A road defect detection device

Abstract

This invention provides a road defect detection device, belonging to the field of road engineering monitoring technology. The device includes a distributed fiber optic acoustic wave sensing system, a sensing fiber optic network, and a data processing unit. The sensing fiber optic network adopts a multi-layered, longitudinally linear arrangement, with its density gradually decreasing from top to bottom. The sensing fiber optic network is connected to the distributed fiber optic acoustic wave sensing system. The data processing unit establishes bidirectional communication with the distributed fiber optic acoustic wave sensing system via Ethernet. This invention solves the problem that existing road defect detection devices based on DAS technology cannot simultaneously meet the monitoring needs of road structures at different depths.

Description

Technical Field

[0001] This utility model relates to the field of road engineering monitoring technology, and in particular to a road defect detection device. Background Technology

[0002] As a major urban transportation infrastructure, the safety of roads directly impacts traffic flow and the safety of people's lives and property. In recent years, frequent occurrences of road collapses, cracks, and subsidence both domestically and internationally have drawn widespread attention. How to effectively monitor and prevent potential road safety defects has become a research hotspot. Improving the perception, early warning, and emergency response capabilities for highway disaster risks, and researching new, efficient, and comprehensive real-time monitoring technologies for the structural health of transportation infrastructure, are crucial for comprehensively improving the monitoring and early warning capabilities for high-risk highway disaster sections.

[0003] Distributed optical fiber acoustic sensing (DAS) technology has advantages such as distributed monitoring, high sensitivity, and fast response speed, and has broad application prospects in road defect detection. However, existing DAS-based road defect detection devices typically only have one optical fiber deployed within the road, resulting in a relatively simple fiber deployment method. This makes it difficult to meet the monitoring needs of road structures at different depths and to comprehensively and accurately detect road defects at different depths.

[0004] In view of this, the present invention provides a new solution to the above problems. Utility Model Content

[0005] The purpose of this invention is to provide a road defect detection device that solves the problem that existing road defect detection devices based on DAS technology cannot meet the monitoring needs of road structures at different depths.

[0006] The above-mentioned technical objective of this utility model is achieved through the following technical solution.

[0007] A road defect detection device, comprising:

[0008] Distributed fiber optic acoustic wave sensing system;

[0009] The sensing fiber optic network adopts a multi-layered vertical linear arrangement, with the density gradually decreasing from top to bottom. The sensing fiber optic network is connected to the distributed fiber optic acoustic wave sensing system.

[0010] The data processing unit establishes bidirectional communication with the distributed fiber optic acoustic wave sensing system via Ethernet.

[0011] A further preferred embodiment is that the sensing fiber optic network comprises a surface fiber optic group, a middle fiber optic group, and a deep fiber optic group;

[0012] The surface fiber optic group is located at a depth of 5-10cm in the road surface layer. The surface fiber optic group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with a spacing of 0.5-1m between adjacent optical fibers.

[0013] The middle layer optical fiber group is located at a depth of 20-40cm in the road base layer. The middle layer optical fiber group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, and the spacing between adjacent optical fibers is 1-1.5m.

[0014] The deep optical fiber group is located at a depth of 50-100cm in the road base layer. The deep optical fiber group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with a spacing of 1.5-2m between adjacent optical fibers.

[0015] A further preferred embodiment is that a monitoring well is provided at the edge of the road, and a trunk optical cable is installed inside the monitoring well. The surface fiber group, the middle fiber group, and the deep fiber group are all connected to the trunk optical cable, and the trunk optical cable is connected to the distributed optical fiber acoustic wave sensing system.

[0016] A further preferred embodiment is that the optical fibers in the surface fiber group, the middle fiber group, and the deep fiber group all include a fiber core and a protective structure disposed on the outer surface of the fiber core.

[0017] A further preferred embodiment is that the protective structure includes a buffer layer, a load-bearing layer, and an outer sheath arranged sequentially from the inside out, with the buffer layer covering the outer surface of the optical fiber.

[0018] A further preferred embodiment is that the buffer layer of the protective structure in the surface fiber group is silicone rubber;

[0019] The buffer layer of the protective structure in the middle fiber optic group is foamed polyethylene;

[0020] The buffer layer of the protective structure in the deep fiber optic assembly is silicone gel.

[0021] A further preferred embodiment is that the load-bearing layer of the protective structure in the surface fiber optic group is a stainless steel wire spiral winding layer;

[0022] The load-bearing layer of the protective structure in the middle fiber optic group is an aramid 1414 fiber woven mesh.

