Multifunctional asphalt mixture rut test method

Abstract

The invention discloses a multifunctional asphalt mixture rut test method which is implemented by using a device integrating loading and measurement, test piece supporting and temperature control drainage, environment simulation and optical measurement and a central control and data acquisition system. A test piece is arranged in the test piece groove, temperature control is realized through circulating a heat-conducting medium in the temperature-conducting cavity, different gradients are formed through the hoisting mechanism and the angle adjusting assembly, the test wheel is driven to perform one-way circulating loading along a closed track and snub at a preset moment, and rolling and sliding friction forces are synchronously collected; in the test process, rainfall is simulated by adopting the watering assembly, incoming water is recycled by the drainage tank, speckle images are acquired by the high-frequency industrial camera, and surface full-field displacement and strain are obtained through digital image correlation analysis. Through time registration and fusion of temperature, gradient, wheel speed, rainfall and friction-deformation data, rut deformation, skid resistance and apparent structure evolution laws of the asphalt mixture under multi-climate and multi-gradient conditions are obtained.

Description

Technical Field

[0001] This invention belongs to the field of road engineering technology, and specifically relates to a multifunctional asphalt mixture rutting test method. Background Technology

[0002] Rutting tests on asphalt mixtures are an important means of evaluating the high-temperature stability of road materials, and the results directly affect road structure design and material selection. However, existing standard rutting test equipment and methods still have several shortcomings in terms of efficiency, simulation accuracy, and detection capabilities.

[0003] First, the work efficiency is low. Traditional rutting tests usually use hot air heating, with a standard test temperature of 60℃. To achieve the required internal temperature of the specimen, it needs to be heated inside the equipment for about 6 to 12 hours. The temperature rise process is slow and the thermal efficiency is low, resulting in a single machine typically being able to complete the testing of only about 3 specimens per day, which is difficult to meet the needs of large-scale testing in actual engineering.

[0004] Secondly, the simulation capabilities are insufficient. Existing rutting test equipment loads the test wheel by making a back-and-forth motion above the specimen. However, in real road environments, vehicles mostly travel in a single direction, and the wheels do not repeatedly move back and forth in the same position. While the back-and-forth loading method can simulate cyclic loading, it is difficult to realistically reproduce the macroscopic deformation and microscopic evolution of asphalt mixture material structures under the cumulative effect of vehicles in one direction. Furthermore, rutting often occurs on uphill or heavily loaded climbing roads, while traditional rutting test equipment operates in a horizontal state, failing to simulate the impact of slope conditions on the wheel-road contact state and material behavior.

[0005] Secondly, the testing function is limited. Traditional rutting tests mainly focus on dynamic stability indicators and cannot simulate low-temperature conditions, rainfall environments, or complex climatic effects; nor can they simulate the mechanical state of vehicles under different speeds and slopes, making it difficult to obtain the evolution of abrasion, polishing, and anti-skid properties of asphalt mixtures under long-term variable-speed loading. In addition, existing equipment lacks refined monitoring of changes in the apparent structure of the mixture, and cannot identify microcracks, texture depth attenuation, and texture wear patterns on the specimen surface through optical measurement or image analysis, thus failing to reveal the true mechanical response and durability change mechanisms of the material.

[0006] In summary, existing rutting test equipment and methods have limitations in terms of temperature control efficiency, simulation of unidirectional cumulative vehicle action, reproduction of slope conditions, simulation of multiple climate loads, and monitoring of surface texture. There is an urgent need for an improved method that can conduct comprehensive performance testing under multiple loads, multiple environments, and multiple slopes to truly reflect the high-temperature stability, skid resistance, and surface texture degradation of asphalt mixtures in actual road service environments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an improved method for conducting comprehensive performance tests under multiple loads, multiple environments, and multiple slopes, so as to truly reflect the high-temperature stability, skid resistance, and surface texture degradation law of asphalt mixtures in actual road service environments.

