Bituminous pavement structure-material integrated design method suitable for large temperature difference environment

Abstract

The invention discloses an asphalt pavement structure-material integrated design method suitable for a large-temperature-difference environment, belongs to the technical field of traffic and transportation engineering, and aims to solve the problem that the durability of an asphalt pavement in the large-temperature-difference environment is insufficient due to the synergistic effect of temperature stress and vehicle load. The method comprises the following steps: step 1, designing mineral aggregate gradation of an asphalt surface layer material; 2, carrying out a Marshall performance test on the asphalt surface layer material; 3, carrying out statistics on meteorological data over the years to obtain an annual average large temperature difference day number D; step 4, carrying out a surface layer asphalt mixture temperature difference cycle test on the Marshall test piece, wherein the cycle index is D * N; 5, carrying out a temperature difference resistance test on the surface layer asphalt mixture; step 6, carrying out a shear resistance test on the asphalt mixture of the middle surface layer; step 7, carrying out an anti-fatigue performance test on the lower surface layer asphalt mixture; 8, determining the optimal asphalt-aggregate ratio of the asphalt surface layer material; and 9, designing a semi-rigid base layer pre-cutting seam according to the flexural-tensile strength of the semi-rigid base layer material.

Description

Technical Field

[0001] The present invention relates to the field of transportation engineering technology, and in particular to a structure-material integrated design method for asphalt pavements in environments with large temperature differences, which is used to improve the durability of semi-rigid base asphalt pavements under drastic temperature changes. Background Art

[0002] my country's widespread climate with wide temperature variations presents a significant challenge for asphalt pavements in these environments. These environments experience dramatic temperature fluctuations. While the surface temperature fluctuates with the air temperature, the temperature below the pavement remains relatively stable due to the influence of the underlying structure, creating a temperature gradient within the pavement. These temperature differences at different depths cause uneven deformation of the pavement material, generating thermal stresses within the pavement structure. These, combined with the dynamic mechanical response generated by vehicle loads, can lead to defects such as cracks and rutting. Furthermore, my country's asphalt pavements primarily utilize a semi-rigid base structure made of cement-based materials. During hydration, shrinkage and thermal stresses combine to produce a large number of uneven cracks. These cracks extend upward to the road surface, forming reflective cracks and exacerbating pavement performance degradation. The combined effects of large temperature variations and vehicle loads lead to significant durability deficiencies in asphalt pavements in these environments. Asphalt pavement durability is directly related to pavement structural design. Therefore, developing design methods for asphalt pavements suitable for environments with wide temperature variations is crucial for improving their durability. Currently, asphalt pavement design mostly aims to improve pavement durability by enhancing material properties. However, existing material design methods do not consider the functional requirements of different structural layers, use the same indicator system for asphalt mixtures in each structural layer, and do not incorporate temperature difference resistance into the design method. As a result, the design results are difficult to meet the needs of large temperature difference environments. On the other hand, reflective cracks formed by cracking of semi-rigid base layers are another important reason for the insufficient durability of asphalt pavements in large temperature difference environments. Pre-cutting technology is an effective method to suppress uneven cracking of semi-rigid base layers. The form of pre-cutting determines the improvement effect of the semi-rigid base layer's crack resistance. Excessive or insufficient cutting will limit the improvement of crack resistance and even aggravate pavement cracking. However, the cutting structure is often designed based on experience, which makes it difficult to achieve the optimal crack resistance effect.

[0003] Currently, asphalt pavement design utilizes an empirical design method that applies the same design specifications throughout the entire thickness. This approach lacks targeted design considerations for the functional requirements of each layer in asphalt pavements operating in environments with wide temperature variations, resulting in insufficient durability. Furthermore, the layout of pre-cut slits in the semi-rigid base layer is empirically determined, resulting in limited effectiveness in suppressing reflective cracks. Currently, there is a lack of a structural-material integrated design method for asphalt pavements operating in environments with wide temperature variations. The functional requirements of each pavement structure vary. Designing asphalt mixtures suitable for environments with wide temperature variations based on these structural and functional requirements and optimizing the layout of pre-cut slits in the semi-rigid base layer are effective methods for improving the durability of asphalt pavements operating in such environments. Therefore, it is necessary to clarify the functional requirements of each layer in an asphalt pavement and propose targeted design methods to develop a structural-material integrated design method suitable for asphalt pavements operating in such environments. Summary of the Invention

[0004] In order to solve the problem of insufficient durability of asphalt pavement in a large temperature difference environment due to the synergistic effect of temperature stress and vehicle load, the present invention provides an asphalt pavement structure-material integrated design method suitable for a large temperature difference environment.