[0023] The load-bearing layer of the protective structure in the deep optical fiber group is a galvanized steel strip gap wrapping layer.

[0024] A further preferred embodiment is that the pitch of the stainless steel wire spiral winding layer is 1.5±0.2mm, and the wire diameter is 0.2±0.02mm;

[0025] The aramid 1414 fiber woven mesh has a weaving density of 60±2 bundles / inch and a single filament tensile strength ≥3000N;

[0026] The thickness of the galvanized steel strip in the gap wrapping layer is 0.5±0.05mm, and the wrapping gap is ≤0.5mm.

[0027] A further preferred embodiment is that the outer sheath of the protective structure in the surface fiber group is a polyurethane sleeve;

[0028] The outer sheath of the protective structure in the middle layer optical fiber group is a polyethylene sheath;

[0029] The outer sheath of the protective structure in the deep optical fiber group is a polyvinyl chloride sheath.

[0030] A further preferred embodiment is that the outer sheath has a thickness of 1.5±0.2mm and a silicon carbide wear-resistant coating with a Mohs hardness ≥9.

[0031] The thickness of the middle outer sheath is 2.0±0.2mm, and the outer surface has a nano-titanium dioxide anti-fouling layer with a contact angle >150°;

[0032] The outer sheath of the deep layer has a thickness of 2.5±0.2mm, and the inner side is composited with a surface resistivity of ≤0.1Ω / m. 2 The copper foil shielding layer.

[0033] In summary, this utility model has the following beneficial effects:

[0034] This utility model's road defect detection device includes a distributed fiber optic acoustic wave sensing system, a sensing fiber optic network, and a data processing unit. The sensing fiber optic network adopts a multi-layered, longitudinally linear arrangement, with its density gradually decreasing from top to bottom. The sensing fiber optic network is connected to the distributed fiber optic acoustic wave sensing system; the data processing unit establishes bidirectional communication with the distributed fiber optic acoustic wave sensing system via Ethernet.

[0035] This invention employs a multi-layered optical fiber array, enabling monitoring of the road structure at different depths. It can promptly detect surface defects such as cracks and potholes, monitor loosening and deformation of the subgrade, and detect potential hazards like settlement and cavities in deeper foundations. This multi-layered arrangement achieves comprehensive monitoring of the road from surface to depth, solving the problem that existing devices cannot simultaneously meet the monitoring needs at different depths. Furthermore, the optical fibers in each layer are arranged in a straight line along the longitudinal direction of the road, reducing construction difficulty. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the overall structure of a road defect detection device according to a preferred embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the layout of a sensor fiber optic network according to a preferred embodiment of the present invention.

[0039] Figure 3 This is a connection architecture diagram of the fiber optic group and the main optical cable in a preferred embodiment of the present invention.

[0040] Figure 4 This is a schematic diagram of an optical fiber structure according to a preferred embodiment of the present invention.

[0041] In the diagram, 1. Distributed fiber optic acoustic sensing system; 2. Sensing fiber optic network; 21. Surface fiber group; 22. Middle fiber group; 23. Deep fiber group; 241. Fiber core; 2421. Buffer layer; 2422. Load-bearing layer; 2423. Outer sheath; 3. Data processing unit; 4. Monitoring well; 51. Surface layer; 52. Base layer; 6. Trunk optical cable; 7. Trunk optical cable distribution frame. Detailed Implementation

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] It should be noted that the Distributed Fiber Optic Acoustic Sensing System (DAS system) is an advanced technology for monitoring acoustic signals based on the light scattering effect. Its core principle utilizes the Rayleigh scattering phenomenon generated when a laser beam propagates through an optical fiber. When a laser pulse propagates through the fiber, it interacts with tiny regions of non-uniform refractive index within the fiber core 241, generating Rayleigh scattered light. When the fiber is subjected to external acoustic vibrations, its length and refractive index undergo minute changes, leading to corresponding alterations in the intensity, frequency, and phase of the Rayleigh scattered light. By emitting laser pulses and receiving and analyzing the returned scattered light signals, the DAS system can convert these changes in optical signals into corresponding acoustic vibration information, thereby achieving real-time monitoring of points along the fiber.

[0044] Specifically, the system determines the location of vibration by measuring the time difference of scattered light at different locations, and judges the intensity and characteristics of vibration by analyzing the changes in the intensity and frequency of the scattered light, thereby identifying the event or structural change causing the vibration. The road defect detection device provided by this utility model is designed based on the DAS system.

