Dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold region

Abstract

The invention discloses a dynamic control method for inhibiting low-temperature cracking of an asphalt pavement in a cold region, and belongs to the technical field of asphalt pavement maintenance. Evaluating pavement cracking, and determining the spatial position of a stress release area; finite element software is used for conducting analogue simulation, geometric parameters of the stress release area are determined, and material replacement and filling simulation is conducted on the stress release area. According to the method, the cracking of the asphalt pavement with different periods and different service performances can be dynamically controlled, the stress release area is arranged according to the cracking rule of the service pavement to release the temperature stress of the pavement, and the cracking possibility of the asphalt pavement at low temperature in the future is reduced; the risk of low-temperature cracking of the asphalt pavement is reduced, and the usability and the service life of the asphalt pavement are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of asphalt pavement maintenance, and in particular relates to a dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold regions. Background Art

[0002] In cold regions, low-temperature cracking is one of the most common diseases of asphalt pavements. Due to the different materials and shrinkage rates of the asphalt surface layer and the semi-rigid base layer, the viscoelasticity of asphalt decreases significantly in a low-temperature environment, forming temperature shrinkage cracks. Once the inside of the road is connected to the outside atmosphere, moisture enters the cracks and changes from liquid to solid, and the volume increases, causing the cracks to expand further. At the same time, under the repeated action of vehicle loads, the overall structure of the pavement with seams will decline, causing structural damage. At present, traditional methods of repairing crack damage, such as caulking repair, seam tape repair, and milling filling, do not combine the cracking law of cracks, and cannot prevent the cracks from continuing to crack, resulting in secondary repairs of cracks during actual maintenance, increasing the maintenance cost of asphalt pavements. Summary of the invention

[0003] In order to solve the above problems, the present invention provides a dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions.

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

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

[0006] S100: Set up a stress relief zone around the crack;

[0007] For the stress release area, the contraction length is as follows:

[0008]

[0009] For the original pavement area, the contraction length is as follows:

[0010]

[0011] Where, σ is the original pavement stress; E 释放 ——Elastic modulus of release area (Mpa); α 释放 ——Temperature shrinkage coefficient of release area (℃); ΔT——Temperature difference (℃); W—— 1 / 2 width of stress relief zone;

[0012] E 原路面 ——Elastic modulus of original pavement (Mpa); α 原路面 ——Original pavement temperature shrinkage coefficient (℃); L1—— 1 / 2 original road length;

[0013] In order to ensure that the length of the asphalt road remains unchanged, the contraction length of the stress release area is the same as the contraction length of the original pavement area, as shown in the following formula:

[0014]

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

[0016]

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

[0018]

[0019] Where, [ε]——allowable deformation; L—— 1 / 2 cracking spacing;

[0020] S200: determining the spatial position of the stress release area;

[0021] By evaluating the cracking of the pavement and determining the crack spacing, the spatial location of the stress relief area is determined;

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

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

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

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

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

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

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

[0029] Count the cracking rate of the in-service pavement and obtain the crack spacing Lcr, which is compared with the predicted crack spacing L p For comparison: If Lcr≤L p , directly take the horizontal through crack as the target and preset it as the treatment position; if Lcr≥L p , with 1 / 2 of the complete section of the in-service pavement as the treatment position, until the spacing is smaller than the predicted cracking spacing.

[0030] Further, in step S300, the geometric parameters of the stress release zone include the ambient temperature, the thermal shrinkage coefficient and the viscoelastic parameters, and the determination process is as follows:

[0031] (1) Determination of ambient temperature

[0032] The lowest temperature values ​​corresponding to different years and different quantiles are calculated based on the continuous low temperature and extreme minimum temperature;

[0033] (2) Determination of thermal shrinkage coefficient

[0034] Determine the linear shrinkage coefficient of asphalt mixture and calculate the shrinkage coefficient in each temperature range as follows:

[0035]

[0036] Where, β1 is the temperature shrinkage coefficient of the asphalt mixture specimen; ΔT is the temperature change difference; ε is the strain difference within ΔT; β2 is the linear expansion coefficient of the standard specimen;

[0037] (3) Determination of viscoelastic parameters

[0038] The shear rheometer is used to scan the frequency of asphalt mixture at different temperatures. After obtaining the viscoelastic information of asphalt mixture at different temperatures or frequencies, the test data is analyzed and the viscoelastic parameters of asphalt mixture are determined.

