Settlement Comparison Used in Tank-Failure Study

An investigation into the possible causes that led to the failure of Tank T-270, a 315,000 barrel, (50,000 cu.m) oil-storage tank in Japan, included a comparative study of the settlement behavior of 33 large tanks on soft-ground sites in Japan and other countries. The comparative study includes the evaluation of the best-fit rigid-settlement tilt plane for the measured tank shell settlements, the differential shell settlements with respect to the tilt plane, and the measured tank-floor settlements with respect to the tilt plane of the tank shell. Empirical data are provided on the behavior of many tanks that experienced large settlements yet continued to perform satisfactorily and on a few tanks that failed. The empirical settlement-behavior studies concluded that many tanks have experienced more severe settlements than Tank T-270 and have not failed, yet some movements that occured in the tank floor and in the foundation materials were judged to have probably contributed to the failure.