By A D M Penman, BRE
This paper was first published in GE’s March 1978 issue
Large oil tanks are sufficiently flexible to transmit their liquid load to the foundation with little structural interaction. Modes of failure and measured distortions of successful tanks have indicated acceptable deformations for the floors and shells of tanks.
The cheapest form of foundation is a pad of compact fill placed directly on the stripped ground surface. When the soil is initially too weak to support the weight of a full tank, it may be consolidated by a surcharge of random fill before the tank is built, or by the weight of the tank itself during initial controlled loading. When this method is used, settlement may be reduced and stability improved by placing a temporary bund to load the soil just outside the tank.
This paper describes eight case histories of failures of tanks on pad and piled foundations and gives several examples of the observed distortions of tanks in service. Methods that have been used to limit differential settlements are discussed and limits are given for acceptable differential settlements under tank floors and shells. The paper concludes with design guidance notes.