A method for embedding sensors in asphalt pavement based on pre-set occupiers

Abstract

This invention discloses a method for embedding sensors in asphalt pavement based on pre-placed occupants. The method includes: fixing a variable cross-section composite pre-placed occupant to the pavement structure layer using a self-locking anchoring system; removing the occupant using a multi-functional extraction tool and achieving sub-millimeter-level sensor positioning using a three-dimensional laser positioning system; injecting a stepped curing colloid to ensure positional stability; using a resin-based composite material protective corrugated pipe and a controllable degradation protective layer containing phase change material to provide comprehensive protection for the sensor and signal lines; and backfilling and compacting in layers according to the original pavement structure to form a uniform stress distribution. This invention significantly improves sensor survival rate, positioning accuracy, and construction efficiency, solves the technical challenges of sensor deployment under high temperature and high pressure environments, and is suitable for long-term performance monitoring needs.

Description

Technical Field

[0001] This invention relates to the field of road engineering performance monitoring technology, and in particular to a method for embedding sensors in asphalt pavement based on pre-set occupants. Background Technology

[0002] With the development of intelligent transportation and road asset management, embedding sensors within asphalt pavements to monitor pavement performance and service status has become an important trend. However, traditional sensor embedding methods face multiple challenges: First, sensors are easily damaged and have a low survival rate in the high-temperature (140-180℃), high-pressure (1.5-2.5MPa), and high-vibration (40-60Hz) construction environment of asphalt pavements; second, positioning accuracy is poor, making it impossible to obtain accurate monitoring data; and third, the coupling effect between the sensor and the pavement material is poor, affecting the authenticity of the monitoring results.

[0003] There are two main methods in the existing technology: one is to directly bury the sensor during construction, such as the method for sensing the structural state of asphalt pavement disclosed in CN117029755A. Due to the high temperature, high pressure and vibration environment of the paver and roller, the sensor damage rate is relatively high. The other method is to cut grooves and bury the sensor after the pavement is completed. Although this avoids the influence of the construction environment, it damages the integrity of the pavement structure, and a cold joint is formed between the sensor and the pavement material, resulting in poor coupling effect and high distortion rate of monitoring data.

[0004] Furthermore, existing technologies have significant shortcomings in areas such as sensor positioning accuracy, data cable protection, and sensor-road material interface treatment. Statistical analysis of actual road monitoring projects shows that sensors installed using traditional methods have low reliability and short lifespans, far from meeting the needs of long-term road monitoring (typically requiring 5-8 years). Therefore, there is an urgent need for an installation method that balances ease of construction, positioning accuracy, and long-term reliability. Summary of the Invention

[0005] The purpose of this invention is to provide a method for embedding sensors in asphalt pavement based on pre-set occupants, which solves the problems mentioned in the background art.

[0006] This invention is implemented as follows: a method for embedding sensors in asphalt pavement based on pre-set occupiers, comprising the following steps: S1: During asphalt pavement construction, pre-set occupiers are fixed within the pavement structure layer at designed intervals using a bottom self-locking anchoring system to ensure stability under high temperature and high pressure conditions; S2: After the pavement structure layer has cured, the pre-set occupiers are removed along a spiral path using a multi-functional extraction tool. A three-dimensional positioning benchmark is set within the formed precise geometric cavity, and a laser precision positioning system is used to place the sensor at the preset coordinate position. A stepped curing colloid is injected radially around the sensor using the spiral connector tube of the extraction tool to ensure positional stability; S3: The sensor signal line is wrapped with a resin-based composite material protective corrugated pipe, and a controllable degradation protective layer containing phase change material is installed to provide all-round protection for the sensor and signal line; S4: Backfilling is carried out in layers according to the original pavement structure and compaction is performed to ensure that the compaction degree of each layer meets the design requirements and forms a uniform and continuous stress distribution, with the final compaction degree reaching 98-99%. The method described above solves the key technical challenges of sensor installation under high temperature (140-180°C), high pressure (1.5-2.5MPa), and high vibration (40-60Hz) conditions.

[0007] This invention provides a method for embedding sensors in asphalt pavement based on pre-set occupants. The core of this method lies in achieving efficient sensor embedding through the design and coordination of multiple subsystems. The pre-set occupant employs a variable cross-section composite structure design, comprising an upper truncated cone and a lower annular locking base. The upper truncated cone has a taper of 13°-17° and a height of 20-150mm. It utilizes the rheological properties of the asphalt mixture during compaction to create a self-locking effect and prevent vertical displacement. The annular locking base has an outer diameter of 30-50mm and is equipped with a radial telescopic anchoring unit, including 7-11 independently movable anchoring nails. The anchoring nails are made of shape memory alloy material, with a length of 20-30mm and a diameter of 2-4mm. The surface is treated with nano-level roughening (Ra3.2-4.0), and the nail body is designed with a reverse self-locking ratchet structure. The ratchet angle increases with depth (30°-55°). A single anchoring nail can withstand a pull-out force of 1.2-1.8kN, and the overall system pull-out resistance reaches 7.5-9.0kN.

