Considering the frequent road failures along parts of the Enugu-Makurdi expressway in Igbo Etiti Local Government Area, Enugu State, southeastern Nigeria, this study aimed to perform a comparative analysis of the geotechnical properties of failed and unfailed sections of the road. The investigation involved reconnaissance surveys, fieldwork, and the collection of soil samples from both failed and unfailed road sections. Soil samples were manually collected using a hand auger from three different locations at depths ranging from 1 to 3 meters. The geotechnical index properties analyzed in the laboratory included moisture content, specific gravity, bulk density, grain size distribution, Atterberg limits, compaction, and California Bearing Ratio (CBR) tests. Moisture content in the failed sections ranged from 12.4% to 14.9%, while the unfailed sections ranged from 12.7% to 21%. The liquid limit of the unfailed sections ranged between 18 and 20, whereas the failed sections had values between 20 and 28. The plastic limit of the failed sections ranged from 13 to 22, while the unfailed sections ranged from 16 to 18. The plasticity index for the failed sections ranged from 8 to 15, while the unfailed sections ranged from 1 to 4. Sieve analysis classified the soil in the study area as poorly graded. The optimum moisture content of the failed sections ranged from 11.7% to 13.7%, compared to 10.9% to 12.0% in the unfailed sections. The maximum dry density of the failed sections ranged from 114.8 kg/m³ to 130.6 kg/m³, while the unfailed sections ranged from 118.1 kg/m³ to 119.0 kg/m³. The CBR values for the failed sections ranged from 120.5% to 175.7%, compared to 93.7% for the unfailed sections. The study concludes that factors such as poor design and maintenance, government and user mismanagement, inadequate geotechnical assessments, poor sub-base and base materials, heavy traffic, gully erosion, and improper drainage systems contributed to the frequent road failures observed. It is recommended that proper geotechnical investigations and drainage systems be implemented to mitigate future failures.
Oba et al. (Fri,) studied this question.