Dynamic control methods to suppress low-temperature cracking of asphalt pavements in cold regions

Abstract

This invention discloses a dynamic control method for suppressing low-temperature cracking of asphalt pavements in cold regions, belonging to the field of asphalt pavement maintenance technology. The method includes the following steps: setting up a stress relief zone around the crack; assessing the pavement cracking and determining the spatial location of the stress relief zone; using finite element software for simulation to determine the geometric parameters of the stress relief zone, and simulating material replacement in the stress relief zone. This invention can dynamically control the cracking of asphalt pavements with different cycles and service performance. By setting up stress relief zones according to the cracking patterns of the serviced pavement, it releases the temperature stress of the pavement, reducing the possibility of future cracking of the asphalt pavement at low temperatures; it reduces the risk of low-temperature cracking of asphalt pavements, and increases the service performance and lifespan of the asphalt pavement.

Description

Technical Field

[0001] This invention belongs to the field of asphalt pavement maintenance technology, and specifically relates to a dynamic control method for inhibiting low-temperature cracking of asphalt pavements in cold regions. Background Technology

[0002] In cold regions, low-temperature cracking is one of the most common defects in asphalt pavements. Due to the difference in material shrinkage rates between the asphalt surface layer and the semi-rigid base layer, the viscoelasticity of asphalt decreases significantly in low-temperature environments, leading to thermal shrinkage cracks. Once the pavement comes into contact with the outside atmosphere, moisture enters the cracks and changes from a liquid phase to a solid phase, increasing in volume and causing the cracks to expand further. Simultaneously, under repeated vehicle loads, the overall structure of the pavement working with cracks deteriorates, causing structural damage. Currently, traditional crack repair methods, such as crack filling, crack sealing tape, and milling filling, do not consider the cracking patterns and cannot prevent the cracks from continuing to expand, resulting in secondary repairs during actual maintenance and increasing the maintenance costs of asphalt pavements. Summary of the Invention

[0003] To address the above problems, this invention provides a dynamic control method for suppressing low-temperature cracking of asphalt pavements in cold regions.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions includes the following steps:

[0006] S100: A stress relief zone is set around the crack;

[0007] For the stress relief zone, its contraction length is as follows:

[0008]

[0009] For the original road surface area, its shrinkage length is as follows:

[0010]

[0011] In the formula, σ—original pavement stress; E 释放 —Release zone elastic modulus (MPa); α 释放 —Coefficient of thermal expansion in the release area (°C); ΔT —Temperature difference (°C); W — 1 / 2 width of the stress relief zone;

[0012] E 原路面 —Original pavement elastic modulus (MPa); α 原路面 —Original pavement thermal shrinkage coefficient (°C); L1— 1 / 2 original road length;

[0013] To ensure that the length of the asphalt road remains constant, the shrinkage length of the stress relief zone is the same as the shrinkage length of the original pavement zone, as shown in the following formula:

[0014]

[0015] For the stress relief zone, the following equation is satisfied:

[0016]

[0017] For the original road surface area, the deformation is less than the allowable deformation, as shown in the following formula:

[0018]

[0019] In the formula, [ε] — allowable deformation; L — 1 / 2 crack spacing;

[0020] S200: Determines the spatial location of the stress relief zone;

[0021] By assessing pavement cracking and determining the crack spacing, the spatial location of the stress relief zone can be determined.

[0022] S300: Use finite element software to perform simulation, determine geometric parameters, and simulate material replacement in the stress relief zone.

[0023] Furthermore, in step S200, pavement cracking is evaluated in the following two cases:

[0024] (1) Assessment of cracking in newly constructed pavement:

[0025] Based on the low-temperature cracking index, the different crack spacing L are determined as follows:

[0026] L = 100(CI+1) -1 ;

[0027] Where: L—crack spacing (m); CI—low-temperature cracking index;

[0028] (2) Assessment of cracking in in-service pavement:

[0029] Statistically analyze the cracking rate of in-service pavements, obtain the crack spacing Lcr, and compare it with the predicted crack spacing L. p Compare: If Lcr ≤ L p The treatment location is pre-set based on the transverse through-crack; if Lcr ≥ L p The treatment location is 1 / 2 of the intact road surface in service, until the spacing is less than the predicted crack spacing.

