Study on fatigue crack propagation failure in semi-rigid base.

• Three-dimensional preset depth crack fatigue propagation models were established. • The propagation of the crack tip section was monitored through the probe. • The fatigue propagation of crack tip inside the semi-rigid base was investigated. Nowadays, it is of non-negligible importance to extend the service life of in-service pavements. As the base form, shrinkage fractures and plate faults are the main reasons for the failure of semi-rigid base and it is of practical significance to study the cracking mechanism of the fracture damage from the microscopic point of view. In order to obtain the fatigue propagation law of the cracks inside the semi-rigid base, a three-dimensional preset depth crack fatigue propagation model was established based on the finite element quasi-static method and ground-penetrating radar detection data, and monitors the propagation of the crack tip section through the probe, obtaining the number of load actions and the crack propagation depth during the destabilization. Subsequently, this paper investigates the stress field distribution and fatigue propagation failure law of crack tip section inside the semi-rigid base based on the ensemble analysis method of stress intensity factor, combined with the macroscopic modulus change of the base structure. The propagation form of single-crack cracks within the base layer is mainly dominated by type I (opening type) cracks, but there are also the remaining two crack propagation trends at the tip. The analysis shows that the smaller the modulus of the semi-rigid base, the less likely the crack is to undergo an initial tip change. In the case of four preset depths, the preset depth of 50 mm is the most vulnerable to crack tip change. Relatively speaking, and the 200 mm preset depth cracks expand the maximum depth when the structure fails in all preset depths. It can be seen from the experiments that the strain field at the crack tip of 50 mm presetting depth is stronger. The strength of stress and strain fields near the crack tip at 200 mm and 150 mm preset depths is mainly related to the modulus of the base layer. The larger the modulus, the stronger the stress and strain fields. The distribution of the field strength at the crack tip of 100 mm and 50 mm presetting depth is less affected by the base layer modulus. In this study, the three-dimensional simulation of the fatigue action of the internal cracks in the semi-rigid base is innovatively proposed, which helps to clarify the distribution of the stress field and the fatigue failure of the internal crack tip of the semi-rigid base, and provides a new way of thinking for the assessment of the service performance of the long-life pavements and the failure mechanism of the microscopic damages. [ABSTRACT FROM AUTHOR]