Intelligent fiber grating based on fiber grating sensing

Abstract

The utility model discloses an intelligent fiber grating based on fiber grating sensing, and belongs to the field of civil engineering intelligent materials. Specifically, flexible optical fiber sensors suitable for monitoring the large deformation of the roadbed are reasonably packaged and designed, and packaged flexible optical fiber sensor bundles are compositely woven in a fiber grid, so that an optical fiber sensing intelligent geogrid capable of enhancing the roadbed and monitoring the large deformation of the roadbed is formed, and an intelligent grid enhanced road system is constructed. The flexible optical fiber sensor is realized by pre-bending an optical fiber and packaging the optical fiber in a soft silica gel mold, so that the measuring range of the sensor can be effectively expanded, and monitoring under the condition of large deformation is realized. Based on the long-scale-distance sensing characteristic of the fiber grating sensor, the packaging technology of the fiber grating sensor is improved, and the flexible fiber grating sensor and the fiber grating are compounded to form the intelligent geogrid, so that the reinforcing and monitoring integrated design of the fiber grating in roadbed engineering is realized; the method has a wide application prospect in civil engineering.

Description

Technical Field

[0001] The utility model belongs to the field of civil engineering intelligent materials, and particularly relates to an intelligent fiber warp knitting grid based on optical fiber grating sensing. Background Art

[0002] The construction of expressways in my country has developed rapidly. Compared with general highways, the stability of the roadbed in expressways has a crucial impact on its service life. It is necessary to strictly control the uneven settlement of the roadbed, especially the high water content, high compressibility, low strength and poor permeability of the soft soil roadbed, which will cause a large deformation of the roadbed, resulting in a sharp drop in bearing capacity and obvious settlement of the roadbed. This not only affects the driving speed, but also easily causes "bridge jumping", and even causes traffic accidents in serious cases. The deformation of the roadbed is an issue that needs to be paid attention to during the construction and operation of expressways. Laying reinforcement materials in the roadbed for reinforcement can effectively reduce the settlement of the road surface and improve the stability of the soft soil roadbed. Fiber warp knitted grid mesh has obvious advantages in roadbed reinforcement due to its high strength, good durability, and clear longitudinal and lateral force directions. At present, carbon fiber warp knitted grid, glass fiber warp knitted grid and basalt fiber warp knitted grid are more commonly used.

[0003] In actual projects, although the use of fiber-reinforced roadbed can alleviate the deformation and settlement of the roadbed to a certain extent, there is a lack of effective monitoring of the deformation of the roadbed during the entire life cycle of the reinforced road operation, and it is impossible to accurately and reliably perform a full-life assessment. Therefore, it is necessary to monitor the deformation of the reinforced roadbed. Existing roadbed settlement monitoring technologies include settlement plate method, settlement cup method, horizontal inclinometer method, electromagnetic layered settlement meter method, hydraulic profile settlement meter method, etc. These traditional roadbed deformation monitoring instruments can only achieve point monitoring, and have the disadvantages of large monitoring errors, complex equipment installation, and low automation level. They cannot accurately achieve global monitoring of large-area roadbed projects. Fiber Bragg grating sensors have the advantages of high sensitivity, strong anti-interference ability, small size, convenient testing, large test scale, and distributed measurement. At present, fiber grating sensors have been applied to monitor long-distance deformation of roadbeds. However, due to the large deformation of roadbeds, the measurement range of fiber grating sensors is small (generally within 10,000 microstrains), making it difficult to monitor large deformation of roadbeds. In addition, optical fibers are brittle and easily damaged when laid in the roadbed. Therefore, the application of fiber grating sensors in monitoring roadbed deformation is also limited. At the same time, existing optical fiber monitoring of roadbed deformation is mostly applied alone, without considering the effective combination with the fiber grid network structure, resulting in low monitoring efficiency and difficulty in achieving global network monitoring. Summary of the invention

