AbstractTo investigate the fracture properties of the rock-concrete interface after fatigue loading, fatigue tests with the maximum loads of 60% and 70% of the ultimate load were carried out under three-point bending (TPB) loading. After 80,000 fatigue loading cycles, the specimens were subjected to quasi-static TPB loading until failure. The fracture parameters—including the nominal initial fracture toughness K1Cini, the nominal unstable fracture toughness K1Cun, the critical crack length ac, the fracture energy Gf, and the characteristic length lch—were obtained based on the experimental results. The test results indicated that the interfacial crack did not initiate in the fatigue tests if the applied maximum fatigue load was lower than the initial cracking load under quasi-static loading. However, microcracks would occur and accumulate around the precrack tip during the fatigue process, which generated a larger damage area than that under the quasi-static load condition. The larger damage area absorbed more energy provided by the applied loading in the subsequent monotonic TPB tests, leading to increases in the initial cracking load and the nominal initial fracture toughness. Accordingly, a distribution model of the nominal initial fracture toughness along the interfacial ligament was derived for the fatigued specimens. Furthermore, a crack propagation criterion based on the nominal initial fracture toughness was proposed and used to simulate the fracture process of the fatigued specimens. Good agreement between the experimental and numerical results validated the proposed distribution model and the crack propagation criterion.

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