ABSTRACT
Fine-grained materials are associated with a higher water retention capacity due to their higher surface energy in comparison with coarser materials. That characteristic is connected to why fine-grained materials also yields more suction when drying. In addition, seasonal variation of the water table subjects fine-grained subgrades to different moisture contents, varying the suction built in the subgrade, consequently affecting its mechanical characteristics. As fine-grained materials are frequently frost susceptible, they can cause issues to the whole pavement cross-section related to Freeze-Thaw (F-T) actions, widely known as frost heave and thaw weakening. This study will seek to investigate if subsequent cycles of closed-system F-T can permanently alter the unsaturated behaviour of fine-grained materials, using as background their Soil Water Retention Capacity obtained using a pressure plate apparatus. Such issues may become more common with permafrost areas being subjected to freeze and thaw cycles due to climate change or extraordinary events creating the circumstances to F-T where it is currently not observed. Two silty sands with low plasticity were tested, and the results show a reduced water retention capacity (WRC) after closed-system F-T cycles. Considering that matric suction changes the state of stress of soils, the findings suggest an impact in the resilient modulus (Mr ) not only seasonally, as it is well established, but also after seasonal freezing and thaw events.