[0004] The technical problem to be solved by the utility model is to provide an intelligent fiber grid with monitoring function and effectively expand the measuring range of the sensor in view of the deficiencies in the above-mentioned prior art.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0006] An intelligent fiber grating based on fiber grating sensing comprises a warp grating branch and a weft grating branch, wherein the warp grating branch and the weft grating branch are staggered to form a grating, wherein flexible fiber grating sensors are arranged in the warp grating branch and the weft grating branch, wherein two or more optical fibers with different elongations are arranged in the flexible fiber grating sensors in the warp grating branch and the weft grating branch, respectively, wherein the optical fibers are anchored to a sensing matrix at an anchoring position to form a monitoring point, wherein the optical fibers with different elongations are straightened with the anchoring position as a stress point under different deformations of the grating branch, and the optical fiber with a low elongation enters a monitoring state before the optical fiber with a high elongation.

[0007] The straightening of optical fibers with different elongation under different deformation of the grid support means that for two optical fibers with one high elongation and one low elongation, the optical fiber with low elongation is straightened first and enters the monitoring state. As the grid support continues to deform, the optical fiber with high elongation also enters the straightening process. After the low elongation optical fiber is broken or loses its monitoring function, the second optical fiber is completely straightened and enters the monitoring state. When there are multiple optical fibers, they enter the monitoring state one by one as the elongation increases from low to high.

[0008] Optical fibers with different elongations include optical fibers with different prestresses and optical fibers with different bending degrees.

[0009] Two optical fibers with different elongation rates are respectively arranged in the flexible fiber grating sensors in the longitudinal grid branches and the latitudinal grid branches, one is a straight optical fiber and the other is a curved optical fiber.

[0010] The flexible fiber grating sensor comprises a silicone mold, and the two or more optical fibers with different elongation rates are packaged in the silicone mold.

[0011] The silicone mold includes a silicone upper mold and a silicone lower mold. A straight optical fiber groove and a curved optical fiber groove are opened in the silicone lower mold. A silicone partition is arranged between the straight optical fiber groove and the curved optical fiber groove. A silicone sheet forming a curved inner groove is attached to the curved optical fiber groove. The optical fiber is placed in the corresponding optical fiber groove.

[0012] The utility model discloses a preparation method of an intelligent fiber grating based on fiber optic Bragg grating sensing, wherein the intelligent fiber grating is formed by weaving warp yarn bundles and weft yarn bundles along the warp direction through warp knitting wires, wherein the warp yarn bundles constitute warp grating branches, and the weft yarn bundles constitute weft grating branches; and the flexible fiber optic Bragg grating sensor is compositely warp-knitted in the warp yarn bundles and the weft yarn bundles.

[0013] The warp grid branches are arranged above the weft grid branches, and braiding wires are attached along the warp grid branches to weave the yarn bundles in the warp grid branches and weave at the intersection of the warp and weft grid branches to prevent deformation of the mesh formed by the warp and weft grid branches.

[0014] Each of the warp grid branches or weft grid branches contains multiple yarn bundles, among which those containing optical fiber sensors are smart yarn bundles, and those without optical fiber sensors are ordinary yarn bundles. The smart yarn bundles are arranged in the middle position of the grid branch, and the ordinary yarn bundles are arranged on both sides of the grid branch.

[0015] The flexible fiber grating sensor is wound on a braiding shaft and woven together with the yarn into an intelligent yarn bundle. The formed intelligent yarn bundle includes the fiber grating sensor located in the center and fibers that wrap and protect the sensor.

[0016] The fiber warp knitted grid after weaving needs to be impregnated with an impregnation liquid, and the impregnation liquid type is styrene-butadiene latex, styrene-acrylic emulsion, epoxy resin, vinyl resin or phenolic resin.

[0017] The intelligent fiber grid based on fiber Bragg grating sensing proposed in the utility model makes full use of the characteristics of fiber Bragg grating distributed sensing, flexibly encapsulates the fiber sensor, and encapsulates at least two optical fibers with different elongation rates, which not only solves the problem of easy brittle fracture of optical fibers, but also expands the strain measurement range of optical fibers, making it applicable to large deformation monitoring in roadbeds. At the same time, the composite weaving of flexible optical fiber sensors and fiber warp knitted grids innovatively proposes intelligent grids for monitoring and enhancing integrated design in roadbeds, which can further realize global network monitoring in roadbeds, which is crucial for full-life monitoring in the construction and operation stages of highways.

