Numerical analysis of effects of clay on a cut rock slope deformation at an open-pit limestone mine, Japan

Abstract

Rock slope instability is one of the major challenges of rock engineering projects, including open-pit mining. In this regard, rock slope deformation due to excavation, change in temperature, and influence of rainfall and snowfall have been previously investigated to understand characteristics and causes of slope deformation observed at an open-pit limestone quarry in Japan. The results only revealed characteristics of the deformation as forward and downward displacement of the cut rock slope, but its causes were not clarified. To deduce the causes of the rock slope deformation, we employed the 2-dimensional finite element method (2-D FEM) to investigate the deterioration effect of clay found at the footwall of the rock slope in terms of reduction in Young's modulus of the clay based on experimental results. Firstly, change in distances was analysed from displacement data measured by the automated polar system (APS) over five years, which decreases gradually with time. Secondly, the simulation results were discussed and then compared with the measured displacement data, which shows similar tendencies at the middle and top of the rock slope revealing maximum displacement at the middle of the rock slope. Conclusively, deterioration of clay at the footwall of the rock slope is one of the possible causes of the deformation in the quarry.