Frost heave characteristics of subgrade silty clay affected by cyclic stress: Experiments and prediction model

To investigate the effects of traffic loads on frost heave behaviors, frost heave tests of silty clay soil were conducted using an improved temperature-controlled cyclic compression-shear device. This research employed three stress modes: vertical cyclic stress, horizontal cyclic shear stress, and complex cyclic stress that combines vertical cyclic stress with horizontal cyclic shear stress. Additionally, it considered the effects of the amplitude and frequency of complex cyclic stress. Test results show vertical cyclic stress densifies specimens and restrains vertical displacement development. Vertical cyclic stress's pumping effect promotes water absorption during frost heave. Horizontal cyclic shear stress can increase in-situ frost heave and induce minor consolidation than vertical cyclic stress, dramatically enhancing vertical displacement. Under complex cyclic stress conditions, vertical cyclic stress and horizontal cyclic shear stress at low amplitudes and frequencies enhance vertical displacement. The primary component that promotes the frost heave ratio is horizontal cyclic shear stress, which could lead to a looser frozen soil structure. Finally, an improved frost heave ratio prediction model was developed, considering the influences of vertical cyclic stress, horizontal cyclic shear stress, and loading frequency.