Laboratory evaluation of different geosynthetics for water drainage

During road construction, soils are often compacted at the optimum water content to achieve maximum dry density and best performance. After construction is completed, the soil water content in the field will inevitably increase with time due to capillary rise, rainfall infiltration, and other factors. Conventional drainage systems rely on geomaterials or geosynthetics with large pores to drain gravity (or free) water but cannot drain out capillary water. The excess water in the road system causes pavement deterioration under repetitive traffic load. Recently, two new types of geosynthetics were used as drainage materials. However, most of the field tests were inconclusive due to complicated site conditions and soil nonuniformity. The relative performances of these drainage geosynthetics and their working mechanisms were largely unclear. In this study, laboratory tests were conducted to quantify the cumulative amount of water drained under different drainage situations. The volumetric water content of soils was monitored by moisture sensors and the water contents of soils under different drainage situations were evaluated and compared. Finally, the working mechanisms of different drainage materials were discussed.