The Influence of Strain Rate on Pore Pressures in Consolidated Undrained Triaxial Tests on Cohesive Soils

Abstract

The influence of strain rates on pore pressures of cohesive soils in consolidated-undrained triaxial tests was experimentally studied. Three types of cohesive soils were used; Kawasaki clay with plasticity index of 30 and two artificial mixtures of Kawasaki clay and Toyoura sand with plasticity index of 20 and 10. Pore pressure measurements were carried out by small transducers at the centre, bottom and periphery of triaxial specimens. It was found that at low strains the pore pressure at the centre was larger than that at the bottom and periphery, while at high strains the difference was less significant. The difference in pore pressures at the three different locations was smaller for lower strain rates and for soils with lower plasticity index. Pore pressures in undrained triaxial specimens of soil with plasticity index up to 30 were considered to be uniform at the strain rate of 4%/h. It was concluded that the test duration given by Blight was satisfactory from the standpoint of pore pressure equalization.