Method for monitoring dynamic response characteristics of thin layer asphalt based on serpentine optical fiber

Abstract

The application discloses a kind of thin layer asphalt strain dynamic response characteristic monitoring methods based on serpentine optical fiber, including the following steps, preparation optical fiber matrix, etching multiple grating zones on the surface of fiber core along axial direction interval;Utilize optical fiber matrix, prepare asphalt sensor;Pour asphalt mixture in the installation groove reserved on the pavement of paving asphalt as bottom layer;Asphalt sensor is laid along S type on the surface of bottom layer, and buckle and metal strip are arranged at the center position of non-etching area of optical fiber matrix;Continue to pour asphalt mixture on the surface of asphalt sensor until that asphalt mixture completely covers sensor, complete the installation of asphalt sensor.The sensor in the application has simple structure, small volume, high precision, high sensitivity, is not affected by electromagnetic interference, reduces the influence caused by the inconsistency of the cooperative deformation of asphalt sensor and asphalt mixture, and improves the measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, specifically a method for monitoring the dynamic response characteristics of strain in thin-layer asphalt based on serpentine optical fibers. Background Technology

[0002] With my country's total highway mileage exceeding 4.77 million kilometers, and over 95% of high-grade highways using asphalt pavement, the importance of monitoring pavement construction quality and long-term service performance is increasingly prominent. In particular, thin-layer asphalt pavement, with a thickness of only 15-30 mm, is a key functional layer for improving bridge deck friction coefficient, and its structural integrity directly affects driving safety and bridge durability. Traditional electrical sensors (such as strain gauges) are limited by surface measurement and poor environmental tolerance, making it difficult to meet the full life-cycle monitoring needs of thin-layer asphalt pavement from the construction period (requiring resistance to 240°C high temperatures and rolling loads exceeding 1.5 MPa) to the service life (requiring corrosion resistance and electromagnetic interference resistance). While existing fiber optic sensors have advantages in electromagnetic interference resistance, the mismatch between the encapsulation material and the asphalt modulus leads to a cooperative deformation error exceeding 15%, severely restricting measurement accuracy. Summary of the Invention

[0003] The purpose of this invention is to provide a method for monitoring the dynamic strain response characteristics of thin-layer asphalt based on serpentine optical fiber, comprising the following steps:

[0004] S1. Prepare an optical fiber substrate, which includes a fiber core and a cladding. Multiple grating regions are etched at intervals along the axial direction on the surface of the fiber core to form a distributed grating array.

[0005] S2. Using the optical fiber substrate from step S1), prepare an asphalt sensor;

[0006] S3. Reserve multiple installation slots on the asphalt-paved road surface and pour asphalt mixture into the slots as the base layer.

[0007] S4. Lay the asphalt sensor along an S-shape on the bottom surface;

[0008] S5. A buckle is arranged at the center of the non-etched area of ​​the optical fiber substrate, and a metal strip is installed at the buckle installation position to form a mechanical interlocking structure with the asphalt mixture.

[0009] S6. Continue pouring asphalt mixture onto the surface of the asphalt sensor until the asphalt mixture completely covers the sensor, thus completing the installation of the asphalt sensor.

[0010] Furthermore, in step S1), the etching process employs femtosecond technology.

[0011] Furthermore, in step S1), the length of each grating region is equal; the spacing between adjacent grating regions is equal.

[0012] Furthermore, in step S2), the preparation of the asphalt sensor includes the following steps:

[0013] S2.1 Install a jumper head at one end of the optical fiber substrate, and connect the demodulator using the jumper head and jumper wire;

[0014] S2.2 Fix both ends of the optical fiber substrate to the displacement platform, stretch the grating area using the displacement platform, and stop stretching when the demodulator detects that the grating wavelength meets the movement requirements;

[0015] S2.3 Spray a protective solution onto the optical fiber substrate. After the protective solution has cured and formed a protective layer, remove the displacement platform.

[0016] S2.4. Use a demodulator to view the waveform of the grating area as an initial value reference.

[0017] Furthermore, in step S2.2), one end of the optical fiber substrate is fixed on the static base of the displacement platform, and the other end is fixed on the slider of the displacement platform, while stretching each grating region.

