Change of hydraulic conductivity during compression of undisturbed and remolded clays

Eight series of falling head hydraulic conductivity tests were performed on both undisturbed and remolded specimens of four clays from China using a modified oedometer to investigate the change of hydraulic conductivity during compression. Similar to their compression behavior, the undisturbed specimens showed the curves of hydraulic conductivity versus effective vertical stress lying above those of the remolded specimens. Past studies showed that the compression curves of remolded clays could be unified into a unique line using the void index. However, such unification between the void index and the hydraulic conductivity for remolded clays was not found in this study. The relationship between the void index (or void ratio) and the hydraulic conductivity for undisturbed specimen was almost identical to that of the remolded specimen. The relationship between the void ratio and the hydraulic conductivity on a logarithm scale was nearly linear with a slope of 0.5 times the initial void ratio at strains < 20%, and became concave upwards within the full range of strains during compression. Similar to the oedometer test data, the relationship between the specific volume and the hydraulic conductivity could be expressed by a straight line in a bilogarithmic plot within the full range of strains during compression.