Slope Stability Analysis of Open Cast Mines Using FLAC 3D

Abstract

Slope stability analysis has the most prominent influence in the productivity and longevity of a mine. Instability of slope of open cast mines can lead to enormous damages to man and machinery. A deterioration of slope in the area being worked of a mine can lead to a severe economic safety as well as great economic catastrophe. The slope failure is largely controlled by maintaining the geometry and geological status within safety limit, which are practically unique to a specific location of rock mass to prevent slope failure. A comprehensive study is necessitated to ensure stable slopes which are aided by numerical, analytical, physical, kinematic and empirical analyses. Using the FLAC 3D software stability of slope is analysed.
The basic objective of the project work was aimed at to study the stability of slopes using numerical modelling; at the same time examine the influence of various parameters such as bench slope angle, cohesion, friction angle, bench height, bench width and change in number of benches on the stability of the slope. The analysis also covers the analysis of effect of defects on the stability of the slope. Numerical modelling was carried out by using FLAC 3D software for finding the factor of safety. It was observed that factor of safety increases with increase in the value of cohesion and friction angle and decreases with increase in cohesion. As the bench width of the open cast mine increases, factor of safety also increases whereas when bench height increases factor of safety decreases. Since bench width and bench height also play an important role in the stability of the slope so, bench width should be maintained between 15-25m and bench height should be maintained between 15-20m for an open cast coal mine. It was also observed that factor of safety of model without defect was 2.69 and with defect of size 5m×5m was 1.74.Thus, it is concluded that even small defect makes the slope unstable and stability of the slope depends on volume of defects.