[0030] Furthermore, in step S300, the geometric parameters of the stress relief zone include ambient temperature, thermostatic shrinkage coefficient, and viscoelastic parameters, which are determined as follows:

[0031] (1) Determination of ambient temperature

[0032] The minimum temperature values ​​corresponding to different years and different quantiles were calculated based on continuous low temperatures and extreme minimum temperatures.

[0033] (2) Determination of the coefficient of thermal shrinkage

[0034] The linear shrinkage coefficient of asphalt mixtures was determined, and the shrinkage coefficients for each temperature range were calculated as follows:

[0035]

[0036] In the formula, β1 is the thermal shrinkage coefficient of the asphalt mixture specimen being tested; ΔT is the temperature difference; ε is the strain difference within ΔT; and β2 is the linear expansion coefficient of the standard specimen.

[0037] (3) Determination of viscoelastic parameters

[0038] A shear rheometer was used to scan the frequency of asphalt mixture at different temperatures to obtain viscoelastic information of asphalt mixture at different temperatures or frequencies. The test data were then analyzed to determine the viscoelastic parameters of the asphalt mixture.

[0039] Furthermore, in step (1) of step S300, when determining the ambient temperature, calculation and analysis are performed based on the generalized extreme value distribution model. After obtaining the fitting parameters of the distribution function, the minimum temperature values ​​corresponding to different years and different quantiles are obtained.

[0040] Furthermore, in step (3) of step S300, during the process of determining the viscoelastic parameters, the obtained viscoelastic information is used to perform translation and superposition processing on the experimental data using the WLF equation and the modified function model proposed based on the Sigmoidal function to obtain the master curve at the given reference temperature, thereby determining the viscoelastic parameters of the required material.

[0041] Furthermore, the predetermined reference temperature is 20°C.

[0042] The technological advancements achieved by this invention compared to existing technologies are as follows:

[0043] This invention, based on the cracking patterns of in-service pavements, releases temperature stress by setting up stress relief zones, reducing the likelihood of future cracking of asphalt pavements at low temperatures. It also replaces the materials in the stress relief zones of asphalt pavements in cold regions, avoiding the drawbacks of later cracking and re-grouting, resulting in a tighter bond between the asphalt pavement mixture and the filler material, further reducing the risk of low-temperature cracking. This invention enables dynamic control of asphalt pavement cracking at different cycles and service performance levels, providing a new method and approach to solving low-temperature cracking in asphalt pavements in cold regions, shifting from a passive to an active approach, and increasing the performance and service life of asphalt pavements. Attached Figure Description

[0044] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0045] In the attached diagram:

[0046] Figure 1 A flowchart illustrating a dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions, provided as an embodiment of the present invention;

[0047] Figure 2 This is a spatial schematic diagram of the stress relief zone in an embodiment of the present invention;

[0048] Figure 3 This is a fitted graph of the probability distribution of extreme minimum temperatures in Harbin.

[0049] Figure 4 This is a schematic diagram of an asphalt pavement structure.

[0050] Figure 5 A finite element model of the road surface structure;

[0051] Figure 6 To incorporate temperature field data into the road surface model;

[0052] Figure 7 This is a model of the pavement structure after material replacement;

[0053] Figure 8 This is a statistical diagram of pavement temperature and stress after the stress relief zone has been filled. Detailed Implementation

[0054] The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0055] like Figure 1 As shown, a dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions includes the following steps:

[0056] S100: A stress relief zone is set around the crack.

[0057] For stress relief zones, such as Figure 2 As shown, the crack spacing is 2L, and the stress relief zone width is 2W. The shaded area is the stress relief zone, and the blank area is the original pavement. Formulas 1 and 2 are applicable.

[0058] L = L1 + W

[0059] (Equation 1)

[0060] L = L² + ΔL + W (Equation 2)

[0061] In the formula, L1—— Original road surface length; L2—— Width of the stress relief zone; ΔL—contraction length;

[0062] Road surface shrinkage can be divided into shrinkage due to its own material and shrinkage due to temperature. Since the stress release zone is continuous with the original road surface area, the stress is equal everywhere during shrinkage.

