CN-117664720-B - Characterization method of modulus decay law of asphalt mixture under three-dimensional stress state

CN117664720BCN 117664720 BCN117664720 BCN 117664720BCN-117664720-B

Abstract

The invention discloses a characterization method of modulus decay law of an asphalt mixture in a three-dimensional stress state, which comprises the steps of preparing test pieces for direct stretching, indirect stretching and uniaxial compression of the asphalt mixture, carrying out direct stretching, indirect stretching and uniaxial compression strength and fatigue tests of the asphalt mixture, establishing a power function relation equation of the asphalt mixture strength and loading rate, respectively establishing modulus decay equations of the asphalt mixture in the direct stretching, indirect stretching and uniaxial compression modes, calculating a fatigue stress strength ratio according to initial equivalent stress of fatigue and equivalent stress in fatigue failure, and establishing a characterization model of modulus decay law of the asphalt mixture in the three-dimensional stress state.

Inventors

HE YONGHAI
LV SONGTAO
PENG XINGHAI
PU CHANGYU
MENG HUILIN
WANG ZIYANG
LEI WEI
Ma Huabao
Xie Nasi

Assignees

河北省交通规划设计研究院有限公司
长沙理工大学

Dates

Publication Date: 20260505
Application Date: 20231107

Claims (5)

1. The characterization method of the modulus decay law of the asphalt mixture in the three-dimensional stress state is characterized by comprising the following steps of: S1, preparing different stress loading test pieces of asphalt mixture; S2, carrying out different stress loading strength and fatigue tests on the asphalt mixture; S3, establishing a power function relation equation of the strength and the recording speed of the asphalt mixture under different stress states, namely fitting the strength value of the asphalt mixture with the loading speed by adopting a power function based on the stress loading strength test results of the asphalt mixture under different loading speeds; s4, respectively establishing asphalt mixture modulus decay equation under different stress loading modes, and fitting through a fatigue test according to the asphalt mixture modulus decay equation to obtain modulus decay equation parameters ; S5, calculating a fatigue stress intensity ratio according to the initial equivalent stress and the fatigue failure equivalent stress, wherein the fatigue stress intensity ratio is based on the asphalt mixture three-dimensional stress state intensity yield surface theory, and fatigue analysis of the stress state and the loading rate influence is considered; s6, establishing a characterization model of the modulus decay law of the asphalt mixture in a three-dimensional stress state, wherein the parameter is based on the modulus decay equation in the step S4 And fatigue stress strength ratio of step S5 Fitting according to a power function growth rule to obtain a power function equation, and combining the power function equation with the asphalt mixture modulus decay equation in the step S4 to obtain a characterization model of the asphalt mixture modulus decay rule in a three-dimensional stress state; The modulus of the asphalt mixture in the step S4 can be continuously measured and calculated through a strain or displacement sensor in a fatigue test, the modulus can describe the damage of the asphalt mixture, and the damage variables are defined as follows: Wherein: The degree of damage of the test piece is calculated, Is the modulus after the fatigue effect of the material, The initial modulus of the test piece; the asphalt mixture modulus decay equation is fitted by a model of 2: 2, 2 Wherein: Is a modulus decay equation parameter, and Fitting can be achieved through fatigue tests; In order to be able to achieve a material with an effective modulus, For the initial modulus of the material, For the number of cycles of loading in the fatigue test, Is fatigue life; the fatigue stress intensity ratio in the step S5 is calculated by the following formula: fatigue stress strength ratio Wherein: initial equivalent stress for fatigue; Equivalent stress in fatigue failure; The equivalent stress is calculated by the following formula: Wherein: In order for the stress to be equivalent to, 、、 First, second, third principal stresses, respectively, of a point; The specific method for establishing the characterization model in the step S6 comprises the following steps: S61, fitting the modulus decay equation parameter in the step S4 and the fatigue stress intensity ratio in the step S5 by adopting a 3 power function equation: 3 Wherein: For the modulus decay equation parameters, In order to achieve a fatigue stress intensity ratio, Fitting parameters; s62, setting the parameters of the decay equation of modulus And fatigue stress strength ratio And (3) the power function equation of (2) and the modulus decay equation in the step (S4) are combined to obtain a characterization model of the modulus decay rule of the asphalt mixture in a three-dimensional stress state: Wherein: for the dynamic modulus during fatigue process, As an initial value of the dynamic modulus, For the number of fatigue load cycles, Is fatigue life; The modulus attenuation equation parameters can be obtained through fatigue test fitting; the stress ratio takes the influence of a stress state and a loading rate into consideration for the fatigue stress intensity ratio, and represents the ratio of the stress level to the corresponding material resistance in the fatigue test of the asphalt mixture; As regression coefficient, by fatigue stress intensity ratio And modulus decay equation parameters Fitting to obtain the final product.
2. The method for characterizing the modulus decay law of an asphalt mixture under a three-dimensional stress state according to claim 1, wherein the stress loading comprises direct stretching, indirect stretching and uniaxial compression, and the step S1 is to prepare test pieces for direct stretching, indirect stretching and uniaxial compression of the asphalt mixture respectively.
3. The method for characterizing the modulus decay law of an asphalt mixture under a three-dimensional stress state according to claim 1, wherein in the step S2, a displacement control mode and a stress control mode are adopted in the strength test, the stress level of the fatigue test is selected based on the strength test result under the displacement control mode, and the selected stress level of the fatigue test is not greater than the strength of the asphalt mixture.
4. The method for characterizing a decay law of a modulus of an asphalt mixture in a three-dimensional stress state according to claim 1, wherein the step S3 of fitting a power function equation of an intensity value of the asphalt mixture and a loading rate is: Wherein: Is the strength of the asphalt mixture; is the loading rate; Is equation parameter The method can be obtained by fitting the strength test results of asphalt mixtures with different loading rates under a stress control mode.
5. The method for characterizing a decay law of a modulus of an asphalt mixture under a three-dimensional stress state according to claim 4, wherein the loading frequency is based on a fatigue test Periodic of Stress level Can find the corresponding loading rate See formula 1: 1 (1) According to formula 1, the loading rates corresponding to different stress levels of the fatigue test can be calculated, and based on the established power function equation of the asphalt mixture strength and the loading rates under different stress states, the ultimate strength under different stress levels of different stress states can be calculated.

