Quantitative analysis of the microstructure of Shanghai muddy clay before and after freezing

Artificial freezing is becoming a common method of enhancing soil quality when undertaking large scale underground structures in Shanghai. This paper presents the variation in the frozen strength of Shanghai muddy clay with temperature. SEM studies were undertaken to analyse the shape and size of the pores in the frozen material compared with the undisturbed clay. The results show that compared with undisturbed soil, the shape and the orientation of the pores in samples frozen at -10, -15 and -20 degrees C did not significantly change after the compression testing, although the pore volume increased with decreasing temperature. The relationship between microstructure and moisture migration is discussed.