CN112033980A - Device and method for monitoring damage of existing building pile foundation - Google Patents
Device and method for monitoring damage of existing building pile foundation Download PDFInfo
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- CN112033980A CN112033980A CN202010911612.1A CN202010911612A CN112033980A CN 112033980 A CN112033980 A CN 112033980A CN 202010911612 A CN202010911612 A CN 202010911612A CN 112033980 A CN112033980 A CN 112033980A
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Abstract
The invention discloses a device and a method for monitoring damage of a pile foundation of an existing building, wherein a coaxial cable is pre-embedded on a main reinforcement of the pile foundation, a TDR (time domain reflectometry) test system is used for transmitting a feedback signal of an electromagnetic wave signal on the coaxial cable in real time, and when an earthquake, a landslide and pile side soil body loss occur near a main body of the pile foundation, the pile foundation is subjected to lateral shear deformation; after the lateral deformation takes place for the pile foundation, pre-buried coaxial cable in the pile foundation can produce shearing and tensile deformation, coaxial cable can cause coaxial cable characteristic impedance to change when producing the deformation, leads to the electromagnetic wave signal feedback signal of transmission on the coaxial cable to change, finally handles the feedback signal on the coaxial cable through monitoring platform, forms feedback signal time domain curve, through the analysis to feedback signal time domain curve, can effectually monitor the pile foundation damage. Compared with other detection methods, the method has the advantages of high detection precision, convenience in implementation and certain use value.
Description
Technical Field
The invention belongs to the field of pile foundation detection of building engineering and bridge engineering, and particularly relates to a device and a method for monitoring damage of an existing building pile foundation.
Background
For a highway or a railway in a mountain area, a plurality of bridge pile foundations are positioned at a steep slope section of a tunnel entrance, and when a side slope collapses under the action of rainstorm or earthquake, an obvious squeezing and pushing effect is generated on the bridge pile foundations; under the conditions of long-term scouring and riverbed change, the loss of soil on the pile side of a bridge pile foundation spanning a large river may cause instability or loss of bearing capacity of the pile foundation; for slope supporting engineering, the large-diameter anti-slide piles are arranged at the slope toe or the slope waist, so that the anti-slide performance of the slope can be effectively improved, and the completeness of the pile foundation structure is ensured, so that the method has very important significance for long-term service. When the pile foundation structure is earthquakes, landslides and the soil body on the side of the pile runs off, whether the damage condition of the pile foundation on the lower part of the building can be detected and monitored becomes a difficult problem to be solved urgently in the current pile foundation monitoring field.
The conventional pile foundation detection technology at present comprises a low-strain reflection wave method, an ultrasonic wave method and a core drilling method, theoretical research results developed by the methods are also rich, the conventional methods are widely used for monitoring the damage of the pile foundation of a newly-built project, the damage degree of the pile foundation can be accurately judged, the detection precision is high, and for the pile foundation detection of the existing building, the influence of an upper structure causes the application of the detection method to have difficulty, and the damage condition of the pile foundation of the existing building can not be effectively detected. For example, when the top of the pile foundation is a structure such as a bearing platform or a pier stud, a low-strain reflection wave method for exciting and receiving a vibration signal at the top of a conventional pile foundation is difficult to implement, even if part of foundation piles are exposed by excavating the foundation, clutter interference of an upper structure is still difficult to eliminate by adopting pile side excitation and vibration pickup, and a pile bottom feedback signal is usually very complex and cannot extract damage information of the pile foundation through conventional analysis; the detection effect of the ultrasonic method and the core drilling method on the newly-built pile foundation is most direct, but the former needs to embed the sounding pipe in the pile body concrete in advance, and the latter requires the pile top to be free and have drilling conditions, which greatly hinders the application of the method in the existing pile foundation detection.
The time domain reflection technology is a green environment-friendly nondestructive testing technology emerging in recent decades, integrates the disciplines of nondestructive testing, electromagnetism, signal processing and the like, and is widely applied to the detection and space positioning of various object morphological characteristics due to the advantages of convenience, safety, economy, numeralization, remote control and the like. At present, the technology is mainly applied to the aspects of power grid defect positioning and identification, soil moisture content, monitoring of rock mass and soil mass deformation, slope stability and the like, but is rarely applied to the aspect of pile foundation defect detection.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a device and a method for monitoring the damage of the existing building pile foundation based on a TDR time domain reflection method.
