Asphalt pavement crack repairing method based on multi-stage stress guidance

Abstract

The invention relates to the technical field of asphalt pavement repair, in particular to an asphalt pavement crack repair method based on multi-stage stress guidance, which comprises the following steps: cleaning the crack surface, removing moisture in the deep part of a crack by using a hot air spray gun, and heating to a preheating temperature; the average crack width W is extracted by collecting the three-dimensional point cloud of the crack area; outputting an outlet temperature, viscosity and component adding instruction of the repairing material according to the width W and the environment temperature; the thermoplastic polymer modified asphalt is adjusted to the determined target temperature and viscosity, and the injection action is executed according to the crack grading result; starting the sectional type infrared heating array, constructing a transverse temperature difference field, and inducing the crack wall surface to generate centripetal displacement by utilizing the thermal expansion difference of the pavement material; and the surface temperature of the repairing material is monitored, when the temperature is reduced to a compaction window threshold value, the repairing area is compacted, the physical occlusal force is enhanced, the tensile stress generated by later environment cooling is more effectively offset, and the cracking recurrence rate after repairing is remarkably reduced.

Description

Technical Field

[0001] This invention relates to the technical field of asphalt pavement repair, and specifically to a method for repairing asphalt pavement cracks based on multi-stage stress guidance. Background Technology

[0002] Asphalt pavement, as one of the main forms of highway transportation, is prone to cracking due to factors such as load, temperature changes, and aging during long-term use. If these cracks are not repaired in time, they will further expand, leading to pavement structure damage, water seepage erosion of the base layer, and even more serious pavement distress, affecting driving safety and pavement service life. Currently, asphalt pavement crack repair technology has become a key research direction in the field of highway maintenance, and various repair methods have emerged, mainly including processes such as grooving and cleaning, material filling, and surface sealing.

[0003] CN101676492A discloses a method for repairing cracks in asphalt pavement. This method includes steps such as grooving, cleaning the grooves, filling with repair material (such as asphalt mixture), and compaction. Specifically, this technology involves setting the grooving size to allow cracks to expand, then removing debris and dust from the grooves, and finally injecting and compacting the repair material to fill the cracks and smooth the pavement. This method is simple to operate and suitable for repairing medium-sized cracks. However, it relies heavily on mechanical filling and compaction, neglecting the thermal activation of the crack walls and the dynamic matching of material viscosity. This results in low interfacial bond strength, making it prone to secondary cracking under temperature cycling, and the repair efficiency is significantly affected by environmental factors.

[0004] CN1629405A discloses a method for repairing cracks in asphalt pavement. This method involves cleaning the crack surface, injecting asphalt adhesive or applying sealing tape, and then applying an asphalt restoring agent to enhance surface protection. Specific processes include removing dust, filling with asphalt adhesive, and applying a restoring agent coating to improve the crack's waterproofness and durability. This technology emphasizes the role of chemical restoring agents, which can restore the asphalt's bonding properties to some extent. However, this method lacks quantitative detection of crack morphology and precise control of material condition, employs only a single filling method, and cannot adapt to the differentiated needs of cracks of varying widths. Furthermore, the repaired pavement is prone to failure due to thermal expansion and contraction. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a multi-stage stress-guided method for repairing asphalt pavement cracks. This addresses the problems of weak interfacial bonding, poor adaptability, and insufficient durability in existing technologies, achieving efficient, intelligent, and long-lasting crack repair.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for repairing asphalt pavement cracks based on multi-stage stress guidance includes the following steps:

[0008] S1. Crack cleaning and thermal activation: Clean the crack surface, then use a hot air gun to spray high-temperature airflow into the crack to remove deep moisture and heat the crack wall to the preheating temperature;

[0009] S2. Crack Detection and Quantification: A three-dimensional point cloud of the crack area is collected using a laser scanning device, and the average crack width W in millimeters is extracted as a control benchmark.

[0010] S3. Material State Matching Calculation: Based on the width W and ambient temperature, the processor searches the preset process database and outputs the target outlet temperature, target viscosity, and component addition instructions for the repair material;

[0011] S4. Temperature and viscosity adjustment and differentiated injection: Control the circulating shear circuit to adjust the thermoplastic polymer modified asphalt to the target temperature and viscosity determined in step S3, and select a needle nozzle or drag flow channel to perform the injection action according to the crack classification results.

