It is generally known that the fatigue life of materials to be effected by repeated stress under fixed conditions fluctuates widely.
The phenomenon of its variation can not be interpreted only by the experimental error or nonhomogeneity of the materials; it is considered that the variation and its statistical properties are the essential attribute against the character of fracture of materials.
From this point, assuming that even the phenomenon of the fluctuation of fatigue life in the field of bituminous mixture could be satisfactorily explained, the author tried to explain it by using the probabilty theory.
The report is the experimental study of investigation of the statistical nature in fatigue life and process of fracture aginst the mixture of DenseGraded Asphalt Concrete and Gap-Graded Asphalt Concrete under controlled load, temperature and support condition.
In experiment, the author used a stress-controlled bending machine in which an elastic leaf spring is installed at right angles to the center of the lower part of the specimen, the number of specimen is fourty per one kind mixture.
The results are as mentioned below :
1) The distribution of fatigue life corresponds to “Weibull Distribution” led by the weakest link theory.
2) It is possible that the phenomenon of fluctuation or wide scatter of fatigue life is explained by stockastic process.
3) The deflection and modulus of deformation when a perceptible crack occures approximate to normal distribution. The coefficient variation is small as compared with its initial condition.
4) Difference of the kind of mixture appears in the rate of crack propagation process, and the rate of Gap Graded Asphalt Concrete is greater than that of Dense-Graded Asphalt Concrete under the constant test conditions.
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