[0008] The technical solution of this invention is as follows: A multifunctional asphalt mixture rutting test method utilizes a test device comprising a chassis, a loading and measurement system, a specimen support and temperature control drainage system, an environmental simulation and optical measurement system, and a central control and data acquisition system. The loading and measurement system includes a test wheel, a test wheel transmission assembly, a friction force testing sensor, an angle adjustment assembly, and a braking actuator. The specimen support and temperature control drainage system includes a specimen groove, a temperature-conducting cavity surrounding the bottom and sidewalls of the specimen groove, a temperature control assembly communicating with the temperature-conducting cavity, a drainage trough surrounding the specimen groove, a wastewater collection unit communicating with the drainage trough, a fixed shaft hinged to the bottom of one side of the temperature-conducting cavity, a lifting shaft connected to the bottom of the other side of the temperature-conducting cavity, and a lifting mechanism for driving the lifting shaft to rise and fall. The machine components; the environmental simulation and optical measurement system includes: a water tank, a water guide channel, a water spray pipe, and a high-frequency industrial camera. The water tank is located on the outer side of the top of the machine casing. The water guide channel is connected to the water tank. One end of the water spray pipe is connected to the water guide channel, and the other end of the water spray pipe is placed at the opening of the drainage channel. The high-frequency industrial camera is located on the inner side wall of the machine casing. The central control and data acquisition system is electrically connected to the test wheel transmission assembly, the braking actuator, the angle adjustment assembly, the temperature control assembly, the water tank, the water guide channel, the water spray pipe, the high-frequency industrial camera, and the friction force test sensor, respectively. The method includes the following steps: Step 1: Place the asphalt mixture specimen in the specimen slot, so that the bottom surface of the specimen is in contact with the bottom of the specimen slot, and spray random powder on the upper surface of the specimen. Step 2: Inject the heat-conducting medium into the temperature control component and start the circulation, so that the heat-conducting medium circulates in the temperature-conducting cavity to control the heating or cooling of the specimen and stabilize the specimen temperature to the preset target temperature; Step 3: Drive the lifting shaft to lift and lower through the crane component, so that the temperature-conducting cavity and specimen groove rotate around the fixed axis to the preset slope, and drive the loading and measurement system to rotate synchronously to the same slope as the specimen groove through the angle adjustment component; Step 4: Apply a preset vertical load so that the test wheel presses against the surface of the specimen, and drive the test wheel to run unidirectionally along the closed trajectory by the test wheel transmission component. During the rolling loading process, the friction force test sensor collects the rolling friction force data between the test wheel and the specimen surface in real time; Step 5: At the preset loading time Step 6: During Step 4 and / or Step 5, simulated rainfall is sprayed onto the test surface through a water tank, water channel, and sprinkler pipe. The water from the test surface is collected by a drainage channel and discharged into the sewage collection unit, forming a controlled rainfall-drainage condition. Step 7: Throughout Step 4-6, the central control and data acquisition system sends a synchronous trigger signal to the high-frequency industrial camera. The high-frequency industrial camera acquires image sequences of the test surface at a set frame rate and inputs the image sequences into the digital image correlation (DIC) analysis unit to calculate the full-field displacement and strain distribution of the test surface.Step 8: The central control and data acquisition system performs time registration and fusion of data on temperature, slope, wheel speed, rainfall, rolling friction, sliding friction, and overall displacement or strain, outputting the asphalt mixture's rutting deformation, skid resistance, and pavement surface texture evolution indicators under the stated temperature, slope, and rainfall conditions.

[0009] Furthermore, the closed trajectory described in step 4 is formed by an elliptical wheel track and guide wheel assembly fixed on the upper structure of the chassis. The test wheel transmission assembly drives the two test wheels to run unidirectionally along the elliptical wheel track, and the installation positions of the two test wheels on the elliptical wheel track are staggered in phase, so that the two test wheels alternately pass through the test piece's action area.

[0010] Furthermore, the heat-conducting medium in step 2 is glycerol, and the temperature control component controls the temperature of the glycerol within the range of -10℃ to 100℃, and circulates it to the temperature-conducting cavity to achieve rapid temperature control of the specimen over a wide temperature range.

[0011] Furthermore, in step 3, the specimen groove and the longitudinal axis of the loading and measurement system are adjusted to form a continuously adjustable slope of 0° to 15°, and under any set slope, the normal of the test wheel relative to the contact area of ​​the specimen surface remains perpendicular.

[0012] Furthermore, in step 4, the wheel speed of the test wheel runs according to a preset wheel speed curve including an acceleration segment, a constant speed segment, and a deceleration segment, and the braking point in step 5 is set within the constant speed segment or the deceleration segment.

[0013] Furthermore, in step 6, the rainfall flow rate and duration are controlled by adjusting the water outlet of the water tank and the opening of the spray holes or nozzles on the sprinkler pipe, so that the rainfall conditions include at least one of the following conditions: constant rainfall intensity condition, phased rainfall intensity variation condition, or composite rainfall intensity condition linked to wheel speed and temperature.

[0014] Furthermore, in step 7, the high-frequency industrial camera establishes a time synchronization relationship with the control signals of the test wheel transmission assembly, temperature control assembly, and water spray pipe. The digital image correlation (DIC) analysis unit calculates the full-field strain cloud map of different time sections on the surface of the specimen based on the image sequence, and performs corresponding analysis on the strain concentration area and the changes in test wheel path, rut depth, and friction force.

[0015] Furthermore, in step 8, multiple sets of test results under different temperatures, slopes, and rainfall conditions are compared and analyzed to obtain the rutting sensitivity evaluation index and skid resistance degradation law of asphalt mixtures on uphill or downhill sections and under dry or rainy conditions, which can be used to guide pavement structure design and material selection.

[0016] The beneficial effects of this invention are: 1. Significantly improves test efficiency and temperature control capability: Through the jacketed circulating temperature control structure of the temperature conduction cavity and temperature control components, the heat conduction medium circulates in the bottom and side walls of the specimen tank to heat or cool the specimen. It can achieve wide temperature range, rapid and uniform temperature adjustment within the range of -10℃ to 100℃. Compared with the traditional hot air heating method, it significantly shortens the heating time of the specimen from the ambient temperature to the target temperature, increases the daily test throughput of a single device, and solves the problem of low efficiency in existing rut testing.

[0017] 2. More realistic simulation of unidirectional cumulative loading and slope conditions: The slope of the specimen groove is adjusted through a lifting axle + fixed axle + crane assembly. An angle adjustment component drives the loading and measurement system to rotate synchronously, ensuring the test wheel maintains a consistent slope with the specimen within the 0°–15° range. This simulates uphill or downhill lane conditions on actual roads. Simultaneously, one or two test wheels are driven in a unidirectional cycle on a closed track (preferably an elliptical wheel-rail system), achieving continuous unidirectional cumulative loading on the same specimen. This avoids the inconsistency between traditional left-right reciprocating loading and the actual unidirectional travel of the vehicle-road system, more closely resembling the real effect of long-term unidirectional vehicle compaction on the road surface.

