Microstructure evolution of soft clay under consolidation loading

Abstract

Oedometer tests and field emission scanning electron microscope tests of soft clay were carried out to study the microstructure evolution during consolidation process to evaluate the relationship between microstructure and macroscopic characteristics. The results show that many smaller aggregates appeared under consolidation pressure, and shapes of soil particles and pores became more complicated. Larger pores were much compressed under lower consolidation pressure while the number of small pores increased under higher consolidation pressure. Pore and soil particle diameters change with consolidation pressure, and the fractal dimensions based on these were used to describe the diameter differences between soil particles or pores. The fractal dimension of pore increased greatly when consolidation pressure was below 100 kPa, while that of soil particle changed slightly. The fractal dimension of pore decreased significantly while the fractal dimension of soil particle increased when consolidation pressure ranged from 100 kPa to 400 kPa. When consolidation pressure was larger than 400 kPa, the microstructure changed in a relatively small degree. The consolidation characteristics was related to the microstructure evolution and equations of macroscopic parameters expressed by microstructure parameters were investigated. The consolidation process of soft clay is divided into three stages: natural structural stage, restructuring stage and slight-change stage. It is important to study on consolidation characteristics of soft clay based on the three stages.