Mass Stabilization of Organic Soils for Steel Tank Support at Port Everglades, Florida

Mass stabilization by dry soil mixing (DSM) is a ground modification technique that involves pneumatically injecting and mechanically mixing dry binder powder (Portland cement or a blend) with in situ soils. This produces a soilcrete mass that has higher strength and lower compressibility than the original soil. DSM by Mass Stabilization is ideally suited for loose or soft soils having high natural moisture content, including organic soils, located within 7 m or less of working grade. During the design process, the required unconfined compressive strength and elastic modulus of the soilcrete are determined based on the magnitude of the loads that are being supported and the amount of settlement that is acceptable. DSM was completed on several soft soil sites at Port Everglades, Florida. A total of fifteen new petroleum storage tanks at three new tank farms, for three different owners, were constructed on standard ring wall foundations after the highly organic in situ soils were improved by mass DSM. The above ground storage tank sizes ranged from 12.19 m to 18.29 m tall, and from 12.19 m to 42.7 m in diameter. Soilcrete material quality was verified during construction by coring and by penetration testing. After the tanks were constructed, full-scale hydrostatic load tests were performed to verify that the tank settlements were within acceptable limits. The load-settlement responses of the tanks were better than anticipated, and easily satisfied the stringent performance criteria. The DSM design procedure and the data from the load testing are presented and discussed.