Effects of faults on slope stability in opencast mines

Abstract

Stability of opencast mine slopes is significantly influenced by the presence of structural features in rock mass. In this work the effect of faults on slope stability is discussed in detail. The slope design in such situations needs to be made keeping in view the relative orientation of these features with respect to the slope orientation. To avoid fault-induced instability the benches should be laid across the strike of fault. Stability of slopes in opencast mines is greatly influenced by the presence of structural features in rock mass.
―Assessment of the stability of of slopes in open pit mines at different stages of mining is important for the safe and economic mining operations. Slopes are generally designed based on the geotechnical data and physio-mechanical properties of rock/soil. From geotechnical data , the rock mass quality is assessed, and from this the rock mass properties are estimated. Using the rock mass properties stability of the slopes is evaluated from empirical, analytical and numerical techniques.
Based on the numerical model analysis, it is concluded that bench failures are likely to occur because of discontinuities in the form of faults. Fault F1 located along the proposed boundary appears to pose instability problems to the high walls. Therefore, it is strongly recommended to monitor the slopes for its stability.
The analysis of stability of slopes for the ultimate pit slope indicated the safety factor exceeding 1.2 for slope angle of 48 degrees without consideration of the faults. However, the presence of fault F1 decreased the safety factor below 1. Therefore it is recommended to extend the boundary of the mine beyond the fault F1, and maintain the overall slope angle not steeper than 48 degrees.