[0018] The intelligent fiber warp knitted grid based on fiber grating sensing proposed in the utility model uses fibers including but not limited to carbon fibers, glass fibers, basalt fibers and other fibers.

[0019] The intelligent fiber warp knitted grid based on fiber grating sensing proposed by the utility model can design the number of yarn bundles in the warp and weft grid branches according to specific force requirements, and the size of the grid mesh can also be adjusted according to specific requirements.

[0020] The intelligent fiber warp knitted grid based on fiber grating sensing proposed in the utility model includes but is not limited to being applied to roadbed reinforcement, and can also be applied to the reinforcement of road surfaces, embankments, slopes, etc. to improve the stress stability.

[0021] The intelligent fiber grid based on fiber grating sensing of the utility model has the following advantages:

[0022] 1) Fiber Bragg grating sensors have high sensitivity, strong anti-interference ability, and good durability, and can realize distributed monitoring.

[0023] 2) When the fiber grating sensor is packaged, there are straight optical fibers and pre-bent optical fibers with different elongation rates, which enter the working state in sequence. The straight optical fiber enters the working state first, and after the straight optical fiber is damaged, the pre-bent optical fiber enters the working state. This can effectively expand the measuring range of the sensor and realize monitoring under large deformation conditions.

[0024] 3) The fiber grid is made of cross-woven longitudinal and transverse yarn bundles, with a clear force direction. It can be laid according to the specific load direction in application, which can effectively improve the strength and stability of structures such as roadbeds and reduce uneven settlement.

[0025] 4) The composite weaving of flexible optical fiber sensors and fiber grids realizes monitoring, enhanced integrated design and global network monitoring, which is of great significance to the long-life design of road projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the intelligent fiber grid based on fiber grating sensing of the utility model;

[0027] Figure 2 It is a schematic diagram of a flexible fiber Bragg grating sensor used in the intelligent fiber grid based on fiber Bragg grating sensing of the utility model;

[0028] Figure 3 The internal structure diagram of the flexible fiber grating sensor used in the intelligent fiber grid based on fiber grating sensing of the utility model is seen by opening the silicone upper mold;

[0029] Figure 4 Schematic diagram of the intelligent yarn bundle structure in the intelligent fiber grid based on fiber grating sensing of the utility model, wherein Figure 4-1 It is a schematic diagram of the longitudinal section structure. Figure 4-2 It is a schematic diagram of the cross-sectional structure;

[0030] Figure 5 Schematic diagram of the common yarn bundle structure in the intelligent fiber grid based on fiber grating sensing of the utility model, wherein Figure 5-1 It is a schematic diagram of the longitudinal section structure. Figure 5-2 It is a schematic diagram of the cross-sectional structure;

[0031] Figure 6 It is a schematic diagram of the nodes at the intersection of the warp grid branches and the weft grid branches in the intelligent fiber grid based on fiber grating sensing of the utility model.

[0032] Among them: 1 is a warp smart yarn bundle; 2 is a warp common yarn bundle; 3 is a weft smart yarn bundle; 4 is a weft common yarn bundle; 5 is a warp knitted wire; 6 is a conductor; 7 is a grid node; 8 is a weft grid branch; 9 is a warp grid branch; 10 is a straight optical fiber; 11 is a pre-bent optical fiber; 12 is a silicone upper mold; 13 is a silicone lower mold; 14 is a flexible fiber grating sensor; 15 is a fiber; 16 is a silicone partition; 17 is a curved silicone sheet. Implementation

