article · American Journal of Traffic and Transportation Engineering
An evaluation of subgrade bearing capacity along the Okene to Auchi Highway in Nigeria examined how heavy traffic loads influence pavement deterioration. Traffic counts at Jattu Junction showed an index daily traffic of 7,985 Equivalent Single Axle Loads per day, equivalent to a daily axle mass of 2,984.86 tonnes, with heavy trucks and trailers generating over 95 percent of the total load. Geotechnical laboratory testing of the subgrade soils showed soaked California Bearing Ratio values ranging from 5 to 45 percent, with more than half of the samples failing the 30 percent threshold required for subgrade design. The investigation links heavy axle loads, soil moisture vulnerability, and insufficient bearing strength to premature pavement failures such as rutting and deformation, demonstrating a need to coordinate geotechnical data with traffic load estimates during design and maintenance.
Roads fail early when underlying soils cannot support the weight of heavy vehicles. By demonstrating that over half the tested subgrade fails minimum strength standards under intense truck traffic, this work highlights the direct link between subgrade soil quality, water exposure, and accelerated road damage. Addressing these issues helps transport authorities prevent premature road destruction, avoid frequent repairs, and improve long-term highway safety.
The findings provide applied, field-tested evidence that civil engineering contractors, road authorities, and transport planners can use to inform highway design, maintenance strategies, and subgrade stabilisation projects. While the research demonstrates an applied investigation rather than a commercial product, the recommended interventions, such as soil stabilisation methods and drainage improvements, represent established civil engineering practices that can be integrated into public procurement and ongoing roadway rehabilitation programmes.
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This study investigates the effects of heavy traffic loading on subgrade bearing capacity using field and laboratory data obtained from Jattu Junction along the Okene–Auchi Highway, Nigeria. Manual traffic count data were converted into Equivalent Single Axle Loads (ESAL), resulting in an Index Daily Traffic (IDT) of 7,985 ESAL/day and a corresponding daily axle mass of 2,984.86 tonnes. Heavy vehicles, including trucks and trailers, account for over 95% of the total traffic loading, imposing substantial stresses on the pavement subgrade. Geotechnical laboratory tests revealed specific gravity values ranging from 2.46 to 2.49, liquid limits of 11–35%, plasticity indices of 5–12%, maximum dry density (MDD) values of 1.81–1.95 Mg/m³, optimum moisture content (OMC) of 10.2–11.8%, and soaked California Bearing Ratio (CBR) values between 5% and 45%. The results indicate that more than half of the sampled soils fail to satisfy the minimum soaked CBR requirement of 30% specified for subgrade design, demonstrating inadequate load-bearing capacity under prevailing traffic conditions. The study establishes a strong relationship between heavy traffic loading, moisture susceptibility, and reduced subgrade strength, all of which accelerate pavement deterioration through rutting, deformation, and premature failure. These findings highlight the importance of integrating traffic loading characteristics with geotechnical properties during pavement design and maintenance planning. To enhance pavement durability and long-term service performance, the study recommends appropriate subgrade stabilization techniques, strict enforcement of axle load regulations, and improved drainage systems to minimize moisture-induced weakening of the subgrade.
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DOI: 10.11648/j.ajtte.20261105.11
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