CN211498983U - Reflected wave receiving device for pile foundation detection - Google Patents
Reflected wave receiving device for pile foundation detection Download PDFInfo
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- CN211498983U CN211498983U CN201922225910.0U CN201922225910U CN211498983U CN 211498983 U CN211498983 U CN 211498983U CN 201922225910 U CN201922225910 U CN 201922225910U CN 211498983 U CN211498983 U CN 211498983U
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- reflected wave
- wave receiving
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- receiving device
- pile foundation
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Abstract
The utility model provides a reflected wave receiving device for pile foundation detection, which comprises a preselection filter group positioned at the foremost end of the reflected wave receiving device; the signal received by the reflected wave receiving device is subjected to frequency selection filtering by a preselection filter bank and then transmitted to a post-stage circuit of the reflected wave receiving device; the preselection filter bank comprises a frequency selection switch, a plurality of filters and a microcontroller; the frequency-selecting switch comprises a switch input end and a multi-way switch output end and is used for switching signal channels; the input ends of the filters are respectively connected with one switch output end of the frequency selection switch, and the output ends of the filters are respectively connected with a back-stage circuit of the reflected wave receiving device; the microcontroller is connected with the frequency selection switch and is used for controlling the frequency selection switch to switch signal channels according to a preset time interval; the utility model discloses can solve and use low back wave method that meets an emergency to examine time measuring to the pile foundation, disturb the technical problem who greatly influences the testing result because of the job site.
Description
Technical Field
The utility model relates to the field of communication technology, concretely relates to back wave receiving arrangement for pile foundation detects.
Background
At present, in civil engineering, for an engineering provided with a pile foundation, the pile foundation needs to be detected, the quality of the pile foundation is determined, and whether the pile foundation has internal holes, is loose or has pile breakage and the like is checked. In a construction site, the pile foundation can be detected by using a low-strain reflection wave method. According to the method, a hammer is used for knocking the top of the pile foundation, a sensor which is bonded to the top of the pile foundation is used for receiving stress reflected wave signals from the pile, and actual measurement speed signals and frequency signals are subjected to inverse analysis, so that the integrity of the pile body is detected, and the defect property, position and influence degree of the pile body are judged. The method is simple and convenient to detect, has high detection speed and is widely adopted.
However, in the prior art, since construction equipment is operated at all places of a construction site, various ground vibrations can occur at the construction site, and vibration waves formed by the vibrations can be transmitted to a pile foundation to be detected along the ground, so that interference is formed on stress reflected wave signals received by a sensor, and detection results are influenced.
SUMMERY OF THE UTILITY MODEL
To the defect among the prior art, the utility model provides a back wave receiving arrangement for pile foundation detects to when the use low back wave method that meets an emergency that exists examines the pile foundation among the solution prior art, disturb great because of the job site, influence the technical problem of testing result.
The utility model adopts the technical scheme that the reflection wave receiving device for pile foundation detection comprises a preselection filter group, wherein the preselection filter group is positioned at the foremost end of the reflection wave receiving device; the signals received by the reflected wave receiving device are subjected to frequency selection filtering by a preselection filter bank and then transmitted to a post-stage circuit of the reflected wave receiving device.
Furthermore, the preselection filter bank comprises a frequency selection switch, a plurality of filters and a microcontroller;
the frequency-selecting switch comprises a switch input end and a multi-way switch output end and is used for switching signal channels; the input ends of the filters are respectively connected with one switch output end of the frequency-selecting switch, and the output ends of the filters are respectively connected with the rear-stage circuit; the microcontroller is connected with the frequency-selecting switch and is used for controlling the frequency-selecting switch to switch signal channels according to a preset time interval.
Furthermore, the output ends of the plurality of filters are respectively connected with a low-noise amplifier, the input end of the low-noise amplifier is connected with the output end of the filter, and the output end of the low-noise amplifier is connected with a post-stage circuit of the reflected wave receiving device.