[0018] Furthermore, in step S2.2), the criterion for determining whether the grating wavelength meets the shift requirement is: when the demodulator detects a grating wavelength shift of 2nm, the stretching is stopped.

[0019] Furthermore, in step S2.3), the protective solution is a polyimide solution.

[0020] Furthermore, in step S1), the linear spacing between adjacent grating regions on the same fiber substrate is greater than 50cm.

[0021] In step S4), the minimum bending radius of the S-shape is greater than the communication standard requirement.

[0022] Furthermore, in step S5), the buckle is a centimeter-sized titanium alloy buckle, and the buckle surface is roughened by sandblasting.

[0023] Furthermore, in step S6), after the asphalt mixture completely covers the sensor, the surface of the mounting groove is leveled.

[0024] After the asphalt has fully cured, the thin layer of asphalt is rolled and the working status of the sensor is observed to determine whether the asphalt sensor is working properly. If it is working properly, the installation is complete; otherwise, the asphalt that has been laid must be removed and a new asphalt sensor must be re-embedded.

[0025] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0026] 1. The method of the present invention uses an optical sensor with advantages such as simple structure, small size, high precision, high sensitivity and immunity to electromagnetic interference, which reduces the impact of the inconsistency of the coordinated deformation between the asphalt sensor and the asphalt mixture. Through specific design and placement methods, the measurement accuracy of the asphalt sensor inside the asphalt is improved.

[0027] 2. This invention creatively employs a serpentine distributed layout design, effectively dispersing the horizontal tensile stress generated by vehicle dynamic loads through periodically bending fiber optic paths. This design effectively reduces the concentration of local stress, significantly improving the sensor's survival rate under axle load cyclic rolling.

[0028] 3. The present invention adds a micro-clamp structure at key points to increase the contact area, which effectively improves the consistency of strain transmission between the sensor and the asphalt mixture. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the fiber optic grating sensor described in this invention;

[0030] In the diagram: 1. Fiber optic cable; 2. Grating; 3. Clip; 4. Mounting slot. Detailed Implementation

[0031] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0032] Example 1:

[0033] A method for monitoring the dynamic strain response characteristics of thin-layer asphalt based on serpentine optical fiber includes the following steps:

[0034] S1. Prepare an optical fiber substrate 1, which includes a fiber core and a cladding. Multiple grating regions 2 are etched at intervals along the axial direction on the surface of the fiber core to form a distributed grating array.

[0035] S2. Using the optical fiber substrate 1 from step S1), prepare an asphalt sensor;

[0036] S3. Reserve multiple installation grooves 4 on the asphalt-paved road surface and pour asphalt mixture into the grooves as the base layer.

[0037] S4. Lay the asphalt sensor along an S-shape on the bottom surface;

[0038] S5. A buckle 3 is arranged at the center of the non-etched area of ​​the optical fiber substrate 1, and a metal strip is installed at the location where the buckle 3 is installed to form a mechanical interlocking structure with the asphalt mixture.

[0039] S6. Continue pouring asphalt mixture onto the surface of the asphalt sensor until the asphalt mixture completely covers the sensor, thus completing the installation of the asphalt sensor.

[0040] Example 2:

[0041] The main structure of this embodiment is the same as that of embodiment 1. Furthermore, in step S1), the etching process adopts femtosecond technology.

[0042] Example 3:

[0043] The main structure of this embodiment is the same as any one of embodiments 1 to 2. Further, in step S1), the length of each grating region is equal; the spacing between adjacent grating regions is equal.

[0044] Example 4:

[0045] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Further, in step S2), the preparation of the asphalt sensor includes the following steps:

[0046] S2.1 Install a jumper head at one end of the optical fiber substrate 1, and connect the demodulator using the jumper head and jumper wire;

[0047] S2.2 Fix both ends of the fiber substrate 1 to the displacement platform, stretch the grating region 2 using the displacement platform, and stop stretching when the demodulator detects that the grating wavelength meets the movement requirements. At this time, the fiber substrate 1 is suspended on the displacement platform.

[0048] S2.3 Spray a protective solution onto the outside of the optical fiber substrate 1. After the protective solution has cured and formed a protective layer, remove the displacement platform.

