Microstructure and Mechanical Properties of Expansive Clay under Drying–Wetting Cycle

Abstract

Expansive clay is one of the most widely distributed soils in the world. Due to its rich content of strongly hydrophilic minerals—such as montmorillonite—expansive clay exhibits substantial swelling and shrinkage properties, and overconsolidation. The formation process of undisturbed expansive clay has a long and complicated geological history and innumerable drying–wetting cycles, resulting in the formation of special internal structures. In this study, the mud-to-natural-consolidation deposition process was simulated using a saturated mud-remolded sample preparation device, and then, mud-remolded soil under a certain consolidation pressure was prepared. Subsequently, the effects of the stress history and drying–wetting cycle on its mechanical properties and microstructure were examined through uniaxial consolidation compression experiments, K0 consolidation experiments, and pressure plate experiments of undisturbed soil, mud-remolded soil, and a drying–wetting cycle sample. The results showed that the mud-remolded soil completely broke the natural structure of the undisturbed soil, with the structural characteristics of the remolded soil being restored to a certain extent after the drying–wetting cycle. This not only reduced the void ratio of the soil sample, but also changed its compressibility and water retention characteristics, revealing the role of atmospheric drying–wetting cycles in the natural overconsolidation state of expansive clay and providing a theoretical basis for understanding their overconsolidation characteristics.