[0018] 3. Strong comprehensive simulation capability of environment and load conditions: Through the rain-drainage system composed of water tank, water guide channel, water spray pipe, drainage channel and sewage collection unit, controlled rainfall can be sprayed onto the surface of the specimen during loading. With the help of temperature control components and slope adjustment mechanism, comprehensive simulation of multiple climate and load conditions such as temperature, slope and rainfall can be achieved. In addition, combined with the braking actuator to implement point braking in the constant speed or deceleration stage, rolling friction and sliding friction data can be obtained at the same time, which expands the limitations of traditional rutting test which can only work under horizontal, dry and single speed conditions.

[0019] 4. Introducing DIC to achieve full-field surface displacement / strain measurement, improving the detection dimension from single-point rutting quantity to multi-index linkage: During the rutting loading process, this invention uses a high-frequency industrial camera to synchronously acquire images of the surface of the specimen with sprayed speckles, and inputs the image sequence into the digital image correlation (DIC) analysis unit to obtain the full-field surface displacement and strain fields; at the same time, the central control and data acquisition system performs time registration and fusion of the DIC full-field data with wheel speed, load, temperature, slope, rainfall, and rolling / sliding friction data, which can not only obtain the rutting depth-strain evolution relationship, but also extract multiple evaluation indicators such as polishing / wearing surface texture changes and anti-skid performance degradation, breaking through the limitations of traditional rutting tests that can only output a single dynamic stability index and cannot observe the macro-micro evolution process of materials.

[0020] 5. Provides higher-dimensional decision-making basis for material design and pavement structure optimization: Through the above multi-condition simulation and full-field measurement, the present invention can systematically characterize the evolution law of rutting sensitivity, wear and skid resistance of asphalt mixture under different temperatures, slopes and dry / rain conditions. It helps to provide quantitative basis from the aspects of material mix optimization, structural combination design and service performance evaluation. It has high engineering applicability and promotion value. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the test apparatus for a multifunctional asphalt mixture rutting test method according to the present invention.

[0022] Figure 2 This is a schematic diagram of the test wheel drive assembly of the test device for a multifunctional asphalt mixture rutting test method according to the present invention.

[0023] Figure 3 This is a schematic diagram of the angle adjustment component of the test device for a multifunctional asphalt mixture rutting test method according to the present invention.

[0024] Figure 4 This is a schematic diagram of the crane assembly of the test device for a multifunctional asphalt mixture rutting test method according to the present invention.

[0025] In the diagram: 1-Test wheel, 2-Friction test sensor, 3-Test wheel transmission assembly, 301-Side plate, 302-Rotating shaft, 303-Drive shaft, 304-Driven shaft, 305-Sprocket, 306-Chain, 307-Support plate, 308-L-shaped connecting plate, 309-Drive motor, 4-Angle adjustment assembly, 401-First guide rail, 402-Second guide rail, 403-Fixed seat, 404-Angle locking pin, 405-Positioning pin 406-Screw jack, 407-Lifting lug, 5-Water tank, 6-Water guide trough, 7-Sprinkler pipe, 8-High frequency industrial camera, 9-Specimen slot, 10-Temperature conduction chamber, 11-Drainage trough, 12-Lifting shaft, 13-Rotating shaft, 14-Crane assembly, 1401-Base, 1402-Scissor linkage, 1403-Screw jack, 1404-Lifting motor, 1405-Bearing seat, 15-Temperature control assembly, 16-Sewage collection unit, 17-Chassis. Detailed Implementation

[0026] The multifunctional asphalt mixture rutting test method of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are for illustrative purposes only and are not intended to limit the invention. Various modifications and equivalent substitutions to the embodiments without departing from the spirit and substance of the invention should fall within the protection scope of the present invention.

[0027] Example 1: As Figure 1-4 As shown, a test device structure suitable for performing the multifunctional asphalt mixture rutting test method of the present invention includes a housing 17, a loading and measurement system, a specimen support and temperature control and drainage system, an environmental simulation and optical measurement system, and a central control and data acquisition system. The above-mentioned device structure is mainly used to support the implementation of each step of the method of the present invention.

[0028] The chassis 17 is a rigid frame structure. The interior is divided into an upper loading and measurement area, a lower specimen support and temperature control and drainage area, and a side equipment installation area by a steel frame. The upper area is used to install the loading and measurement system, and the lower area is used to arrange specimen slots 9, temperature conduction chambers 10, drainage channels 11, lifting shafts 12, fixed shafts 13, crane components 14, etc. The lower side or one end is reserved for the installation of equipment such as temperature control components 15 and sewage tanks 16.

[0029] The loading and measurement system includes a test wheel 1, a test wheel transmission assembly 3, a friction force test sensor 2, an angle adjustment assembly 4, and a braking actuator, all of which are mounted on the upper support frame inside the chassis 17.

