Method and device for testing poisson's ratio of asphalt pavement material based on stress state analysis

Abstract

The application discloses a kind of based on stress state analysis's asphalt pavement material Poisson's ratio test method and equipment, the method includes: step S01. Determine the asphalt pavement structure to be tested and the design parameter of each structure layer pavement material, design parameter includes tension and compression modulus and tension and compression Poisson's ratio;Step S02. Finite element analysis is carried out to asphalt pavement structure, to analyze the stress state of specified key point in asphalt pavement structure;Step S03. According to the stress state of specified key point in asphalt pavement structure, determine the test mode of pavement material Poisson's ratio test;Step S04. According to the test mode determined, Poisson's ratio test under each stress is carried out, and the final test result output is obtained according to the Poisson's ratio corresponding to the stress state of specified key point in the asphalt pavement structure in test result.The application has the advantages of simple implementation method, low cost, high testing accuracy and reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of road engineering, and in particular to a poisson's ratio testing method and device for asphalt pavement material based on stress state analysis. BACKGROUND

[0002] Most high-grade asphalt pavements are semi-rigid base asphalt pavements, in which asphalt mixture and cement stabilized macadam are the most commonly used road materials. The poisson's ratio of asphalt pavement material is a commonly used mechanical parameter in asphalt pavement design and structure analysis, and its value directly affects the accuracy of asphalt pavement structure design, mechanical analysis and performance prediction. In the prior art, the poisson's ratio of pavement material in pavement structure design is usually determined by experience, and there is currently no reliable method for testing the poisson's ratio of asphalt mixture and cement stabilized macadam. In the "Highway Asphalt Pavement Design Specification" (JTG D50-2017), the poisson's ratio of asphalt pavement material is simply recommended as a fixed value, and the compressive poisson's ratio is used as the only lateral deformation parameter of the material.

[0003] However, the tensile and compressive poisson's ratios of different road materials differ greatly, and the poisson's ratio changes significantly with the size of the load. Therefore, directly using the empirical value and the single compressive poisson's ratio of the poisson's ratio parameter in the pavement structure design will seriously affect the accuracy of the mechanical calculation and performance prediction of the asphalt pavement structure, thereby causing a large deviation between the pavement structure design and the actual situation. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a poisson's ratio testing method and device for asphalt pavement material based on stress state analysis, which has the advantages of simple implementation, low cost, high testing precision and reliability.

[0005] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0006] A poisson's ratio testing method for asphalt pavement material based on stress state analysis, comprising the following steps:

[0007] Step S01. Determine the design parameters of the asphalt pavement structure to be tested and the pavement material of each structure layer, including tensile and compressive modulus and tensile and compressive poisson's ratio.

[0008] Step S02. Perform finite element analysis on the asphalt pavement structure to analyze the stress state of the specified key points in the asphalt pavement structure.

[0009] Step S03. Determine the testing method for testing the poisson's ratio of the pavement material according to the stress state of the specified key points in the asphalt pavement structure.

[0010] Step S04. Perform Poisson's ratio test under each level of stress according to the determined test method, and output the final test results according to the Poisson's ratio corresponding to the stress state of the specified key point in the asphalt pavement structure in the test results.

[0011] Further, the step S02 comprises:

[0012] Step S201. Establish a numerical model of the asphalt pavement structure by using finite element software and perform initialization setting;

[0013] Step S202. Assign different tensile and compressive moduli and tensile and compressive Poisson's ratios to each point in the established numerical model of the asphalt pavement structure to perform structure calculation;

[0014] Step S203. Obtain the stress state of the specified key point in each structural layer of the asphalt pavement structure according to the structure calculation results of step S202.

[0015] Further, the initialization setting in step S201 comprises: according to the design parameters of the asphalt pavement structure and the pavement materials of each structural layer, initially setting the number of layers, thickness and material properties of each structural layer.

[0016] Further, in step S03, if the stress state of the specified key point is tensile stress, the test method is determined to be direct tensile test; if the stress state of the specified key point is compressive stress, the test method is determined to be uniaxial compression test.

[0017] Further, the step S04 comprises:

[0018] Step S401. Perform step-by-step loading and unloading test on the test pieces of cement stabilized macadam and asphalt mixture respectively to obtain the Poisson's ratio of each level of load;

[0019] Step S402. Establish the relationship between Poisson's ratio and stress state according to the Poisson's ratio of each level of load obtained by the test;

[0020] Arrangement S403. According to the relationship between Poisson's ratio and stress state, take the Poisson's ratio corresponding to the stress state of the specified key point obtained in step S02 as the final test result output.