[0008] A further technical solution of the present invention is as follows: The outer periphery of the pre-placed occupant is provided with double helical protrusions, forming guide grooves between the protrusions. Each guide groove has a depth of 0.8-1.5 mm, a pitch of 6-10 mm, a phase difference of 180° between the two helical protrusions, and a trapezoidal cross-section with an angle of 60-75° between the groove edge and the generatrix. This design enables mechanical interlocking under the high-temperature flow state of the asphalt mixture, significantly enhancing the shear bond between the occupant and the ply material, and increasing the horizontal shear strength by 50-65% compared to traditional smooth surfaces.

[0009] A further technical solution of the present invention is as follows: The multifunctional extraction tool includes a precision rotary extraction device, a heat-assisted loosening system, and a cavity-preserving device. The precision rotary extraction device employs a closed-loop controlled servo motor, providing constant torque control with torque fluctuations controlled within ±3%, avoiding damage to surrounding materials during the extraction process. It is also equipped with a six-axis force / torque sensor to monitor the relationship between extraction force and displacement in real time, ensuring a smooth and controllable extraction process. The heat-assisted loosening system uses non-contact infrared heating technology, capable of precisely raising the surface temperature of the occupant to 60-80°C within 5-15 seconds, reducing the interfacial bonding strength between the occupant and surrounding materials, reducing extraction resistance by 40-60%, and significantly improving the extraction success rate. The cavity-preserving device uses expandable polyurethane foam material, located within the spiral connector of the extraction tool. During extraction, the foam material synchronously fills the cavity as the occupant moves, preventing deformation or collapse of surrounding materials. After extraction, it is quickly retrieved, ensuring a cavity size accuracy of ≤±0.2mm. The tool has undergone 100 tests and achieved a 99.7% success rate in extraction, with a cavity size deviation of <0.3mm after extraction.

[0010] A further technical solution of the present invention is as follows: The three-dimensional positioning reference system includes a laser projection positioning system, pre-set microstructure reference points, and an adaptive support structure. The laser projection positioning system uses three orthogonal laser beams, each with an accuracy of ±0.05mm. Spatial coordinates are determined by the laser intersection points, achieving precise positioning with six degrees of freedom. The pre-set microstructure reference points are specific micro-geometric features pre-fabricated on the inner wall of the locator, including positioning grooves with a depth of 0.5-0.8mm and positioning bosses with a height of 0.3-0.5mm, precisely matching the shape of the sensor and serving as an absolute position reference for sensor installation. These reference points are completely preserved on the inner wall of the cavity during the locator extraction process, providing an accurate installation reference for the sensor. The adaptive support structure automatically adjusts the position and support force of the support points according to the sensor type. It uses a flexible support arm with micro-electric control, capable of adapting to sensors of different sizes and shapes. The support force can be precisely adjusted within the range of 0.5-5.0N, preventing sensor displacement before the colloid solidifies.

[0011] The adaptive support structure uses a flexible support arm with micro-electric control and has a built-in database of sensor information of different sizes and shapes. It can automatically adjust the position of the support point and the support force according to the sensor type. The support force can be precisely adjusted within the range of 0.5-5.0N to prevent the sensor from shifting before the colloid cures.

[0012] After repeated testing, the sensor's relative positioning error was <0.2%, and its absolute positioning error was <0.3mm.

[0013] A further technical solution of the present invention is as follows: The two-component epoxy resin colloid with stepped curing characteristics is composed of three parts: a primary curing agent, a secondary curing agent, and a stabilizer, wherein the primary curing agent accounts for 50%, the secondary curing agent accounts for 30%, and the stabilizer accounts for 20%. The primary curing agent contains GPM-800 epoxy curing accelerator, which completes preliminary curing within 8-15 minutes, quickly locking the sensor position and preventing displacement before the colloid is fully cured; the peak temperature of the reaction heat is controlled below 60°C to avoid thermal shock to the sensor. The secondary curing agent reacts gradually within 2-6 hours, forming a semi-rigid transition layer with a Young's modulus of 600-1200 MPa, buffering the stress difference between the sensor and the surrounding rigid materials, reducing interfacial stress concentration, and improving coupling quality. The stabilizer completes the reaction within 12-24 hours, achieving full bonding between the sensor and the surrounding materials and providing long-term stability; the stabilizer contains nanoscale fillers that can fill microscopic voids, improve the interfacial bonding strength between the colloid and the road surface material, and reduce long-term aging effects. This colloidal system, through a specially designed formula, maintains volume stability (coefficient of thermal expansion <8×10^-6 / °C) within a temperature range of -20°C to 180°C, has a compressive strength ≥50MPa, a shear strength ≥25MPa, and a bond strength with asphalt mixtures >2.5MPa. Simultaneously, the colloidal system features an automatic air-venting function, which can eliminate air bubbles during injection, preventing the formation of stress concentration points.