[0045] Generally speaking, the core components of a DAS system mainly include the following:

[0046] Laser emission module: This module is the "signal source" of the DAS system, responsible for generating highly stable, narrow-linewidth laser pulses. The quality of the laser pulse directly affects the monitoring accuracy and sensitivity of the system. Erbium-doped fiber lasers are typically used, with output wavelengths generally in the 1550nm communication band to reduce losses during fiber optic transmission.

[0047] The optical receiving and processing module consists of a photodetector, an amplifier, and a signal processing circuit. The photodetector receives the Rayleigh scattered light signal returned from the optical fiber and converts it into an electrical signal. The amplifier amplifies the weak electrical signal for subsequent analysis. The signal processing circuit performs filtering, demodulation, and other operations on the amplified electrical signal to extract useful vibration information.

[0048] Fiber optic couplers and circulators: Fiber optic couplers are used to send laser pulses generated by the laser emitting module into the sensing fiber and guide the scattered light signal returned from the sensing fiber to the optical receiving module. Circulators isolate the emitted and received light, preventing strong emitted light from interfering with weak received light signals and ensuring accurate signal reception.

[0049] Example: A road defect detection device, such as Figure 1 , 2 As shown, the system includes a distributed fiber optic acoustic wave sensing system 1, a sensing fiber optic network 2, and a data processing unit 3. The sensing fiber optic network 2 is connected to the distributed fiber optic acoustic wave sensing system 1, and the data processing unit 3 establishes bidirectional communication with the distributed fiber optic acoustic wave sensing system 1 via Ethernet. The sensing fiber optic network 2 is used to sense acoustic wave signals at different depths of the road. The sensing fiber optic network 2 adopts a multi-layered longitudinal linear arrangement, and the density gradually decreases from top to bottom.

[0050] Preferably, the distributed fiber optic acoustic wave sensing system 1, used to generate probe light pulses and demodulate the backscattered Rayleigh signal, is the core component of the entire detection device. It is responsible for transmitting 1550nm probe light pulses to the sensing fiber optic network 2 and receiving the scattered light signal returned from the fiber optic cable, converting it into a digital signal. It mainly consists of a laser emitter, a photodetector, and a signal processor. During installation, it should be placed in a well-ventilated, dry, and dust-free equipment room to ensure a stable operating environment.

[0051] Data processing unit 3 establishes bidirectional communication with distributed fiber optic acoustic wave sensing system 1 via Ethernet. It processes, analyzes, and stores data transmitted from distributed fiber optic acoustic wave sensing system 1 and can send control commands to it. Data processing unit 3 is located in the monitoring center or related control room and connected to distributed fiber optic acoustic wave sensing system 1 via Ethernet to ensure smooth and stable communication. Data processing unit 3 should be equipped with corresponding software systems for data reception, analysis, storage, and display. Data processing unit 3 can analyze, process, and store acoustic wave signals collected by distributed fiber optic acoustic wave sensing system 1. Through feature extraction and pattern recognition of the signals, it can determine whether road defects exist, as well as the location, type, and severity of the defects, and issue timely warnings, providing timely and accurate data support for road maintenance and management.

[0052] Reference Figure 1-3 The sensing fiber optic network 2 includes a surface fiber optic group 21, a middle fiber optic group 22, and a deep fiber optic group 23, which are arranged sequentially from top to bottom in the road. The road includes a surface layer 51, a base layer 52, and a subbase layer, arranged sequentially from top to bottom. The surface fiber optic group 21 is located at a depth of 5-10 cm in the road surface layer 51 and includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with an adjacent fiber spacing of 0.5-1 m. The middle fiber optic group 22 is located at a depth of 20-40 cm in the road base layer 52 and includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with an adjacent fiber spacing of 1-1.5 m. The deep fiber optic group 23 is located at a depth of 50-100 cm in the road base layer 52 and includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with an adjacent fiber spacing of 1.5-2 m.

[0053] In the above technical solution, the sensor fiber optic network 2 adopts a layered structure with varying densities, designed based on the stress characteristics and defect probability of each road layer. The road surface layer 51 directly bears vehicle loads, resulting in a higher probability of defects. Therefore, the surface fiber optic group 21 is placed at a shallower depth with smaller fiber spacing to improve the detection accuracy of surface defects. As the depth increases, the load on the road base layer 52 gradually decreases, and the probability of defects is relatively lower. Therefore, the spacing of the middle and deep fiber optic groups 23 gradually increases, ensuring detection effectiveness while reducing device costs. Furthermore, the fibers in each fiber optic group are arranged in a straight line along the longitudinal direction of the road, reducing construction difficulty.

