Accurate identification method for semicircular bending fracture process of emulsified asphalt mixture
Through semicircular bending fracture test and full-field strain measurement, the three stages of the fracture process of emulsified asphalt mixture are accurately identified, which solves the error problem of fracture performance evaluation in the existing technology, and realizes an accurate evaluation of the fracture performance of emulsified asphalt mixture.
Patent Information
- Application Number
- CN202411289240.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-27
AI Technical Summary
The prior art cannot accurately identify the three stages of the semicircular bending fracture process of emulsified asphalt mixture, resulting in errors in the evaluation of fracture performance, especially in the case of large differences in mechanical properties.
The load-vertical displacement curve and full-field strain-loading time relationship are obtained through the semicircular bending fracture test, and the average of the full-field horizontal strain-loading time curve is calculated, which is divided into slow growth, rapid growth and decline stages to determine the crack initiation, development and The boundary point of the failure stage is determined by combining the load-load time curve to determine the failure point of the fracture failure, and accurately distinguish the three stages of the fracture process.
The physical and mechanical significance of the fracture process is clarified, the accurate identification of fracture performance is improved, and it is suitable for emulsified asphalt mixtures with different cut-out depths and fracture strengths, reducing the error in fracture performance evaluation.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of road engineering, and specifically to a method for accurately identifying a semicircular bending fracture process of an emulsified asphalt mixture. Background Art
[0002] As energy and environmental issues become increasingly severe, "energy conservation, emission reduction, and low-carbon development" has become the development trend of various industries. In the field of road engineering, energy-saving and environmentally friendly highway construction and maintenance technologies are increasingly valued. Among them, emulsified asphalt mixture is an energy-saving and environmentally friendly asphalt mixture that can be constructed at room temperature. It is expected to replace traditional hot-mix asphalt mixture and be widely used in new construction and recycled pavement projects.
[0003] Emulsified asphalt mixture is an asphalt mixture with emulsified asphalt as the main binder and cement as the auxiliary binder. Due to the effect of cement, emulsified asphalt mixture has high anti-rutting performance, but there is also a risk of fracture. Therefore, crack resistance is one of the important properties of emulsified asphalt mixture. At present, the notched semicircular bending fracture test has been widely used at home and abroad to evaluate the fracture performance of asphalt mixtures. When calculating the fracture performance-related parameters based on the test data, it is necessary to determine the fracture stage of the specimen. Generally, the semicircular bending fracture process includes three stages: crack initiation, crack propagation and failure. However, the current relevant domestic and foreign specifications and research have no clear physical and mechanical significance for the judgment criteria of the fracture stage of semicircular bending specimens, and cannot adapt to the evaluation and comparison of the fracture performance of asphalt mixtures when the mechanical properties are quite different. In view of this, in order to accurately evaluate the fracture performance of emulsified asphalt mixtures, an accurate identification method for the semicircular bending fracture process of emulsified asphalt mixtures is needed. Summary of the invention
[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for accurately identifying the semicircular bending fracture process of emulsified asphalt mixture.
