The natural normally-consolidated diatomaceous soil deposited in Ohita Prefecture of Japan is a natural strongly structured soil. It has a surprising high strength and high consolidation yield stress although its natural water content is very high. In this study

the mercury intrusion porosimetry (MIP) tests were performed on the natural sedimentary diatomaceous soil to investigate the relationship between the change in entrance pore size distribution and the applied stress level. The microstructure investigation results indicate that the entrance pore size distribution varies little when the stress level is smaller than the consolidation yield stress

but changes significantly when the applied stress is in the vicinity of the consolidation yield stress. When the applied stress is larger than the consolidation yield stress

pore space volume decreases

the maximum pore becomes smaller and the pore size gradually becomes uniform with the increase in applied stress level. The relationship between microstructure and macro-mechanical behavior is also investigated.