[0054] Preferably, a monitoring well 4 is provided at the edge of the road, and a trunk optical cable 6 is installed inside the monitoring well 4. The surface fiber group 21, the middle fiber group 22, and the deep fiber group 23 are all connected to the trunk optical cable 6. One end of the trunk optical cable 6 is connected to the distributed fiber optic acoustic wave sensing system 1. The setting of the monitoring well 4 facilitates the layout and maintenance of the trunk optical cable 6, and also protects the trunk optical cable 6 from damage by the external environment.

[0055] More preferably, a trunk optical cable distribution frame 7 is installed inside the monitoring well 4. Optical fibers from each layer are connected to the trunk optical cable distribution frame 7 via mechanical quick connectors, and then converged to the trunk optical cable 6. The trunk optical cable 6 is optically connected to the distributed optical fiber acoustic wave sensing system 1. The trunk optical cable 6 is a 24-core single-mode optical cable (GYTA-24B1). This connection method centralizes the signal transmission path of the optical fiber, reduces interference during signal transmission, and improves the stability of signal transmission.

[0056] Location of monitoring well 4: Monitoring well 4 shall be excavated at regular intervals (e.g., 500m-1km) along the edge of the road. The depth of monitoring well 4 shall be determined according to the road structure and groundwater level, and shall generally be lower than the depth of deep fiber optic group 23.

[0057] Reference Figure 2 , 4 The optical fibers in the surface fiber group 21, the middle fiber group 22, and the deep fiber group 23 all include a fiber core 241 and a protective structure disposed on the outer surface of the fiber core 241. The protective structure includes a buffer layer 2421, a load-bearing layer 2422, and an outer sheath 2423 arranged sequentially from the inside out, with the buffer layer 2421 covering the outer surface of the fiber core 241.

[0058] Preferably, in the surface fiber optic assembly 21, the buffer layer 2421 is silicone rubber with a Shore hardness of 40A and a thickness of 0.3±0.05mm, the load-bearing layer 2422 is a spiral wound layer of 304 stainless steel wire with a pitch of 1.5±0.2mm and a wire diameter of 0.2±0.02mm, and the outer sheath 2423 is a polyurethane sleeve made of polyurethane material with a thickness of 1.5±0.2mm and a silicon carbide wear-resistant coating with a Mohs hardness ≥9 on the surface.

[0059] Preferably, in the middle fiber group 22, the buffer layer 2421 has a density of 0.4 ± 0.05 g / cm³. 3 The foamed polyethylene is 1.0±0.1mm thick. The load-bearing layer 2422 is an aramid 1414 fiber woven mesh with a weaving density of 60±2 bundles / inch and a single filament tensile strength ≥3000N. The outer sheath 2423 is a polyethylene sheath made of high-density polyethylene material with a thickness of 2.0±0.2mm and an outer surface with a nano titanium dioxide antifouling layer with a contact angle >150°.

[0060] Preferably, in the deep fiber optic assembly 23, the buffer layer 2421 is a silica gel with a viscosity of 5000±500 cP and a filling rate of ≥99%; the load-bearing layer 2422 is a galvanized steel strip with a gap wrapping layer, the steel strip thickness is 0.5±0.05 mm, and the wrapping gap is ≤0.5 mm; the outer sheath 2423 is a polyvinyl chloride sheath made of corrosion-resistant PVC material with a thickness of 2.5±0.2 mm, and the inner side is composited with a surface resistivity of ≤0.1 Ω / m. 2 The copper foil shielding layer.