[0005] To achieve the above object, the present invention provides the following technical solution: a method for accurately identifying the semicircular bending fracture process of an emulsified asphalt mixture, the steps of which are:
[0006] (1) Obtain a semicircular bending specimen of emulsified asphalt mixture to be evaluated;
[0007] (2) performing a semicircular bending fracture test on the semicircular bending specimen of the emulsified asphalt mixture obtained in step (1), obtaining a load-vertical displacement curve and a load-loading time curve of the emulsified asphalt mixture through a loading machine, and simultaneously obtaining a full-field strain-loading time relationship of the emulsified asphalt mixture specimen analysis area through a non-contact full-field strain measurement system;
[0008] (3) with respect to the relationship between the full-field strain and the loading time in the analysis area of the emulsified asphalt mixture specimen obtained in step (2), a relationship curve between the average value of the full-field horizontal strain and the loading time in the analysis area of the emulsified asphalt mixture specimen is calculated and obtained;
[0009] (4) for the emulsified asphalt mixture specimen obtained in step (3), the relationship curve between the average value of the horizontal strain in the whole field and the loading time is obtained, and the growth law of the average value of the horizontal strain in the whole field in the analysis area is divided into three stages, namely, a slow growth stage, a rapid growth stage and a decline stage, and at the same time, it is determined that these three stages correspond to the crack initiation stage, the crack development stage and the failure stage respectively;
[0010] (5) for the relationship curve between the average value of the horizontal strain in the whole field and the loading time obtained in step (4), the fracture failure point is determined as the moment when the average value of the horizontal strain in the whole field reaches the maximum value, and the boundary point between the crack initiation stage and the crack development stage is determined as the boundary point between the slow growth stage and the rapid growth stage of the average value of the horizontal strain in the whole field of the analysis area;
[0011] (6) Regarding the boundary point between the crack initiation stage and the crack development stage determined in step (5), considering that there is a certain degree of empirical judgment in determining the slow growth stage and the rapid growth stage of the average horizontal strain in the entire analysis area of the specimen, the load-loading time curve obtained in step (2) can be used to comprehensively determine the boundary point between the crack initiation stage and the crack development stage as the moment corresponding to the maximum load.
[0012] (7) Based on the moments corresponding to the dividing point between the crack initiation and crack development stages and the fracture failure point obtained in steps (5) and (6), and based on the load-vertical displacement curve obtained in step (2), a fracture test load-vertical displacement curve that accurately distinguishes the critical points of the three stages of the fracture process is obtained, and is used to calculate the relevant fracture energy parameters of the specimen.
[0013] In some embodiments, according to step (7), the fracture energy is calculated as follows:
[0014]
[0015] Fracture Energy G f The fracture work W f The fracture surface area is calculated according to formula (1).
[0016] In some embodiments, the work of fracture W f It is the envelope area under the load-vertical displacement curve before the fracture failure point, and A is the ligament surface area, which is obtained by multiplying the distance from the top of the cut to its upper top by the thickness of the specimen.
[0017] Compared with the prior art, the present invention has the following beneficial effects:
[0018] The present invention determines that the maximum value of the average value of the full-field horizontal strain is the fracture failure point of the semicircular complete fracture test through the relationship curve of the average value of the full-field horizontal strain in the analysis area-loading time, and determines that the dividing point between the crack initiation stage and the crack development stage is the dividing point between the slow growth stage and the rapid growth stage of the average value of the full-field horizontal strain in the analysis area, which has a clear physical and mechanical significance. The average value of the full-field horizontal strain reflects the tensile deformation capacity of the specimen. In the crack initiation stage, the specimen has a large deformation resistance, so the average value of the full-field horizontal strain is relatively small; after the fracture failure point, the fractured specimen can no longer withstand more tensile fracture energy, so the average value of the full-field horizontal strain decreases accordingly, so the maximum value of the full-field horizontal strain corresponds to the fracture failure point of the semicircular complete fracture test.
[0019] At the same time, compared with the distinction standards of existing specifications, the identification method of the three stages of the fracture process clarified by the present invention is more accurate and more suitable for emulsified asphalt mixture specimens with different incision depths and different fracture strengths. For example, the US AASHTOTP124-16 specification stipulates that the fracture failure point is defined as the load dropping to 0.1kN. There is a large error in the evaluation of the fracture performance of asphalt mixtures with large differences in fracture strength and toughness.
[0020] Details of one or more embodiments of the present application are presented in the following drawings and descriptions to make other features, purposes and advantages of the present application more concise and easy to understand. The present application is fully described and understood through the embodiments of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is the full-field horizontal strain field obtained by testing based on the non-contact full-field strain measurement system;
[0022] Figure 2 To identify the critical points of the three stages of the fracture process based on the relationship curve between the applied load, the average value of the horizontal strain field and the loading time;
[0023] Figure 3 To distinguish the load-vertical displacement curves of the three stages of the fracture process and the calculation of the fracture work. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.