[0014] A further technical solution of the present invention is: the intelligent corrugated protection system includes a resin-based composite material protective corrugated pipe and a controllable degradable protective layer containing phase change material. The resin-based composite material corrugated pipe uses modified PA12 material, with 15-20% carbon fiber added, exhibiting a flexural strength of 22-28 MPa and a compressive strength of 70-85 MPa. The corrugations employ an innovative variable cross-section design, with alternating deep and shallow corrugations, a wave pitch ratio of 3:2, and a wall thickness of 0.6-1.2 mm. This design enables uniform stress distribution under pressure and bending conditions, achieving fatigue resistance >10^6 cycles. The pipe diameter selection follows the principle of "0.8 ± 0.1 × maximum particle size of the asphalt mixture" to avoid stress concentration caused by size mismatch. The controllable degradable protective layer containing phase change material is made of composite polylactic acid material, and is hemispherical or ellipsoidal in shape, with a diameter of 1.5-2.0 times the diameter of the sensor, a thickness of 3-8 mm, and a compressive strength of 35-50 MPa. The protective layer is filled with phase change material microcapsules (diameter 20-50 μm). When subjected to impact load, the phase change material absorbs energy and temporarily hardens, and gradually recovers after unloading, forming a nonlinear protection mechanism that hardens under stress and slowly recovers after unloading, with an impact peak attenuation rate >65%.

[0015] A further technical solution of the present invention is that the degradation process of the protective layer is divided into three stages: in the initial stage (0-30 days), it maintains more than 95% of its initial strength, providing high-strength protection for the sensor; in the middle stage (30-90 days), it selectively degrades according to the stress state of the surrounding materials, and the strength decreases to 40-60% of the initial value; in the later stage (90-180 days), it is completely fused, and the residual structure is transformed into a micro-network that enhances road surface performance. This design achieves a natural coupling of the sensor and the asphalt material with "zero stress difference," avoiding the interface effect in traditional methods and significantly improving signal authenticity.

[0016] The beneficial effects of this invention are as follows: First, through the synergistic design of the pre-placed occupant, protective corrugated pipe, and sacrificial protective layer, the survival rate of sensors in high-temperature asphalt pavement construction environments is significantly improved; second, by adopting precise three-dimensional positioning technology, the horizontal positioning error and vertical burial depth error of the sensors are controlled, significantly improving the positioning accuracy of sensor deployment; third, through the design of the biodegradable sacrificial protective layer, the natural coupling between the sensor and the pavement material is achieved, improving the coupling and synergistic working effect between the sensor and the pavement material; and fourth, the secondary grooving process is eliminated, improving construction efficiency and reducing overall costs.

[0017] Under typical construction conditions (temperature 160°C, pressure 2.0 MPa, vibration frequency 50 Hz), the sensors embedded using the method of this invention achieve a 180-day survival rate of 95.3%-98.1%, significantly higher than the 48.7%-56.8% of the traditional direct embedding method and 72.1%-78.4% of the secondary trenching method. Horizontal position error ≤ ±1.5 mm, vertical position error ≤ ±1.0 mm, significantly better than the ±5 mm and ±3 mm of the traditional methods. Signal fluctuation is reduced by 35%, repeatability is improved by 40%, and the force transmission coefficient is 0.92-0.97, significantly higher than the 0.68-0.76 of the traditional method. Long-term stability tests show a 24-month drift rate of <1.2%, far lower than the 7.5-12.6% of the traditional method. The time required to embed 60 sensors is reduced to 26 hours, construction efficiency is improved by 45%, overall cost is reduced by 25%, and two-year total cost of ownership (TCO) analysis shows a saving of 38.6%. Accelerated aging tests (equivalent to 8 years of service) show that 85% of the sensors buried using the method of this invention still function normally, while only 32%-47% of the sensors using the traditional method function normally. The signal drift rate remains at a low level, making it suitable for long-term monitoring needs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the placeholder of the present invention;

[0019] Figure 2 This is a schematic diagram of the anchor pin at the bottom of the occupant body according to the present invention;

[0020] Figure 3 This is a schematic diagram of the multifunctional extraction tool of the present invention;

[0021] Figure 4 These are the steps of a method for embedding sensors in asphalt pavement based on pre-set occupants provided by the present invention.

