ABDULFATAI ADINOYI MURANA2023-09-212023-09-212016-01-26https://teras.ng/api/asset/document/d8149a6e-9441-4caf-a3c8-d2e484a54df6https://teras.ng/catalog-item/540378ae-a0fb-4dcb-bc81-de7aedb5892chttp://dspace.teras-network.net:4000/handle/123456789/16480Subgrade materials from different locations in Nigeria were characterized for use in the Mechanistic – Empirical Pavement Design. The basic soil index properties of the subgrade soil materials from Master Test Section (MTS) 1 that identified the material response to external stimuli of traffic loading and environmental conditions were obtained in the laboratory.Three samples each from the MTSs making a total eighteen (18) samples were obtained and subjected to laboratory test to determine their basic physical properties. Testing include particle size distribution, Atterberg limits, specific gravity, compaction characteristics, Unconfined Compression test and the California Bearing Ratio tests. The samples were classified according to American Association of State Highway and Transportation Officials (AASHTO) and the Unified Soil Classification System (USCS).The AASHTO soil classification shows that the subgrade soil samples obtained from the MTS 1 were eitherclayey soil (A-6 and A-7-6) or silty soils (A-4, A-5 and A-2-4). The AASHTO soil classification generally showed that the subgrade samples were ―Fair to Poor‖ in subgrade properties for use as construction materials.The USCS soil classification indicated that most of the samples were lean clay soil with gravel (CL) except few that were either clayey gravel (GC) or clayey sand (SC).This showed that the subgrade samples were mostly clay soil. The California bearing ratio (CBR) values were generally less than 3%. This implies that the strength of the subgrades were poor for engineering construction purposes.Resilient modulus constitutive equation for estimating the resilient modulus of Nigerian subgrade soils was adopted through evaluation of existing resilient modulus constitutive equations using the repeated load triaxial test result conducted on Nigerian subgrade soils. From the evaluation, the National Cooperative Highway Research Programresilient modulus constitutive equation was adopted for purposes of predicting resilient modulus of Nigerian subgrade soils.Comprehensive statistical analysis using multiple linear regression used to develop correlations between basic soil properties and the resilient modulus model parameters.The correlation showed that the resilient modulus model parameters (ki) can be estimated from basic soil properties.These correlations developed can be used to estimate the resilient modulus of the compacted subgrade soils with reasonable accuracy and can be utilized to estimate level 2 resilient modulus input for Mechanistic – Empirical Pavement Design.Research Theses