[0063] For the stress relief zone, its contraction length is as follows:

[0064]

[0065] For the original road surface area, the shrinkage length is as shown in Formula 4:

[0066]

[0067] In the formula, ε σ —Material shrinkage strain; ε T —Material thermal shrinkage strain; W— 1 / 2 width of the stress relief zone;

[0068] σ—Original pavement stress; E 释放 —Release zone elastic modulus (MPa); α 释放 —Coefficient of thermal expansion in the release area (°C); ΔT —Temperature difference (°C);

[0069] E 原路面 —Original pavement elastic modulus (MPa); α 原路面 —Original pavement thermal shrinkage coefficient (°C); L1— 1 / 2 original road length;

[0070] To ensure that the length of the asphalt road remains constant, the shrinkage length of the stress relief zone is the same as the shrinkage length of the original pavement zone, as shown in the following formula:

[0071]

[0072] For asphalt pavements with different service years and service conditions, this invention can dynamically adjust the stress release zone to meet the dynamic control of cracks. Therefore, it is necessary to ensure that the release zone and the original pavement are not damaged.

[0073] For the stress relief zone, equation 6 should be satisfied:

[0074]

[0075] For the original road surface area, its deformation should be less than the allowable deformation, as determined by equations 1 and 5.

[0076] Equation 6 can be used to derive Equation 7:

[0077]

[0078] In the formula, [ε] — allowable deformation; L — 1 / 2 crack spacing.

[0079] S200: Determines the spatial location of the stress relief zone;

[0080] By assessing pavement cracking and determining the crack spacing, the spatial location of the stress relief zone can be determined.

[0081] The following two scenarios will be evaluated:

[0082] (1) Assessment of cracking in newly constructed pavement:

[0083] Since this is a newly constructed road and no cracks have appeared on the pavement, the Low-Temperature Cracking Index (CI), a characterizing low-temperature shrinkage and cracking of asphalt pavement in seasonally frozen areas, can be used as a basis. A simulation prediction method for the transverse crack coefficient of asphalt pavement based on energy principles is employed. Different low-temperature cracking indices (CI) are used as the basis for predicting the crack spacing of the asphalt pavement. Different crack spacings (L) are determined based on different CI indices as follows:

[0084] L = 100(CI+1) -1 ;

[0085] Where: L—crack spacing (m); CI—low-temperature cracking index;

[0086] (2) Assessment of cracking in in-service pavement:

[0087] Since the road is already in service, we can survey and statistically analyze the existing cracking rate, obtain the crack spacing Lcr, and compare it with the predicted crack spacing L. p Compare: If Lcr ≤ L p The treatment location is pre-set based on the transverse through-crack; if Lcr ≥ L pThe treatment location is set at 1 / 2 of the intact road surface in service, until the spacing is less than the predicted crack spacing. The predicted crack spacing L... p For reference, see the invention patent "A simulation prediction method for the transverse crack coefficient of asphalt pavement based on the energy principle" (application number CN202210669516.X).

[0088] S300: Use finite element software to perform simulation, determine the geometric parameters of the stress relief zone, and simulate material replacement in the stress relief zone.

[0089] The geometric parameters of the stress relief zone include ambient temperature, thermal shrinkage coefficient, and viscoelastic parameters, which are determined as follows:

[0090] (1) Determination of ambient temperature

[0091] Based on surveys and statistics, and taking into account local climate zones, local meteorological data were collected from meteorological stations in various regions, and measured temperatures were rationally selected. Appropriate climate indicators were chosen; the continuous (≥5 days) low temperature index is closely related to road surface temperature cracks, and the extreme minimum temperature characterizes the lowest temperature experienced by the road surface during its service life. These two indicators were adopted as parameters for extreme winter climates.

[0092]

[0093] The calculation and analysis are based on a generalized extreme value distribution model. After obtaining the fitting parameters of the distribution function, the minimum temperature values ​​corresponding to different years and different quantiles are obtained. These calculation processes are all existing technologies and will not be described in detail here.

[0094] (2) Determination of the coefficient of thermal shrinkage

[0095] According to the formula in T0720-1993 of the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), the linear shrinkage coefficient of asphalt mixtures was determined, and the shrinkage coefficients for each temperature range were calculated as follows:

[0096]

[0097] In the formula, β1 is the thermal shrinkage coefficient of the asphalt mixture specimen; ε is the strain difference within ΔT; ΔT is the temperature change difference; and β2 is the linear expansion coefficient of the standard specimen.