Furthermore, the frequency selecting switches are 2 switches with 1 branch and 6 branches, and the filters are 12 band-pass filters with the bandwidth of 1 kHz.
Further, the band pass filter is a crystal filter.
Further, the switching time interval between one output end branch and the other output end branch of the frequency selective switch is 1 microsecond.
Further, the signal includes a reflected wave signal and an interference signal.
According to the above technical scheme, the utility model discloses a beneficial technological effect as follows:
1. the preselection filter bank is used, useful reflected wave signals and interference signals can be transmitted in a shunt way, and interference of the interference signals on the reflected wave signals is avoided when the signals are processed subsequently.
2. In the output stage of the preselection filter group, the output end of each filter is respectively connected with a low noise amplifier, so that the intensity of the reflected wave signal can be increased under the condition of eliminating interference signals, and the accuracy of the detection result is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the technical solutions in the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
Fig. 1 is an electrical schematic block diagram of the present invention.
Fig. 2 is another electrical schematic block diagram of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
It is to be noted that unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which the present invention belongs.
Example 1
The utility model provides a back wave receiving arrangement for pile foundation detects, as shown in FIG. 1, include: a reflected wave receiving device for pile foundation detection comprises a preselection filter group, a pre-selection filter group and a pre-selection filter group, wherein the preselection filter group is positioned at the foremost end of the reflected wave receiving device; the signals received by the reflected wave receiving device are subjected to frequency selection filtering by a preselection filter bank and then transmitted to a post-stage circuit of the reflected wave receiving device.
The preselection filter bank comprises a frequency selection switch, a plurality of filters and a microcontroller;
the frequency-selecting switch comprises a switch input end and a multi-way switch output end and is used for switching signal channels; the input ends of the filters are respectively connected with one switch output end of the frequency-selecting switch, and the output ends of the filters are respectively connected with the rear-stage circuit;
the microcontroller is connected with the frequency-selecting switch and is used for controlling the frequency-selecting switch to switch signal channels according to a preset time interval.
The working principle of example 1 is explained in detail below:
the working principle of the low-strain reflection wave method is as follows: and (3) knocking the top of the pile foundation by using a small hammer, vertically exciting the top of the pile body, and downwards transmitting elastic waves along the pile body. When the pile body has an interface with obvious wave impedance difference, such as the pile bottom, the broken pile, the serious segregation and the like, or the area change part of the section of the pile body, reflected waves are generated. Through receiving amplification and digital signal processing, reflection information from different parts can be identified. According to the information, the wave speed of the pile body can be calculated, and the integrity of the pile body and the concrete quality can be judged. In a construction site, a low-strain reflection wave method is adopted to detect the pile foundation, and a commonly used instrument is a low-strain foundation pile dynamic measuring instrument. The low-strain foundation pile dynamic measuring instrument is internally provided with a receiving device for reflected wave signals, and the embodiment is an improvement on the receiving device.
In this embodiment, the reflected wave signals received by the receiving device are transmitted through a sensor bonded to the top of the pile foundation. Because the top of the pile foundation is knocked by the hammer, the generated vertical excitation signal is a low-frequency vibration signal, and the frequency range of the signal is generally 5Hz-12kHz, the receiving device in the prior art generally adopts a direct-mining amplification working principle, and no effective filtering measure is designed at the front end. Like this, various ground vibrations can appear in the in-process of work of other construction equipment at the job site, and the shock wave that these vibrations produced can be passed pile foundation position department along the ground, can be sensed by the sensor, transmits receiving arrangement. These vibration wave signals may interfere with the reflected wave signals.
Although the vibration wave signal and the reflected wave signal are both low-frequency vibration signals, in the detection process, the frequency of knocking the top of the pile foundation by using a small hammer is generally not less than 10 times, and the force of knocking by a person is changed, so that the vibration frequencies of the vibration wave signal and the reflected wave signal cannot be always kept at the same frequency in the whole detection process. In this embodiment, a preselection filter bank is disposed at the frontmost end of the receiving apparatus, and the preselection filter bank is composed of a frequency-selective switch, a plurality of filters operating in different frequency bands, and a microcontroller. Preferably, the plurality of filters are all band pass filters. The signals received by the receiving device, including useful reflected wave signals and useless interference signals, are subjected to frequency-selective filtering by a preselection filter bank and then transmitted to a post-stage circuit of the receiving device.
