Case studies and analyses of soft clay consolidation accelerated by prefabricated vertical drains

• Main Author: Jia, Yin
• Other Authors: Low Bak Kong
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/61057
• Institution: Nanyang Technological University

In the recent years, more reclaimed land has been constructed to meet the demands of rapid urbanization. During the construction of reclamation works, prefabricated vertical drains (PVDs) with preloading are widely used to increase the shear strength of soil and shorten construction schedule. There are two general methods to implement PVDs, namely conventional preloading and vacuum preloading. Different types of vertical drains and their respective installation methods are discussed. In addition, theoretical coefficients and other possible factors that influence efficiency of vertical drains are also described in details. Two numerical programs VDrainSt and Settle3D were used to estimate the final settlement. Three case studies (Hong Kong Chek Lap Kok international airport, Thailand New international airport and Changi East reclamation project) were studied to demonstrate the applications of PVDs with conventional and/or vacuum preloading. The objective is to better monitor and estimate the rate and magnitude of consolidation settlement of soft clay. Subsequently, the analyzed results obtained from numerical programs were compared with field measured settlement to investigate the possible effects of external factors in practice and inadequacy of the numerical programs. Based on the numerical analysis on the three case studies, close installation spacing, small size of mandrel and PVDs with vacuum preloading are preferred. Both programs VDrainSt and Settle3D perform well in the preliminary and sensitivity analysis. VDrainSt normally underestimates settlement while Settle3D normally overestimates settlement. The special visualization capabilities in Settle3D make the date more presentable and interactive. All in all, these two numerical analyses are able to provide a reasonable reference for users. Nevertheless, there are a few areas for further research studies to improve the accuracy of numerical programs, such as the functions in the programs VDrainSt and Settle3D and external factors in practice.