The subgrades of three different rural roads alignment were investigated with the aim to determine their geotechnical properties. The three roads are on two different geologic terrains. Two of the roads, the 18 km Yahe-Waniye-Wanakom road and the 6 km Okpoma-Okuku road are on Cretaceous sediments terrain, while the 8 km Ugboro-Imaje-Okuku road is on the Basement Complex terrain. Based on American Association of Highways and Transportation Officials (AASHTO) most of the soils classify as A-2-4, A-2-6 on the first two roads with A-7-5, A-7-6 soils interspersed between the A-2-4 soils. The A-2-4, A-2-6 soils were also encountered on the only alignment on the basement complex, but the A-7 group of soils were not encountered on this alignment. Based on The Transport Research Laboratory Road Note 31, subgrade quality on all the three alignments is classed into ‘S4 to S6’ subgrade class. In this classification scheme ‘S6’ is the subgrade of the highest quality.
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