[0033] Combine the following Figure 1 to Figure 6 The specific implementation methods of the utility model are described in detail. It should be understood that these implementation methods are only used to illustrate the utility model and are not used to limit the scope of the utility model. After reading the utility model, the various equivalent forms of modifications to the utility model by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0034] The present embodiment provides an intelligent fiber grating based on fiber grating sensing, including latitudinal grating branches 8 and longitudinal grating branches 9, wherein the latitudinal grating branches 8 and the longitudinal grating branches 9 are staggered to form a grating, and flexible fiber grating sensors are arranged in the latitudinal grating branches 8 and the longitudinal grating branches 9, and two or more optical fibers with different elongation rates are respectively arranged in the flexible fiber grating sensors in the latitudinal grating branches 8 and the longitudinal grating branches 9.

[0035] In one embodiment, optical fibers with different elongation rates can be composed of optical fibers with different prestresses or optical fibers with different bending degrees or a combination of linear optical fibers with different prestresses and pre-bent optical fibers with different bending degrees. The pre-bent optical fiber can include one or more groups according to the deformation measurement range, and the pre-bending amount can be determined according to the length of the gauge segment and the deformation measurement range. Specifically, when the gauge segment is L, the limit value of the measurement range of the linear optical fiber sensor is M microstrains. If the measurement range needs to be extended to 2M microstrains, the pre-bending amount of the bending sensor needs to be set to M×L.

[0036] In one embodiment, two optical fibers with different elongations are respectively arranged in the flexible fiber grating sensors in the longitudinal grid branches and the latitudinal grid branches, one is a straight optical fiber 10 (which may or may not be prestressed), and the other is a pre-bent optical fiber 11.

[0037] In one embodiment, the flexible fiber grating sensor comprises a silicone mold, and two or more optical fibers with different elongation rates are encapsulated in the silicone mold.

[0038] In one embodiment, the silicone mold includes a silicone upper mold 12 and a silicone lower mold 13. The inner surfaces of the silicone upper mold 12 and / or the silicone lower mold 13 are grooved according to the shapes of straight and pre-bent optical fibers so that the optical fibers are encapsulated in the silicone mold.

[0039] In one embodiment, the slots of the silicone mold include straight slots and curved slots, wherein the curved slot is a slot in which a silicone sheet 17 is attached to form a curved inner slot, and a silicone partition 16 is provided between the straight slot and the curved slot. The straight optical fiber is in a straightened state, and begins to deform when the load is initially applied; the curved optical fiber is pasted along the inner slot wall of the curved silicone sheet using a flexible glue, and the flexible glue has low strength and low viscosity, and can maintain viscosity for a long time, and is used for temporary fixation of the sensor and the curved inner slot. Under load, the optical fiber can be separated from the curved inner slot wall and gradually straightened. When the optical fiber is completely straightened, the curved optical fiber begins to monitor. The degree of bending of the curved optical fiber is determined according to the deformation extreme value of the straight optical fiber, so as to ensure that when the straight optical fiber fails, the curved optical fiber has been straightened and is in a monitoring state.

[0040] The utility model discloses a method for preparing an intelligent fiber grid based on fiber grating sensing. The intelligent fiber grid is formed by weaving warp yarn bundles and weft yarn bundles along the warp direction with warp knitting wires. The warp yarn bundles form the warp grid branches, and the weft yarn bundles form the weft grid branches. Flexible fiber grating sensors are compositely warp-knitted in the warp yarn bundles and the weft yarn bundles. The weft yarn bundle grid branches are interwoven to form a weaving node 7. The warp grid branches 9 are arranged above the weft grid branches 8. Braiding wires 5 are attached along the warp grid branches to weave the yarn bundles in the warp grid branches and weave at the intersection of the warp and weft grid branches to prevent deformation of the mesh formed by the warp and weft grid branches. At the same time, the yarn bundles in the warp and weft yarn bundle branches can be kept straight, which can effectively protect the fibers and fiber optic sensors in the yarn bundles.