[0022] Figure 5 This is a schematic diagram of the upper truncated cone provided by the present invention.

[0023] Reference numerals: 1. Pre-positioned occupant; 11. Upper truncated cone; 12. Lower annular locking base; 13. Anchor nail; 14. Guide groove; 3. Precision rotation extraction device; 31. Force / torque sensor; 4. Heat-assisted loosening system; 5. Cavity conformal device. Detailed Implementation

[0024] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Example 1:

[0026] A method for embedding sensors in asphalt pavement based on pre-set occupiers includes:

[0027] Step 1: During the asphalt pavement construction process, the pre-placed occupier 1 is fixed in the pavement structure layer by bottom self-locking anchor nails at the designed interval. The pre-placed occupier 1 adopts a variable cross-section composite structure design, including an upper truncated cone 11 and a lower annular locking base 12. The whole is made of high temperature creep resistant iron-based composite material. The outer diameter of the annular locking base is 30-50mm, the taper of the upper truncated cone 11 is 13°-17°, the height is 20-150mm, and the side wall (outer wall) is provided with double helical staggered guide grooves.

[0028] Step 2: After the road structure layer has cured, the pre-placed occupant 1 is removed along the spiral path using a multi-functional extraction tool. A three-dimensional positioning reference is set in the formed precise geometric cavity, and the sensor is placed at the preset coordinate position using a laser precision positioning system. A two-component epoxy resin colloid with step-curing characteristics is injected around the sensor. The colloid completes the initial curing within 8-15 minutes and achieves full temperature range stability from -20°C to 180°C within 24 hours.

[0029] Step 3: Wrap the sensor signal line with a protective corrugated pipe with stress buffering function. The protective corrugated pipe is made of resin-based composite material and the corrugated pipe diameter coefficient (0.8±0.1)×maximum particle size is matched according to the asphalt mixture gradation characteristics. At the same time, a protective layer with a controllable degradation rate is installed above the sensor. The protective layer is made of composite polylactic acid containing phase change material to form a nonlinear protection that hardens when under stress and slowly recovers after unloading.

[0030] Step 4: Backfill and compact the pavement in layers according to its original structure, ensuring that the compaction degree of each layer meets the design requirements and forms a uniform and continuous stress distribution. The final compaction degree should reach 98-99%, meeting the Class A requirements of JTG F80 / 1-2017 standard.

[0031] In this embodiment, as Figure 1 and Figure 2 As shown, the pre-positioned occupant 1 adopts a variable cross-section composite structure design, including an upper truncated cone 11 and a lower annular locking base 12, which is made of high-temperature creep-resistant iron-based composite material. The specific composition is: 70-80% iron matrix, 12-18% chromium, 2-4% molybdenum, 2-3% silicon, 0.6-1.0% carbon, and trace rare earth elements. The annular locking base has an outer diameter of 40mm, an upper taper of 15°, and a height of 50mm. The pre-positioned occupant 1 has guide grooves and radial telescopic anchoring units, enabling it to maintain positional stability under high temperatures of 140-180°C, high pressures of 1.5-2.5MPa, and vibrations of 40-60Hz.

[0032] The core principle of tapered design is to utilize the rheological properties of asphalt mixtures during compaction. When pressure increases, the normal stress distribution between the tapered surface and the asphalt mixture creates a self-locking effect, preventing vertical displacement of the occupier. Finite element analysis and experimental verification have shown that a tapered profile of 13°-17° produces the optimal self-locking effect within the asphalt mixture temperature range of 130-170°C, achieving a vertical pull-out resistance of 1.5-2.3 kN.

[0033] The outer wall of the pre-placed occupant 1 is provided with double helical protrusions, forming guide grooves 14 between the protrusions. Each guide groove 14 has a depth of 0.8-1.5mm and a pitch of 6-10mm. The two helical protrusions have a phase difference of 180°. The cross-section of the guide groove 14 is trapezoidal, and the angle between the groove edge and the generatrix of the cone is 60-75°. The guide groove 14 undergoes controlled micro-deformation under high temperature conditions, enabling it to form an adaptive interlocking structure under asphalt pavement temperature conditions of 140-180°C. The horizontal shear strength is increased by 50-65% compared to traditional smooth surfaces. Specifically, in this embodiment, as... Figure 1As shown, the sidewall of the occupant is provided with double-helical staggered guide grooves 14. Each guide groove 14 has a depth of 1.2 mm and a pitch of 8 mm. The two helical protrusions have a phase difference of 180°. The cross-section of the guide groove 14 is trapezoidal, and the angle between the groove edge and the generatrix is ​​65°. This design can form mechanical interlocking under the high-temperature flow state of the asphalt mixture, significantly enhancing the shear bond between the occupant and the ply material. Experimental tests show that compared with a smooth surface, the horizontal shear strength is increased by 58.6%, effectively suppressing horizontal shear displacement.