[0030] The test wheel 1 is preferably an inflatable rubber tire, with its rim mounted on the center of the axle via a hub bearing. The axle has a drive-side support end and a force-measuring support end at its two ends: the drive-side support end is supported by a pair of rolling bearings in a bearing housing fixed to a load-bearing frame, and connected to the output shaft of the test wheel transmission assembly 3 via a coupling or sprocket to obtain torque; the force-measuring support end is connected to the friction force test sensor 2 via a dedicated force-measuring support, and the axle end is connected to the sensor via a high-rigidity connecting plate, allowing the tangential force between the tire and the specimen surface to be transmitted to the friction force test sensor 2 through the axle; this dual-side support arrangement allows the drive side to primarily perform torque transmission and radial support functions, while the force-measuring side is mainly used to collect tangential friction force, resulting in a clear force flow path and improved friction force measurement accuracy.

[0031] The test wheel transmission assembly 3 includes: a rotary assembly and two rotary shafts 302 disposed on one side of the rotary assembly; one end of each rotary shaft 302 is fixedly connected to the rotary assembly, and the other end extends through the side wall of the housing 17; the rotary assembly includes: two symmetrically arranged side plates 301, a drive shaft 303 and a driven shaft 304 disposed between the two side plates, a sprocket 305, a chain 306, a support plate 307, an L-shaped connecting plate 308, and a transmission motor 309; sprockets 305 are sleeved on both the drive shaft 303 and the driven shaft 304; the chain 306 is connected end to end and sleeved on the sprockets 305 to form a closed rotary link; several support plates 301 are equidistantly installed on the outside of the chain 306 through the L-shaped connecting plate 308 to form an annular rotary surface; the test wheel 1 is installed on the support plate 307; the output shaft of the transmission motor 309 is connected to the drive shaft 303.

[0032] The friction force test sensor 2 can be a shear beam type or flange type force sensor, with its sensitive axis arranged along the running direction of the test wheel 1. It is used to collect rolling friction force in real time under rolling conditions and to collect the peak value of sliding friction force in real time under braking conditions. Preferably, one end of the friction force test sensor 2 is fixed to the bearing frame or a dedicated force measuring beam by bolts, and the other end is connected to the wheel axle force measuring side support seat through a high-rigidity connecting plate. The sensor's sensitive direction is ensured to be consistent with the tangential movement direction of the test wheel 1 through pin holes or positioning steps. To avoid interference from vertical loads and bending moments on the measurement results, an auxiliary guide structure or auxiliary bearing is set near the sensor to bear excess vertical reaction force and part of the bending moment, so that the sensor is mainly subjected to unidirectional shear or tension and compression. This forms a clear friction force measurement chain: tangential force at the tire-specimen interface → tire-wheel axle → force measuring support seat → friction force test sensor 2 → bearing frame. Vertical loads and structural self-weight are mainly transmitted through the drive side bearing seat and other support structures, without passing through the sensor, thus obtaining a relatively pure friction force signal.

[0033] The angle adjustment assembly (4) includes: a first guide rail 401 and a second guide rail 402 disposed on the side wall of the chassis 17, a fixed base 403 disposed below the second guide rail 402, and a screw jack 406 mounted above the fixed base 403; the first guide rail 401 is a limiting hole, the second guide rail 402 is an arc guide rail, and the center of the arc of the second guide rail 402 is located at the center of the first guide rail 401; one of the rotating shafts 302 passes through the first guide rail 401, and the other rotating shaft 302 passes through the second guide rail 402 and is hinged to the top of the screw of the screw jack 406. Next, the screw jack 406 lifts the rotary shaft 302 that passes through the second guide rail 402, driving the test wheel transmission assembly 3 to rotate along the first guide rail 401. Limiting rings are provided on both sides of the connection between the rotary shaft 302 and the second guide rail 402 to limit the rotary shaft 302 on both sides, thereby improving the fixing stability of the test wheel transmission assembly 3. It should be noted that in this embodiment, in order to improve the fixing effect of the test wheel transmission assembly 3, the first guide rail 401 and the second guide rail 402 are provided with an extension section in the direction perpendicular to the side wall of the housing 17.

[0034] The braking actuator is installed at the axle of test wheel 1. It can be a disc brake or a magnetic powder brake. It is controlled by the central control and data acquisition system and applies short-term braking torque to test wheel 1 at a preset time to form a point braking condition.

[0035] The specimen support and temperature control drainage system includes a specimen tank 9, a temperature conducting cavity 10, a drainage tank 11, a lifting shaft 12, a fixed shaft 13, a crane assembly 14, a temperature control assembly 15, and a sewage collection unit 16.

[0036] The specimen groove 9 is a rectangular groove with an inner cavity size that is suitable for asphalt mixture specimens with a length of 300 mm × width of 300 mm × thickness of 40 to 150 mm. This not only ensures that the geometric dimensions of the specimens meet the specifications, but also facilitates the fixing and lateral restraint of the specimens.

[0037] The temperature-conducting cavity 10 adopts a jacket structure and is set around the bottom and all sides of the specimen groove 9. It is connected to the temperature control component 15 through a conduit. The temperature control component 15 is filled with glycerol and is equipped with a heating unit, a cooling unit and a circulation pump. It can control the temperature of glycerol within the range of -10℃ to 100℃ and circulate it to the temperature-conducting cavity 10 to achieve rapid and uniform wide-range temperature control of the specimen.