[0025] The present invention provides a technical solution: a method for accurately identifying the semicircular bending fracture process of an emulsified asphalt mixture, the steps of which are:
[0026] (1) Obtain a semicircular bending specimen of emulsified asphalt mixture to be evaluated;
[0027] (2) A semicircular bending fracture test is performed on the semicircular bending specimen of the emulsified asphalt mixture obtained in step (1). The load-vertical displacement curve and the load-loading time curve of the emulsified asphalt mixture are obtained by a loading machine. At the same time, the full-field strain-loading time relationship of the emulsified asphalt mixture analysis area is obtained by a non-contact full-field strain measurement system (such as Figure 1 shown);
[0028] (3) Based on the relationship between the full-field strain and loading time of the emulsified asphalt mixture specimen analysis area obtained in step (2), a relationship curve between the average value of the full-field horizontal strain of the emulsified asphalt mixture specimen analysis area and the loading time is calculated and obtained (e.g. Figure 2 shown);
[0029] (4) for the emulsified asphalt mixture specimen obtained in step (3), the relationship curve between the average value of the horizontal strain in the whole field and the loading time is obtained, and the growth law of the average value of the horizontal strain in the whole field in the analysis area is divided into three stages, namely, a slow growth stage, a rapid growth stage and a decline stage, and at the same time, it is determined that these three stages correspond to the crack initiation stage, the crack development stage and the failure stage respectively;
[0030] (5) Based on the relationship curve between the average value of the horizontal strain in the whole field and the loading time obtained in step (4), the fracture failure point is determined to be the moment when the average value of the horizontal strain in the whole field reaches the maximum value, and the boundary point between the crack initiation stage and the crack development stage is determined to be the boundary point between the slow growth stage and the rapid growth stage of the average value of the horizontal strain in the whole field of the analysis area (such as Figure 2 shown);
[0031] (6) Regarding the demarcation point between the crack initiation stage and the crack development stage determined in step (5), considering that there is a certain degree of empirical judgment in determining the slow growth stage and the rapid growth stage of the average horizontal strain in the entire field of the specimen analysis area, the load-loading time curve obtained in step (2) can be used to comprehensively determine the demarcation point between the crack initiation stage and the crack development stage as the moment corresponding to the maximum load (e.g. Figure 2 shown).
[0032] (7) Based on the moment corresponding to the demarcation point between the crack initiation and crack development stages and the fracture failure point obtained in step (5) and step (6), and based on the load-vertical displacement curve obtained in step (2), a fracture test load-vertical displacement curve that accurately distinguishes the critical points of the three stages of the fracture process is obtained, and is used to calculate the relevant fracture energy parameters of the specimen (such as Figure 3 shown).
[0033] Through the technical solution of this application,
[0034] The fracture performance experiments of 12 groups of embodiments were conducted respectively, and the fracture performance of emulsified asphalt mixtures under 12 different working conditions were tested, including emulsified asphalt mixtures with 4 different cement contents and 3 different incision depths, with cement contents of 0%, 1.5%, 3%, and 4.5%, and incision depths of 10mm, 20mm, and 30mm. All emulsified asphalt mixtures were graded AC13, and the oil-stone ratio was fixed at 5%. Based on the above method, the maximum load and corresponding vertical displacement, fracture failure point load and corresponding vertical displacement, and fracture energy of the 12 groups of embodiments were obtained, as shown in Table 1.
[0035] In Table 1, the fracture energy G f By the fracture work W f The fracture surface area is calculated according to formula (1).
[0036]
[0037] Fracture work W f That is Figure 3 The envelope area under the load-vertical displacement curve before the mid-fracture failure point, A is the ligament surface area, which can be obtained by multiplying the distance from the top of the cut to the top of its upper part (l) by the specimen thickness (d).
