Slope stability analysis of mine waste dumps at a mine site in Southeastern Nigeria

This paper presents results on the stability of slopes of the mine tailing dumps at Enyigba, Southeastern Nigeria. The geotechnical parameters of the slopes were investigated, and stability analysis was carried out with GeoStudio (R) 2012 developed by Geoslope International Limited. The slope materials were composed of gravel (1.42-30.13%), sand (15.94-33.34%), silt (9.75-26.87%) and clay (32.1-56.25%). The materials have LL, PL and PI ranging from 24 to 49%, 24 to 35% and 9 to 26% respectively, signifying low to medium plastic materials. These results agree with the soil low permeability (10(-4) - 10(-8)cm/s) recorded. The MDD and OMC of the material ranged from 1.86 to 2.22g/cm(3) and 13.45 to 17.05%, while cohesion and internal friction angle were recorded to be 13-34kN/m(2) and 8-37 degrees respectively; implying moderately durable materials capable of slip and shear failures. XRD confirmed the presence of swelling mineral (illite) in soil material, hinting at clay plasticity on absorption of moisture, which is one of the factors influencing all forms of mass wasting. The slopes' computed factor of safety ranged from 0.8 to 1.33, suggesting critical to poor slope stability when exposed to landslide triggering agents. Hence, slope stabilization is required on the mine tailing dumps at Enyigba to prevent major landslide occurrence.