This study systematically investigated the pore structure response of kaolin and illite/smectite mixed-layer rich clay in a reconstituted state to one-dimensional (1D) compression by first performing oedometer tests on saturated clay slurries, followed by characterising their pore structure using multi-scale characterisation techniques, with the primary objective of advancing the current understanding of the microstructural mechanisms underlying the macroscopic deformation of such clays. Under 1D loading, the volume reduction observed at the macro level essentially represented the macroscopic manifestation of changes in inter-aggregate porosity at the pore scale. It was the inter-particle pores that were compressed, despite the interlayer pores remaining stable. Two distinct pore collapse mechanisms were identified: kaolin exhibited a progressive collapse of particular larger pore population in an ordered manner, whereas illite/smectite mixed-layer rich clay demonstrated overall compression of inter-aggregate pores. Accordingly, mathematical relationships between the porosity and compressibility parameters for these two soils were proposed, with the two exhibiting opposite trends arising from their distinct microstructural features. Approaching from the unique perspective of pore structure, quantitative analysis of pore orientation and morphology on the vertical and horizontal planes demonstrated some progressively increasing anisotropy during compression. These findings provide important insights into porescale mechanisms governing clay compression behaviour and enrich the limited microporosity database in soil mechanics.

The creep behavior of net-like red soils mainly depends on the micromechanical behavior of clay mineral atoms at the nanoscale. The 1M-tv configuration of illite determined by the experiments of XRD and SEM-EDS, was utilized to address the mechanical properties along various loading directions using the conventional molecular dynamics (MD) simulation method. Furthermore, a novel MD simulation method based on transition state theory was proposed to discuss temperature effects. Simulated results indicate that the ultimate stress value under tensile perpendicular to the illite layer is minimal relative to the transverse direction, the in-plane shear has more resistance to overcome than the transverse shear. Amounts of the tensile, compressive, and shear strengths of illite decrease with increasing temperature, while the strain of steady-state creep at the same loading applied time increases with the temperature. An energy barrier to enter the accelerated creep destruction phase is about 18 kcal/mol. Moreover, the improved MD simulation method can extend the time scale from 200 ps to 186 days. These results may conclude that the proposed MD simulation method may provide a powerful tool to investigate the creep behaviors of clay minerals at experimentally relevant timescales at the nanoscale.