A numerical method for generating two-dimensional void fraction of porous asphalt mixture

Abstract

The present invention discloses a method for numerically generating two-dimensional void ratio of porous asphalt mixture, comprising the following steps: generating a specified number of random polygonal coarse aggregates of various particle sizes according to the mixture gradation curve; placing polygonal coarse aggregates in a specified two-dimensional area according to the principle of no coverage and no overrun; performing image enhancement processing on the obtained placement results; specifying the distribution probability of growth nuclei and the growth probability in each direction within the void range based on a four-parameter random growth algorithm to generate asphalt mortar particles; identifying and dividing the skeleton, mortar and voids, and assigning microscopic parameters. The present invention is of great significance for numerical simulation of road engineering, and can better control the uniform distribution of voids, greatly improving practicality.

Description

Technical Field

[0001] The invention relates to a numerical method for generating two-dimensional void ratio of porous asphalt mixture, belonging to the technical field of road engineering. Background Art

[0002] Porous asphalt mixture has good drainage and noise reduction performance due to its large voids, so the study of its internal voids is crucial. Due to the opacity of asphalt mixture itself, its internal void structure cannot be directly visualized. With the development of CT scanning technology, this method can accurately reconstruct the internal void structure of the mixture, but this method is time-consuming and costly. In order to facilitate the study of pore structure, domestic and foreign researchers have tried a variety of methods. At present, there are two main methods for randomly generating pore structure: one is the method of random placement of aggregates, and the other is the method of random growth of void / aggregate pixels. The first method is close to the actual generation process of pavement structure, and the gradation curve is relatively stable, but it can only be used for the generation of skeletons. Mortar and asphalt actually need to be randomly distributed and generated, and the speed is slow; the second method is suitable for the semi-random generation of skeletons, mortars and asphalt components, so that the distribution of asphalt mortar has a certain regularity and the generation speed is fast, but it cannot well reflect the gradation curve characteristics of asphalt concrete itself.

[0003] Based on the advantages and disadvantages of the above two random void generation technologies, the present invention proposes a numerical generation method for two-dimensional void ratio of porous asphalt mixture based on random growth algorithm. The coarse aggregate skeleton is first generated by the aggregate placement method, and then the growth phase is set as the void phase in the remaining area, and the initial growth core distribution, the initial growth probability in each direction and the target void ratio are set, and all coordinates in the area are traversed until the target void ratio is reached. Compared with the single four-parameter random growth algorithm to generate voids, the two-dimensional void ratio generation method proposed in the present invention can better fit the actual mixture molding process and accurately characterize its grading curve characteristics; on the basis of the existing aggregate placement method, the fine aggregate placement process is avoided, and the efficiency of two-dimensional void generation of porous asphalt mixture is greatly improved. The method proposed in the present invention is of great significance for numerical simulation of road engineering, and can better control the uniform distribution of voids and greatly improve practicality. Summary of the invention

[0004] The purpose of the present invention is to propose a method for numerically generating two-dimensional void ratio of porous asphalt mixture to solve the shortcomings of existing technologies. The technical solution of the present invention is as follows:

[0005] (1) Generate a specified number of random polygonal coarse aggregates of various particle sizes based on the mixture gradation curve;

[0006] (2) Based on the principle of no coverage and no excess, the products are placed in the designated area;

[0007] (3) Performing image enhancement processing on the acquired delivery results;

[0008] (4) Based on the four-parameter random growth algorithm, the distribution probability of growth nuclei and the growth probability in each direction are specified within the gap range to generate asphalt mortar particles;

[0009] (5) Identify and divide the skeleton, mortar and voids, and assign microscopic parameters.

[0010] As a further improvement of the present invention, in the step (1), the number of coarse aggregate particles in different particle size ranges is calculated based on the mixture gradation curve, and a specified number of polygonal particles in a specified particle size range are randomly generated and used as coarse aggregate particles.

[0011] As a further improvement of the present invention, in step (2), within the specified boundary range, coarse aggregate particles are placed one by one in the order of particle size from large to small. Each placement should ensure that the particles placed this time do not overlap with the particles that have been placed. If overlap occurs, the placement fails and the next placement is carried out until all particles are placed.

[0012] As a further improvement of the present invention, in step (4), based on the four-parameter random growth algorithm, four initial parameters are set: the growth core 𝑃𝑐d randomly distributed in the construction area, the growth probability 𝑃d𝑖 given in different directions, the target void ratio n, and the probability density of mutual influence in the void structure .

[0013] As a further improvement of the present invention, in step (4), the boundary of the porous structure is set. For example, when the boundary of the porous structure is a rectangular parallelepiped, the length, width and height are set.

