Compaction, compression, and hydraulic characteristics of micaceous residual soil

The presence of mica is considered to be why the physical and mechanical properties of micaceous soil differ significantly from those of common clay and sand, such as the difficulty in compacting micaceous soil and its high compressibility and resilience. However, despite micaceous residual soil being widespread in transportation engineering, the specific role played by mica in determining its geotechnical properties remains ambiguous, as does the underlying mechanism for doing so. Presented here is a systematic investigation of the compaction, compression, and hydraulic characteristics of residual soil with varying mica content, with scanning electron microscopy used to scrutinize the structural features of mica and the resulting microstructural changes within the soil under different compression stress levels. The findings show that adding mica to residual soil results in coarser gradation, and the distinctive flaky layered structure and interlayer pores of mica particles characterize the residual soil with high compressibility, water retention, swelling potential, and inadequate compaction. The specific effects of particle arrangement between mica and soil particles—such as bridging and ordering—contribute to the high porosity and permeability of soil. Also, the breakdown of the mica stacking structure and the degradation of bridging and ordering effects under high consolidation stresses decrease the resilience and permeability of soil, leading to further compression deformation. This study elucidates the microscopic mechanism whereby mica influences the physical and mechanical properties of micaceous residual soil, thereby contributing to enhanced insights into the compaction, compression, and hydraulic properties of such soils.