Abstract
The Benin –Akure road has undergone various degrees of failures. Road failures (potholes, surface cracks, ruts and depressions, washouts etc.) have a major strain on the economy of the nation as it affects transport of agricultural produce to urban areas.This research was carried out by evaluating the plasticity indices of the brought in soils used for the subgrade material for the road bed as one of the possible causes of the failure of the road under review. The Benin –Sobe section of the road was divided into four segments representing the four parent materials (Coastal Plain Sand, Bendel Ameki, Basement Complex and Imo Shale) Soil samples were collected at four depths (0 - 30 cm, 30 - 60 cm, 60 - 90 cm, 90 - 120 cm) from the four segments and the imported subgrade laterite from failed and non-failed sections of each segments. The Atterberg’s limits and particle size determinations were carried out. The liquid limits and plastic indices were found to be in the ranges of 38 - 72 and 20 - 45 respectively which indicated imported laterite ranged from high to very high plasticity. The high plasticity index indicates susceptibility to expansion and cracking. The clay content of the in-situ soils were also found to be very high and poorly drained except for the Basement complex soil resulting in poor drainage causing expansion and consequently cracking. The result of this research indicated that lateritic materials used as subgrade were of poor soils quality probably leading to high road failures among other factors.
Keywords:
material
pavement
quality
failure
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