CN211200494U - Cofferdam supporting stress monitoring device based on fiber bragg grating - Google Patents
Cofferdam supporting stress monitoring device based on fiber bragg grating Download PDFInfo
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- CN211200494U CN211200494U CN201921768189.3U CN201921768189U CN211200494U CN 211200494 U CN211200494 U CN 211200494U CN 201921768189 U CN201921768189 U CN 201921768189U CN 211200494 U CN211200494 U CN 211200494U
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Abstract
The utility model discloses a cofferdam support stress monitoring devices based on fiber grating, include: the system comprises at least one supporting beam for monitoring, a first fiber grating sensor, a second fiber grating sensor and a fiber grating sensing demodulator; the supporting beam is provided with a first groove and a second groove which are perpendicular to each other, the first groove is perpendicular to the cross section of the supporting beam, and the second groove is parallel to the cross section of the supporting beam; one end of the first fiber grating sensor is arranged in the first groove, and the other end of the first fiber grating sensor is connected to the fiber grating sensing demodulator; one end of the second fiber grating sensor is arranged in the second groove, and the other end of the second fiber grating sensor is connected to the fiber grating sensing demodulator. The utility model has the advantages of monitoring simple structure, the suitability is strong.
Description
Technical Field
The utility model relates to a cofferdam monitoring field especially relates to a cofferdam support stress monitoring devices based on fiber grating.
Background
Cofferdams are temporary enclosures (usually made of steel) that are built to build permanent hydraulic installations in hydraulic engineering construction. The cofferdam has the functions of preventing water and soil from entering the building position of the building so as to drain water in the cofferdam, excavate a foundation pit and build the building. The cofferdam is mainly used in hydraulic buildings in general, and the cofferdam is dismantled after being used up except for being used as a part of a formal building.
In the construction process of the steel cofferdam, the supporting stress is generally required to be monitored. The support is a supporting structure for providing horizontal axial force in the construction process of a pier, and the support is an important stressed member in the construction process, so that the support has great significance in stress-strain monitoring.
The existing support stress monitoring is complex in monitoring structure, can interfere the structure or strength of the support, and cannot meet the actual use requirement.
SUMMERY OF THE UTILITY MODEL
In view of the above problem, an object of the present invention is to provide a cofferdam support stress monitoring device based on fiber grating, which adopts the fiber grating sensor as the monitoring sensor, and has the characteristics of anti-electromagnetic interference, good electrical insulation performance, safety and reliability, good corrosion resistance and long-term stability, etc., and the fiber grating sensor is very thin, so that the strength influence on the supporting structure is also very small.
The embodiment of the utility model provides a cofferdam support stress monitoring devices based on fiber grating, include: the system comprises at least one supporting beam for monitoring, a first fiber grating sensor, a second fiber grating sensor and a fiber grating sensing demodulator; the supporting beam is provided with a first groove and a second groove which are perpendicular to each other, the first groove is perpendicular to the cross section of the supporting beam, and the second groove is parallel to the cross section of the supporting beam; one end of the first fiber grating sensor is arranged in the first groove, and the other end of the first fiber grating sensor is connected to the fiber grating sensing demodulator; one end of the second fiber grating sensor is arranged in the second groove, and the other end of the second fiber grating sensor is connected to the fiber grating sensing demodulator.
Preferably, the first groove communicates with the second groove and forms an L-shaped groove.
Preferably, the first groove and the second groove are filled with epoxy resin glue.
Preferably, the length of the first groove and the second groove is 50 mm.
Preferably, the width and depth of the first and second grooves are 5 mm.
Preferably, a first fiber grating sensor in the first groove is used for measuring the strain of the support beam caused by deformation and temperature; and the second fiber bragg grating sensor in the second groove is used for measuring the strain of the support beam caused by temperature.
Preferably, the first fiber grating sensor and the second fiber grating sensor are connected to a fiber grating sensing demodulator through a fiber grating sensor transmission line.
Preferably, the support beam is an i-beam.
In summary, the cofferdam support stress monitoring device based on fiber bragg grating provided by the embodiment has the following advantages:
(1) and measuring the stress value by adopting the fiber bragg grating sensor. The fiber grating sensor has the advantages of electromagnetic interference resistance, good durability, light weight, small volume, distributed measurement, absolute measurement, high precision and the like, is suitable for environments with severe conditions such as underwater, humidity, electromagnetic interference and the like, and has stronger durability compared with a metal sensor; and the fiber grating sensor is light, thin, flexible, small in volume, light in weight and convenient to arrange and install.
(2) And the monitoring process of the supporting beam adopts two mutually perpendicular fiber grating sensors, so that the influence of the environmental temperature on the measurement result can be eliminated, and the measurement result is more in line with the actual application requirement.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings required for the embodiments will be briefly described below, and obviously, the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a cofferdam support stress monitoring device based on fiber grating provided by an embodiment of the present invention.