[0061] In the above technical solution, the outer surface of the fiber core 241 is provided with a protective structure consisting of a buffer layer 2421, a load-bearing layer 2422, and an outer sheath 2423. Regarding the buffer layer 2421, the surface layer is made of silicone rubber, which has good elasticity and weather resistance, and can buffer the vibration and impact of vehicle traffic on the surface optical fiber; the middle layer uses foamed polyethylene, which is lightweight and has certain heat insulation properties, reducing the impact of temperature changes in the base layer 52 on the optical fiber; the deep layer uses silicone gel, which has excellent sealing and chemical corrosion resistance, protecting the deep optical fiber from erosion by groundwater, etc. Regarding the load-bearing layer 2422, the surface layer of stainless steel wire spiral winding provides high tensile strength and wear resistance, resisting physical damage from surface construction and vehicle loads; the middle layer of aramid 1414 fiber woven mesh has high strength and lightweight characteristics, and can withstand the tensile force generated by the deformation of the base layer 52; the deep layer of galvanized steel strip gap wrapping has good compressive strength and corrosion resistance, adapting to the complex soil environment in deep layers. Regarding the outer sheath 2423, the surface polyurethane sheath possesses properties such as wear resistance, oil resistance, and aging resistance; the middle polyethylene sheath exhibits good chemical stability and excellent insulation performance; and the deep polyvinyl chloride sheath boasts high mechanical strength and strong corrosion resistance. Furthermore, the special coatings on each layer of the outer sheath 2423 further enhance the protective effect. For example, the surface silicon carbide wear-resistant coating improves the wear resistance of the surface optical fiber, the middle nano-titanium dioxide anti-fouling layer reduces contamination of the optical fiber by dust and oil, and the deep copper foil shielding layer reduces the impact of electromagnetic interference on the signal transmission of the deep optical fiber. These protective structures effectively improve the service life and stability of the optical fiber, ensuring the long-term reliable operation of monitoring work.

[0062] The working process and principle of this utility model are as follows: The laser emitter of the DAS system continuously emits high-stability, narrow-linewidth laser pulses (typically with a wavelength of 1550nm) into the main optical cable 6. The pulses are rapidly transmitted through the main optical cable 6 to the surface, middle, and deep fiber optic groups 23. When the laser pulses propagate in the optical fiber, Rayleigh scattering occurs with the tiny refractive index inhomogeneous regions within the fiber core 241, forming a receivable scattered light signal. After the laser pulses reach each layer of the fiber optic group, they are uniformly distributed along the longitudinal direction of the fiber, making each fiber segment a "distributed sensor." When defects appear in the road, defects in different structural layers will generate specific vibration signals:

[0063] Surface defects (such as cracks and potholes): Vehicle rolling or temperature changes can cause micro-vibrations in the surface asphalt concrete, with frequencies typically ranging from 50 to 500 Hz. The vibration amplitude decreases as the defect depth increases.

[0064] Mid-layer defects (such as loose base layer 52): Displacement or moisture penetration of base layer 52 material can cause low-frequency vibration (10-50Hz), which has a long duration and is periodic.

[0065] Deep defects (such as foundation settlement and underground cavities): Structural changes in deep soil or foundations can generate infrasound level vibrations (0.1-10Hz), which have a wide propagation range but attenuate slowly.

[0066] Each fiber optic layer is tightly coupled to the road material through a protective structure. Vibrations generated by defects are transmitted to the optical fibers through the solid, causing minute deformations (micrometer-level) in the fibers. This deformation changes the refractive index and length of the fiber, altering the intensity, phase, and frequency of Rayleigh scattered light—the greater the vibration intensity, the more pronounced the modulation amplitude of the scattered light.

[0067] The photodetector receives the scattered light signals returned from each layer of optical fiber in real time, converts the optical signals into electrical signals, and the distributed optical fiber acoustic wave sensing system 1 performs preliminary processing on the converted electrical signals before transmitting the data to the data processing unit 3 via Ethernet. The data processing unit 3 performs in-depth analysis and processing of the received electrical signals. Through time-domain and frequency-domain analysis of the signals, characteristic parameters of the acoustic wave signals, such as amplitude, frequency, and phase, are extracted. These characteristic parameters are compared with the acoustic wave signal characteristics of a preset normal road structure to determine if any anomalies exist. Based on the time difference and intensity differences of the signals received by different optical fiber groups, combined with the location information of each optical fiber (known depth and longitudinal position of each fiber in the road), the data processing unit 3 can determine the approximate location (depth and longitudinal range) of the defect. Simultaneously, based on the characteristic patterns of the abnormal signals, the type of defect, such as cracks, settlement, and cavities, is identified, and the severity of the defect is assessed. When the data processing unit 3 determines the existence of a road defect, it will issue corresponding warning signals, such as audible and visual alarms and SMS notifications, and display information such as the location, type, and severity of the defect on the display interface, allowing staff to understand the road conditions in a timely manner and take appropriate measures.

