Preloading Results in Tank Foundation Economics

The details of a field investigation conducted in connection with the design and control of a site preloading program to permit the use of shallow foundation pads for an oil storage tank farm are described. The site in question is underlain with highly compressible glacial lake deposits of varying thickness. The initial phase of the preloading program was also used as a large field load test to afford a basis for an understanding of load-settlement relationships in the northern part of the site where a transitional area from weathered shale at shallow depths to the compressible glacial lake deposits occurs. Settlements resulting from the preload materials ranged from approximately 1.3 in. in the northern end of the site to as much as 20 in. in the southernmost tank location. These settlements occurred quite rapidly, with a maximum waiting period of less than three months required. Recorded post-construction settlements are shown to be well within tolerable limits. The site preload solution saved the owner approximately $160,000 in foundation costs under the cost of a short pile foundation.