[0049] S2.4. Use a demodulator to view the waveform of grating area 2 as an initial value reference.

[0050] Example 5:

[0051] The main structure of this embodiment is the same as that of embodiment 4. Further, in step S2.2), one end of the optical fiber substrate 1 is fixed on the static base of the displacement platform, and the other end is fixed on the slider of the displacement platform.

[0052] Example 6:

[0053] The main structure of this embodiment is the same as any one of embodiments 4 to 5. Further, in step S2.2), the criterion for determining whether the grating wavelength meets the shift requirement is: when the demodulator detects that the grating wavelength has shifted by 2nm, the stretching is stopped.

[0054] Example 7:

[0055] The main structure of this embodiment is the same as any one of embodiments 4 to 6. Further, in step S2.3), the protective solution is a polyimide solution.

[0056] Example 8:

[0057] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, this design achieves a balance of three important functions by optimizing the serpentine configuration parameters:

[0058] 1. Avoid additional bending losses;

[0059] 2. Ensure that the strain decoupling degree between adjacent sensing units exceeds 90%;

[0060] 3. Provide sufficient deformation buffer space for rolling vibration.

[0061] To achieve the first point, in step S4), the minimum bending radius of the S-shape is greater than the communication standard requirement.

[0062] To achieve the second and third points, it is necessary to ensure that the spatial distance between the sensing units is greater than a certain range. For the second point, a path distance greater than 3cm (i.e., fiber length) is generally sufficient to ensure high decoupling. For the third point, a displacement distance of approximately 30cm is required, meaning that after bending the arrangement, the path distance is more than 50cm. Therefore, it is necessary to ensure that there is a distance of more than 50cm between the two.

[0063] Therefore, in order to achieve the second and third points, in step S1), the linear spacing between adjacent grating regions 2 on the same fiber substrate 1 is greater than 50cm.

[0064] Example 9:

[0065] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Further, in step S4), the buckle 3 is a centimeter-sized titanium alloy buckle, and the surface of the buckle 3 is roughened by sandblasting.

[0066] Example 10:

[0067] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Further, in step S6), after the asphalt mixture completely covers the sensor, the surface of the mounting groove 4 is leveled.

[0068] After the asphalt has fully cured, the thin layer of asphalt is rolled and the working status of the sensor is observed to determine whether the asphalt sensor is working properly. If it is working properly, the installation is complete; otherwise, the asphalt that has been laid must be removed and a new asphalt sensor must be re-embedded.

[0069] Example 11:

[0070] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Furthermore, the method of the present invention uses an optical sensor with advantages such as simple structure, small size, high precision, high sensitivity, and immunity to electromagnetic interference, which reduces the impact of the inconsistency in the coordinated deformation of the asphalt sensor and the asphalt mixture. Through specific design and placement methods, the measurement accuracy of the asphalt sensor inside the asphalt is improved.

[0071] I. The main measurement methods are as follows:

[0072] 1. Material preparation and pretreatment

[0073] Fiber Bragg grating: Prepare a 3m long optical fiber, and use femtosecond technology to etch a 10mm grating area every 0.5m, for a total of 5 sensing areas.

[0074] Fiber Bragg grating demodulator: Used to connect to the prepared pitch grating sensor and measure the sensor signal.

[0075] 2. Sensor fabrication

[0076] Fix the etched grating, use the optical fiber at one end of the grating to make a jumper head (not buried in the asphalt), and connect it to a fiber optic grating demodulator to check the wavelength of each grating.

[0077] Fix the gratings at both ends to the displacement stage, move the displacement stage to stretch the gratings, and stop stretching when the wavelength of each grating moves by 2nm and fix it firmly in that position.

[0078] Then, a flexible material, such as polyimide, that can withstand temperatures of at least 240°C and is not easily worn, is coated onto the optical fiber as a tight cladding layer, and left to cure. At this point, the tight cladding layer tightly wraps around the surface of the optical fiber, protecting it.

[0079] Remove the displacement stage and use high-temperature resistant adhesive to attach a metal strip of appropriate size in the middle area of ​​the grating interval to fix it, thereby increasing the contact area.

