A Study on Suction Properties, Subgrade Modulus and Compressibility of Marine Soil Subgrade for Flexible Pavements

Abstract

AbstractOne of the important parameters that governs suitability of soil subgrade for flexible pavements is subgrade modulus and it depends on many factors such as type of loading and its magnitude, soil type and its engineering properties, flexural stiffness of the pavement structure and relative stiffness of the soil subgrade and pavement structure. The strength and stiffness of soil affects its relative stiffness with pavement structure and depends on various factors such as water content, soil type, degree of compaction and soil suction. For most soils, soil suction is mainly due to matric suction. However, for marine soils, soil suction is due to the presence of osmotic suction in addition to matric suction. The evaluation of the influence of both matric and osmotic suction on engineering properties of marine soil would be quite useful to understand its performance as soil subgrade for pavement. In this regard, the present work attempts to understand the relationship between subgrade modulus, suction and compressibility characteristics of marine soil. Experimental studies have been carried out to evaluate the subgrade modulus from California bearing ratio (CBR) tests; matric, total and osmotic suction from filter paper tests; and consolidation and compression characteristics for marine soil from oedometer tests at different degree of compaction. It has been observed that subgrade modulus has good correlation with matric suction in unsoaked condition, however for soaked specimen, the correlation is not conclusive and further studies are envisaged. The study suggests that exhaustive studies on evaluation of variation of soil suction at different water content and degree of compaction for different marine soils can serve as a good tool for understanding the behaviour of soil subgrade for coastal region pavement design.KeywordsMarine soil subgradeFlexible pavementMatric suctionOsmotic suctionSubgrade modulus