Stability analysis of open PIT slope using FLAC

Abstract

Stability analysis of slopes forms a vital component of various opencast mining operations throughout the life cycle of the project. A deterioration of slope in the area being worked of mine can leads to a severe economic safety as well as great economic catastrophe. The elementary failure conditions are both diverse & complicated. These failure mechanisms are largely controlled by local geology status, which are practically unique to a specific location of rock mass. In the recent years also the method of designing slopes are absolutely based on field knowledge and the approaches can be made through safe designing of slopes. The aim of the project is to carry out tri-axial test for estimating cohesion, angle of internal friction of coal samples and stability analysis of slope by finding out the factor of safety, using numerical modelling software viz: FLAC/SLOPE and OASYS by varying different bench parameters. Field visit was conducted to collect coal lumps and valuable mine data. In the laboratory, coal samples were prepared by coring and tri-axial test was performed. Using tri-axial test data cohesion and angle of internal friction was found out by RocLab program. Numerical modelling was carried out by using FLAC SLOPE and OASYS software for finding the factor of safety. It was observed that the factor of safety varies from 4.34 to 5.37 in FLAC SLOPE and from 4.37 to 5.43 in OASYS for the slope angle of 35⁰ to 70⁰ with an interval of 5⁰. The factor of safety increases with increase in the value of cohesion and angle of internal friction. The factor of safety varies on changing the search radius and angle of rotation in case of OASYS, whereas in case of FLAC SLOPE, the factor of safety changes on changing the resolution of the numerical mesh.