Modification of Subgrade material in Sohar university’s campus in Oman based on Subbase and base materials’ specifications

Abstract Flexible pavements consist of four main layers: subgrade, subbase, base, and surface layer. The surface layer is the impermeable layer of the pavement since it contains bitumen. The area the load is distributed over gradually increases in the Base, subbase, and subgrade layers. Subgrade layer is what represents the main foundation that supports the entire basement structure. Flexible pavements must have sufficient strength and stiffness to be able to withstand the subjected high stresses resulting from the applied wheel loads. the pavement layers materials are evaluated based on the soil classification and graduation, and the California bearing ratio. Generally, the main difference between subgrade soil and some beys and based soil is that the upper layers have more strict specifications since they are subjected to lower stress. As a result, if the existing subgrade soil is of sufficient strength, it could be modified in a way that increases its strength and makes it suitable to be used as subbase and base layers. This study aims to evaluate the subgrade soil existing in Sohar university campus and apply suitable modifications to create enhanced soil that is suitable to be used in the upper layers of the pavement. Such modifications are economically beneficial since it gives the opportunity of only having to transport the extra material instead of transporting the entire amount used for constructing the pavement leading to a significant reduction in the construction cost which is the main cost of the construction of the flexible pavement.