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Aim: This engineering geological investigation work was carried to investigate the causes of persistence failure of a section of Emure Ekiti/Akungba Akoko road, Southwestern Nigeria.
Methodology: A total of 10 disturbed soil samples were collected from different locations at a common depth of 2 m. The samples were analyzed for natural moisture content, grain size analysis, Atterberg limits, standard compaction and California Bearing Ratio (CBR) test.
Results: The laboratory tests on the samples revealed that moisture content ranged from 4.10 - 6.20%, liquid limit from 29.01 - 41.13%, plastic limit from 18.05 - 22.30%, linear shrinkage from 4.8 - 8.7% and plasticity index from 10.96 - 20.03%. The grain size analysis showed that the amount of fines ranges from 15.0 - 33.0%. The specific gravity ranged from 2.67 - 2.77, maximum dry density from 1848 – 1888 kg/m3 and optimum moisture content from 17.4 - 18.4%. California Bearing Ratio (CBR) test for the investigated soil samples range from 31 - 39%. The overall results obtained revealed that the subsoil materials have good engineering qualities for engineering purposes in accordance with the Federal Ministry of Works and Housing specification for roads and bridges. Therefore, the reduction in the apparent strength of the subsoil materials that led to the observed road failure is possibly as a result of water infiltration into the structural section of the road pavement, particularly at the base layer.
Conclusion: Therefore, the pavement needs to be strengthened through adequate drainage facilities to improve its capacity, durability and performance.
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