The technical scheme adopted by the invention for solving the technical problems is as follows: a device for monitoring damage of a pile foundation of an existing building comprises a pile foundation main body, 4 coaxial cables, a TDR (time domain reflectometry) test system and a monitoring platform; the pile foundation main body comprises a pile foundation and an upper building; the upper building is positioned above the pile foundation; more than 4 main ribs are arranged inside the pile foundation; the 4 coaxial cables are respectively clung to different main ribs and extend from the bottoms of the main ribs until the coaxial cables penetrate out of an upper building;
the TDR test system is formed by sequentially connecting a coaxial multiplexer, a TDR tester and a data acquisition instrument; the 4 coaxial cables are connected to different channels of the coaxial multiplexer;
the TDR tester can transmit electromagnetic wave signals and transmit the electromagnetic wave signals to the coaxial cable through the coaxial multiplexer, and can also receive feedback signals on the coaxial cable through the coaxial multiplexer; the data acquisition instrument can acquire the feedback signal received on the TDR tester in real time and display the feedback signal on the monitoring platform.
Further, the 4 coaxial cables are subjected to insulation and waterproof treatment.
Further, the distance between the 4 coaxial cables and the center of the pile foundation is equal, and the 4 coaxial cables are arranged in a square shape.
Furthermore, the monitoring platform consists of a computer and a server.
Furthermore, each main rib and the coaxial cable are respectively connected in an integrated manner.
A method for monitoring damage of an existing building pile foundation comprises the following steps of sequentially building an existing building pile foundation damage monitoring device and monitoring:
firstly, before the pile foundation is formed, 4 intact coaxial cables are fixed on 4 different main ribs on the pile foundation, and then the 4 coaxial cables are subjected to waterproof and insulating treatment;
burying 4 coaxial cables and each main rib underground, penetrating the 4 coaxial cables out of the top of the main rib, and then pouring concrete;
thirdly, after the pile foundation is completed and the concrete strength reaches the engineering requirement, connecting 4 coaxial cables into the TDR test system, and then connecting the TDR test system with the monitoring platform;
initializing an electromagnetic wave signal test; respectively calculating the propagation speeds of the electromagnetic waves on the 4 coaxial cables according to the lengths of the 4 coaxial cables and the reflection time of the electromagnetic wave signals; then, the data displayed on the monitoring platform is analyzed, and an initial time domain curve chart of the feedback signals of the 4 coaxial cables is drawn and recorded as a curve A0Curve B0Curve C0Curve D0；
When lateral shear deformation of the pile foundation occurs; the size of the electromagnetic wave feedback signal on the coaxial cable is positively correlated with the shearing or stretching deformation degree of the coaxial cable; at the moment, the data on the monitoring platform are analyzed again, and the time domain curve graph of the feedback signals of the 4 coaxial cables is drawn again and recorded as a curve A1Curve B1Curve C1Curve D1；
Corresponding comparison curve A0Curve B0Curve C0Curve D0And curve A1Curve B1Curve C1Curve D1(ii) a Judging the damage degree of the pile foundation according to the maximum amplitude and frequency curve of one group of mutation positions; the larger the amplitude and the frequency are, the larger the damage of the pile foundation is;
and seventhly, calculating the positions of the coaxial cables where the coaxial cables deform according to the electromagnetic wave reflection time and the known electromagnetic wave propagation speed.
