Critical state of compacted lateritic soil and palm kernel shell ash for earth embankments

Abstract

For most treated soils in compacted form for earth embankments, interest had been limited to the maximum stresses they can sustain before failure. This work studied the stress–strain behaviour of a compacted lateritic soil treated with palm kernel shell ash (PKSA) from 0 to 18% at 3% intervals, with a major focus on the critical-state characteristics (beyond the maximum stresses). The lateritic soil was characterised as A-2-6(0) in the American Association of State Highway and Transportation Officials rating and clayey sand (SC) in the Unified Soil Classification System. The PKSA was found to be pozzolanic. The British Standard light energy level of compaction and drained shear test were carried out on the treated soil. The optimum moisture content increased while the maximum dry density reduced with an increase in PKSA content. The PKSA of 0–18% content by weight of the dry soil improved the strength properties of the lateritic soil by 51·43%. The critical-state parameters (λ, Γ and M) of the soil mixtures were found to be in conformity with the usual range for untreated soils.