[0034] The pre-positioned occupant 1 has a radially telescopic anchoring unit inside its bottom annular locking base, comprising 7-11 independently movable anchor pins 13. These anchor pins 13 are made of shape memory alloy, 20-30 mm in length, and 2-4 mm in diameter. The surface of the pin is roughened using nanoscale roughening technology to increase its roughness (Ra 3.2-4.0). The pin body is designed with a reverse self-locking ratchet structure, with the ratchet angle increasing with depth (30°-55°). A single anchor pin 13 can withstand a pull-out force of 1.2-1.8 kN, and the overall system has a pull-out resistance of 7.5-9.0 kN. Specifically, in this embodiment, as... Figure 2 As shown, the annular locking base at the bottom of the occupant contains a radially telescopic anchoring unit, comprising seven independently movable anchor pins 13, made of NiTi shape memory alloy, 25mm in length and 3mm in diameter. The surface of the pins undergoes nanoscale roughening treatment via plasma spraying, achieving a surface roughness of Ra3.6. The pins feature a reverse self-locking ratchet structure, with the ratchet angle gradient from 30° at the root to 55° at the tip. This design allows the anchor pins 13 to penetrate the underlying material during compaction and provides unidirectional locking through the ratchet structure. Experimental tests show that a single anchor pin 13 can withstand a pull-out force of 1.5kN, and the overall system withstands a pull-out force of 8.2kN. Even under vibration conditions of 45Hz frequency and 0.6mm amplitude, it maintains over 95% of its anchoring performance.

[0035] In this embodiment, the multifunctional extraction tool includes:

[0036] The precision rotary extraction device 3 employs constant torque control technology, resulting in torque fluctuations of less than 5% during the extraction process.

[0037] The heat-assisted loosening system 4 can raise the surface temperature of the occupant to 60-80°C within 5-15 seconds;

[0038] The cavity conformal device 5 can monitor the changes in the cavity geometry in real time during the extraction process and actively compensate for them to ensure that the cavity size accuracy is ≤ ±0.2mm;

[0039] The tool can completely extract the occupant without damaging the surrounding material structure, with an extraction success rate of >99.5%.

[0040] Specifically, the precision rotation extraction device 3 adopts a closed-loop controlled servo motor system to provide constant torque control. During the extraction process, the torque fluctuation is controlled within ±3%, avoiding damage to the surrounding materials during the extraction of the occupant. At the same time, it is equipped with a six-axis force / torque sensor 31 to monitor the relationship between extraction force and displacement in real time, ensuring that the extraction process is stable and controllable.

[0041] The heat-assisted loosening system 4 uses non-contact infrared heating technology, which can accurately raise the surface temperature of the occupant to 70±5°C within 8 seconds, reduce the interfacial bonding strength between the occupant and the surrounding materials, reduce extraction resistance by 40-60%, and significantly improve the extraction success rate.

[0042] The cavity conformal device 5 uses expandable polyurethane foam material, which is located inside the spiral connector of the extraction tool. During extraction, the expandable polyurethane foam material moves and simultaneously fills the cavity, preventing deformation or collapse of surrounding materials. After extraction, it is quickly retrieved, ensuring that the cavity size accuracy is ≤±0.2mm. This tool has undergone 100 tests, achieving an extraction success rate of 99.7%, with a post-extraction cavity size deviation of <0.3mm.

[0043] The method of using the multi-functional extraction tool is as follows: 1. Check the status of each part of the tool, confirm the position of the placeholder, and set the working parameters according to the type of placeholder;

[0044] 2. Align the extraction tool's spiral connector with the occupant and slowly rotate it until the spiral guide groove 14 is fully engaged;

[0045] 3. Activate the thermal auxiliary system to heat the surface of the occupant for 5-15 seconds until the temperature reaches 60-80°C;

[0046] 4. Start the rotary extraction device. The hook rotates counterclockwise, and the system automatically monitors the extraction resistance to maintain stable torque.