[0080] Finally, use a demodulator to view the waveform and use it as an initial value reference.

[0081] 3. Sensor installation and testing

[0082] First, select a 2m × 0.5m groove and pour asphalt mixture as the bottom layer. Then, choose a suitable location and embed the sensor in the asphalt mixture. Continue pouring asphalt mixture until the sensor is completely covered. Smooth the surface and wait 24 hours for the asphalt to fully cure. After installation, compact the thin layer of asphalt and observe the sensor's operation.

[0083] II. Advantages of the present invention

[0084] 1. Regarding structural reliability, a serpentine distributed layout design is creatively adopted, which effectively disperses the horizontal tensile stress generated by the dynamic load of the vehicle through the periodically bending fiber optic path. This design can effectively reduce the concentration of local stress, thereby improving the survival rate of the sensor under axle load cyclic rolling.

[0085] 2. Regarding interface coupling enhancement, this scheme achieves coordinated strain transfer in the sensor-asphalt system through multi-scale collaborative design:

[0086] On a macro scale, the serpentine routing increases the effective contact length within a unit monitoring area;

[0087] At the microscale, small titanium alloy buckles are arranged at intervals in the strain-sensitive area. After the surface is roughened by sandblasting, they form a mechanical interlocking structure with the asphalt.

[0088] 3. This design achieves a balance of three important functions by optimizing the serpentine configuration parameters:

[0089] ① Maintain the minimum bending radius of the optical fiber greater than the communication standard requirement to avoid additional bending loss;

[0090] ② Ensure that the strain decoupling degree between adjacent sensing units exceeds 90%;

[0091] ③ Provide sufficient deformation buffer space for rolling vibration.

[0092] This invention employs an optimized sensor array that maintains wavelength drift stability during asphalt paving and compaction, providing a reliable technical guarantee for accurately inverting the strain field distribution within the asphalt layer. These innovative designs collectively solve two major industry challenges in road engineering applications: low survival rate of fiber optic sensors and strain transmission distortion.

[0093] Example 12:

[0094] The main structure of this embodiment is the same as any one of embodiments 1 to 11. Furthermore, the sensor of the present invention is optimized through multi-scale collaborative optimization, as detailed below:

[0095] At the material level, a polyimide-metal composite packaging system is adopted, and the sensor remains stable in the range of -40 to 250°C through gradient thermal expansion coefficient design.

[0096] At the structural level, a serpentine quasi-distributed grating array was created, which, together with a centimeter-level snap-on anchoring mechanism, increased the sensor-asphalt contact area several times and reduced the interface slip rate to below 5%.

[0097] In terms of signal demodulation, a wavelength demodulation algorithm based on chirp compensation was developed, which can still achieve high strain resolution and strong spatial positioning accuracy under strong vibration environment.

[0098] Since the characteristic wavelength of a grating is proportionally amplified to its axial strain, a wavelength demodulator based on a swept-frequency light source is mainly used for data demodulation. However, this often results in uneven sweep speeds and frequency jitter, i.e., chirp. Therefore, a chirp-compensated wavelength demodulation algorithm is adopted. This algorithm uses a demodulator to measure the characteristic wavelength change of the grating and performs filtering, peak finding, and data fitting to actively correct the nonlinear components (i.e., chirp) of the frequency-time variation in the system, thereby improving the accuracy of wavelength measurement. This demodulation method can still achieve high strain resolution and strong spatial positioning accuracy even under strong vibration environments.

[0099] The implementation of this invention provides a complete solution for the quality control of thin-layer asphalt pavement, from monitoring the compaction degree during construction to early warning of damage during service life, which has important engineering value for improving the intelligent level of my country's transportation infrastructure.

[0100] Example 13:

[0101] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Furthermore, this invention addresses the problems of poor cooperative deformation ability, insufficient environmental tolerance, and low spatial resolution of traditional sensors in thin-layer asphalt strain monitoring. This invention achieves significant improvements through material innovation and structural optimization.

[0102] Specifically, a quasi-distributed sensing network is formed by using a pre-tensioned serpentine fiber grating array, and the fiber grating is wrapped with high-temperature resistant encapsulation materials (such as polyimide or metal coating) to enable it to withstand the high temperature environment above 240°C during asphalt paving; at the same time, micro-clamp structures are added at key points to increase the contact area, which effectively improves the consistency of strain transmission between the sensor and the asphalt mixture.