[0068] In summary, this invention employs a multi-layered optical fiber array with surface, middle, and deep layers, enabling monitoring of road structures at different depths. The surface fiber array 21, located at a depth of 5-10 cm in the road surface layer 51, can promptly detect defects such as cracks and potholes in the road surface. The middle fiber array 22, located at a depth of 20-40 cm in the road base layer 52, can monitor issues such as loosening and deformation of the base layer 52. The deep fiber array 23, located at a depth of 50-100 cm in the road base layer 52, can detect potential hazards such as settlement and cavities in the deep foundation. This multi-layered arrangement achieves comprehensive monitoring of the road from the surface to its depths, solving the problem that existing devices cannot simultaneously meet the monitoring needs at different depths.

[0069] The above are merely preferred embodiments of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are within its protection scope. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within its protection scope.

Claims

1. A road defect detection device, characterized in that: include: Distributed fiber optic acoustic wave sensing system; The sensing fiber optic network adopts a multi-layered vertical linear arrangement, with the density gradually decreasing from top to bottom. The sensing fiber optic network is connected to the distributed fiber optic acoustic wave sensing system. The data processing unit establishes bidirectional communication with the distributed fiber optic acoustic wave sensing system via Ethernet.

2. A road defect detection device according to claim 1, characterized in that: The sensing fiber optic network includes a surface fiber group, a middle fiber group, and a deep fiber group; The surface fiber optic group is located at a depth of 5-10cm in the road surface layer. The surface fiber optic group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with a spacing of 0.5-1m between adjacent optical fibers. The middle layer optical fiber group is located at a depth of 20-40cm in the road base layer. The middle layer optical fiber group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, and the spacing between adjacent optical fibers is 1-1.5m. The deep optical fiber group is located at a depth of 50-100cm in the road base layer. The deep optical fiber group includes multiple optical fibers arranged in a straight line along the longitudinal direction of the road, with a spacing of 1.5-2m between adjacent optical fibers.

3. A road defect detection apparatus according to claim 2, wherein: Monitoring wells are installed along the edge of the road, and a trunk optical cable is installed inside the monitoring wells. The surface fiber group, the middle fiber group, and the deep fiber group are all connected to the trunk optical cable, which is connected to the distributed optical fiber acoustic wave sensing system.

4. A road defect detection apparatus according to claim 2, wherein: The optical fibers in the surface fiber group, middle fiber group, and deep fiber group all include a fiber core and a protective structure disposed on the outer surface of the fiber core.

5. A road defect detection apparatus according to claim 4, wherein: The protective structure includes a buffer layer, a load-bearing layer, and an outer sheath arranged sequentially from the inside out, with the buffer layer covering the outer surface of the fiber core.

6. A road defect detection apparatus according to claim 5, wherein: The buffer layer of the protective structure in the surface fiber optic group is silicone rubber; The buffer layer of the protective structure in the middle fiber optic group is foamed polyethylene; The buffer layer of the protective structure in the deep fiber optic assembly is silicone gel.

7. A road defect detection apparatus according to claim 5, wherein: The load-bearing layer of the protective structure in the surface fiber optic group is a stainless steel wire spiral winding layer. The load-bearing layer of the protective structure in the middle fiber optic group is an aramid 1414 fiber woven mesh. The load-bearing layer of the protective structure in the deep optical fiber group is a galvanized steel strip gap wrapping layer.

8. A road defect detection apparatus according to claim 7, wherein: The pitch of the stainless steel wire spiral winding layer is 1.5±0.2mm, and the wire diameter is 0.2±0.02mm; The aramid 1414 fiber woven mesh has a weaving density of 60±2 bundles / inch and a single filament tensile strength ≥3000N; The thickness of the galvanized steel strip in the gap wrapping layer is 0.5±0.05mm, and the wrapping gap is ≤0.5mm.

9. A road defect detection device according to claim 5, characterized in that: The outer sheath of the protective structure in the surface fiber optic group is a polyurethane sleeve; The outer sheath of the protective structure in the middle layer optical fiber group is a polyethylene sheath; The outer sheath of the protective structure in the deep optical fiber group is a polyvinyl chloride sheath.

10. The road defect detection apparatus according to claim 5, characterized by: The outer sheath has a thickness of 1.5±0.2mm and a silicon carbide wear-resistant coating with a Mohs hardness ≥9 on its surface. The thickness of the middle outer sheath is 2.0±0.2mm, and the outer surface has a nano-titanium dioxide anti-fouling layer with a contact angle >150°; The deep outer sheath has a thickness of 2.5±0.2mm, and the inner side is compounded with a copper foil shielding layer with a surface resistance of ≤0.1Ω / m 2 .

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