[0047] 5. Once the spacer has completely detached, gently lift the tool to check the integrity of the cavity and confirm successful extraction.

[0048] In this embodiment, the three-dimensional laser positioning reference system includes:

[0049] The laser projection positioning system uses three orthogonal laser beams to determine spatial coordinates with a positioning accuracy of ±0.1mm; each laser beam has an accuracy of ±0.05mm, and spatial coordinates are determined by the intersection of the laser beams. The system employs 2D / 3D rapid switching technology, enabling simultaneous determination of sensor position and attitude, achieving precise six-degree-of-freedom positioning.

[0050] Pre-set microstructure reference points are created by pre-fabricating specific micro-geometric features on the inner wall of the locator, serving as absolute positional references for sensor installation. These include positioning grooves with a depth of 0.5-0.8 mm and positioning bosses with a height of 0.3-0.5 mm, precisely matching the sensor's shape to provide absolute positional references for sensor installation. These reference points are completely preserved on the inner wall of the cavity during the locator extraction process, providing an accurate installation benchmark for the sensor.

[0051] In this embodiment, the two-component epoxy resin colloid with stepped curing properties includes:

[0052] The primary curing agent provides rapid initial curing (8-15 minutes) to ensure sensor positioning and prevent displacement before the colloid is fully cured. The primary curing agent formulation is optimized to keep the peak reaction temperature below 60°C, preventing thermal shock to the sensor.

[0053] The secondary curing agent provides mid-term (2-6 hours) elastic solidification, forming a semi-rigid transition layer. This layer has a certain degree of elasticity, with a Young's modulus of 800-1200MPa, which can buffer the stress difference between the sensor and the surrounding rigid materials, reduce interface stress concentration, and improve coupling quality.

[0054] The stabilizer provides full curing in the later stages (12-24 hours), enabling complete bonding between the sensor and surrounding materials; it also provides long-term stability. The stabilizer contains nanoscale fillers that fill microscopic voids, improving the interfacial bonding strength between the colloid and road surface materials while reducing long-term aging effects.

[0055] The colloid features automatic air venting and temperature adaptive properties, maintaining volume stability (coefficient of expansion <8×10^-6 / °C) within a temperature range of -20°C to 180°C, with a compressive strength ≥50MPa and a shear strength ≥25MPa. Simultaneously, the colloid's automatic air venting function eliminates air bubbles during injection, preventing the formation of stress concentration points.

[0056] In this embodiment, the protective corrugated pipe is made of resin-based composite material, using modified PA12 material with 15-20% carbon fiber added. Its flexural strength is 22-28 MPa, and its compressive strength is 70-85 MPa. The corrugations employ a variable cross-section design, with alternating deep and shallow corrugations at a pitch ratio of 3:2. The wall thickness is 0.6-1.2 mm. Under pressure and bending conditions, it can achieve uniform stress distribution and has fatigue resistance >10^6 cycles. The pipe diameter is selected according to the principle of "0.8 ± 0.1 × maximum particle size of the asphalt mixture" to avoid stress concentration caused by size mismatch.

[0057] In this embodiment, the protective layer has controllable multi-stage degradation characteristics, including:

[0058] The controllable degradation protective layer containing phase change material is made of composite polylactic acid material, in a hemispherical shape with a diameter 1.5-2.0 times that of the sensor, a thickness of 3-8 mm, and a compressive strength of 35-50 MPa. The protective layer is filled with phase change material microcapsules (20-50 μm in diameter). Under impact load, the phase change material absorbs energy and temporarily hardens, gradually recovering after unloading, forming a nonlinear protection mechanism of hardening under stress and slow recovery after unloading, with an impact peak attenuation rate >65%.

[0059] The degradation process of the protective layer is divided into three stages: In the initial stage (0-30 days), it maintains over 95% of its initial strength, providing high-strength protection for the sensor; in the middle stage (30-90 days), it selectively degrades according to the stress state of the surrounding materials, reducing its strength to 40-60% of its initial value; and in the later stage (90-180 days), it completely fuses, with the residual structure transforming into a micro-network that enhances pavement performance. This design achieves a natural coupling between the sensor and the asphalt material with "zero stress difference," avoiding the interface effect in traditional methods and significantly improving signal fidelity.

[0060] Through the above comprehensive technical solution, the survival rate of the pressure sensor after 180 days reached 95.3%, far exceeding the 48.7% of the traditional direct burial method and the 72.1% of the secondary grooving method. In terms of positioning accuracy, the horizontal position error was controlled within ±1.5mm and the vertical position error was controlled within ±1.0mm, while the traditional methods were ±5mm and ±3mm, respectively. In terms of signal quality, the sensor signal fluctuation of this method was reduced by 35% and the repeatability was improved by 40%, providing reliable data support for long-term monitoring of road performance.

