Drainage and reinforcement of soft clay tank foundation by sand columns

A series of centrifuge model tests, at acceleration levels of 105 g, is reported, in which loosely placed vertical sand columns and densified sand columns have been used to improve the performance of oil storage tank foundations. A simulated tank of 34 m diameter, with a flexible base, has been subjected to incremental fluid loadings typically to 160 kPa, with foundation drainage permitted. Model preparation included the installation of as many as 572 sand columns in a single foundation. Comparison is made between the experimental results and the analysis of Priebe, which indicates that that analysis will overestimate the improvements if three-dimensional considerations are not taken into account. Comments are also included as to the extent to which model column formation may be deficient.