Frost heaving of subgrade soil under complex traffic loads: Test system and experiments

Soil moisture freezing in cold climates leads to frost heaving, a phenomenon influenced by soil texture, temperature, moisture levels, and applied loads. This investigation explores frost heave characteristics of subgrade soil under traffic-induced cyclic stresses, including cyclic compressive stress and alternating horizontal cyclic shear stress. A new frost heave test system was developed, featuring advanced temperature control and accurate loading path reproduction. Comprehensive frost heave experiments were performed to examine the frost heaving process under various cyclic stress circumstances. Results indicate that cyclic stresses intensify in-situ frost heave of soil, with horizontal cyclic shear stress having a more significant promoting effect than vertical cyclic stress. The combination of vertical cyclic stress and horizontal cyclic shear stress leads to an increase in segregated frost heave. Moreover, vertical cyclic stress amplifies water absorption during soil frost heave. Total vertical deformation encompasses frost deformation in the frozen zone and consolidation in the unfrozen zone. Vertical cyclic stress may inhibit segregated ice lens formation and encourage consolidation in the unfrozen zone, thereby impeding vertical deformation. The simultaneous application of vertical cyclic stress and horizontal cyclic shear stress results in more intense ice segregation and moisture accumulation near the stable frost front.