Analysis of Excavation-Induced Effect of a Rock Slope Using 2-Dimensional Back Analysis Method: A Case Study for Clay-Bearing Interbedded Rock Slope

There exist many rock slopes with weak rocks in mines. However, long-term slope stability, especially for large-scale slopes with weak layers, still remains a challenging issue in mine projects. This study employed in-situ surface displacement monitoring and numerical analysis to assess excavation-induced effects on a high clay-bearing interbedded rock slope. A Japanese limestone quarry with a 250-meter-high rock slope intercalated by a 70-meter-thick clay-bearing rock at the footwall was used as a case study. The characteristics of the slope deformation, including the deformation rate, were first characterized by analyzing surface displacement measured by an automated polar system. Based on the measured data and the 2-dimensional finite element method, a back analysis of mining-induced deformation was performed to estimate the horizontal rock stress of the quarry and the Young’s modulus of the clay-bearing rock. Thereafter, the elastic deformation of the rock slope induced by the excavation and the excavation-induced deterioration of the clay-bearing rock were evaluated. The results demonstrated that the deformation mechanism can be explained by both the deformation mechanism due to the excavation-induced deterioration of the clay-bearing rock and the horizontal stress release. Furthermore, vertical and horizontal advancing excavation patterns are proposed to clarify the deformation mechanism based on the incremental characteristics of distance changes. The findings provide useful insights into understanding the deformation mechanisms of excavation-induced deterioration of clay-bearing rock and the effect of excavation sequence patterns when interpreting the characteristics of measured surface displacement results in open-pit mines.