[0039] Furthermore, in the process of determining the ambient temperature in step (1) of step S300, calculation and analysis are performed based on the generalized extreme value distribution model, and 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 the process of determining the viscoelastic parameters in step (3) of step S300, the viscoelastic information is obtained by using the WLF equation and a correction function model proposed based on the Sigmoidal function to translate and superimpose the test data to obtain the master curve at a given reference temperature, thereby determining the viscoelastic parameters of the required material.

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

[0042] Compared with the prior art, the present invention has the following technical advances:

[0043] The present invention can release the temperature stress of the pavement by setting a stress release zone according to the cracking law of the service pavement, thereby reducing the possibility of future asphalt pavement cracking at low temperatures; the stress release zone of the asphalt pavement in the cold region is filled with materials to avoid the disadvantages of cracking and re-filling in the later stage, so that the combination between the asphalt pavement mixture and the filling material is more tightly integrated, reducing the risk of low-temperature cracking of the asphalt pavement. The present invention can dynamically control the cracking of asphalt pavements with different cycles and different service performances, providing a new method and approach to solve the low-temperature cracking of asphalt pavements in cold regions, changing from passive to active, and increasing the performance and service life of the asphalt pavement. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0045] In the attached picture:

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

[0047] Figure 2 A spatial schematic diagram of a stress release area in an embodiment of the present invention;

[0048] Figure 3 This is the probability distribution fitting diagram of the extreme minimum temperature in Harbin;

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

[0050] Figure 5 It is the finite element model of the pavement structure;

[0051] Figure 6 A pavement model that incorporates temperature field data;

[0052] Figure 7 It is the pavement structure model after replacing the filling material;

[0053] Figure 8 This is a statistical diagram of pavement temperature stress after replacing the stress release area. DETAILED DESCRIPTION

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

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

[0056] S100: Provide stress relief areas around cracks:

[0057] For stress relief areas, such as Figure 2 As shown, the crack spacing is 2L, and the width of the stress release zone is 2W, where the shaded area is the stress release zone and the blank area is the original pavement. There are formulas 1 and 2:

[0058] L=L1+W

[0059] (Formula 1)

[0060] L=L2+ΔL+W (Formula 2)

[0062] In the formula, L1—— Original road length; L2—— Stress release zone width; ΔL——contraction length;

[0063] The shrinkage of the pavement can be divided into shrinkage due to its own material and temperature shrinkage. Since the stress release area is continuous with the original pavement area, the stress is equal everywhere during shrinkage.

[0064] For the stress release area, the contraction length is as follows:

[0065]

[0066] For the original road surface area, its contraction length is as shown in Formula 4:

[0067]

[0068] In the formula, ε σ ——Material shrinkage strain; ε T ——material temperature shrinkage strain; W—— 1 / 2 width of stress relief zone;

[0069] σ—original pavement stress; E 释放 ——Elastic modulus of release area (Mpa); α 释放 ——Temperature shrinkage coefficient of release area (℃); ΔT——temperature difference (℃);

[0070] E 原路面 ——Elastic modulus of original pavement (Mpa); α 原路面 ——Original pavement temperature shrinkage coefficient (℃); L1—— 1 / 2 original road length;

[0071] In order to ensure that the length of the asphalt road remains unchanged, the contraction length of the stress release area is the same as the contraction length of the original pavement area, as shown in the following formula:

[0072]

[0073] For asphalt pavements of different service years and service conditions, the present invention can dynamically adjust the stress release area to meet the dynamic control of cracks. Therefore, it is necessary to ensure that the release area and the original pavement are not damaged.