[0038] The bottom of one side of the temperature-conducting cavity 10 is connected to the rotating shaft 13 via a hinge, and the rotating shaft 13 is supported on the bottom crossbeam inside the housing 17; the bottom of the other side of the temperature-conducting cavity 10 is rigidly connected to the lifting shaft 12, and the lifting shaft 12 is connected to the crane assembly 14. The crane assembly 14 can be an electric screw jack or a hydraulic cylinder, which drives the lifting shaft 12 to rise and fall through the extension stroke, thereby causing the temperature-conducting cavity 10 and the specimen groove 9 to rotate around the rotating shaft 13 to form a slope of 0° to 15°.

[0039] Preferably, the crane assembly 14 includes: a base 1401, a scissor linkage 1402, a lead screw 1403, a crane motor 1404, and a support seat 1405. The scissor linkage 1402 includes two sets of symmetrically arranged hinged rods, one end of each set of hinged rods being hinged to the base 1401 and the other end to the support seat. One end of the hinge point of the two sets of symmetrically arranged hinged rods is connected to the lead screw 1403 via a nut, and the other end is rotatably connected to the lead screw 1403. The end of the lead screw 1403 rotatably connected to the hinge point is drively connected to the output shaft of the crane motor 1404. Driven by the crane motor 1404, the scissor linkage 1402 can be raised and lowered, thereby raising and lowering the support seat and the crane shaft 12. In conjunction with the rotating shaft 13, this allows for the angle adjustment of the specimen slope adjustment assembly.

[0040] The drainage trough 11 is arranged around the outside of the specimen tank 9, and its bottom is connected to the sewage collection unit 16 through a drainage pipe. The surface runoff generated during the test is collected by the drainage trough 11 and discharged into the sewage collection unit 16, realizing a closed loop of rainfall-drainage.

[0041] Water tank 5 is located on the top of the outer casing 17 and is connected to water pipe 7 through water guide channel 6. Water pipe 7 is arranged above specimen tank 9 and multiple spray holes or nozzles are arranged along the length of the pipe to spray onto the specimen surface to form simulated rainfall. A water pump and solenoid valve can be installed between water tank 5 and water pipe 7 to adjust the flow rate and the opening / closing time.

[0042] The high-frequency industrial camera 8 is mounted on an adjustable bracket inside the chassis 17, facing the surface of the specimen. Its field of view covers the entire specimen area. The high-frequency industrial camera 8 is connected to the central control and data acquisition system through an industrial network port. It is used to acquire speckle image sequences on the surface of the specimen at a set frame rate, providing raw image data for digital image correlation (DIC) analysis.

[0043] The central control and data acquisition system can be configured with an industrial computer or PLC plus a host computer. It interacts and controls signals with the test wheel transmission assembly 3, braking actuator, angle adjustment assembly 4, temperature control assembly 15, water tank 5, water guide trough 6, water spray pipe 7, high-frequency industrial camera 8 and friction force test sensor 2 through motion control unit, temperature control unit, I / O unit and image acquisition unit, to realize the automated execution of test steps and the synchronous acquisition and fusion of multi-source data.

[0044] Example 2: Based on the device described in Example 1, this example provides a specific multifunctional asphalt mixture rutting test method, the steps of which are as follows: Step S1, Specimen Installation and Surface Scattering Pattern Preparation: Prepare asphalt mixture specimens according to specifications, with dimensions of 300 mm long × 300 mm wide × 40–150 mm thick. Place the specimens into specimen slots 9, ensuring the bottom surface of the specimens is tightly fitted to the bottom of the slots 9. Secure the specimens with side plates or wedges. Then, spray a black and white random scattering pattern onto the upper surface of the specimens. The size and density of the scattering patterns are designed based on the resolution and field of view of the high-frequency industrial camera 8 to provide texture features for DIC analysis.

[0045] Step S2, Temperature Control: Add glycerin to the temperature control component 15, start the circulation pump and heating / cooling unit to circulate the glycerin in the temperature conduction chamber 10, and control the glycerin temperature within the target temperature range of -10℃ to 100℃ according to the predetermined working conditions, such as -10℃, 20℃, 60℃ or 80℃. During the temperature control process, temperature changes are monitored by temperature sensors arranged at the inlet and outlet of the temperature conduction chamber 10 and inside the specimen. When the specimen temperature stabilizes at the target temperature and the temperature fluctuation is within the allowable range, proceed to the next step.

[0046] Step S3, Slope Adjustment: Based on the required simulated road longitudinal slope (e.g., horizontal, 3° uphill, 8° uphill, or 5° downhill), set the target slope value of the specimen groove 9 through the central control interface. The central control and data acquisition system drives the crane assembly 14 to move, raising or lowering the lifting shaft 12, causing the temperature conducting cavity 10 and the specimen groove 9 to rotate around the fixed shaft 13 to the set angle. Simultaneously, the angle adjustment assembly 4 is driven to adjust the angle of the upper loading and measurement system, ensuring that the loading plane where the test wheel 1 is located maintains the same slope as the specimen groove 9. The system can use angle sensors to provide feedback on the actual angles of the upper and lower structures. When the deviation between the two and the set target angle is within the allowable range, the adjustment stops and the position is locked.