[0014] As a further improvement of the present invention, in the step (4), a growth nucleus of random voids is preset inside the preset porous structure boundary, and the growth nucleus distribution probability is, and the growth nucleus is randomly generated inside the structure according to this distribution probability, and the growth nucleus is used to specify the initial node of the void growth.

[0015] As a further improvement of the present invention, in step (4), the initially randomly distributed growth core is traversed, and the gap is grown in two-dimensional space with the growth core as the starting point. There are 8 growth directions, including 4 main directions and 4 diagonal directions. For each traversal, any single gap node has a probability of 𝑝𝑖 to grow into a new gap node in a certain direction. If the new node to be grown is already a gap, it is skipped. Repeat the above content and iterate continuously until the gap ratio reaches the target gap ratio n.

[0016] As a further improvement of the present invention, in step (5), the two-dimensional porosity of the porous asphalt mixture is obtained through the above steps, the skeleton is identified and divided, the corresponding microscopic parameters are assigned to it, and its void morphology and other characteristics are clarified.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) A novel two-dimensional numerical void structure generation method for porous asphalt mixtures was proposed;

[0019] (2) Compared with the single four-parameter random growth algorithm, it can better restore the actual mixture forming process and accurately characterize its grading curve characteristics;

[0020] (3) Based on the existing aggregate placement method, the process of fine aggregate placement, which requires huge computational effort, is avoided, significantly improving the efficiency of generating the two-dimensional void structure of porous asphalt mixtures;

[0021] (4) The proposed method is of great significance for the numerical simulation of road engineering. It can better control the distribution law of voids and is more suitable for the study of void structure mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the generated coarse aggregate skeleton.

[0023] Figure 2 Schematic diagram of the generated gap.

[0024] Figure 3 Schematic diagram of the final two-dimensional void ratio of porous asphalt mixture.

[0025] Figure 4 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0026] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0027] like Figure 1 As shown, a method for numerically generating two-dimensional void ratio of porous asphalt mixture comprises the following steps:

[0028] (1) Generate a specified number of random polygonal coarse aggregates of various particle sizes based on the mixture gradation curve;

[0029] (2) Based on the principle of no coverage and no excess, the products are placed in the designated area;

[0030] (3) Performing image enhancement processing on the acquired delivery results;

[0031] (4) Based on the four-parameter random growth algorithm, the distribution probability of growth nuclei and the growth probability in each direction are specified within the gap range to generate asphalt mortar particles;

[0032] (5) Identify and divide the skeleton, mortar and voids, and assign microscopic parameters.

[0033] In this embodiment, in step (1), the number of coarse aggregate particles in different particle size ranges is calculated based on the mixture gradation curve, and a specified number of polygonal particles in a specified particle size range are randomly generated and used as coarse aggregate particles.

[0034] In this embodiment, in step (2), within the specified boundary range, coarse aggregate particles are placed one by one in the order of particle size from large to small. Each placement should ensure that the particles placed this time do not overlap with the particles that have been placed. If overlap occurs, the placement fails and the next placement is carried out until all particles are placed.

[0035] In this embodiment, in step (4), based on the four-parameter random growth algorithm, four initial parameters are set: the growth core 𝑃𝑐d randomly distributed in the construction area, the growth probability 𝑃d𝑖 given in different directions, the target void ratio n, and the probability density of mutual influence in the void structure .

[0036] In this embodiment, in step (4), the boundary of the porous structure is set. For example, when the boundary of the porous structure is a rectangular parallelepiped, the length, width and height are set.

[0037] In this embodiment, in step (4), a growth nucleus of random voids is preset inside the preset porous structure boundary, and the distribution probability of the growth nucleus is, and the growth nucleus is randomly generated inside the structure according to this distribution probability, and the growth nucleus is used to specify the initial node of the void growth.

[0038] In this embodiment, in step (4), the initially randomly distributed growth core is traversed, and the gap is grown in two-dimensional space with the growth core as the starting point. There are 8 growth directions, including 4 main directions and 4 diagonal directions. For each traversal, any single gap node has a probability of 𝑝𝑖 to grow into a new gap node in a certain direction. If the new node to be grown is already a gap, it is skipped. Repeat the above content and iterate continuously until the gap ratio reaches the target gap ratio n.

[0039] In this embodiment, in step (5), the two-dimensional porosity of the porous asphalt mixture is obtained through the above steps, the skeleton is identified and divided, the corresponding microscopic parameters are assigned to it, and its void morphology and other characteristics are clarified.

