The stability analysis of a highway embankment founded on lime-stabilized soft soils in Calabar, Southeast Nigeria

Abstract

Highway embankment failures are common phenomena in Southern Nigeria. To this end,in situ geotechnical tests and laboratory analyses were used to characterize the underlying lithologic units along a highway alignment in Calabar, Nigeria. The engineering behaviour of the soils mixed with various lime contents was evaluated after a curing period of 28 days. Limit equilibrium analysis was used to determine the factor of safety (FS) for the most critical slip surface for the embankment with height in the range of 4 to 7 m. Undrained triaxial tests conducted on the unstabilized soil indicate an undrained shear strength of 10 to 17 kPa, while the undrained shear strength of the lime-stabilized soils varied from 87 to 198 kPa, as lime content increased from 3 to 12%. Stability analysis carried out on the unstabilized soil samples indicates that FS ranged from 0.88 to 1.33 for the various embankment heights and analysis methods, while FS for the shallow (1-5 m) stabilization varied from 1.09 to 5.02 for the various embankment heights, lime contents and analysis methods. The stability of the embankment was found to increase with an increase in lime content and depth of stabilization even for the most extreme loading condition.