Abstract

Laboratory analyses of unconsolidated sediments from the ruptured zone of the 2005 Mbonjo Landslide scar were carried out to characterize and evaluate their role as contributory factors in enhancing the slide. Colour, particle size (PS) and particle size distribution (PSD), Atterberg limits [liquid limit (LL), plastic limit (PL) and plasticity index (PI)] and basic geotechnical properties [bulk density (ρ), dry bulk density (ρ_d)_, dry unit weight (γ_d), moisture content (Mc), specific gravity (Gs), void ratio (e) and porosity (n)] were determined. Colour ranged from reddish brown to yellowish brown. Texturally, samples were classified as loam, silty clay loam and silty clay. Liquid limit ranged from [56 to 74 weight percentage (wt%)], PL (37 to 50 wt%) and PI (15 to 36 wt%). Values for geotechnical properties were ρ (2 to 2.25 g/cm³), ρ_d (1.75 to 1.95 g/cm³), Mc (14 to 15 wt%), Gs (2.67 to 2.69 g/cm³), e (0.37 to 0.52) and n (0.27 to 0.34). From results of colour, PS and PSD, Atterberg limits and geotechnical analyses, the samples were reflective of clay-rich sediments with high plasticity and sliding potential. Based on the interpretative data, the studied sediments were qualified as landslide prone with clay interbeds serving as the slide surface.

Key words: Cameroon volcanic line, clay interbeds, geotechnical properties, ruptured zone, slide surface.