A field study of pile-PVD interaction in soft clay
Piles and prefabricated vertical drains (PVDs) are two well established techniques used by geotechnical practitioners when dealing with soft compressible foundations. Induced movements in highly compressible soil can adversely influence the pile response by inducing additional movements and stresses into the piles. Especially, undesirable soil-pile interaction often leads to the development of excess pore pressure during pile installation and negative skin friction caused by the settlement of compressible soil surrounding the piles. Additional drainage by PVDs prior to the installation of a pile could reduce excess pore water pressure, lateral soil movement, and negative skin friction on pile. In this paper, full scale field testing on two trial embankments built on soft soil is reported and the relative behaviour of these embankments are compared and discussed. Soft soil underneath both embankments was consolidated before one pile was installed at the centre of each embankment. The pore pressure, lateral soil movement, surface settlement and associated strain at pile shaft were recorded. The pile capacity was tested immediately and 3 hours after pile installation. The monitoring and testing results indicated that preconsolidation with PVDs before piling can effectively reduce the excess pore water pressure, lateral soil movement and the downdrag on pile.