Secondary consolidation and aging are two often encountered time-dependent geo-processes. Secondary consolidation usually refers to the continuous deformation after excess pore water pressure has been substantially dissipated. Aging generally involves time-dependent increase in the properties of sands, especially strength and stiffness. Many investigators have studied these two subjects for decades. However, at present, because of the complicated soil behavior involved and the limitation of measurement techniques, convincing underlying mechanisms remain unconcluded. This study aims at giving an insightful understanding of these two phenomena from the particulate-scale point of view. Laboratory experiments such as oedometer test, mercury intrusion porosimetry (MIP) and numerical simulati...[ Read more ]

Secondary consolidation and aging are two often encountered time-dependent geo-processes. Secondary consolidation usually refers to the continuous deformation after excess pore water pressure has been substantially dissipated. Aging generally involves time-dependent increase in the properties of sands, especially strength and stiffness. Many investigators have studied these two subjects for decades. However, at present, because of the complicated soil behavior involved and the limitation of measurement techniques, convincing underlying mechanisms remain unconcluded. This study aims at giving an insightful understanding of these two phenomena from the particulate-scale point of view. Laboratory experiments such as oedometer test, mercury intrusion porosimetry (MIP) and numerical simulation are involved.

The first part of this research focuses on the secondary consolidation. Kaolinite samples with different fabric formation were prepared by adjusting the pore fluid conditions. Oedometer test, mercury intrusion porosimetry (MIP) and scanning electron microscopy were performed. The test results reveal that the secondary consolidation is not caused by intra-aggregate pores whose diameter is smaller than 20 Å, which is supported that the secondary consolidation is fundamentally the same as the primary consolidation.

The second part of this research investigates the aging effects of sand. A numerical simulation program using distinct element method (DEM) was developed. The simulation results show that after inducing a small amount contact creep, the contact forces inside the sample redistribute, which results in considerable increase in stiffness for both loose and dense sample, however, the strength and dilatancy increase of the sample are not consistent for loose and dense sample. It is found that the uniformity of the contact force distribution has an influence on the aging effects, and is discussed in detail in the thesis.