In the application of the pile foundation damage deformation monitoring engineering, the time domain reflection method test principle is mainly to measure the change condition of the electromagnetic wave feedback signal of the coaxial cable buried in the pile foundation engineering structure through a TDR test system so as to reflect the deformation state of the coaxial cable. In the process of carrying out the TDR test of the coaxial cable, the impedance characteristic of the coaxial cable can be reflected while electromagnetic wave signals are transmitted in the coaxial cable. When the electromagnetic wave signal encounters a change in the characteristic impedance of the cable, a reflected wave is generated. The propagation time of the electromagnetic wave feedback signal is detected by a special instrument, and the position of the change of the characteristic impedance of the coaxial cable can be calculated according to the transmission time and the speed of the electromagnetic wave signal; through the analysis to the feedback signal amplitude, can calculate the deformation state of cable, and then can realize the monitoring purpose to pile foundation engineering structure.
Compared with the prior art, the device and the method for monitoring the damage of the existing building pile foundation have the following beneficial effects that: before the pile foundation is formed, 4 coaxial cables are respectively clung to different main ribs and extend from the bottoms of the main ribs until the coaxial cables penetrate out of an upper building; therefore, in the subsequent detection work, a construction team can be easily connected with the TDR test system and the monitoring platform through 4 coaxial cables; and then can real-time supervision pile foundation damage condition and trend through TDR test system and monitoring platform, the monitoring result also can in time feed back to engineering maintenance personnel, in time acquire the pile foundation damage condition behind the calamity, and effectively formulate the pile foundation according to the pile foundation damage condition and consolidate the maintenance measure, avoid the pile foundation unstability to appear in the pile foundation or the bearing capacity is not enough and the condition of harm pile foundation main part appears, ensure the normal safe handling of pile foundation.
Drawings
The invention is further described with reference to the following figures and examples.
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a front-to-back comparison of a set of test data in accordance with the present invention.
Detailed Description
The conception, the specific structure and the technical effects of the present invention will be clearly and completely described in conjunction with the embodiments and the accompanying drawings to fully understand the objects, the schemes and the effects of the present invention. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
It should be noted that, unless otherwise specified, when a feature is referred to as being "fixed" or "connected" to another feature, it may be directly fixed or connected to the other feature or indirectly fixed or connected to the other feature. Furthermore, the descriptions of up, down, left, right, front, rear, etc. used in the present invention are only relative to the positional relationship of the respective components of the present invention with respect to each other in the drawings.
Furthermore, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any combination of one or more of the associated listed items.
As shown in fig. 1, the device for monitoring damage to the pile foundation of the existing building comprises a pile foundation main body, 4 coaxial cables 33, a TDR testing system 1 and a monitoring platform 2; the pile foundation main body comprises a pile foundation 31 and an upper building 32; the upper building 32 is positioned above the pile foundation 31; more than 4 main ribs 34 are arranged inside the pile foundation 31; the 4 coaxial cables 33 are respectively clung to different main ribs 34 and extend from the bottoms of the main ribs 34 until penetrating out of the upper building 32; before the pile foundation 31 is molded, 4 coaxial cables 33 are respectively clung to different main ribs 34 and extend from the bottoms of the main ribs 34 until the coaxial cables penetrate out of the upper building 32; therefore, in the subsequent detection work, a construction team can be easily connected with the TDR test system 1 and the monitoring platform 2 through 4 coaxial cables 33; and then can real-time supervision pile foundation 31 damage condition and trend through TDR test system 1 and monitoring platform 2, the monitoring result also can in time feed back to engineering maintenance personnel, in time acquire the calamity back pile foundation 31 damage condition, and effectively formulate pile foundation 31 and consolidate the maintenance measure according to the pile foundation 31 damage condition, avoid pile foundation 31 the unstability of pile foundation 31 or the not enough and the condition of harm pile foundation main part appears in the bearing capacity, ensure the normal safe handling of pile foundation 31.
