THE IMPACT OF GEOTECHNICAL SUBGRADE ENGINEERING PROPERTIES ON FLEXIBLE PAVEMENT PERFORMANCE (A CASE STUDY OF A BORROW PIT LOCATED AT UBULU-UNOR ROAD) OGWASHI-UKU, DELTA STATE.
Abstract
This study investigates the impact of geotechnical subgrade engineering properties
on the performance of flexible pavement systems. Representative soil samples were
collected from the project site and subjected to a series of Geotechnical tests,
including sieve analysis, Atterberg limits, natural moisture content, specific gravity,
compaction test, California Bearing Ratio (CBR) test, permeability test, and
unconfined compressive strength (UCS) test. The sieve analysis results revealed a
well-graded soil with a small proportion of fines, indicating good compaction
potential. The Atterberg limits test showed a low plasticity index (8%), implying
minimal volume change under moisture variation. The optimum moisture content
(12.5%) and maximum dry density (1.92 g/cm³) from the compaction test indicate
favorable load-bearing characteristics, while CBR values of 15% and 13% confirm
suitability for light to medium traffic. Low permeability and moderate UCS further
support the soil’s adequacy as a subgrade material. These findings suggest that, with
appropriate compaction and moisture control, the existing subgrade will provide
adequate support for flexible pavement construction.
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