[0047] Step S4, Unidirectional Circular Rolling Loading and Rolling Friction Measurement: After the specimen temperature and slope stabilize, the vertical loading mechanism is activated to apply a preset vertical load (e.g., 0.7 kN) to the test wheel 1, causing the test wheel 1 to press against the specimen surface; the test wheel transmission assembly 3 is activated to drive the test wheel 1 to circulate unidirectionally along an elliptical closed trajectory, with the wheel speed varying according to a preset wheel speed curve (acceleration segment, constant speed segment, deceleration segment); the two test wheels 1 are staggered in phase on the elliptical wheel track, alternately passing through the specimen's action area, ensuring that at any given moment, at least one test wheel 1 applies a load to the specimen, achieving continuous unidirectional cumulative loading on the same specimen; the friction force test sensor 2 collects the rolling friction force between the test wheel 1 and the specimen surface in real time during the rolling loading process, and records the rolling friction curve as a function of time, wheel speed, temperature, and slope.

[0048] Step S5, Measurement of Pinch Braking Condition and Peak Sliding Friction: In the constant speed or deceleration section of rolling loading, the central control and data acquisition system issues control commands according to the preset conditions, driving the braking actuator to apply short-term braking torque to the test wheel 1 at a specified time, causing the test wheel 1 to slip momentarily, forming a pinch braking condition similar to vehicle braking; the friction force test sensor 2 will output a peak value during the pinch braking process, which corresponds to the peak value of sliding friction between the test wheel 1 and the surface of the specimen; by adjusting the braking torque, the duration of pinch braking and the repetition period, sliding friction-time curves under different slip conditions can be obtained, and combined with rolling friction data, to analyze the anti-skid performance of asphalt mixtures.

[0049] Step S6, Rainfall Simulation and Drainage: To simulate rainy or slippery road conditions, during part or all of the time periods in steps S4 and / or S5, the water sprinkler assembly is activated, allowing water in the water tank 5 to flow into the water pipe 7 through the water guide channel 6, and then be evenly sprayed onto the surface of the specimen through the spray holes or nozzles on the water pipe 7. By adjusting the water pump speed and the opening of the solenoid valve, a constant rainfall intensity or a phased rainfall process can be achieved. Water accumulated on the surface of the specimen flows along the edge into the drainage channel 11, and then into the sewage collection unit 16 through the drainage pipe, forming a controlled rainfall-drainage cycle. During the test, various time courses such as "drying → rainfall → continuous rainfall → stop rainfall → wet decay" can be set as needed to examine the impact of rainfall on rutting development and anti-skid performance.

[0050] Step S7, DIC full-field displacement and strain measurement: During the entire loading and rainfall process, the central control and data acquisition system sends a trigger signal to the high-frequency industrial camera 8 according to the set frame rate. The high-frequency industrial camera 8 synchronously acquires the speckle image sequence on the surface of the specimen. After the acquisition is completed, the image sequence is input into the digital image correlation (DIC) analysis unit. The displacement vector field and strain field of each pixel on the surface of the specimen are solved by the correlation matching algorithm to obtain the full-field strain cloud map at different time sections. By performing time registration and spatial mapping with the test wheel 1 trajectory, rut depth measurement data and friction curve, the strain concentration zone, crack initiation and propagation zone, as well as the surface wear, polishing and texture depth evolution of the asphalt mixture can be identified, thus realizing a visual characterization of rutting mechanism and apparent texture changes.

[0051] Step S8, Data Fusion and Performance Evaluation: After loading and data acquisition, the central control and data acquisition system comprehensively processes multiple sets of test results under different temperatures, slopes, and dry / rainy conditions, including: rutting depth-time curves and dynamic stability indices; the variation of rolling / sliding friction coefficients with wheel speed, temperature, and moisture content; the DIC full-field strain cloud map and its temporal evolution, identifying key strain concentration areas and crack propagation paths; and the temporal variation of apparent texture parameters (such as macroscopic texture depth and microscopic texture smoothing degree). By comparing and analyzing data from different working conditions, the rutting sensitivity evaluation index and skid resistance degradation law of asphalt mixtures on uphill or downhill sections and under dry or rainy conditions can be obtained, providing a basis for pavement structure design, material mix optimization, and maintenance strategies during operation.

[0052] To facilitate understanding and implementation by those skilled in the art, the DIC displacement / strain solution and the calculation of rutting and wear / polishing indices involved in this invention can be performed using the following algorithm flow and mathematical expressions. The following formulas are only preferred implementation methods, and this invention is not limited to specific numerical algorithms.

[0053] Correlation matching and displacement field solution: Let the reference image be... The image at a certain moment after deformation is Several relevant sub-regions (speckle windows) were selected on the surface of the specimen. The coordinates of the center of each sub-region in the reference image are: Its corresponding coordinates in the deformed image are Then the displacement vector of this subregion is .

[0054] Normalized cross-correlation coefficient is preferred as the relevance matching criterion, and its expression is: , in, Given displacement assumptions The correlation coefficient at time t, with a value range of [−1, 1]; For sub-region The average gray level of the internal reference image. For sub-region The average gray level of the image after internal deformation. Let k be the set of pixels in the relevant sub-region. By searching within the displacement search domain, The largest The optimal displacement vector of the sub-region center point can then be obtained: , For all sub-regions By performing the above matching, the discrete displacement field on the surface of the asphalt mixture specimen can be obtained: , For vertical displacement (e.g., to calculate rut depth), image coordinates and physical height coordinates can be mapped to three-dimensional coordinates through calibration. The vertical displacement is obtained. .

