The Influence of Multi-level Loading on Cracking Behavior of Sandstone with a Single Flaw

Underground engineering rocks are highly inclined to cyclic loading caused by various engineering activities such as earthquakes, excavation or blasting. Understanding the process of crack evolution in rocks under cyclic loading is crucial for assessing the stability and safety of engineering structures. Multi-level cyclic loading and unloading tests on flawed sandstone with varying flaw inclinations was conducted to investigate the crack propagation behavior under complex loading conditions. Digital Image Correlation (DIC) technique was utilized in tracking the process of cracking. According to results of the test, during the multiple cyclic loading levels, crack propagation was observed to go through two stages, i.e. stable propagation and unstable propagation. The behavior of cracks in these two stages was influenced by the number of cyclic loads and the upper limit stress of loading.