[0012] S5. Gradient thermal field guided closure: Start the segmented infrared heating array, control the radiation power of the two sides of the crack to be higher than that of the central area, construct a transverse temperature difference field, and use the thermal expansion difference of the road material to induce the crack wall to produce centripetal displacement.

[0013] S6. Monitoring and Compaction: Monitor the surface temperature of the repair material. When the temperature drops to the compaction window threshold, operate the vibratory compaction equipment to compact the repair area.

[0014] The present invention is further configured such that the specific operating parameters of the hot air spray gun in step S1 are:

[0015] Adjust the gas-air mixture ratio of the spray gun to keep the nozzle outlet center temperature between 350℃ and 500℃, and adjust the airflow velocity. ;

[0016] The nozzle is controlled to move along the crack axis at a speed of 3-5 m / min, so that the measured temperature of the inner wall surface of the crack rises to 40℃-60℃.

[0017] The present invention is further configured such that: the matching solution logic and component instructions in step S3 include:

[0018] For a level one crack, if 2 ≤ W < 10 mm, output a penetration-type command: set the target outlet temperature. Target viscosity The material is pure SBS modified bitumen;

[0019] For secondary cracks, if 10 ≤ W ≤ 30 mm, output a filling command: set the target exit temperature. Target viscosity Add 2%-4% polyester fiber by mass to the material;

[0020] For a level 3 crack, if W > 30mm, output a support-type command: Set the target outlet temperature. Target viscosity Add 15%-20% by mass of preheated fine aggregate to the material.

[0021] The present invention is further configured such that: the injection process for Class I cracks in step S4 is as follows:

[0022] Select a needle-type grouting nozzle with an outlet orifice diameter of 1.5-3.0mm;

[0023] Insert the nozzle 5-10 mm below the plane of the crack opening;

[0024] The output pressure of the grouting pump is kept constant in the range of 0.15-0.25 MPa, so that the material fills the deep space of the crack in a jet-like manner.

[0025] The present invention is further configured such that: the injection process for Class II and above cracks in step S4 is as follows:

[0026] A drag-type flow channel with a bottom opening width of 30-50mm is selected;

[0027] Control the output pressure of the grouting pump to <0.05MPa, and adjust the flow valve to keep the injection flow rate at 10-1L / min;

[0028] The scraper at the bottom of the control channel is kept 2-3mm vertically from the road surface, and as the channel moves, it is scraped to form a covering layer on the top of the crack.

[0029] The present invention is further configured such that the structural layout of the segmented infrared heating array in step S5 is as follows:

[0030] The array includes a central heating zone arranged along the crack direction, and lateral driving zones symmetrically distributed on both sides of the central heating zone;

[0031] The inner edge of the lateral drive zone is 50 mm from the center line of the crack, and the outer edge is 150 mm from the center line of the crack.

[0032] The central heating zone covers an area of ​​50mm to the left and right of the center line of the crack.

[0033] The present invention is further configured such that the construction parameters of the transverse temperature difference field in step S5 are:

[0034] Adjust the power supply voltage of the lateral drive zone heating unit to achieve its radiant power density. The corresponding steady-state temperature of the road surface is ;

[0035] Adjust the power supply voltage of the heating unit in the central heating zone to achieve its radiant power density. The corresponding steady-state temperature of the road surface is ;

[0036] Maintain the temperature difference between the lateral drive zone and the central heating zone The heating time is 60-90 seconds.

[0037] The present invention is further configured such that step S5 also includes low-temperature environment compensation logic:

[0038] Temperature sensor collects ambient air temperature ;

[0039] when At that time, the processor automatically performs compensation actions:

[0040] Reduce the moving speed of the hot air spray gun in step S1 to ;

[0041] Extend the heating duration of the lateral drive zone in step S5 by 20-30 seconds.

[0042] The present invention is further configured such that step S5 also includes a closed-loop control action based on displacement feedback:

[0043] The laser displacement sensor reads the relative coordinate changes of the road surface on both sides of the crack in real time and calculates the relative displacement rate V per unit time.

[0044] If V is lower than the preset minimum closing rate, the processor outputs an instruction to increase the duty cycle of the lateral drive area heating unit;

[0045] If V is zero or an increase in the vertical height at the crack closure point is detected, the processor cuts off the power to the heating array.

