Assessment of Gneiss-Derived Residual Soils as Materials Used in Road Pavement Structures

Abstract

Failure of highway pavement and collapse of building in basement complex of Nigeria is often related to the instability of the residual. This study evaluated the strength characteristics of gneiss-derived residual Soils as materials usable for road pavement structures. A total of eleven soil samples derived from granite gneiss were subjected to laboratory geotechnical analyses based on standard practices. The geotechnical analyses reveal the soils’ natural moisture content, specific gravity, grain sizes, consistency limits, shearing strengths, maximum dry density, and optimum moisture content. Based on AASHTO classification, the soil samples are classified as A-7-6, A-6, and A-7-5. The results of the laboratory analyses revealed that the natural moisture content and specific gravity ranged from 8.30 to 22.70% and 2.6 to 2.8 respectively. Particle size analysis reveals that the coarse contents of the soils ranged from 28.8% to 59.8% and amount of fines ranged from 40.2 to 71.2%. The liquid limit ranged from 31.3% to 68.3%, plastic limit ranged from 20% to 28.0%, plasticity index ranged from 4.8% to 38.90% and linear shrinkage ranged from 5.7 to 13.6%. The maximum dry density ranged from 1481 kg/m3 to 1921 kg/m3 and optimum moisture content ranged from 15.2% to 27.6%. Undrained triaxial shear strength (Cu) ranged from 43.0 Kpa to 250.3Kpa, angle of friction ranges from 11.7 to 29.30, and unconfined compressive strength ranged from 153 to 356.5Kpa. The results indicate that the residual soils are poor sub-grade and foundation materials due to their high amount of fines, linear shrinkage values, plasticity, and swelling potential, as well as low maximum dry density.