Analysis of flexible drains in Changi reclamation

Abstract

Vertical drains and surchage were used to accelerate the consolidation of soft marine clay under the second runway at the Changi Airport site. To study this problem further, the consolidation of a strip of layered clay deposit under a large reclamation is analysed as a two-dimensional problem in accordance with Biot's theory using the finite difference method. The operating soil parameters determined by back analysing the field observations in a pilot test were then utilized to predict the behaviour of the main works. As the equivalent soil is obtained by equating the average degree of consolidation, pore pressures cannot be predicted accurately within the drain area. However, the trend of pore pressure variation across the test site is implied by the analysis. The trend showed that pore pressures outside the drain area are found to influence the settlement and pore pressure inside the drain area, causing retardation in the consolidation of the drain area. -from Authors