[0038] As can be seen from Table 1, since both the cement content and the incision depth will affect the maximum load of the fracture test, the failure point load varies with the cement content and the incision depth and cannot be set to a fixed value. At the same time, the determination of the failure point has a great influence on the calculation of the fracture energy value. The fracture energy calculated by the failure point determined by this method remains consistent for any fixed incision depth, that is, the effect of cement content on the fracture performance of emulsified asphalt mixture is: 1.5% cement content> 0% cement content> 3% cement content> 4.5% cement content. If a fixed load value (such as 0.1kN) is used as the failure point criterion, the effect of cement content on the fracture energy of emulsified asphalt mixture is completely disordered. Therefore, this method can accurately determine the three fracture stages of emulsified asphalt mixture, which has important reference significance for accurately calculating the fracture parameters of emulsified asphalt mixture and comparing the fracture performance of emulsified asphalt mixtures with different mechanical properties and compositions.
[0039] Table 1 Maximum load, fracture failure load and fracture work in semicircular bending fracture of emulsified asphalt mixture
[0040]
[0041] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.
[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for accurately identifying the semicircular bending fracture process of emulsified asphalt mixture, characterized by: The steps are: (1) Obtain a semicircular bending specimen of emulsified asphalt mixture to be evaluated; (2) performing a semicircular bending fracture test on the semicircular bending specimen of the emulsified asphalt mixture obtained in step (1), obtaining a load-vertical displacement curve and a load-loading time curve of the emulsified asphalt mixture through a loading machine, and simultaneously obtaining a full-field strain-loading time relationship of the emulsified asphalt mixture specimen analysis area through a non-contact full-field strain measurement system; (3) with respect to the relationship between the full-field strain and the loading time in the analysis area of the emulsified asphalt mixture specimen obtained in step (2), a relationship curve between the average value of the full-field horizontal strain and the loading time in the analysis area of the emulsified asphalt mixture specimen is calculated and obtained; (4) for the emulsified asphalt mixture specimen obtained in step (3), the relationship curve between the average value of the horizontal strain in the whole field and the loading time is obtained, and the growth law of the average value of the horizontal strain in the whole field in the analysis area is divided into three stages, namely, a slow growth stage, a rapid growth stage and a decline stage, and at the same time, it is determined that these three stages correspond to the crack initiation stage, the crack development stage and the failure stage respectively; (5) for the relationship curve between the average value of the horizontal strain in the whole field and the loading time obtained in step (4), the fracture failure point is determined as the moment when the average value of the horizontal strain in the whole field reaches the maximum value, and the boundary point between the crack initiation stage and the crack development stage is determined as the boundary point between the slow growth stage and the rapid growth stage of the average value of the horizontal strain in the whole field of the analysis area; (6) Regarding the boundary point between the crack initiation stage and the crack development stage determined in step (5), considering that there is a certain degree of empirical judgment in determining the slow growth stage and the rapid growth stage of the average horizontal strain in the entire analysis area of the specimen, the load-loading time curve obtained in step (2) can be used to comprehensively determine the boundary point between the crack initiation stage and the crack development stage as the moment corresponding to the maximum load. (7) Based on the moments corresponding to the dividing point between the crack initiation and crack development stages and the fracture failure point obtained in steps (5) and (6), and based on the load-vertical displacement curve obtained in step (2), a fracture test load-vertical displacement curve that accurately distinguishes the critical points of the three stages of the fracture process is obtained, and is used to calculate the relevant fracture energy parameters of the specimen.
2. The method for accurately identifying the semicircular bending fracture process of an emulsified asphalt mixture according to claim 1, characterized in that: According to step (7), the fracture energy is calculated as follows: Fracture Energy G f By the fracture work W f The fracture surface area is calculated according to formula (1).
3. The method for accurately identifying the semicircular bending fracture process of an emulsified asphalt mixture according to claim 2 is characterized in that: Fracture work W f It is the envelope area under the load-vertical displacement curve before the fracture failure point, and A is the ligament surface area, which is obtained by multiplying the distance from the top of the cut to its upper top by the thickness of the specimen.