[0074] For the stress relief area, equation 6 should be satisfied:

[0075]

[0076] For the original road surface area, its deformation should be less than the allowable deformation. According to equations 1, 5 and

[0077] Formula 6 can be used to derive Formula 7:

[0078]

[0079] Where, [ε]——allowable deformation; L—— 1 / 2 cracking spacing.

[0080] S200: determining the spatial position of the stress release area;

[0081] By evaluating the cracking of the pavement and determining the crack spacing, the spatial location of the stress relief area is determined;

[0082] The following two situations are evaluated:

[0083] (1) Assessment of cracking of newly built pavement:

[0084] Since it is a newly built road, there are no cracks on the road surface. The low-temperature cracking index (CI), an indicator for characterizing low-temperature shrinkage and cracking of asphalt surface layers proposed in the "Highway Asphalt Pavement Design Specification" (JTGD50-2017) for seasonally frozen areas, can be used as a basis. A simulation prediction method for the transverse crack coefficient of asphalt pavement based on the energy principle is used, and different low-temperature cracking indices CI are used as the basis for predicting the crack spacing of asphalt pavement. Different crack spacings L are determined according to different CI indices as follows:

[0085] L=100(CI+1) -1 ;

[0086] Where: L——cracking distance (m); CI——low temperature cracking index;

[0087] (2) Assessment of cracking of in-service pavement:

[0088] Since the road is already in service, the existing cracking rate can be investigated and counted to obtain the crack spacing Lcr and the predicted crack spacing L p For comparison: If Lcr≤L p , directly take the horizontal through crack as the target and preset it as the treatment position; if Lcr≥L p, take 1 / 2 of the complete section of the in-service road surface as the treatment position, until the spacing is smaller than the predicted crack spacing. Among them, the predicted crack spacing L p Please refer to the invention patent "A simulation prediction method for transverse crack coefficient of asphalt pavement based on energy principle" (application number CN202210669516.X).

[0089] S300: Use finite element software to perform simulation, determine the geometric parameters of the stress release area, and simulate the material replacement of the stress release area.

[0090] The geometric parameters of the stress release zone include ambient temperature, thermal shrinkage coefficient and viscoelastic parameters, and the determination process is as follows:

[0091] (1) Determination of ambient temperature

[0092] According to the survey statistics, based on the local climate zoning, the local weather is collected with reference to the data of the meteorological stations in each district, and the measured temperature is reasonably selected. The appropriate climate index is selected. The continuous (≧5d) low temperature index is closely related to the pavement temperature cracks. The extreme minimum temperature represents the lowest temperature that the pavement is subjected to during its service. The above two indicators are used as winter extreme climate parameters.

[0093]

[0094] Based on the generalized extreme value distribution model, calculation and analysis are performed to obtain the fitting parameters of the distribution function, and the minimum temperature values ​​corresponding to different years and different quantiles are obtained. These calculation processes are all existing technologies and will not be repeated here.

[0095] (2) Determination of thermal shrinkage coefficient

[0096] According to the formula of T0720-1993 in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG E20-2011), the linear shrinkage coefficient of asphalt mixture is determined, and the shrinkage coefficient of each temperature range is calculated as follows:

[0097]

[0098] Where, β1 is the temperature shrinkage coefficient of the asphalt mixture specimen; ε is the strain difference within ΔT; ΔT is the temperature change difference; β2 is the linear expansion coefficient of the standard specimen;

[0099] (3) Determination of viscoelastic parameters

[0100] The shear rheometer is used to scan the frequency of asphalt mixture at different temperatures. After obtaining the viscoelastic information of asphalt mixture at different temperatures or frequencies, the test data is analyzed and the viscoelastic parameters of asphalt mixture are determined.