[0046] The present invention is further configured such that the compaction operation parameters in step S6 are:

[0047] When the infrared temperature sensor reading is at When necessary, start the vibratory plate compactor or rubber-tired roller;

[0048] Control the vibration frequency of the compaction equipment to 20-30Hz, and compact it back and forth along the repair area 2-3 times until the height difference between the surface of the repair area and the original road surface is less than 1mm.

[0049] Compared with the shortcomings of the prior art, the beneficial effects of the present invention are as follows:

[0050] This invention differs from traditional passive crack filling by introducing a lateral gradient thermal field and utilizing a thermal prestressing mechanism to actively reduce crack width before the material cures. This not only enhances physical interlocking force but also more effectively counteracts the tensile stress generated by subsequent environmental cooling, significantly reducing the crack recurrence rate after repair.

[0051] The optimal material formula and injection process were matched for micro-slits, medium-slits, and wide-slits respectively. This solved the problems of traditional processes where materials could not be injected into narrow slits and were prone to leakage and collapse in wide slits. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0053] Reference Figure 1 The embodiments of the present invention will be further described below.

[0054] This embodiment introduces a method for repairing asphalt pavement cracks based on multi-stage stress guidance:

[0055] First step: Composite crack cleaning and thermodynamic activation:

[0056] To create a clean and highly active bonding interface, construction workers first use a hand-operated crack widening and cleaning machine or a mechanical crack cleaning knife to physically clean the cracks, thoroughly scraping away loose mineral powder, debris, and aged loose asphalt inside the cracks. Subsequently, a high-pressure air purging gun connected to a 0.6-0.8MPa air compressor is used to perform deep purging along the crack direction, forcing the deep-seated micro-dust to be completely removed.

[0057] After physical cleaning, operators use handheld or wheeled pneumatic thermal spray guns for thermal activation. The nozzle of this spray gun has an internal constriction section; operators adjust the gas-air mixture ratio to maintain the nozzle outlet center temperature at [temperature missing]. The interval, while utilizing the Venturi effect to control airflow speed This high-energy, high-temperature jet utilizes powerful wind pressure shear force to instantly strip away residual moisture and activates it through efficient convective heat transfer. Operators control the nozzle to move at a speed of 3-5 m / min, ensuring the measured temperature of the inner surface of the crack rises to 40℃-60℃. This temperature range precisely activates the active molecules on the aged asphalt surface, significantly reducing the contact angle of subsequent grouting materials and providing optimal surface energy for interfacial micro-fusion.

[0058] Step Two: Crack Detection and Process Decision-Making

[0059] After preprocessing, a portable laser scanning detector was used to collect 3D point cloud data of the crack area. The detector transmitted the data to the construction personnel's smart handheld terminal (PDA) via a wireless communication module. The terminal's built-in algorithm module performed noise reduction and feature extraction on the point cloud, calculated the average crack width W in millimeters (mm), and combined it with real-time ambient temperature data. It retrieves information from a preset process database and generates specific ingredient and operation suggestions on the screen.

[0060] The third step, material state matching and composition control:

[0061] This embodiment uses a high-performance asphalt-based elastomer modified injection material as the base material. The base material consists of 20-25 wt% road petroleum asphalt, 4-6 wt% SBS elastomer, 35-50 wt% 100-200 mesh quartz powder, 10-15 wt% rubber particles, 3-6 wt% rosin resin toughening agent, and 1-3 wt% anti-aging additive, with 0.2-0.5 wt% interface wetting agent added to improve deep wetting ability.

[0062] Construction workers used the PDA's instructions to make differentiated adjustments to the substrate on-site.

[0063] Level 1 crack (2≤W<10mm): The screen displays the "Penetration Type" instruction. Construction personnel should maintain the original substrate formulation (pure SBS modified asphalt system) without adding any fillers to maintain low viscosity.

[0064] Secondary crack (10≤W≤30mm): The screen displays the "Fill" instruction. Workers add 2%-4% by mass of polyester fiber to the hot melt reactor. The fibers form a three-dimensional randomized network within the matrix, preventing material flow.

[0065] Level 3 cracks (W>30mm): The screen displays a support-type instruction. Construction workers mix in 15%-20% preheated fine aggregate to construct a skeleton interlocking structure, providing rigid support. The preheated fine aggregate is dry basalt crushed stone with a particle size of 2.36-4.75mm. Before input, it is heated to 150°C using a small onboard heating hopper. Within the cracks, a tight skeletal interlocking structure can form, at which point the softening point of the mixture increases to >110℃ and the viscosity to >800. The preheating process ensures that the temperature of the base asphalt will not decrease after the aggregate is added, and ensures the uniform flowability of the mixture when it is scraped in the flow channel, thus providing rigid support for wide cracks comparable to asphalt concrete after curing.