[0005] The method for integrated design of asphalt pavement structure and materials suitable for environments with large temperature differences according to the present invention comprises the following steps: Step 1: Design of mineral aggregate gradation for asphalt surface material; Step 2: Make Marshall specimens according to the gradation design plan and conduct Marshall performance tests on asphalt pavement materials; Step 3: Statistically calculate the annual average number of days with large temperature differences D based on the meteorological data of previous years; Step 4: Conduct temperature difference cycle test on the surface asphalt mixture of Marshall specimen, the number of cycles is , is the design life; Step 5: Conduct a temperature difference resistance test on the surface asphalt mixture of the Marshall specimen; Step 6: Conduct shear performance test of the middle surface asphalt mixture on the Marshall specimen; Step 7: Conduct fatigue resistance test of the lower layer asphalt mixture on the Marshall specimen; Step 8: Determine the optimal asphalt-to-stone ratio of the asphalt surface material; Step 9: Design the pre-cut seams of the semi-rigid base layer according to the bending and tensile strength of the semi-rigid base layer material.

[0006] Preferably, the mineral aggregate gradation design process of the asphalt surface layer material in step 1 is: Determine the asphalt mixture gradation type for each layer based on the highway grade, climate and traffic conditions. Design 1 to 3 groups of mineral aggregate gradations for the surface layer, middle layer and lower layer respectively within the engineering design gradation range specified in JTGF40-2004. Estimate the optimal oil-stone ratio, make Marshall specimens and measure the gross volume density, void ratio, mineral aggregate gap ratio, asphalt saturation, stability and flow value. Select the gradation that meets the requirements of the specification as the design gradation.

[0007] Preferably, the process of performing the Marshall performance test of the asphalt surface material in step 2 is as follows: The oil-stone ratio of asphalt mixture in each layer is estimated based on engineering experience. The oil-stone ratio of group P is selected with the estimated oil-stone ratio as the median to make Marshall specimens. The gross volume density, maximum theoretical relative density, stability and flow value of the Marshall specimens under different oil-stone ratios are measured. The void ratio, mineral gap ratio and effective asphalt saturation are calculated to check whether they meet the requirements of JTGF40-2004.

[0008] Preferably, the process of collecting statistics on meteorological data over the years in step 3 is as follows: Step 31: Collect historical meteorological data: a series of daily maximum and minimum temperature data with a daily temperature difference of ≥30°C for at least 10 years; Step 32: Use the generalized extreme value distribution model to fit the daily temperature difference distribution , output the estimated values ​​of ξ, μ, and σ:

[0009] Where, is the daily temperature difference observation value, ξ, μ, σ are fitting parameters, where ξ is the shape parameter, μ is the location parameter, and σ is the scale parameter; Step 33: Calculate the 95% percentile of the daily temperature difference according to the following formula :

[0010] Step 34: Obtain the annual average number of days with large temperature differences D and the annual average temperature T based on the meteorological data collected in step 31.

[0011] Preferably, the process of performing the temperature difference cycle test of the surface asphalt mixture on the Marshall specimen in step 4 is as follows: According to the ore gradation determined in step 1 and the P group oil-stone ratio determined in step 2, the Marshall specimens were formed and tested. The second largest temperature difference cycle, a single cycle is: Step 41: Raise the temperature to (T+0.5T) at 1°C / min. 95% ); Step 42: Maintain temperature for 2 hours; Step 43: Cool down to (T-0.5T) at 1°C / min 95% ); Step 44: Maintain temperature for 2 hours; Step 45: Raise the temperature at 1°C / min to (T+0.5T 95% ).

[0012] Preferably, the process of performing the temperature difference resistance test of the surface layer asphalt mixture on the Marshall specimen in step 5 is as follows: Test the splitting tensile strength of the surface asphalt mixture under the oil-stone ratio of group P before and after temperature difference cycle at -10℃ 、 , and then calculate the residual strength ratio S of asphalt mixture under different oil-stone ratios according to the following formula to see whether it meets the requirements. : .

[0013] Preferably, the process of performing the shear performance test of the middle surface asphalt mixture on the Marshall specimen in step six is: testing the dynamic modulus of the middle surface asphalt mixture under the oil-stone ratio of group P at a temperature of 25° C. and a loading frequency of 10 Hz.

[0014] Preferably, the process of the seventh step of the Marshall specimen to perform fatigue resistance test on the lower layer asphalt mixture is as follows: testing the lower layer asphalt mixture under the oil-stone ratio of group P at the target tensile strain of The number of loading times at which the bending modulus drops to 50% of the initial value under standard test conditions.

