Analysis of the use of membranes in oil tank foundations

Impermeable membranes are sometimes incorporated into the bases of large hydrocarbon storage tanks to provide a mechanism for secondary containment, should leakage of the main tank occur. A concern exists that these membranes could result in a structural weakening of the tank foundation, because they provide a plane on which only a low angle of friction can be mobilised. A series of axisymmetric finite element analyses has been carried out to study this problem. The results demonstrate that, for the configurations analysed, the additional settlements or rotations at the base of the tank induced by the presence of the membrane are in most cases negligible by comparison with variations due to other factors.