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Load tests were performed on corrugated step-tapered piles with pipe extensions and pipe piles driven through 120 ft of slightly overconsolidated, medium-to-stiff, fissured clays 1 to 10 ft into dense fine sands and silty sands. Failure loads for the bearing piles of 10¾ to 12¾ in. tip diameter varied from 180 to 280 tons. Design dead loads up to 90 tons, which could be temporarily carried in friction in the upper compressible soils, were expected to be eventually transmitted to the sand stratum. The bearing capacity of the sand was evaluated by subtracting friction in the upper clays, as measured by piles stopped above the sand, from the total load carried by the bearing piles. The developed friction capacity was uncertain because of variations in soil strength between load test locations. However, the following conclusions are indicated by the test data and wave equation analyses of the driven piles: (1) the corrugated step-tapered piles developed frictional resistances in the clays equal to or greater than the minimum undrained shear strength determined by unconfined compression tests, (2) pipe piling frictional resistances were about two thirds of the corrugated pile values, and (3) the bearing capacity of the sand was overestimated 70 to 100 percent by wave equation analyses of the ultimate resistance of bearing piles driven to practical refusal and 150 to 400 percent by bearing capacity formulae using full overburden pressures and bearing capacity factors for laboratory-measured angle of internal friction of the sand.

Previously published data on allowable building settlements have not included cases where the settlements were due to the fill loads. In this paper, comparisons have been made between calculated and observed areal fill settlements of 1 to 4 ft at the San Francisco Airport. The effects of these settlements on buildings supported on pile foundations and spread footings are reported for three aircraft hangars and one terminal building. These data indicate that the Terzaghi theory of consolidation permits reasonably accurate settlement calculations for the consolidation of a postglacial marine clay (bay mud) under fill loads. Differences in fill thickness resulting from shear failures of the soft bay mud during site grading can cause serious problems in building and site behavior. Surcharge fills are effective in reducing postconstruction settlements and hangar foundation costs in areas of shallow bay mud. Light steel frame buildings supported on spread footings can withstand total settlements of 1 ft and differential settlements of several inches. Pile foundations must be designed for the negative friction forces imposed by subsiding soils if settlements are to be controlled.

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