[0015] Preferably, the process of determining the optimal asphalt-to-stone ratio of the asphalt surface material in step eight is as follows: Step 81: Based on the measurement results of step 2 for all surface layers and step 5 for the surface layer, check whether each layer has an oil-stone ratio that meets all performance requirements. If an oil-stone ratio that meets all requirements exists, determine the optimal oil-stone ratio based on the test results and execute step 82. Otherwise, repeat steps 1 to 5 until an oil-stone ratio that meets all requirements exists, and then execute step 82. Step 82: Draw a performance-to-asphalt ratio relationship diagram, where the performance includes bulk density, void ratio, aggregate gap ratio, asphalt saturation, and target performance indicators. The target performance indicator for the surface layer is the residual strength ratio, the target performance indicator for the mid-surface layer is the dynamic modulus, and the target performance indicator for the lower layer is fatigue life. Step 83: Obtain the oil-stone ratio corresponding to the maximum density according to the performance-oil-stone ratio relationship diagram , the oil-stone ratio corresponding to the target porosity or the median of the porosity allowable range , the oil-stone ratio corresponding to the median of the allowable range of mineral gap ratio , the oil-stone ratio corresponding to the median of the allowable range of asphalt saturation And the oil-stone ratio corresponding to the optimal value of the target performance ; Step 84: Calculate the average oil-stone ratio according to the following formula :

[0016] Step 85: Calculate the median oil-stone ratio according to the following formula :

[0017] Where, 、 They are the upper and lower limits of the oil-to-stone ratio that meet all basic technical index requirements; Step 86: Calculate the optimal oil-stone ratio according to the following formula : .

[0018] Preferably, the process of step nine for designing the semi-rigid base pre-cutting seams according to the bending and tensile strength of the semi-rigid base material is as follows: Testing the flexural and tensile strength of semi-rigid base materials , calculate the spacing of pre-cut slits :

[0019] The slit width is 3mm and the slit depth is 1 / 3 of the design value of the semi-rigid base thickness.

[0020] Beneficial effects of the present invention: In response to the current problem of insufficient durability of asphalt pavements in environments with large temperature differences, the present invention proposes a structure-material integrated design method suitable for asphalt pavements in environments with large temperature differences. The asphalt surface layer materials are designed in layers based on functional requirements, and the pre-cut seam arrangement scheme of the semi-rigid base layer is optimized to achieve improved durability of asphalt pavements in environments with large temperature differences.

[0021] The present invention has the following advantages: 1) Targeted design based on structural and functional requirements maximizes the material's performance potential. Balancing multiple performance objectives is the core of asphalt pavement material design. This invention determines the design objectives for each layer based on the structural and functional requirements at different depths of the asphalt pavement under the combined effects of large temperature differences and vehicle loads. This avoids the waste of material performance in traditional balanced design and effectively improves the durability of asphalt pavement materials under large temperature differences.

[0022] 2) Incorporating temperature differential resistance into the surface layer asphalt mixture design method. Material temperature differential resistance design is fundamental to improving the durability of asphalt pavements in environments with large temperature differentials. This invention determines the large temperature differential test conditions based on the climatic environment of the design target. The surface layer asphalt mixture's resistance to low temperatures and thermal fatigue in large temperature differential environments is tested using a residual strength ratio of ≥80% after temperature differential cycling. This addresses the shortcomings of existing design methods that ignore the special climatic conditions of large temperature differential environments. By scientifically designing temperature differential resistance, the durability of asphalt pavements in large temperature differential environments is improved.

[0023] 3) A scientific and rational design method for the pre-slit layout of a semi-rigid base layer. Pre-slit technology for semi-rigid base layers prevents uneven cracking by inducing cracking at the slits in advance. Currently, slit layout parameters such as slit spacing, slit depth, and slit width are primarily determined empirically, failing to maximize the effectiveness of pre-slit technology and resulting in limited improvement in the crack resistance of the base layer. This invention simulates the stress state of real pavement structures through finite element analysis and, through regression analysis, proposes a pre-slit layout design method suitable for different pavement structures, effectively suppressing the occurrence of uneven cracking in the base layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the AC-13 asphalt mixture gradation curve; Figure 2 is the AC-20 asphalt mixture gradation curve; Figure 3 is the AC-25 asphalt mixture gradation curve; Figure 4 is the performance-oil-stone ratio relationship diagram, where Figure 4 (a) is the relationship diagram between gross volume relative density and asphalt stone ratio, Figure 4 (b) is the relationship diagram between porosity and oil-stone ratio. Figure 4 (c) is the relationship diagram between asphalt saturation and oil-stone ratio. Figure 4 (d) is the relationship diagram between the mineral void ratio and the oil-stone ratio. Figure 4 (e) is the relationship diagram between residual strength ratio and asphalt-stone ratio; Figure 5 This is a flow chart of the asphalt pavement structure-material integrated design method suitable for large temperature difference environments described in the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0028] Specific implementation method 1: Figures 1 to 5 This embodiment describes an integrated design method for asphalt pavement structure and materials suitable for environments with large temperature differences. The method includes the following steps: Step 1: Design of mineral aggregate gradation for asphalt surface material; Step 2: Make Marshall specimens according to the gradation design plan and conduct Marshall performance tests on asphalt pavement materials; Step 3: Statistically calculate the annual average number of days with large temperature differences D based on the meteorological data of previous years; Step 4: Conduct temperature difference cycle test on the surface asphalt mixture of Marshall specimen, the number of cycles is , is the design life; Step 5: Conduct a temperature difference resistance test on the surface asphalt mixture of the Marshall specimen; Step 6: Conduct shear performance test of the middle surface asphalt mixture on the Marshall specimen; Step 7: Conduct fatigue resistance test of the lower layer asphalt mixture on the Marshall specimen; Step 8: Determine the optimal asphalt-to-stone ratio of the asphalt surface material; Step 9: Design the pre-cut seams of the semi-rigid base layer according to the bending and tensile strength of the semi-rigid base layer material.

