INDEX PROPERTIES AS PREDICTORS OF CALIFORNIA BEARING RATIO IN MAKURDI SHALE

The bearing capacity of subgrade soils is necessary for the design and construction of transportation infrastructure, such as roads, and airfields. The determination of bearing strength of soil could be tedious, expensive and time-consuming. There is need to establish models that would predict the bearing strength parameters such as California bearing ratio (CBR) using simple and less time-consuming laboratory tests. This study examines the relationship between CBR and index properties of Makurdi shale. Forty-five samples of the shale were collected; index properties and CBR were determined and correlated. Using multiple linear regression analysis, it was established that the soaked CBR could be predicted from the shale index properties such as moisture content, specific gravity,liquid limit, shrinkage limit, optimum moisture content and maximum dry density with adjusted 𝑹𝟐 of 0.838. Also, soaked CBR may be predicted from the soil properties like moisture content, liquid limit, plastic limit, shrinkage limit, optimum moisture content and maximum dry density with adjusted R2 of 0.838. Based on the results of this study, it is recommended that models 1 and 2 could be used for prediction of soaked CBR of Makurdi shale using corresponding soil index properties such as moisture content, specific gravity, liquid limit, plastic limit, shrinkage limit, optimum moisture content and maximum dry density.