[0101] The obtained viscoelastic information uses the theoretical formula WLF equation, and adopts the correction function model proposed on the basis of the Sigmoidal function to translate and superimpose the test data to obtain the main curve at a given reference temperature of 20°C, thereby determining the viscoelastic parameters of the required material. These calculation processes are all existing technologies and will not be repeated here.

[0102] Through the above steps, the ambient temperature, thermal shrinkage coefficient and viscoelastic parameters are obtained; the finite element model is established using abaqus software, and the temperature stress simulation calculation model is established by replacing the high-toughness and high-elasticity materials to compare and analyze the temperature stress accumulation process. These calculation processes are all existing technologies and will not be repeated here.

[0103] The following is the specific process of abaqus finite element simulation:

[0104] (1) Determine the crack spacing

[0105] Considering that the initial low-temperature cracking index of the road develops rapidly, taking 100 meters of road surface as an example, as shown in Table 1:

[0106]

[0107] (2) Determine the temperature range

[0108] Taking cold regions as an example, data from the cold seasons of the past eight years were collected, and the 99.9% percentile value was defined as the annual minimum temperature threshold in Harbin.

[0109] according to Figure 3 It can be seen that the lowest temperature in each of the past 8 years is around -27℃, so the lowest temperature in this simulation is -30℃; referring to the data of 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 pavement structure adopts the overall cooling type.

[0110] (3) Determine the thermal shrinkage coefficient of pavement structure materials

[0111] The asphalt surface layer of this model is 5cmAC-13+6cmAC-20+8cmAC-25, the base layer is 50cm cement stabilized gravel, and the asphalt pavement structure is shown in Figure 4 .

[0112] Calculate the low-temperature shrinkage coefficient of different layers at different temperatures (β2 in this test is 4.2×10 -6 / ℃) is shown in Table 2. The low-temperature shrinkage coefficient decreases as the temperature decreases.

[0113] Table 2 Low temperature shrinkage coefficients of different structural layers (×10 -6 )

[0114]

[0115] (4) Establishing finite element model

[0116] Following the road design, the pavement structure model is established with specific assumptions for finite element calculation. The finite element model uses a three-dimensional 8-node linear elastic isoparametric element. The boundary conditions are: ① no horizontal displacement around; ② the soil base surface is completely fixed; ③ the interface connection between layers is in a bound state. When creating the model, the Z axis is the pavement width direction, the Y axis is the thickness direction and the vertical upward direction is the positive direction, and the X axis is the driving direction. Figure 5 shown.

[0117] After determining the boundary conditions, the data obtained from the temperature field are added to the model. The mean cooling method is adopted, the interlayer friction coefficient is 1, and the temperature load is applied according to different temperatures. The basic parameters of the model are input to establish a full-scale finite element asphalt pavement structure model with a longitudinal length of 100m. Figure 6 shown.

[0118] 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 of 30cm in the x direction and 4cm in the y direction, and then fill in the AC-5 of the same size and activate it in the subsequent analysis step, such as Figure 7 shown.

[0119] (5) Temperature stress analysis

[0120]

[0121] From the above data, it can be seen that replacing the stress release area can effectively reduce the temperature stress of the road surface. Figure 8 As shown in the figure, by comparing the reduction in temperature stress of the pavement before and after setting transverse cracks, it can be judged that when the temperature in cold areas changes greatly, the appearance of cracks in the pavement with cracks set and filled with high-toughness and high-elastic fine materials can be effectively controlled.

[0122] Low-temperature cracking of asphalt pavement is closely related to temperature stress. The present invention realizes the control of temperature stress under the premise of ensuring the integrity of road structure, and provides an effective method for inhibiting low-temperature cracking of asphalt pavement in cold regions.