The TDR test system 1 is formed by sequentially connecting a coaxial multiplexer 11, a TDR tester 12 and a data acquisition instrument 13; the 4 coaxial cables 33 are connected to different channels of the coaxial multiplexer 11; the TDR tester 12 may transmit an electromagnetic wave signal and transmit the electromagnetic wave signal to the coaxial cable 33 through the coaxial multiplexer 11, and the TDR tester 12 may further receive a feedback signal on the coaxial cable 33 through the coaxial multiplexer 11; the data acquisition instrument 13 can acquire the feedback signal received by the TDR tester 12 in real time and display the feedback signal on the monitoring platform 2. So as to generate shearing and stretching deformation when the coaxial cable 33 generates transverse shearing deformation on the pile foundation 31; thereby causing the characteristic impedance of the coaxial cable 33 to change, and finally causing the electromagnetic wave feedback signal transmitted on the coaxial cable 33 to change; meanwhile, the size of the electromagnetic wave feedback signal on the coaxial cable 33 is in positive correlation with the shearing and tensile deformation degree of the coaxial cable 33, and finally, a tester can judge whether the pile foundation 31 is unstable or not through the feedback signal on the coaxial cable 33.
In order to ensure the accuracy of the feedback signal of the coaxial cable 33, the 4 coaxial cables 33 are subjected to insulation and waterproof treatment, and meanwhile, the main ribs 34 are respectively and integrally connected with the coaxial cables 33. In order to better detect the condition of the pile foundation 31 in an all-round manner, the distances from the 4 coaxial cables 33 to the center of the pile foundation 31 are equal, and the 4 coaxial cables 33 are arranged in a square manner.
For the convenience of detection, the monitoring platform 2 is composed of a computer 21 and a server 22.
As shown in fig. 1-2, a method for monitoring damage of an existing building pile foundation 31 includes the following steps of sequentially building and monitoring a damage monitoring device for the existing building pile foundation:
firstly, before the pile foundation 31 is formed, 4 intact coaxial cables 33 are fixed on 4 different main ribs 34 on the pile foundation 31, and then the 4 coaxial cables 33 are subjected to waterproof and insulating treatment;
burying 4 coaxial cables 33 and each main rib 34 underground, penetrating the 4 coaxial cables 33 out of the top of the main rib 34, and then pouring concrete;
thirdly, after the pile foundation 31 is completed and the concrete strength reaches the engineering requirement, connecting 4 coaxial cables 33 into the TDR testing system 1, and then connecting the TDR testing system 1 with the monitoring platform 2;
initializing an electromagnetic wave signal test; the propagation speeds of the electromagnetic waves on the 4 coaxial cables 33 are respectively calculated according to the lengths of the 4 coaxial cables 33 and the reflection time of the electromagnetic wave signals; then, the data displayed on the monitoring platform 2 is analyzed, and an initial time domain curve graph of the feedback signals of the 4 coaxial cables 33 is drawn and recorded as a curve A0Curve B0Curve C0Curve D0；
Fifthly, when the pile foundation 31 generates lateral shearing deformation; the size of the electromagnetic wave feedback signal on the coaxial cable 33 is positively correlated with the shearing or stretching deformation degree of the coaxial cable 33; at this time, the data on the monitoring platform 2 is analyzed again, and the time domain curve graph of the feedback signals of the 4 coaxial cables 33 is drawn again and recorded as a curve A1Curve B1Curve C1Curve D1；
Corresponding comparison curve A0Curve B0Curve C0Curve D0And curve A1Curve B1Curve C1Curve D1(ii) a Judging the damage degree of the pile foundation 31 through the curve with the maximum amplitude and frequency of one group of mutation positions; and the larger the amplitude and the frequency are, the larger the damage of the pile foundation 31 is;
and the position of each coaxial cable 33 where deformation occurs is calculated according to the electromagnetic wave reflection time and the known electromagnetic wave propagation speed.
Claims (6)
1. The utility model provides an existing building pile foundation damage monitoring devices which characterized in that: the test system comprises a pile foundation main body, 4 coaxial cables (33), a TDR test system (1) and a monitoring platform (2); the pile foundation main body comprises a pile foundation (31) and an upper building (32); the upper building (32) is positioned above the pile foundation (31); more than 4 main ribs (34) are arranged in the pile foundation (31); the 4 coaxial cables (33) are respectively clung to different main ribs (34) and extend from the bottoms of the main ribs (34) to penetrate out of the upper building (32);
the TDR test system (1) is formed by sequentially connecting a coaxial multiplexer (11), a TDR tester (12) and a data acquisition instrument (13); the 4 coaxial cables (33) are connected to different channels of the coaxial multiplexer (11);
the TDR tester (12) can emit electromagnetic wave signals and transmit the electromagnetic wave signals to the coaxial cable (33) through the coaxial multiplexer (11), and the TDR tester (12) can also receive feedback signals on the coaxial cable (33) through the coaxial multiplexer (11); the data acquisition instrument (13) can acquire the feedback signals received by the TDR tester (12) in real time and display the feedback signals on the monitoring platform (2).