Fig. 2 is a sectional view of a specific cofferdam construction provided by an embodiment of the present invention.
Fig. 3 is a monitoring plan view of the cofferdam construction of fig. 2.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
Referring to fig. 1, an embodiment of the present invention provides a cofferdam supporting stress monitoring device based on fiber grating, including: the device comprises at least one supporting beam 1 for monitoring, a first fiber grating sensor 2, a second fiber grating sensor 3 and a fiber grating sensing demodulator 4; a first groove 11 and a second groove 12 which are perpendicular to each other are formed in the support beam 1, the first groove 11 is perpendicular to the cross section of the support beam 2, and the second groove 12 is parallel to the cross section of the support beam 1; one end of the first fiber grating sensor 2 is arranged in the first groove 11, and the other end of the first fiber grating sensor 2 is connected to the fiber grating sensing demodulator 4; one end of the second fiber grating sensor 3 is arranged in the second groove 12, and the other end is connected to the fiber grating sensing demodulator 4.
In this embodiment, it is preferable that the first groove 11 is communicated with the second groove 12 to form L-shaped grooves for convenience of construction, however, it should be understood that in other embodiments of the present invention, the first groove 11 is not necessarily communicated with the second groove 12, and it is only necessary that the first groove 11 is perpendicular to the cross section of the support beam 2 and the second groove 12 is parallel to the cross section of the support beam 1.
In this embodiment, after the first fiber grating sensor 2 and the second fiber grating sensor 3 are placed in the first groove 11 and the second groove 12, the first groove 11 and the second groove 12 are preferably filled with epoxy glue to fix the first fiber grating sensor 2 and the second fiber grating sensor 3. Of course, it should be noted that other glue or other fixing methods may also be used for fixing, and the present invention is not limited in particular.
In this embodiment, the length of the first groove 11 and the second groove 12 is preferably 50 mm. The width and depth of the first groove 11 and the second groove 12 are 5 mm. Of course, it can be understood that in other embodiments of the present invention, various parameters such as the length, the width, the depth, etc. of the first groove 11 and the second groove 12 can be set according to actual needs, and these schemes are all within the protection scope of the present invention.
The monitoring principle of the present embodiment is detailed below:
a fiber grating (FBG) is an optical fiber in which a bragg grating is written in the core of the fiber using ultraviolet light. In the grating region, the refractive index of the fiber core changes periodically. Thus, the fiber grating can act as a wavelength specific reflector, reflecting light of a specific wavelength and transmitting light of all other wavelengths, the fiber grating reflecting the central wavelength conditions:
λ＝2nΛ (1)
where λ is the grating center wavelength, n is the core effective index, Λ is the modulation period of the core index, since λ is related to strain and temperature, the wavelength shifts when strain and temperature change.
In the formula peFor elastic optical coefficient, α, ξ are temperature coefficients of influence, Δ is the amount of change in strain, and Δ T is the amount of change in temperature.
In this embodiment, because the environmental temperatures at each measurement are different, the measurement of the fiber grating sensor is a combination of the real strain of the supporting beam 1 and the influence of the environmental temperature, in order to eliminate the influence of the temperature, in this embodiment, a second fiber grating sensor 3 without stress is arranged in the supporting beam 1, and the second fiber grating sensor 3 is parallel to the cross section of the supporting beam 1, so that the supporting beam 1 is ensured not to deform in the longitudinal direction when being deformed by stress, and only can be influenced by the environmental temperature. The other first fiber grating sensor 2 is perpendicular to the section of the support beam 1, so that the first fiber grating sensor 1 is ensured to be deformed in the longitudinal direction when the support beam 1 is deformed under a stress, and the first fiber grating sensor 1 is simultaneously influenced by the deformation of the support beam 1 and the temperature during measurement.
When the two fiber grating sensors measure the central wavelength of the grating, the measurement result of the first fiber grating sensor 2 minus the measurement result of the second fiber grating sensor 3 is just the central wavelength of the grating of the deformation of the support beam 1, and then the strain value of the support beam can be obtained by the relation formula of wavelength shift, and the stress value of the support beam 1 can be obtained by multiplying the strain value by the elastic modulus of the support beam 1.
In order to facilitate understanding of the present invention, an actual construction process will be described as an example.
As shown in figure 2, a certain cofferdam is formed by inserting, beating and enclosing steel sheet piles, the depth of the cofferdam is 13 meters, the embedding depth is 5m, and the cofferdam is provided with four supports. The water depth is 5m, and the thickness of the soil layer is from top to bottom: 2.5m of fine sand (mixed silt), 10.5m of strongly weathered argillaceous siltstone and 18.5m of moderately weathered argillaceous siltstone. The engineering is to monitor the stress values of the five supporting beams 1 so as to judge whether the cofferdam is safe or not in the construction process. The monitoring process of the present invention is illustrated by taking the monitoring of one of the supporting beams as an example.
