Stability analysis of a deep highwall slope using numerical modelling and statistical approach—a case study

Abstract

For opencast working or pit design, understanding the stability of slope is a prime concern for design engineers prior to or during excavation of mineral. The factor of safety is one such index, which has been extensively used for determining the stability of slopes, underground pillars, tunnel structures etc. The numerical simulation of a deep highwall slope of Ramagundam Opencast-II Extension Project (RG OC-II Extn) has been done using finite difference-based software FLAC/SLOPE. Parametric analysis has been conducted by changing one parameter at a time (OPT) and keeping all other parameters fixed in order to understand the influence of various parameters, namely, density, angle of internal friction, cohesion, overall pit slope angle and depth on the stability of the highwall slope. It has been observed that all the parameters undertaken in this study have a strong and well-defined influence on the stability of the same. Kinematic analysis is also performed to illustrate the potential for various modes of highwall slope failures, namely, planar, wedge and toppling failures that may occur due to the presence of unfavourably oriented discontinuities. The analysis revealed that the highwall slope is not susceptible to structurally controlled failure. Subsequently, statistical analysis for building an empirical model for the prediction of factor of safety has been done considering the abovenamed parameters utilizing non-linear regression technique. The developed empirical formula can be used as a guiding tool for estimation of highwall slope stability at any mine in India possessing similar geo-mining conditions.