[0029] The design process of the mineral aggregate gradation of the asphalt surface layer material in step 1 is as follows: The type and gradation of the surface layer asphalt mixture are determined based on the highway grade, climate, and traffic conditions. Design one to three different aggregate gradations for each layer within the engineering design gradation range specified in JTGF40-2004, "Technical Specifications for Highway Asphalt Pavement Construction." Estimate the optimal asphalt-to-stone ratio based on local practical experience. Marshall specimens are prepared for each gradation to measure bulk density, void ratio, aggregate interstitial ratio, asphalt saturation, stability, and flow value. The design gradation that meets or most closely matches the requirements of JTGF40-2004 is selected.

[0030] The process of the Marshall performance test of asphalt surface material in step 2 is as follows: Based on engineering experience, the asphalt-to-rock ratio of each asphalt mixture layer was estimated. Using the estimated asphalt-to-rock ratio as the median, the estimated asphalt-to-rock ratio was increased or decreased by equal amounts. Marshall specimens were prepared using P groups of asphalt-to-rock ratios for each layer, with P = 5. The gross volume density, maximum theoretical relative density, stability, and flow value of the Marshall specimens were measured under different asphalt-to-rock ratios. The void ratio, aggregate interstitial ratio, and effective asphalt saturation of the Marshall specimens were also calculated. The void ratio, aggregate interstitial ratio, effective asphalt saturation, stability, and flow value were verified to ensure they met the ranges specified in the JTGF40-2004 specification.

[0031] The process of statistically analyzing meteorological data over the years in step 3 is as follows: Step 31: Collect historical meteorological data: a series of daily maximum and minimum temperature data with a daily temperature difference of ≥30°C for at least 10 years; Step 32: Use the generalized extreme value distribution model to fit the daily temperature difference distribution , output the estimated values ​​of ξ, μ, and σ:

[0032] Where, is the daily temperature difference observation value, ξ, μ, σ are fitting parameters, where ξ is the shape parameter, μ is the location parameter, and σ is the scale parameter; Step 33: Calculate the 95% percentile of the daily temperature difference according to the following formula :

[0033] Step 34: Obtain the annual average number of days with large temperature differences D and the annual average temperature T based on the meteorological data collected in step 31.

[0034] Step 4: The process of conducting the temperature difference cycle test of the surface asphalt mixture on the Marshall specimen is as follows: According to the ore gradation determined in step 1 and the P group oil-stone ratio determined in step 2, the Marshall specimens were formed and tested. The second largest temperature difference cycle, a single cycle is: Step 41: Raise the temperature to (T+0.5T) at 1°C / min. 95% ); Step 42: Maintain temperature for 2 hours; Step 43: Cool down to (T-0.5T) at 1°C / min 95% ); Step 44: Maintain temperature for 2 hours; Step 45: Raise the temperature at 1°C / min to (T+0.5T 95% ).

[0035] Step 5: The process of conducting the temperature difference resistance test of the surface layer asphalt mixture on the Marshall specimen is as follows: According to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0716 "Split Test of Asphalt Mixtures", the splitting tensile strength of the surface layer asphalt mixture under the oil-stone ratio of group P was tested before and after the temperature difference cycle at -10℃. 、 , and then calculate the residual strength ratio S of asphalt mixture under different oil-stone ratios according to the following formula to see whether it meets the requirements. :

[0036] Require .

[0037] Step 6: The process of conducting the shear performance test of the middle surface asphalt mixture on the Marshall specimen is as follows: according to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0738 "Uniaxial Compression Dynamic Modulus Test of Asphalt Mixture", the dynamic modulus of the middle surface asphalt mixture under the oil-stone ratio of group P is tested at a temperature of 25°C and a loading frequency of 10 Hz.

[0038] Step 7: The process of the fatigue performance test of the lower layer asphalt mixture of the Marshall specimen is as follows: According to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0739 "Four-point Bending Fatigue Life Test of Asphalt Mixture", the lower layer asphalt mixture under the oil-stone ratio of group P is tested at the target tensile strain of The number of loading times at which the bending modulus drops to 50% of the initial value under standard test conditions.

