ANALYSIS AND PERFORMANCE OF PILED RAFTS DESIGNED USING INNOVATIVE CRITERIA

In this paper the main criteria adopted for the design and some aspects of the observed behaviour of the piled foundations of a cluster of circular steel tanks are reported. They were designed to store sodium hydroxide, a toxic liquid with a unit weight of 15.1 kN/m3. Shallow foundations would have been safe against a bearing capacity failure, while the predicted settlement were beyond the allowed limit. Accordingly piles were designed to reduce the settlement and improve the overall performance of the foundations. While conventional capacity based design approach lead to a total of 160 piles to support the 5 tanks the settlement based design approach lead to a total of 65 piles sachieving significant savings on the cost of the project. The settlements of four out of the five tanks were measured and for two out of the five tanks the load sharing among the raft and the piles was also observed. Both the analyses carried out at the design stage and the back-analyses of the observed behaviour were based on the interaction factors method as implemented in the com-puter code NAPRA (Russo, 1998)