Trials to Determine the Usefulness of Vibro Stone Columns in the Prevention of Liquefaction of Silty Sands

A proposed Liquefied Natural Gas (LNG) plant in the south of Trinidad involved the foundation design of two 74.4 m diameter, 30 m high, concrete outer wall , LNG tanks. The site is located 1 km from an active fault. The proposed foundation system was steel tubular driven piles. Vibro stone columns were proposed to densify the silty sand layers above the founding stratum in order to minimise the number and size of piles required. This paper presents the results of trials carried out on the top feed vibro replacement wet method of stone column installation, including CPTs before and after installation. These trials showed the method to be unsuccessful in densifying all the silty sand layers. Hence these silty sands fall into an intermediate category of a material which can liquefy under earthquake conditions, but cannot be densified using this method of stone column installation.