Innovations and performances of PVD and dual function geosynthetic applications

Full-scale test embankments, which were constructed on separate locations but within the site of the Second Bangkok International Airport and at the Campus of the Asian Institute of Technology, confirmed that prefabricated vertical drain (PVD) installation not only accelerated and facilitated uniform consolidation settlements but also aided in recharging the subsoil. Thus, PVD can mitigate the negative piezometric drawdown of the subsoil caused by the excessive pumping of groundwater down to the depth of PVD installation. The compressibility and flow parameters were back-calculated from the performance of the full-scale tests. Further back-analysis proved that every stage of preloading corresponded with certain rate of consolidation, and hence the variation of compressibility parameters of PVD-improved soft clay. Another full-scale test embankment employing vacuum-assisted preloading revealed that the rate of settlement has increased by 60% and the period of preloading was reduced by 4 months. Moreover, the use of electro-conductive PVDs could further shorten the required time of consolidation. In addition, dual function geosynthetic had been proposed to prevent excavation slope failures caused by the drawdown of water level along irrigation/drainage canals. (C) 2003 Elsevier Ltd. All rights reserved.