[0066] Step 4: Constant Temperature Low Pressure and Differentiated Injection

[0067] Construction workers operate a standard heated asphalt crack sealing machine to perform the injection.

[0068] Parameter settings: Based on PDA recommendations, set the target outlet temperature via the equipment's temperature control panel:

[0069] Level 1 seam set as (viscosity <100) );

[0070] Secondary suture setting (Viscosity 300-500) );

[0071] The third-level suture is set as follows: (viscosity > 800) ).

[0072] Replacement and operation of actuators:

[0073] For Class I cracks: The operator installs a needle nozzle with an outlet diameter of 1.5-3.0mm at the end of the crack filling gun and inserts it 5-10mm below the crack opening. Adjust the pump speed to keep the output pressure constant at 0.15-0.25MPa, using the kinetic energy of the jet to force the material to fill the deep micropores.

[0074] For grade II and above cracks: Replace with a drag-type flow channel with a bottom opening width of 30-50mm. Reduce the pump speed to pressure <0.05MPa and maintain a flow rate of 10-15L / min. The operator drags the flow channel, using the scraper at the rear of the channel to maintain a 2-3mm vertical distance from the road surface, directly scraping to form a smooth coating.

[0075] Fifth step: Gradient thermal field guided closure:

[0076] After the grouting is completed, the operators immediately set up a segmented infrared heating array frame above the crack, which is connected to a portable generator via cable.

[0077] Gradient thermal field construction:

[0078] Zone Division and Parameter Settings: The lateral drive zone is defined as a strip-shaped area on both sides, 50mm to 150mm from the center line of the crack. The controller adjusts the infrared heating module (such as a carbon fiber quartz tube) in this zone to high-frequency output, and the radiation power density is set to [value missing]. During the rapid heating period of 60-90 seconds, the surface temperature of the road surface in this area quickly rises to 60℃-70℃.

[0079] The central heating zone is defined as the area covering 50mm to the left and right of the center line of the crack. The controller limits the power density in this zone to 1-2. Only the road surface temperature is maintained between 45℃ and 55℃.

[0080] To prevent lateral heat conduction from blurring the temperature field, a suspended physical insulation plate is installed at the boundary between the "lateral drive zone" and the "central heating zone" of the array. This creates a steep temperature gradient in the lateral dimension.

[0081] This step utilizes the significant thermal expansion and contraction characteristics of asphalt mixtures (coefficient of linear expansion). The physical closure of the crack is achieved by constructing an asymmetric boundary constraint model. Its mechanical process comprises the following three stages:

[0082] Stage 1: Accumulation of potential energy due to volume expansion. This occurs as the temperature in the lateral drive region increases. At that time, the pavement material in this area exhibits a rapid tendency to expand in volume. According to the thermoelastic equation... This region has accumulated a huge amount of internal thermal strain energy.

[0083] Phase Two: Stress Redirection Due to Stiffness Difference. This thermally expanded region lies between two distinct mechanical boundaries: the outer boundary, the side furthest from the crack, is a vast expanse of the original, cold pavement at ambient temperature. Because the modulus of asphalt mixtures increases exponentially with decreasing temperature, the stiffness modulus of the cold matrix is ​​extremely high. This forms a nearly immovable rigid wall, strictly limiting the outward displacement of the heated area.

[0084] The inner boundary, near the crack, consists of physical voids or is filled with repair material still in a low-viscosity flow state, where the lateral constraint force is almost zero. According to the principle of minimum potential energy in mechanics, the expansion displacement of the heated material will be released along the direction of least resistance. Therefore, the originally isotropic volume expansion is forced by the boundary conditions into a unidirectional horizontal displacement vector pointing towards the crack center.

[0085] Phase Three: Centripetal Extrusion and Prestressed Curing. The aforementioned directional displacement vector forces substantial physical displacement on both sides of the crack, with a centripetal displacement of 0.1-0.2 mm on each side. This displacement, like a hydraulic clamp, tightly "clamps" the uncured repair material at the center of the crack, establishing hydrostatic pressure within the material. This process not only forces the fluid to penetrate further into the depths of the micro-cracks, but more importantly, when the heat field is subsequently removed and the road surface cools as a whole, this pre-applied extrusion deformation effectively counteracts the tensile strain caused by the thermal shrinkage of the asphalt surface layer later, thus pre-setting compressive stress at the repair interface and preventing secondary cracking.

