Prediction on residual flexural fatigue life of rock-concrete interface based on a deformation-controlled fatigue crack propagation criterion

To assess the cracking resistance of rock-concrete interface, three-point bending tests were carried on composite rock-concrete specimens under the monotonic and high flexural fatigue loading. The crack opening displacements along the ligament of the beam were continuously recorded in the whole test process. According to the measured crack mouth opening displacements (CMODs), the correlation between the monotonic and fatigue deformations at different cracking statuses was discussed. It has been shown that the deformation development of composite specimens under flexural fatigue loading was mainly caused by the propagation of interfacial crack. The P-CMOD curve under monotonic loading was the envelope curve of those under the different maximum fatigue loads. There were three CMOD control points in the monotonic deformation response to indicate the fatigue crack propagation states, which corresponded to the initial cracking load, the ultimate load and the applied maximum fatigue load in the post-peak part of the monotonic response, respectively. Correspondingly, they manifested the fatigue crack initiation, the inflection point of the fatigue crack propagation rate from deceleration to acceleration and the fatigue failure of the rock-concrete interface. Based on the three CMOD control points, a deformation-controlled fatigue crack propagation criterion was proposed to assess the cracking state of the rock-concrete interface under fatigue loading. Accordingly, a theoretical prediction model, termed as fatigue deformation evolution law, was established to predict its residual flexural fatigue life. This method was verified by the reasonable agreements between experimental and predicted results in the residual fatigue life.