The use of hydro test results for design of steel tanks on stone column improved ground - a case history

This paper describes hydro tests performed on five large storage tanks (80.000 m3 each) located at the Sisak Oil Terminal, Croatia. Because of its small stiffness and low water permeability, foundation soil for each tank was improved with 660 stone columns. In order to reduce the risk of accidents, such as fire, breach or leak, a crude oil storage tank requires stringent security measures. In the case of the Sisak tanks, the hydro tests were conducted as part of technical monitoring to determine a set of documented and interconnected activities which would provide proof of proper functioning of all elements of a tank structure. In case of critical deviations from the operation expected, such activities ensure that such deviations are removed or corrected on time by taking necessary measures approved by experts. Under a procedure for the hydro tests, the phases of tank and bund filling were defined and each phase was followed by visual inspection and measurements of settlements and deformations of the steel structure. Design directions for future foundation and hydro tests of tanks were made accordingly.