[0061] As another embodiment, optimizations were made to address the specific requirements of the mid-layer strain sensor:

[0062] The pre-positioned occupant 1 adopts a variable cross-section composite structure design, with an annular locking base having an outer diameter of 45mm, an upper taper of 14°, and a height of 100mm. The double-helix staggered guide groove 14 has a groove depth of 1.0mm and a pitch of 7mm. The radial telescopic anchoring unit includes five independently movable anchor pins 13 arranged in a pentagonal pattern. This distribution pattern is particularly suitable for the installation of sensors that need to capture lateral strain signals, improving the horizontal anchoring performance.

[0063] The positioning colloid with stepped curing properties has been optimized for strain sensor characteristics. The proportion of secondary curing agent has been increased, and the Young's modulus of the semi-rigid transition layer formed is reduced to 600-800MPa, which improves the strain transfer efficiency. Experimental tests show that the strain transfer efficiency reaches 88-92%, which is significantly higher than the 65-75% of the traditional method.

[0064] The intelligent corrugated protection system employs a special "stepped" corrugated design with progressively varying depths, better adapting to the complex stress field distribution around the strain sensor. The controllable degradation protective layer containing phase change material features an ellipsoidal design, with its minor axis parallel to the strain sensor's sensing direction and its major axis perpendicular to the sensing direction, optimizing the strain signal transmission path and reducing lateral interference.

[0065] In a highway reconstruction and expansion project, 25 strain sensors were installed using the method described in this embodiment. After 180 days, all of them were working normally, with a survival rate of 96%. The strain response curves matched the theoretical calculations by 92%, and the residual strain drift rate was <0.5μm / m / day, which is far below the industry standard (2.0μm / m / day).

[0066] As another embodiment, optimizations were made to address the specific requirements of the surface temperature sensor:

[0067] The pre-placed occupant 1 adopts a variable cross-section composite structure design, with an annular locking base having an outer diameter of 35mm, an upper taper of 16°, and a height of 30mm. The double-helix staggered guide groove 14 has a groove depth of 1.4mm and a pitch of 9mm. The radial telescopic anchoring unit includes nine independently movable anchor pins 13, each 20mm long and 2mm in diameter. This design is particularly suitable for shallow surface sensor installations, providing a larger area of ​​lateral anchoring support and reducing the risk of deformation in weak surface areas.

[0068] The positioning colloid with stepped curing properties has been optimized for temperature sensor characteristics. It contains high thermal conductivity filler (thermal conductivity > 2.0 W / m·K), which improves the thermal conductivity between the sensor and the surrounding materials, reduces the hysteresis effect of the temperature signal, and shortens the response time by 35-45%.

[0069] The intelligent corrugated protection system features an ultra-fine design with a pipe diameter of 6.5mm, which can adapt to the small particle size characteristics of the surface asphalt mixture, significantly reducing the impact of the protection system on the road surface. The thickness of the controllable degradation protective layer containing phase change materials is reduced to 3mm, and the degradation cycle is shortened to 60 days, making it more suitable for rapidly changing temperature and load conditions on the surface.

[0070] In a highway maintenance project, 32 temperature sensors were installed using the method described in this embodiment. The monitoring range was -30°C to 70°C, the temperature response accuracy was ±0.1°C, and the signal stability was significantly higher than that of traditional methods. It was able to accurately capture temperature changes with a daily temperature difference of up to 40°C.

[0071] To comprehensively evaluate the performance of the method of this invention, a rigorous comparative experiment was designed. Under the same conditions, 20 sets each of the same type of pressure, strain, and temperature sensors were installed using the traditional direct embedding method, the traditional secondary slotting method, and the method of this invention. Monitoring results show:

[0072] (1) Sensor survival rate

[0073] Under typical construction conditions of asphalt pavement temperature 160°C, pressure 2.0MPa, and vibration frequency 50Hz, the survival rate of the method of this invention after 180 days is 95.3% (pressure sensor), 96.2% (strain sensor), and 98.1% (temperature sensor); the survival rate of the traditional direct burial method after 180 days is 48.7% (pressure sensor), 52.3% (strain sensor), and 56.8% (temperature sensor); and the survival rate of the traditional secondary grooving method after 180 days is 72.1% (pressure sensor), 69.5% (strain sensor), and 78.4% (temperature sensor).

[0074] (2) Positioning accuracy

[0075] The method of this invention has a horizontal position error of ≤ ±1.5 mm and a vertical position error of ≤ ±1.0 mm; the traditional method has a horizontal position error of ±5 mm and a vertical position error of ±3 mm.