[0098] (3) Determination of viscoelastic parameters

[0099] A shear rheometer was used to scan the frequency of asphalt mixture at different temperatures to obtain viscoelastic information of asphalt mixture at different temperatures or frequencies. The test data were then analyzed to determine the viscoelastic parameters of the asphalt mixture.

[0100] The obtained viscoelastic information was used to obtain the master curve at a predetermined reference temperature of 20°C by employing the theoretical formula WLF equation and a modified function model based on the Sigmoidal function, after shifting and superimposing the experimental data. This allowed for the determination of the viscoelastic parameters of the required material. These calculation processes are existing technologies and will not be elaborated upon here.

[0101] The above steps are used to obtain ambient temperature, thermal shrinkage coefficient, and viscoelastic parameters. A finite element model is established using Abaqus software. By replacing the material with a high-toughness, high-elasticity material, a temperature stress simulation calculation model is established, and the temperature stress accumulation process is compared and analyzed. These calculation processes are all existing technologies and will not be elaborated further here.

[0102] The following is a detailed process of the Abaqus finite element simulation:

[0103] (1) Determine the crack spacing

[0104] Considering the rapid development of the initial low-temperature cracking index of roads, taking a 100-meter road surface as an example, as shown in Table 1 below:

[0105]

[0106] (2) Determine the temperature range

[0107] Taking cold regions as an example, data from the past 8 years of cold season were collected, and the 99.9th percentile value was defined as the threshold for the lowest annual temperature in Harbin.

[0108] according to Figure 3 It is known that the lowest annual temperature over the past 8 years has been around -27℃, therefore the lowest temperature simulated in this study is -30℃; referring to data from the Harbin Meteorological Station, the average temperature of the hottest month is selected as 20℃. The starting temperature is 20℃, the cooling rate is 10℃ / h, and the road surface structure adopts an overall cooling method.

[0109] (3) Determine the thermal shrinkage coefficient of the pavement structure material

[0110] The model uses an asphalt surface layer of 5cm AC-13 + 6cm AC-20 + 8cm AC-25, and a base layer of 50cm cement-stabilized crushed stone. The asphalt pavement structure is shown in [reference needed]. Figure 4 .

[0111] The low-temperature shrinkage coefficient (β2) of different layers was calculated at different temperatures; in this experiment, it was 4.2 × 10⁻⁶. -6 (See Table 2 for the low-temperature shrinkage coefficient / ℃). The low-temperature shrinkage coefficient decreases as the temperature decreases.

[0112] Table 2 Low-temperature shrinkage coefficients of different structural layers (×10) -6 )

[0113]

[0114] (4) Establishing a finite element model

[0115] Following the road design, a pavement structure model was established based on specific assumptions for finite element analysis. The finite element model used was a three-dimensional 8-node linear elastic isoparametric element. The boundary conditions were: ① no horizontal displacement on all sides; ② completely fixed soil base surface; ③ interlayer interfaces were in a bound state. When creating the model, the Z-axis represented the pavement width, the Y-axis the thickness direction (vertically upwards was positive), and the X-axis the driving direction. Figure 5 As shown.

[0116] After determining the boundary conditions, the temperature field data was added to the model. A mean-cooling method was used, with an interlayer friction coefficient of 1. Temperature loads were applied according to different temperatures. The basic parameters of the model were input to establish a full-scale finite element asphalt pavement structure model with a longitudinal length of 100m. Figure 6 As shown.

[0117] Taking CI=2, width 30cm, depth 40cm as an example, the birth and death element method is used to remove the surface layer at both ends along the x-direction (30cm) and y-direction (4cm), and then fill in AC-5 of the same size. This is then activated in subsequent analysis steps. Figure 7 As shown.

[0118] (5) Temperature stress analysis

[0119]

[0120] The data above shows that replacing the stress-relief zone can effectively reduce the temperature stress on the pavement. For example... Figure 8 As shown, by comparing the magnitude of the reduction in temperature stress of the pavement before and after setting transverse cracks, it can be determined that the appearance of cracks can be effectively controlled in pavements with cracks and filled with high-toughness and high-elasticity fine materials when the temperature changes significantly in cold regions.

[0121] Low-temperature cracking of asphalt pavement is closely related to temperature stress. This invention achieves control of temperature stress while ensuring the integrity of the road structure, providing an effective method to suppress low-temperature cracking of asphalt pavement in cold regions.