As shown in fig. 3, for each support beam, the installation process is as follows:
firstly, an L-shaped groove is formed near the central axis of a web plate of a support beam 1, a first groove 11 is perpendicular to the section of the support beam 1, a second groove 12 is parallel to the section of the support beam 1, then a first fiber grating sensor 2 is embedded in the first groove 11, a first fiber grating sensor 3 is embedded in a second groove 12 parallel to the section of the support beam 1, after the completion, epoxy resin glue is coated in the first groove 11 and the second groove 12, the epoxy resin glue is filled in the grooves, after the glue is solidified, the fiber grating sensor and a fiber grating sensing demodulator 4 are connected through a fiber grating sensor transmission line 5, so that the data acquisition of the fiber grating is carried out, and the stress value monitoring of the support beam 1 is realized according to the data acquired by the first fiber grating sensor 2 and the second fiber grating sensor 3.
And when the steps are finished, the other four supporting beams are embedded similarly, and the steps are the same as the steps. And after the five supporting beams are buried with the fiber grating sensors, acquiring data of the fiber grating.
In the present embodiment, the strain value Δ of the support beam can be obtained according to the formula (2). After the strain value Δ is obtained, the stress value σ of the support beam can be obtained from the following equation (3).
σ＝ΔE (3)
If the stress value sigma of the support beam 1 is smaller than the allowable stress value [ sigma ], the stress value of the support meets the requirement, and the construction can be continued. If the stress value sigma of the support is larger than the allowable stress value [ sigma ] and the support stress does not meet the requirement, the constructor needs to withdraw from the site immediately, reports related units and takes related measures, such as filling water into the cofferdam to balance the soil pressure inside and outside the cofferdam.
In summary, the cofferdam support stress monitoring device based on fiber bragg grating provided by the embodiment has the following advantages:
(1) and measuring the stress value by adopting the fiber bragg grating sensor. The fiber grating sensor has the advantages of electromagnetic interference resistance, good durability, light weight, small volume, distributed measurement, absolute measurement, high precision and the like, is suitable for environments with severe conditions such as underwater, humidity, electromagnetic interference and the like, and has stronger durability compared with a metal sensor; and the fiber grating sensor is light, thin, flexible, small in volume, light in weight and convenient to arrange and install.
(2) And the monitoring process of the supporting beam adopts two mutually perpendicular fiber grating sensors, so that the influence of the environmental temperature on the measurement result can be eliminated, and the measurement result is more in line with the actual application requirement.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (8)
1. The utility model provides a cofferdam supports stress monitoring devices based on fiber grating which characterized in that includes: the system comprises at least one supporting beam for monitoring, a first fiber grating sensor, a second fiber grating sensor and a fiber grating sensing demodulator; the supporting beam is provided with a first groove and a second groove which are perpendicular to each other, the first groove is perpendicular to the cross section of the supporting beam, and the second groove is parallel to the cross section of the supporting beam; one end of the first fiber grating sensor is arranged in the first groove, and the other end of the first fiber grating sensor is connected to the fiber grating sensing demodulator; one end of the second fiber grating sensor is arranged in the second groove, and the other end of the second fiber grating sensor is connected to the fiber grating sensing demodulator.
2. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said first groove communicates with said second groove and forms L shaped groove.
3. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said first groove and said second groove are filled with epoxy glue.
4. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said first groove and said second groove have a length of 50 mm.
5. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said first and second grooves have a width and depth of 5 mm.
6. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein a first fiber grating sensor in said first groove is used for measuring the strain of said support beam due to deformation and temperature; and the second fiber bragg grating sensor in the second groove is used for measuring the strain of the support beam caused by temperature.
7. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said first fiber grating sensor and said second fiber grating sensor are connected to a fiber grating sensing demodulator through a fiber grating sensor transmission line.
8. The fiber grating-based cofferdam support stress monitoring device of claim 1, wherein said support beam is an i-beam.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112082676A (en) * | 2020-08-11 | 2020-12-15 | 潍坊科技学院 | A real-time monitoring device and method for ocean engineering cofferdam stress |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112082676A (en) * | 2020-08-11 | 2020-12-15 | 潍坊科技学院 | A real-time monitoring device and method for ocean engineering cofferdam stress |
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Address after: Room 201, building 11, Zhongnan headquarters base, no.688, Section 2, Wanjiali South Road, Tianxin District, Changsha, Hunan 410000 Patentee after: CCCC Central South Engineering Bureau Co.,Ltd. Address before: Room 201, building 11, Zhongnan headquarters base, no.688, Section 2, Wanjiali South Road, Tianxin District, Changsha, Hunan 410000 Patentee before: BRIDGE & TUNNEL ENGINEERING CO., LTD. OF CCCC FIRST HIGHWAY ENGINEERING Co.,Ltd. |
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