Influence of initial defects on the fatigue behaviour of cement-stabilized macadam base through DEM

Fatigue failure of cement-stabilized macadam (CSM) base has always been a concern in highway construction. The microscopic initial defect is an important factor affecting its fatigue performance. The objective of this paper is to investigate the fatigue cracking of CSM materials under cyclic loading through numerical simulation and to analyze the influence of microscopic initial defects. The mesoscale random particle model was established using the discrete element method (DEM). The discrete fracture network (DFN) was used to characterize the microscopic initial defects in cement mortar. A parallel bond evolution method was also developed to simulate the time-dependent fatigue damage under cyclic loading. Then virtual semicircular bending (SCB) fatigue tests were carried out to reproduce the mesoscopic fatigue cracking. The results show that the established mesoscale model can accurately simulate the evolution of microcracks. The fatigue damage presents nonlinear accumulation, and the interface is a weak area of fatigue failure. Through optimizing the cracking propagation path, initial defects induce the penetration crack and reduce the fatigue life. The large-size defects should be more concerned. Fractures with a radius greater than 0.15mm should be controlled within the density range of 20 m/m2, which is beneficial to improve the anti-fatigue performance of CSM.