Ground Improvement for Large Above Ground Tanks Using Deep Mixing

The bearing capacity and settlement behavior of large diameter above-ground petroleum storage tanks are critical in loose and soft soils. On Sand Island in Honolulu, Hawaii, there is a history of large magnitudes of settlement associated with these types of tanks. On a recent tank expansion project, large diameter floating soil-cement columns constructed using in-situ deep mixing were used to improve the bearing capacity and control the settlement of three large diameter storage tanks constructed on sandy lagoonal deposits. Although the settlement of the tanks exceeded predicted values, the deep mixing ground improvement program successfully limited settlement to within the specified and allowable values. Furthermore, deep mixing also provided cost-effective means of treating petroleum-impacted soils at the tank locations.