2. An existing building pile foundation damage monitoring device according to claim 1, characterized in that: the 4 coaxial cables (33) are subjected to insulation and waterproof treatment.
3. An existing building pile foundation damage monitoring device according to claim 1, characterized in that: the distance between the 4 coaxial cables (33) and the center of the pile foundation (31) is equal, and the 4 coaxial cables (33) are arranged in a square shape.
4. An existing building pile foundation damage monitoring device according to claim 1, characterized in that: the monitoring platform (2) is composed of a computer (21) and a server (22).
5. An existing building pile foundation damage monitoring device according to claim 1, characterized in that: and each main rib (34) is integrally connected with the coaxial cable (33) respectively.
6. A method for monitoring damage of an existing building pile foundation (31), which is characterized by sequentially building the device according to any one of claims 1-5 and monitoring the device according to the following steps:
firstly, before a pile foundation (31) is formed, 4 intact coaxial cables (33) are fixed on 4 different main ribs (34) on the pile foundation (31), and then the 4 coaxial cables (33) are subjected to waterproof and insulating treatment;
burying 4 coaxial cables (33) and each main rib (34) underground, penetrating the 4 coaxial cables (33) out of the top of the main rib (34), and then pouring concrete;
thirdly, after the pile foundation (31) is completed and the concrete strength reaches the engineering requirement, connecting 4 coaxial cables (33) into the TDR testing system (1), and then connecting the TDR testing system (1) with the monitoring platform (2);
initializing an electromagnetic wave signal test; calculating the propagation speed of the electromagnetic wave on the 4 coaxial cables (33) respectively according to the lengths of the 4 coaxial cables (33) and the reflection time of the electromagnetic wave signals; then, the data displayed on the monitoring platform (2) is analyzed, and an initial time domain curve graph of the feedback signals of 4 coaxial cables (33) is drawn and recorded as a curve A0Curve B0Curve C0Curve D0；
When the pile foundation (31) is subjected to lateral shear deformation; the size of the electromagnetic wave feedback signal on the coaxial cable (33) is positively correlated with the shearing or stretching deformation degree of the coaxial cable (33); at the moment, the data on the monitoring platform (2) are analyzed again, and a time domain curve graph of the feedback signals of the 4 coaxial cables (33) is drawn again and recorded as a curve A1Curve B1Curve C1Curve D1；
Corresponding comparison curve A0Curve B0Curve C0Curve D0And curve A1Curve B1Curve C1Curve D1(ii) a Judging the damage degree of the pile foundation (31) through a curve with the maximum amplitude and frequency of one group of mutation positions; the larger the amplitude and the frequency are, the larger the damage of the pile foundation (31) is;
and the position of each coaxial cable (33) which is deformed is calculated according to the electromagnetic wave reflection time and the known electromagnetic wave propagation speed.
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| CN202010911612.1A CN112033980A (en) | 2020-09-02 | 2020-09-02 | Device and method for monitoring damage of existing building pile foundation |
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| CN202010911612.1A CN112033980A (en) | 2020-09-02 | 2020-09-02 | Device and method for monitoring damage of existing building pile foundation |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114439056A (en) * | 2022-01-24 | 2022-05-06 | 温州大学 | System for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology and construction and detection method thereof |
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2020
- 2020-09-02 CN CN202010911612.1A patent/CN112033980A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114439056A (en) * | 2022-01-24 | 2022-05-06 | 温州大学 | System for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology and construction and detection method thereof |
| CN114439056B (en) * | 2022-01-24 | 2023-07-07 | 温州大学 | System for detecting pile foundation bearing capacity by using distributed piezoelectric cable impedance sensing technology and construction and detection method thereof |
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