[0040] Taking AC-13 as an example, according to the asphalt mixture grading curve, the number of aggregate particles with a particle size of 2.36 mm or more, including 4.75 mm, 9.5 mm, and 13.2 mm, is calculated. Matlab is used to randomly generate a specified number of polygonal particles in the corresponding particle size interval, and these are used as coarse aggregate particles.

[0041] like Figure 1 As shown, the designated boundary is a 10*10 square. Within the specified range, particles are placed one by one in the order of 13.2mm, 9.5mm, 4.75mm, and 2.36mm in size from large to small. Each placement should ensure that the particles placed this time do not overlap with the particles that have been placed. If overlap occurs, the placement fails and the next placement is carried out until all particles are placed.

[0042] like Figure 2 As shown, based on the four-parameter random growth algorithm, four initial parameters are set: randomly distributed growth nuclei in the construction area = 0.1, given growth probability in different directions = 0.05, target void ratio n = 0.2 and probability density of mutual influence in the void structure I = 0.5. The growth phase is taken as the void, and the boundary of the porous structure is set, which is specified as a square of 10*10 cm.

[0043] like Figure 2 As shown, a growth nucleus of random voids is preset inside the preset porous structure boundary, and the growth nucleus distribution probability is = 0.05. According to this distribution probability, a growth nucleus is randomly generated inside the structure. The growth nucleus is used to specify the initial node of void growth. The coordinates of the growth nucleus cannot overlap with the coarse aggregate. If they overlap, the growth nucleus is regenerated.

[0044] like Figure 2 As shown in the figure, the initially randomly distributed growth core is traversed, and the gap is grown into the two-dimensional space with the growth core as the starting point. There are 8 growth directions, including the 4 main directions and 4 diagonal directions of the boundary square. For each traversal, any single gap node has a probability of = 0.5 to grow into a new gap node in a certain direction. If the new node to be grown is already a gap, it is skipped. Repeat the above content and iterate continuously until the gap ratio reaches the target gap ratio n = 0.2.

[0045] like Figure 3 As shown in the figure, Matlab is used to draw the final two-dimensional void structure of the porous asphalt mixture, and the different components of the structure are divided. The polygonal particles are the coarse aggregate part, the generated white irregular shapes are the voids, and the remaining part is the asphalt mortar. From this, parameters such as the void ratio and effective void ratio of the asphalt mixture can be obtained, which are applied to the study of the microscopic mechanism of voids in asphalt mixtures.

[0046] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above-mentioned technical features. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A method for generating numerical values ​​of two-dimensional void fraction of porous asphalt mixture, characterized by: The following steps are involved: (1) According to the mixture grading curve, determine the number of particles of each grade of aggregate with a sieve hole of 2.36 mm and above, and generate the corresponding number of random polygonal coarse aggregates of various particle sizes; (2) Within the specified boundary, coarse aggregate particles are placed one by one in the order of particle size from large to small. Each time the particles are placed, they should not overlap with the particles that have been placed. If overlap occurs, the placement fails and the next placement is carried out until all particles are placed. (3) Perform image enhancement processing on the obtained coarse aggregate placement results; (4) Based on the four-parameter random growth algorithm, the distribution probability of growth nuclei and the growth probability in each direction are specified within the gap range to generate asphalt mortar particles; (5) Identify and divide the skeleton, mortar and voids, and assign microscopic parameters; In the step (4), based on the four-parameter random growth algorithm, four initial parameters are set: growth nuclei randomly distributed within the boundary range, given growth probabilities in different directions, target void ratio n, and probability density I of mutual influence in void structure; in the step (4), the boundary of the porous structure is set; in the step (4), growth nuclei of random voids are preset inside the set porous structure boundary, and the growth nucleus distribution probability is I'. According to this distribution probability, growth nuclei are randomly generated inside the structure, and the growth nuclei are used to specify the initial nodes of void growth.

2. The method for generating a two-dimensional void fraction numerical value of porous asphalt mixture according to claim 1, characterized in that: In the step (1), the number of coarse aggregate particles in different particle size ranges is calculated according to the mixture gradation curve, and a specified number of polygonal particles in a specified particle size range are randomly generated and used as coarse aggregate particles.

3. The method for generating a two-dimensional void fraction numerical value of porous asphalt mixture according to claim 1, characterized in that: In the step (4), the initially randomly distributed growth core is traversed, and the gap is grown into the two-dimensional space with the growth core as the starting point. There are 8 growth directions, including 4 main directions and 4 diagonal directions. For each traversal, any single gap node has a probability of 𝑝𝑖 to grow into a new gap node in a certain direction. If the new node to be grown is already a gap, it is skipped. Repeat the above content and iterate continuously until the gap ratio reaches the target gap ratio n.

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