[0039] Step 8 The process of determining the optimal asphalt-to-stone ratio of asphalt surface material is as follows: Step 81: Based on the measurement results of step 2 for all surface layers and step 5 for the surface layer, check whether each layer has an oil-stone ratio that meets all performance requirements. If an oil-stone ratio that meets all requirements exists, determine the optimal oil-stone ratio based on the test results and execute step 82. Otherwise, repeat steps 1 to 5 until an oil-stone ratio that meets all requirements exists, and then execute step 82. The specific steps to determine the optimal oil-stone ratio based on the test results include: Step 82: Draw a performance-to-asphalt ratio relationship diagram, where the performance includes bulk density, void ratio, aggregate gap ratio, asphalt saturation, and target performance indicators. The target performance indicator for the surface layer is the residual strength ratio, the target performance indicator for the mid-surface layer is the dynamic modulus, and the target performance indicator for the lower layer is fatigue life. Step 83: Obtain the oil-stone ratio corresponding to the maximum density according to the performance-oil-stone ratio relationship diagram , the oil-stone ratio corresponding to the target porosity or the median of the porosity allowable range , the oil-stone ratio corresponding to the median of the allowable range of mineral gap ratio , the oil-stone ratio corresponding to the median of the allowable range of asphalt saturation And the oil-stone ratio corresponding to the optimal value of the target performance ; Step 84: Calculate the average oil-stone ratio according to the following formula :

[0040] Step 85: Calculate the median oil-stone ratio according to the following formula :

[0041] Where, 、 They are the upper and lower limits of the oil-to-stone ratio that meet all basic technical index requirements; Step 86: Calculate the optimal oil-stone ratio according to the following formula : .

[0042] Step 9: The process of designing the pre-cut seams of the semi-rigid base material according to the bending and tensile strength of the semi-rigid base material is as follows: The type of semi-rigid base material is determined according to the highway grade, climate and traffic conditions. The flexural strength of the semi-rigid base material is tested using the method specified in JTG3441-2024 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering" T0851. , calculate the spacing of pre-cut slits :

[0043] The slit width is 3mm and the slit depth is 1 / 3 of the design value of the semi-rigid base thickness.

[0044] In summary, the innovations of the present invention lie in the following aspects: (1) Design of asphalt surface material and pre-cut semi-rigid base layer for large temperature difference environment with the goal of anti-low temperature-temperature fatigue cracking of surface layer, anti-shear deformation of middle layer, anti-fatigue of lower layer and reduction of uneven cracking of base layer. Using a finite element simulation model of a typical semi-rigid base asphalt pavement structure, the stress state of the pavement structure under temperature and vehicle load was analyzed. This clarified the internal dynamic mechanical response of the pavement under the combined effects of large temperature fluctuations and vehicle loads. The design objectives for the surface layer, mid-layer, lower layer, and base layer of semi-rigid asphalt pavements in large temperature fluctuation environments were determined to be resistance to low temperatures and thermal fatigue, resistance to shear deformation, resistance to fatigue, and reduction of uneven cracking, respectively. Based on the primary failure mechanisms of pavements in large temperature fluctuation environments, targeted design objectives were proposed for each layer to improve the durability of the asphalt pavement.

[0045] (2) The residual strength ratio after temperature difference cycle ≥80% is used as the design standard for the temperature difference resistance performance of the surface layer asphalt mixture in a large temperature difference environment The generalized extreme value distribution is used to statistically analyze the climate characteristics of the large temperature difference environment in which the design object is located, and the temperature difference cycle test parameters are determined based on the design life. Considering that the main failure mode under low temperature and temperature fatigue is tensile stress cracking failure, the correlation between conventional mechanical performance parameters and road tensile performance is analyzed, and the -10℃ splitting tensile strength is determined as the tensile performance evaluation index based on the principle of high correlation. The ratio of the -10℃ splitting tensile strength before and after the temperature difference cycle (referred to as the residual strength ratio in this invention) is used as the evaluation index for the temperature difference resistance of the surface layer asphalt mixture, and the design standard for the temperature difference resistance of the surface layer asphalt mixture is determined to be a residual strength ratio ≥ 80%. This realizes the structure-material integrated design for the large temperature difference environment, and ensures that the tensile performance of the surface layer asphalt mixture meets the use requirements within the design life under the large temperature difference environment.

[0046] (3) A semi-rigid base pre-cut design method for large temperature difference environments was proposed. The finite element simulation method was used to analyze the stress state of the pre-cut semi-rigid base under the combined action of large temperature difference and vehicle load. Orthogonal experiments were designed to clarify the optimal slit arrangement scheme for different pavement structure designs. Through regression analysis, a calculation method for the optimal slit spacing and slit depth was proposed, and the optimal slit width was determined to be 3mm. This achieved the optimized design of the pre-cut slits of the semi-rigid base, which helps to reduce uneven cracking of the semi-rigid base and the formation of reflective cracks in the pavement.