[0021] Further, in step S401, according to the test method determined in step S03, uniaxial compression or direct tensile test is used to test the modulus and Poisson's ratio of the pavement material, and the longitudinal and transverse strain is tested by external extensometer.

[0022] Further, in the load test process, the size of each level of load is determined according to the maximum failure load P mThe cement stabilized macadam adopts five levels of loading and unloading, and the asphalt mixture adopts seven levels of loading and unloading.

[0023] Further, the Poisson ratio is calculated according to the absolute value of the ratio of the transverse strain caused by the uniformly distributed longitudinal stress to the corresponding longitudinal strain within the proportional limit of the material, that is:

[0024]

[0025] Wherein, μ is the Poisson ratio of the test piece, ε h is the transverse strain of the test piece, ε v is the longitudinal strain of the test piece.

[0026] Further, the asphalt pavement structure includes an asphalt surface layer, a cement stabilized macadam base layer, a cement stabilized macadam bottom base layer, a macadam cushion layer and a roadbed, and the design parameters are parameters of each pavement structure under static load conditions.

[0027] A computer device includes a processor and a memory, the memory is used to store a computer program, and the processor is used to execute the computer program to perform the above method.

[0028] Compared with the prior art, the advantages of the present application are that: the present application analyzes the stress state of the asphalt pavement structure to be tested, selects the corresponding test method according to the specific stress state of the key mechanical point in the asphalt pavement, and then tests the Poisson ratio of the material under each level of stress, and obtains the final Poisson ratio test result according to the Poisson ratio corresponding to the specific stress state of the key point in the pavement structure. The relationship between the size of the Poisson ratio and the stress state can be fully utilized to realize the Poisson ratio test of the asphalt mixture and the cement stabilized macadam under different stress states, effectively distinguish the Poisson ratio characteristics of the pavement material under different stress states, make the pavement material Poisson ratio match the stress state in the asphalt pavement structure, and thus obtain accurate and reliable asphalt pavement material Poisson ratio, and then facilitate accurate and comprehensive evaluation of the mechanical properties of the asphalt pavement material. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is the implementation flowchart of the asphalt pavement material Poisson ratio test method based on stress state analysis of the present embodiment.

[0030] Figure 2 It is the vertical stress diagram of the wheel load center along the depth obtained in the specific application embodiment.

[0031] Figure 3 It is the road surface transverse stress diagram obtained in the specific application embodiment.

[0032] Figure 4Fig. 2 is a schematic diagram of longitudinal stress at the bottom of the base obtained in a specific application embodiment.

[0033] Figure 5 Fig. 4 is a schematic diagram of the step-by-step stress- Poisson's ratio relationship of asphalt mixture under uniaxial compression obtained in a specific application embodiment.

[0034] Figure 6 Fig. 5 is a schematic diagram of the step-by-step stress- Poisson's ratio relationship of asphalt mixture under direct tension obtained in a specific application embodiment.

[0035] Figure 7 Fig. 7 is a schematic diagram of the step-by-step stress- Poisson's ratio relationship of cement stabilized gravel under uniaxial compression obtained in a specific application embodiment.

[0036] Figure 8 Fig. 8 is a schematic diagram of the step-by-step stress- Poisson's ratio relationship of cement stabilized gravel under direct tension obtained in a specific application embodiment. DETAILED DESCRIPTION

[0037] The present application is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of protection of the present application is not limited thereby.

[0038] Considering that the Poisson's ratio characteristics of pavement materials are different under different stress states, the present application analyzes the stress state of the asphalt pavement structure to be tested, selects the corresponding test method according to the specific stress state of the key mechanical points in the asphalt pavement, and then tests the Poisson's ratio of the material under each stress level. The final test result of the Poisson's ratio is obtained according to the Poisson's ratio corresponding to the specific stress state of the key points in the pavement structure. The relationship between the size of the Poisson's ratio and the stress state can be fully utilized to realize the Poisson's ratio test of asphalt mixture and cement stabilized gravel under different stress states, effectively distinguish the Poisson's ratio characteristics of pavement materials under different stress states, and make the pavement material Poisson's ratio match the stress state in the asphalt pavement structure, so as to obtain accurate and reliable asphalt pavement material Poisson's ratio, and then facilitate accurate and comprehensive evaluation of the mechanical properties of asphalt pavement materials.