[0086] Environmental Compensation and Closed-Loop Control Logic: To ensure the effectiveness of the above-mentioned mechanical mechanism under different operating conditions, the array's built-in controller executes the following closed-loop logic:

[0087] Low-temperature enthalpy compensation: The array-integrated temperature sensor reads the ambient temperature in real time. .when At this time, due to the enhanced heat absorption effect of the cold substrate, the energy required to establish effective thermal expansion increases. The processor automatically triggers a compensation algorithm to extend the heating duration of the lateral drive zone by 20-30 seconds to accumulate sufficient enthalpy to overcome the heat absorption of the substrate and ensure that the road surface reaches the design expansion temperature.

[0088] Displacement feedback safety control: A laser displacement sensor monitors the rate of change V of the crack width in real time. If V is lower than the preset minimum closing rate, it indicates insufficient thermal driving force, and the controller increases the duty cycle of the lateral drive zone through PWM modulation. If V=0 is detected and the laser ranging shows an increase in the vertical height at the crack, it indicates excessive compression causing material bulging. The controller immediately cuts off the power to prevent damage to the road surface smoothness due to excessive thermal expansion.

[0089] Step 6: Monitoring and Compaction

[0090] Using an infrared thermometer to scan the repair area, when the material temperature cools sequentially from both sides towards the center and drops to the compaction window threshold of 50℃-55℃, a hand-held vibratory plate compactor is used. The vibration frequency is set to 20-30Hz, and the area is compacted 2-3 times repeatedly. This step uses high-frequency vibration to further eliminate air bubbles until the surface height difference with the original road surface is less than 1mm, ensuring flatness.

[0091] In the test section of the highway, the ambient temperature was 15℃. The crack to be repaired was a longitudinal crack, and its average width W = 18 mm was measured by laser scanning (which falls within the range of a secondary crack).

[0092] The specific execution parameters for this embodiment are as follows:

[0093] Step S1: Adjust the gas valve of the hot air spray gun to stabilize the center temperature of the nozzle outlet at 420℃, and set the airflow velocity to 55m / s. The operator controls the spray gun to move along the crack at a constant speed of 4m / min. After verification by an infrared thermometer, the surface temperature of the inner wall of the crack rises to 52℃.

[0094] Step S3: Based on the test result of W=18mm, the processor outputs a "filling" command. The construction personnel add 3.0% by mass of polyester fiber and 0.3% of interfacial wetting agent to the asphalt substrate.

[0095] Step S4 (Constant Temperature Injection): Set the temperature of the hot melt kettle to 145℃. Install a drag-type flow channel with a bottom opening width of 40mm, adjust the grouting pump flow rate to 12 L / min, maintain the grouting pressure at 0.03 MPa, and scrape a uniformly thick covering layer onto the top of the crack. Step S5 (Gradient Thermal Field Construction): Set up a segmented infrared heating array. Lateral Drive Zone: Adjust the power density to 5.2. Continue heating for 75 seconds to bring the steady-state temperature of the road surface in the area 50-150mm from the center of the crack to 68℃. For the central heating zone: adjust the power density to 1.5 to maintain the road surface temperature at 50℃ in the center of the crack.

[0096] Gradient formation: The temperature difference between the sides and the center at this point = 18℃, effectively inducing centripetal compressive stress.

[0097] Step S6 (Compaction): When the surface temperature of the repair material cools naturally to 53°C, start the vibratory plate compactor and compact it three times at a frequency of 25 Hz.

[0098] Comparative Example 1: Step S3 (testing and batching) was not performed. A commercially available general-purpose rubber asphalt sealant was directly selected. This material does not contain polyester fiber or special aggregates; its measured softening point is 85℃, and its application viscosity is 1600-800 kJ / L. .

[0099] The cracks were cleaned with a regular wire brush without undergoing the high-temperature thermal activation of S1. The general-purpose material was heated to 150°C and then filled using a standard crack-filling machine.

[0100] Step S5 was not performed in the post-treatment process. After the injection was completed, the repair material was allowed to cool and cure naturally at ambient temperature.

[0101] Comparative Example 2: The same filler formulation as Example 1 was used, and the heating temperature was 14°C.