Description

Characterization method of modulus decay law of asphalt mixture under three-dimensional stress state Technical Field The invention relates to the technical field of road engineering, in particular to a characterization method of a modulus decay rule of an asphalt mixture in a three-dimensional stress state. Background Asphalt pavement is a pavement structure type mainly adopted by high-grade highways in China, and under the action and influence of factors such as vehicle load, natural environment and the like, fatigue damage can be gradually generated in the structure, and along with the accumulation of the damage, pavement materials and structural performance can be gradually degraded until the damage. In order to prolong the service life of the asphalt pavement, corresponding maintenance measures are needed to be scientifically and timely made. The research on the development process of the fatigue damage of the asphalt mixture is very important to scientific maintenance decision. The modulus of the asphalt pavement material is an important mechanical parameter for determining the service life of the pavement, and the decay rule of the modulus can generally reflect the damage rule of the asphalt pavement. However, on one hand, asphalt pavement materials have viscoelastic properties, the modulus of the asphalt pavement materials is not an inherent property of asphalt mixtures, the asphalt pavement materials have certain stress dependence, the modulus of the asphalt pavement materials also changes when the load condition changes, on the other hand, asphalt pavement materials have the dependence of pavement structure forms, the layers of the asphalt mixtures in the pavement structures are different, the stress states of the asphalt mixtures are different, and the modulus levels of the asphalt mixtures are different. Therefore, the modulus characteristic and decay rule of the asphalt mixture are researched only through indoor simple loading modes, such as material tests in direct stretching, indirect stretching and uniaxial compression modes, and the modulus characteristic and decay rule are greatly different from the actual pavement service state, so that the fatigue damage performance of the asphalt pavement structure is not easy to evaluate, and scientific maintenance decisions are also not easy to conduct. In summary, in order to achieve scientific transformation from material fatigue damage to structural fatigue damage, it is highly desirable to invent a method for establishing a model for representing modulus decay law of an asphalt mixture in a three-dimensional stress state through an asphalt mixture mechanical property test in a simple stress state, so as to achieve uniform representation of modulus decay laws of the asphalt mixture in different loading modes. Disclosure of Invention The invention aims to provide a characterization method of the modulus decay law of an asphalt mixture under a three-dimensional stress state, which solves the problems that the prior art has larger difference from the actual pavement service state, is not beneficial to evaluating the fatigue damage performance of an asphalt pavement structure and is also not beneficial to scientific maintenance decision. The invention is realized in such a way that the characterization method of the modulus decay law of the asphalt mixture in a three-dimensional stress state comprises the following steps: s1, preparing a test piece for direct stretching, indirect stretching and uniaxial compression of an asphalt mixture; s2, performing direct stretching, indirect stretching, uniaxial compression strength and fatigue tests on the asphalt mixture; s3, establishing a power function relation equation of the intensity and the loading rate of the asphalt mixture; s4, respectively establishing an asphalt mixture modulus decay equation under the modes of direct stretching, indirect stretching and uniaxial compression; S5, calculating the fatigue stress intensity ratio according to the initial fatigue equivalent stress and the fatigue failure equivalent stress; and S6, establishing a characterization model of the modulus decay law of the asphalt mixture in a three-dimensional stress state. Further, the asphalt mixture strength test in the step S2 adopts a displacement control mode and a stress control mode, the loading rates of the asphalt mixture direct stretching, the indirect stretching and the uniaxial compression strength test in the displacement control mode are 5mm/min, 50mm/min and 2mm/min respectively, and the asphalt mixture strength test in the stress control mode is carried out at different loading rates, and the direct stretching, the indirect stretching and the uniaxial compression modes adopt 0.02MPa/S, 0.05MPa/S, 0.1MPa/S, 0.5MPa/S, 1MPa/S, 2MPa/S, 4MPa/S and 6MPa/S. Further, the fatigue test of the asphalt mixture in the step S2 adopts a stress control mode, and the stress level of the fatigue test can be selected based on the s