Test Study on Salt-Freeze-Thaw Cycles of Subgrade in Water-Salt-Temperature Coupling Environment

The subgrade structure of asphalt concrete roads in southern Xinjiang is affected by the coupling environment of water, salt, and temperature in the special saline soil environment in southern Xinjiang, the subgrade structure is damaged under the action of dry-wet cycles and salt-freeze-thaw cycles. The developed water-salt-temperature multi-field coupling test system is used to simulate the unique coupling environmental effects of dry-wet cycles and salt-freeze-thaw cycles in saline soil environment in southern Xinjiang, the damage and failure test of asphalt concrete road subgrade structure samples under the action of salt-freeze-thaw cycles environment is carried out. The results show that the distribution of water and salt in a salt-freeze-thaw cycle has obvious variation characteristics along the height of the subgrade structure, the water and salt in subgrade soil migrate and accumulate from bottom to top under the action of temperature gradient, the stress and strain caused by the change of water and salt phase in subgrade structure under the action of salt-freeze-thaw cycles are the main reasons for the damage and deformation of subgrade structure. By controlling and optimizing the water-salt-temperature environmental factors of road subgrade structure, the migration of water and salt in subgrade structure can be blocked, and the influence of salt-freeze-thaw cycles on subgrade structure can be effectively controlled.