change and change made to the above embodiments according to the technical spirit of the present invention still belong to the protection scope of the technical spirit of the present invention.
Claims (3)
1. A method for testing foundation pit anchor cable prestress based on a millimeter wave radar is characterized by comprising the following steps:
a, continuously transmitting electromagnetic waves based on a millimeter wave radar, and reflecting the electromagnetic waves after encountering an anchor cable to obtain corresponding phase change;
b, calculating the vibration change displacement of the anchor cable according to the phase change of the anchor cable, and analyzing by software to obtain an anchor cable vibration frequency time-course curve;
and C, performing discrete Fourier transform on the anchor cable vibration frequency time-course curve, converting the time-domain signal into a frequency-domain signal, and calculating the prestress of the anchor cable.
2. The method for testing foundation pit anchor cable prestress based on millimeter wave radar as claimed in claim 1, wherein: in the step A, firstly, the corresponding relation between the detection anchor cable and the detection signal is determined, and particularly, a divergence-convergence device is arranged between the millimeter radar wave and the anchor cable for realizing the detection;
the divergence-convergence device comprises a signal receiving module, a signal divergence module and a signal processing module, wherein the signal receiving module is designed to be in a convex surface shape and is made of nickel-plated carbon fiber materials, the signal divergence module is designed to be in a concave surface shape and is made of polytetrafluoroethylene materials, the signal receiving module is aligned to the millimeter wave radar to receive electromagnetic wave signals transmitted by the millimeter wave radar, the signal divergence module is aligned to the anchor cable area of the foundation pit, and the signal processing module is used for diverging the received electromagnetic wave signals; the signal processing module realizes the one-to-one correspondence between the detection anchor cables and the emitted detection signals.
3. The method for testing foundation pit anchor cable prestress based on millimeter wave radar as claimed in claim 1, wherein: the principle of the signal processing module is as follows:
the method comprises the steps that a foundation pit anchor cable to be detected is preset as an anchor cable 1, an anchor cable 2, an anchor cable 3 and an anchor cable 4. The amplitude of a signal sent by n anchor cables is known and different, when a signal processing module receives an electromagnetic wave signal transmitted by a signal receiving module, the signal processing module encodes a wave 1, a wave 2, a wave 3, a wave 4. And a wave n which are sent by a millimeter wave radar on the basis of the preset anchor cable 1, the anchor cable 2, the anchor cable 3, the anchor cable 4. And the different amplitude of the anchor cable n, so that the amplitude of the wave 1, the wave 2, the wave 3, the wave 4. And the wave n at the moment has a one-to-one correspondence with the amplitude of the anchor cable 1, the anchor cable 2, the anchor cable 3, the anchor cable 4. And the anchor cable n, and the wave 1, the wave 2, the wave 3, the wave 4. And the wave n are diffused to the anchor cable so as to progress the one-to-one correspondence of the anchor cables.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116499620A (en) * | 2023-06-27 | 2023-07-28 | 南京隼眼电子科技有限公司 | Bridge cable force monitoring method and device based on millimeter wave radar and storage medium |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116499620A (en) * | 2023-06-27 | 2023-07-28 | 南京隼眼电子科技有限公司 | Bridge cable force monitoring method and device based on millimeter wave radar and storage medium |
| CN116499620B (en) * | 2023-06-27 | 2023-09-08 | 南京隼眼电子科技有限公司 | Bridge cable force monitoring method and device based on millimeter wave radar and storage medium |
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Inventor after: Liu Quanwei Inventor after: Yang Zhongnian Inventor after: Wang Xilei Inventor after: Ye Shoujie Inventor after: Huang Cheng Inventor after: Liu Linsheng Inventor before: Liu Quanwei Inventor before: Wang Xilei Inventor before: Ye Shoujie Inventor before: Huang Cheng Inventor before: Liu Linsheng Inventor before: Yang Zhongnian |
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