[0047] The following is a specific example: Taking the design of an asphalt pavement structure in a region with large temperature differences as an example, we will detail the application of this invention. The design process for the surface layer, middle layer, and lower layer is similar, except that the surface layer is tested for temperature differential resistance. Therefore, only the specific design process for the surface layer asphalt mixture is described in detail, while only the design results for the middle layer and lower layer are listed.

[0048] Step 1: Design the gradation of the asphalt surface material. Based on the highway grade, climate, and traffic conditions, the upper layer of the temperature-resistant asphalt mixture uses an AC-13 gradation, the middle layer uses an AC-20 gradation, and the lower layer uses an AC-25 gradation. The design process for the AC-13 asphalt mixture gradation for the upper layer is as follows: The aggregate screening results are shown in Table 1. According to JTGF40-2004 "Technical Specifications for Highway Asphalt Pavement Construction", three groups of mineral aggregate gradations are designed. The proportions of each grade of mineral aggregate are shown in Table 2, the gradation composition is shown in Table 3, and the gradation curve is shown in Figure 1 Based on local experience, the optimal asphalt-rock ratio is estimated to be 5.5%. Marshall specimens were made according to three gradations, and the bulk density, void ratio, aggregate interstitial ratio, asphalt saturation, stability, and flow value were measured, as shown in Table 4.

[0049] Table 1AC-13 aggregate screening results Table 2AC-13 design grading mineral material ratio Table 3 AC-13 design gradation passing percentage Table 4 AC-13 design gradation performance test results As shown in Table 4, only gradation 2 meets all the requirements. Therefore, gradation 2 is determined as the design gradation of AC-13 asphalt mixture for the surface layer.

[0050] Similarly, determine the gradation of AC-20 asphalt mixture in the middle surface layer and AC-5 asphalt mixture in the lower layer as follows: Figure 2 、 Figure 3 shown.

[0051] Step 2: Marshall performance test of asphalt pavement materials. Based on the designed gradation, Marshall specimens of asphalt mixtures for each structural layer were prepared using five different asphalt-to-aggregate ratios. The gross volume density, maximum theoretical relative density, stability, flow value, void ratio, aggregate interstitial ratio, and asphalt saturation of the Marshall specimens were measured at different asphalt-to-aggregate ratios, as shown in Table 5.

[0052] Table 5 Marshall performance test results of different oilstone ratios Step 3: Meteorological data statistics. Collect meteorological data from previous years in the region and use the generalized extreme value distribution model to fit the daily temperature difference distribution. Calculate the 95% quantile of the daily temperature difference. , the annual average number of days with large temperature difference D (daily temperature difference ≥ 30℃), and the annual average temperature T are shown in Table 6.

[0053] Table 6 Statistical results of meteorological data at the location of the design object Step 4: Temperature Difference Cycle Test of Surface Asphalt Mixture. According to the aggregate gradation determined in Step 1 and the five groups of asphalt-aggregate ratios determined in Step 2, Marshall specimens of surface asphalt mixture are formed. The specimens are placed in a high and low temperature test chamber and subjected to (D × design life) times of maximum temperature difference cycle. The process of a single cycle is as follows: Step 41: Raise the temperature to (T+0.5T) at 1°C / min. 95% ); Step 42: Maintain temperature for 2 hours; Step 43: Cool down to (T-0.5T) at 1°C / min 95% ); Step 44: Maintain temperature for 2 hours; Step 45: Raise the temperature at 1°C / min to (T+0.5T 95% ).

[0054] Step 5: Temperature difference resistance test of surface asphalt mixture: According to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0716 "Split Test of Asphalt Mixture", the splitting tensile strength of the surface asphalt mixture under 5 asphalt-stone ratios was tested before and after temperature difference cycle at -10℃. 、 , calculate the residual strength ratio S of the surface layer asphalt mixture after temperature difference cycle. Test whether the asphalt mixture S under different oil-aggregate ratios meets S≥80%. The results are shown in Table 7.

[0055] Table 7 Residual strength ratio of surface layer asphalt mixture under different asphalt-stone ratios Step 6: Shear performance test of middle surface asphalt mixture: According to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0738 "Uniaxial Compression Dynamic Modulus Test of Asphalt Mixture", the dynamic modulus of the middle surface asphalt mixture under 5 oil-stone ratios was tested at a temperature of 25°C and a loading frequency of 10 Hz. The results are shown in Table 8.

[0056] Table 8 Dynamic modulus of asphalt mixture in the middle surface layer under different asphalt-aggregate ratios Step 7: Fatigue resistance test of lower layer asphalt mixture: According to the method described in JTGE20-2011 "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" T0739 "Four-point Bending Fatigue Life Test of Asphalt Mixture", the lower layer asphalt mixtures under 5 asphalt-stone ratios were tested respectively under the standard test conditions of target tensile strain of 400με, and the number of loading times corresponding to the bending stiffness modulus being reduced to 50% of the initial bending stiffness modulus. The results are shown in Table 9.