[0123] In summary, the present invention can dynamically control the low-temperature cracking of asphalt pavements of different cycles and different service performances according to the cracking law of the service pavement, and release the temperature stress of the pavement by setting the stress release area, thereby reducing the possibility of future asphalt pavement cracking at low temperatures. The present invention provides a new method and approach to solve the low-temperature cracking of asphalt pavements in cold regions, turning the passive state into the active state, and increasing the performance and service life of the asphalt pavement.

[0124] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A dynamic control method for inhibiting low-temperature cracking of asphalt pavement in cold regions, characterized in that: The following steps are involved: S100: Set up a stress relief zone around the crack; For the stress release area, the contraction length is as follows: For the original pavement area, the contraction length is as follows: Where, σ is the original pavement stress; E 释放 ——Elastic modulus of release area (Mpa); α 释放 ——Temperature shrinkage coefficient of release area (℃); ΔT——Temperature difference (℃); W—— 1 / 2 width of stress relief zone; E 原路面 ——Elastic modulus of original pavement (Mpa); α 原路面 ——Original pavement temperature shrinkage coefficient (℃); L1—— 1 / 2 original road length; In order to ensure that the length of the asphalt road remains unchanged, the contraction length of the stress release area is the same as the contraction length of the original pavement area, as shown in the following formula: For the stress relief area, the following equation is satisfied: For the original road surface area, its deformation is less than the allowable deformation, as shown in the following formula: Where, [ε]——allowable deformation; L—— 1 / 2 cracking spacing; S200: determining the spatial position of the stress release area; By evaluating the cracking of the pavement and determining the crack spacing, the spatial location of the stress relief area is determined; S300: Use finite element software to perform simulation, determine the geometric parameters of the stress release area, and simulate the material replacement of the stress release area.

2. A dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions according to claim 1, characterized in that: In step S200, the road surface cracking is evaluated in the following two cases: (1) Assessment of cracking of newly built pavement: Based on the low temperature cracking index, different cracking spacings L are determined as follows: L=100(CI+1) -1 ; Where: L——cracking distance (m); CI——low temperature cracking index; (2) Assessment of cracking of in-service pavement: Count the cracking rate of the in-service pavement and obtain the crack spacing Lcr, which is compared with the predicted crack spacing L p For comparison: If Lcr≤L p , directly take the horizontal through crack as the target and preset it as the treatment position; if Lcr≥L p , with 1 / 2 of the complete section of the in-service pavement as the treatment position, until the spacing is smaller than the predicted cracking spacing.

3. A dynamic control method for suppressing 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 release zone include the ambient temperature, the thermal shrinkage coefficient and the viscoelastic parameters, and the determination process is as follows: (1) Determination of ambient temperature The lowest temperature values ​​corresponding to different years and different quantiles are calculated based on the continuous low temperature and extreme minimum temperature; (2) Determination of thermal shrinkage coefficient Determine the linear shrinkage coefficient of asphalt mixture and calculate the shrinkage coefficient in each temperature range as follows: Where, β1 is the temperature shrinkage coefficient of the asphalt mixture specimen; ΔT is the temperature change difference; ε is the strain difference within ΔT; β2 is the linear expansion coefficient of the standard specimen; (3) Determination of viscoelastic parameters The shear rheometer is used to scan the frequency of asphalt mixture at different temperatures. After obtaining the viscoelastic information of asphalt mixture at different temperatures or frequencies, the test data is analyzed and the viscoelastic parameters of asphalt mixture are determined.

4. A dynamic control method for suppressing low-temperature cracking of asphalt pavement in cold regions according to claim 3, characterized in that: In the process of determining the ambient temperature in step (1) of step S300, calculation and analysis are performed based on the generalized extreme value distribution model, and 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 is characterized by: In the process of determining the viscoelastic parameters in step (3) of step S300, the viscoelastic information is obtained by using the WLF equation and a correction function model proposed based on the Sigmoidal function to translate and superimpose the test data to obtain the master curve at a given reference temperature, thereby determining the viscoelastic parameters of the required material.

6. A dynamic control method for suppressing 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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