For the receiving device, the frequency of the useful signal, i.e. the reflected wave signal, is from 5Hz to 12kHz, and in order to achieve better frequency-selective filtering characteristics, in this embodiment, 2 frequency-selective switches are selected, the frequency band of 5Hz to 12kHz is divided into 12 segments, each 1kHz is divided into one segment, and each segment corresponds to one branch of the frequency-selective switch. Specifically, one segment of 5Hz-1kHz corresponds to a first branch of the frequency-selective switch; the section of 1kHz-2kHz corresponds to a second branch of the frequency selective switch; and so on. Each branch is provided with a filter with a corresponding frequency band, namely a first filter and a second filter, and so on; each filter is a band pass filter. In this embodiment, since the band width of the band pass filter needs to be set particularly narrow, it is preferable to use a crystal filter for obtaining a good frequency selection characteristic
When using low foundation pile dynamic testing appearance that meets an emergency to detect the pile foundation, use the sledgehammer to strike the pile foundation top after, paste the sensor at the pile foundation top and receive the back wave signal after, can transmit for receiving arrangement. The frequency selecting switch of the receiving device is controlled by the microcontroller to continuously and uninterruptedly perform multi-channel switching according to a preset time interval. In this embodiment, the time period of the frequency-selective switch traversing the branch is shorter than the detection response time of the low-strain foundation pile movement tester. Specifically, considering that the sampling interval duration of the low-strain foundation pile dynamic measuring instrument is generally in the order of tens of microseconds to hundreds of microseconds, the switching time between the frequency-selective switch branch and the frequency-selective switch branch is set to be 1 microsecond. The reflected wave signal has a continuous oscillation period which is much longer than the detection response time. Therefore, in a time period less than the detection response time, the microcontroller controls the frequency-selecting switch to switch the branches, all the branches can be traversed within 12 microseconds, and the problem that the reflected wave signals cannot be received is avoided.
After entering the receiving device, the reflected wave signal will first pass through the pre-selection filter bank, and the reflected wave signal will only enter the receiving device back-stage link from one of the 12 branches. Such as: the reflected wave signal is 10.8kHz, and the signal power is-50 dBm; 2 interference signals are provided, namely 3.3kHz, signal power of-80 dBm and 5.5kHz respectively, and the signal power of-70 dBm; the 3 signals enter different 3 rd, 5 th and 11 th branches respectively under the action of the frequency selecting switch. The band-pass filter can filter all interference signals except the pass band, so that when a reflected wave signal with the frequency of 10.8kHz and the signal power of-50 dBm passes through the 11 th branch circuit during the amplification processing of the rear stage of the receiving device, the interference signals of 3.3kHz and 5.5kHz cannot enter the branch circuit, and the reflected wave signal cannot be interfered by the signals of 3.3kHz and 5.5 kHz.
In this embodiment, the frequency selective switch may be HMC321A, the microcontroller may be EFM32TG11B, and the crystal filter may be a bandpass crystal filter with a bandwidth of 1 kHz.
Example 2
In a construction site, because of the existence of various interferences, in order to reduce the influence of interference signals on reflected wave signals, the sensitivity of a receiving device is generally not adjusted too high, and more useless interference signals are received into a subsequent link due to the fact that the sensitivity is adjusted too high. However, if the reflected wave signal strength is small, the gain of the receiving device's backward link is not enough to amplify the reflected wave signal with small strength to the ideal level threshold required by the digital signal processing, which may affect the detection result.