[0057] Table 9 Fatigue life of asphalt mixture under different oil-stone ratios Step 8: Determine the optimal oil-to-stone ratio of the asphalt surface material. Taking the AC-13 asphalt mixture of the surface layer as an example, according to the test results of steps 2 and 5, there is an oil-to-stone ratio that meets the requirements of the AC-13 asphalt mixture of the surface layer. The optimal oil-to-stone ratio is determined based on the test results. The specific steps include: (1) Specifically draw the relationship diagram of the gross volume density, void ratio, mineral gap ratio, asphalt saturation and residual strength ratio with the oil-stone ratio. The relationship diagrams of the surface layer are as follows: Figure 4As shown. Obtain the oil-stone ratio corresponding to the corresponding maximum density , the oil-stone ratio corresponding to the median of the target porosity or the median of the allowable porosity range , the oil-stone ratio corresponding to the median of the allowable range of mineral gap ratio , the oil-stone ratio corresponding to the median of the allowable range of asphalt saturation And the oil-stone ratio corresponding to the optimal value of the target performance The values ​​are 6.5%, 5.5%, 5.1%, 5.5%, and 5.7% respectively. Calculate OAC1: OAC1=(a1+a2+a3+a4+a5) / 5=(6.5+5.5+5.1+5.5+5.7) / 5=5.7 (2) Determine the oil-stone ratio range that meets all index requirements except the mineral gap ratio based on the test results, and determine the lower limit of the oil-stone ratio OAC min =5.2, upper limit of oil-stone ratio OAC max =5.8, based on OAC min OAC max The median of is taken as OAC2, then OAC2=(OAC min +OAC max ) / 2=(5.2+5.8) / 2=5.5.

[0058] (3) Taking the average of OAC1 and OAC2 as the optimal oil-stone ratio OAC, the optimal oil-stone ratio of the surface layer OAC = (OAC1 + OAC2) / 2 = (5.66 + 5.5) / 2 = 5.6.

[0059] The same method was used to determine the optimal asphalt-stone ratios of the middle surface layer AC-20 asphalt mixture and the lower layer AC-25 asphalt mixture to be 4.3% and 3.8% respectively.

[0060] Step 9: Design of pre-cut joints for semi-rigid base. Determine the type of semi-rigid base material based on the highway grade, climate, and traffic conditions. The flexural strength of the semi-rigid base material is measured using the method specified in JTG3441-2024 "Test Procedure for Stabilized Materials of Inorganic Binders for Highway Engineering" T0851. =1.25MPa, calculate the spacing of pre-cut slits =5.2m. According to the preliminary design results of the design object, the thickness of the semi-rigid base is 60cm, and the slit depth is 1 / 3 of the designed thickness of the semi-rigid base, which is 20cm.

[0061] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. An integrated design method for asphalt pavement structure and materials suitable for environments with large temperature differences, characterized by: The method comprises the following steps: Step 1: Design of mineral aggregate gradation for asphalt surface material; Step 2: Make Marshall specimens according to the gradation design plan and conduct Marshall performance tests on asphalt pavement materials; Step 3: Statistically calculate the annual average number of days with large temperature differences D based on the meteorological data of previous years; Step 4: Conduct temperature difference cycle test on the surface asphalt mixture of Marshall specimen, the number of cycles is , is the design life; Step 5: Conduct a temperature difference resistance test on the surface asphalt mixture of the Marshall specimen; Step 6: Conduct shear performance test of the middle surface asphalt mixture on the Marshall specimen; Step 7: Conduct fatigue resistance test of the lower layer asphalt mixture on the Marshall specimen; Step 8: Determine the optimal asphalt-to-stone ratio of the asphalt surface material; Step 9: Design the pre-cut seams of the semi-rigid base layer according to the bending and tensile strength of the semi-rigid base layer material.

2. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 1 is characterized in that: The design process of the mineral aggregate gradation of the asphalt surface material in step 1 is as follows: Determine the asphalt mixture gradation type for each layer based on the highway grade, climate and traffic conditions. Design 1 to 3 groups of mineral aggregate gradations for the surface layer, middle layer and lower layer respectively within the engineering design gradation range specified in JTGF40-2004. Estimate the optimal oil-stone ratio, make Marshall specimens and measure the bulk density, void ratio, mineral gap ratio, asphalt saturation, stability and flow value, and select the gradation that meets the requirements of the specification as the design gradation.

3. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 2 is characterized in that: The process of the Marshall performance test of asphalt surface material in step 2 is as follows: The oil-stone ratio of asphalt mixture in each layer is estimated based on engineering experience. The oil-stone ratio of group P is selected with the estimated oil-stone ratio as the median to make Marshall specimens. The gross volume density, maximum theoretical relative density, stability and flow value of the Marshall specimens under different oil-stone ratios are measured. The void ratio, mineral gap ratio and effective asphalt saturation are calculated to check whether they meet the requirements of JTGF40-2004.

4. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 3 is characterized in that: The process of statistically analyzing meteorological data over the years in step 3 is as follows: Step 31: Collect historical meteorological data: a series of daily maximum and minimum temperature data with a daily temperature difference of ≥30°C for at least 10 years; Step 32: Use the generalized extreme value distribution model to fit the daily temperature difference distribution , output the estimated values ​​of ξ, μ, and σ: Where, is the daily temperature difference observation value, ξ, μ, σ are fitting parameters, where ξ is the shape parameter, μ is the location parameter, and σ is the scale parameter; Step 33: Calculate the 95% percentile of the daily temperature difference according to the following formula : Step 34: Obtain the annual average number of days with large temperature differences D and the annual average temperature T based on the meteorological data collected in step 31.

5. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 4, characterized in that: Step 4: The process of conducting the temperature difference cycle test of the surface asphalt mixture on the Marshall specimen is as follows: According to the ore gradation determined in step 1 and the P group oil-stone ratio determined in step 2, the Marshall specimens were formed and tested. The second largest temperature difference cycle, a single cycle is: Step 41: Raise the temperature to (T+0.5T) at 1°C / min. 95% ); Step 42: Maintain temperature for 2 hours; Step 43: Cool down to (T-0.5T) at 1°C / min 95% ); Step 44: Maintain temperature for 2 hours; Step 45: Raise the temperature at 1°C / min to (T+0.5T 95% ).

6. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 5, characterized in that: Step 5: The process of conducting the temperature difference resistance test of the surface layer asphalt mixture on the Marshall specimen is as follows: Test the splitting tensile strength of the surface asphalt mixture under the oil-stone ratio of group P before and after temperature difference cycle at -10℃ 、 , and then calculate the residual strength ratio S of asphalt mixture under different oil-stone ratios according to the following formula to see whether it meets the requirements. : 。 7. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 1, characterized in that: Step 6 The process of conducting the shear performance test of the middle surface asphalt mixture on the Marshall specimen is as follows: testing the dynamic modulus of the middle surface asphalt mixture under the oil-stone ratio of group P at a temperature of 25° C. and a loading frequency of 10 Hz.

8. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 1, characterized in that: Step 7: The process of the fatigue performance test of the lower layer asphalt mixture of the Marshall specimen is as follows: Test the lower layer asphalt mixture under the oil-stone ratio of group P at the target tensile strain of The number of loading times at which the bending modulus drops to 50% of the initial value under standard test conditions.

9. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 1, characterized in that: Step 8 The process of determining the optimal asphalt-to-stone ratio of asphalt surface material is as follows: Step 81: Based on the measurement results of step 2 for all surface layers and step 5 for the surface layer, check whether there is an oil-stone ratio in each layer that meets all performance requirements. If there is an oil-stone ratio that meets all requirements, determine the optimal oil-stone ratio based on the test results and execute step 82; Otherwise, repeat steps 1 to 5 until the oil-stone ratio meets the requirements, and then execute step 82; Step 82: Draw a performance-to-asphalt ratio relationship diagram, where the performance includes bulk density, void ratio, aggregate gap ratio, asphalt saturation, and target performance indicators. The target performance indicator for the surface layer is the residual strength ratio, the target performance indicator for the mid-surface layer is the dynamic modulus, and the target performance indicator for the lower layer is fatigue life. Step 83: Obtain the oil-stone ratio corresponding to the maximum density according to the performance-oil-stone ratio relationship diagram , the oil-stone ratio corresponding to the target porosity or the median of the porosity allowable range , the oil-stone ratio corresponding to the median of the allowable range of mineral gap ratio , the oil-stone ratio corresponding to the median of the allowable range of asphalt saturation And the oil-stone ratio corresponding to the optimal value of the target performance ; Step 84: Calculate the average oil-stone ratio according to the following formula : Step 85: Calculate the median oil-stone ratio according to the following formula : Where, 、 They are the upper and lower limits of the oil-to-stone ratio that meet all basic technical index requirements; Step 86: Calculate the optimal oil-stone ratio according to the following formula : 。 10. The asphalt pavement structure-material integrated design method suitable for large temperature difference environment according to claim 1, characterized in that: Step 9: The process of designing the pre-cut seams of the semi-rigid base material according to the bending and tensile strength of the semi-rigid base material is as follows: Testing the flexural and tensile strength of semi-rigid base materials , calculate the spacing of pre-cut slits : The slit width is 3mm and the slit depth is 1 / 3 of the design value of the semi-rigid base thickness.

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