Critical tension crack depth in rockslides that conform to the three-section mechanism.

The three-section mechanism is a typical mechanism of large-scale rockslides. Such rockslides are typically characterized by sudden instability and can cause many casualties and considerable economic losses due to their high-speed and long-distance runout. Their evolutionary process is closely related to the development of the tension crack at the trailing edge and the sudden brittle failure of the locked section. In this study, the curved failure path of the locked section was verified by means of the numerical simulation conducted using PFC2D. On the basis of that, the critical threshold of the tension crack depth for slope instability was derived based on the limit equilibrium state determined using the vector sum method, and this threshold was then verified through application in a case study. The results show that the critical tension crack depth threshold is not only related to the slope height but also closely related to other geometric and mechanical parameters of the slope. In addition, the case study shows that the result calculated using the methodology proposed in this paper is more accurate than that obtained from the previous empirical equation. Hence, the outcomes of this study are significant for improving stability analyses, instability prediction, and the early warning of instability for such rockslides. [ABSTRACT FROM AUTHOR]