Failure mechanisms of block-flexural toppling: An extensive numerical study

Toppling failure is a common instability in natural rock slopes. The common approaches for investigating toppling failure mechanisms are physical and analytical methods, which encounter special difficulties for the test set-up and limitation in the number of physical experiments as well as complicated governing equations in analytical models. Recent advances in numerical modeling, particularly the discrete element method (DEM), have opened new avenues for understanding the complex mechanisms behind toppling failure. In this work, the ability of numerical method in reproducing toppling mechanism was first investigated through an extensive comparative analysis with physical and analytical methods. Hence, the validated numerical models were employed to statistically examine the individual and interactive effects of different parameters on the block-flexural toppling failure mechanism using the response surface methodology (RSM). To explore the statistical significance of effective parameters, the central composite design (CCD) was employed. The analysis revealed that aspect ratio constitutes the most influential parameter governing block-flexural toppling failure, while block unit weight found to be the least significant factor. Also, it was found out that the block unit weight and the block aspect ratio can cause a decrease in the failure initiation angle. It was concluded that an increase in the joint friction angle and block tensile strength can increase the stability of slope where the joint friction angle can change the shape and location of failure surface. Finally, evaluation of interaction effects showed that the impact of block tensile strength on block-flexural failure increases with an increase in block slenderness.