[0055] Local least squares fitting and displacement gradient: To avoid introducing noise amplification by directly differentiating discrete displacements, this invention preferably uses local least squares fitting in each small neighborhood. The displacement field is smoothly fitted using the local least squares method. In point The neighborhood centered Within this range, it is assumed that the displacement is approximately a first-order polynomial over a small area: , in, and These represent the horizontal and vertical displacement components in the image coordinate system. These are the local fitting coefficients; With all sampling points in the neighborhood Discrete displacement For the observed values, minimize the following expression using the least squares method: , We obtain a set of optimal fitting coefficients: ; Then at point The displacement gradient at that point can be approximated as: .

[0056] Strain field calculation (displacement field → strain field): After obtaining the local displacement gradient, small deformation strain or Green-Lagrange strain can be selected according to the specific application. This invention preferably adopts the Green-Lagrange strain tensor form, which takes into account the applicability of large deformation. Construct the deformation gradient tensor: ; Green-Lagrange strain tensor for: , Where T represents the matrix transpose operation. Given an identity matrix, after expansion, we get: , in, Normal strain components in the principal direction For shear strain components, when the deformation is small, the linear elastic small strain approximation can also be used: , in, The positive strain in the x-direction characterizes the degree of elongation or compression of a material in the x-direction. It is defined as the relative change in length per unit length along the x-direction; a positive value indicates tension, and a negative value indicates compression. The strain is the normal strain in the y-direction, characterizing the degree of elongation or compression of the material in the y-direction; This is the shear strain in the xy plane, characterizing the change in angle between material elements in the xy plane (i.e., the shear deformation between two originally perpendicular line segments). This term is non-zero when the material undergoes shear displacement. Let x be the displacement of the material point in the x-direction. Let be the displacement of the material point in the y-direction.

[0057] DIC Extraction of Rut Depth: Based on the full-field displacement field, this invention considers ruts as the result of local vertical displacement of the asphalt mixture surface. The curve of the wheel track center path in the specimen coordinate system is defined as follows: The discrete points are The corresponding vertical displacement is ; at the moment before loading For reference, the depth of the ruts at any time t It can be defined as: , By analyzing different times calculate This allows us to obtain the evolution curves of rut depth versus time or rut depth versus load cycle number. Similarly, virtual strain gauges can be arranged at the edge of the wheel track or in the transverse section to extract local shear deformation and springback behavior.

[0058] Apparent texture plane fitting and polishing / wear index: To quantitatively characterize polishing / wear and anti-skid performance, this invention selects N calibration points in the rut area, whose three-dimensional coordinates at time t are... Assume that the surface can be approximated by a plane after the experiment: , in, The height coordinates of the surface point at test time t represent the geometric changes of the specimen surface during rutting loading. The coordinates are along the length of the specimen or the direction of travel. The coordinates are along the width of the specimen or perpendicular to the direction of travel. To fit the slope of the plane in the X direction, To fit the slope of the plane in the Y direction, The plane intercept at time t reflects the degree of uplift, subsidence, or wear of the overall surface as it changes over time. Fitting coefficients using the least squares method , and To minimize the sum of squared residuals: , Where N represents the total number of discrete data points extracted from the surface of the specimen at time t for fitting the plane; Define residual: , Based on this, an apparent dispersion (variation) index is defined. : , At the initial moment of the experiment Apparent structural dispersion (variability) index Based on, the termination time The polishing index can be defined as: , in, The polishing index describes the degree to which the surface of an asphalt mixture specimen changes from "rough" to "smooth" during rutting loading. The higher the value, the more pronounced the polishing. At the initial moment of the experiment The larger the standard deviation of surface elevation, the more obvious the initial surface unevenness, the rougher the surface texture, and the better the anti-slip performance. The end time of the experiment Surface elevation standard deviation, if much smaller This indicates that the surface has been significantly smoothed, meaning that the polishing process is severe. when Larger and Significantly lower than When the surface texture is severely worn smooth and the aggregate is noticeably polished; if and If the values ​​are close to or decrease but the residual distribution is discrete, it indicates that the apparent structure is largely retained and the anti-skid performance is well maintained. The aforementioned polishing index, rut depth evolution curve, and rolling / sliding friction coefficient can be used together to establish a quantitative relationship between "rut-structure-friction performance", thereby outputting the law of anti-skid performance degradation and comprehensive evaluation index.