[0039] As shown in Figure 1 , the detailed steps of the asphalt pavement material Poisson's ratio test method based on stress state analysis in the present embodiment include:

[0040] Step S01. Pavement structure determination: Determine the asphalt pavement structure to be tested and the design parameters of the pavement materials of each structural layer, including tensile and compressive modulus and tensile and compressive Poisson's ratio.

[0041] The design parameters for the asphalt pavement structure and the pavement materials of each structural layer can be determined according to relevant specifications and specific application projects. In this embodiment, the asphalt pavement structure specifically includes an asphalt surface layer, a cement-stabilized crushed stone base course, a cement-stabilized crushed stone subbase course, a crushed stone cushion course, and a subgrade. The design parameters are those of each pavement structure under static load conditions. The design parameters for each layer—the asphalt surface layer, the cement-stabilized crushed stone base course, the crushed stone base course, and the subgrade—can be selected according to relevant specifications.

[0042] Step S02. Stress state analysis: Perform finite element analysis on the asphalt pavement structure to analyze the stress state at specified key points in the asphalt pavement structure.

[0043] In this embodiment, finite element analysis is performed on the asphalt pavement structure using finite element software to analyze the stress state at specified key points in the asphalt pavement structure. Specific steps include:

[0044] Step S201. Model Establishment: Establish a numerical model of the asphalt pavement structure using finite element software and perform initialization settings;

[0045] Step S202. Pavement structure calculation: Assign different tensile and compressive moduli and tensile and compressive Poisson's ratios to each point in the established asphalt pavement structure numerical model for structural calculation;

[0046] Step S203. Stress state determination: Based on the structural calculation results of step S202, the stress state of the specified key points of each structural layer in the asphalt pavement structure is obtained.

[0047] The initialization settings in step S201 above specifically include: setting the number of layers, thickness and material properties of each structural layer according to the design parameters of the asphalt pavement structure and the pavement materials of each structural layer.

[0048] In a specific application embodiment, based on the theory of elastic layered systems under uniformly distributed vertical loads on a double-circle pavement, a numerical model of the asphalt pavement structure is established using finite element software. According to the design parameters of the asphalt pavement structure and the pavement materials of each structural layer determined in step S01, the number of layers, thickness, and material properties of each structural layer are initially set. Then, based on the dual-modulus theory, a numerical model of the asphalt pavement is established. According to the different stress states of each point of the pavement structure, corresponding tensile and compressive moduli and tensile and compressive Poisson's ratios are assigned, and structural calculations are performed to select the stress state of key points of each structural layer in the obtained asphalt pavement structure.

[0049] Step S03. Determine the test method for the Poisson's ratio test of the pavement material based on the stress state of the specified key points in the asphalt pavement structure.

[0050] In this embodiment, the stress values ​​are obtained based on the specific stress states of key points in the pavement structure calculated from the pavement structure. A test method is selected based on the stress state. If the stress state of the specified key point is tensile stress, the test method is determined to be direct tensile testing, i.e., the Poisson's ratio of the pavement material is tested using direct tensile testing. If the stress state of the specified key point is compressive stress, the test method is determined to be uniaxial compression testing, i.e., the Poisson's ratio of the pavement material is tested using uniaxial compression testing. Specifically, the test method can be selected based on the maximum stress value: when the maximum stress is tensile stress, direct tensile testing of the pavement material's Poisson's ratio is selected; when the maximum stress is compressive stress, uniaxial compression testing of the pavement material's Poisson's ratio is used.

[0051] Step S04. Perform Poisson's ratio tests under various stress levels according to the determined test method and load values, and obtain the final test result output based on the Poisson's ratio corresponding to the stress state of the specified key points in the asphalt pavement structure in the test results.

[0052] In this embodiment, Poisson's ratio tests are performed on the specimen under various stress levels by progressively loading and unloading the specimen. The specific steps include:

[0053] Step S401. Perform step-by-step loading and unloading tests on the specimens of cement-stabilized crushed stone and asphalt mixture respectively to obtain the Poisson's ratio of each load level;

[0054] Step S402. Establish the relationship between Poisson's ratio and stress state based on the Poisson's ratio of each load level obtained from the test;

[0055] Set up S403. Based on the relationship between Poisson's ratio and stress state, take the Poisson's ratio corresponding to the stress state of the specified key point obtained in step S02 as the final Poisson's ratio test result output.

[0056] In step S401 above, uniaxial compression and direct tensile tests are specifically used to test the modulus and Poisson's ratio of the pavement material. That is, the test method selected in step S03 is followed. If the specific stress state at the key structural points is tensile stress, a direct tensile test is used; otherwise, if the stress state is compressive stress, a uniaxial compression test is used. Longitudinal and transverse strains are tested using an external extensometer.

