Prediction of fatigue crack growth in rock-concrete interface

Rock-concrete interface is found in various engineering structures such as dams, tunnels, bridge piers etc.These structures are subjected to cyclic loading resulting in fatigue.Interface is the weakest and the most critical zone which is susceptible to crack formation and propagation.Understanding the effect of fatigue loading on the rock-concrete interface is useful in predicting the service life of these structures which ultimately ensures the durability of the structure.However, the heterogeneity that lies between rock and concrete poses significant challenge in analyzing the effect of fatigue crack growth at the interface.Further, as seen from the literature the fatigue test data exhibit an enormous scatter due to the inherent variability in the fatigue strength of the material as well as the statistical nature of the load experienced by them.Hence, for a reliable fatigue life estimation a deterministic approach is not sufficient.This paper proposes a generalized model derived from Paris' law to predict fatigue crack propagation in the rock-concrete interface.Additionally, it employs a probabilistic approach to estimate the fatigue life of the interface.In order to incorporate the heterogeneity at the interface, effective Young's modulus is used.The inherent mixed mode condition is included in the Paris' law through the stress intensity factors in both mode I and mode II.The crack propagation as a function of number of load cycles is predicted and the same is validated using available experimental results.