[0041] Each warp grid branch or weft grid branch contains multiple yarn bundles, among which the ones containing optical fiber sensors are smart yarn bundles, and the ones without optical fiber sensors are ordinary yarn bundles. The smart yarn bundles (warp smart yarn bundle 1 and weft smart yarn bundle 3) are arranged in the middle position of the grid branch, and the ordinary yarn bundles (warp ordinary yarn bundle 2, weft ordinary yarn bundle 4) are arranged on both sides of the grid branch.

[0042] The flexible fiber grating sensor is wound on a braiding shaft and woven together with the yarn into a smart yarn bundle. The formed smart yarn bundle includes a fiber grating sensor located in the center and fibers that wrap and protect the sensor.

[0043] The fiber warp knitted grille after weaving needs to be impregnated with an impregnation liquid. The impregnation liquid type is styrene-butadiene latex, styrene-acrylic emulsion, epoxy resin, vinyl resin or phenolic resin, etc. The amount of the impregnation liquid needs to be determined according to the type of impregnation liquid used, and the impregnation liquid needs to be able to protect the surface of the grille.

[0044] The flexible fiber grating sensor is woven with the fibers along the warp and weft directions respectively to form a warp smart yarn bundle 1 and a weft smart yarn bundle 3 , and the ends of each smart yarn bundle are connected by a wire 6 .

[0045] The warp and weft grid branches in the warp knitted grid are composed of warp and weft yarn bundles. The warp grid branch 9 is arranged above the weft grid branch 8. A weaving wire 5 is attached along the warp grid branch, which can weave the yarn bundles in the warp grid branch and weave at the intersection of the warp and weft grid branches to prevent deformation of the mesh formed by the warp and weft grid branches.

[0046] The flexible fiber grating sensor 14 can be wound on a braiding shaft and woven together with the yarn into a warp smart yarn bundle 1 and a weft smart yarn bundle 3. The formed smart yarn bundle includes a fiber grating sensor 14 located in the center and fibers 15 that wrap and protect the sensor.

Claims

1. An intelligent fiber grid based on fiber Bragg grating sensing, comprising a warp grid branch and a weft grid branch, the warp grid branch and the weft grid branch are staggered to form a grid, and flexible fiber Bragg grating sensors are arranged in the warp grid branch and the weft grid branch, characterized in that: Two or more optical fibers with different elongations are respectively arranged in the flexible fiber grating sensors in the longitudinal grid branches and the latitudinal grid branches. The optical fibers are anchored to the sensing matrix at the anchoring position to form monitoring points. The optical fibers with different elongations are straightened with the anchoring position as the stress point under different deformations of the grid branches, and the optical fiber with low elongation enters the monitoring state before the optical fiber with high elongation.

2. The intelligent fiber grid based on fiber grating sensing according to claim 1 is characterized in that: Optical fibers with different elongation rates include straight optical fibers with different prestresses and pre-bent optical fibers with different bending degrees.

3. The intelligent fiber grid based on fiber grating sensing according to claim 1, characterized in that: Two optical fibers with different elongation rates are respectively arranged in the flexible fiber grating sensors in the longitudinal grid branches and the latitudinal grid branches, one is a straight optical fiber and the other is a pre-bent optical fiber.

4. The intelligent fiber grid based on fiber grating sensing according to claim 2 or 3, characterized in that: The flexible fiber grating sensor includes a silicone mold, in which two or more optical fibers with different elongation rates are encapsulated, and the linear optical fiber is in a straightened state and begins to deform when the load is initially applied; the pre-bent optical fiber is adhered along the curved inner groove wall with a flexible adhesive, and under load, the optical fiber separates from the curved inner groove wall and is gradually straightened.

5. The intelligent fiber grid based on fiber grating sensing according to claim 4 is characterized in that: The silicone mold includes a silicone upper mold and a silicone lower mold. The optical fiber groove is designed according to the specific shapes of optical fibers with different elongation rates, including a straight groove and a curved groove. A silicone sheet forming a curved inner groove is attached to the curved optical fiber groove. A silicone partition is provided between the straight groove and the curved groove. Optical fibers with different elongation rates are placed in the corresponding optical fiber grooves.

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