[0057] During the load test, the maximum failure load P of the material is first obtained from the strength test. m Based on the maximum destructive load P of the material m The magnitude of each load level can be obtained. Taking cement-stabilized crushed stone with a five-stage loading and unloading system and asphalt mixture with a seven-stage loading and unloading system as an example, the five-stage loading and unloading system for cement-stabilized crushed stone has a load magnitude of 0.1P per stage. m 0.2P m 0.3Pm ... 0.5P m The load per level for the asphalt mixture is 0.1P. m 0.2P m 0.3P m ... 0.7P m Then, by selecting a stress control mode, the specimen was subjected to progressive loading and unloading tests to obtain the Poisson's ratio for each load level. Based on the measured Poisson's ratios for each load level, the relationship between Poisson's ratio and stress state was established. Then, based on the asphalt pavement structure, the stress response at key points of the asphalt layer and water-stabilized base course was calculated, and the Poisson's ratio corresponding to that stress was taken as the final test value. That is, according to the specific stress state in the structure, the corresponding Poisson's ratio under different stresses was taken as the test value, thus obtaining accurate and reliable Poisson's ratio values ​​for asphalt mixtures and cement-stabilized crushed stone under different stress states in different asphalt pavement structures.

[0058] In a specific application embodiment, the detailed steps for performing step-by-step loading and unloading tests on specimens of cement-stabilized crushed stone and asphalt mixture are as follows:

[0059] (1) The modulus and Poisson's ratio of the pavement material were tested by uniaxial compression and direct tensile tests.

[0060] (2) Cement stabilized crushed stone was tested using cylindrical specimens with a height of 150 mm and a diameter of 150 mm and beam specimens with a length of 400 mm × width of 100 mm × height of 100 mm, respectively, for uniaxial compression and direct tensile tests.

[0061] (3) The uniaxial compression test of asphalt mixture uses a cylindrical specimen with a height of 100±2mm and a diameter of 100±2mm. The direct tensile standard specimen uses a beam specimen with a width of 50mm and a height of 50mm.

[0062] (4) Select an external extensometer to test the longitudinal and transverse strain.

[0063] (5) Before the test, use quick-curing adhesive to fix the extensometer to the pre-marked scale positions on both sides of the specimen; then place it on the MTS, select the stress control mode, and load and unload the specimen step by step. Cement stabilized crushed stone is loaded and unloaded in five stages, and asphalt mixture is loaded and unloaded in seven stages.

[0064] After testing under various loads, Poisson's ratio can be calculated based on the mechanical response of the specimen. Specifically, Poisson's ratio can be calculated as the absolute value of the ratio of the transverse strain caused by uniformly distributed longitudinal stress to the corresponding longitudinal strain within the proportional limit of the material. That is:

[0065]

[0066] Where μ is the Poisson's ratio of the specimen, ε h ε represents the transverse strain of the specimen. v The longitudinal strain of the specimen.

[0067] The following example, using the method described above to test the Poisson's ratio of asphalt pavement materials in a specific application embodiment, further illustrates the present invention. The surface layer specifically uses AC-16 type asphalt mixture, and the base layer uses suspended dense cement-stabilized crushed stone with a 5% cement dosage. Mechanical parameters are measured using standardized testing methods, and the mechanical parameters of the crushed stone layer and subgrade are selected according to specifications. The specific mechanical parameters of the pavement structure are shown in Table 1.

[0068] Table 1 Pavement Structure Parameters

[0069]

[0070] The wheel load center stress state obtained in this embodiment is as follows: Figures 2 to 4 As shown, the test results of the tensile and compressive Poisson's ratios of asphalt mixtures and cement-stabilized crushed stone under progressive stress are as follows: Figures 5 to 8 As shown in the figure, the Poisson's ratio of cement-stabilized crushed stone varies under different stress states, and increases with the increase of load level. Since tensile stress exists only in the wheel gap area of ​​the asphalt mixture, the tensile Poisson's ratio of the asphalt mixture is taken as the value corresponding to the maximum tensile stress on the road surface. However, the tensile stress at the bottom of the water-stabilized base layer gradually decreases with the distance from the center of the wheel gap, eventually approaching 0. Therefore, in this embodiment, the Poisson's ratio at 0.5 times the maximum tensile stress is taken as the tensile Poisson's ratio of cement-stabilized crushed stone. For the compressive Poisson's ratio, the Poisson's ratio corresponding to the maximum compressive stress of the asphalt layer and the base layer is taken. According to the stress calculation method described above, in this embodiment, the tensile stress of the asphalt layer is taken as the maximum tensile stress at the road surface (0.047 MPa), and the compressive stress is taken as the maximum compressive stress at the surface layer (0.7 MPa). The tensile stress of the cement-stabilized crushed stone is taken as 0.5 times the maximum tensile stress at the bottom of the base course, and the compressive stress is taken as the maximum compressive stress at the top of the water-stabilized base course (0.33 MPa). Based on the specific stress state, the final tensile and compressive Poisson's ratios for the asphalt mixture are 0.14 and 0.2, respectively; the tensile and compressive Poisson's ratios for the cement-stabilized crushed stone are 0.16 and 0.17, respectively. Verification shows that the Poisson's ratios obtained according to the method of this invention are accurate and reliable, and can effectively distinguish the Poisson's ratio characteristics of pavement materials under different stress states.

