Unsaturated soil water retention curve of road material using evaporation method

It is imperative to the understanding of water movements and moisture conditions in unbound pavement layers and subgrades for different types of road constructions in various climatic conditions for improving the performance of roads. Especially, soil suction fluctuates significantly in unsaturated zone during drainage and imbibition process due to seasonal variation. Moreover, changing in volumetric moisture content and soil suction might be accelerated for the varying density of materials because of cyclic traffic loading. To address these issues, soil water retention curves (SWRC) of road base materials compacted at moulding moisture content and placement density similar to that expected in real life scenario are reported in this study. Simultaneous and continuous soil moisture and suction measurements are performed with a setup comprising of tensiometers and programmed bench scales. Tensiometer is inserted in the compacted soil mass, and the top surface boundary condition is set to evaporation. Soil suction is measured from tensiometer reading, while moisture content and outflow are obtained by weighing the soil column. In this study, we discuss following four aspects pertaining to the road base material: (i) variation of soil suctions with time; (ii) the SWRC of road base material in drying process; (iii) the estimation of unknown parameters of the existing models; (iv) the suitability of SWRC with existing prediction models. This research is expected to contribute to a better understanding and prediction of moisture migration and solute transport in road structures.