[0103] This design achieves synergistic deformation control by matching the elastic modulus of the encapsulation material, improves the sensor's resistance to rolling (>1.5MPa contact pressure) by dispersing mechanical stress using a serpentine structure, and realizes dynamic analysis of the spatiotemporal evolution characteristics of strain distribution in the inner layer of asphalt based on wavelength demodulation technology.

[0104] This invention has outstanding advantages such as high environmental tolerance (>200°C), high measurement accuracy, and quasi-distributed monitoring capability (single fiber multi-point measurement), providing a reliable technical means for road construction quality monitoring and long-term health monitoring of asphalt layers.

Claims

1. A method for monitoring the dynamic strain response characteristics of thin-layer asphalt based on serpentine optical fiber, characterized in that, Includes the following steps: S1. Prepare an optical fiber substrate (1). The optical fiber substrate (1) includes a fiber core and a cladding. Multiple grating regions (2) are etched at intervals along the axial direction on the surface of the fiber core to form a distributed grating array. On the same optical fiber substrate (1), the linear spacing between adjacent grating regions (2) is greater than 50 cm. S2. Using the optical fiber substrate (1) from step S1), prepare an asphalt sensor; S3. Reserve multiple installation slots (4) on the asphalt-paved road surface and pour asphalt mixture into the slots as the bottom layer; S4. Lay the asphalt sensor along an S-shape on the bottom surface; The minimum bending radius of the S-shape is greater than that required by communication standards. S5. A buckle (3) is arranged at the center of the non-etched area of ​​the optical fiber substrate (1), and a metal strip is installed at the location where the buckle (3) is installed to form a mechanical interlocking structure with the asphalt mixture. S6. Continue pouring asphalt mixture onto the surface of the asphalt sensor until the asphalt mixture completely covers the sensor, thus completing the installation of the asphalt sensor.

2. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 1, characterized in that: In step S1), the etching process employs femtosecond technology.

3. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 1, characterized in that: In step S1), the length of each grating region is equal; the spacing between adjacent grating regions is equal.

4. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 1, characterized in that: In step S2), the preparation of the asphalt sensor includes the following steps: S2.1 Install a jumper head at one end of the optical fiber substrate (1), and connect the demodulator using the jumper head and jumper wire; S2.2 Fix both ends of the fiber substrate (1) to the displacement platform, stretch the grating region (2) using the displacement platform, and stop stretching when the demodulator detects that the grating wavelength meets the movement requirements; S2.3 Spray a protective solution onto the outside of the optical fiber substrate (1). After the protective solution has solidified to form a protective layer, remove the displacement platform. S2.

4. Use a demodulator to view the waveform of the grating area (2) as an initial value reference.

5. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 4, characterized in that: In step S2.2), one end of the optical fiber substrate (1) is fixed on the static base of the displacement platform, and the other end is fixed on the slider of the displacement platform, while stretching each grating region (2).

6. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 4, characterized in that: In step S2.2), the criterion for determining whether the grating wavelength meets the shift requirement is: when the demodulator detects a grating wavelength shift of 2nm, the stretching is stopped.

7. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 4, characterized in that: In step S2.3), the protective solution is a polyimide solution.

8. The method for monitoring the dynamic response characteristics of thin-layer asphalt strain based on serpentine optical fiber according to claim 1, characterized in that: In step S5), the buckle (3) is a centimeter-sized titanium alloy buckle, and the surface of the buckle (3) is roughened by sandblasting.

9. The method for monitoring the dynamic strain response characteristics of thin-layer asphalt based on serpentine optical fiber according to claim 1, characterized in that: In step S6), after the asphalt mixture completely covers the sensor, the surface of the mounting groove (4) is leveled. After the asphalt has fully cured, the thin layer of asphalt is rolled and the working status of the sensor is observed to determine whether the asphalt sensor is working properly. If it is working properly, the installation is complete; otherwise, the asphalt that has been laid must be removed and a new asphalt sensor must be re-embedded.

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