[0059] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art. The general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A multifunctional asphalt mixture rutting test method, characterized in that, The test apparatus includes a chassis (17), a loading and measurement system, a specimen support and temperature control drainage system, an environmental simulation and optical measurement system, and a central control and data acquisition system. The loading and measurement system includes a test wheel (1), a test wheel transmission assembly (3), a friction force test sensor (2), an angle adjustment assembly (4), and a braking actuator. The specimen support and temperature control drainage system includes a specimen groove (9), a temperature-conducting cavity (10) surrounding the bottom and sidewalls of the specimen groove (9), a temperature control assembly (15) communicating with the temperature-conducting cavity (10), a drainage trough (11) surrounding the specimen groove (9), a wastewater collection unit (16) communicating with the drainage trough (11), and a bottom sidewall of the temperature-conducting cavity (10). The system includes a hinged fixed shaft (13), a lifting shaft (12) connected to the bottom of the other side of the temperature conduction cavity (10), and a crane assembly (14) for driving the lifting shaft (12) to rise and fall; the environmental simulation and optical measurement system includes a water tank (5), a water guide channel (6), a sprinkler pipe (7), and a high-frequency industrial camera (8). The water tank (5) is located on the top outside of the chassis (17). The water guide channel (6) is connected to the water tank (5). One end of the sprinkler pipe (7) is connected to the water guide channel (6), and the other end of the sprinkler pipe (7) is placed in the opening of the drainage channel (11). The high-frequency industrial camera (8) is located on the inner wall of the chassis (17); the central control and data acquisition system is connected to the test wheel transmission assembly (3) and the brake actuator respectively. The mechanism, angle adjustment component (4), temperature control component (15), water tank (5), water guide channel (6), water spray pipe (7), high frequency industrial camera (8) and friction force test sensor (2) are electrically connected; the method includes the following steps: Step 1: Place the asphalt mixture specimen in the specimen groove (9), so that the bottom surface of the specimen is in contact with the bottom of the specimen groove (9), and spray a random speckle pattern on the upper surface of the specimen; Step 2: Inject the heat-conducting medium into the temperature control component (15) and start the circulation, so that the heat-conducting medium circulates in the temperature-conducting cavity (10) to heat or cool the specimen, and stabilize the specimen temperature to the preset target temperature; Step 3: Drive the lifting shaft (12) to lift and lower through the crane component (14), so that the temperature-conducting cavity (10) and The specimen groove (9) rotates around the fixed axis (13) to the preset slope, and the loading and measurement system is driven to rotate synchronously to the same slope as the specimen groove (9) by the angle adjustment component (4); Step 4: Apply a preset vertical load so that the test wheel (1) presses against the specimen surface. The test wheel transmission component (3) drives the test wheel (1) to run unidirectionally along the closed trajectory. During the rolling loading process, the friction force test sensor (2) collects the rolling friction force data between the test wheel (1) and the specimen surface in real time; Step 5: At the preset loading time, control the braking actuator to apply a short-time braking torque to the test wheel (1) to form a point braking condition. The friction force test sensor (2) collects the peak value of the sliding friction force between the test wheel (1) and the specimen surface;Step 6: During Step 4 and / or Step 5, simulated rainfall is sprayed onto the specimen surface through the water tank (5), water channel (6), and sprinkler pipe (7). The water from the specimen surface is collected through the drainage channel (11) and discharged into the sewage collection unit (16), forming a controlled rainfall-drainage condition. Step 7: Throughout Step 4-6, the central control and data acquisition system sends a synchronous trigger signal to the high-frequency industrial camera (8). The high-frequency industrial camera (8) acquires image sequences of the specimen surface at a set frame rate and inputs the image sequences into the digital image correlation (DIC) analysis unit to calculate the full-field displacement and strain distribution of the specimen surface. Step 8: The central control and data acquisition system performs time registration and fusion of temperature, slope, wheel speed, rainfall, rolling friction, sliding friction, and full-field displacement or strain data, and outputs the rutting deformation, skid resistance, and road surface texture evolution indicators of the asphalt mixture under the stated temperature, slope, and rainfall conditions.

2. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, The closed trajectory described in step 4 is formed by an elliptical wheel track and guide wheel assembly fixed on the upper structure of the chassis (17). The test wheel transmission assembly (3) drives the two test wheels (1) to run unidirectionally along the elliptical wheel track, and the installation positions of the two test wheels (1) on the elliptical wheel track are staggered in phase, so that the two test wheels (1) alternately pass through the test piece action area.

3. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, The heat-conducting medium in step 2 is glycerol. The temperature control component (15) controls the temperature of glycerol within the range of -10℃ to 100℃ and circulates it to the temperature-conducting cavity (10) to achieve rapid temperature control of the specimen over a wide temperature range.

4. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, In step 3, the specimen groove (9) and the longitudinal axis of the loading and measurement system are adjusted to form a continuous adjustable slope of 0° to 15°, and under any set slope, the test wheel (1) remains perpendicular to the normal of the contact area of ​​the specimen surface.

5. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, In step 4, the wheel speed of the test wheel (1) runs according to a preset wheel speed curve including an acceleration segment, a constant speed segment and a deceleration segment. In step 5, the timing of the point braking is set within the constant speed segment or the deceleration segment.

6. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, In step 6, the rainfall flow rate and duration are controlled by adjusting the water outlet of the water tank (5) and the opening of the nozzles or spray heads on the sprinkler pipe (7), so that the rainfall conditions include at least one of the following conditions: constant rainfall intensity condition, phased rainfall intensity change condition, or composite rainfall intensity condition linked to wheel speed and temperature.

7. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, In step 7, the high-frequency industrial camera (8) establishes a time synchronization relationship with the control signals of the test wheel transmission assembly (3), the temperature control assembly (15) and the sprinkler pipe (7). The digital image correlation (DIC) analysis unit calculates the full-field strain cloud map of different time sections of the specimen surface based on the image sequence, and performs corresponding analysis on the strain concentration area and the path, rut depth and friction force changes of the test wheel (1).

8. The multifunctional asphalt mixture rutting test method according to claim 1, characterized in that, In step 8, multiple sets of test results under different temperatures, slopes, and rainfall conditions are further compared and analyzed to obtain the rutting sensitivity evaluation index and skid resistance degradation law of asphalt mixtures on uphill or downhill sections and under dry or rainy conditions, which can be used to guide pavement structure design and material selection.

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