Highroad Key Facilities Preservation: a Case Study of the Adoru-Nsukka Uzouwani Highway, Southeastern, Nigeria

摘要

The quality of highway pavement is greatly influenced by the subgrade materials, the general geology and the materials used for construction.Investigation into the 82km-long Adoru-Nsukka-Uzouwani highway reveals that the pavement was underlain by three lithologic units which are mostly shale and sandstone.The geotechnical evaluation carried out in this study includes the Atterberg limit test, particle size distribution, specific gravity, compaction test and California Bearing Ratio (CBR).The average specific gravity for the studied borrow pits is 2.58 g/cm3.Liquid limit (LL) ranges from 28％ to 32.5％ while the plastic limit (PL) ranges between 9.6％ and 21％.The plasticity index (PI) of the samples ranges from 9％ to 13 ％.The sieve analysis result shows greater percentage of the coarse sand.The maximum dry density (MDD) ranges from 1.90 to 2.20 kg/m3, while the Optimum Moisture Content (OMC) ranges between 14.o％ and 15.8％.The CBR for soaked and unsoaked samples ranges from 65％ to 72％ and from 77％ to 85％ respectively.All the results satisfy the standard of Nigeria Specification for Construction except the CBR for the base course that needs stabilization.The inclined and instable shale could initiate landslides by sliding over another if activated by water from high rainfall.