[0102] Construction process S1-S4 is the same as in Example 1. After grouting is completed, a wide infrared heating plate is used to cover the crack area without heat insulation partition design.

[0103] For Example 1 and Comparative Examples 1-2 above, we conducted standard tests under the same environmental conditions, and the test results are shown in the table below:

[0104] Table 1:

[0105] Test metrics Test Standards Example 1 Comparative Example 1 Comparative Example 2 Softening point (∘C) GB / T 4507 102∘C 85∘C 102∘C Cone penetration (0.1 mm, 25°C) GB / T 4509 55 75 (Slightly soft) 55 Flow value (mm) JT / T 740 0.6 mm 8.5 mm 0.6 mm

[0106] As shown in Table 1, the general-purpose material used in Comparative Example 1 could not maintain morphological stability in a wide joint with W=18 mm, exhibiting a high high-temperature flow value as high as 8.5 mm, making it highly susceptible to rutting or runoff in summer. In contrast, Example 1, through step S3, matched a fiber-added formulation to construct an internal network structure, achieving a flow value of only 0.6 mm, demonstrating the necessity of graded control for ensuring the quality of wide joint repair.

[0107] Table 2:

[0108] Test metrics Example 1 Comparative Example 2 Comparative Example 1 Lateral / Center Temperature Setting 68∘C / 50∘C (ΔT=18∘C) 68∘C / 68∘C (ΔT=0∘C) Ambient temperature / Ambient temperature Crack width change (ΔW) (positive values ​​represent shrinkage / clamping) +0.15 mm (significant concentric contraction) -0.04 mm (micro-expansion) 0.00 mm (no change) Residual compressive stress (MPa) after cooling 0.12 MPa -0.02 MPa (micro-tensile force) 0 MPa Compaction degree after repair (%) 98.50% 92.00% 88.50%

[0109] As shown in Table 2: Example 1 produced a physical closure of +0.15mm, proving that the lateral expansion restriction principle successfully clamped the crack.

[0110] In Comparative Example 2, although heating was also applied, the uniform heating caused the central region of the crack to soften and expand synchronously, resulting in a 0.04 mm increase in crack width (negative optimization) and failing to establish beneficial compressive stress. This strongly demonstrates that simple heating is ineffective; only by constructing a gradient, non-uniform thermal field can active closure be achieved.

[0111] Table 3:

[0112] Test metrics Example 1 Comparative Example 1 Comparative Example 2 Interfacial shear strength (MPa) 0.94 MPa 0.45 MPa 0.78 MPa Interfacial shear strength (MPa) (after 30 days of thermostatic cycling) 0.91 MPa (retention rate 96.8%) 0.28 MPa (significant attenuation) 0.65 MPa (attenuation occurs) Permeability coefficient (mL / min) (measured after 30 days) 12 mL / min (Excellent, no leakage) 135 mL / min (severe leakage) 48 mL / min (moderate) Macroscopic forms of damage In good condition, with no cracks on the interface. Interface debonding, material depression Microcracks appeared on the interface

[0113] Example 1 showed a high interface strength retention rate of 96.8% after 30 days, with the lowest water permeability coefficient. This was attributed to the residual compressive stress of 0.12 MPa pre-set in step S5, which effectively offset the tensile stress caused by the environmental cooling, thereby preventing interface debonding.

[0114] In contrast, Comparative Example 1 has failed due to material softening and flow and weak interfacial bonding.

[0115] Although the material in Comparative Example 2 is better, it lacks the protection of "thermal prestressing", and its interface durability is still significantly weaker than that of the present invention.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for repairing asphalt pavement cracks based on multi-stage stress guidance, characterized in that, Includes the following steps: S1. Crack cleaning and thermal activation: Clean the crack surface, then use a hot air gun to spray high-temperature airflow into the crack to remove deep moisture and heat the crack wall to the preheating temperature; S2. Crack Detection and Quantification: A three-dimensional point cloud of the crack area is collected using a laser scanning device, and the average crack width W in millimeters is extracted as a control benchmark. S3. Material State Matching Calculation: Based on the width W and ambient temperature, the processor searches the preset process database and outputs the target outlet temperature, target viscosity, and component addition instructions for the repair material; S4. Temperature and viscosity adjustment and differentiated injection: Control the circulating shear circuit to adjust the thermoplastic polymer modified asphalt to the target temperature and viscosity determined in step S3, and select a needle nozzle or drag flow channel to perform the injection action according to the crack classification results. S5. Gradient thermal field guided closure: Start the segmented infrared heating array, control the radiation power of the two sides of the crack to be higher than that of the central area, construct a transverse temperature difference field, and use the thermal expansion difference of the road material to induce the crack wall to produce centripetal displacement. S6. Monitoring and Compaction: Monitor the surface temperature of the repair material. When the temperature drops to the compaction window threshold, operate the vibratory compaction equipment to compact the repair area.

2. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 1, characterized in that, The specific operating parameters for the hot air spray gun in step S1 are as follows: Adjust the gas-air mixture ratio of the spray gun to keep the nozzle outlet center temperature between 350℃ and 500℃, and adjust the airflow velocity. ; The nozzle is controlled to move along the crack axis at a speed of 3-5 m / min, so that the measured temperature of the inner wall surface of the crack rises to 40℃-60℃.

3. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 2, characterized in that, The matching solution logic and component instructions in step S3 include: For a level one crack, if 2 ≤ W < 10 mm, output a penetration-type command: set the target outlet temperature. Target viscosity The material is pure SBS modified bitumen; For secondary cracks, if 10 ≤ W ≤ 30 mm, output a filling command: set the target exit temperature. Target viscosity Add 2%-4% polyester fiber by mass to the material; For a level 3 crack, if W > 30mm, output a support-type command: Set the target outlet temperature. Target viscosity Add 15%-20% by mass of preheated fine aggregate to the material.

4. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 3, characterized in that, The injection process for the first-order fracture in step S4 is as follows: Select a needle-type grouting nozzle with an outlet orifice diameter of 1.5-3.0mm; Insert the nozzle 5-10 mm below the plane of the crack opening; The output pressure of the grouting pump is kept constant in the range of 0.15-0.25 MPa, so that the material fills the deep space of the crack in a jet-like manner.

5. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 4, characterized in that, The injection process for Class II and above cracks in step S4 is as follows: A drag-type flow channel with a bottom opening width of 30-50mm is selected; Control the output pressure of the grouting pump to <0.05MPa, and adjust the flow valve to keep the injection flow rate at 10-1L / min; The scraper at the bottom of the control channel is kept 2-3mm vertically from the road surface, and as the channel moves, it is scraped to form a covering layer on the top of the crack.

6. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 5, characterized in that, The structural layout of the segmented infrared heating array in step S5 is as follows: The array includes a central heating zone arranged along the crack direction, and lateral driving zones symmetrically distributed on both sides of the central heating zone; The inner edge of the lateral drive zone is 50 mm from the center line of the crack, and the outer edge is 150 mm from the center line of the crack. The central heating zone covers an area of ​​50mm to the left and right of the center line of the crack.

7. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 6, characterized in that, The parameters for constructing the transverse temperature difference field in step S5 are as follows: Adjust the power supply voltage of the lateral drive zone heating unit to achieve its radiant power density. The corresponding steady-state temperature of the road surface is ; Adjust the power supply voltage of the heating unit in the central heating zone to achieve its radiant power density. The corresponding steady-state temperature of the road surface is ; Maintain the temperature difference between the lateral drive zone and the central heating zone The heating time is 60-90 seconds.

8. The method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 7, characterized in that, Step S5 also includes low-temperature environment compensation logic: Temperature sensor collects ambient air temperature ; when At that time, the processor automatically performs compensation actions: Reduce the moving speed of the hot air spray gun in step S1 to ; Extend the heating duration of the lateral drive zone in step S5 by 20-30 seconds.

9. A method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 8, characterized in that, Step S5 also includes closed-loop control actions based on displacement feedback: The laser displacement sensor reads the relative coordinate changes of the road surface on both sides of the crack in real time and calculates the relative displacement rate V per unit time. If V is lower than the preset minimum closing rate, the processor outputs an instruction to increase the duty cycle of the lateral drive area heating unit; If V is zero or an increase in the vertical height at the crack closure point is detected, the processor cuts off the power to the heating array.

10. A method for repairing asphalt pavement cracks based on multi-stage stress guidance according to claim 9, characterized in that, The compaction operation parameters in step S6 are: When the infrared temperature sensor reading is at When necessary, start the vibratory plate compactor or rubber-tired roller; Control the vibration frequency of the compaction equipment to 20-30Hz, and compact it back and forth along the repair area 2-3 times until the height difference between the surface of the repair area and the original road surface is less than 1mm.

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