[0122] In summary, this invention can dynamically control low-temperature cracking of asphalt pavements with different service cycles and performance characteristics based on the cracking patterns of in-service pavements. By setting up stress relief zones to release the temperature stress of the pavement, it reduces the possibility of future cracking of asphalt pavements at low temperatures. This invention provides a new method and approach to solving low-temperature cracking of asphalt pavements in cold regions, transforming a passive approach into an active one, and increasing the service performance and lifespan of asphalt pavements.

[0123] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions, characterized in that, Includes the following steps: S100: A stress relief zone is set around the crack; For the stress relief zone, its contraction length is as follows: For the original road surface area, its shrinkage length is as follows: In the formula, σ—original pavement stress; E 释放 —Release zone elastic modulus (MPa); α 释放 —Coefficient of thermal expansion in the release area (°C); ΔT —Temperature difference (°C); W — 1 / 2 width of the stress relief zone; E 原路面 —Original pavement elastic modulus (MPa); α 原路面 —Original pavement thermal shrinkage coefficient (°C); L1— 1 / 2 original road length; To ensure that the length of the asphalt road remains constant, the shrinkage length of the stress relief zone is the same as the shrinkage length of the original pavement zone, as shown in the following formula: For the stress relief zone, the following equation is satisfied: For the original road surface area, the deformation is less than the allowable deformation, as shown in the following formula: In the formula, [ε] — allowable deformation; L — 1 / 2 crack spacing; S200: Determines the spatial location of the stress relief zone; By assessing pavement cracking and determining the crack spacing, the spatial location of the stress relief zone can be determined. S300: Use finite element software to perform simulation, determine the geometric parameters of the stress relief zone, and simulate material replacement in the stress relief zone.

2. The dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions according to claim 1, characterized in that: In step S200, pavement cracking is evaluated in the following two cases: (1) Assessment of cracking in newly constructed pavement: Based on the low-temperature cracking index, the different crack spacing L are determined as follows: L=100(CI+1) -1 ; Where: L—crack spacing (m); CI—low-temperature cracking index; (2) Assessment of cracking in in-service pavement: Statistically analyze the cracking rate of in-service pavements, obtain the crack spacing Lcr, and compare it with the predicted crack spacing L. p Compare: If Lcr ≤ L p The treatment location is pre-set based on the transverse through-crack; if Lcr ≥ L p The treatment location is 1 / 2 of the intact road surface in service, until the spacing is less than the predicted crack spacing.

3. The dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold regions according to claim 2, characterized in that: In step S300, the geometric parameters of the stress relief zone include ambient temperature, thermal shrinkage coefficient, and viscoelastic parameters, and the determination process is as follows: (1) Determination of ambient temperature The minimum temperature values ​​corresponding to different years and different quantiles were calculated based on continuous low temperatures and extreme minimum temperatures. (2) Determination of the coefficient of thermal shrinkage The linear shrinkage coefficient of asphalt mixtures was determined, and the shrinkage coefficients for each temperature range were calculated as follows: In the formula, β1 is the thermal shrinkage coefficient of the asphalt mixture specimen being tested; ΔT is the temperature difference; ε is the strain difference within ΔT; and β2 is the linear expansion coefficient of the standard specimen. (3) Determination of viscoelastic parameters A shear rheometer was used to scan the frequency of asphalt mixture at different temperatures to obtain viscoelastic information of asphalt mixture at different temperatures or frequencies. The test data were then analyzed to determine the viscoelastic parameters of the asphalt mixture.

4. The dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold regions according to claim 3, characterized in that: In step (1) of step S300, when determining the ambient temperature, calculation and analysis are performed based on the generalized extreme value distribution model. After obtaining the fitting parameters of the distribution function, the minimum temperature values ​​corresponding to different years and different quantiles are obtained.

5. The dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions according to claim 3, characterized in that: In step (3) of step S300, during the process of determining the viscoelastic parameters, the obtained viscoelastic information is used to apply the WLF equation and adopt the modified function model based on the Sigmoidal function to translate and superimpose the experimental data to obtain the master curve at the given reference temperature, thereby determining the viscoelastic parameters of the required material.

6. The dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold regions according to claim 5, characterized in that: The established reference temperature is 20°C.

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