In order to solve the technical problem, the following optimization is further performed on the basis of the embodiment 1:
as shown in fig. 2, each path of crystal filter is connected to a low noise amplifier, which is a first path of low noise amplifier, a second path of low noise amplifier, and so on. The output end of each crystal filter is connected with the input end of the low noise amplifier of the branch, and the output end of the low noise amplifier is connected with the post-stage circuit. The low noise amplifier does not substantially affect the signal receiving sensitivity of the receiving device, but can add a larger gain to the receiving device. The low noise amplifier is arranged behind the filter, but not in front of the frequency-selecting switch, so that the interference signal can be prevented from being amplified by the low noise amplifier as soon as the interference signal enters the receiving device. The circuit arrangement can increase the intensity of the reflected wave signal under the condition of eliminating the interference signal and improve the accuracy of the detection result.
Specifically, because the gain of a receiving device inside the low-strain foundation pile dynamic measuring instrument is generally 60-70dB, the ideal level threshold required by digital signal processing is 0-10dBm, and the strength of a reflected wave signal obtained by knocking the top of a pile foundation through a small hammer is generally not less than-100 dBm, in the embodiment, a low-noise amplifier with the gain of 30dB can be selected to meet the use requirement, and particularly, the LT5514 can be selected.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the scope of the embodiments of the present invention, and are intended to be covered by the claims and the specification.
Claims (7)
1. A kind of reflected wave receiving arrangement used for pile foundation detection, characterized by that: the device comprises a preselection filter group, wherein the preselection filter group is positioned at the forefront end of a reflected wave receiving device; the signals received by the reflected wave receiving device are subjected to frequency selection filtering by a preselection filter bank and then transmitted to a post-stage circuit of the reflected wave receiving device.
2. A reflected wave receiving apparatus for pile foundation testing according to claim 1, wherein: the preselection filter bank comprises a frequency selection switch, a plurality of filters and a microcontroller;
the frequency-selecting switch comprises a switch input end and a multi-way switch output end and is used for switching signal channels;
the input ends of the filters are respectively connected with one switch output end of the frequency-selecting switch, and the output ends of the filters are respectively connected with the rear-stage circuit;
and the microcontroller is connected with the frequency selection switch and is used for controlling the frequency selection switch to switch signal channels according to a preset time interval.
3. A reflected wave receiving apparatus for pile foundation testing according to claim 2, wherein: the output ends of the filters are respectively connected with a low-noise amplifier, the input end of the low-noise amplifier is connected with the output end of the filter, and the output end of the low-noise amplifier is connected with a post-stage circuit of the reflected wave receiving device.
4. A reflected wave receiving apparatus for pile foundation testing according to claim 2, wherein: the frequency selecting switches are 2 switches with 1-path and 6-path, and the filters are 12 band-pass filters with the bandwidth of 1 kHz.
5. A reflected wave receiving apparatus for pile foundation testing according to claim 4, wherein: the band-pass filter is a crystal filter.
6. A reflected wave receiving apparatus for pile foundation testing according to claim 2, wherein: the switching time interval between one output end branch and the other output end branch of the frequency selective switch is 1 microsecond.
7. A reflected wave receiving apparatus for pile foundation testing according to claim 1, wherein: the signals include reflected wave signals and interference signals.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922225910.0U CN211498983U (en) | 2019-12-11 | 2019-12-11 | Reflected wave receiving device for pile foundation detection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922225910.0U CN211498983U (en) | 2019-12-11 | 2019-12-11 | Reflected wave receiving device for pile foundation detection |
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| Publication Number | Publication Date |
|---|---|
| CN211498983U true CN211498983U (en) | 2020-09-15 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201922225910.0U Expired - Fee Related CN211498983U (en) | 2019-12-11 | 2019-12-11 | Reflected wave receiving device for pile foundation detection |
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| Country | Link |
|---|---|
| CN (1) | CN211498983U (en) |
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2019
- 2019-12-11 CN CN201922225910.0U patent/CN211498983U/en not_active Expired - Fee Related
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Granted publication date: 20200915 Termination date: 20211211 |
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| CF01 | Termination of patent right due to non-payment of annual fee |