[0071] This embodiment also provides a computer device, including a processor and a memory, the memory for storing a computer program, and the processor for executing the computer program to perform the method as described above.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis, characterized by the following steps: include: Step S01. Determine the design parameters of the asphalt pavement structure to be tested and the pavement materials of each structural layer, including tensile and compressive modulus and tensile and compressive Poisson's ratio; Step S02. Perform finite element analysis on the asphalt pavement structure to analyze the stress state at specified key points in the asphalt pavement structure; Step S03. Based on the stress state of the specified key points in the asphalt pavement structure, determine the test method for the Poisson's ratio test of the pavement material. If the stress state of the specified key points is tensile stress, determine the test method as direct tensile test; if the stress state of the specified key points is compressive stress, determine the test method as uniaxial compression test. Step S04. Perform Poisson's ratio tests under various stress levels according to the determined test method, and obtain the final test result output based on the Poisson's ratio corresponding to the stress state of the specified key points in the asphalt pavement structure as described in the test results. Step S04 includes: Step S401. Perform step-by-step loading and unloading tests on the specimens of cement-stabilized crushed stone and asphalt mixture respectively to obtain the Poisson's ratio of each load level; Step S402. Establish the relationship between Poisson's ratio and stress state based on the Poisson's ratio of each load level obtained from the test; Step S403. Based on the relationship between Poisson's ratio and stress state, take the Poisson's ratio corresponding to the stress state of the specified key point obtained in step S02 as the final test result output.

2. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to claim 1, characterized in that, Step S02 includes: Step S201. Establish a numerical model of the asphalt pavement structure using finite element software and perform initialization settings; Step S202. Assign different tensile and compressive moduli and tensile and compressive Poisson's ratios to each point in the established numerical model of the asphalt pavement structure for structural calculation; Step S203. Based on the structural calculation results of step S202, obtain the stress state of the specified key points of each structural layer in the asphalt pavement structure.

3. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to claim 2, characterized in that, The initialization settings in step S201 include: setting the number of layers, thickness and material properties of each structural layer according to the design parameters of the asphalt pavement structure and the pavement materials of each structural layer.

4. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to claim 1, characterized in that, In step S401, the modulus and Poisson's ratio of the road material are tested by uniaxial compression or direct tensile test according to the test method determined in step S03, and the longitudinal and transverse strains are tested by an external extensometer.

5. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to claim 1, characterized in that, During the load test, the magnitude of each load level is based on the maximum failure load P of the material obtained from the strength test. m The settings are as follows: cement-stabilized crushed stone uses a five-stage loading and unloading system, while asphalt mixture uses a seven-stage loading and unloading system.

6. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to any one of claims 1 to 5, characterized in that, Poisson's ratio is calculated based on the absolute value of the ratio of the transverse strain caused by uniformly distributed longitudinal stress to the corresponding longitudinal strain within the proportional limit of a material. It is: Where μ is the Poisson's ratio of the specimen, ε h ε represents the transverse strain of the specimen. v The longitudinal strain of the specimen.

7. The method for testing the Poisson's ratio of asphalt pavement materials based on stress state analysis according to any one of claims 1 to 5, characterized in that, The asphalt pavement structure includes an asphalt surface layer, a cement-stabilized crushed stone base course, a cement-stabilized crushed stone subbase course, a crushed stone cushion course, and a roadbed. The design parameters are the parameters of each pavement structure under static load conditions.

8. A computer device comprising a processor and a memory, the memory being used to store computer programs, characterized in that, The processor is used to execute the computer program to perform the method as described in any one of claims 1 to 7.

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