Effectiveness of Vertical Drains in Dissipating Excess Pore Pressures Induced by Cyclic Loads in Clays

The purpose of this paper is to investigate the effectiveness of Prefabricated Vertical Drains (PVDs) in dissipating the excess pore water pressures induced by cyclic loading in soft clays. Cyclic triaxial testing on soft clay samples with vertical drains has been carried out using a large scale cyclic triaxial apparatus designed and built at the University of Wollongong. The samples used were 300 mm in diameter and 600 mm in height. The samples were anisotropically consolidated under ko condition to simulate the in-situ stress history of the field. Stress-controlled cycles were then applied to the soil samples with different loading frequencies. The excess pore water pressures were measured by several transducers located at different positions along the radius and height of the soil specimen. The results of the excess pore water pressures and settlements are presented. The advantages of soft subsoil stabilized with PVDs under high frequency cyclic loading conditions are investigated and discussed together with the results of a numerical analysis using PLAXIS finite element code.