Finding Storage Tank Settlement on Granular Soil with Small-Strain Stiffness

Based on the API650 Standard, there are four types of raft foundations for liquefied hydrocarbons storage tanks. Since soil is the only material used in constructing foundation types B.4.1 and B.4.3, we can advance the process through further research to identify their behavior and technical/engineering characteristics. Because settlement is a fundamental problem in foundation design, studying its affecting parameters and estimation approaches are quite important. A study was conducted in South Pars region (Iran) focusing on type B.4.3 foundation, and its settlements were predicted after performing hydro-tests. The general soil profile of the foundation bed was also recorded through some boreholes and crosshole test and some laboratory tests. For settlement estimations on granular soils, we used Schmertmann equation which is a function of the strain influence factor; the values proposed by some researchers for this factor yield conservative values for the settlement of the above storage tanks. In this research, Schmertmann equation was rewritten with the proposed strain influence factor (a function of shear wave velocity) and the amount of settlements of the storage tanks were estimated. Results indicate that, compared with relations presented by other researchers, the proposed relation estimates settlements with highly acceptable precision.