Settlement of soft clay improved by vertical drains

Abstract

A popular method of improving soft grounds is by the installation of vertical drains. Vertical drains accelerate the rate of consolidation by shortening the drainage path. When a mass of soft clay is subjected to both vertical and horizontal drainage boundaries at a consolidation pressure, the rate of dissipation of pore water pressure is expected to be higher in the horizontal direction (ch) than that in the vertical direction (cv).

The study was based on the observations made on the magnitude of settlement for the experiments conducted with and without the installation of vertical drains. Results from the tests conducted reveal that the installation of vertical drains does significantly improve the rate of consolidation of soft clay. The coefficient of vertical and horizontal consolidation increases with increasing consolidation pressure. The coefficient of horizontal consolidation is also significantly larger than that of the coefficient of vertical consolidation. Due to the installed vertical drains, the coefficient of vertical and horizontal permeability shows a decrease with increasing consolidation pressure due to a reduction of void ratio. The findings indicate that the experimental magnitude of settlement differs from the theoretical magnitude of settlement. The reason for such difference was not investigated.