Numerical study of the effect of overburden pressure on the stability of mine dump slope

The stability of an overburdened mine dump is a significant challenge due to limited space and increasing mineral demand. Stability analysis often assumes uniform shear strength parameters, potentially leading to unprecedented slope failure. This study investigates the effect of overburden pressure on the shear strength parameters through direct shear tests under various normal loading conditions. Results show that with increased normal pressure, cohesion increases while friction angle decreases. Shear tests were conducted on dump samples with varying compositions, which were created by combining different ratios of medium, fine, and coarse particles. Numerical simulations in FLAC were performed using Mohr-Coulomb (constant shear strength parameters and varying shear strength parameters) and Hoek-Brown failure criterion, based on laboratory and field-testing results. It was observed that using the uniform value of shear strength parameters can lead to the production of a higher factor of safety (around 10% for coarse particle mix dump and 5% for finer particle mix dump) as compared to models prepared with the non-uniform value of shear strength parameters along the depths of the dump. Also, the huge overburden pressure leads to a decrease in shear strength at the location deep inside the dump body resulting in a deeper depth of failure surface. The effect of Hoek-Brown parameters 'mi' and 'GSI' on the factor of safety of a high overburden dump slope has also been determined.