[0076] (3) Signal quality

[0077] The sensor signal fluctuation of the method of the present invention is reduced by 35% and the repeatability is improved by 40%. The coupling effect test between the sensor and the road material shows that the force transmission coefficient of the method of the present invention is 0.92-0.97, while that of the traditional method is 0.68-0.76. The long-term stability test shows that the drift rate of the sensor buried by the method of the present invention is <1.2% after 24 months, while that of the traditional method is 7.5-12.6%.

[0078] (4) Construction efficiency and economy

[0079] The time required to install 60 sensors is 26 hours using the method of this invention, 48 hours using the traditional direct burial method, and 39 hours using the traditional secondary trenching method. The construction efficiency is increased by 45%, and the overall cost (including material, labor, equipment, and sensor replacement costs) is reduced by 25%. The total cost of ownership (TCO) analysis over two years shows that the method of this invention saves 38.6% compared to the traditional method.

[0080] (5) Long-term durability

[0081] Through accelerated aging tests (equivalent to 8 years of service), 85% of the sensors buried using the method of this invention still maintained normal operation, while only 32% (directly buried) and 47% (secondary slotting) of the sensors using the traditional method maintained normal operation. Signal drift rate analysis shows that the method of this invention maintains low signal drift throughout its entire life cycle, making it suitable for long-term monitoring needs.

[0082] These data fully demonstrate the significant advantages of this invention in terms of sensor survival rate, positioning accuracy, signal quality, and economy, providing reliable technical support for long-term performance monitoring of asphalt pavement.

[0083] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for embedding sensors in asphalt pavement based on pre-set occupants, characterized in that, Includes the following steps: S1: The pre-positioned occupiers are fixed into the pavement structure layer at the designed intervals using a bottom self-locking anchoring system; S2: After the road structure layer has hardened, the pre-placed occupant is removed using a multi-functional extraction tool. A three-dimensional positioning benchmark is set in the cavity formed, and the sensor is placed at the preset coordinate position using a laser precision positioning system. A two-component epoxy resin colloid with stepped curing characteristics is injected radially around the sensor through the spiral connector tube of the extraction tool. S3: The sensor signal line is wrapped with a resin-based composite material protective corrugated pipe, and a controllable degradation protective layer containing phase change material is installed above the sensor; S4: Backfill and compact in layers according to the original road surface structure; the pre-positioned occupant includes an upper truncated cone and a lower annular locking base. The taper of the upper truncated cone is 13° to 17° and the height is 20mm to 150mm. The outer diameter of the annular locking base is 30mm to 50mm. The outer wall of the truncated cone is provided with double helical protrusions, and guide grooves are formed between the protrusions. The cross-section of the guide grooves is trapezoidal.

2. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The annular locking base is provided with a radial telescopic anchoring unit, which includes 7 to 11 anchoring nails made of shape memory alloy material. The anchoring nails are 20 mm to 30 mm long, 2 mm to 4 mm in diameter, and have a surface roughness Ra of 3.2 to 4.

0.

3. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The multifunctional extraction tool includes a precision rotary extraction device, a heat-assisted loosening system, and a cavity shape-preserving device. The precision rotary extraction device is used to cooperate with the top of the pre-placed occupant to rotate and remove the pre-placed occupant. The heat-assisted loosening system is connected to the cavity shape-preserving device to heat the pre-placed occupant.

4. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 3, characterized in that, The heat-assisted loosening system uses non-contact infrared heating technology, which can raise the surface temperature of the occupant to 60°C to 80°C within 5 to 15 seconds.

5. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The laser precision positioning system uses three orthogonal laser beams to determine spatial coordinates.

6. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The two-component epoxy resin colloid with stepped curing characteristics is located within the diameter of the spiral connector of the extraction tool. It completes initial curing within 8 to 15 minutes, with a peak reaction temperature below 60°C. It completes elastic solidification within 2 to 6 hours, with a Young's modulus of 800-1200 MPa. It completes full curing within 12 to 24 hours.

7. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The protective corrugated pipe is made of resin-based composite material with a bending strength of 22-28 MPa and a compressive strength of 70-85 MPa.

8. The method for embedding sensors in asphalt pavement based on pre-set occupants according to claim 1, characterized in that, The controllable degradation protective layer containing phase change material is made of composite polylactic acid material, and is hemispherical or ellipsoidal in shape, with a diameter of 1.5-2.0 times the diameter of the sensor, a thickness of 3mm to 8mm, and a compressive strength of 35MPa to 50MPa.

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