Effects of infilling materials on mechanical behaviors and cracking process of pre-cracked rock: Insights from a hybrid continuum-discontinuum method

•The hybrid continuum-discontinuum method is firstly used to investigate the filled flaws.•The σci presents a downward concave regarding the increasing flaw inclination angle.•Crack initiation sequences in the rock and infillings are closely related with the σci change.•Sliding crack model interprets the variation of mechanical properties of the filled-flaws. The process of crack nucleation, initiation and propagation are of great significance in rock engineering such as hydrofracturing, underground excavation and gas or petroleum industry. In this study, the fracturing process of rock models with filled-flaws are mimicked by the hybrid continuum-discontinuum method. The effects both on mechanical response and cracking behaviors induced by the frictional properties including cohesion and friction coefficients of infilling materials are investigated. The results indicated that the minimum crack initiation stress of infilled flawed specimens lie in the inclination angle of 45–75° with different cohesions. When the friction angle changes, the minimum crack initiation stress appears when the inclination angle is in the range of 15–60°. The inclination angles are in accordance with that value when the normalized stress intensity factor of K1 acquired by changing cohesion and friction angle reaches maximum in the sliding crack model. Besides, with the increasing of cohesion and friction angle, the transition from wing crack to secondary crack appeared. The crack initiation sequence and pattern are comparable with the laboratory test.